JPH08221747A - Method for detecting defect in surface of crystallized glass for magnetic disk - Google Patents

Abstract

PURPOSE: To provide a method for detecting defects by which defects in the surface of crystallized glass can easily be discriminated. CONSTITUTION: At least one kind of coloring component selected from among V2 O5 , Cu2 O, MnO2 , Cr2 O3 , CoO, MoO3 , NiO, Fe2 O3 , TeO2 , CeO2 , Pr2 O3 , Nd2 O3 and Er2 O3 is incorporated by 0.5-5wt.% into crystallized SiO2 -Li2 O-RO glass (RO is MgO, ZnO or PbO) so as to ensure a color luminosity factor in the Munsell luminosity range of 0-7 in a CIE color system. Defects in the surface of the resultant crystallized glass are detected by inspecting the glass by visual inspection or with an automatic inspecting device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting defects on the surface of crystallized glass for magnetic disks used as recording media for computers and the like.

[0002]

2. Description of the Related Art The demand for magnetic disks as an external recording medium for large computers, personal computers and the like has been increasing in recent years, and therefore the development thereof has been progressing rapidly.

Conventionally, an aluminum alloy has been used for a magnetic disk substrate. However, an aluminum alloy substrate causes protrusions or spot-like irregularities on the substrate surface during the polishing process due to various material defects. However, the flatness and the surface roughness are not sufficient, and it is not possible to cope with the high-density recording accompanying the further increase in the amount of information today.

Crystallized glass has a composition crystal grain of 0.02
Since it is possible to obtain a dense one having a size of about 20 μm, the flatness and surface roughness are excellent as compared with the aluminum alloy, and it is suitable for high density recording.
In recent years, a substrate for a magnetic disk formed of crystallized glass is being provided.

When forming a substrate for a magnetic disk from crystallized glass, scratches, cracks, chips,
Defects such as pinholes not only adversely affect the performance of the magnetic disk, but depending on the size and amount of defects,
Since it cannot be used as a magnetic disk substrate, all the surfaces of the glass substrates are visually inspected.

[0006]

However, since the conventional crystallized glass for magnetic disk is mainly transparent or milky white, it is difficult to find a defect by the visual inspection, which imposes a heavy burden on the inspector. Not only that, but sometimes an inspection error occurred. Further, since it is difficult to find a defect as described above, it is extremely difficult to introduce an automatic inspection method using a laser beam or the like, and the inspection for the presence or absence of the defect has been a major obstacle in quality control.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for detecting defects on the surface of crystallized glass for a magnetic disk, which enables easy identification of defects on the surface.

[0008]

Means and Actions for Solving the Problems
As a result of earnest research to achieve the above object, in order to easily identify the defect by visible light or laser light, it is sufficient that the defect is different from an optically normal portion. Attention was paid to the present invention.

That is, if the glass has a high color brightness such as transparent or milky white, when the glass substrate has a defect, the reflected light or scattered light from the glass substrate surface is unlikely to have a significant difference. Therefore, it is difficult to identify defects. Therefore, in the present invention, the brightness of the glass is set within a predetermined range to cause a clear difference in the reflected light or the scattered light between the defect on the glass substrate and the normal (good) peripheral portion, and the defect is detected. It is designed to be easily identified.

A method for detecting defects on the surface of crystallized glass for a magnetic disk which achieves the above-mentioned object of the present invention is as follows:
_{SiO 2 65~83%, Li 2 O} 8~13%, K 2
O0-7%, MgO 0.5-5.5%, ZnO 0-
5%, PbO 0-5%, provided that MgO + ZnO + P
bO 0.5 to 5.5%, P ₂ O ₅ 1 to 4%, Al ₂
O ₃ 0 to 7%, As ₂ O ₃ + Sb ₂ O ₃ 0 to 2%,
And as a coloring component in glass, V, Cu, Mn, C
r, Co, Mo, Ni, Fe, Te, Ce, Pr, N
d, a glass containing 0.5 to 5% by weight of at least one component selected from the group consisting of metal oxides of Er and having a Munsell lightness of 0 to 7 in a CIE color system. And a step of detecting a defect on the surface of the colored crystallized glass by visual inspection or by using an automatic inspection device.

Here, when the intensity of the reflected light from the good surface of the glass is R _A and the intensity of the reflected light from the defect is R _B ,
The more R _B >> R _A , the easier the defect discrimination. That is, the darker the color, the smaller R _A becomes,
Defects can be easily identified. In Munsell brightness, the brightness is 1
The value was evaluated on a scale of 0, and the value approaches 10 as the brightness becomes higher, and the value approaches 0 as the brightness becomes lower. Therefore, the Munsell brightness is set in the range of 0 to 7 as described above. This range is set so that when the Munsell brightness exceeds 7,
This is because the brightness becomes high and it becomes difficult to identify the defect.

