阅读说明：本技术 间隔件、基板的层积体、基板的制造方法和磁盘用基板的制造方法 (Spacer, laminated body of substrate, method for manufacturing substrate, and method for manufacturing substrate for magnetic disk ) 是由 高野正夫 于 2019-03-11 设计创作，主要内容包括：本发明提供间隔件、基板的层积体、基板的制造方法和磁盘用基板的制造方法,该间隔件介于构成层积体的基板中的相邻的基板间,将相邻的基板彼此分开,该间隔件的面积小于进行层积的基板,对于将上述间隔件夹在2个以上的上述基板之间而形成的层积体,从在层积方向施加0.60MPa的压力的按压状态到解除了压力的无按压状态时,根据由于上述压力的解除而发生变化的上述层积体的厚度而计算出的上述间隔件每1片的厚度的变化量ΔW为30μm以下。(The invention provides a spacer, a laminated body of substrates, a method for manufacturing the substrates and a method for manufacturing the substrate for a magnetic disk, wherein the spacer is arranged between adjacent substrates in the substrates forming the laminated body to separate the adjacent substrates, the area of the spacer is smaller than that of the laminated substrates, and when the laminated body formed by clamping the spacer between more than 2 substrates is in a pressing state of applying a pressure of 0.60MPa in the laminating direction to a non-pressing state of releasing the pressure, the variation delta W of the thickness of each 1 piece of the spacer calculated according to the thickness of the laminated body which is changed due to the release of the pressure is less than 30 mu m.)

1. A spacer which is a sheet-like spacer that is interposed between adjacent substrates in a laminate and separates the adjacent substrates from each other when the laminate of 2 or more substrates is formed and end surface treatment of the 2 or more substrates is performed,

the spacer has an area smaller than the substrate,

in a laminated body formed by sandwiching the spacers between 2 or more substrates, when a pressing state is performed in a laminating direction by applying a pressure of 0.60MPa to a non-pressing state in which the pressure is released, a variation Δ W in thickness of each 1 piece of the spacers calculated from the thickness of the laminated body that varies due to the release of the pressure is 30 μm or less.

2. The spacer according to claim 1, wherein the spacer is made of resin.

3. The spacer according to claim 1 or 2, wherein a surface roughness Ra of the spacer is 0.2 μm or more.

4. The spacer according to any one of claims 1 to 3, wherein the spacer has water resistance.

5. A laminate comprising 2 or more substrates and the spacer according to any one of claims 1 to 4 between adjacent substrates of the 2 or more substrates.

6. A method for manufacturing a substrate, comprising the step of treating the side surface of the laminate according to claim 5.

7. A method for manufacturing a substrate, comprising the step of treating a side surface of a laminated body of the substrate according to claim 5,

the processing of the side surface of the laminate includes:

a process of bringing the laminate into a pressed state;

1 st side surface processing of processing a side surface of the laminated body in the pressed state;

a process of releasing the pressed state of the laminated body after the 1 st side surface process;

intermediate treatment, any one of the following operations is carried out: separating the laminate from which the pressed state is released into 2 or more laminates; bonding the laminate released from the pressed state to another laminate in a laminating direction; or maintaining the laminated body released from the pressed state in this state;

a process of bringing the laminated body subjected to the intermediate process into a pressed state after the intermediate process; and

and a 2 nd side surface treatment for further treating the side surface of the laminated body in the pressed state after the intermediate treatment.

8. The method for manufacturing a substrate according to claim 6 or 7, wherein the substrate is a glass plate.

9. A method for manufacturing a magnetic disk substrate, comprising the steps of:

a process for producing a substrate as a substrate blank for a magnetic disk by the method for producing a substrate according to any one of claims 6 to 8; and

and performing post-treatment of at least polishing treatment on the main surface of the substrate after the treatment of the side surface of the laminate.

Technical Field

The invention relates to a spacer, a laminated substrate, a method for manufacturing the substrate, and a method for manufacturing a substrate for a magnetic disk. The spacer is a sheet-like member that is interposed between adjacent substrates in a laminate to separate the adjacent substrates from each other when the laminate of 2 or more substrates is formed and the end face treatment of the 2 or more substrates is performed.

Background

A magnetic disk is used in a hard disk device for data recording, and the magnetic disk is formed by providing a magnetic layer on a disk-shaped nonmagnetic glass plate for a magnetic disk.

When a glass plate for a magnetic disk is manufactured, the main surface and the end surfaces (inner end surface and outer end surface) of the glass plate are ground or polished. In order to improve the work efficiency of polishing the end face of a glass plate, the following methods are used for polishing the end face of the glass plate: a glass plate laminate in which a plurality of glass plates are superposed in the normal direction of the main surface is formed, and the end surfaces of the plurality of glass plates are simultaneously polished by a polishing jig such as a polishing brush. In the laminate, in order to prevent the glass sheets from adhering to each other or the main surfaces of the glass sheets from being scratched by friction, spacers of the end-face polishing glass sheets are provided between the glass sheets to separate the glass sheets from each other.

In the end face polishing of the glass plate, two kinds of polishing of an outer end face and an inner end face are performed. Therefore, when polishing the glass plate laminate as described above, for example, the glass plate is laminated on the outer end surface polishing jig, and the outer end surface is polished in a pressed state, and then the inner end surface is polished. In this case, it is necessary to release the pressed glass laminate and further disassemble the laminate (separated glass plates) between the steps of polishing the outer end surface and polishing the inner end surface.

A glass plate laminating jig capable of polishing the outer end surface and the inner end surface without releasing and disassembling the pressing of the glass laminate is known (patent document 1).

The glass plate laminating jig has a shaft inserted into a circular hole of the glass plate for a magnetic recording medium, and supports the inner end surface of the glass plate laminate to align the position of the glass plate for a magnetic recording medium. The shaft is provided with a chuck bolt fitting portion capable of fitting a chuck bolt to both ends of the shaft, and a shaft fixing portion for supporting the glass plate laminate is provided around the shaft.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2013-73636

Disclosure of Invention

Problems to be solved by the invention

When the glass sheet laminating jig is used, the pressing of the glass sheet laminated body does not need to be released or disassembled, and thus the production efficiency is improved.

