JPH0685301B2 - Color picture tube - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a color picture tube.

[Technical background of the invention and its problems]

As shown in FIG. 2, a color picture tube generally comprises a vacuum envelope composed of a substantially rectangular panel (1), a funnel-shaped funnel (2) and a neck (3). Then, a phosphor screen (4) consisting of striped phosphor layers emitting red, green and blue respectively is adhered and formed on the inner surface of the panel (1), and the neck (3) is horizontally mounted on the panel (1). A so-called in-line type electron gun (6) is arranged which is arranged in a line along the axis and emits three electron beams (14) corresponding to red, green and blue. Further, at a position close to and facing the phosphor screen (4), a peripheral portion thereof is supported by a mask frame, and a large number of slit-shaped apertures are vertically arranged, and this vertical arrangement is a shadow mask in which a large number are horizontally arranged. (5) is supported via the elastic member (12).

The three in-line electron beams (14) are deflected by a deflection device (9) outside the funnel (2) to scan a rectangular range corresponding to the rectangular panel (1), and a shadow mask (5). The color tone is classified through the apertures and landed on the stripe-shaped phosphor layer to reproduce a color image. Also, the electron beam (14) may not be accurately landed on the stripe-shaped phosphor layer due to the influence of an external magnetic field such as the earth's magnetism, so that the color purity of the reproduced image is prevented from deteriorating within the funnel (2). A magnetic shield (8) made of a magnetic metal plate is locked via a frame (7).

In such a color picture tube, the number of pitches of the slit-shaped openings of the shadow mask (5) in the horizontal direction needs to be 1/3 of the pitch of the striped phosphor layer. Therefore, the effective electron beam that normally passes through the slit-shaped aperture is 1/3 or less, and the remaining electron beam impinges on the shadow mask (5) and sometimes heats the shadow mask (5) up to about 80 ° C. I will let you. Also, in a special color picture tube used for aircraft cockpit and other indicators, sometimes the temperature of the shadow mask rises to around 200 ° C. This shadow mask (5) generally has a thickness mainly composed of iron having a relatively large coefficient of thermal expansion.
It is formed of a thin plate with a thickness of about 0.2 mm, and its peripheral portion is fixed by a strong mask frame (7) with a thickness of about 1 mm. Therefore, the electron beam impinging on the shadow mask (5) heats and expands the shadow mask (5) to change the interval (hereinafter referred to as q value) between the phosphor screen (4) and the shadow mask (5), If the change in the q value exceeds the allowable value, the electron beam does not land exactly on the stripe-shaped phosphor, so-called mislanding occurs, and the color purity deteriorates. To prevent this, Japanese Patent Publication No.
As shown in Japanese Patent No. 47, the mask frame (7) is locked to the side wall of the panel through the bimetal, and the entire shadow mask (5) is moved in the phosphor screen (4) direction to change the q value. A method is adopted that keeps it within a practically acceptable range.

However, the method using this bimetal is complicated, and since the number of parts is large, the combination accuracy tends to vary.
Also, the operation principle is slow due to heat conduction in the path of shadow mask → mask frame → bimetal, and the correction effect is not sufficient. As a result, the purity is likely to vary,
A good quality color picture tube is expensive.

[Object of the Invention]

The present invention has been made in view of the above problems,
To provide a color picture tube that suppresses color purity deterioration such as image color shift by sufficiently reducing electron beam mislanding for a long time from the beginning of operation, and improves image reproducibility with a simple support material. Has an aim.

[Outline of Invention]

That is, according to the present invention, when the mask frame supporting the shadow mask is suspended by the strip-shaped elastic member on the stud pin embedded in the inner wall of the panel, the coefficient of thermal expansion of the mask frame in the range of room temperature to 200 ° C. is α _f , the thermal expansion coefficient of the shadow mask at room temperature to 200 ° C is α
_m , and the angle α between the movable piece of the strip-shaped elastic member and the tube axis is between the angle β between the electron beam and the tube axis. The color picture tube is characterized in that the relationship of is established.

