JP6741614B2 - Rare earth activated alkaline earth silicate compound Afterglow phosphor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rare earth activated alkaline earth silicate compound afterglow phosphor that exhibits blue-green to orange light emission by ultraviolet light excitation by daylight such as sunlight and indoor lighting, and continues to emit light even after blocking excitation light.

The afterglow phosphor (phosphorescent material) that can emit light even after the excitation by the light source is cut off is expected to be used as a display object in a dark place, or as an inductive sign or lighting that is effective when the power is lost. There is.
As a conventional afterglow phosphor material, a zinc sulfide-based phosphorescent material and a phosphorescent material having a mother crystal of an aluminate that emits blue to green light are known.

The following 1 and 2 are known as afterglow phosphors exhibiting a warm color afterglow, which have a relatively long afterglow time.
1. Y ₂ O ₂ S:Tix, Mgy, Gda (Patent Document 1)
2. CaS: mainly composed of a compound represented by Eu and Tm, containing 10 ^X mol% of Eu and 10 ^Y mol% of Tm with respect to Ca, and −3≦X≦−1 and −3≦Y. A range of ≦0 and 0≦Y−X≦2 (Patent Document 2).
However, these 1 and 2 warm-colored afterglow phosphors all have weak emission intensity, and are sulfide-based substances, so that they have major problems in stability against ultraviolet rays and heat, and long-term stability such as weather resistance.

In addition to the above 1 and 2, metal oxide afterglow phosphors that are stable against ultraviolet rays and heat are also known.
3. _{(Zn 1-x Mg x)} O · n (Ga 1-y Cr y) 2 O 3 (x in the composition formula, y and n are each satisfy the following numbers .0 ≦ x ≦ 1.0 1×10 ⁻⁵ ≦y≦1×10 ⁻¹ , 0.95≦n≦1.05) (Patent Document 3)
4. A red phosphorescent phosphor comprising a fired body of a compound mainly containing germanate, which contains a Ge—O bond activated by a transition element and a rare earth element and has afterglow characteristics for red (Patent Document 4).
5. Ca _1-X Sr _X TiO ₃ :Pr red phosphorescent material (see Non-Patent Document 1).
However, practical application was difficult.

Patent Document The _{5 Ca 2-x-y-} z M x SiO 4: y Ce 3+, z N (M consists Mg, Sr, Ba, Zn, Na, Al, Ga, Ge, P, As and Fe A silicate phosphor (claim 1) comprising at least one selected from the group, wherein N comprises at least one selected from the group consisting of Eu ²⁺ , Mn ²⁺ , Tb ³⁺ , Yb ²⁺ and Tm ^3+. Has been done. Further, at least the material mixture of the silicate phosphor is selected from the group consisting of MgF ₂ , MgCl ₂ , BaF ₂ , BaCl ₂ , SrF ₂ , SrCl ₂ , CaF ₂ , CaCl ₂ , NH ₄ F, NH ₄ Cl and LiF. It is described that one further is contained as a flux (Claim 7).
However, since there is no description of afterglow, phosphorescent phosphor, phosphorescence, etc. and data showing the measurement results thereof, it can be understood that the phosphor is not a phosphorescent phosphor or the phosphorescent property has not been examined.

WO2007/145167 JP, 9-59615, A JP, 10-259375, A JP, 2001-26777, A JP 2012-251147 A

P.T.Diallo et al.Phys.Status SolidsiA 1997,160.255.

An object of the present invention is to solve the drawbacks of the above-mentioned phosphorescent material (afterglow phosphor), to have afterglow of yellow to red, and to have excellent initial brightness and afterglow brightness Rare earth activated alkaline earth silicate. It is intended to provide a compound afterglow phosphor (hereinafter, may be referred to as a phosphor of the present invention or an afterglow phosphor).

In the present invention, in order to improve the afterglow time and the afterglow brightness in the rare earth activated alkaline earth silicate compound afterglow phosphor, not improvement of the existing warm color afterglow phosphor by the sulfide system. As a result of examination, it was found that it is necessary to promote grain growth during sintering, and the use of a flux (hereinafter sometimes referred to as flux) that forms a liquid phase during sintering is effective as a means for that. Found.

