JP2012162697A - White phosphor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a white phosphor capable of maintaining the hue of the light-emitting color to be the natural daylight color even when a light emission intensity ratio of a blue phosphor with respect to other phosphors is reduced and the color temperature falls by irradiation with an electron beam.SOLUTION: The white phosphor includes a red phosphor including at least one compound selected from YO:Eu and YOS:Eu, a green phosphor including at least one compound selected from YAlO:Tb and Y(Al, Ga)O:Tb, and the blue phosphor including at least one compound selected from ZnS:Ag, Al, ZnS:Ag, Cl and ZnS:Ag, Al, Cl. The white phosphor contains 50-60 wt.% of the blue phosphor based on the total weight, and the weight ratio between the green phosphor and the red phosphor (the weight of the green phosphor/the weight of the red phosphor) is 0.5-2.0, and an average particle diameter of the particles constituting the red phosphor, the green phosphor and the blue phosphor is 3-15 μm.

Description

The present invention relates to a white phosphor, and more particularly to a field emission light source (hereinafter referred to as FEL) using a white phosphor.

In general, the emission of an electron beam excited (cathode luminescence) phosphor has a bias in the emission wavelength, and white light cannot be generated by a single phosphor. For this reason, in order to obtain white light, it is necessary to mix emission from a plurality of phosphors. In a cathode ray tube of a TV, a red phosphor (R) corresponding to the three primary colors of light, a green phosphor (G), and The white light is displayed by mixing the light emission from the three types of phosphors of the blue phosphor (B).

As a field electron emission type light source for generating white light, it is desirable to produce white light by mixing phosphors for cathode ray tubes from the viewpoint of luminous efficiency and color rendering.

As phosphors for cathode-ray tubes, ZnS: Ag, Cl is used as a blue phosphor for general televisions, ZnS: Cu, Al is used as a green phosphor, and Y ₂ O ₂ S: Eu is used as a red phosphor. Is used. On the other hand, as a phosphor for projection television that requires a higher heat-resistant temperature and a larger amount of light than a CRT for general television, ZnS: Ag, Al which is a sulfide phosphor is used as a blue phosphor, and a green phosphor. Y ₃ Al ₅ O ₁₂ : Tb or Y ₃ (Al, Ga) ₅ O ₁₂ : Tb, which is a YAG phosphor, is used, and Y ₂ O ₃ : Eu, which is an yttrium oxide phosphor, is used as a red phosphor. Since phosphors are used, green phosphors and red phosphors that are not sulfides are characterized by higher durability than phosphors for general televisions.

Therefore, since white FEL is required to have higher luminance than a cathode ray tube, it is desirable to produce a white phosphor using a phosphor for projection television.
As for the emission color, the daylight color, the daylight white, the white, the warm white of the JIS standard (JIS Z 9112, (1990) “Classification according to the light source color and color rendering property of the fluorescent lamp”) established for general fluorescent lamps. The light emission color preferably corresponds to one of the light bulb colors, and has coordinates belonging to a category defined by the JIS standard.

However, in projection television phosphors, the blue phosphor ZnS phosphor has higher luminous efficiency than the YAG phosphor, which is a green phosphor, and the yttrium oxide phosphor, which is a red phosphor. Susceptible to quenching.

For this reason, when producing a FEL phosphor by mixing phosphors for projection televisions, if the mixing ratio is determined based on the initial state of light emission, the emission intensity of the blue phosphor changes to other colors as the temperature rises. Therefore, the chromaticity coordinates of the white light may change greatly, and may deviate from the white light region of the fluorescent lamp defined by the JIS standard.

In addition, since the ZnS phosphor is inferior to the YAG phosphor and the yttrium oxide phosphor in terms of durability, the chromaticity of the light emission changes due to long-term use, which deviates from the JIS definition range. There was a thing.

The present invention has been made in view of the above problems. When an electron beam is irradiated, the color temperature decreases as the emission intensity ratio of the blue phosphor to the other phosphor decreases with the passage of time. Another object of the present invention is to provide a white phosphor capable of maintaining the color of the luminescent color in a natural daylight color.

