JPH0790265A - Infrared rays-emitting fluorescent material - Google Patents

Abstract

PURPOSE:To provide an IR light-emitting fluorescent material having a specific chemical structure, high in luminous strength, long in an afterglow-persisting time, improved in a security property, and useful for offset printing, etc. CONSTITUTION:This IR light-emitting fluorescent material comprises a compound of the formula (A is Y, Lu, La; x,y are 0-0.5; x+y=0-1) such as Nd0.1Yb0.1 Y0.8PO4, has a particle diameter of 0.1-3mum, and has an afterglow-persisting time of >=100mus. One kind or more of elements selected from Pr and Tb as a luminous sensitizer is preferably added to the fluorescent material.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an infrared emitting phosphor. More specifically, the present invention relates to microparticulation of an infrared-emitting phosphor having an emission spectrum in the infrared wavelength region, which is excited by infrared rays, and modification of its structure and composition.

[0002]

2. Description of the Related Art In recent years, mainly in the distribution industry, product management by bar codes has been actively performed in each industry.
Bar codes are also printed on various prebate cards or pass cards, and the bar codes are read using an optical reading device such as a scanner. In addition to these cards, for credit cards and the like, various methods have been proposed in which these cards are provided with anti-counterfeiting means, or whether or not the cards are forged. As one of them,
Marks such as barcodes are printed with phosphor-containing ink to form latent image marks, and the latent image marks are irradiated with a semiconductor laser to excite the phosphors, and the light emitted from the phosphors is received to provide barcode information. An optical reader for reading is proposed.

According to this method, since the fluorescence signal is detected only when there is a recorded mark, a forged or altered card can be surely found. Also, since the content of the latent image mark is only known to the authentic card manufacturer, it is possible to falsify or alter the card itself.
It's extremely difficult.

As such a phosphor, for example, the general formula, in _{QD 1-xy Nd x Yb y} P 4 O 12 ( wherein, Q is selected from the group consisting of Li, Na, K, Rb and Cs At least one element, and D is S
at least one element selected from the group consisting of c, Y, La, Ce, Gd, Lu, Ga and In,
0.05 ≦ x ≦ 0.999, 0.001 ≦ x ≦ 0.95
0, x + y ≦ 1.0. ) Is used as the phosphoric acid-based phosphor (see, for example, JP-B-53-40594).
(See Japanese Patent Publication).

[0005]

In order to improve the security of various cards, it has been proposed to use the afterglow of a phosphor as an optical reading method, and the phosphor used for this purpose has a long afterglow. What is needed is a phosphor with a duration.

However, this type of phosphor has a large particle size of 7 μm or more, and it is necessary to pulverize it when it is used for offset printing or an ink ribbon. By this crushing,
There is a problem that the crystallinity and composition of the phosphor are impaired, and the emission intensity is significantly reduced. In addition, the persistence time also became shorter as the emission intensity decreased.

Therefore, an object of the present invention is to solve the problem of particle size, which the above-mentioned conventional products have, and to provide an ultra-fine particle-shaped infrared-emitting phosphor having high emission intensity and long persistence. Is to provide.

[0008]

To SUMMARY OF THE INVENTION To achieve the above object, the present invention, the general formula, in _{A 1-xy Nd x Yb y} PO 4 ( wherein, A is a group consisting of Y, Lu and La At least one element selected from the following: 0 ≦ x ≦ 0.
5; 0 ≦ y ≦ 0.5 and 0 <x + y <1. ), And an infrared-emitting phosphor having an afterglow duration of 100 μs or more. These phosphors may further contain at least one element selected from the group consisting of Pr and Tb as a luminescence sensitizer. The particle size of these phosphors is in the range of 0.1 μm to 3 μm.

[0009]

The novel infrared-emitting phosphor of the present invention, which is ultrafine particles, exhibits high emission intensity with respect to infrared excitation light,
Moreover, the afterglow duration was found to be very long.
The novel infrared-emitting phosphor of the present invention has an afterglow duration of 100 μs or more.

When manufacturing the infrared-emitting phosphor of the present invention,
As a raw material, instead of ammonium phosphate which is used in general conventionally, orthophosphoric acid (H ₃ P0 ₄₎ or phosphate _{(A 3-x H x PO} 4, where, A is an alkali metal or alkaline earth The use of at least one or more of the metals) prevents the generation of ammonia gas during firing, and simplifies the entire manufacturing process by eliminating the need for a detoxification treatment process for this gas. The productivity can be improved and the particle size of the obtained phosphor can be further reduced.

The particle size of the phosphor obtained by the conventional method using ammonium phosphate could be reduced to about 7 μm at most, but according to the method of the present invention, ammonium phosphate was used. 1/1 of the particle size of the phosphor
The particle size can be reduced to 0 or less. In particular, according to the method using phosphate, the particle size of the phosphor can be reduced to 3 μm or less, for example, 0.8 μm or less in average particle size. Further, according to this method, 0.1 μm
It is also possible to obtain a phosphor having a particle size of.