The terms used in this specification are explained below.
Luminescence: A general term for the energy absorbed by an inorganic substance to be emitted as light. In the present specification, it indicates both fluorescence and afterglow.
Excitation light: Energy (light) given to obtain specific light emission.
Fluorescence: Light emission that occurs when given specific energy (light). In the case of an afterglow phosphor, it is not possible to distinguish between light emission and afterglow in the state of light emission that occurs when such energy (light) is applied.
Afterglow: Permanent light emission that continues after excitation is stopped.

That is, the present invention provides the following.
(1) A rare earth activated alkaline earth silicate compound afterglow phosphor containing Cl and having a Cl content measured by an oxidative decomposition-coulometric titration method of 50 ppm or more and 10000 ppm or less (hereinafter, referred to as the present invention. Sometimes called a phosphor).
(2) The rare earth activated alkaline earth silicate compound afterglow according to (1), wherein the Cl is a residue of a chloride or hydroxide of an alkali metal, an alkaline earth metal added during reduction firing. Fluorescent substance.
(3) MgCl ₂ , CaCl ₂ , SrCl ₂ , BaCl ₂ , KCl, NaCl, LiCl, NH ₄ Cl, Mg(OH) ₂ , Ca(OH) ₂ , Sr(OH) ₂ , Ba added during reduction firing. The rare earth activated alkaline earth silicate compound afterglow phosphor according to (2), which is at least one flux selected from the group consisting of (OH) ₂ , KOH, NaOH, and LiOH.
(4) The rare earth activated alkaline earth silicate compound afterglow phosphor contains Cl,
Equation _{(1) (Sr 2- x,} M x) 2-y SiO 4: N y
Here, x is the content of M with respect to Si=1 mol, 0.1 mol≦x≦1.0 mol, y is the content of N, 0.001 mol≦y≦0.100 mol, and M is Mg , Ca and Ba, and N contains at least one of Ce, Pr, Nd, Sm, Eu, Tb, Er and Yb, that is, the content of M with respect to 1 mol of metal Si. Is the afterglow phosphor having a content of 0.1 mol or more and 1.0 mol or less and a N content of 0.001 mol or more and 0.100 mol or less, with the rare earth element according to any one of (1) to (3). Active alkaline earth silicate compound Afterglow phosphor.
(5) The rare earth-activated alkaline earth silica according to any one of (1) to (4), which further contains 0.3% by mass or less of carbon measured by combustion in an oxygen stream-infrared absorption method. Phosphate compound afterglow phosphor.

The phosphor of the present invention having a predetermined amount of chlorine has improved afterglow characteristics. When the phosphor of the present invention is reduction-baked using flux, it is easier to contain an appropriate amount of the phosphor as compared with the phosphor obtained when reduction-baking is performed without using flux.

Sintering in an oxidizing atmosphere in Example 1 (sample in which CaCl ₂ was added as a flux in an amount of 1.0 wt% in terms of Cl amount) and Comparative Example 1 (sample in which no flux was added) measured using TMA (thermo-mechanical analysis) It is a graph which shows shrinkage behavior of temperature and a sintered compact. 3 is a SEM (scanning electron microscope) photograph (3000 times) of the surface of the afterglow phosphor obtained in Example 1 and Comparative Example 1. It is a graph which shows the result of having measured the excitation spectrum with respect to the emission wavelength of 575 nm of the afterglow fluorescent substance obtained in Example 1 (the upper line of a Y-axis) and the comparative example 1 (lower line of a Y-axis). PL intensity is the fluorescence emission intensity. It is a graph which shows the result of having measured the emission spectrum with respect to the excitation wavelength 365nm of the afterglow fluorescent substance obtained in Example 1 (the upper line of a Y-axis) and the comparative example 1 (lower line of a Y-axis). It is a graph which tracked the single wavelength (575 nm) of the afterglow of the afterglow fluorescent substance obtained in Example 1 (the upper line of the Y-axis) and Comparative Example 1 (the lower line of the Y-axis) with time. .. It is a figure which shows an example of the relationship between the light emission wavelength of the fluorescent substance of this invention, and a color (FIG. 5 is a color diagram which shows a color, and submits a color diagram separately in the above statement).