In order to achieve the above object, the white phosphor of the present invention comprises:
A red phosphor containing at least one compound of Y ₂ O ₃ : Eu and Y ₂ O ₂ S: Eu,
A green phosphor containing at least one compound of Y ₃ Al ₅ O ₁₂ : Tb and Y ₃ (Al, Ga) ₅ O ₁₂ : Tb, and
A phosphor comprising a blue phosphor containing ZnS: Ag, Al, ZnS: Ag, Cl, and at least one compound of ZnS: Ag, Al, Cl,
The blue phosphor is contained in an amount of 50 to 60% by weight based on the total weight,
The weight ratio of the green phosphor and the red phosphor (the weight of the green phosphor / the weight of the red phosphor) is 0.5 to 2.0,
The average particle diameter of the particles constituting the red phosphor, the green phosphor and the blue phosphor is 3 to 15 μm.

In the phosphor constituting the white phosphor, for example, “ZnS: Ag, Cl” means a phosphor containing ZnS and Ag as essential components and selectively containing Cl. For example, “ZnS: Ag, Al, Cl” means a phosphor containing ZnS and Ag as essential components and selectively containing Al and Cl. That is, the phosphor includes the element described first in parentheses as an essential component and selectively includes other elements in the parentheses.

Since the white phosphor contains 50% by weight or more of the blue phosphor, when the electron beam is irradiated, the emission intensity of the blue phosphor becomes smaller as compared with other colors as the temperature rises, or as time passes. Even if the emission intensity of the blue phosphor is reduced compared to other colors, the effect is small, and the red, green and blue phosphors can maintain the color of the emitted color in a natural daylight color. It is.
Further, since the content of the blue phosphor is within 60% by weight, even if the content of the blue phosphor is not too much and the chromaticity of the light emission changes due to long-term use, the daylight color defined in JIS Z 9112 Can be kept in the range of white, white, warm white, light bulb color.

If the content of the blue phosphor is less than 50% by weight, the content of the blue phosphor is small. Therefore, if the emission intensity of the blue phosphor decreases as the temperature rises or the time elapses, the effect is large and the light emission It becomes difficult to maintain the color shade in a natural daylight color.
Further, when the content of the blue phosphor exceeds 60% by weight, the content of the blue phosphor is too large, so that even if the emission intensity of the blue phosphor decreases as the temperature rises or the time elapses, the blue phosphor The influence of the body is large, and it is difficult to make the color of the luminescent color a natural daylight color.

Further, since the weight ratio of the green phosphor and the red phosphor (the weight of the green phosphor / the weight of the red phosphor) is 0.5 to 2.0, the green phosphor and the red phosphor can be balanced. (Within the range of chromaticity coordinate points Y and Z in FIG. 1 to be described later), and by adding a blue phosphor thereto, white light can be obtained after a predetermined time has elapsed.
If the weight ratio of the green phosphor and the red phosphor is out of the above range, the balance between the green phosphor and the red phosphor is lost, and therefore, when a predetermined time elapses, the light emission is outside the white light range. .

In the white phosphor of the present invention, since the average particle diameter of the particles constituting the red phosphor, the green phosphor and the blue phosphor is 3 to 15 μm, the density of the coating film to be formed is kept high to some extent. In addition, it is possible to suppress a decrease in luminous efficiency.

In the white phosphor of the present invention, when the chromaticity coordinate point of the initial light emission when irradiated with an electron beam is displayed as the coordinate on the CIE1931 chromaticity diagram, the chromaticity coordinate point B (0.14˜ 0.17, 0.024 to 0.07), the chromaticity coordinate point P (0.327, 0.367) and the chromaticity coordinate point Q (0.475, 0.428) are linearly connected. It is desirable to exist inside the formed triangle PBQ.

The CIE 1931 chromaticity diagram is a chromaticity diagram defined by the CIE (International Commission on Illumination), in which the color of light is displayed in xy plane coordinates. Daylight color, daylight white color, white color, warm white color, and light bulb color specified in JIS Z 9112 can also be displayed on the CIE1931 chromaticity diagram.

