JP4442051B2 - Glass substrate, information recording medium using the same, and optical communication element - Google Patents

Description

【００４７】
【表２】

【００４８】
表１によれば、実施例１〜９のガラス基板では、ヤング率及び、値が高いほど振動に強いとされる比弾性率は、いずれも実用上まったく問題のないレベルであった。また、線熱膨張係数は８０〜９１×１０^-7／℃の範囲と、従来のガラス基板に比べ大きい値となった。さらに、アルカリ溶出量は１．５μｇ／ｃｍ²以下と従来のガラス基板に比べ少なかった。一方、ガラスの溶融性についても問題のないレベルであった。
【００４９】
【表３】

【００５０】
表２によれば、比較例１のガラス基板では、ＳｉＯ₂の含有量が５３．２％と少ないためガラスの構造が軟弱となりアルカリ溶出量が増加した。一方、ＳｉＯ₂の含有量が７７．１％と多い比較例２のガラス基板では、ガラスの溶融性が悪くなると共に、化学的耐久性を向上させるガラス成分の含有量が相対的に少なくなるのでアルカリ溶出量が増加した。比較例３のガラス基板では、ガラスの溶融性を改善し、化学的耐久性を向上させるＢ₂Ｏ₃を含有しないので、アルカリ溶出量が多かった。またＢ₂Ｏ₃を１１．３％と多く含有する比較例４のガラス基板でも、同様にアルカリ溶出量が多かった。Ａｌ₂Ｏ₃の含有量が０．８％と少ない比較例５のガラス基板ではアルカリ溶出量が多かった。逆にＡｌ₂Ｏ₃の含有量が１７．８％と多い比較例６のガラス基板では、アルカリ溶出量は他の比較例のものに比べて少なかったものの、ガラスの溶融性が悪かった。
【００５１】
Ｌｉ₂Ｏを含有しない比較例７のガラス基板ではアルカリ溶出量が多くなる一方、Ｌｉ₂Ｏを１５．５％と多量に含有した比較例８のガラス基板では、線熱膨張係数が充分には大きくならず、しかもアルカリ溶出量が多かった。また、Ｌｉ₂Ｏを含有せず、且つＮａ₂Ｏを１７．０％と多量に含有した比較例９のガラス基板では、アルカリ溶出量が多かった。さらにＫ₂Ｏを１３．４％と多量に含有した比較例１０ガラス基板では線熱膨張係数が小さく、またアルカリ溶出量も多かった。Ｌｉ₂Ｏを含有せず、且つアルカリ金属酸化物の総含有量が１４．０％と少ない比較例１１のガラス基板では、アルカリ溶出量が少なかったものの線熱膨張係数が充分ではなく、またガラスの溶融性も悪かった。逆に、アルカリ金属酸化物の総含有量が２５．５％と多かった比較例１２のガラス基板では、アルカリ溶出量が多かった。
【００５２】
ＣａＯの含有量が６．４％と多い比較例１３のガラス基板では、線熱膨張係数が小さく、またアルカリ溶出量が多かった。Ｔａ₂Ｏ₅の含有量が３．０％と多い比較例１４のガラス基板では、ガラスの溶融性が悪くなるとともに、アルカリ溶出量が多かった。化学強化した比較例１５のガラス基板ではアルカリ溶出量が多かった。
【００５３】
【発明の効果】
本発明に係るガラス基板では、特定のガラス組成を有する構成としたので、線熱膨張係数が高く且つアルカリ成分の溶出は少なく、加えて作製コストを抑えることができる。
【００５５】
本発明に係る情報記録用媒体では、基板として前記ガラス基板を用いる構成としたので、耐久性に優れ、高い記録密度が得られる。
【００５６】
また本発明に係る光通信用素子では、基板として前記ガラス基板を用いる構成としたので、経時変化が少なく、温度・湿度の変化による波長シフトを抑制できる。
【図面の簡単な説明】
【図１】 本発明の情報記録用媒体の一例を示す斜視図である。
【符号の説明】
１ ガラス基板
２ 磁性膜
Ｄ 磁気ディスク[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a glass substrate, and more particularly to a glass substrate used as a substrate for information recording media, optical communication elements, and the like.