The rare earth activated alkaline earth silicate compound afterglow phosphor of the present invention is a afterglow phosphor display that is used as a display in a dark place, and is blue due to ultraviolet excitation by daytime sunlight and indoor lighting. It is an afterglow (yellow to red) phosphor that emits green to orange light and continues to emit light even after the excitation light is blocked. The afterglow phosphor has improved afterglow characteristics due to the sintering effect by the addition of flux. Since it does not contain an S (sulfur) component, it is expected to have excellent weather resistance. Regarding the emission color, it cannot be stated that the emission wavelength is a specific range because the emission wavelength slightly shifts depending on the irradiation wavelength, mother crystal phase, and rare earth species, but for example, the relationship between the emission wavelength and the color of the phosphor of the present invention An example is shown in Fig. 5 (color diagram is submitted by petitions).

Patent Document 1 describes in paragraph [0003] that "in general, the afterglow time of a phosphor is extremely short, and when the external stimulus due to irradiation of ultraviolet rays, electron beams, visible rays, or the like is stopped, the light emission is rapidly attenuated. Even after the external stimulus is given by irradiation with ultraviolet rays or the like, the afterglow can be visually confirmed for a long time, for example, several tens of minutes to several hours even after the external stimulus is stopped. Of the phosphors, those that can be visually confirmed afterglow for a long time are called phosphorescent phosphors, phosphors, etc., which are distinguished from ordinary phosphors." .. Therefore, a general description of a phosphor having no description of phosphorescence, phosphor, afterglow, etc. is understood to be a phosphor that does not show afterglow or is not known to show afterglow. Generally, a silicate compound does not exhibit afterglow even when it is a phosphor.

(Rare earth activated alkaline earth silicate compound afterglow phosphor of the present invention)
The rare earth activated alkaline earth silicate compound afterglow phosphor of the present invention is a rare earth N, such as Eu (europium), Dy (dysprosium), Tb (terbium), Sm (samarium), Ce (cerium), Pr. (Praseodymium), Nd (neodymium), Er (erbium), Yb (ytterbium), etc., and a silicate compound in which a part of Sr (strontium) is replaced with an alkaline earth, and the alkaline earth is, for example, It is a phosphor that shows afterglow with a silicate compound containing Mg (magnesium), Ca (calcium), Ba (barium), etc., and is not particularly limited as long as it contains Cl (chlorine) and its content is 10,000 ppm or less. ..
Preferably, the rare earth activated alkaline earth silicate compound afterglow phosphor contains Cl in an amount of 50 ppm or more and 10000 ppm or less, and preferably has the formula (1) (Sr _2−x , M _x ) _2-y SiO ₄ : A compound of N _y .
In the present invention, the ratio of the rare earth in the basic composition x, y and N of the phosphor is not limited, but is preferably the following.
Here, at least one of M=Mg, Ca, and Ba, at least one of N=Ce, Pr, Nd, Sm, Eu, Tb, Dy, Er, and Yb, and the like, metal Si: 1 mol On the other hand, the content of M is 0.1 mol or more and 1.0 mol or less, and the content of N is 0.001 mol or more and 0.100 mol or less. Therefore, x is the content of M with respect to Si=1 mol, 0.1 mol≦x≦1.0 mol, and y is the content of N, 0.001 mol≦y≦0.100 mol.

The expression “afterglow” means light emission that can be visually confirmed for several minutes or more even after external stimulus is applied by irradiation with ultraviolet rays, electron beams, visible light, or the like and then the external stimulus is stopped. In the phosphor of the present invention, the afterglow intensity at the initial stage (1 minute after blocking the excitation light source) is about 3 times, and the afterglow intensity after 10 minutes is below the detection limit in the comparative example, whereas sufficient afterglow is obtained. The strength was recognized.
The composition of the rare earth-activated alkaline earth silicate compound afterglow phosphor of the present invention may be measured by any analysis method such as a fluorescent X-ray method and Fourier transform infrared spectroscopy (FTIR). Not done. The Cl content can be measured by an oxidative decomposition-coulometric titration method. Organic components such as C and O may be analyzed by gas chromatograph mass spectrometry (GC-MS), and other components may be analyzed by chemical titration analysis. In organic elemental analysis, C, O, H, N, etc. are combusted and decomposed in a combustion oxidation furnace and quantitatively converted to H ₂ O, CO ₂ , N ₂ , and each of these components is quantified by a thermal conductivity detector. There is a way to do it. The C content can be measured by combustion in an oxygen stream-infrared absorption method. In the elemental analysis, the analysis method is not limited in any case.