According to the present invention, this configuration causes a clear difference in the reflected light or scattered light between the defect on the surface of the crystallized glass substrate and the normal surface portion, whereby the defect can be easily identified. You can

Therefore, the visual inspection becomes very easy, and it is of course possible to reduce the burden on the inspector and prevent inspection mistakes. In addition, since it is easy to identify with a laser beam or the like, it is possible to inspect for defects. Can be easily automated.

When the defect is determined, it is desirable that the color of the glass and the color of the inspection light have a relationship of complementary color (complementary color). For example, the color of glass is Y (yellow), M (m
a), C (cyan), the colors of the inspection light are B (blue), G (green), and R (r), respectively.
ed) is desirable.

In the present invention, various ionic species are allowed to coexist with the crystallized glass component to cause color development,
That is, by adding a coloring component to the glass and coloring the glass, the color sensation of the glass is set in the Munsell lightness range of 0 to 7.

Therefore, in the present invention, V, Cu, Mn, Cr and C are added as coloring components in the crystallized glass.
o, Mo, Ni, Fe, Te, Ce, Pr, Nd, Er
0.5 to 5% by weight of at least one component selected from the group consisting of the above metal oxides. Examples of the metal oxide include V ₂ O ₅ , CuO, MnO ₂ ,
Cr ₂ O ₃ , CoO, MoO ₃ , NiO, Fe ₂ O ₃ ,
TeO ₂ , CeO ₂ , Pr ₂ O ₃ , Nd ₂ O ₃ , Er ₂
Examples include O _{3 and the} like.

Here, the content of the coloring component is 0.5
The reason for setting the range to 5% is that if it is less than 0.5%, it is not possible to color it to a predetermined color visual sense, while if it exceeds 5%, the characteristics such as material strength deteriorate. Also,
The coloring component exhibits a color peculiar to the metal ion by itself, but the closer they are mixed, the closer it becomes to black.

In the present invention, the above composition ensures that the color of the crystallized glass is set within the Munsell lightness range of 0 to 7.

The crystallized glass used in the method of the present invention is SiO ₂ --Li ₂ O--RO (where RO is Mg).
O, ZnO or PbO) based glass, M
It is obtained by heat-treating the raw glass containing the gO component as an essential component. This crystallized glass has grown crystal grains (secondary grains) of a crystal phase α-quartz (SiO ₂ ).
Can be used as a crystallized glass for a magnetic disk, which has a spherical particle structure and is polished by controlling the crystal particle size and has excellent surface characteristics.

The colored crystallized glass for magnetic disk used in the present invention is premised to contain the above-mentioned coloring component, and other constituent components of the SiO ₂ —Li ₂ O—RO glass are as follows. It is characterized by that.

In weight percentage, SiO ₂ 65-83%,
Li ₂ O 8 to 13%, K ₂ O 0 to 7%, MgO
0.5-5.5%, ZnO 0-5%, PbO 0-5
%, But MgO + ZnO + PbO 0.5-5.5
_{%, P 2 O 5 1~4%} , Al 2 O 3 0~7%, As
₂ O ₃ + Sb 2 O ₃ It is obtained by heat-treating glass composed of 0 to 2%, and lithium disilicate (Li ₂ O.2SiO ₂ ) and α-quartz (SiO ₂ ) are used as main crystal phases.
₂ ) have.

The composition of this crystallized glass for a magnetic disk can be expressed on an oxide basis as in the case of the original glass, but the reason for limiting the composition range of the original glass as described above is as follows.

That is, the SiO ₂ component is a main crystal of lithium disilicate (Li ₂ O.
2SiO ₂ ) and α-quartz (SiO ₂ ), which are extremely important components for forming crystals, but the amount is 65%.
If it is less than 0.8%, the precipitated crystals of the crystallized glass to be obtained are unstable and the structure tends to become coarse, and if it exceeds 83%, it becomes difficult to melt the raw glass.

The Li ₂ O component is the main crystal of lithium disilicate (Li ₂ O.2SiO) produced by heat treatment of the raw glass.
₂ ) It is a very important component for forming crystals, but if the amount is less than 8%, it becomes difficult to precipitate the above-mentioned crystals and at the same time it becomes difficult to melt the raw glass, and if it exceeds 13%, it is obtained. This is because the precipitated crystals of crystallized glass are unstable and the structure tends to become coarse, and the chemical durability and hardness deteriorate. The amount of Li ₂ O is preferably 8 to 12% in order to make the high hardness and high thermal expansion characteristics of the product (magnetic disk substrate) remarkable and to further reduce the crystal grain size.

The K ₂ O component is an important component for improving the melting property of glass and can be contained up to 7%, but preferably 1 to 6%.

