JPH10316965A - Red phosphor for cathode ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a red phosphor which has fundamental characteristics of a Y2 O3 :Eu phosphor, such as electric current saturation characteristics, temp. characteristics, and film baking characteristics, and which can improve unbalance between the cathode current and a cathode ray tube for blue or green color by mixing a Y2 O3 :Eu phosphor with a Ga2 O3 :Eu phosphor having a monoclinic crystal system. SOLUTION: This phosphor is prepd. by mixing a Ya2 O3 :Eu phosphor with a Ga2 O3 :Eu phosphor having a monoclinic crystal system, pref. in a ratio of (1:2)-(3:1). Pref., the Y2 O3 :Eu phosphor has a particle size larger than that of the Ga2 O3 :Eu phosphor; that of the former phosphor is pref. 4-10 μm, and that of the latter, pref. 2-8 μm. The Ga2 O3 :Eu phosphor having a monoclinic crystal system can be obtd. by heating a Ga2 O3 :Eu phosphor having a cubic crystal system at a high temp. (1,250 deg.C or highwer) followed by quenching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a red phosphor for a cathode ray tube, and more particularly to a red phosphor for a cathode ray tube which can improve the color reproducibility of a projection type cathode ray tube.

[0002]

2. Description of the Related Art As a projection type display device, three projection type cathode ray tubes coated with phosphors emitting blue, green and red are combined, and a display drawn on a phosphor screen of each of the cathode ray tubes is displayed by each cathode ray tube. There is a type in which an image is enlarged and projected on a screen by a projection lens installed on a front surface of a tube, and a single-color display projected on the screen is combined to perform color display.

Usually, in such a projection display device, the display drawn on the fluorescent screen of each cathode ray tube is magnified 10 times or more and projected onto a screen. Is less than 1/100 of the luminance on the phosphor screen of the cathode ray tube.

[0004] In order to make the display on the screen the brightness necessary for observation, a projection type cathode ray tube is required to be 200 mW / cm.
Inputs close to ² are required. In this case, as the phosphor screen, a phosphor that does not cause luminance saturation even at such a high input and does not cause luminance degradation due to heat generation at 60 to 100 ° C. due to the high input is required. Used is a Y ₂ O ₃ : Eu phosphor.

However, since the Y ₂ O ₃ : Eu phosphor has a peak wavelength of the emission spectrum of 611 nm, the emission color is close to orange, and the color tone of the display on the screen is narrow due to its color tone. There's a problem.

Conventionally, in order to widen the color reproduction range of the display on the screen, the Eu output of the Y ₂ O ₃ : Eu phosphor is increased, or the light output of the sub-peak wavelength is suppressed by adding a pigment. There is a proposal for improving the emission color. However, this Y ₂ O ₃ : Eu phosphor has a peak wavelength of the emission spectrum on the short wavelength side near green and has a low light output at the sub-peak wavelength. Therefore, even if the Eu concentration is increased, for example, the light output at the sub-peak wavelength is increased. The change in the emission color due to the change in the amount is small, and the peak wavelength does not change.

Further, a filter for cutting a short wavelength side of an emission spectrum is applied to the projection lens to improve a color reproduction range, or an interference filter is provided on a glass panel as a phosphor screen substrate to provide directivity to luminance. There is known a method of improving the luminance and the color gamut by providing the following. However, even in such a method, it is difficult to obtain a sufficient effect due to the problem of the peak wavelength of the emission spectrum of the phosphor described above. These methods are also expensive.

On the other hand, a Y ₂ O ₂ S: Eu phosphor used in a direct-view type cathode ray tube (color picture tube) has a good emission color, but has a very poor current saturation characteristic, and depends on temperature. Due to the temperature quenching phenomenon that reduces the brightness,
It cannot be used for a cathode ray tube requiring high brightness such as a projection type cathode ray tube.

Furthermore, the Y ₂ O ₃ : Eu phosphor has the following problem.

That is, at present, projection type cathode ray tubes include ZnS: Ag-based phosphor as a blue phosphor and Y ₂ SiO ₅ : Tb, LaOCl: Tb, and Y ₃ A as a green phosphor.
_{l 5 O 12: Tb, Y} 3 Al 3 Ga 2 O 12: Tb phosphor, etc. are used. The blue and green cathode ray tubes coated with such a phosphor and Y ₂ O ₃ : E as a red phosphor are used.
If a white display having a white color temperature of 6000 to 10000 ° C. is to be obtained on a screen by combining a red cathode ray tube coated with a u phosphor, the required luminance of the red phosphor is different from that of other blue and green phosphors. The current transfer (cathode current) of the cathode ray tube coated with the red phosphor (cathode ray tube for red) is less than half of that of the blue and green cathode ray tubes coated with the green phosphor. Become.