The afterglow phosphor of the present invention is a progress of sintering such as liquid phase formation, grain growth, and densification by mixing various alkali metals, which are fluxes described in the production method below, and chlorides of alkaline earths. On the other hand, the decomposition of the carbonate used as the raw material and the decomposition and disappearance of the flux component proceed in parallel. In many ceramic materials, the Cl residue used as the flux is generally thoroughly removed by washing or the like. However, in the present invention, the final result of the sintering behavior at these high temperatures is By intentionally leaving the amount of Cl in the densification process and using this amount as a parameter, it became possible to improve afterglow time and afterglow brightness, which are one of the problems. The characteristics of the afterglow phosphor of the present invention deteriorate if the residual amount of Cl is too large. When the final product, the afterglow phosphor of the present invention, contains 10000 ppm or less of Cl, the afterglow time and the afterglow brightness are improved. The residual amount of Cl is preferably 20 ppm to 10000 ppm, more preferably 20 ppm to 5000 ppm, still more preferably 30 ppm to 2000 ppm, and particularly preferably 50 ppm to 400 ppm.

The amount of residual carbon in the phosphor of the present invention, which is the final product, is preferably 0.3% by mass or less, and more preferably 20 ppm to 2500 ppm, since afterglow time and afterglow brightness are improved.

FIG. 2 shows SEM (scanning electron micrograph) photographs (3000 times) of the surfaces of the afterglow phosphors obtained in Example 1 and Comparative Example 1. In Comparative Example 1 without flux, a state in which fine rounded primary particles were aggregated was observed, and the particles were bonded to each other to the extent that they could be loosened even with a fingertip. On the other hand, it can be seen that the phosphor of the present invention (Example 1), which is a flux-added product and contains a predetermined amount of Cl, maintains the liquid phase, so that the particles are fused with each other to form huge spherical particles.

1. Method for producing rare earth activated alkaline earth silicate compound afterglow phosphor of the present invention (mixing of raw materials and oxidation firing)
The rare earth activated alkaline earth silicate compound afterglow phosphor of the present invention (hereinafter, sometimes referred to as the afterglow phosphor of the present invention) is produced by a compound soluble in a solvent containing a metal element as a raw material, For example, as a precursor of a metal organic compound using a metal organic compound or a nitrate, a metal organic acid salt, β-diketonate, metal alkoxide, or the like can be used. Specific examples thereof include metal acetate, metal diethylhexanoate, metal acetylacetonate, and metal naphthenate, but any metal organic compound that can be dissolved in a solvent can be used without particular limitation. The solvent is preferably methanol, ethanol, propanol, butanol, hexanol, heptanol, ethyl acetate, butyl acetate, toluene, xylene, benzene, acetylacetonate, ethylene glycol, water and the like.
In addition, a compound containing a metal that cannot be dissolved in a solvent or the like, for example, a solid material such as a metal oleate, a metal stearate, an oxide, or a carbonate can also be used. The solid materials are mixed by using a raw material which may be mixed uniformly by a ball mill and may contain a solvent in the form of particles. In the case of wet mixing, it is preferable to carry out drying after mixing to remove the solvent. When an organometallic compound or a nitrate is used as a raw material, a process of removing a solvent and an organic component at a temperature of less than 500° C., a firing process of 500° C. or more and less than 1500° C., and a firing process of 1500° C. or more can be arbitrarily combined. Alternatively, the baking may be performed in a single step.

