JPH05163489A - Fluorescent substance - Google Patents

Abstract

PURPOSE:To obtain an electron ray excited fluorescent substance suitable for constituting a display device of low-voltage drive and a light source device for recording, comprising elements of Lu, Hf, Ta or/and W besides Zn, O and S, having a specific composition. CONSTITUTION:The objective composition consisting of a composition of the formula (M is Lu, Hf, Ta or W; (w), (x), (y) and (z) are numbers larger than 0, satisfying 0.9<=w+x<=1.1, 0.95<=y+z<=1.05 and 10<-6=w+y<=10<-1>).

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A self-activating ZnO phosphor that emits green light is known as a phosphor that emits fluorescence practically sufficient when excited by an electron beam by applying a low voltage. This self-activated Z
The nO phosphor is called a so-called low-speed electron beam excitation phosphor, and is excellent in conductivity, light emission efficiency, light emission threshold value, and chemical stability, so that it is practically used for a fluorescent display tube, for example. This fluorescent display tube is an electron tube having a triode structure, in which electrons emitted / accelerated from a filament excite a phosphor layer (film) on the counter electrode to emit light, and are not used in liquid crystal display devices. Since the visibility is better than that of a light emitting device, it is evaluated as a display element of an information display device. For example, fluorescent display tubes are often used for digital or graphic displays for consumer / home appliances such as televisions, video players, and CD players. In addition, due to the good visibility and high reliability due to self-luminous emission, there are expectations for in-vehicle use or demand. By the way, since it is used under high illuminance of sunlight when used for vehicles, high-brightness display is required to secure the required visibility. The improvement of the light emission brightness of the fluorescent display tube can be achieved by increasing the acceleration voltage, but the driving voltage must be changed to increase the acceleration voltage, which causes complicated problems in the device configuration and the like. Nau.

On the other hand, in order to improve the luminous efficiency of the fluorescent display tube, it has been attempted to add an impurity element to the phosphor to be used, but a sufficient result has not been obtained yet.
In any case, a fluorescent substance with high luminous efficiency that can reduce power consumption is attracting attention not only for in-vehicle applications.

[0004]

The self-activated ZnO phosphor used in the fluorescent display tube still has a problem in the emission brightness as described above. The present inventor studied the influence of the additional element on the light emission mechanism of the self-activated ZnO phosphor in relation to the electron beam accelerating voltage, and obtained the following findings. That is, since there is a non-light emitting layer called a dead layer on the surface of the phosphor as is well known, only electrons exceeding the light emission threshold voltage become effective excitation electrons. Therefore, in order to improve the light emission efficiency, it is necessary to suppress the generation of the non-light emitting layer. However, there are many factors that generate the non-emissive layer in the phosphor manufacturing process. For example, if the phosphor is exposed to a high temperature of 900 to 1100 ° C during the firing process, many defects are generated on the surface of the generated phosphor. Remains after cooling, resulting in a non-emissive layer on the phosphor surface. In addition, mechanical defects in the sieving step after firing may cause the non-emissive layer to be formed. That is, in order to improve the luminous efficiency of the phosphor under the low-speed electron beam excitation, it is necessary to develop means for effectively suppressing or reducing the defect generation.

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

[0006]

The phosphor of the present invention has a general formula: (Zn _w M _x O _y S _z ) (wherein M is at least one element selected from Lu, Hf, Ta and W). , W, x, y, z are all 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, various elements are added to the ZnO phosphor to carry out experiments to suppress the generation of surface layer defects, and as a result, the combination and addition amount of certain additive elements are appropriately selected. This is based on the finding that the phosphor exhibits sufficient emission efficiency as a slow electron beam excited phosphor and also improves the excitation voltage characteristic.

