KR20210114588A - Method of preparing UC fluorescent particle, UC fluorescent particle made thereby and fluorescent ink including the same - Google Patents

Abstract

The present invention relates to a method for preparing an upconversion (UC) phosphor particle, an upconversion phosphor particle prepared thereby, and a phosphor ink including the same. More specifically, the present invention relates to a method for preparing a UC phosphor particle which does not show the loss of UC fluorescent characteristics due to a phase change, even at high temperature, has an excellent luminance, and has a low manufacturing cost, a UC phosphor particle prepared thereby, and a phosphor ink including the same.

Description

Method of preparing UC fluorescent particle, UC fluorescent particle made thereby and fluorescent ink including the same

The present invention relates to a method for manufacturing upconversion phosphor particles, an upconversion phosphor particle manufactured thereby, and a fluorescent ink including the same, and more particularly, to a high temperature without losing UC fluorescence properties due to a phase change and having excellent luminance. And it relates to a method for producing UC phosphor particles, characterized in that the production cost is low, to UC phosphor particles produced by the method, and to a fluorescent ink comprising the same.

A phosphor is a material that emits light corresponding to the energy difference when it receives external energy and is excited from the ground state of electrons to an excited state and then returns to the ground state. Today, phosphors are used in various ways, such as light emitting diodes (LEDs), solar cells, photocatalysts, optical sensors, and semiconductors. According to the change of today's industrial technology, various products are produced, but the problem of the counterfeit product market has come to the fore. In the past, the counterfeit market was dominated by luxury bags and luxury clothing, but now a variety of counterfeit products such as cosmetics, health food, and electronic devices are overflowing. To prevent this, a QR code was introduced into the product, but until recently, until the Board of Audit and Inspection, the QR code means that customs clearance has been completed legally, and the authenticity of the product is unclear, causing confusion among consumers. Therefore, there is a method of using a fluorescent pigment as a technology that can compensate for this.

A specific pattern and mark are made using a luminescent material, and the fluorescent pigment in a specific pattern is made to emit light in a specific pattern by Near Infrared Ray (NIR) or Ultraviolet (UV) light. As an example of a method, it is possible to visually determine whether a bill is forged or not.

Rare-earth bases used for phosphor manufacturing are expensive materials compared to their weight. Therefore, there is an economic problem in mass production in the production of current anti-counterfeiting labels and marks. For this reason, it is necessary to develop a fluorescent pigment that can lead to mass production at a lower unit cost. Among the phosphor matrix, TiO ₂ is the most suitable material for the production of anti-counterfeiting products because it has abundant mineral reserves and is inexpensive and stable. Since the _{band gap of TiO 2} is 3.0 ~ 3.2 eV, which is relatively large compared to other parent materials, it absorbs light in the ultraviolet region and can be used in various fields such as solar cells, photocatalysts, and semiconductors. While TiO ₂ has these advantages, it also has fatal disadvantages for phosphor applications.

Depending on the firing temperature, it is largely divided into an anatase phase and a rutile phase. The anatase phase crystallizes in a narrow region of 400 to 470°C and is used for phosphors and solar cells. It is not suitable as a phosphor due to change, so it is used as a white paint for paints, paints, inks, sunscreens, etc., and has limited phosphor application. Therefore, there is a need for research and development of UC phosphors that can improve thermal stability and luminance by maintaining anatase phase in phosphor applications.

Registered Patent Publication No. 10-1957927 (2019.03.07.)

The present invention has been devised to solve the above problems, and the problem to be solved by the present invention is that it can be manufactured at a lower unit cost compared to the conventional UC phosphor particles, and has excellent luminance without losing fluorescence properties against high temperature heat treatment. To provide a method for producing UC phosphor particles.

Another object of the present invention is to provide a UC phosphor composition for producing the UC phosphor particles, and to provide UC phosphor particles having excellent luminance without losing fluorescence properties even when heat-treated at a high temperature. .

In order to solve the above problems, the present invention is (1) a host precursor mixture comprising each of titanium (Titanium, Ti) and silicon (Silicon, Si), and erbium (Erbium, Er) and ytterbiu (Ytterbiu) , Yb) preparing a spray solution by dissolving a dopant precursor mixture containing each in a solvent;

(2) heating and reacting the spray solution to a predetermined temperature and drying the spray solution to obtain a precursor powder; and

(3) heat-treating the precursor powder; provides an up-conversion (UC) phosphor particle manufacturing method comprising.

In a preferred embodiment of the present invention, step (2) may be performed by a spray pyrolysis method.

In a preferred embodiment of the present invention, titanium may have a greater mole fraction than silicon in the spray solution.

In a preferred embodiment of the present invention, step (3) may be performed by heat treatment at a temperature of 600 °C to 750 °C.

In a preferred embodiment of the present invention, in step (1), the mole fraction of silicon may be 2 mol% to 30 mol%.

In a preferred embodiment of the present invention, the spray solution comprises the erbium and ytterbium in a mole fraction of 0.1 mol% to 1 mol% and 2 mol% to 10 mol% UC phosphor particle manufacturing method .