If the chromaticity coordinate point of the initial light emission when the electron beam is irradiated is inside the triangle PBQ described above, the temperature of the phosphor increases when the electron beam from the field electron-emitting device is irradiated, Even if the emission of the blue phosphor is reduced as time passes, the emission color is less likely to deviate from the daylight trajectory, and white light that is natural to humans can be obtained.
The initial light emission when irradiated with an electron beam refers to light emission within 30 minutes after the start of electron beam irradiation.

Since the white phosphor of the present invention is configured as described above, even if the emission of the blue phosphor is reduced by long-term use, the emission color is less deviated from the daylight trajectory and the emission by the FEL. Can be natural white light for humans, and the product durability of FEL can be improved.

FIG. 1 shows points on the CIE1931 chromaticity diagram of blue phosphor ZnS: Ag, Al, green phosphor Y ₃ (Al, Ga) ₅ O ₁₂ : Tb, red phosphor Y ₂ O ₃ : Eu, and JIS Z 9112 is a graph showing divisions on the chromaticity diagram of daylight color, day white color, white color, warm white color, and light bulb color defined by 9112 1990. FIG. 2 is a graph showing changes in luminance and color temperature of the white phosphor obtained in Example 1 over time. FIG. 3 is a graph showing changes in the CIE1931 chromaticity diagram over time of the white phosphor obtained in Example 1. FIG. 4 is a graph showing changes on the CIE 1931 chromaticity diagram over time of the white phosphor obtained in Comparative Example 1.

(First embodiment)
Hereinafter, an embodiment of the white phosphor of the present invention will be described with reference to the drawings.
The white phosphor of the present invention is a red phosphor containing at least one compound of Y ₂ O ₃ : Eu and Y ₂ O ₂ S: Eu,
A green phosphor containing at least one compound of Y ₃ Al ₅ O ₁₂ : Tb and Y ₃ (Al, Ga) ₅ O ₁₂ : Tb, and
A phosphor comprising a blue phosphor containing ZnS: Ag, Al, ZnS: Ag, Cl, and at least one compound of ZnS: Ag, Al, Cl,
The blue phosphor is contained in an amount of 50 to 60% by weight based on the total weight,
The weight ratio of the green phosphor and the red phosphor (the weight of the green phosphor / the weight of the red phosphor) is 0.5 to 2.0,
The average particle diameter of the particles constituting the red phosphor, the green phosphor and the blue phosphor is 3 to 15 μm.

FIG. 1 shows points on the CIE1931 chromaticity diagram of blue phosphor ZnS: Ag, Al, green phosphor Y ₃ (Al, Ga) ₅ O ₁₂ : Tb, red phosphor Y ₂ O ₃ : Eu, and JIS Z 9112 is a graph showing divisions on the chromaticity diagram of daylight color, day white color, white color, warm white color, and light bulb color defined by 9112 1990.

According to Grassmann's law in additive color mixture, the mixed light of the light emission of the red phosphor whose coordinates on the CIE 1931 chromaticity diagram (hereinafter also simply referred to as chromaticity diagram) and the light emission of the green phosphor whose point is G The coordinates on the chromaticity diagram are on the line segment X connecting the point R and the point G, and various color mixing can be performed on the line segment X by changing the mixing amount.

Finally, white light is produced by adding the light emission of the blue phosphor to the mixed color light of the light emission of the red phosphor and the light emission of the green phosphor. The three kinds of mixing are performed in such a way.
That is, when the mixed composition of the phosphor is mixed with only the green phosphor and the red phosphor, the point on the chromaticity coordinate of the emission of the phosphor is the point B on the chromaticity diagram of the blue phosphor and the light source color classification Green phosphor so that it is in a range (between the points Y and Z on the line segment X) divided by ∠PBQ passing through the point P that is the end point of the light source and the point B that is the end point of the light source color classification And red phosphor are mixed. Further, by adding a blue phosphor to the mixture, the chromaticity coordinates of light emission in the initial light emission stage of the three kinds of white phosphors can be within the triangular region PQB.

When the points P and Q are displayed in coordinates on the chromaticity diagram, they become a chromaticity coordinate point P (0.327, 0.367) and a chromaticity coordinate point Q (0.475, 0.428).
The range delimited by ∠PBQ is because there is a high possibility that the change in the chromaticity diagram over time of the three types of mixed white phosphors will move within the range of the angle of ∠PBQ. is there.

