WO2002052550A1

WO2002052550A1 - Substrates for hard disks and hard disks

Info

Publication number: WO2002052550A1
Application number: PCT/JP2001/010847
Authority: WO
Inventors: Etsuro Matsui; Nobuo Tanaka
Original assignee: Teijin-Bayer Polytec Limited
Priority date: 2000-12-26
Filing date: 2001-12-11
Publication date: 2002-07-04
Also published as: JPWO2002052550A1

Abstract

Substrates for hard disks, characterized by being substantially made of a thermoplastic resin having (A) a specific gravity of 0.95 to 1.25 and (B) a flexural modulus of 2,200 to 3,500 MPa; and hard disks produced by forming a magnetic film on the surface of the substrate. In particular, a substrate for hard disks, characterized by being substantially made of an aromatic polycarbonate resin in which 1,1-bis(4-hydroxy- phenyl)-3,3,5-trimethylcyclohexane accounts for at least 30 mole % of the whole aromatic dihydroxyl component and which satisfies the requirements (A') and (B'): (A') a solution of 0.7 g of the resin in 100 ml of methylene chloride exhibits a specific viscosity ranging from 0.2 to 0.5 at 20°C and (B') the water absorption as defined in the description is 0.18 wt% or below; and hard disks produced by using the substrate. This invention provides substrates for hard disks which are made of thermoplastic resins, particularly a polycarbonate resin having a specific structure, and are excellent in physical characteristics, and hard disks produced by using the substrates.

Description

Hard disk board and hard disk

Detailed description of the invention

The present invention relates to a hard disk substrate. More specifically, the present invention relates to a substrate formed of a thermoplastic resin suitable for magnetic recording media such as magnetic disks and digital video disks. In particular, the present invention relates to a digital video device having an extremely large recording capacity.

Hard disk substrate suitable for disk and formed of thermoplastic resin, and base thereof

Related to hard disks using boards.

Conventional technology

Conventionally, glass and aluminum have been known as typical materials used for hard disk substrates, and since they have rigidity and smoothness, they are also used as materials for hard disk substrates. Widely used. However, there is a drawback that pits and groups cannot be formed, and this improvement is required. In order to increase the recording density by forming pits and groups, a resin having better transferability is required. On the other hand, there is also a demand for a resin having low warpage and good durability, but there is still no hard disk substrate that satisfies these requirements. On the other hand, U.S. Pat. No. 5,633,600 (Japanese Patent Application Laid-Open No. 8-293218) describes a dihydroxydiphenylalkane having a specific structure and a novel aromatic polycarbonate derived therefrom. ing. The tree composition disclosed in this publication is

(a) 1,1,1-bis (4-hydroxyphenyl) -1,3,3,5-trimethylcyclium hexane (component a) and

(b) 4,4,1- (m-phenylenediisopropylidene) diphenol and Z or 2,2-bis (3-methyl-14-hydroxyphenyl) propane (component b) as at least one of the wholly aromatic dihydroxy components 80 mol%, and the ratio of component a to component b is 20:80 to 80:20 in molar ratio. In the above specification, it is described that the obtained aromatic polycarbonate provides an optical disk substrate having a small birefringence and a small warpage and is suitable for an optical disk having an extremely large storage capacity.

On the other hand, Japanese Patent Application Laid-Open No. Hei 5-65535 describes a plastic substrate for a hard disk using a polycarbonate resin and an acrylic resin. The resin allows sector one and zone bit signals to be molded from a mold.

Further, Japanese Patent Application Laid-Open No. 7-150630 describes a plastic substrate for a hard disk using a thermoplastic norpolenene resin. The resin has low hygroscopicity, that is, a small change in shape, and has a high resonance frequency, that is, easy to read a radio mark, and thus enables higher density recording.

However, a substrate formed of norpolenene resin has insufficient physical strength, particularly a flexural modulus, and therefore requires a relatively thick disk substrate. For this reason, a substrate using this resin does not sufficiently exhibit the advantage of weight reduction using the resin. Problems to be solved by the invention

A first object of the present invention is to provide a lightweight resin substrate having a certain level of physical strength, particularly a flexural modulus and specific gravity, which is suitable for a single-disk substrate. A second object of the present invention is to provide a resin substrate having other physical properties such as a coefficient of linear expansion and a water content suitable for an 81-disk substrate.

A third object of the present invention is to provide a resin substrate having excellent flatness and smoothness of a magnetic film forming surface on a hard disk substrate.

Another object of the present invention is to provide a hard disk substrate formed of an aromatic polycarbonate resin capable of exhibiting the various characteristics described above.

Still another object of the present invention is to provide a hard disk substrate having a high density and a high function suitable for a hard disk substrate for video, particularly a video hard disk substrate, etc., and easily formed by melting. Is to do. Means for solving the problem

According to the study of the present inventors, it is formed substantially from a thermoplastic resin,

(A) It is characterized by being formed of a resin having a specific gravity of 0.95 to 1.25 and (B) a flexural modulus of 2,200 to 3,500 OMPa. And a hard disk having a magnetic film formed on the surface of the substrate.

The hard disk substrate of the present invention (A) has a specific gravity of 0.95 to 1.25, preferably 1.0 to 1.15, and a flexural modulus of 2,200 to 3,500 MP. a, preferably a thermoplastic resin having physical properties of 2,300 to 3,400 MPa, particularly preferably 2,400 to 3,0 MPa.

Such physical properties are values that cannot be achieved by conventional thermoplastic norpolene resin or polyphenol resin from bisphenol A, and are valuable values as physical properties of the hard disk substrate as described later.

