JPH0470262B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to electrical parts, electronic parts, magnetic recording/optical recording/magneto-optical recording devices, and reproduction devices thereof;
In particular, the present invention relates to high-strength glass for disks used in high-density recording disk substrates used in memory disks serving as storage elements of the above-mentioned magnetic/optical/magneto-optical devices, that is, substrates for magnetic disks, optical disks, magneto-optical disks, and the like. [Prior Art] Plastics and inorganic glasses are being considered as disk substrates for high-density recording. However, plastic's biggest weakness is that it is highly hygroscopic. Therefore, in order to compensate for these defects, improvement of the moisture resistance of the recording film and improvement of the substrate material are being considered. However, as seen in changes over time, there are many unstable factors in achieving long-term reliability. As seen in chemically strengthened conventional soda lime glass, soda aluminosilicate glass, borosilicate glass, etc.
When used alone, the probability of spontaneous destruction is low, but there is a high probability of explosive destruction due to the tensile stress factor caused by migration (ion movement/diffusion) due to bonding with the recording film. Therefore, when used under bonding conditions, glass ceramics with a crystallized structure are considered to be optimal. The contents of the above-mentioned natural fracture and cracking phenomena will be described in detail. In the case of chemically strengthened glass, the combination of substrate glass, chemically strengthened layer, and recording film (inorganic/organic) is such that the chemically strengthened layer has a compressive stress-strengthened layer, whereas the recording film or other bonding material has a tensile force. A necessary condition is a relationship such that In terms of positive bonding, the ideal combination is for the laminating material to have a melting point lower than that of the glass substrate, but the technique for bonding conditions is not limited to the above, and of course there are a few exceptions. In the case of chemically strengthened glass, depending on the composition, particularly if the chemically strengthened layer is inserted too deeply, peeling or cracking may occur in the direction of shrinkage. In addition, in the case of a composite body with a mating material, it is necessary to match the thermal expansion coefficients of the base substrate glass and the laminating material. However, regardless of whether the mating materials are inorganic or organic, phenomena such as migration occur, and if some form of tensile stress is generated through the mating surfaces, explosive destruction may occur, although there may be slight differences depending on the environmental conditions. It may cause a phenomenon. As described above, chemically strengthened glass is extremely dangerous in some cases, and in many cases it is impossible to use it other than as a single glass. Untreated glass parts for surface compressive stress
It is a common practice that the rapid cooling strengthening method and the chemical strengthening method always require a plate thickness of 3 m/m or more. In the case of current high-density recording disk substrates, many of them have a thickness of 2 m/m or less, and it is thought that the thickness will increase further as densities become higher in the future. Therefore, when compressive stress is uniformly applied to the surface of the glass, external tension is used to cancel out the compressive stress, and the glass is strengthened by that amount. Although this is a chemical strengthening phenomenon, consideration must be given to the case where the chemical strengthening layer (compressive stress strengthening layer) disappears due to migration and tensile stress is directly applied. [Problems to be Solved by the Invention] With the recent progress in electronics technology, especially in information-related technology represented by computers, we have already begun to respond to a more full-fledged information society. Documents, data, photos, etc. using semiconductor lasers
Optical disk memory, which can quickly record and reproduce information such as TV images, has a recording density 50 to 500 times that of conventional magnetic memory, and write-once optical disk memory has been put into practical use as a device that can store large amounts of information. has been done. The characteristics of the above-mentioned optical disk memory are that optical memory ranges from CD (compact disk) and VD (video disk) to CD-ROM (CD-Read Only).
Memory), write-once type (DRAW; Direct Read
Erasable Direct (Erasable Direct)
Read After Write) disks are expected to be introduced soon. The characteristics of optical disk memory are as follows. 1 Recording and playback is possible without contact. 2 Random access is possible. 3. Reproductions are inexpensive. 4 High density and high capacity are possible. While taking advantage of the above features, optical disks
Applications are expanding from consumer products such as CDs and VDs to office automation equipment and information processing equipment such as video filing and document filing. , the development of high-speed search technology has become an issue. At present, plastic is overwhelmingly used as the substrate material for these optical disks, and some optical disks for additional large code data are made of chemically strengthened glass (soda lime glass, soda aluminosilicate glass, soda lime glass, soda aluminosilicate glass, borosilicate glass) has been tested. However, it has been pointed out that conventional plastic substrates have defects such as deformation due to heat, birefringence, and warping due to moisture absorption. Further, in conventional chemically strengthened glass, the apparent strength of the substrate itself is improved, but when combined with a recording film, the chemically strengthened layer is eroded by phenomena such as migration, resulting in a decrease in strength. Further, if tensile stress is generated in the recording film relative to the substrate glass, explosive destruction occurs, causing damage to surrounding equipment. As mentioned above, plastic and chemically strengthened glass are used as substrate materials for optical disk memories.
Each has advantages and disadvantages, and will likely be used depending on the application, but they cannot be used as substrate materials that will require higher performance in the future. As a substrate for optical disks, magneto-optical disks, etc., it has heat resistance, mechanical strength, high processing accuracy, and has low birefringence, and the amount of compressive stress is gently diffused with little migration.
