JP2005105213A - Near-ultraviolet ray excited phosphor and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a near-ultraviolet ray excited phosphor which emits a high luminance of red light, and a method for producing the same. <P>SOLUTION: The near-ultraviolet ray excited phosphor comprises 0.1 mol% or more and 10 mol% or less of Eu introduced in a crystal structure of an anatase-type titanium dioxide or a rutile-type titanium dioxide in place of a part of the titanium, wherein the substance is exited by a near-violet ray having a wavelength of 300 nm or more and 420 nm or less to emit red light. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The invention of this application relates to a near-ultraviolet excited phosphor and a method for producing the same. More specifically, the invention of this application relates to a near-ultraviolet-excited phosphor that emits high-luminance red light and a method for producing the same.

Conventionally, titanium oxide (TiO ₂ ) has been known as a dielectric and an insulator, and the energy gap, which is a measure of ultraviolet absorption, is 3.3 electron volts (the wavelength corresponds to a wavelength of 378 nm). Although known, it was thought that it is not suitable as a light emitting material because it is an indirect transition semiconductor.

On the other hand 1980, substances containing the Cu or Ce in SrS is, which is made studies it can be used as the electroluminescent material emits light by an excitation source having a wavelength of about 300 nm, also, Y ₂ O by the inventors of this application It has been found that a compound obtained by adding Eu to ₃ emits red light with an excitation source having a wavelength of 200 nm. However, Y ₂ O ₃ has a very large forbidden band, and cannot be excited outside the vacuum ultraviolet region with an excitation wavelength of about 200 nm.

On the other hand, in recent years, research on light emitting diodes from blue to near-ultraviolet has been actively conducted, and research on white LEDs using these short wavelength light emission has been actively performed. This white LED is used for liquid crystal display panels and illumination light sources. Application to such as is expected. For example, when blue light (wavelength around 450 nm) is excited and Mn ²⁺ is added to YAG: Ce ³⁺ , it emits orange light (wavelength of about 580 nm). However, the intensity of the red region was weak and the color rendering property was insufficient. In order to overcome this situation, research and development of red light emitting materials was expected.

On the other hand, it is known that light is emitted by adding Eu to anatase TiO ₂ and irradiating it with a xenon lamp or X-ray (Non-patent Document 1). Further improvement in emission intensity has been desired.
James Ovenstone, Philip. J. Titler, Robert Withnall and Jack Silver, "A Study of the Effects of Europium Doping and Calcination on the Luminescence of Titania Phosphor Materials", The Journal of Physical Chemistry, vol. 105, p.7170-7177 2001

  Therefore, the invention of this application has been made in view of the circumstances as described above, and solves the problems of the prior art, and provides a near-ultraviolet-excited phosphor that emits high-intensity red light and a method for manufacturing the same. Is an issue.

In order to solve the above problems, the invention of this application firstly incorporates 0.1 mol% or more and 10 mol% or less of Eu into a crystal structure of anatase TiO ₂ instead of a part of Ti. A near-ultraviolet-excited phosphor that emits red light when excited by near-ultraviolet light having a wavelength of 300 nm to 420 nm.

Secondly, in the invention of this application, 0.1 to 10 mol% of Eu is incorporated in the crystal structure of rutile TiO ₂ in place of a part of Ti, and the wavelength is from 300 to 420 nm. Provided is a near-ultraviolet-excited phosphor that emits red light when excited by near-ultraviolet light.

Thirdly, in the second invention, TiO ₂ is dissolved in an amount of nitric acid that is 25% or more and 35% or less of the solution, and EuCl ₃ that is a luminescent center material is 0.1 mol% or more and 10 mol% or less. A method for producing a near-ultraviolet-excited phosphor is provided which comprises adding, drying, and firing at 850 ° C. to 1000 ° C. to synthesize Eu-added rutile TiO ₂ .

Fourthly, in the third invention, there is provided a method for producing a near-ultraviolet-excited phosphor, characterized in that citric acid is mixed when TiO ₂ is dissolved in nitric acid and EuCl ₃ is added and then dried. provide.

