Quartz glass

Abstract

The present invention provides at least one of the following: a heat-blocking quartz glass which does not require a multistep process for imparting corrosion resistance, and when compared to conventional heat-blocking quartz glass, which is imparted with strong corrosion resistance as a result of a surface treatment; a method for producing the quartz glass; and a quartz glass member that contains the quartz glass and that is for a semiconductor heat-treatment device member. This quartz glass has a pore surface area percentage that exceeds 0% but is no greater than 5% and has a pore surface area ratio of pores having a diameter of 5 μm or less of at least 30%.

Description

Quartz glass

[0001] This disclosure relates to quartz glass, and more particularly to quartz glass suitable as a heat shield for semiconductor heat treatment equipment.

[0002] Quartz glass, which exhibits heat-shielding properties due to its heat-shielding effect, has been conventionally used as a heat-shielding material in semiconductor heat treatment equipment (for example, Patent Documents 1 and 2). Semiconductor heat treatment equipment is used in repeated cycles of processing and acid cleaning. As a result, quartz glass is also exposed to acid cleaning, and surface corrosion progresses during this process. Surface corrosion is accompanied by the generation of particles (fine quartz glass particles), which create surface defects in the quartz glass. The generated particles can contaminate the semiconductor product. On the other hand, the generation of surface defects reduces the mechanical strength of the quartz glass. To suppress surface corrosion and the resulting decrease in mechanical strength, efforts are being made to improve the corrosion resistance of quartz glass.

[0003] For example, Patent Document 3 discloses a multilayer laminated glass plate sandwiched between different types of quartz glass, which is said to improve corrosion resistance.

[0004] Patent Document 1: International Publication No. 2023 / 166547 Patent Document 2: International Publication No. 2023 / 167030 Patent Document 3: Japanese Unexamined Patent Publication No. 2004-091314

[0005] The multilayer laminated glass plate disclosed in Patent Document 3 requires a process of bonding different types of quartz glass, as well as a process of applying corrosion-resistant treatment to the quartz glass layer exposed on the surface in the lamination direction. In addition to requiring multiple steps to impart corrosion resistance during the manufacturing of the multilayer laminated glass plate, it has a low degree of freedom in shape, and it is extremely difficult to process it into shapes other than a plate, such as flanges for semiconductor heat treatment equipment.

[0006] The present disclosure aims to provide at least one of the following: a heat-shielding quartz glass that does not require a multi-step process for imparting corrosion resistance, and which, compared to conventional heat-shielding quartz glass, can be manufactured by surface treatment to provide a higher corrosion resistance effect; a method for manufacturing the same; and a quartz glass for semiconductor heat treatment apparatus components including the same.

[0007] In this disclosure, we investigated the improvement of corrosion resistance of heat-shielding quartz glass, focusing on surface treatment. As a result, we found that simply surface-treating conventional heat-shielding quartz glass does not provide a sufficient improvement in corrosion resistance. Furthermore, by investigating the relationship between the state of the heat-shielding quartz glass and its surface treatment, we found that by creating quartz glass with pores controlled to a specific state, a higher improvement in corrosion resistance can be obtained than with surface treatment.

[0008] In other words, the present invention is as described in the claims, and the gist of this disclosure is as follows: [1] A quartz glass having a porosity ratio greater than 0% and 5% or less, and a porosity area ratio of pores with a diameter of 5 μm or less of 30% or more. [2] The quartz glass according to [1] above, wherein the average pore diameter is 15.0 μm or less. [3] The quartz glass according to [1] or [2] above, wherein the porosity ratio difference is 2.0% or less. [4] The quartz glass according to any one of [1] to [3] above, wherein the sample thickness is 1.0 ± 0.05 mm and the average value of the reflectance at measurement wavelengths of 780 nm to 2500 nm is 30% or more. [5] The quartz glass according to any one of [1] to [4] above, wherein the sample thickness is 1.0 ± 0.05 mm and the average value of the linear transmittance at measurement wavelengths of 380 nm to 780 nm is 20% or less. [6] A quartz glass according to any one of [1] to [5] above, wherein the ring bending strength after fire polishing under the following conditions is 90 MPa or more: Burner: Oxyhydrogen burner Hydrogen flow rate: 21.5 ± 1.0 L / min Oxygen flow rate: 7.2 ± 0.3 L / min Distance between burner tip and quartz glass surface: 2.5 cm Processing time: 5 ± 2 seconds / cm ２[7] A quartz glass member comprising an outer shell layer and a main body made of quartz glass as described in any one of [1] to [6] above. [8] The quartz glass member as described in [7] above, wherein the outer shell layer is a layer made of translucent quartz glass. [9] The quartz glass member as described in [7] or [8] above, wherein the outer shell layer has an average value of 55% or more for linear transmittance at a measurement wavelength of 380 nm to 780 nm at a sample thickness of 0.5 ± 0.05 mm.

[10] The quartz glass member as described in any one of [7] to [9] above, wherein the thickness of the outer shell layer is 5 mm or less.

[11] The tap bulk density is 0.75 g / cm³. ３ 1.15g / cm or more ３ A method for producing quartz glass according to any one of [1] to [6] above, comprising the steps of: molding a silica powder, which is as follows, at a molding pressure of 95 MPa to 270 MPa to obtain a molded body; and sintering the molded body.

[12] The method for producing quartz glass according to

[11] above, wherein the silica powder has a frequency peak in its volume particle size distribution of particle size of 50 μm to 150 μm and a frequency peak of particle size of more than 150 μm and 400 μm or less.

[13] The method for producing quartz glass according to

[11] or

[12] above, wherein the product is held at the molding pressure.

[14] The method for producing quartz glass according to any one of

[11] to

[13] above, wherein the rate of increase in pressure until the molding pressure is reached is 50 MPa / min or less.

[15] The method for producing quartz glass according to any one of

[11] to

[14] above, wherein the rate of increase in temperature from 1000°C to the holding temperature in sintering is slower than the rate of increase in temperature from the start of heating to 1000°C.

[16] The manufacturing method according to any one of

[11] to

[15] above, wherein the holding temperature during sintering is 1400°C or less.

[0009] This disclosure provides at least one of the following: a heat-shielding quartz glass that does not require a multi-step process for imparting corrosion resistance, and which, compared to conventional heat-shielding quartz glass, can be manufactured by surface treatment to provide a higher corrosion resistance; a method for manufacturing the same; and a quartz glass component for semiconductor heat treatment apparatus components including the same.

[0010] A schematic diagram showing a cross-section of quartz glass with an outer shell layer. An optical microscope photograph showing a cross-section of the quartz glass of Example 1 (scale in the figure is 100 μm). A cross-sectional photograph of the quartz glass member of Example 4 (opaque quartz glass with a transparent layer on the surface) (scale in the figure is 1 mm).

[0011] This disclosure will be described in detail with reference to one embodiment. However, this disclosure is not limited to the following embodiment. Furthermore, this disclosure includes any combination of each configuration and parameter disclosed herein, and also includes any combination of upper and lower limits of the values ​​disclosed herein.

[0012] The definitions of terms in this embodiment are as follows:

[0013] In this embodiment, "quartz glass" refers to silica (SiO₂ ２ It is an amorphous solid mainly composed of silicon (Si), and may be an amorphous solid made of quartz. In this embodiment, if the quartz glass contains metallic elements or metalloid elements other than silicon (Si), the content of such elements relative to the mass of the quartz glass is greater than 0 ppm by mass and 10 ppm by mass or less, and moreover than 0 ppm by mass and 5 ppm by mass or less.

[0014] In this embodiment, quartz glass is classified into "opaque quartz glass," "semi-transparent quartz glass," and "transparent quartz glass" based on its light transmittance. Opaque quartz glass, semi-transparent quartz glass, and transparent quartz glass are defined as quartz glass with a sample thickness of 0.5 ± 0.05 mm and an average linear transmittance of 0% to 20%, greater than 20% but less than 80%, and 80% to 100%, respectively, at measurement wavelengths of 380 nm to 780 nm. In this embodiment, semi-transparent quartz glass and transparent quartz glass are collectively referred to as "translucent quartz glass."

[0015] In this embodiment, "linear transmittance" is the ratio [%] of linearly transmitted light to incident light, and "reflectance" is the ratio [%] of reflected light to incident light. "Incident light," "reflected light," and "transmitted light" are the light irradiated onto the quartz glass, the light reflected by the quartz glass, and the light transmitted through the quartz glass, respectively. Furthermore, transmitted light is distinguished into "diffuse transmitted light," which is light that passes through the quartz glass while diffusing, and "linear transmitted light," which is light that passes through the quartz glass without diffusing. These have the following relationship: Incident light = Reflected light + (Linear transmitted light + Diffuse transmitted light)

[0016] In this embodiment, the linear transmittance and reflectance are values ​​at each wavelength (each wavelength range) measured using a general ultraviolet-visible-near-infrared spectrophotometer (e.g., UV-3600Plus, manufactured by Shimadzu Corporation) equipped with an InGaAs detector and a cooled PbS detector, under the following conditions: Measurement wavelength: 380 nm to 2500 nm Wavelength step: 1 nm intervals

[0017] For measuring linear transmittance and reflectance, a quartz glass sample with 1 μm diamond abrasive particles, and both the measurement surface and the surface opposite the measurement surface, should be mirror-polished.

[0018] In this embodiment, "visible light transmittance" is one of the indicators of the density of quartz glass, and is the average value of the linear transmittance at a sample thickness of 1.0 ± 0.05 mm and a measurement wavelength of 380 nm to 780 nm. It is the average value obtained by the same measurement method as the linear transmittance described above, except that the sample thickness of the measurement sample is 1.0 ± 0.05 mm and the measurement wavelength is 380 nm to 780 nm.

