JP3420192B2 - Glass ceramics - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel glass ceramic which is light in weight, yet has good mechanical strength, light transmittance, and an average linear expansion property which is suitable for other materials. It is a thing. In particular, glass ceramics for information storage medium substrates that require thermal expansion characteristics matching the constituent members of the information magnetic storage device and smoothness suitable for high storage density, and their holding members, or good adhesion with a multilayer film. Relating to glass ceramics suitable for optical filter glass ceramics (especially, materials for optical filters for WDM or DWDM, or materials for Gain-Flattening filters) that require high properties, desired thermal expansion characteristics and good light transmittance It is a thing.

[0002]

2. Description of the Related Art In recent years, as personal computers have become multimedia and digital video cameras, digital cameras and the like have become widespread, data such as moving images and voices have been handled, and there is a great demand for information storage devices with high storage density. It is growing. Therefore, in the information storage medium, it is necessary to reduce the size of the bit cell in order to increase the recording density. Then, as the size of the bit cell is reduced, the head operates in a state of being extremely close to the surface of the information storage medium. In this way, the head is in a low flying state (near contact) or a contact state (contact) with respect to the information storage medium.
When it is operated in, the ultra-smoothness of the surface of the information magnetic storage medium substrate is important. Further, a ramp load technology has been developed to completely contact the magnetic head and remove the start / stop of the head from the information magnetic storage medium substrate against the conventional landing zone technology. The demands for are becoming smoother.

Further, as the information capacity increases, the magnetic film becomes finer, more precise, and thinner, and the alkaline components (Li, Na, K) eluted from the substrate material are also reduced in elution amount. Is required to be.

Moreover, these information storage media are used for mobile (APS camera, mobile phone, digital camera, digital video camera, card drive), mobile PC and desktop PC (hard disk drive), server (hard disk drive), new. Applications for high recording density media (perpendicular magnetic storage media, island magnetic storage media, storage media for semiconductor memory), etc. are beginning to be developed.
The physical, chemical, and electrical properties required for substrates have become more sophisticated.

Conventionally, an aluminum alloy has been used as a magnetic disk substrate material. However, in the aluminum alloy substrate, due to the influence of various material defects, protrusions or spot-shaped irregularities are generated on the substrate surface during the polishing process, and the surface is smooth. In terms of properties, it is not sufficient as the substrate for the high density storage medium. Further, since aluminum alloy is a soft material and has a low Young's modulus and surface hardness, it has drawbacks that it is apt to be violently deformed during high-speed rotation of the drive and it is difficult to cope with thinning. . Further, the contact of the head may damage the medium or may not be able to sufficiently meet today's demands for high-density recording, such as deformation due to high-speed rotation.

Aluminosilicate glass (SiO ₂ —Al ₂ O ₃ —Na ₂ O), which is a chemically strengthened glass, is known as a material for solving the problems of the aluminum alloy substrate. In this case, (1) Polishing is performed after chemical strengthening, and the instability factor of the strengthening layer in thinning the disk is high. (2) Since the glass contains Li ₂ O, Na ₂ O, and K ₂ O components as essential components, the film forming characteristics deteriorate, and Li
Etching treatment for preventing elution of ₂ O, Na ₂ O, and K ₂ O and overall barrier coating treatment are required. Further, there is a drawback that it is difficult to achieve low cost and stable productivity of products, such as a problem such as a slight waviness of a substrate.

As a material that overcomes the drawbacks of the chemically strengthened glass substrate, there is crystallized glass.
SiO described in JP-A-6-329440 ₂ -Li ₂
O-MgO-P ₂ O ₅ based crystallized glass has lithium disilicate (Li ₂ O · 2SiO ₂₎ and alpha-quartz (α-SiO ₂₎ as main crystal phase, alpha-quartz (alpha-Si
By controlling the spherical particle size of O ₂ ), the surface roughness Ra (arithmetic mean roughness) obtained by polishing without using the conventional mechanical texture and chemical texture is 15
It is a very excellent material as a textured material on the entire surface of the substrate, which can be controlled in the range of up to 50Å. However, today's target surface roughness Ra (arithmetic mean roughness) is 5.0Å
Hereafter, it is more preferably 3.0 Å or less, and further preferably 2.0 Å or less, and it is not possible to sufficiently cope with the low flying height in line with the rapid increase in recording capacity. Further, it contains lithium disilicate (Li ₂ O.2SiO ₂ ) in the main crystal phase, and although it is in a smaller amount than chemically strengthened glass, it is generated during polishing and further elution of alkaline components which is required today. There is no discussion about the issue of small pits.

S described in JP-A-10-45426
_{iO 2 -Li 2 O-K 2} O-MgO-ZnO-P 2 O 5 -A
1 ₂ O ₃ system or SiO ₂ —Li ₂ O—K ₂ O—MgO—
_{ZnO-P 2 O 5 -Al 2} O 3 -ZrO 2 based crystallized glass, the main crystal phases of lithium disilicate (Li ₂ O · 2Si
O ₂ ), lithium disilicate and α-quartz (α-Si
Disclosed is a glass-ceramic for laser texture characterized by being a mixed crystal of O ₂ ) or at least one kind of a mixed crystal of lithium disilicate and α-cristobalite (α-SiO ₂ ). However, today's target surface roughness Ra (arithmetic mean roughness) is 5.0 Å or less, more preferably 3.0 Å or less, and further preferably 2.0 Å
The following is not enough to cope with the low flying height in line with the rapid increase in recording capacity, and further, lithium disilicate (Li ₂ O.2SiO ₂ ) is contained in the main crystal phase, so that it is required today. There is no discussion about the problem of further elution of a certain amount of alkaline components and the problem of minute pits that occur during polishing.

