JPH07182985A - Color picture tube - Google Patents

Abstract

PURPOSE:To prevent purity drift attributed to thermal expansion by forming a coating of tungsten oxides consisting of tungsten trioxide as a main component is formed in an electron beam impingement side face of a shadow mask in a specified way. CONSTITUTION:A shadow mask 7 of a color television picture tube has a large number of open parts 7a through. which electron beam radiated from an electron gun passes and the surface among the open parts 7a in the electron gun side is coated with a small particle layer 21 and a large particle layer 22 consisting of tungsten trioxide as a main component. To form the layers, suspension l2 iquids containing respective particles and an inorganic binder of denatured alkyl silicate is applied to the surface by utilizing spray guns and firing is carried out while abrupt temperature change being avoided. Consequently, without emission failure of a cathode, uniform inorganic material coatings are formed on the surface of the mask 7 and expansion caused by the heat radiation by electron beam is moderated so as to prevent color purity deterioration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a color picture tube,
In particular, the present invention relates to a color picture tube in which the color shift of the light emission of the phosphor due to the thermal expansion of the shadow mask is prevented.

[0002]

2. Description of the Related Art A shadow mask for a color picture tube has a large number of apertures, and an electron beam emitted from an electron gun has a geometrical one-to-one relationship with the apertures of the shadow mask. It has a function of passing through so as to hit only the layer, and is also called a color selection electrode. This shadow mask is roughly divided into two types: a round hole and a rectangular hole.
There are types, but round holes are generally used for display tubes that display characters and figures in detail, and rectangular holes are used for consumer use in general households.

Normally, when the color picture tube is operated, about 15 to 20% of all electron beams emitted from the electron gun reach the fluorescent screen through the holes of the shadow mask. Yes, the remaining 80 to 85% strikes the shadow mask. As a result, the kinetic energy of the electron beam is converted into thermal energy and the shadow mask is heated to about 80 ° C. Generally, the material used for the shadow mask is an iron cold-rolled material having a plate thickness of 0.1 to 0.3 mm, and its coefficient of thermal expansion is 1 at 20 to 100 ° C.
The temperature is 2 × 10 ⁻⁶ / ° C., and the shadow mask causes thermal expansion called so-called doming due to the above heating. Due to such thermal expansion, the geometrical displacement between the shadow mask aperture and the phosphor layer occurs, and the electron beam that has passed through the aperture does not strike all of the desired phosphor layer, and a portion of the other color fluorescence is emitted. It collides with the body layer and causes deterioration in color purity.

From an ergonomic point of view, FS (Flat S) has a flat screen with less external light reflection and less image distortion.
quare) Although the ratio of tubes is increasing, the FS tube has a large radius of curvature of the shadow mask after press molding, and even if the mask is domed by thermal expansion by the same amount as the conventional shadow mask, the geometry of the shadow mask The amount of positional deviation is large, and the degree of color purity deterioration is larger than that of the conventional tube.

As described above, a color picture tube whose color purity is greatly deteriorated by doming has a thermal expansion coefficient of about 1/10 that of iron.
The use of the iron-nickel alloy amber material as described above as a shadow mask material has been proposed in Japanese Patent Publication No. 42-25446. However, the price of the amber material is high and the yield strength after annealing is high, and the yield of the mask forming is poor. Therefore, the price becomes much higher than that of the color picture tube using the iron mask.

Therefore, it has been conventionally proposed to form a film on a shadow mask and suppress the deterioration of color purity due to doming by the function of the film. The first method is to apply lead borate crystallized glass to the surface of a shadow mask as proposed in JP-A-60-54139,
This is a method of suppressing doming by performing fusion bonding by high temperature heat treatment. In this method, since the glass layer contains lead, which is a harmful substance, caution is required in handling from the viewpoint of working environment and environmental measures.