[0019] In this embodiment, "infrared reflectance" is one of the indicators showing the reflectance to near-infrared light, and is the average value of the reflectance at a sample thickness of 1.0 ± 0.05 mm and a measurement wavelength of 780 nm to 2500 nm. It is the average value obtained by the same measurement method as the reflectance described above, except that the sample thickness of the measurement sample is 1.0 ± 0.05 mm and the measurement wavelength is 780 nm to 2500 nm.

[0020] In this embodiment, L ＊ a＊ b ＊ "Lightness L in the color system" ＊ "(hereinafter simply referred to as ""L"")." ＊ " is one of the indicators indicating opacity, and is a value measured under the following conditions using a spectrophotometer (for example, CM-5, manufactured by Konica Minolta) equipped with an illumination / light-receiving optical system conforming to the geometric condition c of JIS Z 8722. Light source: D65 light source Viewing angle: 10° Measurement method: SCE Measurement diameter: 8 mm in diameter Background color: black"

[0021] "The measurement sample may be the same sample as the measurement sample used for measuring the infrared reflectance."

[0022] "In this embodiment, the ""ring bending strength"" is one of the indicators indicating mechanical strength, and is a value measured by a general precision universal testing machine (for example, AGS-5kNX, manufactured by Shimadzu Corporation) and the following ring bending jig according to the method conforming to ASTM C 1499. Load ring diameter: 12.7 mm in diameter Support ring diameter: 25.4 mm in diameter Ring tip radius: 1 mm"

[0023] "The measurement is performed by applying a load to the measurement sample under the following conditions, and the individual ring bending strength [MPa] of each measurement sample may be obtained from the following formula from the obtained crushing load. The value of the ring bending strength in this embodiment is the average value of the individual ring bending strengths measured for 15 measurement samples. Crosshead speed: 1.1 mm / min Poisson's ratio: 0.17"

[0024] "In the above formula, σ" ｆ "is the ring bending strength [MPa] of each measurement sample, F is the crushing load [N], h is the thickness [mm] of the measurement sample, ν is Poisson's ratio (0.17), D" Ｓ "is the support ring diameter (25.4 [mm]), D" Ｌ "is the load ring diameter (12.7 [mm]), and D is the diameter [mm] of the measurement sample."

[0025] The measurement sample should be a disc-shaped quartz glass with a diameter of 33 ± 0.5 mm and a thickness of 4 ± 0.5 mm, which is then double-sided ground using a rotary grinder (#270) to reduce its thickness to 3 ± 0.2 mm, and polished using a double-sided polishing machine with 7 μm alumina abrasive grains, 0.9 μm ceria abrasive grains, and 0.08 μm colloidal silica abrasive grains in that order, resulting in a disc-shaped quartz glass with a diameter of 33 ± 0.5 mm and a thickness of 2.5 ± 0.1 mm.

[0026] [Opaque Quartz Glass] This embodiment is a quartz glass in which the porosity ratio is greater than 0% and less than or equal to 5%, and the proportion of porosity area with a pore diameter of 5 μm or less is 30% or more. By satisfying these conditions, the quartz glass of this embodiment has heat-shielding properties suitable for flanges of semiconductor heat treatment equipment (hereinafter also referred to as "flange members, etc."), and moreover, the formation of an outer shell layer by surface treatment, particularly the fire polishing treatment (hereinafter also referred to as "FP treatment") described later, is facilitated. As a result, a higher corrosion resistance improvement effect can be obtained compared to conventional quartz glass that exhibits heat-shielding properties.

[0027] The quartz glass of this embodiment is a quartz glass with excellent heat shielding properties, that is, properties that block heat conduction by infrared rays, and is particularly suitable for use as a flange member and the like. The quartz glass of this embodiment exhibits heat shielding properties due to the presence of pores. Therefore, the quartz glass of this embodiment can be considered as quartz glass with pores, or even as quartz glass with pores that exhibits heat shielding properties. Furthermore, since the light transmittance decreases due to the presence of pores, the quartz glass of this embodiment may be opaque quartz glass.

[0028] Furthermore, quartz glass is classified according to its manufacturing method, and one or more types are known, selected from the group consisting of quartz glass obtained by melting (hereinafter also called "fused quartz glass"), quartz glass obtained by chemical synthesis (hereinafter also called "synthetic quartz glass"), and quartz glass obtained by sintering (hereinafter also called "sintered quartz glass"). Sintered quartz glass is preferred for this embodiment because it offers a high degree of freedom in shape and is suitable for so-called near-net molding.

[0029] The porosity of the quartz glass in this embodiment is greater than 0% and less than or equal to 5%. The porosity of the quartz glass in this embodiment is greater than 0%, meaning that the quartz glass in this embodiment has pores. Because it has pores, these pores function as infrared radiation scattering sources, and thus can exhibit heat-shielding properties.

[0030] In this embodiment, "pores" are used interchangeably with "voids," and refer to voids present within the quartz glass, i.e., closed pores present in the quartz glass. In this embodiment, the phrases "having pores" and "containing pores" are used interchangeably, which can be confirmed by the observation of voids in the microstructure of a cross-section of the quartz glass, such as in the microscopic observation described later. In this embodiment, defects exposed on the surface of the quartz glass and forming irregularities on the surface of the quartz glass (surface defects, open pores) are not considered pores for convenience.

[0031] The porosity ratio of the quartz glass in this embodiment is 5% or less. If the porosity ratio exceeds 5%, the presence of pores in the quartz glass becomes excessive. As a result, even if the porosity ratio of pores with a diameter of 5 μm or less, as described later, is satisfied, it becomes difficult to obtain the effect of improving corrosion resistance through surface treatment, such as improving strength. In this embodiment, the porosity ratio of the quartz glass is arbitrary as long as there are enough pores to exhibit heat shielding properties suitable for use as a flange member, etc. The lower limit of the porosity ratio is preferably 1.0% or more, 1.5% or more, or 2.0% or more, and the upper limit of the porosity ratio is preferably 4.5% or less, 4.0% or less, or less than 3.0%. Examples of porosity ratios for the quartz glass in this embodiment include 1.0% or more and 4.5% or less, 1.5% or more and 4.0% or less, or 2.0% or more and less than 3.0%.

[0032] In this embodiment, "porosity ratio" is one of the indicators showing the presence rate of pores inside quartz glass, obtained by analyzing an optical microscope observation image of a cross-section of quartz glass. The optical microscope observation image is obtained using a general optical microscope (e.g., VHX-900F, manufactured by Keyence Corporation) under the following conditions: Magnification: 200x to 1000x Objective lens type: VH-Z100R Illumination: Coaxial incident illumination Illuminance: 255 White balance: Push set R686, G256, B416 Shooting mode: Normal shooting

[0033] Optical microscope observation can be performed on the cross-section of the interior of quartz glass obtained by cutting the glass, after removing defects (such as linear marks) caused by cutting and rough polishing by mirror polishing with 1 μm diamond abrasive grains.

[0034] Using general image analysis software (for example, software name: ImageJ (version: 1.53t)), obtain an 8-bit grayscale image of the optical microscope observation, then binarize this 8-bit grayscale image to obtain a binarized image, and through image analysis, detect stomata and calculate the area of ​​each stomata, the total area of ​​all stomata, and the area of ​​the optical microscope observation image (binarized image). The binarization process should be performed using the following method. The threshold for binarization in ImageJ should be set as follows: Use the Threhold function, select Otsu, uncheck Dark background, Stack histogram, and Raw values, and check Don't reset range. Then, select Auto to determine the binarization threshold.

[0035] In the binarization process, an 8-bit grayscale image obtained from an optical microscope observation is converted into a binarized image consisting of two regions: a white region and a black region. Image analysis involves applying noise reduction settings (e.g., the "Include holes" setting in ImageJ), and then treating the black region in the binarized image as quartz glass and the white region as pore region, with continuous white areas having an area of ​​0.5 μm². ２ The region exceeding the above is considered a stoma. The white area is a continuous portion with an area of ​​0.5 μm². ２ Regions below a certain level are considered measurement noise and should be distinguished from stomata.

[0036] Image analysis can be performed on 3000 or more stomata (e.g., 3500 ± 200), and two or more optical microscope images (e.g., 10 ± 5) may be used for the image analysis.

[0037] Based on the image analysis results, the porosity ratio can be calculated using the following formula: R = S / T Ｓ ×100 In the above formula, R is the pore area ratio [area %] and S is the total area of ​​all pores [μm] ２ ], T Ｓ This is the image area [μm²] of the optical microscope observation image (binarized image). ２ ]

[0038] The porosity area ratio of the quartz glass with a pore diameter of 5 μm or less in this embodiment (hereinafter referred to as "R ５ It is also called ". ) is 30% or more. R ５ If the porosity ratio is less than 30%, even if the above-mentioned porosity ratio is satisfied, surface densification by surface treatment will not progress easily. As a result, although corrosion resistance may be improved, the effect will be limited. Since pores tend to exist in a more dispersed state, R ５ It is preferable that the content is 35% or more, and more preferably 40% or more. If the surface densification by surface treatment progresses, R ５ It doesn't need to be excessively high. ５ The upper limits include 85% or less, 60% or less, 50% or less, or 42% or less, and the R of the quartz glass in this embodiment ５Examples include 30% to 85%, 35% to 60%, 35% to 50%, and 40% to 50%.

