JP2003089551A - Glass substrate, information recording medium, method for manufacturing glass substrate, and tool for chemical tempering treatment of glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chemical tempering treatment method which does not deform a glass substrate in a method for chemically tempering the glass substrate by immersing a glass substrate blank having a shaft-like projecting part at its center in a heated chemical tempering treatment liquid and exchanging the ions on the front surface of the glass substrate blank with the ions in the chemical tempering treatment liquid. SOLUTION: The method for manufacturing the chemically tempered glass substrate 13 by immersing the glass substrate blank 4 having the shaft-like projecting part 4a at its center on one surface into the heated chemical tempering treatment liquid 12 and exchanging the ions on the front surface of the glass substrate blank 4 with the ions in the chemical tempering treatment liquid comprises forming a portion of a front side main surface 5a of the glass substrate blank 4 on the side not formed with the shaft-like projecting part 4a as a mask region 5a1 where the contact with the chemical tempering treatment liquid 12 is not performed, masking this mask region 5a1 with a mask member 9 and equilibrating a compressive stress between the front surface side and the rear surface side thereby preventing the deformation, such as warpage, of the glass substrate 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a cross-sectional shape that is asymmetrical between the front surface side and the back surface side, such as a glass substrate having an axial convex portion in the center of one surface, and at least the front and back surfaces are chemically strengthened. Glass substrate and a manufacturing method thereof. The present invention also relates to a jig used when chemically strengthening such a glass substrate, and an information recording medium using such a glass substrate.

[0002]

2. Description of the Related Art In recent years, the adoption of glass substrates as substrates for information recording media has become a technical trend. A magnetic disk is one of the typical examples of the information recording medium.

In recent years, magnetic disks have been rapidly increased in recording density. In the magnetic disk device,
Random access is realized by slightly moving a recording / reproducing head over a magnetic disk that rotates at a high speed for scanning. In order to achieve both high recording density and high-speed access, it is necessary to increase the number of rotations of the magnetic disk and reduce the distance between the magnetic disk and the head (head flying height). Conventionally, as a substrate material for a magnetic disk, a substrate made of Ni-P plating on aluminum has been the mainstream, but in recent years, a glass having a high surface smoothness that is hard to be deformed even when rotated at a high speed due to its high rigidity. Substrates have come into use.

Conventionally, a glass substrate for an information recording medium is generally subjected to a strengthening treatment in order to increase its strength. A chemical strengthening treatment is generally used as the strengthening treatment method. The chemical strengthening treatment is performed by a method of immersing a glass substrate in a chemical strengthening treatment liquid melted by heating and exchanging ions of the surface layer of the glass substrate with ions in the chemical strengthening treatment liquid, that is, an ion exchange method. The ion exchange method includes a low temperature type ion exchange method, a high temperature type ion exchange method and the like. From the viewpoint of energy efficiency and damage to the glass surface, it is preferable to adopt the low temperature type ion exchange method.

In the low temperature type ion exchange method, a glass substrate is immersed in a chemical strengthening treatment liquid in a temperature range below the glass transition temperature (Tg), and alkali ions near the surface of the glass substrate are converted into alkali ions having a larger ionic radius. To replace. For example, Li ions are replaced with Na ions having a larger ionic radius, or Na ions are replaced with K ions having a larger ionic radius. A strong compressive stress is generated on the glass surface by increasing the volume of the ion-exchanged portion, and the glass surface is strengthened.

Regarding the form of the glass substrate in the magnetic disk, there are a holed type in which a through hole is formed in the center of the substrate and a type with a shaft having a shaft-shaped convex portion in the center of one surface of the substrate. In the case of a magnetic disk using a glass substrate of a shaft type, surface wobbling and shaft wobbling of the disk at high speed rotation can be significantly reduced. This advantageously develops thinner glass substrates and magnetic disks, and faster access.

In the process of immersing the glass substrate material in the chemical strengthening treatment liquid and chemically exchanging the ions on the surface of the glass substrate material with the ions in the chemical strengthening treatment liquid,
Since the compressive stress generated due to ion exchange is different between the surface on which the axial convex portion is formed and the surface on which the axial convex portion is not formed, there is a problem that the glass substrate warps. is there.

Due to the high speed rotation of the magnetic disk, an air layer (air bearing) is generated on the surface of the magnetic disk, and the magnetic head floats above the air layer with a minute interval. When the glass substrate is warped, the warp is also reflected on the magnetic disk manufactured using the glass substrate. If the magnetic disk is warped, the laminar flow of the air bearing is disturbed, and as a result, the flying characteristics of the magnetic head with respect to the magnetic disk are deteriorated, and problems such as hits and crashes occur.

As a conventional technique for suppressing the warp of the glass substrate, there is a method of manufacturing a glass substrate for a recording medium, which is disclosed in Japanese Patent Laid-Open No. 10-194787. This is to reduce the difference in depth between the compressive strain layers formed on the front surface and the back surface of the glass substrate by chemical strengthening by re-chemical strengthening.

The technique disclosed in Japanese Unexamined Patent Publication No. 10-194787 prevents warpage of a glass substrate. The cause of the warp lies in repolishing of the glass substrate after the chemical strengthening treatment. After the chemical strengthening treatment, the glass substrate is re-polished to improve the smoothness of the glass substrate or to remove impurities attached to the substrate during the chemical strengthening treatment. However, the re-polishing causes the glass substrate to warp. The reason is as follows.

In the chemically strengthened glass substrate, a compressive strain layer (compressive stress layer) is formed on the surface layer of the substrate and a tensile stress layer is formed inside the substrate, so that both are well balanced. Has been. However, the re-polishing after the chemical strengthening causes a difference in the depth of each compressive strain layer on the front surface and the back surface of the substrate. This difference in the depth of the compressive strain layer causes the glass substrate to warp.

[0012]

[Patent Document 1] Japanese Patent Application Laid-Open No. 10-1947
The technique disclosed in Japanese Unexamined Patent Publication No. 87 suppresses the warpage of the glass substrate, and the countermeasure is to re-chemically strengthen the glass substrate. However, in the glass substrate to which this conventional technique is applicable, the cause of the warpage is In polishing.

However, when this prior art is applied to the warp of the glass substrate due to the fact that the cross-sectional shape is asymmetric between the front surface side and the back surface side, such as with a shaft,
The expected effect cannot be expected. If the glass substrate having an asymmetrical shape is subjected to the re-chemical strengthening, the warp may be amplified.