However, the apparatus of the glass sheet stacking jig is complicated in structure and difficult to handle, and a polishing jig such as a polishing brush needs to be configured in cooperation with the glass sheet stacking jig, and the versatility in end surface polishing is low. Further, since the glass sheet stacking jig is set or fixed so that the number of stacked sheets is 100 or more, the number of stacked sheets of the inner end surface polishing and the outer end surface polishing cannot be freely distributed in order to improve the production efficiency of glass sheets in consideration of the difference in polishing time between the inner end surface polishing and the outer end surface polishing. From this point of view, the use of the glass sheet laminating jig for end face polishing may be inappropriate.

On the other hand, the stacking jig may be replaced so as to release the pressing in the stacking direction of the glass sheets without disassembling the stacked body of the glass sheets (without separating the glass sheets), and to perform polishing of the inner end surface after polishing of the outer end surface, or to perform polishing of the outer end surface after polishing of the inner end surface. However, in this case, the shape of the spacer provided between the adjacent glass plates is restored by releasing the pressure of the laminated body in the pressed state, and therefore, the spacer is displaced, and further, the adjacent glass plates may be displaced due to the displacement of the spacer. When the laminated body of glass plates is pressed again in a state where the glass plates are misaligned and the end face polishing is performed, the relative positions of the glass plates with respect to the adjacent glass plates change, and as a result, the machining allowance (replacement amount) on the chamfered surface or the side wall surface varies.

Further, since the spacer is displaced, the chamfered surface provided on the end surface may not be appropriately polished. For example, when the spacer interposed between the adjacent glass plates moves to one side of the chamfered surface due to a positional deviation, the contact manner of the polishing brush with the vicinity of the bottom of the recess sandwiched by the chamfered surface changes, and uniform polishing may not be performed.

Since it is difficult to visually confirm the presence or absence of the positional deviation, in order to obtain a laminate free of the positional deviation, it is necessary to disassemble the laminate and to arrange the glass plates and the spacers at predetermined positions again to reconstruct the laminate, and the disassembly and reconstruction of the laminate are complicated operations.

When the pressure is released from the glass plate laminate in the pressed state, the spacers are displaced or the glass plates are further displaced due to deformation caused by the restoration of the spacer shape, which is not preferable.

Accordingly, an object of the present invention is to provide: a spacer is interposed between adjacent substrates in a laminated body of substrates such as glass plates to separate the adjacent substrates from each other, and can suppress the positional deviation of the spacer or further suppress the positional deviation of the substrates generated when pressure is released from the pressed laminated body; further provided are: a laminate of substrates including the spacer; a method for manufacturing a substrate by end-face polishing using the laminate including the spacer, and a method for manufacturing a substrate for a magnetic disk.

Means for solving the problems

One embodiment of the present invention relates to a spacer in a sheet shape, which is interposed between adjacent substrates in a laminate to separate the adjacent substrates from each other when the laminate of 2 or more substrates is formed and end surface treatment of the 2 or more substrates is performed.

The spacer has an area smaller than that of the substrate,

in a laminated body formed by sandwiching the spacers between 2 or more substrates, when a pressing state is performed in a laminating direction by applying a pressure of 0.60MPa to a non-pressing state in which the pressure is released, a variation Δ W in thickness of the spacers per 1 sheet calculated from the thickness of the laminated body that varies due to the release of the pressure is 30 μm or less.

The spacer is preferably made of resin.

The contact angle of the spacer to pure water is preferably 50 degrees or less.

The surface roughness Ra of the spacer is preferably 0.2 [ mu ] m or more.

The spacer preferably has water resistance.

Another aspect of the present invention relates to a laminate including 2 or more substrates and the spacers between adjacent substrates of the 2 or more substrates.

Another embodiment of the present invention relates to a method for manufacturing a substrate, including processing a side surface of the laminate.

Still another embodiment of the present invention relates to a method for manufacturing a substrate, including processing a side surface of a laminated body of the substrate.

The processing of the side surface of the laminate includes:

a process of bringing the laminate into a pressed state;

1 st side surface processing for processing a side surface of the laminated body in the pressed state;

a process of releasing the pressed state of the laminated body after the 1 st side surface process;

performing intermediate processing of any one of the following operations: separating the laminate from which the pressing state is released into 2 or more laminates; bonding the laminate released from the pressed state to another laminate in a laminating direction; or maintaining the laminated body released from the pressed state;

a process of bringing the laminate subjected to the intermediate process into a pressed state after the intermediate process;

and a 2 nd side surface treatment for further treating the side surface of the laminated body in the pressed state after the intermediate treatment.

Preferably, the laminated body is brought into the pressed state by pressing the substrates located at both ends of the laminated body in the laminating direction with a jig.

The substrate is preferably a glass plate.

Still another embodiment of the present invention relates to a method for manufacturing a magnetic disk substrate. The method for manufacturing a magnetic disk substrate includes the following steps:

a process of manufacturing a substrate as a substrate blank for a magnetic disk by a method of manufacturing a substrate including a process of processing a side surface of the laminated body; and

and performing post-treatment of at least polishing treatment on the main surface of the substrate after the treatment of the side surface of the laminate.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the above-described spacer, the laminated body of substrates, the method for manufacturing a substrate, and the method for manufacturing a substrate for a magnetic disk, it is possible to suppress the positional deviation of the spacer or further suppress the positional deviation of the substrate, which is generated when the pressure is released from the laminated body in the pressed state.

Drawings

Fig. 1 shows (a) a perspective view of an example of a glass plate produced in one embodiment, (b) a cross-sectional view of an end face of the glass plate shown in (a), and (c) an example of a spacer used in one embodiment.

Fig. 2 is a diagram for explaining an example of a polishing process for polishing a side surface of a laminated body of glass plates used in one embodiment.

Fig. 3 is a diagram illustrating the amount of change Δ W in the thickness of the spacer from the pressed state to the non-pressed state in which the pressing force is released in the spacer according to the embodiment.

In fig. 4, (a) and (b) are views illustrating changes in the form of the laminated body of glass plates when the 1 st end face polishing is followed by the 2 nd end face polishing according to one embodiment.