A high-strength glass substrate of the present invention, which is characterized by containing ZnO, is required. Although chemically strengthened glass is strengthened, it has been pointed out that it can break as described above and has drawbacks such as being expensive. However, the high-strength glass of the present invention exhibits high mechanical strength even when a recording film is bonded thereto, and the recording density is improved, so that the cost per unit memory is actually lower. Therefore, the characteristics of the chemically strengthened glass substrate of the present invention can be expressed as follows.
Namely: 1. Deterioration of the recording film can be prevented because it does not allow oxygen or moisture in the air to pass through. 2 Almost no birefringence. 3 No warping due to moisture absorption. 4. Due to its high rigidity, there is no deformation during rotation. 5. Machining accuracy is high and eccentric surface runout is less likely to occur. As described above, the substrate using the high-strength glass of the present invention overcomes the drawbacks of conventional substrates and has a completely ideal glass composition. Future technological trends and required characteristics, as well as the characteristics of the high-strength glass of the present invention, are that in optical disks and magneto-optical disks, the light spot position is controlled electro-optically, but this control requires a physical range. Due to the limitations, the mechanical properties of the disk substrate itself must also be sufficiently good. If there is undulation in the circumferential direction, or if the material has orientation (due to the glass forming process), the heat generated by the resistance friction during rotation will cause surface deflection, and if the curvature is large, it will come into contact with the lens surface. There is also a possibility. If the eccentricity is large, the operation will become unstable. Therefore, the flatness and concentricity of the substrate are particularly important factors.Since the disk substrate also protects the recording film, the substrate material must be resistant to environmental conditions such as temperature, humidity, and mechanical strength. desired. Regarding optical properties, the higher the transmittance of the glass substrate, the better, from the relationship between laser output and medium sensitivity. Furthermore, if the birefringence is large, the level of the photodetector will fluctuate, and the amount of light returned to the laser will increase, making it easier to generate noise. Particularly in the case of magneto-optical disks, since signals are detected using the rotation of the plane of polarization of light, the presence of birefringence in the disk substrate is a major hindrance. Also, changes in the tilt and thickness of the substrate cause optical aberrations. In any case, the substrate using the high-strength glass of the present invention has better surface smoothness than substrates made of aluminum or plastic, and in addition, because of its high strength, the wall thickness can be made thinner. It is possible to improve recording density. Bending strength and hardness are also important points, and we achieved accuracy one level higher than conventional technology, with surface roughness of 15 to 20 Å and flatness (for a 5.25-inch disk) of less than 2 μm. [Means for Solving the Problems] The present invention provides highly safe glass that does not spontaneously fracture despite being chemically strengthened glass. That is, the high-strength glass of the present invention contains, based on weight, SiO ₂ 60.0-70.0%, Al ₂ O ₃ 0.5-14.0%, and R ₂ O.
(R is an alkali metal) 10.0 to 32.0%,
It consists of 1.0-15.0% ZnO _and 1.1-14.0% _B2O3 , and the glass surface is immersed in alkali molten salt to convert the alkali ions in the glass surface layer into alkali ions with a larger ionic radius. It is characterized by being a high-strength glass for disks having a stress layer, a linear expansion coefficient of 70×10 ^-7 /°C or more, and a compressive strength and a bending strength of 6000 Kg/cm ² or more. (a) Based on weight, SiO ₂ 60.0-70.0%, Al ₂
O ₃ 1.0-14.0%, R ₂ O (R is an alkali metal)
10.0~32.0%, ZnO1.0~15.0%, _{B2O3 1.1} ~12.0%
(b)Based on weight, PbO, BaO, ZrO ₂ , TiO ₂ ,
It consists of a component containing 12% or less of at least one additive selected from among arbitrary components such as As ₂ O ₃ , Sb ₂ O ₃ , MgO, and SrO, and the glass surface is immersed in an alkali molten salt. It has a stress layer in which the alkali ions on the glass surface layer are ion-exchanged with alkali ions with a larger ionic radius, and the coefficient of linear expansion is 70×.
10 ^-7 /℃ or higher, compressive strength and bending strength are both
It is characterized by being a high-strength glass for disks with a strength of 6000Kg/cm ² or more. Compressive stress is generated on the glass surface due to migration, which remains on the glass surface after cooling and strengthens the glass. It is possible to obtain high-strength glass with excellent reinforcement properties. In particular, the composition of the glass of the present invention is as follows:
Ideal for chemically strengthening thin glass plates of less than m
Because the stress layer is slowly diffused to the depths without damaging the surface, i.e., ions are diffused instead of layered, there is no natural destruction, and after chemical strengthening,
There is no change in the degree of reinforcement even after precision polishing. Chemical strengthening is performed at the transition point of glass (minus 100°C).
Ion exchange is carried out by immersing the glass in a molten alkali salt containing the alkali ions contained in the glass and the alkali ions with a larger ionic radius at a temperature below (near). As a result of the above ion exchange, compressive stress is generated on the glass surface due to the difference in the occupied volume of alkali ions, and this stress remains on the glass surface after cooling, so that it is strengthened. [Example] The following three types of treatment liquids are suitable for use in chemically strengthening the high-strength glass of the present invention. 1 KNO ₃ 100% (wt%) 2 KNO ₃ 60% + NaNO ₃ 40% (wt%) (Especially effective when containing Li ₂ O) 3 KNO ₃ 99.5% + H ₂ SiO ₃ 0.5% (wt%) Above Li ⁺ and Na ⁺ in glass depending on treatment solution
Ions are exchanged with Na ⁺ and K ⁺ ions in the processing solution. Because two types of ion exchange occur at the same time, it exhibits excellent reinforcing properties. Composition 1 (wt%) SiO ₂ 64.0 AlO ₃ 8.5 Na ₂ O 8.0 K ₂ O 7.0 ZnO 2.7 Li ₂ O 1.0 BaO 1.0 B ₂ O ₃ 2.0 TiO ₂ 1.0 ZrO ₂ 4.5 As ₂ O ₃ 0.3 Composition 2 (wt%) SiO ₂ 62.4 Al ₂ O ₃ 2.9 Na ₂ O 9.0 K ₂ O 9.1 CaO 0.1 MgO 2.8 ZnO 11.5 B ₂ O ₃ 1.1 TiO ₂ 0.6 As ₂ O ₃ 0.2 Sb ₂ O ₃ 0.3 In each of the above composition examples 1 and 2 The relationships among the chemical strengthening treatment time, bending strength, shear pie strength, and stress strain layer thickness thus obtained are shown in Table 1 below.
There is almost no difference between Composition Examples 1 and 2.

