JP2012007085A - Emitter, process for producing the same, lighting unit, detergent, ultraviolet shielding material for cosmetic, constructional material and photocatalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an emitter having a wide emission spectral width and a high emission intensity.SOLUTION: A body RH is prepared. This plant RH is subjected to heat treatment in a gas including oxygen to produce an emitter using the plant body RH as a raw material. By doing so, an emitter having a wide emission spectral width and a high emission intensity can be obtained.

Description

  The present invention relates to a light emitter having a wide emission spectrum width and a method for producing the same.

  In a white light source, white light is obtained by exciting a white light emitter with ultraviolet light. Conventional white light emitters used for such white light sources have emission lines in their emission spectra, and color rendering under white light sources using white light emitters is not always sufficient. .

However, in recent years, it has been known that the interface between silica, (SiO ₂ ), and carbon (C) (silica-carbon interface) becomes a white light-emitting source having no emission line. Therefore, in order to obtain a white light-emitting material that does not contain an emission line in the emission spectrum, a method of modifying the surface of fumed silica (Patent Document 1), or after carbon clusters are formed in the pores of porous silicon, silicon is selectively oxidized. A method (Patent Document 2) is proposed. Patent Document 3 describes that a phosphor emitting blue-white to white can be obtained by dispersing carbon or an organic compound activator in porous silica-based fine particles.

International Publication No. 2006/025428 Pamphlet JP 2008-208283 A JP 2009-7356 A

R. Liu, Y. Shi, Y. Wan, Y Meng, F. Zheng, D. Gu, Z. Chen, B. Tu, and D. Zhao, Journal of American Chemical Society, Vol 128 (2006), pp. 11652-11662

  However, in these methods for producing a white light emitter, fumed silica, porous silicon, or porous silica-based fine particles are used as a raw material of the light emitter. These raw materials are generally not easily available, and it is necessary to go through many steps in order to produce the raw materials, and the production of the light emitter is not always easy. This problem is common not only when creating a white illuminant, but generally when creating an illuminant with a wide emission spectrum width.

  The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide a technique for manufacturing a light emitter having a wide emission spectrum width by a simpler method.

  In order to achieve at least a part of the above object, the present invention can be realized as the following forms or application examples.

[Application Example 1]
A light-emitting body that uses a plant body as a raw material and is produced by heat-treating the plant body in a gas containing oxygen. According to this application example, a light emitter having a wide emission spectrum width can be generated by heat-treating an easily available plant. Therefore, a light emitter having a wide emission spectrum width can be more easily manufactured.

[Application Example 2]
A light-emitting body that uses a plant body as a raw material, and is produced by heat-treating the plant body in a gas containing no oxygen and then heat-treating in a gas containing oxygen. According to this application example, a more suitable heat treatment condition can be set according to the atmosphere, so that a light emitter with higher light emission intensity can be obtained.

[Application Example 3]
The light emitter according to Application Example 1 or 2, wherein the light emitter is porous. The porous illuminant has a larger specific surface area than when it is not porous. By increasing the specific surface area of the illuminant, the excitation light easily reaches the skeleton of the illuminant, and the possibility that the light emitted from the skeleton part is absorbed is reduced. Therefore, according to this application example, the emission intensity can be further increased.

[Application Example 4]
4. The light emitter according to any one of application examples 1 to 3, wherein the light emitter has a cell wall structure included in the plant body. By having the cell wall structure, the specific surface area of the light emitter is increased. Therefore, according to this application example, the emission intensity can be further increased.

[Application Example 5]
The light emitter according to any one of Application Examples 1 to 4, wherein the composition ratio of potassium is in a range of 0.2% to 10%. By the presence of 0.2% or more of potassium in the composition ratio, carbon is taken into the potassium silicate produced during the heat treatment, and the amount of binding between carbon and silica, which is considered to contribute to light emission, increases. Moreover, the fall of emitted light intensity can be suppressed because the quantity of potassium which does not contribute to light emission shall be 10% or less. Therefore, according to this application example, the light emission intensity of the light emitter can be further increased.

[Application Example 6]
The light emitter according to any one of Application Examples 1 to 5, wherein the composition ratio of carbon is in a range of 0.5% to 55%. By setting the composition ratio of carbon in the range of 0.5% to 55%, carbon that does not contribute to light emission can be reduced while carbon contributing to light emission remains sufficiently. Therefore, the light emission intensity of the light emitter can be further increased.

[Application Example 7]
The light emitting body according to any one of application examples 1 to 6, wherein the plant body is a plant body of a silicon-accumulating plant. Silicon-accumulating plants have more silica accumulated in the plant than other plants. Therefore, it is possible to obtain a light-emitting body with higher light emission intensity by using a plant of a silicon-accumulating plant having a large amount of silica constituting the light-emitting source.

[Application Example 8]
The light emitting body according to application example 7, wherein the plant body is rice husk. By using rice husks as a raw material for the phosphor, it is possible to effectively use rice husks that are not always easy to process.

[Application Example 9]
A light emitter comprising silicon, oxygen, carbon and potassium. Due to the presence of potassium, carbon is taken into the potassium silicate produced during the heat treatment, and the amount of bonding between carbon and silica, which is considered to contribute to light emission, increases. Therefore, according to this application example, the light emission intensity of the light emitter can be further increased.

[Application Example 10]
A lighting device,
An illumination device comprising: the light emitter according to any one of application examples 1 to 9; and an excitation light source for exciting the light emitter. These light emitters emit light when excited with light. Therefore, according to this application example, a light source having a wide spectrum width can be obtained more easily.