Detailed Description

In the laminated body of glass plates in a pressed state in which the spacers are sandwiched between the glass plates and the glass plates are separated from each other, the pressure is released from the pressed state of the laminated body between the polishing of the inner end face and the polishing of the outer end face, but the glass plates or spacers may be displaced as the pressure is released. It has been found that such a position shift depends on the characteristics of the spacer. In particular, it is known that the larger the change in thickness of the spacer when the pressure is released from the pressed state, the more frequently the above-mentioned positional deviation occurs, the larger the positional deviation amount becomes. The solutions disclosed below are contemplated in light of these insights.

The spacer is a sheet-like member that is interposed between adjacent substrates in a laminate to separate the adjacent substrates from each other when the laminate of 2 or more substrates is formed and the end face treatment of the 2 or more substrates is performed. The spacer may have the same shape as the substrate, for example, a disk shape. Here, the area of the surface of the spacer in contact with the substrate is smaller than that of the substrate.

In the end face treatment of the substrate, for example, in the end face polishing treatment, the end face is polished by a polishing jig (for example, a polishing brush, a polishing pad, a sponge, or the like) while supplying a polishing liquid containing cerium oxide or the like as a polishing agent to the end face (outer end face or inner end face) of the substrate in a state where the laminated body of the substrate is pressed in the laminating direction (thickness direction of the substrate).

In this case, when a laminated body formed by laminating 2 or more substrates with spacers interposed therebetween is pressed in the laminating direction with a pressure of 0.60MPa and then pressed in a non-pressed state with the pressure released, the amount of change Δ W in the thickness of each 1 spacer is 30 μm or less. The amount of change Δ W in the thickness of each 1 spacer is calculated from the thickness of the laminate that changes due to the release of the pressure.

In the case where the amount of change Δ W per 1 spacer is 30 μm or less, the defects after the end face treatment due to the positional deviation of the substrate or the spacer (for example, in the end face polishing treatment, the portion of the surface roughness increases, and the variation in the machining margin between the substrates due to polishing) are reduced.

The change amount Δ W can be measured as a property of the spacer as described below, for example. First, a laminate was produced by sequentially laminating 110 substrates, 1 spacer and 5 substrates from below in a dry state, and the amount of change in the thickness of the laminate when the pressure was released was measured with respect to the thickness of the laminate in a pressed state (pressure 0.60MPa), and the value was defined as the amount of change a. In addition, a laminate similar to the above laminate was produced except that the spacer was not included, and the amount of change in thickness of the laminate before and after the release of the pressure was measured in the same manner as described above, and the value was defined as change B.

From these values, the change amount Δ W is calculated by the following equation.

(variation Δ W) ═ variation a) - (variation B)

Here, the thickness of the spacer is restored by releasing the pressure from the pressed state, and therefore the thickness of the laminated body is increased. Here, since it may take some time to restore the thickness of the spacer depending on the material, the amount of change a and the amount of change B are preferably 1 minute after the pressure is released.

According to one embodiment, the change amount Δ W is preferably 20 μm or less, more preferably 10 μm or less. This can suppress the positional displacement of the substrate or the spacer when the pressure is released. On the other hand, if the variation Δ W is close to zero and the thickness of the spacer is not changed at all, the surface of the substrate may be scratched, which is not preferable. From this viewpoint, the change amount Δ W is preferably 0.05 μm or more, and more preferably 0.1 μm or more.

The change amount Δ W may be 30 μm or less, and the average thickness W1 of 1 spacer in the no-load state (initial state) is not particularly limited. Depending on the material of the spacer, the amount of change Δ W can be made within the above range by reducing the average thickness W1 of the spacer, but if it is too thin, the durability of the spacer is low (it is easily broken and easily broken), and therefore it is not preferable from the viewpoint of durability. The average thickness W1 of 1 spacer is, for example, 50 to 1500 μm. The smaller the average thickness W1, the larger the number of laminated sheets per unit length, which is preferable. From this viewpoint, W1 is preferably 1000 μm or less, more preferably 500 μm or less, and still more preferably 300 μm or less. On the other hand, if the average thickness W1 is too small, the film is easily broken, and the number of times of repeated use is reduced. From this point of view, the average thickness W1 is preferably 100 μm or more.

The substrate described below is a glass plate. However, the substrate includes a plate such as an aluminum alloy substrate, a silicon substrate, or a titanium substrate, in addition to the glass plate. The substrate may have a disk shape with a hole at the center, or may have a shape other than a disk shape, for example, a circular shape with no hole at the center, a quadrangular shape, or the like. The thickness of the substrate is not particularly limited, and is preferably 2mm or less, more preferably 0.7mm or less, and still more preferably 0.6mm or less, from the viewpoint of increasing the number of laminated sheets and improving the processing efficiency. In addition, the method is particularly suitable for manufacturing a glass substrate for a magnetic disk, which requires polishing treatment of both end faces of the inner end face and the outer end face of the substrate and requires strict reduction in manufacturing cost.

The end surface treatment applied to the substrate includes: an end face polishing process of polishing an end face of a substrate by relatively moving the end face of the substrate and a polishing jig abutting on the end face of the substrate in an abutting portion, or a process of grinding the end face. The end face polishing process includes an end face polishing process in which both the end face of the substrate and the polishing jig are moved in the contact portion, and an end face polishing process in which only one of the end face and the polishing jig is moved to perform polishing. In this case, the spacer is smaller in area than the substrate so that the spacer does not protrude from the end face of the substrate.

In the edge face treatment, when the laminated body is pressed in the laminating direction between the 1 st treatment and the 2 nd treatment to be in a non-pressed state in which the pressure is released, the edge face treatment includes a mode of treating different edge faces of the substrate and a mode of treating the same edge face 2 times. The 2-time processing includes, for example, a grinding process and a polishing process, or a rough polishing process and a finish polishing process, which have different processing accuracies.

Fig. 1 (a) is a perspective view of an example of a glass plate whose end face is polished with a spacer interposed therebetween according to an embodiment. Fig. 1 (b) is a view showing an example of a cross section of an end face of the glass substrate shown in fig. 1 (a).