In a preferred embodiment of the present invention, step (2) may be performed at a temperature of 700 °C to 1,100 °C.

In order to solve the above problems, the present invention also provides a UC phosphor composition including a parent precursor mixture including titanium and silicon, respectively, and a dopant precursor mixture including erbium and ytterbium, respectively.

In a preferred embodiment of the present invention, the parent precursor including silicon may be included so that silicon has a mole fraction of 2 mol% to 30 mol%.

The present invention also reacts the UC phosphor composition to solve the above problems It provides UC phosphor particles comprising a compound represented by the following formula (1).

[Formula 1]

(Ti _1-xyz Si _x Er _y Yb _z )O ₂

In Formula 1, 0.02≤x+y+z≤0.4.

In a preferred embodiment of the present invention, Chemical Formula 1 may satisfy at least one of the following conditions 1) to 3).

1) 0.02≤x≤0.3

2) 0.001≤y≤0.01

3) 0.02≤z≤0.1.

The present invention also provides a fluorescent ink comprising the UC phosphor particles.

According to the method for manufacturing UC phosphor particles according to the present invention, the manufacturing cost can be reduced, and manufacturing is possible through a simple process. The prepared UC phosphor particles can be heat-treated at high temperature, but the loss of fluorescence properties due to phase change can not occur or can be minimized.

상기 관계식 1에서, A는 상기 UC 형광체 입자의 XRD 패턴에 나타난 피크 가운데 2θ가 25.3±0.2˚인 영역에서 최고점을 갖는 피크의 영역(area), R은 상기 UC 형광체 입자의 XRD 패턴에 나타난 피크 가운데 2θ가 27.4±0.2˚인 영역에서 최고점을 갖는 피크의 영역(area)을 나타낸다.
도 9는 Si 농도에 따른 TiO₂계 UC 형광체 입자의 열처리 온도에 따른 최대 발광 파장에서의 발광 휘도를 나타낸 그래프이다.
도 10a는 Si 농도에 따른 TiO₂계 UC 형광체 입자를 700℃로 열처리하였을 때의 PL 스펙트럼을 나타낸 그래프이다.
도 10b는 TiO₂계 UC 형광체 입자를 700℃로 열처리하였을 때, Si농도에 따른 최대 방출 파장에서의 방출 강도를 나타낸 그래프이다.
도 10c는 TiO₂계 UC형광체 입자를 700℃로 열처리하였을 때, Si농도에 따른 XRD 패턴의차이를 비교한 도면이다.
도 11a는 Si 2.5 mol%인 TiO₂계 UC 형광체 입자의 TEM 이미지이다.
도 11b는 Si 10 mol%인 TiO₂계 UC 형광체 입자의 TEM 이미지이다.
도 12a는 Si 2.5 mol%인 TiO₂계 UC형광체 입자의 EDX 이미지이다.
도 12b는 Si 10mol%인 TiO₂계 UC 형광체 입자의 EDX 이미지이다.
도 13은 본 발명의 일 실시예에 따른 UC 형광체 입자를 포함하여 제조한 위조방지용 형광 마크를 적용한 시료에 975nm 레이저를 입사시켰을 때 마크가 발광하는 모습을 촬영한 사진이다.1 is a photograph of a bill applied with anti-counterfeiting ink.
2 is a diagram schematically illustrating upconversion fluorescence and downconversion fluorescence phenomena.
3 is a view schematically showing a method of manufacturing upconverted phosphor particles according to a preferred embodiment of the present invention.
4 is a band gap diagram of _{TiO 2 .}
5a is a PL spectrum according to the heat treatment temperature of _{TiO 2} -based UC phosphor particles not containing Si.
FIG. 5b is a PL spectrum according to the heat treatment temperature of _{TiO 2} based UC phosphor particles in which Si is included in a mole fraction of 10 mol%.
FIG. 5c is a graph showing the emission intensity at the maximum emission wavelength according to the heat treatment temperature of _{TiO 2} based UC phosphor particles when Si is 0 mol% and 10 mol%.
6 is a graph showing changes in XRD pattern and crystallite size (D _{c ) according to the heat treatment temperature of TiO 2 -based UC phosphor particles not containing Si.}
7 is a view showing changes in XRD pattern and crystallite size (D _{c ) according to the heat treatment temperature of TiO 2} -based UC phosphor particles containing Si in an amount of 10 mol%.
8 is a graph showing changes in %Rutile, which is the ratio of rutile phase calculated according to Relation 1 below (left) and (right) crystallite size, according to the heat treatment temperature of TiO2-based UC phosphor particles when Si is 0 mol% and 10 mol%; This is the graph shown.
[Relational Expression 1]

