Substrate for magnetic disk and magnetic disk using the same

Abstract

A substrate for a magnetic disk, characterized by being composed of an aluminum alloy containing one or two or more of Fe: 8.5 mass% or less, Mn: 2.5 mass% or less, Ni: 6.5 mass% or less, and Mg: 4.5 mass% or less, with the remainder composed of Al and unavoidable impurities, a resonance frequency being f (Hz), a density being p (g / cm 3 ), and a plate thickness being t (mm), (f x p / t) being 3800 or more, and a magnetic disk using the substrate for a magnetic disk.

Description

Technical Field

[0001] This invention relates to a disk substrate with excellent impact resistance and energy efficiency, and a disk using the disk substrate. Background Technology

[0002] The disks used in computer storage devices are manufactured using disk substrates that have good plating properties and excellent mechanical properties and machinability. These disk substrates are made of aluminum alloy substrates based on aluminum alloys or glass substrates based on glass. For example, aluminum alloy substrates are known to be made of JIS5086 aluminum alloy (Mg: 3.5–4.5 mass%, Fe: 0.50 mass% or less, Si: 0.40 mass% or less, Mn: 0.20–0.70 mass%, Cr: 0.05–0.25 mass%, Cu: 0.10 mass% or less, Ti: 0.15 mass% or less, and Zn: 0.25 mass% or less, with the remainder being Al and unavoidable impurities).

[0003] In typical disk manufacturing, a circular disk substrate is first made by attaching a magnetic material to its surface. For example, a disk using an aluminum alloy disk substrate made of the aforementioned JIS5086 aluminum alloy is manufactured through the following manufacturing process.

[0004] First, an aluminum alloy material with a specified chemical composition is cast. This ingot is then hot-rolled and subsequently cold-rolled to produce a rolled piece with the necessary thickness for use as a magnetic disc. This rolled piece is preferably annealed during the cold rolling process, as needed. Next, the rolled piece is punched into a ring shape to form a ring-shaped aluminum alloy sheet. Furthermore, to remove strain and other defects resulting from the previous manufacturing process, the ring-shaped aluminum alloy sheets are stacked and subjected to pressure annealing, annealing while applying pressure from both top and bottom surfaces to achieve planarization. This produces a ring-shaped aluminum alloy disc.

[0005] The aluminum alloy blanks manufactured in this way are pretreated by machining, grinding, degreasing, etching, and zinc immersion (Zn replacement treatment). Next, as a substrate treatment, Ni-P, a hard non-magnetic metal, is electroless plated, and the plated surface is polished to manufacture an aluminum alloy substrate for disks.

[0006] Then, by sputtering magnetic materials onto the aluminum alloy substrate used for the disk, an aluminum alloy disk is manufactured.

[0007] In addition to aluminum alloy substrates, glass substrates and other materials can also be used as substrates for hard disks.

[0008] However, in recent years, due to the demands of multimedia and other applications, the requirements for larger capacity and higher density of disk devices such as HDDs (Hard Disk Drives) have gradually increased. In order to further pursue larger capacity, the number of disks in storage devices tends to increase, which also requires the disks to be thinner.

[0009] However, reducing the rigidity of the substrate for disk drives leads to a decrease in rigidity. Reduced rigidity means a decrease in the substrate's resistance to impact and thus necessitates improved impact resistance. Furthermore, increasing the number of substrates results in excessive power consumption when used as a disk drive, thus requiring energy efficiency (hereinafter referred to as "energy saving").

[0010] Given this reality, there has been a strong demand in recent years for high-rigidity disk substrates, leading to ongoing research. For example, Patent Document 1 proposes a method to improve rigidity by containing a large amount of Si, which helps to enhance the rigidity of the aluminum alloy substrate.

[0011] Existing technical documents

[0012] Patent documents

[0013] Patent Document 1: International Publication No. 2016 / 068293

[0014] However, in the method disclosed in Patent Document 1 that increases the Si content to improve rigidity, the current situation is that it cannot suppress the decrease in impact resistance to a large extent, and the good impact resistance as the target cannot be obtained. Summary of the Invention

[0015] The technical problem that the invention aims to solve

[0016] The present invention was made in view of the above-mentioned actual situation, and its purpose is to provide a disk substrate with excellent impact resistance and energy saving, and a disk using the disk substrate.

[0017] Methods for solving technical problems

[0018] The inventors of this invention conducted in-depth research on the relationship between the impact resistance and energy efficiency of disk substrates and various substrate characteristics. They ultimately discovered the relationship between the substrate's resonant frequency (f), density (ρ), and thickness (t), as well as the significant impact of substrate weight on impact resistance and energy efficiency. Furthermore, they found that this relationship between resonant frequency (f), density (ρ), and thickness (t), and that substrates within a specified weight range exhibit improved impact resistance and excellent energy efficiency. Based on these insights, the inventors of this invention ultimately completed this invention.

[0019] Claim 1 of this invention relates to a substrate for a hard disk, characterized in that it is made of an aluminum alloy containing one or more of the following: Fe: less than 8.5 mass%, Mn: less than 2.5 mass%, Ni: less than 6.5 mass%, and Mg: less than 4.5 mass%, with the remainder consisting of Al and unavoidable impurities. The resonant frequency is set to f (Hz), and the density is set to ρ (g / cm³). 3 Set the plate thickness to t (mm), and (f×ρ / t) to 3800 or more.

[0020] The present invention relates in claim 2 to a disk substrate as described in claim 1, wherein the aluminum alloy further comprises one or more of the following: Zn: less than 0.7 mass%, Cu: less than 1.0 mass%, Cr: less than 0.30 mass%, Zr: less than 0.20 mass%, Be: less than 0.0015 mass%, Sr: less than 0.1 mass%, Na: less than 0.1 mass%, and P: less than 0.1 mass%.