(Decarburization process)
In the afterglow phosphor of the present invention, the raw material at the time of synthesis may not take an oxide form such as carbonate and hydroxide, and decarburization is particularly important when carbonate is used as the raw material. .. The present invention includes the step of calcining a mixture of various carbonate raw materials in an oxidizing atmosphere before adding the flux. In this step, suppression of sintering of the phosphor material and promotion of decarburization are optimized, and the calcination temperature is 1050°C or lower, preferably 450°C or higher and 1050°C or lower. It is known that at temperatures higher than 1050° C., decarburization is promoted, but crystallization of the raw material mixed powder is promoted, which hinders substitution solid solution of the rare earth element added during reduction firing. The residual carbon amount is preferably 0.3% by mass or less. When it is more than 0.3% by mass, sintering inhibition and deterioration of afterglow characteristics in the reduction baking in the next step are observed.

The rare earth may be added to the raw material from the beginning, or the rare earth may be added when the calcined powder is crushed.
(Adding flux)
The chloride flux that can be used is an alkali metal or alkaline earth metal such as MgCl ₂ , CaCl ₂ , SrCl ₂ , BaCl ₂ , KCl, NaCl, LiCl, or NH ₄ Cl, preferably CaCl ₂ , It is NaCl. As the flux, hydroxides such as Mg(OH) ₂ , Ca(OH) ₂ , Sr(OH) ₂ , Ba(OH) ₂ , KOH, NaOH and LiOH are also effective in addition to these chlorides. At least one selected from these is added at the time of pulverizing the tentatively-named powder before reduction firing or at the time of reduction firing. A combination of hydroxide and chloride may be used as a flux.
When crushing the calcined powder, it is preferable to add a flux as a Cl amount in the range of 0.05% by mass or more and less than 5.0% by mass in the phosphor of the present invention as a final product. If it is less than 0.05% by mass, the amount of liquid phase produced is small and the grain growth is small. If it is 5.0% by mass or more, although the grain growth is large, the amount of residual Cl is large and the afterglow characteristics are deteriorated.

(Reduction firing)
The oxidative firing raw material, which is a calcined powder to which rare earths and fluxes are added, may be used in the form of powder during reduction firing or in the form of pellets by press molding.
The reduction firing is performed at 1300 to 1500° C. for 2 to 6 hours in a hydrogen atmosphere composed of 3 volume% H ₂ -97 volume% N ₂ to obtain the afterglow phosphor of the present invention. Sintering behavior using the thermal loss characteristics by suggestive thermal analysis (TG) and shrinkage behavior by thermo-mechanical analysis (TMA, where the characteristics of the sintering behavior in a reducing atmosphere were measured in the atmosphere). As a result of an intensive investigation, it is preferable for the grain growth that Tf0=Ts1<Td1=Tf1<Tf2=Td2<Ts2 by optimizing the type and addition amount of the flux and minimizing the residual carbon amount during calcination. The conditions have been clarified.
Where Tf0 is the temperature at which the flux forms a liquid phase,
Ts1: aggregation start temperature of the oxidative firing raw material,
Td1: decarburization start temperature of residual carbon,
Tf1: decomposition start temperature of liquid phase,
Tf2: decomposition end temperature of liquid phase,
Td2: decarburization end temperature,
Ts2: temperature at which sintering progresses and shrinkage starts,
Specifically, Tf0 is 300°C to 600°C, Tf1 is 400°C to 800°C, Tf2 is 600°C to 900°C, and Ts2 is 700°C or higher.

FIG. 1 shows the sintering temperature in a hydrogen atmosphere composed of 3% by volume H ₂ -97% by volume N ₂ in Example 1 and Comparative Example 1 measured using TMA (thermo-mechanical analysis) and the sintering target. The difference in shrinkage behavior is shown. From FIG. 1, both of Example 1 and Comparative Example 1 show shrinkage due to aggregation/rearrangement at about 300° C., but in Example 1 in the process of forming the liquid phase, the liquid phase is continuously changed after the aggregation shrinkage. The contraction stops while holding. In Example 1, the liquid phase is generated on the low temperature side, and the liquid phase is retained, and there is a slightly flat period when the flat contraction is stopped, but in Comparative Example 1, the liquid phase is not seen and decarburization is performed after the progress of aggregation. It can be seen that a slight expansion occurs when the weight is reduced by, and the shrinkage rate becomes constant until the end of the measurement at 1050° C., and sintering does not proceed. In Example 1, decarburization and decomposition of liquid phase components occur almost at the same time, and the expansion behavior becomes larger than that of Comparative Example 1. In Example 1, abrupt shrinkage occurred at about 800° C. after decarburization and disappearance of the liquid phase component, and the final shrinkage ratio was equal to that of Comparative Example 1.