In Relation 1, A is the area of the peak having the highest point in the region where 2θ is 25.3±0.2˚ among the peaks shown in the XRD pattern of the UC phosphor particle, and R is the peak area of the peak shown in the XRD pattern of the UC phosphor particle. The area of the peak having the highest point in the region where 2θ is 27.4±0.2° is indicated.
9 is a graph showing emission luminance at the maximum emission wavelength according to the heat treatment temperature of _{TiO 2} -based UC phosphor particles according to the Si concentration.
FIG. 10a is a _{graph showing a PL spectrum when TiO 2} based UC phosphor particles were heat treated at 700° C. according to Si concentration.
FIG. 10b is a graph showing emission intensity at the maximum emission wavelength according to Si concentration when _{TiO 2 based UC phosphor particles were heat treated at 700° C. FIG.}
FIG. 10c is a diagram comparing the difference in XRD patterns according to Si concentration when _{TiO 2 based UC phosphor particles were heat treated at 700° C. FIG.}
11a is a TEM image of _{TiO 2} based UC phosphor particles containing 2.5 mol% of Si.
11B is a TEM image of _{TiO 2} based UC phosphor particles containing 10 mol% of Si.
12a is an EDX image of _{TiO 2} based UC phosphor particles containing 2.5 mol% of Si.
12B is an EDX image of _{TiO 2} based UC phosphor particles containing 10 mol% of Si.
13 is a photograph of a state in which the mark emits light when a 975 nm laser is incident on a sample to which the anti-counterfeiting fluorescent mark manufactured including the UC phosphor particles according to an embodiment of the present invention is applied.

Before describing the present invention in detail, the meaning of the terms used herein is defined.

As used herein, the term “mol fraction” is defined as meaning the molar fraction between metal atoms positioned at the cation lattice site when the parent, activator, deactivator, and dopant constitute the phosphor particle.

Originally, silicon as a metalloid has both metallic and non-metallic properties, but in the present specification, silicon is regarded as a metal. Accordingly, the number of metal atoms for the calculation of the mole fraction includes the number of silicon atoms.

Hereinafter, the present invention will be described in more detail.

As described above, conventional phosphors are down-conversion (DC) phosphors or up-conversion phosphors, which have a high unit cost, such as using a rare earth metal as a matrix. There is a problem in that the fluorescence characteristic is lost or the luminance of light is lowered due to a phase transformation during heat treatment.

In order to solve this problem, the present invention (1) a host precursor mixture containing titanium (Titanium, Ti) and silicon (Silicon, Si), respectively, erbium (Erbium, Er) and ytterbium (Ytterbium, Yb) preparing a spray solution by dissolving a dopant precursor mixture including each in a solvent;

(2) heating and reacting the spray solution to a predetermined temperature and drying the spray solution to obtain a precursor powder; and

(3) heat-treating the precursor powder; provides an up-conversion (UC) phosphor particle manufacturing method comprising.

The UC phosphor particles prepared according to the manufacturing method of the present invention include silicon in the metal cation lattice of the matrix, so that no phase change occurs even during high-temperature heat treatment, thereby maintaining excellent upconversion fluorescence properties.

In particular, preferably, step (2) may be performed by a spray pyrolysis method. In the case of the spray pyrolysis process, an atmospheric pressure process is possible, and there is an advantage in that it can be manufactured in a simple process because it does not need to go through a milling process.

Hereinafter, each step will be described.

3 is a schematic diagram illustrating a method of manufacturing UC phosphor particles step by step according to an embodiment of the present invention.

Referring to Figure 3, the parent titanium precursor TTIP (Titanium (IV) isopropoxide, TiC ₁₂ H ₂₈ O ₄ ), the parent silicon Preparing a spray solution containing each of the precursor TEOS (Tetraethyl orthosilicate, SiC ₈ H ₂₀ O ₄ ) and the dopant precursors Er ₂ O ₃ and Yb ₂ O _{3 ;} reacting the spray solution through spray pyrolysis; and heat-treating (calcining) the precursor powder obtained by spray pyrolysis of the spray solution.

(Step 1

The UC phosphor particles of the present invention have a titanium dioxide (TiO ₂ ) compound as a matrix, and a part of titanium is substituted with silicon (Ti, Si)O ₂ to form a matrix. In order to provide a reaction process containing erbium and ytterbium dopants serving as activators and deactivators in such a matrix, a spray solution containing them is first prepared.

The spray solution means that when the solution of the parent and dopant precursor mixture is heated and reacted, the solution is sprayed according to the spray pyrolysis reaction to perform the spray pyrolysis process in a droplet state. In the case of proceeding to a simple liquid phase reaction rather than a spray pyrolysis reaction, although the term “spray” is included, the spray solution is not sprayed. In the present invention, UC phosphor particles cannot be necessarily prepared only by spray pyrolysis, but may also be prepared by a liquid-phase manufacturing method.

In the case of the liquid manufacturing method, the spray solution is heated to 40°C to 50°C to form particles by a sol-gel reaction, followed by thermal decomposition thereof.

The spray solution includes a mixture of the parent titanium precursor and the parent silicon precursor, and further includes a dopant precursor mixture. The dopant refers to a small amount of impurity metal that replaces a part of the metal cation lattice in the matrix, and includes an activator and a co-activator. Accordingly, the dopant precursor mixture includes an activator precursor and a deactivator precursor. The precursor mixture of the parent _{forms a (Ti, Si)O 2} lattice by subsequent thermal decomposition, thereby forming the matrix of the UC phosphor particles of the present invention.

