A thin glass device

Abstract

The present invention provides a thin glass device, which is made of a high-density, high-specific elastic modulus glass having a density of greater than or equal to 3.00 g / cm 3 , and a specific elastic modulus of greater than 37 GPa·cm 3 / g. The thin glass device of the present invention has a thickness of less than or equal to 0.50 mm, and maintains high rigidity, high-speed rotation stability, low deflection, low thermal post-flatness change, and pure glass phase stability required for a magnetic recording medium substrate after thinning, without any ion exchange strengthening treatment, and is applicable to a disc-shaped device, a through-hole disc, an information recording medium substrate, a magnetic recording medium substrate, an HDD disc substrate, a HAMR disc substrate, a MAMR disc substrate, and related information recording devices.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, specifically, to a thin glass device. Background Technology

[0002] The real-world demand for HDD industry development and continuous capacity expansion: Hard disk drives (HDDs) have long been a fundamental component in the field of high-capacity data storage. In cloud computing, data centers, video archiving, security monitoring, and various cold and warm data storage scenarios, HDDs retain significant engineering value due to their low unit cost, strong capacity scalability, and mature system integration. Public data indicates that enterprise-level HDD platforms for high-capacity applications continue to increase both single-disk capacity and overall system capacity, demonstrating that HDDs remain irreplaceable in medium- to high-capacity storage systems.

[0003] Currently, high-capacity enterprise-grade HDDs primarily utilize a 3.5-inch form factor platform. Publicly available information indicates that these high-capacity platforms have entered the 28TB-36TB capacity range. Seagate has publicly disclosed its 36TB solution using a 10-platter, 0.5mm thick glass platter structure, while Western Digital has unveiled an 11-platter, 32TB data center platform. This means that within a given overall form factor, the practical paths to further increase single-unit capacity mainly include two directions: first, increasing the recording density per platter; and second, accommodating as many platters as possible within a limited cavity space.

[0004] Therefore, one of the fundamental engineering goals for increasing HDD capacity is to further thin the substrate while maintaining the basic performance and reliability of the platters, thereby freeing up space to increase the number of platters. This goal constitutes the direct engineering driving force for the continuous upgrading of substrate materials.

[0005] The evolution of substrate materials from aluminum alloy to glass substrates: Early HDD disk substrates were mostly made of aluminum alloy. Aluminum alloy substrates have advantages such as mature processing and controllable cost, but with the increase in recording density, the reduction of the magnetic head flight altitude and the increase in disk rotation speed, its limitations have gradually been exposed in terms of surface flatness, thermal deformation control, plastic deformation suppression and high-speed rotation stability.

[0006] In comparison, glass substrates typically offer higher surface flatness, less tendency for plastic deformation, better dimensional stability, and greater potential for mirror finishing. Therefore, they are gradually replacing traditional aluminum alloy substrates as a key development path for high-performance magnetic recording media. Publicly available information clearly indicates that glass substrates have advantages such as vibration resistance, impact resistance, and resistance to bending after thinning, and they also help increase the number of platters and overall capacity in a single HDD.

[0007] Therefore, the shift from aluminum alloy to glass substrate as the disk substrate material is not a simple material replacement, but an inevitable result driven by the combined requirements of lower flight altitude, higher recording density, higher rotation speed, and higher capacity.

[0008] Current development path of glass substrate technology: After glass substrates replaced aluminum alloy substrates, the industry has carried out a long-term and systematic technological layout around glass disk substrates. Existing technologies can be broadly divided into the following categories.

[0009] 1. Conventional glass substrate route This is currently the most mainstream approach. The basic idea is to introduce components that can improve the elastic modulus while minimizing the density burden, such as Mg, Ca, and Li, into a good glass framework to obtain higher rigidity and higher specific elastic modulus (E / ρ).

[0010] 2. Ion-exchange (IOX) reinforced glass route Another approach is to introduce a residual compressive stress field on the glass surface through ion exchange to improve the strength of glass components. This approach is significant in fields such as cover glass, but its strengthening effect is fundamentally dependent on the ion concentration distribution and the residual stress field itself.

[0011] 3. Glass-ceramic / microcrystalline strengthening route Another approach involves improving elastic modulus and heat resistance through controlled crystallization or glass-ceramicization. Public information indicates that relevant companies have already been using glass-ceramics in hard drive substrates and have established an industrial-scale presence.

[0012] Overall, existing HDD glass substrate technology has evolved from a simple question of "whether glass can be used" to a comprehensive question of "how to adapt to high-capacity HDDs through material composition, thermal stability, mechanical stability, surface quality, and device profile control".

[0013] New requirements for glass substrates in HAMR HDD: 1. Requirements arising from upgrades in magnetic recording materials and writing principles As traditional perpendicular magnetic recording (HMR) approaches its recording density limit, the industry has developed the HAMR (High-Activity Magnetic Recording) approach. The basic principle of HAMR lies in using a magnetic recording medium with higher magnetic anisotropy and locally heating the medium to make it easier to write during the writing process, thus achieving a balance between high thermal stability and writability. Public data indicates that the local temperature in the HAMR writing area can reach approximately 450°C or even close to 500°C; simultaneously, the disk substrate used for energy-assisted magnetic recording media may undergo high-temperature treatment of approximately 600°C to 800°C before, during, or after the formation of the magnetic layer.

[0014] This means that HAMR substrates must simultaneously possess: higher temperature resistance; better profile stability after thermal history; surface stability during long-term operation at medium and low temperatures; better compatibility with high-temperature coating processes, especially in terms of stress matching between the glass substrate and the coating; and better cleanliness, stability, and thermal stability of high-temperature coating processes.

