JP4128543B2 - Thermophosphor and method for producing thermophosphor - Google Patents

Description

  The present invention relates to a thermoluminescent material and a method for producing a thermoluminescent material.

  Thermophosphors have the property of emitting light when heated after being irradiated with energy rays such as beta rays, gamma rays, X-rays, or ultraviolet rays. Conventionally, they have been used in dosimeters for exposure management and radiotherapy. Yes.

Moreover, the fluorescent substance containing a silica and rare earth compounds is well-known (for example, refer patent document 1, 2).
Japanese Patent Publication No.7-111911 JP-A-11-61113

  By the way, the phosphor described in Patent Document 1 is obtained by attaching silica fine particles to the surface of a phosphor containing a rare earth compound. In both cases, the rare earth compound is also present inside the phosphor particles.

  However, when the rare earth compound is present inside the phosphor particles, the energy rays coming from the outside do not necessarily reach the rare earth compound efficiently, and even if light is emitted inside the phosphor particles, the light is efficiently emitted to the outside. There is a problem that it is not emitted. For this reason, even if a thermophosphor is manufactured by the same method as in each of the above patent documents, the degree of light emission tends to be weak for the amount of rare earth compound added, and the degree of light emission is sufficiently high. Has the disadvantage that the amount of expensive rare earth compound added must be increased.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a thermophosphor that can sufficiently emit light even if the amount of rare earth compound added is suppressed, and a method for producing the thermophosphor. Is to provide.

The characteristic configuration employed in the present invention will be described below.
The thermophosphor of the present invention is obtained by supporting a rare earth oxide on the surface of a carrier mainly composed of silica.

  In the case of a thermophosphor having such a structure, since there are many rare earth compounds on the surface of the thermophosphor particle, energy rays coming from the outside efficiently reach the rare earth compound, and the surface of the thermophosphor particle The light is efficiently emitted to the outside by emitting light. Therefore, since the degree of light emission can be increased relative to the amount of rare earth compound added, a sufficient amount of light emission can be ensured even if the amount of rare earth compound added is suppressed.

In this thermophosphor, the shape of the carrier is arbitrary as long as it is composed mainly of silica. However, when the carrier is spherical silica, the rare earth oxide is more uniformly distributed on the surface of the carrier. This is desirable because it can be supported. In addition, when the support is spherical silica, the contact area between the particles is smaller than that of crushed silica or amorphous silica, and therefore, it is also desirable in that the particles that have become agglomerated after the firing step can be easily loosened. Furthermore, if the carrier is spherical silica, this thermophosphor can be dispersed more easily and uniformly when added to the coating composition or kneaded into other resin materials. desirable.

Further, it is desirable that the carrier can carry the rare earth oxide on the surface of the carrier and the rare earth oxide hardly penetrates into the inside of the carrier.
Further, as a method of supporting the noble earth oxides are available a method of performing sintering rare earth oxides themselves method is supported, or from by supporting various rare earth compound which changes the rare earth oxide with the firing . As the rare earth, europium, cerium, praseodymium, neodymium, samarium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, etc. can be used. Among these, europium, praseodymium, neodymium, terbium, holmium, erbium, etc. Is preferred. In particular, europium is preferable because it has a relatively high luminous efficiency, and europium is also suitable for obtaining red light. As the europium compound, europium oxide which is an oxide, europium nitrate which changes to an oxide upon firing, and the like can be used.

The amount of rare earth oxide supported is 0 . It is desirable to be 001-20 mol%. If the loading amount of the rare earth oxide is too small, there are problems that the luminous efficiency is poor and the active sites are small (the emission center is narrow). If the loading amount of the rare earth oxide is too large , the loading amount is not enough. There is a problem that the light emission efficiency is lowered and cost is increased, and further, there is a problem that a phenomenon that heat is generated instead of light (so-called concentration quenching phenomenon) occurs.

The method for supporting the rare earth oxide on the support may be appropriately selected according to the properties of the rare earth. For example, if a rare earth compound can be dissolved in a solvent to form a rare earth compound solution, a carrier mainly composed of silica and a rare earth compound solution obtained by dissolving the rare earth compound in a solvent are mixed, It is preferable to obtain a thermophosphor by attaching a rare earth compound solution to the surface of the carrier, drying and firing.

To give a more specific example, for example, spherical silica is used as the support, and a solution of a rare earth nitrate compound is used as the rare earth compound solution. It mixes by the compounding ratio which will be 0.001-20 mol% in conversion, a rare earth compound solution is made to adhere to the surface of the said support | carrier, and infrared drying or electrothermal drying is carried out after that, and the temperature of 900-1,600 degreeC is 0.1 By calcination for ˜8 hours, a thermoluminescent material having a rare earth oxide supported on the surface of the carrier can be obtained.