The MgO component is an important component capable of randomly precipitating α-quartz (SiO ₂ ) crystal grains as a main crystal throughout the secondary grain structure, but the amount thereof is less than 0.5%. However, the above effect cannot be obtained, and 5.
If it exceeds 5%, it becomes difficult to deposit desired crystals.

Further, ZnO and PbO components can be added because they have the same effect as MgO, but their amounts are 5% each.
If it exceeds 300, it is difficult to deposit desired crystals.

However, the above-mentioned MgO, ZnO and PbO
The total amount of ingredients should be 0.5-5.5% for similar reasons.

The P ₂ O ₅ component is indispensable as a crystal nucleating agent for glass, but if the amount is less than 1%, desired crystals cannot be produced, and if it exceeds 4%,
Precipitated crystals of the obtained crystallized glass are unstable and easily coarsened.

The Al ₂ O ₃ component is an effective component for improving the chemical durability of the crystallized glass, but if its content exceeds 7%, the meltability deteriorates, and α-quartz as the main crystal is formed. Although the amount of (SiO ₂ ) crystals precipitated decreases, it is preferable to contain 1 to 8%.

The As ₂ O ₃ and Sb ₂ O ₃ components may be added as a fining agent during glass melting, but the total amount of one or two of them is 2% or less.

In the case of producing the colored crystallized glass for a magnetic disk having the above-mentioned structure, the glass having the composition containing the coloring component is melted, hot-molded and / or cold-molded, and then heated to a temperature of 900 ° C. or lower. The crystallization heat treatment is performed in. As a result, lithium disilicate (Li ₂ O.2
A crystallized glass having SiO ₂ ) and α-quartz (SiO ₂ ) and having a color appearance of Munsell lightness in the range of 0 to 7 in the CIE color system is produced. When this crystallized glass is used as a substrate for a magnetic disk, the surface roughness (Ra) is 15 after lapping and lapping by a generally widely known method.
Set within the range of ~ 50Å.

The colored crystallized glass for magnetic disks described above has Munsell brightness set to a color sensation in the range of 0 to 7,
Of course, the defect can be easily identified.
iO ₂ -Li ₂ O-RO (where RO is MgO, Zn
O- and PbO-based glass is obtained by heat treatment, and therefore α-quartz (SiO ₂ ) grown crystal particles (secondary particles) have a spherical particle structure, Since it can be controlled and the surface roughness obtained by polishing has a value in a desired range, it can be suitably used as a magnetic disk substrate.

[0034]

EXAMPLE Next, for a magnetic disk used in the method of the present invention
A preferred example of the colored crystallized glass will be shown. Tables 1 and 2 are books
Colored crystallized glass for magnetic disk used in the method of the invention
The compositions of the components of the respective examples (No. 1 to No. 6) of
3 is conventional SiO₂-Li ₂Comparative set of O-based crystallized glass
The examples show the color and appearance of these crystallized glasses.
Emissivity, Munsell brightness, Ease of defect discrimination, Seed of main crystal phase
It is shown with the class.

The crystallization conditions of each Example and Comparative Example are as follows. (1) Nucleation conditions (temperature x time) Example No. 1 to 6: 540 ° C. × 5 hr Comparative example: 540 ° C. × 5 hr (2) Crystallization conditions (temperature × time) Example No. 1 to 6: 740 ° C. × 2 hr Comparative example: 740 ° C. × 2 hr The crystallized glasses of 1 to 6 are all V ₂
O ₅ , CuO, MnO ₂ , Cr ₂ O ₃ , CoO, MoO
₃ , NiO, Fe ₂ O ₃ , TeO ₂ , CeO ₂ , Pr ₂
At least one component selected from the group consisting of metal oxides such as O ₃ , Nd ₂ O ₃ and Er ₂ O ₃ , in a weight percentage,
The content is 0.5 to 5%, and the Munsell brightness is set in the range of 1 to 7 by this content.

In Tables 1 to 4, Li ₂ Si ₂ O _{5 in the} column showing the main crystal phase is lithium disilicate (Li ₂ O.2SiO ₂ ). Further, ⊚ described in the defect discrimination column indicates that the discrimination is very easy, ○ indicates that the discrimination is easy, and x indicates that the discrimination is difficult.

As can be seen from Tables 1 and 2, No. 1 of the present example. It can be seen that the crystallized glasses of Nos. 1 to 6 each contain the coloring component, exhibit a predetermined color, and have the Munsell brightness set within the range of 1 to 7, and it is easy to discriminate the defects. Further, the crystallized glass of the comparative example does not contain the coloring component, and thus is white or transparent, and has a Munsell brightness of 9 or cannot be displayed, which makes it difficult to determine defects.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

Next, an example of a method for detecting defects on the surface of the crystallized glass substrate for a magnetic disk of the above-mentioned Example 1 using an automatic inspection apparatus will be described.