[Table] The glasses of the above two examples were obtained by putting a powdery mixture in an open crucible, heating and melting it at 1450 to 1500°C, keeping it at this temperature for 4 to 12 hours, and cooling it gradually over 4 hours after clarification. Note that due to structural homogeneity, a stable chemical strengthening method is to perform chemical strengthening treatment after complete gradual straining. Therefore, structural inhomogeneity (strain etc.)
If there is orientation during molding, bending, twisting, etc. will occur. Inspection results using a surface stress meter show that ordinary soda lime glass, soda aluminosilicate glass,
The chemically strengthened layer diffuses more slowly than borosilicate glass and does not lead to natural destruction. The object of the present invention is to obtain a glass composition that does not cause spontaneous breakage or breakage at the composite stage due to tensile stress caused by reaction phenomena such as migration caused by bonding with the recording film as described above. The high-strength glass of the present invention (refractive index 1.510~
1.535 SiO ₂ in the basic component (with an Atsube number in the range of 63.0 to 50.0) is required in an amount of 60.0 to 70.0% based on the total weight. If this amount is less than 60.0%, chemical durability deteriorates, and if it is more than 70%, it becomes difficult to melt and workability decreases. Next, Al ₂ O ₃ is used to improve chemical durability and adjust the viscosity of molten glass, but if the amount is less than 0.5%, these effects are insufficient, and if the amount is more than 14.0% This is not preferable because the viscosity of the glass increases more than necessary, making it difficult to handle. Furthermore, R ₂ O (alkali metal oxides such as NaO ₂
6.0~14.0%, _Li2O0 ~5.0%, _K2O4.0 ~13.0%) on a weight basis for the purpose of adjusting glass viscosity, ion exchange component, thermal expansion coefficient, and lowering melting temperature.
R ₂ O is used in a range of 10.0 to 32.0%. If this amount is less than 10.0%, the glass becomes poorly soluble and chemical strengthening becomes impossible. Moreover, if it exceeds 32%, it is not preferable because it causes a decrease in the viscosity of the glass, a decrease in the refractive index, a deterioration in the chemical durability, and an adverse effect on the strength due to chemical strengthening of the glass. The high-strength glass of the present invention includes, in addition to the above components,
A base component of 1.0-15.0% ZnO is required. This component is necessary for maintaining chemical durability and refractive index.
It also prevents phenomena that can lead to destruction of chemically strengthened glass. In other words, ion exchange does not show a significant reinforcing layer as seen in soda aluminosilicate glass, soda lime glass, borosilicate glass, etc.
Since the diffusion of ions occurs slowly, the chemically strengthened layer does not clearly appear in the form of a layer. Therefore, there is no migration due to reaction and diffusion with the recording film or other mating materials, which does not lead to destruction. In addition to the above basic components, the high-strength glass of the present invention further contains PbO, BaO, ZrO ₂ , TiO ₂ , Li ₂ O,
At least one optional component selected from MgO, CaO, As ₂ O ₃ and Sb ₂ O ₃ can be contained. These are added to improve the meltability, bubble breakability, clarification, etc. of glass, but based on weight, ZrO ₂ is 4.0% or less, PbO is 12.0% or less, BaO is 12.0% or less, TiO ₂
1.0% or less for MgO, 4.0% or less for CaO, _7.0 % or less for _As2O3 and _Sb2
Even if each O ₃ is contained within a range of 1.0% or less, there is no adverse effect on the high strength glass of the present invention. Furthermore, in the present invention, in addition to the above-mentioned basic components or optional components, if UV transmission is not required (NiO and CoO colorants are excluded), coloring components commonly used in the production of ordinary colored glass may be used. can be contained. Such coloring components include, for example, Se,
CuO, _Cu2O , _Cr2O3 , _{Nd2O3 ,} NiO, _CoO ,
Examples include metal oxides such as MnO ₂ (MnO) and Fe ₂ O ₃ (FeO). These may be used alone or in combination of two or more. No problem will arise if the total amount of these coloring components is 3% or less based on the total weight of the high-strength glass of the present invention. Table 2 below shows the characteristic values of the high-strength glass of the present invention made with the composition 1, and Table 3 shows the characteristic values of the high-strength glass of the present invention made with various other compositions.