In Japanese Unexamined Patent Publication No. 9-35234, SiO is disclosed.
₂ -Al ₂ O ₃ -Li ₂ in O-based glass, a magnetic disk main crystalline phase consists lithium disilicate (Li ₂ O · 2SiO ₂₎ and β- spodumene _{(Li 2 O · Al 2 O} 3 · 4SiO 2) Although the substrate for use is described, the main crystalline phase of this crystallized glass is β-spodumene (Li ₂ O.) which has negative thermal expansion properties (resulting in low expansion properties of the substrate).
Al ₂ O ₃ .4SiO ₂ ) and α-quartz (α-Si
O ₂ ) and α-cristobalite (α-SiO ₂ ) crystals such as S
It regulates the precipitation of crystals having the positive thermal expansion characteristics of the iO ₂ system (resulting in the substrate having high expansion characteristics).
This crystallized glass has a surface roughness Ra (arithmetic mean roughness) of 20 Å or less formed by polishing as a magnetic disk (the surface roughness Ra (arithmetic mean roughness) disclosed in Examples is 12 to 20).
17 Å), which is still inferior to the current demand, and cannot sufficiently cope with the low flying height of the magnetic head accompanying the improvement in storage capacity. Further, it is obvious that the material in which the crystal having the negative thermal expansion characteristic is deposited as the main crystal has a bad influence on the difference in the average linear expansion coefficient with the components of the information storage medium device. In addition, regarding the crystallization heat treatment temperature,
It requires a high temperature of 920 ° C., which hinders low cost and mass productivity, while the main crystal phase is lithium disilicate (Li
₂ O · ₂ SiO ₂ ) and no further discussion has been made on the problem of the further reduction in the elution amount of alkali components and the problem of minute pits generated during polishing, which are required today.

International publication number WO 97/01164 includes
Japanese Patent Application Laid-Open No. 9-35234 discloses a crystallized glass for a magnetic disk, which is obtained by newly lowering the crystallization heat treatment of the composition system (680 to 770 ° C.).
The improvement effect is insufficient, and the crystal phases of all the crystallized glasses disclosed in the examples have β-eucryptite (Li ₂ O.Al ₂ O ₃₎ also having negative thermal expansion characteristics.
2SiO ₂ ) is deposited, which adversely affects the difference in the average linear expansion coefficient from the components of the information storage medium device. The main crystal phase is lithium disilicate (L
i ₂ O · 2SiO ₂ ), and no further discussion has been made on the problem of further reduction of the elution amount of alkali components and the problem of minute pits generated during polishing, which are required today.

In Japanese Patent Laid-Open No. 11-343143, S
_{iO 2 -Al 2 O 3 -MgO-} Y 2 O 3 -TiO 2 -Li 2 O
In the system glass, the main crystal phase is a quartz solid solution (MgO-A).
A substrate for an information recording medium containing enstatite (MgAl ₂ O ₃ ) in a quartz solid solution (l ₂ O ₃ —SiO ₂ system) is disclosed. The main crystal phase of this crystallized glass has a negative thermal expansion. Since α-quartz solid solution crystals having properties (resulting in low expansion properties of the substrate) are included in the α of the present invention,
-Quartz and α-cristobalite and those containing these solid solutions are completely different substrates from the viewpoint of thermal expansion characteristics, and thus it is difficult to obtain the desired average linear expansion coefficient described in the present application.

Next, as the use for the optical filter,
There are those that cut or transmit a specific wavelength and those that reduce the light intensity regardless of the wavelength. The former optical filter is a bandpass filter that transmits only specific wavelengths.
There are a notch pass filter that cuts only a specific wavelength, a high pass filter that transmits only a wavelength shorter or a longer wavelength than a specific wavelength, a low pass filter, and the like, and the latter optical filter includes an ND filter.

The optical filter is classified into an absorption type and an interference type. N is a typical absorption type optical filter.
There is a D filter or the like, and a typical example of the interference type optical filter is a bandpass filter. Although plastic is used as a substrate for absorption type optical filters for photography and the like, amorphous glass is mainly used for the substrate of optical filters when a strong laser is used from the viewpoint of durability and heat resistance. There is.

A bandpass filter is, for example, a dielectric thin film (H layer) having a high refractive index on a substrate material such as glass.
And a dielectric multilayer film having a structure in which dielectric thin films (L layers) having a low refractive index are alternately laminated is used.