[0002]
[Prior art]
Conventionally, an aluminum alloy has been widely used as a magnetic disk substrate, but the aluminum alloy is easily deformed and its hardness is insufficient, so that the smoothness of the substrate surface after polishing cannot be said to be sufficient. In addition, when the head mechanically contacts the magnetic disk, there is a problem that the magnetic film is easily peeled off from the substrate. Therefore, development of a glass substrate with little deformation, good smoothness, and high mechanical strength is underway.
[0003]
Glass substrates include chemically strengthened glass with improved mechanical strength by replacing alkali elements on the substrate surface with other alkali elements, and crystallization with fine crystalline particles deposited in amorphous glass. Glass has been developed. However, in chemically strengthened glass, alkali ions on the surface of the substrate move to the surface during the heating process when the magnetic film is formed and are eluted, or the magnetic film is eroded and the adhesion strength of the magnetic film is deteriorated. There was a problem to do. Further, in the crystallized glass, the unevenness after polishing of the substrate surface is large and the smoothness cannot be said to be sufficient due to the difference in wear between the produced microcrystalline particles and the amorphous glass. In addition, any of the above glasses requires a post-treatment process such as a chemical strengthening treatment step or a crystallization step, so that it is difficult to reduce costs.
[0004]
On the other hand, a glass substrate not subjected to chemical strengthening or crystallization strengthening treatment can be reduced in cost, but the linear thermal expansion coefficient is generally about 60 to 70 × 10 ⁻⁷ / ° C. The difference between the coefficient of linear thermal expansion (about 100 to 120 × 10 ⁻⁷ / ° C.) of the clamp and the spindle motor member is large, and a problem sometimes occurs when the recording medium is attached to the recording apparatus or information is recorded.
[0005]
In addition, although a glass substrate is used as a substrate in an optical communication element such as an optical filter or an optical switch, the element may be deteriorated by an alkali component eluted from the glass substrate. In addition, as the density of the film formed on the glass substrate increases, the wavelength shift due to changes in temperature and humidity is suppressed, but there is a limit to the density of the film that can be formed by the conventionally widely used vacuum deposition method. .
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a low-cost glass substrate having a linear thermal expansion coefficient close to that of a motor member and less alkaline component elution. It is what.
[0007]
Another object of the present invention is to provide an information recording medium having excellent durability and high recording density.
[0008]
Furthermore, another object of the present invention is to provide an optical communication element that has little change with time and suppresses wavelength shift due to changes in temperature and humidity.
[0009]
[Means for Solving the Problems]
In order to achieve the object, in the glass substrate of the present invention, the linear thermal expansion coefficient is in the range of 80 to 120 × 10 ⁻⁷ / ° C., and the alkali elution amount is in the range of 0.7 to 1.5 μg / cm ² . The composition of the surface and the interior was uniform. In addition, that the composition of the surface and the inside is homogeneous means that the reinforcing treatment is not performed. Hereinafter, “%” means “mol%” unless otherwise specified.
[0010]
Here, the linear thermal expansion coefficient is a value measured using a differential expansion measuring device under conditions of load: 5 g, temperature range: 25 to 100 ° C., temperature increase rate: 5 ° C./min. The alkali elution amount is a value calculated by immersing the sample glass in 50 ml of reverse osmosis membrane water at 80 ° C. for 24 hours and then analyzing the eluate with an ICP emission spectroscopic analyzer. In addition, in order to make it an acceleration test, the surface of the sample glass to be measured was polished with a # 600 abrasive to make the surface rough beforehand. There is a correlation between the alkali elution amount by this measurement method and the alkali elution amount by the alkali elution test of JIS R 3502, and the elution amount 0.7 to 1.5 μg / cm ² by this measurement method is the alkali elution amount of JIS R 3502. This roughly corresponds to an alkali elution amount of 0.2 to 0.3 mg according to the test.
