JP4969260B2 - Magnetic disk glass substrate manufacturing method, magnetic disk manufacturing method, and magnetic disk glass substrate manufacturing system - Google Patents

Description

The present invention relates to a method of manufacturing a glass substrate for a magnetic disk including a chemical strengthening process a portion of the glass substrate by ion exchange performing chemical strengthening, a method of manufacturing a magnetic disk, relates to a glass substrate manufacturing system for a contact and a magnetic disk.

  In recent years, with the advancement of information technology, information recording technology, particularly magnetic recording technology, has made remarkable progress. As a substrate for a magnetic recording medium such as an HDD (Hard Disk Drive) which is one of such magnetic recording media, an aluminum substrate has been widely used. However, with the miniaturization, thinning, and high-density recording of magnetic disks, there is an increasing demand for glass substrates that have superior substrate surface flatness and substrate strength compared to aluminum substrates.

  In addition, as the recording density of magnetic recording media is increased, the magnetic head has been changed from a thin film head to a magnetoresistive head (MR head) and a large magnetoresistive head (GMR head). The flying height is getting smaller. A magnetic head equipped with such a magnetoresistive element may cause a thermal asperity failure as an inherent failure. In thermal asperity failure, when the magnetic head passes over a minute convex or concave shape on the magnetic disk surface while flying, the magnetoresistive element is heated by adiabatic compression or contact of air, and a read error occurs. It is an obstacle.

  Therefore, for a magnetic head equipped with a magnetoresistive element, the surface of the magnetic disk is required to have extremely high smoothness and flatness. Further, if the magnetic layer is formed with dust and foreign matters attached, convex portions are formed. Therefore, the glass substrate is also required to be highly cleaned to completely remove dust and foreign matters.

  In addition to the smoothness and flatness of the magnetic disk surface, strict accuracy control is required for the inner diameter dimensional error in the circular hole provided in the center of the magnetic disk. This is because the dimensional error of the inner peripheral end surface of the magnetic disk directly affects the installation accuracy when the magnetic disk is fitted to the HDD spindle motor. In addition, if the inner diameter dimensional error is large, there is a possibility of inducing a mechanical error in stacking servo (writing servo information to the magnetic disk) performed before the magnetic disk is assembled in a magnetic disk device such as an HDD, There is a possibility of causing a mating failure with the spindle during disk stacking. The inner peripheral end surface of the magnetic disk has a smaller surface area than the main surface, and if the rotation center of the magnetic disk is displaced due to an inner diameter dimensional error, it becomes difficult to position the HDD head at the correct position on the HDD. Will not be able to record / play.

  Further, since data is read and written while the magnetic disk rotates at a high speed, it is necessary to prevent data on the magnetic disk from being blurred even at the high speed rotation. Accordingly, it is particularly important to manage the accuracy of the inner diameter error of the magnetic disk substrate.

  Further, paying attention to the data access of the HDD, in order to accurately store / reproduce the data of the magnetic disk incorporated in the HDD, a servo pattern serving as a positioning index is written in advance on the magnetic disk. The servo pattern is written by inserting a magnetic disk in a device called a servo writer. Then, the magnetic disk on which the servo pattern is written is once detached from the servo writer, and is inserted into the HDD spindle motor as a product.

  If the inner diameter error of the magnetic disk is large, the position of the servo pattern and the recording / reproducing head of the HDD as a product will be shifted when the magnetic disk is incorporated into the HDD, so that data recording / reproducing is still normal. Will not be done. Although a technique for adjusting alignment to correct such a positional relationship has been disclosed (for example, Patent Document 1), a fundamental solution for suppressing an inner diameter dimensional error has not been made.

As described above, the demand for higher recording density of magnetic disks is increasing further in recent years, and management of inner diameter dimensional errors that are more severe than those of conventional glass substrates for magnetic disks is required.
JP 2004-199841 A

  Such a glass substrate for a magnetic disk is formed through a plurality of processes. First, a single wafer is cut into a disk shape, and an inner hole is formed to form a glass substrate. Thereafter, the outer peripheral end surface and the inner peripheral end surface of the cut glass substrate are chamfered, and both end surfaces are polished. Subsequently, the main surface of the glass substrate is also polished, and finally the glass substrate that has been polished is subjected to a chemical strengthening treatment. Such chemical strengthening treatment can improve the impact resistance and vibration resistance of the glass substrate, and can prevent the glass substrate from being damaged by the impact and vibration.

  The chemical strengthening step for performing this chemical strengthening treatment is performed by, for example, heating and melting a molten salt of an alkali salt and immersing it in the molten salt (chemical strengthening treatment liquid) in a state where the glass substrate to be treated is stored in a glass substrate holder. The ion exchange is performed between the glass substrate and the molten salt.

  At this time, a phenomenon occurs in which the inner diameter of the glass substrate changes before and after the chemical strengthening step, that is, the inner diameter changes as the glass substrate expands toward the center of the inner diameter. This is because when the glass substrate is subjected to a chemical strengthening treatment, a compressive stress is generated on the surface of the glass substrate, and the dimensions of the glass substrate change due to the compressive stress.

  Further, the composition of the chemical strengthening treatment liquid changes with time. Specifically, in the chemical strengthening treatment, the ions contained in the chemical strengthening treatment liquid and the ions contained in the glass substrate are ion-exchanged, so that the chemical strengthening treatment proceeds as the chemical strengthening treatment proceeds. In the strengthening treatment liquid, ions contained in the ion-exchanged glass substrate increase. This change in composition contributes to changing the inner diameter of the glass substrate during chemical strengthening. The amount of change in the inner diameter is not negligible with respect to the inner diameter error of the glass substrate, which is more strictly demanded. Therefore, the glass substrate has a high inner diameter including the amount of change in the inner diameter in the chemical strengthening process. Dimensional accuracy is required.

  Further, in the case of mass production of glass substrates, a chemical strengthening treatment tank is provided in each of the plurality of lines and each contains a chemical strengthening treatment solution independently. In order to obtain a high degree of inner diameter dimensional accuracy, it was necessary to individually control a plurality of such chemical strengthening treatment tanks. However, it is difficult to equalize the state of each chemical strengthening treatment liquid in a plurality of chemical strengthening treatment tanks. When the state of the chemical strengthening treatment liquid is different, the amount of change in the inner diameter of the glass substrate caused by the chemical strengthening treatment is different even under the same chemical strengthening treatment condition.

  As a result of intensive studies on the above problems, the inventors of the present application have variations in the inner diameter of each glass substrate before the chemical strengthening process, and further, the amount of change in the inner diameter for each chemical strengthening treatment tank that performs the chemical strengthening process. In order to reduce the error in the inner diameter of the glass substrate that is finally obtained, the combination of the inner diameter of the glass substrate before chemical strengthening and the amount of change caused by the chemical strengthening is adjusted. And it discovered that an internal-diameter dimension error could be made small by selecting the chemical strengthening processing tank optimal for chemical strengthening, and came to complete this invention.

The present invention has been made in view of the above-described problems of conventional glass substrates, and the object of the present invention is new and improved, which can reduce the inner diameter dimensional error of the glass substrate for magnetic disks. method of manufacturing a glass substrate for a magnetic disk, a method of manufacturing a magnetic disk is to provide a glass substrate manufacturing system for you and a magnetic disk.

  In order to solve the above problems, according to one aspect of the present invention, a disk-shaped glass substrate having a circular hole formed in the center is brought into contact with any one of a plurality of chemical strengthening treatment baths. The method for producing a glass substrate for a magnetic disk including a chemical strengthening step of chemically strengthening the glass substrate by replacing some ions contained in the glass substrate with ions in the chemical strengthening treatment liquid, An inner diameter measurement process that measures the inner diameter of the previous glass substrate, a grasping process that grasps the amount of change in the inner diameter of the glass substrate caused by the chemical strengthening process for each of the multiple chemical strengthening treatment tanks, and the inner diameter is measured based on the amount of change. And a combination determining step for determining a chemical strengthening treatment tank for performing chemical strengthening so that the inner diameter after the chemical strengthening step of the glass substrate is a desired value. In the chemical strengthening step, Characterized by chemically strengthening the glass substrate by strengthening treatment bath, method of manufacturing a glass substrate for a magnetic disk is provided.