The parent titanium precursor is preferably one or more selected from an alkoxide of titanium, titanium sulfate hydrate, TiCl ₄ , and TiO _{2 nanoparticles.} The alkoxide of titanium may be, for example, TTIP described above, but is not necessarily limited thereto, and is not necessarily limited to the alkoxide of titanium. A parent precursor may be selected from coordination compounds capable of stably providing titanium (IV).

The parent silicon precursor supplies Si cations to the titanium oxide matrix to replace a part of Ti with Si in the matrix, and the titanium oxide matrix in which Si is partially substituted has better stability to high temperature.

The parent silicon precursor may be one or more selected from TEOS and other TMOS (Tetramethyl orthosilicate), SiCl ₄ , and SiO ₂ nanoparticles, preferably TEOS, but is not necessarily limited thereto. Among the coordination compounds that can stably provide Si cations, the parent silicon precursor can be selected.

In addition to the parent titanium precursor and the parent silicon precursor, the spray solution also includes a dopant precursor. Among them, the activator precursor includes erbium, and may preferably be erbium oxide. An example of an erbium oxide is Er ₂ O ₃ . The deactivator precursor comprises ytterbium and may preferably be ytterbium oxide. An example of ytterbium oxide is Yb ₂ O ₃ .

The activator is substituted in the cation lattice site in the matrix like the silicon, receives energy from the parent metal and is excited, then falls to the ground state and emits energy, and determines the energy involved in the luminescence process. It affects the luminous color and luminous efficiency. In the present invention, the erbium ion (Er ³⁺ ) serves as an activator.

In addition, the sub-activator is a material added together with the activator in order to improve the luminous efficiency of the phosphor particles. Like the activator, the sub-activator is excited by receiving energy and then falls to the ground state and transfers energy to the activator. In the present invention, the ytterbium ion (Yb ³⁺ ) serves as a deactivator.

Step (1) is preferably

(1-1) preparing an active solution by dissolving an activator and a precursor of a sub-activator in a solvent; and

(1-2) preparing a spray solution by adding the parent precursor mixture to the active solution;

It can be carried out as a method of preparing a spray solution by performing sequentially.

In step (1-1), the active solution may be prepared by dissolving the activator and the sub-activator precursor with an acid. For example, the active solution may be an aqueous solution in which an active agent and a de-active agent precursor are dissolved in nitric acid. However, the acid is not necessarily limited to nitric acid.

For example, when Er ₂ O ₃ as the activator precursor and Yb ₂ O ₃ as the deactivator precursor are used to prepare an aqueous solution by dissolving the activator precursor and the deactivator precursor in nitric acid, the reaction formulas are the following Reaction Schemes 1 and 2 same as

[Scheme 1]

Er ₂ O ₃ + 6HNO ₃ → 2Er(NO ₃ ) ₃ + 3H ₂ O

[Scheme 2]

Yb ₂ O ₃ + 6HNO ₃ → 2Yb(NO ₃ ) ₃ + 3H ₂ O

Here, since the reactions according to Schemes 1 and 2 are both exothermic reactions, it is preferable to dissolve them while cooling by adding distilled water together.

Subsequently, in step (1-2), a spray solution may be prepared by further adding the parent precursor mixture and other additives to the active solution prepared in step (1-1) above. The spray solution may preferably be an aqueous solution in which the solvent is water.

The spray solution may have a greater mole fraction of titanium than silicon. Preferably the silicone may have a mole fraction of 2 mol % to 30 mol %. When the molar fraction of silicon is less than 2 mol%, the crystal phase of the parent undergoes a lot of phase change from anatase to rutile during the heat treatment process, thereby reducing luminance or losing luminescence properties. In addition, when the mole fraction of silicon exceeds 30 mol%, the crystallite size of the prepared UC phosphor particles decreases, which causes a decrease in luminance of light emission.

The mole fraction of silicone may more preferably be 5 mol% to 20 mol%. When the molar fraction of the silicon dopant is 5 mol% to 20 mol%, UC phosphor particles having the best luminance of emission can be realized.

The spray solution may preferably have the largest mole fraction of titanium among metals. Therefore, the prepared UC phosphor particles basically have the properties of titanium oxide.

The spray solution may preferably contain the active agent and the deactivator in a molar fraction of 0.1 mol% to 1 mol% and 2 mol% to 10 mol%, respectively.

If the molar fraction of the active agent in the composition is less than 0.1 mol%, all of the energy transmitted by the deactivator is not received, so that the luminescence luminance of the UC phosphor particles is lowered, and the molar fraction of the active agent is excessively high in excess of 1 mol% In this case, there is a problem in that the luminance is lowered due to a concentration fading phenomenon due to the transfer of non-luminescent energy between the activators.

In addition, when the molar fraction of the sub-active agent is low (less than 2 mol%), the energy cannot be sufficiently transferred to the activator and the luminance is lowered. There is a problem in that the non-luminous energy is transmitted between the sub-activators rather than the

Specifically, the activator may be an erbium ion (Er ³⁺ ), and the deactivator may be a ytterbium ion (Yb ³⁺ ).

