JPS59191237A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To suppress surface reflection of phosphor substance and to obtain a cathode-ray tube of low exterior light reflection rate and high contrast by using phosphor substance covered with silica and by making the quantity of silica covering the phosphor substance a predetermined quantity. CONSTITUTION:The phosphor substance is preferably to have a mean particle diameter being 3mu upto 15mu, and upon the phosphor substance surface a continuous film of amorphous silica being from 1.0 upto 15 by weight against the phosphor substance 100 by weight is formed. When the average thickness of silica layers against these phosphor substance of various particle diameters is not greater than 0.1mu preferably from 0.09mu upto 0.1mu, the surface reflection of the phosphor substance is decreased, and a color television picture tube having low exterior light reflection rate and high contrast can be obtained.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a cathode ray tube, and particularly relates to a fluorescent surface thereof. , has dot or stripe-shaped phosphor layers that emit blue light, and if necessary) gaps between these phosphor layers are coated with a non-emissive light absorbing material. Conventionally, in such color picture tubes, in order to improve the contrast of the screen, it has been known to reduce the reflectance of external light by attaching or mixing pigments having almost the same color tone as the phosphor's emitted light color to the phosphor. ing.

However, even if such a method is used, it has not been possible to sufficiently improve the surface reflection of the phosphor surface. The reason for this is that in the case of the pigment method, it is technically impractical to completely cover the surface of the phosphor, and it is also not advisable in terms of the performance of the color picture tube.

On the other hand, according to Japanese Patent Application Laid-Open No. 55-65286, a method of forming a silica coating on the surface of the phosphor has been proposed, but in this method, the silica film is not thick enough to sufficiently suppress surface reflection. Therefore, it was not possible to obtain a sufficiently satisfactory reduction in external light reflectance.

[Purpose of the invention]

An object of the present invention is to improve surface reflection by forming a silica film of an appropriate thickness on the surface of a phosphor, and to obtain a cathode ray tube having low external light reflectance and high contrast.

[Summary of the invention]

In the present invention, a phosphor coated with silica is used, and the amount of silica coated on the phosphor is adjusted to 100 parts by weight of the phosphor.
By setting the amount to 1.0 parts by weight to 15 parts by weight, a cathode ray tube with high contrast and low external light reflectance with suppressed reflection on the surface of the phosphor can be obtained.

[Embodiments of the invention]

Hereinafter, an embodiment in which the present invention is applied to a color picture tube will be described in detail.

The phosphor applied to the present invention has an average particle diameter of 3μ to 1μ.
5μ is preferable, and the surface of the phosphor has a thickness of 1μ to the phosphor.
．． A continuous coating of 0 to 15 parts by weight of amorphous silica is formed. Formation of such a film can be carried out, for example, by using the technique disclosed in Japanese Patent Publication No. 46-9555.

The average thickness of the silica layer for these phosphors of various particle sizes is 0.1μ or less, preferably 0.09μ to 0.1μ.
It has been found that when this is done, the surface reflection of the phosphor is reduced, and a color picture tube with low external light reflectance and high contrast can be obtained. This is presumed to be due to the following reasons.

Now, when the refractive index of the phosphor is n2, the refractive index of the silica film is n8, the film thickness is d1, and the wavelength of the incident light is λ, then nd-↓λ
−・(1) +1 4 n,=τ・−・・(2) (], ), f2) If the following conditions are satisfied, surface reflection of the pigment can be prevented. That is, if nl<n, reflection decreases, and if nl>n2, reflection increases. In particular, the reflected light becomes zero from n 1 ""4 to n, d, -"λ.For the - leg, condition (1) can be satisfied relatively easily, but condition (2) cannot be achieved. However, in the case of the present invention, n2 = 2.3 to 2.4, n
, = 1.46, it is possible to approximately satisfy equation (2).

On the other hand, when considering equation (1), to the naked eye, λ−0,
Since the light of 55μ is felt most strongly, the film thickness d must be determined so that the reflectance around λ-0, 55μ is the lowest. That is, from equation (1), d+=0.094μ does not hold. Therefore, if the model of the silica-coated pigment is a sphere, the ratio of silica]! -2,2, the specific gravity of the phosphor = 4.1, so when the pigment diameter is -2X and the silica coating weight % = y, then Y = 0.37X-"[(X+0.094)"- X”)
=...= It is expressed as (3). The average particle diameter of the phosphor used in the present invention is preferably 3 μm to 15 μm, and from equation (3), the amount of silica coated is 2.0% by weight. If the average particle diameter is 3.0 μ or less, the dispersibility is poor.
If a phosphor with a diameter of 15.0 μm or more is used, the quality of so-called filming for forming a metal thin film performed after the phosphor layer is formed is undesirable. The preferred average particle size of the phosphor is 4 μ to 10 μ, and from equation (3), the amount of silica coated in this case is 3.0% by weight to 8.0% by weight.

Specific examples of the present invention will be described below.

Blue, Green, and Red phosphors having an average particle size of 7.0 μ and coated with 4.6% by weight of silica are used to form the phosphor surface of a color picture tube in a conventional manner.

The white luminance of such a color picture tube (+27M at 9300°
The total cathode current required to make the white color of the PCD 32 fA' brighter = W) and external light reflectance (brightness of the tube surface when irradiated with a standard light source from an angle of 45 degrees above the tube surface) (measured in the horizontal direction and calculated as a ratio to a standard white plate) and compared with the white brightness and external light reflectance of a conventional color picture tube made with untreated phosphor. Light reflectance reduction -10 coefficient white brightness improvement +3 coefficient was obtained.

In the above embodiments, the present invention is applied to a color picture tube, but it goes without saying that the present invention can also be applied to other cathode ray tubes such as a sheep color tube.

〔Effect of the invention〕

As described above, according to the present invention, a color picture tube with higher brightness and contrast than conventional cathode ray tubes can be obtained by preventing surface reflection on the surface of the phosphor.

Claims (2)

[Claims] (1) A phosphor with a phosphor surface that emits light upon cathode ray stimulation is coated with silica, and the amount of coated silica is 1.0 parts by weight to 15 parts by weight per 100 parts by weight of the phosphor. A cathode ray tube characterized by: (2) The cathode ray according to claim 1, characterized in that the average particle size of the phosphor is 3 μ to 15 μ and the thickness of the silica layer covering the phosphor is 0.1 μ or less. tube.