  In the present invention, the inner diameter of the glass substrate is measured, and finally the difference from the desired inner diameter is derived. And the chemical strengthening processing tank used as the variation | change_quantity close | similar to the derived | led-out difference is selected. Accordingly, even when the inner diameter of the glass substrate changes, an appropriate chemical strengthening treatment tank is selected so that the glass substrate after the chemical strengthening step has a desired inner diameter each time. It becomes possible to manufacture a glass substrate for a magnetic disk with a small dimensional error.

In order to solve the above problems, according to another aspect of the present invention, any one of a plurality of disk-shaped glass substrates each having a circular hole at the center is brought into contact with a chemical strengthening treatment liquid in a chemical strengthening treatment tank. A method for producing a glass substrate for a magnetic disk comprising a chemical strengthening step of chemically strengthening the glass substrate by replacing some ions contained in the glass substrate with ions in the chemical strengthening treatment liquid , is the chemical strengthening process each of a plurality of glass substrates before in variations in the inner diameter, the inner diameter measuring step of measuring the inner diameter thereof, and grasping step of grasping a variation of the inner diameter of the glass substrate caused by a chemical strengthening process, the amount of change in based on, as the inner diameter after the chemical strengthening process is desired value, the combination determining step of determining the glass substrate to perform chemical strengthening process from a plurality of glass substrates was measured inner diameter, further including In the chemical strengthening process, the glass substrate is determined, characterized in that chemical strengthening by chemical strengthening treatment bath, method of manufacturing a glass substrate for a magnetic disk is provided.

  In the present invention, the amount of change in a specific chemical strengthening treatment tank is calculated, and an optimum glass substrate to be immersed in the chemical strengthening treatment tank is selected from the plurality of glass substrates. Therefore, even when the chemical strengthening treatment conditions of the chemical strengthening treatment liquid in the chemical strengthening treatment tank change with time, an appropriate glass substrate is selected so as to have a predetermined inner diameter each time. (ID) It is possible to manufacture a glass substrate for a magnetic disk with a small dimensional error.

  In order to solve the above-described problem, according to still another aspect of the present invention, each of a plurality of disk-shaped glass substrates each having a circular hole formed in the center thereof is treated with any one of a plurality of chemical strengthening treatment tanks. A method for producing a glass substrate for a magnetic disk, comprising a chemical strengthening step of chemically strengthening the glass substrate by replacing some ions contained in the glass substrate with ions in the chemical strengthening treatment liquid by contacting with the strengthening treatment liquid An inner diameter measuring step for measuring the inner diameter of each of the plurality of glass substrates before the chemical strengthening step, and a grasping step for grasping the change amount of the inner diameter of the glass substrate caused by the chemical strengthening step for each of the plurality of chemical strengthening treatment tanks. A combination determining step for determining a chemical strengthening treatment tank for performing chemical strengthening so that the inner diameter after the chemical strengthening step of the plurality of glass substrates whose inner diameters have been measured becomes a desired value based on the change amount; Further comprising a, in the chemical strengthening process, characterized by chemically reinforced with respective chemical strengthening treatment bath to the determined plurality of glass substrates, the manufacturing method of the magnetic disk glass substrate is provided.

  In the present invention, the inner diameters of a plurality of glass substrates and the amount of change in a plurality of chemical strengthening treatment tanks are calculated, and finally a glass substrate having a desired inner diameter is obtained. A tank is selected. Therefore, even when the inner diameter of the glass substrate changes, and when the chemical strengthening treatment conditions of the chemical strengthening treatment liquid in the chemical strengthening treatment tank change over time, it is appropriate to have a predetermined inner diameter each time. Since a combination of a glass substrate and a chemical strengthening treatment tank is selected, it is possible to manufacture a magnetic disk glass substrate having a small inner diameter (ID) dimensional error as a result.

  In the combination determination step, chemical strengthening is performed so that the sum of squares of the difference between the final expected inner diameter of each combination and the desired value of the inner diameter when the glass substrate and the chemical strengthening treatment tank are temporarily combined is minimized. You may determine each chemical strengthening processing tank.

  Even if one combination of the glass substrate and the chemical strengthening treatment tank is good, the overall combination including the other combinations is not always optimal. Therefore, the above-described configuration using the least square method can reduce the overall inner diameter dimension error.

  The grasping step may grasp the amount of change from the difference in the inner diameter of the glass substrate before and after the chemical strengthening step.

  As a grasping method of the change amount in the grasping process, there are (1) a method of actually measuring the change amount of the inner diameter of the glass substrate and (2) a method of estimating the change amount from the state of the chemical strengthening treatment liquid. The present invention measures the inner diameter of the glass substrate before and after the chemical strengthening step, and grasps the amount of change by calculating the difference between the inner diameters. With this configuration, an actual change amount can be accurately grasped based on actual measurement, and accordingly, an accurate machining amount can be fed back.

  The grasping process includes the concentration of specific components contained in the chemical strengthening treatment liquid, the cumulative number of glass substrates that have been subjected to the chemical strengthening treatment using the chemical strengthening treatment liquid, and the chemical strengthening treatment performed using the chemical strengthening treatment liquid. You may grasp | ascertain the variation | change_quantity based on one or more of the accumulated time of the glass substrate which finished.

  (2) The method of estimating the amount of change from the state of the chemical strengthening treatment solution is as follows: (a) the concentration of a specific component, (b) the glass substrate The amount of change can be estimated based on the accumulated number of processed sheets and (c) the accumulated processing time of the glass substrate. With such a configuration, it becomes possible to easily grasp the amount of change, and in particular (b) and (c), it is not necessary to directly measure the glass substrate or the chemical strengthening treatment liquid. By measuring the accumulated time, the amount of change can be estimated. Therefore, it is possible to grasp the amount of change in the glass substrate without using a special measuring instrument, and it is possible to reduce the inner diameter dimensional error of the glass substrate for magnetic disk while reducing the cost and improving the efficiency of the manufacturing process. It becomes.

  Moreover, (a) About the density | concentration of a specific component, when a glass substrate is formed with the aluminosilicate glass containing Li ion, a specific component can be made into Li ion.

  In the grasping step, the change amount can be grasped by using a change amount table in which the concentration of the specific component and the change amount are associated with each other.

  With this configuration, it is possible to easily derive the amount of change from the concentration by simply referring to a previously prepared change amount table without calculating a multidimensional relational expression between the concentration and change amount of a specific component in real time. be able to. Therefore, it is possible to reduce the processing load and to avoid a shift in the amount of change due to a rounding error when deriving a multidimensional function.

In addition, the method includes a step of forming at least a magnetic layer on the surface of a glass substrate obtained by the method for manufacturing a glass substrate for magnetic disk, the system for manufacturing the glass substrate for magnetic disk, and the method for manufacturing the glass substrate for magnetic disk. producing how the magnetic disk is also provided.

  Such a magnetic recording medium may be a perpendicular magnetic recording medium in which a recording layer is magnetized in a direction perpendicular to the plane of the magnetic disk. Since the perpendicular magnetic recording medium has a higher recording density than the horizontal (in-plane) magnetic recording medium, the inner diameter dimensional error allowed in the horizontal magnetic recording medium cannot be allowed in the perpendicular magnetic recording medium. Therefore, the magnetic recording medium according to the present invention capable of reducing the inner diameter dimensional error is also effective in the perpendicular magnetic recording medium.

  As described above, according to the present invention, it is possible to reduce the inner diameter dimensional error of the magnetic disk glass substrate by combining the glass substrate and the chemical strengthening treatment tank so as to have a desired inner diameter.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

(Adjustment of combination of glass substrate and chemical strengthening tank)
With the miniaturization, thinning, and high-density recording of magnetic disks, high smoothness and flatness of the inner peripheral surface of the glass substrate are required. The present embodiment focuses on the inner peripheral end surface of the glass substrate, particularly the amount of change in the chemical strengthening process, and aims to reduce the final inner diameter (ID) dimensional error of the glass substrate. Hereinafter, a glass substrate manufacturing system 300 capable of performing a series of steps including a chemical strengthening step will be described.