The glass plate 1 shown in fig. 1 (a) is a disk-shaped thin glass plate having a circular hole in the center. The glass plate 1 can be used as a magnetic disk glass substrate. When the glass plate 1 is used as a magnetic disk glass substrate, the size of the magnetic disk glass substrate is not limited, and the magnetic disk glass substrate is, for example, a magnetic disk glass substrate having a nominal diameter of 2.5 inches or 3.5 inches. In the case of a magnetic disk glass substrate having a nominal diameter of 3.5 inches, for example, the outer diameter is 95mm, the inner diameter of the circular hole is 25mm, and the thickness is 0.3 to 2.0 mm. A magnetic disk was produced by forming a magnetic layer on the main surface of the glass plate 1.

The glass plate 1 includes a pair of main surfaces 11p,12p, a side wall surface 11w formed on an end surface, and chamfered surfaces 11c,12c interposed between the side wall surface 11w and the main surfaces 11p,12 p.

The side wall surface 11w includes the center position of the glass plate 1 in the plate thickness direction. The inclination angle of the chamfered surfaces 11c,12c with respect to the main surfaces 11p,12p is not particularly limited, and is, for example, 45 °. The boundary between the side wall surface 11w and the chamfered surfaces 11c and 12c is not limited to the shape having an edge as shown in the figure, and may be a smoothly continuous curved surface.

Fig. 1 (c) shows an example of a spacer used in one embodiment.

The spacer 20 shown in fig. 1 (c) is a disk-shaped sheet member having a circular hole in the center. When a laminate of disk-shaped glass plates 1 is formed by polishing the end surfaces of the inner end surface and the outer end surface of the glass plate 1, the spacer 20 is interposed between adjacent glass plates of the laminate to separate the adjacent glass plates 1 from each other. That is, the laminated body includes 2 or more glass plates 1 and spacers 20, and the spacers 20 are interposed between one glass plate 1 and another glass plate 1 laminated on the glass plate 1, and separate the adjacent glass plates 1 from each other. In fig. 1 (c), the surface of the spacer 20 that is in the shape of a circular disk and contacts the glass plate 1 in the laminated body is referred to as a main surface.

The inner diameter of the circular disk-shaped hole of the spacer 20 is larger than the inner diameter of the circular hole of the circular disk-shaped glass plate 1, and the outer diameter of the circular disk-shaped hole of the spacer 20 is smaller than the outer diameter of the circular disk-shaped glass plate 1. That is, the area of the main surface of the spacer 20, which is the portion in contact with the glass plate 1, is smaller than the area of the main surface of the glass substrate 1. The inner diameter of the circular hole of the spacer 20 and the outer diameter of the disk shape are set so that the inner end and the outer end of the spacer 20 do not protrude from the positions of the chamfered surfaces 11c,12c (specifically, the positions of the boundaries between the chamfered surfaces 11c and the main surface 11 p) and are spaced apart from the ends of the chamfered surfaces 11c,12c by a predetermined distance when the spacer 20 is sandwiched between the glass plates 1. The predetermined distance is, for example, 5 μm to 5 mm. When the distance between the inner end and the outer end of the spacer 20 and the chamfered surfaces 11c and 12c is changed, the contact manner of the grinding jig such as a grinding brush and the chamfered surfaces 11c and 12c during end surface grinding differs between the glass plates 1, and the degree of grinding (surface roughness of the end surfaces) of the chamfered surfaces 11c and 12c varies. Therefore, the inner diameter of the circular hole of the spacer 20 and the outer diameter of the disk shape are set with high accuracy.

In the spacer 20, when the laminated body formed by alternately laminating the spacers 20 and the glass substrates 1 is in a pressed state in which a pressure of 0.60MPa is applied in the laminating direction by using a pressing jig and in a non-pressed state in which the pressure is released, the amount of change Δ W in the thickness of each 1 sheet of the spacer 20 that changes due to the release of the pressure is 30 μm or less.

According to one embodiment, the material of the spacer 20 is preferably made of resin, in order to prevent the surface of the substrate from being scratched easily. For example, a sheet or film of a resin such as nylon, acrylic (acrylic), aramid, Polyethylene (PE), polypropylene (PP), Polyurethane (PU), polyethylene terephthalate (PET), or a woven or nonwoven fabric of fibers of these resins is preferable. The resin may contain additives such as fillers and inorganic materials. The material of the spacer 20 may be, in addition to resin, paper obtained by making pulp fibers, paper obtained by making both pulp fibers and resin fibers, synthetic paper, or the like. The spacer 20 may be a member obtained by stacking a plurality of sheets or the like.

Fig. 2 is a diagram illustrating an example of a polishing process for polishing the end face of the glass plate 1 by polishing the side face of the laminated body 30.

As shown in fig. 2, in the laminated body 30, the glass plates 1 are separated from each other with spacers 20 interposed between the glass plates 1 and the adjacent glass plates 1. At this time, the laminated body 30 is pressed by applying pressure P from both sides in the laminating direction (thickness direction of the glass plate 1) to bring the laminated body 30 into a pressed state. The reason why the laminated body 30 is pressed is that when the laminated body 30 and the polishing jig are rotated relative to each other to polish the end face, it is possible to prevent a part of the glass plates 1 in the laminated body 30 from being rotated differently from the adjacent glass plates 1 and polishing from being performed unevenly. In fig. 2, a polishing brush 32 is shown as an example of a polishing jig. During polishing, the laminated body 30 is pressed in the laminating direction, and the end face (outer end face or inner end face) of the glass sheet 1 is polished by a polishing jig while supplying a polishing liquid thereto. In the end face polishing, for example, the polishing jig and the glass plate 1 are rotated so that the polishing jig and the end face (outer end face or inner end face) of the glass plate 1 move relatively.

Fig. 3 is a diagram schematically illustrating the amount of change Δ W in the thickness of the spacer 20 per 1 sheet when the spacer 20 of one embodiment is in a non-pressed state from a pressed state to a released pressure state. In fig. 3, the difference between W2+ Δ W and W1 is shown in a highlighted manner for easy understanding, but the difference between W2+ Δ W and W1 may be small and substantially close to zero. As shown by the hatched area in fig. 3, the compressed thickness of the spacer 20 in the pressed state is smaller than the average thickness W1 per 1 sheet in the non-pressed state (initial state), and the compressed thickness becomes the average thickness W2 per 1 sheet. When the pressure is released after leaving in this state for, for example, 3 minutes or more, the spacer 20 is thickened in order to return to its original shape. The variation in thickness is Δ W.