According to the present invention, there is provided a hard disk substrate having excellent physical properties as well as surface characteristics on a magnetic film forming surface. That is, the surface on which the magnetic film is formed has excellent smoothness and excellent flatness (flatness). The center line average roughness (Ra) on the magnetic film forming surface of the hard disk substrate is 2 nm or less, preferably 1 nm or less. The flatness in the circumferential direction of the magnetic film forming surface of the hard disk substrate is 1 Om or less, preferably 7 m or less. By forming a magnetic film on the surface of the substrate having such smoothness and flatness, the hard disk has a high degree of reliability without any trouble in the operation of recording and reading information on the hard disk. Is obtained.

It is important that the hard disk substrate of the present invention has substantially no coarse projections having a height of 25 nm or more on the surface on which the magnetic film is formed. For that purpose, as described later, it is necessary to prevent large undissolved particles from being mixed in the resin or to remove large particles with a filter.

The hard disk substrate of the present invention preferably has a linear expansion coefficient and water absorption It also has excellent physical properties. That is, the linear expansion coefficient 6. 5X 10 ^"5 deg- ¹ or less, preferably 5. 5~6. 3 X 10- ^{5 deg-} ^1. The water absorption is 0.18 wt% or less, preferably 0 17% by weight or less, particularly preferably 0.15% by weight or less When the coefficient of linear expansion and water absorption satisfy the above ranges, deformation and warping of the substrate with respect to heat and temperature are extremely small. This increases the reliability of the hard disk.

The resin forming the hard disk substrate of the present invention may contain chlorine depending on the manufacturing process. If the chlorine content is high, the molding die is corroded, the thermal stability of the resin is reduced, and the magnetic film of the hard disk is corroded, which is not desirable. It is therefore recommended that the chlorine content be less than 10 ppm, preferably less than 7 ppm, particularly preferably less than 5 ppm. The term "chlorine content" as used herein means a value obtained by measuring the resin by a combustion method using a total organic halogen analyzer TOX10 manufactured by Mitsubishi Iridaku.

Examples of the resin that achieves the physical properties of the above-mentioned substrate include an aromatic polycarbonate resin.

That is, as such an aromatic polycarboxylic acid resin, an aromatic polycarbonate resin in which at least 30% of a wholly aromatic dihydroxy component is 1,1-bis (4-hydroxyphenyl) -1,3,3,5-trimethylcyclohexane. Resin. 1,1-bis (hydroxyphenyl) -3,3,5-trimethylcyclohexane (bisphenol TMC) as aromatic dihydroxy component forming aromatic resin and aromatic poly force from it One-ponate resin is known from US Pat. No. 4,982,014 (JP-A-2-88634). A representative example disclosed in this publication is an aromatic polycarbonate using bisphenol TMC in an amount of 100 to 2 mol% of the total dihydroxy component. Specifically, bisphenol TMC was used in an amount of 100 to 30 mol%. It is a homo- or co-polycarbonate.

According to the above publication, the advantages and applications of the aromatic resin obtained are excellent in high heat resistance compared to conventional polycarbonate resins. It is described for use in the field of coating and glazing. The use of optical discs is described as a polyphenol resin of 65 mol% of bisphenol A and 55 mol% of bisphenol TM C, but this resin is compared with the conventional resin from bisphenol A. It just shows that the heat resistance has been improved. Further, the above publication has no suggestion to use the obtained aromatic polycarbonate for a hard disk substrate.

According to the study of the present inventor, it has been found that aromatic polycarbonate resin from bisphenol TM C alone is not suitable as a hard disk substrate. Further, the specific copolymer described in the above-mentioned publication, that is, a copolymer polystyrene resin from bisphenol TMC and bisphenol A is similarly hardened regardless of the copolymerization ratio. It was found that the disk substrate was not particularly excellent as compared with the conventional poly-polycarbonate resin substrate from bisphenol A, except that it had improved heat resistance.

However, according to the study of the present inventors, it has been found that aromatic polystyrene obtained by using a specific terminal modifier for bisphenol TM C and / or copolymerizing a certain proportion of a dihydroxy compound having a specific structure is used. It has been found that the force component resin has a high flexural modulus, a low coefficient of linear expansion, a low specific gravity, an extremely low water absorption, and a substrate having a small warpage as a hard disk substrate.

Hereinafter, the aromatic polystyrene resin will be described. The aromatic polycarbonate resin advantageously used as the material of the hard disk substrate of the present invention is 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane represented by the following formula: (Bisphenol TMC) is a polycarbonate resin composed of at least 30 mol% based on the total aromatic dihydroxy component.

The aromatic polycarbonate resin uses the bisphenol TM C in an amount of at least 30 mol%, preferably at least 40 mol%, of the total aromatic dihydroxy component. When the ratio of this bisphenol TMC is less than 30 mol%, the obtained hard disk substrate or hard disk is unsatisfactory in any of heat resistance, mechanical properties, water absorption, transferability or warpage or surface properties. Thus, a hard disk substrate or a hard disk satisfying these characteristics cannot be obtained. Bisphenol TMC may be 100 mol%, but it tends to have a high water absorption or poor fluidity. Therefore, when bisphenol TMC is in such a high proportion, a specific amount of bisphenol TMC will be used as described later. It is desirable to modify the terminal with a terminal modifier.

In the aromatic polycarbonate resin, it is necessary to use the bisphenol TMC as an aromatic dihydroxy component in a certain ratio, and the aromatic polycarbonate resin is roughly classified to have desired characteristics, particularly, a water absorption of 0.18% by weight or less. Two means are employed. One is to combine a specific dihydroxy component with the bisphenol TMC to form a copolymerized polycarbonate resin, and the other means is to introduce a terminal modifier having a specific structure into the terminal group. It is. These two means may be used alone or in combination.

′ The aromatic polycarbonate resin has a bisphenol TMC ratio of 30 to 70 mol% in a wholly aromatic dihydroxy component constituting the resin, but preferably 40 to 60 mol%. Is particularly preferred.