The present invention was devised in view of the above circumstances, and warps and other deformations are caused due to the asymmetric cross-sectional shape such as having a shaft-shaped convex portion at the center of one surface. It is an object of the present invention to provide a technique for suppressing deformation such as warpage of a glass substrate that may occur. The glass substrate targeted by the present invention is
The glass substrate is not limited to a substrate for an information recording medium such as a magnetic disk, but is a glass substrate having a wide shape and asymmetrical shape such as an optical component, a mechanical component, and a building component that require a high degree of flatness.

[0015]

The present invention solves the above problems by taking the following means. The object of the invention is that the cross-sectional shape is asymmetric between the front surface side and the back surface side,
It is a glass substrate having at least both front and back surfaces chemically strengthened. Here, at least means that the peripheral surface may or may not be chemically strengthened. Due to the asymmetric cross-sectional shape, a difference occurs between the compressive stress along the front-side main surface and the compressive stress along the back-side main surface. The main cause of the cross-sectional shape asymmetry is that there are convex portions, concave portions, slopes, etc. with respect to the main surface. Here, the convex portion, the concave portion, and the slope are out of the main surface, and the compressive stress due to the chemical strengthening applied to the convex portion, the concave portion, and the slope is not the element (component) of the compressive stress of the main surface. I won't. If there is a convex portion, a concave portion, or a slope on the main surface, the compressive stress along the main surface will be in the case of a glass substrate where the main surface is entirely flat without such protrusions, depressions, or slopes. It becomes smaller than. That is, the compressive stress along the main surface differs between the front surface side and the back surface side.

Therefore, in the glass substrate according to the present invention, the aspect of chemical strengthening on the front surface side and the chemical reaction on the back surface side are canceled so as to cancel out the difference between the compressive stress along the main surface on the front surface side and the compressive stress along the main surface on the rear surface side. It differs from the mode of strengthening. In other words, by appropriately differentiating the mode of chemical strengthening on the front surface side and the mode of chemical strengthening on the back surface side, as a result, compressive stress along the main surface on the front surface side and compressive stress along the main surface on the rear surface side are obtained. It cancels the difference with. Since the compressive stress is substantially equal on the front surface side and the back surface side, it is possible to suppress deformation such as warpage of the glass substrate.

In the above, as a preferred embodiment, a specific technique of canceling out the difference between the compressive stress along the main surface of the front surface and the compressive stress along the main surface of the rear surface to make both the compressive stresses substantially equal. The content is to make the chemically strengthened area on the front surface side main surface and the chemically strengthened area on the back surface side main surface substantially equal. The difference in compressive stress is due to the difference in shape, and the difference in shape is due to the convex portions, concave portions, slopes, and the like. If there is a convex portion, a concave portion, or a slope, there will be a difference in the chemically strengthened area. This difference in chemically strengthened area causes a difference in compressive stress. Therefore, the chemically strengthened area is made substantially equal on the front surface side and the back surface side by appropriate means. By doing so, it is possible to make the compressive stress equal on the front surface side and the back surface side, and suppress deformation such as warpage of the glass substrate.

In the above description, it is assumed that the cross-sectional shape asymmetry is due to the convex portion protruding on the back surface side, and the front surface side is entirely flat. In this case, there is a form in which a non-chemically strengthened region that does not locally undergo chemical strengthening is secured in a region on the front surface side corresponding to the convex portion on the back surface side. The convex portion on the back surface side is off the main surface on the back surface side. Regardless of whether or not the convex portion is chemically strengthened, the area of the back-side main surface itself to be chemically strengthened, that is, the chemically strengthened area is smaller by the convex portion than in the case where there is no convex portion. In order to balance this, a non-chemically strengthened region that is not locally subjected to chemical strengthening is secured on the flat surface side, corresponding to the convex portion on the back surface side. Accordingly, the chemically strengthened area on the front surface-side main surface and the chemically strengthened area on the back surface-side main surface can be substantially equalized, and deformation such as warpage of the glass substrate can be suppressed.

The essence of the present invention is to equalize the compressive stress in the main surface on the front surface side and the compressive stress in the main surface on the rear surface side. To make the chemically strengthened areas equal on the front and back is part 1
It is just a form. The position of the non-chemically strengthened region does not necessarily have to be at the center, and the number of the non-chemically strengthened regions does not have to be limited to one as long as the chemically strengthened areas are equal on both sides. A plurality of non-chemically strengthened regions may be appropriately dispersed and arranged. In that case, the shapes and sizes of the non-chemically strengthened regions may be unified,
Alternatively, they may be different. The manner in which the compressive stress is made different between the main surface on the front surface side and the main surface on the back surface side is such that the depth of ion exchange is different, the level of ion exchange is different, and the exchanged ion species of ion exchange is different. You can also deal with things.

In the above, there is a form in which the convex portion on the back surface side is the shaft portion in the center of the substrate. This corresponds to a glass substrate with a shaft. The information recording medium manufactured by using the glass substrate in which the deformation such as the warp is suppressed, the surface runout and the axial runout at the time of high-speed rotation are significantly reduced,
This advantageously develops a thinner information recording medium and faster access.

In the above, there is a form in which the chemical strengthening is based on ion exchange. For ion exchange,
There are a low temperature type ion exchange method, a high temperature type ion exchange method, a surface crystallization method, a glass surface dealkalization method and the like. From the viewpoint of the glass transition point, a low temperature type ion exchange method in which ion exchange is performed in a region not exceeding the glass transition temperature is preferable.

In the above, there is a form in which the main component of the glass substrate is soda lime glass, aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, or zinc silicate glass. Aluminoborosilicate glass is preferable because it is highly effective by the chemical strengthening treatment, a high-strength substrate is obtained, the softening point is low, and the molding is easy. However, although slightly inferior,
It may be aluminosilicate glass, borosilicate glass, zinc silicate glass, or soda lime glass.

The present invention regarding an information recording medium is an information recording medium having at least a recording layer formed on the surface of a glass substrate, wherein the glass substrate is composed of any one of the glass substrates described above. It is a thing. In this information recording medium, deformation such as warpage is well suppressed, and improvement in the flying characteristics of the recording / reproducing head can be expected. Applicable information recording medium,
There are an information recording medium whose recording layer is a magnetic recording layer, a magneto-optical recording medium whose recording layer is a thermomagnetic thin film, and an optical recording medium whose recording layer is a dye or an alloy.

The present invention regarding the method for manufacturing a glass substrate is premised on manufacturing a glass substrate by subjecting both front and back surfaces of a glass substrate material whose cross-sectional shape is asymmetrical between the front surface side and the back surface side to chemical strengthening treatment. I am trying. In the first step, the shape peculiarity on the back surface side, which is the cause of the shape asymmetry, is set so that the chemically strengthened area on the main surface on the front surface side and the chemically strengthened area on the main surface on the back surface side of the glass substrate material are substantially equal. Masking is performed in order to remove the required region (mask region) of the front surface-side main surface corresponding to the region (projection or the like) from the target of the chemical strengthening treatment. In the second step, a chemical strengthening treatment is applied to both the front and back surfaces of the glass substrate material with the mask on the front surface side main surface.