[Application Example 11]
A detergent, comprising the illuminant according to any one of Application Examples 1 to 9, wherein the illuminant is in a powder form. In this application example, the whiteness of the clothes after washing is increased by including these light emitters that emit light with ultraviolet or blue excitation light. Moreover, these light emitters contain almost no substance that becomes an allergen. Therefore, it is possible to reduce the possibility of problems such as allergies caused by the light emitters attached to the clothing.

[Application Example 12]
An ultraviolet shielding material for cosmetics, comprising the light emitter according to any one of Application Examples 1 to 9, wherein the light emitter is in a powder form. Like porous silica, these phosphors scatter incident light well. In addition, these light emitters absorb ultraviolet rays and emit visible light. Therefore, according to this application example, it is possible to more easily suppress sunburn by shielding ultraviolet rays well, and to suppress dull skin color when using cosmetics by emitted visible light. Moreover, these light emitters contain almost no substance that becomes an allergen. Therefore, it is possible to reduce the possibility of problems such as allergies caused by the illuminant contained in the cosmetic.

[Application Example 13]
A building material, comprising the light emitter according to any one of application examples 1 to 9, wherein the light emitter is powdered. These light emitters are phosphorescent. Therefore, by using the building material of this application example, it is possible to suppress an accident that may occur when the light is darkened after the light is turned off or during a power failure. Further, these light emitters contain almost no allergen or volatile substance. Therefore, according to this application example, it is possible to reduce the possibility of problems such as allergies and sick house syndrome. Furthermore, when a porous illuminant is used, it is possible to adsorb odors and the like.

[Application Example 14]
A photocatalyst comprising the luminescent material according to any one of Application Examples 1 to 9. These illuminants function as a photocatalyst that decomposes organic substances when irradiated with light. Therefore, according to this application example, a photocatalyst can be obtained more easily.

  Note that the present invention can be realized in various modes. For example, a light emitting body, a method for manufacturing the light emitting body and a light emitting body manufactured by the manufacturing method, a lighting device using the light emitting body, a detergent, a building material, a photocatalyst, a UV shielding material for cosmetics, and an ultraviolet ray for cosmetics It can be realized in the form of cosmetics using a shielding material.

Process drawing which shows the manufacturing process of the light-emitting body in 1st Embodiment. The photograph which shows the light emission state of the sample obtained in the Example of 1st Embodiment. Process drawing which shows the manufacturing process of the light-emitting body in 2nd Embodiment. The photograph which shows the light emission state of the sample obtained in the Example of 2nd Embodiment. The graph which shows the evaluation result of the emission spectrum by photoluminescence. The graph which shows the evaluation result of the emission spectrum by photoluminescence. The photograph which shows the form evaluation result of the sample by SEM. The graph which shows the state evaluation result of the sample by FT-IR. The graph which shows the state evaluation result of the sample by XPS. The graph which shows the state evaluation result of the sample by XPS. The graph which shows the state evaluation result of the sample by XPS.

Embodiments of the present invention will be described in the following order.
A. First embodiment:
A1. First embodiment:
A2. Example of the first embodiment:
B. Second embodiment:
B1. Second embodiment:
B2. Example of the second embodiment:
C. Variations:
D. Other application forms:

A1. First embodiment:
FIG. 1 is a process diagram showing manufacturing steps of the light emitter in the first embodiment. In the first embodiment, first, as shown in FIG. 1A, rice husk RH is prepared as a raw material of the light emitter. As shown in FIG. 1B, the prepared rice husk RH is inserted into the chamber 110 of the heat treatment furnace 100 and subjected to heat treatment in the air. Air is supplied into the chamber 110 by rotating a fan 120 provided at one end of the chamber 110 and blowing air into the chamber 110. By supplying and heating the heater 130 while supplying air into the chamber 110, the rice husk RH is carbonized and a part of carbon (C) contained in the rice husk RH is desorbed. The rice husk carbide thus generated (rice husk carbide) functions as a light emitter, as will be described later.

In the example of FIG. 1, the heat treatment is performed in air, but in a gas containing oxygen (O ₂ ) at a predetermined ratio (for example, 5% to 30%) (hereinafter also referred to as “oxygen-containing gas”). It is also possible to perform a heat treatment. As the oxygen-containing gas, it is possible to use a gas in which oxygen and an inert gas are mixed in addition to air. As the inert gas, various gases can be used as long as they do not react with silicon (Si) or carbon (C). For example, nitrogen (N ₂ ), argon (Ar), helium (He) or the like can be used. Can be used.

  In the heat treatment, first, after the rice husk RH is inserted into the chamber 110 at room temperature, supply of oxygen-containing gas (air in the example of FIG. 1) is started. With the oxygen-containing gas supplied into the chamber 110, the temperature is increased at a predetermined temperature increase rate (for example, 0.5 to 20 ° C./min). After the temperature inside the chamber 110 reaches a predetermined heat treatment temperature (for example, 200 to 900 ° C.) due to the temperature rise, the inside of the chamber 110 is held at the heat treatment temperature. After a predetermined heat treatment time (for example, 1 to 5 hours) has elapsed, the temperature is decreased at a predetermined temperature decrease rate (for example, 0.5 to 20 ° C./min). Then, after the temperature of the heat treatment furnace reaches room temperature, the supply of the oxygen-containing gas is stopped, and the generated rice husk carbide is taken out from the chamber 110. The rice husk carbide taken out from the chamber 110 is pulverized as necessary. The heat treatment conditions such as the heat treatment temperature and the heat treatment time are appropriately set according to the oxygen concentration in the heat treatment atmosphere so that the rice husk RH is sufficiently carbonized and the desorption of carbon contributing to light emission is suppressed. The

