KR100724308B1 - Preparation of long persistent blue emitting phosphor - Google Patents

Abstract

The present invention relates to the synthesis of calcium aluminate-based blue photoluminescent material having high brightness and long afterglow. Although long afterglow materials using europium as an activator and neodymium as an activator have been known, high luminance and long afterglow of photoluminescent powders have a great effect on practical use unlike fluorescence due to the characteristics of photoluminescence. The blue brightness of the calcium aluminate-based photoluminescent powder is affected by the crystal field and symmetry of the europium metal ion, which is an active agent, in the crystal. The present invention improves the energy transfer probability of europium, an activator, by replacing and modifying the crystal structure of calcium aluminate-based blue photoluminescent powder with some impurities, thereby synthesizing a powder having high luminance and long afterglow.

Photoluminescent, photoluminescent material, afterglow time, calcium aluminate, blue photoluminescent powder, active agent, active agent, energy transfer, transition probability

Description

Manufacturing method of photoluminescent material of blue long afterglow {Preparation of long persistent blue emitting phosphor}

1 is a diagram showing the photoluminescent Decay curve of CaAl ₂ O ₄ : Eu, Nd according to the Eu content,

2 is a diagram showing the photoluminescent Decay curve of CaAl ₂ O ₄ : Eu, Nd according to the SiO ₂ content,

3 is a diagram showing the photoluminescent Decay curve of CaAl ₂ O ₄ : Eu, Nd according to the content of alkaline earth metal ions,

4 is a view showing a photoluminescent Decay curve of CaAl ₂ O ₄ : Eu, Nd according to the content of Sr ions,

5 is a diagram showing the photoluminescent Decay curve of CaAl ₂ O ₄ : Eu, Nd according to the content of alkali metal ions,

6 is a diagram showing the photoluminescent Decay curve of CaAl ₂ O ₄ : Eu, Nd according to the content of Li ions,

7 is a diagram showing the emission spectrum of CaAl ₂ O ₄ : Eu, Nd photoluminescent material.

The present invention relates to the manufacture of a photoluminescent material, and more particularly, to a method of improving the photoluminescence function by slightly modifying the crystal lattice by substituting a trace amount of calcium aluminate photoluminescent material dyed with europium and neodymium.

In the mid-1990s, a material called strontium aluminate, which excites rare earth elements, was synthesized, and the research on the practical use was actively undertaken as a groundbreaking invention in which the phosphorescence intensity and the afterglow time were improved by 10 times or more than the existing phosphorescent materials. Matsuzawa, Y. Aoki, N. Takeuchi, and Y. Murayama, J. Electrochem.Soc., Vol. 143, No. 8, 2670, 1996.Nemoto & Co., Ltd., European Patent, Phosphorescent Phosphor, 0622440B1, 1996) In the past, research has mainly focused on active agents and active agents.

According to the present invention, the calcium lattice is expanded or shrunk by replacing some of the alkali metal and alkaline earth cations with or less than the calcium ions in the matrix, and the empty lattice is created due to the difference in the number of charges. The result is an increase in the probability of electron transfer of europium ions, thereby producing a light-emitting material with a stronger brightness.

The ion radius of the active europium cation in the calcium aluminate base crystal is slightly larger than the radius of the calcium cation (Ca ⁺² 114pm, Eu ⁺² 131pm) and the europium has almost the same symmetry as calcium. Not large (RD Shannon, Acta Crystallogr., 1976, A32, 751). According to spectroscopic theory, the symmetry of europium ions greatly affects the transfer probability of electron energy of europium (II) ions. Therefore, by breaking this symmetry, the photoluminescence intensity of the active agent europium can be increased. In order to break the symmetry of europium ions, it is necessary to replace some calcium with metal ions that are much larger or smaller than the radius of calcium ions within the range that the background crystal can accommodate, or to replace the silicon ions with silicon ions instead of some aluminum ions to create empty crystal lattice sites. It can be said to be the main technical subject of this invention. As an impurity metal ion to be substituted with calcium, an alkali metal ion, an alkaline earth metal ion, or a silicon ion can be used as an ion to be substituted with aluminum.