As the kind of acid for dissolving the rare earth compound, acetic acid, citric acid, oxalic acid, succinic acid and the like can be used in addition to the nitric acid.
When such a rare earth compound solution is used, the rare earth compound can be more uniformly supported on the surface of the support as compared with the case where the rare earth compound powder is used.

  In the case where a rare earth compound powder is used, a carrier mainly composed of silica, a rare earth compound powder, and a liquid for adhering the powder to the carrier are mixed to form a surface of the carrier. A thermoluminescent material may be obtained by attaching rare earth compound powder, drying, and firing.

More specific examples include, for example, spherical silica as the carrier, rare earth oxide powder as the rare earth compound powder, acetone, alcohol, or water as the liquid, and the carrier and rare earth compound powder. And the liquid are mixed at a compounding ratio such that the supported amount of the rare earth is 0.001 to 20 mol% in terms of oxide, and the rare earth compound powder is adhered to the surface of the support, and then infrared drying or electrothermal drying is performed. Thereafter, the phosphor is fired at a temperature of 900 to 1,600 ° C. for 0.1 to 8 hours, whereby a thermoluminescent material having a rare earth oxide supported on the surface of the carrier can be obtained.

  When such a rare earth compound powder is used, it becomes difficult for the rare earth compound to permeate into the inside of the carrier as compared with the case where the rare earth compound solution is used. Therefore, a carrier that can easily penetrate the solution can be used.

  As described above, according to the present invention, it is possible to provide a thermophosphor that can sufficiently emit light even if the amount of rare earth compound added is suppressed, and a method for producing the thermophosphor.

Next, an embodiment of the present invention will be described.
[Example 1]
By dissolving a europium compound (europium oxide in this example) in 95 mol% of spherical silica (manufactured by Fuji Silysia Chemical Co., Ltd.) having an average particle diameter of 20 μm and 2 mol / L of nitric acid, the supported amount as a rare earth oxide is 5 mol. % Was mixed with an aqueous europium nitrate solution prepared so as to be%, and then dried by infrared rays. Thereafter, it was baked in air at 1,300 ° C. for 2 hours, and lightly pulverized in a mortar to obtain a thermoluminescent material.

  Place 0.1 g of the obtained thermophosphor sample in an aluminum container with a diameter of 10 mm, irradiate X-rays to an absorbed dose of 15 Gy (gray) in 1 hour, place the sample in a dark box, and use a projection lamp. The light emission obtained by heating up to 300 ° C. at a rate of temperature increase of 10 ° C. per minute is guided to a spectrometer-integrated simple multichannel (manufactured by Hamamatsu Photonics Co., Ltd .; PMA10) with an optical fiber, and the result is analyzed. Imported into computer.

  FIG. 1 shows the wavelength distribution of the intensity when heated at a temperature of 150 ° C. From this figure, light emission due to electronic transition of trivalent europium having an apex wavelength at 610 nm was observed. The emission intensity increased with increasing europium concentration.

  FIG. 2 shows the emission intensity obtained by fixing the wavelength to 610 nm and heating to 300 ° C. at a rate of temperature increase of 10 ° C. per minute with a projection lamp. From this figure, it can be seen that the emission intensity around 150 ° C. is the strongest.

[Example 2]
A small amount of acetone was added to 95 mol% of spherical silica (manufactured by Fuji Silysia Chemical Co., Ltd.) having an average particle size of 20 μm and 5 mol% of europium oxide and wet-mixed, followed by drying to remove acetone. Thereafter, it was baked in air at 1,300 ° C. for 2 hours, and lightly pulverized in a mortar to obtain a thermoluminescent material.

  Place 0.1 g of the obtained thermophosphor sample in an aluminum container with a diameter of 10 mm, irradiate X-rays to an absorbed dose of 15 Gy (gray) in 1 hour, place the sample in a dark box, and use a projection lamp. The light emission obtained by heating up to 300 ° C. at a rate of temperature increase of 10 ° C. per minute is guided to a spectrometer-integrated simple multichannel (manufactured by Hamamatsu Photonics Co., Ltd .; PMA10) with an optical fiber, and the result is analyzed. Imported into computer.

