Method for manufacturing silicon oxynitride glass, method for manufacturing optical waveguide, silicon oxynitride glass, optical waveguide, infrared image furnace, window material, and optical component

Abstract

Silicon oxynitride glass can easily be produced according to a method for producing silicon oxynitride glass that includes bringing silica particles into contact with ammonia gas under heating, and sintering the silicon oxynitride particles obtained through said contact by heating to a temperature exceeding 1500°C using a spark plasma sintering method.

Description

[Technical Field]

[0001] The present invention relates to a method for producing silicon oxynitride glass, a method for producing an optical waveguide, silicon oxynitride glass, an optical waveguide, an infrared image furnace, a window material, and an optical member. [Background technology]

[0002] Silicon oxynitride glass is known, obtained by substituting nitrogen for oxygen in silica glass. Non-Patent Document 1 describes a method for producing such silicon oxynitride glass, in which an aerogel obtained by hydrolysis and polycondensation of tetraethoxysilane is contacted with ammonia gas under heating to nitride it, and the nitrided aerogel is sintered in a vacuum at 1600°C. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Journal of Non-Crystalline Solids,2001,vol 286,p.58-63 Summary of the Invention [Problem to be solved by the invention]

[0004] Non-Patent Document 1 discloses creating an aerogel, nitriding it, and then heating the nitrided aerogel to 1600°C under vacuum. However, using the above method, it was difficult to produce a large bulk body of silicon oxynitride glass (not of particle size) suitable for optical components. In fact, the above document does not describe the light transmittance of silicon oxynitride glass.

[0005] Furthermore, the procedures for producing aerogel are complicated and require specialized equipment, and heating nitrided aerogel to 1600°C under vacuum also poses significant equipment limitations. As a result, industrial use of silicon oxynitride glass using the above method has been extremely difficult.

[0006] Therefore, an object of the present invention is to provide a method for producing silicon oxynitride glass that can easily produce silicon oxynitride glass, and also to provide silicon oxynitride glass, optical waveguides, infrared image furnaces, window materials, and optical components. [Means for solving the problem]

[0007] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the following configuration.

[0008] [1] A method for producing silicon oxynitride glass, comprising: contacting silica particles with ammonia gas under heating; and heating and sintering the silicon oxynitride particles obtained by said contacting at a temperature exceeding 1500°C by a spark plasma sintering method. [2] The method for producing silicon oxynitride glass according to [1], wherein the average primary particle diameter of the silica particles is 1000 nm or less. [3] The method for producing silicon oxynitride glass according to [1] or [2], wherein the ratio of the mass-based nitrogen atom content to the mass-based silicon atom content in the silicon oxynitride particles is 0.10 or more. [4] The method for producing silicon oxynitride glass according to any one of [1] to [3], wherein the silicon oxynitride glass contains 12.0 mass % or more of nitrogen and has a light transmittance of 65% or more at a thickness of 1.94 mm in a wavelength range of 2000 to 2500 nm. [5] A method for producing an optical waveguide that propagates infrared light, comprising the method for producing silicon oxynitride glass according to any one of [1] to [4]. [6] Silicon oxynitride glass containing 12.0% or more by mass of nitrogen and having an optical transmittance of 65% or more at a thickness of 1.94 mm in the wavelength range of 2000 to 2500 nm. [7] The silicon oxynitride glass according to [6], which has a light transmittance of 50% or more at a thickness of 1.94 mm in the wavelength range of 400 to 700 nm. [8] The silicon oxynitride glass according to [6] or [7], having a thermal conductivity of 2.00 W / (m·K) or more. [9] The silicon oxynitride glass according to any one of [6] to [8], which has a light transmittance of 65% or more at a thickness of 1.94 mm in the wavelength region of more than 2500 nm and not more than 2875 nm.

[10] The silicon oxynitride glass according to any one of [6] to [9], which has a refractive index of 1.60 or more in a wavelength region of 400 to 700 nm.

[11] The silicon oxynitride glass according to any one of [6] to

[10] , wherein the mass ratio of the nitrogen atom content to the silicon atom content is 0.27 or more.

[12] The silicon oxynitride glass according to any one of [6] to

[11] , which has a Young's modulus of 100 GPa or more.

[13] An optical waveguide for propagating infrared light, comprising the silicon oxynitride glass according to any one of [6] to

[12] .

[14] An infrared image furnace comprising the optical waveguide according to

[13] .

[15] A window material comprising the silicon oxynitride glass according to any one of [6] to

[12] .

[16] An optical member comprising the silicon oxynitride glass according to any one of [6] to

[12] . [Effects of the Invention]

[0009] The present invention provides a method for producing silicon oxynitride glass, which allows silicon oxynitride glass to be produced easily. The present invention also provides a method for producing an optical waveguide, silicon oxynitride glass, an optical waveguide, an infrared image furnace, a window material, and an optical component. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a flowchart showing the steps of one embodiment of a method for producing silicon oxynitride glass of the present invention. [Figure 2] FIG. 1 is a schematic diagram of a spark plasma sintering apparatus. [Figure 3] 1 is an explanatory diagram of an embodiment of an optical waveguide of the present invention. [Figure 4] 1 is an explanatory diagram of an embodiment of an infrared image furnace of the present invention. [Figure 5] 1 is an explanatory diagram of an embodiment of a temperature distribution measuring device of the present invention. [Figure 6] 1 is an explanatory diagram of an embodiment of a radiation thermometer of the present invention. FIG. [Figure 7] This is a transmission spectrum measured by an ultraviolet-visible spectrophotometer. [Figure 8] This is a transmission spectrum measured by a Fourier transform infrared spectrophotometer. [Figure 9] FIG. 10 is a diagram showing the measurement results of the refractive index. [Figure 10] 1 is a photograph of a sample obtained by the method for producing silicon oxynitride glass of the present invention. [Figure 11] This is a transmission spectrum measured by an ultraviolet-visible spectrophotometer. [Figure 12] This is a transmission spectrum measured by a Fourier transform infrared spectrophotometer. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below. The following description of the components may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0012] The embodiment shown below is an example that embodies the technical concept of the present invention, and the technical concept of the present invention does not limit the materials, shapes, structures, and arrangements of the components to the following embodiment. The drawings are schematic. Therefore, the relationship and ratio between thickness and planar dimensions may differ from the actual ones, and the relationship and ratio between dimensions may also differ between the drawings.

[0013] Furthermore, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0014] In this specification, "silica glass" refers to glass having a three-dimensional network structure in which oxygen atoms at the vertices of silicon dioxide (SiO4) tetrahedra are shared, and pure silica glass that does not substantially contain dopants is preferred.