According to the study of the present inventors, it has been found that a copolymer polycarbonate resin obtained by combining a specific dihydroxy component with the bisphenol TM C is particularly suitable as a hard disk substrate. Was issued. That is, the copolymerized polycarbonate resin comprises (a) bisphenol TM C (this is referred to as component a) and (b) 4,4 ′-(m-phenylenediisopropylidene) diphenol (hereinafter referred to as “bisphenol M”). And Z or 2,2-bis (3-methyl-4-hydroxyphenyl) propane (hereinafter sometimes abbreviated as "bisphenol C") [these are referred to as component b] are wholly aromatic At least 90 mol% of the dihydroxy component, and the ratio of component a to component b is 30:70 Polycarbonate resin having a thickness of up to 70:30, preferably 40:60 to 60:40 is particularly preferred as a hard disk substrate.

One preferred embodiment of the copolymerized polycarbonate resin is a combination in which the component a is bisphenol TM C and the component b is bisphenol M, in which case the ratio of the component a to the component b is a molar ratio. It is preferable that the ratio be in the range of 40:60 to 60:40, and more preferably in the range of 45:55 to 55:45.

It is desirable that the component (a) and the component (b) occupy at least 90 mol%, preferably at least 95 mol%, of the total aromatic dihydroxy component in the aromatic polysiloxane resin. (Component C) may be contained in an amount of 10 mol% or less, preferably 5 mol% or less, based on the total aromatic dihydroxy component.

The component C may be any component other than the component a and the component b, which are usually used as the dihydroxy component of the aromatic polycarbonate, such as hydroquinone, resorcinol,, 4, -biphenol, 1,1-bis ( 4-Hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl) 1-1-phenylethane 1,1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl) pentane, 4,4,1- (p-phenylenediisopropylidene) diphenol, 9,9 1-bis (4-hydroxyphenyl) fluorene, 1,1-bis (4-hydroxyphenyl) -14 before it can be used as a hard disk substrate The aromatic polycarbonate resin is a reaction means known per se for producing a normal aromatic polycarbonate resin, for example, by reacting an aromatic dihydroxy component with a carbonate precursor such as phosgene or carbonic acid diester. It is manufactured by a method. Next, the basic means of these manufacturing methods will be briefly described.

In a reaction using, for example, phosgene as a forceponate precursor, the reaction is usually performed in the presence of an acid binder and a solvent. Examples of the acid binder include sodium hydroxide, Alkali metal hydroxides such as hydroxylated lime or amine compounds such as pyridine are used. As the solvent, for example, a halogenated hydrocarbon such as methylene chloride or chlorobenzene is used. Further, a catalyst such as a tertiary amine or a quaternary ammonium salt can be used to promote the reaction. At that time, the reaction temperature is usually 0 to 40 ° C, and the reaction time is several minutes to 5 hours. '

In the transesterification reaction using carbonic acid diester as a force component precursor, a predetermined ratio of an aromatic dihydroxy component is stirred with carbonic acid diester while heating under an inert gas atmosphere to distill off the generated alcohol or phenols. It is done by the method of making it. The reaction temperature varies depending on the boiling point of the alcohol or phenols to be formed, but is usually in the range of 120 to 330 ° C. The reaction is completed under reduced pressure from the beginning while distilling off the alcohol or phenols formed. Further, a catalyst usually used in a transesterification reaction to promote the reaction can also be used. Examples of the carbonic acid diester used in the transesterification reaction include diphenyl carbonate, dinaphthyl carbonate, bis (diphenyl) carbonate, dimethyl carbonate, getyl carbonate, dibutyl carbonate and the like. Of these, diphenyl alcohol is particularly preferred. · The aromatic polycarbonate of the present invention uses bisphenol TM C or a mixture of bisphenol TM C and another aromatic dihydroxy component as the aromatic dihydroxy component as described above, It can be prepared according to the reaction of polycarbonate formation.

In the polymerization reaction, monofunctional phenols which are usually used as a terminal terminator can be used. In particular, in the case of reactions using phosgene as the precursor of the monoponate, monofunctional phenols are generally used as a terminator for controlling the molecular weight, and the resulting aromatic polycarbonate resin has Since it is blocked by a group based on monofunctional phenols, it has better thermal stability than those not.

As such monofunctional phenols, any one may be used as long as it is used as a terminal terminator for an aromatic polycarbonate resin. Generally, phenol or lower alkyl is used. A monofunctional phenol represented by the following general formula:

[In the formula, A represents a hydrogen atom or an aliphatic hydrocarbon group having 1 to 9, preferably 1 to 8 carbon atoms, and r represents an integer of 1 to 5, preferably 1 to 3. ]

Specific examples of the monofunctional phenols include, for example, phenol, p_tert_butylbutylphenol, p-cumylphenol and isooctylphenol. These monofunctional phenols are desirably introduced into at least 5 mol%, preferably at least 10 mol%, of the terminals of the obtained aromatic polycarbonate resin.

Using phenols having long-chain alkyl groups or aliphatic polyester groups as substituents, or benzoic acid chlorides or long-chain alkyl carboxylic chlorides to terminate the terminal groups of the aromatic polycarboxylic acid resin. The blocking not only functions as a terminal terminator or a molecular weight regulator as in the case of the above-mentioned monofunctional phenols, but also serves to modify the obtained aromatic polycarbonate resin.

That is, phenols having a long-chain alkyl group or aliphatic polyester group as a substituent, or benzoic acid chlorides or long-chain alkyl sulfonic acid chlorides (hereinafter, these are distinguished from the monofunctional phenols) Is sometimes abbreviated as "terminal modifier"). By bonding to the terminal of the aromatic polyphenol resin, the melt flowability of the resin is improved and the molding process becomes easier. The physical properties of the substrate are also improved. In particular, it has the effect of lowering the water absorption of the resin.

