JPH0714519A - Color cathode-ray tube and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce the color drift of an image by providing an electron beam reflecting film made of a heavy metal oxide on an electron beam incidence face, and forming an electron beam attracting film containing magnesium on the inner face of an internal magnetic shield. CONSTITUTION:An electron beam reflecting film 8 made of a heavy metal oxide such as bismuth oxide is provided on the electron beam incidence face of a shadow mask 5. An internal magnetic shield 6 is arranged between an electron gun 4 and the mask 5, and an electron beam attracting film 9 containing magnesium is formed on its inner face. The electron beam attraction factor of the film 9 is larger than that of a blackened film Fe3O3. The film 9 attracts most of the electron beam reflected by the mask 5, and the quantity of the electron beam returned to the mask 5 again is sharply reduced. The temperature rise of the mask 5 is reduced, the thermal expansion of the mask 5 is reduced, the color drift of an image is reduced, and a high-resolution, large- sized, high-intensity cathode-ray tube can be easily obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shadow mask type color cathode ray tube having an internal magnetic shield and a method for manufacturing the same.

[0002]

2. Description of the Related Art FIG. 3 shows the structure of a conventional shadow mask type color cathode ray tube. In FIG. 3, 1 is an envelope for maintaining a high vacuum inside, 2 is a translucent glass panel forming a part of the envelope 1, and 3 is a fluorescent surface that emits light in red, green and blue. The stripes or dots of the phosphor to be applied are sequentially applied to the inner surface of the glass panel 2, and the stripes or dots are provided in such a positional relationship that they correspond to each other accurately in terms of electronics. Reference numeral 4 is an electron gun for emitting three electron beams, and 5 is a shadow mask constituting a color selection electrode, which is made of, for example, thin low carbon steel having many slits or dots. An internal magnetic shield 6 shields the electron beam from electromagnetic waves of terrestrial magnetism or unnecessary radiation from a deflection yoke or the like so that the electron beam draws a normal trajectory. Reference numeral 7 is a deflection yoke for scanning the electron beam.

In FIG. 3, the three electron beams emitted from the three cathodes of the electron gun 4 are deflected by the deflection yoke 7 so as to scan the entire phosphor screen 3, and reach the shadow mask 5. As is well known, the shadow mask 5 causes the three electron beams to project only phosphor stripes or dots of colors corresponding to respective ones formed at predetermined positions on the phosphor screen 3. Has a color selection function. And, as described above, these positional relationships are originally set so that accurate correspondence can be achieved. However, in such a color cathode ray tube, about 80% of the electron beam emitted from the electron gun 4 collides with the shadow mask 5 and is shielded, and the shadow mask 5 is imparted with a meaningless thermal energy, resulting in a shadow. The temperature of the mask is raised. As a result, the shadow mask 5 is deformed due to thermal expansion, and the positional relationship between the shadow mask 5 and the phosphor stripes or dots on the phosphor screen 3 that have been accurately corresponding to each other is displaced, resulting in a color shift of the image. is there.

As a method for solving these problems, Japanese Patent Application Laid-Open No. 55-76553 discloses a film made of a substance having a higher electron beam reflectance than the substance forming the shadow mask on the electron beam irradiation surface of the shadow mask. And in Japanese Patent Publication No. 60-14459, 70
It has been proposed to provide a heavy metal material having an atomic number of more than 1, and bismuth oxide (Bi2 O3) is used as the heavy metal oxide. Thus, in the conventional color cathode ray tube, generally, as shown in FIG. 3, an electron beam reflecting coating 8 made of bismuth oxide or the like is provided on the electron beam incident surface of the shadow mask 5, and the reflecting coating 8 causes the shadow mask. Most of the energy of the electron beam that irradiates is taken away by the reflected electrons to reduce the temperature rise of the shadow mask and reduce the amount of color shift due to thermal expansion of the shadow mask. In order to cope with higher resolution, larger size, flatness and higher brightness of the color cathode ray tube, the effect of suppressing the doming (color misregistration) by the electron beam reflection coating is still insufficient, and its function improvement is More demanded.

[0005]

However, in the conventional cathode ray tube, since the electron beam reflecting coating is provided on the electron incident surface of the shadow mask to prevent the doming (color shift) as described above, this coating is used. While the reflected electron beam is multiply reflected between the shadow mask and the internal magnetic shield, the electron beam is gradually absorbed by the shadow mask. Therefore, there is a problem that the temperature rise of the shadow mask cannot be sufficiently prevented and the thermal expansion of the shadow mask cannot be sufficiently reduced. Furthermore, when operating a color cathode ray tube with higher resolution, larger size, or higher brightness, color misregistration is likely to occur even with a slight amount of thermal deformation of the shadow mask, and the color misregistration prevention effect (doming suppression effect) should be improved. Has become essential.

