JPH0748348B2 - Color cathode ray tube manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a color cathode ray tube having a shadow mask, and more specifically, to the electron beam irradiation surface side of the shadow mask for reducing the doming amount of the shadow mask. The present invention relates to a method for manufacturing a color cathode ray tube, which forms a film of a substance that suppresses thermal deformation.

[Conventional technology]

The structure of an ordinary shadow mask type color cathode ray tube is
It will be described with reference to the drawings. In FIG. 1, 1 is an envelope for maintaining a high vacuum inside, 2 is an electron gun for emitting three electron beams, and 3 is a shadow mask constituting a color selection electrode. It consists of a thin iron plate with slits. Reference numeral 4 denotes a light-transmissive glass panel that constitutes a part of the envelope 1. Reference numeral 5 denotes a fluorescent surface, and stripes of phosphors that emit red, green, and blue are sequentially applied to the inner surface of the glass panel 4. The stripe groups are provided in such a positional relationship that they correspond to the respective slit groups of the shadow mask 3 electronically and accurately.

Next, the operation of the color cathode ray tube will be described. The three electron beams emitted from the electron gun 2 are deflected by the deflecting device 6 so as to scan the entire fluorescent surface 5 and reach the shadow mask 3. The shadow mask 3 has a color selection function that causes the three electron beams to hit only the phosphor stripes of the corresponding colors. And, as described above, these positional relationships are originally set so that accurate correspondence can be achieved.

However, when the cathode ray tube is operated, about 80% of the electron beam emitted from the electron gun 2 collides with the shadow mask 3 and is blocked, and the shadow mask 3 is provided with meaningless thermal energy, so that the shadow mask 3 3 is heated. As a result, the shadow mask 3 is deformed due to thermal expansion, and the positional relationship between the shadow mask 3 and the phosphor stripe, which corresponded exactly to each other, is shifted, which causes a large color shift.

As a method for solving these problems, as shown in FIG. 1, in JP-A-55-76553, the electron beam irradiation surface of the shadow mask 3 is more exposed to the electron beam than the substance forming the shadow mask 3. Providing a coating 7 made of a substance having a high reflectance is also disclosed in Japanese Patent Publication No. 60-14459.
It has been proposed to spray-coat a solution containing a heavy metal material having an atomic number exceeding 0 to provide the electron beam reflection film 7, and lead, tungsten, and bismuth are selected as the heavy metal materials. Their usefulness is also described for these carbides, sulfides, and oxides. In FIG. 1, the shadow mask 3 and the phosphor screen
5, and the reflection film 7 are exaggeratedly drawn.

When manufacturing a color cathode ray tube using a shadow mask provided with a reflective film disclosed in JP-B-60-14459, no matter which heavy metal material is used, the average particle size of the fine particles is set to 1 μm or less. Is preferable, and when bismuth oxide is selected as the coating material, for example, particles having a large particle diameter of several μm to several tens μm are usually crushed and used. Normally, the ball mill method is used as the crushing method,
At the time of ball milling, bismuth oxide, water glass and an appropriate amount of water are added at the same time, and ball milling is carried out for about 5 to 7 days.
It is obtained by again adding an appropriate amount of water glass and water, applying it on a shadow mask, drying it, and then subjecting it to a usual color cathode ray tube manufacturing process. As the water glass, potassium-based water glass is used.

That, Bi ₂ O ₃ a potassium-based water glass and an appropriate amount of water is added to and subjected to a ball mill, an average particle size of the Bi ₂ O ₃ 1
It is pulverized to a size of less than μm, spray-coated on a shadow mask, air-dried, and then baked in air at 400 ° C. for 30 minutes.