Therefore, when the ratio of bisphenol TM C is at least 80 mol%, especially at least 90 mol%, based on the total aromatic dihydroxy component, the water absorption of the obtained resin exceeds 0.18 wt%. In such a case, in such a case, it is necessary to use the terminal modifier. Thus, the water absorption of the resin can be suppressed to 0.18% by weight or less. Since the terminal modifier is, of course, a monofunctional conjugate, it also has a function as a terminal stopper or a molecular weight regulator. Depending on the composition of the aromatic polycarbonate resin, the proportion of the powerful terminal modifier is not constant, but it is used so as to bind at least 5 mol%, preferably at least 10 mol%, to all terminals. Is done. Terminal modifiers can be used in combination with the monofunctional phenols. As the terminal modifier, compounds represented by the following general formulas [Ia] to [Ih] can be used.

T- -C Ji _n "H

... [l-c]

[i-g]

CI-CC _n H _{2n + 1} -t'-h]

[In each formula, X is one R—〇—, —R—CO—O— or —R—〇—CO—, wherein R is a single bond or a group having 1 to 10, preferably 1 to 5 carbon atoms. T represents a divalent aliphatic hydrocarbon group, T represents a single bond or a bond similar to the above X, and n represents an integer of 10 to 50. Q represents a halogen atom or a monovalent aliphatic hydrocarbon group having 1 to 10, preferably 1 to 5 carbon atoms; p represents an integer of 0 to 4; Y represents 1 to 10 carbon atoms, preferably shows a 1-5 divalent aliphatic hydrocarbon group, W ¹ is a hydrogen atom, -CO-R one CO- O-R ² or R ^3, where RR ² and R ³ are each A monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, a monovalent alicyclic hydrocarbon group having 4 to 8 carbon atoms, preferably 5 to 6 carbon atoms or 6 to 15 carbon atoms, preferably Represents a monovalent aromatic hydrocarbon group of 6 to 12. t represents an integer of ~ 20, preferably 5-10, m represents an integer of 1-100, preferably 3-60, particularly preferably 4-50, Z represents a single bond or carbon number 1-10, It preferably represents a divalent aliphatic hydrocarbon group having 1 to 5; W ² represents a hydrogen atom; a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, preferably 5 to 6 carbon atoms; And preferably a monovalent alicyclic hydrocarbon group of 5 to 6 or a monovalent aromatic hydrocarbon group of 6 to 15, preferably 1 to 12 carbon atoms. ]

Among the above terminal modifiers [I-a] to [I-h], preferred are substituted phenols of [I_a] and [I_b]. As the substituted phenols of [Ia], those having n of 10 to 30, particularly preferably 10 to 26 are preferable. Specific examples thereof include decyl phenol, dodecyl phenol and tetradecyl phenol. Hexadecylphenol, octadecylphenol, eicosylphenol, docosylphenol and triacontylphenol. As the substituted phenols represented by [Ib], compounds in which X is -R-C〇-0- and R is a single bond are suitable, and n is 10 to 30, especially 10 to 26. Specific examples thereof include decyl hydroxybenzoate, dodecyl hydroxybenzoate, tetradecyl hydroxybenzoate, hexadecyl hydroxybenzoate, eicosyl hydroxybenzoate, docosyl hydroxybenzoate and tricontyl hydroxybenzoate. No.

In the substituted phenols or substituted benzoyl chlorides represented by the above general formulas [Ia] to [Ig], the position of the substituent is generally preferably the p-position or the o-position, and a mixture of both is preferable. preferable.

[Ia] and [Ib] among the above-mentioned terminal modifiers are particularly excellent. The reason for this, as described above, is that when these are introduced as terminal groups into the aromatic polycarbonate resin, not only the melt fluidity thereof is improved but also the effect of lowering the water absorption is reduced. Wholly aromatic diphenyls constituting the aromatic polycarbonate resin When the ratio of bisphenol TMC in the droxy component is high, for example, 80 mol% or more, especially 90 mol% or more, the water absorption of the resin may exceed 0.18% by weight. It is possible to reduce the water absorption to 0.18% by weight or less by using the terminal modifiers [I-a] and [I-b] described above. However, it is to be noted that the aromatic polysiloxane resin of the present invention may use the above-mentioned terminal modifier as long as the proportion of bisphenol TMC is at least 30 mol%, preferably at least 40 mol%. Not even.

The aromatic polycarbonate resin is obtained by dissolving 0.7 g of the resin in 10 Oml of methylene chloride and having a specific viscosity measured at 20 ° C. in the range of 0.2 to 0.5. It is in the range of 0.25 to 0.4. If the specific viscosity is less than 0.2, the molded product becomes brittle. If the specific viscosity is higher than 0.5, the melt fluidity is poor and molding failure occurs, and it is difficult to obtain a good disk substrate for a hard disk.

The hard disk substrate of the present invention can be obtained by molding the aromatic polycarbonate resin by any method such as an injection molding method, a compression molding method, an extrusion molding method, and a solution casting method. The hard disk substrate obtained by the injection molding method is preferable. Further, it is necessary that the polyacrylonitrile resin of the present invention has a water absorption of 0.18% by weight or less, preferably 0.17% by weight or less, as measured by ASTM D-0570. When the water absorption exceeds 0.18% by weight, a hard disk having a metal film formed on the surface of the hard disk substrate is liable to be warped by water absorption and to cause a tracking error, which is preferable. Absent. A particularly preferred water absorption is 0.15% by weight or less.

The hard disk substrate of the present invention is preferably formed from an aromatic polycarbonate resin having a flexural modulus of 2,200 to 3,500 MPa, preferably 2,300 to 3,40 OMPa. Particularly preferred flexural modulus is from 2,400 to 3,000 OMPa. If the flexural modulus is lower than 2,20 OMPa, it becomes unsuitable as a hard disk substrate. On the other hand, to obtain a resin having a flexural modulus exceeding 3,40 OMPa, it is necessary to increase the degree of polymerization, in which case molding becomes difficult. The hard disk substrate of the present invention, the linear expansion coefficient of 6. 5X 10- ⁵ deg one ¹ Hereinafter, it is advantageous to be formed from an aromatic polycarbonate resin having preferably 5.5 to 6.3 × ¹⁰ ⁵ deg- ¹ . If the linear expansion coefficient is to use a polycarbonate resin of greater than 6. 5X 10- ⁵ deg one ¹ as a hard disk, which may hinder the reading of the recording by the use condition.