Fifth, in the first invention, EuCl ₃ as a luminescent center material is added to titanium alkoxide or titanium chloride in an amount of 0.1 mol% or more and 10 mol% or less to cause hydrolysis, and then 500 ° C. or more and 800 ° C. or less. And a method for producing a near-ultraviolet-excited phosphor, characterized by synthesizing Eu-added anatase-type TiO ₂ .

Sixth, in the second invention, EuCl ₃ , which is a luminescent center material, is added to titanium alkoxide or titanium chloride at 0.1 mol% or more and 10 mol% or less to cause hydrolysis, and then 800 ° C. or more and 1000 ° C. or less. A method for producing a near-ultraviolet-excited phosphor, characterized by synthesizing Eu-added rutile-type TiO ₂ by firing at a low temperature, is provided.

Seventhly, in the fifth or sixth invention, there is provided a method for producing a near-ultraviolet excited phosphor, wherein the titanium alkoxide is Ti (OC ₂ H ₅ ) ₄ and the titanium chloride is TiCl _4. provide.

  The invention of this application has the features as described above, and an embodiment thereof will be described below.

In the near-ultraviolet-excited phosphor of the invention of this application, 0.1 mol% or more and 10 mol% or less of Eu is incorporated in the crystal structure of anatase TiO ₂ instead of a part of Ti, and the wavelength is 300 nm or more and 420 nm. It emits red light when excited by the following near ultraviolet rays.

Alternatively, in the near-ultraviolet-excited phosphor of the invention of this application, 0.1 to 10 mol% of Eu is incorporated in the crystal structure of rutile TiO ₂ instead of a part of Ti, and the wavelength is 300 nm. It emits red light when excited by near ultraviolet rays of 420 nm or less.

  The near-ultraviolet-excited phosphor as described above can provide a phosphor that emits high-luminance red light. As a result, it is highly likely that the phosphor can be used as a white LED used as an excitation light source of the phosphor. Applications to liquid crystal display panels and illumination light sources can be expected.

In the method for producing a near-ultraviolet-excited phosphor according to the invention of this application, TiO ₂ is dissolved in nitric acid in an amount that is 25% or more and 35% or less of the solution, and EuCl ₃ that is the luminescent center material is 0.1 mol% or more. It is characterized by the addition of 10 mol% or less, drying, and firing at 850 ° C. or more and 1000 ° C. or less to synthesize Eu-added rutile TiO _2. By using this manufacturing method, high-luminance red light emission is realized. Thus, a near-ultraviolet excited phosphor that is a phosphor to be obtained can be obtained.

At this time, TiO ₂ was dissolved in nitric acid, EuCl ₃ was added, and then dried, by mixing citric acid, citric acid became a dispersing agent, and Eu was more uniformly dispersed in TiO ₂ . This method is generally called a citric acid gel method.

Also, a so-called sol-gel method, in which EuCl ₃ , which is a luminescent center material, is added to titanium alkoxide or titanium chloride in an amount of 0.1 mol% to 10 mol%, hydrolyzed, and then fired at 500 ° C. to 800 ° C. It is also possible to synthesize Eu-added anatase TiO ₂ . Similarly, a so-called sol-type, in which EuCl ₃ as a luminescent center material is added to titanium alkoxide or titanium chloride in an amount of 0.1 mol% to 10 mol%, hydrolyzed, and then fired at 850 ° C. to 1000 ° C. Eu-added rutile TiO ₂ can also be synthesized using a gel method.

At this _{time, Ti (OC 2 H 5)} 4 or quality Eu added ANATA by using TiCl ₄ as a titanium chloride, as a titanium alkoxide - can be synthesized peptidase type TiO ₂ or Eu added rutile TiO _2.

That is, for example, Ti (OC ₂ H ₅ ) ₄ and C ₂ H ₅ OH are mixed, EuCl ₃ is added thereto to make a solution, and water is further added to cause hydrolysis.
Ti (OC ₂ H ₅ ) ₄ + 4H ₂ O → TiO ₂ + 4C ₂ H ₅ OH
TiO ₂ is formed by the reaction, the Eu added TiO ₂ by the TiO ₂ Eu of EuCl ₃ are incorporated are combined, by adjusting the calcination temperature during firing, Eu added anatase - peptidase type TiO ₂ or Eu-added rutile TiO ₂ can be synthesized.