【table】

【table】

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〔Effect of the invention〕

Since the high-strength glass of the present invention has the composition described in the claims, it does not spontaneously fracture even though it has been chemically strengthened, is highly safe, and has a high plate thickness. can be made thinner. Therefore, it is suitable as a substrate material for optical disks and magneto-optical disks, and when the recording substrate is made of the glass of the present invention, deterioration of the recording film can be prevented. Benefits include almost no birefringence, no warping due to moisture absorption, high rigidity so no deformation during rotation, and high processing accuracy to prevent eccentric surface runout.

Claims (1)

[Claims] 1 Based on weight, SiO ₂ 60.0-70.0%, Al ₂ O ₃ 0.5
~14.0%, R ₂ O (R is an alkali metal) 10.0
~32.0%, ZnO1.0~15.0%, and _{B2O3 1.1} ~14.0%, and the glass surface is immersed in alkali molten salt to transform the alkali ions in the glass surface layer into alkali ions with a larger ionic radius. It has an ion-converted stress layer, a linear expansion coefficient of 70×10 ^-7 /℃ or more, and a compressive strength and bending strength of 6000 Kg/cm ²
The above is the high-strength glass for disks. 2 (a) Based on weight, SiO ₂ , 60.0 to 70.0%,
Al ₂ O ₃ 1.0-14.0%, R ₂ O (R is an alkali metal) 10.0-32.0%, ZnO 1.0-15.0%, B ₂ O ₃
88% or more of the basic components consisting of 1.1 to 12.0%, and (b) based on weight, PbO, BaO, ZrO ₂ , TiO ₂ ,
At least one additive component selected from optional components of As ₂ O ₃ , Sb ₂ O ₃ , MgO, SrO, and CaO
It has a stress layer in which the glass surface is immersed in a molten alkali salt to exchange the alkali ions on the glass surface layer with alkali ions having a larger ionic radius. High-strength glass for disks, which has a compressive strength of 70×10 ^-7 /°C or more and a compressive strength and a bending strength of 6000 Kg/cm ² or more.