JPH061604A - Glassy carbon and method for producing the same - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To provide glassy carbon having favorable characteristics as a substrate for a recording medium. [Structure] Glassy carbon having a bending strength of about 24 kgf / mm ² or more. And a method for producing glassy carbon comprising a curing step of curing a thermosetting resin and a carbonizing and firing step of heating and carbonizing a resin material obtained by this curing step, wherein the carbonizing and firing step is A first treatment step in which heat treatment is performed at about 1000 to 1400 ° C. in an inert atmosphere, an inert atmosphere, and about 1000
And a second treatment step of performing heat treatment at about 1500 to 2000 ° C. under a pressure equal to or higher than atmospheric pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to glassy carbon used as a substrate for recording media and a method for producing the same.

[0002]

BACKGROUND OF THE INVENTION Currently, aluminum alloys are mainly used as a material for hard disk substrates, and Ni-P of about 10 μm is formed on the surface of the aluminum alloy.
Plated ones are used. However,
The aluminum alloy substrate has a problem that its rigidity becomes insufficient when the thickness becomes thin. In other words, if the rigidity is insufficient, the substrate will be wavy during mirror surface processing and cannot be flattened. Therefore, when a wavy substrate is used as a disk, uneven rotation will occur and the flying height of the magnetic head will be small. There is an inconvenience that it cannot be done, and further, there is an inconvenience that the disk is deformed when chucking the spindle.

Further, a disk is generally manufactured by forming a magnetic film on a substrate by a thin film forming means such as sparring. At this time, since the substrate temperature is several hundreds of degrees, heat resistance is required. To be done. However, the substrate made mainly of an aluminum alloy has a problem of insufficient heat resistance, and as a result, the substrate is thermally deformed.

Furthermore, it is known that the coercive force of the magnetic film increases when the substrate is heated after film formation. From this viewpoint, heat treatment may be carried out, and therefore heat resistance is further required. By the way, glass such as crystallized glass and tempered glass is considered as a substrate material having high rigidity and heat resistance.
In addition, although glass is excellent in surface smoothness and hardness required for a substrate, it has a drawback that it is vulnerable to breakage (impact) and that water is likely to be adsorbed on the surface. Also, during sputtering to form a magnetic film,
In order to obtain a high-performance magnetic film, it is necessary to raise the degree of vacuum, but there is also the disadvantage that moisture is exuded from inside the glass due to reduced pressure (vacuum), making it difficult to raise the degree of vacuum. Furthermore, when heating the substrate, an infrared heater is often used, but infrared rays penetrate the substrate and the heating efficiency of the substrate is poor,
Further, since the substrate has a high specific resistance, dust is likely to be attached due to static electricity, which also causes an increase in error rate. Therefore, there is currently no prospect that glass will replace aluminum alloy as a substrate material.

For these reasons, carbon, particularly glassy carbon, has begun to attract attention as a material completely different from the above-mentioned aluminum alloy and glass. That is, glassy carbon generally has a three-dimensional network structure, and is obtained by firing and carbonizing a cured product of a thermosetting resin having an insoluble / infusible property in an inert atmosphere. And
This material has excellent gas impermeability, high hardness, and has an isotropic structure. Furthermore, in addition to characteristics such as light weight, heat resistance, high electrical conductivity, corrosion resistance, high thermal conductivity, and high lubricity,
Since it is homogeneous and does not generate carbon powder even when used for sliding parts, it is expected to be widely used in various fields including the electronics industry, nuclear power industry and space industry. From this point of view, the applicant of the present invention has also proposed to utilize glassy carbon as a substrate for a hard disk (Japanese Patent Laid-Open No. 60-33333).

Conventional glassy carbon obtained from a raw material containing a thermosetting resin such as phenol resin or furan resin as a main component has pores and pores (pores, pores) of the order of μm or more. ing. Therefore, even if it is attempted to polish the glassy carbon to obtain a hard disk substrate with excellent surface smoothness, the closed holes existing inside the material become open due to the polishing, and minute defects occur on the polished surface, resulting in poor surface smoothness. It is difficult to obtain a rich substrate, and it is difficult to obtain a recording medium having excellent recording / reproducing characteristics.

