JPH0731984B2 - Cathode ray tube - Google Patents

Description

The present invention relates to a cathode ray tube having a shadow mask.
More specifically, the present invention relates to a cathode ray tube formed by forming a film on the electron beam irradiation surface side of the shadow mask with a substance that suppresses thermal deformation in order to reduce the doming of the shadow mask.

[Prior Art] FIG. 1 shows the structure of a conventional shadow mask type color cathode ray tube. 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. And is made of, for example, a thin iron plate having many slits. (4) is an envelope, a translucent glass panel forming a part of (1), (5) is a fluorescent surface, the stripes of phosphors that emit red, green, and blue of the glass panel (4) The stripe masks are sequentially applied to the inner surface, and each of these stripe groups is the shadow mask.
The slit groups of (3) are provided in a positional relationship so as to correspond to each of the slit groups 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 deflector (6).
As a result, the entire surface of the phosphor screen (5) is deflected so as to scan and reaches the shadow mask (3). This shadow mask (3) has a color selection function that causes 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 made.

However, in this case, about 80% of the electron beam emitted from the electron gun (2) impinges on the shadow mask (3) and is blocked, giving completely insignificant thermal energy to the shadow mask (3) and causing shadows. The mask (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 correspond exactly to each other, is shifted, which causes a large color shift.

As a method for solving these problems, JP-A-55-76553
In JP-A-60-14459, the electron beam irradiation surface of the shadow mask (3) is provided with a film made of a material having a higher electron beam reflectance than the material forming the shadow mask (3). In the publication, it is proposed to provide a coating film (7) for reflecting the electron beam by spray coating a solution containing a heavy metal material having an atomic number of more than 70, and lead as the heavy metal material, Tungsten and bismuth are selected, and their usefulness is also described for their carbides, sulfides and oxides.

When manufacturing a cathode ray tube using a shadow mask provided with the coating film (7) disclosed in JP-B-60-14459,
When any heavy metal material is used, it is preferable that the average particle size of the fine particles is 1 μm or less. For example, when bismuth oxide (Bi ₂ O ₃ ) is selected as the coating material, it is usually several μm. Particles having a large particle size of about several tens of μm are crushed and used. Conventionally, a ball mill method has been used as a crushing method. At the time of ball milling, bismuth oxide, water glass and an appropriate amount of water are added at the same time, ball milling is carried out for 5 to 7 days, and then water glass and water are again added in appropriate amounts and applied onto a shadow mask. Then, the shadow mask for reducing the doming is manufactured by drying and then subjected to an ordinary color cathode ray tube manufacturing process.

That is, Bi ₂ O ₃ is mixed with water glass and an appropriate amount of water, and the mixture is crushed by a ball mill until the average particle size of Bi ₂ O ₃ powder becomes 1 μm or less, and then coated on a shadow mask and dried. Then, it is baked at about 450 ° C for about 30 minutes.

[Problems to be Solved by the Invention] However, when the cathode ray tube is manufactured as described above, after the cathode ray tube is assembled, a large amount of outgas may be produced, which may result in a product having a short life. As a result of earnest studies by the present inventors, it was found that the main reason for this is that Bi ₂ O ₃ reacts with CO ₂ to produce Bi ₂ O ₂ CO ₃ .1 / 2H ₂ O. This reaction was easily promoted in the ball mill because water glass easily absorbs CO ₂ gas in the air. Also, in potassium-based water glass used as a binder
The absorption of CO ₂ gas produces K ₂ CO ₃ , and since this compound is strongly hygroscopic, it further promotes the above reaction. (WAWink's “Industrial and Engineering Chemistry (Industri
al and Engineering Chemistry), 18, p. 251, 1964
Year ").

It is an object of the present invention to provide a cathode ray tube with less outgassing and requiring less meticulous attention to control in the manufacturing process.

