JPH0775147B2 - 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 of the invention and its problems]

Generally, in a shadow mask type color picture tube, as shown in FIG. 1, a vacuum envelope is composed of a substantially rectangular panel (1), a funnel-shaped funnel (2) and a neck (3). There is. 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) has a water surface of the panel (1). 3 arranged in a row along the axis, corresponding to red, green and blue
A so-called in-line type electron gun (6) for emitting a book electron beam (5) is arranged. Further, at a position close to and facing the phosphor screen (4), a large number of slit-shaped apertures are arranged in the vertical direction, and a shadow mask (7) in which the vertical arrangement is arranged in the horizontal direction is a mask frame (8). It is supported and fixed by. Furthermore, the mask frame (8) is made of elastic material.
The stud pin (10) embedded in the inner wall of the upright edge portion of the panel (1) through the (9) holds the panel (1) in the panel.

The three in-line array electron beams (5) are funnels (2)
Of the striped phosphor layer, which is deflected by an external deflection device (12), scans a rectangular area corresponding to the rectangular panel (1), and is color-selected through the apertures of the shadow mask (7). Landing on, it is designed to reproduce color images. In addition, the electron beam 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, and in order to prevent the color purity of the reproduced image from deteriorating, the ferromagnetic metal inside the funnel (2). A magnetic shield (11) made of a plate is locked via the frame (8). Here, the effective electron beam amount that passes through the through hole of the shadow mask (7) is 1/3 or less due to its mechanism, and the remaining electron beam impinges on the shadow mask and is converted into heat energy, which causes the operation of general television. Then, heat the shadow mask to about 80 ° C. Also, special color picture tubes used for aircraft cockpit etc. sometimes display 200
The temperature of the shadow mask may rise up to around ℃. The shadow mask (7) generally has a coefficient of thermal expansion of 1.2 × 10
^{It is made of} so-called cold-rolled steel with a large iron content of ⁻⁵ / ° C. and a thickness of 0.1 mm to 0.3 mm.
The mask frame (8) supporting the skirt portion of the shadow mask (7) is made of the same cold-rolled steel having a strong L-shaped cross-section blackening treatment with a thickness of about 1 mm. Therefore, the heated shadow mask (7) easily causes thermal expansion, but since the peripheral part is in contact with the mask frame (8) with a large heat capacity subjected to the blackening treatment, the shadow is generated by radiation or conduction. Heat is transferred from the periphery of the mask to the mask frame, and the temperature around the shadow mask becomes lower than that at the center. Therefore, a temperature difference is generated between the central portion and the peripheral portion of the shadow mask (7), and a so-called doming phenomenon occurs in which the central portion of the shadow mask (7) is heated and expanded. As a result, the distance between the shadow mask (7) and the phosphor screen (4) changes,
The exact landing of the electron beam is disturbed and the color purity deteriorates. The phenomenon of mislanding due to such doming is remarkable especially in the initial stage of operation of the color picture tube. In addition, when a high-intensity image is partially projected on the image surface, 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 may be partially generated in the shadow mask. Then, a local doming phenomenon occurs.

With respect to the doming of such a color picture tube, it has been proposed to electrostatically correct the mislanding of the electron beam associated with the doming to reduce the mislanding. For example, Japanese Examined Patent Publication (Kokoku) No. 57-18824 proposes an example in which an electron absorption layer having a low conductivity is formed corresponding to a non-luminous region on the surface of a screen which is hit by an electron beam. If such a structure is adopted, in the screen area where mislanding occurs, the electron beam will impinge on the electron absorbing layer in the non-light emitting region where no phosphor exists, and the electron absorbing layer will be negatively charged. become. As a result, a local deceleration electric field is generated between the screen and the shadow mask, and the deceleration electric field corrects the trajectory of the electron beam that has caused the mislanding, thereby reducing the mislanding. However, such a structure has the following drawbacks. First, since the deceleration electric field due to the negative charging of the electron absorption layer begins to act only after the doming phenomenon of the shadow mask and the mislanding occur, 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-emitting phosphor group is only a portion where mislanding occurs, and is limited to an extremely small area. Therefore, it is insufficient as a deceleration electric field sufficient to correct the trajectory of the electron beam. Thirdly, the action of the negative charge of the electron absorption layer is effective for the mislanding during the local doming phenomenon in which the current density is locally high, but is effective against the mislanding during the initial doming phenomenon. Not very effective for the reasons mentioned above. Fourthly, forming such an electron absorption layer on a limited portion of the screen is extremely inadequate in industrial mass productivity from the viewpoint of increasing the number of working steps and controlling the forming accuracy. That is, in a screen of a general color picture tube, a light absorption layer is provided between each color light emitting phosphor, and a metal pack made of a metal thin film of aluminum or the like is further provided on the entire surface. Therefore, in order to form the light absorption layers of red, green and blue, the shadow mask is detached and attached a total of four times to form the phosphor screen by the light exposure method. Therefore, the light absorption layer itself cannot be an electron absorption layer. That is, this electron absorption layer must be formed only on the portion corresponding to the light absorption layer on the metal pack, and for this purpose, after the completion of the screen, the shadow mask is detached at least once and the light exposure method is performed. Will be formed. Such a forming method is extremely disadvantageous in terms of workability, accuracy, and industrial mass productivity, and lacks practicality.

