WO2025215729A1 - Black quartz glass, method for producing same, and member and product using same - Google Patents

Abstract

In a cross section of the glass structure of this black quartz glass, the number of pores having a pore diameter of 30 μm or more is 5/mm² or less. The method for producing the black quartz glass includes sintering a silica powder to which Si powder and SiO powder or only Si powder have been added in a predetermined ratio. The silica powder contains 10-40 mass% of fumed silica and 10-40 mass% of a first spherical silica having a predetermined D₅₀, with the balance being a second spherical silica having a predetermined D₅₀ larger than the D₅₀ of the first spherical silica, based on the total mass. The present invention can provide a black quartz glass having an excellent light-blocking property, excellent mechanical strength, heat resistance, and thermal shock resistance. The black quartz glass poses no risk of causing contamination in processes in which black quartz glass is used, can be made larger, and has sufficient color uniformity even when made larger. In addition, a method for producing the black quartz glass and a member and a product that use the black quartz glass are provided.

Description

Black quartz glass, its manufacturing method, and components and products that use it

The present invention relates to black quartz glass, its manufacturing method, and components and products that utilize it. More specifically, the present invention relates to black quartz glass that can be suitably used as a material for components (e.g., optical cells, light-blocking components, infrared absorbing components, and heat storage components) for various products (e.g., optical analysis equipment, semiconductor manufacturing equipment, and infrared heating equipment). It also relates to a method for efficiently manufacturing this black quartz glass and to products that include this black quartz glass as a component.

Quartz glass has excellent optical transparency from the ultraviolet to infrared ranges, heat resistance, chemical resistance, and a low coefficient of thermal expansion. Taking advantage of these advantages, it is used in a variety of applications, including lighting equipment, optical equipment, semiconductor manufacturing equipment, and scientific and chemical equipment.

In addition, black quartz glass is also known, which is obtained by adding trace amounts of transition metal oxides to the above-mentioned transparent quartz glass. Like ordinary transparent quartz glass, black quartz glass has excellent heat resistance, chemical resistance, and a low coefficient of thermal expansion, while also having light-blocking properties. Taking advantage of its light-blocking properties, black quartz glass is used in areas of equipment and devices where localized light blocking is required. Black quartz glass can be bonded to transparent quartz glass using bonding methods such as thermocompression bonding, and is used as a component for a variety of equipment and devices.

Furthermore, black quartz glass has excellent infrared absorption and heat storage properties, as well as high purity, and these advantages are utilized for its use as an infrared absorption or heat storage material in semiconductor manufacturing. Black quartz glass is placed in a position that shields items other than the object to be heated from infrared rays during the infrared heat treatment process in the semiconductor manufacturing process, absorbing the infrared rays and storing heat. This reduces contamination within the equipment while also reducing heating loss caused by items other than the object to be heated absorbing infrared rays and the heat leaking out.

In recent years, as components have become increasingly miniaturized and thinner, the light-blocking properties of conventional black quartz glass have sometimes become insufficient, creating a demand for black quartz glass with even greater light-blocking properties.

Black quartz glass is manufactured, for example, by the following method:

Patent Document 1 discloses a method for producing black quartz glass, in which quartz glass powder is mixed with niobium pentachloride, the niobium pentachloride is converted to niobium pentoxide, and then the mixture is heated to 1,800°C or higher to reduce and melt the mixture, thereby obtaining black quartz glass.

Patent Document 2 discloses a method for producing black quartz glass, in which a volatile organosilicon compound is subjected to a gas-phase reaction with porous silica glass, followed by heating and firing at a temperature of 1200°C or higher and 2000°C or lower, to obtain black quartz glass containing carbon derived from the organosilicon compound.

Patent Document 3 discloses a method for producing black quartz glass, in which fused silica powder, which is made by powdering fused quartz glass, is wet-mixed with a silicon-containing powder, the mixture is molded by a casting method, dried, and the resulting molded body is heated at a sintering temperature below the melting temperature of silicon, thereby obtaining black quartz glass in which elemental Si regions are embedded in a fused silica matrix.

In addition, Patent Document 4 discloses a colored sintered glass body in which carbon is dispersed as colored particles at a volume ratio of 0.1% to 30% in the matrix of the sintered glass body.

JP 2014-94864 A (claims and other details) JP 2013-1628 A (claims and other details) JP 2020-73440 A (claims and other details) JP 2003-146676 A (claims and other details)

However, the black quartz glass described in Patent Document 1 may not have sufficient color uniformity when it is made larger (for example, when producing ingots). Non-uniform color results in variations in light-blocking properties, which can lead to insufficient light-blocking properties. Furthermore, temperatures of 1,800°C or higher are required to produce black quartz glass, which requires the use of high-quality furnace and heater materials, and also requires a great deal of energy for heating, posing productivity challenges. In addition, the niobium compounds contained in black quartz glass may cause contamination in processes using black quartz glass, so the black quartz glass described in Patent Document 1 cannot be used in semiconductor manufacturing processes.

The black quartz glass described in Patent Document 2 may also lack sufficient color uniformity when enlarged. Furthermore, a non-oxidizing atmosphere is required to manufacture the black quartz glass, which complicates the furnace structure and makes the process cumbersome, making it difficult to improve productivity. Due to such a complex furnace structure, it is difficult to flexibly accommodate larger sizes of black quartz glass. Additionally, the carbon contained in the black quartz glass may cause contamination in processes in which the black quartz glass is used, making the black quartz glass described in Patent Document 2 unsuitable for use in semiconductor manufacturing processes.

The black quartz glass described in Patent Document 3 also sometimes lacks sufficient color uniformity when made into a large size, and due to the presence of micropores within the structure, it lacks strength, heat resistance, and thermal shock resistance during mechanical processing. Furthermore, limitations on slip casting make it difficult to make large-sized black quartz glass. Additionally, the slip casting and drying processes are cumbersome, making production time lengthy.

The black quartz glass described in Patent Document 4 may also lack sufficient color uniformity when enlarged. Furthermore, when enlarged, the black quartz glass described in Patent Document 4 poses a high risk of breakage when the molded body is sintered. Additionally, the carbon contained in the black quartz glass may cause contamination during processes in which the black quartz glass is used, making the black quartz glass described in Patent Document 4 unsuitable for use in semiconductor manufacturing processes.

The problem that this invention aims to solve is to provide black quartz glass that has excellent light-blocking properties, as well as excellent mechanical strength, heat resistance, and thermal shock resistance, that does not cause contamination in processes in which the black quartz glass is used, that can be made large, and that maintains sufficient color uniformity even when made large.

Another object of the present invention is to provide a method for producing black quartz glass that enables the black quartz glass of the present invention to be produced with excellent productivity and in large sizes.

A further object of the present invention is to provide a black quartz glass member manufactured from the black quartz glass of the present invention and a product containing the same.

As a result of extensive research to solve the above problems, the inventors discovered that by mixing silica powder containing fumed silica and multiple spherical silica particles with different small average particle sizes with Si powder and SiO powder or Si powder alone in specific ratios, and then sintering this mixed powder, it is possible to obtain black quartz glass that has excellent light-blocking properties as well as excellent mechanical strength, heat resistance, and thermal shock resistance. Furthermore, it was discovered that this black quartz glass does not cause contamination in processes in which it is used, can be made large, and maintains sufficient color uniformity even when made large, which led the inventors to complete the present invention.