In particular, in recent years, hard disk devices have become smaller and higher in density, and the disk drive itself has been made smaller, so that the hard disk substrate tends to be made thinner. With the increase in density, the areal recording density has become extremely large, that is, the recording area per bit has become small, and even minute defects have become unacceptable. Therefore, a high degree of surface smoothness is required also from this point of view.

Incidentally, Kobe Steel Technical Report (Vol. 39 N
o. No. 4 (1989)) was filled with phenol / formaldehyde resin powder in a mold, molded by hot pressing, and then pre-baked at a temperature of 1200 to 2000 ° C. in an inert gas, and hot isostatic pressing at an ultrahigh temperature. A technique of performing pressure treatment to eliminate closed pores (micropores) is disclosed. That is, in the glassy carbon obtained from the thermosetting resin (phenol / formaldehyde resin) powder, bubbles in the material that could not be completely removed by hot pressing, 1200-2
Micro-porosity exists due to pyrolysis gas generated in the pre-baking stage at a temperature of 000 ° C and crystal grain boundaries generated because the raw material is powder. Has occurred. Therefore, ultra-high temperature hot isostatic pressing treatment, that is, heat treatment at 2500 ° C. under a pressure of 200 MPa densifies the material and eliminates micropores,
This is to prevent microscopic defects from occurring on the polished surface after mirror polishing. However, with this method, 200MP
a, an ultra-high temperature hot isostatic pressing device of 2000 ° C. or higher is required, and 200 MPa, which has become popular in recent years,
A hot isostatic pressing device for ceramics up to 2000 ° C cannot be used, and it is very burdensome in terms of equipment and cost. Moreover, the glassy carbon material thus obtained is 180 to 200 MPa (18 to 20 kgf /
The strength is only about mm ² ), and it is hard to say that it is still sufficient in terms of reliability.

[0009]

DISCLOSURE OF THE INVENTION The present inventor pays attention to the items required for a hard disk substrate, that is, cracks and chips are less likely to occur at the time of inner / outer peripheral processing and chamfer processing at the time of processing a substrate, and the formation of a texture or a thin film. In order to achieve high recording density, it is necessary to reduce the waviness of the substrate due to the followability of the magnetic head because of the high strength in terms of reliability during handling during formation, and the high rigidity of the substrate material. The surface smoothness of the substrate is good,
There are no microscopic defects, the substrate is non-magnetic in order to improve the characteristics of the magnetic film, it has good corrosion resistance and weather resistance, it has excellent impact resistance, reliability during manufacturing, and CSS characteristics. From the standpoint of (durability), it has a high hardness, the CSS characteristics are improved, and the spindle load of the hard disk drive is reduced. The board is lightweight. Focusing on the fact that the specific resistance is small, the present invention has been completed after intensive studies.

That is, there is provided a method for producing glassy carbon comprising a curing step of curing a thermosetting resin and a carbonizing and firing step of heating and carbonizing the resin material obtained by the curing step. The firing step is a first treatment step of heat treatment at about 1000 to 1400 ° C. in an inert atmosphere, and a second treatment heat treatment at about 1500 to 2000 ° C. under an inert atmosphere and a pressure of about 1000 atmospheres or more. And a step of curing a thermosetting resin capable of containing about 20% by weight or more of water in the state of an initial condensation product before curing. A method for producing glassy carbon, which comprises a step and a carbonizing and firing step of heating and carbonizing the resin material obtained by this curing step, wherein the carbonizing and firing step comprises an inert atmosphere. About 1000~1400 ℃ in below
First treatment step of heat treatment in an inert atmosphere, and
About 1500 to 20 under a pressure of about 1000 atmospheres or more
The present invention has led to the invention of a method for producing glassy carbon characterized by comprising a second treatment step of heat treatment at 00 ° C., and the glassy carbon obtained by such a method has a bending strength of 24 kgf / mm. are those having ^two or more properties, particularly flexural strength has a 24kgf / mm ² or more characteristics, it can be seen that diameter of the pores is 0.1μm or less, such glassy carbon disc substrate As a result, they have found that they sufficiently satisfy the required characteristics.

