JP2007091527A - Crystallized glass body, method for manufacturing crystallized glass body, method for manufacturing crystallized glass substrate blank, method for manufacturing magnetic disk substrate, and method for manufacturing magnetic disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide crystallized glass bodies which each have a columnar shape and can be simultaneously sliced in a high precision when a plurality of them are stacked in a state aligned in the longitudinal direction; a method for manufacturing the same; a method for manufacturing crystallized glass substrate blanks; a method for manufacturing magnetic disk substrates from the crystallized glass substrate blanks, and a method for manufacturing magnetic disks from the magnetic disk substrates. <P>SOLUTION: The crystallized glass bodies are each obtained by heat treating a glass formed body and each have such a columnar shape that the tolerance of the outer diameter is ≥-0.2 mm and ≤0.2 mm, and the straightness is ≤5×10<SP>-5</SP>×L mm, wherein, L is length of the glass body. The method for manufacturing the crystallized glass bodies is also provided. The method for manufacturing the crystallized glass substrate blanks comprises slicing each crystallized glass body. The method for manufacturing the magnetic disk substrates comprises polishing the main surface of each crystallized glass substrate blank. The method for manufacturing the magnetic disks comprises forming a magnetic recording layer on each magnetic disk substrate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a crystallized glass body, a method for producing the crystallized glass body, a method for slicing the crystallized glass body to produce a crystallized glass substrate blank, and polishing a main surface of the crystallized glass substrate blank. The present invention relates to a method for manufacturing a magnetic disk substrate and a method for manufacturing a magnetic disk by forming a magnetic recording layer on the magnetic disk substrate.

As a glass-based information recording medium substrate, a chemically strengthened glass substrate is the mainstream, but on the other hand, a crystallized glass substrate crystallized by heat-treating glass as disclosed in Patent Document 1 is also used. Yes. A crystallized glass substrate has advantages such as a required strength without chemical strengthening and high heat resistance. When heat resistance is high, when a film is formed on the substrate or when the film is heat-treated, there is an effect that the substrate is not thermally deformed even when heated to a high temperature. Therefore, a crystallized glass substrate having such an effect is obtained. There is a need for an efficient manufacturing method.
JP 2001-180975 A

  As a method for manufacturing the crystallized glass substrate, a method of crystallizing, slicing and polishing a cylindrical glass molded body to manufacture a disk-shaped crystallized glass substrate can be considered. In addition, by stacking a plurality of cylindrical crystallized glass bodies having the same outer diameter in the longitudinal direction, and slicing them at the same time, a large number of crystallized glass substrates can be produced in one slice. It is considered that the mass productivity can be improved.

  However, when the present inventor has examined, in the conventional columnar crystallized glass body, a plurality of columnar crystallized glass bodies are aligned in the longitudinal direction, and a plurality of stacked crystallized glass bodies are obtained by slicing them simultaneously. It has been found that the thickness of the film may become uneven and the roundness may be low.

  The present invention provides a crystallized glass body having a columnar shape capable of simultaneously slicing with high accuracy when a plurality of the same are stacked in the longitudinal direction, a method for producing the crystallized glass body, and the crystallized glass described above A method of manufacturing a crystallized glass substrate blank by slicing a body, a method of manufacturing a magnetic disk substrate by polishing the main surface of the crystallized glass substrate blank, and forming a magnetic recording layer on the magnetic disk substrate It is an object of the present invention to provide a method for manufacturing a disc.

  As a result of extensive studies by the inventor in order to solve the above-mentioned problems, the thickness of the disk-shaped substrate obtained is uneven by using a crystallized glass body having a cylindrical shape whose outer tolerance and straightness are not more than predetermined values. And the present invention has been completed based on this finding.

That is, the present invention
(1) obtained by heat-treating a glass molded body,
A crystallized glass body characterized by having a cylindrical shape having a length L [mm], an outer diameter tolerance of ± 0.2 mm or less, and a straightness of 5 × 10 ⁻⁵ × L [mm] or less,
(2) The crystallized glass body according to the above (1), which contains enstatite and / or enstatite solid solution as a crystal phase,
(3) The crystallized glass body according to the above (1) or (2), wherein the length L [mm] is 100 mm or more and the outer diameter is 16 to 70 mm,
(4) The crystallized glass body according to any one of the above (1) to (3), wherein the average roughness Ra of the outer peripheral surface is 0.3 μm or less,
(5) The crystallized glass body according to any one of (1) to (4), which is a base material of a magnetic disk substrate,
(6) A method for producing a crystallized glass body, characterized in that a cylindrical glass molded body is held while being rotated in the circumferential direction around the center axis of the cylinder, heated, and crystallized.
(7) The method for producing a crystallized glass body according to (6), wherein the crystallized glass body obtained is the crystallized glass body according to any one of (1) to (5) above,
(8) A method for producing a crystallized glass substrate blank, characterized by slicing the crystallized glass body according to any one of the above (1) to (5) perpendicularly to a central axis of a cylinder,
(9) A method for producing a magnetic disk substrate comprising polishing a main surface of a crystallized glass substrate blank produced by the method described in (8), and (10) a method described in (9) above. A magnetic disk manufacturing method is provided, wherein a magnetic recording layer is formed on a manufactured magnetic disk substrate.

  According to the present invention, it is possible to provide a crystallized glass body having a columnar shape that can be sliced with high accuracy simultaneously when a plurality of the crystallized glass bodies are stacked with the longitudinal direction aligned. A method of manufacturing, a method of manufacturing the crystallized glass substrate blank by slicing the crystallized glass body, a method of manufacturing a magnetic disk substrate by polishing the main surface of the crystallized glass substrate blank, and the magnetic disk substrate A method of manufacturing a magnetic disk by forming a magnetic recording layer can be provided.

[Crystallized glass body]
First, the crystallized glass body of the present invention will be described.
The crystallized glass body of the present invention is
Obtained by heat-treating a glass molded body,
It has a cylindrical shape having a length L [mm], an outer diameter tolerance of ± 0.2 mm or less, and a straightness of 5 × 10 ⁻⁵ × L [mm] or less.

  In the present specification, the length L [mm] of the crystallized glass body means the length of the side surface of the cylinder along the center axis of the cylinder, and uniquely when the bottom surface of the cylinder intersects the center axis perpendicularly. In other cases, it means the shortest length among the lengths of the cylindrical side surfaces measured along the direction parallel to the central axis of the cylinder. The outer diameter of the crystallized glass body means the diameter of a vertical cross section (circle) with respect to the central axis of the cylinder, and the outer diameter tolerance is the outer diameter measured along the length L [mm]. It means the tolerance obtained from the maximum and minimum values.

  As described above, when stacking a plurality of the same in the longitudinal direction, it is preferable to set the length L [mm] of the crystallized glass body to 100 mm or more in order to simultaneously process a large number of slices with high accuracy. It is more preferable to set it as 100-1000 mm, and it is still more preferable to set it as 100-500 mm. This is because it is difficult to obtain the required straightness if the crystallized glass body is too long, and it is desirable to have the above length in consideration of setting a laminated structure in a slicing apparatus. is there.

  Moreover, in the crystallized glass body of this invention, it is calculated | required that an outer diameter exists in the predetermined range in the arbitrary parts of a crystallized glass body. Therefore, the outer diameter tolerance of the crystallized glass body of the present invention is ± 0.2 mm or less, preferably ± 0.1 mm or less, more preferably ± 0.08 mm or less, and further preferably ± 0.05 mm or less.

  Since a crystallized glass body takes longer to slice than a glass molded body made of amorphous glass, a crystallized glass body having a relatively small outer diameter may be used as a base material for a small-diameter magnetic disk substrate. desirable. Therefore, the outer diameter of the crystallized glass body is preferably 16 to 70 mm, more preferably 16 to 50 mm, and still more preferably 16 to 30 mm.

Moreover, in the crystallized glass body of the present invention, the straightness of the columnar crystallized glass body is 5 × 10 ⁻⁵ × L [mm] or less, and 4.0 × 10 ⁻⁵ × L [mm] or less. Preferably, it is 3.0 × 10 ⁻⁵ × L [mm] or less, more preferably 2.8 × 10 ⁻⁵ × L [mm] or less.

  For example, when the length L [mm] is 180 mm, the straightness is 0.009 mm or less, preferably 0.0072 mm or less, more preferably 0.0054 mm or less, and further preferably 0.0050 mm or less.

  In addition, as described above, when a plurality of crystallized glass bodies are aligned in the longitudinal direction and the side surfaces are brought into close contact with each other, in order for the central axes of the crystallized glass bodies to be parallel to each other, crystallized glass The average roughness Ra of the outer peripheral surface of the body is preferably 0.3 μm or less.

  Although the crystallized glass body of the present invention has a cylindrical shape, if the ridge where the side surface and the bottom surface intersect is sharp, problems such as damage during handling of the crystallized glass body may occur. It is preferable to chamfer the ridge portion, chamfer the ridge where the side surface and the bottom surface intersect at the stage of the glass molded body before crystallization, or to configure the ridge with a curved surface.

Next, the crystallized glass constituting the crystallized glass body of the present invention will be described.
The crystallized glass constituting the crystallized glass body of the present invention preferably contains enstatite and / or enstatite solid solution as a crystal phase. Hereinafter, this aspect will be described.

In recent years, the information recording density of a magnetic disk, that is, a disk-shaped magnetic recording medium has been increasing, for example, information recording of 60 Gbit / (inch) ² or more (60 × 10 ⁹ bits / (inch) ² or more). In the magnetic disk mounted on the apparatus, the size of the portion for recording 1 bit is approximately 35 nm × 350 nm or less. If the crystal grains (corresponding to individual crystal phases) are detached from the substrate surface in this region, the information recorded in this portion is completely lost. Therefore, in order to maintain the reliability of the magnetic disk, it is necessary to prevent detachment of the crystal particles from the substrate.