The present invention is as follows.
[1]
A black quartz glass containing 0.5 to 10 parts by mass of Si and 0 to 5 parts by mass of SiO per 100 parts by mass of silica, wherein the glass structure is substantially free of pores, the number of pores having a diameter of 30 μm or more is 5/mm2 or ^less in a microscopic image of a cross section of the glass structure, and the SCE reflectance at wavelengths of 350 nm to 750 nm is 10% or less.
[2]
The black quartz glass according to [1], having a water absorption rate of 0.1% or less.
[3]
The black quartz glass according to [1] or [2], which has a density whose difference in density compared to the theoretical density is 1% or less in absolute value.
[4]
^{[1] The black quartz glass according to any one of [1] to [3], having a lightness L* of 30 or} less, an absolute value of chroma a ^* of 3.5 or less, and an absolute value of chroma b ^* of 4 or less in the L*a*b* color system.
[5]
The black quartz glass according to any one of [1] to [4], wherein the content of each of metal impurities in the black quartz glass is 1 ppm or less.
[6]
The black quartz glass according to any one of [1] to [5], which satisfies one or more of the following (a) to (i):
(a) the black quartz glass has a density of 2.19 to 2.30 g/cm ³ ;
(b) the black quartz glass has a specific heat of 1090 to 1130 J/kg·K at a temperature of 500°C;
(c) the black quartz glass has a thermal diffusivity of 7×10 ⁻⁷ to 8×10 ⁻⁷ m ² /s at a temperature of 500° C.;
(d) the black quartz glass has a thermal conductivity of 1.5 to 2.1 W/mK at a temperature of 500°C;
(e) the black quartz glass has a thermal expansion coefficient of 2×10 ⁻⁷ to 12×10 ⁻⁷ /°C in the range of 30°C to 600°C;
(f) the black quartz glass has a thickness of 1 mm and a light transmittance of 0.5% or less in the wavelength range of 200 to 3000 nm;
(g) In a machining test of black quartz glass, the number of chips having a maximum length of 0.5 mm or more is 1/100 ^cm2 or less, and the number of discolored areas having a maximum length of 1 mm or more is 1/100 ^cm2 or less.
Here, the machining test is carried out by polishing the surface of the black quartz glass to a roughness Ra of 0.8 μm.
(h) In a heating test of black quartz glass, the number of bubbles having a maximum length of 1 mm or more is 1/100 ^cm2 or less, and the number of discolored areas having a maximum length of 1 mm or more is 1/100 ^cm2 or less.
Here, the heating test is carried out by heating the black quartz glass at 1370°C for 3 hours.
(i) In a rapid cooling/thermal shock test of black quartz glass, the number of chips having a maximum length of 0.5 mm or more is 1/100 ^cm2 or less, and the mass change is 10 ppm or less;
Here, the quenching/thermal shock test is carried out by polishing both surfaces of a test piece measuring 75 mm square and 10 mm thick to a roughness Ra of 0.8 μm, heating the polished test piece at 900° C. for 30 minutes, and then immersing it in water at room temperature.
[7]
the silica portion in the glass structure is a sintered body of 10 to 40 mass% of fumed silica, 10 to 40 mass% of first spherical silica having a D ₅₀ of 0.05 to 3.0 μm, and the remaining second spherical silica having a D ₅₀ of 0.25 to 15 μm, based on the total mass of the silica portion;
The black quartz glass according to any one of [1] to [6], wherein the D ₅₀ of the second spherical silica is at least 5 times the D ₅₀ of the first spherical silica.
[8]
The first spherical silica has a _D10 that is 1/5 or more of the _D50 of the first spherical silica and a _D90 that is 10 times or less of the _D50 ,
The black quartz glass according to [7], wherein the second spherical silica has a _D10 of at least 1/5 of the _D50 of the second spherical silica and a _D90 of at most 10 times the _D50 .
[9]
At least a part of the Si in the glass structure is present as Si particles,
The black quartz glass according to any one of [1] to [8], wherein the Si particles have a particle size distribution in which D ₅₀ is 5 to 10 μm.
[10]
At least a part of the SiO in the glass structure is present as SiO particles,
The black quartz glass according to any one of [1] to [9], wherein the SiO particles have a particle size distribution in which D ₅₀ is 3 to 15 μm.
[11]
A method for producing the black quartz glass according to any one of [1] to [10],
Si powder and silica powder to which SiO powder has been added, or silica powder to which Si powder has been added, are mixed and compacted;
The powder obtained by mixing and compacting is then pressed to produce a pressed compact;
A manufacturing method comprising sintering a pressed compact in air at a maximum temperature of 1300 to 1400°C to obtain black quartz glass, wherein:
The amount of Si powder added is 0.5 to 10 parts by mass per 100 parts by mass of silica powder,
The amount of SiO powder added is 0 to 5 parts by mass per 100 parts by mass of silica powder,
The silica powder comprises, based on the total mass of the silica powder, 10 to 40 mass % of fumed silica, 10 to 40 mass % of a first spherical silica having a D ₅₀ of 0.05 to 3.0 μm, and the remaining second spherical silica having a D ₅₀ of 0.25 to 15 μm;
The _D50 of the second spherical silica is at least five times the _D50 of the first spherical silica.
[12]
The first spherical silica has a _D10 that is 1/5 or more of the _D50 of the first spherical silica and a _D90 that is 10 times or less of the _D50 ,
The method according to [11], wherein the second spherical silica has a _D10 of at least 1/5 of the _D50 of the second spherical silica and a _D90 of at most 10 times the _D50 .
[13]
The manufacturing method according to [11] or [12], wherein the Si powder has a particle size distribution in which D ₅₀ is 5 to 10 μm.
[14]
The method according to any one of [11] to [13], wherein the SiO powder has a particle size distribution in which _D50 is 3 to 15 μm.
[15]
[15] The method according to any one of [11] to [14], wherein the silica powder contains one or more types of spherical silica having different particle sizes other than the first and second spherical silica.
[16]
[16] The method according to any one of [11] to [15], wherein sintering is carried out for 0.5 to 5 hours.
[17]
The method according to any one of [11] to [16], wherein the fumed silica satisfies one or more of the following (i) to (iv):
(i) the fumed silica has a tapped bulk density of 0.03 to 0.08 g/cm ³ ;
(ii) the fumed silica has a BET specific surface area of 50 to 100 m ² /g;
(iii) the fumed silica has an OH group concentration of 0.5 to 1.0 mass %, and (iv) the content of metal impurities in the fumed silica is each 1 ppm or less.
[18]
[18] The method according to any one of [11] to [17], wherein the mixed compaction is carried out so that the tapped bulk density of the powder obtained by the mixed compaction is 5 to 20 times the tapped bulk density of the fumed silica.
[19]
A black quartz glass member manufactured from the black quartz glass according to any one of [1] to [10].
[20]
The black quartz glass member according to [19], which is an optical component, a light-shielding component, an infrared absorbing component, or a heat storage component.
[21]
The black quartz glass member according to [20], which is an optical component such as a spectroscopic cell, a projector reflector, or an optical fiber connector, or a light-shielding member for semiconductor manufacturing equipment or infrared heating equipment.
[22]
A product comprising the black quartz glass member according to any one of [19] to [21].

The present invention provides black quartz glass that has excellent light-blocking properties, as well as excellent mechanical strength, heat resistance, and thermal shock resistance. It does not cause contamination in processes in which the black quartz glass is used, can be made large, and maintains sufficient color uniformity even when made large.

According to another aspect of the present invention, a method for producing black quartz glass is provided that enables the black quartz glass of the present invention to be produced with excellent productivity and in large sizes.

Furthermore, according to another aspect of the present invention, there are provided black quartz glass members manufactured from the black quartz glass of the present invention and products containing the same.

1 is a microscope image of a cross section of the black quartz glass of Example 1. 1 is a microscope image of a cross section of the black quartz glass of Comparative Example 3.

[Black quartz glass]
The black quartz glass of the present invention is black quartz glass containing 0.5 to 10 parts by mass of Si and 0 to 5 parts by mass of SiO per 100 parts by mass of silica, and is black quartz glass that is substantially free of pores in its glass structure, has a microscopic image of a cross section of the glass structure in which the number of pores with a diameter of 30 μm or more is 5/mm2 or ^less , and has an SCE reflectance of 10% or less at wavelengths of 350 nm to 750 nm. As described below, the black quartz glass of the present invention is a sintered body of a mixed powder containing a major amount of silica ( _SiO2 ) powder and a small amount of Si (silicon) powder and optional SiO (silicon monoxide) powder, and has a glass structure in which Si regions and SiO regions (if present) are dispersed in a silica matrix region.

The Si content in the glass structure is 0.5 to 10 parts by mass per 100 parts by mass of silica. A Si content of 0.5 parts by mass or more sufficiently reduces the SCE reflectance, sufficiently reduces the lightness L ^* in the L ^* a ^* b ^* color system, and sufficiently reduces the absolute values of the saturations a ^* and b ^* , resulting in a blacker color tone and improved light-blocking properties. A Si content of 10 parts by mass or less does not inhibit sintering of the raw material powder in the manufacturing process of the black quartz glass, ensuring sufficient mechanical strength of the sintered black quartz glass of the present invention.

The Si content is preferably in the range of 1.0 to 5 parts by mass, more preferably 1.5 to 3 parts by mass.

At least a portion of the Si in the glass structure of the black quartz glass of the present invention is present as Si particles, and the Si particles preferably have a particle size distribution with a _D50 (volume-based median diameter) of 5 to 10 μm. When the _D50 of the Si particles is 5 μm or more, the absolute values of the saturations a ^* and b ^* become smaller, the color tone of the black quartz glass becomes darker, and the light-blocking properties are further improved. When the _D50 of the Si particles is 10 μm or less, the lightness L ^* and SCE reflectance become lower, resulting in black quartz glass with better light-blocking properties. Furthermore, sintering of the raw material powder in the manufacturing process of the black quartz glass is not inhibited, and the mechanical strength of the sintered black quartz glass of the present invention can be more sufficiently ensured.

The Si particles preferably have a particle size distribution in which _D10 is 1 μm or more and _D95 is 30 μm or less, and particularly preferably have a particle size distribution in which _D50 is 5 to 10 μm, _D10 is 1 μm or more and _D95 is 30 μm or less. When the Si particles have a _D10 of 1 μm or more and a _D95 of 30 μm or less, the absolute values of the saturations a ^* and b ^* tend to be smaller.

The _D50 of the Si particles is preferably 5.5 to 9.5 μm, more preferably 6.0 to 9.0 μm. The _D10 of the Si particles is preferably 2 μm or more, more preferably 3 μm or more. The _D95 of the Si particles is preferably 20 μm or less, more preferably 15 μm or less.

The SiO content in the glass structure is 0 to 5 parts by mass per 100 parts by mass of silica. SiO does not have to be present, but it is preferable for SiO to be present. By including SiO, the SCE reflectance can be further reduced, the lightness L ^* in the L ^* a ^* b ^* color system can be further reduced, and the absolute values of the saturations a ^* and b ^* can be further reduced, resulting in a blacker color tone of the black quartz glass and improved light-blocking properties. By keeping the SiO content at 5 parts by mass or less, sintering of the raw material powder in the manufacturing process of the black quartz glass is not inhibited, and the mechanical strength of the sintered black quartz glass of the present invention can be sufficiently ensured.

When the maximum sintering temperature in the manufacturing process for black quartz glass is 1300-1390°C, the SiO content is preferably in the range of 0.15-4.0 parts by mass, more preferably 0.20-3.0 parts by mass, and particularly preferably 0.30-2.0 parts by mass. When the maximum sintering temperature is 1390-1400°C, the SiO content is preferably in the range of 0-0.15 parts by mass, more preferably 0-0.10 parts by mass, and SiO may not be present.

When SiO is present in the glass structure of the black quartz glass of the present invention, at least a portion of the SiO is present as SiO particles, and the SiO particles preferably have a particle size distribution with a _D50 of 3 to 15 μm. When the _D50 of the SiO particles is 3 μm or more, the absolute values of the chroma a ^* and b ^* become smaller, the color tone of the black quartz glass becomes darker, and the light-blocking properties are further improved. When the _D50 of the SiO particles is 15 μm or less, the lightness L ^* and SCE reflectance become lower, resulting in black quartz glass with better light-blocking properties. Furthermore, sintering of the raw material powder in the manufacturing process of the black quartz glass is not inhibited, and the mechanical strength of the sintered black quartz glass of the present invention can be more sufficiently ensured.

The SiO particles preferably have a particle size distribution in which _D10 is 1 μm or more and _D90 is 35 μm or less, and particularly preferably have a particle size distribution in which _D50 is 3 to 15 μm, _D10 is 1 μm or more and _D90 is 35 μm or less. When the SiO particles have a _D10 of 1 μm or more and a _D90 of 35 μm or less, the absolute values of the saturations a ^* and b ^* tend to be smaller.

