Method for manufacturing disk-shaped substrate and magnetic recording medium

Abstract

Provided are a method for manufacturing a disk-shaped substrate having excellent flatness of a plating layer and excellent thickness uniformity of a chemically strengthened layer, and a magnetic recording medium. [Solution] A method for manufacturing a disk-shaped substrate, which comprises subjecting a disk-shaped substrate ground with a grinding fluid to at least one treatment selected from the group consisting of (1) heating, (2) washing with an organic solvent, and (3) ultraviolet light irradiation treatment, to remove at least a portion of the polymeric components of the grinding fluid on the surface of the disk-shaped substrate.

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a disk-shaped substrate and a magnetic recording medium. [Background technology]

[0002] 2. Description of the Related Art Magnetic recording media used in hard disk drives (HDDs) employ disk-shaped substrates. Generally, aluminum substrates or aluminum alloy substrates are used as disk-shaped substrates, with the demand for glass substrates also increasing in recent years.

[0003] The disk-shaped substrate is machined into a doughnut shape with a circular through hole in the center, and the main surface and end surface are ground using a grinding fluid. In the next step, the ground disk-shaped substrate is surface-treated using a plating fluid (see, for example, Patent Document 1) for aluminum substrates and aluminum alloy substrates, and a chemical strengthening fluid (see, for example, Patent Document 2) for glass substrates. After these treatments, a magnetic layer is formed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-107382 A [Patent Document 2] International Publication No. 2015 / 041301 Summary of the Invention [Problem to be solved by the invention]

[0005] The plating layer and the chemically strengthened layer obtained by the above surface treatment may have low uniformity in thickness. If the plating layer has low thickness uniformity and poor flatness, the magnetic layer provided on the plating layer will conform to the surface shape of the plating layer, reducing flatness and degrading the writability and readability of the magnetic head element. In addition, if the thickness of the chemically strengthened layer is not uniform and there are thin portions of the chemically strengthened layer, the glass substrate may easily crack from those portions. In particular, in recent years, there has been a demand for thinner magnetic recording media, which has led to glass substrates being more susceptible to cracking. Therefore, an object of the present disclosure is to provide a method for manufacturing a disk-shaped substrate and a magnetic recording medium that have excellent flatness of a plating layer and excellent thickness uniformity of a chemically strengthened layer.

[0006] The present disclosure includes the following aspects. <1> A method for manufacturing a disk-shaped substrate, comprising the steps of: (1) heating a disk-shaped substrate that has been ground with a grinding fluid; (2) washing the disk-shaped substrate with an organic solvent; and (3) exposing the disk-shaped substrate to at least one treatment selected from the group consisting of ultraviolet light irradiation treatment to remove at least a portion of the polymer component of the grinding fluid from the surface of the disk-shaped substrate. <2> The grinding fluid contains at least one selected from the group consisting of an oiliness agent, an extreme pressure additive, a surfactant, a preservative, and an antifoaming agent. <1> 2. A method for producing the disk-shaped substrate according to claim 1 . <3> The disk-shaped substrate is an aluminum substrate, an aluminum alloy substrate, or a glass substrate; <1> or <2> 2. A method for producing the disk-shaped substrate according to claim 1 . <4> the water contact angle of the surface of the disk-shaped substrate after the treatment is 45° or less; <1> ~ <3> 13. A method for producing a disk-shaped substrate according to any one of the above. <5> <1> ~ <4> A disk-shaped substrate obtained by the manufacturing method according to any one of the above items 1 to 5, a magnetic layer provided on the disk-shaped substrate; A magnetic recording medium comprising: Effect of the Invention

[0007] According to the present disclosure, there are provided a method for manufacturing a disk-shaped substrate having excellent flatness of a plating layer and excellent thickness uniformity of a chemically strengthened layer, and a magnetic recording medium. [Brief description of the drawings]