  Although a substrate containing lithium disilicate as a crystal phase is also useful as a magnetic disk substrate, the crystal particles made of lithium disilicate are almost spherical, and if any force is applied to the crystal particles on the substrate surface, It has the property of easily leaving. A magnetic disk substrate is manufactured by polishing a crystallized glass substrate blank in order to flatten and smooth the surface. This polishing process simultaneously polishes crystal particles near the surface and the surrounding amorphous phase. The When focusing on one crystal particle, if half of the crystal particle is polished, such a crystal particle is simply a state where hemispherical particles are embedded in an amorphous phase. Easy to leave. Similarly, in the case of crystal grains in which more than half are polished, they are easily detached. The number of crystal particles exposed on the surface of the substrate is enormous, and almost half or more than half of the crystal particles are polished, so in the case of materials containing spherical crystal particles, the crystal particles are detached. Every time that happens, the recorded information will be lost. Since the crystal grain size of lithium disilicate is usually in the range of 5 to 50 nm at least, if one crystal particle is detached, the region for recording the 1 bit is lost.

  On the other hand, in the form including the crystal phase of enstatite and / or enstatite solid solution as the crystal phase, the ratio of the major axis to the minor axis (major axis / minor axis) of the crystal particles can be increased, and the ratio is 3 or more. Preferably, it is 3.5 or more, more preferably 4 or more, still more preferably 4.5 or more, and particularly preferably 5 or more. Thus, a crystal phase with a large ratio may be more appropriate to call a crystal fiber than a crystal grain. In addition, such crystalline fibrous crystal phases may be connected to form a two-dimensional crystal phase. Hereinafter, in the present specification, the above crystal phases are also collectively referred to as crystal particles. However, in the crystallized glass body of this embodiment, the crystal particles are difficult to separate from the surface of the crystallized glass body due to the shape of the crystal particles. It can be said that there is. Therefore, if the substrate is made of a crystallized glass body made of such crystallized glass, the loss of the magnetic recording region due to the separation of the crystal particles from the substrate surface can be prevented, and the reliability as a magnetic disk can be improved. Can be increased. In addition, although there is no restriction | limiting in particular in the upper limit of the ratio of the said crystal grain major axis and minor axis, 20 or less can be used as a standard.

  The major axis and minor axis of the crystal particles can be measured as follows. From a direction perpendicular to the surface obtained by slicing the crystallized glass using a transmission electron microscope, or the surface on which the magnetic recording layer of the substrate made from the crystallized glass is to be formed (main surface of the substrate) Magnify the crystal grains in the sample. From this enlarged image, the length of the longest portion of the elongated crystal particle is measured to obtain the major axis of the crystal particle, and the length in the direction orthogonal to the major axis is measured to obtain the minor axis of the crystal particle.

  The ratio of the major axis to the minor axis (major axis / minor axis) of the crystal particle made of lithium disilicate is almost 1, and it is easy to detach from the substrate surface, but like the crystal particle made of enstatite and / or enstatite solid solution, When the ratio of the major axis to the minor axis (major axis / minor axis) is 3 or more, detachment of crystal particles from the substrate surface is reduced or prevented.

  In measurement of the major axis and minor axis of a crystal particle using a transmission electron microscope, the crystal particle in the crystallized glass is observed from one direction. Therefore, when the observation direction is the same as the longitudinal direction of the crystal particles, the value of the major axis / minor axis is small, and when the observation direction is orthogonal to the longitudinal direction of the crystal particle, the value of the major axis / minor axis is large. However, in the crystallized glass body of the present invention, since the longitudinal directions of the crystal particles constituting the crystallized glass are randomly distributed, all the longitudinal directions of the crystal particles are the observation direction in the enlarged image of the transmission electron microscope. And the probability that all the longitudinal directions of the crystal grains are orthogonal to the observation direction may be considered to be substantially zero. Therefore, crystal grains having a large major axis / minor axis value are selected from the enlarged image, and those having a major axis / minor axis value of 3 or more may be considered as the crystallized glass of this embodiment. The ratio of the crystal particles having a major axis / minor axis value of 3 or more present in the enlarged image (ratio of the number of crystal particles) is preferably 10% or more, and more preferably 15% or more. And more preferably 20% or more.

  Further, it is desirable that the ratio of crystal grains having a major axis / minor axis value of 3.5 or more (ratio of the number of crystal grains) is 5% or more, and ratio of crystal grains of 4 or more (ratio of the number of crystal grains). ) Is more preferably 5% or more, and the ratio of crystal grains of 4.5 or more (ratio of the number of crystal grains) is more preferably 5% or more. The ratio of crystal grains of 5 or more (crystal grains) It is particularly desirable that the ratio of the number of

  Enstatite crystal grains are formed of Si, Mg, and O, and the crystal structure has a chain structure in which Si and O are repeatedly connected. A plurality of Si—O chain structures are connected to each other via Mg and O, and the chain structure is spread in a planar shape. However, the bonds between the chain structures due to Mg and O are weak and easily broken. On the other hand, since the strength in the direction in which the chain structure of Si—O extends is high, the crystal seed has a structure in which chain crystal particles are woven. For this reason, even if a portion is exposed on the surface, if it is enstatite-based crystal particles, the crystal particles are firmly bound to the substrate by the amorphous phase that constitutes part of the crystallized glass, thus preventing the above separation can do.

  Since enstatite has low hardness (Mohs's hardness 5.5), crystallized glass containing enstatite or a solid solution thereof, in particular, a crystal having the largest volume fraction of crystal phase composed of enstatite or enstatite solid solution. Crystallized glass (the main crystal is enstatite or enstatite solid solution) or crystallized glass with the largest volume ratio of the crystal phase consisting of enstatite and the crystal phase consisting of enstatite solid solution (the main crystal is enstatite and enstatite solid solution) It is very easy to polish and can obtain a desired surface roughness in a relatively short time. Furthermore, enstatite is considered to have a high Young's modulus even if the particle size is small because the crystal grains are difficult to form an amorphous phase because of the crystal shape in which the chain structure is continuous in a plane. The enstatite includes clinoenstatite and protoenstatite.

  Even if other crystal seeds are contained, the crystal structure is prevented from being detached from the substrate surface since the other crystal particles are firmly bound to the substrate by the structure of the enstatite crystal particles. However, it is preferable not to contain spinel as a crystal phase. The spinel crystal phase has a high hardness (Mohs's hardness 8), and the polishing speed of the crystal phase and the amorphous phase differs when polishing the substrate surface. This is because the particles are easily detached.

  In addition, as a crystal seed with a high crystal particle detachment | desorption prevention effect by an enstatite type crystal particle, a quartz solid solution and a titanate can be illustrated. Therefore, in addition to crystal particles consisting of enstatite and / or enstatite solid solution, crystallized glass containing crystal particles consisting of quartz solid solution, crystal particles consisting of enstatite and / or enstatite solid solution, and titanate In addition to crystallized glass containing crystal particles, and crystal particles made of enstatite and / or a solid solution of enstatite, crystallized glass containing crystal particles made of quartz solid solution and crystal particles made of titanate are preferable.

  In addition, in order to satisfy various properties required for a magnetic disk substrate and to obtain the above-described effect of preventing the separation of crystal grains, when it contains a crystal phase other than enstatite, it is contained most in crystallized glass by volume%. The crystal seed (hereinafter referred to as the main crystal) is preferably enstatite and / or a solid solution of enstatite. In particular, the total content of enstatite and / or its solid solution in crystallized glass is 70 to 90% by volume, titanate is 10 to 30% by volume, and the total of enstatite and / or its solid solution and titanate The content is more preferably 90% by volume or more. There are crystallized glass containing a quartz solid solution in the crystal phase and crystallized glass containing no quartz solid solution.

  Since the enstatite crystal phase has the crystal structure as described above, a chain structure that is weakly bonded to each other is separated during surface polishing, and a surface with excellent smoothness can be realized.

  The crystal phase dispersed in the crystallized glass is precipitated in the glass by heat treatment of the amorphous glass (base glass).

In this embodiment, the Young's modulus of the crystallized glass is preferably 130 GPa or more, and more preferably 140 GPa or more. By increasing the Young's modulus, high-speed rotational stability of the magnetic disk, particularly good high-speed rotational stability can be obtained even when the substrate is thinned. The Young's modulus is about twice as large as Li ₂ O—SiO ₂ crystallized glass such as lithium disilicate. The specific elastic modulus (value obtained by dividing Young's modulus by its density) is preferably 37 MN · m / kg or more from the viewpoint of obtaining high-speed rotational stability.

  The presence of enstatite crystal phase is thought to contribute to the realization of high Young's modulus. As described above, the enstatite crystal phase is strongly bonded in the direction of the chain structure in the crystal. It is considered that the above characteristics are realized by dispersing a large number of such crystal fiber structures in random directions.

When a magnetic disk is incorporated in an information recording apparatus, a clamp for fixing the magnetic disk is made of a metal such as stainless steel. Therefore, crystallized glass having characteristics close to the thermal expansion coefficient of a metal material is desired. Furthermore, when various properties required for the substrate are taken into consideration, the average linear expansion coefficient at 100 to 300 ° C. of the crystallized glass is preferably 50 × 10 ⁻⁷ / ° C. or more, and 50 × 10 ^{−7 to} 120 ° C. more preferably × ^{10 -7} / ℃, it more preferably from ^{55 × 10 -7 ~110 × 10 -7} / ℃, a ^{60 × 10 -7 ~100 × 10 -7} / ℃ Particularly preferred.

  The size, number density, and crystallinity of crystallized glass crystallized glass affect various properties of the substrate. These values can be indirectly evaluated using the transmittance. When the above evaluation is performed using transmittance, the transmittance with respect to light having a wavelength of 600 nm is preferably 10% or more, more preferably 20% or more, and more preferably 50% or more in terms of a thickness of 1 mm. More preferably it is.

  The crystal ratio (crystallinity) in the crystallized glass is preferably 20 to 70% by volume. Further, the crystallinity is preferably 50% by volume or more in order to obtain a substrate having a high Young's modulus. However, in consideration of the ease of post-crystallization (substrate grinding and polishing) after crystallization, the crystallinity can be 20 to 50% by volume, and further 20 to 30% by volume. In the case where the Young's modulus is more important than the ease of the post-process after crystallization, the crystallinity is preferably 50 to 70% by volume. Furthermore, the size of the crystal particles contained in the crystallized glass is preferably 100 nm or less, and more preferably 50 nm or less. In addition, the size of a particularly preferable crystal particle can be set to 1 to 50 nm, and more desirably 1 to 40 nm. The crystal particle size corresponds to the above-mentioned major axis.