[0021] In other embodiments of the present invention, as in claim 3, a disk substrate is characterized in that it is composed of a glass material with SiO2 as the main component (55-75 mass%), and Al2O3 (0.3-25 mass%) and CaO (0-20 mass%) added, wherein the resonant frequency is set to f (Hz) and the density is set to ρ (g / cm³). 3 Set the plate thickness to t (mm), and (f×ρ / t) to 3800 or more.

[0022] Furthermore, in claim 4 of the present invention, the substrate for the disk as described in claim 3, the glass material further contains one or more of the following: Li2O: 0.01-6 mass%, Na2O: 0.7-12 mass%, K2O: 0-8 mass%, MgO: 0-7 mass%, ZrO2: 0-10 mass%, and TiO2: 0-1 mass%.

[0023] Furthermore, in claim 5 of the present invention, the glass material of the disk substrate as described in claim 3 or 4 further contains one or more of B2O3, SrO, BaO, ZnO, SnO2, Fe2O3, As2O3 and Sb2O3 at a concentration of 15% or less.

[0024] In claim 6 of the present invention, the disk substrate as described in any one of claims 1 to 5, wherein (f×ρ / t) is 4000 or more.

[0025] In claim 7 of the present invention, the disk substrate as described in any one of claims 1 to 5, wherein (f×ρ / t) is 4200 or more.

[0026] In claim 8, the disk substrate of any one of claims 1 to 7, the weight of the disk substrate of each disk is 6.0 to 11.0 g.

[0027] In claim 9, the disk substrate of any one of claims 1 to 7, the weight of the disk substrate of each disk is 6.0 to 10.5 g.

[0028] In claim 10, the disk substrate as described in any one of claims 1 to 7, wherein the weight of the disk substrate for each disk is 6.0 to 8.7 g.

[0029] The present invention relates to a disk in claim 11, characterized in that the surface of the disk substrate according to any one of claims 1 to 10 has a magnetic layer.

[0030] Invention Effects

[0031] According to the present invention, a disk substrate with excellent impact resistance and energy efficiency, and a disk using the disk substrate, can be provided. Attached Figure Description

[0032] Figure 1 A flowchart illustrating a method for manufacturing an aluminum alloy substrate as a disk substrate according to the present invention is shown.

[0033] Figure 2 A flowchart illustrating a method for manufacturing a glass substrate as a disk substrate according to the present invention is shown.

[0034] Figure 3 A graph showing the relationship between (f×ρ / t) and impact resistance is shown. Detailed Implementation

[0035] This invention relates to a substrate for a disk (hereinafter, sometimes referred to as "substrate"), and to a disk in which a magnetic layer is provided on the surface of the substrate. It will now be described in detail.

[0036] 1. Disk baseboard

[0037] In the disk substrate of the present invention, the resonant frequency is set to f (Hz), and the density is set to ρ (g / cm³). 3 By setting the plate thickness to t (mm) and specifying (f×ρ / t) to 3800 or higher, excellent impact resistance can be obtained. Furthermore, by specifying the weight of the disk substrate for each disk to be 6.0–11.0 g, impact resistance can be further improved, and energy efficiency can also be enhanced. In addition, the unit of (f×ρ / t) is [(Hz)·(g / cm³)]. 3)·(mm －1 )).

[0038] 1-1.(f×ρ / t)

[0039] According to the inventors' research, increasing the f×ρ / t of the substrate improves its impact resistance. When a disk drive is dropped, the substrate vibrates, but the frequency varies depending on the acceleration during the fall, ranging from approximately 500 to 1500 Hz. A larger f value makes resonance less likely, thus suppressing substrate deformation and preventing a decrease in impact resistance. A smaller f value makes the substrate more prone to resonance even under relatively small forces, such as when a disk drive is dropped, leading to greater substrate deformation and reduced impact resistance in collisions with other components. Furthermore, since the value of f varies with t, a value calculated by dividing f by t is used for standardization.

[0040] Next, for ρ, it has always been set that a smaller value results in good impact resistance. Figure 3 This is a graph illustrating the relationship between (f×ρ / t) and impact resistance as defined by the inventors of this invention. The four points represent points where t and f are approximately the same, while ρ varies significantly. The vertical axis of the graph shows the impact height varied by setting the acceleration (G) during the fall to 30–50G and the impact time to 2 msec. The substrate was allowed to fall naturally in the vertical direction with an initial velocity of 0 m / s, and the deflection (displacement) of the outer periphery of the substrate upon impact with the ground was measured. The displacement / acceleration was calculated from the acceleration and displacement (μm) data (12 points). Furthermore, tests were conducted by colliding the inner periphery of the substrate with the block portion fixed to it, with the block portion impacting the ground.

[0041] Depend on Figure 3 It can be seen that (f×ρ / t) is relatively large, meaning that the displacement is smaller when ρ is larger. In substrates with smaller ρ, the vibration time is longer due to the influence of buoyancy, making displacement easier. In situations such as the falling of a disk drive, the displacement is more likely to occur. Figure 3 The increased displacement of the substrate leads to increased damage due to collisions with other components (such as ramp loading at the retraction position of other disks or heads) in the disk. In this invention, the ability to withstand such damage is defined as impact resistance. To avoid a decrease in impact resistance, the substrate's (f×ρ / t) should be specified as 3800 or higher. (f×ρ / t) is preferably 4000 or higher, more preferably 4200 or higher. Furthermore, the upper limit of the substrate's (f×ρ / t) is not particularly limited, but is determined independently based on the substrate's material or composition and manufacturing conditions; in this invention, it is preferably set to around 5500.