[0015] 2. Requirements arising from higher rotational speeds and lower flight altitudes On the other hand, as the head-platter distance continues to decrease, thermal fly-up control technology is used to compensate for head-platter distance fluctuations caused by writing heat and environmental changes. The smaller the head-platter distance, the more sensitive the disk surface profile, dynamic deflection, and thermal deformation are to the impact on reliability.

[0016] Therefore, the requirements for glass substrates in HAMR HDD are not simply "more heat resistant", but also include: higher rigidity; lower deflection and vibration during high-speed rotation; and higher feasibility of surface processing quality.

[0017] Features and shortcomings of existing technologies (I) The traditional ordinary glass route with "increasing E (elastic modulus) and reducing density" as its core. Regarding the question of "how to maintain rigidity on thinner discs," the most direct traditional solution in the industry is to use lighter and stiffer materials. In materials science terms, this means increasing the elastic modulus E while minimizing the density ρ, thereby increasing the E / ρ ratio, or specific elastic modulus.

[0018] This type of approach has been represented by many publicly available patents.

[0019] 1. A scheme to improve rigidity using a high-Mg route. For example, CN121464482A explicitly claims that the glass composition for information recording media has an elastic modulus of 98 GPa or higher and contains 17–30 mol% MgO; its dependent claims further claim a specific elastic modulus of 36 MNm / kg or higher, and allow the introduction of 0.2–3 mol% Li2O and 0.2–3 mol% B2O3. Meanwhile, its specific composition includes 50–65 mol% SiO2, 7.5–26 mol% Al2O3, 15–30 mol% MgO, 0–8 mol% CaO, 0–3 mol% B2O3, and 0–3 mol% Li2O, and further limits the total amount of TiO2 and Y2O3 to no more than 3 mol%.

[0020] The core characteristic of this type of approach is that, based on a good glass framework, high magnesium (Mg) content is used to improve rigidity while maintaining a low density load. Its drawback is that while high Mg content is beneficial for increasing elastic modulus (E), it also significantly enhances the tendency for crystallization, making the glass stability region tend to narrow. When the Mg content reaches a certain proportion, the tendency for crystallization becomes strong, which is detrimental to continuous production and also makes it difficult to obtain glass substrates with higher specific modulus of elasticity. Essentially, it is a "low density priority" technical path to achieve higher rigidity.

[0021] 2. A scheme targeting a combination of high E, low specific gravity, and high Tg. For example, CN121488294A directly claims that the glass plate for information recording media has an elastic modulus of 94 GPa or more, a specific gravity of 2.8 g / cm3 or less, and a glass transition temperature of 700°C or more; its dependent claims further propose that the MgO content is 15–30 mol%, the elastic modulus is 100 GPa or more, the specific elastic modulus is 36 MNm / kg or more, and the thickness is 1 mm or less.

[0022] This type of solution more explicitly targets the combination of "high rigidity, low specific gravity, and high Tg" than the previous one. Its shortcoming is that, with "low specific gravity" as the core premise, the technical logic still follows the path of "lighter and stronger" perfect glass, and further improving the specific elastic modulus is limited by the limited availability of lightweight high-modulus oxides.

[0023] 3. HOYA / NEG represents the low-density, high-rigidity ordinary glass route. For example, US12479755B2 explicitly uses the easy deformation of aluminum alloy substrates and insufficient surface flatness after polishing as the background for replacing glass substrates, and further advocates an amorphous oxide glass with SiO2 of 56–80 mol%, Li2O≤10 mol%, B2O3 of 0–4 mol%, and MgO+CaO of 9–40 mol%, while requiring a glass transition temperature of 650℃ or higher, an elastic modulus of 90 GPa or higher, and a specific gravity of 2.75 g / cm3 or lower.

[0024] For example, US12579997B2 further introduces a more complex alkaline earth / alkali metal / minor rare earth synergistic scheme into the ordinary glass route. Its claims cover compositions such as MgO 3–28%, CaO 0–18%, TiO2 0–5%, ZrO2 0–3%, and total alkali metals 3.5–13%, and explicitly include a specific elastic modulus ≥31 MNm / kg as one of the targets, while requiring confirmation of no crystals. Its specification also repeatedly emphasizes that lower specific gravity is more conducive to reducing HDD power consumption, while higher specific elastic modulus is more conducive to reducing deformation.

[0025] For example, US20250263325A1 further advances this traditional approach towards the HAMR scenario, and its disclosed glass magnetic recording medium substrate requires a linear expansion coefficient of 30×10⁻⁶ at 30–380°C. -7 / ℃ to 70×10 -7 / ℃, elastic modulus above 80 GPa, specific elastic modulus 30 GPa / g·cm -3 The strain temperature is above 700℃; its typical composition is based on SiO2 55–65%, Al2O3 15–25%, B2O3 2–5.5%, MgO 0.1–10%, CaO 0.1–10%, and ZrO2 0–1%. The specification clearly states that: CaO increases the modulus but is beneficial for reducing high-temperature viscosity, and too high a concentration will weaken the resistance to crystallization; ZrO2 increases the modulus, but too high a concentration will reduce the resistance to crystallization; too high a concentration of BaO and SrO will increase the density and reduce the specific elastic modulus.

[0026] The common characteristics of this major category of schemes can be summarized as follows: using ordinary glass as the main body; based on a better glass framework; introducing elements such as Mg, Ca, Li, and B, which are beneficial to improving elastic modulus or improving meltability; and pursuing a higher specific modulus of elasticity from the direction of "increasing elastic modulus and reducing density".

