Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
  • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
  • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
  • B42D25/30—Identification or security features, e.g. for preventing forgery
  • B42D25/36—Identification or security features, e.g. for preventing forgery comprising special materials
  • B42D25/378—Special inks
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent materials, e.g. electroluminescent or chemiluminescent
  • C09K11/08—Luminescent materials, e.g. electroluminescent or chemiluminescent containing inorganic luminescent materials
  • C09K11/77—Luminescent materials, e.g. electroluminescent or chemiluminescent containing inorganic luminescent materials containing rare earth metals

Definitions

• This disclosure relates to an infrared afterglow oxysulfide phosphor and a luminescent composition that have afterglow in the infrared region and are used for authenticity determination.
• the light emitted from the phosphor is visible light, it can be detected with the naked eye, and if it is infrared light, it can be received by an optical reader or the like to detect the latent image mark.
• the latent image mark for determining authenticity is hardly visible to the naked eye, it is difficult for a counterfeiter to print this latent image mark, and counterfeit or altered cards and counterfeit articles can be detected reliably.
• the contents recorded by the latent image mark can only be known by the genuine card manufacturer or article manufacturer, it is extremely difficult to counterfeit or alter cards, etc.
• phosphors that are excited by at least one of visible light and infrared light and emit light in the infrared region have been used.
• infrared-emitting phosphors for example, the following phosphors are known.
• Na 5 (Yb, Nd) (MoO 4 ) 4 see, for example, Japanese Patent Application Laid-Open No. 3-288984)
• Y,La,Lu) PO4 :Yb,Nd see, for example, Japanese Patent No. 3438188
• VO4 Yb, Nd
• These infrared emitting phosphors have emission peak wavelengths in the infrared region around 980 nm and 1020 nm.
• infrared emitting phosphors when excited by at least one of ultraviolet and visible light, emit afterglow even after the excitation is stopped.
• the following phosphors are known as this type of phosphor.
• Sr 2 SnO 4 :Nd see, for example, Japanese Patent No. 6249476)
• These infrared afterglow phosphors have an afterglow peak wavelength around 1100 nm.
• phosphors having different emission characteristics from those described above which can be distinguished from or used in combination with the above phosphors.
• the present disclosure aims to provide an oxysulfide phosphor and a luminescent composition for authenticity determination that have afterglow peaks in the infrared region around 980 nm and 1020 nm for several seconds to several tens of seconds after excitation.
• oxysulfide phosphors activated with specific elements have distinctive afterglow properties and are useful as infrared afterglow oxysulfide phosphors and luminescent compositions for authenticity determination for the above-mentioned purposes.
• the present disclosure includes the following aspects.
• Ln is at least one element selected from Y, La, Gd and Lu
• R is at least one element selected from Mg, Sr, Ba, Zn, Ga, Zr, Mo, Mn, Sc, Hf, Ta and Nb.
• ⁇ 5> The infrared afterglow oxysulfide phosphor according to any one of ⁇ 1> to ⁇ 3>, wherein Ln is Gd.
• ⁇ 6> The infrared afterglow oxysulfide phosphor according to any one of ⁇ 1> to ⁇ 5>, wherein R is at least one element selected from the group consisting of Mg and Ga.
• ⁇ 7> A light-emitting composition for determining authenticity, comprising the infrared afterglow oxysulfide phosphor according to any one of ⁇ 1> to ⁇ 6>.
• the disclosed infrared afterglow oxysulfide phosphor and luminescent composition for authenticity determination can provide an oxysulfide phosphor and luminescent composition for authenticity determination that have afterglow in the infrared region for several seconds to several tens of seconds after excitation.
• FIG. 1 is a graph showing a spectrum of afterglow emission of an infrared afterglow oxysulfide phosphor in Example 2 according to the present disclosure, measured by a silicon photodiode detector.
• FIG. 2 is a graph showing a spectrum of the afterglow emission of the infrared afterglow oxysulfide phosphor in Example 2 according to the present disclosure, measured by an InGaAs photodiode detector.
• FIG. 3 is a graph showing the spectra of afterglow light emitted by the infrared afterglow oxysulfide phosphors in Examples 1 and 2 and Comparative Example 2 according to the present disclosure, measured by a silicon photodiode detector.
• FIG. 1 is a graph showing a spectrum of afterglow emission of an infrared afterglow oxysulfide phosphor in Example 2 according to the present disclosure, measured by a silicon photodiode detector.