As mentioned above, the technical core of the present invention is to replace the photoluminescent material crystals with impurities to determine the photoluminescence intensity and afterglow time of the calcium aluminate-based photoluminescent material in consideration of spectroscopic properties and crystal structure modification of the europium ion as an activator in the background crystal. It is to provide a method of manufacturing a more practical photoluminescent material by maximizing.

Formula of the photoluminescent material to be synthesized in the present invention will be represented by a general formula such as Ca _1-abcd Eu _a Nd _b P _c Q _d Al _e Si _f O ₄ . Where P and Q represent alkali metal ions and alkaline earth metal ions, respectively, and the subscripts a, b, c, d, e and f represent the number of atoms in which the corresponding metal ions are substituted in the photoluminescent material.

CaCO ₃ , Al ₂ O ₃ , Eu ₂ O ₃ , Nd ₂ O ₃ , and SiO _{2, which} are the main raw materials in the synthesis of base crystals, use high purity grade (luminescent grade). In particular, the smaller the particle size of Al ₂ O ₃ is preferable, and in general, fine particles of 1 μ or less are used. Alkali metals such as Li, Na, K, and alkaline earth metals such as Mg, Sr, and Ba mainly take carbonates as raw materials, and oxides may be used depending on circumstances. As the flux, H ₃ BO ₃ or B ₂ O ₃ is used.

The flux H ₃ BO ₃ or B ₂ O ₃ is suitably 0.1-0.3 mole relative to the synthetic photoluminescent material.

Neodymium as an active agent was found to exhibit the best photoluminescence at b / a = 1 as the active agent europium, as in the conventional invention, but when the value of europium was changed while maintaining b / a = 1, europium was a = 0.004-0.008 It was found to exhibit strong photoluminescence even at low concentrations (0.002-0.004 moles) (see FIG. 1).

When some Al ⁺³ is replaced with Si ⁺⁴ , two effects can be expected due to the difference in the ion radius and the number of charges. According to the literature (RD Shannon, Acta Crystallogr., 1976, A32, 751) the ionic radii of Al ⁺³ and Si ⁺⁴ are 53 pm (1 pm = 10-9 m) and 40 pm in the fourth coordination crystal, with some Al ⁺³ crystals. Substitution of the lattice with Si ⁺⁴ results in a slight lattice expansion due to a slight decrease in the size of the crystal lattice and the formation of empty crystal lattice sites with increasing charge from Al ⁺³ to Si ⁺⁴ . This is expected to increase the photoluminescence efficiency of europium. Increasing the content (f) of SiO ₂ indicates an increase in the photoluminescent efficiency at 0.001 to 0.03, and in particular, the highest photoluminescent efficiency at 0.01 to 0.02 (see FIG. 2).

When some Ca ⁺² is replaced with alkaline earth metal ions, there is no change in the number of charges, but a change in the radius of the ion can be expected. The ion radius of Ca ions is 114pm (1pm = 10-9m) in the 6th coordination crystal and the radius of alkaline earth metal ions of the same group is Mg 86pm, Sr 132pm, Ba 149pm. Therefore, when some calcium ions are substituted with alkaline earth metal ions Mg, Sr, Ba, etc., the europium ions in the crystal shrink or expand according to the size of the substituted alkaline earth metal ion radius, resulting in poor symmetry of the europium lattice. As shown in FIG. 3, the substitution of Sr and Ba metal ions increases the photoluminescence intensity but the lowest increase occurs when Mg ions are substituted. This shows that the lattice strain is not large as the calcium lattice is replaced with Mg ions, which in turn does not change the electron transfer probability. The content of Sr metal is increased at d = 0.005-0.02 with respect to 1 mol of photoluminescent material, and decreased at d> 0.03 (see FIG. 4).

When some Ca ⁺² is substituted with alkali metal ions, photoluminescence effect is expected due to two factors such as change of charge and change of ion radius size. The change of the charge number causes the lattice vacancies, and the change in the ion radius can be expected to cause the lattice contraction or expansion. For reference, the radius of alkali metal ions is Li at 90pm, Na at 116pm, and K at 152pm. The photoluminescent intensity of the photoluminescent material substituted with these alkali metal ions is smaller than that of Ca metal ions as shown in FIG. It shows the brightest photoluminescence in ions and shows lower photoluminescence in both Na and K ions. In the case of Li ions, the content shows a relatively high photoluminescent intensity at c = 0.002-0.04, and the c value represents a maximum of photoluminescent intensity at ~ 0.02 (see FIG. 6).

