JPH0320855B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a phosphor of a cathode ray tube in which a phosphor screen is formed by coating a mixed phosphor composed of two or more types of phosphors by a precipitation method. This invention relates to a method for manufacturing surfaces.

[Prior art]

The fluorescent surface of a cathode ray tube is required to have various characteristics depending on the use of the cathode ray tube. For this reason,
If there is no single phosphor that can meet these requirements, it is possible to form a phosphor surface using a mixture of several different phosphors to obtain a phosphor surface with characteristics that meet the required performance. It will be done.

As a specific example of such a mixed phosphor, for example, as shown on the chromaticity diagram in FIG.
0.295, y=0.608);
B (x = 0.630, y = 0.350) A mixed phosphor made by mixing a certain amount of a red-emitting B phosphor indicates C.
(x=0.450, y=0.480) yellow emission is obtained.

A method of forming a fluorescent surface using such a mixed phosphor by a sedimentation method will be explained with reference to FIG. First, as shown in A, after thoroughly cleaning the inner surface of the glass bulb 1, which is the vacuum envelope of the cathode ray tube,
The face plate 2, which constitutes a part of the glass bulb and has a phosphor layer formed on its inner surface, is placed facing downward, and a certain amount of an electrolyte solution 3 such as barium acetate is injected into the glass bulb 1. Next, as shown in b, A phosphor 5
A suspension liquid 6 in which a mixed phosphor of phosphor B and phosphor B 4 is well dispersed in an aqueous solution of water glass is injected into the glass bulb 1 containing the electrolyte solution 3 described in A above. Thereafter, as shown in (c), when the phosphors 4 and 5 are allowed to stand still for a while, they gradually settle down and are deposited on the face plate 2 of the glass bulb 1, where they undergo silicic acid polymerization with the face plate 2. After the phosphors 4 and 5 have almost completely settled down as shown in (d), the dispersion liquid is discharged, and as shown in (e), a phosphor layer 8 is formed on the inner surface of the face plate 2 of the glass bulb 1.
is formed. The phosphor layer 8 is fixed to the surface of the face plate 2 by silicic acid polymerization.

When coating a mixed phosphor by a precipitation method to form a fluorescent surface in this manner, the homogeneity of the phosphor layer 8 coated by a precipitation method is an important issue. Figure 3b shows a cross-sectional view of the fluorescent surface formed by the sedimentation method;
As is clear from the figure, the phosphor layer 8 of the phosphor screen coated by the sedimentation method is not homogeneous, with more B phosphor on the face plate 2 side, and conversely, A phosphor on the metal back film 10 side. It is formed with many distributed. When a cathode ray tube having such a non-uniform phosphor layer 8 is operated, a problem arises in that the color of the emitted light emitted by the electron beam 9 when the phosphor layer 8 is excited varies depending on the excitation conditions. That is, when the phosphor layer 8 is excited by the electron beam 9, the depth x _p that the electron beam 9 penetrates into the phosphor layer 8 is determined by _TERILL 's formula (x _p = αV ² V: acceleration voltage of the electron beam ), but in the case shown in FIG. 3b, the ratio of both A and B phosphors changes in the depth direction of the phosphor layer 8, so that the acceleration voltage V of the electron beam 9 during cathode ray tube operation changes. This causes a problem in that the color of the emitted light changes. On the other hand, in the case shown in a of FIG. 3, in the depth direction of the phosphor layer 8,
Since the ratio of both AB fluorophores does not change and is homogeneous, the emission color does not vary depending on the excitation conditions.

[Summary of the invention]

This invention deals with the instability of emitted light color due to non-uniformity of the phosphor layer that occurs when a mixed phosphor composed of two or more types of phosphors is applied by a precipitation method to form a phosphor surface. This was done in view of the problem of
The object of the present invention is to provide a method for producing a fluorescent surface that can obtain a homogeneous phosphor layer whose emission color does not vary depending on excitation conditions even in the case of a fluorescent surface using mixed phosphors.