  When the size of the crystal particles exceeds 100 nm, not only the mechanical strength of the glass is lowered, but also the crystal surface roughness may be deteriorated by causing crystal loss during polishing. Such control of the size of the crystal particles can be mainly performed by the kind of the crystal phase contained and the heat treatment conditions of the glass molded body.

Examples of the crystallized glass of the present invention include those containing an enstatite crystal phase, those containing lithium disilicate, those containing cordierite, and those containing eucryptite as the crystal phase. However, as described above, those containing an enstatite crystal phase are most preferable.
[Method for producing crystallized glass body]
Next, the manufacturing method of the crystallized glass body of this invention is demonstrated.
The method for producing a crystallized glass body according to the present invention is characterized in that a cylindrical glass molded body is held, rotated, and crystallized while being rotated in the circumferential direction around the center axis of the cylinder.

  First, a columnar glass molded body serving as a base material for a crystallized glass body will be described.

The columnar glass molded body that is the base material of the crystallized glass body has a shape corresponding to the obtained crystallized glass body, and the straightness of the glass molded body having a length L [mm] is 3 × 10 ^−3. It is preferable to set it as xL [mm] or less, and it is more preferable to set it as 2 ^x10 < ^-3 > xL [mm] or less. In addition, the outer diameter tolerance of the glass molded body is preferably within ± 0.3 mm, and more preferably within ± 0.25 mm. Furthermore, it is particularly preferable to have the same outer diameter tolerance, outer diameter, length, and straightness as described in the description of the crystallized glass body of the present invention.

  Next, based on FIGS. 1-6, the manufacturing method of a glass forming body is demonstrated concretely.

  As shown in FIG. 1 or FIG. 2, when producing a glass molded body, a mold 3 having a cylindrical through hole having a straight central axis is arranged so that the central axis is vertical, It is preferable to produce the glass molded body 4 by pouring the molten glass 2 into the hole from the lower part of the pipe 1 and filling the mold 3.

  As shown in FIG. 1 or FIG. 2, it is preferable that the longitudinal direction of the pipe 1 is a vertical direction. By arranging in this way, the disturbance of the glass flow in the mold as described later is reduced. be able to.

  The through hole of the mold 3 has a linear center axis. The shape of the through hole is not particularly limited, but in order not to hinder the movement of the glass in the mold 3, a vertical cross-sectional shape with respect to the moving direction of the glass at an arbitrary position of the through hole is required. The same thing is preferable, for example, cylindrical shape, elliptical shape, and prismatic shape are mentioned. In addition, a shape (tapered shape) in which the cross-sectional area increases from the entrance to the exit direction of the through hole is also preferable, and by forming the shape of the through hole into a tapered shape, glass with low viscosity at the time of outflow is formed. When using a mold made of a material with high glass wettability, it is possible to prevent the glass from being baked on the mold.

  A glass molded body that is a base material for a crystallized glass body is obtained by melting a glass raw material and molding a molten glass. The composition of this glass is determined so that a required crystal phase is easily precipitated by heat treatment. And has a property that crystals are likely to precipitate in the process of producing a glass molded body. For this reason, when shape | molding molten glass, unless the cooling speed is made very large, glass will devitrify by crystallization. Crystals precipitated on the glass molded body before the heat treatment are incidentally generated without controlling the temperature conditions, etc., so that the crystal grains become coarse or the dispersion and precipitation of the crystal phase is uneven. Thus, the crystal cannot be used as a magnetic disk substrate material. Therefore, crystals must not be precipitated in the glass molded body before the heat treatment of the glass molded body.

  As shown in FIG. 1 or 2, by filling the molten glass 2 in the through hole of the mold 3, the molten glass 2 is brought into contact with the inner peripheral surface of the through hole, and the mold 3 is deprived of the heat of the glass, Glass can be cooled rapidly. In addition, by arranging the mold 3 so that the central axis of the through hole is vertical or inclined with respect to the horizontal, the flow of the molten glass 2 flowing out from the pipe 1 to the mold 3 is prevented from being disturbed as much as possible. The occurrence of striae in the glass molded body 4 can be reduced or prevented. By using the homogeneous glass molded body 4 having no striae, a more uniform crystallized glass body can be produced.

  As shown in FIG. 1 or FIG. 2, the glass rapidly cooled in the through hole is formed into a shape corresponding to the shape of the through hole, and is taken out from the through hole outlet, that is, the take-out port of the mold 3 at a predetermined speed.

  As a method for controlling the speed at which the glass molded body 4 is taken out, the speed of the glass molded body 4 taken out from the outlet of the through hole is controlled by holding the surface formed by the inner wall of the through hole (side surface of the glass molded body 4). A method can be mentioned. For example, as shown in FIG. 1, the rotation speed of the roller 5 is set in a state where the side surface 6 of the glass molded body is sandwiched between the plurality of rollers 5 so that the roller 5 and the side surface 6 of the glass molded body do not slip. By controlling it, the downward moving speed of the glass molded body 4 can be controlled. As shown in FIG. 1, it is preferable that a plurality of sets of rollers 5 are arranged along the movement path of the glass molded body 4 and the gravity acting on the glass molded body 4 is dispersed and supported by the plurality of sets of rollers. As shown in FIG. 1, the roller 5 is preferably arranged in a molding furnace 7 to be described later.

  According to this method, since the lower part of the glass molded body that has passed through the molding furnace 7 can be cut or cleaved while the glass molded body 4 is being molded, the productivity of the glass molded body can be increased.

  On the other hand, in the method of holding the side surface of the glass molded body 4 and controlling the take-out speed as described above, the glass is damaged if the force for sandwiching the glass molded body 4 is excessively increased. Cannot be added. Therefore, when the weight of the glass molded body 4 increases, the glass molded body 4 slides between the rollers, and speed control becomes difficult. In order to avoid such a situation, as shown in FIG. 2, the tip of the glass molded body 4 taken out from the outlet of the through hole is supported by the support mechanism 10 to control the speed at which the glass molded body 4 is taken out. do it.

  In any of the take-out speed control methods shown in FIGS. 1 and 2, the liquid level sensor 8 monitors the height of the molten glass liquid surface in the mold 3 and outputs a control signal from the controller 9 to control the take-out speed. Can be controlled.

  By the way, if the glass molded body 4 taken out from the mold 3 is rapidly cooled, a large temperature difference occurs between the surface and the center of the glass molded body, which causes a problem that the glass molded body 4 is destroyed. Therefore, as shown in FIG. 1 or FIG. 2, a molding furnace 7 is provided at the lower part of the through-hole outlet, the atmosphere temperature is set near the glass transition temperature by the molding furnace 7, and the temperature of the surface and the center of the glass molded body 4 It is preferable to prevent the glass molded body 4 from being damaged by slowly reducing the difference. The glass molded body 4 that has passed through the molding furnace 7 can not only adjust the temperature of the surface and the center part, but also reduce distortion.

  Next, the removed glass molded body is cut or cleaved to a predetermined length. The specific example of the cleaving method of a glass molded object is shown in FIGS.

  In the embodiment shown in FIG. 3, a marking line is formed on a part of the side surface at a predetermined position of the glass molded body by scribing. The marking line is preferably formed in a direction perpendicular to the direction of taking out the glass molded body. A fulcrum for locally supporting the glass molded body is placed on the side surface opposite to the position where the scribe processing is performed across the central axis of the glass molded body, and the fulcrum moves the glass molded body above the fulcrum. Restrict. On the other hand, by applying horizontal pressure to the glass molded body at the lower part of the scribe processing position, as shown in FIG. 4, the glass molded body is broken from the scribe-processed portion around the fulcrum and cleaved. It becomes possible to do.

  Further, when cleaving a glass molded body having a large outer diameter, as shown in FIG. 5, a water channel was formed inside the scribing position of the glass molded body subjected to the scribe processing ((a) figure). A metal jacket (water-cooled jacket) is locally contacted (Fig. (B)), and a crack is generated from the marking line toward the inside of the glass due to thermal shock, and the marking line of the marking line is sandwiched between the central axes of the glass molded body. Supporting the opposite side surface with a fulcrum (Fig. (C)), and applying a force in the horizontal direction to the glass molded body below the marking line, the torque works so that the crack grows in the fulcrum direction. Can be cleaved ((d) in FIG.).

  The glass molded body that has been cleaved or cut as described above is preferably annealed to reduce strain.

  Next, a side pressure cutting method, which is a particularly preferable method for cleaving the annealed glass molded body, will be described with reference to FIGS. First, as shown in FIG. 6, a rod-shaped glass molded body 11 in which a scribing line is put at a position where a side surface is desired to be cut and a high-pressure container 12 are prepared, and the glass molded body 11 is formed in an opening of the high-pressure container 12. While being inserted, the space between the side wall of the high-pressure vessel 12 and the glass molded body 11 is sealed. The scribing portion is arranged so as to be near the center of the high-pressure vessel 12, and then liquid (preferably water) is introduced from the liquid inlet 13 of the high-pressure vessel 12 to fill the vessel with the liquid. To increase the pressure in the sealed high pressure vessel 12. In the high-pressure vessel 12, pressure is evenly applied to the side of the glass molded body 11 that is not scribed, but the pressure acts to open the processed part at the scribe part, and the central axis of the glass molded part 11 The glass molded body can be cleaved by growing cracks in the vertical direction and dividing both sides of the scribe portion as shown in FIG.

  The glass molded body thus produced can be used for the production of the crystallized glass body of the present invention, but in order to improve the undulation of the outer peripheral surface (side surface) of the glass molded body or the straightness of the glass molded body, It is preferable to perform the outer peripheral surface processing, and it is preferable to finish the glass molded body having the outer diameter tolerance and the straightness described in the explanation of the crystallized glass of the present invention by the outer peripheral surface processing. For the processing of the outer peripheral surface, for example, a known centerless processing can be adopted.

  In the method for producing a crystallized glass body of the present invention, the columnar glass molded body is heated and crystallized to obtain a crystallized glass body.

