WO2006025428A1

WO2006025428A1 - Visible light-emitting material utilizing surface modification of silica particle and method for producing same

Info

Publication number: WO2006025428A1
Application number: PCT/JP2005/015864
Authority: WO
Inventors: Takashi Uchino; Natsuko Sagawa
Original assignee: The New Industry Research Organization
Priority date: 2004-08-31
Filing date: 2005-08-31
Publication date: 2006-03-09
Also published as: JPWO2006025428A1; JP2007290873A; JP4961526B2

Abstract

Disclosed is a visible light-emitting material which emits light in a wide wavelength range in the visible region using an ultraviolet LED device having an emission wavelength of 400 nm as the excitation light source. Specifically disclosed is a silica particle having visible light-emitting characteristics which is produced by a process comprising at least the following two steps: (a) a surface modification step for surface modifying a silica particle with a hydrocarbon group; and (b) a heat treatment step for heat treating the surface-modified silica particle for a certain time at 150-300˚C. The surface of a silica particle such as fumed silica is modified with a hydrocarbon group by utilizing the high reactivity of an -SiCl3 bond at the end of an alkylchlorosilane (CnH2n-1SiCl3) with a hydroxyl group.

Description

Visible light emitting material using surface modification of silica fine particles and method for producing the same

[0001] The present invention relates to a visible light-emitting material using silica fine particles and a method for producing the same, and more specifically, the silica fine particles are modified by subjecting the silica fine particles to surface modification and heat treatment, and the wavelength of visible light. This technology is related to the manufacture of light emitting device materials with broad emission characteristics.

Background art

[0002] New Energy Industrial Technology Development Organization (NEDO) project, “High-efficiency electro-optic conversion composite compound development (common name: strength of the 21st century)” project, about twice that of fluorescent lamps Development of a compound semiconductor for LED and its application as a light source for illumination, aiming to solve the technical problem of putting a light source (LED) with high energy consumption efficiency into practical use! We have been developing the technology necessary for use as

[0003] In the industrial world, the resulting UV LED element (external quantum efficiency of 43% is extremely high, GaN-based LED emitting ultraviolet light, emission wavelength is 405nm) is used as a light source for white LED. Utilization is required.

[0004] Currently, white LEDs have a problem in that green light with a wavelength of around 520 nm, which is mainly achieved by phosphors using blue LEDs and rare earth elements, cannot be produced well. For example, a white LED composed of an InGaN-based blue LED and a phosphor coated with a YAG phosphor is said to have the disadvantage of poor green color rendering with a low spectral intensity of the phosphor.

[0005] In addition, in this InGaN-based blue LED phosphor, since the excitation spectrum intensity decreases at wavelengths longer than 400 nm, various phosphors have been proposed (for example, Patent Document 1). . In the industry as described above, there is a movement to use an ultraviolet LED element having an emission wavelength of 405 nm as an excitation light source, and a new fluorescent material having a broad fluorescence spectrum with visible light at an excitation wavelength of 405 nm is required. And

[0006] On the other hand, the -SiCl bond at the terminal of alkylchlorosilane (CH 3 SiCl) has conventionally been a hydroxyl group. It is known that it is very easy to react with a group, and many studies have been made on surface modification of a silica surface with a hydrocarbon group using its high reactivity (for example, Non-Patent Document 1)

[0007] In addition, silicon carbide (SiC) is well known for its excellent semiconductor properties such as wide band gap and high thermal conductivity! It is attracting attention as a material. While many studies have been conducted, it is known that ion implantation of silicon and carbon into a silica glass thin film induces a SiC-derived defect structure in the silica glass network, which causes strong light emission. For example, ion implantation of C + or Si + into SiO

2

There is an example in which a visible light emitting material has been successfully produced by introducing a carbon-carbide bond in silica by introducing it or by plasma CVD (Non-patent Document 2).

However, such an ion implantation method is useful for inducing the emission center derived from silicon carbide (SiC). However, in the ion implantation, the ion and carbon are ionized. When there is a need for special vacuum equipment, there is a problem.

[0008] In addition, in the process of producing silica glass by the sol-gel method, a technique for obtaining a white light emitter by adding an organic compound such as carboxylic acid and performing heat treatment has been reported (Patent Document 2,). Non-patent document 3).

Patent Document 1: Japanese Patent Application Laid-Open No. 2001-214162

Patent Document 2: WO 98/59015

Non-Patent Document 1: R. Wang and S. L. Wunder, Langmuir 16 (2000) 5008

Non-Patent Document 2: R. Perez-Rodriguez et al, J. Appl. Phys. 94, 254 (2003), S.Y. Seo et al. Appl Phys. Lett. 84, 717 (2004))

(Non-Patent Document 3: W. H. Green et al., Science 276, 1826 (1997))

Disclosure of the invention

Problems to be solved by the invention

The problem to be solved by the present invention is to provide a light-emitting element of a next-generation optical device that can emit white light by photoluminescence (PL). In other words, unlike the LED, which has a narrow emission spectrum half-width and high monochromaticity, we developed a device with broad emission characteristics that has a broad emission spectrum half-width in the visible wavelength range. It is to be.