Example of Invention

Hereinafter, an embodiment of the color picture tube of the present invention will be described in detail, but the overall structure of the color picture tube is almost the same as that of the conventional example and will not be described.

FIG. 1 is a diagram showing a main part of an embodiment of the color picture tube of the present invention.

That is, on the inner surface of the substantially rectangular panel (1), red,
A phosphor screen (4) composed of a stripe-shaped phosphor layer that emits green and blue light is adhered and formed. A large number of slit-shaped apertures are vertically arranged at a position close to and facing the phosphor screen (4). The vertical arrangement has a plate thickness of about 0.2 mm and a normal temperature to 200 mm. Thermal expansion coefficient α _m in the range of ℃ is about 1.2 × 10 ^-5
The side wall of the shadow mask (15) made of cold-rolled steel plate of deg ^-1 is relatively thick with a thickness of about 1 mm, and the thermal expansion coefficient α _f in the range of room temperature to 200 ° C is about 1.2 × 10 ^-5 deg ^-1 The stud pin (10) fixed to the mask frame (17) made of cold-rolled steel plate and planted on the inner surface of the mask frame (17) and the panel (1) is a spring material having a thickness of about 0.4 mm, for example, Consists of precipitation hardening SUS 631. Stud pin (1
A strip-shaped elastic member (22) is provided between the strip-shaped elastic member (22) and the tube axis (20) of the movable piece (22a) of the strip-shaped elastic member (22) and the strip-shaped elastic member. The electron beam (2 that passes through the outermost hole of the shadow mask in the vicinity where (22) is placed (2
The angle β with the tube axis (20) in 4) is Is set to be

In this case, the shadow mask (15) and the mask frame (1
8) may be integrally formed. Further, it is preferable that the strip-shaped elastic members (22) are arranged at the corners of the rectangular panel (1) which can maintain a relatively high mechanical strength.

Next, the correction of the thermal expansion of the shadow mask (15) by the strip-shaped elastic member (22) will be described in detail.

That is, the angle α formed with the tube axis (20) of the movable piece portion (22a) of the strip-shaped elastic member (22) is such that the color picture tube is a 90-degree deflection tube and the strip-shaped elastic member (22) is rectangular. Shaped panels (1)
When it was installed in the four corners of the, the angle was set to about 57 °. When the mask frame (18) thermally expands, the top portion A of the strip-shaped elastic member (22) formed relatively thin due to the amount of thermal expansion moves toward the phosphor screen (4) direction (A ′) due to the geometric structure. Will be done. Therefore, the mask frame (18) and the shadow mask (15) fixed to the strip-shaped elastic member (22) can be moved to the phosphor screen (4) side, and as a result, mislanding can be corrected. You can

In more detail, the shadow mask (15) is thermally expanded by its temperature rise t _m, the amount that is, the movement of the apertures of the shadow mask, corresponds to the distance m to P 'from the point P of FIG. 1 To do. Therefore, this shadow mask (15)
When the displacement of the electron beam due to the thermal expansion of the shadow mask is to be corrected, the aperture of the shadow mask that has moved to the point P'is elastic member (2
You can move to point Q according to 2). That is, this required correction amount D can be expressed geometrically as follows. That D = m · tan (90- β) = α m · t m · l m · tan (90-β) - a (2). Here l _m is the distance from the tube axis to the shadow mask outer wall, is t _m is the temperature rise of the shadow mask.

However, the reason why the aperture of the shadow mask is actually moved from the point P ′ to the point Q is that the elastic member accompanying the thermal expansion f (temperature rise t _f ) of the mask frame (17) is used as described above. It is performed by moving from the top A to the point A '. Therefore, the correction amount d due to the movement of the top portion A can be geometrically expressed as follows.

d = f · tan (α) = α f · t f · tan (α) - (3) where _{t f} indicates the temperature rise of the mask frame.

