JP2006347791A - Crystallized layer-stacked glass, and glass substrate for magnetic disk using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide crystallized layer-stacked glass in which a crystallized layer is stacked at least on a part of the surface in a glass base material, to provide crystallized layer-stacked glass in which the thickness of at least a part of a crystallized layer-stacked on the surface of a glass base material is different from that of the other part, to provide a glass substrate for a magnetic disk using crystallized layer-stacked glass, and to provide a glass substrate for a magnetic disk in which at least a part of the region in the edge face is provided with a crystallized layer. <P>SOLUTION: A starting raw material to be the preform of glass and, as necessary, a prescribed amount of additive are weighed with an electronic balance so as to be mixed. The mixture is melted by a crucible, and is cooled to be formed into glass. The glass is reheated so as to stack a crystallized layer on the surface of the glass, and the main surface is partially polished, thus the crystallized layer-stacked glass is produced. Using the same, e.g., a glass substrate for a magnetic disk is produced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides a crystallized layer laminated glass in which a crystallized layer is laminated on at least a part of the surface of a glass substrate, and a thickness of at least a part of the crystallized layer laminated on the surface of the glass substrate is different from that of the other part. Relates to a different crystallized layer laminated glass, a glass substrate for a magnetic disk using the crystallized layer laminated glass, and a glass substrate for a magnetic disk having a crystallized layer in at least a part of the end face portion.

  In recent years, it has been studied to apply a glass substrate to an electronic device or an electronic component by applying a tempering treatment or the like, and it has been proposed to be used for a magnetic disk substrate. Patent Document 1 discloses a method of forming a chemically strengthened layer on a glass substrate by a chemical strengthening method.

JP 2000-207730 A

  The present invention provides a crystallized layer laminated glass in which a crystallized layer is laminated on at least a part of the surface of a glass substrate, and a thickness of at least a part of the crystallized layer laminated on the surface of the glass substrate is different from that of the other part. And a glass substrate for a magnetic disk using the crystallized layer laminated glass, and a glass substrate for a magnetic disk having a crystallized layer in at least a part of the end surface portion. To do.

  As a first means for solving the above problems, the crystallized layer laminated glass of the present invention has a structure in which a crystallized layer is laminated on at least a part of the surface of a glass substrate. Or the thickness of at least one part of the crystallization layer laminated | stacked on the surface of the glass base material was set as the structure different from another part.

  As a second means for solving the above problems, the glass substrate for a magnetic disk of the present invention has a configuration using a crystallized layer laminated glass. Or it was set as the structure which has a crystallization layer in at least one part of the end surface part of the glass substrate for magnetic discs using crystallization layer laminated glass.

  As described below, the crystallized layer-laminated glass of the present invention can be obtained by laminating a crystallized layer on at least a part of the surface of a glass substrate or laminating a crystallized layer having a thickness different from that of other parts. In addition, it is possible to efficiently stack the crystallized layer on a tangential cross-sectional portion having a non-planar shape such as unevenness or a through hole. The crystallized layer laminated glass of the present invention is suitable as a glass substrate for a magnetic disk, and is useful as a magnetic disk substrate having excellent mechanical strength and the like by laminating a crystallized layer on a disk end surface portion.

Hereinafter, embodiments of the present invention will be described. There are many types of glass, and an appropriate base material may be selected depending on the application, and the glass is not necessarily limited to the following explanation examples. There are many types of crystallized layers to be formed on the glass surface, which may be selected appropriately depending on the application, and are not necessarily limited to the following explanation examples. Here, a case where lithium aluminosilicate glass (Li ₂ O—Al ₂ O ₃ —SiO ₂ ) which is one form of oxide glass is used as the glass base material will be described as an example.

First, as a starting material to be a glass base material, a predetermined amount of each powder of lithium carbonate (Li ₂ CO ₃ ), aluminum oxide (Al ₂ O ₃ ), and silicon dioxide (SiO ₂ ) (for example, on an oxide weight basis, respectively) 15 wt%, 20 wt%, 65 wt%) were measured with an electronic balance and placed in an alumina mortar. Here, lithium carbonate gives glass component Li ₂ O. Further, as an additive, for example, cuprous oxide (Cu ₂ O) powder is measured with an electronic balance so as to be a predetermined amount (for example, 1% by weight of the glass base material), and is put in the mortar described above. Stir well and mix. Additives can be appropriately selected and added as necessary. Then, it moved to the platinum crucible, put into the heating apparatus, heated in air atmosphere (1450 ° C. for 1 hour) to melt, and then cooled to room temperature. The glass at this time was a blue transparent glass up to the inside.

Copper ions in the glass becomes Cu ⁺ in colorless and transparent, to become blue in Cu ²⁺ transparent, so that it contains copper ions of at least Cu ²⁺ in the glass. However, it cannot be said that all of the added cuprous oxide has changed to Cu ²⁺ , and it is considered that Cu ⁺ is also contained. In the above example, for simplification, the heat treatment is performed in an air atmosphere, but this is a heat treatment in an oxidizing atmosphere. In addition, it can be performed in a reducing atmosphere, a non-oxidizing atmosphere, or an inert atmosphere (for example, H ₂ , N ₂ , ammonia decomposition gas, vacuum, etc.), and may be appropriately selected depending on the application. In the case of heat treatment other than in an oxidizing atmosphere, more Cu ⁺ remains in the glass. In particular, when performed in a reducing atmosphere, most of the added cuprous oxide is considered to remain as Cu ^{+ in the} glass.