  FIG. 1 is a functional block diagram showing a glass disk substrate manufacturing system 300 according to the present embodiment. Here, a thick arrow indicates a processing flow of the glass substrate 102, and a thin arrow indicates a flow of information. 1 includes an inner peripheral end surface grinding device 110, an inner peripheral end surface polishing device 120, a chemical strengthening treatment tank 130, a grasping device 140, a memory 150, and an inner diameter measuring device. 210 and the combination determination apparatus 310 are comprised. Here, in order to facilitate understanding, the manufacturing system 300 for the magnetic disk glass substrate has been described with reference to the manufacturing process relating to the inner peripheral end surface of the glass substrate 102 in particular. It goes without saying that the manufacturing process of the outer peripheral end face is also included.

  The inner peripheral end surface grinding device 110 functions as an inner peripheral processing device, and, for example, the inner peripheral end surface in a circular hole formed at the center of a disk-shaped glass substrate 102 made of multicomponent glass is ground by a grinding amount. To do. The inner peripheral end surface grinding device 110 can be configured in various forms as long as the inner peripheral end surface of the glass substrate 102 can be ground. For example, the inner peripheral end surface is chamfered (chamfer: chamfer). It is also possible to configure with a device. Further, the grinding amount is a value obtained by adding a grinding amount determined by a grinding amount determination device 160 described later to a desired grinding amount in the grinding process.

  FIG. 2 is an explanatory diagram for explaining a grinding process of the inner peripheral end surface grinding apparatus 110. Here, as shown in FIG. 2A, the inner peripheral end surface 114 formed by the circular holes 112 of the disk-shaped glass substrate 102 is ground and chamfered.

  In the inner peripheral end surface grinding apparatus 110, as shown in FIG. 2B, an inner diameter grinding wheel 116 for grinding is inserted into the circular hole 112. The plurality of glass substrates 102 stacked in a cylindrical shape are sandwiched between two upper and lower bottom surfaces by a sandwiching member. The inner diameter grinding wheel 116 is a pulley-like rotary grinding wheel, and its outer periphery is a grinding surface.

  The glass substrate 102 and the inner diameter grinding wheel 116 are rotationally driven by a fixed driving means (not shown), and the inner diameter grinding wheel 116 is brought into contact with the inner peripheral end surface 114 of the cylindrical glass substrate 102 so that each glass is brought into contact with each other. The substrate 102 is subjected to uniform inner diameter processing. The rotation direction is set so as to be the opposite direction at each contact point. The inner peripheral end face 114 and the chamfer 114a as shown in FIG. 2C are formed by the grinding process of the inner peripheral end face. In addition, the outer peripheral end face can be ground simultaneously with the grinding of the inner peripheral end face 114.

  The inner peripheral end surface polishing apparatus 120 functions as an inner peripheral processing apparatus like the inner peripheral end surface grinding apparatus 110, and further polishes the inner peripheral end face 114 of the glass substrate 102 ground by the inner peripheral end surface grinding apparatus 110 by a polishing amount. To do. This polishing amount is a value obtained by adding a polishing amount determined by a polishing amount determination device 170 described later to a polishing value desired in the polishing step.

  FIG. 3 is a longitudinal sectional view for explaining the configuration of the inner peripheral end surface polishing apparatus 120. The plurality of glass substrates 102 stacked in a cylindrical shape are fixed to the fixing portion 122 of the inner peripheral end surface polishing apparatus 120. One or both of the glass substrates 102 is arranged so that the glass substrate 102 and the polishing body 124 inserted into the circular hole of the glass substrate 102 are relatively rubbed with the center axis of the disk of the glass substrate 102 as the center of rotation. Is rotated to polish the inner peripheral end surface of the glass substrate 102.

  In the polishing body 124, a polishing cloth 126 formed of a soft polisher made of suede or velor, or a hard polisher such as hard velor, foam resin, or pitch-impregnated suede is arranged to form a part of a cylindrical shape. May be. Further, the polishing body 124 may polish the entire inner peripheral end surface 114 of the glass substrate 102 by swinging slowly (stroke) in the direction of the rotation axis within the circular hole with respect to the glass substrate 102.

  Further, the nozzle 128 of the inner peripheral surface polishing apparatus 120 supplies a polishing liquid containing polishing abrasive grains between the polishing body 124 and the glass substrate 102. As this abrasive grain, although depending on the shape of the target end face, for example, normal abrasive grains such as alumina, cerium oxide, colloidal silica, etc. can be used. Further, the dispersion medium in which the abrasive grains are dispersed is not particularly limited, and water is preferable from the viewpoint of cost, but any dispersion medium used for normal polishing is preferably used. be able to.

  The chemical strengthening treatment tank 130 includes a treatment tank containing a chemical strengthening treatment liquid and a control unit thereof. In the chemical strengthening process, the chemical strengthening treatment bath 130 immerses the glass substrate 102 in a chemical strengthening treatment liquid in which a chemically strengthened salt is dissolved by heating, and some ions of the glass substrate (aluminosilicate glass containing Li ions), for example, Monovalent metal ions such as Li ions and Na ions are replaced with monovalent ions having a larger ion diameter than the above ions in the chemical strengthening treatment liquid, for example, Na ions and K ions. By such an ion exchange method, a compressive stress layer is formed on the surface of the glass substrate, and it is possible to obtain a large mechanical strength in which cracks and cracks are hardly generated.

  As the chemical strengthening treatment liquid (treated molten salt) containing Na ions and K ions, sodium nitrate, potassium nitrate, lithium nitrate and mixed molten salts thereof are preferably used, but are not limited to nitrates. , Sulfate, bisulfate, carbonate, halide and the like may be used.

  FIG. 4 is an explanatory diagram for explaining the immersion of the glass substrate 102 in the chemical strengthening treatment liquid. Here, a glass substrate holder 132 made of a metal material and a treatment tank 134 containing a chemical strengthening treatment liquid are shown. The glass substrate holder 132 is provided with a holding portion 136 in which a plate-like thin plate is curved, and a plurality of protrusions are formed in a wave shape in the longitudinal direction on the surface on the bulging side. One glass substrate 102 is held in each V-shaped groove formed between the protrusions. And after all the glass substrates 102 which should be processed by one chemical strengthening are arrange | positioned, the glass substrate 102 is immersed in the processing tank 134 with the glass substrate holder 132 for a predetermined time.

  The temperature of the chemical strengthening treatment liquid is preferably set to be about 50 to 150 ° C. lower than the strain point of the material of the glass substrate 102, and more preferably the temperature of the chemical strengthening treatment liquid itself is set to about 350 to 400 ° C. Is done. This is because when the temperature is set lower than 150 ° C. than the strain point of the material of the glass substrate 102, the chemical strengthening process is not sufficiently performed, and when set higher than 50 ° C., the glass substrate is likely to be distorted in the chemical strengthening process. Because.

  By such chemical strengthening treatment, a compressive stress layer is formed on the surface and the end face of the glass substrate 102. The compressive stress layer formed on the end face, particularly the inner peripheral end face, causes deformation of the inner peripheral end face in the present embodiment, and the amount of expansion (elongation) is grasped as the amount of change. The thickness of the compressive stress layer is preferably 20 to 150 μm by adjusting the chemical strengthening treatment conditions for the chemical strengthening. This is because if it is less than 20 μm, the strength of the glass substrate 102 may be reduced, and if it exceeds 150 μm, its production efficiency is unnecessarily deteriorated.

FIG. 5 is an explanatory view showing an example of a change in the inner diameter dimensional error due to the chemical strengthening process. The glass substrate 102 that has finished the inner peripheral end surface polishing step by the inner peripheral end surface polishing apparatus 120 has an inner peripheral end surface 114 that faces the inner diameter of the circular hole 112, that is, the center of the circular hole 112, as shown in FIG. This distance d ₁ is finished to an inner diameter dimensional error within a predetermined range depending on the diameter of the polishing body 124, the concentration of the polishing liquid, and the polishing time. However, in the chemical strengthening step, as shown in FIG. 5B, a compressive stress layer 118 is formed, and the inner peripheral end surface 114 of the glass substrate 102 changes in the direction of decreasing the inner diameter, resulting in an inner diameter dimensional error. affect. Accordingly, the inner diameter decreases from d ₁ to d ₂ .