Therefore, the phosphor obtained by the method of the present invention can be directly used in use without secondary processing such as pulverization. Although the emission intensity is reduced when the phosphor obtained by the method using the conventional ammonium phosphate is finely pulverized, the infrared emission phosphor of the present invention has a very high emission intensity in the state of ultrafine particles, The afterglow duration is also long. Since the infrared-emitting phosphor of the present invention is ultrafine particles,
When it is used for offset printing or ink ribbon, not only the paint preparation becomes extremely easy, but also microencapsulation becomes possible.

According to the method of the present invention, orthophosphoric acid or phosphate may be used alone or in combination. In order to obtain high emission intensity, among phosphates (A _3-x H _x PO ₄ , where A is at least one element selected from alkali metals and alkaline earth metals), , X are preferably large.

The infrared-emitting phosphor of the present invention emits light due to the forbidden transition of 4f electrons of Nd and Yb. The reason why the emission intensity is high in spite of the ultrafine particles is that the crystallinity of the orthophosphate as a base material is high. Is good, and a lot of Nd and Yb
It is thought that this is due to the fact that Further, it is considered that the crystallinity is further improved and the emission intensity is improved by adding a small amount of alkali metal or alkaline earth metal. Further, the reason why the afterglow persistence time is longer than that of the conventional phosphor is considered to be that it is difficult to cause concentration quenching because there are few emission centers of Nd + Yb.

When producing the phosphor of the present invention, at least one compound selected from neodymium (Nd) and ytterbium (Yb) and at least one element selected from the group consisting of Y, Lu and La. Orthophosphoric acid (H ₃ PO ₄ ) or A _3-x H _x PO ₄ (wherein A is at least one element selected from alkali metals and alkaline earth metals) Is added, the mixture is baked at a temperature in the range of 400 to 1500 ° C., then air-cooled, and then hydrothermal treatment at 50 ° C. or higher is performed to remove impurities such as excess phosphate.

In the infrared emitting phosphor of the present invention, as the compounds of neodymium and ytterbium, for example, oxides, chlorides, carbonates, nitrates, acetates, etc. of these can be preferably used. Similarly, compounds of the elements Y, Lu and La include, for example, oxides of these,
Chlorides, carbonates, nitrates, acetates and the like can be preferably used. These compounds can also be used by dissolving them in a dilute mineral acid (eg dilute sulfuric acid, dilute hydrochloric acid, dilute nitric acid, etc.) before firing.

For firing, the raw materials are put in a crucible, and in the air,
400-1500 ° C, preferably 650 ° C-1000
It is carried out by heating at a temperature of about 2 hours to 24 hours.

Hereinafter, the production of the infrared light emitting phosphor of the present invention will be specifically illustrated with reference to Examples.

Example 1 Nd ₂ O ₃ : 3.5 g, Yb ₂ O ₃ : 4.0 g, Y ₂ O
_3: 18.0 g and H ₃ PO _4: raw material were mixed thoroughly made of 60.0 g, it was filled in a covered crucible made of alumina, placed in an electric furnace, to 700 ° C. position from room constant heating rate At room temperature for 2 hours, then 700 ° C for 6
Burned for hours. Immediately after the firing was completed, it was taken out of the electric furnace and allowed to cool in air. Next, boiling water of 100 ° C. was put into the crucible, boiled, the phosphor was taken out from the crucible, washed with 1N nitric acid, washed with water, and dried to obtain a desired phosphor. The composition of the obtained phosphor is Nd _0.1 Yb
_{It was 0.1} Y _0.8 PO ₄ .

Example 2 The raw material composition in Example 1 was changed to Nd ₂ O ₃ : 3.5 g,
Yb ₂ O ₃ : 4.0 g, La ₂ O ₃ : 9.8 g, Y ₂ O
_A phosphor was obtained by the same method as that described in Example 1 except that the amount was changed to ₃ : 11.3 g and H ₃ PO ₄ : 60.0 g. The composition of the obtained phosphor is Nd _0.1 Yb
_{It was 0.1} La _0.1 Y _0.7 PO ₄ .

Example 3 The raw material composition of Example 1 was changed to Nd ₂ O ₃ : 3.5 g,
Yb ₂ O ₃ : 4.0 g, La ₂ O ₃ : 3.3 g, Y ₂ O
_A phosphor was obtained by the same method as described in Example 1 except that the amounts were changed to ₃ : 15.3 g and LiH ₂ PO ₄ : 65.0 g. The composition of the obtained phosphor is Nd _0.1.
It was Yb _0.1 La _0.1 Y _0.7 PO ₄ .

Example 4 A phosphor was obtained in the same manner as in Example 3 except that the firing temperature was changed to 900 ° C. The composition of the obtained phosphor is Nd _0.1 Yb _0.1 L
It was a _0.1 Y _0.7 PO ₄ .

Example 5 The raw material composition in Example 1 was changed to Nd ₂ O ₃ : 3.5 g,
A phosphor was obtained by the same method as described in Example 1 except that Yb ₂ O _{3 was} 4.0 g, Lu ₂ O _{3 was} 31.8 g, and LiH ₂ PO _{4 was} 65.0 g. .
The composition of the obtained phosphor is Nd _0.1 Yb _0.1 Lu _0.8 P
It was O ₄ .