WDM (Wavelength Divi)
ssion Multiplexing: DWDM (Dense Wavelength)
hDivision Multiplexing: In a bandpass filter used in an optical communication system, when the bandwidth of the passing wavelength is set narrow and the signal to be transmitted / received is made to have a high density wavelength, the center wavelength of the band is Temperature stability becomes a problem. In other words, since it is a sensitive element in which the center wavelength of the band fluctuates even with a slight temperature change, temperature compensation should be performed with a temperature controller in its use, but due to space problems when using it You can't practically turn on the temperature controller. This temperature stability of the central wavelength is more important because it is necessary to narrow the bandwidth as the amount of optical information increases.

Conventionally, as described above, amorphous glass is used as the substrate material of the bandpass filter, but since the thermal expansion characteristics are not sufficiently high and the mechanical strength is low, the compressive stress and durability applied to the film are reduced. It wasn't good enough. Furthermore, amorphous glass has a low surface hardness, and since it needs to contain a large amount of an alkali component in order to obtain large thermal expansion characteristics, it has problems such as alkali elution during film formation and alkali elution over time. It cannot fully meet the requirements for future optical filter substrate materials, especially bandpass filter substrate materials.

[0017]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the prior art while avoiding the problems of super-smoothing of the substrate and elution of alkaline components with the increase in storage capacity of the information storage medium. While eliminating the above-mentioned glass ceramics and various drawbacks found in the above-mentioned prior art, an optical filter (particularly a bandpass filter or a Gain-Flatt) is provided.
Ening filter) avoids the fluctuation of the central wavelength at the operating temperature of the filter member formed with a single-layer or multi-layered film (that is, the substrate material has a high coefficient of thermal expansion, which gives a compressive stress to the film, and the center of the film with respect to the temperature). A glass for optical filters, which has never been before, having both expansion characteristics for improving wavelength stability) and mechanical characteristics in consideration of durability and processability, and the glass ceramics itself has a good light transmittance. It is to provide a ceramic substrate material.

[0018]

Means for Solving the Problems As a result of extensive studies conducted in order to achieve the above object, the present inventor has found that the main crystal phase is α- Lithium disilicate (Li ₂ O · 2SiO ₂ ), lithium silicate (Li ₂ O ·) while containing at least one selected from cristobalite, α-cristobalite solid solution, α-quartz, and α-quartz solid solution.
SiO ₂ ), β-spodumene, β-eucryptite, β-quartz, mica and fluororichterite (flu
orrichiterite) is not substantially contained, it is possible to deal with the problem of further elution of alkaline components and fine pits that occur during polishing, which are required today, and crystal particles are also extremely fine (less than 0.1 μm). It is possible to obtain glass ceramics that can be controlled and have a lower surface smoothness than that of conventional ones, and that can be controlled to have thermal expansion characteristics that match drive components, and that is suitable for glass substrates for information storage media. That the specific thermal expansion coefficient range, mechanical strength, and light transmittance that are possessed by are extremely useful as glass ceramics for optical filters (especially for WDM and DWDM bandpass filters and Gain-Flattening filters). The present invention has been found under the heading.

That is, the invention according to claim 1 contains at least one selected from α-cristobalite, α-cristobalite solid solution, α-quartz, and α-quartz solid solution in the main crystal phase, Lithium disilicate (Li ₂ O ・ 2SiO ₂ ), lithium silicate (Li ₂ O ・
SiO ₂ ), β-spodumene, β-eucryptite, β-quartz, mica and fluororichterite (fl
uorrichterite) and substantially no Cr and Mn components, and an average linear expansion coefficient at −50 to + 70 ° C. of + 65 × 10 ⁻⁷ to + 140 × 10.
Glass ceramics, characterized in that the crystal grain size (average) of the main crystal phase is less than 0.10 μm in the range of ⁻⁷ / ° C., and the Young's modulus of the invention according to claim 2 is 8
It is 0 GPa or more, It is glass ceramics of Claim 1 characterized by the above-mentioned, The invention of Claim 3 is characterized by specific gravity being 2.3-2.7. The glass ceramic according to claim 2, or the invention according to claim 4, wherein the light transmittance of a material having a plate thickness of 10 mm is 90% or more at a wavelength of 950 to 1600 nm. The glass ceramic according to any one of claims 1 and 3, and the invention according to claim 5 has a bending strength of 250 MPa or more. The invention is a glass-ceramic, and the invention according to claim 6 has a Vickers hardness of 600 to 800. The glass-ceramic according to any one of claims 1, 2, 3, 4, and 5, Claim The invention according to is the composition of the glass ceramic mass percentage (oxide basis), less than _{SiO 2 65 ~75% Li 2 O} 4 ~ 7% K 2 O 0 ~ 3% Na 2 O 0 ~ 3% MgO + ZnO + SrO + BaO + CaO 2 〜15% Y ₂ O ₃ + WO ₃ + La ₂ O ₃ + Bi ₂ O ₃ 0 to 3% SnO ₂ 0 to 3% P ₂ O ₅ 1.0 to 2.5% ZrO ₂ 2.0 to 7% Al ₂ O ₃₅ and _{~ 9% Sb 2 O 3 +} as 2 O 3 0 , characterized in that it contains the components of ~ 1% range, according to any of claims 1,2,3,4,5,6 According to the invention of claim 8, the raw glass is heat-treated at 400 ° C to 600 ° C for 1 to 7 hours to form nuclei, and then heat-treated at 650 ° C to 750 ° C for 1 to 7 hours for crystal growth. Claims 1, 2, characterized in that it is obtained by
The glass ceramic according to any one of 3, 4, 5, 6, and 7.