[0008] [Figure 1]1 is a cross-sectional schematic diagram showing an example of an assisted magnetic recording medium in which a disk-shaped substrate according to the present disclosure is used as a substrate for a magnetic recording medium. [Diagram 2] 1 is a perspective view showing an example of a magnetic storage device using a magnetic recording medium according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments of the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments. In the following embodiments, the components (including element steps, etc.) are not essential unless specifically stated. The same applies to the numerical values ​​and their ranges, and do not limit the present disclosure. In the present disclosure, a numerical range indicated using "~" includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in the present disclosure in stages, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value of the numerical range may be replaced with a value shown in the examples. In the present disclosure, each component may contain multiple types of the corresponding substance. When multiple substances corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple substances present in the composition, unless otherwise specified. In the present disclosure, the particles corresponding to each component may include multiple types. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified. In this disclosure, the term "layer" includes cases where the layer is formed over the entire area when the area in which the layer exists is observed, as well as cases where the layer is formed over only a portion of the area.

[0010] <Method of manufacturing disk-shaped substrate> The method for manufacturing a disk-shaped substrate of the present disclosure comprises subjecting a disk-shaped substrate ground with a grinding fluid to at least one treatment selected from the group consisting of (1) heating, (2) washing with an organic solvent, and (3) ultraviolet light irradiation treatment to remove at least a portion of the polymer component of the grinding fluid on the surface of the disk-shaped substrate. The reason why the above problems are solved in the manufacturing method having the above configuration is believed to be as follows.

[0011] It was found that polymeric components contained in the grinding fluid adhere to the surface of the disk-shaped substrate ground with the grinding fluid. It is believed that the presence of these polymeric components affects the wettability of the plating solution and chemical strengthening solution in the next process, as well as physical properties other than wettability, thereby reducing the flatness of the plating layer and the uniformity of the thickness of the chemically strengthened layer. Therefore, before applying the plating solution or chemical strengthening solution, the ground disk-shaped substrate is subjected to at least one treatment selected from the group consisting of (1) heating, (2) washing with an organic solvent, and (3) ultraviolet irradiation treatment. By heating the disk-shaped substrate, at least a part of the polymer components present on the surface is burned off. By washing the disk-shaped substrate with an organic solvent, at least a part of the polymer components present on the surface is washed away. By subjecting the disk-shaped substrate to ultraviolet irradiation treatment, at least a part of the molecular chains of the polymer components are cut and reduced in molecular weight, and at least a part of the polymer components are removed. It is believed that the disk-shaped substrate from which the polymer components have been removed from the surface by these treatments will have improved flatness of the plating layer formed in the next process, or improved uniformity of the thickness of the chemically strengthened layer.

[0012] The disk-shaped substrate may be an aluminum substrate, an aluminum alloy substrate, or a glass substrate. Hereinafter, the aluminum substrate, the aluminum alloy substrate, and the glass substrate are collectively referred to as "substrate." The aluminum substrate and the aluminum alloy substrate are collectively referred to as "aluminum substrate."

[0013] The aluminum substrate may be any aluminum substrate commonly used in this field, and from the standpoint of strength, plating ability, grindability, etc., JIS-A5086 aluminum alloy is preferred.

[0014] The glass substrate may be made of amorphous glass, crystallized glass, or the like, which is used as a glass substrate for a normal magnetic recording medium. Specific examples of the glass substrate include glass substrates made of soda lime, aluminosilicate, lithium silicate, lithium aluminosilicate, aluminoborosilicate, and the like. Examples of the crystallized glass include glass obtained by reheating glass under controlled conditions to precipitate and grow a large number of minute crystals. Examples of the crystallized glass include Al2O3-SiO2-Li2O and B2O3-Al2O3-SiO2-Li2O glasses. The thickness of the glass substrate for the magnetic recording medium is not particularly limited, and typically has a thickness of about 0.4 mm to 1 mm.

[0015] The main surface and the end surface of the substrate having a circular through hole in the center are ground using a grinding fluid. The grinding of the main surface and the end surface may be performed together, in a series, or separately. The grinding of the end surface may be performed on the inner and outer peripheral end surfaces of the substrate, and may further include chamfering. The grinding process and the end face processing may be performed, for example, in the order of a main surface grinding step and an inner and outer periphery end face grinding step.