As the aromatic polycarbonate resin used for the hard disk substrate of the present invention, those having a specific gravity of 0.95 to 1.25, preferably 1.0 to 1.15 are advantageously used. Resins having a specific gravity in this range are light in weight and have little value in the operation and operation of the disk, and thus have value in themselves.

When an aromatic polycarbonate resin is produced using phosgene as a carbonate precursor and using a chlorine-based solvent such as methylene chloride as a solvent, a considerable amount of chlorine remains. If the chlorine content is large, the mold is corroded, the thermal stability of the aromatic polycarbonate resin is reduced, and the magnetic film of the hard disk is corroded, which is not desirable. It is therefore recommended that the chlorine content be less than 10 ppm, preferably less than 7 ppm, particularly preferably less than 5 ppm. The chlorine content as referred to herein means a value obtained by measuring the aromatic polycarbonate resin by a combustion method using a total organic octogen analyzer TOX10 manufactured by Mitsubishi Chemical Corporation.

For the hard disk substrate, an aromatic polysiloxane resin having an oligomer content of 10% or less, preferably 6% or less, particularly preferably 4% or less is used. The value of the oligomer content is a value measured using the following method and column. That is, TSKge1 manufactured by Tosouichi Co., Ltd., one each of G2000HXL and G3000HXL columns, connected in series, using a chromate form as eluent, and diverted to 0.7 ml Z minutes after diversion. The oligomer content is the ratio of the total area of the oligomer peaks after the retention time of the GPC chart measured by a method of injecting the chloroform solution of the polycarbonate resin of 19 minutes to the total peak area. Oligomer—If the content exceeds 10%, the mold surface may be contaminated during molding, which is undesirable, and the contamination tends to be more pronounced as the oligomer content increases. On the other hand, the oligomers are produced during the production of aromatic polycarbonate resin, Cannot be zero (0).

The content of the oligomer may be not more than the above-mentioned content, and as long as the value is satisfied, the content of the oligomer may be small. When the oligomer is present in a small proportion of 0.1% or more, preferably 0.15% or more, the melt flowability is improved as compared with the oligomer having a small content. Therefore, the oligomer content is particularly preferably in the range of 0.15 to 4%.

In order to control the oligomer content in the aromatic polycarbonate resin within the above range, it is necessary to complete the polymerization sufficiently so that a large amount of oligomer is not contained in the resin, and the catalyst and polymerization conditions are appropriately adjusted. A choice is required. If the oligomer content exceeds the above range, a treatment for removing the oligomer by means such as extraction is employed. This extraction is performed by dropping a solution of the aromatic polycarbonate resin (for example, a methylene chloride solution) into a poor solvent or a non-solvent (for example, acetone or methanol), or removing the resin from the poor solvent or It can be carried out by a method such as a method of extracting the oligomer by immersion in a non-solvent.

Since the aromatic polycarbonate resin is used as a hard disk substrate, particularly a video hard disk substrate, the amount of undissolved particles therein should be controlled to a certain fixed amount or less.

That is, the polycarbonate resin was prepared by dissolving 20 g of the solution in 1 L of methylene chloride. The number of undissolved particles having a diameter of 0.5 m or more and the number of undissolved particles having a diameter of 1 m or more is not more than 1,200 per gram of the polycarbonate resin. Desirably. If the undissolved particles of 0.5 im or more exceed the force of 12, 000 particles or the undissolved particles of 1 m or more exceed the force of 200 particles, the information written on the disc will be adversely affected and the error rate will be reduced. It is not preferable because it becomes large. More preferably, the number of undissolved particles of 0.5 m or more is 100,000 or less, and the number of undissolved particles of 1 m or more is 100 or less. Undissolved particles of 1 O ^ m or more should not be substantially present. In order to keep the amount of the undissolved particles in the aromatic polycarbonate resin within the above range, a means for preventing the undissolved particles from being mixed in or removing the particles during the polymerization process and the granulation process should be adopted. Such means include, for example, performing the operation in a clean room, and using a granulator equipped with a device for removing undissolved particles (specific examples include a bearing unit used in Example 1 described later). In this case, granulation is performed using an apparatus (eg, a spray dryer type granulator) that does not allow resin particles to touch the sliding part. Another method for removing undissolved particles is to filter the resin solution with a small-opening filter (0.2-0.m) or to melt the resin and then use a metal filter (5 -20 m), a method for removing solid particles is adopted. The hard disk substrate of the present invention is required for its purpose to have an extremely smooth magnetic film forming surface. It is desirable that the smoothness be 2 nm or less, preferably 1 nm or less, particularly preferably 0.5 nm or less, as expressed by the center line surface roughness (Ra). If the surface roughness (Ra) exceeds 2 nm, it will affect the smoothness of the surface of the magnetic film formed on the surface, which will hinder recording and removal.

The center line average roughness (R a) is a value defined in JISB0601, and the standard length L (measurement length) is sampled. The average line of the sampled portion is X-axis, and the direction of the vertical magnification is Y When the extraction curve is represented by y = f (x) as the axis, it is the value obtained by the following equation.

The hard disk substrate of the present invention has excellent flatness. The flatness is 1 or less, preferably 7 m or less in the circumferential direction on the surface on which the magnetic film is formed, as flatness. Actually, it is desirable that the flatness in the radial direction is also approximately the same.

Further, the hard disk substrate of the present invention has a height of 25 nm on the magnetic film formation surface. It is important that the above-mentioned coarse projections do not substantially exist. For this purpose, it is necessary to prevent large undissolved particles from entering as described above, or to remove large particles with a filter.