[Problems to be Solved by the Invention]

In the conventional manufacturing method for color cathode ray tubes, a large amount of outgas (CO ₂ ) is generated when the reflection film obtained on the shadow mask surface is irradiated with an electron beam, and this outgas (C
There is a problem that stable emission life characteristics cannot be obtained due to O ₂ ). The cause of this is that potassium-based glass is a result of intensive investigations by the present inventors.
Resulting carbonate (K ₂ CO ₃₎ absorbs CO _2, the carbonate (K ₂
If CO ₃ ) is present in the resulting reflective film, this carbonate (K 3
₂ CO ₃ ) is a metal oxide (Bi ₂ O ₃ ) present in the reaction film,
Irradiation with an electron beam causes the reaction of the following formula,
As shown in Fig. ₂ , it was found that an endothermic reaction started to occur at 914K (641 ° C) and outgas (CO ₂ ) was generated.

Bi ₂ O ₃ + K ₂ CO ₃ → Bi ₂ O ₃ · K ₂ O (eutectic liquid) + CO ₂ ↑ Note that the Bi ₂ O ₃ · K ₂ O eutectic itself can be used even after CO ₂ gas is released. Melting occurs reversibly many times.

The present invention has been made to solve the above problems, and an electron beam in which the content of a carbonate which reacts with a heavy metal oxide to generate outgas (CO ₂ ) by irradiation of an electron beam is reduced. It is an object of the present invention to provide a method for producing a color CRT, in which a color CRT in which the reflective film is formed on a shadow mask is obtained.

[Means for Solving the Problems]

The manufacturing method of the color cathode-ray tube according to the present invention, the powder of the heavy metal oxide, the mixture ratio of the mixture of sodium-based water glass and potassium-based water glass having a ratio of 3: 1 to 30: 1 is mixed as a binder, and obtained The obtained mixture is applied onto the surface of the shadow mask to form a coating film, and the coating film is baked to form a reflection film of an electron beam on the shadow mask surface.

[Action]

In the present invention, the reflection film formed by using a mixture of lath and potassium water glass as the water glass in which the sodium water having the above mixing ratio (3: 1 to 30: 1) is contained therein. The content of carbonates (K ₂ CO ₃ , Na ₂ CO ₃ ) depends on the content of carbonates contained in the reflection film when formed by using water glass of other compounding ratios and other material systems. This is a significant reduction. Therefore, the amount of outgas (CO ₂ ) generated by irradiating the reflective film with an electron beam is reduced, and the color CRT configured by using the shadow mask formed on the surface of the reflective film has an excellent emission. It has characteristics.

Further, the reflection film formed by using a mixture of last potassium water glass as the water glass is sodium-based water having the above-mentioned compounding ratio (3: 1 to 30: 1) is a carbonate (K Not only is the content of ₂ CO ₃ , Na ₂ CO ₃ ) small, but the fluctuation of the content due to the season is also small, so the dry state of the obtained reflective film is also reproducible, and the above emission characteristics are seasonal. It does not change depending on.

〔Example〕

Table 1 shows changes in the total amount of carbonate when various mixed water glasses having different mixing ratios of sodium-based water glass and potassium-based water glass were used.

That is, Bi ₂ O ₃ 30 g, water glass 7.5 g, water 19 g spray solution of standard composition total amount of carbonate in the sample dried in argon gas, also after the sample was fired in air at 450 ℃, 30 minutes The total amount of carbonates was shown, and the ratio of both (after baking / after drying) was shown as a reduction rate. A reduction rate of 1 or less means that some carbonates contained in the dried sample decompose, for example, during firing.
This is because some Bi ₂ O ₂ CO ₃ (BOC) is included. Further, since the argon gas does not contain CO ₂ gas, the total carbonate amount in the dried sample is equal to the total carbonate amount contained in the spray liquid before drying. The total carbonate content was determined by applying the baseline method to the infrared absorption spectrum of the sample shown in FIG.
The 1050 cm ^-1 as 1, in which determined the relative absorbance of C-O asymmetric stretching absorption band at 1400 cm ^-1 vicinity.