  The rice husk carbide produced by heat treating the rice husk RH contains silicon (Si), carbon and oxygen (O) contained in the rice husk RH. The rice husk carbide is considered to function as a light emitter having a wide spectrum width by forming a predetermined bonding state of these elements. Further, in the first embodiment, the rice husk RH is heat-treated in an oxygen-containing gas (in the example of FIG. 1, air), so that excess carbon that does not contribute to light emission reacts with oxygen and is desorbed. By desorbing excess carbon, it is presumed that light absorption by carbon is suppressed and the emission intensity of rice husk carbide increases. As described above, according to the first embodiment, the heat treatment of the rice husk RH in the oxygen-containing gas can generate a light emitter having a wide spectrum width and a sufficiently high light emission intensity. Becomes easier. The carbon composition in the rice husk carbide is preferably 5% or more so that carbon contributing to light emission remains sufficiently. On the other hand, in order to sufficiently reduce excess carbon that does not contribute to light emission, the composition of carbon in rice husk carbide is preferably 55% or less.

In addition, since rice husk is generally slow to corrode, it is not easy to compost the rice husk as it is, and it is often incinerated. In this case, the heat generated by burning the rice husk can be used as renewable energy. However, since the rice husk contains a lot of silica (SiO ₂ ), the incineration ash of the rice husk is bulky, and the treatment of the incineration ash is not easy. On the other hand, according to the first embodiment, it is possible to effectively utilize rice husks that are not necessarily easy to process by using rice husks as a raw material of the luminous body.

  On the cell wall that forms the skeleton of the rice husk, pores such as protoplasmic communication that connect cells are formed. Therefore, the luminous body produced by heat-treating the rice husk is porous with pores. The porous illuminant has a larger specific surface area, which is the ratio of the surface area to the unit weight, compared to the case where the porous illuminant is not porous. By increasing the specific surface area of the illuminant, the excitation light easily reaches the skeleton of the illuminant, and the possibility that the light emitted from the skeleton part is absorbed is reduced. Therefore, it is considered that the luminous intensity of the porous luminescent material is higher than that of the non-porous luminescent material. Note that the illuminant is not necessarily porous. The non-porous illuminant can be generated, for example, by crushing the illuminant generated by heat treatment by applying a high pressure. It is also possible to generate a non-porous illuminant by applying a heat shock by increasing the temperature rise / fall rate during the heat treatment and breaking the porous structure by the heat shock. In this case, the produced light emitter is a fine powder having a small particle size (˜100 nm).

  Furthermore, the luminous body produced by heat-treating rice husks under predetermined heat treatment conditions has a cell wall structure that constitutes the skeleton of rice husks. By having the cell wall structure, the specific surface area of the illuminant becomes larger than that without the cell wall structure. Therefore, it is preferable that the light emitter has a cell wall structure that the rice husk has, in that a light emitter with higher emission intensity can be obtained.

  Rice husk contains potassium (K) as a main constituent element in addition to carbon, silicon and oxygen. Potassium combines with silica during the heat treatment to form potassium silicate. Since this potassium silicate melts during the heat treatment, it is presumed that carbon is taken into the molten potassium silicate. Thus, it is considered that the amount of carbon and silica that are considered to contribute to light emission increases due to carbon being incorporated into potassium silicate, and the light emission intensity of the light emitter is increased. Therefore, it is more preferable that the light emitter contains potassium in addition to carbon, silicon and oxygen. In order to sufficiently generate potassium silicate and to incorporate carbon into potassium silicate, the composition of potassium in the light emitter is preferably 0.2% or more. On the other hand, since potassium is considered not to directly contribute to light emission, excessive potassium may cause a decrease in light emission intensity. Therefore, the composition of potassium in the light emitter is preferably 10% or less.

  Furthermore, in the phosphor generated by heat treating the rice husk, potassium constituting the rice husk remains, whereas among the phosphors containing silicon, carbon, and oxygen, the chemically generated phosphor is: Contains almost no potassium. Therefore, whether or not a phosphor containing silicon, carbon, and oxygen is produced using rice husks as a raw material, does the phosphor contain a significant amount (for example, a composition ratio of 0.01% or more) of potassium? Judgment can be made based on whether or not.

A2. Example of the first embodiment:
[Sample preparation]
To prepare the sample, the rice husk was heat-treated in air. Specifically, a rice husk as a raw material was prepared, and after the prepared rice husk was inserted into a heat treatment furnace, supply of air to the heat treatment furnace was started. Next, the temperature was raised at a heating rate of 4 ° C./min in the heat treatment furnace, and the temperature was kept at a predetermined heat treatment temperature for 3 hours. After maintaining the heat treatment temperature for 3 hours, the temperature was lowered by setting the temperature lowering rate of the heat treatment furnace to 4 ° C./min. Then, when the temperature of the heat treatment furnace reached room temperature, the supply of air to the heat treatment furnace was stopped and the produced rice husk carbide was taken out. The extracted rice husk carbide was pulverized to obtain a powdered phosphor sample using rice husk as a raw material. The heat treatment temperature was set to four conditions of 300 ° C., 400 ° C., 600 ° C., and 900 ° C., and four types of samples were obtained.

The samples thus obtained are shown in the following table. Hereinafter, the evaluated sample is referred to using symbols (A1 to A4).