The _D50 of the SiO particles is preferably 4.5 to 13 μm, more preferably 5.0 to 11 μm. The _D10 of the SiO particles is preferably 2 μm or more, more preferably 3 μm or more. The _D90 of the Si particles is preferably 20 μm or less, more preferably 15 μm or less.

The remainder of the glass structure of the black quartz glass of the present invention, excluding Si and SiO, is silica.

The silica portion in the glass structure of the black quartz glass of the present invention is a sintered body of 10 to 40 mass% of fumed silica, 10 to 40 mass% of first spherical silica having a _D50 of 0.05 to 3.0 μm, and the remaining second spherical silica having a _D50 of 0.25 to 15 μm, based on the total mass of the silica portion, and the _D50 of the second spherical silica is preferably at least 5 times the _D50 of the first spherical silica.

In the black quartz glass of the present invention, pores are substantially absent in the glass structure. "Substantially absent" means that the number of pores having a diameter of 30 μm or more in a microscopic image of the cross section of the glass structure is 5/ ^mm2 or less. That is, in the black quartz glass of the present invention, the number of pores having a diameter of 30 μm or more in a microscopic image of the cross section of the glass structure is 5/ ^mm2 or less. By limiting the number of pores in the cross section of the glass structure to 5/ ^mm2 or less, the number of pores that can serve as starting points for mechanical or thermal fracture is reduced, and the black quartz glass of the present invention exhibits excellent mechanical strength, heat resistance, and thermal shock resistance.

The number of pores in the cross section of the glass structure is preferably as small as possible from the viewpoint of obtaining better mechanical strength, heat resistance, and thermal shock resistance, and is preferably 4 pores/ ^mm2 or less, more preferably 2 pores/mm2 or ^less , even more preferably 1 pore/ ^mm2 or less, and most preferably 0 pores/ ^mm2 .

The black quartz glass of the present invention has an SCE reflectance of 10% or less at wavelengths of 350 nm to 750 nm. SCE reflectance is measured in accordance with JIS Z8722. With an SCE reflectance of 10% or less, the black quartz glass of the present invention exhibits excellent light-blocking properties.

In order to obtain better light-blocking properties, it is preferable that the SCE reflectance is lower, preferably 9% or less, and more preferably 8% or less. There is no particular restriction on the lower limit of the SCE reflectance, and it can be 1% or more or 2% or more.

The black quartz glass of the present invention preferably has a water absorption rate of 0.1% or less. Water absorption rate is another index for evaluating the number of pores in the black quartz glass; the lower the water absorption rate, the fewer the number of pores in the black quartz glass. With a water absorption rate of 0.1% or less, the black quartz glass of the present invention exhibits superior mechanical strength, heat resistance, and thermal shock resistance.

In order to obtain better mechanical strength, heat resistance, and thermal shock resistance, it is preferable that the water absorption rate is as low as possible, preferably 0.05% or less, and more preferably 0.01% or less. There is no particular lower limit for the water absorption rate, and it can be 0.001% or more or 0.002% or more.

The black quartz glass of the present invention preferably has a density where the difference in density compared to the theoretical density is 1% or less, expressed as an absolute value. The difference in density compared to the theoretical density is another index for evaluating the number of pores in the black quartz glass; the smaller the density difference, the fewer the number of pores in the black quartz glass. Theoretical density refers to the density of ideal glass calculated from the density of pure quartz glass and the amount of added Si and SiO; detailed calculation methods are explained in the examples. With a density difference of 1% or less, expressed as an absolute value, the black quartz glass of the present invention exhibits superior mechanical strength, heat resistance, and thermal shock resistance.

In order to obtain better mechanical strength, heat resistance, and thermal shock resistance, it is preferable that the density difference be as low as possible, preferably 0.5% or less, and more preferably 0.1% or less. There is no particular lower limit to the density difference, and it can be 0.01% or more or 0.02% or more.

In the black quartz glass of the present invention, from the viewpoint of obtaining particularly excellent mechanical strength, heat resistance, and thermal shock resistance, it is preferable that the number of pores in the cross section of the glass structure is 5 pores/ ^mm2 or less, the water absorption is 0.1% or less, and the density difference compared to the theoretical density is 1% or less in absolute value.

The black quartz glass of the present invention preferably has a lightness L ^* of 30 or less in the L ^* a ^* b ^* color system. A lightness L ^* of 30 or less not only prevents color unevenness, but also allows the black quartz glass to exhibit a sufficient black color without light transmission, stray light, or scattering. Additionally, the black quartz glass of the present invention preferably has an absolute value of chroma a ^* of 3.5 or less and an absolute value of chroma b ^* of 4 or less in the L ^* a ^* b ^* color system. By having the lightness L ^* , chroma a ^* , and b ^* within the above ranges, the color tone of the black quartz glass of the present invention becomes darker, and the black quartz glass can have a lower SCE reflectance.

From the viewpoint of obtaining a blacker color tone, the lightness L ^* is preferably 28 or less, more preferably 20 or less. The lower limit of the lightness L ^* is not particularly limited and may be 15 or more, or 16 or more. From the viewpoint of obtaining a blacker color tone, the absolute value of the chroma a ^* is preferably 2.8 or less, more preferably 2.5 or less. The lower limit of the absolute value of the chroma a ^* is not particularly limited and may be 1.8 or more, or 2.0 or more. From the viewpoint of obtaining a blacker color tone, the absolute value of the chroma b ^* is preferably 3.8 or less, more preferably 3.7 or less. The lower limit of the absolute value of the chroma b ^* is not particularly limited and may be 3.0 or more, or 3.5 or more.

The content of metal impurities in the black quartz glass of the present invention is preferably 1 ppm or less by mass. Silicon (Si), which constitutes the black quartz glass of the present invention, is not included in the meaning of "metal impurity." Having a content of metal impurities of 1 ppm or less reduces the risk of the black quartz glass becoming a source of contamination in various processes that use the black quartz glass (e.g., semiconductor production lines). Furthermore, even when the black quartz glass of the present invention is used as a component of an optical analysis device, there is no adverse effect on the accuracy of the optical analysis because there is no influence from fluorescence generated by metal impurities. The content of metal impurities can be analyzed using methods such as atomic absorption analysis, for example.

The black quartz glass of the present invention preferably satisfies one or more of the following (a) to (i), more preferably two or more, three or more, or four or more, and most preferably all of them, thereby further improving the light-shielding properties, mechanical strength, heat resistance, and thermal shock resistance, and further improving the performance as a component:
(a) the black quartz glass has a density of 2.19 to 2.30 g/cm ³ ;
(b) the black quartz glass has a specific heat of 1090 to 1130 J/kg·K at a temperature of 500°C;
(c) the black quartz glass has a thermal diffusivity of 7×10 ⁻⁷ to 8×10 ⁻⁷ m ² /s at a temperature of 500° C.;
(d) the black quartz glass has a thermal conductivity of 1.5 to 2.1 W/mK at a temperature of 500°C;
(e) the black quartz glass has a thermal expansion coefficient of 2×10 ⁻⁷ to 12×10 ⁻⁷ /°C in the range of 30°C to 600°C;
(f) the black quartz glass has a thickness of 1 mm and a light transmittance of 0.5% or less in the wavelength range of 200 to 3000 nm;
(g) In a machining test of black quartz glass, the number of chips having a maximum length of 0.5 mm or more is 1/100 ^cm2 or less, and the number of discolored areas having a maximum length of 1 mm or more is 1/100 ^cm2 or less.
Here, the machining test is carried out by polishing the surface of the black quartz glass to a roughness Ra of 0.8 μm.
(h) In a heating test of black quartz glass, the number of bubbles having a maximum length of 1 mm or more is 1/100 ^cm2 or less, and the number of discolored areas having a maximum length of 1 mm or more is 1/100 ^cm2 or less.
Here, the heating test is carried out by heating the black quartz glass at 1370°C for 3 hours.
(i) In a rapid cooling/thermal shock test of black quartz glass, the number of chips having a maximum length of 0.5 mm or more is 1/100 ^cm2 or less, and the mass change is 10 ppm or less;
Here, the quenching/thermal shock test is carried out by polishing both surfaces of a test piece measuring 75 mm square and 10 mm thick to a roughness Ra of 0.8 μm, heating the polished test piece at 900° C. for 30 minutes, and then immersing it in water at room temperature.

(a)
The black quartz glass of the present invention preferably has a density of 2.19 to 2.30 g/ ^cm3 . With a density within this range, the density of the black quartz glass is close to the theoretical density, the number of pores in the black quartz glass is reduced, and better mechanical strength, heat resistance, and thermal shock resistance are obtained. The density is preferably in the range of 2.17 to 2.27 g/ ^cm3 , and more preferably in the range of 2.18 to 2.25 g/ ^cm3 .

(b)
The black quartz glass of the present invention preferably has a specific heat of 1090 to 1130 J/kg K at a temperature of 500° C. The specific heat at a temperature of 500° C. can be measured by differential scanning calorimetry (DSC). The specific heat is preferably in the range of 1095 J/kg K or more and 1120 J/kg K or less, and more preferably in the range of 1100 J/kg K or more and 1114 J/kg K or less.

(c)
The black quartz glass of the present invention preferably has a thermal diffusivity of 7×10 ⁻⁷ to 8×10 ⁻⁷ m ² /s at a temperature of 500° C. The thermal diffusivity at a temperature of 500° C. can be measured by the flash method in accordance with JIS R1611. The thermal diffusivity is preferably in the range of 7.2×10 ⁻⁷ m ² /s or more and 7.9×10 ⁻⁷ m ² /s or less, and more preferably in the range of 7.4×10 ⁻⁷ m ² /s or more and 7.6×10 ⁻⁷ m ² /s or less.

(d)
The black quartz glass of the present invention preferably has a thermal conductivity of 1.5 to 2.1 W/mK at a temperature of 500°C. The thermal conductivity at a temperature of 500°C can be calculated by multiplying the density of the sintered body by the specific heat and the thermal diffusivity. The thermal conductivity is preferably in the range of 1.6 W/mK or more and 2.0 W/mK or less, and more preferably in the range of 1.7 W/mK or more and 1.9 W/mK or less.