[0042] 1-2. Weight

[0043] In this invention, to improve the aforementioned shock resistance, the weight of the disk substrate for each disk is also important, and is preferably set to 6.0 to 11.0 g. This further improves the shock resistance. The shock resistance of the substrate is improved by preventing collisions with other components when the substrate vibrates due to forces applied to it during disk drop. The heavier the substrate, the shorter the time required for the substrate's vibration to converge, thereby reducing the chance of contact with other components and suppressing contact-induced damage. However, if the substrate is too heavy, the power consumption when used with the disk is excessive, resulting in poor energy efficiency. Specifically, the power consumption of the spindle motor used to rotate the disk increases, leading to poor energy efficiency. Power consumption is related to power and can be expressed as the product of rotational speed (rpm), torque (N·m), and a coefficient. If the substrate weight increases, the torque increases, thus increasing the power and power consumption.

[0044] The inventors of this invention have discovered that when the weight of the disk substrate in each disk is 6.0 to 11.0 g, excellent shock resistance and energy efficiency are achieved. When the weight is less than 6.0 g, sufficient shock resistance cannot be achieved, and when it exceeds 11.0 g, power consumption is excessive and energy efficiency is lacking. In this invention, it is preferable to set this weight to 6.00 to 11.0 g, more preferably to 6.0 to 10.5 g, and even more preferably to 6.0 to 8.7 g.

[0045] 1-3. Material

[0046] As the material for the disk substrate of the present invention, metallic materials such as aluminum alloy can be used. Alternatively, glass can also be used. In the following description, a disk substrate made of aluminum alloy (hereinafter referred to as "aluminum alloy disk substrate") and a disk substrate made of glass (hereinafter referred to as "glass disk substrate") will be described.

[0047] 1-3-1. Aluminum alloy substrate for hard disks

[0048] The disk substrate of the present invention can be made of aluminum alloy. The alloy composition and manufacturing method of the aluminum alloy substrate for disks of the present invention will be described in detail below.

[0049] (a) Alloy composition

[0050] The aluminum alloy used in the disk disk aluminum alloy substrate of the present invention preferably contains elements such as Fe, Mn, Ni, and Mg that can improve the resonant frequency or density.

[0051] Specifically, it is characterized by containing one or more of the following: Fe: 8.5 mass% or less (hereinafter abbreviated as "%), Mn: 2.5% or less, Ni: 6.5% or less, and Mg: 4.5% or less, with the remainder consisting of Al and unavoidable impurities. Furthermore, it may also contain one or more of the following: Zn: 0.7% or less, Cu: 1.0% or less, Cr: 0.30% or less, Zr: 0.20% or less, Be: 0.0015% or less, Sr: 0.1% or less, Na: 0.1% or less, and P: 0.1% or less.

[0052] Fe:

[0053] Fe mainly exists as second-phase particles (Al-Fe intermetallic compounds, etc.), and partly exists in a matrix-like solid solution, which increases the f and ρ of the aluminum alloy substrate. The increased amount of dissolved Fe results in a good f through the interaction between dissolved Fe and Al. Furthermore, Fe has a larger ρ than Al, so an increase in Fe content leads to an increase in ρ. The Fe content in the aluminum alloy is 8.5% or less, further enhancing the effect of increasing the f and ρ of the aluminum alloy substrate. In addition, a significant increase in substrate weight can be suppressed. As a result, a substrate with excellent impact resistance and energy efficiency can be obtained. Therefore, the Fe content in the aluminum alloy is preferably in the range of 8.5% or less. More preferably, it is 1.8% or less. The lower limit is preferably set to 0.1%, and more preferably to 0.2%.

[0054] Mn:

[0055] Mn mainly exists as second-phase particles (Al-Mn intermetallic compounds, etc.), and a portion exists in a matrix-like solid solution, contributing to the increase of f and ρ in the aluminum alloy substrate. The increased amount of dissolved Mn results in a better f through the interaction between dissolved Mn and Al. Furthermore, Mn has a larger ρ than Al, so an increase in Mn content leads to a larger ρ. The Mn content in the aluminum alloy is 2.5% or less, which further enhances the effect of increasing the f and ρ of the aluminum alloy substrate. In addition, a significant increase in substrate weight can be suppressed. As a result, a substrate with excellent impact resistance and energy efficiency can be obtained. Therefore, the Mn content in the aluminum alloy is preferably in the range of 2.5% or less. More preferably, it is 1.8% or less. The lower limit is preferably set to 0.1%, and more preferably to 0.2%.

[0056] Ni:

[0057] Ni mainly exists as second-phase particles (Al-Ni intermetallic compounds, etc.), and partly exists in a matrix-like solid solution, contributing to increasing the f and ρ of the aluminum alloy substrate. The increased amount of dissolved Ni results in a good f through the interaction between dissolved Ni and Al. Furthermore, Ni has a larger ρ than Al, so an increase in Ni content leads to a larger ρ. A Ni content of 6.5% or less in the aluminum alloy further enhances the effect of increasing the f and ρ of the aluminum alloy substrate. In addition, a significant increase in substrate weight can be suppressed. As a result, a substrate with excellent impact resistance and energy efficiency can be obtained. Therefore, the Ni content in the aluminum alloy is preferably in the range of 6.5% or less. More preferably, it is 5.5% or less. The lower limit is preferably set to 0.1%, and more preferably to 0.2%.