Although the chromaticity coordinate point B varies depending on the type of phosphor, in order for light emission to fall within the range of white white and white when a long time has elapsed, the chromaticity coordinate point B (0.14 to 0.17, 0.024 to 0.07) is preferred.

At this time, the weight of the green phosphor and the red phosphor is used in order to create mixed color light of the red phosphor and the green phosphor so as to be between the points Y and Z on the line segment X. The ratio (weight of the green phosphor / weight of the red phosphor) is preferably 0.5 to 2.0.
Moreover, it is preferable to adjust the mixing amount so that the blue phosphor contains 50 to 60% by weight with respect to the total weight.

The phosphors mixed in such a manner have chromaticity coordinate points at the initial stage of light emission, which are daylight color, daylight white, and JIS standard (JIS Z 9112 1990 “classification according to light source color and color rendering properties of fluorescent lamp”). It is located on the lower left side in the chromaticity coordinates from any of white, warm white, and bulb color. However, blue phosphors belonging to ZnS phosphors are more susceptible to temperature quenching than YAG phosphors and yttrium oxide phosphors, and have a shorter lifetime, so that only red and green phosphors gradually emit light. It moves linearly toward the chromaticity coordinates.

With regard to the luminance reduction due to temperature quenching and lifetime in the emission of this blue phosphor, the luminance change after the luminance has been reduced to a certain degree will be gradual, so the weight ratio of the blue phosphor is determined in anticipation of the luminance reduction beforehand By doing so, it is possible to emit light stably in the daylight white, white, and other regions classified according to JIS standard Z9112 1990.

In addition, the slope of the chromaticity coordinate change due to the blue phosphor emission reduction can be adjusted by adjusting the chromaticity coordinates of the blue phosphor and the mixing ratio of the red phosphor and the green phosphor. By making the distance close to, it becomes possible to minimize the change in hue due to the reduced emission of the blue phosphor.
In the present invention, it is desirable to contain 50 to 60% by weight of the blue phosphor with respect to the total weight.

In addition, the smaller the particle diameter of the phosphor, the smaller the amount of the phosphor used when forming the phosphor layer, and the smaller the particle diameter, the higher the density of the formed coating film. . However, the larger the particle size, the higher the luminous efficiency. This is because there is a layer having a lower luminous efficiency than the inside on the surface of the phosphor, and in the case of small particles, the probability that the electron beam passes through the low-efficiency layer is high.

In the white phosphor of the present invention, since the average particle diameter of the particles constituting the red phosphor, the green phosphor and the blue phosphor is 3 to 15 μm, the density of the coating film to be formed is kept high to some extent. In addition, it is possible to suppress a decrease in luminous efficiency.
Luminous efficiency will fall that the average particle diameter of the particle | grains which comprise the said fluorescent substance is less than 3 micrometers. On the other hand, when the average particle diameter of the phosphor exceeds 15 μm, the luminous efficiency increases, but it becomes difficult to form a highly dense phosphor layer, and it becomes difficult to form a good coating film.

The production method of the white phosphor of the present invention is not particularly limited, and a spray coating method, a sedimentation method, a doctor blade method, and the like, which are conventionally applied to a slurry containing a phosphor, can be used. When using a sedimentation method, a doctor blade method, or the like, it is desirable that the slurry be well kneaded.

(Example)
Examples that more specifically disclose the first embodiment of the present invention will be described below. In addition, this invention is not limited only to these Examples.

Example 1
When producing a white phosphor for FEL for emitting in daylight and daylight, ZnS: Ag, Al (diameter intermediate value: 9.6 μm) as a blue phosphor and Y ₃ (Al, Ga) ₅ as a green phosphor O ₁₂ : Tb (median diameter: 7.2 μm) and Y ₂ O ₃ : Eu (median diameter: 8.2 μm) were used as the red phosphor. The median diameter is also called the average particle size.