[0016] In the main surface grinding process, both main surfaces of the substrate (surfaces that will eventually become the recording surfaces of the magnetic recording medium) are ground. In the grinding process, the substrate is sandwiched between a pair of surface plates that rotate in opposite directions, a grinding fluid is supplied, and both main surfaces of the substrate are ground by grinding pads provided on the surface plates. Multiple substrates may be placed between the pair of surface plates and ground all at once. Abrasive grains such as diamond are fixed to the grinding pads with a binder, and both main surfaces of the substrate are ground by these abrasive grains.

[0017] From the viewpoint of reducing the environmental load, the grinding fluid is preferably an aqueous solution using water as a medium, and from the viewpoint of lubrication, cooling, removal of cutting chips, etc. during grinding, it may contain at least one selected from the group consisting of oiliness agents, extreme pressure additives, surfactants, preservatives, and antifoaming agents. At least a part of these may remain as polymer components on the surface of the disk-shaped substrate after grinding. In particular, the oiliness agents, antifoaming agents, etc. tend to remain as polymer components on the surface of the disk-shaped substrate after grinding.

[0018] The oily agent is not particularly limited so long as it is one that is commonly used in abrasive applications, and examples thereof include animal and vegetable oils and hydrogenated products thereof; fatty acids and their salts; fatty acid esters; sulfides of unsaturated carboxylic acids; polyoxyalkylene compounds; and the like. The oily agents may be used alone or in combination of two or more.

[0019] The fatty acid is not particularly limited as long as it is one that is normally used for abrasives, and includes fatty acids having 14 or more carbon atoms, preferably 16 to 24 carbon atoms. The fatty acid may be a saturated fatty acid or an unsaturated fatty acid. The fatty acid may be a straight chain or a branched chain. Specific examples of the fatty acid include oleic acid, linoleic acid, stearic acid, isostearic acid, palmitic acid, lauric acid, maleic acid, etc. The fatty acids may be used alone or in combination of two or more.

[0020] Examples of the salts of fatty acids include alkali metal salts, alkaline earth metal salts, amine salts, etc. Examples of the alkali metals include sodium and potassium, and examples of the alkaline earth metals include magnesium, calcium, barium, etc.

[0021] Examples of the fatty acid ester include esters of the above-mentioned fatty acids and alcohols, such as methanol and ethanol.

[0022] An example of the sulfide of an unsaturated carboxylic acid is a sulfide of oleic acid.

[0023] Examples of the polyoxyalkylene compound include compounds represented by the following general formula (1) or (2).

[0024] R 1 O-(R 2 O) i -R 3 (1)

[0025] In formula (1), R 1 and R 3 each independently represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms; R 2 represents an alkylene group having 2 to 4 carbon atoms, and i represents an integer such that the number average molecular weight of the compound represented by general formula (1) is 100 to 3,500.

[0026] E-[(R 4 O) j -R 5 ] k (2)

[0027] In formula (2), E represents a residue obtained by removing some or all of the hydrogen atoms of the hydroxyl groups of a polyhydric alcohol having 3 to 10 hydroxyl groups, and R 4 represents an alkylene group having 2 to 4 carbon atoms, R 5 represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, j represents an integer such that the number average molecular weight of the compound represented by general formula (2) is 100 to 3500, and k represents the same number as the number of hydrogen atoms removed from the hydroxyl groups in E.

[0028] Examples of the extreme pressure additives include sulfur-based extreme pressure additives such as sulfurized fatty oils, chlorine-based extreme pressure additives such as chlorinated paraffins and chlorinated fatty acid esters, and phosphorus-based additives such as zinc dialkyldithiophosphate. The extreme pressure additives may be used alone or in combination of two or more kinds.

[0029] Examples of the surfactant include anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc. The surfactants may be used alone or in combination of two or more kinds. The surfactant preferably contains an anionic surfactant, and an anionic surfactant may be used in combination with a nonionic surfactant.

[0030] The anionic surfactant is not particularly limited as long as it is one that is commonly used in abrasive applications, and examples thereof include higher alkyl sulfate ester salts (e.g., sodium lauryl sulfate and potassium lauryl sulfate), alkyl ether sulfate ester salts (e.g., POE-triethanolamine lauryl sulfate and sodium POE-lauryl sulfate, POE stands for polyoxyethylene), and the like.