[0058] Mg:

[0059] Mg mainly exists in a matrix-like solid solution, with some existing as second-phase particles (Mg-Si intermetallic compounds, etc.). Compared to Al, Mg has a smaller ρ, so increasing the Mg content reduces the substrate weight, which is beneficial from an energy-saving perspective. On the other hand, if the Mg content exceeds 4.5%, the f decreases due to the interaction between the solid-solid Mg and Al. Therefore, the Mg content in the aluminum alloy is preferably 4.5% or less. More preferably, it is 2.5% or less, and even more preferably 1.0% or less. The lower limit is preferably set to 0.1%, and even more preferably 0.2%.

[0060] Zn, Cu, Cr, Zr, Be, Sr, Na and P:

[0061] Regarding these elements, by adding them respectively within the aforementioned content ranges, either as intermetallic compounds or existing in a matrix-like solid solution, they exert an effect of increasing the f and ρ of the aluminum alloy substrate. Furthermore, the increased solid solution content results in a better f through the interaction between the dissolved substances and Al.

[0062] Other elements such as unavoidable impurities

[0063] Aluminum alloys may also contain the aforementioned essential components as well as unavoidable impurities other than the selected components. Examples of such elements include Si, Ti, V, and Ga, and their content will not impair the effectiveness of the present invention if each element is less than 0.10% and the total content is less than 0.30%.

[0064] (b) Manufacturing method

[0065] The following describes in detail each step and process condition of the manufacturing process of the aluminum alloy substrate for disk disks according to this embodiment. Figure 1 This is a flowchart illustrating the aluminum alloy substrate for a disk drive according to this embodiment, and a method for manufacturing a disk using the same. Figure 1In this process, the aluminum alloy composition adjustment step (step S101) to cold rolling and stamping (step S105) involves manufacturing aluminum alloy raw materials through melt casting, forming them into aluminum alloy sheets, and further processing them into ring shapes. Next, an aluminum alloy blank is manufactured through a pressure planarization step (step S106). Then, the manufactured blank undergoes a pretreatment process including cutting, grinding (step S107), and heat treatment (step S108). Following this, it undergoes zinc immersion treatment (step S109), Ni-P plating treatment (step S110), and surface grinding (step S111) to manufacture an aluminum alloy substrate for a magnetic disk. The magnetic disk is then manufactured by attaching a magnetic material to the surface-ground (step S111) aluminum alloy substrate for a magnetic disk. The process will continue below... Figure 1 The process details the content of each step. Furthermore, the substrate after cutting and grinding (step S107) can also be used as an aluminum alloy substrate for disks. By not performing Ni-P plating, there are no plating limitations, thus improving f.

[0066] First, the aluminum alloy material having the above-described composition is heated and melted using a general method to prepare the alloy (step S101). Next, the aluminum alloy material prepared by casting is cast from the melt using a semi-continuous casting (DC casting), mold casting, or continuous casting (CC casting) method (step S102). The manufacturing conditions for the aluminum alloy material in the DC casting and CC casting methods are described below.

[0067] In DC casting, molten metal injected through a nozzle is cooled and solidified by the base, the water-cooled mold walls, and cooling water sprayed directly onto the outer periphery of the ingot, resulting in an aluminum alloy ingot that is then extracted downwards. In mold casting, molten metal injected into a hollow mold made of cast iron or similar materials is cooled and solidified by the mold walls, forming an ingot.

[0068] On the other hand, in the CC casting method, molten metal is supplied between a pair of rolls (or a belt casting machine, a block casting machine) through a casting nozzle, and aluminum alloy sheets are directly cast using the heat dissipation from the rolls.

[0069] A significant difference between DC casting and CC casting lies in the cooling rate during casting. In CC casting, with its higher cooling rate, the second-phase particles are characterized by smaller sizes compared to DC casting. Mold casting tends to have a faster cooling rate than DC casting. In either casting method, the cooling rate during casting is preferably set to 0.1°C / s or higher. By setting the cooling rate during casting to 0.1°C / s or higher, the solid solution content of Fe, etc., increases, and f increases. When the cooling rate during casting is less than 0.1°C / s, the solid solution content of Fe, etc., may decrease, and f will decrease.

[0070] For aluminum alloy ingots, homogenization treatment is performed as needed (step S103). During homogenization, it is preferable to heat the ingot at 280–420°C or 500–620°C for 0.5–30 hours, and more preferably at 300–350°C or 510–600°C for 1–24 hours. If the heating temperature during homogenization is less than 280°C or the heating time is less than 0.5 hours, the homogenization is insufficient, and the deviation of f in each aluminum alloy substrate may increase. If the heating temperature during homogenization exceeds 420°C but is less than 500°C, the solid solution content of Fe, etc., may decrease, and f will decrease. If the heating temperature during homogenization exceeds 620°C, the aluminum alloy ingot may melt. Even if the heating time during homogenization exceeds 30 hours, the effect becomes saturated, and the above-mentioned significant improvement effects cannot be obtained.

[0071] Next, aluminum alloy ingots (DC casting, mold casting) that have undergone homogenization treatment or not, as needed, are hot-rolled to form plates (step S104). The conditions for hot rolling are not particularly limited, but the starting temperature of hot rolling is preferably set to 300-420°C or 500-600°C, and the ending temperature of hot rolling is preferably set to 230-400°C.

[0072] Then, the hot-rolled sheet or the cast sheet cast by CC casting is cold-rolled to produce a cold-rolled sheet of approximately 1.3 mm to 0.45 mm (step S105). The desired product sheet thickness is achieved through cold rolling. The cold rolling conditions are not particularly limited and can be determined according to the required product sheet strength or thickness; preferably, the rolling rate is set to 10–95%. Annealing can be performed before or during cold rolling to ensure cold-rolled processability. When annealing is performed, for example, if intermittent heating is used, it is preferably carried out at 300–420°C for 0.1–10 hours; if continuous heating is used, it is preferably carried out at 500–600°C for 0–60 seconds. Here, a holding time of 0 seconds means that cooling is performed directly after reaching the desired holding temperature.