When the amount of change in thickness Δ W per 1 sheet of the spacer 20 is large, if the pressure of the laminated body 30 is released between the polishing of the inner end face and the polishing of the outer end face and the non-pressed state is achieved, the spacer 20 provided between the adjacent glass plates 1 is largely displaced by the restoration, and further the positional displacement of the glass plate 1 and the adjacent glass plate 1 is easily caused by the positional displacement of the spacer 20. When the end face polishing is performed by pressing the laminated body of the glass plate 1 again in a state where the positional deviation occurs, the relative position of the glass plate 1 where the positional deviation occurs and the adjacent glass plate changes, and the machining allowance for polishing varies. When the position of the end (inner end or outer end) of the spacer 20 is shifted toward the chamfered surfaces 11c and 12c, the grinding of the chamfered surfaces 11c and 12c may vary between the glass plates 1.

Therefore, as described above, the amount of change Δ W in the thickness of each 1 piece of the spacer 20 is 30 μm or less.

The end surface polishing of the glass plate 1 is a part of the process of the glass plate manufacturing method. The following describes a method for producing a glass plate, taking as an example a method for producing a glass substrate for a magnetic disk.

The glass blank plate as a raw material of the glass plate 1 is a plate having a constant plate thickness manufactured by a float method or a down-draw method, for example. Alternatively, the glass raw plate may be a plate obtained by press-molding a glass block using a mold. The thickness of the glass blank plate is increased, for example, by about several micrometers to several hundred micrometers, relative to the amount of machining allowance for the target thickness-increasing grinding and polishing when the glass substrate for a magnetic disk, which is a final product, is formed.

Then, the glass blank is subjected to shape processing to form a disk-shaped glass plate 1. In the shape processing, for example, a scribe line may be mechanically formed on the glass blank plate using a scriber and cut along the scribe line; the glass blank may be cut by heating the glass blank by using a laser to denature a part of the glass blank and thereby easily cause a crack.

Next, the cut surface of the glass blank plate shaped into a disk shape is subjected to shape processing for forming chamfered surfaces 11c,12 c. The chamfered surfaces 11c,12c are formed using a mold grindstone or the like, for example. Thus, a glass plate 1 having a shape shown in fig. 1 (b) was produced.

Subsequently, the end face of the glass plate 1 is polished. In the end face polishing of the glass plate 1, as shown in fig. 2, 2 or more glass plates 1 and spacers 20 are laminated by sandwiching the spacers 20 between the glass plates 1, and in a state where the obtained laminated body 30 is pressed in the laminating direction by applying a pressure P, a polishing liquid is supplied to a side face of the laminated body 30 (an inner side face formed by an inner end face of the glass plate 1 or an outer side face formed by an outer end face of the glass plate 1), and polishing is performed using a polishing jig (e.g., a polishing brush 32).

In the polishing of the inner side surface corresponding to the inner side surface of the glass plate 1 using the laminated body 30, the laminated body 30 is fixed by pressing the region in the vicinity of the outer side surface of the main surface of the glass plate 1 located on the upper surface or the lower surface of the laminated body 30 with a fixing jig not shown. Thereafter, a polishing jig is inserted into a space of the laminate 30 corresponding to the circular hole of the glass plate 1, and the polishing jig is pushed from the inside to polish the inner side surface.

In the polishing of the outer side surface corresponding to the outer end surface of the glass plate 1 using the laminated body 30, a fixing jig, not shown, is inserted into a space corresponding to the circular hole of the glass plate 1 of the laminated body 30, and the laminated body 30 is fixed by pressing a region near the inner side surface of the main surface of the glass plate 1, which is located on the upper surface or the lower surface of the laminated body 30, using the fixing jig, not shown. Then, the polishing jig is pushed from the outside to the outer side surface of the laminate 30, and the outer side surface is polished.

Subsequently, the main surface of the glass plate 1 subjected to the end face polishing is ground and polished.

In grinding the glass plate 1, the main surface of the glass plate 1 is ground using a double-side grinding apparatus provided with a planetary gear mechanism. Specifically, the main surfaces on both sides of the glass plate 1 are ground while holding the outer end surface of the glass plate 1 in a holding hole provided in a holding member of a double-side grinding apparatus. The double-side grinding apparatus has a pair of upper and lower surface plates (upper surface plate and lower surface plate) to which grinding members are attached, and the glass plate 1 is held between the upper surface plate and the lower surface plate. Then, by moving either or both of the upper surface plate and the lower surface plate and moving the glass plate 1 and each surface plate relatively while supplying the coolant, both main surfaces of the glass plate 1 can be ground. For example, a fixed abrasive grain in which diamond is fixed by resin may be formed into a sheet shape, and the obtained sheet-shaped grinding member may be attached to a surface plate to be ground.

Next, the main surface of the glass plate 1 after grinding was subjected to the 1 st polishing. Specifically, the outer end face of the glass plate 1 is held in a holding hole provided in a polishing carrier of a double-side polishing apparatus, and the main surfaces on both sides of the glass plate 1 are polished. The purpose of the 1 st polishing is to remove scratches (キズ) and deformation (distortion み) remaining on the main surface after the grinding treatment, or to adjust fine surface irregularities (fine waviness, roughness).

In the 1 st polishing, the glass plate 1 is polished while supplying the polishing slurry using a double-side polishing apparatus having the same configuration as that of the double-side polishing apparatus used in the above-described polishing treatment using fixed abrasive grains. In the 1 st grinding, a grinding slurry containing free abrasive grains was used. As the free abrasive grains used in the first polishing, for example, abrasive grains of cerium oxide, zirconium oxide, or the like are used. The double-side polishing apparatus also sandwiches the glass plate 1 between the pair of upper and lower surface plates, similarly to the double-side polishing apparatus. A flat polishing pad (e.g., a resin polisher) having a disk shape as a whole is attached to the upper surface of the lower surface plate and the bottom surface of the upper surface plate. Thereafter, by moving either or both of the upper surface plate and the lower surface plate, the glass plate 1 and each surface plate are moved relatively, whereby both main surfaces of the glass plate 1 are polished. The abrasive grains preferably have an average particle diameter (D50) in the range of 0.5 to 3 μm.