[0015] In this specification, silicon oxynitride glass refers to silica glass in which some of the oxygen (O) atoms in the above-mentioned silica glass have been replaced with nitrogen atoms (N). Typically, when the total mass of silicon (Si), oxygen, nitrogen, and other elements (e.g., impurities such as carbon) constituting the silicon oxynitride glass is taken as 100 mass%, the nitrogen content is 0.01 to 99 mass%, preferably 1 to 90 mass%, more preferably 2 to 80 mass%, and even more preferably 3 to 50 mass%. Note that silicon oxynitride glass does not include silicon nitride (Si3N4). The nitrogen content is measured by the method described in the Examples below.

[0016] Silicon oxynitride glass refers to a bulk material having a relative density (bulk density / true density) of 90% or more, preferably 95% or more. Silicon oxynitride glass preferably has a light transmittance of 20% or more at a thickness of 1.94 mm in the wavelength range of 400 to 700 nm.

[0017] [Method for manufacturing silicon oxynitride glass] A method for producing silicon oxynitride glass according to an embodiment of the present invention (hereinafter also referred to as "the present production method") includes contacting silica particles with ammonia gas under heating, and sintering the particles obtained by the contacting by heating them to above 1500°C using a spark plasma sintering method.

[0018] 1 is a flow chart showing the steps of this manufacturing method. In step S10, silica (SiO2) particles are brought into contact with ammonia gas (NH3) under heating (nitriding step). This nitriding step replaces some of the oxygen atoms of the silica with nitrogen atoms, resulting in silicon oxynitride particles (silicon oxynitride particles).

[0019] Conventionally, silicon oxynitride, a raw material for the production of silicon oxynitride glass (bulk), has been thought to be obtained by nitriding silica aerogel, which has a large surface area. In other words, it has been thought that the appropriate raw material for producing silicon oxynitride glass is silica aerogel, which is nitrided by contacting it with ammonia gas under heating. It has been thought that by sintering this nitrided silica aerogel, a high relative density, transparent silicon oxynitride glass (bulk) can be obtained.

[0020] However, conventional methods such as those described in Non-Patent Document 1 have not been able to produce silicon oxynitride glass with a high nitrogen content (for example, one containing 12 mass % or more of nitrogen). Even if they could be produced, they were in the form of particles or extremely small solids, and it was not possible to produce a bulk body suitable for application to optical components, etc.

[0021] However, the present inventors have been unconstrained by the above-mentioned common technical knowledge and have been actively investigating a method for producing transparent, high-quality silicon oxynitride glass without using silica aerogel, because they believed that the method for producing silicon oxynitride glass via aerogel has significant limitations in terms of production equipment and cost, and it is difficult to produce large bulk bodies, posing problems for industrial application.

[0022] After extensive research, the inventors discovered that high-quality silicon oxynitride glass can be produced more easily by nitriding silica particles and subjecting the resulting compact to spark plasma sintering (SPS), leading to the completion of the present invention. One of the features of this production method is that silica is nitrided in the particle (powder) state and then SPS is performed under specified temperature conditions. The materials used in each step and the procedures are described in detail below.

[0023] Returning to FIG. 1, the silica particles (silicon dioxide particles) used in the nitriding step of step S10 are not particularly limited, and known silica particles can be used. Specific examples include particles of natural silica, synthetic silica, silica balloons, mesoporous silica, silica gel, quartz, etc. Among these, amorphous silica particles are preferred from the viewpoint of obtaining silicon oxynitride glass having superior optical properties and mechanical properties.

[0024] Silica particles that can be used include those produced from natural silica, those synthesized by the sol-gel method and / or by hydrolysis of chlorosilane, and those obtained by reducing impurities such as aluminum, sodium, and iron from these through metal removal purification.

[0025] The content of impurities in the silica particles is not particularly limited, but for example, in the case of aluminum, the content is preferably 0.1 to 50 mass ppm, more preferably 0.1 to 10 mass ppm, in one embodiment. When the aluminum content is 50 mass ppm or less, crystal formation during sintering is further suppressed, and when it is 0.1 mass ppm or more, cost-effectiveness is improved, but it is preferable that the silica particles are substantially free of aluminum (the content is below the detection limit).

[0026] In the case of sodium, the content is preferably 0.01 to 1 ppm by mass, more preferably 0.05 to 1 ppm by mass, in one embodiment. If the sodium content is 1 ppm by mass or less, the resulting silicon oxynitride glass tends to have better light transmittance, and if it is 0.01 ppm by mass or more, the cost-effectiveness is better, but it is preferable that the silica particles are substantially free of sodium.

[0027] In the case of iron, the content is preferably 0.1 to 5 ppm by mass, more preferably 0.1 to 2 ppm by mass, in one embodiment. When the iron content is 5 ppm by mass or less, the resulting silicon oxynitride glass tends to have better light transmittance, and when it is 0.1 ppm by mass or more, the cost-effectiveness is better, but it is preferable that the silica particles are substantially free of iron.

[0028] The average diameter of the primary particles of the silica particles (average particle diameter) is not particularly limited, but from the viewpoint of allowing nitridation to proceed more efficiently and of the resulting silicon oxynitride glass being likely to have better optical properties and / or better mechanical properties, it is preferably 1000 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less. There is no particular lower limit, but generally, 3 nm or more is preferred.

[0029] In step S10, the silica particles are brought into contact with ammonia gas under heating, which is thought to incorporate nitrogen atoms into the silica network structure, resulting in nitridation. It is thought that when ammonia gas comes into contact with silica at high temperatures, silanol moieties and / or siloxane moieties interact with ammonia to form amines.

[0030] The heating temperature during nitriding is not particularly limited, but the maximum temperature (ultimate temperature) is preferably 600° C. or higher, more preferably 800° C. or higher, and even more preferably 900° C. or higher. The upper limit is preferably 1200° C. or lower, and more preferably 1100° C. or lower.

[0031] Furthermore, the method for contacting silica particles with ammonia gas is not particularly limited, but one example is a method in which silica particles placed in a tubular furnace are heated and a predetermined amount of ammonia gas is passed through the tubular furnace. The flow rate of the ammonia gas at this time is not particularly limited, but for example, when a tubular furnace with an interior of 65 mmφ×300 L and a furnace core tube of 60 mmφ is used, the flow rate is preferably 10 to 1000 mL / min, and more preferably 200 to 700 mL / min.

[0032] In this case, the rate of temperature rise up to the maximum temperature is not particularly limited, but in one embodiment it is preferably 1 to 20°C / min, more preferably 2 to 10°C / min. The holding time at the maximum temperature is not particularly limited, but is preferably 0.5 to 24 hours, more preferably 1 to 18 hours.

[0033] The silica particles are nitrided by the nitriding step. The content of nitrogen atoms contained in the nitrided silica particles (silicon oxynitride particles) (when a particle mixture is used, the average value taking the composition into consideration) is not particularly limited, but from the viewpoint of the resulting silicon oxynitride glass having better optical properties, better thermal properties, and / or better mechanical properties, it is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, when the mass of the entire particles is taken as 100% by mass. The upper limit is not particularly limited, but generally it is preferably 50% by mass or less, more preferably 40% by mass or less. In this specification, the content of nitrogen atoms contained in silicon oxynitride particles means the content of nitrogen atoms measured by the method described in the Examples section below.