[0073] Then, the aluminum alloy sheet obtained by cold rolling is punched into a ring shape (step S105) to form a ring-shaped aluminum alloy sheet. The ring-shaped aluminum alloy sheet is then subjected to a pressure planarization process (step S106) to form a coil. In the pressure planarization process, a planarized billet is produced by pressure annealing in the atmosphere, for example at 200 to 420°C for 0.5 to 10 hours.

[0074] For the blank, a pretreatment including cutting, grinding (step S107), and heat treatment (step S108) is performed before zinc immersion treatment, etc. During the heat treatment, the temperature is held for 0.5 to 10.0 hours, for example, within the range of 130 to 280°C. This heat treatment suppresses the reduction of dislocations, thereby improving chatter characteristics or impact resistance. When the heat treatment temperature exceeds 280°C, or the heat treatment time exceeds 10.0 hours, dislocations decrease, and as a result, chatter characteristics or impact resistance may decrease. On the other hand, when the heat treatment temperature is less than 130°C, or the heat treatment time is less than 0.5 hours, the strain introduced by the processing is not sufficiently removed, and as a result, the flatness of the substrate deteriorates over time, making it difficult to use as an aluminum alloy substrate for disks. For the above reasons, the heat treatment of the blank after cutting and grinding is preferably performed within the range of 130 to 280°C for 0.5 to 10.0 hours.

[0075] In addition, in order to adjust the weight of the substrate, the cutting allowance of the inner or outer periphery of the substrate can be appropriately changed during the cutting process.

[0076] Next, the surface of the coil is degreased and etched, and then subjected to zinc immersion treatment (Zn replacement treatment) (step S109). During the zinc immersion treatment, a zinc coating is formed on the surface of the coil. The zinc immersion treatment can use a commercially available zinc immersion solution, preferably performed at a temperature of 10–35°C, a treatment time of 0.1–5 minutes, and a concentration of 100–500 mL / L. The zinc immersion treatment can be performed at least once, or more than twice. By performing multiple zinc immersion treatments, fine Zn can be precipitated, forming a uniform zinc coating. In the case of performing more than two zinc immersion treatments, Zn stripping treatment can be performed between them. The Zn stripping treatment uses an HNO3 solution, preferably performed at a temperature of 15–40°C, a treatment time of 10–120 seconds, and a concentration of 10–60%. Furthermore, subsequent zinc immersion treatments are preferably performed under the same conditions as the initial zinc immersion treatment.

[0077] Furthermore, the surface of the zinc-immersed coil is treated as a substrate for attaching magnetic materials, and an electroless Ni-P plating process is performed (step S110). The electroless Ni-P plating process preferably uses a commercially available plating solution, and the plating process is carried out under the conditions of a temperature of 80-95°C, a treatment time of 30-180 minutes, and a Ni concentration of 3-10 g / L.

[0078] Increasing the thickness of the Ni-P coating can improve the impact resistance as ρ increases. Therefore, the thickness of the Ni-P coating is preferably 7 μm or more, and more preferably 18 μm or more.

[0079] The plated surface after electroless Ni-P plating is subjected to surface polishing for smoothing (step S111). In this polishing step, it is preferable to perform polishing in multiple stages, adjusting the diameter of the abrasive grains. For example, the main surface is coarsely polished using an abrasive slurry containing large-diameter abrasive grains with a particle size of 0.1 to 1.0 μm and a hard or soft abrasive pad. Next, a fine polishing polish is performed on the surface using an abrasive slurry containing small-diameter abrasive grains with a particle size of approximately 0.01 to 0.1 μm and a soft abrasive pad. Through the processes described above, an aluminum alloy substrate for disk drives is manufactured. Furthermore, from the viewpoints of energy saving and impact resistance, the substrate after the cutting and grinding processes (step S107) can also be used as an aluminum alloy substrate for disk drives.

[0080] 1-3-2. Glass substrate for hard disks

[0081] The disk substrate of the present invention can be made of glass. Hereinafter, details will be provided regarding the applicable glass materials and the manufacturing method of the glass substrate for the disk of the present invention.

[0082] (Glass material)

[0083] The glass used as a substrate for disk drives is preferably a glass with SiO2 as the main component (55-75%) and the addition of Al2O3 (0.3-25%) and CaO (0-20%). More preferably, it contains one or more of the following: Li2O (0.01-6%), Na2O (0.7-12%), K2O (0-8%), MgO (0-7%), ZrO2 (0-10%), and TiO2 (0-1%).

[0084] The SiO2 content is 55-75%, thereby increasing the f (fi) of the glass substrate. The SiO2 content in the glass is preferably in the range of 55-75%, more preferably 60-75%. The Al2O3 content is 0.3-25%, thereby increasing the p (ρ) of the glass substrate. The Al2O3 content in the glass is preferably in the range of 0.3-25%, more preferably 1.0-25%. The CaO content is 0-20%, thereby increasing both the f and p of the glass substrate. The CaO content in the glass is preferably in the range of 0-20%, more preferably 1-20%.

[0085] In addition, the aforementioned glass may also contain: B2O3 (an essential component in aluminoborosilicate and borosilicate glasses) which reduces viscosity and improves melt flow and clarity; SrO or BaO which reduces high-temperature viscosity, improves melt flow, clarity, and formability, while also increasing Young's modulus; ZnO which improves ion exchange performance without reducing low-temperature viscosity but reduces high-temperature viscosity; SnO2 which improves clarity and ion exchange performance; and Fe2O3 as a colorant. As a clarifying agent, As2O3 or Sb2O3 may also be included. Furthermore, oxides of La, P, Ce, Sb, Hf, Rb, Y, etc., may also be included as trace elements. These components may be present in quantities of 15% or less.