[0011] In addition, a white LED composed of an InGaN-based blue LED and a phosphor coated with a YAG phosphor has a low spectral intensity of the phosphor! A luminescent material that improves green color rendering The purpose is to provide. At the same time, the purpose of the present invention is to provide a luminescent material that can be used as an excitation light source as an excitation light source, which is the result of the above-mentioned “21st Century Light” project, which is an ultraviolet LED element having an emission wavelength of 405 nm.

[0012] Further, there is a problem that a light emitting material derived from silicon carbide (SiC) is produced by a simpler method other than an ion implantation method that requires special vacuum equipment for ionization. Means to solve

[0013] As a result of intensive research on the defect generation process in the amorphous structure of silica glass, the present inventors have mixed silica particles with inorganic particles having semiconductivity or conductivity to perform pressure molding and It has been found in previous research that a silica glass light-emitting material having visible light emission characteristics can be obtained by performing the firing step.

Further research has been conducted, and the above-mentioned conventional alkylchlorosilane (C H SiCl

n 2n-l 3) -SiC

1

By utilizing the high reactivity of 3 bonds with hydroxyl groups, the surface of silica fine particles is modified with hydrocarbon groups and heat-treated under appropriate conditions to produce visible light emitting materials that emit light in a wide wavelength range. The present invention has been completed by finding that it can be produced.

[0014] In the present invention, as a simpler method for producing a light emitting material derived from silicon carbide (SiC), attention was paid to hydrolysis and dehydration condensation reaction between silica fine particles and alkylchlorosilane. When silica fine particles react with alkylchlorosilane, the alkylchlorosilane is hydrolyzed by the OH groups on the surface of the silica fine particles and the adsorbed water present around them, and adsorbed on the surface of the silica fine particles.

[0015] A sample in which Si-C bonds exist on the surface of the silica fine particle as shown in the structural formula of Fig. 1 is generated. In this reaction, the ability of the adsorbed alkyl groups to form a self-assembled film has been studied a lot! /

[0016] The present invention succeeds in inducing a SiC-derived structure on the surface of the silica fine particle by heat-treating the sample in which the Si-C bond is present on the surface of the silica fine particle. How the light emission from this sample depends on the heat treatment temperature, the heat treatment atmosphere, and the length of the alkyl group that modifies the surface of the silica fine particles will be described later.

[0017] The silica fine particles having visible light emission characteristics according to the present invention include: (a) a surface modification step of surface-modifying silica fine particles with a hydrocarbon group; and (b) silica fine particles after surface modification at 150 to 300 ° C. It is manufactured by a heat treatment process in which heat treatment is performed for a predetermined time in a temperature range. Here, the heat treatment is performed in order to form a SiC / C complex in the silica fine particles during the thermal decomposition of the hydrocarbon group, and to make it a visible light emission center of the silica fine particles.

[0018] In addition, the silica fine particles having visible light emission characteristics according to the present invention can be formed into a pressure-molded product, and (a) a surface modification step of surface-modifying the silica fine particles with a hydrocarbon group; and (b) surface modification. A pressing step for forming a pressure-molded body by pressure-molding the subsequent silica fine particles, and (c) a heat treatment step in which the pressure-formed body is heat-treated in a temperature range of 150 to 300 ° C. for a predetermined time.

[0019] Further, when the surface of the silica fine particles in the above-described production method is modified with a hydrocarbon group! , Alkylchlorosilane (C H SiCl) (n is an integer of 4 or more), silica fine particles

n 2n-l 3

It is produced by modifying the hydrocarbon surface on the child surface. This is an alkylchlorosilane (

By utilizing the fact that the -SiCl bond at the end of C H SiCl) is very reactive with the hydroxyl group,

The surface of the Lica fine particles is modified with a hydrocarbon group.

[0020] In addition, in the heat treatment step of the silica fine particles or the pressure-formed body in the above-described production method, the light emission intensity can be increased by heat treatment in a nitrogen atmosphere or an air atmosphere. The nitrogen atmosphere is used to exclude oxygen, and the emission intensity can be improved by excluding oxygen. In addition to the nitrogen atmosphere, an inert gas atmosphere such as argon may be used. In addition, although it is possible even in a vacuum, as will be described later, in the case of the vacuum, the emission intensity is not improved, and the following results are obtained.