[0034] The mass ratio (N / Si) of the nitrogen atom content to the silicon atom content in the silicon oxynitride particles is not particularly limited, but from the viewpoint that the obtained silicon oxynitride glass is likely to have better optical properties and better mechanical properties, it is preferably 0.10 or more, more preferably 0.20 or more, and even more preferably 0.27 or more. The upper limit is not particularly limited, but in one embodiment, it is preferably 0.50 or less.

[0035] The atomic ratio of nitrogen atoms to silicon atoms (N / Si) in the silicon oxynitride particles is not particularly limited, but is preferably 0.7 or more, more preferably 0.8 or more, from the viewpoint that the resulting silicon oxynitride glass is likely to have better optical properties and better mechanical properties. The upper limit is not particularly limited, but in one embodiment, it is preferably 1.2 or less, more preferably 1.0 or less.

[0036] Next, in step S11, a powder compact is produced from the silicon oxynitride particles obtained in step S10, and then, in step S12, this powder compact is subjected to spark plasma sintering (SPS) at a temperature exceeding 1500° C. Steps S11 and S12 may be performed sequentially or simultaneously. In step S10, silica particles and / or silicon oxynitride particles with different nitrogen contents may be mixed with the silicon oxynitride particles to form the green compact. By adding other particles, the nitrogen content in the raw material powder (green compact) can be more easily adjusted.

[0037] Spark plasma sintering is a method in which particles are filled into a mold, compressed under pressure using a press made of a conductive material to form a powder compact, and then a pulsed voltage is applied to this powder compact to heat it to a predetermined temperature.The production of the powder compact and sintering are carried out sequentially or simultaneously. According to the SPS, the powder compact is heated by Joule heat and sintered efficiently by the high energy of discharge plasma generated by pulsed electric energy. Note that the powder compact may be prepared in advance before SPS is performed.

[0038] Figure 2 is a schematic diagram of an SPS apparatus. A sample 20 is packed into a high-strength carbon mold consisting of a cylindrical graphite die 13 with a carbon sheet 14 wound around its inner surface and graphite punches 12 fitted into the upper and lower openings. Each graphite punch 12 is connected to a pair of electrodes 11 connected to a DC power supply 15, and a pulse current is applied. Compressive stress (symbol "P") is applied to the graphite punch 12 from above and below, and a reaction takes place in a chamber 16.

[0039] The pressing force is not particularly limited, but in one embodiment, it is preferably 1 to 100 MPa. The lower limit is more preferably 50 MPa or more, and even more preferably 70 MPa or more. The upper limit is preferably 90 MPa or less. During the reaction, the chamber 16 is preferably filled with an inert gas, and more preferably filled with nitrogen gas.

[0040] The sintering temperature (maximum temperature, holding temperature) is above 1500°C. If the sintering temperature is below 1500°C, sintering will not proceed sufficiently, and transparent silicon oxynitride glass will not be obtained. In this respect, the sintering temperature is preferably 1550°C or higher, and more preferably above 1550°C. On the other hand, although there is no particular upper limit, a temperature of 2000°C or less is more cost-effective. In this respect, 1800°C or less is more preferable, and 1700°C or less is even more preferable. The temperature-raising program is also not particularly limited. In one embodiment, it is preferable to adjust the temperature-raising rate from a predetermined temperature to the holding temperature to about 5 to 150°C / min. The temperature may be raised from room temperature to the holding temperature at a constant temperature, or may be raised in stages. Other processing conditions may be determined appropriately by referring to known literature, for example, Japanese Patent Application Laid-Open No. 11-11961.

[0041] The silicon oxynitride glass obtained by the above method has excellent optical properties, excellent mechanical properties, and excellent thermal properties, and can be used for optical waveguides, infrared image furnaces, window materials, optical components, etc.

[0042] [Silicon oxynitride glass] The silicon oxynitride glass according to the embodiment of the present invention is a silicon oxynitride glass that can be produced by the method for producing silicon oxynitride glass already explained above (hereinafter also referred to as "the present silicon oxynitride glass").

[0043] This silicon oxynitride glass contains at least 12.0 mass% nitrogen atoms. Conventionally, silicon oxynitride glass has been produced by nitriding an aerogel obtained by a sol-gel process and then densifying it, as described in Non-Patent Document 1. This is because the large surface area of ​​the aerogel allows nitriding to proceed efficiently, which has been thought to be advantageous for producing silicon oxynitride glass.

[0044] On the other hand, the inventors, not being bound by the above-mentioned common technical knowledge, came up with the idea of ​​carrying out nitriding treatment simply and efficiently by making the raw material into powder (particles) and nitriding it in the powder state. Furthermore, by adopting SPS, which allows pressure sintering in a nitrogen atmosphere (not even under vacuum), they succeeded in producing silicon oxynitride glass with an ease incomparable to conventional methods.

[0045] Furthermore, we have discovered that the nitrogen content can be easily adjusted (increased) by using a non-traditional nitriding method, and that the silicon oxynitride glass obtained by a non-traditional nitriding and sintering method has distinctive properties.

[0046] That is, the silicon oxynitride glass has a light transmittance of 65% or more at a thickness of 1.94 mm (converted) in the wavelength range of 2000 to 2500 nm. The light transmittance mentioned in this specification means that the light transmittance is constant or higher over the entire wavelength range of 2000 to 2500 nm. That is, the light transmittance is 65% or higher over the entire wavelength range of 2000 to 2500 nm. The light transmittance is a value measured by the method described in the Examples. When using a sample with a thickness other than 1.94 mm in the evaluation of light transmittance, the measured value (transmittance) at that thickness shall be converted to a value for a thickness of 1.94 mm and used.

[0047] Conventional methods for producing silicon oxynitride glass via aerogel have not been able to obtain samples large enough to evaluate the optical properties described above. Furthermore, silica glass generally varies in its OH group content and other properties depending on the production method, leading to significant differences in various physical properties, particularly optical properties. Therefore, it is unlikely that the distinctive optical properties described above could have been obtained with silicon oxynitride glass obtained by conventional methods (whose optical properties cannot be evaluated). It is believed that these unique optical properties were first achieved with silicon oxynitride glass obtained by the present production method.

[0048] If the light transmittance in the above wavelength range is less than 65%, the transmittance of near-infrared light will be insufficient, which may make it difficult to use the material as an optical waveguide that propagates infrared light, or as a window material or optical component that transmits infrared light. The light transmittance in the above wavelength range is preferably 70% or more, more preferably 75% or more, and even more preferably 80% or more. There is no particular upper limit, but generally, it is preferably 100% or less.