The glass transition point of the aromatic polycarboxylic acid resin is preferably 120 ° C. or higher, more preferably 130 ° C. or higher, and even more preferably 144 ° C. or higher. If the glass transition point is low, the heat resistance of the disk substrate will be insufficient. The fluidity of the aromatic polycarbonate resin is preferably 25 g / 10 minutes or more, more preferably 30 g / 10 minutes or more, and more preferably 45 gZ10 minutes or more in terms of MFR. More preferred. If the fluidity is low, the moldability is inferior and a desired disk substrate cannot be obtained.

A phosphorus-based heat stabilizer can be added to the aromatic polycarbonate resin as needed. As the phosphorus-based heat stabilizer, phosphites and phosphates are preferably used. Examples of the phosphite include triphenyl phosphite, trisnonyl phenyl phosphite, tris (2,4-DG tert-butyl phenyl) phosphite, tridecyl phosphite, trioctyl phosphite, trioctadecyl phosphite Phyto, didecyl monophenyl phosphite, dioctyl monophenyl phosphite, diisopropyl monophenyl phosphite, monobutyi diphenyl phosphite, monodecyl diphenyl phosphite, monooctyl diphenyl phosphite, bis (2,6-zy tert- Butyl-1-methylphenyl) pentaerythritol diphosphite, 2,2-methylenebis (4,6-di-tert-butylphenyl) octyl phosphite, bis (noerphenyl) pentaerythryl diphosphite Phosphorous acid such as iso-, bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite, tetrakis (2,4-di-tert-butylphenyl) -4,4-diphenylenephosphonite Examples include triesters, diesters, and monoesters. Of these, tris nonylphenyl phosphite and distearyl pentaerythryl diphosphite phosphite are preferred.

On the other hand, phosphate esters used as heat stabilizers include, for example, triptyl phosphate, trimethyl phosphate, tricresylyl phosphate, Triphosphate, trichlorophenyl phosphate, triethyl phosphate, diphenyl cresyl phosphate, diphenyl monoorthoxenyl phosphate, tributoxyshethyl phosphate, dibutyl phosphate, octyl phosphate, Examples thereof include diisopropyl phosphate, and among them, triphenyl phosphate and trimethyl phosphate are preferable.

The phosphorus-based heat stabilizers may be used alone or in combination of two or more. The phosphorus-based heat stabilizer is suitably used in the range of 0.001 to 0.05% by weight based on the aromatic polycarboxylic acid resin.

An antioxidant commonly known for the purpose of preventing oxidation can be added to the aromatic polycarbonate resin. Examples thereof include phenolic antioxidants, and specifically, for example, triethylene glycol-bis (3- (3-tert-butyl-15-methyl-14-hydroxyphenyl) propionate), 6-Hexanediol-bis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, pentaerythritol-tetrakis (3- (3,5-di-tert-butyl-1-hydroxyphenyl) ) Propionate), octadecyl-3_ (3,5-ditert-butyl-4-hydroxyphenyl) propionate, 1,3,5_trimethyl-1,2,4,6_tris (3,5-ditert) -Butyl-4-hydroxybenzyl) benzene, N, N-hexamethylenepis (3,5-zy tert-butyl-4-hydroxy-monohydrocinnamide), 3,5-di-te 1-t Hydroxy monobenzyl phosphonate-getyl ester, tris (3,5-di-tert-butyl 4-hydroxybenzyl) isocyanurate, 3,9-bis {1,1-dimethyl-2-ίβ-(3-tert- Butyl-1,4-hydroxy-5-methylph: nyl) propionyloxy] ethyl} 1,2,4,8,10-tetraoxaspiro (5,5) indecan, etc. Preferred amounts of these antioxidants Is in the range of 0.0001 to 0.05% by weight based on the weight of the aromatic polyphenol.

Further, a higher fatty acid ester of a polyhydric alcohol can be added to the aromatic polycarboxylic acid resin if necessary. To add this high-grade] 3 fatty acid ester As a result, the thermal stability of the aromatic polycarbonate resin is improved, the fluidity of the resin during molding is improved, and the mold releasability of the substrate from the mold after molding is improved, thereby releasing the mold. The deformation of the disk substrate due to the defect can be prevented. The higher fatty acid ester is preferably a partial ester or a total ester of a polyhydric alcohol having 2 to 5 carbon atoms and a saturated fatty acid having 10 to 30 carbon atoms. The polyhydric alcohols include glycols, glycerol or Penis Ellis!

The higher fatty acid ester is added in the range of 0.005 to 2% by weight, preferably in the range of 0.02 to 0.1% by weight, based on the aromatic poly-carbonate tree JI. Is appropriate. If the amount is less than 0.01% by weight, the above effect cannot be obtained. On the other hand, if the amount exceeds 2% by weight, it is not preferable because it causes stains on the mold surface.

Additives such as a coloring agent, an antistatic agent, and a lubricant can be further added to the aromatic polycarbonate resin as long as the transparency is not impaired. Further, other polycarbonate resins and thermoplastic resins can be added in a small proportion as long as the object of the present invention is not impaired.

In the hard disk substrate of the present invention, a hard disk can be obtained by forming a metal thin film as a magnetic film on the surface thereof. This metal includes Fe, Co, Cr and the like, and Co ₂₈ Pt ₁₂ Cri. Is suitable. The thin film can be formed by means such as sputtering and vapor deposition. Means for forming these metal thin films can be performed by a method known per se. Example

Hereinafter, the present invention will be further described with reference to examples. Parts in Examples are parts by weight, and% is% by weight. The evaluation was performed by the following method.

Specific viscosity: 0.7 g of the polymer was dissolved in 10 Oml of methylene chloride and measured at a temperature of 20 ° C.

Glass transition point (Tg): Measured by DuPont Model 910 DSC.

Fluidity (MFR): In accordance with JISK-7210, using Toyo Seiki Semi-Olt Melt Indexer, 280 at a load of 2.16 kg for 10 minutes It is shown by the amount of polymer (g).