[0021] Further, in the heat treatment step of the silica fine particles or the pressure-molded body in the above-described production method, heat treatment is performed for a predetermined time in a nitrogen atmosphere, and then heat treatment is performed for a predetermined time in an air atmosphere. The wavelength can be controlled. Compared to a sample sintered only in a nitrogen atmosphere, a sample sintered in a nitrogen atmosphere and then re-sintered in an air atmosphere emits light as the time for re-sintering in the air atmosphere increases. Long peak wavelength Shift to the side.

[0022] From another viewpoint, the silica fine particles having visible light emission characteristics according to the present invention are:

(a) a surface modification step for surface modification of silica fine particles with tetra-salt silicate (SiCl), and (b) surface

Four

The modified silica fine particles are prepared by a heat treatment process in which heat treatment is performed for a predetermined time in a temperature range of 150 to 300 ° C.

[0023] In addition, a novel light-emitting element can be provided by using the saccharification material and silica molding material containing silica fine particles obtained by the above-described production method as a phosphor. This is because it is easier to commercialize the glyceride material industrially.

[0024] Further, the silica fine particles having visible light emission characteristics according to the present invention have a silica fine particle as a nucleus and a Si-C-0-based light emitter on the surface of the nucleus, whereby a novel light emitting material is obtained. Is to provide.

Here, the silica fine particles used in the production method according to the present invention are artificial amorphous (non-crystalline) silicon dioxide, and the particle diameter of the fine particles is several ηπ! Use fumed silica, a high-purity ultrafine particle of ~ 10 nm! This focuses on the surface activity of fumed silica.

In addition, fumed silica is used to minimize the size of the silica particles, thereby increasing the OH groups per unit surface area and improving the luminous efficiency. The particle size of the fumed silica force is 1 to: LOOnm, but it is desirable that the particle size be narrow.

The invention's effect

[0026] The silica fine particles or the silica molded body according to the present invention has an effect of emitting light with a broad emission spectrum in the visible light wavelength range with an excitation light wavelength of 300 to 400 nm.

[0027] In addition, an ultraviolet LED element (wavelength: 405 nm), which is the result of the “21st Century Light” project, is used as a light source, and it can be expected to be used as a light emitting material for white LEDs. In particular, a white LED composed of an In GaN blue LED and a phosphor coated with a YAG phosphor has a low spectral intensity of the phosphor, and a luminescent element as a phosphor that improves green color rendering. May be used as a child.

[0028] Furthermore, a phosphor element such as a white LED is obtained by saccharifying the silica fine particles according to the present invention. It is highly possible to put it into practical use!

[0029] Note that since the light-emitting element can be manufactured with low heating temperature, short heating time, it is possible to manufacture the light-emitting element at low cost by using a simple and inexpensive manufacturing facility. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

Example 1

[0031] The silica fine particles according to the present invention include (a) a surface modification step of surface-modifying silica fine particles with a hydrocarbon group, and (b) silica fine particles after surface modification at a temperature range of 150 to 300 ° C for a predetermined time. The force produced by the heat treatment step for heat treatment One embodiment of this production method will be described in detail below.

[0032] For example, fumed silica is used as the silica fine particles used for producing the silica glass. Fumed silica is a 1100-1400 ° C burned gas mixture of H and O

twenty two

It is produced by oxidizing and hydrolyzing tetra-salt key gas (SiCl 3) gas in the flame of

Four

Spherical particles mainly composed of amorphous diacid silicate (SiO 2) whose average particle size is about lOnm

2

It is an ultrafine particle. Fumed silica is an ultrafine particle and has a chemically active surface structure because it is produced by rapid cooling.

[0033] Here, fumed silica is used as the silica fine particles used in the production of silica glass.

Here, the fumed silica actually used is as follows.

• Manufacturer: Sigma, St. Louis, Missouri, USA

• Model number: S 5130

• Particle size: 7nm

The analytical values of standard fumed silica impurities are shown below. • A1 0 0.001% or less, Fe 0 0.0001% or less, ΉΟ 0.001% or less

2 3 2 3 2

[0034] Next, a surface modification step for modifying the surface of silica fine particles with a hydrocarbon group will be described. In this example, an alkylchlorosilane having 1 to 18 carbon atoms in which all alkyl groups are linear with respect to fumed silica. (CH SiCl) using pentane as the solvent and Ar atmosphere It is made to react with. After that, the sample is prepared by centrifuging to remove unreacted alkylchlorosilane and drying at room temperature. In addition, the sample thus prepared is formed into a pellet shape, and is subjected to heat treatment for a predetermined time in a temperature range of 150 to 300 ° C. in air or nitrogen to prepare a sample.

[0035] In the data shown in the examples, n = l, 3,8,18 is represented by n 2n-1 3 as alkylchlorosilane (C 3 H 3 SiCl).