[0039] From the viewpoint of making it easier to obtain improved corrosion resistance through surface treatment of quartz glass regardless of the part, the difference in porosity ratio between the vicinity of the surface and the interior of the quartz glass in this embodiment is preferably 2.0% or less, 1.5% or less, or 1.0% or less, and the lower limit of the difference in porosity ratio is preferably 0.1% or more. Examples of the difference in porosity ratio of the quartz glass in this embodiment include 0.1% to 2.0%, 0.1% to 1.5%, or 0.1% to 1.0%.

[0040] In this embodiment, the "porosity ratio difference" between the surface and the interior is the absolute value of the difference between the porosity ratio at a depth of 10 mm from the surface of the quartz glass (the porosity ratio obtained by measuring the cut surface after cutting a thickness of 10 mm from the surface of the quartz glass) and the porosity ratio at a depth of 15 mm from the surface of the quartz glass (the porosity ratio obtained by measuring the cut surface after cutting a thickness of 15 mm from the surface of the quartz glass). The "porosity ratio difference" is an indicator of the uniformity of the pores in the quartz glass.

[0041] For similar reasons, the porosity area ratio of the quartz glass of this embodiment with a pore diameter of 15.0 μm or less (hereinafter referred to as "R") １５ It is also called ". ) preferably has a ratio of 45% or more, 55% or more, or 70% or more, and may also be 95% or less, 90% or less, or 85% or less. Specific R １５ Examples include 45% to 95%, 55% to 90%, or 70% to 85%.

[0042] The quartz glass of this embodiment has pores as described above R ５ The following conditions are met, and moreover, this is contained in a dispersed state that also possesses the aforementioned porosity ratio. Being a quartz glass containing pores in this state makes it easier to obtain improved corrosion resistance through surface treatments such as FP treatment while retaining the heat-shielding properties that make it suitable for use as a flange member, etc.

[0043] In this embodiment, the "porosity area ratio" is one of the indicators that shows the proportion of pores with a specific range of pore diameters among the pores present in quartz glass, and is a value [area %] obtained from image analysis of a binarized graph obtained by the same method as the measurement of the porosity area ratio described above.

[0044] When calculating the pore area ratio, the pore diameter can be determined by approximating each detected pore as a circle and using the following formula as the diameter of the resulting approximate circle. Ｐ = (4S Ｐ / π) ０．５ In the above equation, D Ｐ The pore diameter [μm] of each pore, and S Ｐ The area of ​​each pore [μm²] ２ ]

[0045] R ５ and R １５ Each of these represents the total area of ​​all stomata [μm²]. ２ The total area of ​​pores with a diameter of 5 μm or less in the area [μm] ２ The percentage of [area %] and the total area of ​​all pores [μm²] ２ The total area of ​​pores with a diameter of 15 μm or less in the area [μm] ２ It can be calculated from the ratio [area %] of ].

[0046] The average pore size of the quartz glass in this embodiment is determined by the above-mentioned pore area ratio and R ５ While any of the above conditions are met, examples include 15.0 μm or less, 10.0 μm or less, less than 7.0 μm, or 6.5 μm or less, and also 2.5 μm or more, 5.0 μm or more, or 6.1 μm or more. Examples of the average pore size in the quartz glass of this embodiment include 2.5 μm or more and 15.0 μm or less, 5.0 μm or more and 10.0 μm or less, 5.0 μm or more and less than 7.0 μm, or 6.1 μm or more and 6.6 μm or less.

[0047] Similarly, the 10% pore size of the quartz glass of this embodiment may be 3.0 μm or less, 2.5 μm or less, less than 2.0 μm, or 1.8 μm or less, and may also be 1.5 μm or more, 1.3 μm or more, or 1.0 μm or more, with examples including 1.5 μm or more and 3.0 μm or less, 1.3 μm or more and 2.5 μm or less, or 1.0 μm or more and 1.8 μm or less. Furthermore, the 90% pore size of the quartz glass of this embodiment may be 39 μm or less, 36 μm or less, less than 33 μm, or 30 μm or less, and may also be 18 μm or more, 20 μm or more, 23 μm or more, or 25 μm or more, with examples including 18 μm or more and 39 μm or less, 20 μm or more and 36 μm or less, 23 μm or more and less, or 25 μm or more.

[0048] In this embodiment, "10% pore diameter," "average pore diameter," and "90% pore diameter" are D, respectively, obtained by the same method as the pore area ratio. Ｐ This is the value obtained from. That is, all of the D obtained Ｐ A pore size-area frequency distribution can be created from this, and the pore sizes corresponding to 10%, 50%, and 90% frequencies in this distribution can be defined as the 10% pore size, average pore size (50% pore size), and 90% pore size, respectively. The quartz glass of this embodiment only needs to satisfy the above-mentioned 10% pore size, average pore size (50% pore size), and 90% pore size, and may contain pores with a maximum length greater than these. The maximum pore length of the pores contained in the quartz glass of this embodiment can be 50 μm or less or 30 μm or less, or 6 μm or more, 10 μm or more, or 20 μm or more. Furthermore, the maximum pore length can be 6 μm or more and 50 μm or less, 10 μm or more and 30 μm or less, or 20 μm or more.

[0049] In this embodiment, the "maximum pore length" is the length of the longest side of the pore with the longest diameter, as observed in an optical microscope observation diagram obtained by the same method as the measurement of the pore area ratio described above.

[0050] When calculating the pore area ratio, the pore diameter can be determined by approximating each detected pore as a circle and using the following formula as the diameter of the resulting approximate circle.

[0051] The pores present in the quartz glass of this embodiment are irregular in shape, and are preferably non-spherical. The above-mentioned pore area ratio and R ５ The conditions are met, and furthermore, the pores are irregular in shape and non-spherical, which facilitates mass transfer due to surface treatment. As a result, densification of the outer shell layer is more easily achieved. Generally, pores originating from foaming agents or pore-forming agents are spherical or nearly spherical. In contrast, irregularly shaped pores are thought to originate from voids between silica particles during the manufacturing of quartz glass. Therefore, it is preferable that the pores present in the quartz glass of this embodiment originate from voids between raw material particles.

[0052] Because defects are less likely to occur when used as a flange component, the measured density of the quartz glass in this embodiment is 2.17 g / cm³. ３ Above, or 2.18 g / cm³ ３ It is preferable that the above is true. The upper limit of the measured density is 2.20 g / cm³. ３ The following can be cited: The measured density of the quartz glass in this embodiment is 2.17 g / cm³. ３ 2.20g / cm or more ３ Below, 2.17g / cm ３ 2.20g / cm or more ３ The following, or 2.18 g / cm³ ３ 2.20g / cm or more ３ The following are some examples:

[0053] In this embodiment, the "measured density" is the bulk density measured in accordance with JIS R 1634. Prior to measurement, the sample to be measured may be pretreated by boiling.

[0054] The quartz glass of this embodiment may have any shape, for example, one or more shapes selected from the group consisting of plate-like, columnar, ring-like, substantially ring-like, spherical, substantially spherical, polyhedral, substantially polyhedral, conical, and substantially conical shapes, or various ingot shapes, semiconductor heat treatment device component shapes, and other shapes according to the application.

[0055] In this embodiment, it is preferable that the infrared reflectance of the quartz glass is 30% or more, 35% or more, or 40% or more. An infrared reflectance of 30% or more results in quartz glass with higher heat shielding properties. The quartz glass in this embodiment only needs to have heat shielding properties that allow it to be used as a flange member, etc., and the upper limit of the infrared reflectance can be, for example, 70% or less, 65% or less, or 60% or less. In this embodiment, the infrared reflectance of the quartz glass can be 30% to 70%, 35% to 65%, or 40% to 60%.

[0056] In this embodiment, the visible light transmittance of the quartz glass is preferably 20% or less, 5% or less, 3% or less, 1% or less, or 0.5% or less. Visible light transmittance tends to be higher as the density of the quartz glass increases. On the other hand, even if the density is similar, the visible light transmittance tends to increase when the pore size exceeds a certain level. The quartz glass in this embodiment has the above-mentioned pore area ratio and R ５ It is preferable that the porosity is present while satisfying the above conditions, and that the visible light transmittance is as described above. The visible light transmittance of the quartz glass in this embodiment may be 0.01% or more, 0.05% or more, 0.08% or more, or 0.1% or more, and may also be 0.01% to 20%, 0.05% to 3%, 0.08% to 1%, or 0.1% to 0.5%.

[0057] The quartz glass of this embodiment can have any opacity as long as it exhibits heat-shielding properties suitable for use as a flange member, etc., L ＊ This includes being 50 or older, 60 or older, or 65 or older. ＊ As L increases, light transmittance tends to decrease, ＊ L of the quartz glass in this embodiment may be 100 or less, 90 or less, less than 85, or 80 or less. ＊ Examples include a range of 50 to 100, 60 to less than 85, or 65 to 80.

[0058] The ring bending strength of the quartz glass in this embodiment is preferably 55 MPa or more, 60 MPa or more, or 70 MPa or more. This provides mechanical strength suitable for use as a component of semiconductor manufacturing equipment, such as a flange member. The ring bending strength should be such that defects are unlikely to occur during component processing, and examples of ring bending strengths for the quartz glass in this embodiment include 100 MPa or less, 90 MPa or less, or 85 MPa or less, with 55 MPa to 100 MPa, 60 MPa to 90 MPa, or 70 MPa to 85 MPa being examples.