  FIG. 3 shows the emission intensity obtained by fixing the wavelength to 610 nm and heating to 300 ° C. at a temperature increase rate of 10 ° C. per minute with a projection lamp. From this figure, a thermophosphor having the highest emission intensity at about 150 ° C. was obtained. However, when compared with Example 1, the emission intensity is reduced to about 1/10.

[Example 3]
In Example 1 above, the firing temperature was 1,300 ° C., but this firing temperature was 1,100 ° C., and other conditions and procedures were the same as in Example 1 to obtain a thermoluminescent material.

  When the wavelength distribution of the emission intensity when heated at a temperature of 150 ° C. was measured by the same method as in Example 1, the emission due to the electronic transition of trivalent europium having an apex wavelength at 610 nm was observed as in FIG. It was seen.

[Example 4]
Instead of europium nitrate used in Example 1, praseodymium nitrate was used, and other conditions, procedures, etc. were obtained in the same manner as in Example 1 to obtain a thermoluminescent material.

  When the wavelength distribution of the emission intensity when heated at a temperature of 150 ° C. was measured in the same manner as in Example 1, the electrons of trivalent praseodymium having apex wavelengths at 468 nm, 485 nm, 520 nm, 550 nm, 560 nm, and 570 nm were measured. Luminescence due to the transition was observed.

[Example 5]
Instead of the europium nitrate used in Example 1, neodymium nitrate was used, and other conditions, procedures, etc. were obtained in the same manner as in Example 1 to obtain a thermoluminescent material.

  When the wavelength distribution of the emission intensity when heated at a temperature of 150 ° C. was measured by the same method as in Example 1, it was attributed to the electronic transition of trivalent neodymium having apex wavelengths at 500 nm, 515 nm, 530 nm, and 590 nm. Luminescence was seen.

[Example 6]
Instead of europium nitrate used in Example 1, terbium nitrate was used, and other conditions, procedures, etc. were obtained in the same manner as in Example 1 to obtain a thermoluminescent material.

  When the wavelength distribution of the emission intensity when heated at a temperature of 150 ° C. was measured by the same method as in Example 1, the emission due to the electronic transition of trivalent terbium having an apex wavelength at 550 nm was observed.

[Example 7]
A thermophosphor was obtained in the same manner as in Example 1 except that holmium nitrate was used instead of the europium nitrate used in Example 1 above.

  When the wavelength distribution of the emission intensity when heated at a temperature of 150 ° C. was measured by the same method as in Example 1, light emission due to the electronic transition of trivalent holmium having apex wavelengths at 510 nm and 545 nm was observed. It was.

[Example 8]
A thermoluminescent material was obtained in the same manner as in Example 1 except that erbium nitrate was used instead of the europium nitrate used in Example 1 above.

  When the wavelength distribution of the emission intensity when heated at a temperature of 150 ° C. was measured in the same manner as in Example 1, the electron transition of trivalent erbium having apex wavelengths at 480 nm, 500 nm, 525 nm, 535 nm, and 545 nm was observed. The resulting luminescence was seen.

[Example 9]
Instead of the spherical silica used in Example 1, crushed silica gel (product name: BW200, manufactured by Fuji Silysia Chemical Co., Ltd.) was used, and the other conditions and procedures were the same as in Example 1, and the thermophosphor was used. Obtained.

  When the wavelength distribution of the emission intensity when heated at a temperature of 150 ° C. was measured by the same method as in Example 1, it was found that there were many broad wavelength distributions such as 590 nm in addition to 610 nm. The strength was also 1/20 compared with Example 1.

[Comparative Example 1]
Only spherical silica (manufactured by Fuji Silysia Chemical Co., Ltd.) having the same average particle diameter of 20 μm as in Example 1 was baked in air at 1,300 ° C. for 2 hours.

When thermofluorescence measurement was performed in the same manner as in Example 1, no light emission was observed even when heated.
[Comparative Example 2]
An aqueous europium nitrate solution prepared by dissolving a europium compound in 95 mol% of silica sol, Snowtex 40 (manufactured by Nissan Chemical Co., Ltd.) and 2 mol / L of nitric acid, so that the supported amount as a rare earth oxide is 5 mol%. After mixing, infrared drying was performed.
Then, it baked at 1,300 degreeC for 2 hours in the air, and lightly grind | pulverized with the mortar.