Here, the glass substrate material is a material before the chemical strengthening treatment. The shape-specific region is a region having a shape that hinders flatness such as a convex portion, a concave portion, or a slope. Since the shape is asymmetric, if the chemical strengthening treatment is simply performed without masking, the chemical strengthening area on the front side main surface and the back side main surface due to the protrusions, recesses, slopes, etc. as described above. The difference between the chemically strengthened area and the chemically strengthened area causes a difference in compressive stress and induces deformation such as warpage. Therefore, the required area of the front surface-side main surface is masked with respect to the shape-specific areas such as the convex portion, the concave portion, and the sloped surface on the back surface side so as to be excluded from the target of the chemical strengthening treatment. The area of the mask is such that the originally existing difference between the chemically strengthened areas is canceled and the chemically strengthened areas of the front surface-side main surface and the back surface-side main surface are substantially equal to each other in the mask state. By making the chemically strengthened areas equal to each other, the compressive stress can be made equal on both the front and back surfaces, and the glass substrate can be prevented from being deformed such as warped.

In the above, the chemical strengthening treatment may be carried out by immersing the glass substrate material in a heated chemical strengthening treatment liquid. Further, the chemical strengthening treatment may be performed by ion exchange.

In the above, as a preferred embodiment, as the glass substrate material, a glass substrate material having a flat front surface and a convex portion on the back surface and having an asymmetric cross-sectional shape is subjected to the chemical strengthening treatment. Is. A typical example thereof is a glass substrate having a shaft-shaped convex portion at the center of one surface.

In the above, regarding the mask,
In some cases, masking is performed by bringing a mask member into contact with a required region of the front surface side main surface corresponding to the convex portion on the back surface side. The surface of the glass substrate material is highly flattened. If the mask member is flattened to a certain extent, the two can be brought into a vacuum contact state relatively easily by only bringing the mask member into contact with the front surface-side main surface. By this,
The region covered with the mask member is not exposed to the chemical strengthening treatment liquid while the glass substrate material is immersed in the chemical strengthening treatment liquid. That is, it is possible to easily realize that the chemically strengthened area on the main surface is reduced by the mask area.

In the above, regarding the mask,
As another aspect, masking is performed by bringing a convex portion on the back surface side of another glass substrate material into contact with a required region (mask region) on the front surface side main surface corresponding to the convex portion on the back surface side. is there. This is the case when two or more glass substrate materials are simultaneously subjected to chemical strengthening treatment. Since a plurality of processes are processed at the same time, productivity is improved. In order to balance the chemically strengthened area on both the front and back sides, the area of the back side convex portion and the mask area of the front side main surface should be equal. Therefore, glass substrate materials having the same specifications are laminated, and the convex portion of another glass substrate material is brought into contact with the region of the main surface on the front surface side to be masked. The axial convex portion of the glass substrate material is also used as a mask member for another glass substrate material. Equivalence of chemically strengthened areas is achieved reasonably and easily. According to this, the mask member can be reduced.

In the above, before the first masking step, there may be a step of heating and pressing the glass material to form the glass substrate material. This describes a manufacturing method including even a step of manufacturing a glass substrate material having an asymmetric cross-sectional shape. In another manufacturing method, a glass substrate material manufactured in advance is obtained, and the above manufacturing method is applied to the glass substrate material. However, this manufacturing method is integrated production including the production of the glass substrate material. The mode is molding by heating and pressing a glass material, that is, press molding.

In the glass substrate for the information recording medium,
It is preferable that the minute protrusions that cause hits or crashes of the recording / reproducing head be as small as possible. This is a difference from a normal optical glass element. The glass substrate of the information recording medium is required to have high surface smoothness, flatness and high rigidity. In order to obtain such a glass substrate, it is not possible to cope with the cost aspect by polishing the molded glass as in the case of an optical glass element, but in the case of press molding, it can be satisfactorily dealt with, smoothness,
It is easy to obtain a glass substrate material with excellent flatness.

The present invention further relates to a jig for glass chemical strengthening treatment. That is, a jig used for chemically strengthening a glass substrate material, the structure of which is a support portion for mounting and supporting the glass substrate material, and the glass substrate material which is connected to the support portion in a plane direction. And a mask member that is brought into contact with the glass substrate material that is supported by the support portion and that is positionally regulated by the position regulating portion, and a pressing portion that presses the mask member against the glass substrate material. . The support portion is a reaction force portion against pressing. That is, the glass substrate material is sandwiched between the supporting portion and the pressing portion. The position regulating portion regulates the position of the glass substrate material prior to the sandwiching and facilitates the positioning of the mask member. During the sandwiching, the mask member can be brought into close contact with the glass substrate material, and the chemical strengthening treatment liquid can be surely prevented from acting on the mask region of the front surface-side main surface. The structure is also relatively simple.

Another jig for glass chemical strengthening treatment of the present invention corresponds to a plurality of glass substrate materials. That is, the glass substrate material has a shape in which the front surface side is flat and the back surface side has a convex portion. A plurality of such glass substrate materials are coaxially laminated in the same posture to form a laminated body. A support part for placing and supporting the laminated body, a position restricting part that is continuously provided to the supporting part and restricts the position of the laminated body of the glass substrate material in a plane direction, and a position restricting part that is supported by the supporting part. A mask member that is brought into contact with the uppermost glass substrate material of the laminated body whose position is regulated, and a pressing member that presses the mask member against the uppermost glass substrate material and consequently presses the glass substrate materials in the laminated body together. Part. Productivity is good because chemical strengthening processing can be performed on a plurality of glass substrate materials at once. A mask member for a glass substrate material other than the topmost one can also be used as the convex portion of the laminated glass substrate, and the structure is compact and simple.

In the above, it is a preferred embodiment that the pressing portion is a weight that presses by its own weight.
Further, if the pressing portion and the mask member are provided in a row, the positioning of the front surface-side main surface with respect to the mask region becomes easy and accurate, which is more preferable. The biasing means may be replaced, or the biasing means may be used as the weight means.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a method for manufacturing a glass substrate according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic view showing a state in which a glass substrate material is produced by press molding. In FIG. 1, reference numeral 1 is a glass material, 2 is an upper mold having a smooth and flat molding surface 2a on the lower surface, and 3 is a smooth and flat molding surface 3a having a recess 3b formed in the center. It is a lower mold that has. The glass material 1 is placed on the molding surface 3a of the lower mold 3 and aligned with the recess 3b at the center. In this state, the upper die 2 is moved downward by extension of a hydraulic cylinder (not shown), and the glass material 1 is sandwiched between the lower die 3 and the upper die 2 with a small force, and the upper die 2 and the lower die 3 are clamped. The upper die 2 and the lower die 3 are heated by energizing a heater (not shown) connected in series, and the glass material 1 is heated and softened by the propagation of heat.