[0027] Their common shortcomings are: their technical logic is still "low density priority"; the high Mg route tends to increase the tendency to crystallize; although the alkali metal route such as Li / Na improves processability, it is sensitive to migration and contamination under high temperature coating or high temperature thermal history; the publicly disclosed target specific elastic modulus is generally concentrated in the range of about 30-36 MNm / kg, and the mainstream target range can be considered to be concentrated in the range of about 31-35 MNm / kg, and no systematic approach to significantly improve E / ρ under higher density conditions is provided.

[0028] Therefore, although this type of solution represents the mainstream approach for ordinary glass substrates, in thinner disk substrates and HAMR scenarios, it is necessary to further improve the specific elastic modulus to maintain the performance of the glass substrate, which brings the solution for glass disks to the limit.

[0029] (II) Disk-based approach focusing on device structure and low vibration In addition to the materials themselves, the industry has also developed solutions to reduce the problem of thin disks from the perspective of device structure.

[0030] For example, CN120937077A discloses a disk for information recording media and its substrate. The background directly points out that in order to increase the storage capacity of HDD devices, it is preferable to reduce the thickness of the disk for information recording media and increase the number of disks mounted while increasing the magnetic layer recording density. However, the thinner the disk, the less strong it is and the greater the jitter. Therefore, it is desirable to use a material with a higher elastic modulus and a harder substrate.

[0031] The value of this type of solution lies in its accurate grasp of the engineering relationship between increasing overall capacity and reducing disk thickness. However, its shortcoming is that it alleviates the problem more from the perspective of device structure, intermediate layer, or composite disk, rather than fundamentally answering the question of "what new combined properties should the glass material itself possess under further thinning conditions" from the perspective of the material itself.

[0032] (III) Precision machining route with surface, edge and contour control as the core Another category of patents focuses on issues such as surface waviness, edge profile, chamfer curvature, concentricity, and surface slope. For example, US9105293B2 reduces morphological differences in the outer edge region by controlling the microscopic waviness in the 60–500 μm wavelength band and is specifically designed for magnetic head scenarios with flight altitudes below 5 nm. US9564166B2 emphasizes surface tilt distribution, low roughness, and high recording density adaptation.

[0033] These approaches are crucial for ultra-low flight altitudes and high recording density scenarios. However, they rely on the material itself being sufficiently stable, rigid, and heat-resistant. If the material itself undergoes significant deflection, changes in thermal flatness, or crystallization instability after thinning, then simply relying on surface and contour processing control cannot fundamentally solve the problem.

[0034] (iv) Shortcomings of ion exchange enhancement route and glass-ceramic route 1. Shortcomings of the IOX route The core of the ion-exchange (IOX) reinforced glass approach lies in establishing a surface compressive stress field through ion concentration differences, thereby enhancing strength. However, this strengthening process is inherently dependent on the ion concentration distribution and the residual stress field itself. Public research indicates that at higher temperatures, ions in the ion-exchange layer undergo further redispersement, while the glass experiences viscoelastic relaxation, leading to stress redistribution, attenuation of surface compressive stress, and a decrease in the strengthening effect. Therefore, under conditions of localized hot writing at 450–500°C and coating / heat treatment at 600–800°C, the IOX approach struggles to fundamentally address the high-temperature stability issues of HAMR disk substrates.

[0035] 2. Shortcomings of the glass-ceramic route The glass-ceramic approach improves elastic modulus and heat resistance by introducing crystalline phases, effectively enhancing elastic modulus and rigidity within the glass framework. However, the crystalline phase size in this approach is typically on the order of tens of nanometers to higher. Publicly available data indicate crystalline phase sizes of approximately 10–150 nm. This means that the glassy and crystalline phases coexist within the material, leading to differences in their removal behavior during surface polishing. This makes it difficult to consistently achieve the extremely low roughness, extremely low waviness, and extremely high morphological consistency required for HAMR disk substrates. Therefore, while this approach is effective in improving rigidity, it presents inherent processing challenges under ultra-demanding surface requirements.

[0036] In summary, the primary problem faced by existing technologies is that, in order to increase the overall capacity of HDDs, all key performance characteristics need to be maintained simultaneously on thinner glass substrates.

[0037] Given the current highly crowded 3.5-inch, 95 mm-class, and 10–11-platter platforms, a crucial and practical way to further increase overall system capacity is to further reduce platter thickness. Summary of the Invention

[0038] To address the problems existing in the prior art, the inventors of this application have developed a novel pure glass phase magnetic recording medium substrate material. This material can provide sufficient material performance for thin glass disk substrates with a thickness ≤0.5 mm, such as ≤0.45 mm, ≤0.43 mm, ≤0.40 mm, ≤0.38 mm, ≤0.35 mm, ≤0.33 mm, and ≤0.30 mm. This allows the substrate to maintain the high rigidity, high-speed rotational stability, low deflection, low thermal flatness change, and pure glass phase stability required for magnetic recording medium substrates even after thinning.

[0039] This invention enables a silicate glass system to achieve the high elastic modulus, high glass transition temperature, and high specific elastic modulus required to support thin disk substrates, while maintaining a pure glass phase and low crystallization risk.

[0040] Unlike existing "low-density priority" conventional glass routes, ion exchange residual stress strengthening routes, and glass-ceramic crystallization strengthening routes, this invention does not achieve a higher specific elastic modulus by drastically reducing density. Instead, it allows for a higher density level and improves the elastic modulus and glass skeleton stability by significantly increasing the elastic modulus, so that the material still has sufficient rigidity and heat resistance at a thinner thickness, thereby meeting the application requirements of HDD, especially HAMR HDD disk substrates.

[0041] Specifically, the present invention provides a high-density, high-specific-modulus glass, wherein the density of the glass is greater than or equal to 3.00 g / cm³. 3 Specific elastic modulus greater than 37 GPa·cm 3 / g.

[0042] In one embodiment, the density of the glass of the present invention is greater than 3.05 g / cm³. 3 .