[0031] The nonionic surfactant is not particularly limited as long as it is one that is commonly used in abrasive applications, and examples thereof include sorbitan fatty acid esters (e.g., sorbitan monooleate, glycerin or polyglycerin fatty acids (e.g., glycerin monostearate), sucrose fatty acid esters, and the like.

[0032] As the preservative, an organic amine is preferable, and an organic amine containing a hydroxyl group is more preferable. The organic amine is not particularly limited so long as it is one that is commonly used in abrasive applications, and examples thereof include trialcoholamines such as trimethanolamine, triethanolamine, tripropanolamine, and tributanolamine. The preservatives may be used alone or in combination of two or more kinds.

[0033] Examples of the defoaming agent include silicone-based defoaming agents, polyoxyalkylene-based defoaming agents, and mineral oil-based defoaming agents. Examples of the silicone-based defoaming agent include dimethylpolysiloxane and modified polysiloxane. Examples of the polyoxyalkylene-based defoaming agent include polyoxypropylene and polyoxybutylene. Examples of the mineral oil-based defoaming agent include naphthene-based and paraffin-based defoaming agents. The antifoaming agents may be used alone or in combination of two or more.

[0034] The substrate ground with the grinding fluid is subjected to at least one treatment selected from the group consisting of (1) heating, (2) washing with an organic solvent, and (3) ultraviolet ray irradiation.

[0035] The substrate is preferably heated to 250° C. or higher, more preferably 270° C. or higher, and even more preferably 290° C. or higher. There is no particular upper limit to the heating temperature, but from the viewpoint of suppressing damage to the substrate due to heating, in the case of an aluminum substrate, the heating temperature is preferably 360° C. or lower, more preferably 340° C. or lower, and even more preferably 310° C. or lower, while in the case of a glass substrate, the heating temperature is preferably 700° C. or lower, more preferably 600° C. or lower, and even more preferably 500° C. or lower.

[0036] The heating time is preferably 10 minutes or more, more preferably 15 minutes or more, and even more preferably 20 minutes or more, and from the viewpoint of reducing the energy load, is preferably 60 minutes or less, more preferably 45 minutes or less, and even more preferably 30 minutes or less.

[0037] The heating device is not particularly limited as long as it can heat to the desired temperature, and any known heating device can be used. Specifically, the heating device can be an oven, an electric furnace, or the like.

[0038] The organic solvent used for cleaning is preferably a non-polar solvent, since the grinding fluid used in the previous step is an aqueous solution. Examples of non-polar solvents include isopropyl alcohol (IPA) and hydrofluoroether (HFE).

[0039] The method of cleaning with an organic solvent is not particularly limited, and a general cleaning method and cleaning device can be used. For example, a method of spin rinsing at room temperature using a spin rinse device can be mentioned.

[0040] The ultraviolet irradiation treatment can be carried out using a light source such as an excimer laser, a high-pressure mercury lamp, or an arc lamp.

[0041] The irradiation intensity of the ultraviolet irradiation treatment was set to 300 mW / m from the viewpoint of effectively cutting the molecular chains of the polymer components remaining on the surface of the disk-shaped substrate. 2 More than 600mW / m is preferable. 2 More preferably, 1200mW / m 2 The above is even more preferable.

[0042] The irradiation time of the ultraviolet irradiation treatment is preferably 2 seconds or more, may be 5 seconds or more, or may be 7 seconds or more, from the viewpoint of uniformity of the irradiation range.

[0043] From the viewpoint of enhancing the wettability of the plating solution or chemical strengthening solution in the next process, the water contact angle of the surface of the disk-shaped substrate after performing at least one treatment selected from the group consisting of (1) to (3) is preferably 45° or less, more preferably 30° or less, even more preferably 20° or less, and particularly preferably 15° or less.

[0044] The water contact angle is measured using a contact angle meter, and the contact angle (after 0.2 seconds) of a water droplet (pure water, 2.0 μL) on the substrate surface at 25° C. is measured.