In the present specification, "substantially free of lithium disilicate ..." Does not affect the physicochemical properties of the glass ceramics, that is, less than 3%, It preferably means less than 1% or an impurity level.

Further, in the present specification, "substantially free of Cr component ... ......" means that the content of the component does not affect the physical and chemical characteristics of the glass ceramics, that is, at the impurity level. Means there is.

The main crystal phase of the glass-ceramics of the present invention and the crystal grain size (average) / average linear expansion coefficient, surface characteristics,
The reasons for limiting the composition, heat treatment conditions, etc. will be described below.
The composition is expressed in mass% based on the oxide as in the original glass. In the present specification, the main crystal phase refers to all crystal phases having a relatively large precipitation ratio. That is, in the X-ray chart in X-ray diffraction (the vertical axis is the X-ray diffraction intensity, the horizontal axis is the diffraction angle), the X-ray diffraction intensity of the main peak (highest peak) of the crystal phase with the highest precipitation ratio is 100.
In such a case, all those having a ratio of X-ray diffraction intensities (hereinafter, referred to as X-ray intensity ratio) of main peaks (highest peaks in each crystal phase) of each precipitated crystal phase of 30 or more are called main crystal phases.

First, regarding the main crystalline phase, in order to obtain a desired thermal expansion coefficient, α-cristobalite, α-cristobalite solid solution, α-quartz, which has a relatively large positive expansion coefficient in the main crystalline phase, Those containing at least one selected from α-quartz solid solutions are preferable. In particular, by selecting the above-mentioned main crystal phase, it is possible to easily obtain one having excellent chemical durability and physical properties. The X-ray intensity ratio of crystals other than the main crystal phase is 20.
It is preferably less than 10, more preferably less than 10, and most preferably less than 5.

By not containing lithium disilicate in the main crystal phase, it is possible to reduce fine holes (pits) on the surface of the substrate due to the mechanochemical influence at the time of polishing. It is preferable. The main crystal phase of the glass-ceramics of the present invention includes β-spodumene, β-eucryptite, which has negative thermal expansion characteristics,
It is preferable that β-cristobalite (β-SiO ₂ ), other lithium silicate (Li ₂ O.SiO ₂ ), diopsite, enstatite, mica, α-tridymite, fluorrichiterite and the like are not included as much as possible. .

Next, the average linear expansion coefficient will be described in detail. As the recording density is improved, positioning of the magnetic head and the medium is required to be highly accurate, so that high dimensional accuracy is required for each component of the medium substrate and the magnetic information storage device. Therefore, the influence of the difference in the average linear expansion coefficient on these components cannot be ignored, and the difference in these average linear expansion coefficients must be minimized. More strictly, it is often preferable that the average linear expansion coefficient of the medium substrate is extremely slightly larger than the average linear expansion coefficient of these components. Particularly, the thermal expansion coefficient of the components used for a small-sized magnetic information storage medium is often + 90 × 10 ⁻⁷ to + 100 × 10 ⁻⁷ / ° C., and the substrate needs to have such a thermal expansion coefficient. However, depending on the drive manufacturer, the coefficient of thermal expansion deviates from this range (around +60 to +135
A material having a front-back direction of 10 ⁻⁷ / ° C.) may be used for the component. For the above reasons, the average linear expansion coefficient range must be determined so that the crystal system of the present invention can be widely compatible with the materials of the components to be used while striking the balance with the strength, and the range is −50. in the range of ~ + 70 ° C., it is preferably ^{+ 65 × 10 -7 / ℃ ~} + 140 × 10 -7 / ℃. The average linear expansion coefficient is + 70 × 10 ^-7
/ ° C. or higher is more preferable, and + 120 × 10 ⁻⁷ / ° C. or lower is further preferable.

From the viewpoint of glass ceramics for optical filters, the temperature stability of the central wavelength of the band is very important as described above, and it is necessary that the coefficient of thermal expansion be larger than that of the film constituent material. The reason for this will be described below.
Especially band pass filters and Gain-Flatten
In an ing filter or the like, the stability of the central wavelength with respect to temperature depends on the temperature coefficient of refractive index of the dielectric material that constitutes the thin film, but besides that, it is greatly affected by the thermal expansion coefficient of the substrate material. This is because the refractive index is determined by the filling factor of the thin film. That is, the higher the filling factor of the thin film (that is, the higher the refractive index), the smaller the change in the central wavelength with temperature. The filling factor of the thin film is greatly influenced by the thermal expansion coefficient of the optical filter substrate material on which the thin film is formed. That is, the substrate material during film formation is about 200
Although the temperature is around ℃, the substrate material itself greatly expands due to the heat, and the thin film is formed on the expanded substrate material, and as the substrate material is cooled, the difference in the coefficient of thermal expansion causes the thin film. Undergoes compressive stress. As a result, the refractive index increases as the filling rate of the thin film increases, and thus the stability of the central wavelength of transmitted light with respect to temperature is improved. The change in the refractive index tends to saturate above a certain stress, and the rate of increase in the change in the refractive index decreases even if the compressive stress is increased. For this reason, the larger the thermal expansion coefficient of the substrate material, the greater the compressive stress applied to the formed dielectric thin film, and as a result, the variation in the refractive index due to the operating temperature decreases. Therefore,
When the temperature stability of the central wavelength is emphasized, it is desirable to set the thermal expansion coefficient of the glass ceramics larger than the thermal expansion coefficient of the dielectric thin film.