[0011]
The glass substrate of the present invention for achieving the above object, in _{mol%, SiO 2: 55.0~75.0%} , B 2 O 3: 1.0~ 5.1%, Al 2 O 3: 3 0.0 to 16.0%, Li ₂ O: 5.0 to 15.0%, Na ₂ O: 14.0% or less, K ₂ O: 12.0% or less, Li ₂ O + Na ₂ O + K ₂ O: 16 _{.0~25.0%, T a 2 O 5} : have a 0.001 to 2.0 percent of the glass _{composition, P 2 O 5, RO (} R is Ca, Mg, Ba, Sr, Zn, and Pb Selected metal) and further does not contain Fe, Mn, Ce, Ti, V, Cr, Co, Ni, Ag, Sn, Cu, Zn, Te, Er, Nd and Pb metal components . .
[0013]
According to the invention, there is provided an information recording medium characterized in that an information recording layer is formed directly or via another layer on the surface of the glass substrate described above. Moreover, an optical communication element characterized by using the glass substrate as described above as a substrate is provided.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
When a glass contains a large amount of an alkali component, the coefficient of linear thermal expansion increases, but the amount of alkali elution increases simultaneously. Therefore, it has been difficult to increase the coefficient of linear thermal expansion and reduce the amount of alkali elution. However, as a result of repeated studies by the present inventors, when each content and total content of a specific alkali metal oxide are within a specific range, the linear thermal expansion coefficient can be increased and at the same time the alkali elution amount can be suppressed. In addition, we obtained the knowledge that adding a specific amount of Al ₂ O ₃ , B ₂ O ₃ and Ta ₂ O ₅ improves the chemical durability and further suppresses the alkali elution amount. Invented the invention.
[0015]
Hereinafter, the reason why the components of the glass substrate of the present invention are limited will be described. First, SiO ₂ is an essential component for forming glass. If the content is less than 55.0%, the glass structure becomes weak and the alkali elution amount increases. On the other hand, if the content exceeds 75.0%, the meltability of the glass is poor. Moreover, since the content of the glass component that improves chemical durability is relatively reduced, the amount of alkali elution increases. Therefore, the content was determined to be in the range of 55.0-75.0%. A more preferable range is 60.0 to 68.0%.
[0016]
B ₂ O ₃ has the effect of improving the melting property of the glass and improving the chemical durability. If the content is less than 1.0%, such an effect cannot be obtained, and the alkali elution amount increases. On the other hand, even if the content exceeds 10.0%, the chemical durability is lowered and the alkali elution amount is increased. Therefore, the content is determined to be in the range of 1.0 to 10.0%. A more preferable range is 4.0 to 5.1 %.
[0017]
Al ₂ O ₃ has the effect of improving the chemical durability of the glass. If the content is less than 3.0%, such an effect cannot be obtained and the alkali elution amount increases. On the other hand, if the content exceeds 16.0%, the meltability of the glass becomes worse. Therefore, the content is determined to be in the range of 3.0 to 16.0%. A more preferable range is 5.0 to 11.0%.
[0018]
Alkali metal oxides of Li ₂ O, Na ₂ O, and K ₂ O all have the effect of improving the meltability of the glass and increasing the linear thermal expansion coefficient. When Li ₂ O coexists with other alkali metal oxides, the amount of alkali elution can be greatly reduced. Therefore, Li ₂ O is an essential component, and Na ₂ O and K ₂ O are contained at least one. And what is important here is that when the content of alkali metal oxide is increased, the amount of alkali elution usually increases, but when the content of alkali metal oxide is defined in the present invention, the amount of alkali elution is increased. The increase is suppressed (so-called alkali mixing effect). Hereinafter, the content of each alkali metal oxide will be described.
[0019]
The content of Li ₂ O was in the range of 5.0 to 15.0%. When the content is less than 5.0%, the linear thermal expansion coefficient cannot be increased, and the melting property of the glass cannot be improved. On the other hand, when the content exceeds 15.0%, the alkali elution amount increases. A more preferable content is in the range of 9.0 to 13.5%.
[0020]
The contents of Na ₂ O and K ₂ O were 14.0% and 12.0% or less, respectively. When the content of Na ₂ O and K ₂ O exceeds 14.0% and 12.0%, respectively, the alkali elution amount increases. More preferably, Na ₂ O is in the range of 4.0 to 9.0%, and K ₂ O is in the range of 3.0 to 7.0%.