[0049] Furthermore, the silicon oxynitride glass preferably has a light transmittance of 65% or more in the wavelength region of more than 2500 nm and not more than 2875 nm. If the light transmittance within the above range is 65% or more, the transmittance of near-infrared light will be more sufficient, making the film more suitable for use as an optical waveguide that propagates infrared light, and as a window material or optical component. In this respect, 68% or more is preferred, 70% or more is more preferred, and 75% or more is even more preferred. There is no particular upper limit, but in one embodiment, 100% or less is preferred.

[0050] The silicon oxynitride glass has a nitrogen content of 12.0% by mass or more, preferably 13.0% by mass or more, and more preferably 13.5% by mass or more. When the silicon oxynitride glass has a nitrogen content of 12.0% by mass or more, the light transmittance in the wavelength range of 2 μm (2000 nm) or more tends to be higher. Furthermore, when the nitrogen content is 13.0% by mass or more, more preferably 13.5% by mass or more, silicon oxynitride glass having better mechanical properties (particularly modulus of rigidity) can be obtained. On the other hand, although there is no particular upper limit to the nitrogen content, in one embodiment, a nitrogen content of 50.0% by mass or less provides better cost-effectiveness in terms of light transmittance at wavelengths of 2 μm (2000 nm) or more. In this respect, a nitrogen content of 20.0% by mass or less is preferred, and 15.0% by mass or less is more preferred. In addition, in order to produce oxynitride glass containing 12.0 mass% or more of nitrogen atoms using the above-mentioned method for producing silicon oxynitride glass, in one embodiment, the content of nitrogen atoms in the silicon oxynitride glass (particles) or compact is preferably 13.0 mass% or more and preferably 20.0 mass% or less.

[0051] The ratio of the nitrogen atom content to the silicon atom content (N / Si) in the silicon oxynitride glass is not particularly limited, but is preferably 0.27 or more, more preferably 0.28 or more, and even more preferably 0.29 or more, in order to obtain a silicon oxynitride glass with better optical properties, thermal properties, and / or mechanical properties. The upper limit is not particularly limited, but in one embodiment, it is preferably 0.50 or less, more preferably 0.40 or less, and even more preferably 0.35 or less.

[0052] The atomic ratio of nitrogen atoms to silicon atoms (N / Si) in the present silicon oxynitride glass is not particularly limited, but is preferably 0.6 or more and 1.0 or less, in order to obtain silicon oxynitride glass with better optical properties, thermal properties, and / or mechanical properties.

[0053] The light transmittance of the silicon oxynitride glass at a thickness of 1.94 mm in the wavelength range of 400 to 700 nm (hereinafter also referred to as the "visible light region") is not particularly limited, but is preferably 50% or more. When the light transmittance in the visible light region is 50% or more, the silicon oxynitride glass is more suitable for use as a window material, etc. From the above viewpoint, the light transmittance in the visible light region is preferably 53% or more. There is no particular upper limit, but in one embodiment, it is preferably 100% or less.

[0054] The light transmittance of the silicon oxynitride glass in the visible light region means the value measured by the method described in the Examples section below, and the definition of light transmittance is as described above.

[0055] The refractive index of the silicon oxynitride glass in the visible light region is preferably 1.60 or more. If the refractive index within the above wavelength range is 1.60 or more, it is more suitable for use as an optical component, etc. From the above viewpoint, the refractive index in the visible light region is more preferably 1.62 or more. There is no particular upper limit, but in one embodiment, it is preferably 1.80 or less.

[0056] The thermal conductivity of the silicon oxynitride glass is preferably 2.00 W / (m·K) or more, more preferably 2.20 W / (m·K) or more, even more preferably 2.40 W / (m·K) or more, and particularly preferably 2.60 W / (m·K) or more. There is no particular upper limit, but in one embodiment, it is preferably 15.00 W / (m·K) or less, more preferably 10.00 W / (m·K) or less, even more preferably 5.00 W / (m·K) or less, and particularly preferably 4.00 W / (m·K) or less. Note that the thermal conductivity in this specification refers to a value measured by the method described in the Examples section below.

[0057] The specific heat of the silicon oxynitride glass is preferably 0.800 J / (g K) or more, more preferably 0.900 J / (g K) or more. There is no particular upper limit, but in one embodiment, it is preferably 2.200 J / (g K) or less. Note that the specific heat in this specification refers to a value measured by the method described in the Examples section below.

[0058] The thermal diffusivity of this silicon oxynitride glass is 0.90 mm 2 The upper limit is not particularly limited, but in one embodiment, it is 6.00 mm 2 / s or less is preferable, 3.00 mm 2 / s or less is more preferable, and 2.00 mm 2 The thermal diffusivity in this specification refers to a value measured by the method described in the examples below.

[0059] The Young's modulus of the silicon oxynitride glass is preferably 100 GPa or more. When the Young's modulus is within the above range, optical components and the like having superior robustness can be obtained. From the above viewpoint, the Young's modulus is more preferably 120 GPa or more, even more preferably 130 GPa or more, particularly preferably 140 GPa or more, and most preferably 145 GPa or more. There is no particular upper limit, but in one embodiment, it is preferably 300 GPa or less, more preferably 200 GPa or less. In this specification, the Young's modulus refers to a value measured by the method described in the Examples below.

[0060] The Vickers hardness of the silicon oxynitride glass is preferably 10.0 GPa or more. When the Vickers hardness is within the above range, optical components and the like having superior toughness can be obtained. From the above viewpoint, the Vickers hardness is preferably 11.0 GPa or more, more preferably 12.0 GPa or more, and even more preferably 15.0 GPa or more. There is no particular upper limit, but in one embodiment, 20.0 GPa or less is preferable. In this specification, the Vickers hardness refers to a value measured by the method described in the Examples below.

[0061] The rigidity modulus of the silicon oxynitride glass is preferably 40 GPa or more. When the rigidity modulus is within the above range, optical components and the like having superior robustness can be obtained. From the above viewpoint, the rigidity modulus is more preferably 50 GPa or more, even more preferably 55 GPa or more, and particularly preferably 60 GPa or more. There is no particular upper limit, but in one embodiment, it is preferably 100 GPa or less. In this specification, the rigidity modulus refers to a value measured by the method described in the Examples below.

[0062] The Poisson's ratio of the silicon oxynitride glass is preferably 0.180 or more, more preferably 0.190 or more, even more preferably 0.200 or more, and particularly preferably 0.210 or more. There is no particular upper limit, but in one embodiment, it is preferably 0.250 or less. In this specification, the Poisson's ratio refers to a value measured by the method described in the Examples below.

[0063] The glass transition temperature of the present silicon oxynitride glass is preferably at least 1200° C., more preferably at least 1300° C. In this specification, the glass transition temperature refers to the glass transition temperature measured by differential thermal analysis.