• FIG. 4 is a graph showing the spectra of afterglow emission of the infrared afterglow oxysulfide phosphors in Examples 2, 10, and 13 according to the present disclosure and Comparative Example 2, measured by a silicon photodiode detector.
• FIG. 5 is a graph showing glow curves obtained by thermoluminescence measurement of the infrared afterglow oxysulfide phosphor in Example 1 according to the present disclosure and the infrared oxysulfide phosphor in Comparative Example 1.
• the raw materials of the infrared afterglow oxysulfide phosphor are prepared as follows: yttrium oxide (Y 2 O 3 ) as a raw material for yttrium (Y), elemental sulfur (S) as a raw material for sulfur (S), ytterbium oxide (Yb 2 O 3 ) as a raw material for ytterbium (Yb) used as an activator, magnesium carbonate (MgCO 3 ) as a raw material for magnesium (Mg) used as a coactivator, and gallium oxide (Ga 2 O 3 ) as a raw material for gallium (Ga).
• oxides are exemplified as raw materials, but other compounds that change into oxides when fired, such as carbonates, may be selected.
• the flux for example, an alkali metal carbonate such as sodium carbonate ( Na2CO3 ) or sodium hydrogen carbonate ( NaHCO3 ), a phosphate such as lithium phosphate ( Li3PO4 ), potassium phosphate ( K3PO4 ) or potassium hydrogen phosphate ( K2HPO4 ), a boron compound such as boric acid ( H3BO3 ) , or an alkali metal sulfate such as potassium sulfate ( K2SO4 ) can be suitably used .
• an alkali metal carbonate such as sodium carbonate ( Na2CO3 ) or sodium hydrogen carbonate ( NaHCO3
• a phosphate such as lithium phosphate ( Li3PO4 ), potassium phosphate ( K3PO4 ) or potassium hydrogen phosphate ( K2HPO4 )
• a boron compound such as boric
• the raw material powders are placed in a pot containing alumina balls and mixed in a ball mill to produce a uniform mixture.
• This mixed powder is filled into a heat-resistant container such as an alumina crucible.
• This may be further placed into a larger quartz crucible to form a double crucible.
• This is placed in an electric furnace and fired at a temperature range of 900° C. to 1300° C., preferably 950° C. to 1250° C., for 1 hour to 8 hours, preferably 2 hours to 6 hours.
• a phosphor having a predetermined particle size is obtained through appropriate steps such as a crushing step, a washing step, a drying step, and a sieving step.
• a light-emitting composition for determining authenticity that contains the infrared afterglow oxysulfide phosphor will be described.
• a luminescent composition as exemplified below is prepared.
• a transparent ink is mixed with an infrared afterglow oxysulfide phosphor to prepare an ink-like luminescent composition.
• This ink-like luminescent composition can be applied to a genuine product for marking.
• a transparent resin is mixed with an infrared afterglow oxysulfide phosphor to prepare a resin-like composition.
• this can be formed into a film and used as a part of a card or the like.
• the film-like composition can also be cut into strips and mixed with paper or a resin film to be used for banknotes or securities.
• a luminescent composition for authenticity determination can be obtained by mixing a translucent medium with an infrared afterglow oxysulfide phosphor.
• the infrared afterglow oxysulfide phosphor according to this embodiment may have lattice defects in the crystals contained in the infrared afterglow oxysulfide phosphor.
• lattice defects may be due to substitutional solid solution of Yb or R, or may be due to interstitial solid solution.
• Yb 3+ is present in the crystal in a state in which at least a portion of the Ln, and probably most of the dissolved Yb 3+, is substituted for Ln, and the phosphor exhibits excellent afterglow characteristics as described below.
• the infrared afterglow oxysulfide phosphor of the present disclosure and its characteristics will be described.
• the present disclosure is not limited to these examples.
• Example 1 As raw materials, 100 g of yttrium oxide ( Y2O3 ), 7.7 g of ytterbium oxide ( Yb2O3 ) , 4.8 g of magnesium carbonate ( MgCO3 ), and 55.1 g of elemental sulfur (S) were weighed out, and as fluxes, 52.5 g of sodium carbonate ( Na2CO3 ) and 32.7 g of potassium phosphate trihydrate ( K3PO4.3H2O ) were weighed out, and the above raw materials and fluxes were thoroughly mixed using a ball mill . The mixture was filled into an alumina crucible and fired in air at 1200°C for 4 hours using an electric furnace .