[Embodiments of the invention]

When a fluorescent surface is formed using a mixed phosphor by a precipitation method, the formed phosphor layer 8 becomes non-uniform because of the following reasons.
It is thought that the main cause is that there is a difference in the sedimentation speed of each component phosphor in the phosphor sedimentation process shown in FIG. 2C. The average particle diameter is several microns like fluorescent material.
In the case of microparticles with a size of approximately 20 μm to 20 μm, the sedimentation velocity in a liquid is given by the equation S _TOKES . That is, ν=1/18(ρ−ρ ₀ )g/ηd ² ∝(ρ−1)d ² ν: Sedimentation velocity ρ: Specific gravity of particle η: Viscosity resistance of liquid g: Acceleration of weight ρ ₀ : Specific gravity of liquid d: Particle diameter.

Therefore, if the sedimentation speeds ν _A and ν B of each component phosphor of a mixed phosphor consisting of two types of phosphors A and _B are made approximately the same, the phosphor layer 8 formed by sedimentation
becomes homogeneous as shown in Figure 3a. Therefore, (ρ _A −1) d ² _A = (ρ _B −1) d ² _B ρ _A : Specific gravity of A phosphor ρ _B : Specific gravity of B phosphor d _A : Average particle diameter of A phosphor d _B : If (d _A , d _B ) are selected so as to satisfy the average particle diameter of the B phosphor, it is possible to obtain a phosphor layer in which both the A and B phosphors are homogeneously mixed.

Although the above embodiments have described a mixed phosphor consisting of two types of component phosphors, A and B, the present invention is not limited to this. When obtaining Si=(ρi−1)d ² i If ρi is the specific gravity of each component phosphor, and di is the average particle diameter of each component phosphor, then if Si is approximately the same, a homogeneous mixed fluorophore can be obtained. It is possible to obtain a photolayer.

However, due to subtle variations in the specific gravity and particle size of each component phosphor, differences tend to occur in the Si values of each component phosphor to be mixed, so it is difficult to keep the Si value of each component phosphor constant. This is realistically difficult.

Therefore, in this invention, we conducted measurements on various mixed phosphors to determine the extent to which variation in the Si value of each component phosphor is allowed within the range of variation in the accelerating voltage of cathode ray tubes currently in general use. As a result, when the largest Si of each component phosphor is Smax and the smallest Si is Smin, (Smax/Smin) is
We have come to the conclusion that if the value is maintained at 1.5 or less, fluctuations in emitted light color can be sufficiently suppressed within the range of current acceleration voltage fluctuations of cathode ray tubes.

[Effects of the Invention] As described above, according to the present invention, when a mixed phosphor consisting of two or more types of phosphors is applied by a precipitation method to form a phosphor screen, the maximum Si content of each component phosphor is By setting the ratio (Smax/Smin) between the maximum value Smax and the minimum value Smin to 1.5 or less, regardless of the variation in the Si value of each component phosphor due to variation in specific gravity or average particle size,
A very high-quality phosphor screen for cathode ray tubes that can suppress fluctuations in emitted light color due to changes in accelerating voltage of currently commonly used cathode ray tubes within an acceptable range can be manufactured using a simple sedimentation method. It has the effect of making it possible.

[Brief explanation of the drawing]

Figure 1 is a chromaticity diagram showing an example of a mixed phosphor, Figure 2 A to E are diagrams showing a method of forming a phosphor using a mixed phosphor by the precipitation method, and Figure 3 a and b are sedimentation diagrams. FIG. 2 is a cross-sectional view of the fluorescent surface of a mixed phosphor coated by a method. 1... Glass bulb, 2... Face plate, 3... Electrolyte solution, 4... B phosphor, 5...
A phosphor, 6... Suspension liquid, 8... Fluorescent layer, 9... Electron beam, 10... Metal back film.
Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. Two or more types of phosphors selected to have specific gravity and average particle diameter that satisfy (ρi−1)di ² =Si, where ρi is the specific gravity of the phosphor and di is the average particle diameter. A method for manufacturing a phosphor screen for a cathode ray tube, in which a mixed phosphor consisting of phosphors is applied by a precipitation method to form a phosphor screen, in which the largest Si of each component phosphor is Smax, and the smallest Si is Smin
A method for manufacturing a phosphor screen for a cathode ray tube, characterized in that (Smax/Smin) is set to 1.5.