To solve such a conventional defect, the same applicant as the present application provides a low-conductivity layer on the electron gun side of the shadow mask, and the low-conductivity layer is negatively charged when the shadow mask causes a large current to cause doming. Several proposals have been made to reduce the mislanding by electrostatically deflecting the displacement of the electron beam associated with doming. For example, Japanese Patent Application No. 59-
In Japanese Patent No. 2613 and Japanese Patent Application No. 59-49172, the low conductive layer is formed of lead borate glass containing tin oxide (SnO ₂ ), and is provided on the electron gun side of the shadow mask. However, in the case of this lead borate glass containing SnO ₂ , there is a problem that SnO ₂ is likely to settle out during production, so that the dispersibility is poor and the insulating part and the conductive part are separated. As a result, unnecessary electrification occurs on the insulating part, which causes abnormal deformation of the electron beam. Of course, it can be reduced by improving the manufacturing method such as stirring, but it is not so preferable as a mass production method.

[Object of the Invention]

The present invention, when electrostatically deflecting and correcting the displacement of an electron beam due to doming of a shadow mask, eliminates deformation of the electron beam due to abnormal charging, and effectively reduces mislanding due to displacement of the electron beam. Is what you get.

[Outline of Invention]

The present invention, in a color picture tube comprising 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 for causing a phosphor on the screen to emit light through the shadow mask, an electron-absorbing layer to the electron gun side main surface of the shadow mask, substantially electron permeability on the surface of the electron absorbing layer composed mainly of barium thickness corresponding to 1 [mu] g / cm ² to 100 [mu] g / cm ² Is a color picture tube in which the displacement of the electron beam due to the doming of the shadow mask is effectively suppressed and the deformation of the electron beam due to abnormal charging is eliminated by providing the low conductive layer.

Example of Invention

Hereinafter, the present invention will be described in detail based on examples.
Since the member constitution of the color picture tube of the present invention is the same as that shown in FIG. 1, detailed description thereof will be omitted. First
In a color picture tube as shown, the screen (4)
A glass layer made of crystalline lead borate glass containing, for example, about 75% by weight of lead oxide (PbO) is sealed by a high temperature heat treatment on the electron gun side main surface of the shadow mask (7) arranged close to and facing the Bonding is performed, and a coating layer mainly containing barium, for example, is formed on the surface.

Before the panel (1) and the funnel (2) are sealed, this glass layer is made of a crystalline lead borate glass melted with a butyl acetate solution containing nitrocellulose of several% to form a shadow mask (7). It is applied to the electron gun side, and this shadow mask (7) is mounted inside the panel (1). Then, after this, the panel (1) and the funnel (2) are 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, the shadow mask (7) A crystallized lead borate glass layer can be formed on the electron gun side.

On the other hand, as a substantially electron-transmissive low conductive layer formed on the electron gun side of the layer mainly composed of lead borate glass, for example, a getter coating, for example, a metal compound of Ba and Al and Ni have a weight ratio of about It can be formed by arranging a boat filled with a dispersible getter having a ratio of 1: 1 so as to face the shadow mask, and heating by high frequency after exhausting. It goes without saying that the getter coating has a property of adsorbing the gas generated in the color picture tube.

When operating a color picture tube with such a configuration,
The state when the electron beam impinges 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 part (A) of FIG. 2). ), The second
In FIG. 3 and FIG. 3, the electron beam (10) in a state where the shadow mask (5) does not cause the doming phenomenon lands on a predetermined position (12) of the screen (4). Here, if the electron beam density incident on the shadow mask increases and the shadow mask is heated to cause the doming phenomenon,
That is, the electron beam (11) in the heat state of the shadow mask (5a) moves in the tube axis (16) direction along with the doming of the shadow mask (5a), and the landing point of the electron beam also moves from (12) to (12a). . That is, the electron beam that should originally land to the point (12) mislandes to the point (12a) on the tube axis side due to the doming phenomenon, and the amount of mislanding at the points (12) and (12a) depends on the arrangement of the phosphor groups for each color. If the landing margin limit is exceeded, the color purity will deteriorate. Here, in the case of the present invention, since the electron absorption layer (14-1) is formed on the main surface of the shadow mask on the electron gun side, it is negatively charged according to the electron flow density. This means that this electron absorption layer has a thickness of about the average depth at which electrons penetrate or more, about 10 μm in this embodiment, and the primary electron energy, usually 1 or less secondary electrons for 10 KeV to 30 KeV. Means to have an emission coefficient.
And this negative charge, especially the through-hole (1
The negative charge on the tube axis (16) side surface of (5) is the electron beam (1
The orbit (10a) is deflected in the direction in which 1) is moved away from the tube axis (16). Therefore, due to the doming phenomenon, the landing point (12a) of the electron beam, which should move in the direction of the tube axis (16) from the predetermined landing point (12), is restored to the original landing point (1
It acts so as to cancel back to 2), and mislanding of the electron beam can be suppressed and reduced even if the doming phenomenon occurs. Since the electron absorption layer (14-1) is formed in the non-penetrating part of the main surface of the shadow mask on the electron gun side, the effect of suppressing mislanding can be obtained according to the electron flow density of each part of the main surface. The layer (14-1) has a negative charge distribution, and this landing suppression effect is weak at a level of electron flow density during normal image projection and is well within the range of landing margin, but it seems to cause a doming phenomenon. In such cases, it works more effectively in cooperation with the doming suppression effect. Further, since the electron beam always hits the electron absorbing layer as long as the tube is operating, its active area portion is much smaller than that of the conventional one disclosed in Japanese Patent Publication No. 57-18824. It is large and there is almost no time delay for the suppression effect.