[Evaluation of luminous intensity]
The luminescence intensity of the four types of samples (A1 to A4) obtained was evaluated. The evaluation of light emission intensity was performed by irradiating the sample with ultraviolet light from an ultra-high pressure mercury lamp as excitation light and comparing the light emission from the sample visually. FIG. 2 is a photograph showing the light emission state of each obtained sample. The photo was taken in the state where the excitation light of the same intensity was irradiated.

  As can be seen from FIG. 2, the sample (A2) having the heat treatment temperature of 400 ° C. has the highest light emission intensity among the four types of samples (A1 to A4) obtained, and then the heat treatment temperature of 600 ° C. The emission intensity of (A3) was high. The sample (A1) having a heat treatment temperature of 300 ° C. was confirmed to emit light, although the intensity was low. On the other hand, in the sample (A4) in which the heat treatment temperature was 900 ° C., no luminescence was confirmed visually. All of the samples (A1 to A3) that were confirmed to emit light with sufficient intensity emitted blue-white light. Moreover, about the sample (A1-A3) by which light emission was confirmed, when the light inject | emitted from a white light emitting diode was applied, changing the irradiation position, the locus | trajectory of the irradiation position was confirmed. In this way, a phosphorescent luminescent material having a wide spectral width could be obtained by heat treating the rice husk in air. Moreover, the light-emitting body with higher light emission intensity was able to be obtained by setting heat processing conditions suitably.

B1. Second embodiment:
FIG. 3 is a process diagram showing manufacturing steps of the light emitter as the second embodiment. The second embodiment is different from the first embodiment in that a heat treatment in an inert gas is performed prior to a heat treatment in an oxygen-containing gas. Other points are the same as in the first embodiment.

  Also in the second embodiment, first, a rice husk RH as a raw material is prepared (FIG. 3A). Next, in order to carbonize the rice husk RH, as shown in FIG. 3B, heat treatment is performed in an inert gas (nitrogen in the example of FIG. 3). The inert gas is supplied to the chamber 110 of the heat treatment furnace 100 a through a flange 112 provided at one end of the chamber 110. The inert gas that has passed through the chamber 110 is exhausted through a flange 114 provided at the other end of the chamber 110. As the inert gas, various gases that do not react with silicon and carbon such as argon and helium can be used in addition to nitrogen. In the heat treatment in the inert gas in the second embodiment, carbonization of rice husk RH proceeds. Therefore, hereinafter, the heat treatment in the inert gas in the second embodiment is also referred to as “carbonization treatment”.

  In the carbonization process, the inert gas supply is started after the rice husk RH is inserted into the chamber 110 at room temperature. Next, the temperature is increased at a predetermined temperature increase rate (for example, 0.5 to 20 ° C./min) in a state where the inert gas is supplied into the chamber 110. After the temperature of the heat treatment furnace reaches a predetermined carbonization temperature (for example, 200 to 1000 ° C.) due to the temperature rise, the inside of the chamber 110 is maintained at the carbonization temperature. After a predetermined carbonization time (for example, 1 to 5 hours) has elapsed, the temperature is decreased at a predetermined temperature decrease rate (for example, 0.5 to 20 ° C./min). Then, after the temperature of the heat treatment furnace reaches room temperature, the supply of the inert gas is stopped, and the generated rice husk carbide is taken out from the chamber 110. The extracted rice husk carbide is pulverized to produce powdered rice husk carbide RHC. In addition, carbonization conditions, such as carbonization temperature and carbonization time, are appropriately set so that rice husk RH is sufficiently carbonized.

  The produced powdered rice husk carbide RHC is heat-treated in an oxygen-containing gas (air in the example of FIG. 3) as shown in FIG. In the heat treatment in the oxygen-containing gas in the second embodiment, partial carbon desorption from the rice husk carbide RHC proceeds. Therefore, hereinafter, the heat treatment in the oxygen-containing gas in the second embodiment is also referred to as “partial decarburization treatment”. Since the procedure of the partial decarburization process is the same as the heat treatment of the first embodiment, the description thereof is omitted here.

  The decarburization treatment conditions such as the heat treatment temperature (decarburization treatment temperature) and the heat treatment time (decarburization treatment time) are such that excess carbon contained in the rice husk carbide RHC is desorbed and desorption of carbon contributing to light emission is suppressed. As described above, it is appropriately set according to the oxygen concentration in the oxygen-containing gas. The heat treatment conditions are preferably set so that the carbon composition in the rice husk carbide after the partial decarburization treatment is 0.5 to 55%. For example, when the oxygen-containing gas is air, the decarburization treatment temperature is preferably set to 200 to 1000 ° C., and the decarburization treatment time is preferably set to 1 to 5 hours.

  Thus, also in 2nd Embodiment, the rice husk carbide | carbonized_material obtained by performing a carbonization process and a partial decarburization process to rice husk RH contains the silicon, carbon, and oxygen which are contained in rice husk RH. Further, by subjecting rice husk carbide RHC to partial decarburization, excess carbon that does not contribute to light emission in rice husk carbide RHC is eliminated. Therefore, also in the second embodiment, as in the first embodiment, a light emitter having a wide spectrum width and a sufficiently high emission intensity can be generated.