That is, the glassy carbon according to the present invention is
Mechanical strength is improved such as bending strength of 24 kgf / mm ² or more, there are almost no cracks or chips that may be a concern in the magnetic disk manufacturing process, and the elastic modulus is 2000 Kgf / mm ² compared to conventional glassy carbon. To about 2500 Kgf
/ Mm ² or more such as about 2-3% or more even though improved, are those that do not swell problems, and surface smoothness of the mirror-polished (center line average roughness Ra) of up to about 1.0nm It is possible, minute defects (open holes, crystal grain boundaries, etc.) are hardly recognized on the material surface, and the density is 1.6 to 1.
It has a light weight of 8, a low specific resistance, good corrosion resistance and weather resistance, and high hardness and non-magnetic property.
Therefore, from the above, it is understood that this glassy carbon has extremely preferable characteristics as a substrate of a recording medium.

A preferable thermosetting resin in the present invention is one which can contain 20% by weight or more of water in the state of an initial condensate before curing. Here, the "initial condensate" means a resin before curing, which may contain a considerable amount of raw material monomers, but refers to a resin composition having a high viscosity due to addition and / or condensation reaction to some extent. . A characteristic of the thermosetting resin composition is that a low boiling point substance such as condensed water does not accumulate during curing, that is, the initial condensate having a high viscosity before the thermosetting resin is cured. By making the resin hydrophilic enough to contain 20% by weight or more of water in the above state, even if the low-boiling substance is trapped in the resin (or in the cured product), The accumulation of things will not occur.
In order to completely disperse and dissolve the low-boiling substance in the resin, a resin composition that can contain 30% by weight or more of water is desirable.

At what viscosity the thermosetting resin composition has, if the water-solubility of the resin composition exceeds 20% by weight, almost no pores will be formed after curing and carbonization. It depends on the type of raw material resin, the degree of polymerization, the blending ratio, etc.
20% by weight in a viscosity state of 8000 cps / 20 ° C
It has been found that a water-soluble capacity exceeding 10 is sufficient.

The initial condensate of the thermosetting resin in the present invention can be appropriately designed depending on the kind of raw material resin, blending ratio, control of polymerization degree, modification and the like. Examples of the thermosetting resin used in the present invention include phenol resin, epoxy resin, unsaturated polyester resin, ester resin,
Furan resin, urea resin, melamine resin, alkyd resin, xylene resin and the like can be mentioned, and these resins are used as they are, or by blending or modifying them. Resins based on modified phenol-furan resins are preferred, for example JP-A-60-17120.
No. 8, JP-A-60-171209, JP-A-6
The thermosetting resins disclosed in JP-A No. 0-171210 and JP-A No. 60-171121 are mentioned. As those that can be modified into a thermosetting resin, the above-mentioned phenolic resins, thermosetting resins such as furan resin, or asphalt, materials having a naturally high carbonization yield such as pitches, lignin, cellulose, Examples thereof include hydrophilic substances having a relatively high carbonization yield, such as tragacanth gum, gum arabic, humic acid, and various sugars.

In addition, a filler may be added in carrying out the present invention. As the filler, various carbon materials including the above-mentioned thermosetting resin, for example, polyacrylonitrile-based carbon material, cellulose-based carbon material, rayon-based carbon material, pitch-based carbon material, lignin-based carbon material, phenol resin-based carbon material, furan In addition to resin-based carbon materials, epoxy resin-based carbon materials, alkyd resin-based carbon materials, unsaturated polyester-based carbon materials, and xylene resin-based carbon materials, there are various types of graphite, carbon black, and the like.

Then, the thermosetting resin, filler or the like as described above is put into a mold having a predetermined shape according to the intended use before curing, and a curing step by heating or the like is performed to obtain a predetermined shape. A resin material is obtained. In the carbonization and firing step of heating and carbonizing the resin material having a predetermined shape obtained in this manner, about 1000 in an inert atmosphere.
˜1400 ° C., then about 1500-2 at a pressure of about 1000 atm or more in an inert atmosphere.
Heat treatment at 000 ° C.

By such treatment, the glassy carbon becomes
It is substantially non-porous, more packing, and the micropores present inside the material are smaller in size and densified. Moreover, since the pressure heat treatment step was set to 2000 ° C. or less, graphitization of glassy carbon was suppressed, the density was high, and the mechanical strength (bending strength) was greatly improved to 24 kg / mm ² or more,
The cracks and chips during substrate processing are drastically reduced, and the reliability of handling when forming a thin film is improved.