[0043] In one embodiment, the specific elastic modulus of the glass of the present invention is greater than 38.0 GPa·cm. 3 / g, preferably greater than 38.5 GPa·cm 3 / g, more preferably greater than 39.5 GPa·cm 3 / g.

[0044] According to this application, the glass of the present invention is a non-chemically strengthened glass.

[0045] According to this application, the glass of the present invention is a pure glass phase glass, or wherein the content of heterogeneous particles is less than 5 wt%, preferably less than 3 wt%, and more preferably less than 1 wt%.

[0046] According to this application, the oxide composition of the glass of the present invention includes SiO2, Al2O3, MgO and Y2O3; Based on the sum of the molar percentages of all oxide components in the glass of this invention being 100%: SiO2 content is 38–45 mol%, for example, 39–41 mol%; Al2O3 is 15–22 mol%, for example, 15–20 mol%; MgO concentration is 26–32 mol%, for example, 28–32 mol%. Y₂O₃ is 2–15 mol%, for example: greater than 2 mol% and less than or equal to 15 mol%; greater than 2 mol% and less than or equal to 10 mol%; greater than 2 mol% and less than or equal to 7.5 mol%.

[0047] In one embodiment, the molar percentage of Y2O3 in the glass of the present invention is greater than 2 mol% and less than or equal to 5 mol%.

[0048] In one embodiment, the molar percentage of Y2O3 in the glass of the present invention is 5–15 mol, preferably greater than 10 mol% and less than or equal to 15 mol%.

[0049] In one embodiment, the oxide composition of the glass of the present invention further includes one or more of B2O3, TiO2, Li2O, ZrO2, CaO, and high modulus rare earth oxides.

[0050] In the oxide composition of the glass of the present invention, B2O3 is 0–3 mol%; TiO2 is 0–5 mol%, preferably 1–5 mol%; Li2O is 0–5 mol%; ZrO2 is 0–5 mol%; CaO is 0–5 mol%; and high modulus rare earth oxides are 0–5 mol%.

[0051] In one embodiment, the molar percentage of TiO2 is 1–5 mol%, and the molar percentages of B2O3, Li2O, ZrO2, and CaO are 0.

[0052] According to this application, the high modulus rare earth oxide contained in the glass of the present invention is selected from one or more of La2O3, Gd2O3, Sc2O3, Lu2O3, and Yb2O3.

[0053] In one embodiment, the ratio of the molar percentage of Y2O3 to the molar percentage of Al2O3 in the oxide composition of the glass of the present invention is 0.20–1.00.

[0054] In one embodiment, the ratio of the molar percentage of MgO to the molar percentage of Al2O3 in the oxide composition of the glass of the present invention is 1.18–2.14.

[0055] In one embodiment, the ratio of the sum of the molar percentages of SiO2 and B2O3 to the molar percentage of Al2O3 in the oxide composition of the glass of the present invention is 1.8–3.0.

[0056] According to this application, the glass of the present invention also has one of the following characteristics: Elastic modulus: greater than 100 GPa; Glass transition temperature: greater than 550℃; The coefficient of linear expansion in the temperature range of 100–380℃ is: 50 × 10⁻⁶ -7 / K to 68.5×10 -7 / K.

[0057] In one embodiment, the elastic modulus of the glass of the present invention is greater than 105 GPa, preferably greater than 110 GPa.

[0058] In one embodiment, the glass transition temperature (Tg) of the glass of the present invention is greater than 700°C, preferably greater than 750°C.

[0059] In one embodiment, the density of the glass of the present invention is 3.0–3.40 g / cm³. 3 Its elastic modulus is greater than 110 GPa, and its specific elastic modulus is greater than 39.5 GPa·cm. 3 / g, glass transition temperature greater than 750℃.

[0060] According to this application, the DSC chart of the glass of the present invention has an endothermic peak between 810.0 and 920.0 °C.

[0061] On the other hand, this application also relates to thin glass devices made from the glass of the present invention. The definitions of the various technical features of the glass of the present invention described above also apply to the thin glass devices of the present invention.

[0062] The glass of this invention can be prepared using any method known in the art. The glass of this invention can be further processed to obtain thin glass devices.

[0063] According to this application, the glass device of the present invention is made of high-density, high-specific-modulus glass, wherein the density of the high-density, high-specific-modulus glass is greater than or equal to 3.00 g / cm³. 3 Specific elastic modulus greater than 37 GPa·cm 3 / g.

[0064] According to this application, the glass device of the present invention has not undergone any ion exchange strengthening treatment for establishing a surface compressive stress layer.

[0065] According to this application, the thickness of the glass device of the present invention is less than or equal to 0.50 mm.

[0066] In one embodiment, the thickness of the glass device of the present invention is less than or equal to 0.45 mm. For example, the thickness of the glass device of the present invention may be less than or equal to 0.43 mm, less than or equal to 0.40 mm, less than or equal to 0.38 mm, less than or equal to 0.35 mm, less than or equal to 0.33 mm, or less than or equal to 0.30 mm.

[0067] According to this application, the glass device of the present invention may be a disk-shaped device, a through-hole disk, a ring substrate, an information recording medium substrate, or a magnetic recording medium substrate.

[0068] In one embodiment, the glass device of the present invention is a through-hole disk, wherein the outer diameter of the through-hole disk is 97±5 mm and the inner diameter is 25±2 mm.

[0069] According to this application, the deflection of the through-hole disk of the present invention at a rotational speed of 7200 RPM is less than 5 μm, preferably less than 4.8 μm, and more preferably less than 4 μm.