After the 1 st polishing, the glass plate 1 may be chemically strengthened. In this case, the glass plate 1 is immersed in a chemical strengthening solution, for example, a mixed melt of potassium nitrate and sodium sulfate. Thereby, a compressive stress layer can be formed on the surface of the glass plate 1 by ion exchange. Chemical strengthening may also be performed after the 2 nd polishing. Whether or not chemical strengthening is required may be appropriately selected in consideration of the glass composition and the necessity.

The glass plate 1 is then subjected to the 2 nd polishing. The purpose of the 2 nd polishing process is mirror polishing of the main surface. In the 2 nd polishing, a double-side polishing apparatus having the same configuration as that of the double-side polishing apparatus used in the 1 st polishing was also used. Specifically, the outer end face of the glass plate 1 is held in a holding hole provided in a polishing carrier of a double-side polishing apparatus, and the main surfaces on both sides of the glass plate 1 are polished at the same time. The kind and particle size of the free abrasive grains in the 2 nd grinding are different and the hardness of the resin polisher is different from those in the 1 st grinding. The hardness of the resin polisher is preferably less than that of the 1 st grind. For example, a polishing liquid containing colloidal silica as free abrasive grains is supplied between a polishing pad of a double-side polishing apparatus and the main surface of the glass plate 1, and the main surface of the glass plate 1 is polished. The abrasive grains used in the 2 nd polishing preferably have a size in the range of 5 to 50nm in terms of an average particle diameter (D50).

In addition to the 1 st polishing and the 2 nd polishing, other polishing may be further performed, and polishing of 2 main surfaces may be completed by 1 polishing. The order of the above-described processes may be changed as appropriate.

The glass plate 1 after the 2 nd polishing was cleaned.

By polishing the main surface of the glass plate 1 in this manner, a magnetic disk glass substrate satisfying the conditions required for a magnetic disk glass substrate can be obtained.

In this way, in the end face polishing in the glass plate manufacturing method, even when the laminated body 30 is pressed to a non-pressed state where the pressure is released, the spacers 20 are less likely to be displaced or the glass plate 1 is less likely to be displaced by setting the amount of change Δ W in the thickness of each 1 spacer 20 to 30 μm or less. Therefore, the variation in polishing of the glass plate 1 in the laminate 30 can be suppressed.

According to one embodiment, the contact angle of the spacer 20 to pure water is preferably 50 degrees or less. Since the polishing liquid contains water as a main component, the surface of the spacer 20 is easily wetted by setting the contact angle thereof to pure water to 50 degrees or less. The lower limit of the contact angle is not particularly limited, and is, for example, 0 degree or more. By using such a hydrophilic spacer 20, a proper amount of water can be retained between the glass plate 1 and the spacer 20 in the laminate 20 even in a pressed state, so that the adhesion is increased and the glass plate 1 and the spacer 20 are less likely to be displaced. In addition, the main surface of the glass plate 1 is less likely to be scratched due to contact with the spacer 20. Further, even when the laminate is formed in a dry state without wetting the laminate in advance and polishing treatment is performed in a pressed state, moisture in the polishing liquid can be quickly infiltrated between the glass plate 1 and the spacer 20. This means that a laminate can be formed in a dry state, and the spacer is particularly easy to handle, which is lightweight, free from tension, and extremely low in rigidity, and therefore, the production efficiency is improved. In particular, a spacer which is lightweight, has no tension, and has extremely low rigidity is likely to adhere to various members when wetted, and is likely to cause wrinkles when adhered, and therefore, it is likely to make it difficult to form a laminated body.

In the measurement of the contact angle, 1 μ l (microliter) of the polishing liquid was dropped onto the surface of the spacer 20, and the contact angle 10 seconds after dropping the polishing liquid was measured using a contact angle measuring apparatus. When the surface of the spacer 20 is contaminated, the surface is cleaned in advance and the measurement is performed in a completely dry state.

In addition, according to one embodiment, the spacer 20 is preferably water-resistant so that the spacer 20 can maintain a high strength state even when wetted with the polishing liquid. Thus, even if the spacer 20 is inserted into the laminate in a wet state, the spacer 20 is not easily broken, and thus the durability is improved. In addition, since the spacer 20 can be used repeatedly, the production cost can be reduced.

The water resistance can be achieved by using a material that is hardly soluble in water as the material of the spacer 20, providing a surface layer that prevents water from penetrating on the surface of the spacer, or performing surface treatment, for example. When the spacer 20 is made of fibers such as woven fabric or nonwoven fabric, for example, fibers that are hardly soluble in water may be used, or fibers having a water-resistant coating applied to the surface thereof may be used.

As described above, since the end surfaces of the glass plates 1 can be polished by polishing the side surfaces of the laminated body 30 including 2 or more glass substrates 1 and spacers 20, the glass plates 1 can be produced efficiently, and the glass plates 1 can be polished substantially uniformly.

According to one embodiment, the surface roughness Ra (arithmetic mean roughness JIS B0601:2001) of the spacer 20 is preferably 0.2 μm or more. When the surface roughness Ra of the spacer 20 is less than 0.2 μm, the adhesion force to the substrate such as the glass plate 1 becomes too strong, and the spacer 20 is difficult to be peeled off from the substrate, and workability is lowered, and the spacer 20 may not be peeled off from the substrate. On the other hand, when the surface roughness Ra is more than 5.0. mu.m, the surface of the substrate may be scratched. Therefore, the upper limit of the surface roughness Ra is preferably 5.0. mu.m. The surface roughness Ra of the main surface of the spacer 20 was measured using a stylus type roughness meter.