[0086] (c) Manufacturing method

[0087] Next, an example of the method for manufacturing a glass substrate for a disk according to this embodiment will be described. Figure 2 This is a flowchart illustrating an example of a glass substrate for a disk and a method for manufacturing a disk using the same, according to this embodiment.

[0088] First, a glass plate is manufactured as raw material (step S201). Next, the glass plate manufactured in step S201 is nucleated and shaped to form a ring-shaped glass substrate (step S202).

[0089] Next, chamfered surfaces are formed on the inner and outer peripheral end faces of the formed glass substrate (step S203). After grinding the inner and outer peripheral end faces of the glass substrate with chamfered surfaces, surface grinding is performed. This grinding process consists of coarse grinding (step S204) and fine grinding (step S205). In the coarse grinding (step S204) step, the main surface is coarsely ground using an abrasive slurry containing large-diameter abrasive grains with a particle size of 0.1 to 1.0 μm and a hard or soft abrasive pad. In the subsequent fine grinding (step S205) step, the main surface of the coarsely ground glass substrate is further finely ground using an abrasive slurry containing small-diameter abrasive grains with a particle size of about 0.01 to 0.1 μm and a soft abrasive pad. Through the processes described above, a glass substrate for a disk of the present invention is manufactured. In addition, in order to adjust the weight of the substrate, the grinding allowance can be appropriately changed during the grinding of the inner and outer peripheral end faces.

[0090] The following is a detailed explanation of each process. First, regarding the manufacturing of the glass plate in step S201, known manufacturing methods such as the float glass process, the down-drawing process, and the direct pressure process, which use molten glass as raw material, can be used. Furthermore, heating and softening the base glass plate manufactured using the float glass process or similar methods, and using the re-down-drawing process to extend the desired thickness, makes it relatively easy to manufacture glass plates with smaller thickness deviations, which is therefore preferred.

[0091] Furthermore, amorphous glass or crystallized glass, and other glass ceramics, can be used as the material for the glass sheet. From the viewpoint of formability, processability, or surface roughness of the product, amorphous glass is preferred, such as aluminosilicate glass, soda-lime glass, sodium aluminum silicate glass, aluminum borosilicate glass, borosilicate glass, etc. In addition, chemical strengthening treatment based on sodium nitrate solution or potassium nitrate solution can be performed during the grinding process.

[0092] Next, regarding the nucleation and forming of the annular glass substrate in step S202, the glass plate prepared in step S201 is formed into an annular glass substrate through a nucleation process and an inner and outer peripheral end face grinding process. The formed glass substrate is an annular glass substrate with two main surfaces and a circular hole formed in the center. Further, step S203, chamfering, is performed.

[0093] Next, in the rough grinding process of step S204, a commercially available intermittent double-sided simultaneous grinding machine can be used. This double-sided simultaneous grinding machine includes: an upper and lower pressure plate made of cast iron; a support plate holding multiple glass substrates between the upper and lower pressure plates; and a grinding pad made of rigid polyurethane or the like, mounted on the contact surfaces of the upper and lower pressure plates and the glass substrates. Furthermore, "rigid" here refers to a hardness (asker C) of 85 or higher as determined by the testing method specified in the Japan Rubber Industry Association standard specification (standard specification: SRIS0101).

[0094] This double-sided simultaneous polishing machine holds multiple glass substrates between an upper and lower pressure plate via a support plate. The upper and lower pressure plates clamp each glass substrate under a predetermined processing pressure, and the substrates pass together through a polishing pad. Then, while a predetermined amount of polishing slurry is supplied between the polishing pad and each glass substrate, the upper and lower pressure plates rotate in opposite directions. This causes the glass substrates to slide on the surface of the polishing pad, simultaneously polishing both surfaces. Furthermore, a polishing slurry containing abrasive particles composed of cerium oxide with a particle size of 0.1–1.0 μm is preferably used.

[0095] Next, the precision grinding process in step S205 will be described. In this process, the grinding pad of the double-sided simultaneous grinding machine is replaced with a softer precision grinding pad, such as one made of foamed polyurethane. A grinding slurry containing abrasive particles made of colloidal silica with a particle size of 0.01 to 0.10 μm is supplied, and the glass substrate is ground using the aforementioned grinding pad. Here, "soft" refers to a hardness of 60 to 80. As a result, the main surface of the glass substrate is mirror-polished, producing a glass substrate for a disk drive.

[0096] When cutting surfaces such as through grinding, the thickness of each single side is reduced by 30% or more, preferably 40% or more. This generates greater residual stress on the glass substrate surface, which can improve the efficiency (f). For example, in a glass plate with a thickness of 5 mm before grinding, it is preferable to cut at least 1.5 mm per single side, and more preferably at least 2 mm. An upper limit is not specifically set, but excessive cutting reduces productivity; therefore, the upper limit is set to approximately 45% of the thickness per single side.

[0097] 2. Disk

[0098] 2-1. Made of aluminum alloy

[0099] The magnetic material is attached to the aluminum alloy substrate for the disk by sputtering (step S112). Thus, an aluminum alloy disk is manufactured.

[0100] 2-2. Glass

[0101] The magnetic material is attached to the polished surface of the glass substrate for the disk by sputtering (step S206). Thus, a glass disk is manufactured.

[0102] 3. Disk drive

[0103] By mounting 10 or more aluminum alloy disks manufactured in this manner inside a casing, a disk drive containing aluminum alloy disks is manufactured. Similarly, by mounting 10 or more glass disks manufactured in this manner inside a casing, a disk drive containing glass disks is manufactured.