[0064] The shape and size of the silicon oxynitride glass are not particularly limited and may be determined appropriately depending on the application. As one form, if it is in the form of a plate, it is preferably 1 mm or more in thickness and 0.5 cm x 0.5 cm or more in size.

[0065] As described above, the new silicon oxynitride glass, which is produced by a new method that has not been previously considered, has better heat resistance, better optical properties, and better mechanical properties than silica glass. In particular, with regard to optical properties, the glass has a light transmittance of 65% or more at a thickness of 1.94 mm in the wavelength range of 2000 to 2500 nm, making it suitable for use as an optical waveguide for transmitting infrared light, an optical component, etc. Compared with silica glass produced by a special manufacturing method that has conventionally been used for this purpose, the silicon oxynitride glass of the present invention has the same or higher infrared light transmittance and can be produced by a simpler method. The silicon oxynitride glass of the present invention can be preferably used as an optical waveguide, an infrared image furnace, a window material, and an optical member, which will be described later.

[0066] [Optical waveguide] An optical waveguide according to an embodiment of the present invention (hereinafter also referred to as "the optical waveguide") is an optical waveguide that contains the silicon oxynitride glass and propagates infrared light. Fig. 3 is an explanatory diagram of the optical waveguide. The optical waveguide 30 has a cylindrical core 31 made of silicon oxynitride glass and a cladding 32 arranged to cover the outer periphery of the core 31, and can be used to propagate infrared rays in the vertical direction of the drawing.

[0067] The optical waveguide 30 uses silicon oxynitride glass, which has excellent light transmittance in the wavelength range of 2 μm or more, as the core 31, so that even if the optical waveguide 30 is fibrous and long, it can achieve smaller transmission loss.

[0068] Although the optical waveguide 30 has a cladding 32, the optical waveguide according to the embodiment of the present invention may not have the cladding 32. As described above, silicon oxynitride glass has a high refractive index and tends to reduce transmission loss. The optical waveguide 30 may further have a protective coating on the outer periphery of the cladding 32.

[0069] The outer diameter of the core is not particularly limited and may be adjusted as appropriate depending on the application, but may be 1 μm to 2 mm in one embodiment. The thickness of the cladding is not particularly limited and may be 20 μm to 2 mm in one embodiment, or may be 20 to 200 μm in one embodiment. The material of the cladding is not particularly limited and may be silica glass in one embodiment.

[0070] Although the optical waveguide 30 is fiber-shaped, the shape of the optical waveguide according to the embodiment of the present invention is not limited to the above and can be appropriately changed. For example, the optical waveguide may be flat, having a cladding layer on a substrate and a core 31 containing silicon oxynitride glass.

[0071] The core (layer) of this optical waveguide contains the above-mentioned silicon oxynitride glass, which has high transmittance for light in the region of 2 μm or more and a high refractive index, and therefore tends to reduce transmission loss.

[0072] [Infrared image furnace] The infrared image furnace of the present invention (hereinafter also referred to as "the present infrared image furnace") includes the above-mentioned optical waveguide. Fig. 4 is an explanatory diagram of an infrared image furnace according to an embodiment of the present invention. The infrared image furnace 40 has a pair of opposing half-ellipsoidal mirrors 42 and 43, an infrared light source 44 arranged at the focal position of one of the half-ellipsoidal mirrors 42, and an optical waveguide 30 arranged at the focal position of the other half-ellipsoidal mirror 43.

[0073] Infrared light 45 emitted from the infrared light source 44 is reflected and focused by the reflecting surfaces 41 of the two half-ellipsoidal mirrors 42 and 43, enters one end of the optical waveguide 30 located at the focal position of the half-ellipsoidal mirror 43, propagates through the optical waveguide 30, and exits from the other end (focused infrared light 46 in the figure), and is irradiated onto the object 47.

[0074] This infrared image furnace (infrared heating device) has an optical waveguide 30 incorporated for infrared propagation, resulting in smaller transmission loss and excellent efficiency. Furthermore, as already explained, the silicon oxynitride glass of the present invention has excellent heat resistance, so damage to the optical waveguide 30 is more likely to be suppressed even when the temperature of the object becomes higher. This makes it an excellent heating device to be incorporated into experimental equipment and the like that requires higher temperature heating and / or heating of a small area.

[0075] [Temperature distribution measuring device] The temperature distribution measuring device of the present invention includes the above-mentioned optical waveguide. Figure 5 is an explanatory diagram of the temperature distribution measuring device of the present invention. The temperature distribution measuring device 50 has an objective lens 51, an optical waveguide 30, an infrared camera 53, and a display device 52. The temperature distribution measuring device 50 collects infrared light 55 emitted from an object 54 using the objective lens 51, and receives this light via the optical waveguide 30 using the infrared camera 53. The obtained signal is transmitted wirelessly 56 (or may be transmitted via a wire) to the display device 52 and displayed as a temperature distribution.

[0076] This temperature distribution measuring device uses the above-mentioned optical waveguide 30 for the propagation of infrared rays. The above-mentioned optical waveguide 30 has excellent heat resistance, making it suitable for use when the object to be measured is at a higher temperature. In addition, because it has high light transmittance in the wavelength range of 2 μm or more, it has less transmission loss and enables more accurate measurements.

[0077] [Radiation thermometer] The radiation thermometer of the present invention includes the optical waveguide. Fig. 6 is an explanatory diagram of the radiation thermometer of the present invention. The radiation thermometer 60 has an optical waveguide 30 with anti-reflection coatings 63 applied to both ends, a band-pass filter 61, and an infrared sensor 62. Infrared light 65 emitted from an object 64 enters the optical waveguide 30 from one end via the anti-reflection coating 63 and exits from the other end via the anti-reflection coating 63. The exiting light enters the infrared sensor 62 via the band-pass filter 61.

[0078] The optical waveguide 30 has an excellent refractive index and an excellent light transmittance in the wavelength region of 2 μm or more, so that the transmission loss is smaller and more accurate temperature measurement is possible.

[0079] As described above, the silicon oxynitride glass according to the embodiment of the present invention has excellent heat resistance, excellent refractive index, and excellent light transmittance in the wavelength region of 2 μm or more, and therefore can be used as an optical component incorporated into optical devices. Furthermore, because it has excellent light transmittance even in the visible light region, it can also be used as a window material for internal monitors in high-temperature heating furnaces, which was not possible with conventional silica glass. [Example]

[0080] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0081] (Synthesis of silicon oxynitride particles: Synthesis Example 1) Amorphous silica (a-SiO2) (product name "AEROSIL-300", manufactured by Nippon Aerosil Co., Ltd., specific surface area by BET method: 300 m2 1 g of particles (μm / g, average primary particle diameter 7 nm) was placed in an alumina boat (boat-shaped vessel) and placed in a tubular furnace (TSW-520, Nikkato) equipped with a silica core tube. NH3 gas was introduced at a flow rate of 300 mL / min, and the temperature was raised to 1000 °C at a rate of 5 °C / min, after which the furnace was maintained at this temperature for 12 hours. The temperature was then lowered to room temperature at a rate of 5 °C / min, and the NH3 gas was stopped.