Here, the inert atmosphere in the pretreatment step (first treatment step) is an atmosphere containing no oxygen and usually containing at least one gas selected from the group consisting of helium, argon, nitrogen and the like. Or, it means a reduced pressure or vacuum state. Further, the temperature in the pretreatment step is required to be about 1000 to 1400 ° C, more preferably about 1100 to 1300 ° C. In this case, the carbonization firing time may be appropriately selected depending on the type and shape of the resin material and the firing temperature.

If the pretreatment firing temperature is too low, that is, lower than 1000 ° C., sufficient carbonization has not yet been reached in the pretreatment process stage, and the pores have not become sufficiently small. or,
Hydrogen and oxygen remaining in the material are not sufficiently removed in the pretreatment process, and if pressure heat treatment is performed with residual hydrogen and oxygen present, the release of hydrogen and oxygen is suppressed, and The above reaction may be caused, the carbon-carbon bond may be broken, and the strength may be reduced. Therefore, the target characteristics are not reached even after the subsequent pressure heat treatment step.

On the contrary, when the pretreatment firing temperature is higher than 1400 ° C. and is too high, pores are scarcely found and the structure is very dense, but graphitization is progressing, and after-treatment is performed. Even if the pressure heat treatment is performed, the strength becomes insufficient. For this reason, chipping or the like is likely to occur even with a slight impact during the manufacturing process of the recording medium. The inert atmosphere in the pressure heat treatment step which is the post-treatment step (second treatment step) is usually at least one gas atmosphere selected from the group consisting of argon, nitrogen and the like. The temperature in the pressure heat treatment step needs to be about 1500 to 2000 ° C. 1
If the temperature is too low below 500 ° C, the expected effect cannot be obtained. On the other hand, at a temperature higher than 2000 ° C. and too high, graphitization proceeds and the density becomes high, but the mechanical strength decreases. For this reason, chipping or the like is likely to occur even with a slight impact during the manufacturing process of the recording medium.

As a method of applying pressure, a method of applying a hydraulic pressure or other mechanical force from the outside into a closed container to directly or indirectly apply a pressure to the material being processed can be used. By this method, the atmospheric pressure in the closed container can be increased to 1000 atmospheric pressure or higher, and this pressure can be used to apply an isotropic pressure to the internal sample. Such treatment can be carried out by a hot isostatic press.

Good results are obtained when the pressure in the pressure heat treatment step is 1000 atm or higher, particularly about 1500 atm or higher, regardless of the type of the thermosetting resin composition. The glassy carbon thus obtained has a large mechanical strength and has a surface smoothness of R after mirror polishing.
It is possible for a to be up to about 1.0 nm, and minute defects (opening, grain boundaries, etc.) are hardly recognized on the material surface. or,
It also has the properties of glassy carbon itself, that is, low specific resistance, good corrosion resistance and weather resistance, light weight, high hardness, and non-magnetic properties.

Therefore, when the obtained glassy carbon was used as a substrate material for a hard disk, it was remarkably preferable as compared with conventional glass and ceramics. Hereinafter, the present invention will be described in more detail with reference to Examples.

[0024]

【Example】

[Example 1] Furfuryl alcohol 500 parts by weight, 92
% Paraformaldehyde (480 parts by weight) and water (30 parts by weight) are dissolved by stirring at 75 ° C., and phenol 5 is added under stirring.
20 parts by weight, sodium hydroxide 8.8 parts by weight and water 4
5 parts by weight of the mixed solution was added dropwise. After finishing the dropping, 3 at 75 ℃
Reacted for hours. Then, a mixed solution of 80 parts by weight of phenol, 8.8 parts by weight of sodium hydroxide and 45 parts by weight of water was further added dropwise and reacted at 75 ° C. for 4.5 hours. Thirty
After cooling to ° C, it was neutralized with a 60% aqueous paratoluenesulfonic acid solution. The neutralized product is dehydrated under reduced pressure to 170
By weight of water was removed, and 500 parts by weight of furfuryl alcohol was added and mixed. The viscosity of the obtained resin is 37 at 20 ° C.
It was 0 cps. The water content of the resin was measured and found to be 39% by weight.