[0021]
The total content of _{Li 2 O, Na 2 O,} K 2 O is in the range of 16.0 to 25.0%. When the total content is less than 16.0%, the alkali mixing effect of suppressing the alkali elution amount while increasing the linear thermal expansion coefficient cannot be obtained. On the other hand, when the total content exceeds 25.0%, the alkali elution amount increases.
[0022]
Moreover, in the glass substrate of this invention, you may further contain CaO in 6% or less of range as needed. CaO has the effect | action which improves the meltability of glass, and when content exceeds 6%, the amount of alkali elution will increase. A more preferable content is 5.5% or less.
[0023]
Ta ₂ O ₅ has an effect of improving chemical durability. This action is that of Ta ₂ O ₅ that has not been known so far. This effect can be obtained even with a very small content of 0.001%. However, if the content exceeds 2%, the meltability of the glass deteriorates. A more preferable content is in the range of 0.1 to 1.5%.
[0024]
For the glass substrate of the present invention, conventionally known glass components such as clarifiers such as As ₂ O ₃ and Sb ₂ O ₃ , or alkaline earth metal oxides other than TiO ₂ and CaO in order to improve weather resistance. And additives may be added within a range that does not impair the effects of the present invention.
[0025]
There is no limitation in particular in the manufacturing method of the glass substrate of this invention, A conventionally well-known manufacturing method can be used. For example, the corresponding oxides, carbonates, nitrates, hydroxides, etc. are used as raw materials for each component, weighed to a desired ratio, and thoroughly mixed with powder to obtain a blended raw material. This is put into, for example, a platinum crucible in an electric furnace heated to 1,300 to 1,550 ° C., melted and clarified, stirred and homogenized, cast into a preheated mold, and gradually cooled to a glass block. . Next, it is reheated to the vicinity of the glass transition point, and is slowly cooled to remove strain. Then, the obtained glass block is sliced into a disk shape, and the inner periphery and the outer periphery are concentrically cut out using a core drill. Further, after both surfaces are roughly polished, polishing is performed to obtain a glass substrate.
[0026]
When the glass substrate of the present invention is used as a substrate for an information recording medium, the linear thermal expansion coefficient is preferably in the range of 80 to 120 × 10 ⁻⁷ / ° C. If the linear thermal expansion coefficient is out of this range, the difference from that of the material of the drive unit to which the information recording medium is attached becomes large, and the information recording medium is loosely fixed, and there is a possibility that reading and writing cannot be performed. .
[0027]
When the glass substrate of the present invention is used as a substrate for an information recording medium, the alkali elution amount is preferably 1.5 μg / cm ² or less. This is because if the alkali elution amount exceeds 1.5 μg / cm ² , a recording film such as a magnetic film formed on the substrate surface may be deteriorated.
[0028]
The glass substrate of the present invention is not limited in size, and can be a small-diameter disk of 3.5, 2.5, 1.8 inches or less, and the thickness thereof is 2 mm, 1 mm, 0. It can be as thin as 63 mm or less.
[0029]
Next, the information recording medium of the present invention will be described. A major feature of the information recording medium of the present invention is that the glass substrate is used as a substrate. With such a configuration, excellent durability and high recording density are realized. The information recording medium of the present invention will be described below with reference to the drawings.
[0030]
FIG. 1 is a perspective view of a magnetic disk. This magnetic disk D is obtained by directly forming a magnetic film 2 on the surface of a circular glass substrate 1. As a method for forming the magnetic film 2, a conventionally known method can be used. For example, a method in which a thermosetting resin in which magnetic particles are dispersed is spin-coated on a substrate, or a method by sputtering or electroless plating is used. A method is mentioned. The film thickness by spin coating is about 0.3 to 1.2 μm, the film thickness by sputtering is about 0.04 to 0.08 μm, and the film thickness by electroless plating is 0.05 to 0.1 μm. From the viewpoint of thinning and densification, film formation by sputtering and electroless plating is preferable.