Used. For convenience of explanation, n = 18 (Octadecy Trichloro Silane, `` OT

Abbreviated as “S”. ) Will be described in detail as an example.

[0036] (Sample preparation method)

Put fumed silica (2g) and a stir bar in an eggplant flask and put a three-way cock in the glove box to create an argon (Ar) atmosphere. Next, take out the flask from the glove box, pour Ar with the force of one side of the three-way cock, and add pentane (50 ml) and OTS (0.5 ml) with the other force using the syringe while stirring. Close one side of the three-way cock, and since salty hydrogen is generated on the other side, attach a rubber balloon and leave it for a day. Then remove the stopper and remove at room temperature to remove the pentane solvent.

[0037] Next, 0.3 g of the prepared sample is weighed, and a pellet having a diameter of 19 mm is produced at a pressure of 176 MPa using a high-pressure molding machine (300 kN NT wave N3036- ΟΟ, ΝΡa system).

The molded pellets were 150% in the atmosphere using an electric furnace (super-burn, Motoyama Co., Ltd.).

By performing the heat treatment in a temperature range of ˜300 ° C. for a predetermined time, the silica molding material having visible light emission characteristics according to the present invention can be obtained. Here, a sample is prepared for a predetermined time of 2 hours.

Note that there is a correlation between temperature and time. If the temperature is high, a short heating time is required. If the temperature is low, a long heating time is required.

[0038] Fig. 2 shows changes in the emission spectrum of the obtained silica molding material depending on the heat treatment temperature in the atmosphere. Here, the emission spectrum is measured using a fluorescence spectrophotometer (a 75 w xenon flash lamp as a light source).

[0039] As shown in FIG. 2, it can be understood that the emission intensity reaches a maximum at a heating temperature of 200 ° C.

. Here, the excitation light wavelength is 400 nm. This sample has been confirmed to emit light in the excitation wavelength range of 300 to 400 nm, as in FIG. [0040] In addition, a broad emission of light longer than 430 nm was observed in the non-heated sample, and the emission intensity increased slightly with heating at 150 ° C, and the emission intensity increased with heating at 200 ° C! The emission peak position is shifted, and emission is observed on the longer wavelength side. It can be understood that when the heating temperature is 250 ° C or higher, there is no change in the emission peak position, and the emission intensity decreases!

[0041] (Emission spectrum)

Next, we will discuss the effect of the length of the alkyl group that modifies the surface of fumed silica on the light emission.

V will explain. The excitation wavelength is known to emit light with excitation of 350 to 400 nm in the case of carbon carbide! / Luminous emission was measured at an excitation wavelength of 400 nm.

FIG. 3 is a luminescence vector diagram measured after heat-treating each sample having a different carbon number at 200 ° C. in the atmosphere. In alkyl chlorosilane (C H SiCl), n = l, 3,8, 18 alkyl n 2n- 1 3

For luchlorosilane, the emission spectrum of the sample with n = l, 3 showed no significant luminescence for both the non-heat-treated and heat-treated samples, whereas the sample with n = 8,18 , Visible luminescence can be observed by heating. When n = l, 3, no clear light emission was observed even when heat-treated at different temperatures. From this, it can be understood that an alkyl group having a certain length is necessary for the light emission.

[0043] (Light emission mechanism)

The microscopic mechanism of light emission in the sample of the above example will be described below. By introducing C + or Si + into SiO by ion implantation or plasma CVD, carbon in silica

2

-There are examples of successful formation of visible light emitting materials by forming a key complex, but the emission spectrum of these SiC / C composites is similar to the emission spectrum from this sample! From this, it can be inferred that even in this sample, a SiC / C composite was formed in the sample during the thermal decomposition of the hydrocarbon group, and this was the visible emission center of this sample. .

[0044] Further, as a related prior art as described above, a technique for obtaining a white luminescent material by adding an organic compound such as carboxylic acid and performing heat treatment in the process of producing silica glass by a sol-gel method has been reported. However, the difference from this prior art will be described.

In the prior art, the addition of a carboxylic acid such as acetic acid is an indispensable condition when preparing a luminescent sample. The production method according to the present invention does not require the addition of carboxylic acid, The main difference is the use of hydrolysis and thermal decomposition reactions of chlorosilanes with basic groups. In addition, the sample obtained by the production method according to the present invention can emit light even when heated in a nitrogen atmosphere (no oxidation reaction is observed!), Which is different from the prior art. I think it is.

Example 2

[0046] As another example, in Example 1 described above, it is possible to produce visible light emission characteristics as silica fine particles without producing a pressure-molded body by pressure molding. A method for producing silica fine particles having visible light emission characteristics will be described below.