To 100 parts by weight of this thermosetting resin, 3.5 parts by weight of a mixed solution of 70 parts by weight of paratoluenesulfonic acid, 20 parts by weight of water and 10 parts by weight of cellosolve was added, and after sufficiently stirring, the thickness was increased. It was poured into a 5 mm mold and degassed under reduced pressure. Next, it was heat-cured at 50 ° C. for 3 hours and further at 80 ° C. for 2 days. The obtained resin cured product is put in an organic firing furnace (made by Chugai Furnace Industry Co., Ltd.), heated to 700 ° C. at a heating rate of 2 to 5 ° C./hour in a nitrogen atmosphere, and further placed in a vacuum of about 0.5 mTorr. 1200 ℃ at a heating rate of 5 to 20 ℃ / hour
The mixture was heated and calcined up to, held at this temperature for 2 hours, and then cooled.

Next, the glassy carbon obtained in the pretreatment step was inserted into a sample chamber of a hot isostatic pressing (HIP) apparatus, and pressurized with argon gas at a temperature rising rate of 500 ° C./hour. The mixture was heated to 1500 ° C., kept at 1500 ° C. and 2000 atm for 1 hour, and then cooled. The density of the obtained glassy carbon was 1.65 g / cm ³ , and the fracture surface was clearly glassy.

Then, with # 500 to # 8000 abrasive grains
Mirror-polished, and the surface pore condition and pore diameter of the polished surface are determined by scanning
Observed with a microscope. Pore size is 0.05-0.01 μm
The following are problems that may cause problems (opening and grain boundaries).
Etc.) did not exist. The surface smoothness is Ra 1.0
nm, which was extremely good. In addition, the material
Bending strength measured according to JIS standard R1601
As a result, bending strength is 29.8 kg / mm²Met. Bullet
The sex rate is 2500 kgf / mm ²Met.

The glassy carbon thus obtained is
Since the mechanical strength is improved, the problem of cracking and chipping during substrate processing is extremely unlikely to occur, and the reliability during handling in the magnetic disk manufacturing process (cleaning, texturing, film formation, evaluation tests) is improved. It was rich.
Further, since the elastic modulus is improved, the problem of undulation is also improved. Furthermore, the impact resistance is also improved.

Then, a magnetic film was prepared by providing a magnetic film on the substrate made of the above-mentioned glassy carbon by a predetermined thin film forming means, and the magnetic disk was mounted on a recording / reproducing apparatus to try recording / reproducing. Characterized. [Example 2] The glassy carbon obtained by the pretreatment process of Example 1 was similarly heat-treated under pressure by HIP. HIP
The final treatment temperature is 2000 ° C., the pressure is 2000 atm, and the rate of temperature increase and the holding time are the same.

The density of the glassy carbon obtained was 1.75 g.
/ Cm³, The fracture surface is glass-like, and the surface of the polished surface is hole-like
The state is the same as in Example 1, and the pore size is 0.05 to 0.01.
It is less than μm, and there is no problematic defect.
It was The surface smoothness is Ra of 1.3 nm, which is extremely
It was good. In addition, the bending strength of the material is specified by JIS
As a result of measurement based on the rating R1601, the bending strength was 25.
9 kg / mm²Met. The elastic modulus is 2600 kgf
/ Mm ²Met.

The glassy carbon thus obtained is
Since the mechanical strength is improved, the problem of cracking and chipping during substrate processing is extremely unlikely to occur, and the reliability during handling in the magnetic disk manufacturing process (cleaning, texturing, film formation, evaluation tests) is improved. It was rich.
Further, since the elastic modulus is improved, the problem of undulation is also improved. Furthermore, the impact resistance is also improved.

Then, a magnetic film was prepared by providing a magnetic film on the above-mentioned glassy carbon substrate by a predetermined thin film forming means, and the magnetic disk was mounted on a recording / reproducing apparatus to attempt recording / reproducing. Characterized. [Example 3] The glassy carbon obtained in the pretreatment step of Example 1 was similarly heat-treated under pressure by HIP. HIP
The final treatment temperature was 1750 ° C., the pressure was 2000 atm, and the temperature rising rate and holding time were the same.

