JP2018095755A - Ultraviolet light emitting phosphor, light emitting element, and light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultraviolet light emitting phosphor that exhibits a strong emission peak particularly in an ultraviolet region around 360 nm by ultraviolet irradiation.SOLUTION: An ultraviolet light emitting phosphor contains cerium elements, calcium elements, phosphorus elements, and oxygen elements, with the molar ratio x of cerium elements contained being 0<x≤0.7, where the phosphor is excited by ultraviolet irradiation to emit ultraviolet light.SELECTED DRAWING: Figure 8

Description

  The present invention relates to an ultraviolet light emitting phosphor that emits ultraviolet light when excited by ultraviolet light, and more particularly to an ultraviolet light emitting phosphor that can emit light in the ultraviolet region with an emission peak wavelength of around 360 nm.

  In recent years, the field of ultraviolet light emission has increased industrial value as the use of ultraviolet light has expanded to the medical field, the photocatalyst field, the food field, and the like. One application field of such ultraviolet light emission is ultraviolet curable resin (UV curable resin) in the synthetic resin field.

  In such a synthetic resin field, technological improvements of ultraviolet curable resins have progressed, and resins that can be cured by irradiation with ultraviolet rays having a longer wavelength (mild) than before have been developed. As described above, when curing a UV curable resin, the advantage of irradiating with longer wavelength ultraviolet rays is that the resin is irradiated with lower energy ultraviolet rays, so that damage to the resin is further suppressed. Thus, it becomes possible to synthesize an excellent quality resin in which damage during synthesis is suppressed.

  Further, since lower energy ultraviolet rays are used for irradiation, the energy required for the production of the resin can be suppressed, and the production cost can be reduced. As ultraviolet rays irradiated to such an improved UV curable resin, ultraviolet rays having an emission peak wavelength of around 360 nm are considered desirable.

  Similarly, in the field of synthetic resins, as a similar photopolymerization technique for irradiating a resin with ultraviolet rays, formation of a liquid crystal photo-alignment film (PSA technique: Polymer Stabilized Alignment) is also known. In this PSA technique, a liquid crystal to which a small amount of a photopolymerizable monomer is added is irradiated with ultraviolet rays, and the orientation of the liquid crystal is fixed by a polymer polymerized by the irradiation. Also in this PSA technique, from the viewpoint of suppressing damage, irradiation with lower energy ultraviolet rays (for example, ultraviolet rays having an emission peak wavelength of around 360 nm similar to the above) is desired.

Conventional ultraviolet light emitting phosphors that emit ultraviolet rays are, for example, phosphors excited by an electron beam, and the general formula of the phosphor is Zn _(1-x) A _x S: Ag, D (A in the formula ₎ Is at least one 2A group element selected from the group of Be, Mg, Ca, Sr and Ba, D is at least one group 3B or 7B group element, and the mixed crystal ratio x is 0 <x <0.5 ) Or Ga _1-x Al _x N: M, X (where 0 ≦ x ≦ 1, where M is Be, Mg, Ca, Sr, Ba, Zn, Cd, Hg) At least one element selected from the group, X is at least one element selected from C, Si, Ge, Sn, and Pb, and the phosphor is a mixture ratio crystal x (0 ≦ x ≦ 1), There is a phosphor having at least one peak wavelength of 360 to 375 nm (see Patent Document 1). .

Further, as a conventional ultraviolet light emitting phosphor that emits ultraviolet light, for example, an ultraviolet-excited phosphor having a general formula M ⁴ ₃ P ₂ O ₈ (wherein M ⁴ is Ca, Sr, Ba, Zn and 2 or more selected from the group consisting of Mg, or a compound represented by Ca, Zn, Mg.), Ce, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er as activators. A phosphor containing at least one selected from the group consisting of Tm, Yb, and Mn, and is substantially a phosphor containing Eu as a suitable activator, containing the Eu There is a phosphor in which only the synthesis of Ca _0.98 Eu _0.02 Mg ₂ P ₂ O ₈ is confirmed (see Patent Document 2).