In order to detect defects on the surface of the crystallized glass substrate for a magnetic disk of Example 1, a known disk surface inspection device with a microscope (type RS-1310 manufactured by Hitachi Electronics Engineering Co., Ltd.) was used. In this apparatus, a laser beam emitted from a He-Ne laser light source (output nominal value 10 mV) passes through a converging lens and converges as a spot on the surface of the magnetic disk (projecting area 565 μ).
m ² , beam system 12 μm in the circumferential direction, 60 μ in the radial direction
m, wavelength 633 nm). The light receiving system of this device is LIGHT
It has three detection light receivers, a light receiver, a DARK light receiver, and a regular reflection light receiver. The LIGHT receiver receives the diffracted light from the surface of the substrate and detects scratches, stains, and dirt on the substrate. The DARK photodetector receives the scattered light and detects foreign matter adhering to the substrate surface. The specular reflection light receiver receives the specular reflection light and detects pit defects and scratches on the substrate. The received light signal indicating any defect is converted into an electric signal by the photomultiplier and the photodetector.

Table 4 shows the noise level and DC level of the DARK light receiving signal obtained from the magnetic disk substrate (hereinafter referred to as "DISK1") made of crystallized glass having the same composition as in Example 1 except that the coloring component was not included. Table 5 shows the noise level of the DARK light receiving signal obtained from the magnetic disk substrate made of crystallized glass of Example 1 (hereinafter referred to as "disk 2"). Similarly, Table 6 shows the noise level and DC level of the LIGHT light reception signal obtained from DISK1, and Table 7 shows the noise level of the LIGHT light reception signal obtained from DISK2.

[0044]

[Table 4]

[0045]

[Table 5]

[0046]

[Table 6]

[0047]

[Table 7]

From Table 4, when the photomultiplier applied voltage exceeds 450 V, the influence of the scattered light from the surface of the crystallized glass not containing the coloring component is enhanced, and as a result, the DC component (mV) at the background level is increased. I understand.
To detect the faint light generated by defects on the substrate surface,
Such a state is not desirable. It was found that when the photomultiplier applied voltage was set to a more preferable value of 500 V, the noise value of the uncolored crystallized glass substrate was significantly higher than the noise value of the crystallized glass substrate of Example 1. This shows that the crystallized glass substrate of Example 1 is much easier to detect defects using the automatic inspection device than the uncolored crystallized glass substrate.

Similarly, in Table 7 showing the LIGHT received light signal data, although not so remarkable as the DARK received light signal data, the crystallized glass substrate of Example 1 has a significant noise value than the uncolored crystallized glass substrate. Turned out to be small.

In the above example using a He-Ne laser (wavelength 633 nm) as a light source for defect detection, cyan-based colored crystallized glass has less noise than non-colored crystallized glass and defects can be easily detected. It turns out that Similarly, when a green light source is used, magenta-based colored crystallized glass, and when a blue light source is used, dark-yellow-based colored crystallized glass produces less noise than non-colored crystallized glass and detects defects. It turns out that is easy. It was also found that when a light source close to neutral light such as a halogen lamp light is used, the crystallized glass colored in a dark system with low Munsell brightness is easier to detect defects than the uncolored crystallized glass. .

[0051]

As described above, according to the present invention, the Munsell brightness 0 to 0 formed by heat-treating a raw glass having a specific composition according to claim 1 containing a coloring component.
Defects on the surface of the crystallized glass substrate for a magnetic disk can be easily detected by visually or visually inspecting the surface of the colored crystallized glass having a color appearance in the range of 7.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G11B 5/82 G11B 5/82

Claims (2)

[Claims] 1. SiO ₂ 65-83 by weight percentage.
%, Li ₂ O 8 to 13%, K ₂ O 0 to 7%, MgO
0.5-5.5%, ZnO 0-5%, PbO 0
5%, but MgO + ZnO + PbO 0.5-5.
5%, P ₂ O ₅ 1 to 4%, Al ₂ O ₃ 0 to 7%, As
₂ O ₃ + Sb ₂ O ₃ 0 to 2%, and V, Cu, Mn, Cr, Co, Mo, N as coloring components in glass.
By heat-treating a glass containing 0.5 to 5% by weight of at least one component selected from the group consisting of metal oxides of i, Fe, Te, Ce, Pr, Nd, and Er, the CIE A step of forming a colored crystallized glass having a color appearance of Munsell lightness in the range of 0 to 7, and a step of detecting defects on the surface of the colored crystallized glass by visual inspection or using an automatic inspection device. A method for detecting defects on the surface of crystallized glass for magnetic disk, comprising: 2. The main crystal phase of the colored crystallized glass is lithium disilicate (Li ₂ O.2SiO ₂ ) and α-.
4. Quartz (SiO ₂ ), characterized in that
The described method.