JPS60124333A - Cathode ray tube and its manufacturing method - Google Patents

Abstract

PURPOSE:To restrain the degradation of color purity and obtain a high dielectric strength and long service life cathode ray tube by providing a layer mostly consisting of glass on the surface of an internal magnetic shield element. CONSTITUTION:On the surface of an internal magnetic shield element 11, liquefied lead borate glass is applied and dried, and then it is placed in a coil, which is connected to the high-frequency power source, for heating. The lead borate glass can be perfectly crystallized and bonded on the internal magnetic shield element 11. In this way, the falling off of blackened coating and the outgassing are restrained and the discharge voltage and the degree of vacuum within the tube can be maintained at high values. In addition, not only the absorption of heat from a shadow mask 5 but also the dispersion of this absorbed heat from the internal magnetic shield element 11 are improved, and therefore the doming of the shadow mask 5 can be restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a cathode ray tube, and more particularly to an internal magnetic shield mounted within the cathode ray tube.

[Technical background and problems of the invention]

Cathode ray tubes, especially color picture tubes with a three-electron beam system that incorporate color selection electrodes such as shadow masks, are susceptible to mislanding of the electron beams due to the influence of external stray magnetism such as the earth's magnetism. An internal magnetic shield is mounted along the inner wall of the funnel.

Next, an example of such a color picture tube will be explained with reference to FIG. That is, in general, a shadow mask type color picture tube has an envelope typically made of glass, as shown in FIG. /(2) and a neck (3). The inner surface of the panel (1) is provided with, for example, a striped phosphor screen (4) emitting red, green and blue light respectively, while the net (3) is provided along the horizontal axis of the nozzle (1). It emits three electron beams (10) arranged in a line and corresponding to red, green, and blue), so-called in-line type'-
The sub-gun (6) is tucked inside. Further, a shadow mask (5) having a main surface with a large number of through holes is disposed closely facing the screen (4).

The peripheral part of the shadow mask (5) has a skirt part (8) which is bent in accordance with the outer shape of the groove, and this skirt part (8) has a mask frame (force ( -Therefore, it is supported and fixed, and the mask frame (
7) is locked with a pin (not shown) embedded in the inner wall of the nozzle (1) via a spring (9) b)
Ru.

It has an internal magnetic shield aυ fixed to the mask frame (7) of the solar panel and extending toward the electron gun side (6). This internal magnetic shield (11) is shaped like a cone (=
However, in order to obtain the desired shielding effect, it is necessary to make the surface area of the internal magnetic shield α1) sufficiently large. In such a color picture tube,
Three electron beams (10) emitted from the electron gun (6)
is a deflection device (
(not shown) to scan a substantially rectangular area corresponding to the rectangular panel (1), and the colors are sorted through the through hole of the shadow mask (5), so that each color emitting stripe is deflected. Correctly collide with the phosphor to make a color image appear. Here, the effective amount of electron beam passing through the hole in the shadow mask (5) is 1/3 or less due to its mechanism. The remaining electron beam impinges on the shadow mask and is converted into thermal energy, sometimes heating the shadow mask up to about 80°C.

The shadow mask (5) is generally a thin plate with a thickness of 0.1 to 0.3 mm made of so-called cold-rolled steel whose main component is iron, which has a large coefficient of thermal expansion at 0 to 100 degrees Celsius of 1.2 x 10" and 7 degrees Celsius. The mask frame (7) that supports the skirt portion (8) of this shadow mask (5) is made of a strong cross-sectional blackened steel with a thickness of approximately 1 mm. The shadow mask (5) is made of rolled steel.Therefore, the heated shadow mask (5) easily undergoes thermal expansion, but its periphery is in contact with the mask frame (7), which has a large heat capacity and has been subjected to a blackening treatment. Because of this, heat moves from the periphery of the shadow mask to the mask frame by radiation and conduction, and the temperature around the shadow mask becomes lower than the center.This creates a temperature difference between the center and periphery of the shadow mask (5), causing a relative This causes a so-called doming phenomenon in which the central part is heated and expanded.As a result, a shadow mask (5)
The distance between the electron beam and the phosphor screen (4) changes, disturbing the accurate landing of the electron beam and causing deterioration of color purity.