(2) step

The spray solution prepared as described above is a UC phosphor particle composition, and may be heated and reacted to a predetermined temperature to produce UC phosphor particles.

The predetermined temperature may be preferably 700 °C to 1,100 °C.

In addition, step (2) may be preferably performed as a spray pyrolysis process, and in the case of spray pyrolysis, the reaction at normal pressure is possible, and the process can be simplified, such as omitting the milling process. There are advantages.

In the case of spray pyrolysis, preferably

(2-1) forming droplets by spraying the spray solution; and

(2-2) forming the precursor powder by thermally decomposing and drying the droplets; may be performed sequentially.

This spray pyrolysis step may be performed using a spray pyrolysis device including a droplet generating unit that generates droplets using an ultrasonic vibrator, a kiln in which thermal decomposition occurs with high-temperature energy, and a collecting unit in which dried particles are collected.

Since the device is maintained at a high temperature in the pyrolysis process, it is preferable to continuously flow the cooling water around the vibrator of the droplet generator, and a flow rate of about 10 L/min to 50 L/min for smooth flow of the droplets generated in the droplet generator air can flow through

(3) step

After collecting the crystallized and dried precursor powder by the reaction of step (2), heat treatment may be performed to prepare UC phosphor particles.

The heat treatment may be performed at a temperature of 600 °C to 750 °C. When the heat treatment temperature is less than 600 ° C, crystallites do not grow sufficiently and the luminance is low. Conversely, when the heat treatment temperature exceeds 750 ° C, the crystallites grow to a sufficient size, but the crystal structure of _{TiO 2 is anatase} ) to the rutile phase is increased, so there is a problem in that the UC fluorescence characteristic is reduced. Therefore, it has the most excellent light emission luminance within the above range.

Hereinafter, an upconversion (UC) phosphor composition obtained according to the production method of the present invention and UC phosphor particles prepared therefrom will be described.

The UC phosphor composition according to the present invention includes the spray solution obtained in step (1) of the above production method.

That is, the UC phosphor composition according to the present invention may include a parent precursor mixture including titanium and silicon, respectively; and a dopant precursor mixture comprising erbium and ytterbium, respectively. As described above, erbium acts as an activator by being substituted in the metal cation lattice of the parent, and ytterbium acts as a deactivator.

Here, the types, roles and contents of the parent precursor, the activator precursor, the deactivator precursor, and the silicon dopant precursor are the same as those described above, and thus a description thereof will be omitted.

The UC phosphor particles according to the present invention are prepared by heating and drying the UC phosphor composition, as described above in the production method.

The UC phosphor particles according to the present invention are characterized in that they include a compound represented by the following formula (1).

[Formula 1]

(Ti _1-xyz Si _x Er _y Yb _z )O ₂

In Formula 1, 0.02≤x+y+z≤0.4.

Therefore, in the compound of Formula 1, Ti occupies the largest mole fraction in the cation lattice with a content of 0.5 or more, and thus, the UC phosphor particles according to the present invention have TiO ₂ crystal properties as described above.

In a preferred embodiment of the present invention, Chemical Formula 1 may satisfy at least one of the following conditions 1) to 3).

1) 0.02≤x≤0.3

2) 0.001≤y≤0.01

3) 0.02≤z≤0.1.

The above condition 1) relates to the content of the silicon dopant, and conditions 2) and 3) relate to the contents of the activator and the deactivator, respectively, and the effects thereof are the same as described above, and thus a detailed description thereof will be omitted.

In addition, according to a preferred embodiment of the present invention, the average crystallite size (Dc) of the UC phosphor particles may be 4.5 nm to 20 nm. When Dc is smaller than 4.5 nm, the emission luminance may decrease. When the crystal valence size exceeds 20 nm, the emission luminance increases, but rather, the luminance decreases because the rutile phase increases in the process of increasing the crystallite size. , the UC fluorescence properties themselves may be lost.

The crystallite size Dc may be calculated by the following Relational Equation (2).

[Relational Expression 2]

In Relation 2, k is a Scherrer constant, its value is 0.9, λ is an X-ray wavelength of 0.1542 nm, β _s is a peak width at half maximum (FWHM) in an XRD spectrum, and θ is a central diffraction angle.

In addition, in the UC phosphor particles according to the present invention, the %Rutile obtained according to the following relation 1 in the crystal structure may be 15% or less.

[Relational Expression 1]

In Relation 1, A is the area of the peak having the highest point in the region where 2θ is 25.3±0.2˚ among the peaks shown in the XRD pattern of the UC phosphor particle, and R is the peak area of the peak shown in the XRD pattern of the UC phosphor particle. The area of the peak having the highest point in the region where 2θ is 27.4±0.2° is indicated.

_{This indicates the degree to which the anatase phase of TiO 2} is changed to the rutile phase by heat in the heat treatment step during the manufacturing process of the UC phosphor particles, and indicates that the higher the %Rutile, the greater the degree of phase change.