[0070] In one embodiment, the deflection of the through-hole disk of the present invention at a rotational speed of 7200 RPM exhibits the following negative power function relationship with the specific elastic modulus of glass: y=111.47x 0.93 in: y represents deflection, in μm; x is the specific elastic modulus, in GPa·cm. 3 / g.

[0071] According to this application, the average flatness change of the through-hole disc of the present invention before and after heat treatment from room temperature to 700°C for 60 minutes is less than 20%, preferably less than 10%.

[0072] According to this application, the through-hole disk of the present invention is an HDD disk substrate, an HAMR disk substrate, or a MAMR disk substrate.

[0073] According to this application, the oxide composition of the high-density, high-specific-modulus glass used in the glass device of this invention, based on molar percentage, comprises: SiO2: 38–45 mol% Al2O3: 15–22 mol% MgO: 26–32 mol% Y2O3: 2–15 mol% B2O3: 0–3 mol% TiO2: 0–5 mol% Li2O: 0–5 mol% ZrO2: 0–5 mol% CaO: 0–5 mol%; and High modulus rare earth oxides: 0–5 mol% The sum of the molar percentages of all oxide components in the high-density, high-specific-modulus glass is 100%.

[0074] According to this application, the high-density, high-specific-modulus glass used in the glass device of the present invention contains high-modulus rare earth oxides selected from one or more of La2O3, Gd2O3, Sc2O3, Lu2O3, and Yb2O3.

[0075] On the other hand, this application also provides an information recording device, which includes the glass device of the present invention.

[0076] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. It can provide a material basis for thinner substrates. The high-density, high-specific-modulus glass of this invention can provide sufficient high rigidity and high-speed rotational stability for thin glass disk substrates with a thickness of ≤0.5 mm, or even ≤0.45 mm, ≤0.43 mm, ≤0.40 mm, ≤0.38 mm, ≤0.35 mm, ≤0.33 mm or ≤0.30 mm, thereby providing conditions for increasing the number of disks in the whole machine.

[0077] 2. Achieving high elastic modulus and relatively high specific elastic modulus under the premise of pure glass phase. This invention does not follow the "low density priority" logic of the ordinary glass route, but rather, under the premise of a pure glass phase, it obtains the high elastic modulus and relatively high specific elastic modulus required to support thin disks through the Y–Mg–Al–Si system design.

[0078] 3. Improve the adaptability of HAMR process The high-density, high-specific-modulus glass of this invention has a higher Tg and better post-thermal-history stability, making it more suitable for localized hot writing environments at 450–500℃ and magnetic layer preparation / heat treatment processes at 600–800℃.

[0079] 4. Reduce the inherent risks of traditional routes Compared with conventional methods, the present invention can at least avoid or mitigate the following problems: a) The risk of crystallization associated with the pure high-Mg route; b) High-temperature migration and contamination sensitivity resulting from the Li / Na route; c) Stress decay risk of the IOX route under high temperature conditions; d) The difficulties of microcrystalline routes in the machining of extremely harsh and precision surfaces. 5. Providing new material pathways for higher overall machine capacity According to existing technology, to increase HDD capacity, it is necessary to thin the disk and control vibration and flatness variations. However, simply optimizing the device structure or profile cannot fundamentally solve the problems of insufficient rigidity, thermal deformation, and crystallization instability of the material body under thinning conditions.

[0080] This invention addresses the issue from the perspective of the material itself, providing a basis for thinner disks with sufficiently high elastic modulus, high Tg, and pure glass phase stability.

[0081] 6. Compared with the IOX route, this invention does not rely on residual stress strengthening, thus avoiding the natural risk of stress decay in high-temperature processes and high-temperature local writing environments; compared with the glass-ceramic route, this invention maintains a pure glass phase, thereby avoiding the problem of narrowing the surface precision processing window due to the presence of crystalline phase. Attached Figure Description

[0082] Figure 1 This is a differential scanning calorimeter (DSC) image of the glass in Example 1.

[0083] Figure 2 This is a DSC image of the glass from Example 2.

[0084] Figure 3 This is a DSC image of the glass from Example 3.

[0085] Figure 4 The graph is a power function image obtained by fitting the deflection of the through-hole disk of the present invention at a rotation speed of 7200 RPM to the glass specific elastic modulus, wherein: ■ represents the lower limit of the deflection calculated by the fitted function (μm); ▲ represents the upper limit of the deflection calculated by the fitted function (μm); ● represents the measured deflection (μm).

[0086] Figure 5 This is a comparison diagram of the average flatness of the through-hole disc of the present invention before and after heat treatment at room temperature to 700°C for 60 minutes. Detailed Implementation

[0087] To make the objectives, technical solutions, and advantages of the present invention clearer, the high-density, high-specific-modulus glass of the present invention and the thin glass devices made from the glass will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0088] To provide sufficient material properties for thin glass substrates with a thickness of ≤0.5 mm, or even thinner such as ≤0.30 mm, so that they can maintain the high rigidity, high-speed rotational stability, low deflection, low thermal flatness change, and pure glass phase stability required for magnetic recording media substrates after thinning, the traditional approach in this field is to introduce elements that contribute high elastic modulus while minimizing density burden on a good glass framework, making the material "lighter and stiffer." In materials science terms, this means increasing the specific elastic modulus E / ρ. Therefore, while existing conventional glass substrate approaches superficially pursue "high specific elastic modulus," their underlying logic is actually: to adjust elements such as Mg, Ca, Li, and B to maximize E while minimizing ρ, thereby achieving a higher E / ρ.

[0089] However, in thinner substrates and HAMR scenarios, this traditional approach is gradually showing its limitations: increasing E with high Mg content can easily lead to crystallization risks; improving processability with alkali metals such as Li and Na may introduce sensitivity to high-temperature coating contamination; strengthening with IOX may cause stress decay in high-temperature processes and localized hot writing environments; and increasing E with microcrystal strengthening will face challenges in precision surface processing.