[Means for Solving the Problems] The present invention is prepared by applying a mixture of water glass and a compound of Bi ₂ O ₃ and an oxide of a group IV element having an atomic number of 32 or less onto a shadow mask and baking it. relates cathode ray tube, characterized in that, Bi ₂ O ₃ in place of CO ₂ and easily compound Bi ₂ O ₃ and SiO _2, G
It uses a compound with eO ₂ or TiO ₂ .

[Operations and Examples] Bi ₂ O ₃ and oxides of group IV elements having an atomic number of 32 or less that can be used in the present invention include SiO ₂ , GeO ₂ and TiO ₂ .
As a compound of Bi ₂ O ₃ and those oxides, Bi ₁₂ Si
Examples include O ₂₀ , Bi ₁₂ GeO ₂₀ , and Bi ₁₂ TiO ₂₀ . Bi
₁₂ SiO ₂₀ , Bi ₁₂ GeO ₂₀ or Bi ₁₂ TiO ₂₀ is Bi ₂ O ₃ 6
Mole of SiO _{2 and} 1 mole of SiO _2, 1 mole of GeO ₂ or 1 mole of TiO ₂ , for example, Bi ₁₂ SiO ₂₀ has a melting point of about 900.
It is a substance at ° C. SiO ₂ , GeO ₂ or TiO ₂ content is only 2
Though only only to 3.6%, these compounds do not produce a compound with CO ₂ at all. It is also a stable compound with a higher melting point than Bi ₂ O ₃ alone (EMLevin (EMLe
vin) et al., "Journal of Research of the
National Bureau of Standards (JOURNA
L OF RESEARCH of the National Bureau of Standard
s), Volume 68A, 2, 201, 1964 ").

Bi ₂ O ₃ and SiO ₂ as compounds of Bi ₁₂ SiO ₂₀ , Bi ₂ O ₃ and GeO
_When Bi ₁₂ GeO ₂₀ as a compound with ₂ and Bi ₁₂ TiO ₂₀ as a compound with Bi ₂ O ₃ and TiO ₂ are used, 6 mol of Bi ₂ O ₃ and 1 mol of SiO ₂ powder, GeO ₂ powder or Synthesized by firing TiO ₂ powder at 600 ℃ or higher, preferably 800 ℃ or lower
Bi ₁₂ SiO ₂₀ powder, Bi ₁₂ GeO ₂₀ powder or Bi ₁₂ TiO ₂₀ powder
Use powder.

Examples of the water glass used in the present invention include sodium-based water glass and potassium-based water glass.

0.6 to 0.8 parts of water and water glass to 1 part (part by weight, hereinafter the same) of the compound of Bi ₂ O ₃ and SiO ₂ , GeO ₂ or TiO ₂
0.2 to 0.4 parts are used. Bi ₁₂ SiO ₂₀ powder, Bi ₁₂ GeO
₂₀ powder or Bi ₁₂ TiO ₂₀ powder and water are crushed by a ball mill method or the like until the average particle diameter becomes 1 μm or less, and then an appropriate amount of water glass is added to prepare a coating solution. The obtained coating liquid is applied to the electron beam irradiation surface side of the shadow mask by a conventional method so that the thickness of the coating film before drying becomes 3 to 7 μm, and then naturally dried at room temperature.

Next, 400-500 ℃, preferably 450 ℃, for 15-45 minutes,
The cathode ray tube of the present invention is manufactured through baking in air, preferably for 30 minutes, and the usual cathode ray tube manufacturing process.

The shadow mask used in the present invention may be one conventionally used for a cathode ray tube.

For example Bi ₁₂ SiO ₂₀ powder, Bi ₁₂ GeO ₂₀ powder or Bi ₁₂
The case of using 3 kg of TiO ₂₀ powder will be described below.