JP 2007-294698 A JP 2003-313551 A

  However, for example, in the phosphor excited by electron beam as shown in Patent Document 1, since the electron beam is high energy, the phosphor itself is greatly damaged by irradiation with the electron beam, and durability in long-term use is high. There was a problem in (degradability).

Further, since the ultraviolet-excited phosphor is not irradiated with a high-energy electron beam, it has superior durability as compared with such an electron-beam-excited phosphor. What can exhibit a strong emission peak in the ultraviolet region with a wavelength of 300 nm to 400 nm, especially around 360 nm, including Ca _0.98 Eu _0.02 Mg ₂ P ₂ O ₈ using the activator Eu unknown. Further, for example, an ultraviolet-excited phosphor such as Ca _0.98 Eu _0.02 Mg ₂ P ₂ O ₈ using the activator Eu shown in Patent Document 2 has a severe temperature condition during synthesis and is fired at about 1300 ° C. However, there is a problem that stable synthesis is difficult and practical application is difficult by firing at a general firing temperature of about 1000 ° C. to 1500 ° C., such as being easily dissolved before the phosphor is produced.

  The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an ultraviolet light-emitting phosphor that exhibits a strong emission peak in the ultraviolet region having a wavelength of 300 nm to 400 nm, particularly around 360 nm when irradiated with ultraviolet rays. And

  As a result of extensive research, the present inventors have found that the above problems can be solved by using a specific oxide phosphor containing cerium element (Ce) in a certain mixing ratio. Derived.

  That is, the ultraviolet light-emitting phosphor disclosed in the present application is composed of a cerium element, a calcium element, a phosphorus element, and an oxygen element, and the blending molar ratio x of the cerium element is 0 <x ≦ 0.7. A phosphor that emits ultraviolet light when excited by irradiation with ultraviolet light is provided. In addition, a light-emitting element including the ultraviolet light-emitting phosphor disclosed in the present application is also provided. A light-emitting device including the light-emitting element is also provided.

The X-ray-diffraction result of the ultraviolet light-emitting phosphor according to the present invention is shown (Ce: 0.001 mol, 0.005 mol). The X-ray-diffraction result of the ultraviolet light-emitting phosphor according to the present invention is shown (Ce: 0.01 mol, 0.02 mol). The X-ray-diffraction result of the ultraviolet light-emitting phosphor according to the present invention is shown (Ce: 0.05 mol, 0.1 mol). The X-ray-diffraction result of the ultraviolet light-emitting phosphor according to the present invention is shown (Ce: 0.2 mol, 0.3 mol). The X-ray-diffraction result of the ultraviolet light-emitting phosphor according to the present invention is shown (Ce: 0.4 mol, 0.6 mol). The X-ray-diffraction result of the ultraviolet light-emitting phosphor according to the present invention is shown (Ce: 0.7 mol, 0.75 mol). The X-ray diffraction result of the ultraviolet light-emitting phosphor according to the present invention is shown (Ce: 0.8 mol). The result (a) of the emission spectrum by ultraviolet excitation of the ultraviolet light-emitting phosphor according to the present invention, and the graph (b) showing the correlation between the integrated intensity (light emission intensity) and the Ce substitution amount (mixing molar ratio) are shown. The graph showing the correlation of the light emission peak wavelength of the ultraviolet light emission fluorescent substance which concerns on this invention, and Ce substitution amount (compounding molar ratio) is shown.

  As described above, the ultraviolet light-emitting phosphor disclosed in the present application is composed of a cerium element, a calcium element, a phosphorus element, and an oxygen element, and the mixing molar ratio x of the cerium element is 0 <x ≦ 0.7. If it is fluorescent substance which is, it will not specifically limit.

Such One preferred UV-emitting phosphor, for example, the general formula _{Ca 3-x Ce x (PO} 4) 2 ( where, 0 <x ≦ 0.7) include those represented by. Here, since it is sufficient that the cerium element is included as one of the constituent elements, a part of the cerium element included as the constituent element may be replaced with another rare earth element of the same family as the cerium element. Examples of such other rare earth elements include scandium, lanthanum, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.