Oligomer content: A solution prepared by dissolving 50 mg of a sample in 5 m 1 of Clos-form while using Tosoh's GPC columns TSKg e 1 G2000HXL and T SKg e 1 G3000HXL with eluent flowing at 0.7 m 1 Z min. The retention time of the GPC chart obtained by the method of injecting 201 into the sample was shown as a percentage of the total peak area of the peak area of one component after 19 minutes.

Water absorption: Measured according to ASTM D-0570.

Undissolved particles of methylene chloride: A solution obtained by dissolving 20 g of the polycarbonate resin in 1 L of methylene chloride is converted into scattered light of latex particles by a laser sensor method using a liquid particle carrier model 1 100 manufactured by Hyattcroico. The conversion method was used.

Flexural modulus: Measured according to ASTM D-790.

: Measured according to ASTM D-696.

It was measured by JIS K-7112.

Center line average roughness (Ra): Measured according to JIS B0601.

Warp: After leaving the hard disk substrate in a constant temperature and humidity machine of 8 O and 85% RH for 1,000 hours, the warpage of the substrate was measured using an LM-1200 optical disk inspection device manufactured by Ono Sokki.

Flatness

By irradiating the substrate with laser light and measuring the return angle of the laser light, the inclination of the substrate was calculated and obtained. As a representative, the flatness in the circumferential direction was measured at a point 40 mm from the center in the radial direction. For the measurement, DLD-3000 manufactured by Japan II Chem was used.

Coarse projection

The measurement of coarse projections having a height of 25 nm or more was performed as follows.

Measured at 5 points at a 100 m square at each of 15 points, 15 mm, 28 mm, and 4 Omm from the center in the radial direction, 8 points each in the circumferential direction, 24 points in total, measuring the presence or absence of 25 or more protrusions did. Atomic force microscope for measurement (SPI-3800N manufactured by Seiko Instruments Inc.) was used.

Example 1

In a reactor equipped with a thermometer, stirrer and reflux condenser, 929.2 parts of ion-exchanged water and 61.3 parts of a 48% aqueous caustic soda solution were charged, and 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethyl was added. Cyclohexane 35.1 1 part, 4,4,-(m-phenylenediisopropylidene) diphenol 48.0 parts and hydrosulfite 0.17 parts are dissolved, and then p-tert-butylphenol 1.51 Then, 63.9 parts of methylene chloride and 0.09 part of triethylamine were added, and then 32.4 parts of phosgene was blown in under stirring at 15 to 25 for 40 minutes. After the injection of phosgene was completed, 15.6 parts of a 48% aqueous sodium hydroxide solution was added, and the mixture was stirred at 28 to 33 for 1 hour to complete the reaction. After the reaction is completed, the product is filtered through a filter (0.2 m) with a small opening, the product is diluted with methylene chloride, washed with water, acidified with hydrochloric acid, and washed with water. The conductivity of the aqueous phase is almost the same as that of ion-exchanged water. Then, the methylene chloride was evaporated in a kneader provided with an isolation chamber having a foreign-matter extraction port on the shaft receiving portion, and the molar ratio of bisphenol TMC to bisphenol M was 45:55. Colorless polymer—88.1 parts obtained (98% yield).

The specific viscosity of this polymer was 0.284, the oligomer content was 2.4%, the chlorine content was 1.3 ppm, 146 was 146, and MFR was 80 gZ for 10 minutes. The water absorption was 0.15% by weight. To this polymer was added 0.03% of tris (nonylphenyl) phosphate, 0.005% of trimethyl phosphate, and 0.004% of monoglyceride stearate, and the mixture was pelletized using a Sumitomo Heavy Industries DI SK5M111, 90ηιπιΦ, 1.2 It was injection molded into a disk having a thickness of mm. The undissolved particles of methylene chloride were 10,000 Zg at 0.5 / am or more, and 90 / g at 1 m or more. The flexural modulus 2, 80 OMP a, coefficient of linear expansion 6. ¹ X 10- ⁵ deg- 1, specific gravity 1.13, warpage 0. 15 mm, the surface roughness (R a), the magnetic film is formed It was 0.86 nm in the plane. The flatness was 5 m. No coarse protrusions with a height of 25 nm or more were present on the magnetic film formation surface.

Example 2 The 1,1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane of Example 1 was added to 23'.4 parts, 4,4,1- (m-phenylenedisopropylidene). 88.2 parts of a polymer having a molar ratio of bisphenol TMC to bisphenol M of 30:70 was obtained in the same manner as in Example 1 except that the diphenol was changed to 60.9 parts (yield). 97%). The specific viscosity of this polymer was 0.291, the oligomer content was 2.7%, the chlorine content was 1.5 ppm, and the temperature was 132 ° (: MFI ^ ¾93 g / 10 min. 0.13% by weight.

This polymer was molded in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The undissolved particles of the methylene chloride salt were 10,000 Zg for 0.5 m or more and 80 Zg for 1 m or more. / g. The flexural modulus is 2,850 MPa, the linear expansion coefficient is 6.1 X 10-5 deg- ¹ , the specific gravity is 1.13, the warpage is 0.10 mm, and the surface roughness (Ra) is It was 0.88 nm. The flatness was 6 m. No coarse protrusions with a height of 25 nm or more were present on the surface on which the magnetic film was formed.

Example 3

1,1_bis (4-hydroxyphenyl) 13,3,5-trimethylcyclohexane of Example 1 54.7 parts, 4,4,-(m-phenylenediisopropylidene) diphenol Was carried out in the same manner as in Example 1 except that the ratio of bisphenol TM C to bisphenol M was 70:30 in a molar ratio of 70:30. Obtained.