When the cathode current is unbalanced as described above, the resolution of the cathode ray tube is generally determined by the beam spot diameter of the focused electron beam on the phosphor screen. The larger the cathode current, the larger the beam spot diameter. Therefore, the beam spot diameter of the red cathode ray tube with a small cathode current becomes smaller than the beam spot diameter of the blue and green cathode ray tubes, and when white characters are displayed, the periphery of the characters becomes blue and green. Occurs. Further, the cathode ray tube for red has a smaller cathode current than the cathode ray tubes for blue and green, so that the cathode is less deteriorated even when used for a long time. Therefore, the color shift based on the difference in the life characteristics occurs, in which the color is initially adjusted so as to obtain a white display on the screen, and gradually changes to reddish.

[0012]

As described above, conventionally,
Combining three projection cathode ray tubes coated with phosphors that emit blue, green, and red light, the display drawn on the phosphor screen of each cathode ray tube is enlarged by an optical system installed in front of each cathode ray tube. A Y ₂ O ₃ : Eu phosphor is used for a phosphor screen of a red cathode ray tube of a projection type display device that projects on a screen.

However, with respect to this phosphor, (a) the color tone is poor, and the color reproduction range of the display on the screen is narrow. (B) The Eu concentration is increased, or the light output at the sub-peak wavelength is suppressed by adding a pigment. However, sufficient improvement effect cannot be obtained. (D) The required luminance of the Y ₂ O ₃ : Eu phosphor is other blue,
Because it is higher than the green phosphor, the current transfer of the red cathode ray tube is unbalanced with respect to the blue and green cathode ray tubes, and when displaying white characters, the surroundings of the characters are colored blue and green. Since the cathode current of the red cathode ray tube is smaller than that of the blue and green cathode ray tubes, color shift occurs due to the difference in life characteristics when used for a long time. Even if a filter is provided, there are problems that it is difficult to obtain a sufficient effect and the cost is high.

The present invention has been made to solve the above-mentioned problems, and maintains the basic characteristics of the Y ₂ O ₃ : Eu phosphor, such as current saturation characteristics, temperature characteristics, and film burning characteristics. It is another object of the present invention to obtain a red phosphor which can improve the imbalance of a cathode current with a cathode ray tube for green.

[0015]

The red phosphor for a cathode ray tube is made of a Y ₂ O ₃ : Eu phosphor and a monoclinic crystal.
a ₂ O ₃ : A mixture with an Eu phosphor.

The mixture ratio of the Y ₂ O ₃ : Eu phosphor and the Ga ₂ O ₃ : Eu phosphor having a monoclinic crystal form is in the range of 1: 2 to 3: 1.

The particle size of the Ga ₂ O ₃ : Eu phosphor is smaller than that of the Y ₂ O ₃ : Eu phosphor.

Further, the Y ₂ O ₃ : Eu phosphor has an average particle size of 4 μm to 10 μm, and is composed of a monoclinic crystal system Ga.
The average particle size of the ₂ O ₃ : Eu phosphor was set to 2 μm to 8 μm.

In addition, Ga made of a monoclinic crystal system
_{The 2} O ₃ : Eu phosphor was a phosphor obtained by rapidly cooling a cubic Ga ₂ O ₃ : Eu phosphor from high-temperature heating.

Further, Ga ₂ O composed of a monoclinic crystal system
₃ : The Eu phosphor was a phosphor obtained by rapid cooling from high-temperature heating by thermal plasma.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

The rare earth sesquioxide can be used as a phosphor by activating it. Its crystal form includes
There are three types: hexagonal, monoclinic and cubic.
Ga ₂ O ₃ is usually in a cubic form, but is known to change to a monoclinic form when rapidly cooled from a high temperature of 1250 ° C. or higher.

The Ga ₂ O ₃ : Eu phosphor, which is obtained by activating Ga ₂ O ₃ having a cubic form with Eu, has a peak wavelength of an emission spectrum of 611 nm similarly to the Y ₂ O ₃ : Eu phosphor. The emission color is close to orange. However, the cubic Ga ₂ O ₃ : Eu phosphor was heated to a high temperature by a high-frequency induction thermal plasma containing Ar gas as a main component, and the quenched phosphor was examined. As a result, the crystal structure became monoclinic. As a result, as shown in FIG. 1, the emission spectrum was found to be a deep red emission color having a peak wavelength of 623 nm. However, this monoclinic Ga ₂ O ₃
The Eu phosphor has a luminance of about 30 times that of Y ₂ O ₃ : Eu phosphor.
%, So it cannot be used alone.