[0090] The inventors of this application made an unexpected discovery: through the synergistic ratio of Y₂O₃, MgO, Al₂O₃, and SiO₂, a density greater than or equal to 3.00 g / cm³ can be achieved without reducing the density. 3 Under these conditions, a high specific modulus can still be obtained while maintaining a pure glass phase. Therefore, for thinner disk substrates and HAMR scenarios, it is not necessary to adhere to the "low density priority" principle. In some chemical systems, a certain density level can be accepted, and the same or even higher specific modulus can be obtained through a more significant increase in modulus.

[0091] In existing technologies, Y2O3 often appears only as a general optional rare earth oxide component, or is restricted along with components such as TiO2, and has not become the core design focus of ordinary HDD glass routes.

[0092] In contrast, this invention explicitly uses Y₂O₃ as the core effective component for high modulus and high Tg, and makes it synergistic with the Mg, Al, and Si framework. This means that this invention is not simply "adding a little Y₂O₃ as an auxiliary" step in the traditional glass production process, but rather establishing a new equilibrium window around Y.

[0093] Specifically, this invention uses Y–Mg–Al–Si as the core chemical system, and introduces small amounts of B, Ti, Zr, Li, etc., when necessary to fine-tune the framework and modulus, thereby constructing a glass system that can simultaneously meet the following requirements while ensuring the stability of the pure glass phase: It has a high elastic modulus sufficient to support a thin disk substrate; It has a high glass transition temperature suitable for HAMR high-temperature processes; It maintains a high specific modulus of elasticity even under high density conditions; Maintain a pure or near-pure glass phase and avoid significant crystallization; Suitable for subsequent flatness changes to obtain high surface quality, high contour accuracy, and low thermal history.

[0094] 1. Establishment and maintenance of the main network framework In this invention, SiO2 and optionally B2O3 jointly undertake the main framework construction function of the glass network. SiO2 is fundamental to ensuring glass formation, structural continuity, chemical stability, and compatibility with precision surface processing. Optional B2O3 is used to adjust meltability and structural flexibility when necessary, but its usage is strictly limited to avoid increased volatility, compositional fluctuations, and sensitivity to high-temperature process contamination. Therefore, this invention prioritizes maintaining a sufficiently strong glass framework throughout the system, rather than indiscriminately weakening the network agglomerate content for modulus enhancement.

[0095] 2. The constraining effect of glass stabilizing components In this invention, Al₂O₃ is one of the main components of the network framework and a key component for providing stability to the glass. The role of Al is not only to increase the glass transition temperature (Tg), but also to provide necessary network constraints under high Mg and high Y conditions, making the system less prone to localized ordering and significant crystallization regions. Therefore, this invention does not regard Al as a simple, conventional auxiliary component, but rather as a key constraining component balancing the relationship between "high modulus promotion" and "pure glass phase stability".

[0096] 3. High modulus promotes synergistic arrangement of components. In this invention, MgO and Y2O3 together constitute the high modulus promoting components, but their mechanisms of action and side effects are different. Mg is beneficial for improving the elastic modulus and has a lower density burden compared to some heavy rare earth oxides, thus it is an important component in the traditional high specific elastic modulus ordinary glass route; however, its significant problem is that high content can significantly enhance the tendency to crystallize. Y has a stronger modulus-improving ability and a higher contribution to thermal stability, but its significant problem is that it increases density, thus making the traditional "low density priority" logic no longer applicable.

[0097] The key to this invention is not to increase Mg or Y alone, but to achieve a greater increase in elastic modulus by synergistic arrangement of Mg and Y, while accepting a certain increase in density, and to stabilize the system in the pure glass region by using Al and the framework components as constraints.

[0098] 4. Assisting in enhancing and fine-tuning the boundaries of components This invention allows for the introduction of small amounts of TiO2 as an auxiliary reinforcing component when necessary. Ti can further improve the high modulus and high Tg level, but its content must be limited to avoid inducing additional crystallization tendency. Similarly, components such as Li2O, Na2O, CaO, ZrO2, Nb2O5, La2O3, and Yb2O3 are not absolutely excluded, but they do not constitute the core design axis of this invention and are only used as limited fine-tuning components when necessary.

[0099] The key to determining whether a system can achieve high elastic modulus, high Tg, and high specific elastic modulus while maintaining a pure glass phase under high-density conditions lies not only in the oxide content but also in the synergistic control of the proportional relationships between Y2O3 / Al2O3, MgO / Al2O3, and (SiO2+B2O3) / Al2O3. This approach rationally mitigates the competition between high Y and high Mg, thereby ensuring that the system maintains the required overall performance even under thinner substrate applications.

[0100] 1. Y2O3 / Al2O3 Y significantly improves E and thermal stability, but if Y is too high and there is insufficient Al constraint, the stable region of the system will narrow, and the density will increase too quickly, which is not conducive to obtaining the overall optimal performance. Therefore, the molar percentage of Y2O3 must be in a reasonable ratio with the molar percentage of Al2O3 so that the high modulus gain can be effectively retained under the constraint of glass stability.

[0101] 2. MgO / Al2O3 Mg is an important modulus-enhancing component, but when Mg content is too high relative to Al, the system is more prone to shifting towards the crystallization region. Therefore, the molar percentage ratio of MgO to Al2O3 is one of the key parameters for controlling the balance between "modulus enhancement" and "crystallization risk".