[0031]
The magnetic material used for the magnetic film is not particularly limited, and a conventionally known material can be used. However, in order to obtain a high coercive force, Ni having a high crystal anisotropy is basically used, and Ni or A Co-based alloy to which Cr is added is suitable. Specific examples include CoPt, CoCr, CoNi, CoNiCr, CoCrTa, CoPtCr, and CoNiPt containing Co as a main component, CoNiCrPt, CoNiCrTa, CoCrPtTa, CoCrPtB, and CoCrPtSiO. The magnetic film may have a multilayer structure (for example, CoPtCr / CrMo / CoPtCr, CoCrPtTa / CrMo / CoCrPtTa) that is divided by a nonmagnetic film (for example, Cr, CrMo, CrV, etc.) to reduce noise. Addition to the above magnetic material, ferrite, iron - rare-earth or be in a non-magnetic film made of _{SiO 2, BN Fe, Co,} FeCo, etc. granular structure magnetic particles are dispersed, such CoNiPt Also good. Further, the magnetic film may be of any recording type of inner surface type and vertical type.
[0032]
In addition, a lubricant may be thinly coated on the surface of the magnetic film in order to improve the sliding of the magnetic head. Examples of the lubricant include those obtained by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a freon-based solvent.
[0033]
Furthermore, you may provide a base layer and a protective layer as needed. The underlayer in the magnetic disk is selected according to the magnetic film. Examples of the material for the underlayer include at least one material selected from nonmagnetic metals such as Cr, Mo, Ta, Ti, W, V, B, Al, and Ni. In the case of a magnetic film containing Co as a main component, Cr alone or a Cr alloy is preferable from the viewpoint of improving magnetic characteristics. Further, 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. For example, a multilayer underlayer such as Cr / Cr, Cr / CrMo, Cr / CrV, NiAl / Cr, NiAl / CrMo, or NiAl / CrV may be used.
[0034]
Examples of the protective layer that prevents wear and corrosion of the magnetic film include a Cr layer, a Cr alloy layer, a carbon layer, a hydrogenated carbon layer, a zirconia layer, and a silica layer. These protective layers can be formed continuously with an in-line type sputtering apparatus, such as an underlayer and a magnetic film. In addition, these protective layers may be a single layer, or may have a multilayer structure including the same or different layers. Note that another protective layer may be formed on the protective layer or instead of the protective layer. For example, in place of the protective layer, colloidal silica fine particles are dispersed and coated on a Cr layer with tetraalkoxylane diluted with an alcohol solvent, and then fired to form a silicon oxide (SiO2) layer. May be.
[0035]
As described above, the magnetic disk has been described as one embodiment of the information recording medium of the present invention. However, the information recording medium of the present invention is not limited to this, and a magneto-optical disk or an optical disk using the glass substrate is used. Is naturally included in the information recording medium of the present invention.
[0036]
Next, the optical communication element of the present invention will be described. A major feature of the optical communication element of the present invention is that the glass substrate is used as the substrate. That is, in the glass substrate, the alkali elution amount is as small as 1.5 μg / cm ² or less, and the film on the substrate is not deteriorated by the alkali component eluted from the substrate. In addition, since the linear thermal expansion coefficient is as large as 80 to 120 × 10 ⁻⁷ / ° C. compared to a conventional glass substrate (about 60 to 70 × 10 ⁻⁷ / ° C.), the glass substrate heated in the vapor deposition step As the glass substrate is cooled, the amount of shrinkage increases, and the shrinkage of the glass substrate compresses the film formed on the substrate surface, thereby increasing its density. As a result, wavelength shift due to changes in temperature and humidity is suppressed.
[0037]
Hereinafter, the optical communication element of the present invention will be described taking an optical filter for wavelength division division (“DWDM”) as an example. An optical filter using a dielectric multilayer film has a high refractive index layer and a low refractive index layer, and has a structure in which these layers are laminated. A method for forming these layers is not particularly limited, and a conventionally known method such as a vacuum deposition method, a sputtering method, an ion plating method, or an ion beam assist method can be used. Among these, vacuum deposition is recommended because of its high productivity. Vacuum deposition is a method of forming a thin film by heating a deposition material in vacuum and condensing and adhering the generated vapor onto a substrate. There are various methods such as resistance heating, an external heating crucible, an electron beam, a high frequency, and a laser as a method for heating the deposition material. As specific vapor deposition conditions, the degree of vacuum is about 1 × 10 ^{−3 to} 5 × 10 ⁻³ Pa. During the deposition, the amount of introduced oxygen is adjusted by controlling the solenoid valve so that the degree of vacuum is constant. Then, when the predetermined layer thickness is reached by the layer thickness monitor, the shutter is closed and the deposition is finished.