[0059] The quartz glass of this embodiment is more readily available for improved corrosion resistance through surface treatment compared to conventional heat-insulating quartz glass, and as a result, its mechanical strength after surface treatment is more easily improved. In other words, the improvement in corrosion resistance through surface treatment is mainly due to the removal of fine defects on the surface, and at the same time, the removal of fine defects also functions as the removal of fracture sources. Therefore, unlike quartz glass that simply has high ring bending strength, this quartz glass is more readily available for improved mechanical strength through surface treatment, which is thought to make it easier to obtain the effect of improved corrosion resistance. One example of such a surface treatment is FP treatment. The quartz glass of this embodiment preferably has a ring bending strength (hereinafter also referred to as "post-treatment ring bending strength") of 90 MPa or more, 95 MPa or more, or 100 MPa or more after FP treatment under the following conditions. The post-treatment ring bending strength is preferably high, but upper limits include 150 MPa or less, 120 MPa or less, or 110 MPa or less, and the range can be 90 MPa to 150 MPa, 95 MPa to 120 MPa, or 100 MPa to 110 MPa. <FP Treatment Conditions> Burner: Oxyhydrogen burner Hydrogen flow rate: 21.5 ± 1.0 L / min Oxygen flow rate: 7.2 ± 0.3 L / min Distance between burner tip and quartz glass surface: 2.5 cm Treatment time: 5 ± 2 seconds / cm ２

[0060] The processing speed is the FP processing time per unit area of ​​quartz glass. The ring bending strength after processing can be measured in the same way as the ring bending strength, except that the measurement sample is quartz glass similar to the quartz glass used for measuring the ring bending strength, and the entire surface of the disc-shaped quartz glass is subjected to the FP processing under the conditions described above.

[0061] In this embodiment, the ring bending strength after treatment (hereinafter also referred to as the "ring strength ratio") relative to the ring bending strength of the quartz glass is preferably 1.1 or higher, 1.2 or higher, or 1.3 or higher. The upper limit of the ring strength ratio is 2.0 or lower, 1.8 or lower, or 1.6 or lower. Therefore, the ring strength ratio can be 1.1 or higher and 2.0 or lower, 1.2 or higher and 1.8 or lower, or 1.3 or higher and 1.6 or lower. The quartz glass in this embodiment may have an outer shell layer (hereinafter, quartz glass with an outer shell layer is also referred to as "outer shell quartz glass"). This results in a member that exhibits corrosion resistance and mechanical strength more suitable for flange members, etc. When an outer shell layer is present, it can be considered as a quartz glass member consisting of an outer shell layer and a main body made of the quartz glass of this embodiment, and the quartz glass of the main body has the above-mentioned porosity ratio and R ５ It is sufficient to satisfy the following conditions.

[0062] The outer shell layer is the surface layer of the quartz glass in this embodiment, and is a layer with a different state from the interior. Preferably, the outer shell layer is a surface layer made of quartz glass with higher corrosion resistance than the quartz glass in this embodiment, and more preferably, a layer made of translucent quartz glass. Furthermore, preferably, the outer shell layer is a layer obtained by surface treatment of the quartz glass in this embodiment, and more preferably, a layer formed by FP treatment of the quartz glass in this embodiment. Because the outer shell layer is a layer formed by surface treatment, distortions and the like that caused by compositional differences between the outer shell layer and the interior (main body) of the molded glass are less likely to occur.

[0063] The following description of the outer shell quartz glass will be given as an example, using a quartz glass member (hereinafter also referred to as "the quartz glass member of this embodiment") which consists of an outer shell layer made of translucent quartz glass and a main body made of quartz glass having a porosity ratio of more than 0% and 5% or less, and a porosity ratio of 30% or more of pores with a pore diameter of 5 μm or less.

[0064] Figure 1 is a schematic diagram showing a cross-section of the quartz glass member of this embodiment. In the cross-section of the quartz glass member (outer shell quartz glass) 100, the surface of the main body portion 10 is covered with an outer shell layer 11. In the quartz glass member of this embodiment, the main body portion 10 has the above-mentioned porosity ratio and R ５ It is sufficient if the following conditions are met.

[0065] Figure 1 shows a configuration in which the entire surface of the opaque portion 10 is covered by the outer shell layer 11, but the outer shell layer 11 does not have to cover the entire surface of the opaque portion 10. That is, when the quartz glass member 100 is used as a semiconductor heat treatment member such as a flange member, it is sufficient for the outer shell layer 11 to be present in the areas exposed to acid cleaning, and it is sufficient for the outer shell layer 11 to be present on all or at least a part of the surface of the main body portion 10. On the other hand, the quartz glass member of this embodiment may have the outer shell layer 11 on the entire surface of the main body portion 10. In Figure 1, the outer shell layer 11 and the main body portion 10 are shown in contact via an interface. However, the outer shell quartz glass 100 does not have to have a clear interface between the outer shell layer 11 and the main body portion 10, and may have a structure that changes in a gradual manner from the outer shell layer 11 to the main body portion 10. Furthermore, it is preferable that the outer shell layer 11 and the main body portion 10 are in contact without an intervening bonding agent or bonding layer, i.e., have a continuous structure.

[0066] The upper limit of the thickness of the outer shell layer 11 is sufficient to provide the quartz glass member with sufficient corrosion resistance to be used as a flange member, etc. For example, the thickness of the outer shell layer 11 may be 5 mm or less or 3 mm or less. The lower limit of the outer shell layer 11 is sufficient to provide the thickness necessary to suppress particle generation due to acid cleaning, and it is preferable that the lower limit of the thickness of the outer shell layer 11 is greater than 0 mm, 0.1 mm or more, 0.5 mm or more, or 1 mm or more. In this embodiment, the thickness of the outer shell layer 11 of the outer shell quartz glass may be greater than 0 mm and 5 mm or less, 0.1 mm or more and 3 mm or less, or 1 mm or more and 3 mm or less. Also, in Figure 1, the thickness of the outer shell layer 11 is uniform. However, the outer shell layer 11 does not need to have a uniform thickness across the entire surface of the quartz glass member; it may have a thickness suitable for its shape and application. Therefore, the quartz glass member of this embodiment may have outer shell layers of different thicknesses. Furthermore, the thickness of the outer shell layer is the distance from the surface of the quartz glass member to the point where the color changes, in the direction toward the interior of the quartz glass member (thickness direction). This can be confirmed from the surface of the quartz glass member by observing a cross-sectional view of the quartz glass member.

[0067] The outer shell layer 11 is preferably an outer shell layer formed by the surface treatment of quartz glass according to this embodiment, and more preferably an outer shell layer made of translucent quartz glass formed by FP treatment. Since such an outer shell layer has the same composition as the main body 11, problems caused by compositional differences are less likely to occur, and the outer shell layer can be of any thickness depending on the shape and application of the main body 11. In addition, the outer shell layer formed by FP treatment can be an outer shell layer formed at the required thickness at the required locations on the surface of the main body 11.

[0068] In this embodiment, the presence of an outer shell layer (i.e., a quartz glass member (outer shell quartz glass)) and the thickness of the outer shell layer can be confirmed from the microstructure observation diagram. An example of a cross-section of the quartz glass member of this embodiment is shown in Figure 3. In Figure 3, the different color tones between the cross-section and the interior indicate that the quartz glass member consists of an outer shell layer and a main body. In Figure 3, there is no clear interface between the outer shell layer and the main body, and it can be confirmed that the thickness of the outer shell layer is between 0.4 mm and 0.8 mm.

[0069] The outer shell layer 11 is preferably made of translucent quartz glass, and it is preferable that the average value of the linear transmittance (hereinafter also referred to as "surface transmittance") at a measurement wavelength of 380 nm to 780 nm at a sample thickness of 0.5 ± 0.05 mm is 50% or more, 55% or more, 60% or more, or 65% or more. If the surface transmittance is such a value, the outer shell layer becomes dense enough that particle detachment due to repeated acid washing is less likely to occur. The higher the surface transmittance, the denser the outer shell layer 11 becomes, but the surface transmittance of the outer shell layer 11 is 80% or less or 70% or less. Examples of surface transmittance for translucent quartz glass in the outer shell layer 11 include 50% to 80%, 55% to 80%, 60% to 70%, or 65% to 70%.

[0070] In this embodiment, the surface transmittance is a value that can be measured in the same way as the visible light transmittance, except that the following quartz glass is used as the measurement sample. That is, the outer shell layer (the surface of the outer shell quartz glass) is cut out to a thickness of 1.0 mm in the direction from the surface of the outer shell quartz glass toward the main body (thickness direction), and then the cut surface (the surface facing the surface of the outer shell quartz glass) is polished to obtain a cut piece with a thickness of 0.7 mm. The cut surface and the surface facing it are then mirror-polished using 1 μm diamond abrasive grains to obtain a quartz glass sample with a thickness of 0.5 ± 0.05 mm, which can then be used as the measurement sample.

[0071] The quartz glass and quartz glass members of this embodiment can be used in known applications of quartz glass, particularly opaque quartz glass, and can be used as at least one of plasma-resistant members and heat-shielding members. They are particularly suitable for use as members for semiconductor manufacturing equipment, and even more so as heat-shielding members for semiconductor manufacturing equipment, and even more so as flange members for semiconductor manufacturing equipment.

[0072] [Method for Manufacturing Opaque Quartz Glass] The manufacturing method of the quartz glass of this embodiment is arbitrary as long as it has the above-described characteristics. The manufacturing method of the quartz glass of this embodiment is preferably a sintering method, and more preferably a method for manufacturing quartz glass that includes the steps of molding silica powder to obtain a molded body and sintering the molded body. A preferred manufacturing method for the quartz glass of this embodiment is one in which the tap bulk density is 0.75 g / cm³. ３ 1.15g / cm or more ３ A method for manufacturing quartz glass (hereinafter also referred to as "the manufacturing method of this embodiment") is provided, which includes the steps of: molding silica powder, as described below, at a molding pressure of 95 MPa to 270 MPa to obtain a molded body; and sintering the molded body. The manufacturing method of this embodiment provides opaque quartz glass that has heat-shielding properties suitable for use as flange members, etc., and in which the formation of an outer shell layer made of translucent quartz glass by FP treatment proceeds more easily.

