JPH0640465B2 - Color picture tube - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a shadow mask type color picture tube, and more particularly to the shadow mask thereof.

[Technical background and problems of the invention]

Generally, a shadow mask type color picture tube has an envelope, which is typically made of glass, as shown in FIG. 1. The envelope is a substantially rectangular panel (1), a funnel-shaped funnel (2) and a neck (3). )
Composed of and. On the inner surface of the panel (1) is provided, for example, a striped fluorescent screen (4) which emits red, green and blue respectively, while the neck (3) is arranged in a line along the horizontal axis of the panel (1). A so-called in-line type electron gun (6) which is arranged in a row and which emits three electron beams (10) corresponding to red, green and blue is internally provided. Further, a shadow mask (5) having a main surface in which a large number of through holes are formed is arranged in close proximity to the screen (4). The peripheral portion of the shear mask (5) has a skirt portion (8) which is bent in accordance with the outer shape of the panel, and the skirt portion (8) is supported by a mask frame (7) having an L-shaped cross section. The mask frame 7 is fixed, and is further locked by a pin (not shown) embedded in the inner wall of the panel 1 via the spring 9.
In such a color picture tube, the three electron beams (10) emitted from the electron gun (6) are deflected by a deflecting device (not shown) arranged outside the funnel (2), The color is selected so as to scan a rectangular area corresponding to the substantially rectangular panel (1) and through the through holes of the shadow mask (5), and it is possible to correctly correspond to the strobe-like phosphors of each color. At the very least, make the color image appear. Here, the effective electron beam amount passing through the through hole of the shed mask (5) is 1/3 or less due to its mechanism, and the remaining electron beam impinges on the shed mask and is converted into thermal energy. Let it heat. Shed mask
(5) generally has a coefficient of thermal expansion of 1.2 × 10 ^-5 / ° C at 0-100 ° C
And a mask frame (7) that supports the skirt (8) of this sheer dough mask (5) is formed from a thin plate with a thickness of 0.1 mm to 0.3 mm made of so-called cold rolled steel whose main component is large iron. It is made of the same cold-rolled steel with a strong L-shaped blackening treatment with a thickness of about 1 mm. Therefore, the heated shadow mask (5) easily undergoes thermal expansion, but the periphery of the shadow mask is in contact with the blackened mask frame (7) with a large heat capacity, so the periphery of the shadow mask is affected by radiation and conduction. Heat is transferred from the mask frame to the mask frame, and the temperature around the sheer dough mask becomes lower than that at the center. For this reason, a temperature difference occurs between the central portion and the peripheral portion of the shear mask (5), and a so-called doming phenomenon occurs in which the central portion is relatively heated and expanded. As a result, the distance between the shadow mask (5) and the fluorescent screen (4) is changed, and the accurate landing of the electron beam is disturbed, resulting in deterioration of color purity. The phenomenon of mislanding due to such doming is remarkable especially in the initial stage of operation of the color picture tube.
In addition, a high-intensity image is partially projected on the image plane, and especially when this high-intensity image part is stopped for a certain period of time, an electron beam with a high electron flow density is partially generated in the shadow mask. A local doming phenomenon occurs.

With respect to the doming phenomenon in the early stage of operation among the doming of the color picture tube, many proposals have been made from the viewpoint of preventing heat conduction to the shadow mask. For example, in Japanese Unexamined Patent Publication No. 50-44771, a porous layer made of, for example, manganese dioxide is deposited on the electron gun side of a screen, an aluminum layer is formed on the porous layer, and nickel oxide or nickel iron oxide is further formed on the aluminum layer. A structure in which each layer is vacuum-deposited has been proposed. If such a structure is adopted, since the thermal conductivity coefficient of the porous layer is extremely small, the heat generated at the collision surface of the electron beam is not transferred to the mask and is radiated in the direction away from the mask. Therefore, the rise in the temperature of the shear mask can be effectively suppressed. However, even though the shear mask having such a structure is effective for the doming phenomenon in the initial stage of operation, it cannot follow the local doming phenomenon and cannot sufficiently exert the doming suppressing effect. Further, in order to form a triple layer on the surface of the shear mask by vacuum vapor deposition, a huge amount of equipment and working time are required, which is not very desirable in industrial mass productivity and is not preferable.