The density of the glassy carbon obtained was 1.70 g.
/ Cm³, The fracture surface is glass-like, and the surface of the polished surface is hole-like
The state is the same as in Example 1, and the pore size is 0.05 to 0.01.
It is less than μm, and there is no problematic defect.
It was The surface smoothness Ra is 1.0 nm, which is extremely
It was good. In addition, the bending strength of the material is specified by JIS
As a result of measurement based on the rating R1601, the bending strength was 28.
9 kg / mm²Met. The elastic modulus is 2550 kgf
/ Mm ²Met.

The glassy carbon thus obtained is
Since the mechanical strength is improved, the problem of cracking and chipping during substrate processing is extremely unlikely to occur, and the reliability during handling in the magnetic disk manufacturing process (cleaning, texturing, film formation, evaluation tests) is improved. It was rich.
Further, since the elastic modulus is improved, the problem of undulation is also improved. Furthermore, the impact resistance is also improved.

Then, a magnetic film was formed on the above-mentioned substrate made of glassy carbon by a predetermined thin film forming means to prepare a magnetic disk, which was mounted in a recording / reproducing apparatus and recording / reproducing was tried. Characterized. [Example 4] The glassy carbon obtained in the pretreatment process of Example 1 was similarly heat-treated under pressure by HIP. HIP
The final treatment temperature is 1500 ° C., the pressure is 1500 atm, and the temperature rising rate and holding time are the same.

The density of the glassy carbon obtained was 1.60 g.
/ Cm³, The fracture surface is glass-like, and the surface of the polished surface is hole-like
The state is the same as in Example 1, and the pore size is 0.05 to 0.01.
It is less than μm, and there is no problematic defect.
It was The surface smoothness Ra is 1.1 nm, which is extremely
It was good. In addition, the bending strength of the material is specified by JIS
As a result of measurement based on the rating R1601, the bending strength was 26.
1 kg / mm²Met. The elastic modulus is 2500 kgf
/ Mm ²Met.

The glassy carbon thus obtained is
Since the mechanical strength is improved, the problem of cracking and chipping during substrate processing is extremely unlikely to occur, and the reliability during handling in the magnetic disk manufacturing process (cleaning, texturing, film formation, evaluation tests) is improved. It was rich.
Further, since the elastic modulus is improved, the problem of undulation is also improved. Furthermore, the impact resistance is also improved.

Then, a magnetic disk was prepared by providing a magnetic film on the substrate made of glassy carbon by a predetermined thin film forming means, and a magnetic disk was mounted on a recording / reproducing apparatus to attempt recording / reproducing. Characterized. [Example 5] The same procedure as in Example 1 was carried out except that the final treatment temperature in the pretreatment step was 1100 ° C.

The density of the obtained glassy carbon was 1.64 g.
/ Cm³, The fracture surface is glass-like, and the surface of the polished surface is hole-like
The state is the same as in Example 1, and the pore size is 0.07 to 0.01.
It is less than μm, and there is no problematic defect.
It was The surface smoothness is Ra of 1.5 nm, which is extremely
It was good. In addition, the bending strength of the material is specified by JIS
As a result of measurement based on the rating R1601, the bending strength was 28.
6 kg / mm²Met. The elastic modulus is 2500 kgf
/ Mm ²Met.

The glassy carbon thus obtained is
Since the mechanical strength is improved, the problem of cracking and chipping during substrate processing is extremely unlikely to occur, and the reliability during handling in the magnetic disk manufacturing process (cleaning, texturing, film formation, evaluation tests) is improved. It was rich.
Further, since the elastic modulus is improved, the problem of undulation is also improved. Furthermore, the impact resistance is also improved.

Then, a magnetic film was provided on the above-mentioned substrate made of glassy carbon by a predetermined thin film forming means to prepare a magnetic disk, and this was mounted in a recording / reproducing apparatus, and recording / reproducing was tried. Characterized. [Example 6] The same procedure as in Example 1 was carried out except that the final treatment temperature in the pretreatment step was set to 1300 ° C.