  When crystallizing a glass molded body, first, the glass is phase-separated by heat treatment, and a large number of crystal nuclei are precipitated in the glass. Next, the glass is slowly heated to a temperature higher than that in the phase separation step to grow crystal nuclei, whereby a large number of desired crystal phases are dispersed in the amorphous glass. Then, the crystallized glass is cooled at a temperature lowering rate that does not damage, and the crystallization process is completed.

  In the above series of steps, the volume of the glass molded body slightly shrinks. If the entire crystallized glass body undergoes uniform volume shrinkage, there is no problem, but if the non-uniform volume shrinkage occurs, the straightness of the resulting crystallized glass body is reduced even if the glass molded body has a cylindrical shape in advance. Thus, a process for processing the side surface of the crystallized glass becomes necessary. Crystallization of glass increases the hardness and increases the time and labor required for processing, which is inconvenient for mass production of highly accurate disk-shaped articles with high productivity.

  For this reason, in order to produce a disk-shaped article having a high degree of parallelism and flatness by slicing a cylindrical crystallized glass, it is important not to impair the straightness of the cylindrical glass molded body as much as possible.

  In the method for producing a crystallized glass body according to the present invention, a cylindrical glass molded body is held while being rotated in the circumferential direction around the central axis of the cylinder so that the straightness of the glass molded body is maintained. A crystallized glass body is manufactured.

  By holding the glass molded body while rotating in the circumferential direction around the cylinder central axis, the glass molded body can be heated uniformly around the cylinder central axis. As a result, the volumetric shrinkage of the glass can be made uniform around the center axis of the cylinder.

  The phase separation of the glass constituting the glass molded body is performed by heating the glass molded body to near the glass transition temperature, and the crystal nucleus growth process is performed at a higher temperature. It has fallen to the extent to do. Therefore, when heat treatment is performed in a state where a part of the glass molded body is gripped, the straightness of the glass molded body is reduced due to deformation due to its own weight.

  For this reason, it is preferable that the heat treatment of the cylindrical glass molded body is performed while rotating the glass molded body in the circumferential direction around the central axis of the cylinder. Holding this while rotating the glass molded body in the circumferential direction around the central axis of the cylinder, heating, crystallizing, and producing a crystallized glass body so that the straightness of the glass molded body is maintained, The glass molded body can be crystallized while maintaining the straightness as much as possible. Such crystallization is preferable from the viewpoint of improving the homogeneity of the crystal phase and obtaining a magnetic disk substrate blank having a constant quality.

  The rotation of the glass molded body is performed in a state where the side surface of the glass molded body is held, but the side of the glass molded body is preferably held over the entire length in the central axis direction.

  As a method of holding the glass molded body while rotating it in the circumferential direction around the center axis of the cylinder, the method is to use a plurality of heat-resistant rollers arranged at intervals smaller than the outer diameter of the glass molded body and the crystallized lath body. The glass molded body is placed on the surface, and the roller is rotated to rotate the glass molded body, or the glass molded body is placed on the plane so that the cylinder central axis is parallel, and the glass molded body is placed on the plane. The method of rotating by rolling can be illustrated. Further, it can be rotated by the following method. The glass molded body is inserted into a heat-resistant cylindrical body having an inner diameter larger than the outer diameter of the glass molded body, and the central axis of the cylindrical body and the cylindrical central axis of the glass molded body are made parallel. In this state, the central axis of the cylindrical body is made horizontal or inclined from the horizontal so that the glass molded body does not slide out from the cylindrical body. When the cylindrical body is rotated about the center axis, the glass molded body rolls on the inner peripheral surface of the cylindrical body and rotates around the central axis of the cylinder.

  In any of the above rotation methods and rotation methods other than the above, it is preferable that the glass molded body is continuously rotated at a constant rotation speed until it becomes crystallized glass.

  Moreover, in order to prevent a deformation | transformation of a glass molded object, it is preferable to reduce the inclination of the central axis of a glass molded object with respect to a horizontal surface, and it is more preferable to make the said central axis horizontal.

  As the material for the roller, the material for forming a flat surface for rolling the glass molded body, and the material for forming the cylindrical body, silicon carbide or the like is preferable because glass is hardly fused and heat resistance is high.

  The heat treatment of the glass molded body is preferably performed in a heating furnace, and the temperature distribution in the furnace is preferably uniform. Further, in the case where the heat treatment is performed while rotating the glass molded body in the furnace, the inside of the furnace may be divided into a plurality of regions so that the temperature in each region can be set independently. In that case, it is desirable to make the temperature distribution in each region uniform.

  What is necessary is just to set the rotation speed of a glass forming body suitably according to the arrangement | positioning method and setting temperature of the heater in a furnace, the dimension of a glass forming body, etc. At that time, the heat treatment is performed in advance under some rotational speed conditions, and the conditions for increasing the straightness of the obtained crystallized glass are selected. The target straightness may be the straightness of the crystallized glass body of the present invention.

  The outer diameter and length of the obtained crystallized glass body are preferably equal to the outer diameter and length of the corresponding glass molded body. However, since the volumetric shrinkage of the glass occurs in the heat treatment process as described above, it is preferable to use a glass molded body that is prepared in advance so that the size of each part is increased by the size reduction due to volume shrinkage.

In order to obtain crystallized glass having an outer peripheral surface with a small surface roughness, it is preferable to reduce the average roughness Ra of the outer peripheral surface (side surface) of the glass molded body.
The crystallized glass body of the present invention can be produced by such a production method.

  Next, the method for producing a crystallized glass body of the present invention will be described in detail by taking a crystallized glass containing an enstatite crystal phase as an example.

First, a cylindrical glass molded body is prepared using glass (amorphous glass) containing SiO ₂ , MgO, TiO ₂ , and (Tg−35 ° C.) to (Tg + 60 ° C.) of this glass molded body. A phase separation step and a crystallization step are performed at a temperature in the range (where Tg is the glass transition temperature of the base glass).

  In the heat treatment step, a relatively low temperature in the initial stage, for example, (base glass transition temperature (Tg) −35 ° C.) to (Tg + 60 ° C.), preferably (Tg−35 ° C.) to (Tg + 60 ° C.). More preferably, it is heated at Tg to (Tg + 60 ° C.) to generate a large number of crystal nuclei. Specifically, these temperatures are in the range of 700 to 850 ° C. Thereafter, it is preferable to raise the temperature to 850 to 1150 ° C. to grow the crystal from the viewpoint of miniaturizing the crystal. At this time, after the temperature of the glass reaches 500 to 850 ° C., the rate of temperature rise is more preferably 0.1 to 10 ° C./min from the viewpoint of precipitation of fine crystal particles and prevention of external deformation of the plate glass. . Although there is no restriction | limiting in particular in a temperature increase rate until glass becomes 500-850 degreeC, It is preferable to set it as 5-50 degreeC / min. In the above method, the allowable temperature range of crystal nucleation heat treatment and crystal growth heat treatment for producing crystallized glass having the same Young's modulus, the same crystal grain size, or the same crystallization homogeneity is a temperature of 30 ° C. or more. Due to the width, the manufacturing process of crystallization can be easily controlled.

Further, in the above crystallization step, it is desirable that the heat treatment conditions that enstatite solid solution having a composition of enstatite and (Mg · Al) SiO ₃ having a composition of MgO · SiO ₂ by heat treatment is deposited as main crystals. As such conditions, the heat treatment temperature for crystallization is preferably 850 to 1150 ° C, and more preferably 875 to 1050 ° C. When the heat treatment temperature is less than 850 ° C., enstatite and its solid solution are difficult to precipitate, and when it exceeds 1150 ° C., crystals other than enstatite and its solid solution are likely to precipitate. Moreover, by setting it as 875-1000 degreeC, the average particle diameter of enstatite and / or its solid solution can be comparatively small, for example, can be 100 nm or less, Preferably it is 50 nm or less. The heat treatment time for crystallization affects the crystallinity and crystal grain size in relation to the heat treatment temperature, and can be appropriately selected depending on the desired crystallinity and crystal grain size. In the case of heat treatment at 1150 ° C., it is preferably 1 to 4 hours.

As the crystallized glass, it is preferable to use glass not containing ZnO or Li ₂ O in order not to precipitate a spinel type crystal phase or a lithium disilicate crystal phase. In addition to SiO ₂ , MgO, and TiO ₂ , Al _{2 O 3, ZrO 2, K 2} O, comprises _{Y 2 O 3, SiO 2,} MgO, TiO 2, Al 2 O 3, ZrO 2, K 2 O, the total content of Y 2 _{O 3} is 99 mol% or more The thing of 100 mol% is more preferable.

Further, the total content of SiO ₂ , MgO, TiO ₂ , Al ₂ O ₃ , Y ₂ O ₃ is preferably 99 mol% or more, more preferably 100 mol%.

However, in addition to the glass component, and it can also include Sb ₂ O ₃ as a defoaming fining agent.

  The following can be illustrated as a composition of glass suitable as base material glass. Here, the content of each component is expressed in mol%.

Glass containing SiO ₂ 35 to 65%, Al ₂ O _{3 over} 5% to 20%, MgO 10 to 40%, TiO ₂ 5 to 15%, and the total of the above components being 92% or more.

Within the above composition range, the molar ratio of Al ₂ O ₃ and MgO (content of Al ₂ O ₃ / content of MgO) is preferably 0.2 or more and less than 0.5, and SiO ₂ 40-60 %, Al ₂ O ₃ 7 to 20%, MgO 12 to 39%, TiO ₂ 5.5 to 14% is more preferable, and TiO ₂ containing 8 to 14% is more preferable.

Over the glass in _general, those containing Y 2 _{O 3} is preferred. When Y ₂ O ₃ is introduced, the amount introduced is preferably 10% or less, and more preferably 0.1 to 10%.

Further, over the glass in general, those containing ZrO ₂ is preferred. When ZrO ₂ is introduced, the amount introduced is preferably 10% or less, more preferably 1 to 10%, and even more preferably 1 to 5%.

Furthermore, it is preferable that the content of the alkali metal oxide is 0 to 5% throughout the glass. However, it is preferable not to introduce Li ₂ O because it causes generation of lithium disilicate which is a spherical crystal particle. The alkali metal oxide, preferably Na ₂ O and _{K 2} O, more than 0% of the total content of Na ₂ O and _{K 2} O, and more preferably 5% or less. Among them, it is more preferable to introduce only K ₂ O as the alkali metal oxide.