On the other hand, a proposal has been made to reduce the mislanding of the electron beam on the screen side. For example, Japanese Patent Publication 57-1
In Japanese Patent No. 8824, an example is proposed in which an electron absorption layer having a low conductivity is formed corresponding to a non-light emitting area on the surface of the screen where the electron beam impinges. If such a structure is adopted, in the area of the screen where mislanding occurs, the electron beam will also strike the electron absorbing layer in the non-light emitting region where no fluorescent substance exists, and the electron absorbing layer will be negatively charged. It will be. As a result, a local deceleration electric field is generated between the screen and the shadow mask, and the orbit of the electron beam that causes mislanding is corrected by the deceleration electric field, and the mislanding can be reduced. However, such a structure has the following drawbacks. First, since the deceleration electric field due to the negative charging of the electron absorption layer starts to act only after the doming phenomenon of the shear mask and the mislanding occurs, the action of reducing the mislanding always involves a certain time delay. Secondly, the negatively charged portion of the electron absorption layer formed only between the phosphors of each color-generating phosphor group is only a portion where mislanding occurs and is limited to an extremely small area. It is insufficient as a deceleration electric field sufficient to correct the trajectory. Thirdly, the action due to the negative band of the electron absorption layer is effective for the misriding during the local doming phenomenon where the current density is locally high, but the misriding during the doming phenomenon at the initial stage of operation is described above. Not very effective for some reason. Fourthly, forming such an electron absorption layer on a limited portion of the screen is extremely lacking in industrial mass productivity from the viewpoint of increasing the number of working steps and controlling the forming accuracy. That is, in the screen of a general color picture tube, a light absorbing layer is provided between light emitting phosphors of respective colors, and a metal pack made of a metal thin film such as A is provided on the entire surface. Therefore, in order to form the light absorption layers of red, green and blue, the shed mouse is desorbed four times in total and the fluorescent surface is formed by using the light exposure method, but this electron absorption layer has a conductive metal back. Therefore, the light absorption layer itself cannot be an electron absorption layer. That is, this electron absorption layer must be formed on the metal back only in the portion corresponding to the light absorption layer. For this purpose, the screen is completed and the shutter mask is attached / detached at least once to form the light absorption method. It will be. Such a forming method is extremely disadvantageous in terms of workability, accuracy, and industrial mass productivity, and lacks practicality.

[Object of the Invention]

The present invention has been made in view of the above points, and an object of the present invention is to provide a color picture tube that is rich in industrial mass productivity and that is capable of reducing the doming of the shear mask and preventing the deterioration of the color purity due to the color shift of the image. To do.

[Outline of Invention]

The present invention relates to a color picture tube including at least a shadow mask having a large number of through holes on its main surface in the vicinity of a screen and an electron gun for emitting an electron beam which causes a phosphor on the screen to emit light through the shadow mask. By providing a low-conductivity coating layer on the main surface of the shear mask on the electron gun side, this is a color picture tube that suppresses the doming of the shear mask and also prevents mislanding of the electron beam against localized doming.

Example of Invention

Hereinafter, the present invention will be described in detail based on examples. still,
The member constitution itself of the color picture tube of the present invention is the same as that shown in FIG. 1, and therefore its detailed description is omitted.

Fig. 1 shows the screen of a color picture tube as shown.
A coating layer mainly made of lead borate glass containing SnO ₂ is formed on the electron gun side main surface of the shadow mask (5) arranged so as to closely face (4). This coating layer is, for example, Pb
O: About 80 wt%, B ₂ O ₃ : About 10 wt%, SiO ₂ : About 5 wt% lead borate glass containing at least SnO ₂ : About 95% wt% Sb ₂ O ₃ : About 5
It has a weight ratio of 1: 1 with that to which% wt% is added. When forming such a lead borate glass on the main surface of the sheer dough mask, it is necessary to consider clogging of the sheer dough mask through holes and uniformization of the formed film thickness. Therefore, brush coating is not very preferable. As a simple and highly mass-producible method, for example, a method of applying lead borate glass dissolved in a butyl acetate solution of nitrocellulose dissolved in several percent by a spray method is available.

