JP2868657B2 - Phosphor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam-excited phosphor suitable for a low-voltage driven display device or recording light source device.

[0002]

2. Description of the Related Art Self-activated ZnO phosphors that emit green light are known as phosphors that emit practically sufficient fluorescence when excited with an electron beam by applying a low voltage. This self-activation type Z
The nO phosphor is referred to as a so-called slow-electron-beam-excited phosphor, and is practically used, for example, for a fluorescent display tube because of its excellent conductivity, luminous efficiency, luminous threshold, and chemical stability. This fluorescent display tube is an electron tube having a triode structure, in which electrons emitted and accelerated from a filament excite a phosphor layer (film) on a counter electrode to emit light. Since it has better visibility than a light emitting device, it is evaluated as a display element of an information display device. For example, fluorescent display tubes are frequently used for digital or graph displays for consumer and home appliances such as televisions, videos, and CD players. In addition, applications or demands for in-vehicle use are expected due to good visibility and high reliability due to self-emission. By the way, in the case of use for in-vehicle use, since it is used under high illuminance of sunlight, high brightness display is required to secure required visibility. The emission luminance of the fluorescent display tube can be improved by increasing the accelerating voltage. However, the driving voltage must be changed to increase the accelerating voltage. Now.

On the other hand, in order to improve the luminous efficiency of the fluorescent display tube, attempts have been made to add an impurity element to the phosphor used, but no satisfactory results have yet been obtained.
In any case, not only for in-vehicle applications, but also for phosphors with high luminous efficiency that enable reduction of power consumption, are attracting attention.

[0004]

As described above, the self-activation type ZnO phosphor used in the fluorescent display tube still has a problem in light emission luminance. The present inventors have studied the effects of the added elements on the light emission mechanism of the self-activated ZnO phosphor in relation to the electron beam acceleration voltage, and have obtained the following findings. That is, since a non-light emitting layer called a dead layer exists on the phosphor surface as is well known, only electrons exceeding the light emission threshold voltage are effective excitation electrons. Therefore, in order to improve luminous efficiency, it is necessary to suppress generation of a non-light emitting layer. However, there are many factors that generate a non-light-emitting layer in the phosphor manufacturing process. For example, when exposed to a high temperature of 900 to 1100 ° C. in the firing process, many defects occur on the surface of the generated phosphor, and these defects are generated. Remain after cooling, resulting in a non-light emitting layer on the phosphor surface. Further, a mechanical defect in the sieving process after the baking may cause generation of a non-light emitting layer. That is, in order to improve the luminous efficiency of the phosphor under the slow electron beam excitation, it is necessary to develop a means for effectively suppressing or reducing the defect generation.

The present invention has been made in view of such circumstances, and has as its object to provide a self-activated ZnO-based phosphor exhibiting a high luminous intensity (luminous efficiency) suitable for a fluorescent display tube.

[0006]

Phosphor SUMMARY OF THE INVENTION The present invention has the general _{formula: (Zn w M x O y} S z) ( wherein, M is Lu, Hf, at least one selected from Ta and W element , W, x, y, and z are numbers greater than 0, and 0.9 ≦ w + x ≦ 1.1, 0.95 ≦ y + z ≦
1.05, 10 ⁻⁶ ≦ x + z ≦ 10 ⁻¹ ).

According to the present invention, as a result of repeated experiments for adding various elements to the ZnO phosphor to suppress the generation of surface layer defects, it was found that the combination and amount of certain kinds of additional elements were appropriately selected. Is based on the finding that the phosphor exhibits sufficient luminous efficiency as a low-speed electron beam-excited phosphor and also has improved excitation voltage characteristics.