  When introducing an alkaline earth metal oxide other than MgO, the total content of CaO, SrO and BaO is preferably 0 to 5%, more preferably 0 to 1%, and 0%. Is more preferable.

Furthermore, if there are bubbles in the information recording medium substrate even if they are very small, defective products will be generated. The reason is that when bubbles appear on the surface due to polishing of the substrate surface, the portion becomes a depression, which impairs the smoothness of the substrate surface. Therefore, it is necessary to sufficiently degas the base glass. Sb ₂ O ₃ and As ₂ O ₃ can be mentioned as clarifying agents effective for performing sufficient defoaming. When Sb ₂ O ₃ and As ₂ O ₃ are used, introduction of 2% or less is preferable in terms of the total content. Furthermore, As ₂ O ₃ has toxicity, it is preferable not to introduce As ₂ O ₃ from the viewpoint of environmental impact. Therefore, 0 to 2% of Sb ₂ O ₃ is preferably introduced as a fining agent, more preferably more than 0% and 2% or less.

  Next, each glass component will be described in detail.

SiO ₂ is a formation of a base glass network structure, and is a constituent component of enstatite having a composition of MgO · SiO ₂ and an enstatite solid solution having a composition of (Mg · Al) SiO ₃ , which are main precipitated crystals. is there. If the content of SiO ₂ is less than 35%, the melted glass is very unstable, so that high-temperature molding may not be possible, and crystals as described above are also difficult to precipitate. On the other hand, if the SiO ₂ content is less than 35%, the chemical durability of the remaining glass matrix phase (amorphous phase in the crystallized glass) tends to deteriorate or the heat resistance tends to deteriorate. On the other hand, when the content of SiO ₂ exceeds 65%, enstatite is difficult to precipitate as the main crystal, and the Young's modulus of the crystallized glass tends to decrease rapidly. Therefore, the content of SiO ₂ is preferably in the range of 35 to 65% in consideration of the precipitated crystal species and the amount of precipitation, chemical durability, heat resistance and molding / productivity. From the viewpoint of obtaining crystallized glass having more preferable physical properties, the content of SiO ₂ is more preferably in the range of 40 to 60%. Incidentally, in combination with other components, the surface smoothness is somewhat inferior, but since a crystallized glass having a high Young's modulus of 160 GPa or more may be obtained, the content of SiO ₂ is 35 to 55%. It may be preferable.

Al ₂ O ₃ is an intermediate oxide of glass and contributes to improvement of glass surface hardness. However, if the content of Al ₂ O ₃ is 5% or less, the chemical durability of the glass matrix phase also decreases, and the strength required for the substrate material tends to be difficult to obtain. On the other hand, if the content of Al ₂ O ₃ exceeds 20%, enstatite as the main crystal is difficult to precipitate, the melting temperature is high, the glass is difficult to melt, and devitrification is easy. It tends to be difficult to mold. Therefore, the content of Al ₂ O ₃ is preferably in the range of more than 5% to 20% and more preferably in the range of 7 to 20% in consideration of the solubility of glass, high temperature formability, precipitated crystal seeds, and the like. Incidentally, in combination with other components, the surface smoothness is somewhat inferior, but since a crystallized glass having a high Young's modulus of 160 GPa or more may be obtained, the content of Al ₂ O ₃ is 9 to 20%. May be preferred.

MgO is a modified component of the glass, is also the main component of crystals of enstatite solid solution having a composition of enstatite and (Mg · Al) SiO ₃ having a composition of MgO · SiO _2. If the content of MgO is less than 10%, the above crystals are difficult to precipitate, the glass has a tendency to devitrify and the melting temperature is high, and the working temperature range of glass forming tends to be narrow. On the other hand, if the MgO content exceeds 40%, the high-temperature viscosity of the glass rapidly decreases and becomes thermally unstable, the productivity deteriorates, and the Young's modulus and durability tend to decrease. Therefore, the content of MgO is preferably in the range of 10 to 40% and more preferably in the range of 12 to 39% in consideration of glass productivity, chemical durability, high temperature viscosity and strength. . In addition, in combination with other components, the surface smoothness is somewhat inferior, but since a crystallized glass having a high Young's modulus of 160 GPa or more may be obtained, the content of MgO is 20 to 39%. May be preferred.

However, it is preferable to adjust the contents of MgO and Al ₂ O ₃ so that the molar ratio (Al ₂ O ₃ / MgO) is less than 0.5. This is because when the molar ratio (Al ₂ O ₃ / MgO) is 0.5 or more, the Young's modulus of the crystallized glass tends to rapidly decrease.

By setting Al ₂ O ₃ /MgO<0.5, crystallized glass having a high Young's modulus of 150 GPa or more can be obtained. Preferably Al ₂ O ₃ /MgO<0.45. However, if the molar ratio of Al ₂ O ₃ / MgO is too small, the high temperature viscosity of the glass tends to decrease and the crystal particles may increase, so the Al ₂ O ₃ / MgO ratio is preferably 0.2 or more, It is suitable that it is 0.25 or more.

TiO ₂ is a nucleating agent for crystal phase precipitation of enstatite having a composition of MgO · SiO ₂ and enstatite solid solution having a composition of (Mg · Al) SiO ₃ . Furthermore, TiO ₂ also has an effect of suppressing devitrification of glass when the content of SiO ₂ is small. However, when the content of TiO ₂ is less than 5%, the effect as a nucleating agent of the main crystal cannot be sufficiently obtained, and the glass is crystallized on the surface, so that it is difficult to produce a homogeneous crystallized glass. is there. On the other hand, if the content of TiO ₂ exceeds 15%, the high-temperature viscosity of the glass becomes too low, causing phase separation or devitrification, and thus the glass productivity tends to be extremely deteriorated. Therefore, in consideration of glass productivity, chemical durability, high temperature viscosity, crystal nucleation and the like, the content of TiO ₂ is preferably 5 to 15%, more preferably 5.5 to 14%, and more preferably 8 to 14%. Further preferred. When the Young's modulus is more important than the surface smoothness in combination with other components, a crystallized glass having a high Young's modulus of 160 GPa or more may be obtained. Therefore, the content of TiO ₂ is 8. It may be preferable that it is 5 to 14%.

The base material glass may contain Y ₂ O ₃ . By introducing Y ₂ O ₃ , the Young's modulus of the crystallized glass can be increased by about 10 GPa, and the liquidus temperature can be reduced by about 50 to 100 ° C. That is, the introduction of a small amount of Y ₂ O ₃ can significantly improve the properties and productivity of the glass. If the content of Y ₂ O ₃ is 0.1% or more, the effect of Y ₂ O ₃ can be obtained. The content of Y ₂ O ₃ is preferably 0.3% or more, more preferably 0.5% or more. However, since Y ₂ O ₃ has the power to suppress the growth of the main crystal contained in the glass, if the content of Y ₂ O ₃ is too large, in the heat treatment performed for the purpose of crystallizing the glass, surface crystals There is a tendency that the target crystallized glass cannot be produced. From such a viewpoint, the content of Y ₂ O ₃ is preferably 10% or less. The content of Y ₂ O ₃ is more preferably 8% or less, and further preferably 3% or less.

Further, the glass can contain 10% or less of ZrO ₂ . ZrO ₂ increases the stability of the glass and can play a major role in improving the stability of the glass containing a large amount of MgO. Also, it acts as a nucleating agent, and assists TiO ₂ to promote the glass phase separation during the pretreatment and to help refine the crystal grains.

However, if the content of ZrO ₂ exceeds 10%, the high-temperature solubility and homogeneity of the glass may be deteriorated, so the introduction amount is suitably 1 to 10%.
Furthermore, taking into consideration the high-temperature solubility of glass and the homogeneity of crystal grains, the amount of ZrO ₂ introduced is preferably 0 to 6%, more preferably 1 to 5%.

The base glass preferably has a total content of SiO ₂ , Al ₂ O ₃ , MgO, and TiO ₂ of 92% or more from the viewpoint of maintaining characteristics such as high Young's modulus and homogeneous crystallinity, and 93 % Or more is more preferable, and 95% or more is further preferable.

Within the above range, as components other than the above, alkali metal oxides R ₂ O (for example, Li ₂ O, Na ₂ O, K ₂ O, etc.) and a range that does not impair the desired properties of the crystallized glass, and Components such as alkaline earth metal oxides RO (for example, CaO, SrO, BaO, etc.) may be included. The alkali metal oxide and / or alkaline earth metal oxide can use nitrate as a glass raw material. When the alkali metal oxide is contained, the alkali metal oxide tends to lower the Young's modulus, so the content is suitably 5% or less. On the other hand, alkali metal oxides have the effect of lowering the melting temperature of glass and the effect of ionizing and dissolving platinum contaminants from the platinum melting furnace. In this case, addition of 0.1% or more is effective. is there.

In particular, K ₂ O is preferable because it has an effect of lowering the melting temperature of glass and an effect of ionizing and dissolving platinum contaminants from the platinum melting furnace and an effect of hardly lowering the Young's modulus. When K ₂ O is contained, the content is suitably 5% or less, more preferably 0.1 to 2%, and still more preferably 0.1 to 1%.

In addition, when an alkaline earth metal oxide other than MgO is included, the alkaline earth metal oxide has a tendency to enlarge crystal particles. Therefore, the content is suitably 5% or less. -1% is more preferable. When the alkali metal oxide is included, the amount is preferably 0.1 to 5%, more preferably 0.1 to 2%, and further preferably 0.1 to 1%. It is preferable to introduce only K ₂ O as the alkali metal oxide. Therefore, in this case, the amount of the alkali metal oxide is equal to the amount of K ₂ O.

  Moreover, it is preferable that the said base material glass does not contain ZnO and NiO substantially. This is because ZnO makes it easy to form spinel, which is a hard crystal. NiO is preferably not contained from the viewpoint of facilitating the formation of spinel and from the viewpoint of being a component that affects the environment.

In addition, the said glass can be manufactured using a well-known method. For example, bubbles or undissolved substances can be obtained by high-temperature melting method, that is, by melting glass raw materials at a predetermined ratio in the air or in an inert gas atmosphere and homogenizing the glass by bubbling, adding a defoaming agent or stirring. A homogeneous base glass that does not contain foreign substances can be obtained. The melting temperature can be 1400 to 1650 ° C., but it may be dissolved at 1500 to 1650 ° C., more preferably 1550 to 1600 ° C. When lowering the melting temperature, it is preferable to introduce K ₂ O.