[0038]
Each film thickness is not particularly limited, but the optical film thickness is basically ¼ of the wavelength, and is generally about 1 μm. Moreover, the total number of layers generally exceeds 100 layers. Examples of the film material to be used include dielectrics, semiconductors, and metals. Among these, dielectrics are particularly preferable.
[0039]
As described above, the optical filter for DWDM has been described as one embodiment of the optical communication element of the present invention. However, the optical communication element of the present invention is not limited to this, and an optical switch using the glass substrate, Of course, a multiplexing / demultiplexing element is also included in the optical communication element of the present invention.
[0040]
【Example】
Example 1-9 and Comparative Example 1-26
A specified amount of raw material powder was weighed into a crucible, mixed, and then melted at 1,550 ° C. in an electric furnace. After the raw materials were sufficiently dissolved, a stirring blade was inserted into the glass melt and stirred for about 1 hour. Thereafter, the stirring blade was taken out and allowed to stand for 30 minutes, and then the melt was poured into a jig to obtain a glass block. Thereafter, the glass block was reheated to near the glass transition point of each glass, and slowly cooled to remove strain. The obtained glass block was sliced into a disk shape having a thickness of about 1.5 mm, and the inner and outer circumferences were concentrically cut out using a cutter. Then, both surfaces were subjected to rough polishing and polishing to produce glass substrates of Examples and Comparative Examples. The following characteristics evaluation was performed about the produced glass substrate. In addition, about the glass substrate of the comparative example 15, the chemical strengthening process was performed. The results are shown in Table 1, Table 2, and Table 3.
[0041]
(specific gravity)
It was measured by the Archimedes method using ethanol as an immersion liquid.
[0042]
(Young's modulus) and (Specific modulus)
It measured according to the dynamic elastic modulus test method of the elastic test method of JIS R 1602 fine ceramics. The specific modulus was calculated by dividing Young's modulus by specific gravity.
[0043]
(Linear thermal expansion coefficient)
Using a differential expansion measuring device, the measurement was performed under the conditions of load: 5 g, temperature range: 25 to 100 ° C., temperature increase rate: 5 ° C./min.
[0044]
(Melting property)
After the molten glass is held at 1,550 ° C. for 2 hours, it is poured onto a heated iron plate, the degree of viscosity of the molten glass is visually observed, and “◎”, “○”, “ “×”. In addition, “x” is attached only to those that are considered to cause problems in production.
[0045]
(Alkaline elution amount)
After polishing the glass surface with a # 600 abrasive to roughen the surface in advance, the sample glass was immersed in 50 ml of reverse osmosis membrane water at 80 ° C. for 24 hours, and the eluate was analyzed with an ICP emission spectrometer. The amount of alkali elution was calculated.
[0046]
[Table 1]

[0047]
[Table 2]

[0048]
According to Table 1, in the glass substrates of Examples 1 to 9 , the Young's modulus and the specific elastic modulus, which is considered to be more resistant to vibration as the value is higher, are at a level where there is no practical problem at all. Further, the linear thermal expansion coefficient was in the range of 80 to 91 × 10 ⁻⁷ / ° C., which was a value larger than that of the conventional glass substrate. Furthermore, the alkali elution amount was 1.5 μg / cm ² or less, which was smaller than that of the conventional glass substrate. On the other hand, there was no problem with respect to the meltability of the glass.