  When the glass substrate 102 is mass-produced, the chemical strengthening treatment tank 130 as described above is provided in each of the plurality of lines, and each contains the chemical strengthening treatment liquid independently. Since it is difficult to equalize the states of the chemical strengthening treatment liquids in the plurality of chemical strengthening treatment tanks 130, even if the chemical strengthening treatment conditions are the same, the chemical strengthening treatment liquid is different due to the chemical strengthening treatment. The amount of change in the inner diameter of the resulting glass substrate 102 will be different.

  Therefore, the inventors of the present invention take the variation of the inner diameter of the glass substrate 102 before the chemical strengthening step and the variation of the inner diameter variation for each chemical strengthening treatment tank 130 performing the chemical strengthening step, and finally In order to reduce the inner diameter dimensional error of the glass substrate 102 obtained in an effective manner, the combination of the inner diameter of the glass substrate 102 before the chemical strengthening treatment and the amount of change due to the chemical strengthening treatment is adjusted, so It has been found that the inner diameter dimension error can be reduced by selecting the treatment tank 130.

  The grasping device 140 grasps (calculates) the amount of change in the inner diameter of the glass substrate 102 that is deformed by the chemical strengthening process of the chemical strengthening treatment tank 130. The grasping device 140 grasps the amount of change by (1) a method of actually measuring the amount of change in the inner diameter of the glass substrate 102 or (2) a method of estimating the amount of change from the state of the chemical strengthening treatment liquid.

  FIG. 6 is a functional block diagram showing an outline when the grasping device 140 grasps the amount of change by (1) a method of actually measuring the amount of change in the inner diameter of the glass substrate 102. The grasping device 140 measures the inner diameter of the glass substrate 102 before the chemical strengthening process, and further measures the inner diameter of the same glass substrate 102 after the chemical strengthening process. And the variation | change_quantity is derived | led-out by calculating | requiring the difference of the internal diameter. With this configuration, the actual change amount can be accurately grasped, and accordingly, an accurate feedback value (grinding amount or polishing amount) can be set.

  The method (2) of estimating the amount of change from the state of the chemical strengthening treatment liquid is based on the fact that the state of the chemical strengthening treatment liquid and the amount of change have a correlation. For example, at the same immersion time and the same temperature, (a) the concentration of a specific component, (b) the processed cumulative number of glass substrates 102, (c) the processed cumulative time of glass substrates 102, and the amount of change are constant. Therefore, it is possible to grasp or estimate the amount of change depending on the state of any one of (a), (b), and (c) described above or a plurality of chemical strengthening treatment liquids.

  Further, when the magnetic disk glass substrate manufacturing system 100 is performed for the first time, the initial grinding amount and polishing amount of the inner peripheral end surface grinding device 110 and the inner peripheral end surface polishing device 120 must be determined. The amount of change is estimated by the grasping device 140.

  FIG. 7 is a correlation diagram showing the correlation between (a) Li ion concentration (ppm) and variation (μm). By expressing such a correlation in, for example, a multidimensional relational expression, it is possible to estimate the amount of change only by measuring the Li ion concentration.

  In such a relational expression, if the number of times of chemical strengthening treatment is repeated, the concentration of Li ions in the molten salt increases, so that the chemical strengthening treatment capability decreases, and the amount of change decreases at the same immersion time and the same temperature. to cause. That is, in the chemical strengthening process, when the concentration of Li ions is low, the rate of ion exchange is high and the amount of change increases accordingly, but as the time and number of times of the chemical strengthening process elapses, the Li from the glass substrate 102 increases. Since ions are accumulated in the molten salt, the concentration of Li ions increases, the rate of ion exchange decreases and the amount of change decreases.

  In addition, (b) the cumulative number of sheets and (c) the cumulative time does not require direct measurement to the glass substrate 102 or the chemical strengthening treatment liquid, but indirectly measures (counts, counts) the cumulative number of sheets or the cumulative time. Just guess the amount of change. Therefore, the amount of change in the glass substrate 102 can be grasped without using a special measuring instrument, and the error in the inner diameter of the magnetic disk glass substrate can be reduced while reducing the cost and increasing the efficiency of the manufacturing process. It becomes possible.

  The grasping device 140 may grasp the change amount by a relational expression between the reference value and the change amount such as (a) density, (b) accumulated number of sheets, (c) accumulated time, etc., but is associated with one to one. The change amount may be grasped using the change amount table. Note that linear interpolation may be used for interpolation between numerical values described in the change amount table.

  FIG. 8 is an explanatory diagram showing an example of a change amount table in which the correlation between the Li ion concentration (ppm) and the change amount (μm) in FIG. 7 is tabulated. Here, it is only necessary to refer to a change amount table prepared in advance as shown in FIG. 8 without calculating a multidimensional relational expression as shown in FIG. 7 between the concentration and change amount of Li ions in real time. The amount of change can be derived from the concentration of Li ions. With such a configuration, it is possible to reduce the processing load and to avoid a shift in the amount of change due to a rounding error when deriving a multidimensional function.

  The memory 150 stores such a change amount table, a machining amount table, a strengthening condition table, and the like, which will be described later, and refers to the contents of the change amount table and the like in response to a request from the grasping device 140 and the like.

  The inner diameter measuring device 210 measures the inner diameter of the glass substrate 102 before chemical strengthening in the chemical strengthening treatment tank 130. The inner diameter of the glass substrate 102 is obtained by actual measurement here, but may be, for example, an inner diameter set value (inner diameter predicted value) in the inner peripheral end surface polishing step.

  In the present embodiment, three main situations for performing the chemical strengthening step are assumed. That is, (a) a situation in which the optimal chemical strengthening treatment tank 130 for chemically strengthening one glass substrate is selected from a plurality of chemical strengthening treatment tanks 130; This is a situation in which the most suitable glass substrate 102 is selected from the plurality of glass substrates 102, and (c) a situation in which the plurality of glass substrates 102 and the plurality of chemical strengthening treatment tanks 130 are combined. One glass substrate shown here includes the concept of a plurality of glass substrates housed in the same glass substrate holder that is chemically strengthened simultaneously. Therefore, the plurality of glass substrates 102 shows a state in which groups of a plurality of glass substrates that are chemically strengthened at the same time are further arranged in a plurality of lines.

  In the situation of (a), the combination determination device 310 desires the inner diameter after the chemical strengthening step of the glass substrate 102 whose inner diameter is measured by the inner diameter measuring device 210 based on the change amount grasped by the grasping device 140. The chemical strengthening treatment tank 130 for performing chemical strengthening is determined so as to have a value. In the situation (a), the glass substrate 102 to be subjected to the chemical strengthening process is determined based on the amount of change so that the inner diameter after the chemical strengthening process becomes a desired value. Based on the amount of change, the chemical strengthening treatment tank 130 for performing chemical strengthening is determined so that the inner diameters after the chemical strengthening process of the plurality of glass substrates 102 whose inner diameters have been measured have desired values.

  In any situation, an optimal combination of the glass substrate 102 and the chemical strengthening treatment tank 130 is selected in order to finally obtain the glass substrate 102 having a desired inner diameter. Therefore, even when the inner diameter of the glass substrate 102 changes before the chemical strengthening step, and when the chemical strengthening treatment condition of the chemical strengthening treatment liquid in the chemical strengthening treatment bath 130 changes with time, the inner diameter is consequently changed. (ID) It is possible to manufacture a glass substrate for a magnetic disk with a small dimensional error.

  Further, in such a combination, the combination determining apparatus 310 calculates the sum of squares of the difference between the final predicted inner diameter of each combination and the desired value of the inner diameter when the glass substrate 102 and the chemical strengthening treatment tank 130 are temporarily combined. Each of the chemical strengthening treatment tanks 130 for performing chemical strengthening may be determined so as to minimize the above. The chemical strengthening treatment tank 130 for performing chemical strengthening may be determined so that the square sum of the difference between each combination of the measured inner diameter and the amount of change and the desired value of the inner diameter is minimized.