The temperature of the glass material 1 is the glass transition point (Tg).
When reaching the vicinity, the hydraulic cylinder (not shown) is further extended, the upper mold 2 is moved downward, and a sufficiently large pressure is applied to the glass material 1 in the softened state by the upper mold 2 and the lower mold 3. Energization to a heater (not shown) is continued, and heating and pressing are performed while further raising the temperature of the glass material 1. By this heating and pressurization, the surface states of the molding surfaces 2a and 3a of both molds are transferred to the glass material 1 which is sandwiched and pressed by both molds. A part of the glass material 1 is pushed into the recess 3b, and the shape of the recess 3b is transferred. The temperature of the glass material 1 during heating and pressing is controlled to be equal to or lower than the glass softening point (Ts).

After heating and pressurizing for a predetermined time, the applied pressure is slightly reduced and the cooling step is performed. When the cooling to the glass transition point (Tg) or lower is completed, the hydraulic cylinder (not shown) is contracted to raise the upper mold 2, and the mold is opened.

As a result of the above, as shown in FIGS. 2 (a) and 2 (b), a disk-shaped glass substrate material 4 integrally having a shaft-shaped convex portion 4a in the central portion on the back surface side is obtained. In the above press molding, a glass substrate material 4 having a smooth surface with a center line average roughness of 1 nm or less can be obtained.

The type, size and shape of the glass material 1 are not particularly limited. The glass material may be, for example, soda lime glass, aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, zinc silicate glass, or the like. Of these, aluminoborosilicate glass is preferable because it has a large effect by chemical strengthening treatment, a high-strength substrate can be obtained, a glass softening point is low, and molding is easy. However, the type, size, and shape of glass are not particularly limited.

The chemical strengthening treatment is performed by an ion exchange method. In the ion exchange method, a glass substrate is immersed in a chemically strengthened treatment liquid melted by heating, and ions in the surface layer of the glass substrate are ion-exchanged with ions in the chemically strengthened treatment liquid. The ion exchange method includes a low temperature type ion exchange method and a high temperature type ion exchange method. From the viewpoint of energy efficiency and damage to the glass surface, it is preferable to employ the low temperature ion exchange method. In the low temperature type ion exchange method, the glass substrate is immersed in a chemical strengthening treatment liquid in a temperature range below the glass transition point (Tg) to replace alkali ions near the surface of the glass substrate with alkali ions having a larger ionic radius. For example, Li ions (Li ⁺ ) are replaced with Na ions (Na ⁺ ) having a larger ionic radius, or Na ions (Na ⁺ ) are replaced with K ions (K ⁺ ) having a larger ionic radius. . A strong compressive stress is generated on the glass surface by increasing the volume of the ion-exchanged portion, and the glass surface is strengthened.

The pre-preparation of immersing the glass substrate material 4 integrally having the axial convex portion 4a in the central portion on the back surface side in the chemical strengthening treatment liquid will be described below. This preparatory step is a masking process for balancing the compressive stress generated by the chemical strengthening process with the compressive stress along the main surface on the front side.

Here, the main surface of the glass substrate material 4 will be described with reference to the sectional view of FIG.

The surface side of the glass substrate material 4 is a flat main surface 5a on the front surface side, and the back surface side is not the main surface but the central surface has a shaft-shaped convex portion 4a. is doing. Therefore, the cross-sectional shape of the glass substrate material 4 is asymmetric between the front surface side and the back surface side. That is,
This axial convex portion 4a is the cause of the shape asymmetry.

The main surface 5a of the glass substrate material 4 is 1
This is along the plane Pa, and the entire surface on the front surface side of the glass substrate material 4 is the front surface side main surface 5a. The back surface side main surface 5b of the glass substrate material 4 is along the one plane Pb, and on the back surface side of the glass substrate material 4, the axial convex portion 4a is formed.
The part corresponding to is missing. That is, the range indicated by the broken line 4b is a missing region that is not included in the back-side main surface 5b. Therefore, the area of the back-side main surface 5b is smaller than the area of the front-side main surface 5a by the area of the missing region 4b (circle) indicated by the broken line.

When such a glass substrate material 4 is directly immersed in the chemical strengthening treatment liquid and subjected to the chemical strengthening treatment, the chemically strengthened area on the front side main surface 5a is larger than the chemical strengthened area on the back side main surface 5b. It becomes larger by the amount of the missing area 4b. Therefore, the compressive stress along the front-side main surface 5a is
It becomes larger than the compressive stress along b. A tensile stress layer is formed as a reaction force inside (deep side) of the compressive stress layer along the main surface. The tensile stress layer is larger on the front surface side main surface 5a side than on the back surface side main surface 5b side. As a result, when the glass substrate material 4 is immersed in the chemical strengthening treatment liquid as it is, the glass substrate material 4 has the axial convex portion 4 as shown by the chain double-dashed line in FIG.
It will warp as it approaches the side of a. Such deformation such as warpage becomes a factor that makes the flying characteristics of the recording / reproducing head unstable in an information recording medium manufactured using the glass substrate material 4. Although the surface of the axial convex portion 4a is also subjected to the chemical strengthening treatment, this portion has a relatively small area and a relatively large distance from the back surface side main surface 5b, so that the back surface side main surface 5b has a relatively large size. It hardly contributes to the tensile stress.

As a preparation for suppressing the occurrence of deformation such as warpage as described above, the range (circle) indicated by 5a ₁ in the central portion of the front surface-side main surface 5a corresponding to the axial convex portion 4a is masked. Of. The area of the mask region 5a ₁ is equal to the area of the missing region 4b shown by the broken line.

Next, the jig for glass chemical strengthening treatment
A description will be given with reference to FIGS. 5 and 6. 5 is a side view,
FIG. 6 is a plan view. This jig 6 was subjected to a chemical strengthening treatment.
When immersing the glass substrate material 4 in the chemical strengthening treatment liquid for
Then, the mask region 5a ₁To ensure that
is there. That is, the shape of the back side that is the cause of the shape asymmetry
The main surface 5a of the front surface side is different from the axial convex portion 4a which is a peculiar region.
Use a mask to exclude the required area from the chemical strengthening treatment.
To do.