The density of the glassy carbon obtained was 1.68 g.
/ Cm³, The fracture surface is glass-like, and the surface of the polished surface is hole-like
The state is the same as in Example 1, and the pore size is 0.05 to 0.01.
It is less than μm, and there is no problematic defect.
It was The surface smoothness Ra is 1.0 nm, which is extremely
It was good. In addition, the bending strength of the material is specified by JIS
As a result of measurement based on the rating R1601, the bending strength was 27.
7 kg / mm²Met. The elastic modulus is 2550 kgf
/ Mm ²Met.

The glassy carbon thus obtained is
Since the mechanical strength is improved, the problem of cracking and chipping during substrate processing is extremely unlikely to occur, and the reliability during handling in the magnetic disk manufacturing process (cleaning, texturing, film formation, evaluation tests) is improved. It was rich.
Further, since the elastic modulus is improved, the problem of undulation is also improved. Furthermore, the impact resistance is also improved.

Then, a magnetic disk was prepared by providing a magnetic film on the substrate made of the above glassy carbon by a predetermined thin film forming means, and this was mounted in a recording / reproducing apparatus, and recording / reproducing was tried. Characterized. [Example 7] The same procedure as in Example 1 was repeated except that the final treatment temperature in the pretreatment step was 1200 ° C, the final treatment temperature by HIP was 2000 ° C, and the pressure was 1500 atm.

The density of the glassy carbon obtained was 1.71 g.
/ Cm³, The fracture surface is glass-like, and the surface of the polished surface is hole-like
The state is the same as in Example 1, and the pore size is 0.05 to 0.01.
It is less than μm, and there is no problematic defect.
It was The surface smoothness is Ra of 1.2 nm, which is extremely
It was good. In addition, the bending strength of the material is specified by JIS
As a result of measurement based on the rating R1601, the bending strength was 24.
5 kg / mm²Met. The elastic modulus is 2600 kgf
/ Mm ²Met.

The glassy carbon thus obtained is
Since the mechanical strength is improved, the problem of cracking and chipping during substrate processing is extremely unlikely to occur, and the reliability during handling in the magnetic disk manufacturing process (cleaning, texturing, film formation, evaluation tests) is improved. It was rich.
Further, since the elastic modulus is improved, the problem of undulation is also improved. Furthermore, the impact resistance is also improved.

Then, a magnetic film was provided on the above-mentioned substrate made of glassy carbon by a predetermined thin film forming means to prepare a magnetic disk, and this was mounted in a recording / reproducing apparatus, and recording / reproducing was tried. Characterized. Comparative Example 1 In Example 1, HIP after the pretreatment process
The same procedure was performed except that the treatment was omitted.

The density of the glassy carbon obtained was 1.49 g.
/ Cm < ³ >, the pore diameter was 0.05 to 0.01 [mu] m, the surface smoothness was Ra 1.4 nm, and the bending strength based on JIS standard R1601 was 12.6 kg / mm < ² >. The elastic modulus was 2000 kgf / mm ² . When the glassy carbon thus obtained was processed into a substrate, the occurrence rate of cracks and chips was high due to insufficient strength, and the reliability during handling was low. Further, since the impact resistance is insufficient and the elastic modulus is small, the disk is slightly deformed when chucked on the spindle.

[Comparative Example 2] The glassy carbon obtained in the pretreatment process of Example 1 was similarly heat-treated under pressure by HIP. The final treatment temperature by HIP is 1300 ° C., the pressure is 2000 atm, and the heating rate and holding time are the same. The obtained glassy carbon had a density of 1.57 g / cm ³ , a pore diameter of 0.05 to 0.01 μm, and a surface smoothness of Ra of 1.1.
Bending strength based on JIS standard R1601 is 20.
It was 9 kg / mm ² . The elastic modulus is 2200 kgf
/ Mm ² .

When the glassy carbon thus obtained was processed into a substrate, the occurrence rate of cracks and chips was high due to insufficient strength, and the reliability during handling was low. or,
The impact resistance was also insufficient. [Comparative Example 3] The glassy carbon obtained in the pretreatment process of Example 1 was similarly heat-treated under pressure by HIP. HIP
The final treatment temperature was 1,500 ° C., the pressure was 800 atm, and the temperature rising rate and holding time were the same.