In the phosphor represented by the above general formula (Zn _w M _x O _y S _z ), 0.9 ≦ w + x ≦ 1.1, 0.95 ≦ y +
In each case, z ≦ 1.05 is selected, and in any case outside this range, not only the precipitation due to the metal element or the generation of oxygen defects causes coloring, but the luminous efficiency is deteriorated. This is because it is sensitive to changes in the firing temperature and tends to cause variations in characteristics. FIG. 1 shows an example of the relationship between (w + x) and the emission intensity of the phosphor, where M = Ta in the above general formula, and the curve 1a shows (y + z = 1.0).
0), curve 1b (y + z = 0.98), curve 1c (y + z =
The case of 1.02) is shown respectively. Further, FIG. 2 shows an example of the relation between (y + z) and the emission intensity of the phosphor, where M = Ta in the above general formula, and the curve 2a shows (w + x = 1.0).
0), the curve 2b is (w + x = 0.95), and the curve 2c is (w + x =
The case of 1.02) is shown respectively. Furthermore, the general formula (Z
In the phosphor represented by n _w M _x O _y S _z , 10 ⁻⁶ ≦
The reason why x + z ≦ 10 ⁻¹ ) is selected is that if x + z is out of this range, the effect of co-activation cannot be obtained. FIG. 3 shows that in the general formula, M = Ta, (w = 1-x), (y
= 1-z), the change in emission intensity when the phosphor is made to emit light with an electron beam excitation voltage of 0.1 KV is shown. Curve 3a shows the case of (z = 0.05x) and curve 3b Is (z
= 0.2x) and the curve 3c is (z = x)
It is selected within the range of ^-6 ≤ x + z ≤ 10 ^-1 . In each figure, the emission intensity is 100% that of the conventional ZnO phosphor.
It is the relative intensity as%.

[0009]

The phosphor according to the present invention has a composition in which a heavy metal element that suppresses defect formation and a sulfur element that relaxes lattice strain caused by the introduction of the heavy metal element are added to ZnO at a predetermined composition ratio. Thus, it exhibits high efficiency and excellent excitation voltage characteristics. That is, among the heavy metal elements, by adding at least one element of 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. In addition, the decrease in the luminous efficiency that tends to occur with the addition of the heavy metal element is completely prevented or suppressed by the sulfur (S) element that is also introduced. FIG. 4 shows the relationship between the type of activator and the luminous efficiency of the phosphor represented by the general formula (Zn _w M _x O _y S _z ). The straight line 4a is (w = 1.0, x = 0.0, y = 1.0, z = 0.0)
… Conventional example…, curve 4b shows (w = 0.995, x = 0.005, y = 1.0,
z = 0.0) ... Comparative example ..., the curve 4c is (w = 0.995, x = 0.00).
5, y = 0.999, z = 0.0001) ... The present invention.

[0010]

EXAMPLES Examples of the present invention will be described below.

Example 1 ZnO: 98.630 g, Ta ₂ O ₅ : 1.346 g, ZnS: 0.
0237 g was weighed as a starting material, put into a ball mill, and sufficiently pulverized and mixed. Then, put this raw material mixture in a quartz crucible, and hydrogen 3% + nitrogen 97%
It was fired at 900 ° C. for 3 hours in a weak reducing atmosphere. The fired product thus obtained was crushed, further treated with water and the like, and the composition of the obtained phosphor was chemically analyzed. As a result, the composition shown in the following formula was obtained.

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

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

Zn _0.999 Ta _0.002 O _0.9999 S _{0.0004 The} above phosphor was applied to a glass plate coated with a conductive film and mounted on a triode electron tube prepared in a model of a fluorescent display tube to evaluate the light emission characteristics. That is, when excited with an accelerating voltage of 100 V, the emission intensity was 132% as compared with the case of using the conventional ZnO phosphor.

Example 3 ZnO: 99.491 g, Ta ₂ O ₅ : 0.270 g, ZnS: 0.
Using 239 g of each as a starting material, each was weighed, charged into a ball mill, and sufficiently pulverized and mixed. Then, put this raw material mixture in a quartz crucible, and hydrogen 3% + nitrogen 97%
In a weakly reducing atmosphere, the product was baked at 950 ° C for 3 hours. The fired product thus obtained was crushed, further treated with water and the like, and the composition of the obtained phosphor was chemically analyzed. As a result, the composition shown in the following formula was obtained.