The present invention has been made to solve the above problems, and it is intended to reduce the temperature rise of the shadow mask and reduce the color shift of the image due to the deformation due to the thermal expansion of the shadow mask. It is an object of the present invention to provide a color cathode ray tube and a method for manufacturing the same.

[0007]

A color cathode ray tube according to the present invention is arranged so as to face a phosphor screen, and a shadow mask for projecting a plurality of electron beams emitted from an electron gun to predetermined positions on the phosphor screen. An internal magnetic shield disposed between the shadow mask and the electron gun to shield an electron beam incident on the shadow mask from an external magnetic field, and a heavy metal oxide on an electron beam incident surface of the shadow mask. And an electron beam absorbing film containing magnesium is formed on the inner surface of the inner magnetic shield. Further, in the method for manufacturing a color cathode ray tube according to the present invention, the electron beam absorbing coating is provided on the inner surface of the internal magnetic shield.
It is formed by spraying water glass mixed with magnesium powder.

[0008]

According to the color cathode ray tube of the present invention, the electron beam absorbing film containing magnesium on the inner surface of the inner magnetic shield absorbs most of the electron beam reflected from the shadow mask and returns it to the shadow mask again. Since the amount of the electron beam generated is greatly reduced, the temperature rise of the shadow mask is reduced, the thermal expansion of the shadow mask is reduced, and the color shift of the image is also reduced.

Further, according to the method of manufacturing a color cathode ray tube of the present invention, since the electron beam absorbing coating is formed by spraying water glass mixed with magnesium powder onto the inner surface of the inner magnetic shield, the adhesiveness is good and the desired result is obtained. It is possible to easily form an electron beam absorbing coating having a film thickness, and to use two types of water glass, sodium type and potassium type, and to set the compounding ratio range from 3: 1 to 30: 1. While maintaining good adhesion, the amount of gas released from the coating is suppressed, and the life characteristics of the cathode ray tube are kept good.

[0010]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view showing an embodiment of a color cathode ray tube according to the present invention. 1 is an envelope, 2 is a translucent glass panel, 3 is a fluorescent screen, 4 is an electron gun, 5 is a fluorescent screen 3 Is a shadow mask made of a thin low carbon steel plate arranged between the electron gun 4 and the electron gun 4, and the electron beam incident surface thereof has an electron beam reflection coating 8 made of a heavy metal oxide such as bismuth oxide (Bi ₂ O ₃ ). Is provided. Reference numeral 6 denotes an internal magnetic shield arranged between the electron gun 4 and the shadow mask 5, and an electron beam absorbing coating 9 containing magnesium is formed on the inner surface thereof as shown in FIG. The electron beam absorbing coating 9 is formed by spraying water glass mixed with magnesium (Mg) powder on the inner surface of the inner magnetic shield as described later.

Generally, the electron beam absorptivity of a substance is inversely proportional to the density and atomic number, so that the material of the electron electron beam absorbing film 9 is a blackened film (Fe) of a low carbon steel plate constituting the inner magnetic shield 6. _It is suitable to be composed of an element having a density lower than that of the ₃ O ₄ film), an element having an atomic number smaller than the equivalent atomic number of the blackened film, or an inorganic compound containing these elements. Examples thereof include metal elements such as magnesium, beryllium, titanium, manganese, and aluminum, and oxides, nitrides, and carbides thereof.

In the present invention, the density and atomic number of the magnesium powder used for the electron beam absorption coating 9 are 1.7 g / cm ³ and 12, respectively, and the Fe ₃ O ₄ coating obtained by blackening the conventional surface is used. Only 5.2 g / c of those of the inner magnetic shield coating are formed.
Since both are smaller than m ³ and 21, the electron beam absorptivity of the coating film 9 is larger than that of the blackened film Fe ₃ O ₄ . As a result, the electron beam absorbing film 9 absorbs most of the electron beam reflected from the shadow mask 5 and significantly reduces the amount of the electron beam returned to the shadow mask 5, so that the temperature of the shadow mask 5 is raised. Is reduced, the thermal expansion of the shadow mask 5 is reduced, and the color shift of the image is also reduced. The densities and atomic numbers of the above elements are shown in "Metal Data Book" edited by Japan Institute of Metals (Showa 4).
9th edition, published by Maruzen Co., Ltd.) and Iwanami Shoten, "Iwanami Physics and Chemistry 3rd Edition," page 515, and the equivalent atomic number calculation method is "PHYSICAL REVIEW" VOLU
ME 93, NUMBER 4 (FEBRARY 15,1954) Nos. 891-892
RULPH H. MULLER "Interactio
See n of Beta Particles with Matter.