The jig 6 includes a disc-shaped support portion 7 for mounting and supporting the glass substrate material 4, and four pieces for restricting the position of the glass substrate material 4 mounted and supported by the supporting portion 7 in the plane direction. The rod-shaped position restricting portion 8 and the position restricting portion 8 supported by the supporting portion 7.
The mask member 9 that is brought into contact with the mask region 5a _{1 at} the center of the front surface-side main surface 5a of the glass substrate material 4 whose position is regulated, and a disc-shaped pressing portion that presses the mask member 9 against the glass substrate material 4. And 10. The rod-shaped position restricting portions 8 ... Stand upright from the supporting portion 7 at four positions that are evenly arranged at 90 degrees in the circumferential direction on an arc centered on the center of the disc-shaped supporting portion 7. The erections are vertical and parallel to each other. The position regulating portions 8 ... Regulate the positions of the entire glass substrate material 4 by regulating the positions of four positions on the outer peripheral surface of the glass substrate material 4. Disc-shaped pressing part 1
0 has four through holes 10a ... Slidably fitted in the four rod-shaped position restricting portions 8. The disc-shaped pressing portion 10 is a weight that presses the mask member 9 against the glass substrate material 4 by its own weight. Pressing part 1
Regarding the relationship between 0 and the mask member 9, they may be integrated with each other, or may be fitted as separate members so as to regulate the mutual positions. The mask member 9 is preferably made of glass from the viewpoint of ensuring adhesion with the glass substrate material 4. It is also preferable that the same material and the same material as the glass substrate material 4 are used.

The surface of the mask member 9 that contacts the main surface 5a of the glass substrate material 4 is made as smooth and flat as possible. The main surface 5a on the front surface side of the glass substrate material 4 is a highly smooth flat surface. As described above, when both of them are excellent in smoothness and flatness, a vacuum adhesion state is obtained, and even when immersed in the chemical strengthening treatment liquid, the chemical strengthening treatment liquid does not penetrate into the contact interface between them.

Next, the chemical strengthening process will be described with reference to FIG.

The molten salt of the chemical strengthening treatment liquid 12 contained in the chemical strengthening treatment tank 11 is melted by heating. By mounting the glass substrate material 4 on the jig 6, the mask member 5 masks the mask area 5 a ₁ of the glass substrate material 4. The glass substrate material 4 is preheated together with the jig 6. The preheated glass substrate material 4 together with the jig 6 is immersed in the molten chemical strengthening treatment liquid 12. The mask area 5a ₁ masked by the mask member 9 on the glass substrate material 4 corresponds to the axial projection 4a.

[0053] surface side main surface 5a except the mask area 5a ₁ of the glass substrate material 4, the back side main surface 5b, the surface and the circumferential surface of the shaft-shaped protrusions 4a, chemical strengthening the outer peripheral surface of the glass substrate material 4 The liquid 12 comes into contact and acts, and a chemical strengthening treatment is performed by ion exchange.

The reason why the glass substrate material 4 is preheated and then immersed in the chemical strengthening treatment liquid 12 is to prevent the glass substrate material 4 from cracking or cracking during the chemical strengthening treatment, and in the chemical strengthening treatment liquid. The molten salt of the glass substrate material 4
This is to prevent crystallization on the peripheral surface. The preheating is preferably 200 ° C to 350 ° C.

The chemical strengthening treatment liquid 12 is a molten salt of potassium nitrate (KNO ₃ ), sodium nitrate (NaNO ₃ ), potassium carbonate (K ₂ CO ₃ ), or a mixture of these salts (for example, KNO _3). + NaNO ₃ , KNO ₃ + K ₂
A molten salt of CO ₃ or the like) can be used.

The temperature of the chemical strengthening treatment liquid 12 is preferably high in order to promote ion exchange, but is preferably below the glass transition point (Tg) in order to prevent deformation of the glass substrate. For example, the glass transition point is 45
When the glass substrate material 4 made of a glass material having a temperature of 0 ° C to 800 ° C is chemically strengthened, the temperature of the chemical strengthening treatment liquid is preferably 300 ° C to 700 ° C, particularly preferably 320 ° C to 400 ° C. The reason is as follows.

The glass transition point Tg of the molding glass material is generally 450 ° C to 500 ° C. The molding temperature of the glass material is preferably low, and the temperature of the chemical strengthening treatment liquid is preferably 320 ° C to 400 ° C. This is because if the temperature is lower than this, the effect of the chemical strengthening treatment becomes insufficient, and if the temperature is higher than this, the strain is relaxed and the compressive stress decreases.

The immersion time is preferably 0.5 to 20 hours. If it is less than 0.5 hours, the effect of chemical strengthening is insufficient, and if it exceeds 20 hours, the surface becomes rough and the smoothness is lowered. If it is in the range of 0.5 to 20 hours,
The advantage is that the effect of chemical strengthening is sufficient and the smoothness is excellent. When the predetermined immersion time has elapsed, the jig 6 is pulled up from the glass substrate material 4 together with the glass substrate material 4.

In any of the above manufacturing steps, if necessary, scrub cleaning, cleaning with an appropriate cleaning agent (neutral detergent, surfactant, alkaline detergent, etc.),
Known cleaning treatments such as pure water cleaning, solvent cleaning, and solvent vapor drying can be performed. In addition, heating or ultrasonic wave application may be performed in each cleaning step. Particularly, the glass substrate after the jig 6 is pulled up from the chemical strengthening treatment tank 11 and removed from the jig 6 needs to be washed.

As a result of the above, the glass substrate 13 as shown in FIG. 8 is obtained. The glass substrate 13 has an asymmetric cross-sectional shape on the front surface side and the back surface side due to the presence of the central axial convex portion 4a on the back surface side. The mode of chemical strengthening on the front surface side and the mode of chemical strengthening on the back surface side are made different so as to cancel the difference between the compressive stress along the back surface side main surface 5b and the compressive stress along the back surface side main surface 5b.

That is, even though the cross-sectional shape is asymmetric, the chemically strengthened area on the front side main surface 5a and the chemically strengthened area on the back side main surface 5b are substantially equal to each other.
The non-chemically strengthened region 5c which is not subjected to the chemical strengthening treatment is secured in the center of the front surface-side main surface 5a. The non-chemically strengthened region 5c is arranged corresponding to the position of the axial convex portion 4a so as to be symmetrical with respect to the missing region 4b on the back-side main surface 5b. As a result, it is possible to obtain the glass substrate 13 in which the compressive stress of the surface layer and the tensile stress of the deep layer as a reaction force thereof are balanced despite the shape asymmetry. The glass substrate 13 with the axial convex portion 4a
Both the front and back surfaces are smooth and flat, and deformation such as warpage is effectively suppressed.