As a result of the test research conducted by the present inventor, -20
If the coefficient of thermal expansion at ℃ to +70 ℃ is 65 × 10 ^-7 / ℃ or more, band-pass filter and Gain-Fla
It was found that a sufficient compressive stress can be applied to the film in the temperature range used as a tenting filter or the like. On the other hand, however, when it exceeds 140 × 10 ⁻⁷ / ° C., the difference in thermal expansion coefficient from the film becomes too large, and problems such as peeling of the film tend to occur. A more preferable range is 9
0 × 10 ⁻⁷ / ° C. or higher, 130 × 10 ⁻⁷ / ° C. or lower, more preferable range is 95 × 10 ⁻⁷ / ° C. or higher, 125 × 10 ⁻⁷ /
It is in the range of ℃ or less.

Next, the crystal grain size (average) of the main crystal phase will be described. As described above, as the areal recording density of the information storage medium is improved, the flying height of the head is significantly reduced to 0.025 μm or less, that is, the near-contact recording method or the contact recording method of complete contact is currently underway. To cope with this, the smoothness of the disk surface must be better than that of the conventional product.
Even if an attempt is made to perform high-density input / output to / from a magnetic recording medium with the smoothness of the conventional level, input / output of magnetic signals cannot be performed due to the large distance between the head and the medium. When this distance is reduced, the projection of the medium collides with the head, and the head or the medium is damaged. Therefore, in order to prevent head damage and medium damage even at this extremely low flying height or in contact, the surface roughness Ra (arithmetic mean roughness) of the disk is preferably 5.0 Å or less. It is more preferably 0 Å or less, and 2.0
It is more preferably Å or less. In order to obtain such an ultra-smooth polished surface, the crystal grain size (average) of the main crystal phase is preferably less than 0.10 μm, and 0.0
It is more preferably 5 μm or less, still more preferably 0.02 μm or less.

The mechanical strength of the glass ceramics can be improved by uniformly depositing finer crystals. In particular, since the precipitated crystal grains prevent the growth of fine cracks, fine chipping due to chipping or the like during polishing can be significantly reduced. Further, when used for an optical filter, the light transmittance thereof becomes a problem, but the light transmittance is improved by making the precipitated crystals fine. From this point of view, the precipitated crystal grain size (average) is preferably less than 0.10 μm, more preferably 0.05 μm or less, still more preferably 0.02 μm or less.

Next, Young's modulus and bending strength, which are mechanical strength, will be described. When used as a magnetic recording medium substrate, these mechanical strengths are important factors. This is because, as the recording density is improved, the disc itself is rotated at a higher speed. Therefore, in order to reduce the vibration due to this rotation, the Young's modulus and the bending strength are not less than a predetermined value, that is, the Young's modulus is 8% or more.
The bending strength is preferably 0 GPa or more and 250 MPa or more. Also, when it is used for an optical filter, it is desirable that it has a high Young's modulus and a high bending strength. When this is used for a special WDM filter, it is processed into a minute chip shape (2 mm or less × 2 mm or less × 2 mm or less), and therefore, if the strength is low, such minute processing becomes difficult. Therefore, from this aspect as well, the Young's modulus is 8
It is preferable that the bending strength is 0 GPa or more and the bending strength is 250 MPa or more. More preferably, the Young's modulus is 85 GPa or more, the bending strength is 290 MPa or more, and even more preferably, the bending strength is 300 MPa or more.

Next, regarding the light transmittance, when viewed as an optical filter, a low light transmittance naturally causes inconvenience in signal extraction (decrease in S / N ratio). Therefore, a larger value is preferable. , Light transmittance is 90%
It must be above. In particular, the wavelength used for the bandpass filter or the Gain-Flattening filter is 950 nm to 1600 nm, and it is necessary that the light transmittance of this wavelength in a material having a plate thickness of 10 mm is 90% or more. The light transmittance at the above wavelength is preferably 95% or more, more preferably 97% or more.

Next, regarding specific gravity, in order to enable high-speed rotation in the information storage device, in addition to the Young's modulus described above, specific gravity is also an important factor. That is, if the specific gravity is large, even if the Young's modulus is high, vibration is likely to occur at high speed rotation. On the other hand, if the specific gravity is too low, it becomes difficult to obtain the desired mechanical strength, especially Young's modulus. Therefore, considering these balances, the ratio of Young's modulus to specific gravity (Young's modulus / specific gravity) is 30 to
It is preferably 65 (GPa). In particular, the ratio of Young's modulus to specific gravity (Young's modulus / specific gravity) is more preferably 33 to 60 (GPa).