(e)
The black quartz glass of the present invention preferably has a thermal expansion coefficient of 2×10 ⁻⁷ to 12×10 ⁻⁷ /°C in the temperature range of 30°C to 600°C. The thermal expansion coefficient at temperatures of 30°C to 600°C can be measured by thermomechanical analysis (TMA). The thermal expansion coefficient is preferably in the range of 4×10 ⁻⁷ /°C or more and 11×10 ⁻⁷ /°C or less, and more preferably in the range of 6×10 ⁻⁷ /°C or more and 10×10 ⁻⁷ /°C or less.

(f)
The black quartz glass of the present invention preferably has a light transmittance of 0.5% or less at a wavelength of 200 to 3000 nm at a thickness of 1 mm. The light transmittance at a wavelength of 200 to 3000 nm is measured using a spectrophotometer. With a light transmittance of 0.5% or less, the black quartz glass exhibits better light-blocking properties. From the viewpoint of obtaining better light-blocking properties, the light transmittance is preferably low, preferably 0.4% or less, and more preferably 0.3% or less. The lower limit of the light transmittance is not particularly limited, and can be 0.01% or more, or 0.1% or more.

(g)
In a machining test of the black quartz glass of the present invention, it is preferable that the number of chippings (depressions due to chipping) having a maximum length of 0.5 mm or more is 1/100 ^cm2 or less, and the number of discolored areas having a maximum length of 1 mm or more is 1/100 ^cm2 or less. By keeping the number of chippings and discolored areas at 1/100 ^cm2 or less, better mechanical strength, heat resistance, and thermal shock resistance can be obtained. Details of the machining test will be explained in the examples.

The number of chippings occurring is preferably 0.5 chips/100 ^cm2 or less, more preferably 0.1 chips/100 ^cm2 or less. There is no particular limit on the lower limit of the number of chippings occurring, and it is preferable that no chipping occurs. The number of discolored areas occurring is preferably 0.5 chips/100 ^cm2 or less, more preferably 0.1 chips/100 ^cm2 or less. There is no particular limit on the lower limit of the number of discolored areas occurring, and it is preferable that no discolored areas occur.

(h)
In a heating test of the black quartz glass of the present invention, it is preferable that the number of bubbles having a maximum length of 1 mm or more is 1/100 ^cm2 or less, and the number of discolored areas having a maximum length of 1 mm or more is 1/100 ^cm2 or less. By keeping the number of bubbles and discolored areas at ^{1/100 cm2} or less, better mechanical strength, heat resistance, and thermal shock resistance can be obtained. Details of the heating test will be explained in the examples.

The number of bubbles generated is preferably 0.5 bubbles/100 ^cm2 or less, more preferably 0.1 bubbles/100 ^cm2 or less. There is no particular restriction on the lower limit of the number of bubbles generated, and it is preferable that no bubbles are generated. The number of discolored areas generated is preferably 0.5 bubbles/100 ^cm2 or less, more preferably 0.1 bubbles/100 ^cm2 or less. There is no particular restriction on the lower limit of the number of discolored areas generated, and it is preferable that no discolored areas are generated.

(i)
In a quenching/thermal shock test of the black quartz glass of the present invention, it is preferable that the number of chips having a maximum length of 0.5 mm or more is 1 chip/100 ^cm2 or less and the mass change is 10 ppm or less. By keeping the number of chips 1 chip/100 ^cm2 or less and the mass change 10 ppm or less, better mechanical strength, heat resistance, and thermal shock resistance can be obtained. Details of the quenching/thermal shock test will be explained in the examples.

The number of chippings occurring is preferably 0.5 chips/100 ^cm2 or less, more preferably 0.1 chips/100 ^cm2 or less. There is no particular limit on the lower limit of the number of chippings occurring, and it is preferable that no chipping occurs. The mass change is preferably 8 ppm or less, more preferably 6 ppm or less, and even more preferably 4 ppm or less. There is no particular limit on the lower limit of the mass change, and it can be 0.5 ppm or more or 1 ppm or more.

The black quartz glass of the present invention has a thermal expansion coefficient as small as that of regular quartz glass when used in high-temperature environments requiring dimensional accuracy, and its other thermal properties are also comparable to those of regular quartz glass. Therefore, the black quartz glass of the present invention can be used in the same environments as regular quartz glass.

The black quartz glass of the present invention is particularly useful as a spectroscopic cell for optical analysis, a projector reflector, an optical fiber connector, or as a light-shielding material, infrared-absorbing material, or heat-storing material for semiconductor manufacturing equipment or infrared heating equipment. However, the uses of black quartz glass are not limited to these materials.

Because the black quartz glass of the present invention does not contain metal impurities, it is useful as a component of heat treatment equipment used in semiconductor manufacturing. For example, in a wafer heat treatment equipment, by constructing all parts other than the infrared-transmitting window out of the black quartz glass of the present invention, it is possible to efficiently block heat radiating outside the furnace. As a result, energy efficiency is improved and the temperature distribution within the furnace is made more uniform.

The black quartz glass of the present invention can be produced by the manufacturing method of the present invention described below.

[Method of manufacturing black quartz glass]
The method for producing the black quartz glass of the present invention is as follows.
Si powder and silica powder to which SiO powder has been added, or silica powder to which Si powder has been added, are mixed and compacted;
The powder obtained by mixing and compacting is then pressed to produce a pressed compact;
A manufacturing method comprising sintering a pressed compact in air at a maximum temperature of 1300 to 1400°C to obtain black quartz glass, wherein:
The amount of Si powder added is 0.5 to 10 parts by mass per 100 parts by mass of silica powder,
The amount of SiO powder added is 0 to 5 parts by mass per 100 parts by mass of silica powder,
The silica powder comprises, based on the total mass of the silica powder, 10 to 40 mass % of fumed silica, 10 to 40 mass % of a first spherical silica having a D ₅₀ of 0.05 to 3.0 μm, and the remaining second spherical silica having a D ₅₀ of 0.25 to 15 μm;
The _D50 of the second spherical silica is at least five times the _D50 of the first spherical silica.

Si powder refers to powder of elemental silicon, and SiO powder refers to powder of silicon monoxide.

Fumed silica is a finely powdered silica obtained by burning silicon tetrachloride gas or similar in the gas phase.

Spherical silica is not particularly limited as long as it is spherical in shape and has a particle size within the above-mentioned range, and may be silica powder synthesized by either a dry method or a wet method. Dry-synthesized silica powders include spherical, high-purity synthetic fused silica obtained by reacting silicon tetrachloride gas or the like in the gas phase. Wet-synthesized silica powders include silica obtained by hydrolyzing and condensing silicon alkoxide in water or a mixed medium containing water and an organic solvent to produce a silica cake, which is then calcined. Synthetic fused silica is preferred as the spherical silica due to the high circularity of the silica particles.

The manufacturing method of the present invention makes it possible to provide black quartz glass that has excellent light-blocking properties, as well as excellent mechanical strength, heat resistance, and thermal shock resistance. It does not cause contamination in the processes in which the black quartz glass is used, can be made into large sizes, and maintains sufficient color uniformity even when made into large sizes. The reasons for this are unclear, but are thought to be as follows.

The black quartz glass of the present invention is a sintered body of silica powder to which Si powder and SiO powder have been added, or a sintered body of silica powder to which Si powder has been added, and has a glass structure in which Si regions and SiO regions (if present) are dispersed in a silica matrix region. Due to the presence of Si and SiO regions or Si regions dispersed in the matrix region, the black quartz glass has an SCE reflectance of 10% or less and exhibits excellent light-blocking properties. The color uniformity of the black quartz glass can be sufficiently ensured by thoroughly mixing the raw material powders before sintering.

Fume silica typically has a small particle size of 10 to 30 nm, has a very low bulk density, and is unsuitable for granulation or molding. The density of the sintered body obtained by sintering fumed silica is low and is not satisfactory as quartz glass. In contrast, in the present invention, fumed silica is mixed with silica powders (first and second spherical silica) having larger particle sizes. The fumed silica functions as a sintering agent, filling the gaps between the silica powders having larger particle sizes and promoting the sintering of the silica powders, thereby suppressing the generation of pores in the sintered body.

Furthermore, the silica powder, which has a particle size larger than that of fumed silica, contains multiple types of spherical silica powder that have small average particle sizes and are different from one another. This further reduces the gaps between the silica powder that forms the matrix of the sintered body, suppressing the generation of pores in the sintered body.

As a result of the suppression of pore formation in the sintered body as described above, it is believed that a sintered body was obtained that was essentially pore-free and had a density that closely matched the theoretical density. Because there are essentially no pores that could serve as starting points for mechanical or thermal destruction, the black quartz glass of the present invention exhibits excellent mechanical strength, heat resistance, and thermal shock resistance.

In addition, the black quartz glass of the present invention is composed essentially of silicon and oxygen and does not contain elements that have a significant impact as impurities in the semiconductor manufacturing process (such as transition metals and carbon), so there is no risk of it causing contamination. Furthermore, the black quartz glass of the present invention can be manufactured simply by molding the powder into the desired shape and sintering it at 1,400°C or less, which simplifies the manufacturing process and allows for energy-saving production. Therefore, the black quartz glass of the present invention can be flexibly manufactured in larger sizes and can be manufactured with good productivity.

The manufacturing method of the present invention has the advantage that it can be carried out at a relatively low temperature range, with a maximum temperature of 1300 to 1400°C. Normally, when manufacturing quartz glass by sintering, eliminating pores within the glass structure requires raising the maximum temperature to approximately 1800°C, melting at least a portion of the raw materials, and removing air bubbles. If raw material powder to which Si powder and SiO powder have been added is heated to 1800°C, the Si and SiO will melt and be oxidized to the surrounding silica (SiO ₂ ), resulting in a non-black quartz glass. However, the manufacturing method of the present invention surprisingly allows sintering at a relatively low temperature range where Si and SiO do not melt. This is thought to be because the raw material powder for sintering is composed of a specific mixed powder, i.e., a mixed powder in which Si powder and SiO powder, or Si powder alone, are added at specific concentrations to and mixed with a silica powder containing fumed silica, first spherical silica, and second spherical silica.