[0045] The amount of polymer components on the surface of the disk-shaped substrate is preferably reduced to 0.001% by mass or less after the treatments (1) to (3), with the amount before the treatments (1) to (3) being taken as 100% by mass, and may be 0% by mass. The amount of polymer components on the surface of the disk-shaped substrate can be measured by time-of-flight secondary ion mass spectrometry (TOF-SIMS).

[0046] After the processes (1) to (3), a plating layer is formed on the aluminum substrate using a plating solution, and a chemically strengthened layer is formed on the glass substrate using a chemically strengthening solution.

[0047] As the plating method, a known method can be used, and it is preferable to use an electroless plating method. In general, a NiP-based nickel alloy plating layer is formed. As the plating solution used to form the NiP alloy plating layer, for example, a plating solution containing nickel sulfate as a nickel source and hypophosphite as a phosphorus source can be mentioned. Mo salt or W salt may be further added to the plating solution to form a NiMoP alloy plating layer or a NiWP alloy plating layer.

[0048] The chemical strengthening process is a process in which the glass substrate is immersed in a chemical strengthening liquid to exchange ions in the chemical strengthening liquid with ions in the glass. The chemical strengthening process can be a known method performed on glass substrates. The chemical strengthening liquid can be a high-temperature molten salt, and preferably contains KNO3, NaNO3, or the like.

[0049] The disk-shaped substrate obtained by the manufacturing method of the present disclosure can be suitably used as a magnetic recording medium for hard disk drives (HDDs).

[0050] <Magnetic recording media> The magnetic recording medium of the present disclosure has a disk-shaped substrate obtained by the manufacturing method of the present disclosure, and a magnetic layer provided on the disk-shaped substrate. The disk-shaped substrate obtained by the manufacturing method of the present disclosure has excellent uniformity in the thickness of a plated layer or a chemically strengthened layer when the plated layer or the chemically strengthened layer is formed.

[0051] When a magnetic layer is provided on a plating layer having excellent flatness, the magnetic layer has excellent flatness and excellent writability and readability by a magnetic head element. The number of concave defects in the plating layer on the disk-shaped substrate can be 500 or less on one side, preferably 50 or less, more preferably 30 or less, and even more preferably 4 or less. The number of concave defects in the plating layer can be confirmed by observation using an optical inspection machine (e.g., OSA7100 manufactured by KLA Tencor).

[0052] Furthermore, according to the manufacturing method of the present disclosure, the chemically strengthened layer has excellent thickness uniformity, which prevents partial reduction in strength of the glass substrate and reduces the frequency of occurrence of breakage defects.

[0053] The magnetic recording medium may further include a carbon protective layer, a lubricant layer, and the like on the magnetic layer. The magnetic recording medium may further include, between the substrate and the magnetic layer, an adhesion layer, a soft magnetic underlayer, a seed layer, an orientation control layer, etc. Each of these layers may consist of one layer or two or more layers. Materials for forming the magnetic layer, carbon protective layer, lubricant layer, adhesion layer, soft magnetic underlayer, seed layer, orientation control layer, etc. can be general materials used for magnetic recording media.

[0054] Fig. 1 is a cross-sectional schematic diagram showing an example of an assisted magnetic recording medium in which a disk-shaped substrate according to the present disclosure is applied as a magnetic recording medium substrate 1. As shown in Fig. 1, an assisted magnetic recording medium 40 includes a magnetic recording medium substrate 1, a seed layer 41, a first underlayer 42, a second underlayer 43, a magnetic layer 44, a protective layer 45, and a lubricant layer 46 laminated in this order. The magnetic recording medium 40 can be used in a magnetic storage device.

[0055] Fig. 2 is a perspective view showing an example of a magnetic storage device using the magnetic recording medium according to the present disclosure. As shown in Fig. 2, the magnetic storage device 50 includes an assist magnetic recording medium 40, a magnetic recording medium driving unit 51 for rotating the assist magnetic recording medium 40, a magnetic head 52, a head moving unit 53 for moving the magnetic head 52, and a recording and reproducing signal processing unit 54. The magnetic head 52 has a recording head and a reproducing head (not shown), and the recording head has a laser light generating unit for heating the assist magnetic recording medium and a waveguide for guiding the laser light generated from the laser light generating unit to the near-field light generating element. The magnetic storage device 50 attaches the center of the assisted magnetic recording medium 40 to the rotating shaft of a spindle motor, and writes or reads information to the assisted magnetic recording medium 40 while a magnetic head 52 floats and runs above the surface of the assisted magnetic recording medium 40, which is rotated by the spindle motor. EXAMPLES

[0056] The present disclosure will be specifically described below using examples, but the scope of the present disclosure is not limited to these examples.