Therefore, in this embodiment, Y ₂
O _3: Eu phosphor quenched from a high temperature as described above comprising a crystal system monoclinic obtained by Ga ₂ O _3: was a red phosphor by mixing Eu phosphor.

As described above, when the Y ₂ O ₃ : Eu phosphor is mixed with the Ga ₂ O ₃ : Eu phosphor composed of a monoclinic crystal system to form a red phosphor, the Y ₂ O ₃ : Eu phosphor is current saturation characteristics having, maintaining the temperature characteristics, such as a membrane burn characteristics, in particular Y ₂
O ₃ : Utilizing the luminance of the Eu phosphor to maintain the luminance to the extent that there is no practical problem, greatly improve the color tone, expand the color reproduction range of the red phosphor, and use it for the blue color constituting the projection display device. The imbalance of the cathode current of the green and red cathode ray tubes can be improved. As a result, there is no difference in beam spot diameter on the fluorescent screen of each cathode ray tube, and color bleeding when displaying white characters with a high current peak can be reduced. Further, the life characteristics of the respective cathode ray tubes are substantially the same, and the color shift caused by the difference in the life characteristics can be reduced.

[0026] That is, Y ₂ O _3: Eu consisting of phosphor and the crystal system monoclinic Ga ₂ O _3: The mixing ratio of the Eu phosphor 1: 2 to 3: 1 range, and Y ₂ O ₃ : Ga ₂ O ₃ consisting of a monoclinic crystal system with respect to the particle size of the Eu phosphor:
The particle size of the Eu phosphor is reduced, and preferably, Y ₂ O ₃ :
The average particle size of the Eu phosphor is 4 μm to 10 μm, and the average particle size of the monoclinic Ga ₂ O ₃ : Eu phosphor is 2 μm to 8 μm, and these Y ₂ O ₃ : Eu phosphors are The above effect can be maximized by mixing with a Ga ₂ O ₃ : Eu phosphor composed of an oblique crystal system.

Table 1 shows that the cubic Ga
Ga ₂ O ₃ : Eu composed of a monoclinic crystal system obtained by heating a ₂ O ₃ : Eu phosphor to a high temperature by high frequency induction thermal plasma containing Ar gas as a main component and then rapidly cooling it.
Phosphor, Y conventionally used in projection cathode ray tubes
₂ O ₃ : Eu phosphor and pigmented Y ₂ O ₂ S: Eu phosphor used in a direct-view cathode ray tube were each applied to a 7-inch projection cathode ray tube, and the result of comparison of luminance and emission spectrum was obtained. Is shown. FIG. 1 shows the emission spectrum distribution of the Ga ₂ O ₃ : Eu phosphor composed of the monoclinic crystal system, FIG. 2 shows the emission spectrum distribution of the Y ₂ O ₃ : Eu phosphor, and FIG. 5 shows the emission spectrum distribution of a Y ₂ O ₂ S: Eu phosphor.

[0028]

[Table 1] The phosphors were applied by applying 9 cc of 1.9% barium nitrate aqueous solution and 491 pure water to a 7-inch projection type cathode ray tube bulb.
cc, and 20 cc of a 25% water glass solution and pure water 18
A phosphor dispersion liquid in which 0 cc and a predetermined amount of a phosphor were uniformly stirred was injected, allowed to stand for 30 minutes to precipitate the phosphor, and after the supernatant was discharged, the attached phosphor was dried to form. .

The luminance shown in Table 1 indicates that the anode voltage was 32 kV,
The luminance at the center of the effective screen measured by changing the cathode current Ik to 200 μA, 1200 μA, and 3500 μA in an effective screen of 6 inches (122 × 91 mm ² ). The emission spectrum shown in Table 1 and the emission spectrum shown in FIGS. The distribution is a measurement result at a cathode current of 200 μA.

As shown in FIGS. 1 to 3 and Table 1,
The emission spectrum distribution of the Ga ₂ O ₃ : Eu phosphor composed of a monoclinic crystal system and the X and Y values of the emission spectrum are represented by Y ₂ O ₃ : Eu phosphor and Y ₂ O ₂ S with pigment:
It is close to the emission spectrum distribution of the Eu phosphor and is good as a red phosphor, but has a luminance of ₃ % of Y ₂ O ₃ : Eu phosphor.
It does not satisfy 0% and cannot be used alone because it is too low.

However, as shown in Table 2, the Ga ₂ O ₃ : Eu phosphor composed of this monoclinic crystal system was converted to Y ₂ O ₃ : E
When mixed with the u phosphor, the luminance of the Y ₂ O ₃ : Eu phosphor can be suppressed to a practical range and the color tone can be improved.