After forming the lead borate glass on the main surface of the shedow mask in this manner, the shedow mask is placed on a predetermined frame and passed through a furnace having a maximum temperature of about 440 ° C. and a holding time of 35 minutes or more. A vitrified lead borate glass layer can be formed on the electron gun side of 5). This lead borate glass vitrifies in the range of 44 to 93% by weight of PbO, but 70 to 85% is stable against crystallization, and this range is suitable for mass production. Further, in general, when arriving at metal and glass, it is necessary to prevent unreasonable strain on the glass. In glass, the pressure strength is about 10 times the tensile strength, and therefore it is better to put a slight compressive stress on the glass after sealing. It is preferably slightly larger. Generally, the coefficient of thermal expansion of the shear dough mask (5) made of associative pressure rolled steel plate is about 1.2 × 10 ^-5 / ° C.
However, the coefficient of thermal expansion of the lead borate glass having a weight percentage of PbO of 70 to 85 is 0.7 to 1.2 × 10 ⁻⁵ / ° C.,
Very suitable for sealing to a cold rolled steel shed mask. By the way, in order to crystallize such lead borate glass, it is necessary to have a maximum temperature of 600 to 450 ° C and a furnace capable of holding the maximum temperature for 30 minutes or more. However, the panel (1) and the funnel (2) are sealed. If it is crystallized in a sealing furnace at the same time as it is adhered, or if it is crystallized simultaneously in the stabilization process of the combination of the shear mask (5) and the mask frame (7), it is necessary to prepare a special heating furnace or provide a heating process. Not very industrially very advantageous. Thus, ZnO or CuO may be added to the lead borate glass, if necessary, in order to optimize the bonding under the conventional sealing furnace conditions.

In this case, it is possible to crystallize at a lower temperature without changing the thermal expansion coefficient so much.

A state in which an electron beam generated when the color picture tube having the above-mentioned configuration is operated is incident on the coating layer will be described with reference to FIGS. 2 and 3. In the figure, the same reference numerals indicate the same parts, and FIG. 3 shows the vicinity of the portion (A) of FIG. In FIGS. 2 and 3, the electron beam (10) is landed on the predetermined position (12) of the screen (4) in the state where the shear mask (5) does not cause the doming phenomenon. Here, if the electron beam density incident on the shadow mask is increased and the shadow mask is heated to cause the doming phenomenon, that is, the shadow mask (5a) is in an electron beam in a heated state (11).
Moves in the direction of the tube axis (16) along with the doming of the shadow mask (5a), and the landing point of the electron beam is also from (12) to (1
Move to 2a). That is, the electron beam that should be landed to the original point (12) is affected by the doming phenomenon (1
If the misriding at point 2a) occurs and the misriding amount at points (12) and (12a) exceeds the limit of the riding margin due to the arrangement of the phosphor groups for each color, color purity will be deteriorated. Here, in the case of the present invention, a coating layer (14) is formed in the non-permeable portion (13) of the electron gun side main surface of the shear mask, particularly when a locally high electron flow density portion occurs,
Since the coating layer (14) is made of a low-conductivity material, it is negatively charged according to the electron flow density. That is, it serves to temporarily absorb electrons. Then, the negative charge due to the absorbed electrons, especially the negative charge charged on the surface of the through hole (15) of the shear mask (5) on the tube axis (16) side moves the electron beam (11) away from the tube axis (16). Bias the orbit (10a) in the direction. Therefore, due to the doming phenomenon, the electron beam landing point (12a), which should move from the predetermined landing point (12) in the direction of the tube axis (16), is returned to the original landing point (1
It acts to cancel each other back to 2), and it is possible to suppress and reduce the mislanding of the electron beam even if the doming phenomenon occurs or the electron beam mislanding occurs. Since the coating layer (14) is formed in the non-penetrating portion of the main surface of the electron gun side of the shear mask, such a mislanding suppressing effect is obtained, the coating layer (14) of the coating layer (14) corresponds to the electron flow density of each portion of the main surface. Negative charge distribution is generated, and it is weak against this riding suppression effect at the electron flow density at the time of normal image projection and is within the range of sufficient riding margin, but in the case of causing a doming phenomenon, it is a doming suppression effect. It works more effectively in cooperation with. Further, since the electron beam always hits the coating layer as long as the tube is in operation, its active area portion is much smaller than that shown in the conventional Japanese Patent Publication No. 57-18824. It can be considered that there is a large time delay with almost no inhibition. By the way, in such a coating layer (14), for example, when the high electron flow density locally disappears, the negative electric charge charged in the coating layer (14) must have a phenomenon corresponding to the disappearance of doming. . When the image returned to the same background part from the state where the electron beam density was locally large and ΔC was higher by ΔC than the negative charge density in the back shadow part, the doming disappeared almost. At the worst, Δ
C must be reduced to 20-30%.
For this purpose, the conductivity of the coating layer is 10 ^{-5 to} 10 _-12 Ω at room temperature.
Must be ^-1 m ^-1 . That is, if the conductivity of the coating layer is better than the above, the negative charging phenomenon does not work sufficiently, and conversely, if it is poor, the negative charging phenomenon is close to an insulator and the negative charging phenomenon is not eliminated within a predetermined time, which conversely promotes misriding. become. When the coating layer is mainly composed of lead borate glass, the conductivity can be changed by adding SnO ₂ . The addition amount of SnO ₂ can be appropriately selected according to the shape and size of the shear mask or the tube type, but the addition amount of SnO ₂ is set to 10 to 50% by weight in order to fall within the above range of conductivity. do it. For example, when SnO ₂ was added in an amount of about 50% by weight as in the above Example, the conductivity was about 10 ^-5 Ω ^-1 m ^-1 .