[0047] First, in the same manner as in Example 1, fumed silica (2g) and a stirrer are placed in an eggplant flask, and a three-way cock is put in the glove box to make an argon (Ar) atmosphere. Also remove the flask from the glove box force, pour Ar from one side of the three-way cock, and add pentane (50 ml) and OTS (0.5 ml) using a syringe from the other side while stirring. Close one side of the three-way cock, and salty hydrogen will be generated on the other side. Then, to remove the pentane solvent, remove the stopper and dry at room temperature.

[0048] Next, the dried fumed silica is subjected to a heat treatment in the atmosphere at 200 ° C for 2 hours using an electric furnace (super-burn, Motoyama Co., Ltd.), for example. Silica fine particles having visible light emission characteristics according to the present invention can be obtained.

Example 3

[0049] In the above examples, it is understood that there is a correlation between the temperature of the heat treatment, the heating time, and the gas atmosphere, which affects the intensity of visible light emission of the finally produced silica fine particles or silica compact. it can. Hereinafter, this correlation will be described.

In the following, data is shown using a sample whose surface is modified with an alkylsilane having 18 carbon atoms, which has the maximum emission intensity.

[0050] FIG. 4 shows the result of measuring the emission spectrum at 200 ° C, which shows the maximum emission intensity, while changing the heat treatment time. According to Fig. 4, it can be understood that light emission having a peak at around 440 nm appears in the heat treatment of 0.5 h, the light emission intensity becomes maximum in the heat treatment of lh, and the light emission intensity decreases in the heat treatment of 2 h or more!

It is also clear that the emission peak position shifts to the longer wavelength side with the heat treatment time. The

[0051] The spectrum shown in FIG. 5 shows the change in the infrared spectrum with the heat treatment time. In the sample heat-treated for lh or longer where long wavelength light emission was observed, the absorption intensity due to C-H stretching vibration decreased due to the thermal decomposition of the alkyl group, and the absorption due to the carbo group was observed in the vicinity of 1700 (wave number) cm- ^1. I can confirm. From this, it can be inferred that light emission on the long wavelength side is related to the thermal decomposition and oxidation process of the alkyl group. In the short-wavelength side emission observed with the heat treatment of 0.5 h, no change was seen in the infrared spectrum, which is different from the long-wavelength side emission, which is related to the thermal decomposition of the alkyl group and the oxidation process. ! / Think of it as a dull luminescence.

[0052] FIG. 6 shows a fumed n 2n-1 1 3 surface-modified with alkylchlorosilane (C H SiCl) n = 18.

It shows the excitation wavelength dependence (excitation wavelength: 400 nm or less) of the emission spectrum of a sample of silica heated in the atmosphere at 200 ° C for 2 hours. It can be understood that as the excitation wavelength becomes longer at 350 nm force 375 nm and 400 nm, the emission intensity increases and the emission peak wavelength shifts to around 480 ηm.

[0053] FIG. 7 shows fu n 2n-1 1 3 that has been surface-modified with alkylchlorosilane (C 3 H 3 SiCl) n = 18.

This shows the excitation wavelength dependence (as-prepared is for the unheated sample) (excitation wavelength: 350 nm) of the emission spectrum of the sampled silica heated in nitrogen, vacuum, and atmosphere at 200 ° C for 2 hours. When the excitation wavelength is 350 nm, it can be understood that the sample heated in a nitrogen atmosphere has the highest emission intensity.

[0054] Similarly, FIG. 8 shows a structure in which n 2n-1 3 3, which has been surface-modified with alkyl chlorosilane (C H SiCl) n = 18.

Excitation wavelength dependence of the emission spectrum of a sample heated from 200 ° C for 2 hours in nitrogen, vacuum and air (as-prepared is that of an unheated sample) (excitation wavelength: 400 nm) ing. Even when the excitation wavelength is 400 nm, the sample heated in a nitrogen atmosphere has the highest emission intensity. In addition, it can be understood that the emission intensity of the sample heated in the atmosphere is as high as that of the sample heated in the nitrogen atmosphere as compared with the case where the excitation wavelength is 350 nm.

[0055] Considering the emission spectrum of the heat treatment performed at 200 ° C for 2 hours in a nitrogen atmosphere, the emission of the sample force that was heat-treated in nitrogen showed a light emission peak on the short wavelength side as compared to the one that was heat-treated in air. I understand that. [0056] In addition, in the infrared spectrum of FIG. 9, there is no decrease in the infrared absorption intensity of the alkyl group observed by heat treatment in the atmosphere, and no absorption by the carbo group. This force is also considered that the light emission on the short wavelength side from the sample heat-treated in the above atmosphere is related to the thermal decomposition of the alkyl group and the oxidation process.