The density of the glassy carbon obtained was 1.56 g.
/ Cm ^3, pore size 0.05～0.01Myuemu, surface smoothness was 1.4 nm, the bending strength based on JIS standard R1601 is a 15.3 kg / mm ² in Ra. The elastic modulus was 2150 kgf / mm ² . When the glassy carbon thus obtained was processed into a substrate, the occurrence rate of cracks and chips was high due to insufficient strength, and the reliability during handling was low. Moreover, the impact resistance was also insufficient.

Comparative Example 4 The final treatment temperature in the pretreatment step of Example 1 was 1500 ° C., and the glassy carbon material obtained in this pretreatment step was also heat treated under pressure by HIP. Final processing temperature by HIP is 200
The temperature is 0 ° C., the pressure is 2000 atm, and the temperature rising rate and the holding time are the same.

The obtained glassy carbon undergoes graphitization
And its density is 1.80 g / cm ³, The pore size is 0.05
~ 0.01 μm, surface smoothness Ra 1.4 nm, JI
Bending strength based on S standard R1601 is 18.5 kg / m
m²Met. The elastic modulus is 2650 kgf / mm²so
there were. The glassy carbon thus obtained was added to the substrate.
When processed, the rate of occurrence of cracks and chips is high due to lack of strength,
The reliability at the time of handling was low. In addition, shock resistance
The shotability was also insufficient.

Comparative Example 5 The final treatment temperature in the pretreatment step of Example 1 was set to 900 ° C., and the glassy carbon obtained in this pretreatment step was similarly heat-treated under pressure by HIP. Final treatment temperature by HIP is 1500 ℃,
The pressure is 2000 atm, and the rate of temperature increase and the holding time are the same.

The density of the obtained glassy carbon material is 1.5.
The surface roughness was 4 g / cm ³ , the pore size was 2.0 to 0.8 μm, the surface smoothness Ra was 9.4 nm, and the bending strength based on JIS standard R1601 was 9.4 kg / mm ² . The elastic modulus is 1
It was 850 kgf / mm ² . The substrate made of glassy carbon thus obtained is not sufficiently removed of hydrogen and oxygen remaining in the material in the pretreatment step, and is subjected to pressure heat treatment in the presence of residual hydrogen and oxygen. Because
Release of hydrogen and oxygen is suppressed, which causes a reaction inside the material, the carbon-carbon bond is broken, and the strength is reduced. Therefore, when the substrate was processed, the rate of occurrence of cracks and chips was remarkably high due to insufficient strength, and the reliability during handling was low.

Furthermore, since there are minute defects on the surface of the substrate, which are thought to be caused by pores, this causes bit errors, and
There was also a problem of waviness, and the recording / reproducing characteristics were also poor.

[0057]

[Effect] Glassy carbon having properties preferable as a substrate of a recording medium can be obtained.

Claims (5)

[Claims] 1. A glassy carbon having a bending strength of about 24 kgf / mm ² or more. 2. A glassy carbon having a bending strength of about 24 kgf / mm ² or more and a pore diameter of about 0.1 μm or less. 3. The glassy carbon according to claim 1, which is used as a substrate of a recording medium. 4. A curing step of curing a thermosetting resin,
A method for producing glassy carbon, comprising a carbonizing and firing step of heating and carbonizing the resin material obtained by the curing step, wherein the carbonizing and firing step is heat treatment at about 1000 to 1400 ° C. in an inert atmosphere. And a second treatment step in which a heat treatment is performed at about 1500 to 2000 ° C. under an inert atmosphere and a pressure of about 1000 atmospheres or more. Method. 5. A curing step of curing a thermosetting resin which can contain about 20% by weight or more of water in the state of precondensate before curing, and heating the resin material obtained by this curing step. A method for producing glassy carbon, comprising: a carbonization and firing step of carbonizing by means of a carbonization and firing step, wherein the carbonization and firing step comprises a first treatment step of heat treatment at about 1000 to 1400 ° C. under an inert atmosphere, and an inert atmosphere, And about 100
And a second treatment step in which a heat treatment is performed at about 1500 to 2000 ° C. under a pressure of 0 atm or more.