  In the second embodiment, carbonization by heat treatment in an inert gas and partial carbon desorption by heat treatment in an oxygen-containing gas are performed separately, so that heat treatment conditions for sufficient carbonization of rice husk RH ( It is possible to separately set carbonization treatment conditions) and heat treatment conditions (decarburization treatment conditions) for desorbing excess carbon of rice husk carbide RHC. Therefore, the second embodiment is preferable to the first embodiment in that the rice husk RH can be sufficiently carbonized and the amount of carbon desorbed from the rice husk carbide RHC can be more appropriately controlled. Further, by performing the carbonization treatment before the partial decarburization treatment, a strong bond between carbon and silica is formed, and desorption of carbon contributing to light emission by the partial decarburization treatment is suppressed. Therefore, it is easier to remove excess carbon, so the second embodiment is preferable to the first embodiment. On the other hand, the first embodiment is preferable to the second embodiment in that the number of heat treatments can be reduced.

  In the second embodiment, the rice husk carbide obtained by carbonizing the rice husk RH is pulverized to obtain powdered rice husk carbide RHC, and the obtained powdered rice husk carbide RHC is partially decarburized. However, it is also possible to subject the RH to partial decarburization treatment to non-powdered rice husk carbide. In this case, the luminous body obtained by the partial decarburization treatment is pulverized and powdered as necessary.

B2. Example of the second embodiment:
[Sample preparation]
In order to prepare a sample, carbonization of rice husk was first performed. Specifically, rice husk as a raw material was prepared, and after the prepared rice husk was inserted into a heat treatment furnace, supply of nitrogen to the heat treatment furnace was started. Next, the temperature was raised at a heating rate of 4 ° C./min in the heat treatment furnace, and the temperature was maintained at a predetermined carbonization temperature for 3 hours. After maintaining the carbonization temperature for 3 hours, the temperature was decreased by setting the temperature decrease rate of the heat treatment furnace to 4 ° C./min. When the temperature of the heat treatment furnace reached room temperature, the supply of nitrogen to the heat treatment furnace was stopped, and the produced rice husk carbide was taken out. And the taken rice husk carbide was pulverized to obtain powdered rice husk carbide. The carbonization temperature was set to four conditions of 400 ° C., 600 ° C., 900 ° C., and 1200 ° C. to obtain four types of rice husk carbides.

  Next, partial carbonization treatment was performed on each of the obtained four types of rice husk carbide. Specifically, after the powdered rice husk carbide obtained as described above was inserted into a heat treatment furnace, the supply of air to the heat treatment furnace was started. Next, the temperature was raised at a heating rate of 4 ° C./min in the heat treatment furnace, and the temperature was maintained at a predetermined decarburization temperature for 3 hours. After maintaining the decarburization treatment temperature for 3 hours, the temperature was lowered by setting the temperature lowering rate of the heat treatment furnace to 4 ° C./min. Then, when the temperature of the heat treatment furnace reached room temperature, the supply of air to the heat treatment furnace was stopped, the rice husk carbide subjected to the partial decarburization treatment was taken out, and a sample of a luminescent material using rice husk as a raw material was obtained. . The decarburization temperature was one condition of 400 ° C., and four types of samples with different carbonization temperatures were obtained. Moreover, about the rice husk carbide | carbonized_material obtained by the carbonization process whose carbonization process temperature is 600 degreeC, while making the part into the control sample which does not perform a partial decarburization process, 300 degreeC, 500 degreeC, 600 degreeC, and 1000 degreeC 4 The sample which changed the decarburization processing temperature on condition was created.

  The samples thus obtained are shown in the following table. In the following, the evaluated samples are referred to using symbols (B1 to B4, C1 to C4, D).

[Evaluation of luminous intensity]
Evaluation of the luminescence intensity of the four types of samples (B1 to B4) and the control sample (D) with a decarburization treatment temperature of 400 ° C. was performed in the same manner as in the example of the first embodiment. FIG. 4 is a photograph showing the light emission state of each sample (B1 to B4), and the photograph was taken in a state in which excitation light having the same intensity was irradiated.

  As can be seen from FIG. 4, among the four types of samples (B1 to B4), the sample (B2) having a carbonization temperature of 600 ° C. has the strongest emission, and then the sample (B1) having a carbonization temperature of 400 ° C. ) Was strong. Although the intensity | strength was low, the sample (B3) which made the carbonization temperature 900 degreeC was able to confirm light emission. On the other hand, the sample (B4) having a carbonization temperature of 1200 ° C. could not be confirmed visually. Further, although not shown in FIG. 4, the control sample (D) not subjected to the partial decarburization treatment could not confirm luminescence. All of the samples (B1 to B3) in which luminescence was confirmed emitted blue white. Moreover, about the sample (B1-B3) by which light emission was confirmed, when the irradiation position of the excitation light was changed, the locus | trajectory of the excitation light irradiation position was confirmed. From these results, it was found that a phosphorescent luminescent material having a wide spectrum width can be obtained by subjecting rice husks to carbonization treatment and partial decarburization treatment. It was also found that a light emitter with higher emission intensity can be obtained by appropriately setting the conditions for carbonization treatment and partial decarburization treatment.

[Evaluation of emission spectrum by photoluminescence]
5 and 6 are graphs showing the evaluation results of the emission spectrum by photoluminescence. In each graph of FIG. 5 and FIG. 6, the horizontal axis represents the wavelength, and the vertical axis represents the emission intensity. In FIG. 5, the emission intensity is expressed in arbitrary units (AU). In FIG. 6, the light emission intensity at 600 nm is represented by relative light emission intensity normalized to 1. Photoluminescence was evaluated by exciting the sample with 250 nm or 370 nm light and measuring the emission spectrum from the sample.