[0057] [Comparative Example 1] (Aluminum alloy substrate manufacturing) The aluminum alloy plate used was equivalent to A5086 (Mg: 4 mass%, Mn: 0.5 mass%, Fe: 0.3 mass%, Cr: 0.2 mass%, Si: 0.2 mass%, Zn: 0.2 mass%, balance Al). This plate was produced by rolling an aluminum alloy ingot obtained by semi-continuous casting.

[0058] Next, the 1.2 mm thick plate material was punched into a doughnut disk shape to obtain an aluminum alloy substrate having a diameter of 97 mm and a center hole, which was then annealed for 1 hour at 380° C. Thereafter, both main surfaces and end surfaces of the aluminum alloy substrate were machined with a diamond bit to obtain an aluminum alloy substrate having a diameter of 95 mm and a thickness of 0.8 mm.

[0059] Next, a grinding device was used to grind both main surfaces of the aluminum alloy substrate using grinding wheels provided on upper and lower plates while performing planetary motion on the aluminum alloy substrates held in the openings of each carrier plate.

[0060] The grinding equipment used was a 4-way type double-sided grinding machine (16B model manufactured by Hamai Sangyo Co., Ltd.), with the rotation speed of the table set at 30 rpm and the processing pressure set at 110 g / cm. 2 The grinding was performed for 5 minutes. The grinding fluid used was a water-soluble grinding fluid containing 30% by mass of oleic acid diluted with water to 1.0% by mass.

[0061] (Water contact angle measurement) For the aluminum alloy substrate after grinding, the contact angle (after 0.2 seconds) of a water droplet (pure water, 2.0 μL) on the substrate surface at 25° C. was measured using DM-501 manufactured by Kyowa Interface Science Co., Ltd.

[0062] (Formation of plating layer) The obtained aluminum alloy substrate was immersed in a NiP-based plating solution, and a 88Ni-12P (P content: 12 mass %, balance: Ni) layer was formed as a NiP-based plating layer on the surface of the aluminum alloy substrate by electroless plating.

[0063] The NiP-based plating solution contained nickel sulfate (nickel source) and sodium hypophosphite (phosphorus source), and the amounts of the components were adjusted so that a NiP-based plating layer of the above composition was obtained. The temperature of the NiP-based plating solution used to form the NiP-based plating layer was adjusted to 90°C. The aluminum alloy substrate was immersed in the NiP-based plating solution for 2 hours.

[0064] Next, the aluminum alloy substrate on which the NiP-based plating layer was formed was heated at a required temperature for a required time to obtain an aluminum alloy substrate with a NiP-based plating layer. To remove the irregularities in the NiP plating layer, a polishing device with polyurethane foam polishing cloths on the upper and lower plates was used to polish the substrate surface by moving the upper and lower plates in a planetary motion while an abrasive containing alumina, zirconia, titania, colloidal silica, etc. was ejected.

[0065] (Evaluation of concave defects in plating layer) The entire surface of the aluminum alloy substrate was observed using an optical inspection machine (OSA7100 manufactured by KLA Tencor Corporation), and the number of concave defects on the entire surface of the substrate was counted. The evaluation criteria based on the number of concave defects on one side of the substrate are as follows. A and B are considered to be acceptable.

[0066] A: The number of pit defects is 50 or less. B: The number of concave defects is more than 50 and 500 or less. C: The number of concave defects is more than 500 and not more than 1,000. D: The number of pit defects exceeds 1,000.

[0067] [Comparative Example 2] In Comparative Example 1, before forming a plating layer, the aluminum alloy substrate after grinding was scrubbed twice with a polyvinyl alcohol (PVA) sponge at room temperature while discharging a detergent (nonionic surfactant), and then spin-rinsed in a spin-rinsing device while discharging pure water, and then spin-dried.