[0082] (Synthesis of silicon oxynitride particles: Synthesis Example 2) Instead of "AEROSIL-300," "AEROSIL90G" (manufactured by Nippon Aerosil Co., Ltd., specific surface area by BET method: 90m) was used as the raw material. 2 Silicon oxynitride particles were synthesized in the same manner as in Synthesis Example 1, except that silicon oxynitride particles (0.1g / g, average primary particle diameter 20nm) were used.

[0083] (Synthesis of silicon oxynitride particles: Synthesis Example 3) The raw material was spherical fused silica (FB-15D, manufactured by Denka Co., Ltd., specific surface area 1.3 m 2 Silicon oxynitride particles were synthesized in the same manner as in Synthesis Example 1, except that silicon oxynitride particles (0.1g / g, particle diameter (d50) 15 μm) were used.

[0084] (Synthesis of silicon oxynitride particles: Synthesis Example 4) Silicon oxynitride particles were synthesized in the same manner as in Synthesis Example 1, except that NH3 gas was flowed at a flow rate of 500 mL / min and the temperature increase rate was set to 2.5°C / min.

[0085] (Synthesis of silicon oxynitride particles: Synthesis Example 5) Instead of "Aerosil300," we used "Aeroperl300 Pharma" (manufactured by Nippon Aerosil Co., Ltd., specific surface area 300m2 by BET method). 2 Silicon oxynitride particles were synthesized using a crystalline silicon dioxide powder (Aerosil 300 Pharma) with an apparent specific gravity of approximately 270 g / L (Aerosil 300 is approximately 50 g / L).

[0086] (Synthesis of silicon oxynitride particles: Synthesis Example 6) Instead of "Aerosil 300," we used "VP4200" (manufactured by Nippon Aerosil Co., Ltd., specific surface area by BET method: 200 m 2 Silicon oxynitride particles were synthesized in the same manner using a silicon dioxide powder (0.1g, average primary particle diameter 12nm, apparent specific gravity approximately 150g / L).

[0087] Each of the silicon oxynitride particles was subjected to component analysis by fluorescent X-ray analysis, and the results are shown in Table 1. [Table 1]

[0088] In Table 1, [mass%] indicates mass %, [at%] indicates atomic %, and "-" indicates that no measurement was performed. The results in Table 1 show that nitriding was possible (silicon oxynitride particles could be produced) in all of the synthesis examples. In particular, synthesis example 1, in which the average primary particle diameter of the raw material particles was 1000 nm or less, was able to be nitrided more efficiently than synthesis example 3. In the following, tests were carried out using silicon oxynitride particles synthesized under various conditions.

[0089] (Sintering by SPS) The resulting particles were then sintered by the SPS method.

[0090] Specifically, 0.5 g of silicon oxynitride particles synthesized based on "AEROSIL-300" and having the composition listed in Table 5 was first packed into a high-strength carbon mold with an inner diameter of 10 mm, which was then placed in a spark plasma sintering apparatus (Fuji Electric Power Co., Ltd.) and uniaxially pressed at 80 MPa. The pressure was maintained constant until the end of the sintering period. After the atmosphere was replaced with nitrogen gas, heating was initiated. The heating rate was varied in three stages. First, the temperature was raised from room temperature to 600°C in 1 minute. Next, the temperature was raised from 600°C to a temperature 50°C lower than the holding temperature (holding temperature T - 50°C) at a predetermined heating rate (Δt1). Next, the temperature was raised from T - 50°C to the holding temperature T at a predetermined heating rate (Δt2). Finally, the temperature was held at the holding temperature T for a predetermined time and then cooled. The temperature was measured using an optical pyrometer. After holding, the temperature was cooled to room temperature at the furnace cooling rate. In addition, non-nitrided silica particles (Aerosil 300) were sintered as a comparison sample at a holding temperature of 1200°C. The heating conditions (heating program) are listed in Table 6. In Comparative Example 4, the temperature was raised to 900° C. over 3 minutes, raised to 1350° C. in Δt1, and then raised to 1400° C. in Δt2 and maintained at that temperature.

[0091] The samples sintered by the SPS method were polished on both sides using #220 to #2000 abrasive paper (Refine Tech), and then mirror-polished using 6 μm diamond slurry (41-606, Refine Tech) and a polishing buff (56-208, Refine Tech).

[0092] The product with a holding temperature (maximum temperature) during sintering of 1600°C was designated Example 1 (symbol "Ex1"), the product with a holding temperature of 1500°C was designated Comparative Example 1 (symbol "C1"), the product with a holding temperature of 1400°C was designated Comparative Example 3 (symbol "C3"), and the product obtained by sintering silica particles was designated Comparative Example 2 (symbol "C2").

[0093] [Example 2, Example 4, Comparative Examples 5 to 10, Comparative Example 12, Comparative Example 15] Silicon oxynitride glass was produced using two types of silicon oxynitride particles synthesized based on "AEROSIL-300" in the same manner as in Synthesis Example 1. The raw material particles were a mixture of two types of silicon oxynitride particles. The mixing ratio of the two types of silicon oxynitride glass was adjusted so that the N / Si atomic ratio of the raw material particles as a whole was the value listed in Table 5. The composition and mixing ratio of each particle are shown in Table 5. Silicon oxynitride glass was produced from the obtained raw material particles in the same manner as in Example 1, except that the SPS conditions (pressure, holding temperature, and heating program) were adjusted as shown in Table 6. In Table 5, examples and comparative examples written in two columns each indicate that the powder compact was produced by mixing the particles shown in the upper and lower columns.

[0094] [Example 3, Comparative Examples 11 and 13] Each silicon oxynitride glass was produced in the same manner as in Example 1, except that the silicon oxynitride particles shown in Table 5 (all of which were synthesized using "AEROSIL-300" by the same method as in Synthesis Example 1) were used as raw materials and the SPS conditions were as shown in Table 6.

[0095] [Comparative Example 14] Silicon oxynitride glass was produced in the same manner as in Example 1, except that silicon oxynitride particles synthesized based on "AEROSIL-300" and silica particles ("AEROSIL-300") were mixed in the ratio shown in Table 5 to obtain raw material particles, and the SPS conditions were as shown in Table 6.

[0096] Comparative Example 4 Silicon oxynitride glass was produced in the same manner as in Example 1, except that "Aeroperl (Japan Aerosil)" was used instead of "AEROSIL-300" and the SPS conditions were as shown in Table 6. In the following table, "-" indicates that there is no measurement data.