  A more preferable composition range can be set by arbitrarily combining the preferable ranges of the contents of the respective components. Among these, preferred combinations are specifically shown.

_{SiO 2 35~55%, Al 2 O} 3 9~20%, MgO 12~39%, TiO 2 8~14%, Y 2 O 3 0~10%, ZrO 2 1~10%, K 2 O0.1 Glass having a total amount of ˜2%, alkaline earth metal oxides other than MgO of 0-5%, and a total amount of SiO ₂ , Al ₂ O ₃ , MgO, TiO ₂ of 93% or more.

_{SiO 2 35~55%, Al 2 O} 3 9~20%, MgO 12~39%, TiO 2 8~14%, Y 2 O 3 0.1~10%, ZrO 2 1~10%, K 2 O0 .1～2%, the total amount of alkaline earth metal oxides other than MgO _{is 0~5%, SiO 2, Al 2} O 3, MgO, the total amount of TiO ₂ is 93% or more of the glass.

_{SiO 2 35~55%, Al 2 O} 3 9~20%, MgO 12~39%, TiO 2 8~14%, Y 2 O 3 0.1~8%, ZrO 2 1~5%, K 2 O0 .1～1%, the total amount of alkaline earth metal oxides other than MgO _{is 0~1%, SiO 2, Al 2} O 3, MgO, the total amount of TiO ₂ is 93% or more of the glass.

_{SiO 2 35~55%, Al 2 O} 3 9~20%, MgO 20~39%, TiO 2 8~14%, Y 2 O 3 0.1~3%, ZrO 2 1~5%, K 2 O0 .1～2%, the total amount of alkaline earth metal oxides other than MgO _{is 0~1%, SiO 2, Al 2} O 3, MgO, the total amount of TiO ₂ is 95% or more of the glass.

_{SiO 2 35~55%, Al 2 O} 3 9~20%, MgO 20~39%, TiO 2 8~14%, Y 2 O 3 0.1~3%, ZrO 2 1~5%, K 2 O0 Glass having 0.1 to 1%, total amount of alkaline earth metal oxides other than MgO of 0 to 1%, and total amount of SiO ₂ , Al ₂ O ₃ , MgO and TiO ₂ of 95% or more.

Further, in any case, those not containing Li ₂ O, ZnO, NiO, As ₂ O ₃ , PbO, and F are preferable. A more preferred composition is that the total amount of SiO ₂ , Al ₂ O ₃ , MgO, K ₂ O, ZrO ₂ , Y ₂ O ₃ , and TiO ₂ is 99% or more, particularly preferably 100 in any of the above composition ranges. %belongs to. A composition obtained by adding only Sb ₂ O ₃ as a defoaming clarifier to the more preferable composition is a more preferable composition.

[Method for producing crystallized glass substrate blank]
The method for producing a crystallized glass substrate blank of the present invention is characterized by slicing the crystallized glass body of the present invention perpendicularly to the central axis of a cylinder.

  As a method for slicing the crystallized glass body, a method using a slicing apparatus called a multi-wire saw is preferable. This device arranges each wire on the same plane so that a plurality of wires are parallel to each other and equidistant in a region where a glass molded body as a workpiece is sliced, and each wire rotates in its length direction. A plurality of rollers are applied so as to obtain, and the region is repeatedly traversed at a constant pitch. And in the area | region which slices the said glass molded object, the center axis | shaft of a glass molded object is positioned so that it may orthogonally cross in the length direction of a wire, and while moving a wire at the predetermined speed in the length direction, a crystallized glass body It is pressed against a predetermined position on the outer peripheral surface (side surface) and sliced. At this time, the position of the wire may be fixed and the crystallized glass body as the workpiece may be moved and sliced, or the crystallized glass body as the work may be fixed and the wire may be moved and sliced. Alternatively, both the wire and the workpiece may be moved and sliced.

  Slicing may be performed by immersing a crystallized glass body, which is a workpiece, in a slurry, or may be performed in a dry state.

  The moving speed of the wire may be determined in consideration of the size of the crystallized glass body, the size of the crystallized glass substrate blank, mechanical properties, and the like. As the multi-wire saw, a commercially available multi-wire saw processing machine may be used.

  The sliced disk-shaped crystallized glass body is washed to obtain a crystallized glass substrate blank. According to this method, a large number of crystallized glass substrate blanks can be produced in one slice.

  In order to further improve productivity, it is preferable to construct a laminated structure of crystallized glass bodies and slice this laminated structure. In the manufacturing method of the crystallized glass substrate blank of the present invention, since the laminated structure is constituted by the crystallized glass body of the present invention, it is possible to make the central axis of each crystallized glass body orthogonal to the wire with high accuracy. And a crystallized glass substrate blank with good parallelism and flatness of the main surface can be produced. In order to adhere the side surfaces of the crystallized glass bodies and obtain a laminated structure having a stable structure, it is preferable to use crystallized glass bodies having the same outer diameter.

  When the number of glass molded bodies forming the laminated structure is small, as shown in FIG. 8, it is preferable to form each layer with a certain number of crystallized glass bodies and to laminate each layer. By slicing such a laminated structure from a direction perpendicular to each layer, the crystallized glass bodies constituting the laminated structure can be cut simultaneously, and the cutting conditions such as the slicing speed can be kept constant. Stable slice processing becomes possible. In the embodiment shown in FIG. 8, the laminated structure is laminated so that the central axis of each glass molded body forms a square lattice when viewed from the central axis direction of the crystallized glass body constituting the laminated structure. Yes.

  On the other hand, when there are many crystallized glass bodies which form a laminated structure, it is preferable to reduce the number of crystallized glass bodies which comprise each layer as it laminates | stacks. In general, as the number of crystallized glass bodies increases, the stability of processing decreases, but by gradually reducing the number of crystallized glass bodies as described above, the center of gravity of the structure can be lowered. A stable laminated structure can be obtained. As a more preferred embodiment, the structure laminated so that the central axis of each crystallized glass body forms a lattice of equilateral triangles when viewed from the direction of the central axis of the crystallized glass body constituting the laminated structure. Can be mentioned. This structure is a close-packed structure of crystallized glass bodies when viewed from the same direction.

  In preparing the laminated structure, an epoxy adhesive is used, the crystallized glass bodies are brought into close contact with each other, and the laminated structure as a work is bound and fixed on a table. After slicing, the adhesive adhering to the sliced workpiece is dissolved and removed with an organic solvent, washed and dried to obtain a disk-shaped crystallized glass substrate blank.

  By the way, the main surface of the magnetic disk substrate is required to have high parallelism and high flatness, and in order to produce such a substrate by polishing, the crystallized glass body before polishing, that is, the main part of the crystallized glass substrate blank is used. The parallelism of the surface (thickness of the central part in the main surface, variation obtained by measuring the thickness at four or more parts equally selected in the peripheral part) and flatness are below a certain value. It is desirable. For this reason, in the manufacturing method of the crystallized glass substrate blank of this invention, the parallelism of the main surface of the crystallized glass substrate blank obtained is preferably 10 μm or less, more preferably 5 μm or less, further preferably 3 μm or less, and 1 μm or less. Is particularly preferred. The flatness of the main surface of the crystallized glass substrate blank is preferably 15 μm or less, more preferably 10 μm or less, further preferably 5 μm or less, particularly preferably 3 μm or less, and even more preferably 2 μm or less.

[Method of manufacturing magnetic disk substrate]
The method for producing a magnetic disk substrate of the present invention is characterized in that the main surface of the crystallized glass substrate blank produced by the method for producing a crystallized glass substrate blank of the present invention is polished.

  Here, the main surface is a surface having the largest area of the crystallized glass substrate blank, that is, an opposing flat surface having a circular shape.

  Polishing of the main surface can be performed by a known method using synthetic abrasive grains such as synthetic diamond, silicon carbide, aluminum oxide and boron carbide, and natural abrasive grains such as natural diamond and cerium oxide.

  Further, machining other than the main surface can be performed by known grinding, precision polishing, and inner / outer diameter machining.

  The substrate surface is preferably finished to a surface smoothness of 1 nm or less with an average roughness Ra (JIS B0601) measured with an atomic force microscope (AFM). The average surface roughness Ra (JIS B0601) greatly affects the recording density of the magnetic disk. If the surface average roughness exceeds 1 nm, it is difficult to achieve high recording density. Considering higher recording density, Ra is more preferably 0.7 nm or less, further preferably 0.5 nm or less, and particularly preferably 0.3 nm or less.

A magnetic disk substrate made of a crystallized glass body containing an enstatite crystal phase is useful as a magnetic disk substrate because of its high strength, high hardness, high Young's modulus, and excellent chemical durability and heat resistance. . Further, since the substrate is alkali-free or low-alkaline, or contains only K ₂ O as an alkali metal oxide, it is possible to greatly reduce the erosion of a film such as a magnetic recording film. Can keep the best.

  Since the magnetic disk substrate is strictly required to be clean, it is preferable to clean the substrate appropriately in the final process or in an intermediate process. At that time, it is preferable to perform ultrasonic cleaning in order to efficiently clean the substrate. The conditions for ultrasonic cleaning can be known conditions. In a crystallized glass substrate containing an enstatite crystal phase, the crystal particles on the substrate surface are not easily detached, and therefore, the crystal particles on the substrate surface are not detached from the substrate together with dirt by ultrasonic cleaning.

  Unlike a magnetic disk substrate made of amorphous glass, a magnetic disk substrate made of crystallized glass has sufficient mechanical strength without chemical strengthening, and thus has a feature that the thickness of the substrate can be reduced. Yes. The thickness of the magnetic disk substrate is preferably 0.4 mm or less, more preferably 0.3 mm or less, further preferably 0.28 mm or less, and particularly preferably 0.1 to 0.25 mm.

  The shape of the magnetic disk substrate is preferably a disk shape, and preferably has a circular hole for attachment to the recording device at the center. The outer diameter of the substrate is preferably 16 to 70 mm, more preferably 16 to 50 mm, still more preferably 16 to 30 mm, and particularly preferably 20 to 30 mm.