This phenomenon is particularly noticeable in color picture tubes having an internal magnetic shield (11). i.e. internal magnetic shield 0
．． In a color picture tube with 1), the electron beam (1
When the heat of the shadow mask (5) heated by the regular collision of +) is dissipated from the shadow mask (5), the internal magnetic shield α1) prevents this heat diffusion.
5) The temperature becomes difficult to fall.

To solve this problem with the internal magnetic shield of a color picture tube, conventionally, a blackened film is formed on the surface of the internal magnetic shield to improve heat absorption. This blackened coating is applied, for example, with H, O, before the internal magnetic shield is installed in the color picture tube.
-N, or eyes: Co, -N.

When heated to 560°C to 600°C in an atmosphere such as, Fe50. It is possible to form a blackened film mainly composed of. This blackened film improves heat absorption and radiation, and also has the function of preventing the formation of cracks on the surface of the internal magnetic shield during the heat process during the manufacturing process of color picture tubes. .

However, although this blackening film exhibits the above-mentioned excellent effects, it also has some disadvantages. That is, the adhesion of the blackened film deteriorates due to thermal cycles in the thermal process during the manufacturing process, and when vibration is applied, a portion of the blackened film may peel off and small pieces may fall off. When the blackened film generated in this way is sealed to the shadow mask, it clogs the pores and deteriorates the image characteristics on the fluorescent surface, and it also adheres to the electron gun and induces sparks between the electrodes, causing voltage resistance. Deteriorate properties.

On the other hand, the internal magnetic shield, like the shadow mask, has a very large surface area, and once an unstable gas or its source is brought into the color picture tube by the internal magnetic shield, a considerable amount of gas is released through its large surface. This may lead to a deterioration in the quality of color picture tubes that require high visibility or long life.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and provides a cathode ray tube that suppresses deterioration of color purity, has excellent withstand voltage and life characteristics, and is highly suitable for industrial mass production, and a method for manufacturing the same.

[Summary of the invention]

The present invention includes at least a phosphor screen that emits light by an electron beam emitted from an electron gun, and an internal magnetic shield disposed between the electron gun and the screen so as to partially or completely surround the electron beam passage area. In the cathode ray tube and its manufacturing method, a layer mainly made of glass is provided on the surface of the internal magnetic shield to suppress deterioration of color purity and prevent foreign matter from falling off and gas release from the surface of the internal magnetic shield. It is characterized by reducing the

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail based on an embodiment applied to color image reception 1. The component structure of the color picture tube applied to the present invention is the same as that shown in FIG. 1, so detailed explanation will be omitted.

In a color picture tube as shown in Fig. 1, a shadow mask (5) is arranged in close proximity to the screen (4).
A layer mainly composed of glass, for example lead-borate glass, is formed on the surface of the frame supporting the electron gun (internal magnetic shield (1) extending toward the electron gun side (6)). The lead borate glass layer covers the panel (1) and the funnel (
2) Before the panels are sealed, lead borate glass dissolved in a butyl acetate alcohol solution containing a few percent of nitrocellulose is applied to the surface of the internal magnetic shield αD. After drying, the inside of the panel (1) is sealed. The frame that holds the shadow mask (5) attached to the frame (fixed to the bottom of the force).Then, after that, place the panel (1) and funnel (2) on a predetermined frame, and When the temperature is increased at a heating rate and passed through a furnace with a maximum temperature of about 440° and a holding time of 30 minutes or more, a vitrified lead-borate glass layer is formed on the surface of the internal magnetic shield θD. It is possible.This lead t1
Borate glass has a PbO weight percentage of 44-93%
Vitrification occurs within the range of 70, but stable against crystallization is 70.
~85%, and this range is suitable for mass production. Also,
Generally, when sealing metal and glass, it is necessary to prevent excessive strain from being applied to the glass.