However, the essence of the present invention is that the front side main surface 5a
Since it is to equalize the compressive stress at the same time as the compressive stress at the back side main surface 5b, and making the chemically strengthened area equal on the front and back is only one form, but the chemical strengthened area on the front and back is equal. The position of the non-chemically strengthened region 5c does not necessarily have to be at the center, and the number thereof does not have to be limited to one. For example, a plurality of non-chemically strengthened regions are appropriately dispersed and arranged so that the total non-chemically strengthened region area is the missing region 4b.
The area may be equal to the area. In that case, the shapes and sizes of the plurality of non-chemically strengthened regions may be uniform or different. As an example, it is conceivable to arrange ring-shaped ones concentrically. The multiple ring-shaped non-chemical strengthening regions are
All may be arranged on the center side of the glass substrate 13,
You may arrange a part on the center side and a part on the outer peripheral side,
Alternatively, all of them may be arranged on the outer peripheral side.

FIG. 9 shows another embodiment of a jig for glass chemical strengthening treatment. In this jig 14, a plurality of glass substrate materials 4 are collectively mounted, and each mask area 5a ₁
To mask.

This jig 14 comprises a plurality of glass substrate materials 4
Are mounted in the state of a laminated body 15 in which the .. The disc-shaped support portion 16 is for mounting and supporting the laminated body 15. The four long position restricting parts 17, which are provided upright from the supporting part 16, are for restricting the position of the laminated body 15 in the plane direction as a whole.

The lowest glass substrate in the laminated body 15
Mask area 5a of material 4₁Is the second glass substrate material
Masked by the axial convex portion 4a of the glass substrate material 4 of FIG.
Be done. Mask area 5a of the second glass substrate material 4
₁Is the axis of the glass substrate material 4 in the third upper layer
It is masked by the convex portion 4a. Similarly for each glass
The substrate material 4 has a mask area 5a.₁One higher rank
It is masked by the shaft-shaped convex portion 4 a of the substrate material 4. So
Then, the mask area 5a of the uppermost glass substrate material 4 ₁To
Then, the mask member 18 masks it.

A disc-shaped pressing portion 19 for pressing the mask member 18 against the uppermost glass substrate material 4 is provided. The rod-shaped position restricting portions 17 ... Are equidistantly arranged at 90 degrees in the circumferential direction on an arc centered on the center of the supporting portion 16.
It is erected from the support portion 16 at some point. The erections are vertical and parallel to each other. The position regulating portions 17 ... Regulate the position of each of the glass substrate materials 4 as a whole by regulating the positions of four positions on the outer peripheral surface of the laminated body 15 of the glass substrate materials 4. Disc-shaped pressing part 1
9 is provided with four through holes 19a that are slidably fitted in the four rod-shaped position restricting portions 17. The disc-shaped pressing portion 19 is a weight that presses the mask member 18 against the uppermost glass substrate material 4 by its own weight. The pressing portion 19 not only presses the uppermost glass substrate material 4, but also indirectly presses the individual glass substrate materials 4 in the laminated body 15. The weight of the upper glass substrate material 4 exerts a pressing action on the lower glass substrate material 4.
Regarding the relationship between the mass pressing portion 19 and the mask member 18,
Both may be integrated, or as a separate body,
The two may be fitted so as to regulate the mutual position.

FIG. 10 shows how the jig 14 of FIG. 9 is used for the chemical strengthening process. The molten salt of the chemical strengthening treatment liquid 21 contained in the chemical strengthening treatment tank 20 is melted by heating. By mounting the glass substrate material 4 on the jig 14, the mask region 5a ₁ of the glass substrate material 4 is masked by the axial convex portion 4a and the mask member 18. The glass substrate material 4 is preheated together with the jig 14. The preheated glass substrate material 4 is immersed in the molten chemical strengthening treatment liquid 21 together with the jig 14.

In the jigs 6 and 14, the number of rod-shaped position restricting portions 8 and 17 may be at least 3 and may be 5 or more. The shape of the position restricting portions 8 and 17 does not have to be a rod shape, and any shape may be adopted as long as the desired function of position restricting is exhibited. For example, there is one in which a part of a cylinder having a radius of curvature along the outer circumference of the glass substrate material 4 is formed in a columnar shape. In this case, if the central angle of the partial cylinder is appropriately large, the desired position regulation can be exerted even if the number of the partial cylinders is two.

Regarding the arrangement of the plurality of position restricting portions 8 ..., 17 ..., the glass substrate material 4 has a disk shape, but is arranged equally on one circumference, but it is not always necessary to make the arrangement even. Instead, they may be arranged symmetrically. The shapes of the glass substrate material 4 and the glass substrate 13 are not limited to circular shapes, and any shape such as an ellipse, a rectangle, a square, or a rhombus can be adopted. The shapes of the supporting portions 7 and 16 and the pressing portions 10 and 19, the shapes of the position regulating portions 8 and 17, and the number thereof may be appropriately adjusted according to the shape of the glass substrate material.

Although the pressing portions 10 and 19 are made to be weights and pressed by weight, it is not always necessary to be caught by them, and the biasing force of the spring may be used, or the weight and the biasing force are combined. It may be configured as follows.

The mask members 9 and 18 are not limited to the form in which they are brought into close contact with the mask region 5a ₁ of the glass substrate material 4, but as shown in FIG. 11, one side in the axial direction is open and the other side is closed. The bottomed cylindrical mask member 22 may be used. In this case, the bottomed cylindrical mask member 22
Contacts only along the outer peripheral edge of the mask region 5a _1, the upper portion of the mask region 5a ₁ but there is space 23, the space 23 is sealed. Therefore, invasion of the chemical strengthening treatment liquid is prevented.

Although the glass substrate 13 with the axial convex portion 4a obtained as described above is asymmetric in shape, the surface compressive stress and the deep tensile stress are balanced on both front and back surfaces,
Excellent flatness and no deformation such as warpage.

Next, a magnetic recording medium is manufactured using such a glass substrate 13 having excellent smoothness and flatness. That is, as shown in FIG. 12, at least a magnetic recording layer is formed on the glass substrate 13 having the above-mentioned shaft-shaped protrusion 4a.
More specifically, the underlayer 24 is formed on the glass substrate 13, the magnetic recording layer 25 is formed thereon, the protective layer 26 is further formed thereon, and the lubricant layer 27 is formed on the uppermost layer. Then, the magnetic recording medium 28 is obtained.