FIG. 9 is an explanatory diagram for explaining a combination determining step by the combination determining apparatus 310. For example, when the inner diameter measuring device 210 measures the inner diameters of three glass substrates A, B, and C in three lines and the inner diameters are 20.000 mm, 20.006 mm, and 20.09 mm, respectively, the grasping device Suppose that 140 estimates that the amount of change in the three chemical strengthening treatment tanks D, E, and F is 10 μm, 7 μm, and 3 μm. If the desired value of the final inner diameter is 20.000 mm, and the combination of the glass substrate and the chemical strengthening treatment tank is AF, BE, and CD, the sum of squares of the difference is the minimum value. 2 μm ² .

  Even if such a combination of the glass substrate 102 and the chemical strengthening treatment tank 130 is good, an overall combination including the other combinations is not always optimal. Therefore, the above-described configuration using the least square method can reduce the overall inner diameter dimension error.

  Further, the change amount table described above turns off the feedback of the magnetic disk glass substrate manufacturing system 100 and changes with reference values ((a) concentration, (b) cumulative number, (c) cumulative time, etc.) in open loop control. It can be obtained by deriving the correlation with the quantity.

  That is, when creating a change amount table of Li ion concentration and change amount, the inner diameter before and after the chemical strengthening process and the Li ion concentration during the chemical treatment process are measured at the same timing, and the difference in inner diameter is calculated. The amount of change is associated with the concentration of Li ions. By measuring such correspondence processing at a plurality of concentrations of Li ions, a relational expression between the Li ion concentration and the change amount and a change amount table are derived, for example, as shown in FIGS.

  Other reference values (b) cumulative number of sheets and (c) cumulative time are also measured at the same timing as the inner diameters before and after the chemical strengthening process, and the relational expression is derived by the correspondence. At this time, it is desirable that other chemical strengthening treatment conditions such as immersion time and temperature other than the concentration of Li ions are equal during measurement and actual manufacturing process.

(Method for producing glass substrate for magnetic disk)
In addition, a method for manufacturing a glass substrate for a magnetic disk is provided using the above-described system 300 for manufacturing a glass substrate for a magnetic disk. In this method of manufacturing a magnetic disk glass substrate, each of the plurality of disk-shaped glass substrates 102 having a circular hole formed in the center is brought into contact with any one of the plurality of chemical strengthening treatment baths 130. Thus, a chemical strengthening step of chemically strengthening the glass substrate 102 by substituting some ions contained in the glass substrate 102 with ions in the chemical strengthening treatment liquid, and a plurality of pre-chemical strengthening steps before the chemical strengthening step is included. An inner diameter measuring step for measuring the inner diameter of each glass substrate 102, a grasping step for grasping the change amount of the inner diameter of the glass substrate 102 caused by the chemical strengthening step for each of the plurality of chemical strengthening treatment tanks 130, and the inner diameter based on the change amount. Combinations for respectively determining chemical strengthening treatment baths 130 for performing chemical strengthening so that the inner diameters after the chemical strengthening process of the plurality of glass substrates 102 for which the chemical strength is measured become a desired value. Further comprising a constant step, and the chemical strengthening process, chemically reinforced with respective chemical strengthening treatment bath 130 to the determined plurality of glass substrates 102.

  Here, by combining the glass substrate 102 and the chemical strengthening treatment tank 130 so as to have a predetermined inner diameter, it becomes possible to reduce the inner diameter dimensional error of the magnetic disk glass substrate.

  As described above, the combination of the glass substrate and the chemical strengthening treatment tank was adjusted to reduce the inner diameter error of the magnetic disk glass substrate. Sufficient machining accuracy can be obtained by taking this process into consideration, but the adjustment process of such chemical strengthening process conditions includes the following (A) adjustment of chemical strengthening process conditions in the chemical strengthening process, (B) By adding a process such as adjustment of the processing amount of the circumferential processing process, the error of the glass substrate and the chemical strengthening treatment tank itself can be reduced to some extent, and the final inner diameter dimension error can be reduced. Hereinafter, an embodiment in which such an adjustment process is added will be described.

((A) Adjustment of chemical strengthening treatment conditions in chemical strengthening process)
FIG. 10 is a functional block diagram showing a magnetic disk glass substrate manufacturing system 100 showing adjustment of chemical strengthening treatment conditions in the chemical strengthening step. Here, for easy understanding, the adjustment of the combination of the glass substrate and the chemical strengthening treatment tank already described in detail is omitted, and only the adjustment of the chemical strengthening treatment conditions in the chemical strengthening process will be described. The manufacturing system 100 of the magnetic disk glass substrate 102 of FIG. 10 is configured to further include a grinding amount determining device 160 and a polishing amount determining device 170 in addition to the above-described magnetic disk glass substrate manufacturing system 200. . In addition, since the inner peripheral end surface grinding device 110, the inner peripheral end surface polishing device 120, the chemical strengthening treatment tank 130, the grasping device 140, and the memory 150 described above have substantially the same functions, redundant description is omitted. Now, the grinding amount determination device 160 and the polishing amount determination device 170 having different configurations will be mainly described.

  The grinding amount determination device 160 and the polishing amount determination device 170 function as a processing amount determination device so that the inner diameter of the glass substrate 102 after the next chemical strengthening step becomes a desired value based on the grasped change amount. Next, the grinding amount in the inner peripheral end face grinding step and the polishing amount in the inner peripheral end face polishing step are determined. From the next time, the glass substrate 102 is processed by reflecting (adding) the set grinding amount and polishing amount to the grinding amount and polishing amount so far. That is, the inner diameter is fed back by the amount of change in either one or both of the inner peripheral end surface grinding step and the inner peripheral end surface polishing step. Such feedback may be performed every batch or every day. Thereby, even when a large number of glass substrates for magnetic disks are manufactured, an inner diameter dimensional error between the plurality of glass substrates 102 can be reduced as compared with the conventional case.

  FIG. 11 is a table showing processing amounts (grinding amount and polishing amount) when the change amount is shared and fed back to both the inner peripheral end surface grinding step and the inner peripheral end surface polishing step. For example, when the grasping device 140 grasps that the amount of change is 15.00 μm, the total amount of processing for setting the inner diameter to a desired value is 15.00 μm. Accordingly, referring to the processing amount table of FIG. 11, the grinding amount determination device 160 adds the grinding amount by 13.00 μm (+13.000 μm), and the polishing amount determination device 170 adds the polishing amount by 2.00 μm ( +2.00 μm). Then, the inner peripheral end surface grinding device 110 and the inner peripheral end surface polishing device 120 perform processing by reflecting (adding) the set grinding amount and polishing amount, respectively.

  In addition, the inner peripheral end surface grinding step can take a large machining allowance compared to the inner peripheral end surface polishing step described later, and the amount of cutting per unit time is large, so that it is easy to control and further compared with the inner peripheral end surface polishing step. It becomes possible to improve the efficiency of the manufacturing process.

  The amount of change can also be fed back only in either the inner peripheral end face grinding step or the inner peripheral end face polishing step.

  FIG. 12 is a processing amount table when the change amount is fed back only by the grinding amount in the inner peripheral end surface grinding step. Here, since the additional polishing in the inner peripheral end face polishing step is not performed, adjustment with the change amount is performed only by the grinding amount. Therefore, if the desired inner diameter value is constant after the chemical strengthening step, the grinding amount becomes a value proportional to the amount of change. The same processing amount table can be used when feedback is performed only by the inner peripheral end face polishing step.

  FIG. 13 is a table in which the change amount table and the processing amount table are combined. By referring to such a table, it is possible to derive the grinding amount and polishing amount directly from the reference value that is the basis of calculation, here, the concentration of Li ions, and the processing burden can be reduced.

  The above closed loop configuration, which grasps the amount of change and feeds back the machining amount to the inner circumferential machining process, makes it possible to absorb the inner diameter dimension error in the chemical strengthening process in the previous process and make complicated adjustment of the chemical strengthening process conditions. As a result, it is possible to manufacture a glass substrate for a magnetic disk having a smaller inner diameter dimensional error.