[0104] Furthermore, the number of disks mounted in the disk drive is set to 10 or more, preferably 11, and more preferably 12. There is no particular upper limit to this number; however, if the number of disks is too large, it will not fit, so it is preferable to set it to around 12.

[0105] Example

[0106] The present invention will now be described in more detail based on embodiments, but the invention is not limited thereto. In this embodiment, multiple aluminum alloy substrates and glass substrates are used as substrates for disk drives for performance evaluation.

[0107] A. Manufacturing of aluminum alloy substrates for hard disks

[0108] First, the alloy materials shown in Table 1 No. 1 to 8 are melted according to the general method, the aluminum alloy composition is adjusted, and the aluminum alloy melt is prepared (step S101).

[0109] [Table 1]

[0110] Table 1

[0111]

[0112] Next, the molten aluminum alloy is cast under the conditions shown in Table 2 to produce ingots of the thickness shown in Table 2 (step S102). Then, the surface of the ingots other than No.7 is face-cut to remove the segregation layer present on the surface of the ingots.

[0113] [Table 2]

[0114]

[0115] Then, the ingot is homogenized under the conditions shown in Table 2 (step S103). Afterwards, except for No. 7, the ingot is hot-rolled to produce a hot-rolled sheet (step S104). The obtained hot-rolled sheet or CC ingot is cold-rolled to produce an aluminum alloy sheet with a thickness of less than 1 mm, which is then punched into a ring shape with an outer diameter of 98 mm and an inner diameter of 24 mm to produce a ring-shaped aluminum alloy sheet (step S105).

[0116] The annular aluminum alloy plates thus produced are subjected to pressure annealing (pressure planarization treatment) for 3 hours at the temperatures shown in Table 2 to form coils (step S106). Then, each coil is face-machined (cutting) to form an outer diameter of 97 mm and an inner diameter of 25 mm, and then ground (grinding process) (step S107). For coils other than No. 1 and 7, the process ends at this stage. For coils No. 1 and 7, a further heat treatment is performed at 300°C for 0.5 hours (step S108). Afterward, a degreasing treatment is performed at 60°C for 5 minutes using AD-68F (trade name, Uemura Kogyo Co., Ltd.), followed by an acid etching treatment at 65°C for 1 minute using AD-107F (trade name, Uemura Kogyo Co., Ltd.), and a desmut treatment is performed for 20 seconds using a 30% HNO3 aqueous solution (room temperature).

[0117] After adjusting the surface condition in this way, the blank is immersed in a zinc immersion solution of AD-301F-3X (trade name, Uemura Kogyo Co., Ltd.) at 20°C for 0.5 minutes to perform zinc immersion treatment on the surface (step S109). In addition, the zinc immersion treatment is performed twice in total. Between the first and second zinc immersion treatments, the blank is immersed in a 30% HNO3 aqueous solution at room temperature for 20 seconds to perform surface stripping treatment. Next, the zinc-treated surface is subjected to Ni-P electroless plating using an electroless Ni-P plating solution (Nimodane HDX (trade name, Uemura Kogyo Co., Ltd.)) at about 90°C to achieve the plating thickness shown in Table 2 (step S110).

[0118] Furthermore, the obtained plated surface was coarsely ground using an alumina slurry with an average particle size of 800 nm and a polyurethane foam abrasive pad. The coarse grinding depth was set to 0.2 μm per side. Next, a fine polishing process (polishing process) was performed using a colloidal silica and a polyurethane foam abrasive pad (step S111). In addition, during the polishing process, a polyurethane foam abrasive pad and a polishing slurry containing colloidal silica with a particle size of 70–90 nm and an average particle size of 80 nm, which was mixed with water to form free abrasive particles, were used, and only a thickness of 0.1 μm was ground per side. Using the above method, a Ni-P plating layer was applied only to No.1 and No.7 to produce a polished aluminum alloy substrate for disks (outer diameter 97 mm, inner diameter 25 mm, plate thickness 0.5 mm). Using the substrates produced in this way, samples for weight measurement were made.

[0119] On the other hand, except for No. 1 and 7, the blank after the pressure planarization treatment in step S106 is subjected to end face machining (cutting) and grinding to produce an aluminum alloy substrate for disks without a Ni-P plating layer (outer diameter 97 mm, inner diameter 25 mm, plate thickness 0.5 mm). Using the substrate produced in this way, a sample for weight measurement is made.

[0120] B. Glass substrate for disk drives

[0121] The glass plate is made using materials composed of the components shown in Tables 3 (Nos. 9 to 12) and manufactured using the method shown in Table 4. Furthermore, No. 10 has a thickness of 5 mm, while Nos. 9, 11, and 12 have a thickness of 1 mm or less. In No. 10, the surface is cut by 4.2 mm (2.1 mm per side), and the thickness is set to 1 mm or less (step S201).

[0122] [Table 3]

[0123]

[0124] [Table 4]

[0125] Table 4

[0126]

[0127] The glass plate manufactured above with a thickness of less than 1 mm is nucleated to form a ring-shaped glass substrate. Chamfered surfaces are further formed on the inner and outer circumferences to manufacture a glass substrate with an outer diameter of 97 mm and an inner diameter of 25 mm for the circular hole (steps S202 to S203).

[0128] Next, these glass substrates are subjected to a coarse grinding process (step S204) and a precision grinding process (step S205) using a double-sided simultaneous grinding machine according to the manufacturing method described above.

[0129] Here, in the rough grinding process (step S204), a polyurethane grinding pad and a grinding slurry made by adding water to cerium oxide abrasive grains with a particle size of 0.1 to 0.4 μm and an average particle size of 0.19 μm are used to rough grind both sides of a glass substrate having the above-mentioned characteristics.

