JP2013107784A - Non-doped white fluorescent synthetic silica glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-doped white fluorescent synthetic silica glass which emits white fluorescence upon irradiation with ultraviolet radiation, without doping carbon, Cu or a phosphor.SOLUTION: The synthetic silica glass has an OH group content of ≤1 ppm, a chlorine content of ≤30 ppm, a viscosity (logη) at 1,280°C of ≥12.2 P, a Cu content of ≤1 ppm and a C content of ≤100 ppm, and emits ≥1 s delayed fluorescence in the visible light region upon irradiation with ultraviolet radiation, wherein the fluorescence emitted upon irradiation with ultraviolet radiation is white fluorescence.

Description

  The present invention relates to a non-doped white fluorescent silica glass utilizing white fluorescence generated when irradiated with light having a shorter wavelength than visible light, particularly a silica glass lamp, a silica glass optical jig, a silica glass fiber, a silica glass microchip, The present invention relates to a non-doped white fluorescent synthetic silica glass that effectively utilizes an optical feature that converts the wavelength of incident light into visible light, such as solar power generation and wavelength conversion laser.

  It is known that conventional silica glass products generate fluorescence in the visible light region when irradiated with ultraviolet rays from a general low-pressure mercury lamp. However, the fluorescence in the visible light region is often generated when natural silica glass has a wavelength of 400 nm or when synthetic silica glass is used. Also, the intensity of fluorescence was very weak, and the efficiency of converting fluorescence into the visible light region was very small.

  For example, Patent Document 1 proposes converting light of 250 nm or less into a long wavelength of 250 to 450 nm, but its use is limited because it is not conversion into light in the visible light region. Fluorescence generated from silica glass has a wavelength of up to 600 nm even when the wavelength is long, and it is very difficult to generate fluorescence of 600 nm or more. For this reason, conversion into white light using the fluorescence of silica glass was very difficult.

  In LED (Light Emitting Diode) and the like, there is a method of creating white by combining red, blue, and green, but recently, a white LED has been developed. The white LED is made into a white LED by covering the surface of the blue LED with a conversion substance that generates yellow when stimulated with blue light.

  In Patent Document 2, it is proposed that the silica glass is doped with Cu to generate fluorescence, but it is necessary to dope Cu to the silica glass as much as 30 to 1000 ppm, and the silica glass is colored. The fluorescence generated was not white. Further, in Patent Document 3, a fluorescent silica gel containing 0.05 to 0.5% by weight of carbon in silica gel has been proposed, but by containing carbon, the glass itself is colored black, The shape was only silica glass and particles.

JP 2009-154090 A JP-A-2005-272243 JP2003-155478A

  In view of the present situation, the present inventors have conducted extensive research on the mechanism of delayed fluorescence generation of silica glass, and as a result, the SiSiSi bond having the lowest excited triplet excitation level in the silica glass in the wavelength region of 200 nm to 180 nm is efficiently obtained. It was discovered that if ultraviolet light having a wavelength of 300 nm or less is absorbed and the ultraviolet light having a wavelength of 300 nm or less is absorbed, fluorescence is also generated in the wavelength region of 600 nm or more in the visible light region after the crossing of the inverse terms to the lowest excitation singlet excitation level. .

  In addition, this long wavelength fluorescence is not colored because it is not doped with carbon, Cu or phosphor, etc., is very stable in shape, is not deteriorated by irradiation with ultraviolet rays, and changes in temperature. It is also stable.

  The present invention has been made in view of the above-mentioned problems of the prior art, and provides a non-doped white fluorescent synthetic silica glass whose fluorescence when irradiated with ultraviolet rays is white fluorescence without doping carbon, Cu or phosphorescent substances. For the purpose.

  The non-doped white fluorescent synthetic silica glass according to the present invention has an OH group content of 1 ppm or less, a chlorine content of 30 ppm or less, a viscosity at 1280 ° C. (Log η) of 12.2 poise or more, and a Cu content. A synthetic silica glass having an amount of 1 ppm or less and a C content of 100 ppm or less and generating a delayed fluorescence of 1 second or more in the visible light region when irradiated with ultraviolet rays, and the fluorescence when irradiated with ultraviolet rays is white It is characterized by being fluorescent. The lifetime of delayed fluorescence is 1 second or longer, and is very long, for example, about 1 to 10 seconds, and the occurrence of delayed fluorescence can be visually observed.