Compared with the citric acid gel method, Eu synthesized uniformly in TiO ₂ and synthesized with this sol-gel method can obtain good light emission characteristics.

  Embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Of course, the present invention is not limited to the following examples, and it goes without saying that various aspects are possible in detail.

<Example 1>
Titanium alkoxide was dissolved in ethanol as a starting material, and 2 mol% of luminescent center material EuCl ₃ was added, followed by hydrolysis, drying, and firing. The firing temperature was 200 ° C., 500 ° C., 750 ° C., and 1000 ° C., the firing time was 3 hours, and the firing was performed in air. Eu-added anatase-type titanium oxide at 500 ° C. or higher and 750 ° C. or lower, and Eu-added rutile-type titanium oxide at 1000 ° C., and those with a firing temperature of 200 ° C. were amorphous (non-crystallized amorphous).

And the baking dependence of the ultraviolet excitation light emission intensity (PL intensity) and the electron beam excitation light emission intensity (CL intensity) of the obtained sample was measured. The result is shown in FIG. The PL spectrum in FIG. 1 is a He—Cd laser (wavelength 325 nm), and the CL spectrum is an emission spectrum obtained by excitation with an anode voltage V _A of ² kV and a current density J _s of 180 μA / cm ² . As is apparent from FIG. 1, the emission intensity of Eu-added anatase-type titanium oxide baked at 750 ° C. is the highest, and the emission intensity of Eu-added rutile-type titanium oxide baked in air at 1000 ° C. for 3 hours is anatase-type titanium oxide Compared to the ones.

  FIG. 2 shows the relationship between the wavelength of the irradiation light (irradiation laser) for exciting the Eu-added anatase-type titanium oxide fired at 750 ° C. and the excitation spectrum (monitor wavelength 615 nm). Thus, there is a broad absorption band near 325 nm, and there are steep absorption bands at 380 nm and 395 nm. The three spectra on the right show the intensities of the emission spectra excited at wavelengths of 325 nm, 380 nm, and 395 nm, and showed good red emission at 615 nm when excited at 395 nm. In addition, the excitation at 380 nm has a peak at 615 nm, but light emission having a main peak at 680 nm in the near infrared region was obtained.

On the other hand, the two curves on the right side of FIG. 3 are obtained by dissolving ready-made TiO ₂ as starting materials in 20% and 30% nitric acid, adding 1 mol% of the luminescent center material EuCl ₃ , and mixing citric acid. Then, the relationship between the wavelength of irradiation light for exciting Eu-added rutile titanium oxide synthesized at a drying and firing temperature of 1000 ° C. and the PL intensity is shown, but the emission spectrum of the TiO ₂ powder used as a starting material is also shown as a comparison. As a result of measurement, this TiO ₂ showed broad light emission having a peak in the vicinity of 400 nm to 500 nm, but the intensity was very weak. On the other hand, the powder prepared with Eu added at a nitric acid concentration of 30% showed broad emission near 450 nm and a bright line spectrum in the red region. Since these emission line spectra coincide with the emission of Eu ³⁺ , it can be seen that TiO ₂ : Eu ³⁺ is formed. On the other hand, those prepared at a nitric acid concentration of 20% showed insufficient TiO ₂ dissolution, almost no Eu ³⁺ emission, and a broad emission having a peak at 500 nm. This light emission is considered to be an oxygen defect of TiO ₂ or light emission of Eu ²⁺ .

  Next, the excitation spectra of these emissions were measured, and the results are shown by the three dotted lines on the left side in FIG.