(Method for producing glass substrate for magnetic disk)
A method for manufacturing a glass substrate for a magnetic disk is also provided using the above-described system for manufacturing a glass substrate for a magnetic disk. In this method of manufacturing a glass substrate for magnetic disk, the inner diameter of the glass substrate 102 after the next chemical strengthening step is desired based on the grasping result of the grasping step in the step of adjusting the chemical strengthening treatment conditions in the above-described chemical strengthening step. The processing amount determination step of determining the processing amount of the inner diameter of the glass substrate 102 is further included so that the inner peripheral end surface of the glass substrate 102 is processed based on the processing amount.

  When the adjustment of the processing amount in the inner peripheral processing step described above is added to the adjustment of the combination of the glass substrate and the chemical strengthening treatment tank, the change amount is grasped, and the change amount is determined by the inner peripheral end surface grinding process or the inner peripheral end surface polishing. With the above closed loop configuration that feeds back as the grinding amount or polishing amount of the process, the grinding amount is set in anticipation of the amount of change due to the chemical strengthening process, and the change in the inner diameter dimensional error based on the numerous parameters of the chemical strengthening process is determined. As a result, it is possible to manufacture a glass substrate for a magnetic disk with a smaller inner diameter dimensional error.

((B) Adjustment of chemical strengthening treatment conditions in chemical strengthening process)
FIG. 14 is a functional block diagram showing a magnetic disk glass substrate manufacturing system 200 showing adjustment of chemical strengthening treatment conditions in the chemical strengthening step. Here, in order to facilitate understanding, the adjustment of the combination of the glass substrate and the chemical strengthening treatment tank already described in detail will be omitted, and only the adjustment of the chemical strengthening treatment conditions will be described. The magnetic disk glass substrate manufacturing system 200 shown in FIG. 14 includes a strengthening condition determining device 220 in addition to the magnetic disk glass substrate manufacturing system 300 described above. Further, since the inner peripheral end surface grinding device 110, the inner peripheral end surface polishing device 120, the chemical strengthening treatment tank 130, the memory 150, and the inner diameter measuring device 210 described above have substantially the same functions, redundant description is omitted. Here, the reinforcement condition determination device 220 having a different configuration will be mainly described.

  The strengthening condition determining device 220 determines the chemical strengthening treatment condition in the chemical strengthening treatment tank 130 based on the difference between the inner diameter measured by the inner diameter measuring device 210 and the desired inner diameter after the chemical strengthening step. Here, first, the inner diameter of the glass substrate 102 is measured by the inner diameter measuring device 210, and finally a difference from the desired inner diameter is derived. Then, the chemical strengthening process condition is determined so as to follow the difference from which the amount of change in the subsequent chemical strengthening step is derived. With such a configuration, even if the inner diameter of the glass substrate 102 before the chemical strengthening process deviates from a predetermined design value, the final inner diameter of the glass substrate 102 is set to a desired value by adjusting the amount of change. A glass substrate for a magnetic disk that can be formed and has a small inner diameter dimensional error can be manufactured.

  Here, the chemical strengthening treatment conditions are (a) the concentration of a specific component contained in the chemical strengthening treatment liquid, (b) the immersion time of the glass substrate 102 in the chemical strengthening treatment liquid, and (c) the temperature of the chemical strengthening treatment liquid. One or two or more conditions selected from the group may be used.

  In the chemical strengthening process by the chemical strengthening treatment tank 130, mainly (a) the concentration of a specific component contained in the chemical strengthening treatment liquid, (b) the immersion time of the glass substrate 102 in the chemical strengthening treatment liquid, and (c) the chemical strengthening treatment. There is a correlation between the temperature of the liquid and the amount of change in the inner diameter of the glass substrate 102. Therefore, even if one or more of these chemical strengthening treatment conditions are fixed and the chemical strengthening process is performed, the amount of change can be adjusted by changing the other one or more chemical strengthening treatment conditions. The final inner diameter error of the glass substrate 102 in the process can be further reduced.

  Moreover, (a) About the density | concentration of a specific component, when the glass substrate 102 is formed with the aluminosilicate glass containing Li ion, a specific component can be made into Li ion.

  For example, the strengthening condition determination apparatus 220 may not adjust or cannot adjust the concentration of Li ions as the chemical strengthening treatment condition because it does not want to affect the lifetime of the chemical strengthening treatment salt. By adjusting either one or both of the temperatures, the inner diameter of the glass substrate 102 can be set to a desired value.

  Similarly, when performing chemical strengthening treatment using a plurality of chemical strengthening treatment tanks 130, changing the heating time of one chemical strengthening treatment tank 130 will change the finishing time with other chemical strengthening treatment tanks, When it is not desired or possible to adjust the immersion time because the time control of the entire manufacturing site is complicated, the concentration and / or the temperature are adjusted. In addition, when the heating temperature is set higher than a predetermined temperature, for example, the chemical strengthening treatment tank 130 is excessively heated, and the temperature is adjusted for the reason that particles such as Fe and SUS are generated. If you don't want or can't, adjust either or both the concentration and / or immersion time.

  The strengthening condition determination device 220 determines the chemical strengthening process condition using a strengthening condition table in which the difference between the inner diameter measured by the inner diameter measuring device 210 and the desired inner diameter after the chemical strengthening process is associated with the chemical strengthening process condition. May be.

  FIG. 15 is an explanatory diagram showing an example of a strengthening condition table in which the correlation between the difference (μm) and the Li ion concentration (ppm) is tabulated. In the strengthening condition table of FIG. 15, the immersion time is constant at 180 minutes and the temperature is 350 ° C., and the only chemical strengthening treatment condition that can be changed is the Li ion concentration (ppm). Therefore, a difference required to reach a desired inner diameter is derived based on the inner diameter measured by the inner diameter measuring device 210, and the Li concentration is adjusted to change the inner diameter by the difference. For example, when the desired inner diameter is less than 5 μm, by changing the Li concentration to 150 ppm, a glass substrate with a small inner diameter dimensional error can be obtained in the subsequent chemical strengthening step. Such a change in the Li concentration is performed by discarding a predetermined amount of the chemical strengthening treatment liquid and adding sodium nitrate, potassium nitrate, lithium nitrate or a mixed molten salt thereof.

  By using such a strengthening condition table, the chemical strengthening process condition can be calculated from the difference only by referring to the strengthening condition table prepared in advance without calculating a complicated relational expression between the difference and the chemical strengthening process condition in real time. It can be easily derived. Therefore, it is possible to reduce the processing load and to avoid a shift in chemical strengthening processing conditions due to a rounding error when deriving a multidimensional function.

  Such a strengthening condition table turns off the feedback of the glass substrate manufacturing system 200 for magnetic disks, and derives the correlation between the Li ion concentration, the immersion time, and the temperature in the open loop control and the amount of change in the chemical strengthening treatment conditions. You can ask for it. Such a change amount can be obtained by measuring a difference in inner diameter before and after the chemical strengthening step.

  FIG. 16 is an explanatory diagram showing the correlation between the Li ion concentration, the immersion time, the temperature, and the amount of change in the chemical strengthening treatment conditions. In order to generate a final strengthening condition table, a more accurate strengthening condition table can be generated by taking as many samples as possible by shifting the Li ion concentration, the immersion time, and the temperature within an allowable range. And when using as a reinforcement | strengthening condition table, a certain thing is first mentioned as a chemical strengthening process condition (in FIG. 15, immersion time and temperature), and only the data matched with the chemical strengthening process condition are extracted. For example, when only the chemical strengthening treatment conditions with an immersion time of 180 min and a temperature of 350 ° C. are extracted in FIG. 16, the strengthening condition table of FIG. 15 is generated. When other chemical strengthening process conditions are adjusted, the strengthening condition table can be generated by the same extraction process from the table of FIG. 16 showing the correlation.