Furthermore, with the manufacturing method of the present invention, the presence of fine fumed silica in the gaps between the silica powder makes the structure of the sintered body more uniform, and the heating time to the maximum temperature can be shortened.

The manufacturing method of the present invention will be described below.
The manufacturing method of the present invention involves mixing and consolidating Si powder and silica powder to which SiO powder has been added, or silica powder to which Si powder has been added.

The amount of Si powder added is 0.5 to 10 parts by mass per 100 parts by mass of silica powder. When the amount of Si powder added is 0.5 parts by mass or more, the SCE reflectance is sufficiently reduced, the lightness L ^* in the L ^* a ^* b ^* color system is sufficiently reduced, and the absolute values of the saturations a ^* and b ^* can be sufficiently reduced, resulting in a blacker color tone of the black quartz glass and improved light-blocking properties. When the amount of Si powder added is 10 parts by mass or less, sintering of the raw material powder in the black quartz glass manufacturing process is not inhibited, and the mechanical strength of the sintered black quartz glass of the present invention can be sufficiently ensured.

The amount of Si powder added is preferably 1.0 to 6.0 parts by mass, and more preferably 1.5 to 4.0 parts by mass.

The Si powder preferably has a particle size distribution with a _D50 of 5 to 10 μm. When the _D50 of the Si powder is 5 μm or more, the absolute values of the saturations a ^* and b ^* become smaller, the color tone of the black quartz glass becomes darker, and the light-blocking properties are further improved. When the _D50 of the Si powder is 10 μm or less, the lightness L ^* and SCE reflectance become lower, resulting in black quartz glass with better light-blocking properties. Furthermore, sintering of the raw material powder in the manufacturing process of the black quartz glass is not inhibited, and the mechanical strength of the sintered black quartz glass of the present invention can be more sufficiently ensured.

The Si powder preferably has a particle size distribution in which _D10 is 1 μm or more and _D95 is 30 μm or less, and particularly preferably has a particle size distribution in which _D50 is 5 to 10 μm, _D10 is 1 μm or more and _D95 is 30 μm or less. When the Si powder has a _D10 of 1 μm or more and a _D95 of 30 μm or less, the absolute values of the saturations a ^* and b ^* tend to be smaller.

The _D50 of the Si powder is preferably 5.5 to 9.5 μm, more preferably 6.0 to 9.0 μm. The _D10 of the Si powder is preferably 2 μm or more, more preferably 3 μm or more. The _D95 of the Si powder is preferably 20 μm or less, more preferably 15 μm or less.

The amount of SiO powder added is 0 to 5 parts by mass per 100 parts by mass of silica powder. While SiO powder does not necessarily have to be added, it is preferable to add SiO powder. Adding SiO powder further reduces the SCE reflectance, further reduces the lightness L ^* in the L ^* a ^* b ^* color system, and further reduces the absolute values of the saturations a ^* and b ^* . As a result, the color tone of the black quartz glass becomes darker and the light-blocking properties are improved. By adding SiO powder in an amount of 5 parts by mass or less, sintering of the raw material powder in the manufacturing process of the black quartz glass is not inhibited, and the mechanical strength of the sintered black quartz glass of the present invention can be sufficiently ensured.

When the maximum sintering temperature in the manufacturing process for black quartz glass is 1300-1390°C, the amount of SiO powder added is preferably in the range of 0.15-4.0 parts by mass, more preferably 0.20-3.0 parts by mass, and particularly preferably 0.30-2.0 parts by mass. When the maximum temperature is 1390-1400°C, the amount of SiO powder added is preferably in the range of 0-0.15 parts by mass, more preferably 0-0.10 parts by mass, and SiO powder need not be added.

When SiO powder is added, the SiO powder preferably has a particle size distribution with a _D50 of 3 to 15 μm. When the _D50 of the SiO powder is 3 μm or more, the absolute values of the chroma a ^* and b ^* become smaller, the color tone of the black quartz glass becomes darker, and the light-blocking properties are further improved. When the _D50 of the SiO powder is 15 μm or less, the lightness L ^* and SCE reflectance become lower, resulting in black quartz glass with better light-blocking properties. Furthermore, sintering of the raw material powder in the manufacturing process of the black quartz glass is not inhibited, and the mechanical strength of the sintered black quartz glass of the present invention can be more sufficiently ensured.

The SiO powder preferably has a particle size distribution in which _D10 is 1 μm or more _{and D90} is 35 μm or less, and particularly preferably has a particle size distribution in which _D50 is 3 to 15 μm, _D10 is 1 μm or more and _D90 is 35 μm or less. When the SiO powder has a _D10 of 1 μm or more and a _D90 of 35 μm or less, the absolute values of the chroma a ^* and b ^* tend to be smaller.

The _D50 of the SiO powder is preferably 4.5 to 13 μm, more preferably 5.0 to 11 μm. The _D10 of the SiO powder is preferably 2 μm or more, more preferably 3 μm or more. The _D90 of the Si powder is preferably 20 μm or less, more preferably 15 μm or less.

The silica powder contains, based on the total mass of the silica powder, 10 to 40 mass% fumed silica, 10 to 40 mass% first spherical silica having a _D50 of 0.05 to 3.0 μm, and the remaining second spherical silica having a _D50 of 0.25 to ₁₅ μm, with the _D50 of the second spherical silica being at least five times that of the first spherical silica. By ensuring that the content of each silica material falls within the above ranges, the number of pores in the glass structure is reduced. Furthermore, the resulting sintered body exhibits superior light-shielding properties, can be sintered at relatively low temperatures, the structure of the sintered body is more uniform, the heating time to the maximum temperature during sintering is shortened, and sufficient strength is easily obtained even when the black quartz glass is large. The silica powder may contain multiple types of first spherical silica. Alternatively, the first spherical silica may be a mixed powder of multiple types of spherical silica, with an overall _D50 in the range of 0.05 to 3.0 μm. The silica powder may contain multiple types of second spherical silica, or the second spherical silica may be a mixed powder of multiple types of spherical silica, with a _D50 of 0.25 to 15 μm as a whole.

The content of fumed silica is preferably 13 to 35% by mass, and more preferably 15 to 30% by mass. This further reduces the number of pores in the glass structure, resulting in better light-blocking properties, enabling sintering at relatively low temperatures, and making it easier to obtain sufficient strength even when the black quartz glass is large. For similar reasons, the content of the first spherical silica is preferably 13 to 35% by mass, and more preferably 15 to 30% by mass. The content of the second spherical silica is the remainder of the silica material and is adjusted as appropriate.

In the manufacturing method of the present invention, the silica powder may contain spherical silica other than the first and second spherical silicas, i.e., one or more types of spherical silica having different particle sizes and a _D50 of less than 0.05 μm or more than 15 μm (each type is referred to as a third spherical silica, a fourth spherical silica, ..., an nth spherical silica). When the silica powder contains the third to nth spherical silicas, the content of the second spherical silica is the remainder excluding the total content of the fumed silica, the first spherical silica, and the third to nth spherical silicas. For example, the total content of the third to nth spherical silicas is preferably 0 to 20 mass%, and more preferably 0 to 10 mass%, based on the total mass of the silica powder. From the viewpoints of suppressing the generation of pores in the glass structure and further improving the handleability of the silica material, it is preferable that the silica powder does not contain spherical silica having a _D50 of less than 0.05 μm or more than 15 μm.

In addition, in the manufacturing method of the present invention, it is preferable that the silica powder does not include amorphous granular silica powder synthesized by a wet method (such as a precipitation method, gel method, or hydrolysis method). Silica powder synthesized by a wet method is usually non-spherical and has a relatively large particle size, which makes it easy for gaps to form between the silica particles and pores to form in the glass structure.

The first spherical silica preferably has a _D50 of 0.05 to 0.2 μm. This further reduces the number of pores in the glass structure, resulting in better light-blocking properties, enabling sintering at relatively low temperatures, and making it easier to obtain sufficient strength even when the black quartz glass is large. The _D50 of the first spherical silica is more preferably 0.08 to 0.18 μm, and even more preferably 0.10 to 0.17 μm.

The first spherical silica preferably has a _D10 of at least 1/5 of the _D50 of the first spherical silica and a _D90 of at most 10 times the _D50 . This further reduces the number of pores in the glass structure, resulting in better light-blocking properties, enabling sintering at relatively low temperatures, and making it easier to obtain sufficient strength even when the black quartz glass is large. The _D10 of the first spherical silica is more preferably at least 1/4 of the _D50 of the first spherical silica, and even more preferably at least 1/3 of the D50 of the first spherical silica. The _D90 of the first spherical silica is more preferably at most 7 times the D50 of the first spherical silica, and even more preferably at most 6 times the _D50 of the first spherical silica.

In one embodiment, the first spherical silica preferably has a _D10 of 0.03 μm or more and a _D90 of 0.3 μm or less. In particular, the _D10 of the first spherical silica is preferably 0.04 μm or more, more preferably 0.05 μm or more. The _D90 of the first spherical silica is preferably 0.25 μm or less, more preferably 0.23 μm or less.

The second spherical silica preferably has a _D50 of 0.30 to 14 μm. This reduces the number of pores in the glass structure, provides better light-blocking properties, allows sintering at relatively low temperatures, and makes it easier to obtain sufficient strength even when the black quartz glass is large. The _D50 of the second spherical silica is more preferably 0.50 to 12 μm, and even more preferably 0.70 to 11 μm.

The second spherical silica preferably has a _D10 of at least 1/5 of the _D50 of the second spherical silica and a _D90 of at most 10 times the _D50 . This further reduces the number of pores in the glass structure, resulting in better light-blocking properties, enabling sintering at relatively low temperatures, and making it easier to obtain sufficient strength even when the black quartz glass is large. The _D10 of the second spherical silica is more preferably at least 1/4 of the _D50 of the second spherical silica, and even more preferably at least 1/3 of the D50 of the second spherical silica. The _D90 of the second spherical silica is more preferably at most 7 times the D50 of the second spherical silica, and even more preferably at most 6 times the _D50 of the second spherical silica.