  Further, it is preferable that the ultraviolet light has a wavelength of 160 nm to 400 nm.

  In particular, it is preferable that the ultraviolet light has a wavelength of 254 nm or 185 nm of a low-pressure mercury lamp, a wavelength of 193 nm of an ArF excimer laser, or a wavelength of 172 nm of an Xe excimer lamp.

  The delayed fluorescence is preferably fluorescence due to oxygen deficiency having a peak at a wavelength of 460 nm.

  The delayed fluorescence is white fluorescence generated by fluorescence having a wavelength of 460 nm and delayed fluorescence having a wavelength of 600 nm or more, and the chromaticity coordinate in the CIE chromaticity diagram of the white fluorescence has x of 0.2 or more and 0.4 or less, y Is more preferably 0.2 or more and 0.4 or less.

  According to the present invention, it is possible to provide a non-doped white fluorescent synthetic silica glass that generates white delayed fluorescence of 1 second or more in the visible light region by irradiating ultraviolet rays without doping carbon, Cu or phosphor. There is a great effect that you can.

It is a graph which shows the relationship between fluorescence intensity and fluorescence wavelength (nm). It is the graph which expanded the fluorescence wavelength 550nm -700nm part of the graph shown in FIG. 2 is a graph of chromaticity coordinates of Example 1. 5 is a graph of chromaticity coordinates of Comparative Example 1. 10 is a graph of chromaticity coordinates of Comparative Example 2.

  Embodiments of the present invention will be described below, but these are exemplarily shown, and it goes without saying that various modifications are possible without departing from the technical idea of the present invention.

  The non-doped white fluorescent synthetic silica glass of the present invention is a synthetic silica glass having absorption of SiSiSi bond at a wavelength of 300 nm or less, particularly, silica glass is irradiated with ultraviolet light of 300 nm or less, and generates fluorescence in a wavelength region of 600 nm or more in the visible light region. The long-wavelength fluorescence is used to generate white light, and the white light necessary for human life is effectively generated without the use of a medium such as electricity.

  In the silica glass of the present invention, the OH group content is 1 ppm or less, and more preferably 0.5 ppm or less. Further, the chlorine content is 30 ppm or less, and more preferably 10 ppm. The Cu content is 1 ppm or less, and more preferably 0.5 ppm or less. The C content is 100 ppm or less, and more preferably 50 ppm or less.

  The silica glass of the present invention is a high heat-resistant synthetic silica glass, and has a viscosity (Log η) at 1280 ° C. of 12.2 poise or more, preferably 12.3 poise or more.

  In particular, the silica glass of the present invention does not contain a phosphorescent substance, and since it is the silica glass itself, it can be formed into various shapes.

  For example, it can be drawn into a fiber shape, polished into a thin film, or a prism, lens, or spherical product can be provided.

  It has been found that the SiSiSi bond at the lowest excited triplet excited level in silica glass has absorption in the vicinity of a wavelength of 190 nm or less with a wavelength of 300 nm or less. Further, it has been found that the lowest excitation singlet excitation level has absorption in the vicinity of a wavelength of 240 nm, which is 300 nm or less. This lowest excited singlet excitation level is also known to generate fluorescence at a wavelength of 460 nm.

  By including both the lowest excited triplet excited level and the lowest excited singlet excited level in the silica glass, fluorescence is generated at a long wavelength of 600 nm or more. In conventional silica glass, only the lowest excited singlet excited level has been formed, the delayed fluorescence phenomenon has not been confirmed, and only normal fluorescence has been detected.

  However, when the SiSiSi bond in the silica glass is further increased, electrons excited by irradiation with ultraviolet light are primarily trapped in the SiSiSi bond at the lowest excited triplet excited level, and then generate a fluorescence of 600 nm or more. Fluorescence is generated at a long wavelength. Fluorescence having a long wavelength of 600 nm or more generates fluorescence commensurate with the power of incident ultraviolet light of 300 nm or less. For this reason, it becomes possible to efficiently convert the wavelength of ultraviolet light of 300 nm or less into a visible light region by silica glass.