[0073] The manufacturing method of this embodiment results in a tap bulk density of 0.75 g / cm³. ３ 1.15g / cm or more ３ The process includes a step of molding the silica powder described below at a molding pressure of 95 MPa to 270 MPa to obtain a molded body (hereinafter also referred to as the "molding step").

[0074] Silica powder is supplied in the molding process. The silica powder mainly consists of silica (silicon dioxide; SiO₂). ２The powder is composed of silica particles, and the mass ratio of silica particles to the mass of silica powder (hereinafter also referred to as "silica content") is 90% by mass or more, and more specifically, 95% by mass or more or 98% by mass or more. The silica powder may be a powder consisting only of silica (silica content of 100% by mass), but the silica content may be 100% by mass or less, less than 100% by mass but 99.85% by mass or less, or 99.8% by mass or less.

[0075] The silica powder used in the molding process (hereinafter referred to as "raw material powder") may consist mainly of amorphous silica particles, and may include amorphous silica powder obtained by known manufacturing methods, and may also include one or more selected from the group consisting of sol-gel silica, precipitated silica, gas-phase silica, and flame-fused silica, and preferably two or more selected from the group consisting of sol-gel silica, precipitated silica, gas-phase silica, and flame-fused silica.

[0076] The shape of the silica particles constituting the raw material powder can be arbitrary, and may be one or more selected from the group consisting of polyhedral, spherical, and irregular shapes.

[0077] The tap bulk density of the raw material powder is 0.75 g / cm³. ３ 1.15g / cm or more ３ The following conditions apply. Even if raw material powder with a lower tap bulk density is used for molding, the resulting molded body will have significant void variations. Applying FP treatment to quartz glass obtained by sintering such a molded body will result in defects, limiting the improvement in corrosion resistance. If the tap bulk density exceeds these values, the raw material powder itself becomes too dense, and a molded body cannot be obtained by molding such raw material powder. The tap bulk density is 0.75 g / cm³. ３ or more, or 0.80 g / cm³ ３ Preferably, it is 1.15 g / cm³ or more. ３ Below, 1.00g / cm ３ The following or 0.90 g / cm³ ３ The following is preferable: The tap bulk density of the raw material powder is 0.75 g / cm³. ３ 1.00g / cm or more ３ The following, or 0.80 g / cm³ ３ 0.90g / cm or more ３ The following are listed:

[0078] In this embodiment, "tap bulk density" refers to the mass per unit bulk volume occupied by the powder [g / cm³] when the sample is dispersed and placed in a container, and the container is subjected to a tapping motion, at which point the volume change of the sample ceases. ３ This value is measured using a measurement method compliant with the constant volume measurement method specified in JIS R 1628.

[0079] The raw material powder preferably has a multimodal volume particle size distribution, and more preferably a bimodal volume particle size distribution. Furthermore, in its volume particle size distribution, it is preferable to have at least a frequency peak for particle sizes greater than 100 μm, and more preferably a frequency peak for particle sizes greater than 100 μm and less than or equal to 300 μm. When silica particles have a multimodal particle size distribution and contain a large amount of silica particles of such sizes, interparticle pores that can be filled with fine silica particles are more easily formed. As a result, even when having the same tap bulk density, pore removal during sintering is more easily promoted, and a denser quartz glass can be obtained. The raw material powder preferably has a frequency peak in its volume particle size distribution for particle sizes between 50 μm and 150 μm, and a frequency peak for particle sizes greater than 150 μm and less than or equal to 400 μm. This further improves the packing efficiency of silica particles. Since the packing efficiency of silica particles tends to be high, the frequency peak in the volume particle size distribution for particle sizes of 50 μm to 150 μm (hereinafter also referred to as the "first frequency peak") is preferably the frequency peak for particle sizes of 70 μm to 120 μm, or the frequency peak for particle sizes of 80 μm to 100 μm. Furthermore, the frequency peak in the volume particle size distribution for particle sizes greater than 150 μm to 400 μm (hereinafter also referred to as the "second frequency peak") is preferably the frequency peak for 200 μm to 300 μm, or the frequency peak for 260 μm to 280 μm.

[0080] The ratio of the frequency of the first frequency peak to the frequency of the second frequency peak of the raw material powder (hereinafter also referred to as the "frequency ratio") is 0.5 or more or 0.6 or more, and is also 0.9 or less or 0.8 or less, and furthermore, is 0.5 or more and 0.9 or 0.6 or more and 0.8 or less.

[0081] As long as the above-mentioned tap bulk density is met, the particle size of the raw material powder is arbitrary, but the average particle size of the raw material powder should be 50 μm or more or 80 μm or more, and preferably 300 μm or less, 200 μm or less, or 150 μm or less. Furthermore, it is preferable that the above-mentioned tap bulk density is met and the average particle size of the raw material powder is greater than 100 μm or 105 μm or more. This makes it easier for the pores to become more homogeneous. The average particle size of the raw material powder should be 50 μm or more and 300 μm or less or 80 μm or more and 150 μm or less, and preferably greater than 100 μm and 200 μm or less or 105 μm or more and 150 μm or less.

[0082] The volume particle size distribution of the silica powder in this embodiment is obtained using a general laser diffraction scattering particle size distribution analyzer (e.g., MT3100 II, manufactured by Microtrac) under the following conditions. The particle size of the frequency peak is the particle size of the peak top of the frequency extremum in the volume particle size distribution, and the average particle size is the particle size corresponding to D50 of the volume particle size distribution. Measurement method: Dry method Refractive index: 1.46

[0083] The raw material powder may contain silicon monoxide (SiO) to facilitate sintering. The sintering-promoting effect is easily obtained when the mass ratio of silicon monoxide to the mass of the raw material powder [mass ppm] is 500 mass ppm or more, 1000 mass ppm or more, or 1500 mass ppm or more. On the other hand, there is no upper limit for silicon monoxide, and it is not necessary to include it in excess. Therefore, the silicon monoxide content of the raw material powder may be 3000 mass ppm or less, 2500 mass ppm or less, or 2000 mass ppm or less, and examples include 500 mass ppm or more and 3000 mass ppm or less, 1000 mass ppm or more and 2500 mass ppm or less, or 1500 mass ppm or more and 2000 mass ppm or less.

[0084] The raw material powder can be any silica powder that satisfies the above-mentioned tap bulk density, but the manufacturing method is arbitrary. For example, a manufacturing method that includes a step of mixing silica powders with different BET specific surface areas (hereinafter also referred to as the "powder mixing step") can be used.

[0085] In the powder mixing step, silica powders with different BET specific surface areas (hereinafter also referred to as "precursor powders") are provided. Thereby, particle rearrangement during molding of the obtained raw material powder is likely to be promoted. Preferred precursor powders include a mixed powder of silica powder having a BET specific surface area of 0.5 m ２ / g or more and 10 m ２ / g or less (hereinafter also referred to as "low BET silica"), and silica powder having a BET specific surface area of more than 10 m ２ / g and 400 m ２ / g or less (hereinafter also referred to as "high BET silica"). The low BET silica preferably has a BET specific surface area of 0.8 m ２ / g or more or 1.2 m ２ / g or more, and preferably 8 m ２ / g or less or 5 m ２ / g or less, and examples include 0.8 m ２ / g or more and 8 m ２ / g or less, or 1.2 m ２ / g or more and 5 m ２ / g or less. The high BET silica preferably has a BET specific surface area of 60 m ２ / g or more or 80 m ２ / g or more, and preferably 150 m ２ / g or less or 100 m ２ / g or less, and preferably 60 m ２ / g or more and 150 m ２ / g or less, or 80 m ２ / g or more and 100 m ２ / g or less.

[0086] The BET specific surface area in this embodiment is the specific surface area of silica powder measured by the BET multipoint method under the following conditions with nitrogen as the adsorption medium in accordance with JIS Z8830 static volumetric method, and can be measured using a general BET specific surface area measuring device (for example, device: BEL SORP - miniIII manufactured by MicrotracBEL). Pretreatment: 150 °C × 2 hours, vacuum degassing Measurement method: Nitrogen adsorption method (multipoint method)

[0087] The precursor powder may be an amorphous silica powder obtained by the same production method as the raw material powder, or may be a commercially available silica powder.

[0088] The shape of the silica particles constituting the precursor powder can be arbitrary, and may be one or more selected from the group consisting of polyhedral, spherical, and irregular shapes.

[0089] In the powder mixing process, the silica particles should be mixed so that the precursor powder becomes the raw material powder described above. However, it is preferable that the mixing is such that the ratio of the increase in the BET specific surface area of ​​the raw material powder relative to the BET specific surface area of ​​the precursor powder (hereinafter also referred to as the "BET increase rate") is 1% or more or 3% or more. Mixing and consolidation aimed at increasing tap bulk density is well known, and this was a mixing that did not involve a change in BET specific surface area. In contrast, the above-described mixing utilizes the plastic deformation of silica particles and disperses the aggregation of fine silica particles without crushing the silica particles, applying a load to the silica particles that changes the surface state, and it is thought that this results in an increase in BET specific surface area. As a result, it is thought that even between silica particles with large particle sizes, the contact between them becomes stronger, and a fine pore network is formed that can promote pore removal during sintering. To prevent the pulverization of silica particles, the mixture is preferably one in which the BET increase rate is 10% or less or 8% or less, and preferably one in which the BET increase rate is 1% to 10% or 3% to 8%.