From Table 1, the total amount of carbonate after drying is small in the mixed water glass and large in the 100% potassium water glass or the sodium water glass. Especially, the sodium: potassium mixture ratio of 3: 1 to 9: 1 shows a small value. Next, looking at the values after firing, from 100% potassium-based water glass to mixed water glass with a sodium: potassium mixing ratio of 1: 1 and 100
% Sodium-based water glass is high, but the mixing ratio is 3: 1 to 30:
A mixed water glass of 1 shows a small value of 1/2 to 1/5. Among them, 9: 1 has the smallest value. To produce CRTs with excellent life properties, the total carbonate content must be reduced as much as possible, for this purpose a mixed water glass with a sodium: potassium mixing ratio of 3: 1 to 30: 1 is preferred. It is clear from Table 1. Especially the mixing ratio
The 9: 1 ratio has the best performance. Incidentally, the reduction rate of carbonate due to firing is large on the potassium water glass side,
It becomes smaller on the sodium-based water glass side.

In addition, the sample consisting of Bi ₂ O ₃ (3g), potassium water glass (0.75g), and K ₂ CO ₃ (30mg) shown in Fig. ₂ was repeatedly measured using a differential scanning calorimeter (DSC). No sample consisting of Bi ₂ O ₃ (3 g), sodium-based water glass (0.75 g), and Na ₂ CO ₃ (30 mg) with the same composition ratio was shown for the melting reaction. 906K is Bi ₂ O ₃ and potassium water glass and K
It is the eutectic temperature of a sample composed of ₂ CO ₃ .

In addition, the generated Na ₂ CO ₃ can be kept dry up to 95% RH (CLKusik, HPMeisner, “Industrial and Engineering Chemistry, Process Design and Development”). (Industri
al and Engineering Chemistry, Process Design and De
velopment), 12: 122, 1973 ''). Therefore, compared to the case of using potassium-based water glass that produces K ₂ CO ₃ , the dry state of the coating film after spray coating is always reproducible when sodium-based mixed water glass is used, and the dry state varies depending on whether it is sunny or rainy. It will not be done.

An embodiment of the method for manufacturing a color cathode ray tube according to the present invention will be described below.

1 part of the above-mentioned heavy metal oxide powder (parts by weight, the same applies below) and pure water are preferably mixed in an amount of 0.6 to 0.8 parts and then mixed for about 3 days by a ball mill method or the like. Mixing ratio 9: 1 to this mixture
Add 0.2 to 0.4 parts of the binder mixture of sodium-based water glass and potassium-based water glass in (1) and roll for about 1 day.

The obtained mixture is applied to the electron beam irradiation surface side of the shadow mask 3 by a conventionally used spraying method such as an air spray method. The thickness of the electron beam reflecting coating 7 is preferably such that the electron beam does not pass through,
Usually, the thickness after heat treatment is about 2 to 5 μm.

The shadow mask 3 used in this embodiment may be one conventionally used for a color cathode ray tube.

Further, even if the mixed ratio of the mixed water glass used is such that the sodium: potassium ratio is in the range of 3: 1 to 30: 1, it is possible to obtain an electron beam reflective coating having substantially the same performance.

The electron beam reflective coating 7 composed of a heavy metal oxide powder and a mixture of sodium-based water glass and potassium-based water glass having a compounding ratio of 9: 1 will be described more specifically.

First, 3000 g of Bi ₂ O ₃ crushed to an average particle size of about 1 μm by a ball mill method and 1900 g of pure water were mixed for 3 days by a ball mill method, and this mixture was mixed with sodium-based water glass and potassium-based water with a mixing ratio of 9: 1. 750 g of a glass mixture was added and rolled for about 1 day. A coating liquid consisting of the obtained mixture,
After the electron beam irradiation surface of the blackening-treated shadow mask 3 is applied by the air spray method to form the electron beam reflective coating 7, the electron beam reflective coating 7 is put into a normal color cathode ray tube manufacturing process, and the 90 ° deflection 25 An inch type color cathode ray tube was manufactured.