Regarding the Vickers hardness, when used in an information storage device, unless it has a predetermined value or more, it is easily scratched and cannot be used as a substrate for a magnetic recording medium. However, if it is too high, the workability will be significantly reduced. Therefore, considering these balances, 6
It is preferably from 00 to 800. Also for optical filters, if the Vickers hardness is low, the scratches are likely to occur, and the transmitted light causes scattering at that portion, which significantly impairs the characteristics as a filter. On the other hand, if it is too high, the problem of workability arises as described above, and cracks and chips are likely to occur especially when processing fine chips. Even considering these balances, it is preferably 600 to 800. The range of 650 to 760 is more preferable.

Next, the reason why the composition range of the raw glass is limited as described above will be described below. The SiO ₂ component is an extremely important component that produces α-cristobalite, α-cristobalite solid solution, α-quartz, and α-quartz solid solution that precipitate as a main crystalline phase by heat treatment of the raw glass, but the amount thereof is 65%. When the amount is less than the above, the precipitated crystals of the obtained glass ceramics are unstable and the structure is apt to coarsen, and when it exceeds 75%, the melting / formability of the raw glass becomes difficult. Preferably above 65% and / or 75
%, More preferably 68% or more and 74% or less.

The Li ₂ O component is an important component for improving the melting property of the current glass. However, if the amount is less than 4%, the above effect cannot be obtained and it becomes difficult to melt the raw glass.
If it is 7% or more, the problem of Li ion elution occurs or the production of lithium disilicate crystals increases. Preferably 4.5
% Or more and 6.5% or less, more preferably 4.5% or more,
It is 6.0% or less.

The K ₂ O and Na ₂ O components are components having the effect of lowering the melting temperature, and further having the effect of suppressing the elution of alkali ions from the glass matrix when mixed with the Li ₂ O component. . This is because by mixing and coexisting a small amount of these alkali components, the electrical properties (volume resistivity) are improved, and the relative L
Mixing and coexisting K ₂ O and Na ₂ O components in a glass having a large proportion of i ₂ O components improves the volume resistivity, suppresses the mobility of alkali ions in the glass, and finally elutes the alkali ions. The effect of suppressing is obtained. Regarding the content of these components, K ₂ O component is 3
%, The Na ₂ O component is 3% or less, and if it is contained more than this, the alkali elution amount tends to increase. A more preferable range is K ₂ O and Na ₂ O.
Both are 0 to less than 3%, and more preferable ranges are Na ₂ O = 0 to 2.5% and K ₂ O = 0.1 to 2.5%.

MgO, ZnO, SrO, BaO, CaO
The components are components that improve the meltability of the glass and at the same time prevent coarsening of the precipitated crystals, but the total amount of each component is 2
% Or more, and if it exceeds 15%, the obtained crystals are unstable and the structure tends to become coarse.

In the present invention, the P ₂ O ₅ component is indispensable as a crystal nucleating agent for glass, but its amount is 1.0 in order to promote crystal nucleation and prevent coarsening of the precipitated crystal phase.
% Or more, and preferably 2.5% or less in order to prevent devitrification of the raw glass and to maintain mass production stability.

Like the P ₂ O ₅ component, the ZrO ₂ component functions as a crystal nucleating agent for glass, and also serves to make the precipitated crystals uniform and fine, improve the mechanical strength of the material and improve the chemical durability. It is a very important ingredient found to have a significant effect. The amount is preferably 2.0% or more. However, if added excessively, it becomes difficult to melt the raw glass, and at the same time, unmelted residue such as ZrSiO ₄ easily occurs,
The amount of ZrO ₂ component is preferably 7% or less. It is more preferably 2% or more and 6% or less, and further preferably the upper limit is 5%.
It is the following.

Like the ZrO ₂ component, the SnO ₂ component is a component that functions as a crystal nucleating agent for glass, but its amount is preferably 3% or less.

The Al ₂ O ₃ component is a component that improves the chemical durability and mechanical strength of the glass ceramics, especially the hardness, and the amount thereof is preferably 5% or more.
If it is contained excessively, the meltability and devitrification resistance are deteriorated, and the precipitated crystal phase is low expansion crystal β-spodumene (Li ₂ O).
_{· Al 2 O 3 · 4SiO 2} ) and made to result in. The precipitation of β-spodumene (Li ₂ O.Al ₂ O ₃ .4SiO ₂ ) significantly lowers the average linear expansion coefficient of the material, and therefore the precipitation of this crystal must be avoided. Therefore, Al ₂ O ₃
The component is preferably 9% or less. More preferably, the lower limit is more than 5% and the upper limit is less than 9%, and even more preferably the lower limit is 6% or more and the upper limit is less than 8%.

Each of the Y ₂ O ₃ , WO ₃ , La ₂ O ₃ and Bi ₂ O ₃ components improves the meltability which has been lowered in the composition containing a small amount of Li ₂ O component, and increases the Young's modulus of the glass. It is a component to bring, but the total amount of 3% or less is sufficient,
If it exceeds 3%, stable precipitation of crystals becomes difficult.

The Sb ₂ O ₃ and As ₂ O ₃ components can be added as a fining agent during glass melting, but the sum of these components is 1% or less.