[0090] The specific mixing method is preferably dry mixing, and this includes dry mixing using a general mixing device. The mixing device used for dry mixing is preferably one or more selected from the group consisting of a stirrer, ball mill, vibratory mill, rocking mixer, cross mixer, and V-type mixer, and more preferably at least one of a rocking mixer and a ball mill, and more preferably a ball mill. Dry mixing using a ball mill can be exemplified by dry mixing using a ball mill with at least one of ceramics and polymers as the grinding medium, and dry mixing using a ball mill with a polymer grinding medium is preferred. Polymer grinding media have a low load on the silica powder to be mixed and are less likely to cause excessive grinding of particles. Therefore, by using such a grinding medium, it is easier to apply a load suitable for mixing the precursor powder. Examples of polymer (resin) grinding media include at least one grinding medium selected from the group consisting of silicon, nylon, polyurethane, Teflon®, polyethylene, polypropylene, and Duracon, and more preferably at least one of silicon grinding media and nylon grinding media. The grinding medium can be any grinding ball, and may be a grinding ball with a diameter of 5 mm to 30 mm, or more specifically, a grinding ball with a diameter of 10 mm to 20 mm. A specific example of a grinding medium is a polymer ball (resin ball) with a diameter of 10 mm to 20 mm. The polymer ball may be a commercially available polymer ball (for example, https: / / enet.kokugo.shop / category / 103106 / (searched on January 22, 2025)). When producing a raw material powder containing silicon monoxide, it may be mixed at the same time as the precursor powder, or silicon monoxide may be mixed after the precursor powder has been mixed.

[0091] In the molding process, a molded body is obtained by molding at a molding pressure of 95 MPa to 270 MPa. It is believed that molding efficiently rearranges the silica particles constituting the raw material powder, resulting in a molded body with appropriately dispersed voids between the powder particles. By sintering such a molded body, the pores of the quartz glass obtained without the pore-forming effect of foaming agents, etc., become heat-insulating, making it suitable for use as a flange member, etc. Furthermore, it is believed that a dense outer shell layer can be easily formed by surface treatments such as FP treatment.

[0092] The molding pressure is 270 MPa or less, preferably 200 MPa or less, 150 MPa or less, or 140 MPa or less. If the molding pressure exceeds these values, even when molding raw material powder that satisfies the above-mentioned tap bulk density, the frequency of contact between silica particles with relatively large particle sizes increases, which is thought to locally inhibit sintering shrinkage. As a result, the porosity of the quartz glass obtained after sintering increases. In order to make the molded body more easily obtainable with the quartz glass of this embodiment through sintering, the molding pressure is preferably 95 MPa or more, 100 MPa or more, or 120 MPa or more, and furthermore, examples of molding pressures that are 95 MPa or more and 200 MPa or less, 100 MPa or more and 150 MPa or less, or 120 MPa or more and 140 MPa or less can be given.

[0093] In conventional quartz glass manufacturing methods using the sintering method, the molding pressure is usually adjusted solely from the perspective of shape retention, that is, to prevent collapse during sintering. The molding pressure is determined from the viewpoints of shape retention and yield (production aspect), as well as manufacturing cost (equipment aspect). In contrast, in the manufacturing method of this embodiment, as described above, the molding pressure is controlled from the viewpoint of controlling the voids between silica particles in the molded body.

[0094] In the molding process, the raw material powder may be pressurized and then immediately depressurized after reaching the molding pressure, but it is preferable to hold the molding pressure. This suppresses uneven pressure distribution and tends to reduce the difference in surface and internal conditions of the resulting molded body. Examples of holding time at molding pressure include 0.1 minutes or more, 1 minute or more, or 2 minutes or more, and also 8 minutes or less, or 4 minutes or less, and further, 0.1 minutes or more and 8 minutes or 2 minutes or more and 4 minutes or less.

[0095] The rate at which the pressure is increased until the molding pressure is reached is arbitrary, but in order to suppress the occurrence of density unevenness due to rapid pressure increase, it is preferable that the rate of increase is 50 MPa / min or less, 40 MPa / min or less, or 30 MPa / min or less. On the other hand, the rate of increase can be 1 MPa / min or more, 5 MPa / min or more, or 10 MPa / min or more. Examples of rate of increase in pressure during molding include 1 MPa / min to 50 MPa / min, 5 MPa / min to 40 MPa / min, or 10 MPa / min to 30 MPa / min.

[0096] The molding method includes methods for obtaining a molded body (compacted body), and includes one or more selected from the group consisting of uniaxial pressing, cold isostatic pressing (hereinafter also referred to as "CIP"), slip casting, sheet molding, injection molding, and three-dimensional molding, and it is sufficient if at least one of uniaxial pressing and CIP is used. Since the pores tend to become more uniform, it is preferable that the molding process is performed using CIP.

[0097] The manufacturing method of this embodiment includes a step of sintering the molded body (hereinafter also referred to as the "sintering step"). By going through the sintering step, the quartz glass of this embodiment is obtained as sintered quartz glass.

[0098] Unlike the melting method for manufacturing quartz glass, the sintering method for manufacturing quartz glass is greatly influenced by the state of the molded body. In other words, in the melting method, quartz glass is obtained after the raw material powder is melted (liquefied), so pore removal is performed without being affected by the properties of the molded body. In contrast, in the sintering method, quartz glass is obtained without the melting of the raw material powder, so the properties of the molded body, especially the state of the pores of the molded body, are reflected in the state of the pores of the quartz glass. In the manufacturing method of this embodiment, by subjecting the molded body obtained through the molding process described above to sintering, pores are efficiently removed despite it being a sintering method, and as a result, the quartz glass of this embodiment can be obtained.

[0099] To avoid excessive porosity removal from the molded body, it is preferable that the sintering process be carried out at atmospheric pressure. In this embodiment, "atmospheric pressure sintering" refers to a method of sintering by heating the material to be sintered (molded body) without applying any external force during the sintering process.

[0100] The sintering atmosphere can be any oxidizing atmosphere, but an atmospheric atmosphere is preferred.

[0101] The holding temperature during sintering should be below the softening temperature of the raw material powder, preferably 1400°C or lower, or 1350°C or lower. The holding temperature should be at a temperature at which densification progresses, preferably 1200°C or higher, or 1250°C or higher. Examples of holding temperatures during sintering include 1200°C to 1400°C and 1250°C to 1350°C.

[0102] Preferably, the heating rate to the holding temperature differs between the heating rate from the starting temperature to 1000°C (hereinafter also referred to as the "early heating rate") and the heating rate from 1000°C to the holding temperature (hereinafter referred to as the "later heating rate"), with the later heating rate being particularly slower than the early heating rate. In the production of quartz glass by sintering, sintering proceeds from the surface of the sintered material (molded body). By having a slower later heating rate in the temperature range where silica particle fusion and sintering proceed compared to the early heating rate in the temperature range where sintering progresses almost nonexistent, overheating of the surface of the sintered material (molded body) prior to sintering is suppressed, and the difference in the degree of sintering between the surface and the interior of the sintered material becomes smaller. As a result, the pore state of the resulting quartz glass becomes more uniform, the pore area ratio of the entire quartz glass tends to decrease, and it is thought that it becomes easier to control the difference in pore area ratio in the quartz glass within the range described above.

[0103] The average heating rate to the holding temperature is preferably 50°C / hour or more or 100°C / hour or more, and preferably 200°C / hour or less or 150°C / hour or less. In the sintering process, the average heating rate to the holding temperature can be 50°C / hour or more and 200°C / hour or less, or 100°C / hour or more and 150°C / hour or less.

[0104] The holding time at the holding temperature can be adjusted as appropriate depending on the size of the molded body to be subjected to the sintering process and the characteristics of the sintering furnace, but examples include 0.5 hours or more or 1 hour or more, and 5 hours or less or 3 hours or less, and it is acceptable to have a holding time of 0.5 hours or more and 5 hours or 1 hour or more and 3 hours or less.

[0105] In the sintering process, particularly preferred sintering conditions include the following: Sintering method: atmospheric pressure sintering Sintering atmosphere: atmospheric atmosphere Holding temperature: 1250°C or higher and 1350°C or lower Heating rate: Early heating rate 100°C / hour or higher and 150°C / hour or lower Late heating rate 10°C / hour or higher and 80°C / hour or lower

[0106] The manufacturing method of this embodiment may include a step of fire polishing (FP treatment) of quartz glass to form an outer shell quartz glass (hereinafter also referred to as the "FP process"). The FP process is a surface treatment of quartz glass, and more specifically, a surface treatment of quartz glass using a flame, and further specifically, a process to reduce or remove defects on the surface of quartz glass using a flame. It can also be considered as a process to reduce or remove surface defects at high temperature and in a short time. Through the FP process, the surface of the quartz glass of this embodiment (opaque quartz glass) melts, and an outer shell layer made of translucent quartz glass is obtained. This gives rise to the quartz glass member (outer shell quartz glass) of this embodiment.

[0107] The FP treatment can be any treatment that melts the surface of the quartz glass, but it is preferably a surface treatment using an oxyhydrogen flame, and more preferably a surface treatment using an oxyhydrogen flame using a premixed combustion type or diffusion combustion type oxyhydrogen burner. An oxyhydrogen flame can be obtained by flowing oxygen and hydrogen so that the hydrogen flow rate is 4 ± 2 times the oxygen flow rate. A preferred FP treatment is one performed under the following conditions: Burner: Oxyhydrogen burner Hydrogen flow rate: 21.5 ± 1.0 L / min Oxygen flow rate: 7.2 ± 0.3 L / min Distance between burner tip and quartz glass: 2.5 ± 0.5 cm Treatment speed: 3 seconds / cm ２ More than or equal to 4 seconds / cm ２ That's all, and also 7 seconds / cm ２ Less than or equal to 6 seconds / cm ２ below

[0108] If the manufacturing method of this embodiment includes an FP (Fiber Processing) step, it may include a step of cleaning the quartz glass (hereinafter also referred to as the "cleaning step") prior to the FP step. The cleaning in the cleaning step should be any cleaning that can remove impurities from the surface of the quartz glass, and examples include acid cleaning and acid cleaning with hydrofluoric acid.