In the second method, a coating solution containing particles of a heavy metal substance having an atomic number of more than 70, such as that proposed in Japanese Patent Publication No. 60-14459, is sprayed on the electron beam incident side surface of a shadow mask. A method of depositing an electron beam reflective coating. It is said that it is effective to spray an aqueous suspension containing heavy metal fine particles such as bismuth oxide onto the electron beam incident side surface of the shadow mask. However, the effect of preventing color purity deterioration due to doming of the shadow mask is only due to a single element such as bismuth oxide, and the effect is not sufficient as compared with the case of the shadow mask having no electron beam reflective coating. .

The third method is a method of suppressing mask doming by increasing heat conduction and heat radiation efficiency in addition to the above-described electron beam reflection. In Japanese Patent Laid-Open No. 4-48530, bismuth oxide, tungsten particles, and partial A method has been proposed in which graphitized carbon particles are mixed with water glass to form a composite coating on the electron beam incident side of a shadow mask. In this method, the intended effect of preventing deterioration of color purity is relatively good, but since the raw material has a large particle size, it is crushed and stirred by a ball mill until the average particle size becomes about 2 microns, but uniform crushing is difficult and sharp. It is difficult to make a particle size distribution. Therefore, in order to prevent the shape of the mask openings from collapsing and the mask holes from clogging, the deposition layer is controlled to a thickness of about 3 microns, but the particle size distribution is not sharp and it is uniform because it is a mixture of substances with different specific gravities. Since it cannot be sprayed in a state of being mixed with, it is difficult to completely cover the shadow mask with the coating liquid.

As a fourth method, an amorphous metal oxide or the like is used as a binder to form a layer containing a metal having a small atomic number to improve the thermal emissivity and to stabilize the electron beam trajectory by charging. Japanese Patent Application Laid-Open No. 62-110240 discloses a method of preventing color purity deterioration by electrostatic correction.

[0010]

As described above, conventionally, as a means for preventing the deterioration of color purity due to doming of the shadow mask, an electron beam reflecting coating or a coating having good heat conduction or heat radiation is formed on the surface of the shadow mask. Is being done. However, the above-mentioned means have a problem that they do not have sufficient color purity deterioration preventing effect and adhesive force.

That is, when forming a coating film of bismuth oxide, tungsten particles, etc. and water glass on the surface of the shadow mask, uniform coating is difficult, and if a pinhole portion is formed in the coating portion, red rust occurs during the manufacturing process. However, the rust progresses, and the coating is likely to fall off, resulting in poor pressure resistance. Further, since the metal particles are not melted by the heat treatment, the metal particles adhered to the mask openings in a lump state due to poor dispersion remain in a fixed state, which causes a defect when the fluorescent screen is formed.
Further, although the deposited film is in a composite state, it is impossible to make its structure uniform, and variations locally occur, and the doming suppression effect also locally changes.

Further, the tungsten particles have a better thermal emissivity than tungsten trioxide, but the oxidation starting temperature is 27.
Since the temperature is about 0 to 310 ° C., a black oxide film forming step in the color picture tube manufacturing step, a panel and funnel sealing step,
It is oxidized when passing through a heat treatment process such as an exhaust process.
Although these heat treatment processes are performed in the air atmosphere, the method disclosed in Japanese Patent Laid-Open No.
Even if it is in an oxidizing gas atmosphere containing carbon dioxide as a main component, which is proposed in Japanese Patent No. 48530, the oxidation progresses to some extent. As a result of the heat treatment, the gas containing oxygen molecules that has diffused and permeated the inorganic binder layer deteriorates the formed inorganic binder layer, and from the state of the black tungsten particle layer firmly bound to the mask surface before the heat treatment, by hand, A layer state is formed in which tungsten oxide particles that easily fall off when rubbed are mixed. Therefore, the tungsten oxide particles generated during the transportation of the color picture tube manufacturing process are likely to fall off, and the rate of occurrence of defective withstand pressure increases, so that the use of the tungsten particles poses a practical problem.