Therefore, when the displacement of the electron beam due to the thermal expansion of the shadow mask (15) is corrected, the correction amount D required to move the aperture of the shadow mask from the point P ′ to Q and the elastic member (22 It is necessary to make the actual correction amount d according to () equal. That is, it is necessary to set D = d- (4). This equation (4) is added to the above equation (2),
Substituting (3) Becomes

Where shadow mask (15) and mask frame (17)
Are made of the same material, for example, a cold rolled steel sheet, the thermal expansion coefficients α _m and α _f are exactly the same. Becomes

On the other hand, the thickness of the mask frame (17) is usually about 1 mm. Becomes

Substituting the above equations (6) and (7) into the above equation (5), Becomes

Where shadow mask (15) and mask frame (17)
If the temperature rises are equal _{(t m / t f = 1} ) is ,, correction angle α of the equation (8) an elastic member (22), the angle between the electron beam (24) and the pipe axis (20) It can be seen that the displacement of the electron beam due to the thermal expansion of the shadow mask (15) can be almost corrected if it is determined as follows using β.

α = 90−β− (9) Therefore, in the case of 90 ° deflection (β = 45 °), the correction angle α of the elastic member is 45 ° from the equation (9), which is just half the deflection angle. Such an idea has already been disclosed in, for example, Japanese Examined Patent Publication No. 58-144 as shown in FIG.
Here, the elastic member is indicated by (12). However, since the temperature of the shadow mask of the color picture tube during actual operation and the temperature of the mask frame are significantly different, the displacement of the electron beam due to the thermal expansion of the shadow mask is sufficiently considered in the idea of the above-mentioned known art. It turned out that it could not be corrected.

That is, FIG. 4 shows temperature changes during normal operation of the shadow mask and the mask frame, which were obtained by the present inventors through experiments using the 21-inch color picture tube having the structure according to the above-described embodiment of the present invention. Is. As a result, the temperature of the shadow mask during operation rises by about 47 ° C, but the temperature of the mask frame rises by about 30 ° C. Therefore, such 90 degree deflection (β =
The correction angle α of the elastic member (22) as shown in FIG. 1 for correcting the displacement of the electron beam due to the thermal expansion of the shadow mask of the color picture tube of 45 ° is calculated from the above formula (8). Becomes Therefore, it is apparent that the displaced electron beam cannot be sufficiently corrected by the elastic member (12) having an angle equal to half the deflection angle as in the known example of FIG.

By the way, the reason why the temperature of the mask frame becomes lower than that of the shadow mask is considered as follows. That is, in a general television receiver, the deflection angle of the electron beam is set to a large value in advance in order to prevent the scan area from being insufficient, that is, the screen is cut off due to the variation of the deflection angle due to the change of the high voltage of the television set. However, if the deflection angle is set too large, in addition to the energy loss of increasing the deflection power, the electron beam (24) reflected by the side wall of the shadow mask (15) or frame (17) as shown in FIG.
The a) comes to the phosphor screen (4) and causes the phosphor to emit light unnecessarily, which significantly deteriorates the color purity. For this reason, the increase in the deflection angle for preventing screen breakage is generally suppressed within 3%. Therefore, the electron beam always hits the shadow mask (15) in operation and a part of its peripheral portion to raise the temperature, but it hardly hits the mask frame (17) directly. Therefore, the only factor that raises the temperature is the conduction including the radiation from the high temperature shadow mask (15). Therefore, in a general color picture tube, the temperature of the mask frame (17) is always kept lower than the temperature of the shadow mask (15).

Furthermore, as shown in FIG. 5, when the displacement f due to thermal expansion of the mask frame (17) occurs, the elastic thin shape (22) also bends in various shapes, making it very difficult to make the ideal correction as described above. .
For example, when a displacement f occurs due to thermal expansion of the mask frame (17), the top B of the elastic strip (22) always bends in the same direction as the thermal expansion of the mask frame (17) by f ′,
It becomes the position of B ', and due to this deflection, the force that originally moves the top portion A of the elastic strip (22) to the position of the phosphor screen (4) side A'is offset, and in an extreme case, mislanding is promoted. There is also this.