The difference in behavior in the above reduction sintering step is also shown in FIG. 2, which is a surface SEM (scanning electron microscope photograph) photograph (3000 times) of the afterglow phosphors obtained in Example 1 and Comparative Example 1. Has been done. That is, the SEM (scanning electron microscope photograph) photograph of the afterglow phosphor of the present invention obtained in Example 1 shows that the presence of the liquid phase causes smooth grain growth and that the homogeneity of the afterglow phosphor is Although it is shown to be high, in Comparative Example 1, since no liquid phase is seen during reduction sintering, it is shown that the particles before sintering are slightly necked.

The sintered powder or sintered pellet obtained by reduction firing was pulverized in the range of particle diameter of 75 μm or less, and classified as required to obtain a sample for evaluation. It has been clarified that the classification has a suitable effect on the afterglow brightness and the afterglow time, but in using the afterglow phosphor of the present invention, the final particle size is not particularly limited.

The inventor believes that the mechanism of the present invention is not limited, but is as follows. The afterglow phosphor of the present invention exhibits afterglow by optimizing rare earths, and the afterglow time is lengthened by controlling the particle size by intentionally remaining Cl due to the addition of a flux and the firing conditions. I believe. Although the production conditions of the present invention do not limit the afterglow phosphor of the present invention, it is a preferable method in the laboratory to produce the afterglow phosphor of the present invention.
1) When the final product, the afterglow phosphor of the present invention, contains 10000 ppm or less of Cl, afterglow time and afterglow brightness are improved.
2) The preferable production conditions for leaving Cl in the final product under the conditions of 1) above are two-stage atmosphere firing, which is oxidation firing in the air and reduction firing in a hydrogen-containing atmosphere. It is preferable to add the fluxing agent before the oxidation firing, or after the oxidation firing and before the reduction firing.
3) The decarburization step is important for removing carbon to some extent and leaving Cl in the final product under the conditions of 1) in the subsequent reduction step. That is, in the decarburization step, it is preferable to remove carbon at a temperature as low as possible under a temperature at which the crystal phase of the mother crystal is not determined, that is, under the condition that crystallization does not occur. The preferable condition of the oxidation firing (decarburization step) is 1050° C.×4 hours, and when the temperature is lowered, the time is extended. However, the temperature should not exceed 1100°C.

<Example 1>
(1) Mixing of raw materials and calcination Sr, Ca, and Si, which are main raw materials, are mixed with SrCO ₃ :CaCO ₃ :SiO ₂ =1.583:0.383:1.0 in composition ratio (mol), and rare earth. As a composition, Eu ₂ O ₃ and Dy ₂ O ₃ are added at a composition ratio (mol) of 0.0025 and 0.015 with respect to metal Si=1 mol, respectively, and wet-mixed and dried, and then at 1050° C.×4 hours in the atmosphere. Firing was performed to obtain a calcined powder.
(2) Addition of flux When crushing the calcined powder in a mortar, 1.0% by mass of CaCl ₂ as a flux was added as a flux to the total weight and mixed. Table 1 shows the amount of the flux added in Example 1 and Comparative Examples 1 to 3.
(3) Reduction firing The mixed powder was put in an alumina boat and fired in a hydrogen atmosphere at 1400° C. for 4 hours to obtain an afterglow phosphor. The obtained afterglow phosphor was pulverized to have a particle size of 75 μm or less and used as an optical property evaluation sample. The amount of residual Cl and the amount of residual carbon are shown in Table 1 together with the result of Comparative Example 1.
A SEM (scanning electron microscope) photograph of the surface of the obtained afterglow phosphor is shown in FIG. 2 together with a photograph of a comparative example.