(Method for producing glass substrate for magnetic disk)
A method for manufacturing a glass substrate for a magnetic disk is also provided using the above-described system for manufacturing a glass substrate for a magnetic disk. Such a method for manufacturing a glass substrate for a magnetic disk includes the step of adjusting the combination of the glass substrate and the chemical strengthening treatment tank described above, based on the difference between the measured inner diameter and the desired inner diameter after the chemical strengthening step. It further includes a chemical strengthening process condition determining step for determining the chemical strengthening process condition of the process, and in the chemical strengthening process, the glass substrate 102 is chemically strengthened based on the determined chemical strengthening process condition.

  When the adjustment of the chemical strengthening treatment condition in the chemical strengthening step described above is added to the adjustment of the combination of the glass substrate and the chemical strengthening treatment tank, the inner diameter of the glass substrate 102 before the chemical strengthening treatment is determined from a predetermined design value. Even if there is a deviation, by adjusting the amount of change, the final inner diameter of the glass substrate 102 can be formed to a desired value, and a glass substrate for a magnetic disk with a smaller inner diameter dimensional error can be manufactured.

  Hereinafter, specific examples of the above-described embodiment will be described. In this example, a glass substrate for magnetic disk and a magnetic disk were manufactured through the following steps.

(1) Shape processing step and first lapping step First, the melted aluminosilicate glass was molded into a disk shape by direct pressing using an upper die, a lower die, and a barrel die to obtain an amorphous plate glass. In addition, the glass for chemical strengthening was used as aluminosilicate glass. In addition to direct pressing, a disk-shaped glass substrate for a magnetic disk may be obtained by cutting with a grinding wheel from sheet glass formed by a fusion method, a downdraw method, or a float method. As the aluminosilicate _glass, SiO 2: 58 to 75 _{wt%, Al} 2 O 3: _{5~23 wt%,} Li 2 O: 3 to 10 _wt%, Na 2 O: 4 to 13 principal component weight% Chemically strengthened glass contained as In addition to the aluminosilicate glass, soda lime glass or the like can also be used.

  Next, both main surfaces of the plate glass were lapped to form a disk-shaped glass base material. This lapping process was performed using alumina free abrasive grains with a double-sided lapping apparatus using a planetary gear mechanism. Specifically, the lapping platen is pressed on both sides of the plate glass from above and below, the grinding liquid containing free abrasive grains is supplied onto the main surface of the plate glass, and these are moved relative to each other for lapping. went. By this lapping process, a glass base material having a flat main surface was obtained.

(2) Cutting process (coring, forming)
Next, the glass base material was cut using a diamond cutter, and a disk-shaped glass substrate was cut out from the glass base material. Next, using a cylindrical diamond drill, a circular hole was formed in the center of the glass substrate to obtain a donut-shaped glass substrate (coring).

(3) End surface grinding process And the inner peripheral end surface and the outer peripheral end surface were ground with a diamond grindstone, and predetermined chamfering was performed (forming).

(4) Second Lapping Step Next, a second lapping process was performed on both main surfaces of the obtained glass substrate in the same manner as in the first lapping step. By performing this second lapping step, it is possible to remove in advance the fine unevenness formed on the main surface in the cutting step and end surface polishing step, which are the previous steps, and shorten the subsequent polishing step on the main surface. Will be able to be completed in time.

(5) End surface polishing process Next, the end surface of the glass substrate was mirror-polished by a brush polishing method. At this time, as the abrasive grains, a slurry (free abrasive grains) containing cerium oxide abrasive grains was used. By this end surface polishing step, the end surface of the glass substrate was processed into a mirror surface state capable of preventing generation of particles and the like.

(6) Main surface polishing step As the main surface polishing step, first, a first polishing step was performed. This first polishing step is mainly intended to remove scratches and distortions remaining on the main surface in the lapping step described above. In the first polishing step, the main surface was polished using a hard resin polisher by a double-side polishing apparatus having a planetary gear mechanism. As the polishing liquid, cerium oxide abrasive grains were used.

  The glass substrate which finished this 1st grinding | polishing process was immersed in each washing tank of neutral detergent, a pure water, and IPA (isopropyl alcohol) one by one, and was wash | cleaned.

  Next, a second polishing step was performed as the main surface polishing step. The purpose of this second polishing step is to finish the main surface into a mirror surface. In the second polishing step, mirror polishing of the main surface was performed using a soft foamed resin polisher by a double-side polishing apparatus having a planetary gear mechanism. As the polishing liquid, cerium oxide abrasive grains finer than the cerium oxide abrasive grains used in the first polishing step were used.

  The glass substrate which finished this 2nd grinding | polishing process was immersed in each washing tank of neutral detergent, a pure water, and IPA (isopropyl alcohol) sequentially, and was wash | cleaned. Note that ultrasonic waves were applied to each cleaning tank.

(7) Chemical strengthening process and cooling process Next, the glass substrate which finished the above-mentioned lapping process and polishing process was chemically strengthened. By performing the chemical strengthening step, a high compressive stress can be generated in the surface layer portion of the magnetic disk substrate, and the impact resistance can be improved.

  For chemical strengthening, a chemical strengthening solution prepared by mixing potassium nitrate (60%) and sodium nitrate (40%) is prepared, and the chemically strengthened solution is heated to 400 ° C. and the cleaned glass substrate is heated to 300 ° C. The sample was preheated and immersed in a chemical strengthening solution for about 3 hours.

  Thus, by immersing in the chemical strengthening solution, Li ions and sodium ions in the surface layer of the glass substrate are respectively replaced with sodium ions and potassium ions in the chemical strengthening solution, and the glass substrate is strengthened. At this time, the thickness of the compressive stress layer at the inner diameter of the glass substrate was about 100 μm to 200 μm, and the amount of change was 15 μm or less. The technique described in the embodiment was adopted in the example, and the yield could be greatly improved.

以上のように、歩留まりが著しく向上することが理解できる。 [Example]
When matching between the glass substrate and the chemical strengthening treatment tank was performed, the following results were obtained as compared with the case where matching was not performed. However, the number of samples of the glass substrate is 10,000, and the target value in the table is an inner diameter of 20.0 ± 0.05 mm.

As described above, it can be understood that the yield is remarkably improved.

  Then, the glass substrate which finished the chemical strengthening process was immersed in a 20 degreeC water tank, cooled, and maintained for about 10 minutes. And the glass substrate which finished cooling was immersed in the concentrated sulfuric acid heated at about 40 degreeC, and was wash | cleaned. Further, the glass substrate that had been washed with sulfuric acid was washed by sequentially immersing it in each washing tank of pure water and IPA (isopropyl alcohol). In addition, ultrasonic waves were applied to each cleaning tank.

  As described above, by applying the first lapping step, the cutting step, the second lapping step, the end surface polishing step, the main surface polishing step, the chemical strengthening step, and the cooling step, a flat and smooth, high-rigidity magnetic disk is used. A glass substrate was obtained.

(8) Precision cleaning step Next, the glass substrate for magnetic disk on which the texture was formed was precisely cleaned. This is to remove abrasive residues and foreign iron-based contaminants that cause head crush and thermal asperity failure, and to obtain a glass substrate with a smooth surface and a clean surface. As a precision cleaning process, a water rinse cleaning and an IPA cleaning process were performed after cleaning with an alkaline aqueous solution.

(9) Magnetic disk manufacturing process On both surfaces of the glass substrate obtained through the above-described processes, an adhesion layer made of a Cr alloy, a soft magnetic layer made of a CoTaZr-based alloy, an underlayer made of Ru, and a CoCrPt group on the surface of the glass substrate A perpendicular magnetic recording disk was manufactured by sequentially forming a perpendicular magnetic recording layer made of an alloy, a protective layer made of hydrogenated carbon, and a lubricating layer made of perfluoropolyether. Although this configuration is an example of a configuration of a perpendicular magnetic disk, a magnetic layer or the like may be configured as an in-plane magnetic disk.