[0008] The general formula _{(Zn w M x O y S} z) in the phosphor represented by, 0.9 ≦ w + x ≦ 1.1 , 0.95 ≦ y +
The reason for selecting z ≦ 1.05 is that, in any case, if the value is out of this range, coloring due to precipitation of a metal element or generation of oxygen defects occurs, not only lowering the luminous efficiency, but also reducing the firing atmosphere and This is because they are sensitive to changes in the firing temperature and tend to cause variations in characteristics. FIG. 1 illustrates the relationship between (w + x) and the emission intensity of the phosphor in the above general formula, where M = Ta, and the curve 1a is (y + z = 1.0).
0), curve 1b is (y + z = 0.98), curve 1c is (y + z = 0.98)
1.02). FIG. 2 illustrates the relationship between (y + z) and the emission intensity of the phosphor in the above general formula, where M = Ta, and the curve 2a shows (w + x = 1.0
0), curve 2b is (w + x = 0.95), curve 2c is (w + x = 0.95)
1.02). Further, the general formula (Z
n _w M _x O _y S _z ): 10 ⁻⁶ ≦
x + z ≦ 10 ⁻¹ ) is selected because the effect of coactivation cannot be obtained if x + z is out of this range. FIG. 3 shows that in the general formula, M = Ta, (w = 1−x), (y
= 1-z) shows the change in the emission intensity when emitting light at an electron beam excitation voltage of 0.1 KV. Is (z
= 0.2x), curve 3c is the case of (z = x), 10
^-6 is selected within the range of ≦ x + z ≦ 10 ^-1. In each figure, the luminous intensity is 100% of the luminous intensity of the conventional ZnO phosphor.
% Is the relative strength.

[0009]

The phosphor according to the present invention has a composition in which a heavy metal element for suppressing the generation of defects and a sulfur element for alleviating lattice distortion caused by the introduction of the heavy metal element are added to ZnO at a predetermined composition ratio. As a result, it exhibits high efficiency and excellent excitation voltage characteristics. In other words, by adding at least one of the heavy metal elements Lu, Hf, Ta, and W at the time of manufacturing the ZnO phosphor, the emission threshold voltage is significantly reduced, in other words, the excitation voltage characteristic is significantly improved. And the decrease in luminous efficiency, which is likely to occur with the addition of the heavy metal element, is entirely prevented or suppressed by the sulfur (S) element introduced. Figure 4 is the phosphor represented by the general formula _{(Zn w M x O y S} z), shows the relationship between the luminous efficiency and the kind of the activator, the straight line 4a is (w = 1.0, x = 0.0, y = 1.0, z = 0.0)
... Conventional example ..., curve 4b is (w = 0.959, x = 0.005, y = 1.0,
z = 0.0) Comparative example, curve 4c is (w = 0.959, x = 0.00)
5, y = 0.9999, z = 0.0001) This is the case of the present invention.

[0010]

Embodiments of the present invention will be described below.

Example 1 ZnO: 98.630 g, Ta ₂ O ₅ : 1.346 g, ZnS: 0.
[0237] Each of the starting materials was weighed as 0237 g, and charged into a ball mill, sufficiently pulverized and mixed. Next, this raw material mixture was placed in a quartz crucible, and 3% of hydrogen and 97% of nitrogen were used.
And calcined at 900 ° C for 3 hours in a weak reducing atmosphere. The fired product thus obtained was pulverized, further treated with water washing and the like, and the composition of the obtained phosphor was chemically analyzed. As a result, the phosphor had the composition shown by the following formula.

Zn _0.995 Ta _0.005 O _0.9998 S _{0.0002 The} phosphor was applied to a glass plate coated with a conductive film, and mounted on a triode made to simulate a fluorescent display tube to evaluate the light emission characteristics. That is, when excited at an acceleration voltage of 100 V, the emission intensity was 140% as compared with the case where the conventional ZnO phosphor was used.

Example 2 ZnO: 99.412 g, Ta ₂ O ₅ : 0.540 g, ZnS: 0.
0477 g was weighed as a starting material, and these were charged into a ball mill, sufficiently pulverized and mixed. Next, this raw material mixture was placed in a quartz crucible, and 3% of hydrogen and 97% of nitrogen were used.
In a weak reducing atmosphere at 1000 ° C. for 3 hours. The fired product thus obtained was pulverized, further treated with water washing and the like, and the composition of the obtained phosphor was chemically analyzed. As a result, the phosphor had the composition shown by the following formula.