Comparative Example 1 The raw material composition of Example 1 was changed to Nd ₂ O ₃ : 30.0.
g, Yb ₂ O ₃ : 4.0 g, Li ₂ CO ₃ : 11.0 g
And a phosphor similar to the method described in Example 1 except that the amount of (NH ₄ ) H ₂ PO ₄ was changed to 140 g. The composition of the obtained phosphor was LiNd _0.9 Yb.
_{It was 0.1} P ₄ O ₁₂ .

Comparative Example 2 The phosphor obtained in Comparative Example 1 was placed in a zirconia ball mill and wet-ground using water as a medium. The composition of the obtained phosphor remained as in Comparative Example 1.

Table 1 below shows the average particle size and emission characteristics of the phosphors obtained in Examples 1-5 and Comparative Examples 1-2. The average particle size of the phosphor was measured using a centrifugal sedimentation particle size distribution meter. The emission characteristics were measured by exciting with a light source with a wavelength of 810 nm and receiving the emitted light with a silicon photodetector at 980 nm to measure the emission intensity. The luminescence intensity was displayed with the value of the sample of Comparative Example 1 being 100. Also, turn off 300
After μs, afterglow characteristics were measured by receiving afterglow with a silicon photodetector having a peak sensitivity of 980 nm.

[0027]

[Table 1] Table 1 Average particle size Emission afterglow Sample composition (μm) Characteristics Characteristics Example 1 Nd _0.1 Yb _0.1 Y _0.8 PO ₄ 0.8 85 125 2 Nd _0.1 Yb _0.1 La _0.1 Y _0.7 PO ₄ 1. 0 90 130 3 Nd _0.1 Yb _0.1 La _0.1 Y _0.7 PO ₄ 0.9 90 130 4 Nd _0.1 Yb _0.1 La _0.1 Y _0.7 PO ₄ 2.8 115 150 5 Nd _0.1 Yb _0.1 Lu _0.8 PO ₄ 0.8 90 125 125 Comparison Example 1 LiNd _0.9 Yb _0.1 P ₄ O ₁₂ 7.5 100 100 2 LiNd _0.9 Yb _0.1 P ₄ O ₁₂ 0.6 15 2

As is clear from the results shown in Table 1 above, according to the present invention, it is possible to obtain an infrared-emitting phosphor having an average particle size of 3.0 μm or less and excellent in emission characteristics and afterglow characteristics. You can

The emission spectra of the phosphor obtained in Example 1 and the phosphor obtained in Comparative Example 1 are shown in FIG. Figure 1
1A is the emission spectrum of the phosphor obtained in Example 1, and FIG. 1B is the emission spectrum of the phosphor obtained in Comparative Example 1. As is clear from a comparison of the emission spectra shown in FIGS. 1 (a) and 1 (b), the infrared light emitting phosphor of the present invention has characteristics which are completely different from those of the infrared light emitting phosphor of Comparative Example 1. It can be understood that it is an infrared-emitting phosphor having the same.

A scanning electron micrograph showing the particle structures of the phosphor obtained in Example 1 and the phosphor obtained in Comparative Example 1 is shown in FIG. 2 (a) is a scanning electron micrograph showing the particle structure of the phosphor obtained in Example 1, and FIG.
(B) is a scanning electron micrograph showing the particle structure of the phosphor obtained in Comparative Example 1. 2 (a) and 2
As is clear from comparison of the photographs of (b), it can be understood that the phosphor of the present invention is ultrafine particles having a completely different particle shape and a significantly smaller particle size than the phosphor of Comparative Example 1.

[0031]

As described above, according to the present invention, it is possible to obtain a novel infrared-emitting phosphor which is ultrafine particles and has a high emission intensity and a long afterglow duration.

[Brief description of drawings]

FIG. 1A is a waveform diagram showing an emission spectrum of a phosphor obtained in Example 1, and FIG. 1B is a waveform diagram showing an emission spectrum of a phosphor obtained in Comparative Example 1.

FIG. 2 (a) is a scanning electron microscope photograph showing the particle structure of the phosphor obtained in Example 1, and FIG. 2 (b) shows the particle structure of the phosphor obtained in Comparative Example 1. It is a photograph figure by a scanning electron microscope.

Claims (3)

[Claims] 1. A general _{formula, A 1-xy Nd x Yb} y PO 4 ( wherein, A is Y, is at least one element selected from the group consisting of Lu and La; 0 ≦ x ≤0.
5; 0 ≦ y ≦ 0.5 and 0 <x + y <1. ) And having an afterglow duration of 100 μs or more. 2. The infrared-emitting phosphor according to claim 1, further containing at least one element selected from the group consisting of Pr and Tb as a luminescence sensitizer. 3. The infrared-emitting phosphor according to claim 1, having a particle size in the range of 0.1 μm to 3 μm.