2 l of water was added to the powder, and ball milling was performed for 3 days. Sodium-based water glass (solid content 28.25%,
600 ml of molar ratio SiO ₂ / Na ₂ O = 3.43) was added and mixed well (1
On the electron beam irradiation side of the shadow mask,
It was applied so that the thickness of the coating film before drying was 10 μm. After drying in air at room temperature for 0.15 hours, baking was performed in air at 450 ° C. for 30 minutes to produce a shadow mask provided with a coating film. The shadow mask thus obtained was used to manufacture a cathode ray tube through a normal cathode ray tube manufacturing process. A similar cathode ray tube can be obtained by using potassium-based water glass instead of sodium-based water glass.

FIG. 2 is a graph showing an infrared absorption spectrum of a coating film made of Bi ₂ O ₃ and potassium water glass used in a conventional cathode ray tube. In the figure, (11) is the spectrum before the electron beam irradiation, (12) is the spectrum after the electron beam irradiation, the peak of (a) is Bi
₁₂ shows absorption of SiO _{4 in} SiO ₂₀ , and the peak of (b) is Bi ₁₂
2 shows absorption of Bi—O in SiO ₂₀ . As is clear from FIG. 2, when the coating film on the shadow mask made of the above mixture is irradiated with an electron beam, Bi ₂ O ₃ becomes S in water glass.
May react with iO ₂ to form Bi ₁₂ SiO ₂₀ . This reduces the adhesive strength of the coating. However, Bi ₁₂ SiO ₂₀ , Bi ₁₂ GeO ₂₀ or Bi ₁₂ TiO ₂₀ used in the present invention
Does not react further with water glass, so that a coating film having stable adhesive strength over a long period of time can be obtained.

[Effects of the Invention] The cathode ray tube of the present invention has the following effects.

Since a compound of Bi ₂ O ₃ and SiO ₂ , GeO ₂ or TiO ₂ does not combine with CO ₂ , a substance that causes outgassing is not generated, and a stable and high-performance cathode ray tube can be obtained.

Since the compound of Bi ₂ O ₃ and SiO ₂ , GeO ₂ or TiO ₂ does not react with SiO _{2 in} water glass, the adhesive strength of the coating film does not decrease.

The electron beam scattering ability of the compound of Bi ₂ O ₃ and SiO ₂ , GeO ₂ or TiO ₂ is exactly the same as Bi ₂ O ₃ .

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing the structure of an ordinary shadow mask type color cathode ray tube, and FIG. 2 is a coating film consisting of Bi ₂ O ₃ and potassium water glass before and after electron beam irradiation. It is a graph which shows an infrared absorption spectrum.

Front page continuation (72) Inventor Mutsumi Hattori, No. 1 Baba Institute, Nagaokakyo, Kyoto Prefecture Mitsubishi Electric Co., Ltd. Kyoto Factory (72) Norio Morio Yamamoto, No. 1 Baba Institute, Nagaokakyo Kyoto Prefecture, Mitsubishi Electric Corporation Kyoto Factory (72) Inventor Hiroshi Okuda 1 Baba Institute, Nagaokakyo City, Kyoto Prefecture Mitsubishi Electric Corporation Kyoto Plant (72) Inventor Tetsuya Watanabe 1 Baba Institute, Nagaokakyo Kyoto Prefecture Mitsubishi Electric Corporation Kyoto Plant (56) Reference Document JP-A-62-281241 (JP, A)

Claims (4)

[Claims] 1. A cathode ray tube comprising a mixture of Bi ₂ O ₃ and an oxide of a group IV element having an atomic number of 32 or less and water glass coated on a shadow mask and baked. 2. An oxide of a group IV element having an atomic number of 32 or less is Si.
Claims that are O ₂ , GeO ₂ and / or TiO ₂ .
The cathode ray tube according to item (1). 3. A compound of Bi ₂ O ₃ and an oxide of a Group IV element having an atomic number of 32 or less is Bi ₁₂ SiO ₂₀ , Bi ₁₂ GeO ₂₀ and / or Bi ₁₂ TiO ₂₀ . The cathode ray tube according to the item 1). 4. The cathode ray tube according to claim 1, wherein the water glass is sodium water glass or potassium water glass.