The compressive strength of glass is about 10 times the tensile strength, so it is best to leave the glass with a slight compressive stress after sealing, so that the thermal expansion of the sealing metal is smaller than the thermal expansion of the glass. The larger the value, the better. Generally, the thermal expansion coefficient of the internal magnetic shield 011 made of cold-rolled steel plate is about 1.2 x 10 / 0, but the Pb
The coefficient of thermal expansion of lead borate glass with O weight percentage of 70-85% is 0.7-1.2X10. /°C,
It is very suitable for sealing to the internal magnetic shield (11) of cold rolled steel plate. By the way, in order to crystallize such lead borate glass, a maximum temperature of 600 to 450°C and a furnace that can maintain it for more than 30 minutes are required, which is somewhat disadvantageous industrially. If (1) and funnel (2) can be crystallized at the same time in a sealing furnace when they are sealed,
It is very advantageous industrially. In order to achieve optimized crystallization under conventional sealing furnace conditions, ZnO and Cu are added as necessary.
O may be added to the lead borate glass. In this case, it becomes possible to crystallize at a lower temperature without significantly changing the coefficient of thermal expansion.

By the way, by such a method, the internal magnetic shield α1)
When forming a glass layer on a glass layer, there are the following problems. First, when attaching the internal magnetic shield αυ coated with liquefied lead borate glass to the 7th frame (7) in the panel (11), there is a risk that the glass will drip into the panel (1). 2, when panel (1) and funnel (2) are combined and heated at a heating rate of 10°C/min, butyl acetate alcohol containing nitrocellulose, which is a binder, decomposes and dissipates, and then inside the furnace. temperature is 440
When the maximum temperature of 'O is reached, the lead-borate glass begins to crystallize, but by the time this inder has dissipated and the lead-borate glass has begun to bond with the internal magnetic shield (11), the furnace Due to vibrations inside the funnel, the lead borate glass (
2) There is a risk of falling inside. In this case, if the lead borate glass is semi-melted and temporarily fixed to the internal magnetic shield 01), at least the above problem will be solved.
Furnace heating using thermal power or electricity requires a large amount of equipment, and it takes time for the internal magnetic shields (1, 11) to reach the required temperature, making it unsuitable for mass production.However, it is not suitable for mass production. The method of placing the internal magnetic shield 0D inside a coil and heating it is a method that is very suitable for mass production because it heats up instantly. Coating lead borate glass containing at least about 75% by weight of PbO and about 9% by weight of Bρ, the transformer output is about 15KVA, and the frequency used is 4QQ.
)G(z) When heated in a coil connected to a high frequency power supply, the temperature of the internal magnetic shield (11) reaches the softening point of lead borate glass, 400°C, within 5 seconds, and after 5 minutes, lead The balatate glass can be semi-fused and temporarily fixed to the internal magnetic shield (1η). In this way, lead can be temporarily fixed to the internal magnetic shield Ql. By doing so, there is a very small possibility that the lead borosilicate glass will fall off during the subsequent manufacturing process of the color picture tube.By the way, using high frequency heating in this way is very effective in removing the internal magnetic shield. 01), it is possible to raise the temperature of normal glass-to-metal adhesion (fF tl ), rather than the softening point of glass as mentioned above, to 7m degrees, for example, to around 440 degrees Celsius for lead borate glass. However, it goes without saying that if the holding time is also the time necessary for crystallization, for example 30 minutes, the lead borate glass can be completely crystallized and bonded to the internal magnetic shield (11). The internal magnetic shield (11) whose surface is covered with such lead-borate glass suppresses the blackening film from falling off from its inner surface and the release of gas, and reduces the discharge voltage inside the tube and the internal magnetic shield (11). It becomes possible to maintain the degree of vacuum at a high value. Here, the lead-borate glass formed on the surface of this internal magnetic shield 0]) forms a strong chemical bond with the internal magnetic shield aυ through the blackened film, so this lead-borate glass It goes without saying that the number of dropouts from the internal magnetic shield α1) is very small. By the way, a black pigment is added to this lead borate glass in advance to form a black lead borate glass layer as an internal magnetic shield (
11) When formed on the surface of the conventional internal magnetic shield OD
It is possible to form a black layer with better heat absorption than a blackened film mainly composed of Fe, 04, and to reduce the doming phenomenon of the shadow mask (5) that occurs during the production of color picture tubes. The inventors have confirmed that this is possible.