• Y2O3 yttrium oxide
• Yb2O3 ytterbium oxide
• MgCO3 magnesium carbonate
• S elemental sulfur
• Example 2 A compound represented by Y 1.88 O 2 S:Yb 0.005 , Mg 0.115 was obtained in the same manner as in Example 1, except that the elements and their molar ratios were changed as shown in Table 1.
• Example 3 A compound represented by Y 1.8849 O 2 S:Yb 0.0001 , Mg 0.115 was obtained in the same manner as in Example 1, except that the elements and their molar ratios were changed as shown in Table 1.
• Example 4 A compound represented by Y 1.685 O 2 S:Yb 0.2 ,Mg 0.115 was obtained in the same manner as in Example 1, except that the elements and their molar ratios were changed as shown in Table 1.
• Example 5 A compound represented by Y 1.9199 O 2 S:Yb 0.08 , Mg 0.0001 was obtained in the same manner as in Example 1, except that the elements and their molar ratios were changed as shown in Table 1.
• Example 6 A compound represented by Y 1.905 O 2 S:Yb 0.08 , Mg 0.015 was obtained in the same manner as in Example 1, except that the elements and their molar ratios were changed as shown in Table 1.
• Example 7 A compound represented by Y 1.72 O 2 S:Yb 0.08 , Mg 0.2 was obtained in the same manner as in Example 1, except that the elements and their molar ratios were changed as shown in Table 1.
• Example 8 A compound represented by Y 1.52 O 2 S:Yb 0.08 ,Mg 0.4 was obtained in the same manner as in Example 1, except that the elements and their molar ratios were changed as shown in Table 1.
• Example 9 A compound represented by Y 1.12 O 2 S:Yb 0.08 ,Mg 0.8 was obtained in the same manner as in Example 1, except that the elements and their molar ratios were changed as shown in Table 1.
• Comparative Example 1 A compound represented by Y 1.92 O 2 S:Yb 0.08 was obtained in the same manner as in Example 1, except that the elements and their molar ratios were changed as shown in Table 1.
• Example 10 As raw materials, 100 g of gadolinium oxide (Gd 2 O 3 ), 0.29 g of ytterbium oxide (Yb 2 O 3 ), 2.84 g of magnesium carbonate (MgCO 3 ), and 32.9 g of elemental sulfur (S) were weighed out, and as fluxes, 31.1 g of sodium carbonate (Na 2 CO 3 ) and 19.5 g of potassium phosphate trihydrate (K 3 PO 4.3H 2 O) were weighed out, and the above raw materials and fluxes were thoroughly mixed using a ball mill. This mixture was treated in the same manner as in Example 1 to obtain a compound represented by Gd 1.88 O 2 S:Yb 0.005 ,Mg 0.115 .
• Gd 1.88 O 2 S:Yb 0.005 ,Mg 0.115 100 g of gadolinium oxide (Gd 2 O 3 ), 0.29 g of ytterbium oxide (Yb 2 O 3 ), 2.84 g of magnesium carbonate (MgCO 3
• Example 11 As raw materials, 100 g of yttrium oxide ( Y2O3 ), 8.1 g of lanthanum oxide ( La2O3 ), 0.49 g of ytterbium oxide ( Yb2O3 ) , 4.8 g of magnesium carbonate ( MgCO3 ), and 55.9 g of elemental sulfur (S) were weighed out, and as fluxes, 52.8 g of sodium carbonate ( Na2CO3 ) and 33.1 g of potassium phosphate trihydrate ( K3PO4.3H2O ) were weighed out, and the above raw materials and fluxes were thoroughly mixed using a ball mill . This mixture was treated in the same manner as in Example 1 to obtain a compound represented by Y1.78La0.1O2S : Yb0.005 , Mg0.115 .
• Example 12 As raw materials, 100 g of yttrium oxide ( Y2O3 ), 9.9 g of lutetium oxide ( Lu2O3 ), 0.49 g of ytterbium oxide ( Yb2O3 ) , 4.8 g of magnesium carbonate ( MgCO3 ), and 55.9 g of elemental sulfur (S) were weighed out, and as fluxes, 52.8 g of sodium carbonate ( Na2CO3 ) and 33.1 g of potassium phosphate trihydrate ( K3PO4.3H2O ) were weighed out, and the above raw materials and fluxes were thoroughly mixed using a ball mill . This mixture was treated in the same manner as in Example 1 to obtain a compound represented by Y 1.78 Lu 0.1 O 2 S:Yb 0.005 ,Mg 0.115 .