When the _D50 of the second spherical silica is 5 to 15 μm, the second spherical silica preferably has a _D10 of 1 μm or more and a _D90 of 70 μm or less. In particular, the _D10 of the second spherical silica is preferably 1.5 μm or more, more preferably 2.0 μm or more. The _D90 of the second spherical silica is preferably 65 μm or less, more preferably 60 μm or less.

When the _D50 of the second spherical silica is 0.25 to 5 μm, the second spherical silica preferably has a _D10 of 0.05 μm or more and a _D90 of 25 μm or less. In particular, the _D10 of the second spherical silica is preferably 0.08 μm or more, more preferably 0.10 μm or more. The _D90 of the second spherical silica is preferably 20 μm or less, more preferably 15 μm or less.

In the manufacturing method of the present invention, the _D50 of the second spherical silica is at least 5 times the _D50 of the first spherical silica. This further reduces the number of pores in the glass structure, resulting in better light-blocking properties, enabling sintering at relatively low temperatures, and making it easier to obtain sufficient strength even when the black quartz glass is large. From the viewpoint of improving the handleability of the silica material, the _D50 of the second spherical silica is at most 300 times the _D50 of the first spherical silica. The _D50 of the second spherical silica is preferably at least 7 times, at least 8 times, at least 9 times, at least 10 times, at least 20 times, or at least 30 times the _D50 of the first spherical silica, and may be at least 40 times, at least 50 times, at least 55 times, at least 60 times, or at least 65 times. The _D50 of the second spherical silica is preferably 250 times or less, ₂₀₀ times or less, or 150 times or less, and may be 140 times or less, 130 times or less, 120 times or less, 110 times or less, or 100 times or less, of the D50 of the first spherical silica.

The fumed silica preferably satisfies one or more of the following (i) to (iv), more preferably two or more or three or more, and most preferably all of them, which further reduces the number of pores in the glass structure, provides better light-shielding properties, allows sintering at relatively low temperatures, and makes it easier to obtain sufficient strength even when the black quartz glass is large.
(i) the fumed silica has a tapped bulk density of 0.03 to 0.08 g/cm ³ ;
(ii) the fumed silica has a BET specific surface area of 50 to 100 m ² /g;
(iii) the fumed silica has an OH group concentration of 0.5 to 1.0 mass %, and (iv) the content of metal impurities in the fumed silica is each 1 ppm or less.

Powder mixing and consolidation is carried out by uniformly mixing dry, agglomerated Si powder and silica powder with SiO powder or Si powder alone. During this mixing, smaller particles fill the gaps between larger particles, simultaneously consolidating the powder. In the present invention, this operation is called "mixing and consolidation" because consolidation occurs simultaneously with mixing. As a result of mixing and consolidation, a mixed powder for pressure molding is obtained.

Mixing and compaction is preferably carried out so that the tapped bulk density of the mixed powder obtained by mixing and compaction is 5 to 20 times the tapped bulk density of the fumed silica. When the tapped bulk density of the mixed powder is 5 or more times the tapped bulk density of the fumed silica, the density of the sintered body tends to be higher. When the tapped bulk density of the mixed powder is 20 or less times the tapped bulk density of the fumed silica, the strength of the molded body is less likely to decrease. The tapped bulk density of the mixed powder is preferably 6 to 15 times, and more preferably 7 to 10 times, the tapped bulk density of the fumed silica. The tapped bulk density of the mixed powder can be controlled by adjusting the blending of the raw materials and mixing conditions such as the powder mixing method and mixing time. Mixing and compaction can be carried out using common mixing equipment such as an agitator mixer, ball mill, rocking mixer, cross mixer, or V-type mixer.

The manufacturing method of the present invention involves press-molding the powder obtained by mixing and consolidating to produce a pressed compact.

The mixed powder obtained by mixing and consolidating can be pressure-molded into the desired shape. Any method known in the ceramics field can be used as the pressure-molding method. For example, dry methods such as die press molding and cold isostatic pressing can be used. A pressure of 10 to 300 MPa is appropriate. A pressure of 10 MPa or higher will prevent the molded body from collapsing and will maintain yield during molding. A pressure of 300 MPa or less is desirable, as it does not require large-scale equipment, is highly productive, and reduces production costs.

The manufacturing method of the present invention involves sintering the pressed compact in air at a maximum temperature of 1300-1400°C to obtain black quartz glass.

According to the manufacturing method of the present invention, a sintered body with substantially no pores in the glass structure can be obtained under conditions of a relatively low maximum temperature of 1300 to 1400°C. In particular, when the amount of SiO powder added is 0.15 to 5 parts by mass per 100 parts by mass of silica powder, the maximum temperature is 1305 to 1390°C, preferably 1310 to 1385°C, more preferably 1320 to 1380°C, even more preferably 1330 to 1375°C, and particularly preferably 1340 to 1370°C. When the amount of SiO powder added is 0 to 0.15 parts by mass per 100 parts by mass of silica powder, the maximum temperature is preferably 1390 to 1400°C. By keeping the maximum temperature of the sintering process at 1400°C or less, the Si and SiO in the raw material powder are incorporated into the glass structure without being oxidized, resulting in a sintered body with excellent light-blocking properties. Furthermore, production costs can be reduced because expensive equipment and materials are not required. By maintaining a maximum sintering temperature of 1,300°C or higher, a sintered body with excellent light-blocking properties, sufficient mechanical strength, and minimal porosity within the structure is obtained.

The sintering time at the maximum temperature can be adjusted appropriately taking into account the physical properties of the sintered body, and is, for example, in the range of 0.5 to 5 hours. A sintering time of 0.5 hours or more tends to prevent a decrease in density and bending strength. A sintering time of 5 hours or less improves productivity and tends to reduce production costs.

The black quartz glass obtained in this way has no color unevenness and is sufficiently black to prevent light transmission, stray light, or scattering, making it useful in the optical field in general. Furthermore, not only does it have extremely high light-shielding performance, but it can also be bonded to regular quartz glass, making it ideal for producing quartz glass optical analysis cells.

[Black quartz glass components and products]
The black quartz glass member of the present invention is a member manufactured from the above-mentioned black quartz glass of the present invention, and is, for example, an optical component, a light-shielding component, an infrared absorbing component, or a heat storage component. The black quartz glass member can be manufactured by processing a black quartz glass ingot with a known processing machine (such as a band saw, a wire saw, or a core drill) used in manufacturing quartz components. Alternatively, the black quartz glass member can be obtained as a sintered body by sintering a molded body formed in a mold corresponding to the shape of the desired component.

The black quartz glass member of the present invention has excellent light-blocking properties as well as excellent mechanical strength, heat resistance, and thermal shock resistance, and is therefore particularly suitable for use as an optical component such as a spectroscopic cell, a projector reflector, or an optical fiber connector, or as a light-blocking member for semiconductor manufacturing equipment or infrared heating equipment.

The product of the present invention is a device or apparatus that includes the black quartz glass member of the present invention, such as an optical analysis instrument that includes the member as an optical component, a projector that includes the member as an optical component, a semiconductor manufacturing device that includes the member as a light-blocking component, and an infrared heating device that includes the member as an infrared-absorbing component.

The present invention will be explained in detail below using examples, but the present invention is not limited to these examples.

The properties of black quartz glass were measured or obtained using the following methods and procedures.

(1) Number of pores in cross section of glass structure A test piece was cut and the cut surface was polished in accordance with JIS B0601 until the Ra was 0.20 μm or less.
The polished surface was observed with a scanning electron microscope or an optical microscope (observation magnification: approximately 500 to 3000 times) to obtain images (multiple images as necessary). The images were then processed using the open-source, public domain image processing software "ImageJ" to measure the area A of each pore, and the area A was then substituted into the following formula (1) to determine the pore diameter D.
Pore diameter D=(4×A/π) ^1/2 (1)
The number N of pores with a pore diameter D of 30 μm or more was counted, and the number N of pores and the total area TS (mm ² ) of the entire image were substituted into the following formula (2) to determine the pore number density. A total area TS of the entire image of about 600 mm ² is sufficient.
Pore number density = N / TS (2)

(2) SCE Reflectance The SCE reflectance was measured on a 7 mm thick test piece using a spectrophotometer in accordance with JIS Z 8722. The maximum value in the wavelength range of 350 to 750 nm was shown as the result.

(3) Water absorption The water absorption was measured using the Archimedes method in accordance with JIS A1509-3. Specifically, the water absorption was calculated according to the following formula (3): where W _aq represents the mass of the water-saturated test piece, and W _dry represents the mass of the dry test piece.
Water absorption rate = (W _aq - W _dry ) / W _dry (3)

(4) Density Difference Compared to Theoretical Density The density ρ of the black quartz glass (sintered body) was measured by the Archimedes method.
The theoretical density ρ ₀ of the black quartz glass was calculated according to the following formula (4) using the charged amount of Si powder W1 (mass%) and the charged amount of SiO powder W2 (mass%).
ρ ₀ =100/(W1/2.32+W2/2.13
+(100-W1-W2)/2.20) (4)
The density difference compared to the theoretical density was calculated according to the following formula (5) using the density ρ of the black quartz glass and the theoretical density ρ ₀ .
Density difference = |ρ ₀ −ρ | /ρ ₀ (5)

(5) L ^* a ^* b ^* Color System The lightness L ^* and chroma a ^* and b ^{* of the L*a*b* color system} were measured using a spectrophotometer in accordance with JIS Z8722.

(6) Specific Heat The specific heat was measured by differential scanning calorimetry (DSC) at a temperature of 500°C using a test piece processed to a size of φ6 mm x thickness 1 mm.

(7) Thermal Diffusivity The thermal diffusivity was measured for a test piece processed to a size of φ10 mm×thickness 1 mm at a temperature of 500° C. by the flash method in accordance with JIS R1611.

(8) Thermal Conductivity The thermal conductivity was calculated using the following formula based on the specific heat and thermal diffusivity at a temperature of 500°C and the density ρ of the black quartz glass (sintered body).
Thermal conductivity = specific heat × thermal diffusivity × ρ

(9) Thermal Expansion Coefficient The thermal expansion coefficient was measured for a test piece processed to a size of 3 mm x 4 mm x 20 mm at 30 to 600°C by thermomechanical analysis (TMA) in accordance with JIS R1618.