[Method of manufacturing magnetic disk]
The magnetic disk manufacturing method of the present invention is characterized in that a magnetic recording layer is formed on a magnetic disk substrate manufactured by the magnetic disk substrate manufacturing method of the present invention.

  Although the magnetic recording layer is also called a magnetic layer, the layers other than the magnetic layer include a base layer, a protective layer, a lubricating layer, and the like from the functional aspect, and are formed as necessary. Various thin film forming techniques such as sputtering can be used to form these layers.

  The material of the magnetic layer is not particularly limited, and examples of the magnetic layer include a Co-based material, a ferrite-based material, and an iron-rare earth-based material. The magnetic layer may be a magnetic layer used in either the horizontal magnetic recording method or the perpendicular magnetic recording method. Specific examples of the magnetic layer include magnetic thin films such as CoPt alloy, CoCr alloy, CoCrTa alloy, CoPtCr alloy, CoCrPtTa alloy, CoCrPtB alloy, and CoCrPtSiO alloy mainly composed of Co. Can do. Moreover, it is good also as a multilayer structure which divided | segmented the magnetic layer by the nonmagnetic layer and aimed at noise reduction.

  The material of the underlayer is selected according to the material of the magnetic layer. As the material of the underlayer, for example, at least one material selected from non-magnetic metals such as Cr, Mo, Ta, Ti, W, V, B, and Al, or oxides, nitrides, and carbides of these metals Etc. In the case of a magnetic layer containing Co as a main component, a Cr alloy is preferable from the viewpoint of improving magnetic characteristics. For example, a CrW alloy, a CrMo alloy, and a CrV alloy can be used. The underlayer is not limited to a single layer, and may have a multi-layer structure in which the same or different layers are stacked. Further, an unevenness control layer for preventing the magnetic head and the magnetic disk from adsorbing (head stiction) may be provided between the substrate and the magnetic layer or above the magnetic layer. By providing this unevenness control layer, the surface roughness of the magnetic disk is adjusted appropriately, so that the magnetic head and the magnetic disk are not attracted and a highly reliable magnetic disk can be obtained.

  Examples of the protective layer include a carbon protective layer. Various proposals have been made for the lubricating layer, but in general, perfluoropolyether, which is a liquid lubricant, is diluted with a freon-based solvent, and the surface of the medium is dipped, spin-coated, sprayed, etc. The method of apply | coating and forming by heat-processing as needed can be mentioned.

In consideration of the head stiction, the surface roughness of the magnetic disk is preferably the maximum surface roughness Rmax = 2 to 30 nm, and more preferably Rmax = 3 to 10 nm. When Rmax is less than 2 nm, the surface of the magnetic disk is almost flat, which is not preferable because the magnetic head and the magnetic disk are damaged or a head crash occurs. On the other hand, when Rmax exceeds 30 nm, the glide height (glide height) increases and the recording density is lowered, which is not preferable. A texturing process may be applied to the substrate surface.
In this way, the magnetic disk can be mass-produced with high productivity.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

Hereinafter, methods for measuring physical properties and the like in this example will be described.
[Transmittance at a wavelength of 600 nm (%)]
A sample with a thickness of 1 mm obtained by precision optical polishing of two opposed planes in parallel was used as a transmittance measurement sample, and the measurement apparatus measured the transmittance (%) at a measurement wavelength of 600 nm using a HITACHI spectrometer U-3410.

[Specific gravity (density)]
The glass sample itself was used as a sample for measuring specific gravity. As an apparatus, an electronic hydrometer (Mirage Trading Co., Ltd. MD-200S) using the Archimedes method was used. The measurement accuracy of specific gravity at room temperature is ± 0.001 (± 0.001 g / cm ³ in terms of density).

[Young's modulus (GPa), Poisson's ratio]
A parallel sample having an end area of 10 mm square to 20 mm square and a length of about 95 mm was used, and before measuring Young's modulus, specific gravity (density) measurement and sample length were measured with calipers, and these were used as measurement conditions. As the apparatus, UVM-2 manufactured by Ultrasonic Industry Co., Ltd. was used. When measuring the longitudinal wave (Tl1, Tl2) and the transverse wave (TS1, TS2), the depth touch medium is “water” in the case of the longitudinal wave and “Sonicoat SHN20 or SHN-B25” in the case of the transverse wave. It applied to a touch element and a sample end surface. The same sample was subjected to repeated measurements of 2 or more longitudinal waves and 5 or more transverse waves, and the average was calculated.
By this operation, Poisson's ratio can be obtained at the same time. The Young's modulus measurement accuracy is ± 1 GPa, and the Poisson's ratio measurement accuracy is ± 0.001.

(Crystal seed)
X-ray diffraction was measured for powdered glass after crystallization using Cu Kα rays (apparatus: X-ray diffractometer MXP18A manufactured by Mac Science, tube voltage: 50 kV, tube current: 300 mA, scanning angle 10 to 10). 90 °). The deposited crystals were identified from the obtained X-ray diffraction peaks.

[Crystallinity]
For the crystallized glass sample, the total scattering intensity of X-rays is measured, and from the result, the crystallinity x (%) can be obtained by the following equation. As the X-ray diffractometer, an X-ray diffractometer MXP18A manufactured by Mac Science was used.

x = (1- (Ia / Ia100)) × 100
x = (Ic / Ic100) × 100
Ia: Scattering intensity of amorphous part of unknown substance Ic: Scattering intensity of crystalline part of unknown substance Ia100: Scattering intensity of 100% amorphous sample Ic100: Scattering intensity of 100% crystalline sample 100% amorphous sample The scattering intensity distribution of is a broad spectrum, and the scattering intensity distribution of a 100% crystalline sample is a spectrum with a narrow line width. The scattering intensity distribution of crystallized glass has a shape in which a spectrum having a narrow line width is superimposed on the broad spectrum. Ia is the scattering intensity corresponding to the height of the broadest portion of the broad spectrum with reference to the horizontal line connecting the base portions of the spectrum. Each scattering intensity is a value calculated using a horizontal line connecting the bottom of the spectrum as a baseline.

[Specific elastic modulus (MN · m / kg)]
From the Young's modulus and the density at room temperature, the specific elastic modulus was calculated by the formula: Young's modulus / density.

[Average linear expansion coefficient (× 10 ⁻⁷ / ° C.]]
It was measured by thermomechanical measurement (Thermal Mechanical Analysis: TMA for short).
A glass sample was cut out and ground into a cylindrical shape of φ50 mm × 20 mm to obtain a sample for TMA measurement. As a measuring device, TAS100 manufactured by Rigaku Corporation was used. The measurement conditions were a temperature increase rate of 4 ° C./min and a maximum temperature of 350 ° C., and an average linear expansion coefficient at 100 to 300 ° C. was measured.
In addition, the thermal characteristics other than the average linear expansion coefficient were obtained by cutting a test piece from the crystallized glass sample after crystallization, grinding it into a cylindrical shape of φ5 mm × 20 mm, and using the above TAS100 manufactured by Rigaku Corporation. Measurements were made at a rate of 4 ° C / min and a maximum temperature of 350 ° C.

[Surface average roughness (Ra), maximum surface roughness (Rmax)]
The measurement was performed using an atomic force microscope (AFM for short).
A crystallized glass sample was processed to 30 × 25 × 1 mm, and two planes of 30 × 15 mm were precisely optically polished to obtain a sample for atomic force microscope measurement. As the apparatus, NanoScope III manufactured by Digital Instrument was used. The measurement conditions were a tapping mode AFM, a measurement range of 2 × 2 μm or 5 × 5 μm, a sample number of 256 × 256, a scan rate of 1 Hz, data processing conditions, Planefit Auto order 3 (X, Y), and Flatten Auto order 3 . Integral gain, Proportion gain, and Set point were adjusted for each measurement. As a pretreatment for the measurement, the polished sample was washed with pure water, isopropyl alcohol, or the like with a large-scale washer in a clean room.

[Crystal particle size and crystal particle major axis / minor axis ratio]
The crystal particles in the crystallized glass were magnified using a transmission electron microscope (TEM), and the length of the longest part of the crystal particles was taken as the major axis and the length of the shortest part was taken as the minor axis from the enlarged image.
The size of the crystal particles was measured as described above. Note that the transmission electron microscope was observed from a direction perpendicular to the polished surface, using a thin plate sample whose surface was precisely polished so that a good enlarged image was obtained.

Example 1 (Production Example of Crystallized Glass Body)
As starting materials, SiO ₂ , Al ₂ O ₃ , Al (OH) ₃ , MgO, Y ₂ O ₃ , TiO ₂ , ZrO ₂ , KNO are used so that the base glass having the composition shown in Table 1 and Table 2 can be obtained. ₃ , Sr (NO ₃ ) _{2 and the} like were weighed in a total of 250 to 300 g. Although not shown in the table, 0.03 mol% of Sb ₂ O ₃ was added to all the glasses as an external percentage. The weighed raw materials were sufficiently mixed to form a preparation batch, which was put into a melting vessel, and the glass was melted in air for 4 to 5 hours while stirring at 1550 ° C.

  As shown in FIG. 1, the molten glass in the melting vessel is continuously fed from the pipe 1 connected to the melting vessel to the casting port of the mold 3 made of a heat-resistant material provided with a straight through hole. The molten glass 2 was filled in the through hole and molded. In addition, the positions of the pipe 1 and the mold 3 were adjusted so that the central axis of the through hole was vertical, and the central axis of the through hole and the central axis of the pipe 1 were aligned.

  As shown in FIG. 1, a molten glass 2 is continuously discharged from a pipe 1 connected to a melting vessel at a constant flow rate, and continuously cast into a casting port of a heat-resistant mold 3 provided with a through hole. The molten glass 2 was filled in the through-holes and molded. The temperature of the molten glass flowing out from the pipe 1 was adjusted within a temperature range in which devitrification does not occur. Further, the mold 3 was arranged so that the central axis of the through-hole was vertical and the central axis of the through-hole and the central axis of the pipe 1 coincided.