[0109] If the manufacturing method of this embodiment includes an FP (Functional Processing) step, it is preferable to include a step of heat-treating the outer quartz glass (hereinafter also referred to as the "annealing step"). The outer quartz glass may be distorted due to the temperature distribution on the glass surface and inside during or after the FP treatment. By reducing and eliminating the distortion of the outer quartz glass through heat treatment after the FP treatment, stress concentration is reduced, and the outer quartz glass becomes less prone to breakage.

[0110] The heat treatment in the annealing process can be any method that can reduce and remove the strain of the outer quartz glass. For example, it can be heat treatment using a general heat treatment furnace (e.g., a box-shaped furnace), and the heat treatment can be performed at a temperature above the strain point. Preferred heat treatment conditions include the following: Heat treatment atmosphere: Air atmosphere Heat treatment temperature: 1050°C or higher, 1100°C or higher, or 1150°C or higher, and 1300°C or lower, 1250°C or lower, or 1200°C or lower

[0111] The heat treatment time can be adjusted as appropriate depending on the heat treatment furnace and the size of the outer quartz glass, but examples include 30 minutes to 2 hours, or 1 hour to 1.5 hours.

[0112] The contents of this disclosure will be described in detail below with reference to examples and comparative examples. However, this disclosure is not limited to the examples.

[0113] (Tap bulk density) Tap bulk density was measured using a measurement method in accordance with the constant volume measurement method specified in JIS R 1628.

[0114] (Porosity ratio and difference in porosity ratio) The porosity ratio was obtained by analyzing optical microscope images of the cross-section of quartz glass obtained by optical microscope observation using a general optical microscope (device name: VHX-900F, manufactured by Keyence Corporation) under the following conditions: Magnification: 200x to 1000x Objective lens type: VH-Z100R Illumination: Coaxial incident illumination Illuminance: 255 White balance: Push set R686, G256, B416 Shooting mode: Normal shooting

[0115] For optical microscope observation, the observation surface was the cross-section of the interior of quartz glass obtained by cutting the glass, after removing defects (such as linear marks) caused by cutting and rough polishing by mirror polishing with 1 μm diamond abrasive grains.

[0116] The optical microscope images were analyzed using image analysis software (software name: ImageJ (version: 1.53t)). The optical microscope images were binarized to obtain binarized images, and the stomata were detected, and the area of ​​each stomata, the total area of ​​all stomata, and the area of ​​the optical microscope image (binarized image) were calculated using the image analysis described above. The binarization process was performed using the following method. The threshold for binarization in ImageJ was set using the following method. The Threhold function was used, Otsu was selected, Dark background, Stack histogram, and Raw values ​​were unchecked, and Don't reset range was checked. Then, by selecting Auto, the binarization threshold was determined.

[0117] Image analysis was performed on 3500 ± 200 stomata. The stomata area ratio was calculated from the image analysis results using the following formula: R = S / T Ｓ ×100 In the above formula, R is the pore area ratio [area %] and S is the total area of ​​all pores [μm] ２ ], T Ｓ This is the image area [μm²] of the optical microscope observation image (binarized image). ２ ]

[0118] Furthermore, for the quartz glass obtained in the examples and comparative examples, the porosity area ratio at a depth of 10 mm from the surface (the porosity area ratio obtained by measuring the cut surface after cutting a thickness of 10 mm from the surface of the quartz glass) and the porosity area ratio at a depth of 15 mm from the surface (the porosity area ratio obtained by measuring the cut surface after cutting a thickness of 15 mm from the surface of the quartz glass) were measured, and the absolute value of the difference between them was determined as the difference in porosity area ratio.

[0119] (Porous area ratio, R ５ and R １５The pore area ratio [area %] was determined from image analysis of the binarized graph obtained by the same method as the measurement of the pore area ratio described above. In calculating the pore area ratio, the pore diameter was determined by approximating each detected pore with a circle and using the following formula as the diameter of the resulting approximate circle. D Ｐ = (4S Ｐ / π) ０．５ In the above equation, D Ｐ The pore diameter [μm] of each pore, and S Ｐ The area of ​​each pore [μm²] ２ ]

[0120] R ５ and R １５ Each of these represents the total area of ​​all stomata [μm²]. ２ The total area of ​​pores with a diameter of 5 μm or less in the area [μm] ２ The percentage of [area %] and the total area of ​​all pores [μm²] ２ The total area of ​​pores with a diameter of 15 μm or less in the area [μm] ２ This was calculated from the ratio [area %] of ].

[0121] (Average pore size) The average pore size is obtained by the same method as the pore area ratio, using all D Ｐ A stomatal diameter-area frequency distribution was created, and the stomatal diameter corresponding to 50% of the frequency in this distribution was defined as the average stomatal diameter (50% stomatal diameter).

[0122] In calculating the average pore diameter, the pore diameter was determined by approximating each detected pore as a circle and using the following formula as the diameter of the resulting approximation circle: D Ｐ = (4S Ｐ / π) ０．５ In the above equation, S Ｐ The area of ​​each pore [μm²] ２ ]

[0123] (Measured Density) The measured density of quartz glass was determined in accordance with JIS R 1634. Prior to measurement, the sample was pretreated by boiling.

[0124] (Visible light transmittance / Near-infrared reflectance) Visible light transmittance and near-infrared reflectance were measured using a general ultraviolet-visible-near-infrared spectrophotometer (device name: UV-3600Plus, manufactured by Shimadzu Corporation) equipped with an InGaAs detector and a cooled PbS detector, respectively, under the following conditions: Measurement wavelength: 380 nm to 2500 nm Wavelength step: 1 nm intervals

[0125] For visible light transmittance and near-infrared reflectance, 1 μm diamond particles were used as the measurement sample, and quartz glass with the measurement surface and the surface opposite the measurement surface mirror-polished was used.

[0126] Visible light transmittance was calculated by averaging the linear transmittance at a sample thickness of 1.0 ± 0.05 mm and measurement wavelengths from 380 nm to 780 nm. Infrared reflectance was calculated by averaging the reflectance at a sample thickness of 1.0 ± 0.05 mm and measurement wavelengths from 780 nm to 2500 nm.

[0127] (Lightness) Lightness L ＊ The measurements were taken using a spectrophotometer (device name: CM-5, manufactured by Konica Minolta) equipped with illumination and light-receiving optics conforming to geometric condition c of JIS Z 8722, under the following conditions: Light source: D65 light source; Field of view: 10°; Measurement method: SCE; Measurement diameter: 8 mm; Background color: Black

[0128] The measurement samples used were the same as those used for the measurement of infrared reflectance.

[0129] (Ring bending strength, post-treatment ring bending strength, and ring strength ratio) The ring bending strength and post-treatment ring bending strength [MPa] were measured using a general precision universal testing machine (device name: AGS-5kNX, manufactured by Shimadzu Corporation) and the following ring bending jig, in accordance with the ASTM C 1499 method. Load ring diameter: 12.7 mm Support ring diameter: 25.4 mm Ring tip radius: 1 mm

[0130] The measurement was performed by applying a load to the sample under the following conditions, and the individual ring bending strength (σ) of each sample was calculated from the crushing load obtained using the above formula. ｆ) [MPa] was determined, and the individual ring bending strength (σ) measured for 15 measurement samples was calculated. ｆ The average value of the values ​​was used as the ring bending strength. Crosshead speed: 1.1 mm / min Poisson's ratio: 0.17

[0131] For measuring the ring bending strength, the sample used was a disc-shaped quartz glass with a diameter of 33 ± 0.5 mm and a thickness of 4 ± 0.5 mm. This sample was then double-sided ground using a rotary grinder (#270) to reduce its thickness to 3 ± 0.2 mm, and polished using a double-sided polishing machine with 7 μm alumina abrasive grains, 0.9 μm ceria abrasive grains, and 0.08 μm colloidal silica abrasive grains in that order. The resulting disc-shaped quartz glass sample had a diameter of 33 ± 0.5 mm and a thickness of 2.5 ± 0.1 mm.

[0132] For measuring the bending strength of the ring after treatment, the sample used was quartz glass similar to the quartz glass used for measuring the bending strength of the ring, and the entire surface of the disc-shaped quartz glass was treated with FP under the following conditions: <FP Treatment Conditions> Burner: Oxyhydrogen burner Hydrogen flow rate: 21.5 ± 1.0 L / min Oxygen flow rate: 7.2 ± 0.3 L / min Distance between burner tip and quartz glass surface: 2.5 cm Treatment time: 5 ± 2 seconds / cm ２ The ring strength ratio was calculated from the obtained ring bending strength and the ring bending strength after treatment.