Synthesis reaction of photoluminescent material is well mixed with reaction materials and placed in a large crucible which is a reaction vessel. A small crucible with activated carbon as a reducing agent is placed in a large raw crucible and then covered with a crucible lid and heated to a high temperature of 1300 ° C. in an electric furnace. Continue heating at ˜1300 ° C. for 3-5 hours to complete the reaction. In the case of using a reducing gas as a reducing agent, the reaction may be performed while flowing a 3% H ₂ -N ₂ mixed gas during the reaction time.

Hereinafter, the present invention will be described in detail with reference to the following examples, but the present invention is not limited only to the following examples.

Example 1

Weigh the reactants CaCO ₃ , Eu ₂ O ₃ , Nd ₂ O ₃ , Al ₂ O ₃ , SiO ₂ , and H ₃ BO ₃ using chemical scales exactly as shown in Table 1, and mix them in agate mortar. .

Mix well the reactants in the crucible and chop slightly. Put 1-2g of activated carbon powder in a separate small crucible and chop it slightly over the reaction material of the large crucible and close the lid of the large crucible. The large crucible is heated to 1300 ° C. in an electric furnace and continued to react at 1300 ° C. for 3 hours. After the reaction, the crucible is cooled to room temperature, taken out, and the reaction product is pulverized to obtain a photoluminescent powder. The composition of the raw materials shown in Table 1 shows the raw material composition of the reactants according to the Eu ₂ O ₃ content by fixing the atomic ratio of Nd / Eu to 1. The photoluminescence change with time was measured for the photoluminescent sample obtained by reacting four compositions, and the results are shown in FIG. 1. As shown in FIG. 1, Eu ₂ O ₃ has the highest photoluminescent intensity at 0.003 mole of Eu ₂ O ₃ with respect to 1 mole of photoluminescent material, and concentration quenching phenomenon occurs at 0.003 mole or more.

Example 2

CaCO ₃ , Eu ₂ O ₃ , Nd ₂ O ₃ , Al ₂ O ₃ , SiO ₂ , H ₃ BO ₃ as a reaction raw material were mixed in the composition as shown in Table 2, and the activated carbon was added to the crucible in the same manner as in Example 1. Add and react under the same conditions in an electric furnace.

As shown in FIG. 2, the afterglow property of the reaction product can be observed to increase the photoluminescence intensity by Si substitution and exhibits a maximum value at 0.01 to 0.02 mol of SiO ₂ with respect to 1 mol of CaAl ₂ O ₄ : Eu and Nd.

Example 3

In reaction raw materials stated _{CaCO 3, Eu 2 O 3,} Nd 2 O 3, Al 2 O 3, SiO 2, Li 2 CO 3, H 3 BO 3 and an alkaline earth metal compound, MgO, SrCO ₃ and BaCO ₃ are shown in Table 3 It is taken as described in Example 1 and placed in the crucible in the same manner as in Example 1, activated carbon is added, and reacted under the same conditions in an electric furnace.

3 shows the afterglow characteristics of the photoluminescence obtained by replacing part of Ca with Mg, Sr, and Ba as an alkaline earth metal. As shown in FIG. 3, it can be seen that when the Ca crystal lattice is replaced with Sr or Ba having a large difference in size between Ca and the ion radius, photoluminescence characteristics are improved. However, when substituted with Mg it is shown that the increase in the photoluminescence intensity is less than the case of Sr, Ba.

Example 3

The composition ratio of the reaction raw materials CaCO ₃ , SrCO ₃ , Eu ₂ O ₃ , Nd ₂ O ₃ , Al ₂ O ₃ , SiO ₂ , H ₃ BO ₃ according to the Sr content is taken as described in Table 4 and the same method as in Example 1 Into the crucible, add activated carbon, and react in the same conditions in an electric furnace.