[0032]

[Table 2] That is, Ga ₂ O ₃ : Y to the Y ₂ O ₃ : Eu phosphor
If the mixture of Eu phosphors is small and the mixture of Ga ₂ O ₃ : Eu phosphors is less than 3: 1, the decrease in luminance is small, but
No improvement in color tone is observed, and no mixing effect appears. Conversely, if the Ga ₂ O ₃ : Eu phosphor mixture is more than 1: 2, the color tone will be good, but the brightness will be greatly reduced, making it impractical. Practically satisfy both luminance and color Y ₂ O _3: Eu phosphor and Ga ₂ O _3: mixing ratio of the Eu phosphor _{Y 2 O 3: Eu / Ga} 2 O 3: Eu is 1: 2
3: 1.

Regarding the particle size of the phosphor, the particle size of the Ga ₂ O ₃ : Eu phosphor is made smaller than that of the Y ₂ O ₃ : Eu phosphor in order to suppress a decrease in luminance due to the mixture of the two phosphors. Preferably, the average particle size of the Y ₂ O ₃ : Eu phosphor is 4
μm to 10 μm, whereas the average particle size of the Ga ₂ O ₃ : Eu phosphor composed of a monoclinic crystal system is 2 μm to 8 μm.
m is good.

[0034]

The red phosphor for a cathode ray tube is made of Y ₂ O ₃ : E.
u consists phosphor and monoclinic crystalline form Ga ₂ O _3: constituted by a mixture of Eu phosphor, also the Y ₂ O _3: Eu consisting of phosphor and monoclinic crystalline form Ga ₂ O _3: mixing ratio of the Eu phosphor is 1: 2 to 3: 1 range, also, Y ₂
O _3: Eu phosphor than the particle size Ga ₂ O _3: reduced towards the particle diameter of the Eu phosphor, and further, the Y ₂ O _3: Eu
The average particle diameter of the phosphor is 4 μm to 10 μm, and the average particle diameter of the Ga ₂ O ₃ : Eu phosphor composed of a monoclinic crystal system is 2 μm.
When the thickness is set to m to 8 μm, the current saturation characteristics, temperature characteristics, film burning characteristics, and the like of the Y ₂ O ₃ : Eu phosphor are maintained.
Utilizing the luminance of the ₂ O ₃ : Eu phosphor, the luminance can be maintained to the extent that there is no practical problem, and the color reproduction range of the red phosphor can be expanded. The imbalance of the cathode current of the cathode ray tube can be improved. As a result, there is no difference in beam spot diameter on the fluorescent screen of each cathode ray tube, and color bleeding when displaying white characters with a high current peak can be reduced. Further, the life characteristics of the respective cathode ray tubes are substantially the same, and the color shift caused by the difference in the life characteristics can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an emission spectrum distribution of a Ga ₂ O ₃ : Eu phosphor having a monoclinic crystal form.

FIG. 2 is a diagram showing an emission spectrum distribution of a Y ₂ O ₃ : Eu phosphor.

FIG. 3 is a diagram showing an emission spectrum distribution of a pigment-containing Y ₂ O ₂ S: Eu phosphor.

Claims (6)

[Claims] 1. A red phosphor for a cathode ray tube, comprising a mixture of a Y ₂ O ₃ : Eu phosphor and a Ga ₂ O ₃ : Eu phosphor composed of a monoclinic crystal system. 2. A mixture ratio of a Y ₂ O ₃ : Eu phosphor and a Ga ₂ O ₃ : Eu phosphor composed of a monoclinic crystal system is in a range of 1: 2 to 3: 1. The red phosphor for a cathode ray tube according to claim 1. 3. The particle size of Ga is larger than the particle size of Y ₂ O ₃ : Eu phosphor.
_{2. The} red phosphor for a cathode ray tube according to claim 1, wherein the ₂ O ₃ : Eu phosphor has a smaller particle diameter. 4. The Y ₂ O ₃ : Eu phosphor has an average particle size of 4 μm.
m to 10 μm, and a monoclinic crystal system Ga ₂ O
_{3. The} red phosphor for a cathode ray tube according to claim 3, wherein the average particle size of the Eu phosphor is 2 μm to 8 μm. 5. A monoclinic crystal system of Ga ₂ O ₃ : E.
_{2. The} red phosphor for a cathode ray tube according to claim 1, wherein the u phosphor is a phosphor obtained by rapidly cooling a cubic Ga ₂ O ₃ : Eu phosphor from high-temperature heating. 6. A monoclinic crystal system of Ga ₂ O ₃ : E.
6. The red phosphor for a cathode ray tube according to claim 5, wherein the u phosphor is a phosphor obtained by rapidly cooling from high-temperature heating by thermal plasma.