  The molded glass molded body 4 was taken out from the outlet of the mold 3 at a constant speed. The glass molded body 4 was taken out by holding the side surface 6 of the glass molded body with a plurality of pairs of rollers 5 and controlling the rotational speed of the rollers 5. The rotational speed of the roller 5 is obtained by monitoring the molten glass liquid level in the through hole of the mold 3 by the optical method with the liquid level sensor 8 and outputting a speed adjustment signal from the controller 9 to the roller 5 based on the monitor signal. The liquid level was controlled to be constant.

  As shown in FIG. 1, the glass molded body 4 taken out from the take-out port is placed in the lower part of the mold 3 and passes through a molding furnace 7 set in a temperature range near the glass transition temperature. The temperature difference between the outer surface and the center of the molded body 4 was adjusted to prevent the glass molded body 4 from being damaged.

  As shown in FIG. 3, the glass molded body that has passed through the molding furnace is marked with a scribing line by scribing at a predetermined position on the side surface before being completely cooled, and the scribing is performed with the position facing the scribing position as a fulcrum. By pressing the lower part of the processing position in the horizontal direction, torque was applied to the glass molded body around the fulcrum, and this was cleaved (see FIG. 4). At that time, as shown in FIG. 5, a water-cooled jacket may be pressed against the scribe processing site, a crack may be generated from the scribe processing site toward the fulcrum, and cleaved with a small torque.

  By the cleaving, the columnar glass molded body separated from the glass molded body being pulled out was annealed to remove strain.

  Next, the side surface of the cylindrical glass molded body was precisely processed by centerless processing. In addition, since the process of a cylindrical side surface may be performed after crystallization, the centerless process of the said cylindrical glass molded object can also be abbreviate | omitted.

  The glass molded body subjected to the centerless processing is placed between the rollers made of silicon nitride arranged in parallel in the heat treatment furnace so that the axis of the roller and the central axis of the glass molded body are parallel, and the roller is mounted. The glass molded body was heat-treated while rotating.

  In the heat treatment, the temperature is increased at a temperature increase rate of 300 ° C./hour (first temperature increase rate) to the primary heat treatment temperature (crystal nucleation heat treatment temperature) shown in Tables 1 and 2, and the temperature is 4 The first heat treatment was performed for about an hour. Immediately after the completion of the first heat treatment, a temperature increase rate of 240 ° C./hour (second temperature increase) from the first heat treatment temperature to the second heat treatment temperature (crystallization heat treatment temperature) shown in Tables 1 and 2 The crystallized glass body was fabricated by cooling to room temperature in the furnace after raising the temperature at (temperature) and maintaining the secondary heat treatment temperature for about 4 hours. Measurement results such as Young's modulus and specific gravity of the crystallized glass constituting the obtained crystallized glass body are shown in Tables 1 and 2 together with the glass composition. The crystallinity of the crystallized glass was 20 to 70% by volume, and enstatite, which is a crystal particle in the crystallized glass, and its solid solution had a Mohs hardness of 5.5.

  Furthermore, as a result of analyzing the composition of each crystallized glass, the difference in composition between the base glass and the crystallized glass was within ± 0.1 mol%. Therefore, the base glass compositions shown in Tables 1 and 2 may be considered to be substantially the same as the crystallized glass composition.

[note]
(1) The first temperature increase rate is a temperature increase rate when the temperature is raised to the crystal nucleation heat treatment temperature, and the second temperature increase rate is when the temperature is raised from the crystal nucleation heat treatment temperature to the crystallization heat treatment temperature. Shows the speed.
(2) Enstatite in the table indicates enstatite and a solid solution of enstatite.
(3) The glass transition temperature in the table indicates the glass transition temperature of the crystallized glass.

  As is clear from the results shown in Tables 1 and 2, each crystallized glass had a major axis / minor axis ratio of 3 or more of crystal particles. In addition, strength properties such as Young's modulus (140 GPa or more) and specific modulus (in the range of 40 to 60 MN · m / kg) are large. Therefore, it can be seen that when these glasses are used for substrates for information recording media such as magnetic disk substrates, even if these substrates rotate at a high speed, the substrates are less likely to warp or shake and can be made thinner. . No. 1, no. 3 and no. When the liquid phase temperature of the glass before heat treatment of No. 5 was measured, it was 1300 ° C., 1290 ° C., and 1270 ° C., respectively, satisfying the liquid phase temperature (for example, 1350 ° C. or less) required from the viewpoint of glass melting and forming It was something to do.

  Next, the rod-like crystallized glass body is centerless processed to obtain 25 cylindrical crystallized glass bodies having an outer diameter of 28.8 mm, an outer diameter tolerance within ± 0.050 mm, a length of 180 mm, and a straightness of 0.005 mm. Got.

Example 2 (Production Example of Crystallized Glass Substrate Blank, Magnetic Disk Substrate, and Magnetic Disk)
As shown in FIG. 8, when the columnar crystallized glass body produced in Example 1 is viewed from the central axis direction of each columnar crystallized glass body while aligning the longitudinal direction of each columnar crystallized glass body In addition, five cylinders were stacked per layer so that each central axis formed a square lattice to obtain a laminated structure. Each crystallized glass body constituting the laminated structure was fixed in a state where the side surfaces were in close contact with each other on a work fixing base of a commercially available multi-wire saw processing machine using an epoxy adhesive.

  And the said laminated structure was brought close from the underside of the wire saw in drive, the side surface was pressed against the wire saw, and it sliced at fixed speed. Slicing was performed in the slurry, and the interval between the wires was 0.5 mm.

  The cut workpiece was put in an organic solvent to dissolve the adhesive, and then ultrasonic cleaning was performed to obtain about 5400 disc-shaped crystallized glass having the same diameter and the same thickness. These disk-shaped crystallized glasses are used as crystallized glass substrate blanks, and both main surfaces are precision polished so that the average surface roughness Ra (JIS B0601) is 0.4 nm and the maximum surface roughness Rmax is 4 nm. Diameter processing was performed to obtain a magnetic disk substrate made of crystallized glass. The outer diameter of the magnetic disk substrate is 28.70 mm, the center hole diameter is 7 mm, and the thickness is 0.381 mm.

  In addition, although the process of ultrasonically washing a board | substrate was added suitably, a crystal particle did not detach | leave from the surface of the board | substrate which consists of crystallized glass containing an enstatite type crystal phase by ultrasonic application. In this step, the frequency of the ultrasonic wave was 20 kHz.

  On the magnetic disk substrate thus obtained, an underlayer, a magnetic layer (magnetic recording layer), a protective layer, and a lubricating layer were sequentially formed to produce a magnetic disk. Specifically, each layer is a CrV thin film with a thickness of 25 nm, and the composition ratio is Cr: 80 at% and V: 20 at%. The magnetic layer is a CoCrPtB thin film with a thickness of about 15 nm, and the composition ratio is Co: 60 at%, Cr: 20 at%, Pt: 14 at%, and B: 6 at%. The protective layer is a hydrogenated carbon thin film having a thickness of 6 nm. The lubricating layer is made of perfluoropolyether.

In manufacturing the magnetic disk, first, the magnetic disk substrate is set on a substrate holder, and then sent to a preparation chamber of a stationary opposed type device. Then, an underlayer, a magnetic layer, and a protective layer are sequentially formed using an Ar-based gas. The film was formed by DC magnetron sputtering. Here, in forming the protective layer, Ar + H ₂ gas in which 20% of hydrogen was mixed with Ar gas was used. Thereafter, a perfluoropolyether was applied to the surface of the hydrogenated carbon protective layer by a dipping method to form a lubricating layer having a thickness of 1.0 nm to obtain a magnetic recording medium.

  When the magnetic recording medium was incorporated in a recording apparatus and an operation test was conducted, good results were obtained as shown in Tables 1 and 2.

  As described above, magnetic disk substrates and magnetic disks could be produced with high productivity.

  According to the present invention, it is possible to obtain a crystallized glass body having a cylindrical shape capable of simultaneously slicing with high accuracy when a plurality of the same are stacked in the longitudinal direction. Thus, a crystallized glass substrate blank, a magnetic disk substrate, and a magnetic disk can be suitably produced.

It is a figure which shows an example of the manufacturing apparatus of a glass molded object. It is a figure which shows an example of the manufacturing apparatus of a glass molded object. It is a figure which shows an example of the cleaving method of a glass molded object. It is a figure which shows an example of the cleaving method of a glass molded object. It is a figure which shows an example of the cleaving method of a glass molded object. It is a figure which shows an example of the cleaving method of a glass molded object. It is a figure which shows an example of the cleaving method of a glass molded object. It is a figure which shows an example of the method of stacking and slicing a plurality of columnar glass with the longitudinal direction aligned.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pipe 2 Molten glass 3 Mold 4 Glass molded body 5 Roller 6 Side surface of glass molded body 7 Molding furnace 8 Liquid level sensor 9 Controller 10 Support mechanism 12 High pressure vessel 13 Liquid inlet

Claims (10)

Obtained by heat-treating a glass molded body,
Length L [mm], the following outer diameter tolerance ± 0.2 mm, the straightness of ^{5 × 10 -5 × L [mm} ] crystallized glass body, comprising the following cylindrical.   The crystallized glass body according to claim 1, comprising enstatite and / or enstatite solid solution as a crystal phase.   The crystallized glass body according to claim 1 or 2, wherein the length L [mm] is 100 mm or more and the outer diameter is 16 to 70 mm.   The crystallized glass body according to any one of claims 1 to 3, wherein an average roughness Ra of the outer peripheral surface is 0.3 µm or less.   The crystallized glass body according to any one of claims 1 to 4, which is a base material of a magnetic disk substrate.   A method for producing a crystallized glass body, characterized in that a cylindrical glass molded body is held while rotating in the circumferential direction about a cylinder central axis, and heated and crystallized.   The method for producing a crystallized glass body according to claim 6, wherein the crystallized glass body obtained is the crystallized glass body according to any one of claims 1 to 5.   A method for producing a crystallized glass substrate blank, comprising slicing the crystallized glass body according to any one of claims 1 to 5 perpendicularly to a central axis of a cylinder.   A method for producing a magnetic disk substrate, comprising polishing a main surface of a crystallized glass substrate blank produced by the method according to claim 8.   A method for manufacturing a magnetic disk, comprising forming a magnetic recording layer on a magnetic disk substrate manufactured by the method according to claim 9.

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