[0097] [Table 5]

[0098] [Table 6]

[0099] (density measurement) The bulk density of each sample was calculated from its mass, diameter, and thickness. The density of approximately 0.4 g of each sample was measured using a dry density meter (Shimadzu Accupyk II 1345) equipped with helium gas, and this value was used as the true density.

[0100] (composition analysis) Composition analysis was performed using a wavelength dispersive X-ray fluorescence spectrometer (WDXRF) (ZSX Primus II, manufactured by Rigaku Corporation). The composition of the raw material particles was measured by molding 0.6 g of nitrided particles into a 12 mm diameter pellet by uniaxial pressure of 10 MPa / 5 min, and fixing it in a holder with a 10 mm inner diameter hole.

[0101] Table 2 shows the results of density measurement and composition analysis for Example 1 and Comparative Examples 1, 2, and 3. Fig. 10 is a photograph of the obtained samples, with each lattice having a side length of 5 mm. The results of density measurement and composition analysis for other Examples and Comparative Examples will be described later.

[0102] [Table 2]

[0103] As shown in Fig. 10, transparent samples (bulk bodies) were obtained in Example 1 ("Ex1", sintering temperature: 1600°C) and Comparative Example 2 ("C2", silica particles sintered at 1200°C). On the other hand, transparent samples were not obtained in Comparative Example 1 (C1, sintering temperature: 1500°C) and Comparative Example 3 (C3, sintering temperature: 1400°C). Similarly, transparent silicon oxynitride glass (bulk body) was obtained in Examples 2 to 4. On the other hand, in Comparative Examples 1 to 15, transparent silicon oxynitride glass (bulk body) was not obtained.

[0104] Furthermore, from the results in Table 1, the samples of Example 1, Comparative Example 1, and Comparative Example 3 contained a certain amount of nitrogen (N) in their compositions derived from the raw material powder, with the amount being 19.0 atomic % (at %) in Example 1. On the other hand, no nitrogen was detected in the sample of Comparative Example 2.

[0105] Furthermore, the bulk density and true density measurements showed that the relative density of the samples of Example 1 and Comparative Example 2 was 90% or more, and that uniform bulk bodies were obtained in all cases. In the table, "-" indicates that there is no data or that measurements were not performed.

[0106] (Light transmittance measurement) The light transmittance was measured using a UV-visible spectrophotometer (SolidSpec-3700, Shimadzu Corporation) and a Fourier transform infrared (FT-IR) spectrophotometer (SpectrumGX 2000R, Perkin-Elmer). A mask with a diameter of 6 mm was used for the measurements. The measurement parameters for the UV-visible spectrophotometer were as follows. The measured values ​​were corrected assuming a sample thickness of 1.94 mm. The thickness of each sample used is listed in Table 8.

[0107] Slit width: 2.0 mm Scan speed: Medium Sampling pitch: 1.00nm Grating switching wavelength: 870nm Light source switching wavelength: 310nm Detector switching wavelength: 830, 1650 nm

[0108] The measurement parameters of the Fourier transform infrared (FT-IR) spectrophotometer are as follows:

[0109] Resolution: 2.00cm -1 Interval: 0.5cm -1 Beam Splitter:KBr Number of Scans: 10

[0110] Figure 7 shows the transmittance spectrum measured by a UV-visible spectrophotometer, and Figure 8 shows the transmittance spectrum measured by an FT-IR spectrophotometer. Note that each spectrum is before correction for thickness, and the thickness of each sample is listed in Table 8.

[0111] In the figure, R3 indicates the measurement result of commercially available silica glass (Shin-Etsu Chemical's synthetic quartz glass "Viosil-SQ," not silicon oxynitride glass, 2.00 mm thick). The results in Figure 3 show that the sample of Example 1 (Ex1, sintering temperature 1600°C) has a transmittance (equivalent to a thickness of 1.94 mm) of 50% or more (53% or more) for light in the wavelength range of 400 to 700 nm.

[0112] 8, it was found that the sample of Example 1 had a transmittance (converted to a thickness of 1.94 mm) of 80% or more for light in the wavelength range of 2000 to 2500 nm. In contrast, the samples of Comparative Example 1 ("C1", sintering temperature: 1500°C) and Comparative Example 2 ("C2", silica particles sintered at 1200°C) had absorption peaks derived from hydroxy groups in the molecules, and Comparative Example 1 ("C1") had a region where the transmittance (converted to a thickness of 1.94 mm) was about 70%, while Comparative Example 2 ("C2") had a region where the transmittance was about 40%.

[0113] Furthermore, it was found that the sample of Example 1 had a transmittance (equivalent to a thickness of 1.94 mm) of 75% or more for light in the wavelength range of 2875 nm, exceeding 2500 nm. In contrast, the samples of Comparative Example 1 ("C1", sintering temperature: 1500°C) and Comparative Example 2 ("C2", sintered silica particles) had absorption peaks derived from hydroxy groups in the molecules, and the sample of Comparative Example 1 (C1) had a region where the transmittance was less than 70%, while the sample of Comparative Example 2 had a region where there was almost no transmittance. It was also found that Example 1 had superior transmittance compared to R3 (commercially available silica glass).

[0114] From the above, it was found that the sample of Example 1 has high transmittance in a wide wavelength range of 2000 to 2850 nm, and that transparency to light in this range can be ensured by a simple method that differs from the method of reducing hydroxy groups that has conventionally been used for silica glass.

[0115] (Refractive index measurement) A spectroscopic ellipsometer ("M-2000U", manufactured by JA Woollam) was used to measure the refractive index. The incident angle was in the range of 50 to 80°, and measurements were taken in the wavelength range of 250-1000 nm at 10° intervals. The number of measurements was 40, and the incident light polarization angle was 45°.

[0116] 9 shows the results of measuring the refractive index. Note that the spectrum is before thickness correction, and the thickness of each sample is listed in Table 8. From the results in FIG. 9, it was found that the sample of Example 1 ("Ex1", sintering temperature: 1600°C) had a refractive index of 1.63 or higher in the wavelength range of 400 to 700 nm. On the other hand, the sample of Comparative Example 2 (C2) had a refractive index of about 1.50 to 1.60, and the commercially available silica glass "R3" (thickness: 2.00 mm) had a refractive index of about 1.44 to 1.51. It was found that the sample of Example 1 ("Ex1") had a high refractive index over a wide wavelength range.

[0117] (Thermophysical property measurement) The specific heat, thermal diffusivity, and thermal conductivity were measured using a thermal diffusivity / thermal conductivity measuring device ("LFA447", manufactured by NETZSCH Japan KK). To prevent light transmission, the sample surface was coated with carbon spray before measurement. The obtained temperature rise curve was corrected for finite pulse width, and the thermal diffusivity α was calculated using the Cowan model. The specific heat capacity C p Pylex was used as the standard sample for the calculation of bulk density (kg / m 3 ) is ρ, and the thermal conductivity κ is given by the following formula: κ = αρC p The results are shown in Table 3.