When thermofluorescence measurement was performed in the same manner as in Example 1, almost no light emission was observed even when heated.
Since silica sol is gelled when infrared drying is performed, the obtained pulverized product is silica gel containing europium, and the blending amount of silica and europium is the same as that of the thermophosphor of Example 1. . However, in the case of the pulverized product of Comparative Example 2, it is considered that most of the europium has a structure contained in the pulverized product, and unlike the case where europium is supported on the surface of the silica gel support, It is presumed that the absolute amount of europium present in the sample is small, and this is considered to be the reason that almost no luminescence is observed even when heated. Therefore, in order to obtain a thermoluminescent material with good performance, it is considered important to support a rare earth on the surface of a support mainly composed of silica.

As mentioned above, although embodiment of this invention was described, this invention is not limited to said specific one Embodiment, In addition, it can implement with a various form.
For example, in the above embodiment, specific numerical values and conditions are shown for the amount of rare earth supported, the physical properties of the support, and other manufacturing conditions. However, as long as the properties as a thermoluminescent material are not impaired. These numerical values and conditions can be appropriately adjusted.

  Further, in the above embodiment, in order to obtain a europium nitrate aqueous solution, a method of dissolving europium oxide in nitric acid was adopted. However, a method for obtaining a rare earth compound solution is arbitrary, and a rare earth oxide such as europium oxide is used. In addition, for example, a rare earth compound solution may be prepared using a rare earth metal, a rare earth hydroxide, a rare earth carbonate, a rare earth formate, a rare earth acetate, a rare earth oxalate, or the like as a starting material.

It is a graph which shows wavelength distribution of the emitted light intensity when it heats at the temperature of 150 degreeC about the thermoluminescent material of Example 1. FIG. It is a graph which shows the change of emitted light intensity when a wavelength is fixed to 610 nm and it heats to 300 degreeC with the temperature increase rate of 10 degreeC per minute about the thermoluminescent material of Example 1. FIG. It is a graph which shows the change of emitted light intensity when a wavelength is fixed to 610 nm and it heats to 300 degreeC with the temperature increase rate of 10 degreeC per minute about the thermoluminescent material of Example 2. FIG.

Claims (9)

Thermophosphors obtained by carrying a rare earth oxide on the surface of a carrier mainly composed of silica (excluding those carrying Ba, Mg, Al on the surface of the carrier) . A thermophosphor obtained by supporting only a rare earth oxide on the surface of a carrier mainly composed of silica. The thermoluminescent material according to claim 1 or 2 , wherein the carrier is spherical silica. The thermoluminescent material according to any one of claims 1 to 3, wherein the rare earth is praseodymium, neodymium, europium, terbium, holmium, or erbium. The amount of the rare earth oxide supported is 0 . The thermoluminescent material according to any one of claims 1 to 4 , wherein the thermoluminescent material is 001 to 20 mol%. A carrier mainly composed of silica and a rare earth compound solution obtained by dissolving a rare earth compound in a solvent are mixed, and the rare earth compound solution is adhered to the surface of the carrier, dried, and at a temperature of 900 to 1,600 ° C. The method for producing a thermoluminescent material according to any one of claims 1 to 5 , wherein a thermoluminescent material having a rare earth oxide supported on the surface of the carrier is obtained by firing. The carrier is spherical silica;
The rare earth compound solution is a solution of the rare earth nitrate compound;
The carrier and the rare earth compound solution are mixed at a blending ratio in which the supported amount of the rare earth is 0.001 to 20 mol% in terms of oxide, and the rare earth compound solution is adhered to the surface of the carrier, and is dried by infrared rays or Electrothermal drying, followed by firing at a temperature of 900 to 1600 ° C. for 0.1 to 8 hours, to obtain a thermophosphor having a rare earth oxide supported on the surface of the carrier. Item 7. A method for producing a thermophosphor according to Item 6 . A carrier comprising silica as a main component, a rare earth compound powder, and a liquid for adhering the powder to the carrier are mixed, and the rare earth compound powder is adhered to the surface of the carrier, followed by drying . The thermoluminescent material according to any one of claims 1 to 5 , wherein a thermoluminescent material obtained by supporting a rare earth oxide on the surface of the support is obtained by firing at a temperature of 600 ° C. Production method. The carrier is spherical silica;
The rare earth compound powder is a rare earth oxide powder,
The liquid is acetone, alcohol, or water;
The carrier, the rare earth compound powder and the liquid are mixed at a blending ratio in which the supported amount of the rare earth is 0.001 to 20 mol% in terms of oxide, and the rare earth compound powder is adhered to the surface of the carrier. And infrared drying or electrothermal drying, followed by firing at a temperature of 900 to 1600 ° C. for 0.1 to 8 hours to obtain a thermoluminescent material having a rare earth oxide supported on the surface of the carrier. The method for producing a thermoluminescent material according to claim 8 .

Images