JPS5846517Y2 - cathode ray tube - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a cathode ray tube, for example, a color television receiver, and is configured to reduce or prevent the phenomenon in which the face plate portion is colored brown due to electron beam irradiation. It is.

Conventionally, the operating voltage and current density of cathode ray tubes used in color television receivers are higher than those of cathode ray tubes used in monochrome television receivers, and it is widely known that the irradiated surface of the face plate is colored brown by the electron beams. It is being

Furthermore, in the cathode ray tube for a projector as previously proposed by the present applicant, this phenomenon is even greater than in the cathode ray tube for the color television receiver.

Further, this is particularly problematic when a part of the cathode ray tube is continuously irradiated with an electron beam without the picture moving, as in a video game.

According to experiments by the present inventor, for example, when a metal back layer is formed on silicate glass that constitutes the face plate of a cathode ray tube, an electron beam is emitted from an electron gun at a cathode current of 0.9 mA and a current density of 4 at the face plate. .7μA
When the electron beam was irradiated for 30 hours under the conditions of "/cin" and an anode voltage of 22 KV, the spectral transmittance of the electron beam irradiated surface was colored brown and decreased to 18.6% at a wavelength of 400 mμ.

Furthermore, it was confirmed that when quartz glass and low alkali glass were tested under these conditions, the degree of brown coloring was extremely reduced compared to the above-mentioned silicate glass.

From these results, it is considered that the main cause of the browning of glass bodies caused by electron beams is the action of cations, ie, alkaline components, that constitute modified oxides in the glass.

Generally, oxide glasses are glass-forming oxides (SiO2,
B2O3, P2O5, etc.) and their modified oxides (including intermediate oxides). Possible modified oxides include Li2O, Na2O, 20, etc., and cations include Li ions, Na ions, K ions. In particular, lead oxide PbO is added to the glass that makes up the face plate of cathode ray tubes as an intermediate oxide to prevent the radiation of X-rays caused by electron beam irradiation. PbO also causes the brown coloring phenomenon.

However, if the glass body constituting the face plate of the cathode ray tube is made of glass with extremely low alkaline content, such as quartz glass or low-alkali glass, the browning phenomenon caused by the electron beam can be minimized. However, quartz glass, low-alkali glass, and the like are expensive and difficult to process and mold, making it virtually impossible to use them as the face plate of a cathode ray tube due to production costs.

Therefore, various attempts have been made to prevent coloring of the silicate glass commonly used in the face plate portion of cathode ray tubes, and as a countermeasure, methods of improving the glass composition have been considered.

For example, there have been methods to reduce the presence of reducible oxides, methods to include cerium oxide, and methods to use a combination of manganese oxide and titanium oxide.

However, in both cases, although the effect is somewhat better than that of ordinary glass, the phenomenon of browning occurs and the effect is not satisfactory.

As described above, it is extremely difficult to prevent silicate glass used as the face plate portion of a cathode ray tube from becoming brown by the method described above.

Further, as a result of various experimental measurements, in a cathode ray tube, the distance that an electron beam emitted from an electron gun penetrates into the face plate glass can be obtained from the following formula, which is generally accepted as an experimental formula.

That is, the transmission distance of the electron beam is λp=2.5X10-12δ-1V 2 (cm) λp:
Transmission distance of electron in crystal δ: Density of crystal V: Accelerating voltage (range of 103 to 105), and now when calculating using silicon monoxide (SiO2) as a crystal,
In the above formula, the crystal density δ is 2.2 g/.

When m3 acceleration voltage ■ is 19000 V, λp=2.5x1o-”'x2.2-1x190002
-=:4.1x 1O-4crn=4.1μ.

In other words, the electron beam is directed toward the face plate by the phosphor,
Including the metal back etc., it will transmit 4.1μ,
Furthermore, the particles of the phosphor have an average size of about 5μ, and are coated on the inner surface of the face plate in approximately 2 to 3 layers, but in reality, they are not coated on average and there are cases where only one layer is used. However, since there is no coating between the blue, red, and green color phosphors, the face plate glass is colored brown.

The present invention employs a method of reprocessing a face plate molded from silicate glass using conventional methods, and coats the electron beam irradiated surface of the face plate with a transparent substance that can prevent browning. It is.

However, this coating material must be inorganic so that it does not decompose under electron beam irradiation and produce abnormal gases, and must be transparent enough to not reduce brightness.
The processing conditions must be below the annealing point of the glass, the heat resistance must be above 430°C, and the phosphor coated on the inner surface of the face plate must not be adversely affected. However, as a result of various experiments, silicon dioxide (silicon dioxide), which satisfies the above-mentioned conditions and hardly causes the brown coloring phenomenon, was selected as the coating material.
SiO2) and aluminum oxide (Al□03) were found to be optimal.

The former method of forming silicon dioxide (SiO2) is a method of applying a commercially available solution (for example, the coating dispersing agent Si-film manufactured by Tokyo Ohka Kogyo KK and SILICA-FILM 5000 manufactured by Emulsion Company of America, both of which are commercially available) There is a name).

However, with this method, it is impossible to apply the coating to a thickness that should prevent the browning phenomenon caused by the electron beam (8
000A or more) and the price is high.

Other methods include the sputtering method and the CVD method, but these methods are also quite expensive in terms of cost and mass production, resulting in an increase in the cost.

Therefore, the present invention is based on the latter aluminum oxide (Al□03).
) to provide a cathode ray tube in which the browning phenomenon of the face plate can be reduced or prevented easily and inexpensively.