Further, since the thermal expansion coefficient of the coating layer of lead borate glass of the embodiment of the present invention is smaller than the thermal expansion coefficient of the shadow mask as described above, the residual tensile stress always exists in the shadow mask at room temperature, and Thermal expansion can be suppressed. Furthermore, the thermal conductivity of this coating layer is about 6 W / m / K, which is about the same as that of the shadow mask of cold rolled steel plate.
Since it is as small as 1/8, the amount transmitted to the shadow mask is reduced, and the temperature rise of the shadow mask can be effectively suppressed. Therefore, it goes without saying that the normal doming phenomenon including the doming of the shadow mask in the initial stage of operation can be effectively suppressed.

〔The invention's effect〕

As described above, according to the present invention, the doming phenomenon of the shear mask and the mislanding of the electron beam are effectively suppressed and reduced without causing a large-scale manufacturing facility, an increase in workability and an increase in work time, and a color shift or a color shift occurs. It is possible to improve the deterioration of color purity such as color unevenness, and to provide a color picture tube that is highly industrially mass-producible.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of a shadow mask type color picture tube, FIG. 2 is a schematic diagram for explaining the operation in the vicinity of the shadow mask, and FIG. 3 is an enlarged view showing an enlarged portion A of FIG. It is a schematic diagram. (1) …… panel, (2) …… funnel (3) …… net, (4) …… screen (5) …… sheep mask, (6) …… electron gun (7) …… frame, (10) …… Electron beam (14) …… Coating layer, (15) …… Through hole

Claims (4)

[Claims] 1. A screen on which a group of phosphors having different emission colors is formed, a shed mask having a main surface having a large number of through-holes in close proximity to the screen, and a screen on the screen through the shed mask. In a color picture tube equipped with an electron gun that emits an electron beam that selectively emits light, a coating layer mainly composed of glass containing at least SnO ₂ of low conductivity is formed on the electron gun side main surface of the shear mask. A color picture tube characterized by having. 2. A color picture tube according to claim 1, wherein the glass in the coating layer is lead borate glass. 3. The coating layer has a conductivity of 10 ^{−5 to} 10 ⁻¹² Ω ^−1.
The color picture tube according to claim 1 or 2, wherein the color picture tube is m ^-1 . 4. A color picture tube according to claim 3, wherein the amount of the SnO ₂ added is 10 to 50% by weight.