As described above, it is apparent that the displacement of the electron beam due to the thermal expansion of the shadow mask cannot be sufficiently corrected by simply making the angle of the elastic member half the deflection angle.

On the other hand, as shown in FIG. 6, the elastic member (12) is attached to the shadow mask (5) without using the mask frame,
A technique for correcting the electron beam by making the so-called correction angle of the elastic member (12) approximately half of the deflection angle of 90 °, that is, 45 °, is also disclosed in Japanese Patent Publication No. 46-4104. In this case, since the mask frame is not used as described above, the thermal expansion of the shadow mask directly has the effect of correcting the elastic member. Therefore, when the deflection angle is 90 °, the electron beam happens to be corrected. Required correction amount D represented by the above formula (2) and the elastic member (12) represented by the above formula (3)
The correction amount d due to can be made substantially equal. However, for example, the deflection angle, which is the mainstream of large color picture tubes, is 110
In the case of the angle .alpha., The angle .alpha. Of the elastic member is 55.degree. Because it is half the deflection angle according to the above-mentioned known example, and the necessary correction amount D and the correction amount d of the elastic member are expressed by the above equations (2) and (3). Each becomes as follows. That is, β = α = 55 °, D = α _m · t _m · l _m · tan (90−55) − (11) d = α _f · t _f · l _f · tan (55) − (12) Becomes

Therefore, the relationship between the required correction amount D and the correction amount d due to the elastic member is α _f · t _f · because the mask frame is not used.
l _f / α _m · t _m · l _m = 1 and is as follows.

That is, in the technique disclosed in Japanese Patent Publication No. 46-4104, the difference between the required correction amount D and the correction amount d due to the elastic member becomes remarkable, and the correction amount d due to the elastic member is equal to the required correction amount D of 2
It was found that this publicly known example is very limited, because it is nearly doubled, and instead of correcting the displacement of the electron beam, the color purity is deteriorated.

Next, the results of an experiment conducted by the present inventors using a 28-inch 110-degree deflecting color picture tube will be described in detail with reference to FIG. In FIG. 7, the horizontal axis shows the operation elapsed time (minutes), and the vertical axis shows the change amount of the electron beam displacement, that is, the mislanding amount. The above-mentioned color picture tube is a normal high voltage 25KV,
This is a measurement of the displacement of the electron beam at a point on the diagonal line 330 mm away from the center of the screen when operating on a white screen with a beam current of 1.2 μA / cm ^{2, and} the direction away from the center of the phosphor screen in the horizontal direction is positive. And, conversely, the movement toward the center of the screen was performed negatively.