[0014] was applied to Zn _0.999 Ta _0.002 O _0.9999 S _0.0004 glass plate coated with a conductive layer using the phosphor, Luminescent characteristics were evaluated by a fluorescent display tube mounted in triode electron tube created to mimic. That is, when excited at an acceleration voltage of 100 V, the emission intensity was 132% as compared with the case where the conventional ZnO phosphor was used.

Example 3 ZnO: 99.491 g, Ta ₂ O ₅ : 0.270 g, ZnS: 0.
239 g was weighed as a starting material, respectively, and these were charged into a ball mill, sufficiently pulverized and mixed. Next, this raw material mixture was placed in a quartz crucible, and 3% of hydrogen and 97% of nitrogen were used.
And calcined at 950 ° C for 3 hours in a weak reducing atmosphere. The fired product thus obtained was pulverized, further treated with water washing and the like, and the composition of the obtained phosphor was chemically analyzed. As a result, the phosphor had the composition shown by the following formula.

Zn _0.999 Ta _0.001 O _0.9999 S _{0.0002 The} phosphor was applied to a glass plate coated with a conductive film, and mounted on a triode made to simulate a fluorescent display tube to evaluate the light emission characteristics. That is, when excited at an acceleration voltage of 100 V, the emission intensity was 128% as compared with the case where the conventional ZnO phosphor was used.

Examples 4 and 5 ZnO: 98.763 g, Lu ₂ O ₃ : 1.214 g, ZnS: 0.
[0238] Each of the starting materials was weighed using 0238 g, and these were charged into a ball mill, sufficiently pulverized and mixed. Next, this raw material mixture was placed in a quartz crucible, and 3% of hydrogen and 97% of nitrogen were used.
In a weak reducing atmosphere at 1000 ° C. for 3 hours. The fired product thus obtained was pulverized, further treated with water washing and the like, and the composition of the obtained phosphor was chemically analyzed. As a result, the phosphor had the composition shown by the following formula.

Zn _0.995 Lu _0.005 O _0.9998 S _{0.0002 The} above-mentioned phosphor was applied to a glass plate coated with a conductive film, and the phosphor was mounted on a triode electron tube simulating a fluorescent display tube to evaluate the light emission characteristics. That is, when excited at an acceleration voltage of 100 V, the emission intensity was 132% as compared with the case where the conventional ZnO phosphor was used.

Under the same conditions and procedures except that the composition ratio was changed in the above, a phosphor having a composition represented by the following formula was obtained.

[0020] Zn _0.999 Lu _0.002 O _0.9999 S _0.0004 Evaluation of the emission characteristics under the same conditions as the use of the phosphor, compared to the case of using the conventional ZnO phosphor,
The emission intensity was 123%.

Examples 6, 7 ZnO: 98.742 g, HfO ₂ : 2.47 g, ZnS: 0.02
38 g were weighed as starting materials, respectively, and these were charged into a ball mill, sufficiently pulverized and mixed. Next, this raw material mixture was placed in a quartz crucible and fired at 1000 ° C. for 3 hours in a weak reducing atmosphere of 3% hydrogen and 97% nitrogen. The fired product obtained in this way is crushed and further treated with water washing and the like,
When the composition of the obtained phosphor was chemically analyzed, the composition was as shown by the following formula.

Zn _0.995 Hf _0.005 O _0.9998 S _{0.0002 The} phosphor was applied to a glass plate coated with a conductive film, and mounted on a triode made to simulate a fluorescent display tube to evaluate the light emission characteristics. That is, when excited at an acceleration voltage of 100 V, the emission intensity was 130% as compared with the case where the conventional ZnO phosphor was used.

Under the same conditions and procedures except that the composition ratio was changed in the above, a phosphor having a composition represented by the following formula was obtained.

The emission characteristics of this phosphor were evaluated under the same conditions as described above using Zn _0.999 Hf _0.002 O _0.9999 S _0.0004. As compared with the conventional ZnO phosphor,
The emission intensity was 125%.