[0130] In the subsequent precision grinding process (step S205), a polyurethane foam grinding pad and a grinding slurry containing colloidal silica with a particle size of 70–90 nm and an average particle size of 80 nm, mixed with water to form free abrasive particles, are used to precisely grind each surface of the coarsely ground glass substrate to a thickness of 1 μm. In this manner, a glass substrate for disk drives (outer diameter 97 mm, inner diameter 25 mm, thickness 0.5 mm) is produced, forming a sample for weight measurement.

[0131] C. Characteristic evaluation of the manufactured disk substrate

[0132] For the blank after step S106, the aluminum alloy substrate after step S110, and the glass plate after step S201, the weight and f×ρ / t are evaluated using the following method. Alternatively, the aluminum alloy disk after step S112 and the glass disk after step S206 can also be used to evaluate the weight and f×ρ / t.

[0133] f×ρ / t

[0134] This relates to f×ρ / t as specified in claims 1, 3, 6, and 7. A 60mm × 8mm sample is used, and the resonant frequency is determined by the resonance method. Furthermore, the dimensions (length, width, and thickness) and weight of individual samples are measured, and the density is calculated. Then, f×ρ / t is calculated based on the thickness of the substrate. The resonant frequency is measured using a JE-RT type measuring apparatus manufactured by Techno-plus Co., Ltd., Japan, at room temperature. When measuring transparent glass, carbon spray is applied until conductivity is achieved before measurement. A carbon film thickness of approximately 1 μm is acceptable.

[0135] weight

[0136] This relates to the weight specified in claims 8-10. The weight of the disk substrate with a thickness of 0.5 mm (outer diameter 97 mm, inner diameter of the circular hole 25 mm) described above was measured using an electronic balance. Alternatively, the weight can be calculated from the density of each material or the plating density.

[0137] The evaluation results of various characteristics of the disk substrate manufactured in this embodiment are shown in Tables 2 and 4.

[0138] As shown in Tables 2 and 4, the specified f×ρ / t can be obtained in Examples 1 to 7 and 9 to 11.

[0139] In contrast, as shown in Tables 2 and 4, in Comparative Examples 8 and 12, the f×ρ / t of the substrate is too small.

[0140] This invention can be implemented and modified in various ways without departing from its broad spirit and scope. Furthermore, the above-described embodiments are illustrative and do not limit the scope of the invention. That is, the scope of the invention is defined not by the embodiments, but by the claims. Moreover, all modifications implemented within the scope of the claims and their equivalents are considered to be within the scope of the invention.

[0141] This application is based on Japanese Patent Application No. 2020-115353, filed on July 3, 2020. The description, claims, and all drawings of Japanese Patent Application No. 2020-115353 are incorporated herein by reference.

[0142] Industrial availability

[0143] According to the present invention, a disk substrate with excellent impact resistance and energy efficiency, and a disk using the disk substrate can be obtained.

Claims

1. A substrate for a hard disk, characterized in that, If we set the resonant frequency to f Hz, the density to ρ g / cm³, and the plate thickness to t mm, then f × ρ / t is greater than 3800. It is composed of an aluminum alloy containing one or more of the following: Fe: less than 8.5 mass%, Mn: less than 2.5 mass%, Ni: less than 6.5 mass%, and Mg: less than 4.5 mass%. The aluminum alloy also contains one or more of the following: Zn: less than 0.7 mass%, Cu: less than 1.0 mass%, Cr: less than 0.30 mass%, Zr: less than 0.20 mass%, Be: less than 0.0015 mass%, Sr: less than 0.1 mass%, Na: less than 0.1 mass%, and P: less than 0.1 mass%. The remainder consists of Al and unavoidable impurities. Each disk weighs between 6.0 and 11.0 grams.

2. The disk substrate according to claim 1, The value of f×ρ / t is above 4000.

3. The disk substrate according to claim 1, The value of f×ρ / t is above 4200.

4. The disk substrate according to claim 1, Each disk weighs between 6.0 and 10.5 grams.

5. The disk substrate according to claim 1, Each disk weighs between 6.0 and 8.7 grams.

6. The disk substrate according to claim 1, The outer diameter is 97 mm.

7. A substrate for a hard disk, characterized in that, It is composed of a glass material with SiO2 as the main component (55-75 mass%), Al2O3 (0.3-25 mass%), and CaO (0-20 mass%). The resonant frequency is set to f Hz, the density to ρ g / cm³, and the plate thickness to t mm. The value of f × ρ / t is above 3800. Each disk weighs between 6.0 and 11.0 grams.

8. The disk substrate according to claim 7, The glass material also contains one or more of the following: Li2O: 0.01–6 mass%, Na2O: 0.7–12 mass%, K2O: 0–8 mass%, MgO: 0–7 mass%, ZrO2: 0–10 mass%, and TiO2: 0–1 mass%.

9. The substrate for a disk drive according to claim 7 or 8, The glass material further contains, in amounts of 15% or less, B2O3, SrO, BaO, ZnO, SnO2, Fe2O3, As2O3, and Sb2O3. One or more.

10. The substrate for a disk drive according to claim 7 or 8, The value of f×ρ / t is above 4000.

11. The substrate for a disk drive according to claim 7 or 8, The value of f×ρ / t is above 4200.

12. The disk substrate according to claim 7 or 8, Each disk weighs between 6.0 and 10.5 grams.

13. The substrate for a disk drive according to claim 7 or 8, Each disk weighs between 6.0 and 8.7 grams.

14. The disk substrate according to claim 7 or 8, The outer diameter is 97mm.

15. A disk, characterized in that, The surface of the disk substrate as described in any one of claims 1 to 14 has a magnetic layer.

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