Further, when water glass which is a mixture of Na ₂ O, K ₂ O and SiO ₂ is used as a binder,
Absorbs carbon dioxide in the air to form carbonate. This carbonate decomposes due to heat energy during the manufacturing process to release carbon dioxide. Therefore, when water glass is used, carbon dioxide poisons the cathode, resulting in poor emission.

Therefore, according to the present invention, a layer made of a uniform inorganic material is formed on the surface of the shadow mask without causing emission defects of the cathode, and the thermal expansion due to the heat generated by the electron beam bombardment is alleviated. An object of the present invention is to provide a color picture tube that prevents deterioration in purity.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is arranged in close proximity to a fluorescent screen formed on the inner surface of a panel of an envelope and is emitted from an electron gun. In a color picture tube having a shadow mask having a large number of apertures for passing an electron beam, and having a coating on the electron beam incident side surface of the shadow mask, the coating has a small amount of tungsten oxide containing tungsten trioxide as a main component. A particle layer and a large particle layer formed on the small particle layer, which is larger than the tungsten oxide in the small particle layer, and the small particle layer and the large particle layer are composed of a modified alkyl silicate inorganic binder, and a suspension is applied and baked. It is a color picture tube characterized by being formed by.

[0016]

The tungsten oxide particles are spherical fine powders having a particle size of 1 micron or less, and can form a dense structure with a small amount. Therefore, the surface of the shadow mask can be covered without affecting the shape of the electron beam passage hole of the shadow mask. Also, the thermal emissivity of a perfect blackbody is 1
Then, bismuth oxide is 0.8 to 0.85, tungsten is 0.95 to 0.98, and tungsten trioxide is 0.92 to 0.95. That is, the thermal emissivity of the coating formed of tungsten oxide particles containing tungsten trioxide as the main component is almost the same as that of the coating of tungsten particles, and is superior to that of iron trioxide and bismuth oxide. Further, it also has a high electron beam reflection ability. Also,
The coating itself accumulates charges on the surface due to the electron beam bombardment, forming an electrostatic field, and the electron beam is bent in a direction that corrects the purity drift.

In the present invention, first, the surface of the shadow mask substrate is covered with small particles of tungsten oxide, and the large particles of tungsten oxide are applied onto the surface of the shadow mask substrate. Porosity can be satisfied at the same time.

Therefore, the energy transfer from the electron beam to the shadow mask substrate is suppressed, and furthermore, the heat radiated by the tungsten oxide and the reflected electrons are not left inside the tungsten oxide film, and the emission to the funnel side is easy. Can be

Further, since the modified alkyl silicate containing no alkali metal is used as the inorganic binder, carbon dioxide is hardly released by the heat during the production process, and hydrogen is a reducing gas although a small amount of hydrogen is released. Therefore, it has the effect of extending the life of the emission.

As described above, when the film is formed on the surface of the shadow mask with the tungsten oxide particles containing tungsten trioxide as a main component, the temperature rise of the shadow mask is significantly suppressed, and the electrostatic field formed on the surface of the film is suppressed. By correcting the electron beam trajectory at, the purity drift caused by mask thermal expansion of the shadow mask type color picture tube is remarkably improved.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a color picture tube generally comprises a rectangular panel 1, a funnel-shaped funnel 2 and a neck 3. On the inner surface of panel 1, red,
A phosphor layer 4 that emits light in green and blue is formed in a stripe shape, and an electron beam 5 corresponding to red, green, and blue arranged in a row along the horizontal axis of the panel 1 is formed on the neck 3. An in-line type electron gun 6 for ejecting is installed inside. In addition, a shadow mask 7 having a large number of fine holes is supported by a mask frame 8 around its periphery at a position close to and facing the phosphor layer 4, and the mask frame 8 is further provided with a holder 9 inside the panel. It is supported by the inner surface of the panel by being retained by the stud pins 10 embedded in the vertical inner wall portion of, and the distance between the shadow mask 7 and the phosphor layer 4 is kept within the design value. And
An image is reproduced by deflecting and scanning the electron beam 5 by the deflecting device 12.