According to one embodiment, the treatment of the side faces of the laminate 30 of the glass panel 1 comprises:

a process of pressing a laminated body 30 in which glass plates 1 and spacers 20 are alternately laminated;

1 st side surface processing for processing the side surface of the laminated body 30 in a pressed state;

a process of releasing the pressed state of the laminated body 30 after the 1 st side surface process;

performing intermediate processing of any one of the following operations: separating the laminate 30 from which the pressing state is released into 2 or more laminates; bonding the laminate 30 from which the pressed state is released to another laminate in the laminating direction; or the laminated body 30 released from the pressed state is maintained in this state;

a process of bringing the laminate subjected to the intermediate process into a pressed state after the intermediate process; and

and a 2 nd side surface treatment for further treating the side surface of the laminated body in the pressed state after the intermediate treatment.

In the process of bringing the laminated body 30 into the pressed state, the substrates, for example, dummy substrates, positioned at both ends of the laminated body 30 in the laminating direction are pressed by using the pressing jig to be brought into the pressed state.

Fig. 4 (a) is a diagram illustrating an example of a process of polishing an end face of a glass plate according to an embodiment.

For example, the 1 st end face polishing process (1 st side face process) is performed with the inner end face of the glass plate 1 as the 1 st end face and the inner side face of the laminated body 30 as the 1 st side face, and in the 2 nd end face polishing process thereafter, the outer end face of the glass plate 1 is processed as the 2 nd end face and the outer side face of the laminated body 30 is processed as the 2 nd side face (2 nd side face process). In the 2 nd end face polishing treatment, the laminate 30 is bonded to the laminate 33 of the glass plate 1 which has been separately subjected to the 1 st end face polishing treatment, and the resulting bonded laminate 34 is subjected to end face polishing. Alternatively, the 1 st end face polishing process (1 st side face process) is performed with the outer end face of the glass plate 1 as the 1 st end face and the outer side face of the laminated body 30 as the 1 st side face, and in the 2 nd end face polishing process thereafter, the inner end face of the glass plate 1 is processed as the 2 nd end face and the inner side face of the laminated body 30 is processed as the 2 nd side face (2 nd side face process). In the 2 nd end face polishing treatment, the laminate 30 is bonded to the laminate 33 of the glass plate 1 which has been separately subjected to the 1 st end face polishing treatment, and the resultant bonded layer body 34 is subjected to end face polishing.

Fig. 4 (b) is a diagram illustrating an example of the end face polishing process of the glass plate according to another embodiment different from the embodiment shown in fig. 4 (a).

For example, the 1 st end face polishing process (1 st side face process) is performed with the inner end face of the glass plate 1 as the 1 st end face and the inner side face of the laminated body 30 as the 1 st side face, and in the 2 nd end face polishing process thereafter, the outer end face of the glass plate 1 is processed as the 2 nd end face and the outer side face of the laminated body 30 is processed as the 2 nd side face (2 nd side face process). In the 2 nd end face polishing treatment, the laminate 30 is separated into 2 or more separated laminates 36, and 1 separated laminate 36 is subjected to end face polishing. Alternatively, the 1 st end face polishing process (1 st side face process) is performed with the outer end face of the glass plate 1 as the 1 st end face and the outer side face of the laminated body 30 as the 1 st side face, and in the 2 nd end face polishing process thereafter, the inner end face of the glass plate 1 is treated as the 2 nd end face and the inner side face of the laminated body 30 is treated as the 2 nd side face (2 nd side face process). In the 2 nd end face polishing treatment, the laminate 30 is separated into 2 or more separated laminates 36, and then one of the separated laminates 36 is subjected to end face polishing.

In the example shown in fig. 4 (b), the thickness of the laminate 30 after the 1 st end face polishing treatment is shown to be the same as the thickness of the bonding laminate 34 shown in fig. 4 (a), but the thickness of the laminate 30 may be different from the thickness of the bonding laminate 34.

In this way, by performing the 2 nd end face polishing process using the bonded laminate 34 or the separation laminate 36, even if the number of processing sheets of the glass plate 1 in the 1 st end face polishing process is greatly different from the number of processing sheets in the 2 nd end face polishing process, the waiting time of the laminate before the 2 nd end face polishing process is performed after the 1 st end face polishing process can be reduced, and the polishing efficiency of the glass plate 1 can be improved. In other words, since the processing times of the 1 st end face polishing process and the 2 nd end face polishing process can be made close to each other, neither polishing process becomes a bottleneck. Therefore, the efficiency of the entire end face polishing process can be improved.

For example, the circumferential length of the outer side surface to be polished is longer than the circumferential length of the inner side surface to be polished, and the total amount of the machining allowance for polishing the outer side surface is larger than the total amount of the machining allowance for polishing the inner side surface under the same polishing conditions, which takes a longer polishing time. Therefore, the outer end surface of the glass plate 1 can be polished in a larger amount at a time by using the bonded laminate 34 in which the laminates 30 and 33 having the inner side surfaces polished are bonded, and the polishing efficiency of the glass plate 1 can be improved. In addition, in the case of using an end face polishing apparatus capable of dividing into 2 layered bodies and polishing the 2 nd side face of the layered body at one time, since the 2 nd side face of the 2 separated layered bodies 36 can be simultaneously polished, the polishing efficiency of the glass plate 1 can be improved.

In the examples shown in fig. 4 (a) and (b), the 2 nd end face polishing process is performed by joining or separating the 1 st end face polished laminate 30 in either case, but the 2 nd end face polishing process may be performed on the laminate 30 maintained in its original state without joining or separating the laminate 30.

In the example shown in fig. 4 (a) and (b), the end faces to be processed in the 1 st end face polishing process and the 2 nd end face polishing process are different end faces of the glass plate 1, but the end faces to be processed may be the same, and may be, for example, inner end faces or outer end faces. That is, in the 1 st end face polishing process and the 2 nd end face polishing process, either the inner end face or the outer end face may be continuously polished. In this case, the precision of grinding can be made different as in rough grinding and finish grinding.

The glass plate 1 of the laminate subjected to the 1 st end face polishing treatment and the 2 nd end face polishing treatment shown in (a) and (b) of fig. 4 can be shipped to another processing company by the processing company subjected to the 1 st end face polishing treatment and the 2 nd end face polishing treatment, and the other processing company can perform post-treatment including grinding and polishing of the main surface and the like of the glass plate 1. That is, the glass sheet 1, that is, the end-face-treated glass sheet 1 may be used as the intermediate material. The intermediate material glass plate 1 is also referred to as a substrate in this specification.