The weight percentage with respect to the total weight is 51% by weight of the blue phosphor, 26.2% by weight of the green phosphor, and 22.8% by weight of the red phosphor, respectively, and the weight ratio of the green phosphor to the red phosphor (green phosphor). Weight / red phosphor weight) = 1.15, and this was mixed in a potassium water glass aqueous solution (Okaseal B, manufactured by Tokyo Ohka Kogyo Co., Ltd.) containing 100 g / L of potassium silicate to form a slurry. A fluorescent plate was prepared by spray coating.

(Measurement of change in emission spectrum of white phosphor over time)
Next, this fluorescent plate is excited and emitted by irradiating an electron beam from a field electron-emitting device in a vacuum in a vacuum, and the emission intensity and the change in the elapsed time of the spectrum are measured with a spectral luminance meter (Topcon manufactured by Topcon Corporation). Measurement was performed every 3 minutes using SR-3). The pulse current is applied by connecting a high-voltage switch from a DC high-voltage power supply output at a voltage of 6 kV to a field electron-emitting device, and driving the high-voltage switch at a repetition frequency of 500 Hz and an on / off ratio of 2%. Was pulsed. The electron beam irradiation density to the phosphor was 0.4 mA / cm ² when the high voltage switch was on.

FIG. 2 is a graph showing changes in luminance and color temperature of the white phosphor obtained in Example 1, and FIG. 3 shows changes in the CIE1931 chromaticity diagram over time of the white phosphor. It is a graph which shows.

As is clear from the graph shown in FIG. 2, the luminance and the color temperature are decreasing with the elapsed time. This indicates that the blue phosphor having a peak on the lower wavelength side in the emission spectrum is larger than the green phosphor and the red phosphor. In addition, with the passage of time, the light emission rate of the blue phosphor is gradually reduced, and the overall emission brightness and color temperature change gradually accordingly.

Further, as apparent from FIG. 3, since the emission intensity of the blue phosphor is high at the start of emission, the chromaticity x of the blue phosphor is close to x = 0.145 and y = 0.06 in the chromaticity diagram. , It was out of daylight. However, when the blue phosphor is weakened, it gradually moves toward the point on the chromaticity diagram determined by the emission intensity ratio of the green phosphor and the red phosphor, and emits light in the daylight color, day white, and white regions. It became so. After this, it is thought that it hardly moves.

(Comparative Example 1)
The weight percentage of each phosphor with respect to the total weight is changed to 51 wt% of blue phosphor, 37.5 wt% of green phosphor, and 11.5 wt% of red phosphor, respectively. A white phosphor was produced in the same manner as in Example 1 except that the weight ratio (green phosphor weight / red phosphor weight) was changed to 3.26, and the change in the emission spectrum of the white phosphor over time was changed. It was measured.

FIG. 4 is a graph showing the result, that is, the change over time on the CIE1931 chromaticity diagram.
In Comparative Example 1, since the weight ratio of the green phosphor and the red phosphor (green phosphor weight / red phosphor weight) is 3.26, as the blue phosphor becomes weaker as time passes, The daylight white color moved away from the white area, and the emission color was not white.

Claims (2)

A red phosphor containing at least one compound of Y ₂ O ₃ : Eu and Y ₂ O ₂ S: Eu,
A green phosphor containing at least one compound of Y ₃ Al ₅ O ₁₂ : Tb and Y ₃ (Al, Ga) ₅ O ₁₂ : Tb, and
A phosphor comprising a blue phosphor containing ZnS: Ag, Al, ZnS: Ag, Cl, and at least one compound of ZnS: Ag, Al, Cl,
Containing 50-60% by weight of the blue phosphor with respect to the total weight;
The weight ratio of the green phosphor and the red phosphor (the weight of the green phosphor / the weight of the red phosphor) is 0.5 to 2.0,
An average particle diameter of particles constituting the red phosphor, the green phosphor and the blue phosphor is 3 to 15 μm. When the chromaticity coordinate point of the initial light emission when the electron beam is irradiated is displayed as a coordinate on the CIE1931 chromaticity diagram, the chromaticity coordinate point B (0.14 to 0.17, 0.024 to 0.07) And a chromaticity coordinate point P (0.327, 0.367) and a chromaticity coordinate point Q (0.475, 0.428) are present inside a triangle PBQ formed by connecting them linearly. The white phosphor according to 1.

Images