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

Examples 4, 5 ZnO: 98.763 g, Lu ₂ O ₃ : 1.214 g, ZnS: 0.
0238 g was weighed out as a starting material, put into a ball mill, and sufficiently pulverized and mixed. Then, put this raw material mixture in a quartz crucible, and hydrogen 3% + nitrogen 97%
It was fired at 1000 ° C. for 3 hours in the weak reducing atmosphere. The fired product thus obtained was crushed, further treated with water and the like, and the composition of the obtained phosphor was chemically analyzed. As a result, the composition shown in the following formula was obtained.

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

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

Zn _0.999 Lu _0.002 O _0.9999 S _{0.0004 When} this phosphor was used to evaluate the emission characteristics under the same conditions as above, it was found that it was compared with the case of using a conventional ZnO phosphor.
The emission intensity was 123%.

Examples 6 and 7 ZnO: 98.742 g, HfO ₂ : 2.47 g, ZnS: 0.02
Using 38 g of each as a starting material, each was weighed, 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 weakly reducing atmosphere of 3% hydrogen + 97% nitrogen. The fired product thus obtained is crushed, and further treated with water,
When the composition of the obtained phosphor was chemically analyzed, the composition was as shown in the following formula.

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

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

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

Examples 8 and 9 ZnO: 98.565 g, WO ₃ : 1.411 g, ZnS: 0.0237
Each g was weighed as a starting material, 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 weakly reducing atmosphere of 3% hydrogen + 97% nitrogen. The fired product thus obtained was crushed, further treated with water and the like, and the composition of the obtained phosphor was chemically analyzed. As a result, the composition shown in the following formula was obtained.

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 mounted on a triode electron tube prepared in a model of a fluorescent display tube to evaluate the light emission characteristics. That is, when excited with an accelerating voltage of 100 V, the emission intensity was 124% as compared with the case of using the conventional ZnO phosphor.

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

Zn _0.999 W _0.002 O _1.0 S _{0.0004 Using} this phosphor, the luminescent properties were evaluated under the same conditions as described above, and as compared with the case of using the conventional ZnO phosphor,
The emission intensity was 118%.

Examples 10 to 13 In the same manner as in Example 1 above, ZnO, Ta
₂ O ₅ , Lu ₂ O ₃ , HfO ₂ , WO ₃ , and ZnS were weighed to a predetermined composition ratio, put 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 weakly reducing atmosphere of 3% hydrogen + 97% nitrogen. The fired product thus obtained was crushed, further treated with water and the like, and the composition of the obtained phosphor was chemically analyzed. As a result, the composition shown in the following formula was obtained.

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 emission characteristics were evaluated by mounting on a triode electron tube created by simulating a fluorescent display tube. That is, when excited with an accelerating 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 of using the conventional ZnO phosphor. %, In the case of Example 13 12
It was 1%.

In the above embodiment, the 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]

EFFECTS OF THE INVENTION As can be seen from the above description, the phosphor according to the present invention has improved voltage characteristics due to the co-activating effect of the heavy metal element and sulfur without lowering the emission intensity. At the same excitation voltage as the phosphor, it exhibits a significantly improved emission intensity. Therefore, it is possible to display with high brightness even when used under high illuminance such as in a vehicle. Further, since the phosphor according to the present invention has a high luminous efficiency by nature, it has an advantage of contributing to reduction of power consumption.

[Brief description of drawings]

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

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

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

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

[Explanation of symbols]

 None

Claims (1)

[Claims] 1. A general formula: (Zn _w M _x O _y S _z ) (wherein M is at least one element selected from Lu, Hf, Ta and W, and w, x, y and z are all A number greater than 0 and 0.9≤w + x≤1.1, 0.95≤y + z≤
A phosphor having a composition represented by 1.05,10 ^-6 ≤x + z ≤10 ^-1 ).