(10) Light Transmittance The light transmittance was measured in the range of 200 to 3000 nm using a spectrophotometer on a 1 mm thick test piece. The maximum value in the wavelength range of 200 to 3000 nm was shown as the result.

(11) Machining test (evaluation of machining strength)
A test piece measuring 75 mm square x 10 mm was cut from the sintered body, and the widest surface of the test piece was polished to a roughness Ra of 0.8 μm.
The polished surface was observed visually or under an optical microscope, and the number of chips having a maximum length of 0.5 mm or more and the number of discolored areas having a maximum length of 1 mm or more were counted.
Based on the number of occurrences and the total area of the observation range, the number of occurrences per 100 ^cm2 area was calculated. A total area of the observation range of about 100 ^cm2 is sufficient. If necessary, the total area of the observation range can be adjusted by testing multiple test pieces prepared under the same conditions.
When the number of chippings and discolored areas is 10 or less per 100 ^cm2 , the black quartz glass is judged to have a mechanical strength that satisfies the objective of the present invention.

(12) Heating test (evaluation of heat resistance)
The test piece was heated at 1370°C for 3 hours, and then the test piece was left to stand and cooled naturally to room temperature (about 23 to 25°C).
After cooling, the surface of the test piece was observed visually or under an optical microscope, and the number of bubbles having a maximum length of 1 mm or more and the number of discolored areas having a maximum length of 1 mm or more were counted.
Based on the number of occurrences and the total area of the observation range, the number of occurrences per 100 ^cm2 area was calculated. A total area of the observation range of about 100 ^cm2 is sufficient. If necessary, the total area of the observation range can be adjusted by testing multiple test pieces prepared under the same conditions.
When the number of bubbles and discolored areas is 10 or less per 100 ^cm2 , the black quartz glass is judged to have the heat resistance required by the present invention.

(13) Quenching/Thermal Shock Test (Evaluation of Thermal Shock Resistance)
A test piece measuring 75 mm square and 10 mm thick was cut from the sintered body, and both sides of the test piece were polished to a roughness Ra of 0.8 μm using the same polishing method as described in (1) above. The polished test piece was heated at 900°C for 30 minutes, then placed in a water bath at room temperature (approximately 23 to 25°C), and after sufficient cooling, it was removed from the water bath, water droplets adhering to the test piece were thoroughly wiped off, and the test piece was left to dry naturally.
After drying, the surface of the test piece was observed visually or under an optical microscope, and the number of chips having a maximum length of 0.5 mm or more was counted.
The number of occurrences per 100 ^cm2 was calculated based on the number of occurrences and the total area of the observation range. A total area of the observation range of about 100 ^cm2 is sufficient. If necessary, the total area of the observation range can be adjusted by testing multiple test pieces prepared under the same conditions.
In addition, the mass change (ppm) was calculated based on the mass of the test piece before and after the test.
If the number of chips occurring is 10 or ^less per 100 cm2 and the mass change is 10 ppm or less, the black quartz glass is judged to have thermal shock resistance at a level that meets the objectives of the present invention.

[Raw materials]
The following raw materials were used:
(1) Fumed silica: tapped bulk density 0.06 g/cm ³ , BET specific surface area 85 ^{m 2} /g, OH group concentration 0.7 mass %, and metal impurity content each 1 ppm or less.
(2) Spherical silica A: _D50 0.15 μm, _D10 0.07 μm, _D90 0.20 μm, and the content of metal impurities is each 1 ppm or less.
(3) Spherical silica B: D ₅₀ 11 μm, D ₁₀ 3 μm, D ₉₀ 52 μm, and the content of metal impurities is each 1 ppm or less.
(4) Silica powder synthesized by hydrolysis of silica alkoxide: D ₅₀ 80 μm, D ₁₀ 48 μm, D ₉₅ 160 μm, and metal impurity content of 1 ppm or less.
(5) Si powder A: D ₅₀ 6 μm, D ₁₀ 3 μm, D ₉₅ 13 μm, and the content of metal impurities is each 1 ppm or less.
(6) Si powder B: D ₅₀ 7 μm, D ₁₀ 4 μm, D ₉₅ 11 μm, and metal impurity content of 1 ppm or less.
(7) Si powder C: D ₅₀ 8 μm, D ₁₀ 3 μm, D ₉₅ 20 μm, and the content of metal impurities is each 1 ppm or less.
(8) Si powder D: D ₅₀ 6 μm, D ₁₀ 4 μm, D ₉₅ 10 μm, and the content of metal impurities is each 1 ppm or less.
(9) SiO powder A: D ₅₀ 5 μm, D ₁₀ 2 μm, D ₉₀ 9 μm, and the content of metal impurities is each 1 ppm or less.
(10) SiO powder B: D ₅₀ 10 μm, D ₁₀ 5 μm, D ₉₀ 20 μm, and the content of metal impurities is each 1 ppm or less.

[Example 1]
A silica mixed powder was obtained by mixing 20% by mass of fumed silica, 20% by mass of spherical silica A, and 60% by mass of spherical silica B. 2.0 parts by mass of Si powder A and 0.2 parts by mass of SiO powder A were added to 100 parts by mass of silica powder, and the mixture was mixed and consolidated in a ball mill without using a solvent. The mixed powder had a tapped bulk density of 0.79 g/ ^cm3 , and the metal impurity content was each 1 ppm or less. The mixed powder was pressed at 90 MPa to produce a pressed compact. The pressed compact was heated and sintered in air at a maximum temperature of 1370°C for 3 hours to obtain a sintered body as black quartz glass.

[Example 2]
A silica mixed powder was obtained by mixing 18% by mass of fumed silica, 18% by mass of spherical silica A, and 64% by mass of spherical silica B. 2.0 parts by mass of Si powder A was added to 100 parts by mass of silica powder, and the mixture was mixed and consolidated in a ball mill without using a solvent. The mixed powder had a tapped bulk density of 0.79 g/ ^cm3 , and the content of metal impurities was 1 ppm or less. The mixed powder was pressed at 90 MPa to produce a pressed compact. The pressed compact was heated and sintered in air at a maximum temperature of 1400°C for 3 hours to obtain a sintered body as black quartz glass.

[Comparative Example 1]
To 100 parts by weight of silica powder, 2.0 parts by weight of Si powder B and 0.5 parts by weight of SiO powder B were added to fumed silica, and the mixture was mixed and consolidated in a ball mill without using a solvent. The mixed powder had a tapped bulk density of 0.45 g/ ^cm3 , and the metal impurity contents were each 1 ppm or less. The mixed powder was pressed at 90 MPa to produce a pressed compact. The pressed compact was heated and sintered in air at a maximum temperature of 1250°C for 3 hours to obtain a sintered body as black quartz glass.

[Comparative Example 2]
Fumed silica was mixed with 1.0 part by weight of Si powder C and 1.0 part by weight of SiO powder B per 100 parts by weight of silica powder, and the mixture was mixed and consolidated in a ball mill without the use of a solvent. The mixed powder had a tapped bulk density of 0.45 g/ ^cm3 , and the metal impurity content was 1 ppm or less. The mixed powder was pressed at 90 MPa to produce a pressed compact. The pressed compact was heated and sintered in air at a maximum temperature of 1250°C for 3 hours to obtain a sintered body as black quartz glass.

[Comparative Example 3]
A silica mixed powder was obtained by mixing 50% by mass of fumed silica and 50% by mass of synthetic silica powder. 2.0 parts by mass of Si powder D and 0.5 parts by mass of SiO powder B were added to 100 parts by mass of silica powder, and the mixture was mixed and consolidated in a ball mill without using a solvent. The mixed powder had a tapped bulk density of 0.60 g/ ^cm3 , and the metal impurity content was 1 ppm or less. The mixed powder was pressed at 90 MPa to produce a pressed compact. The pressed compact was heated and sintered in air at a maximum temperature of 1300°C for 3 hours to obtain a sintered body as black quartz glass.

[Comparative Example 4]
A silica mixed powder was obtained by mixing 40% by mass of fumed silica, 18% by mass of spherical silica B, and 42% by mass of synthetic silica powder. 1.0 part by mass of Si powder A and 0.5 parts by mass of SiO powder A were added to the silica mixed powder per 100 parts by mass of silica powder, and the mixture was mixed and consolidated in a ball mill without using a solvent. The mixed powder had a tapped bulk density of 0.79 g/ ^cm3 , and the metal impurity content was each 1 ppm or less. The mixed powder was pressed at 90 MPa to produce a pressed compact. The pressed compact was heated and sintered in air at a maximum temperature of 1300°C for 3 hours to obtain a sintered body as black quartz glass.

[Comparative Example 5]
0.5 parts by mass of Si powder B was added to fumed silica per 100 parts by mass of silica powder, and the mixture was mixed and consolidated in a ball mill without using a solvent. The content of each metal impurity in the mixed powder was 1 ppm or less. The mixed powder was pressed at 90 MPa to produce a pressed compact. The pressed compact was heated and sintered in air at a maximum temperature of 1250°C for 3 hours to obtain a sintered body as black quartz glass.

[result]
The results of Examples 1 and 2 and Comparative Examples 1 to 5 are shown in Tables 1 to 5.

[Explanation of results]
The black quartz glass of Example 1 had a maximum SCE reflectance of 5.2%. In the cross section of the glass structure of the black quartz glass of Example 1, the number of pores with a diameter of 30 μm or more was 0.6/ ^mm² , confirming that the glass structure was substantially free of pores. FIG. 1 is a microscopic image of the cross section of the black quartz glass of Example 1, and the black dots in the image represent pores. From FIG. 1, it can be seen that the glass structure of the black quartz glass of Example 1 was substantially free of pores. As a result, no defects were confirmed in any of the machining test, heating test, and quenching/thermal shock test. This demonstrates that the black quartz glass of Example 1 has excellent light-shielding properties as well as excellent mechanical strength, heat resistance, and thermal shock resistance.