• Example 13 Next, 100 g of yttrium oxide ( Y2O3 ), 0.46 g of ytterbium oxide ( Yb2O3 ) , 4.6 g of magnesium carbonate ( MgCO3 ), 0.044 g of gallium oxide ( Ga2O3 ) , and 52.9 g of elemental sulfur (S) were weighed out as raw materials, and 49.9 g of sodium carbonate ( Na2CO3 ) and 31.4 g of potassium phosphate trihydrate ( K3PO4.3H2O ) were weighed out as fluxes, and the above raw materials and fluxes were thoroughly mixed using a ball mill. This mixture was treated in the same manner as in Example 1 to obtain a compound represented by Y1.879O2S : Yb0.005 , Mg0.115 , Ga0.001 . These are summarized in Table 2.
• Comparative Example 2 As an existing infrared afterglow phosphor, a compound represented by Sr 1.98 SnO 4 :Nd 0.02 based on the description in Japanese Patent No. 6249476 was prepared.
• Example 14 As raw materials, 100 g of yttrium oxide ( Y2O3 ), 0.44 g of ytterbium oxide ( Yb2O3 ) , 1.7 g of strontium carbonate ( SrCO3 ), and 50.5 g of elemental sulfur (S) were weighed out, and as fluxes, 47.7 g of sodium carbonate ( Na2CO3 ) and 32.2 g of potassium phosphate trihydrate ( K3PO4.3H2O ) were weighed out, and the above raw materials and fluxes were thoroughly mixed using a ball mill . This mixture was treated in the same manner as in Example 1 to obtain a compound represented by Y 1.97 O 2 S:Yb 0.005 ,Sr 0.025 .
• Example 15 As raw materials, 100 g of yttrium oxide ( Y2O3 ), 0.46 g of ytterbium oxide ( Yb2O3 ) , 10.7 g of barium carbonate ( BaCO3 ), and 52.9 g of elemental sulfur (S) were weighed out, and as fluxes, 49.9 g of sodium carbonate ( Na2CO3 ) and 33.8 g of potassium phosphate trihydrate ( K3PO4.3H2O ) were weighed out, and the above raw materials and fluxes were thoroughly mixed using a ball mill . This mixture was treated in the same manner as in Example 1 to obtain a compound represented by Y 1.88 O 2 S:Yb 0.005 ,Ba 0.115 .
• Example 16 As raw materials, 100 g of yttrium oxide ( Y2O3 ), 0.44 g of ytterbium oxide ( Yb2O3 ) , 0.91 g of zinc oxide (ZnO), and 50.5 g of elemental sulfur (S) were weighed out, and as fluxes, 47.7 g of sodium carbonate ( Na2CO3 ) and 32.2 g of potassium phosphate trihydrate ( K3PO4.3H2O ) were weighed out, and the above raw materials and fluxes were thoroughly mixed using a ball mill . This mixture was treated in the same manner as in Example 1 to obtain a compound represented by Y 1.97 O 2 S:Yb 0.005 , Zn 0.025 .
• Example 17 As raw materials , 100 g of yttrium oxide ( Y2O3 ), 0.46 g of ytterbium oxide ( Yb2O3 ), 5.1 g of gallium oxide ( Ga2O3 ) , and 52.9 g of elemental sulfur (S) were weighed out, and as fluxes, 49.9 g of sodium carbonate ( Na2CO3 ) and 33.8 g of potassium phosphate trihydrate ( K3PO4.3H2O ) were weighed out, and the above raw materials and fluxes were thoroughly mixed using a ball mill . This mixture was treated in the same manner as in Example 1 to obtain a compound represented by Y 1.88 O 2 S:Yb 0.005 ,Ga 0.115 .