  Moreover, in general organic LED material, when delayed fluorescence is generated, heat is released, so that energy is lost and conversion efficiency is deteriorated. For this reason, in order to improve the exchange efficiency, a treatment such as cooling the material with liquid nitrogen or the like was necessary. However, since the silica glass of the present invention does not release heat, sufficient conversion efficiency even at room temperature. It is possible to obtain

  Further, since ultraviolet rays of 300 nm or less are absorbed by silica glass, there is an advantage that ultraviolet rays can be completely converted into visible light. With long wavelength fluorescence of 600 nm or more, (i) electrons that have received energy move to a place where the singlet excited electrons have the highest energy level. (ii) Singlet excited electrons do not directly return to the ground state, but once move to triplet excited electrons having a low energy level. (iii) Return to ground state from triplet excited electrons. (iv) Long-wavelength fluorescence of 600 nm or longer is generated at this time.

  By forming many triplet excited electron level SiSiSi bonds in silica glass and also forming singlet excited electron level absorption at 240 nm, delayed fluorescence can be observed even at room temperature. became. Therefore, wavelength conversion, which could not be achieved at room temperature with organic LED materials until now, has become possible by using this delayed fluorescence phenomenon.

  In the case of the silica glass of the present invention, it is preferable that the fluorescence wavelength includes a wavelength having a peak at 460 nm and delayed fluorescence including 600 nm or more, and the delayed fluorescence preferably lasts for several seconds. However, the fluorescence wavelength may vary depending on the absorption wavelength of each potential level, and can be changed to a visible light region of 360 nm to 780 nm.

  Since this delayed fluorescence is generated even at room temperature, it is not necessary to cool it with liquid nitrogen or the like as in the case of conventional organic EL materials, and because it is silica glass, a large substrate having a fiber shape or 1 m square or more is also produced. It is possible. In addition, because it is possible to create prisms, lens shapes, and spherical products, it is easy to irradiate laser light, which makes it possible to obtain visible light having a peak at 460 nm that has been efficiently converted in wavelength. It is.

  By virtue of such delayed fluorescence of visible light, visible light can be generated even in silica glass that does not contain a phosphorescent substance. Therefore, it can be applied to backlights of liquid crystal televisions and lighting devices. Further, by irradiating with an ultraviolet laser, it becomes possible to generate laser light having a wavelength changed to visible light.

  Furthermore, in the space where ultraviolet rays and cosmic rays exist, infinite ultraviolet rays and cosmic rays can be directly converted into white light, so that light can be efficiently converted into white light without using conventional power equipment. So it becomes a very effective material for space development.

  In the silica glass of the present invention, the method for efficiently forming the SiSiSi bond of the lowest excited triplet excited level is not particularly defined. For example, a synthetic silica glass soot base material is reacted with a compound containing Cl to form Si-Cl. After forming the bond, it can be achieved by extracting Cl from the Si-Cl bond in a reducing atmosphere.

  The present invention will be described more specifically with reference to the following examples. However, it is needless to say that these examples are shown by way of illustration and should not be construed as limiting.

Example 1
A silica glass soot base material was prepared by hydrolyzing silicon tetrachloride (SiCl ₄ ) gas in a flame of hydrogen and oxygen and depositing it on the target material. Next, this soot base material is dehydrated in an organosilicon compound gas, baked in a hydrogen atmosphere, heated in a reducing atmosphere, and then vitrified at 1550 ° C. in a vacuum furnace to produce synthetic silica having oxygen deficiency. A glass base material was created.

(Comparative Example 1)
A silica glass soot base material was prepared by hydrolyzing silicon tetrachloride SiCl4 gas in a flame of hydrogen and oxygen and depositing it on the target material. Next, the soot base material was dehydrated in an organosilicon compound gas, heated in a reducing atmosphere, and then vitrified in a vacuum furnace at 1550 ° C. to prepare a synthetic silica glass base material having oxygen deficiency.

(Comparative Example 2)
A silica glass soot base material was prepared by hydrolyzing silicon tetrachloride SiCl4 gas in a flame of hydrogen and oxygen and depositing it on the target material. Next, this soot base material was heated at 1550 ° C. in a vacuum furnace to prepare a synthetic silica glass base material having no oxygen deficiency.

  Table 1 shows the results of transmittance measurement of 200 nm or less of the silica glass of Example 1 and Comparative Examples 1 and 2. The OH group content was measured from an infrared absorption spectrum of 2.7 μm with an infrared spectrophotometer. The Cl content was measured by fluorescent X-ray analysis. The viscosity was measured by a beam bending method.