TiO ₂ hardly emits light, and therefore the excitation spectrum is very weak. When the nitric acid concentration was 30%, excitation spectra having peaks at about 400 nm and 380 nm were obtained. Since the band gap of TiO ₂ is 3.3 eV, it is considered that matrix excitation occurs. On the other hand, it was confirmed that there was a peak at about 380 nm and 400 nm even when the nitric acid concentration was 20%, but the peak was also confirmed at 335 nm, and it was confirmed that there was absorption in a wide range of 250 nm to 400 nm.
<Example 2>
Further, Ti (OC ₂ H ₅ ) ₄ (tetraethoxytitanium) and ethanol are mixed using a sol-gel method, and then 2 mol% of EuCl ₃ is added, followed by hydrolysis with water and addition of Eu. TiO ₂ was synthesized and further baked in air at 1000 ° C. for 3 hours to synthesize Eu-added rutile TiO ₂ .

Then, the PL intensity of the emission spectrum by excitation of the synthesized Eu-added rutile TiO ₂ He—Cd laser (wavelength: 325 nm) was measured. The result is shown in FIG. As is clear from FIG. 4, a peak was confirmed at 627 nm, and a wide range of light emission near 500 nm hardly appeared, and good red light emission was obtained.

  As described in detail above, the invention of this application provides a near-ultraviolet-excited phosphor that emits high-luminance red light and a method for producing the same, and this near-ultraviolet-excited phosphor is a white LED used as an excitation light source for the phosphor. In the end, it is expected to be applied to liquid crystal display panels and illumination light sources.

It is the graph which illustrated the baking temperature dependence of PL intensity | strength and CL intensity | strength of the near-ultraviolet excitation fluorescent substance of invention of this application. Sol of the invention of this application - is a graph illustrating the excitation and emission spectra by near ultraviolet excitation of Eu added consisting of anatase TiO ₂ near ultraviolet excitation phosphors formed gel method. Is a graph illustrating the excitation and emission spectra by near ultraviolet excitation citric acid gel method near ultraviolet excitation phosphors consisting Eu added rutile TiO ₂ formed by the invention of this application. It is the graph which illustrated the emission spectrum by near ultraviolet excitation of the gold ultraviolet excitation fluorescent substance which consists of Eu addition rutile type TiO2 formed by the sol-gel method of invention of this application.

Claims (7)

In the crystal structure of anatase-type TiO ₂ , 0.1 mol% or more and 10 mol% or less of Eu is incorporated in place of a part of Ti, and red light is emitted when excited by near ultraviolet light having a wavelength of 300 nm or more and 420 nm or less. A near-ultraviolet-excited phosphor. In the rutile TiO ₂ crystal structure, 0.1 mol% or more and 10 mol% or less of Eu is incorporated in place of a part of Ti, and red light is emitted by being excited by near ultraviolet light having a wavelength of 300 nm or more and 420 nm or less. A near-ultraviolet-excited phosphor. TiO ₂ is dissolved in nitric acid in an amount of 25% to 35% of the solution, EuCl ₃ as a luminescent center material is added in an amount of 0.1 mol% to 10 mol% and dried, and then 850 ° C. to 1000 ° C. The method for producing a near-ultraviolet-excited phosphor according to claim ₂ , wherein the Eu-doped rutile TiO ₂ is synthesized by baking. After the TiO ₂ was added EuCl ₃ was dissolved in nitric acid, when the drying method of the near-ultraviolet excitation phosphors of claim 3, wherein the mixing citric acid. EuCl ₃ , which is the luminescent center material, is added to titanium alkoxide or titanium chloride in an amount of 0.1 mol% to 10 mol%, hydrolyzed, and then fired at 500 ° C. to 800 ° C., and Eu-added anatase TiO _{2. The} method for producing a near-ultraviolet excited phosphor according to claim 1, wherein ₂ is synthesized. EuCl ₃ , which is the luminescent center material, is added to titanium alkoxide or titanium chloride at 0.1 mol% or more and 10 mol% or less to cause hydrolysis, and then calcined at 850 ° C. or more and 1000 ° C. or less to obtain Eu-added rutile TiO ₂ . The method for producing a near-ultraviolet-excited phosphor according to claim 2, wherein the phosphor is synthesized. 7. The method for producing a near-ultraviolet excited phosphor according to claim 5, wherein the titanium alkoxide is Ti (OC ₂ H ₅ ) ₄ and the titanium chloride is TiCl ₄ .

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