• Example 18 As raw materials, 100 g of yttrium oxide ( Y2O3 ), 0.44 g of ytterbium oxide ( Yb2O3 ) , 0.27 g of zirconium oxide ( ZrO2 ) , and 49.9 g of elemental sulfur (S) were weighed out, and as fluxes, 47.2 g of sodium carbonate ( Na2CO3 ) and 21.9 g of potassium phosphate trihydrate ( K3PO4.3H2O ) were weighed out, and the above raw materials and fluxes were thoroughly mixed using a ball mill . This mixture was treated in the same manner as in Example 1 to obtain a compound represented by Y 1.99 O 2 S:Yb 0.005 , Zr 0.005 .
• Example 19 As raw materials, 100 g of yttrium oxide ( Y2O3 ), 0.44 g of ytterbium oxide ( Yb2O3 ) , 0.32 g of molybdenum oxide ( MoO3 ), and 49.9 g of elemental sulfur (S) were weighed out, and as fluxes, 47.2 g of sodium carbonate ( Na2CO3 ) and 31.9 g of potassium phosphate trihydrate ( K3PO4.3H2O ) were weighed out, and the above raw materials and fluxes were thoroughly mixed using a ball mill . This mixture was treated in the same manner as in Example 1 to obtain a compound represented by Y 1.99 O 2 S:Yb 0.005 ,Mo 0.005 .
• Example 20 As raw materials, 100 g of yttrium oxide ( Y2O3 ), 0.44 g of ytterbium oxide ( Yb2O3 ) , 0.26 g of manganese carbonate ( MnCO3 ), and 49.9 g of elemental sulfur (S) were weighed out, and as fluxes, 47.2 g of sodium carbonate ( Na2CO3 ) and 31.9 g of potassium phosphate trihydrate ( K3PO4.3H2O ) were weighed out, and the above raw materials and fluxes were thoroughly mixed using a ball mill . This mixture was treated in the same manner as in Example 1 to obtain a compound represented by Y 1.99 O 2 S:Yb 0.005 ,Mn 0.005 .
• Example 21 As raw materials, 100 g of yttrium oxide ( Y2O3 ), 0.44 g of ytterbium oxide ( Yb2O3 ) , 0.08 g of scandium oxide ( Sc2O3 ) , and 49.9 g of elemental sulfur (S) were weighed out , and as fluxes, 47.1 g of sodium carbonate ( Na2CO3 ) and 31.9 g of potassium phosphate trihydrate ( K3PO4.3H2O ) were weighed out, and the above raw materials and fluxes were thoroughly mixed using a ball mill . This mixture was treated in the same manner as in Example 1 to obtain a compound represented by Y 1.9925 O 2 S:Yb 0.005 , Sc 0.0025 .
• Example 22 As raw materials, 100 g of yttrium oxide ( Y2O3 ), 0.44 g of ytterbium oxide ( Yb2O3 ) , 0.94 g of hafnium oxide ( HfO2 ) , and 50.1 g of elemental sulfur (S) were weighed out, and as fluxes, 47.3 g of sodium carbonate ( Na2CO3 ) and 32.0 g of potassium phosphate trihydrate ( K3PO4.3H2O ) were weighed out, and the above raw materials and fluxes were thoroughly mixed using a ball mill . This mixture was treated in the same manner as in Example 1 to obtain a compound represented by Y 1.985 O 2 S:Yb 0.005 , Hf 0.01 .
• Example 23 100 g of yttrium oxide (Y 2 O 3 ), 0.44 g of ytterbium oxide (Yb 2 O 3 ), 0.25 g of tantalum pentoxide (Ta 2 O 5 ), and 50.0 g of elemental sulfur (S) were weighed out as raw materials, and 47.1 g of sodium carbonate (Na 2 CO 3 ) and 31.9 g of potassium phosphate trihydrate (K 3 PO 4.3H 2 O) were weighed out as fluxes, and the above raw materials and fluxes were thoroughly mixed using a ball mill. This mixture was treated in the same manner as in Example 1 to obtain a compound represented by Y 1.9925 O 2 S:Yb 0.005 , Ta 0.0025 .
• Example 24 100 g of yttrium oxide (Y 2 O 3 ), 8.1 g of ytterbium oxide (Yb 2 O 3 ), 13.7 g of niobium pentoxide (Nb 2 O 5 ), and 52.9 g of elemental sulfur (S) were weighed out as raw materials, and 52.5 g of sodium carbonate (Na 2 CO 3 ) and 32.7 g of potassium phosphate trihydrate (K 3 PO 4.3H 2 O) were weighed out as fluxes, and the above raw materials and fluxes were thoroughly mixed using a ball mill. This mixture was treated in the same manner as in Example 1 to obtain a compound represented by Y 1.72 O 2 S:Yb 0.08 ,Nb 0.2 . These are summarized in Table 3.