[0133] Example 1: Gas-phase silica (SiO ２ The BET specific surface area is 85 m² such that 30% by mass of ) and 70% by mass of flame-fused silica. ２ Gas-phase silica with a concentration of / g and a BET specific surface area of ​​1.4 m² ２ Flame-fused silica at a concentration of 1 / g was weighed and mixed to obtain a mixed powder. Next, silicon monoxide powder with a D50 diameter of 0.9 μm was mixed with the mixed powder so that the mass of silicon monoxide (SiO) was 1996 ppm by mass (0.2% by mass as the mass of silicon monoxide relative to the total mass of gas-phase silica and flame-fused silica), resulting in a BET specific surface area of ​​26.5 m². ２5 kg of raw material powder with a concentration of 1 / g was obtained. Mixing was performed by dry mixing using a ball mill with polymer balls (resin balls) with a diameter of 15 mm as the mixing medium. As a result, the BET specific surface area was 27.9 m². ２ The weight per gram and the bulk density of the tapped area are 0.8 g / cm³. ３ A raw material powder was obtained (BET increase rate: 5.3%). The raw material powder had a bimodal volume particle size distribution, with a first frequency peak at a particle size of 81 μm and a second frequency peak at a particle size of 271 μm, with a frequency ratio of 0.7.

[0134] The raw material powder was filled into a disc-shaped mold with a diameter of 350 mm, and then subjected to CIP treatment by increasing the pressure at a rate of 20 MPa / min to a holding pressure of 100 MPa and holding for 3 minutes to obtain a disc-shaped molded body (compacted powder) with a diameter of 280 mm and a thickness of 90 mm.

[0135] The molded body was heated from room temperature to 1000°C at a heating rate of 100°C / hour, and then heated from 1000°C to 1300°C at a heating rate of 50°C / hour. After heating to 1300°C, it was fired in an air atmosphere at a holding temperature of 1300°C for 3 hours, and then allowed to cool naturally to obtain the quartz glass of this embodiment.

[0136] Example 2 The quartz glass of this example was obtained in the same manner as in Example 1, except that the CIP treatment was performed at a CIP pressure of 130 MPa.

[0137] Example 3 The quartz glass of this example was obtained in the same manner as in Example 1, except that the CIP treatment was performed at a CIP pressure of 150 MPa.

[0138] Comparative Example 1: The quartz glass of this comparative example was obtained in the same manner as in Example 1, except that the CIP treatment was performed at a CIP pressure of 280 MPa.

[0139] Comparative Example 2: A commercially available opaque quartz glass (product name: OP-3, manufactured by Tosoh SGM Co., Ltd.) was used as the quartz glass for this comparative example.

[0140] Comparative Example 3: A commercially available fused transparent quartz glass (product name: N, manufactured by Tosoh SGM Co., Ltd.) was used as the quartz glass for this comparative example.

[0141] Comparative Example 4 Opaque quartz glass was obtained by the same method as in Example 9 of Patent Document 2. That is, 30% by mass of fumed silica (tap bulk density 0.6 g / cm³) ３ , BET specific surface area 85m ２ ( / g) and 70% by mass of spherical silica (D ５０ is 10 μm, D １０ is 2 μm and D ９０ A mixture of particles (31 μm) was compacted and mixed in a ball mill without the use of a solvent to obtain a mixed powder. The BET increase rate at this time was 0%. The mixed powder was press-molded at 90 MPa and sintered at 1325°C to obtain the quartz glass of this comparative example.

[0142] The evaluation results for the examples and comparative examples are shown in the table below.

[0143]

[0144] The quartz glass in the examples all had a visible light transmittance of less than 20%, and even less than 1%, confirming that they were opaque quartz glass. Furthermore, the near-infrared reflectance was 30% or more, confirming that it exhibited higher heat shielding properties compared to the conventional opaque quartz glass in Comparative Example 2. Figure 2 shows an optical microscope image of the cross-section of the quartz glass of Example 1. From Figure 2, it was confirmed that the pore shape was non-spherical, and that the pores of the quartz glass in this example consisted of irregularly shaped pores. In addition, the largest pore in the quartz glass of Example 1 had a maximum length of 26 μm.

[0145] Furthermore, in all of the examples, the ring strength ratio was 1.2 or higher, confirming a significant improvement in mechanical strength and suggesting that a corrosion resistance-improving effect can be expected. In contrast, the opaque quartz glass of Comparative Example 4, which had a porosity ratio exceeding 10%, had a ring strength ratio of 1.05, and in both cases, it was confirmed that the corrosion resistance-improving effect was smaller compared to the examples.

[0146] Examples 4 to 6 and Comparative Examples 5 to 7 The quartz glass of the Examples and Comparative Examples was used as the raw material glass, and by subjecting it to FP treatment under the following conditions, a quartz glass member having an outer shell layer was obtained. Burner: Oxyhydrogen burner Hydrogen flow rate: 21.5 ± 1.0 L / min Oxygen flow rate: 7.2 ± 0.3 L / min Distance between burner tip and quartz glass: 2.5 ± 0.5 cm Processing speed: 5 ± 2 seconds / cm ２

[0147] The surface transmittance of the obtained quartz glass member having an outer shell layer was measured under the following conditions. The outer shell layer (surface of the outer shell quartz glass) was cut out in the thickness direction of the quartz glass member (outer shell quartz glass) to a thickness of 1.0 mm, and the cut surface (the surface facing the outer shell quartz glass surface) was polished to obtain a cut piece with a thickness of 0.7 mm. The polished cut surface and the surface facing it were mirror polished using 1 μm diamond abrasive grains to obtain a measurement sample with a thickness of 0.5 ± 0.05 mm. The surface transmittance was measured in the same manner as the visible light transmittance described above, except that the obtained measurement sample was used.

[0148]

[0149] In all of the examples, it was confirmed that the quartz glass member consisted of an outer shell layer made of translucent quartz glass with a surface transmittance of 60% or more, and a main body made of quartz glass with a pore area ratio exceeding 0% and being 5% or less, and a pore area ratio of 30% or more with a pore diameter of 5 μm or less. Furthermore, from Comparative Example 6, it was confirmed that the quartz glass member obtained from conventional opaque quartz glass had a surface transmittance of 55% or less, indicating that the low surface transmittance made it difficult for the outer shell layer to densify, and the quartz glass member of Comparative Example 7 had a transmittance of 40% or less. From this, it was confirmed that the quartz glass of Examples 1 to 3 is opaque quartz glass that is easily formed into a dense outer shell layer by FP treatment.

[0150] Figure 3 shows a cross-sectional photograph of the quartz glass member of Example 4. It was confirmed that the thickness of the outer shell layer of this quartz glass member was between 0.4 mm and 0.8 mm.

[0151] Comparative Example 8: The quartz glass of this comparative example was obtained in the same manner as in Example 3, except that the temperature was raised from room temperature to 1300°C at a constant rate over 1 hour, then fired at a holding temperature of 1300°C for 40 minutes, and finally allowed to cool naturally. The evaluation results are shown in the table below.

[0152]

[0153] The difference in pore area ratio in Example 3 was 0.3%, confirming that the pore distribution was uniform. On the other hand, the difference in pore area ratio in Comparative Example 8 was a large 2.3%, confirming that the pore distribution was non-uniform. In Comparative Example 8, the pore area ratio at 15 mm from the surface was larger than that at 10 mm from the surface, suggesting that the sintering progressed in the interior was insufficient compared to the surface of the quartz glass.

[0154] 100 Outer shell quartz glass 10 Outer shell layer 11 Main body

Claims

1. Quartz glass in which the porosity ratio is greater than 0% but less than or equal to 5%, and the proportion of porosity area with a pore diameter of 5 μm or less is 30% or more.

2. The quartz glass according to claim 1, wherein the average pore size is 15.0 μm or less.

3. The quartz glass according to claim 1 or 2, wherein the difference in porosity ratio is 2.0% or less.

4. The quartz glass according to claim 1 or 2, wherein the sample thickness is 1.0 ± 0.05 mm and the average value of the reflectance at measurement wavelengths of 780 nm to 2500 nm is 30% or more.

5. The quartz glass according to claim 1 or 2, wherein the sample thickness is 1.0 ± 0.05 mm and the average value of the linear transmittance at measurement wavelengths of 380 nm to 780 nm is 20% or less.

6. The quartz glass according to claim 1 or 2, wherein the ring bending strength after fire polishing under the following conditions is 90 MPa or more: Burner: Oxyhydrogen burner Hydrogen flow rate: 21.5 ± 1.0 L / min Oxygen flow rate: 7.2 ± 0.3 L / min Distance between burner tip and quartz glass surface: 2.5 cm Processing time: 5 ± 2 seconds / cm ２ 7. A quartz glass member comprising an outer shell layer and a main body made of quartz glass as described in claim 1 or 2.

8. The quartz glass member according to claim 7, wherein the outer shell layer is a layer made of translucent quartz glass.

9. The quartz glass member according to claim 7, wherein the outer shell layer has an average value of 55% or more for linear transmittance at a measurement wavelength of 380 nm to 780 nm at a sample thickness of 0.5 ± 0.05 mm.

10. The quartz glass member according to claim 7, wherein the thickness of the outer shell layer is 5 mm or less.

11. Tap bulk density is 0.75 g / cm³ ３ 1.15g / cm or more ３ A method for producing quartz glass according to claim 1, comprising the steps of: molding silica powder, which is as follows, at a molding pressure of 95 MPa or more and 270 MPa or less to obtain a molded body; and sintering the molded body.

12. The manufacturing method according to claim 11, wherein the silica powder has a frequency peak in its volume particle size distribution for particle sizes of 50 μm or more and 150 μm or less, and a frequency peak for particle sizes greater than 150 μm and 400 μm or less.

13. The manufacturing method according to claim 11 or 12, wherein the molding pressure is used to hold the object.

14. The manufacturing method according to claim 11 or 12, wherein the rate of pressure increase until the molding pressure is reached is 50 MPa / min or less.

15. The manufacturing method according to claim 11 or 12, wherein the heating rate from 1000°C to the holding temperature during sintering is slower than the heating rate from the start of heating to 1000°C.

16. The manufacturing method according to claim 15, wherein the holding temperature is 1400°C or lower.

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