[0057] Fig. 10 shows the fume n 2n-1 3 surface-modified with alkylchlorosilane (C H SiCl) n = 18.

This shows the excitation wavelength dependence (excitation wavelength: 400 nm or more) of the emission spectrum of a sample heated at 200 ° C for 2 hours in atmospheric air. From Fig. 10, it is understood that when the excitation wavelength is 400 nm or more, the emission wavelength dependence of the emission spectrum is not so noticeable, and the peak wavelength of the emission spectrum is slightly shifted to around 500 nm. it can.

Example 4

[0058] Fig. 11 shows the results of time-resolved luminescence measurement of the luminescence observed from the sample heat-treated in the atmosphere. Here, the pulsed neodymium laser is excited at 355 nm, the third harmonic, and the delay time is 0, 25, 50, 75 ns, and the gate width is all 20 ns.

From Fig. 11, it can be seen that as the delay time is delayed, the light emission intensity decreases and the light emission almost disappears in 75 ns.

The luminescence lifetime of this sample is shorter than the time resolution of this device, so it is difficult to accurately measure the lifetime. The luminescence lifetime is expected to decay several ns to 10 ns.

[0059] The spectrum shown in Fig. 12 shows a spectrum with a delay time of 0ns and a spectrum with 50ns multiplied by 20 times. It can be understood that light emission on the short wavelength side is shorter than light emission on the long wavelength side because light emission intensity on the short wavelength side is reduced with light emission with a delay time of 50 ns compared to light emission with 0 ns. This also indicates that there are two luminescent components in the sample heat-treated in the atmosphere.

[0060] There are two light emission components on the short wavelength side and the long wavelength side in the light emission of the sample force produced as described above, and the light emission on the short wavelength side has a short emission life on the long wavelength side. In the heat treatment in nitrogen, light emission on the short wavelength side was observed, and in the sample heat-treated in the air that showed light emission on the long wavelength side, a carbo group was generated from the infrared absorption measurement. Emission on the long wavelength side is considered to be emission associated with thermal decomposition of the alkyl group and oxidation process. [0061] Regarding the change and deterioration of the light emission characteristics of the silica fine particles and the silica molded product according to the present invention over time, the characteristic change and deterioration do not occur even when stored in a normal storage state for more than half a year. I can confirm that.

Example 5

[0062] In Example 5, the silica fine particles were surface-modified with a hydrocarbon group, and then the surface-modified silica fine particles were added for a predetermined time in a nitrogen atmosphere at a temperature range of 150 to 300 ° C. It will be explained that the emission peak wavelength can be controlled by heat treatment and then heat treatment in an air atmosphere for a predetermined time.

[0063] FIG. 13 shows fumed n 2n-1 1 3 which has been surface-modified with alkylchlorosilane (C H SiCl) n = 18.

It shows the difference in emission spectrum between silica sintered in a nitrogen atmosphere and one sintered in a nitrogen atmosphere and then sintered in an air atmosphere. Here, the excitation wavelength was 40 Onm. The excitation wavelength was compared at 400 nm, as shown in Fig. 6 above, with fumed silica surface-modified with alkylchlorosilane (C H SiCl) n = 18, a large n 2n-1 3

This is based on the excitation wavelength dependence of the emission spectrum of a sample heated in air at 200 ° C for 2 hours.

[0064] In Fig. 13, a is sintered for 2 hours in a nitrogen atmosphere, b is a sample of a sintered in the air for 1 hour, and c is a sample of a sintered in the air for 1.5 hours. The result, d, was the sample of a sintered for 2 hours in the atmosphere, and d was sintered for 2 hours in the atmosphere. The sintering temperature condition is 200 ° C.

The emission peak intensity of sample a and sample b is observed around 60 nm, whereas the emission peak intensity of sample c is observed around 70 nm, the emission intensity of sample d is observed around 80 nm, and the emission intensity of sample e is around 80 nm. Emission peak intensity force Observed around 70nm! Speak. This is because samples that were sintered in a nitrogen atmosphere and then re-sintered in an air atmosphere, compared to samples that were sintered only in a nitrogen atmosphere, increased the time required for re-sintering in the air atmosphere. This shows that the emission peak wavelength shifts to the longer wavelength side.

[0065] In addition, the emission peak intensities of the prepared samples a to d hardly change (in FIG. 13, the scale on the vertical axis has meaning only for the emission spectrum intensity of each sample, and the emission of the samples a to d). It doesn't make sense for the spectral strength.) O [0066] From the above, fu n 2n-l 3 which was surface-modified with alkylchlorosilane (CH 3 SiCl) n = 18

It is possible to control the emission peak position between 450 nm force and 490 nm by sintering the silica in a nitrogen atmosphere and then in an air atmosphere (using a 400 nm excitation wavelength).