  FIG. 5 is a graph showing an emission spectrum of a sample (B2) having the highest emission intensity among four types of samples (B1 to B4) having a decarburization treatment temperature of 400 ° C. In the graph of FIG. 5, the solid line indicates the emission spectrum when the wavelength of the excitation light (excitation wavelength) is 250 nm, and the broken line indicates the emission spectrum when the excitation wavelength is 370 nm. In the emission spectrum when the excitation wavelength is 370 nm, the emission intensity is reduced on the wavelength side shorter than 420 nm because of the filter that removes the excitation light. As shown in FIG. 5, the emission spectrum width of the sample (B2) obtained by setting the carbonization temperature to 600 ° C. and the decarburization temperature to 400 ° C. was wide. This is consistent with the fact that the emission of the sample (B2) was bluish white, and it was confirmed that the spectrum width of the phosphor obtained by subjecting the rice husks to carbonization and partial decarburization was wide. It was.

  FIG. 6 is a graph showing emission spectra of samples (B2, C1 to C4) having different decarburization treatment temperatures. The measurement was performed using a filter that removes excitation light with an excitation wavelength of 370 nm. Therefore, in each spectrum, the emission intensity is reduced on the shorter wavelength side than 420 nm.

  As shown in FIG. 6, the emission intensity on the short wavelength side increased as the decarburization temperature was increased from 300 ° C. to 600 ° C. Accordingly, the emission color of the sample (C1) having a decarburization treatment temperature of 300 ° C. was white, but the sample (B2) having a decarburization treatment temperature of 400 ° C. was bluish white, and the decarburization treatment temperature was 500 ° C. The sample at 600 ° C. (C2, C3) turned blue. However, in the sample (C4) in which the decarburization treatment temperature was 1000 ° C., the short wavelength component decreased and the light emission became white. From this, it was found that the luminescent material produced by subjecting rice husks to carbonization and partial decarburization can change the emission color by adjusting the decarburization temperature.

  The change in the emission color due to the change in the decarburization temperature is caused by the fact that the short wavelength (ie, blue) emission originates from silica defects and the amount of silica defects changes by the following mechanism. It is considered a thing. First, when the decarburization temperature is low, since there are many silica defects, the majority of the defects act as non-radiative centers and short wavelength components do not appear (300 ° C. or lower), resulting in a high decarburization temperature. Accordingly, defects acting as non-luminescent centers decrease and short wavelength components increase (400 ° C. to 600 ° C.). And if the decarburization process temperature becomes still higher, the defect in a silica will lose | disappear and a short wavelength component will reduce (1000 degreeC or more).

[Sample morphology evaluation]
FIG. 7 is an electron micrograph showing the result of evaluating the sample form with a scanning electron microscope (SEM) in order to evaluate the effect of heat treatment on the form of the sample. The photograph of FIG. 7 is a photograph of the sample (B2) having the highest emission intensity among the four types of samples (B1 to B4) having a decarburization treatment temperature of 400 ° C. From this photograph, it was found that also in the sample (B2) after the carbonization treatment and the partial decarburization treatment, the cell wall structure existing in the rice husk of the raw material was maintained. Moreover, when the specific surface area was evaluated about the sample (B2), the specific surface area was 99.5 m < ² > / g. Thus, the sample obtained by subjecting rice husks to carbonization and partial decarburization had a large specific surface area.

[Sample composition evaluation by EDX]
Table 3 below shows the results of evaluating the composition of the sample using energy dispersive X-ray spectroscopy (EDX). The composition was evaluated by the sample (B2) having the highest luminescence intensity among the four types of samples (B1 to B4) having a decarburization treatment temperature of 400 ° C. and the control sample (D) not subjected to the partial decarburization treatment (D ) And went. For sample (B2), the composition at two locations was evaluated, and for the control sample (D), the composition at four locations was evaluated.

  As shown in Table 3, the carbon composition of the sample (B2) subjected to the partial decarburization treatment was decreased as compared with the control sample (D) not subjected to the partial decarburization treatment. From this, it was found that carbon was desorbed by subjecting rice husk carbide to partial decarburization treatment. Further, since the control sample (D) hardly emitted light, it was found that the carbon composition of the light emitter is preferably 55% or less.

[Evaluation of sample binding state]
In order to investigate the origin of white light emission, the constituent elements of the sample are analyzed using Fourier Transform-Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). The binding state of was evaluated. In the evaluation, among samples subjected to carbonization treatment at a carbonization treatment temperature of 600 ° C., a sample (B2) subjected to partial decarburization treatment at 400 ° C. and a control sample (D) not subjected to partial decarburization treatment are used. Using.

  In the evaluation of the sample using FT-IR, the infrared absorption spectrum was measured by a transmission method. FIG. 8 is a graph showing the state evaluation results of these two samples (B2, D) by FT-IR, and shows the infrared absorption spectrum of each sample. In the graph of FIG. 8, the horizontal axis represents the wave number of infrared rays, and the vertical axis represents the transmittance.

As shown in FIG. 8, an absorption peak showing a Si—O—C bond was observed at a position where the wave number was about 1100 cm ⁻¹ regardless of the presence or absence of the partial decarburization treatment. Thus, since the Si—O—C bond exists, it is presumed that silica and carbon contained in the rice husk are bonded by carbonizing the rice husk. On the other hand, in the sample (B2) subjected to the partial decarburization treatment, an absorption peak indicating a C—O—C bond having a wave number of about 1200 cm ⁻¹ was observed, but the sample (D) not subjected to the partial decarburization treatment (D ), No absorption peak showing a C—O—C bond was observed. This C—O—C bond is considered to be a combination of oxygen in air so as to bridge a plurality of carbons bonded to silicon or oxygen. In general, carbon clusters that are not bonded to other atoms (carbon clusters) are weakly bonded between carbon atoms, and thus combine with oxygen in the air to be desorbed as carbon dioxide. On the other hand, it is considered that a plurality of carbons bonded to silicon or oxygen do not desorb and form a C—O—C bond because the bond between silicon or oxygen and carbon is strong.