In addition, the black quartz glass of Example 1 is composed essentially of silicon and oxygen and does not contain elements that have a significant impact as impurities in the semiconductor manufacturing process, so there is no risk of it causing contamination. Furthermore, the black quartz glass of Example 1 can be manufactured simply by molding the powder into the desired shape and sintering it at 1400°C or less, which simplifies the manufacturing process and allows for energy-saving production. Therefore, the black quartz glass of Example 1 can be flexibly adapted to larger sizes and can be manufactured with good productivity.

The black quartz glass of Example 1 was a sufficiently black color without color unevenness, preventing light transmission, stray light, or scattering. It was visually confirmed to be uniform, and had an excellent aesthetic appearance.

The maximum SCE reflectance of the black quartz glass of Example 2 was 5.3%. The number of pores with a diameter of 30 μm or more in the cross section of the glass structure of the black quartz glass of Example 2 was 0.7/ ^mm² , confirming that the glass structure was substantially free of pores. As a result, no defects were found in any of the machining test, heating test, and quenching/thermal shock test. This demonstrates that the black quartz glass of Example 2 has excellent light-shielding properties, as well as excellent mechanical strength, heat resistance, and thermal shock resistance.

In addition, the black quartz glass of Example 2 is composed essentially of silicon and oxygen and does not contain elements that have a significant impact as impurities in the semiconductor manufacturing process, so there is no risk of it causing contamination. Furthermore, the black quartz glass of Example 2 can be manufactured simply by molding the powder into the desired shape and sintering it at 1400°C or less, which simplifies the manufacturing process and allows for energy-saving production. Therefore, the black quartz glass of Example 2 can be flexibly adapted to larger sizes and can be manufactured with good productivity.

The black quartz glass of Example 2 was a sufficiently black color without color unevenness, preventing light transmission, stray light, or scattering. It was visually confirmed to be uniform, and had an excellent aesthetic appearance.

In the black quartz glass of Comparative Examples 1 to 4, the maximum SCE reflectance was 5.2 to 7.6%, and the light-shielding properties were sufficient. However, the number of pores with a diameter of 30 μm or more in the cross section of the glass structure exceeded 5/ ^mm2 . Figure 2 is a microscopic image of the cross section of the black quartz glass of Comparative Example 3, and the black dots in the image are pores. Unlike Figure 1, many pores can be seen in Figure 2. As a result, serious defects were confirmed in the black quartz glass of Comparative Examples 1 to 4 in at least one of the mechanical processing test, heating test, and quenching/thermal shock test.

The black quartz glass of Comparative Example 5 had a high maximum SCE reflectance of 13.0% and a high L ^* value of 36.2 in the L ^* a ^* b ^* color system, indicating insufficient light blocking properties. Furthermore, the black quartz glass of Comparative Example 5 had color unevenness and was insufficient in terms of light transmission and prevention of stray light and scattering.

The black quartz glass of the present invention can be suitably used as a material for components (e.g., optical cells, light-shielding components, infrared-absorbing components, and heat-storing components) for various products (e.g., optical analysis equipment, semiconductor manufacturing equipment, and infrared heating equipment). In particular, the black quartz glass of the present invention is useful as an optical cell, light-shielding component, infrared-absorbing component, or heat-storing component in the fields of optical analysis, semiconductor manufacturing, or infrared heating.

Claims (22)

A black quartz glass containing 0.5 to 10 parts by mass of Si and 0 to 5 parts by mass of SiO per 100 parts by mass of silica, wherein the glass structure is substantially free of pores, the number of pores having a diameter of 30 μm or more is 5/mm2 or ^less in a microscopic image of a cross section of the glass structure, and the SCE reflectance at wavelengths of 350 nm to 750 nm is 10% or less. The black quartz glass of claim 1, having a water absorption rate of 0.1% or less. Black quartz glass according to claim 1 or 2, having a density whose difference in absolute value compared to the theoretical density is 1% or less. 3. The black quartz glass according to claim 1, having a lightness L ^* of 30 or less, an absolute value of chroma a ^* of 3.5 or less, and an absolute value of chroma b ^* of 4 or less in the L ^{* a *} b* color system. The black quartz glass according to claim 1 or 2, wherein the content of metal impurities in the black quartz glass is 1 ppm or less. The black quartz glass according to claim 1 or 2, which satisfies one or more of the following (a) to (i):
(a) the black quartz glass has a density of 2.19 to 2.30 g/cm ³ ;
(b) the black quartz glass has a specific heat of 1090 to 1130 J/kg·K at a temperature of 500°C;
(c) the black quartz glass has a thermal diffusivity of 7×10 ⁻⁷ to 8×10 ⁻⁷ m ² /s at a temperature of 500° C.;
(d) the black quartz glass has a thermal conductivity of 1.5 to 2.1 W/mK at a temperature of 500°C;
(e) the black quartz glass has a thermal expansion coefficient of 2×10 ⁻⁷ to 12×10 ⁻⁷ /°C in the range of 30°C to 600°C;
(f) the black quartz glass has a thickness of 1 mm and a light transmittance of 0.5% or less in the wavelength range of 200 to 3000 nm;
(g) In a machining test of black quartz glass, the number of chips having a maximum length of 0.5 mm or more is 1/100 ^cm2 or less, and the number of discolored areas having a maximum length of 1 mm or more is 1/100 ^cm2 or less.
Here, the machining test is carried out by polishing the surface of the black quartz glass to a roughness Ra of 0.8 μm.
(h) In a heating test of black quartz glass, the number of bubbles having a maximum length of 1 mm or more is 1/100 ^cm2 or less, and the number of discolored areas having a maximum length of 1 mm or more is 1/100 ^cm2 or less.
Here, the heating test is carried out by heating the black quartz glass at 1370°C for 3 hours.
(i) In a rapid cooling/thermal shock test of black quartz glass, the number of chips having a maximum length of 0.5 mm or more is 1/100 ^cm2 or less, and the mass change is 10 ppm or less;
Here, the quenching/thermal shock test is carried out by polishing both surfaces of a test piece measuring 75 mm square and 10 mm thick to a roughness Ra of 0.8 μm, heating the polished test piece at 900° C. for 30 minutes, and then immersing it in water at room temperature. the silica portion in the glass structure is a sintered body of 10 to 40 mass% of fumed silica, 10 to 40 mass% of first spherical silica having a D ₅₀ of 0.05 to 3.0 μm, and the remaining second spherical silica having a D ₅₀ of 0.25 to 15 μm, based on the total mass of the silica portion;
The black quartz glass according to claim 1 or 2, wherein the _D50 of the second spherical silica is at least 5 times the _D50 of the first spherical silica. The first spherical silica has a _D10 that is 1/5 or more of the _D50 of the first spherical silica and a _D90 that is 10 times or less of the _D50 ,
The black quartz glass according to claim 7, wherein the second spherical silica has a _D10 of at least 1/5 of the _D50 of the second spherical silica and a _D90 of at most 10 times the _D50 of the second spherical silica. At least a part of the Si in the glass structure is present as Si particles,
3. The black quartz glass according to claim 1, wherein the Si particles have a particle size distribution with a D ₅₀ of 5 to 10 μm. At least a part of the SiO in the glass structure is present as SiO particles,
3. The black quartz glass according to claim 1, wherein the SiO particles have a particle size distribution with a D ₅₀ of 3 to 15 μm. A method for producing the black quartz glass according to claim 1,
Si powder and silica powder to which SiO powder has been added, or silica powder to which Si powder has been added, are mixed and compacted;
The powder obtained by mixing and compacting is then pressed to produce a pressed compact;
A manufacturing method comprising sintering a pressed compact in air at a maximum temperature of 1300 to 1400°C to obtain black quartz glass, wherein:
The amount of Si powder added is 0.5 to 10 parts by mass per 100 parts by mass of silica powder,
The amount of SiO powder added is 0 to 5 parts by mass per 100 parts by mass of silica powder,
The silica powder comprises, based on the total mass of the silica powder, 10 to 40 mass % of fumed silica, 10 to 40 mass % of a first spherical silica having a D ₅₀ of 0.05 to 3.0 μm, and the remaining second spherical silica having a D ₅₀ of 0.25 to 15 μm;
The _D50 of the second spherical silica is at least five times the _D50 of the first spherical silica. The first spherical silica has a _D10 that is 1/5 or more of the _D50 of the first spherical silica and a _D90 that is 10 times or less of the _D50 ,
The method of claim 11, wherein the second spherical silica has a _D10 of at least 1/5 of the _D50 of the second spherical silica and a _D90 of at most 10 times the _D50 of the second spherical silica. The method according to claim 11 or 12, wherein the Si powder has a particle size distribution with a D ₅₀ of 5 to 10 μm. The method according to claim 11 or 12, wherein the SiO powder has a particle size distribution with a D ₅₀ of 3 to 15 μm. The manufacturing method described in claim 11 or 12, wherein the silica powder contains one or more types of spherical silica having different particle sizes other than the first and second spherical silica. The manufacturing method described in claim 11 or 12, wherein sintering is carried out for 0.5 to 5 hours. The method according to claim 11 or 12, wherein the fumed silica satisfies one or more of the following (i) to (iv):
(i) the fumed silica has a tapped bulk density of 0.03 to 0.08 g/cm ³ ;
(ii) the fumed silica has a BET specific surface area of 50 to 100 m ² /g;
(iii) the fumed silica has an OH group concentration of 0.5 to 1.0 mass %, and (iv) the content of metal impurities in the fumed silica is each 1 ppm or less. The manufacturing method described in claim 11 or 12, wherein the mixed compaction is carried out so that the tapped bulk density of the powder obtained by mixed compaction is 5 to 20 times the tapped bulk density of the fumed silica. A black quartz glass member manufactured from the black quartz glass of claim 1 or 2. The black quartz glass member according to claim 19, which is an optical component, a light-shielding component, an infrared absorbing component, or a heat storage component. The black quartz glass member according to claim 20, which is an optical component such as a spectroscopic cell, a projector reflector, or an optical fiber connector, or a light-shielding member for semiconductor manufacturing equipment or infrared heating equipment. 20. An article of manufacture comprising the black quartz glass member of claim 19.