  Further, since it is sufficient that the calcium element is included as one of the constituent elements, a part of the calcium element included as the constituent element may be replaced with another alkali metal element or alkaline earth metal element. Examples of such other elements include lithium, sodium, potassium, rubidium, strontium, barium, and radium.

  The excitation source of the ultraviolet light emitting phosphor according to the present application is not particularly limited as long as it is a light source that emits ultraviolet light. The term “ultraviolet rays” as used herein refers to the entire ultraviolet region including vacuum ultraviolet rays. As such a light source that emits ultraviolet light, for example, a light source having a wavelength of 200 nm to 300 nm can be used. For example, a light source having a wavelength of 254 nm that has been widely used as an excitation source can be used. For example, vacuum ultraviolet rays having a wavelength of 200 nm or less can be used. For example, a light source having a wavelength of 146 nm or a wavelength of 185 nm that has been widely used as an excitation source can be used.

  The ultraviolet light-emitting phosphor disclosed in the present application can emit ultraviolet rays in various ultraviolet regions by irradiation with ultraviolet rays from such an excitation source, for example, 300 nm to 400 nm, which is useful for various applications, for example, It is possible to emit light in the ultraviolet region of around 360 nm, which is suitable for irradiation of liquid crystal for fixing the orientation in the PSA technology, which has been improved in recent years.

In fact, an example of an ultraviolet-emitting phosphors disclosed in the present application the formula _{Ca 3-x Ce x (PO} 4) 2 ( where, 0 <x ≦ 0.7) with a phosphor represented by blending cerium element In the range of 0 <x ≦ 0.7, the molar ratio x has been confirmed to exhibit light emission with an excellent intensity that the emission peak intensity is higher than 100 at an emission wavelength of about 360 nm (Examples described later). reference).

  Although the mechanism by which the ultraviolet light-emitting phosphor according to the present application exhibits such an excellent effect has not yet been elucidated in detail, when ultraviolet light is irradiated, the phosphor does not emit light with respect to the wavelength in the ultraviolet region. In the crystal structure, the cerium element is present in the range where the blending molar ratio x is in the range of 0 <x ≦ 0.7, so that the action as the emission center inherent to the cerium element is enhanced. It is possible that the factors are inherent. That is, when irradiated with ultraviolet rays, the presence of the cerium element contained in the blending ratio favorably affects the distance between the atoms constituting the phosphor and the length of the wavelength of the ultraviolet rays. It is presumed that it is easy to transition to an energy level that specifically emits light in the region.

As an example of the method for producing the ultraviolet light-emitting phosphor disclosed in the present application, an oxide of each constituent element is used as a raw material and mixed at a stoichiometric ratio so as to obtain a desired phosphor composition. To do. For example, an example of the ultraviolet-emitting phosphor according to the present general formula _{Ca 3-x Ce x (PO} 4) 2 ( where, 0 <x ≦ 0.7) in order to obtain a phosphor represented by the raw materials Each powder of calcium carbonate (CaCO ₃ ), diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ), and cerium oxide (CeO ₂ ), which are oxides of the constituent elements, can be used.

  By mixing these powders and firing at a high temperature in a reducing atmosphere (for example, in a nitrogen / hydrogen reducing atmosphere), a desired phosphor can be obtained. In this high-temperature firing, for example, a desired phosphor can be obtained as a sintered body by firing at a temperature of 1000 ° C. to 1500 ° C. for 2 to 6 hours.

  The use of the ultraviolet light-emitting phosphor thus obtained is diverse. For example, the ultraviolet light-emitting phosphor according to the present application can be used as a light source for fixing the orientation of liquid crystals in the recently improved UV curable resin or PSA technology. In this case, since the ultraviolet light-emitting phosphor according to the present application can exhibit a strong light emission peak in the ultraviolet region having a wavelength of around 360 nm, the curing of the UV curable resin and the fixing of the liquid crystal orientation in the PSA technology have been improved in recent years. It can be used as a suitable light source. In other words, since it is possible to irradiate ultraviolet rays with a gentle energy that has not existed before, the damage to the resin is gentle, synthesis of UV curable resin with higher quality than before, and alignment of liquid crystals in PSA technology Sex fixation can be realized.