Further, as shown in FIG. 2, the shadow mask has a large number of openings 7a, and tungsten trioxide as a main component is mainly formed on the surface between the openings 7a on the electron gun side of the base material. A layer 21 of small particles and a layer 22 of large particles are formed.

The shadow mask manufacturing method of the present invention will be described below. The shadow mask 7 is manufactured through a flat mask manufacturing process by photo etching and a molding process by pressing. The flat flat mask having a desired opening size formed by the photoetching process is fired in a hydrogen reducing atmosphere in a temperature range of 700 ° C. to 800 ° C. to reduce the mechanical strength of the material. Then, it is press-molded to form a desired curvature, and after molding, the molding oil is degreased with an organic solvent or a high temperature alkaline solution.
After that, 550 ° C to 6 containing carbon dioxide gas as a main component
By passing through a high-temperature gas atmosphere at 50 ° C., a black oxide film containing Fe ₃ O ₄ as a main component and having corrosion resistance is formed on the mask surface. Then, the coating of the present invention is formed on the electron gun side of the blackened shadow mask. The black oxide film is a black oxide film having corrosion resistance, and not only suppresses the generation of red rust during the heat treatment process even if pinholes or the like are formed in the inorganic coating of the present invention, it is compared with the surface of the shadow mask. Since there are many fine irregularities, the adhesiveness of the coating film made of an inorganic material is improved and peeling is made difficult.

Next, a coating film of the present invention made of tungsten oxide particles containing tungsten trioxide as a main component is formed on the electron gun side of the shadow mask which has been blackened. Although modified alkyl silicate is used for the inorganic binder,
As an example, ethyl silicate using isopropyl alcohol as a solvent was used. In this, the hydrolysis reaction is repeated in the coexistence of phosphoric acid with an acidic catalyst, and an organosilica sol having —OH and —OC ₂ H ₅ on the side chain of the siloxane bond is formed. 15 to 7 small particles of tungsten oxide containing tungsten trioxide as a main component and having a particle diameter of 0.3 to 0.8 μm are added to the inorganic binder.
Add 0 wt% to prepare a mud-like suspension. Addition amount is 1
If it is less than 5 wt%, it is difficult to disperse uniformly, and conversely 70 wt
%, The adhesion of the tungsten oxide becomes weak and the tungsten oxide falls off.

The suspension thus prepared is sprayed or sprayed using an airless spray gun to form a small particle layer of 1.5 to 3.0 μm on the electron gun side of the shadow mask on which the black oxide film is formed. To do. Since the amount of this small particle layer is sufficient to cover the mask substrate, the thickness of 1.5 μm is sufficient. The hydrolyzed solution of ethyl silicate in the coating film causes the siloxane molecules to become huge due to the fusion of the colloidal particles remaining on the surface after evaporation of the solvent and the dealcoholization reaction due to the reaction with moisture in the atmosphere, resulting in a large siloxane molecule. It forms a good film.

Next, 15 to 70 wt% of large particles of tungsten oxide containing tungsten trioxide as a main component and having a particle size of 0.8 to 2.0 μm are added to the modified ethyl silicate on the small particle layer to form a mud. A suspension is prepared to form a large particle layer of tungsten oxide containing 2.0 to 8.0 μm of tungsten trioxide as a main component in the same manner as in the case of the small particle layer. If this large particle layer is thinner than 2.0 μm, the surface area is not sufficient, and if it is thicker than 8.0 μm, clogging of the shadow mask and dropping of tungsten trioxide particles are likely to occur.

Thereafter, in order to form a film having a strong binding force with the shadow mask without causing cracks in the entire film, the film is placed in a drying furnace and baked. It is desirable to prevent sudden temperature increases and decreases. As an example, firing is 30
After raising the temperature to 80 ° C over 30 minutes, maintaining it for 30 minutes, then raising it to 250 ° C over 30 minutes, maintaining it for 30 minutes, and after the end, 10 ° C
Cool to room temperature at a rate of / min.