You can understand that it is V).

[0067] Next, the time decay process of the emission intensity was measured for a sample obtained by sintering the surface-modified fumed silica in a nitrogen atmosphere and a sample sintered in the air atmosphere. The following equipment is used for the measurement.

[0068] (Apparatus used for measuring time decay process of emission intensity)

• Excitation wavelength: 400nm (Excitation source: Spectra Physics, Mode-locked titanium sapphire laser Tsunami + frequency doubler Model39)

• Detector: Hakomatsu Photonicus Picosecond fluorescence lifetime measuring device C4780

[0069] FIG. 14 shows fumed n 2n-1 1 3 that has been surface-modified with alkylchlorosilane (C H SiCl) n = 18.

It is a figure which shows the time decay process of the emitted light intensity of a silica. Here, the excitation wavelength was 400 nm, the measurement wavelength was 470 nm, and the measurement temperature was 300K. a is a sample sintered for 2 hours at 200 ° C in a nitrogen atmosphere, and b is a sample sintered for 2 hours at 200 ° C in an air atmosphere.

From Fig. 14 showing the measurement results, sample a has a light emission intensity of about 50 ns for a light emission intensity of 1% or less, while sample b has a light emission intensity of about 30 ns for a light emission intensity of 1% or less.

From this, it can be understood that the sample a sintered in the nitrogen atmosphere has a slightly longer decay time constant than the sample sintered in the air atmosphere.

[0070] This result suggests that different emission centers are generated in the sample obtained by sintering the surface-modified fumed silica in a nitrogen atmosphere and in the sample sintered in an air atmosphere. ing. In samples sintered in the atmosphere, the thermal decomposition of hydrocarbon groups was observed, suggesting that the thermal decomposition process of the hydrocarbon groups changed the local structure of the emission center.

Example 6

[0071] In Example 6, (a) surface modification in which silica fine particles are surface-modified with tetrasalt silicate (SiCl 3)

Four

And (b) a heat treatment step in which the surface-modified silica fine particles are heat-treated in a temperature range of 150 to 300 ° C. for a predetermined time. Light up.

Figure 15 shows a sample of a fumed silica whose surface is modified with tetrasalt silicate (SiCl).

Four

The emission spectrum is shown. Here, light emission was observed in the excitation wavelength range of 300 to 350 nm, where almost no emission intensity was observed at the excitation wavelength of 400 nm, compared with the sample surface-modified with the hydrocarbon group described above. Note that FIG. 15 shows an excitation wavelength of 340 nm. Fig. 15 shows a sample in which the surface of fumed silica is surface-modified with tetra-salt silicate (SiCl).

Four

1S You can understand that it has a peak near 420nm and has a broad emission spectrum up to 600nm!

Industrial applicability

[0072] The silica fine particles and the silica molding material having visible light emission characteristics according to the present invention are produced by a simple process by surface-modifying silica fine particles and pressurizing and heating, and visible light. Therefore, it can be used as a light emitting material such as a white light emitting element.

[0073] In addition, since the optimum excitation light is around 400 nm, the ultraviolet LED element (wavelength is 405 nm), which is the result of the “21st Century Akari” project, can be used as the light source. There is a possibility that it can be widely used in industrial products.

Brief Description of Drawings

[0074] [Fig. 1] The surface of the silica fine particles shows the generated Si-C bond.

[Fig.2] Emission spectrum of the silica molding material produced at each heat treatment temperature (150 ° C, 200 ° C, 250 ° C, 300 ° C) (when alkylchlorosilane (CH SiCl) n = 18) N 2n- 1 3

The

[Fig. 3] Shows emission spectra measured after heat-treating samples with different carbon numbers at 200 ° C.

[Fig. 4] Shows the results of measuring the emission spectrum at 200 ° C, showing the maximum emission intensity, with different heat treatment times.

[Fig. 5] Shows change in infrared spectrum with heat treatment time.

[Fig. 6] Excitation wavelength dependence of the emission spectrum of a sample heated at 200 ° C for 2 hours in the atmosphere (excitation wavelength: 400 nm or less) (when alkylchlorosilane (C H SiCl) n = 18).

n 2n-l 3 [Fig. 7] Excitation wavelength dependence of the emission spectrum of a sample heated at 200 ° C for 2 hours in nitrogen, vacuum, and atmosphere (as-prepared is for an unheated sample) (excitation wavelength: 350 nm).

[Fig. 8] Excitation wavelength dependence of the emission spectrum of a sample heated at 200 ° C for 2 hours in nitrogen, vacuum and air (as-prepared is for an unheated sample) (excitation wavelength: 400 nm).

[Fig. 9] Shows changes in infrared spectra when heat treatment was performed at 200 ° C for 2 hours in each atmosphere.