The thickness of the electron beam absorbing coating 9 is determined by the penetration depth of the electron beam into the coating, and this penetration depth depends on the density of the coating, the atomic number and the energy of the electron beam. The energy of the electron beam reflected from the electron beam reflection coating 8 of the shadow mask 5 is several tens eV to 30.
Since it is distributed in a wide range of KeV, when the film thickness of the electron beam absorption coating 9 made of magnesium is less than 0.5 μm, the electron beam passes through the coating 9 and the energy of the electron beam cannot be sufficiently absorbed. On the other hand, when the film thickness exceeds 3 μm, the absorptivity of the energy is saturated, the adhesion of the film is reduced, and the cathode ray tube is clogged and the withstand voltage characteristic is deteriorated.

Example 2. The electron beam absorption coating 9 as described above is made of magnesium (M
A coating solution is prepared by pulverizing a mixture of g) and an adhesive water glass, pure water, etc. by means of a ball mill or the like and uniformly dispersing the coating solution.
Is formed by spraying on the inner surface of the inner magnetic shield 6 opposed to the above by an air spray method or the like until the film thickness becomes 0.5 to 3 μm. A specific example will be described below. 1.8 kg of magnesium powder with high electron beam absorption rate, 5110 cc of adhesive water glass (breakdown: sodium type = 4599 c)
c, potassium-based = 511 cc, the compounding ratio of which is sodium-based: potassium-based = 9: 1) and 7,000 cc of pure water are ball-milled for about 3 hours until the powder has an average particle size of about 2 μm. Roll it for about 1 hour so that the water glass is evenly dispersed to make a coating solution. This coating solution was sprayed onto the inner surface of the blackened 25-inch internal magnetic shield 6 for a color cathode ray tube by an air spray method to coat the coating to a thickness of about 1 .mu.m, and an electron beam absorbing coating 9 was formed.
To form. Then, the internal magnetic shield 6 and the shadow mask 5 with the electron beam reflection coating 8 and the like are put into a normal cathode ray tube manufacturing process to manufacture a cathode ray tube with a 25-inch electron beam absorption coating 9.

In this case, when forming the electron beam absorbing film 9, all the carbonates which become the generation source of carbon dioxide gas which deteriorates the emission life characteristics of the cathode which emits electrons in the electron gun 4 (this is called emission) are formed. The important point is to reduce the amount produced. When the total amount of carbonates increases, the amount of carbon dioxide gas in the color cathode ray tube increases, the cathode is poisoned and the electron emission amount decreases, and as a result, the brightness of the color cathode ray tube deteriorates significantly and the cathode ray tube The life is shortened. As a countermeasure against this, in the present invention, two types of sodium water and potassium water are used as the adhesive water glass, and the range of the compounding ratio is 3: 1.
To 30: 1, the hygroscopicity of the water glass can be reduced while maintaining good adhesion of the coating film 9, and the amount of gas adsorbed by the coating film 9 in the cathode ray tube manufacturing process ( For example, water vapor or carbon dioxide) is greatly reduced. Therefore, the amount of gas emitted from the electron beam absorbing coating 9 due to thermal and electron beam irradiation is greatly reduced, the degree of contamination of the cathode of the electron gun 4 with the gas emitted from the coating 9 is reduced, and the emission amount is deteriorated. Is reduced, and the life characteristics of the cathode ray tube are maintained well.

Next, in order to explain the effect of the present invention, a method for measuring the amount of local doming (color shift) in a 25-inch color cathode ray tube will be described below. The measurement conditions are monochromatic (usually green) no signal, electron beam current (1 cathode) of 0.15 mA, and electron beam acceleration pressure of 29K.
V, the heater voltage is 6.3V, and the raster has two symmetrical locations around the center of the screen. They are the same size and 120x12.
0 (mm), the measurement position is the center of the raster size,
There are two locations of (± 180,0) respectively. The measuring method is a method using an ordinary landing measuring device, a pattern gelation device, an electromagnetic purity coil, or the like.