Further, within the range where the above various characteristics are not impaired, 3%
Ga, Ge, C up to (both in% by mass based on oxide)
u, Fe, Co, Nb, Ti, V, Ce, Gd and B components can be contained. In addition, Mo, Ta, Mn,
It is preferable that the Cr and F components are not substantially contained if possible.

Next, in order to produce the glass-ceramic according to the present invention, first, the glass having the above composition is melted, hot-formed and / or cold-worked, and then 40
Crystallization is performed by heat treatment at a temperature in the range of 0 to 600 ° C. for about 1 to 7 hours to form crystal nuclei, and then heat treatment at a temperature in the range of 650 to 750 ° C. for about 1 to 7 hours.

The main crystal phase of the glass ceramic crystallized by the heat treatment is α-cristobalite, α
-At least one selected from cristobalite solid solution, α-quartz, and α-quartz solid solution,
The particle size (average) was in the range of less than 0.10 μm.

Next, the heat-treated crystallized glass ceramics are lapped by a conventional method and then polished to obtain a glass ceramics having a surface roughness Ra (arithmetic mean roughness) of 1.0 Å or more and 5.0 Å or less. A substrate material was obtained. Then, a magnetic film and, if necessary, Ni—P plating, or an underlayer, a protective layer, a lubricating film, etc., are formed on the glass ceramic substrate material to obtain an information magnetic storage medium disk capable of high density recording. Was given. In addition, Ta ₂ O ₅ /
In the case where the SiO ₂ multilayer film was formed and processed into a chip of 1 mm × 1 mm × 1 mm, an optical filter with good wavelength resolution, in which the fluctuation of the central wavelength due to the temperature change was smaller than that of the conventional one, was obtained. This filter was suitable as a bandpass filter or a Gain-Flattening filter.

[0048]

BEST MODE FOR CARRYING OUT THE INVENTION Next, preferred embodiments of the present invention will be described. Tables 1 to 4 show practical composition examples (No. 1 to 10) of the glass ceramics of the present invention and _two conventional Li ₂ O—SiO ₂ based glass ceramics as comparative composition examples (Comparative Example 1: JP-A-62-72547). JP-A-9-35234, Comparative Example 2: JP-A-9-35234).
Nucleation temperature, crystallization temperature of these glass ceramics,
The values of the crystal phase, the crystal grain size (average), the average linear expansion coefficient (the temperature range is −50 to + 70 ° C.), the specific gravity, and the surface roughness Ra (arithmetic mean roughness) formed by polishing are also shown. Regarding the crystal phases in the table, the α-cristobalite solid solution was described as “α-cristobalite SS” and the α-quartz solid solution was described as “α-quartz SS”.

In each of the glasses of the examples of the present invention, raw materials such as oxides, carbonates and nitrates are mixed, and this is melted at a temperature of about 1350 to 1450 ° C. with a normal melting apparatus and homogenized with stirring. After that, it was molded into a disk shape and cooled to obtain a glass molded body. After that, at 400-600 ° C for about 1-7
After heat treatment for a long time to form crystal nuclei, the temperature is about 1 at 650 to 750 ° C.
Heat treatment and crystallization were performed for about 7 hours to obtain a desired glass ceramic. Next, the above glass ceramics are added to 800 # -2
Lapping with 000 # diamond pellets for about 5 to 30 minutes, then particle size (average) 0.02 to 3.0 μm
The polishing agent (cerium oxide) was used for polishing for about 30 to 60 minutes to finish.

The crystal grain size (average) of each crystal phase was determined by a transmission electron microscope (TEM). The crystal species of each crystal phase was identified by an X-ray diffraction (XRD) device.

Further, the surface roughness Ra (arithmetic mean roughness) was determined by an atomic force microscope (AFM).

The amount of Li ion eluted was measured by ion chromatography. The measurement conditions of the measurement are as follows: 80 ml of ultrapure water (room temperature) and a disk (diameter 65 mm × thickness 0.635 mm) are packed in a film pack, and then the product is kept in a dryer kept at about 30 ° C. for 3 hours, The disk was taken out and ion chromatography measurement was performed.

The average linear expansion coefficient is measured by JOGIS (Japan Optical Glass Industry Association Standard) 16, and the Young's modulus is measured by JOGIS.
Bending strength is measured according to JIS R1601 (3-point bending strength) by the ultrasonic pulse method of IS R1602.
Regarding the measurement of Vickers hardness, according to JIS R1610, plate thickness 10 at a light ray wavelength of 950 to 1600 nm
The light transmittance of mm material is measured by a spectrophotometer, and the specific gravity is measured by JOGIS (Japan Optical Glass Industry Association Standard) 05.
Was measured.