When the %Rutile exceeds 15%, the UC fluorescence properties of the anatase phase may be reduced, so that the luminance may not be sufficient to use the phosphor particles as a security ink.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments so that those skilled in the art can easily carry out the present invention. However, the scope of the present invention is not limited to the following examples, and the present invention may be embodied in various different forms, all of which are included in the scope of the present invention.

<Example>

Example 1: Preparation of UC Phosphor Particles

(1) Preparation of spray solution

Er ₂ O ₃ (Alfa Aesar, 99.9% _{purity) was selected as the activator precursor, and Yb 2} O ₃ (Alfa Aesar, 99.9% purity) was selected as the deactivator precursor, and an active solution was prepared by dissolving each with nitric acid.

To prepare an active solution, put _{Er 2} O ₃ 2g and Yb ₂ O ₃ 10g in a 1,000 ml round Erlenmeyer flask _{each containing 50 ml of water (H 2} O), respectively, and then dissolve while slowly adding _{nitric acid (HNO 3 ).} gave. Distilled water is added little by little in the middle to prevent the heat generated during the melting process. As for the amount of nitric acid, 10 times the number of moles compared to the number of moles _{of Er 2} O ₃ or Yb ₂ O _{3 was used.} When the oxide was completely dissolved to form a transparent aqueous solution, distilled water was added to make a total of 1,000 g, and a 2 wt% Er activator solution and 10 wt% Yb deactivator solution were prepared.

A spray solution containing 82.7 mol% Ti, 10 mol% Si, 0.3 mol% and 7.0 mol% Yb in the parent composition was prepared as follows. To a 500 ml beaker containing 45 ml of 60% aqueous nitric acid solution and 300 ml of water _{, 48.46 g of TiO 2} precursor TTIP (Sigma Aldrich, purity 97%) was slowly added, followed by stirring until it became a clear solution. In another 500 ml beaker, 100 ml of water and 5 ml of nitric acid were put, and 4.25 g of a silicon precursor TEOS (Sigma Aldrich, 98% purity) solution was dissolved. After mixing the aqueous solution of TTIP and TEOS, the active solution was added. At this time, the weight of each active solution was to contain Er ₂ O ₃ 0.115 g, Yb ₂ O ₃ 2.76 g. Then, distilled water was added so that the total solution volume was 1,000 ml. The total concentration of the solution in which the phosphor precursor was dissolved was fixed at 0.2 M.

The prepared UC phosphor particles had _{a chemical formula of (Ti 1-xyz} Si _x Er _y Yb _z )O ₂ , where x was 0.1 and y and z were 0.003 and 0.07, respectively.

(2) Spray pyrolysis

The spray solution was subjected to spray pyrolysis using a spray pyrolysis device to obtain a precursor powder.

In a specific method, 200 ml of the spraying solution is divided so as not to overflow the spray bottle, and air is flowed at a temperature of 900° C. at a flow rate of 30 L/min to spray and thermally decompose, thereby recovering the crystallized powder, that is, the precursor powder.

(3) heat treatment step

The obtained precursor powder was heat treated at 700° C. for 3 hours. During the heat treatment, air was flowed at a flow rate of 600 cc/min.

UC phosphor particles were obtained through heat treatment.

Examples 2 to 42: Preparation of UC Phosphor Particles

UC phosphor particles were prepared in the same manner as in Example 1 except that the Si mole fraction and the heat treatment temperature were changed as shown in Table 1 below.

division (Zr _1-xyz Si _x Er _y Yb _z )O ₂
at x Heat treatment temperature (℃) Example 2 0.1 500 Example 3 0.1 600 Example 4 0.1 800 Example 5 0.1 900 Example 6 0.1 1,000 Example 7 0.025 500 Example 8 0.025 600 Example 9 0.025 700 Example 10 0.025 800 Example 11 0.025 900 Example 12 0.025 1,000 Example 13 0.05 500 Example 14 0.05 600 Example 15 0.05 700 Example 16 0.05 800 Example 17 0.05 900 Example 18 0.05 1,000 Example 19 0.15 500 Example 20 0.15 600 Example 21 0.15 700 Example 22 0.15 800 Example 23 0.15 900 Example 24 0.15 1,000 Example 25 0.2 500 Example 26 0.2 600 Example 27 0.2 700 Example 28 0.2 800 Example 29 0.2 900 Example 30 0.2 1,000 Example 31 0.3 500 Example 32 0.3 600 Example 33 0.3 700 Example 34 0.3 800 Example 35 0.3 900 Example 36 0.3 1,000 Example 37 0.5 500 Example 38 0.5 600 Example 39 0.5 700 Example 40 0.5 800 Example 41 0.5 900 Example 42 0.5 1,000

Comparative Examples 1 to 6: Preparation of UC phosphor particles

UC phosphor particles were prepared in the same manner as in Example 1 except that the Si mole fraction and the heat treatment temperature were changed as shown in Table 2 below.

division (Zr _1-xyz Si _x Er _y Yb _z )O ₂
at x heat treatment temperature Comparative Example 1 0 500 Comparative Example 2 0 600 Comparative Example 3 0 700 Comparative Example 4 0 800 Comparative Example 5 0 900 Comparative Example 6 0 1,000 Comparative Example 7 0.1 No heat treatment

<Experimental example>

Experimental Example 1: Security ink production and light emission confirmation

A security ink was prepared by mixing the phosphor particle powder according to Example 1 with 10% PVDF (polyvinylidene fluoride) and a BYK dispersant as follows.