(4) When the emission wavelength was 575 nm, an excitation spectrum having a peak at 290 nm to 400 nm was shown (FIG. 3A).
(5) When the excitation wavelength was 365 nm, an emission spectrum having a peak at 500 nm to 600 nm was shown (FIG. 3B).
(6) FIG. 4 shows the results obtained by irradiating the ultraviolet ray with 365 nm for 5 minutes, and tracing the single wavelength (575 nm) of the afterglow with the lapse of time after the irradiation was stopped. It showed afterglow for more than 7 minutes.

(7) The composition of the sample after reduction firing was measured by the fluorescent X-ray method (XRF), and Sr, Ca, Si, Eu, and Dy showed good agreement with the charged composition. The value of Cl measured using oxidative decomposition-coulometric titration method Mitsubishi Chemical Analytech TOX-2100H type was about 400 ppm.
Further, the carbon content by combustion in an oxygen stream-infrared absorption method was 0.01% by mass.
(8) The obtained afterglow phosphor is Sr ₂ SiO ₄ (orthorhombic; Pnma(62)) or Ca _0.5 Sr _1.5 SiO ₄ (orthorhombic) by X-ray diffraction (XRD). Crystal: Pmnb(62)) was obtained as a main phase and a compound composed of two or more crystal phases was obtained.

<Comparative Examples 1 to 3>
The afterglow phosphor of Comparative Example 1 was obtained in the same process as in Example 1 except that the flux CaCl ₂ was not added. Table 1 shows the amount of residual Cl and the amount of residual carbon. The SEM photograph of the surface of the obtained afterglow phosphor is shown in FIG. Comparative Example 1 shows an excitation spectrum having a peak at 290 nm to 400 nm when excited at an emission wavelength of 575 nm as in Example 1 (FIG. 3A). When excited with ultraviolet light of 365 nm, it showed an emission spectrum having a peak at 500 nm to 600 nm (FIG. 3B). FIG. 4 shows the results obtained by irradiating the ultraviolet ray with 365 nm for 5 minutes and tracing the single wavelength of the afterglow with the lapse of time after the irradiation was stopped. As shown in Table 1, the afterglow was 0% after 10 minutes, which was below the detection limit. The afterglow intensity is shown as a relative value with the afterglow intensity of Example 1 at each elapsed time taken as 100%.
Table 1 shows the optical characteristics of Comparative Example 2 in which the amount of Cl contained in the afterglow phosphor is less than 50 ppm and Comparative Example 3 in which the amount of CaCl ₂ added is more than 400 ppm.

<Examples 2 to 6>
Chlorides other than CaCl ₂ were used for the flux, and the afterglow phosphors of Examples 2 to 6 were obtained in the same steps as in Example 1. The optical characteristics (after 1 minute and 10 minutes) are shown in Table 2.

The rare earth-activated alkaline earth silicate compound afterglow phosphor of the present invention is used as an afterglow phosphor display object used as a display object in a dark place, an inductive sign that exhibits an effect at the time of power loss, and illumination. , An afterglow (yellow to red) phosphor that emits blue-green to orange light when excited by ultraviolet rays due to daytime sunlight and indoor lighting and continues to emit light after excitation. Since it has high afterglow characteristics, it can be effectively used industrially as a display object in a dark place. Further, since it does not contain a sulfur (S) component, it is expected to have excellent weather resistance, and is highly useful in industry.

Claims (2)

Cl is contained, and the Cl content measured by oxidative decomposition-coulometric titration is 50 ppm or more and 10000 ppm or less ,
Equation _{(1) (Sr 2-x} , M x) 2-y SiO 4: N y
Here, x is the content of M with respect to Si=1 mol, 0.1 mol≦x≦1.0 mol, y is the content of N, and 0.001 mol≦y≦0.100 mol, M includes at least one of Mg and Ca, N includes Eu, and at least one selected from the group consisting of Pr, Nd, Sm, Tb, Dy, Er, and Yb.
And a rare earth activated alkaline earth silicate compound afterglow phosphor. The rare earth activated alkaline earth silicate compound afterglow phosphor according to claim 1, further containing 0.3 mass% or less of carbon measured by combustion in an oxygen stream-infrared absorption method .