As a result of measuring the photoluminescence intensity and the afterglow property of the synthesized photoluminescent material according to the Ca crystal lattice and the amount of substituted Sr, FIG. 4 is obtained. As shown in FIG. 4, as the content of Sr increases, the photoluminescence intensity increases from 0.005 to 0.02 mole and decreases over the photoluminescent material.

Example 4

Reaction materials include CaCO ₃ , SrCO ₃ , Eu ₂ O ₃ , Nd ₂ O ₃ , Al ₂ O ₃ , SiO ₂ , H ₃ BO ₃ and alkali metal compounds Li ₂ CO ₃ , Na ₂ CO ₃ and K ₂ CO ₃ Take the as shown in Table 5, put into the crucible in the same manner as in Example 1, add the activated carbon and react under the same conditions in an electric furnace.

5 shows the results of measuring the photoluminescence intensity and the afterglow property of the photoluminescent material obtained by substituting a part of Ca with Li, Na, and K. As shown in FIG. 5, the Ca crystal lattice shows maximum photoluminescence intensity for Li ions smaller than the Ca ion radius, and similar photoluminescence intensities for Na and K ions equal to or larger than the Ca ion radius.

Example 5

According to Li content, the composition ratio of CaCO ₃ , SrCO ₃ , Eu ₂ O ₃ , Nd ₂ O ₃ , Al ₂ O ₃ , SiO ₂ , H ₃ BO ₃ was taken as specified in Table 6 and the same method as in Example 1 Into the crucible, add activated carbon, and react in the same conditions in an electric furnace.

The photoluminescence intensity and the afterglow property of the synthesized photoluminescent material were measured according to the Ca crystal lattice and the amount of Li ions substituted. As shown in FIG. 6, as the Li content is increased, the photoluminescence intensity increases from 0.002 to 0.04 mole with respect to the photoluminescent material and decreases thereafter. The photoluminescent spectrum of the photoluminescent material obtained as a reference shows a violet-luminescent blue photoluminescence as shown in FIG. 7.

In addition to calcium aluminate-based photoluminescent materials dyed with activators and deactivators, the crystal structure of the photoluminescent material is modified by replacing alkali metals, alkaline earth metal ions, or silicon with larger or smaller ionic radii than calcium ions. Lowering the efficiency of electrons and increasing the probability of energy transfer, the result is that the luminous intensity and afterglow time of the calcium aluminate-based photoluminescent material stained with activator and deactivator are improved.

Claims (9)

Low concentrations of europium and neodymium in a 1: 1 (molar ratio) of calcium aluminate photoluminescent materials stained with europium and neodymium, and silicon ions instead of some aluminum, alkali metals with some ions larger or smaller than calcium and some calcium Instead, a method of manufacturing a photoluminescent material of calcium aluminate-based blue long afterglow with improved photoluminescence intensity and afterglow time by substituting a metal ion containing an alkaline earth metal whose ion radius is larger or smaller than calcium. The method of claim 1, wherein the composition of europium and neodymium is colored at a low concentration of 0.001 to 0.01 mole ratio with respect to 1 mole of the photoluminescent material, thereby producing a calcium aluminate photoluminescent material having improved photoluminescence intensity and afterglow time. A method for producing a calcium aluminate photoluminescent material having improved photoluminescence intensity and afterglow time by using Li, Na and K as alkali metals in claim 1. The preferred composition of the alkali metal ion in claim 3 is 0.003 to 0.03 moles with respect to 1 mole of the photoluminescent material and has a maximum photoluminescent intensity at 0.01 to 0.03. A method for producing a calcium aluminate photoluminescent material having improved photoluminescence intensity and afterglow time by using Mg, Sr, Ba, etc. as alkaline earth metal ions in claim 1. A method for producing a calcium aluminate photoluminescent material having a composition of alkaline earth metal ions of claim 5 in an amount of 0.01 to 0.02 mol per mol of the photoluminescent material. Claim 1 claim that the silicon ion to be substituted is a calcium aluminate photoluminescent material manufacturing method having a composition in the range of 0.001 to 0.03 mol of silicon dioxide per 1 mol of the photoluminescent material. delete delete

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