Here, known magnetic recording layers and other layers can be used. As the underlayer 24, a Cr underlayer is formed by using, for example, a sputtering method. As the magnetic recording layer 25, for example, a Co—Cr—Pt based magnetic layer is formed. As the protective layer 26, a carbon protective layer is formed. For the lubricant layer 27, a fluorine-based liquid lubricant is applied by using, for example, a dip coating method.

Despite the above-mentioned shape asymmetry, the surface layer compressive stress and the deep layer tensile stress are balanced on both the front and back surfaces, the flatness is excellent, and the glass substrate which is not deformed such as warp is only the magnetic recording medium. Broad, magneto-optical recording medium,
It can be applied as a substrate of an information recording medium such as an optical recording medium. Further, it can be applied to optical materials, building materials, machine parts and the like.

Example 1 [Molding] As the glass material 1, aluminoborosilicate glass spheres having a diameter of 8 mm were used. As the upper mold 2 and the lower mold 3, those made of cemented carbide were used. The cemented carbide has a center line average roughness of 1 nm on the surface, and a protective film made of a platinum alloy is formed on the surface. The lower mold 3 is provided with a recess 3b having a diameter of 3 mm and a depth of 1 mm at the center of the surface thereof. The recess 3b is for forming the shaft-shaped protrusion 4a in the glass substrate 13.

The above-mentioned aluminoborosilicate glass spheres were placed on the lower mold 3 and, while being sandwiched between the upper molds 2, heated to a temperature near the glass softening point (Ts).

Then, the upper die 2 is moved downward by the extension operation of the hydraulic cylinder, the glass balls sandwiched by the upper and lower dies are pressurized to a predetermined position with a pressure of 350 kg / cm ² , and then allowed to cool. To do. As a result, the substrate diameter is 25 mm, the substrate thickness is 0.5 mm, the axial convex portion diameter is 3 mm, and the axial convex portion axial length is 1.
A glass substrate material 4 having a size of mm was obtained.

[Chemical Strengthening Treatment] The glass substrate material 4 produced by the molding step was washed and then chemically strengthened. The chemical strengthening process was performed as follows. That is,
A chemical strengthening treatment liquid prepared by mixing potassium nitrate (60%) and sodium nitrate (40%) was prepared. Glass substrate material 4
Is preheated to 300 ° C and the chemical strengthening treatment liquid is added to 35
Heat the glass substrate material 4 to 0 ° C and add 1 to the chemical strengthening treatment liquid.
Soak for hours. At the time of dipping, a mask member 9 made of glass having a diameter of 3 mm and a thickness of 2 mm is superposed on the surface of the glass substrate material 4 on which the shaft-shaped convex portion 4a is not formed, that is, the front-side main surface 5a, and the chemical strengthening treatment is performed. It was held so that it would not come into contact with the liquid (see FIGS. 5 and 7).

【Ah】

【Ah】).

The glass substrate 13 that has been subjected to the chemical strengthening treatment
Was gradually cooled to 200 ° C., then immersed in a 20 ° C. water bath to be rapidly cooled, and left for about 20 minutes. After that, scrub cleaning with a PVA (polyvinyl alcohol) sponge impregnated with a neutral detergent is performed, and then alkaline detergent cleaning (2% semi-clean, pH = 12, manufactured by Yokohama Yushi Co., Ltd.) is performed, and then over 18 MΩ or more. It was thoroughly rinsed with pure water and vapor-dried with isopropyl alcohol (IPA).

[Film Formation] The glass substrate 13 that has been subjected to the above-mentioned treatment.
In addition, a Cr underlayer 24, Co-Cr-
A Pt-based magnetic layer 25 and a C protective layer 26 are sequentially formed, and a fluorine-based liquid lubricant 27 is applied using a dip coating method,
The disk-shaped magnetic recording medium 28 was used.

(Embodiment 2) The glass substrate 1 on the side on which the shaft-shaped convex portion 4a is not formed during the immersion in the chemical strengthening treatment liquid.
The axial convex portion 4a of the glass substrate 13 having the same shape was superposed on the central portion of the surface-side main surface 5a which is the surface of No. 3, and was held so as not to come into contact with the chemical strengthening treatment liquid (FIG. 9, FIG. 1).
0). The other points were the same as in Example 1.

(Comparative Example) The same procedure as in Example 1 was carried out except that the glass substrate surface on the side where the axial projections were not formed was held in contact with the chemical strengthening treatment liquid during the immersion.

A glass substrate for a magnetic recording medium has a diameter of 25.
In the case of mm, flatness of 2 μm or less is required.

Table 1 shows the results of measuring the flatness of Examples 1 and 2 and Comparative Example. The flatness of the glass substrate was measured with an optical flatness meter (GPI-XP manufactured by Zygo).

[0086]

[Table 1] According to Examples 1 and 2, the flatness required as the glass substrate for the magnetic recording medium was 2 μm or less. On the other hand, in the comparative example, the flatness was all 5 μm or more in the chemical strengthening treatment.

It was confirmed that in the magnetic recording media obtained in Examples 1 and 2, no defect was generated in the film such as the magnetic layer.

Further, when a glide height test was conducted on a magnetic disk drive using the glass substrate obtained according to the present invention, no crash of the magnetic head was observed. The glide height test could not be performed on the magnetic disk drive using the glass substrate obtained in the comparative example.

[0089]

According to the present invention, a chemically strengthened glass substrate whose cross-sectional shape is asymmetrical between the front surface side and the back surface side because it has an axial convex portion, etc. As a result, the difference between the compressive stress along the main surface on the front side and the compressive stress along the main surface on the back surface is canceled, and the compressive stress is substantially equal on the front surface and the rear surface. Therefore, it is possible to prevent the glass substrate from being deformed such as warped.

The information recording medium manufactured by using the glass substrate with a shaft in which the deformation such as the warp is suppressed can be expected to improve the flying characteristics of the recording / reproducing head. In addition, surface runout and shaft center runout during high-speed rotation are greatly reduced,
Advantageously, a thinner information recording medium and higher speed access will be developed.

Further, according to the present invention of the jig for chemical strengthening treatment, the mask member is brought into close contact with the glass substrate material to ensure that the chemical strengthening treatment liquid acts on the mask region of the main surface on the front side. It can be avoided. The structure is also relatively simple. In the case of a jig for a laminated body in which a plurality of glass substrate materials are coaxially laminated in the same posture, the productivity is good, and a mask member for a glass substrate material other than the topmost glass substrate is laminated on the jig. The convex portion can also be used, and it is possible to handle with a compact and simple structure.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a state in which a glass substrate material according to an embodiment of the present invention is produced by press molding.

FIG. 2 is a side view and a perspective view showing the glass substrate material according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating the main surface of the glass substrate material according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram of warpage of a glass substrate material.