1 g of the phosphor powder according to Example 1, 1 g of PVDF (10%), and 0.03 g of BYK were placed in a sample container and mixed for 3 minutes using a centrifugal mixer.

Then, by measuring the thickness of the mark paper with graphite, the gap between the thickness and the mark frame was adjusted, placed in a screen printer, and vacuum was applied to fix the paper so that it does not fall from the device.

Thereafter, the ink was applied to make a mark, and then dried until dry.

As a result of confirming light emission by applying a 975 nm IR laser, it was observed that yellow light was emitted as shown in FIG. 13 .

Experimental Example 2: TEM, EDX mapping image observation

TEM and EDX images were observed for the phosphor particles according to Examples 1 and 9.

TEM and EDX images according to Example 1 are shown in 11a and 12a, respectively, and TEM and EDX images according to Example 9 are shown in 11b and 12b, respectively.

Referring to FIG. 11 , the prepared phosphor particles are spherical and fine, and have a typical anatase titania (TiO ₂ ) crystal structure. Referring to FIG. 12B , it can be seen that the added Si, Er, and Yb are uniformly and well distributed throughout the particles. From this, it was confirmed that Si was _{well dispersed in the TiO 2} lattice, and (Ti, Si, Er, Yb)O ₂ phosphor particles having a uniform composition were prepared.

Experimental Example 3: Upconversion luminescence characteristics according to heat treatment temperature and Si mole fraction

1) Si-doped phosphor particles: heat treatment temperature and luminescence characteristics

Emission spectra were prepared by exposing the phosphor particles according to Comparative Examples 1 to 6 to 975 nm IR laser using a PL measuring device, Perkin Elmer, LS 55, and a fluorescence spectrometer. Conditions were performed in biolum mode with Slit 15, scan speed 1,200 nm/s, and the results are shown in FIG. 5A, respectively. In addition, a graph showing emission intensity at a wavelength showing the maximum intensity according to temperature is shown in FIG. 5C .

Referring to FIG. 5c , it was confirmed that the emission intensity was significantly reduced in the range out of 600 to 750°C.

In addition, the crystalline phase, crystallite size (Dc), and %Rutile of the phosphor particles according to Comparative Examples 1 to 6 were confirmed using an X-ray diffractometer (MiniFlex 300/600).

The results are shown in FIG. 6 and Table 3 below.

Referring to FIG. 6 , it can be seen that the crystallite size increases significantly from 800° C., but the rutile phase crystal structure appears. Therefore, it can be seen that the UC fluorescence properties are lost due to a phase change in the case of heat treatment at a temperature of 750° C. or higher.

division heat treatment temperature
(℃) %rutile Crystalline size (nm) anatase rutile Comparative Example 1 500 0.0 5.5 - Comparative Example 2 600 0.0 6.2 - Comparative Example 3 700 12.7 7.9 1.2 Comparative Example 4 800 59.5 14.0 33.9 Comparative Example 5 900 100.0 0.0 42.6 Comparative Example 6 1,000 100.0 0.0 47.8

In addition, when checking Table 3, it can be seen that the rutile phase starts to occur when the heat treatment temperature is 700° C., and when it exceeds 800° C., the rutile phase becomes dominant and virtually loses the upconversion fluorescence properties of the anatase phase.

2) Phosphor particles having Si dopant: heat treatment temperature and light emission characteristics

The PL spectra of the phosphor particles of Examples 1 to 6 were prepared in the same way and shown in FIG. 5B, and in FIG. 5C, the emission intensity at a wavelength having the maximum emission intensity of Examples 1 to 6 and Comparative Examples 1 to 6 is shown at the temperature. A graph is shown according to

Referring to FIGS. 5B and 5C, it can be seen that the phosphor particles heat-treated at a temperature of 600°C to 750°C, whether or not Si doped, have excellent emission intensity, and when heat-treated at a temperature exceeding 750°C, peak It can be seen that the emission intensity is significantly lowered.

The XRD patterns of the phosphor particles according to Examples 1 to 6 and Comparative Example 7 are shown in FIG. 7 . It was found that the phosphor particles according to Examples 1 to 6 and Comparative Example 7 having a Si mole fraction of 10 mol% hardly showed a rutile phase pattern even after heat treatment at 100° C., but when the heat treatment temperature was over 750° C., anatase It was found that the pattern of the phase was blurred, and when it exceeded 1000°C, the pattern was different from that of the anatase phase. Therefore, it was confirmed that heat treatment at a temperature of 750° C. or less was preferable, and it was evaluated that the phosphor particles according to Comparative Example 7, which were not heat treated at all, had too small crystallite size to exhibit good fluorescence properties.