Further, the glass sheet 1 of the laminated body subjected to the 1 st end face polishing treatment and the 2 nd end face polishing treatment may be subjected to a post-treatment including grinding and polishing of the main surface and the like of the glass sheet 1 by the same processing manufacturer. According to one embodiment, the method for manufacturing the substrate, which includes the 1 st end face polishing process and the 2 nd end face polishing process of the laminated body, includes a process of manufacturing the glass plate 1 (substrate) as a substrate blank for a magnetic disk, and a post-process of performing at least the polishing process on the main surface of the glass plate 1 (substrate) after the 2 nd end face polishing process of the laminated body.

(Experimental example 1)

In order to confirm the effect of the spacer 20 used in the method for producing the glass sheet 1, end face polishing was performed on the glass sheet 1 laminated using the spacer 20 (the outer diameter was 95.05mm, the inner diameter of the circular hole was 24.95mm, the thickness was 0.7mm, the width of the chamfered surface of the outer end and the inner end in the main surface direction was 150 μm, the angle was 45 °, and the roundness of the outer end (outer diameter) and the inner end (inner diameter) was 2 μm or less). The target values of the machining allowance (replacement) by end face grinding were 50 μm in diameter conversion at both the outer end and the inner end.

In the spacer, various materials and materials having various thicknesses are used, and the amount of change Δ W in the thickness of each 1 piece of the spacer is changed. The end face of the glass plate 1 is polished using a laminate 30 composed of 101 glass plates 1 and 100 spacers 20. Here, since 2 glass substrates 1 at both ends of the laminate 30 are used as dummy substrates, the glass substrates 1 to be processed are 99 sheets other than these 2 sheets. Both the glass plate 1 and the spacer are prepared as members in a dry state, and the spacer is alternately laminated so that the centers of the two coincide without protruding from the main surface 11p of the glass plate 1 by using a laminating apparatus.

In the end face polishing, the polishing of the inner side face of the laminated body 30 in the pressed state (pressure P of 0.60MPa) is performed by end face polishing in a state where the stacking direction is the vertical direction, then the laminated body 30 is released from the pressed state in a state where the stacking direction is the vertical direction to be in the non-pressed state, and then the polishing of the outer side face of the laminated body 30 is performed by bringing the laminated body 30 into the pressed state again (pressure P of 0.60 MPa). Before the pressed state is again formed, such an operation as correcting the positional displacement of the glass plate 1 and the spacer (for example, the disassembly and the re-lamination of the laminated body) is not performed.

The contact angle of pure water to the spacer is 50 degrees or less, and the roughness Ra of the spacer surface is in the range of 0.2 to 5 [ mu ] m.

When the laminated body 30 is brought from the pressed state to the non-pressed state, a positional deviation in the main surface direction of the spacer 20 or the glass plate 1 occurs, and the polishing result of the outer end surface varies between the glass plates 1 due to the positional deviation. Therefore, the roundness of the outer end surfaces of all the glass sheets 1 after the outer end surfaces of the glass sheets 1 were polished was measured, and the presence or absence of the glass sheets 1 whose roundness was significantly deteriorated was confirmed. Specifically, the case where 99 glass plates (even 1 glass plate) with a circularity of 10 μm or more were found was regarded as a defect.

Table 1 below shows the material of the spacer, the thickness of the spacer (average thickness W1), the amount of change Δ W in the thickness of each 1 spacer, and the results of the pass or fail at this time. In examples 1 to 8 and comparative examples 2 to 4, sheets were used, and in comparative example 1, a nonwoven fabric made of fibers of a polyester resin was used.

[ Table 1]

As is clear from table 1, by using spacers having a variation Δ W in thickness per 1 spacer of 30 μm or less, positional displacement of the spacers or the glass plates 1 is less likely to occur, and thus variation in the polishing results of the outer end surfaces can be reduced. It is also found that, even if the spacer thickness (average thickness W1) is greater than 200 μm as in examples 5, 6, and 8, the variation Δ W is 30 μm or less, and the result of non-defective is acceptable; even if the spacer thickness is 200 μm or less as in examples 1, 2, 4, and 7 and comparative examples 2 to 4, the variation Δ W is 30 μm or less or more than 30 μm, and the results of non-acceptance vary. That is, it is known that the quality cannot be judged only by the thickness of the spacer.

(Experimental example 2)

A spacer 20 having the same specification as in example 2 was prepared, end face polishing (polishing of the inner side surface and polishing of the outer side surface of the laminated body) as in experimental example 1 was performed, and workability at the time of separation (disassembly) of the laminated body after the end face polishing was evaluated, except that the surface roughness Ra of the spacer was changed variously.

For separation of the laminate, a known laminate separation apparatus is used. With this apparatus, after separating 1 glass plate 1 with a vacuum chuck, a process of blowing away the spacer 20 stuck on the glass plate 1 by blowing air is performed. However, if the attraction force between the glass 1 and the spacer 20 is too strong, the spacer 20 cannot be smoothly peeled off, and a separation error occurs. The presence or absence of the separation error was evaluated. Even if 1 spacer 20 has a separation error, it is also described as "having a separation error".

[ Table 2]

As is clear from table 2, workability without separation error can be improved by making the surface roughness Ra of the spacer 20 0.2 μm or more.

The spacer, the laminated body of substrates, the method for manufacturing a substrate, and the method for manufacturing a substrate for a magnetic disk of the present invention have been described above in detail, but the spacer, the laminated body of substrates, the method for manufacturing a substrate, and the method for manufacturing a substrate for a magnetic disk of the present invention are not limited to the above-described embodiments and examples, and it is needless to say that various improvements and modifications can be made without departing from the scope of the present invention.

Description of the symbols

1 glass plate

11p,12p major surface

11w side wall surface

11c,12c chamfer

20 spacer

30,33 laminate

32 grinding brush

34 bonding the laminate

36 separating the layered bodies.