FIG. 5 is a side view showing a jig for glass chemical strengthening treatment in the embodiment of the present invention.

FIG. 6 is a plan view showing a jig for chemically strengthening glass according to the embodiment of the present invention.

FIG. 7 is an explanatory diagram of a chemical strengthening process in the embodiment of the present invention.

FIG. 8 is a perspective view showing a glass substrate subjected to a chemical strengthening treatment according to an embodiment of the present invention.

FIG. 9 is a side view showing a jig for glass chemical strengthening treatment according to another embodiment of the present invention.

FIG. 10 is an explanatory diagram of a chemical strengthening process according to another embodiment of the present invention.

FIG. 11 is a cross-sectional view showing another form of the mask member according to the embodiment of the present invention.

FIG. 12 is a cross-sectional view of an information recording medium according to an embodiment of the present invention 1. Glass material 2 Upper mold 3 Lower mold 4 Glass substrate material 4a Shaft-shaped convex portion 4b Missing area 5a Surface side main surface 5a ₁ Mask area 5b Back side principal surface 6 Jig for glass chemical strengthening treatment 7 Support portion 8 Position regulating portion 9 Mask member 10 Pressing portion 11 Chemical strengthening treatment tank 12 Chemical strengthening treatment liquid 13 Glass substrate 14 Glass chemical strengthening treatment jig 15 Lamination Body 16 Supporting portion 17 Position regulating portion 18 Mask member 19 Pressing portion 20 Chemical strengthening treatment tank 21 Chemical strengthening treatment liquid 22 Mask member 24 Underlayer 25 Magnetic recording layer 26 Protective layer 27 Lubricant layer 28 Magnetic recording medium

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tatsumi Kawada             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. F-term (reference) 4G059 AA08 AB06 AC16 AC30 HB03                       HB13 HB14                 5D006 CB04 CB07 DA03                 5D112 AA02 BA03 GA28

Claims (17)

[Claims] 1. A glass substrate having a cross-sectional shape asymmetrical between the front surface side and the back surface side, at least the front and back surfaces of which are chemically strengthened, wherein a compressive stress along the main surface on the front surface side due to the cross-sectional shape asymmetry. And a mode of chemical strengthening for the front surface side and a mode of chemical strengthening for the back surface side so as to cancel out the difference between the compressive stress along the main surface on the back surface side and the back surface side. 2. The compressive stress along the main surface on the front surface side and the main surface on the rear surface side are made substantially equal by making the chemically strengthened area on the main surface on the front surface side substantially equal to the chemically strengthened area on the main surface on the rear surface side. The glass substrate according to claim 1, wherein the difference between the compressive stress along the surface and the compressive stress is canceled so that the compressive stresses are substantially equal to each other. 3. The asymmetry of the cross-sectional shape is due to a convex portion protruding on the back surface side, and the entire surface is formed flat on the front surface side, and is locally formed in a region on the front surface side corresponding to the convex portion on the back surface side. The glass substrate according to claim 1 or 2, wherein a non-chemically strengthened region that is not chemically strengthened is secured. 4. The glass substrate according to claim 3, wherein the convex portion on the back surface side is a shaft portion in the center of the substrate. 5. The glass substrate according to any one of claims 1 to 4, wherein the chemical strengthening is based on ion exchange. 6. The glass substrate main component is any of soda lime glass, aluminosilicate glass, aluminoborosilicate glass, borosilicate glass or zinc silicate glass. Glass substrate. 7. An information recording medium in which at least a recording layer is formed on the surface of a glass substrate, wherein the glass substrate comprises the glass substrate according to any one of claims 1 to 6. Information recording medium. 8. A method for producing a glass substrate by subjecting a glass substrate material having a cross-sectional shape asymmetrical to each other on a front surface side and a back surface side to a chemical strengthening treatment on both front and back surfaces of the glass substrate material. In order to make the chemically strengthened area on the side main surface substantially equal to the chemically strengthened area on the back side main surface, the front side main surface corresponding to the shape unique region on the back side which is the cause of the shape asymmetry. Manufacture of a glass substrate including a first step of masking a required area of the surface to exclude it from the target of the chemical strengthening treatment, and a second step of performing the chemical strengthening treatment on both front and back surfaces of the masked glass substrate material. Method. 9. The method for manufacturing a glass substrate according to claim 8, wherein the chemical strengthening treatment is performed by immersing the glass substrate material in a chemical strengthening treatment liquid. 10. The method for manufacturing a glass substrate according to claim 8, wherein the chemical strengthening treatment is performed by ion exchange. 11. The glass substrate material as the glass substrate material, wherein the glass substrate material having a flat front surface and a convex portion on the back surface and having an asymmetric cross-sectional shape is subjected to the chemical strengthening treatment. The method for manufacturing a glass substrate according to any one of 1 to 3 above. 12. The masking method according to claim 8, wherein the masking is performed by bringing a masking member into contact with a required region of the front surface side main surface corresponding to the convex portion on the back surface side. Of manufacturing glass substrate of. 13. The method according to claim 8, wherein the mask is made by bringing a convex portion on the back surface side of another glass substrate material into contact with a required region of the main surface on the front surface side corresponding to the convex portion on the back surface side. The method for manufacturing a glass substrate according to claim 11. 14. The glass according to claim 8, further comprising a step of heating and pressing a glass material to form the glass substrate material before the first step of performing the masking. Substrate manufacturing method. 15. A jig used when chemically strengthening a glass substrate material, comprising a support portion for mounting and supporting the glass substrate material, and a surface of the glass substrate material that is connected to the support portion. A position regulating portion that regulates the position in a direction, a mask member that is supported by the supporting portion and is brought into contact with the glass substrate material that is positionally regulated by the position regulating portion, and a pressing portion that presses the mask member against the glass substrate material. Jig for glass chemical strengthening treatment including. 16. A jig used when chemically strengthening a glass substrate material, wherein the glass substrate material has a shape in which the front surface side is flat and the rear surface side has a convex portion, and a plurality of glass substrate materials are provided. A support portion for placing and supporting a laminated body in which materials are coaxially laminated, a position regulating portion that is connected to the supporting portion and regulates a position of the laminated body of the glass substrate material in a plane direction, and the support. And a mask member which is brought into contact with the uppermost glass substrate material of the laminated body which is supported by the position regulating portion and whose position is regulated by the position regulating portion, and the glass in the laminated body by pressing the mask member against the uppermost glass substrate material. A jig for glass chemical strengthening treatment, which includes a pressing portion that presses substrate materials against each other. 17. The jig for glass chemical strengthening treatment according to claim 15, wherein the pressing portion is a weight that presses by its own weight.