  9 to 11 are graphs showing the state evaluation results of the two samples (B2, D) and the XPS of the rice husks not subjected to heat treatment. In each graph of FIGS. 9 to 11, the horizontal axis represents the binding energy, and the vertical axis represents the signal intensity. In these graphs, in order to compare the coupling state, the signal intensity is normalized at the maximum intensity. In XPS, evaluation was performed by embedding a powder sample in indium (In).

FIG. 9 shows the bonding state of silicon 2p orbitals. As shown in FIG. 9, a peak of silica (SiO ₂ ) was observed in the sample (D) not subjected to the partial decarburization treatment. In contrast, in the sample (B2) subjected to the partial decarburization treatment, the silica peak observed in the sample (D) was shifted to the silicon carbide (SiC) bonding side. This is considered that the C—C bond of the carbon cluster existing in the vicinity of the silica is cut by the presence of oxygen, and a part of the carbon is bonded to the silicon constituting the silica. The rice husk not subjected to heat treatment has the same bond as the sample (D) not subjected to partial decarburization, but has a noisy peak due to the low composition ratio of silicon.

FIG. 10 shows the bonding state of the carbon 1s orbital. In the rice husk, in addition to the peak of the C—O bond, a broad shoulder derived from organic substances was observed on the high energy side. This is considered to be because most of the composition of the rice husks not subjected to heat treatment is composed of organic matter. In the sample (D) that was not subjected to the partial decarburization treatment, a peak of carbon cluster (C ₄ ) was observed. This is considered to be because carbon clusters, which are aggregates of carbon, are generated by carbonization by decomposition of organic substances and generation of carbon. On the other hand, in the sample (B2) subjected to the partial decarburization treatment, the peak of the carbon cluster (C ₄ ) representing the C—C bond decreases and the peak of the C—Si ₄ bond and the C—O bond. Appeared. This is because carbon inside the carbon cluster is desorbed and the C—C bond of the carbon cluster existing in the vicinity of the silica is broken by the presence of oxygen, and the carbon is bonded to silicon and oxygen constituting the silica. It is done.

FIG. 11 shows the bonding state of the 1s orbital of oxygen. Note that the peak appearing at the position of indium oxide (In ₂ O ₃ ) in the graph of FIG. 11 is derived from indium in which the sample is embedded. As shown in FIG. 11, a peak was observed in the vicinity of 534.5 eV in the rice husk and the sample (D) not subjected to the partial decarburization treatment. This bond peak is considered to be derived from the bond between O and C in the organic substance. In addition, a shoulder was recognized at a position substantially corresponding to silica (SiO ₂ ). This indicates that the rice husk itself already contains some silica. On the other hand, in the sample (B2) subjected to the partial carbonization treatment, the peak near 534.5 eV derived from the organic matter disappeared, and the peak composed of C═O and SiO ₂ bond appeared. It is considered that this is because only carbon bonded to silica remains, and further, C═O bond is generated by bonding with oxygen in the air.

  From the above result, in 2nd Embodiment, it is estimated that a light-emitting body is formed with the following mechanisms by performing a carbonization process and a partial decarburization process to a rice husk. First, the rice husk is heat-treated (carbonized) in an inert gas to generate carbon clusters from organic substances contained in the rice husk, and a part of carbon in the carbon clusters is bonded to silica. Next, the produced carbon clusters are heat treated (partial decarburization treatment) in rice husk carbide in an oxygen-containing gas, so that carbon is oxidized and desorbed as carbon dioxide in carbon clusters where silica is not present in the vicinity. In the carbon cluster in which silica is present, the carbon-carbon bond (C—C) bond is cut and bonded to silica. Further, the carbon bonded to the silica is not desorbed by the oxygen in the air, and the oxygen in the air is bonded to the carbon bonded to the silica. And it is thought that the joint part of silicon, carbon, and oxygen formed in this way becomes a light emission source of rice husk carbide.

C. Variations:
The present invention is not limited to the above-described embodiments and examples, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

  In each of the embodiments and examples described above, rice husk is used as a raw material for the light emitter, but various plant bodies containing silica can be used as the raw material for the light emitter. Here, the “plant” refers to at least a part of plant organs such as roots, stems, leaves, seeds and fruits, or single cell plants such as algae themselves. Generally, plants take up silicates in soil or water and accumulate as silica in the plant body. Therefore, the plant body of an arbitrary plant can be used as the plant body as a raw material. However, it is more preferable to use plant bodies of silicon-accumulating plants such as gramineous plants, laceaceae plants, lichens, or diatoms as the plant body that is the raw material of the luminous body. preferable. In addition, when using another plant body as a raw material instead of a rice husk, heat treatment conditions are suitably changed according to the kind of plant body as a raw material.

D. Application form:
In each of the above embodiments, the characteristics of the sample obtained by each embodiment as a light emitter have been described, but the obtained sample can be applied to various applications. The luminous body obtained by each embodiment can be used in the following application forms, for example.

D1. Application form 1:
As described above, a luminous body obtained by heat-treating a plant body (hereinafter also referred to as “plant-derived luminous body”) emits blue or white light having a wide spectrum width when irradiated with excitation light. Therefore, by using an excitation light source that irradiates these samples with excitation light, a visible light illumination device having high luminance and a wide spectrum width can be configured. Specifically, a fluorescent lamp that uses ultraviolet light generated by discharge as excitation light, a light-emitting diode that emits white light using blue to near ultraviolet light generated by electroluminescence as excitation light, or these fluorescent lamps, Various lighting devices such as a backlight using a light emitting diode can be configured.