[0102] 3. (SiO2+B2O3) / Al2O3 There is also a balance between the strength of the framework and the constraint of glass stability. If the main components forming the framework are insufficient, the rigidity of the system may be locally improved, but the stability of the pure glass phase and the adaptability to precision surface processing will be affected; if the main components forming the framework are excessive, the modulus improvement efficiency may be insufficient. Therefore, the ratio of the sum of the molar percentages of SiO2 and B2O3 to the molar percentage of Al2O3 reflects the balance between the framework strength and the constraint strength.

[0103] The glass of the present invention can be prepared by any method known in the art, for example, by the following methods: Weigh the corresponding raw materials according to the design formula, add them to a Y-type mixer and mix until uniform. Then add the mixture to a glass furnace and melt the raw materials into molten glass at 1400~1650℃. Gradually cool the molten glass to 800℃~1300℃ to form the desired glass. Forming methods include rolling, drawing, casting, overflow, float glass, etc. Drawing can include transverse drawing and longitudinal drawing.

[0104] In this application, the term "heterogeneous particles" refers to discrete regions existing within a continuous glass matrix that differ identifiable from the surrounding glass matrix in chemical composition, structure, or phase. These include crystalline particles, phase-separated particles, incompletely melted raw material residues, and solid inclusions introduced during melting or forming. The equivalent circular diameter of the heterogeneous particles is not less than 3 nm, and their size and content can be identified and determined using scanning electron microscopy, backscattered electron imaging, energy dispersive spectroscopy, transmission electron microscopy, X-ray diffraction, or a combination of these methods. Normal compositional fluctuations and short-range ordered structures at the atomic or nanoscale within the glass matrix are not considered heterogeneous particles as defined in this application.

[0105] Example 1. Performance Testing 1. Glass transition temperature (Tg) According to GB / T7962.16 The 2010 standard specifies a method for determining the Tg temperature of glass.

[0106] 2. Density The density of glass is as specified in GB / T7962.20. Test according to the 2010 standard method.

[0107] 3. Elastic modulus The longitudinal and transverse wave velocities of the glass are tested using ultrasonic waves, and then the elastic modulus (Young's modulus) of the glass is calculated using the following formula: E: E=(4G2-4GVT2ρ) / (G-VT2ρ) G=VS2ρ Where: E is Young's modulus, Pa; G is shear modulus, Pa; VT is the longitudinal wave velocity, in m / s; VS represents the transverse wave velocity, in m / s; ρ is the density of glass, in g / cm³ 3 .

[0108] 3. Coefficient of Expansion The coefficient of linear expansion of glass, α (100–380℃, 10 7 / k) The test method is based on the national standard: Test Methods for Colorless Optical Glass Part 16: Coefficient of Linear Expansion, Transition Temperature and Sag Temperature; Standard No.: GB / T7962.16 2010.

[0109] 4. Deflection At a rotational speed of 7200 RPM, the axial displacement change of the through-hole disk of the present invention was measured using a non-contact laser displacement sensor KEYENCE LK-G5000, and the maximum out-of-plane displacement was used to characterize the actual deflection data.

[0110] 5. Flatness The flatness of the through-hole disk of the present invention was measured using a ZYGO laser interferometer before and after heat treatment at room temperature to 700 °C for 60 min. The change in flatness before and after heat treatment is represented by ΔF.

[0111] Preparation Examples 1. Glass In the following examples and comparative examples, glass was prepared according to the following method: According to the designed glass formula, weigh the corresponding raw materials of each component, add them to the Y-type mixer and mix them until uniform. Then add them to the glass furnace and melt them into glass liquid at about 1600°C. After melting the glass liquid, gradually cool it down to about 1300°C and form it by rolling to obtain the target glass.

[0112] The raw materials used for each component are as follows: The raw material for SiO2 is quartz sand; the raw material for Al2O3 is Al2O3; the raw material for MgO is MgO; the raw material for Y2O3 is yttrium oxide; the raw material for B2O3 is boric acid; the raw material for TiO2 is titanium oxide; the raw material for Li2O is lithium carbonate; the raw material for ZrO2 is zirconium oxide; the raw material for CaO is CaCO3; the raw material for La2O3 is lanthanum oxide; and the raw material for Sb2O3 is antimony oxide.

[0113] The oxide composition, molar percentage content, and properties of the glasses prepared in each embodiment and comparative example are listed in Table 1 below.

[0114] 2. Through-hole disc The glass prepared in each embodiment was processed into a through-hole disk with an outer diameter of 97±0.5 mm, an inner diameter of 25±0.5 mm, and a thickness of 0.43±0.005 mm.

[0115] The deflection (represented by y) and specific elastic modulus (represented by x) of the through-hole disks prepared in each embodiment are listed in Table 2 below. The flatness and its change before and after heat treatment of the through-hole disks prepared in each embodiment are listed in Table 3 below.

[0116] Table 1. Glass formulations used in each embodiment and comparative example, and properties of the prepared glass.

[0117] Table 1 (Continued - 1)

[0118] Table 1 (Continued - 2)

[0119] Table 1 (Continued - 3)

[0120] Table 1 (Continued - 4)

[0121] Table 2. Deflection and specific elastic modulus data of the through-hole disks prepared in each embodiment.

[0122] Table 3. Flatness and its changes of the through-hole disks prepared in each embodiment before and after heat treatment.

[0123] As shown in Table 1, the glasses in Examples 1-24 exhibit excellent overall performance, fully meeting the application requirements of HDD, especially HAMR HDD disk substrates, with a density greater than 3.00 g / cm³. 3 Specific elastic modulus greater than 37 GPa·cm 3 / g, elastic modulus greater than 110 GPa, Tg greater than 720℃.