[Fig. 10] Shows the excitation wavelength dependence of the emission spectrum of a sample heated at 200 ° C for 2 hours in the atmosphere (excitation wavelength: 400 nm or more) (in the case of alkylchlorosilane (C H SiCl) n = 18).

n 2n-l 3

[Fig. 11] Shows the results of time-resolved luminescence measurements of luminescence observed from samples heat-treated in air.

[Fig. 12] The time-resolved luminescence measurement results in Fig. 11 show the spectrum with a delay time of 0ns and a spectrum with 50ns multiplied by 20 times.

[Fig. 13] Emission spectrum (excitation wavelength 400nm) of OTS-modified fumed silica sintered in different sintering atmospheres. In the figure, a is sintered at 200 ° C in a nitrogen atmosphere, b is a sample of a in the atmosphere for 1 hour, c is a sample of a in the atmosphere for 1.5 hours, d is of a The sample was sintered in air for 2 hours, and d was sintered in air for 2 hours.

FIG. 14 shows the time decay process of emission intensity of OTS-modified fumed silica (excitation wavelength 400 nm, measurement wavelength 470 nm, measurement temperature 300 K). a is a sample sintered for 2 hours at 200 ° C in a nitrogen atmosphere, and b is a sample sintered for 2 hours at 200 ° C in an air atmosphere.

[Fig.15] Development of a sample in which the surface of fumed silica is surface-modified with tetrasalt silicate (SiCl)

Four

Show the light spectrum.

Explanation of symbols

1 Silica molding material

Claims

The scope of the claims

[1] (a) a surface modification step of modifying silica fine particles with a hydrocarbon group;

(b) a heat treatment step in which the silica particles after the surface modification are heat treated for a predetermined time in a temperature range of 150 to 300 ° C;

A process for producing silica fine particles having visible light emission characteristics, comprising:

[2] (a) a surface modification step for modifying the surface of silica fine particles with a hydrocarbon group;

(b) a pressurizing step of press-molding the silica fine particles after the surface modification to form a press-molded body;

(c) A method for producing a silica molding material having visible light emission characteristics, comprising: a heat treatment step of heat-treating the pressure-molded body for a predetermined time in a temperature range of 150 to 300 ° C.

[3] Silica fine particles or silica molding material having visible light emission characteristics, characterized in that in the heat treatment step in the production method according to claim 1 or 2, the heating temperature is 200 ° C. and the heating time is 2 hours. Manufacturing method.

[4] In the surface modification step in the production method according to any one of claims 1 to 3, by using alkylchlorosilane H SiCl) (n is an integer of 4 or more), hydrocarbon groups are formed on the surface of the silica fine particles by n 2n-l 3

A method for producing silica fine particles or a silica molding material having visible light emission characteristics, characterized by modifying.

[5] A method for producing silica fine particles or silica molding material having visible light emission characteristics, characterized in that in the heat treatment step in the production method according to any one of claims 1 to 4, calo-heat treatment is performed in a nitrogen atmosphere.

[6] A method for producing silica fine particles or a silica molding material having visible light emission characteristics, characterized in that in the heat treatment step in the production method according to any one of [1] to [4], calo-heat treatment is performed in an air atmosphere.

[7] In the heat treatment step of the manufacturing method according to any one of claims 1 to 4, it has a visible light emission characteristic characterized by heat-treating for a predetermined time in a nitrogen atmosphere and then heat-treating for a predetermined time in an air atmosphere. A method for producing silica fine particles or silica molding material.

[8] (a) a surface modification step for surface modification of silica fine particles with tetrasalt silicate (SiCl 3);

Four

(b) The surface-modified silica fine particles are heat-treated for a predetermined time in a temperature range of 150 to 300 ° C. A heat treatment step;

[9] The production method according to any one of claims 1 to 8, wherein the silica fine particles are synthesized by a vapor phase method, and are fumed silica (Fumed Silica) that are high-purity nano-sized silica fine particles having a particle size of 1 to 100 nm. A method for producing a silica fine particle or silica molding material having visible light emission characteristics, characterized in that:

[10] A light-emitting material comprising silica fine particles as nuclei and a Si—C-0-based illuminant provided on the surface of the nuclei.

[11] The silica fine particle force according to claim 10, characterized in that it is fumed silica, which is a high-purity nano-sized silica fine particle having a particle size of 1 to: LOOnm, synthesized by a gas phase method. Luminescent material.

[12] A saccharified material containing silica fine particles obtained by the production method according to any one of claims 1, 3 to 8.

[13] A light emitting device using as a phosphor a silica molding material obtained by the production method according to any one of claims 2 to 7.

[14] A light emitting device using the saccharifying material according to [12] as a phosphor.