In FIG. 7, the characteristic A is that of the conventional method in which the mask frame is locked to the substantially central side wall of each side of the rectangular panel via the bimetal as shown in Japanese Patent Publication No. 44-3547.
It shows the change of 21-inch 90 degree deflection color picture tube. On the other hand, the characteristic B shows the data in the case of the 21-inch, 90-degree deflection color picture tube according to the present invention. That is, the shadow mask (15) supported by the mask frame (17) by the elastic members (22) shown in FIG. 1 is locked to the side walls at the four corners of the rectangular panel. At this time,
Angle α between the movable piece (22a) of the elastic member and the tube axis (20)
Is set to 57 degrees in consideration of the temperature difference during the operation of the mask frame and the shadow mask as represented by the above formula (10) and the deflection of the elastic member (22) as indicated by f'in FIG. did. As is clear from FIG. 7, in the characteristic B according to the embodiment of the present invention, the time change of mislanding is significantly reduced as compared with the conventional characteristic A, and the electron beam returns to the position almost at the start of operation. It can be seen that the deterioration of the color purity due to the mislanding is satisfactorily suppressed for a long time from the initial operation. On the other hand, the characteristic C in FIG.
In the type 90-degree deflection color picture tube, the angle α formed by the movable piece of the elastic member and the tube axis is set to almost the same temperature without considering the temperature difference during operation of the mask frame and the shadow mask. In the end, it is a characteristic when the deflection angle is half that of the above-mentioned known example. With this elastic member, the correction effect is small, so the mislanding 90 minutes after the start of operation is about 40
μm will occur. Further, the characteristic D is that in the 28-inch 110-degree deflection tube, the above-mentioned known examples, Japanese Patent Publication No. 58-144 and Japanese Patent Publication No.
As disclosed in Japanese Laid-Open Patent Publication No. 6-4104, there is shown a change over time in mislanding when the angle α of the elastic member is half the deflection angle, that is, 55 ° in the case of 110 ° deflection. However, conversely, the mislanding amount 90 minutes after the start of the operation was increased to 50 μm or more, and the angle α of the elastic member was simply set to half the deflection angle without considering the temperature difference between the mask frame and the shadow mask. It has also been found that it is very difficult to maintain good color purity over a long period of time alone.

By the way, in recent color picture tubes, in order to suppress the displacement of the landing position of the electron beam due to the thermal expansion of the shadow mask, it is necessary to use 36% Ni-Fe alloy, so-called amber material, as the shadow mask material. Has been put to practical use.
Since the coefficient of thermal expansion of this amber material is as small as about 1/10 of that of the conventional cold-rolled steel sheet, the thermal expansion of the shadow mask can be significantly suppressed. However, when this amber material is used for a shadow mask, the mask frame is also amber in order to prevent damage due to the difference in coefficient of thermal expansion from the mask frame, for example, thermal deformation of the shadow mask in the thermal process of manufacturing a color picture tube. It is preferable to use wood. However, since this amber material is a Ni alloy, which is expensive, when it comes to practical use, the reality is that the mask frame uses cold-rolled steel material to improve the characteristics while suppressing the cost increase of the color picture tube as much as possible. Is. Now, in this way, the amber material that has recently begun to be used for color picture tubes is used for the shadow mask material, and the mask frame is the same cold tube as that of the color picture tube which obtained the characteristics A to D in FIG. Using a rolled steel plate material, the angle α of the elastic member is set to
The characteristic E in FIG. 7 shows the change over time in the mislanding amount of the 28-inch 110-degree deflection tube when the deflection angle is set to half, that is, 55 degrees disclosed in Japanese Patent Publication No. 58-144 and Japanese Patent Publication No. 46-4104. Indicated. This characteristic E was large as the mislanding amount was 80 μm or more after 90 minutes from the start of the operation, and was worse than the characteristic D of the conventional shadow mask despite the use of the low thermal expansion shadow mask. This is because the shadow mask of amber material does not expand much, but only the mask frame of cold-rolled steel plate undergoes large thermal expansion, and the correction effect of the elastic member accompanying the thermal expansion of this mask frame is abnormal. Since it is large, it is shown that the result is not the correction of the mislanding but the promotion of the conversely. This can be applied only to the technique disclosed in the above-mentioned known example, that is, only to the color picture tube in which it is extremely limited to make the angle α of the elastic member half the deflection angle. When applied to a commonly used color picture tube, the effect of suppressing mislanding is remarkably small, or conversely, there is a high possibility that the damage caused by promoting mislanding will occur.

On the other hand, according to the present invention, the displacement of the electron beam due to the thermal expansion of the shadow mask fixed to the mask frame by an elastic member having a movable piece forming an angle α with the tube axis without using a bimetal. Can be effectively suppressed by setting the angle α as follows in consideration of the temperature difference between the operating mask frame and the shadow mask.