By the way, such an electron absorption layer (14-1) can be used, for example, when the high electron flow density locally disappears.
The negative charge charged in 1) must be reduced corresponding to the disappearance of doming. That is, if the conductivity of the electron absorption layer is good, the negative charging phenomenon does not sufficiently act. . When a low conductive layer (14-2) capable of substantially transmitting an electron beam is provided on the surface of the electron absorption layer as in the present invention, the conductivity of the low conductive layer (14-2) is reduced. By changing it, this phenomenon can be suppressed.

That is, according to the experiments conducted by the present inventors, as a result of measuring the amount of movement of the electron beam due to doming when the 21-inch color picture tube according to the present invention is operated, the results shown in FIG. 4 were obtained. In Fig. 4, the vertical axis shows the amount of movement of the electron beam as a relative value, and the horizontal axis shows the getter coating amount per 1 cm ² formed on the surface of the lead borate glass layer provided on the electron gun side of the shadow mask. Is shown.

As measurement conditions, anode high voltage Eb = 26KV, anode current Ib = 11
At 00 μA, the screen reproduction pattern was a partial white pattern as shown in FIG. In FIG. 5, the shaded area is black, that is, the non-light emitting area. Also, * indicates a measurement point.

From FIG. 4, the thickness of the low-conductivity layer (14-2) mainly made of barium which is substantially permeable to an electron beam and is provided on the surface of the electron absorption layer (14-1) made of an insulator is changed. Thus, it can be seen that the density of charges temporarily charged on the surface of the electron absorption layer (14-1) can be suppressed, and therefore the doming suppression effect due to the charging can be optimally selected. When the low conductive layer (14-2) is mainly composed of barium, its thickness is 1 μg / cm ^{2 to} 100 μm.
It was confirmed that the intended purpose was achieved if g / cm ² was equivalent. Of course, this electron transparent low conductive layer (14-2) is
Other metals such as aluminum may be used, but when using metals other than getters. Since new equipment for vapor deposition is required, it can be said that use of a getter substance essential for a color picture tube is very suitable for mass production.

〔The invention's effect〕

As described above, according to the present invention, it is possible to effectively reduce the doming of the shadow mask and improve the color purity deterioration such as the color shift and the color unevenness without increasing the large-scale manufacturing equipment and the working time. And has an extremely high industrial value.

[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 movement of an electron beam due to doming of a shadow mask, and FIG. 3 is a part A of FIG. FIG. 4 is an enlarged schematic diagram, and FIG. 4 is a characteristic diagram showing a change in the amount of movement of an electron beam due to doming of a shadow mask when the amount of a getter layer formed on an insulating layer according to the present invention is changed. FIG. 5 is a schematic diagram showing a screen reproduction pattern used when measuring the characteristics shown in FIG. (1) …… panel, (2) …… funnel (3) …… neck, (4) …… screen (5) …… electron beam, (6) …… electron gun (7) …… shadow mask

Claims (2)

[Claims] 1. A shadow mask comprising a main surface in the vicinity of the screen, in which a large number of through holes are formed, and a skirt portion extending to a peripheral portion of the main surface, and a phosphor on the screen via the shadow mask. In a color picture tube having at least an electron gun for emitting an electron beam for selectively emitting light, an electron absorbing layer is provided on the electron gun side of the shadow mask, and the electron beam is transmitted through the electron absorbing layer on the surface of the electron absorbing layer. A color picture tube having a low-conductivity layer having a thickness such that an electron beam can reach the absorption layer. 2. The low conductive layer is 1 μg / cm ^{2 to} 100 μg / cm
The color picture tube according to claim 1, characterized in that barium having a thickness corresponding to ² is mainly used.