  For the above three types of synthetic silica glass, put a UV350 filter on the detector side, irradiate UV light at 254 nm, cut off fluorescence caused by Si-Si generated at 280 nm, and emit fluorescence at longer wavelength side than 350 nm. A graph showing the relationship between the fluorescence intensity and the fluorescence wavelength (nm) when measured is shown in FIG. Moreover, the graph which expanded the fluorescence wavelength 550nm -700nm part of the graph shown in FIG. 1 is shown in FIG. 1 and 2, the synthetic silica glass of Example 1 has a fluorescence peak at a wavelength of 460 nm, has a fluorescence wavelength at a wavelength of 600 nm or more, and has fluorescence at a wavelength of 460 nm and delayed fluorescence at a wavelength of 600 nm or more. It can be seen that the white fluorescence is generated.

  The state of delayed fluorescence when the above three kinds of synthetic silica glasses were irradiated with ultraviolet rays of 254 nm was measured and shown in Table 2. Only in Example 1 and Comparative Example 1 containing triplet excited electron levels and singlet excited electron levels, fluorescence at 460 nm of 1 second and 10 second levels was observed. White fluorescence was observed only in Example 1. In Comparative Example 2, the fluorescence was slightly observed in the visible light during the ultraviolet irradiation, but the fluorescence disappeared as soon as the ultraviolet irradiation was stopped.

  In addition, Table 3 shows the content of impurities in the above three types of synthetic silica glass.

  Table 4 shows fluorescence charts when the above three types of synthetic silica glass were irradiated with ultraviolet rays of 254 nm.

  The chromaticity coordinates in the CIE chromaticity diagram when the three types of synthetic silica glass were irradiated with ultraviolet rays of 254 nm are shown in Table 5, and the chromaticity coordinate graphs are shown in FIGS. The chromaticity coordinates were measured by fluorescence when irradiating UV light of 254 nm of a low-pressure mercury lamp on Example 1 and Comparative Examples 1 and 2 using a multichannel spectrometer PMA-12 manufactured by Hamamatsu Photonics.

  Furthermore, the results of visual fluorescence observation when irradiated with ultraviolet light from a low-pressure mercury lamp (wavelength 185 nm), irradiated with ArF excimer laser (wavelength 193 nm), and irradiated with light from a Xe excimer lamp (172 nm) are shown. This is shown in FIG. White fluorescence was observed only in Example 1. In Comparative Example 1, blue fluorescence was observed in all cases. In Comparative Example 2, when ultraviolet light from a low-pressure mercury lamp (wavelength 185 nm) was irradiated, purple fluorescence was obtained, and when irradiated with an ArF excimer laser (wavelength 193 nm) and Xe excimer lamp (172 nm) was irradiated. In some cases, fluorescence from purple to red was observed.

Claims (5)

  The OH group content is 1 ppm or less, the chlorine content is 30 ppm or less, the viscosity (Log η) at 1280 ° C. is 12.2 pise or more, the Cu content is 1 ppm or less, and the C content is 100 ppm or less. A synthetic silica glass that generates delayed fluorescence of 1 second or more in the visible light region when irradiated with ultraviolet rays, and the fluorescence when irradiated with ultraviolet rays is white fluorescence. Silica glass.   2. The non-doped white fluorescent synthetic silica glass according to claim 1, wherein the ultraviolet ray has a wavelength of 160 nm to 400 nm.   3. The non-doped white fluorescent synthetic silica glass according to claim 1, wherein the ultraviolet light has a wavelength of 254 nm or 185 nm of a low-pressure mercury lamp, a wavelength of 193 nm of an ArF excimer laser, or a wavelength of 172 nm of an Xe excimer lamp. .   The non-doped white fluorescent synthetic silica glass according to any one of claims 1 to 3, wherein the fluorescence is fluorescence due to oxygen deficiency having a peak at a wavelength of 460 nm.   The fluorescence is white fluorescence generated by fluorescence having a wavelength of 460 nm and delayed fluorescence having a wavelength of 600 nm or more, and the chromaticity coordinate in the CIE chromaticity diagram of the white fluorescence has an x of 0.2 or more and 0.4 or less, and y The non-doped white fluorescent synthetic silica glass according to any one of claims 1 to 4, which is 0.2 to 0.4.

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