The color picture tube that is generally used here reduces the deflection power and keeps the scanning area of the electron beam (24) to the minimum necessary. The beam does not hit. Consequently, the proportion of the temperature difference of the insulating value of different shadow mask according to the type of the color picture tube (t _m) and a mask frame (t _f) is substantially the characteristic as shown in FIG. 4 (t m _/ t _f) It is generally about 1.57. Therefore, when the elastic member is designed according to the present invention, if the angle α is determined by the following equation, a good mislanding suppressing effect can be obtained even when applied to a general color picture tube.

Further, when the shadow mask and the mask frame are made of the same material, α _m / α _f = 1 so that the design can be easily performed by the following equation.

tan (α) = 1.6 tan (90−β) − (16) If the shadow mask is suspended at the four corners of the rectangular panel as in the above embodiment, the mask frame as a supporting frame becomes more steel, and In addition, the mask frame can be made thinner than before. For example, set the mask frame thickness to 0.
If it is set to 5 mm, the size of the 21-inch color picture tube of this embodiment is 1.6
Weight is reduced by about 70% compared to mm. That is, the next 1.6mm
The weight of the mask frame is about 1.6 kg, but the 0.5 mm mask frame is about 0.
The weight can be extremely reduced to 5 kg, and this weight reduction also suppresses the amount of displacement of the electron beam when the color picture tube is impacted.

On the other hand, although the present embodiment has been described with the color picture tube having the structure in which the shadow mask is suspended at the four corners of the rectangular panel, the present invention is not limited to this range, and for example, the long sides of the rectangular panel. , Applicable to all color picture tubes that have a structure in which the shadow mask is suspended at approximately the center of the short side, as well as a structure in which the shadow mask is suspended through an elastic member that fits into the stud pin, and a considerable effect can be obtained It's okay to say so.

〔The invention's effect〕

As described above, the amount of mislanding can be significantly reduced from the beginning of operation for a long time with a simple structure,
It has become possible to provide a color picture tube which is capable of effectively improving the deterioration of color purity such as color shift and color unevenness and which is very suitable for industrial mass production. .

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of an essential part showing an embodiment according to the present invention, FIG. 2 is a sectional view of a color picture tube for explaining an embodiment according to the present invention, and FIG. 3 is a conventional color picture tube. FIG. 4 is an enlarged cross-sectional view of an essential part showing a change in temperature of the shadow mask and the mask frame depending on the elapsed time of operation, and FIG. 5 is an enlarged cross-sectional view of an essential part for explaining the operation of the elastic member. FIG. 7 is an enlarged cross-sectional view of a main part of a conventional color picture tube, and FIG. 7 is a characteristic view showing a change in mislanding amount depending on elapsed time of operation. (1) ... Panel, (4) ... Phosphor screen (5), (15) ... Shadow mask, (7), (17) ...
… Mask frame (10) …… Stud pin, (12), (22) …… Elastic member (12a), (22a)… Movable piece

Claims (2)

[Claims] 1. A vacuum envelope in which a substantially rectangular panel is connected to a funnel-shaped funnel and a neck, a phosphor screen formed on the inner surface of the panel, and a phosphor housed in the neck. At least an electron gun that emits a plurality of electron beams that excite the screen to emit light, and a shadow mask that is suspended by a strip-shaped elastic member through a rectangular frame-shaped mask frame so as to closely face the phosphor screen are provided. In the color picture tube, the coefficient of thermal expansion of the mask frame at room temperature to 200 ° C. is α _f , the coefficient of thermal expansion of the shadow mask at room temperature to 200 ° C. is α _m , and the strip-shaped elastic member is movable. The angle formed by the tube and the tube axis is α, and the electric current is deflected toward the end of the phosphor screen corresponding to the panel on which the shadow mask is suspended. The angle between the sub beam and the tube axis is β
And when A color picture tube characterized by the relationship of. 2. The color picture tube according to claim 1, wherein the strip-shaped elastic members are suspended from the panel at four corners of the shadow mask.