That is, about 1% by weight of at least one of MnO and CO20s is added to lead borate glass containing at least about 75% by weight of PbO and about 9% by weight of B2O3 to form an internal magnetic shield (I). ]) shadow mask (5)
When applied and sintered on the main surface (11, -1) facing
The heat absorption rate of the main surface (11-],) facing the shadow mask (5) of this internal magnetic shield (11) is higher than that of conventional Fe,
0. It was possible to improve this by about 10% compared to that of a blackened film mainly composed of. If this black lead borate glass layer is formed on the entire surface of the internal magnetic shield (11), not only the heat absorption from the shadow mask (5) will be improved, but also the absorbed heat will be shielded from the internal magnetic shield. Since the heat dissipation property of diffusing from the body αυ is also improved, it becomes possible to further suppress doming of the mask (5). Furthermore, since this lead borate glass contains a large amount of lead, which has excellent shielding properties against X-rays, conventional lead is generated from the shadow mask (5), passes through the funnel (2), and leaks out of the color picture tube. The X-rays that were being emitted are attenuated by the lead borate glass layer formed on the surface of the internal magnetic shield (111), making it possible to significantly suppress the leakage of X-rays to the outside of the color picture tube.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to improve the withstand voltage characteristics and life characteristics of cathode ray tubes without requiring large-scale manufacturing equipment or an increase in working hours, and particularly for shadow mask type color picture tubes. If applied, the doming of the shadow mask can be effectively reduced and color purity deterioration such as color shift and color unevenness can be improved, and the industrial value is extremely high.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing the structure of a shadow mask type color picture tube. (1)・Panel (2)・Funnel (3)・・
Neck (4)...Screen (5)...Shadow mask (6)...Electron gun (7)...Frame (
11)...Internal magnetic shield agent Patent attorney Nori Chika
Kensuke (and 1 other person) Figure 1

Claims (1)

[Claims] 1) A panel having a screen formed on its inner surface made of a phosphor layer that emits light upon impact with an electron beam, and an electron gun mounted in a neck connected to this panel via a funnel. and a cathode ray tube comprising at least an internal magnetic shield disposed between the electron gun and the screen so as to partially or completely surround the passage area of the electron beam, the surface of the internal magnetic shield A cathode ray tube characterized by having a layer mainly made of glass formed thereon. 2) The layer mainly composed of glass contains at least Pbo.
, B@OH and ZnO or PbO, B, 0. and C
The cathode ray tube according to claim 1, characterized in that the cathode ray tube is made of lead borate glass containing uO. 3) PbO contained in the lead borate glass is 70%
3. The cathode ray tube according to claim 2, wherein the content of the cathode ray tube is 85% by weight. 4) MnO2 or co! in the lead borate glass!
The cathode ray tube according to claims 2 and 3, characterized in that the cathode ray tube contains at least one of O8. 5) The cathode ray tube according to claim 4, wherein the layer mainly made of glass is formed only on the main surface of the internal magnetic shield facing the screen. 6) The cathode ray tube according to any one of claims 2 to 5, characterized in that an oxide film is interposed between the internal magnetic shield and the layer mainly composed of lead-bolate glass. 7) A panel having an inner surface covered with a screen made of a phosphor layer that emits light when an electron beam hits it; an electron gun mounted in a neck connected to this panel via a funnel; and the electron gun and the above. In the method for manufacturing a cathode ray tube, the cathode ray tube includes at least an internal magnetic shield disposed between the screen and the screen so as to partially or completely surround the passage area of the electron beam, wherein a glass main body is provided on the surface of the internal magnetic shield. a step of heating the glass formed on the internal magnetic shield until it becomes semi-molten; and a step of heating and sintering the glass layer formed on the internal magnetic shield. A manufacturing method on a cathode ray characterized by the following. 8) The step of heating the glass layer formed on the internal magnetic shielding body until it becomes semi-molten and the step of heating and sintering the glass layer formed on the internal magnetic shielding body are successively performed in the same process. 8. A method for manufacturing a cathode ray tube according to claim 7. 9) In the step of semi-melting the glass layer formed on the internal magnetic shield, the internal magnetic shield is held at a maximum temperature equal to or higher than the softening point of the glass for 5 minutes or more. The method for manufacturing a cathode ray tube according to items 7 and 8. 10) Claim 7, characterized in that the step of sintering the glass layer formed on the internal magnetic shielding body comprises a heating step at a maximum temperature of 400° C. to 600° C. for a holding time of 30 minutes or more. 10. The method for manufacturing a cathode ray tube according to item 9. 11) At least one of the steps of heating the glass layer formed on the internal magnetic shielding body is characterized in that the internal magnetic shielding body is heated by a high frequency coil. A method of manufacturing cathode ray tubes.