[0049]
[Table 3]

[0050]
According to Table 2 , the glass substrate of Comparative Example 1 had a low SiO ₂ content of 53.2%, so that the glass structure was soft and the alkali elution amount was increased. On the other hand, in the glass substrate of Comparative Example 2 having a high SiO ₂ content of 77.1%, the meltability of the glass deteriorates and the glass component content for improving chemical durability is relatively low. Alkaline elution amount increased. The glass substrate of Comparative Example 3 contained a large amount of alkali elution because it did not contain B ₂ O ₃ which improves the meltability of the glass and improves the chemical durability. Further, the amount of alkali elution was also large in the glass substrate of Comparative Example 4 containing a large amount of B ₂ O ₃ as 11.3%. In the glass substrate of Comparative Example 5 having a low Al ₂ O ₃ content of 0.8%, the alkali elution amount was large. On the contrary, in the glass substrate of Comparative Example 6 having a high Al ₂ O ₃ content of 17.8%, the alkali elution amount was smaller than those of the other Comparative Examples, but the glass meltability was poor.
[0051]
In the glass substrate of Comparative Example 7 that does not contain Li ₂ O, the amount of alkali elution increases, whereas the glass substrate of Comparative Example 8 that contains Li ₂ O in a large amount of 15.5% has a sufficient linear thermal expansion coefficient. It did not increase, and the amount of alkali elution was large. Moreover, in the glass substrate of Comparative Example 9 which did not contain Li ₂ O and contained a large amount of Na ₂ O as 17.0%, the amount of alkali elution was large. Further, the glass substrate of Comparative Example 10 containing K ₂ O in a large amount of 13.4% had a small coefficient of linear thermal expansion and a large amount of alkali elution. In the glass substrate of Comparative Example 11 which does not contain Li ₂ O and the total content of alkali metal oxides is as low as 14.0%, the linear thermal expansion coefficient is not sufficient although the alkali elution amount is small, and the glass The meltability of was also poor. On the contrary, in the glass substrate of Comparative Example 12 in which the total content of alkali metal oxides was as high as 25.5%, the amount of alkali elution was large.
[0052]
In the glass substrate of Comparative Example 13 having a large CaO content of 6.4%, the linear thermal expansion coefficient was small and the amount of alkali elution was large. In the glass substrate of Comparative Example 14 having a large Ta ₂ O ₅ content of 3.0%, the meltability of the glass deteriorated and the amount of alkali elution was large. In the chemically strengthened glass substrate of Comparative Example 15, the amount of alkali elution was large.
[0053]
【The invention's effect】
Since the glass substrate according to the present invention has a specific glass composition, the linear thermal expansion coefficient is high and the elution of alkali components is small, and in addition, the production cost can be suppressed .
[0055]
In the information recording medium according to the present invention, since the glass substrate is used as the substrate, it has excellent durability and high recording density.
[0056]
In the optical communication element according to the present invention, since the glass substrate is used as a substrate, there is little change with time, and a wavelength shift due to changes in temperature and humidity can be suppressed.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an example of an information recording medium of the present invention.
[Explanation of symbols]
1 Glass substrate 2 Magnetic film D Magnetic disk

Claims (3)

mol%,
SiO _2: 55.0~75.0%,
B ₂ O ₃ : 1.0 to 5.1%,
Al ₂ O ₃ : 3.0 to 16.0%,
Li ₂ O: 5.0 to 15.0%,
Na ₂ O: 14.0% or less,
K ₂ O: 12.0% or less,
Li ₂ O + Na ₂ O + K ₂ O: 16.0 to 25.0%,
Ta ₂ O ₅ : 0.001 to 2.0%,
Having a glass composition of
P ₂ O ₅ , RO (R is a metal selected from Ca, Mg, Ba, Sr, Zn, Pb),
Does not contain Fe, Mn, Ce, Ti, V, Cr, Co, Ni, Ag, Sn, Cu, Zn, Te, Er, Nd and Pb metal components,
A sample glass whose linear thermal expansion coefficient is in the range of 80 to 120 × 10 ⁻⁷ / ° C. and whose surface is polished with an abrasive of # 600 is immersed in 50 ml of reverse osmosis membrane water at 80 ° C. for 24 hours, followed by ICP emission. A glass substrate whose surface and internal composition are homogeneous when the amount of alkali elution calculated by analyzing the eluate with a spectroscopic analyzer is in the range of 0.7 to 1.5 μg / cm ² . An information recording medium, wherein an information recording layer is formed directly or via another layer on the surface of the glass substrate according to claim 1 . An optical communication element using the glass substrate according to claim 1 as a substrate.

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