That is, in the present invention, as shown in FIG.
Face plate portion 2 formed of silicate glass
A film 3 containing aluminum oxide as a main component is formed on the inner surface of the
A fluorescent surface 4 is formed on top.

The film 3 may be composed of an aluminum oxide film, or a film formed by overcoating an aluminum oxide film and another oxide film that satisfies the above-mentioned conditions.

In addition, although the film thickness of the film 3 is allowed to be 1.5μ or more,
For example, in the case of only an aluminum oxide film, if the thickness exceeds 8 μm, cracks may occur in the film, and the film becomes milky white, resulting in a decrease in real transmittance.

In the case of an aluminum oxide film, if the thickness is about 4 to 6 μm, the transparency of the film itself is good, although the transmittance is only reduced by about 5%.

According to this configuration, since the coating 3 containing aluminum oxide as a main component is formed on the inner surface of the face plate portion 2, browning of the face plate portion 2 due to electron beam irradiation is reduced, and the image remains clear for a long time. You can get a good image.

Furthermore, the film 3 whose main component is aluminum oxide can be easily formed to a desired thickness by a coating method as shown in the following example, so it can be easily mass-produced and provided at low cost. .

Next, the present invention will be illustrated using examples.

Example (1) Alumina sol 200 (trade name, hereinafter referred to as alumina sol) manufactured by Nissan Chemical Industries, Ltd. is used.

The properties of this alumina sol are as follows. A1□0
310% or more Specific gravity 1.09 to 1.14 Particle type Feather-like particle size Average 100 mμ x 10 mμ The concentration and rotational coating speed of this alumina sol were arbitrarily selected to coat the inner surface of the face plate of the cathode ray tube as an Al2O3 film of 6μ. Apply it to make it thick.

This face plate was irradiated with an electron beam for 30 hours at an anode voltage of 19 KV and a cathode current density of 4.7 μA/cm2, and the spectral transmittance was measured (underwater measurement) using a double beam spectrophotometer. and curve A in FIG.

In the same way, using the above alumina sol, a 1.5μ thick Al
A 2O3 film was coated on the inner surface of the face plate, and the spectral transmittance after electron beam irradiation was measured, and the results were as shown in the table attached below and curve B in FIG.

Example (2) Applying and dispersing agent B 11260 (trade name) manufactured by Tokyo Ohka Kogyo Co., Ltd. (based on B203) was used, and 5000 A was applied to the inner surface of the face plate.
Apply to a thickness of .

This face plate was irradiated with an electron beam under the same conditions as in Example (1), and its spectral transmittance was measured, and the result was as shown in the table attached below and curve C in FIG. 2.

In addition, the above coating diffusion agent B-11 was applied to the inner surface of the face plate.
After applying 260 to a thickness of 500 OA, the alumina sol of Example (1) was further coated to a thickness of 5000 Å (total 1μ), and irradiated with an electron beam under the same conditions as Example (1). After that, the spectral transmittance was measured, and the result was as shown in the curve shown in FIG.

Example (3) Alumina sol was applied to the inner surface of the face plate to a thickness of 500 OA, and GF# manufactured by Nikko Marzion Co., Ltd. in the United States was applied to the inner surface of the face plate.
306 (product name) (based on B203) 5
00OA thickness (total 1μ), Example (1
), the spectral transmittance was measured after irradiation with an electron beam under the same conditions as those shown in Table 1 and curve E (corresponding to the curve) in Figure 2.

Incidentally, a similar spectral transmittance in a state where nothing is coated on the inner surface of the face plate and only glass is applied is shown as curve F in FIG.

As is clear from the attached table and Figure 2, aluminum oxide (A120
3) For those coated with a film of 6 μm (curve A in FIG. 2), browning due to electron beam irradiation can be prevented without any problem.

Further, even when the thickness of the aluminum oxide film is 1.5 μm, it has sufficient practical value (see curve B in FIG. 2).

On the other hand, in the case of Example (2) shown by curve C in FIG. 2, it is difficult to apply coating agent B-11260 (trade name) in an amount of 500 A or more.

That is, if more than 8000 A is applied, cracks or peeling will occur in the coating film.

However, if A1□03, which can be applied thickly, is applied over the coating film of B-11260 (trade name), the effect of preventing browning will be improved as shown by the curve in FIG.

And GF# 306 (product name) and B-11260
It can be assumed that Al2O3 (trade name) is the same product, and the effect can be fully expected whether Al2O3 is used as an undercoat or a topcoat, as shown by the curve and curve E in Figure 2.

Even in the case of these overcoatings, it is practical if the total thickness is 1.5 μm or more.

In addition, in the case of overcoating, since the film thickness is extremely thin, the two films may not be clearly distinguished and may be mixed together.

In the above examples, the alumina sol film was formed using a spin coating machine, but similar results could be obtained using a dipping method, a brush coating method, an evaporation drying method, or the like.

As described above, according to the present invention, it is possible to significantly reduce the phenomenon in which the face plate of a cathode ray tube of a color television receiver that is commonly used is colored brown due to electron beam irradiation. The service life of the camera is extended, and clear images can be obtained for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional side view showing a cathode ray tube according to the present invention, and FIG. 2 is a spectral transmittance curve diagram according to an embodiment of the present invention. 1 is a cathode ray tube, 2 is a face plate portion, 3 is a film whose main component is aluminum oxide, and 4 is a fluorescent surface.

Claims (1)

[Scope of utility model registration request] A cathode ray tube that has a film mainly composed of aluminum oxide formed on the electron beam irradiation side of the face plate.