• Example 2 a multichannel spectrometer (type: PMA-12 silicon photodiode detector, manufactured by Hamamatsu Photonics) was used to measure the afterglow spectrum from 800 nm to 1100 nm. After irradiating ultraviolet light for 1 minute using an ultraviolet lamp (peak emission wavelength 365 nm) to create an excited state, the afterglow spectrum was measured using the multichannel spectrometer based on the count integrated value for 10 seconds immediately after the end of irradiation. The results are shown in FIG. 1.
• PMA-12 silicon photodiode detector manufactured by Hamamatsu Photonics
• the infrared afterglow oxysulfide phosphors of Examples 1 to 9 according to the present disclosure all exhibit higher afterglow intensity than Comparative Example 2. Comparative Example 1 did not exhibit clear afterglow. Therefore, the afterglow intensity is based on Comparative Example 2.
• the infrared afterglow oxysulfide phosphor according to the present disclosure is a phosphor that, unlike conventional infrared afterglow phosphors, exhibits detectable strong afterglow in the infrared region having peaks near 980 nm and near 1010 nm, which are characteristic of Yb3 +, within several seconds to several tens of seconds after excitation.
• the infrared afterglow oxysulfide phosphor according to the present disclosure is a phosphor that, unlike conventional infrared afterglow phosphors, exhibits detectable strong afterglow in the infrared region having peaks near 980 nm and near 1010 nm, which are characteristic of Yb3 +, within several seconds to several tens of seconds after excitation.
• the afterglow characteristics were investigated for Examples 14 to 24.
• the relative afterglow intensity results are shown in Table 6, with Comparative Example 2 set as 100.
• thermoluminescence intensity measured at a constant temperature rise rate and plotted as a function of temperature is called a glow curve, and this thermoluminescence intensity depends on the density of carriers (electrons or holes) trapped in lattice defects. Since the lattice defect concentration and the trapped carrier density are also proportional to each other, the thermoluminescence intensity increases as the lattice defect concentration increases.
• Figure 5 compares the glow curves of each sample at a temperature rise rate of 20 K/s.
• the infrared afterglow oxysulfide phosphor according to the light-emitting composition for authenticity determination of the present disclosure is a phosphor that exhibits detectable afterglow having peaks in the infrared region near 980 nm and near 1010 nm, which are characteristic of Yb 3+ , for several seconds to several tens of seconds after excitation.
• the phosphor since it exhibits characteristics different from conventional infrared afterglow phosphors, it is a phosphor that can be clearly distinguished from existing phosphors for authenticity determination by detecting afterglow having peaks in the infrared region near 980 nm and near 1010 nm, which are characteristic of Yb 3+ , for example, several seconds after excitation. In addition, it may be used in combination with existing phosphors for authenticity determination.
• the infrared afterglow oxysulfide phosphor and the luminescent composition for determining authenticity of the present disclosure exhibit excellent afterglow characteristics different from those of conventional infrared afterglow phosphors, and therefore can be suitably used for forming a latent image mark for determining authenticity to prevent counterfeiting.
• the infrared afterglow oxysulfide phosphor and the light-emitting composition for authenticity determination according to the present disclosure unlike conventional infrared afterglow phosphors, exhibit detectable afterglow in the infrared region for several seconds to several tens of seconds after excitation, and have peaks at around 980 nm and 1010 nm, which are characteristic of Yb 3+ , and therefore can be differentiated from existing phosphors for authenticity determination, and by combining with existing phosphors for authenticity determination, a latent image mark with even higher security can be formed.
• the composition can be suitably used for preventing counterfeiting of securities, banknotes, prepaid cards, ID cards, various passes, and credit cards, as well as for preventing counterfeiting of brand-name products and genuine products.
• the infrared afterglow oxysulfide phosphor and the luminescent composition for authenticity determination disclosed herein emit excellent infrared afterglow, they can be provided on a subject to serve as a marker, and are also suitable for tracing applications in which the subject can be identified and tracked in the dark using a night vision scope or the like.
• the infrared afterglow oxysulfide phosphor and the luminescent composition for authenticity determination disclosed herein further have a sustained afterglow in the infrared region, and are therefore expected to be used for in vivo optical imaging.

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