[0054]

[Table 1]

[0055]

[Table 2]

[0056]

[Table 3]

[0057]

[Table 4]

As shown in Tables 1 to 3, the crystal phases of the present invention and the comparative example of the conventional Li ₂ O--SiO ₂ glass ceramics are different, and the glass ceramics of the present invention are
There was no precipitation of lithium disilicate (Li ₂ Si ₂ O ₅ ), and all were at least one selected from α-cristobaray, α-cristobalite solid solution, α-quartz, and α-quartz solid solution. Further, the glass ceramic of Comparative Example 1 has a crystal particle size (average) of lithium disilicate.
Is 1.5 μm, and the glass-ceramics of Comparative Example 2 have a relatively large needle-shaped or rice-grained shape with a β-spodumene crystal particle size (average) of 0.2 μm, which requires smoothness. Under the circumstances, the surface roughness Ra and the defects formed by polishing are affected, and the glass ceramics of Comparative Examples 1 and 2 all have a surface roughness Ra (arithmetic mean roughness) of 11 Å or more, which is extremely smooth. This shows that it is difficult to obtain excellent surface characteristics (Ra is 5 Å or less). Also, the average linear expansion coefficient (× 10 ^-7 / ° C)
Has a low expansion of 48 and 49 and is unsuitable as a substrate material for a magnetic information storage medium and as a material for an optical filter.

Further, on the glass ceramics obtained in the above embodiment, a Cr intermediate layer (8
0 nm), a Co—Cr magnetic layer (50 nm), and a SiC protective film (10 nm). Then, a perfluoropolyether lubricant (5 nm) was applied to obtain an information storage medium. The information storage medium obtained in this way can reduce the head flying height more than before due to its good surface roughness, and by the lamp loading method,
Even when inputting / outputting with the head and the medium in contact, magnetic signals could be input / output without damaging the head or the medium. Further, the glass ceramics of the present invention exhibit a stable bump shape even in the laser texture performed by the landing zone method.

Further, a dielectric multilayer film (for example, TiO ₂ / SiO ₂ , Ta ₂ O ₅ / SiO ₂ , Nb _{2) is} formed on the glass ceramic substrate obtained in the above embodiment by a sputtering method.
O ₅ / SiO ₂ etc.) was deposited to obtain an optical filter. The optical filter thus obtained was able to remarkably reduce the change of the central wavelength of the transmitted light with temperature and had a good resolution of the wavelength.

[0061]

As described above, according to the present invention, it is possible to eliminate the drawbacks found in the above-mentioned prior art and at the same time, to reduce the flying height of the head or to make contact with the head, which is compatible with higher recording density. Lithium disilicate (Li ₂ O ・ 2SiO ₂ ) crystals, which have ultra-smoothness and are capable of reducing alkali components in glass as much as possible, and at the same time are susceptible to surface defects (pits) during alkali elution and polishing Glass ceramics for information storage media that suppresses the above-mentioned phenomenon, and is ultra-smooth so that chipping or chipping is unlikely to occur during processing, good adhesion with the wavelength selection multilayer film, and sufficient compressive stress can be applied to this multilayer film. A glass ceramic for an optical filter can be provided.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References US Patent 4239521 (US, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C03C 1/00-14/00 G11B 5/62-5 / 82 WPI

Claims (8)

(57) [Claims] 1. The main crystalline phase is α-cristobalite, α-
Lithium disilicate (Li ₂ O · 2SiO ₂ ), lithium silicate (Li ₂ O · SiO ₂ ), β while containing at least one selected from cristobalite solid solution, α-quartz, and α-quartz solid solution. -Spodium, β
-Eucryptite, β-quartz, mica and fluorrichterite are substantially absent, and Cr component and Mn component are substantially absent,-
Average linear expansion coefficient at 50 to + 70 ° C. is + 65 × 10
^-7 / ° C. ~ in the range of + 140 × 10 ^-7 / ℃, glass ceramic, wherein the crystal grain size of the main crystal phase (average) is less than 0.10 .mu.m. 2. The glass-ceramic according to claim 1, which has a Young's modulus of 80 GPa or more. 3. The glass ceramics according to claim 1, which has a specific gravity of 2.3 to 2.7. 4. The light transmittance of a material having a plate thickness of 10 mm has a wavelength of 95.
90% or more in 0 to 1600 nm, Glass ceramics in any one of Claims 1, 2 and 3 characterized by the above-mentioned. 5. The glass-ceramic according to any one of claims 1, 2, 3 and 4, which has a bending strength of 250 MPa or more. 6. The glass-ceramic according to any one of claims 1, 2, 3, 4, and 5, which has a Vickers hardness of 600 to 800. 7. The composition of the glass ceramics is a mass percentage (based on oxide) of SiO ₂ 65 to 75% Li ₂ O 4 to less than 7% K ₂ O 0 to 3% Na ₂ O 0 to 3% MgO + ZnO + SrO + BaO + CaO 2 15% Y ₂ O ₃ + WO ₃ + La ₂ O ₃ + Bi ₂ O ₃ 0 to 3% SnO ₂ 0 to 3% P ₂ O ₅ 1.0 to 2.5% ZrO ₂ 2.0 to 7% Al ₂ O ₃ The glass according to any one of claims 1, 2, 3, 4, 5 and 6, characterized in that it contains each component in the range of 5 to 9% Sb ₂ O ₃ + As ₂ O ₃ 0 to 1%. Ceramics. 8. The raw glass is 1 to 7 at 400 ° C. to 600 ° C.
After heat treatment for nucleation for 1 hour, 1 at 650 ° C to 750 ° C
The glass-ceramic according to any one of claims 1, 2, 3, 4, 5, 6 and 7, characterized in that it is obtained by heat treatment for 7 hours to grow crystals.