Next, the results of examining the emission life characteristics of the obtained cathode of the color cathode ray tube will be described. Electron beam current 0.9mA, electron beam acceleration voltage 25kV, heater voltage 6.3
When the emission life characteristic of the cathode is measured with V, the color cathode ray tube using the shadow mask 3 obtained by the above manufacturing method has a good maximum emission current life characteristic of about 20% higher than that of the conventional product of the same shape. Results were obtained.

That is, the electron beam reflective coating 7 using a mixture of sodium-based water glass and potassium-based water glass with a compounding ratio of 3: 1 to 30: 1 as a binder has a constant dry state of the film, and no longer affected by the weather, total carbonate resulting from binder component: amount of change (eg K ₂ CO ₃₎ is reduced, total carbonate produced by the CO ₂ absorption of the binder component (eg: K ₂ CO ₃₎ small amount Therefore, it is considered that the good life characteristics described above were obtained.

Although heavy metal oxide powder is used as the substance forming the reflective coating 7 in the above-mentioned embodiment, this is a substance having a large electron beam reflectance and having a higher density or atomic number than the substance forming the shadow mask 3. A heavy metal powder or a mixed powder of a heavy metal oxide and a heavy metal may be used as long as it contains a large element.

〔The invention's effect〕

As described above, according to the method for producing a color cathode-ray tube according to the present invention, the mixture of sodium-based water glass and potassium-based water glass having a mixing ratio of 3: 1 to 30: 1 is added to the powder of heavy metal oxide. Mix as a binder, apply the resulting mixture on the shadow mask surface to form a coating film,
By baking this coating film, a reflection film for the electron beam is formed on the shadow mask surface, so that it is contained in the reflection film for the electron beam, and the heavy metal is irradiated by the electron beam in the reflection film. The content of carbonates (K ₂ CO ₃ , Na ₂ CO ₃ ) generated by water glass that reacts with oxides to generate outgas (CO ₂ ) can be reduced compared to the conventional method. As a result, there is an effect that it is possible to obtain a color CRT in which good emission characteristics are maintained for a long period of time.

[Brief description of drawings]

Fig. 1 is a schematic partial cross-sectional view showing the structure of a shadow mask type color cathode ray tube, and Fig. 2 is a graph of the endothermic reaction between Bi ₂ O ₃ and K ₂ CO ₃ measured using a DSC (differential scanning calorimeter). FIG. 3 is a diagram showing an infrared absorption spectrum of a mixture sample of Bi ₂ O ₃ and water glass. 3 is a shadow mask, and 7 is an electron beam reflective coating.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunio Takeoka 1 Baba Institute, Nagaokakyo City, Kyoto Prefecture Mitsubishi Electric Co., Ltd. Kyoto Factory (72) Inventor Masayasu Koitabashi 8-1-1 Tsukaguchihonmachi, Amagasaki City, Hyogo Prefecture Ryoden Co., Ltd. Central Research Institute (72) Inventor Hiroshi Kimura 8-1-1 Tsukaguchi Honcho, Amagasaki City, Hyogo Sanryo Electric Co., Ltd. Central Research Laboratory (72) Inventor Katsuhiro Ohno 8-chome, Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture No. 1 Sanritsu Electric Co., Ltd. Materials Research Laboratory (56) References JP-A-62-281240 (JP, A) JP-A-62-281241 (JP, A)

Claims (1)

[Claims] 1. A heavy metal oxide powder having a compounding ratio of 3: 1.
Mixing a mixture of sodium-based water glass and potassium-based water glass that is 30 to 30: 1 as a binder, apply the obtained mixture on the shadow mask surface to form a coating film, and bake this coating film. A method of manufacturing a color cathode ray tube, wherein a reflection film for an electron beam is formed on the surface of the shadow mask by.