Here, the doming control effect and the method of calculating D1 and D2 in the conventional cathode ray tube and the cathode ray tube of the present invention will be described. Each of them is calculated by the following equation using the doming amount measured by the above measuring method. D1 = {1- (doming amount of conventional cathode ray tube) / (doming amount of standard cathode ray tube)} * 100 (%) ... (1) D2 = {1- (doming of cathode ray tube of the present invention Amount) / (doming amount of standard cathode ray tube)} × 100 (%) (2) However, in the color cathode ray tube of the present invention, the electron composed of the internal magnetic shield 6 with the electron beam absorbing coating 9 and bismuth oxide is used. A cathode ray tube provided with a shadow mask 5 with a beam reflection coating 8 and the like, a conventional cathode ray tube is a cathode ray tube provided with an internal magnetic shield 6 without an electron beam absorption coating 9 and a shadow mask 5 with an electron beam reflection coating 8 etc. The cathode ray tube is a cathode ray tube which does not have the respective coatings 8 and 9 on the surfaces of the shadow mask 5 and the inner magnetic shield 6.

The doming (color shift) amount of the cathode ray tube of the present invention produced by the production method of the second embodiment and the conventional cathode ray tube are set to the above-mentioned measurement conditions, and each is measured by the ordinary measurement method. Measure, doming control effect,
Obtaining D1 and D2 respectively, it can be found from the equation (1) that D1 = (1-70 / 100) x 100 = 30% in the conventional cathode ray tube is that from the equation (2) that D2 = ( 1-55 / 100) × 100 = 45%, which is about 15% higher than that of the conventional cathode ray tube.

[0019]

As described above, according to the present invention, the electron beam absorbing film containing magnesium is formed on the inner surface of the inner magnetic shield, and most of the electron beam reflected from the shadow mask is absorbed by the film. Since the amount of electron beam returned to the shadow mask is greatly reduced, the temperature rise of the shadow mask is reduced, the thermal expansion of the shadow mask is reduced, the color shift of the image is also reduced, and the resolution and size are increased. A flattened or brightened cathode ray tube can be easily obtained.

Further, since the electron beam absorbing coating is formed by spraying water glass mixed with magnesium powder on the inner surface of the inner magnetic shield, the electron beam absorbing coating having good adhesion and a desired thickness can be easily formed. It is possible to obtain, and as a water glass, sodium-based and potassium-based 2
Depending on the type, the blending ratio range is from 3: 1 to 30: 1
By this, there is an effect that the amount of gas released from the film can be suppressed and the life characteristics of the cathode ray tube can be maintained satisfactorily while maintaining the adhesive force of the film favorable.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a color cathode ray tube showing an embodiment of the present invention.

FIG. 2 is a partially enlarged cross-sectional view of an internal magnetic shield in FIG.

FIG. 3 is a schematic sectional view showing an example of a conventional color cathode ray tube.

FIG. 4 is a partially enlarged sectional view of the shadow mask in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Envelope 2 ... Glass panel 3 ... Phosphor screen 4 ... Electron gun 5 ... Shadow mask 6 ... Internal magnetic shield 7 ... Deflection yoke 8 ... Electron beam Reflective coating 9 ... Electron beam absorption coating

Claims (4)

[Claims] 1. A shadow mask, which is arranged so as to face a fluorescent screen and projects a plurality of electron beams emitted from an electron gun onto predetermined positions on the fluorescent screen, and between the shadow mask and the electron gun. And an internal magnetic shield that shields an electron beam incident on the shadow mask from an external magnetic field, and an electron beam reflection coating made of a heavy metal oxide is provided on an electron beam incident surface of the shadow mask. A color cathode ray tube characterized in that an electron beam absorbing coating containing magnesium is formed on the inner surface of a magnetic shield. 2. The electron beam absorbing coating has a thickness of 0.5 to 3
The color cathode ray tube according to claim 1, wherein the color cathode ray tube has a thickness of μm. 3. A shadow mask, which is disposed so as to face the fluorescent screen and projects a plurality of electron beams emitted from the electron gun onto predetermined positions on the fluorescent screen, and between the shadow mask and the electron gun. And an internal magnetic shield that shields an electron beam incident on the shadow mask from an external magnetic field, and an electron beam reflection coating made of a heavy metal oxide is provided on an electron beam incident surface of the shadow mask. On the inner surface of the magnetic shield, in the method of manufacturing a color cathode ray tube for forming an electron beam absorption coating containing magnesium, on the inner surface of the inner magnetic shield,
A method of manufacturing a color cathode ray tube, characterized in that the electron beam absorbing coating is formed by spraying water glass mixed with magnesium powder. 4. The color cathode ray tube according to claim 3, wherein the water glass is a mixture of sodium-based water glass and potassium-based water glass, and the mixing ratio thereof is 3: 1 to 30: 1. Manufacturing method.