Examples 8, 9 ZnO: 98.565 g, WO ₃ : 1.411 g, ZnS: 0.0237
g was weighed as a starting material, and these were charged into a ball mill, sufficiently pulverized and mixed. Next, this raw material mixture was placed in a quartz crucible and fired at 1000 ° C. for 3 hours in a weak reducing atmosphere of 3% hydrogen and 97% nitrogen. The fired product thus obtained was pulverized, further treated with water washing and the like, and the composition of the obtained phosphor was chemically analyzed. As a result, the phosphor had the composition shown by the following formula.

Zn _0.995 W _0.005 O _1.0 S _{0.0002 The} above-mentioned phosphor was applied to a glass plate coated with a conductive film, and the phosphor was mounted on a triode electron tube simulating a fluorescent display tube to evaluate the light emission characteristics. That is, when excited at an acceleration voltage of 100 V, the emission intensity was 124% as compared with the case where the conventional ZnO phosphor was used.

Under the same conditions and procedures except that the composition ratio was changed in the above, a phosphor having a composition represented by the following formula was obtained.

The emission characteristics of this phosphor were evaluated under the same conditions as above using Zn _0.999 W _0.002 O _1.0 S _0.0004 .
The emission intensity was 118%.

Embodiments 10 to 13 According to the case of Embodiment 1 and the like, ZnO, Ta
₂ O ₅ , Lu ₂ O ₃ , HfO ₂ , WO ₃ , and ZnS were weighed at a predetermined composition ratio, and they were charged into a ball mill, and sufficiently pulverized and mixed. Next, this raw material mixture was placed in a quartz crucible and fired at 1000 ° C. for 3 hours in a weak reducing atmosphere of 3% hydrogen and 97% nitrogen. The fired product thus obtained was pulverized, further treated with water washing and the like, and the composition of the obtained phosphor was chemically analyzed. As a result, the phosphor had the composition shown by the following formula.

Zn _0.996 Ta _0.002 Lu _0.002 O _0.9999 S _0.0001 Example 10 Zn _0.996 Ta _0.002 Hf _0.002 O _0.9999 S _0.0001 Example 11 Zn _0.996 Ta _0.002 W _0.002 O _1.0 S _0.0001 Example 12 Zn _0.996 Lu _0.002 Hf _0.002 O _0.9999 S _0.0001 Example 13 These phosphors were applied to a glass plate coated with a conductive film.
The device was mounted on a triode electron tube simulating a fluorescent display tube, and the emission characteristics were evaluated. That is, when excited at an acceleration voltage of 100 V, the emission intensity was 133% in Example 10, 129% in Example 11, and 120% in Example 12 as compared with the case where the conventional ZnO phosphor was used. %, 12 in Example 13
1%.

In the above-mentioned embodiment, T
Although a, Lu, Hf, W and the like are used in the form of oxides, these metal elements can of course be used in the form of other compounds.

[0032]

As can be seen from the above description, the phosphor according to the present invention has improved voltage characteristics without lowering the emission intensity due to the co-activating effect of the heavy metal element and sulfur. At the same excitation voltage as compared to the phosphor, it exhibits a significantly improved emission intensity. Therefore, even when used under high illuminance, such as in-vehicle use, high-luminance display is possible. In addition, since the phosphor according to the present invention has essentially high luminous efficiency, there is an advantage that it contributes to reduction of power consumption.

[Brief description of the drawings]

FIG. 1 is a curve diagram showing an example of the relationship between the composition ratio of a phosphor according to the present invention and emission intensity.

FIG. 2 is a curve diagram showing another example of the relationship between the composition ratio of the phosphor according to the present invention and the emission intensity.

FIG. 3 is a curve diagram showing still another example of the relationship between the composition ratio of the phosphor according to the present invention and the emission intensity.

FIG. 4 is a curve diagram showing acceleration voltage dependence of a phosphor according to the present invention in comparison with a conventional phosphor and the like.

[Explanation of symbols]

 None

Claims (1)

(57) [Claims] 1. A general formula: _{(Zn w M x O y S} z) ( wherein, M is Lu, Hf, at least one element selected from Ta and W, w, x, y, any z is A number greater than 0 and 0.9 ≦ w + x ≦ 1.1, 0.95 ≦ y + z ≦
1.05, 10 ⁻⁶ ≦ x + z ≦ 10 ⁻¹ )).