D2. Application form 2:
The plant-derived luminescent material emits blue or white light having a wide spectrum width when irradiated with ultraviolet or blue excitation light. For this reason, by adding the plant-derived luminescent material to the detergent, the plant-derived luminescent material attached to the clothing after washing emits light by near-ultraviolet or blue light, so that the whiteness of the clothing is increased. That is, the plant-derived phosphor powder can be used as a whitening agent for detergents. In addition, since plant-derived light emitters are made from plant bodies, and the organic matter contained in the plant bodies is carbonized, the plant-derived light emitters are almost free of allergens such as organic matter and rare earth metals. . Therefore, the use of a plant-derived luminescent material as a detergent whitening agent can reduce the possibility of problems such as allergies.

D3. Application form 3:
In general, porous silica powder and silica fine powder scatter incident light well. The plant-derived luminescent material is a porous material or fine powder containing silica and carbon. Therefore, the plant-derived illuminant scatters incident light satisfactorily in the same manner as porous silica powder and silica fine powder. The plant-derived luminescent material absorbs ultraviolet rays and emits visible light. Therefore, the plant-derived phosphor powder can also be used as an ultraviolet scattering / absorbing material (ultraviolet shielding material) or an opacifying material in a cosmetic product having a sunscreen function such as sunscreen cream or foundation. Furthermore, since the visible light is emitted by using the powder of the plant-derived illuminant, it becomes possible to suppress the dullness of the skin color that darkens the skin color when using cosmetics. Further, as described above, the plant-derived illuminant has almost no substance that becomes an allergen. Therefore, by using a plant-derived illuminant as an ultraviolet shielding agent in cosmetics, the risk of problems such as allergies can be reduced.

D4. Application form 4:
As described above, since the plant-derived luminescent material has phosphorescence, it continues to emit light for a certain period of time after the excitation light is no longer irradiated. Therefore, by blending it into building materials such as ceiling materials, wall materials, wallpaper, flooring materials, carpets, or anti-slip tape for stairs, it will continue to emit light even when the excitation light is turned off. It is possible to suppress the occurrence of accidents such as collision with obstacles in the dark room and stepping off stairs during a power failure. Moreover, since the organic substance which a plant body has carbonized in the plant-derived light-emitting body, the substance used as an allergen and a volatile substance hardly exist. Therefore, by using a plant-derived illuminant as a building material, it is possible to reduce the possibility of problems such as allergies and sick house syndrome. Further, when a porous illuminant is used, molecules such as odor components are adsorbed in the pores of the illuminant, so that it is possible to adsorb odors and the like.

D5. Application form 5:
Moreover, the density | concentration of the dye fell by throwing a plant-derived light-emitting body into the water containing an organic dye, and irradiating light. Therefore, it is considered that the plant-derived luminescent material functions as a photocatalyst for decomposing organic matter by light irradiation. As described above, since the plant-derived luminescent material is obtained by heat-treating the plant body, it is possible to generate the photocatalyst more easily.

100, 100a ... Heat treatment furnace 110 ... Chamber 112, 114 ... Flange 120 ... Fan 130 ... Heater RH ... Rice husk RHC ... Rice husk carbide

Claims (18)

A luminous body made from a plant body,
A luminous body produced by heat-treating the plant body in a gas containing oxygen. A luminous body made from a plant body,
A phosphor produced by heat-treating the plant body in a gas containing no oxygen and then heat-treating the plant body in a gas containing oxygen.   The light emitter according to claim 1 or 2, wherein the light emitter is porous.   The light emitter according to any one of claims 1 to 3, wherein the light emitter has a cell wall structure of the plant.   The light emitter according to any one of claims 1 to 4, wherein the phosphor has a composition ratio of potassium in a range of 0.2% to 10%.   The light emitter according to claim 1, wherein the composition ratio of carbon is in a range of 0.5% to 55%.   The light emitting body according to any one of claims 1 to 6, wherein the plant body is a plant body of a silicon-accumulating plant.   The light emitting body according to claim 7, wherein the plant body is rice husk. A light emitter,
A phosphor containing silicon, oxygen, carbon and potassium. A method of manufacturing a light emitter,
(A) preparing a plant;
(B) The process of heat-processing the said plant body in the gas containing oxygen. A method of manufacturing a light emitter,
(1) a step of preparing a plant body;
(2) a step of heat-treating the plant in a gas not containing oxygen;
(3) a step of heat-treating the plant subjected to the heat treatment in the step (2) in a gas containing oxygen;
A method of manufacturing a light emitter.   The method according to claim 10 or 11, wherein the plant body is a plant body of a silicon-accumulating plant.   The method according to claim 12, wherein the plant body is rice husk. A lighting device,
The light emitter according to any one of claims 1 to 9,
An illumination device comprising: an excitation light source for exciting the light emitter. A detergent,
A light emitter according to any one of claims 1 to 9,
The luminous body is in a powder form,
detergent. UV shielding material for cosmetics,
A light emitter according to any one of claims 1 to 9,
The luminous body is in a powder form,
UV shielding material for cosmetics. Building materials,
A light emitter according to any one of claims 1 to 9,
The luminous body is in a powder form,
Building materials. A photocatalyst,
A photocatalyst comprising the light emitter according to claim 1.