  In order to further clarify the features of the present invention, examples are shown below, but the present invention is not limited to these examples.

(Example)
(1) Production of phosphors Using calcium carbonate (CaCO ₃ ), diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ), and cerium oxide (CeO ₂ ) as raw materials, stoichiometrically Ca _{3− x} Ce _x mixed _{(PO 4)} in proportions such that the composition formula represented by _2. After mixing, the mixture was placed in an alumina crucible and fired at 1300 ° C. for 3 hours in a nitrogen / hydrogen reducing atmosphere to obtain a sintered body. For this sintered body, 13 types of samples of x = 0.001, 0.005, 0.01, 0.02, 0.05, 0.1, 0.2, 0.3, 0.4, 0.6, 0.7, 0.75, 0.8 were obtained for the molar ratio x of cerium element. It was.

(2) Identification of phosphor The X-ray diffraction result of the sintered body obtained above was obtained with an X-ray diffractometer whose source is CuKα. The X-ray diffraction results for the 13 types of samples (x = 0.001 to 0.8) of the obtained sintered body are shown in FIGS. In any samples, from the resulting peak value, that crystallized was confirmed certainly _{Ca 3-x Ce x (PO} 4) 2 composition.

(3) Measurement of the 13 types of light-emitting intensity of _{Ca 3-x Ce x (PO} 4) sample of ₂ crystals (Sample No. 1-13), luminous intensity (integrated intensity) by ultraviolet excitation with excitation wavelength lambda = 254 nm It was confirmed. The result of the obtained emission spectrum is shown in FIG. Further, FIG. 8B shows a graph showing the correlation between the emission intensity (integrated intensity) and the cerium element (Ce) substitution amount (mixing molar ratio), where the horizontal axis is the mixing molar ratio x of cerium element. From the results obtained, the ultraviolet-emitting phosphor _{Ca 3-x Ce x (PO} 4) 2 according to the present embodiment, the mixing molar ratio x of cerium element is greater than 0, and exhibit high luminous intensity, In particular, it was confirmed that the emission intensity was high at 0.02 ≦ x ≦ 0.4, and that the emission intensity was particularly high at 0.02 ≦ x ≦ 0.3. It was also confirmed that the emission intensity decreased sharply when the mixing molar ratio x of the cerium element was larger than 0.7.

  A graph showing the correlation between the emission peak wavelength and the cerium element (Ce) substitution amount (mixing molar ratio) is shown in FIG. 9 with the horizontal axis being the mixing molar ratio x of cerium element. From the obtained results, it was confirmed that the cerium element (Ce) substitution amount (mixing molar ratio) was shifted to a long wavelength from 0.01 to 0.2, and shifted to a low wavelength when it was larger than 0.2. It was. Further, it was confirmed that the emission peak wavelength of each phosphor was within the range of 340 nm to 370 nm, that is, emission in the ultraviolet region having an emission peak wavelength of around 360 nm was obtained. As a result of the light emission obtained in this way, any phosphor can be used as an ultraviolet light source for irradiating UV curing resin, which has been improved in recent years, or an ultraviolet light source for fixing the orientation of liquid crystals in the PSA technology. It has been confirmed that this is an optimum one that has not existed before.

Claims (4)

A phosphor composed of a cerium element, a calcium element, a phosphorus element, and an oxygen element, and a mixing molar ratio x of the cerium element is 0 <x ≦ 0.7, and is excited by irradiation with ultraviolet rays. An ultraviolet light-emitting phosphor characterized by emitting ultraviolet light. The ultraviolet light-emitting phosphor according to claim 1,
A phosphor represented by the general formula Ca _3-x Ce _x (PO ₄ ) ₂ (where 0 <x ≦ 0.7), and is characterized by emitting ultraviolet rays when excited by irradiation with ultraviolet rays. Ultraviolet light emitting phosphor. A light-emitting element using the ultraviolet light-emitting phosphor according to claim 1. A light-emitting device comprising the light-emitting element according to claim 3.

Images