In addition, the crystallite size and the ratio of the rutile phase of the phosphor particles according to Examples 1 to 6 are shown in Table 4 below.

division heat treatment temperature
(℃) %Rutile Crystalline size (nm) anatase prize Rutile Award Example 1 700 0.0 6.8 - Example 2 500 0.0 5.8 - Example 3 600 0.0 6.0 - Example 4 800 0.0 5.9 - Example 5 900 9.6 10.5 1.2 Example 6 1000 27.9 20.8 32.1

Referring to Table 4, in the phosphor particles according to Examples 1 to 6 in which the mole fraction of Si is 10 mol%, the %rutile does not significantly increase even when the heat treatment temperature exceeds 750°C, and the %Rutile does not increase until 900°C. It can be seen that it is maintained as low as less than 15% and exhibits excellent fluorescence properties.

This difference is shown in FIG. 8 . 8 is a graph showing the correlation between %Rutile and crystallite size according to heat treatment temperature of UC phosphor particles according to Comparative Examples 1 to 6 in which the Si mole fraction is 0 mol% and Examples 1 to 6 in which the Si mole fraction is 10 mol%. It is a graph.

Referring to FIG. 8 , while the %rutile of the phosphor particles according to the comparative example significantly increased as the heat treatment temperature increased, the phosphor particles of the example having 10 mol% Si did not show a significant change in %rutile as the heat treatment temperature increased. can be known Therefore, it can be seen that the phosphor particles according to the embodiment have excellent durability against temperature.

3) Si mole fraction and luminescence properties

9 is a graph showing the emission intensity at the wavelength having the maximum emission intensity in the PL spectrum of the phosphor particles according to Examples 1 to 42 and Comparative Examples 1 to 6 in correlation with temperature, and Examples 1 and 9 , 15, 21, 27, 33, 39 and PL spectra of the phosphor particles according to Comparative Example 3 are shown in FIG. 10A .

In addition, a graph showing the emission intensity at the wavelength having the maximum emission intensity in the PL spectrum of the phosphor particles according to Examples 1, 9, 15, 21, 27, 33, 39 and Comparative Example 3 in correlation with the Si mole fraction are shown in FIG. 10b, and their XRD patterns and crystallite sizes are shown in FIG. 10c.

Referring to FIG. 10B , it was confirmed that the Si mole fraction had the best emission intensity when the Si mole fraction was 10 mol%. When the Si mole fraction was more than 30 mol%, it was found that the emission intensity significantly decreased as the mole fraction increased.

This can also be confirmed with reference to FIG. 10C. As the Si mole fraction exceeded 10 mol%, it was found that the XRD pattern of the anatase phase gradually became blurred, and the crystallite size was also reduced, thereby deteriorating the UC fluorescence properties.

Claims (12)

(1) A host precursor mixture containing titanium (Titanium, Ti) and silicon (Si), respectively, and a dopant precursor containing erbium (Er) and ytterbium (Ytterbium, Yb), respectively dissolving the mixture in a solvent to prepare a spray solution;
(2) heating and reacting the spray solution to a predetermined temperature and drying the spray solution to obtain a precursor powder; and
(3) heat-treating the precursor powder; up-conversion (UC) phosphor particle manufacturing method comprising a. According to claim 1,
The step (2) is a method for producing UC phosphor particles, characterized in that performed by a spray pyrolysis method. According to claim 1,
UC phosphor particle manufacturing method, characterized in that titanium has a greater molar fraction than silicon in the spray solution. According to claim 1,
The step (3) is a UC phosphor particle manufacturing method, characterized in that heat treatment at a temperature of 600 ℃ to 750 ℃. According to claim 1,
In step (1), the mole fraction of silicon is 2 mol% to 30 mol% UC phosphor particle manufacturing method, characterized in that. According to claim 1,
The spray solution comprises the erbium and ytterbium in a mole fraction of 0.1 mol% to 1 mol% and 2 mol% to 10 mol% UC phosphor particle manufacturing method. According to claim 1,
The step (2) is a UC phosphor particle manufacturing method, characterized in that it is carried out at a temperature of 700 ℃ to 1,100 ℃. A UC phosphor composition comprising a parent precursor mixture comprising titanium and silicon, respectively, and a dopant precursor mixture comprising erbium and ytterbium, respectively. 9. The method of claim 8,
A UC phosphor composition comprising silicone to have a mole fraction of 2 mol% to 30 mol%. UC phosphor particles prepared by reacting the UC phosphor composition according to claim 8 and comprising a compound represented by the following formula (1):
[Formula 1]
(Ti _1-xyz Si _x Er _y Yb _z )O ₂
In Formula 1, 0.02≤x+y+z≤0.4. 11. The method of claim 10,
Formula 1 is a UC phosphor particle, characterized in that it satisfies at least one of the following conditions 1) to 3):
1) 0.02≤x≤0.3
2) 0.001≤y≤0.01
3) 0.02≤z≤0.1. A fluorescent ink comprising the UC phosphor particles according to claim 10 .

Images