The heat-treated shadow mask is combined with the frame, but it is also possible to form the film after combining with the frame. According to the present embodiment, the small particle layer functions to increase the coverage and prevent the electron beam from hitting the shadow mask substrate, and the large particle layer increases the surface porosity to increase the surface area and further increase the heat radiation. And it becomes possible to efficiently perform electron reflection.

Using the 25-inch color picture tube in which the shadow mask manufactured as described above is installed, the amount of movement of the electron beam caused by the doming of the shadow mask was measured and compared with the conventional tube. Measurement, as shown in FIG. 3, a strip-shaped white pattern with a width of 88 mm is 1 each from the center of the screen.
Anode voltage is displayed at 26 KV and cathode current is displayed at 1330 μA at a position 60 mm apart, and the position of the electron beam that moves with time due to thermal expansion of the shadow mask after switching on is measured at a measurement point A using a microscope. It was measured. Table 1 shows the result of measurement of the maximum amount of movement of the electron beam that has moved in a specified time.

[0030]

[Table 1]

Although the doming suppression effect of the shadow mask manufactured according to the present invention depends on the amount of tungsten oxide, it may be appropriately adjusted so as to obtain a predetermined effect.
The addition of 15 to 60% by weight to the inorganic binder has an effect of suppressing electron beam movement by about 30%. This is due to the synergistic effect of the electron beam reflection ability of tungsten oxide itself and the electron beam trajectory correction by the electrostatic field formed near the mask hole into which the electron beam is incident.

In coating the electron gun side of the shadow mask, since the metal particles do not melt at the temperature applied in the manufacturing process of the color picture tube, the linearity of the opening edge of the mask is deteriorated or There is a high possibility that a defect that blocks a part of Therefore, by forming a thin layer of tungsten oxide containing tungsten trioxide as a main component on the periphery of the opening portion as compared to the electron gun side surface of the shadow mask, or by making the layer thinner, it has a sufficient purity suppressing characteristic. As it is, it is possible to prevent the deterioration of the quality of the fluorescent screen due to the defective opening edge and the occurrence of the defective fluorescent screen due to the clogging of the mask opening.

As the inorganic binder, in addition to ethyl silicate, n-butyl silicate or a mixture of both, and the surface resistance of the coating is 10 ^{9 to} 10 ¹¹
In order to adjust to Ω / cm ² , tin oxide or antimony oxide may be added as a conductive substance.

[0034]

As described above, according to the present invention,
A color that can form a uniform film of an inorganic material on the surface of the shadow mask without causing cathode emission defects, and alleviates thermal expansion due to heat generation due to electron beam bombardment and prevents color purity deterioration. A picture tube can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a color picture tube according to the present invention.

FIG. 2 is a cross-sectional view of essential parts showing a shadow mask of the color picture tube shown in FIG.

FIG. 3 is a diagram showing measurement points when measuring characteristics of the present invention.

[Explanation of symbols]

7 ... Shadow mask 21 ... Small particle layer of tungsten oxide containing tungsten trioxide as a main component 22 ... Large particle layer of tungsten oxide containing tungsten trioxide as a main component

Claims (1)

[Claims] 1. A shadow mask, which is arranged close to and facing a phosphor screen formed on the inner surface of a panel of an envelope and has a large number of apertures through which an electron beam emitted from an electron gun passes, the shadow mask In a color picture tube having a coating on an electron beam incident side surface of a mask, the coating has a small particle layer of tungsten oxide containing tungsten trioxide as a main component and a larger particle than the tungsten oxide formed on the small particle layer. Consisting of a large particle layer of
A color picture tube, wherein the small particle layer and the large particle layer are formed by coating and firing a suspension composed of a modified alkyl silicate inorganic binder.