[0124] Compared to Examples 1-24, Comparative Examples 1-4 represent a low-density route, with the density of their glass all being less than 2.90 g / cm³. 3 Comparative Example 1 represents the traditional high-Si, low-Mg route, with an elastic modulus of only 99.40 GPa and a relatively low specific elastic modulus; Comparative Example 2 represents the high-Li route, with a Tg of only 555℃, which is significantly low; Comparative Example 3 has the lowest density and a relatively low Tg; Comparative Example 4 has a high specific elastic modulus, but its Tg is still relatively low.

[0125] The glass samples prepared in the embodiments of the present invention were subjected to differential scanning calorimetry (DSC). The DSC image of the glass in Example 1 is shown below. Figure 1 As shown, from Figure 1 It can be seen that the glass of Example 1 has an endothermic peak between 822.7-913.0℃, with a peak temperature of 881.0℃ and a peak area of ​​-231.7 J / g; the DSC chromatogram of the glass of Example 2 is shown below. Figure 2 As shown, from Figure 2 It can be seen that the glass in Example 2 has an endothermic peak between 820.7-910.8℃, with a peak temperature of 881.5℃ and a peak area of ​​-206 J / g; Figure 3 This is the DSC image of the glass in Example 3, from... Figure 3 It can be seen that the glass in Example 3 has an endothermic peak between 817.5-909.7℃, with a peak temperature of 876.9℃ and a peak area of ​​-211.1 J / g.

[0126] Fitting the measured deflection and glass specific elastic modulus in Table 2 reveals a negative power function relationship between them. Figure 4 As shown, the power function relationship between the measured deflection and the specific elastic modulus of the glass is as follows: y=111.47x 0.93 in: y represents deflection, in μm; x is the specific elastic modulus, in GPa·cm. 3 / g.

[0127] Figure 4 This indicates that the through-hole disk of the present invention has relatively high stability under high-speed rotation of 7200 RPM.

[0128] The average flatness changes of the through-hole disks prepared in each embodiment before and after heat treatment at room temperature to 700°C for 60 minutes are as follows: Figure 5 As shown in Table 3, the flatness change of the through-hole disk of the present invention before and after heat treatment is relatively low, with an average ΔF value of less than 10%.

[0129] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A thin glass device, characterized in that, The glass device is made of high-density, high-specific-modulus glass, wherein the density of the high-density, high-specific-modulus glass is greater than or equal to 3.00 g / cm³. 3 Specific elastic modulus greater than 37 GPa·cm 3 / g.

2. The glass device according to claim 1, characterized in that, The glass device was not subjected to any ion exchange strengthening treatment to establish a surface compressive stress layer.

3. The glass device according to claim 1 or 2, characterized in that, The thickness of the glass device is less than or equal to 0.50 mm.

4. The glass device according to claim 3, characterized in that, The thickness of the glass device is less than or equal to 0.45 mm.

5. The glass device according to claim 4, characterized in that, The thickness of the glass device is less than or equal to 0.43 mm.

6. The glass device according to claim 5, characterized in that, The thickness of the glass device is less than or equal to 0.40 mm.

7. The glass device according to claim 6, characterized in that, The thickness of the glass device is less than or equal to 0.38 mm.

8. The glass device according to claim 7, characterized in that, The thickness of the glass device is less than or equal to 0.35 mm.

9. The glass device according to claim 8, characterized in that, The thickness of the glass device is less than or equal to 0.33 mm.

10. The glass device according to claim 9, characterized in that, The thickness of the glass device is less than or equal to 0.30 mm.

11. The glass device according to any one of claims 1-10, characterized in that, The glass device is a disk-shaped device, a through-hole disk, a ring substrate, an information recording medium substrate, or a magnetic recording medium substrate.

12. The glass device according to claim 11, characterized in that, The glass device is a through-hole disk with an outer diameter of 97±5 mm and an inner diameter of 25±2 mm.

13. The glass device according to claim 12, characterized in that, The through-hole disk has a deflection of less than 5 μm at a rotational speed of 7200 RPM.

14. The glass device according to claim 13, characterized in that, The through-hole disk has a deflection of less than 4.8 μm at a rotational speed of 7200 RPM.

15. The glass device according to claim 14, characterized in that, The through-hole disk has a deflection of less than 4 μm at a rotational speed of 7200 RPM.

16. The glass device according to claim 13, characterized in that, The deflection of the through-hole disk at 7200 RPM exhibits the following negative power function relationship with the glass specific elastic modulus: y=111.47x 0.93 in: y represents deflection, in μm; x is the specific elastic modulus, in GPa·cm. 3 / g.

17. The glass device according to claim 12, characterized in that, The average flatness change of the through-hole disk before and after heat treatment from room temperature to 700℃ for 60 minutes is less than 20%.

18. The glass device according to claim 17, characterized in that, The average flatness change of the through-hole disk before and after heat treatment from room temperature to 700℃ for 60 minutes is less than 10%.

19. The glass device according to claim 12, characterized in that, The through-hole disk is an HDD disk substrate, a HAMR disk substrate, or a MAMR disk substrate.

20. The glass device according to any one of claims 1-19, characterized in that, The oxide composition of the high-density, high-specific-modulus glass, based on molar percentage, comprises: SiO2: 38–45 mol% Al2O3: 15–22 mol% MgO: 26–32 mol% Y2O3: 2–15 mol% B2O3: 0–3 mol% TiO2: 0–5 mol% Li2O: 0–5 mol% ZrO2: 0–5 mol% CaO: 0–5 mol%; and High modulus rare earth oxides: 0–5 mol% The sum of the molar percentages of all oxide components in the high-density, high-specific-modulus glass is 100%.

21. The glass device according to claim 20, characterized in that, The high-modulus rare earth oxide is selected from one or more of La2O3, Gd2O3, Sc2O3, Lu2O3, and Yb2O3.

22. An information recording device, characterized in that, The information recording device includes the glass device as described in any of the preceding claims.

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