[0068] After cleaning, the water contact angle of the aluminum alloy substrate was measured by the above-mentioned method. In addition, a plating layer was formed on the washed aluminum alloy substrate in the same manner as in Comparative Example 1.

[0069] [Example 1] In Comparative Example 2, cleaning was performed by replacing the detergent with a non-polar solvent of HFE. After cleaning, the water contact angle of the aluminum alloy substrate was measured by the above-mentioned method. In addition, a plating layer was formed on the washed aluminum alloy substrate in the same manner as in Comparative Example 1.

[0070] [Example 2] In Comparative Example 1, before forming a plating layer, the ground aluminum alloy substrate was heated at 300° C. for 30 minutes using a conveyor-type continuous atmospheric furnace as an electric furnace. After heating, the water contact angle of the aluminum alloy substrate was measured by the above-mentioned method. In addition, a plating layer was formed on the heated aluminum alloy substrate in the same manner as in Comparative Example 1.

[0071] [Example 3] In Example 2, heating was performed at a temperature of 200°C. After heating, the water contact angle of the aluminum alloy substrate was measured by the above-mentioned method. In addition, a plating layer was formed on the heated aluminum alloy substrate in the same manner as in Comparative Example 1.

[0072] [Example 4] In Comparative Example 1, before forming the plating layer, the electric field was 1200 mW / m 2 The ultraviolet ray irradiation treatment was performed for 2 seconds using Ballast for High power UV Lamp manufactured by SUN ENERGY. After the ultraviolet ray irradiation treatment, the aluminum alloy substrate was measured for water contact angle by the above-mentioned method. Further, a plating layer was formed in the same manner as in Comparative Example 1 on the aluminum alloy substrate after the ultraviolet ray irradiation treatment.

[0073] [Table 1]

[0074] It can be seen that Example 1, in which cleaning with an organic solvent was performed before forming the plating layer, Examples 2 and 3, in which annealing was performed, and Example 4, in which ultraviolet irradiation treatment was performed, have significantly reduced plating dent defects compared to Comparative Example 1, in which these treatments were not performed. In addition, in Comparative Example 2, washing with water was performed before the plating layer was formed, but it was found that the number of plating concave defects was not significantly reduced.

Claims

1. The disk-shaped substrate ground with the grinding fluid is subjected to at least one treatment selected from the group consisting of (1) heating, (2) washing with at least one organic solvent selected from the group consisting of isopropyl alcohol and hydrofluoroether, and (3) ultraviolet light irradiation treatment, thereby removing at least a part of the polymer component of the grinding fluid on the surface of the disk-shaped substrate; The method for producing a disk-shaped substrate, wherein the surface of the disk-shaped substrate after the treatment has a water contact angle of 45° or less.

2. A method for manufacturing a disk-shaped substrate, comprising subjecting a disk-shaped substrate ground with a grinding fluid to at least one treatment selected from the group consisting of (1) heating and (3) ultraviolet light irradiation treatment to remove at least a portion of the polymer component of the grinding fluid on the surface of the disk-shaped substrate.

3. The method includes a grinding process for grinding the disk-shaped substrate with a grinding fluid, and a plating layer forming process for forming a plating layer on the disk-shaped substrate, A method for manufacturing a disk-shaped substrate, comprising the steps of: washing the disk-shaped substrate with at least one organic solvent selected from the group consisting of isopropyl alcohol and hydrofluoroether after the grinding process and before the plating layer forming process; and removing at least a portion of the polymer component of the grinding fluid on the surface of the disk-shaped substrate.

4. The method for producing a disk-shaped substrate according to any one of claims 1 to 3, wherein the grinding fluid contains at least one selected from the group consisting of an oiliness agent, an extreme pressure additive, a surfactant, an antiseptic, and an antifoaming agent.

5. The method for producing a disk-shaped substrate according to any one of claims 1 to 3, wherein the disk-shaped substrate is an aluminum substrate, an aluminum alloy substrate, or a glass substrate.

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