[0118] [Table 3]

[0119] In Table 3, Reference Example 1 refers to the literature value (same as in Table 4) for silica glass ("ES", a synthetic quartz glass obtained by hydrolyzing and melting SiCl4 in an oxyhydrogen flame) manufactured by Tosoh Corporation. Also, Reference Example 2 refers to the literature value (same as in Table 4) for Si3N4 (SN-240) manufactured by Kyocera. Also, the values ​​in parentheses in the table are calculated values.

[0120] The results in Table 3 show that the sample of Example 1 has a larger specific heat, a larger thermal diffusivity, and a larger thermal conductivity than the samples of Comparative Example 2 and Reference Example 1.

[0121] (Young's modulus measurement) Young's modulus was measured using the ultrasonic pulse method. Ultrasonic waves (longitudinal and transverse waves) were propagated through a buffer rod attached to the sample, and the round-trip time of the waves (longitudinal wave time t l , shear wave time t t ) was read, and the wave propagation velocity (V = L / 2 × 1 / t) was calculated from the sample thickness L. Furthermore, the obtained wave propagation velocity was used to calculate the Poisson's ratio ν and the rigidity modulus G p , and Young's modulus E p was calculated, where ρ is the bulk density (kg / m 3 ), V l : longitudinal wave velocity (m / s), V t : is the speed of the shear wave (m / s).

number

[0122] (Vickers hardness measurement) Vickers hardness was measured using a micro Vickers hardness tester ("MVK-VL", manufactured by Akashi Seisakusho). A Vickers indenter was driven into the surface of the sample. The indentation load was 100 gf, and the loading time was 15 seconds. After unloading, the diagonal lines of the indentation were measured, and the Vickers hardness was calculated from the average value. The indentation was observed with an optical microscope ("ECLPSE LV100", manufactured by Nikon Solutions Co., Ltd.). Table 4 summarizes the results of the Young's modulus measurement and the Vickers hardness measurement.

[0123] [Table 4]

[0124] The results in Table 4 show that the sample of Example 1 has a higher modulus of rigidity, Young's modulus, and Vickers hardness than the samples of Comparative Example 2 and Reference Example 1, being approximately twice as high, and has excellent mechanical properties.

[0125] Table 7 shows the composition and physical property measurements of the sintered bodies obtained in each Example and Comparative Example. Table 8 shows the light transmittance measurements of the sintered bodies obtained in each Example and Comparative Example. FIG. 11 shows the transmission spectra of the silicon oxynitride glasses of Examples 2 to 4 measured by an ultraviolet-visible spectrophotometer. FIG. 12 shows the transmission spectra of the silicon oxynitride glasses of Examples 2 to 4 measured by a Fourier transform infrared spectrophotometer. In the figure, Examples 2 to 4 are denoted as "Ex2," "Ex3," and "Ex4," respectively. Note that some of the results overlap with those in Tables 2 to 4.

[0126] [Table 7]

[0127] [Table 8]

[0128] The results in Tables 7 and 8 reveal that the silicon oxynitride glasses of Examples 1 to 4 produced by SPS at temperatures above 1500° C. have a light transmittance of 65% or more at 2000 to 2500 μm. Furthermore, the silicon oxynitride glasses of Examples 1 to 4, which have a nitrogen content of 12.0 mass% or more, have a light transmittance of 65% or more at 2000 to 2500 μm.

[0129] The silicon oxynitride glass of Example 1, in which the SPS pressing force was 70 MPa or more, had better light transmittance (2000-2500 nm, more than 2500 nm to 2875 nm or less, 400-700 nm) than the silicon oxynitride glass of Example 2. [Explanation of symbols]

[0130] 11: electrode, 12: graphite punch, 13: graphite die, 14: carbon sheet, 15: DC power supply, 16: chamber, 20: sample, 30: optical waveguide, 31: core, 32: cladding, 40: infrared image furnace, 41: reflecting surface, 42, 43: 1 / 2 ellipsoidal mirror, 44: infrared light source, 45, 46, 55, 65: infrared light, 47, 54, 64: object, 50: temperature distribution measuring device, 51: objective lens, 52: display device, 53: infrared camera, 56: wireless transmission, 60: radiation thermometer, 61: bandpass filter, 62: infrared sensor, 63: anti-reflection coating

Claims

1. contacting the silica particles with ammonia gas under heating; and heating the silicon oxynitride particles obtained by the contacting to a temperature exceeding 1500°C by spark plasma sintering and sintering them at a pressing force of 70 MPa or more.

2. 2. The method for producing silicon oxynitride glass according to claim 1, wherein the average primary particle diameter of the silica particles is 1000 nm or less.

3. 2. The method for producing silicon oxynitride glass according to claim 1, wherein the silicon oxynitride particles have a mass ratio of nitrogen atom content to silicon atom content of 0.10 or more.

4. 2. The method for producing silicon oxynitride glass according to claim 1, wherein the silicon oxynitride glass contains 12.0 mass% or more of nitrogen and has a light transmittance of 65% or more at a thickness of 1.94 mm in a wavelength region of 2000 to 2500 nm.

5. A method for producing an optical waveguide that propagates infrared light, comprising the method for producing silicon oxynitride glass according to any one of claims 1 to 4.

6. A silicon oxynitride glass containing 12.0% by mass or more of nitrogen and having a light transmittance of 70% or more at a thickness of 1.94 mm in a wavelength range of 2000 to 2500 nm.

7. 7. The silicon oxynitride glass according to claim 6, which has a light transmittance of 50% or more at a thickness of 1.94 mm in the wavelength region of 400 to 700 nm.

8. 7. The silicon oxynitride glass according to claim 6, which has a thermal conductivity of 2.00 W / (m·K) or more.

9. 7. The silicon oxynitride glass according to claim 6, which has an optical transmittance of 65% or more at a thickness of 1.94 mm in the wavelength region of more than 2500 nm and not more than 2875 nm.

10. 7. The silicon oxynitride glass according to claim 6, which has a refractive index of 1.60 or more in the wavelength region of 400 to 700 nm.

11. 7. The silicon oxynitride glass according to claim 6, wherein the ratio of the nitrogen atom content to the silicon atom content on a mass basis is 0.27 or more.

12. 7. The silicon oxynitride glass according to claim 6, having a Young's modulus of 100 GPa or more.

13. An optical waveguide for propagating infrared light, comprising the silicon oxynitride glass according to any one of claims 6 to 12.

14. An infrared image furnace comprising the optical waveguide of claim 13.

15. A window material comprising the silicon oxynitride glass according to any one of claims 6 to 12.

16. An optical member comprising the silicon oxynitride glass according to any one of claims 6 to 12.

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