Next, the above glass was reheated at a temperature higher than the crystallization start temperature and in an air atmosphere to form a black thin film on the glass surface. The reheating temperature is preferably in the range of 500 to 1000 ° C. More desirably, it is the range of 560-600 degreeC. When the temperature is lower than 500 ° C., crystallization does not occur. Conversely, when the temperature exceeds 1000 ° C., the thickness of the crystallized layer is not uniform depending on the portion of the glass. When the glass surface reheated under such conditions is analyzed by thin film XRD (Thin Film X-ray Diffraction), the appearance of CuO peak and the appearance of β-eucryptite (LiAlSiO ₄ ) peak I was able to confirm. Furthermore, when this black thin film was removed and analyzed by thin film XRD, the appearance of a peak mainly composed of β-eucryptite (LiAlSiO ₄ ) could be confirmed. The removal of the black thin film may be mechanical removal such as polishing, or may be performed by immersing in hydrochloric acid (1 mol / l) at room temperature for about 10 minutes.

In this way, a crystallization layer can be provided on the glass surface. The thickness of the crystallized layer is preferably 50 to 150 μm. More desirably, the thickness is 80 to 100 μm. If the thickness is less than 50 μm, there is no effect on impact resistance, and if it exceeds 150 μm, the effect on impact resistance is saturated, which is not economical. In addition, when the cross section of glass is analyzed by thin film XRD, the appearance of the above-mentioned β-eucryptite (LiAlSiO ₄ ) peak cannot be confirmed, and it is understood that crystallization has not occurred. That is, the crystallized layer can be laminated only on the surface layer. By crystallizing this crystallized layer laminated glass with mechanical polishing or chemical polishing using hydrofluoric acid, the crystallized layer has a crystallized layer at a desired site or a crystallized layer with a different thickness compared to other sites. A laminated glass can be produced.

Glass includes oxide glass and non-oxide glass. The oxide glass is a glass in which a small amount of an oxide glass or a substance other than an oxide such as a nitride is added. The oxide glass is composed of an oxide and contains SiO ₂ , B ₂ O ₃ , P ₂ O ₅ , GeO ₂ , TeO _2, etc., or a combination thereof as a main component. For example, the glass mainly composed of SiO ₂ includes silica glass, soda lime glass, potassium glass, lead crystal glass, borosilicate glass, aluminosilicate glass, and lithium aluminosilicate glass. Note that the optical fiber is also a form of oxide glass. Examples of oxides other than the above include Li ₂ O, Na ₂ O, MgO, K ₂ O, CaO, BaO, Al ₂ O ₃ , ZnO, and PbO.

The non-oxide glass is a non-oxide glass or, if necessary, a small amount of additives such as oxides and nitrides. Non-oxide glasses include chalcogenide glasses made from chalcogenides (sulfur, selenium, and tellurium compounds) and halide glasses made from halides (fluorine, chlorine, bromine compounds). The chalcogenide glass is mainly composed of As ₂ S ₃ , GeS ₂ , AsSe _{3 and the} like, and the halide glass is mainly composed of a plurality of components such as ZrF ₄ , BaF ₂ and AlF ₃ .

Examples of additives include various oxides such as B ₂ O ₃ , Na ₂ O, K ₂ O, CaO, MgO, ZnO, TiO ₂ , ZrO ₂ , V ₂ O ₅ , Nb ₂ O ₅ , La ₂ O. ₃ , Cr ₂ O ₃ , CoO, Co ₃ O ₄ , NiO, CuO, CeO ₂ , Nd ₂ O ₃ , Er ₂ O ₃ , and a mixture thereof can be used. In addition to oxides, nitrides may be used.

  As described above, the crystallized layer laminated glass could be produced. This crystallized layer laminated glass can be used as a component such as a substrate material. For example, a glass substrate for a magnetic disk for use in a hard disk. In hard disk applications, cracks are likely to form on the outer and inner end surfaces of the magnetic disk glass substrate, which is useful for protecting this part. In addition, the crystallized layer can be efficiently stacked even on a tangible cross-sectional shape having a non-planar shape such as an unevenness or a through hole.

Lithium carbonate (Li ₂ CO ₃ ), aluminum oxide (Al ₂ O ₃ ), and silicon dioxide (SiO ₂ ) as starting materials to be used as glass base materials are 15% by weight, 20% by weight, and 65% by weight, respectively, based on oxide weight. %, Measured with an electronic balance and put in an alumina mortar. As an additive, cuprous oxide (Cu ₂ O) was measured with an electronic balance so as to be 1% by weight of the glass base material. The mixture was stirred well with a pestle and mixed. Thereafter, the glass was transferred to a platinum crucible, placed in a heating device, heated in air (1450 ° C. for 1 hour), melted and placed in a mold, and then cooled to room temperature to produce a glass for disk use. Next, the glass was reheated in the air atmosphere (at 560 ° C. for 3 hours) to form a crystallized layer of 100 μm on the glass surface. Thereafter, the main surface other than the end face was polished to partially remove the crystallized layer, thereby producing a glass substrate for magnetic disk.

By adding cuprous oxide or the like, it is possible to provide a glass substrate for a magnetic disk having an improved impact resistance by providing a crystallized layer on the glass surface.

Claims (4)

A crystallized layer-laminated glass, characterized in that a crystallized layer is laminated on at least a part of the surface of a glass substrate. The crystallized layer laminated glass according to claim 1, wherein the thickness of at least a part of the crystallized layer laminated on the surface of the glass substrate is different from that of the other part. A glass substrate for a magnetic disk, wherein the crystallized layer laminated glass according to claim 1 or 2 is used. 4. The glass substrate for a magnetic disk according to claim 3, wherein a crystallized layer is provided on at least a part of the inner peripheral part or the outer peripheral part.