  The obtained magnetic disk was confirmed to be free from defects in the film such as the magnetic layer due to foreign matter. In addition, when the glide test was performed, no hit (the head bited against the protrusion on the surface of the magnetic disk) or crash (the head collided with the protrusion on the surface of the magnetic disk) was not recognized. Furthermore, when a reproduction test was conducted with a magnetoresistive head, no malfunction of reproduction due to thermal asperity was found.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

The present invention utilizes a portion of the glass substrate manufacturing method of a glass substrate for a magnetic disk including a chemical strengthening step of performing chemical strengthening by ion exchange, a method of manufacturing a magnetic disk, a glass substrate manufacturing system for you and a magnetic disk Is possible.

It is the functional block diagram which showed the manufacturing system of the glass substrate for magnetic discs. It is explanatory drawing for demonstrating the grinding process of an internal peripheral end surface grinding apparatus. It is a longitudinal cross-sectional view for demonstrating the structure of an inner peripheral end surface grinding | polishing apparatus. It is explanatory drawing for demonstrating the immersion to the chemical strengthening process liquid of a glass substrate. It is explanatory drawing which showed the example of a change of the internal diameter dimension error by a chemical strengthening process. It is the functional block diagram which showed the outline in case a grasping | ascertainment device grasps | ascertains the variation | change_quantity by the method of actually measuring the variation | change_quantity of the internal diameter of a glass substrate. It is the correlation figure which showed the correlation with the density | concentration (ppm) of Li ion, and variation | change_quantity (micrometer). It is explanatory drawing which showed the example of the variation | change_quantity table which tabulated the correlation of the density | concentration (ppm) of Li ion of FIG. 7, and variation | change_quantity (micrometer). It is explanatory drawing for demonstrating the combination determination process by a combination determination apparatus. It is the functional block diagram which showed the manufacturing system of the glass substrate for magnetic discs. It is the table which showed the processing amount (grinding amount and polishing amount) in the case of sharing and feeding back a variation | change_quantity to both processes of an inner peripheral end surface grinding process and an inner peripheral end surface grinding | polishing process. It is a processing amount table when the amount of change is fed back only by the grinding amount in the inner peripheral end face grinding process. This table is a combination of a change amount table and a machining amount table. It is the functional block diagram which showed the manufacturing system of the glass substrate for magnetic discs It is explanatory drawing which showed the example of the reinforcement | strengthening condition table which tabulated the correlation with a difference (micrometer) and the density | concentration (ppm) of Li ion. It is explanatory drawing which showed correlation with Li ion concentration, immersion time, temperature, and the variation | change_quantity in the chemical strengthening process conditions.

Explanation of symbols

100, 200, 300 Glass disk substrate manufacturing system for magnetic disk 102 Glass substrate 110 Inner peripheral end surface grinding device 112 Circular hole 114 Inner peripheral end surface 120 Inner peripheral end surface polishing device 130 Chemical strengthening treatment tank 140 Grasping device 160 Grinding amount determining device 170 Polishing Quantity determining device 210 Inner diameter measuring device 220 Strengthening condition determining device 310 Combination determining device

Claims (10)

By bringing a disc-shaped glass substrate having a circular hole in the center into contact with a chemical strengthening treatment solution in any of a plurality of chemical strengthening treatment tanks, some ions contained in the glass substrate are chemically strengthened. A method for producing a glass substrate for a magnetic disk comprising a chemical strengthening step of chemically strengthening the glass substrate by substituting with ions in a treatment liquid,
An inner diameter measuring step for measuring an inner diameter of the glass substrate before the chemical strengthening step;
A grasping step for grasping the amount of change in the inner diameter of the glass substrate generated by the chemical strengthening step for each of the plurality of chemical strengthening treatment tanks;
And a combination determining step of determining a chemical strengthening treatment tank for performing chemical strengthening so that the inner diameter after the chemical strengthening step of the glass substrate whose inner diameter is measured becomes a desired value based on the amount of change. ,
In the chemical strengthening step, the glass substrate is chemically strengthened in the determined chemical strengthening treatment tank. By contacting one of a plurality of disk-shaped glass substrates having a circular hole in the center with a chemical strengthening treatment liquid in a chemical strengthening treatment tank, some ions contained in the glass substrate are chemically strengthened. A method for producing a glass substrate for a magnetic disk comprising a chemical strengthening step of chemically strengthening the glass substrate by substituting with ions in a treatment liquid,
Wherein the chemical strengthening process each of the plurality of glass substrate before there is variation in each of the inner diameter, the inner diameter measuring step of measuring the inner diameter thereof,
A grasping step for grasping the amount of change in the inner diameter of the glass substrate caused by the chemical strengthening step;
A combination determining step of determining a glass substrate for executing the chemical strengthening step from a plurality of glass substrates whose inner diameters are measured based on the change amount so that the inner diameter after the chemical strengthening step becomes a desired value. And further including
In the chemical strengthening step, the glass substrate thus determined is chemically strengthened in the chemical strengthening treatment tank. Each of the plurality of disk-shaped glass substrates having a circular hole formed in the center is brought into contact with any one of the chemical strengthening treatment liquids of the plurality of chemical strengthening treatment tanks, thereby including a part of the glass substrate. A method for producing a glass substrate for a magnetic disk comprising a chemical strengthening step of chemically strengthening the glass substrate by substituting ions in the chemical strengthening treatment liquid,
An inner diameter measuring step for measuring an inner diameter of each of the plurality of glass substrates before the chemical strengthening step;
A grasping step for grasping the amount of change in the inner diameter of the glass substrate generated by the chemical strengthening step for each of the plurality of chemical strengthening treatment tanks;
Based on the amount of change, a combination determination step of determining a chemical strengthening treatment tank for performing chemical strengthening so that the inner diameter after the chemical strengthening step of the plurality of glass substrates whose inner diameters are measured becomes a desired value; Further including
In the chemical strengthening step, the plurality of glass substrates are chemically strengthened in each of the determined chemical strengthening treatment tanks.   In the combination determination step, the chemical strengthening is performed so that the sum of squares of the difference between the final expected inner diameter of each combination and the desired value of the inner diameter when the glass substrate and the chemical strengthening treatment tank are temporarily combined is minimized. The method for producing a glass substrate for a magnetic disk according to claim 3, wherein the chemical strengthening treatment tank for performing the step is determined.   5. The method for manufacturing a glass substrate for a magnetic disk according to claim 1, wherein the grasping step grasps a change amount from a difference in inner diameter of the glass substrate before and after the chemical strengthening step. .   The said grasping process grasps | ascertains the variation | change_quantity based on the density | concentration of the specific component contained in the said chemical strengthening process liquid, The manufacture of the glass substrate for magnetic discs in any one of Claims 1-4 characterized by the above-mentioned. Method. The glass substrate is formed of aluminosilicate glass containing Li ions,
The method for manufacturing a glass substrate for a magnetic disk according to claim 6, wherein the specific component is Li ion.   8. The magnetic disk glass according to claim 6, wherein in the grasping step, the amount of change is grasped using a change amount table in which the concentration of the specific component and the amount of change are associated with each other. A method for manufacturing a substrate.   The method for producing a magnetic disk according to claim 1, comprising a step of forming at least a magnetic layer on the surface of the glass substrate obtained by the method for producing a glass substrate for a magnetic disk. .   By contacting one of a plurality of disk-shaped glass substrates having a circular hole in the center with the chemical strengthening treatment liquid, some ions contained in the glass substrate are contained in the chemical strengthening treatment liquid. A system for manufacturing a glass substrate for a magnetic disk comprising a plurality of chemical strengthening treatment tanks that replace ions and chemically strengthen the glass substrate,
  An inner diameter measuring device that measures inner diameters of the plurality of glass substrates before the chemical strengthening treatment tank performs chemical strengthening,
  A grasping device for grasping the amount of change in the inner diameter of the glass substrate generated by the chemical strengthening treatment tank for each of the plurality of chemical strengthening treatment tanks,
  Based on the amount of change, a combination of determining a chemical strengthening treatment tank for performing chemical strengthening so that the inner diameter after chemical strengthening of the chemical strengthening treatment tank of the plurality of glass substrates whose inner diameters are measured becomes a desired value. And a determination device,
  The system for manufacturing a glass substrate for a magnetic disk, wherein the plurality of glass substrates are chemically strengthened in each of the determined chemical strengthening treatment tanks.

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