The specific viscosity of this polymer was 0.286, the oligomer content was 2.8%, the chlorine content was 1.5 ppm, the temperature was 155 ° <0, and the MFR was 66 g / 10 min. The water absorption was 0.16% by weight. When this polymer was evaluated in the same manner as in Example 1, the number of undissolved methylene chloride particles was 10,000 particles / g at 0.5 m or more and 85 particles / g at 1 m or more. The flexural modulus 2, 900 MPa, the linear expansion coefficient of 6. 2 X 10- ⁵ deg- specific gravity 1.13, warpage 0. 10 mm, surface roughness (Ra), 0. 86 nm in the magnetic film forming surface Met. The flatness was 5. No coarse protrusions with a height of 25 nm or more were present on the magnetic film formation surface.

Comparative Example 1 1,4-bis (4-hydroxyphenyl) -1,3,5-trimethylcyclohexane of Example 1, 78 parts of 4,4- (m-phenylenediisopropylidene) diphenol 80.3 parts (95% yield) of a homopolymer of bisphenol TM C was obtained in the same manner as in Example 1 except that phenol was not used. The specific viscosity of this polymer was 0.290, Tg was 232 ° C, and the water absorption was 0.3% by weight. An attempt was made to obtain a substrate of this polymer by injection molding in the same manner as in Example 1, but the melt fluidity was poor and molding was not possible.

Comparative Example 2

15.6 parts of 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane of Example 1 and 69 parts of 4,4- (m-phenylenediisopropylidene) diphenol were added. 89.3 parts of a polymer having a molar ratio of bisphenol TMC to bisphenol M of 20:80 was obtained in the same manner as in Example 1 except that the amount was changed to 7 parts (96% yield). The specific viscosity of this polymer was 0.288, Tg was 117 ° C., and MFR was 95 gZl 0 min. The water absorption was 0.13% by weight. When this polymer was evaluated in the same manner as in Example 1, this substrate had a low Tg of 117 and was insufficient in heat resistance for hard disk applications.

Comparative Example 3

Substrate molding and evaluation were performed in the same manner as in Example 1 except that the polymer solution of Example 1 was used and granulation was performed using a binder without a separation chamber having a foreign substance outlet at the bearing portion. The number of undissolved methylene particles was as large as 86,00 Oiei / g for 0.5 111 or more and 2,700 Zg for 1.0 m or more. When evaluated in the same manner as in Example 1, the surface roughness (Ra) was 9.5 nm on the surface on which the magnetic film was formed, which was unsuitable for a hard disk substrate.

The invention's effect

According to the method of the present invention, a hard disk substrate formed of a resin having excellent physical properties can be obtained, and thus is suitably used as a hard disk, particularly a video hard disk.

Claims

The scope of the claims

1. Substantially formed of thermoplastic shelves, the resin satisfies (A) a specific gravity of 0.95 to 1.25 and (B) a flexural modulus of 2,200 to 3,500 MPa. A hard disk substrate formed of:

2. The hard disk substrate according to claim 1, wherein a center line average roughness (Ra) on a surface on which the magnetic film is formed is 2 nm or less.

3. The hard disk substrate according to claim 1, wherein a flatness in a circumferential direction on a magnetic film forming surface is 10 m or less.

4. The hard disk substrate according to claim 1, wherein substantially no coarse protrusions having a height of 25 nm or more are present on the surface on which the magnetic film is formed.

5. The resin, hard disk substrate of claim 1 wherein the linear expansion coefficient is 6. 5X 10- ⁵ deg ¹ below.

6. The hard disk substrate according to claim 1, wherein the resin has a water absorption of 0.18% by weight or less.

7. The hard disk substrate according to claim 1, wherein the resin has a chlorine content of 10 ppm or less.

8. The hard disk substrate according to claim 1, wherein the resin is an aromatic polycarbonate.

9. The aromatic polycarbonate resin is undissolved as measured in dimethyl chloride solution. 9. The hard disk substrate according to claim 8, wherein 12,000 or less particles having a particle equivalent diameter of 0.5 m or more and 200 or less particles having a particle equivalent diameter of 1 m or more per 1 g of the polycarbonate resin.

10. The hard disk substrate according to claim 8, wherein the aromatic polycarbonate resin has an oligomer content of 10% or less as measured by the method defined herein.

11. The hard disk according to claim 8, wherein the aromatic polysiloxane resin has a specific viscosity measured in a solution obtained by dissolving 0.7 g of the resin in 100 ml of methylene chloride in a range of 0.2 to 0.5. substrate.

12. In the aromatic polycarbonate resin, at least 30 mol% of the total aromatic dihydroxy component is 1,1-bis (4-hydroxyphenyl) _3,3,5-trimethylcyclohexane. The hard disk substrate described in 8.

13. The aromatic polystyrene salt means that 30 to 70 mol% of the total aromatic dihydroxy component is transferred to the 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylsilicone mouth. 9. The hard disk substrate according to claim 8, which is xane.

14. The aromatic polycarbonate resin,

(a) 1,1-bis (4-hydroxyphenyl) _3,3,5-trimethylcycline hexane (component a) and

(b) 4,4,-(m-phenylenediisopropylidene) diphenol and Z or 2,2-bis (3-methyl-1-hydroxyphenyl) propane (component b) at least 9. The hard disk substrate according to claim 8, wherein the mole ratio is 90 mol%, and the ratio of component a to component b is 30:70 to 70:30 in molar ratio.

15. The hard disk substrate according to claim 14, wherein the component b is 4,4 '-(m-phenylenediisopropylidene) diphenol.

16. The hard disk substrate according to claim 14, wherein the ratio of component a: component b is 40:60 to 60:40 in molar ratio.

17. A hard disk according to claim 1, wherein a magnetic film is formed on a surface of the substrate.

18. A video hard disk having a magnetic film formed on the surface of the hard disk substrate according to claim 1.

19. 30-70 mol% of the wholly aromatic dihydroxy component is formed substantially from the aromatic polycarboxylic acid resin which is 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane; The polycarbonate resin is (A) the 0.

A solution of 7 g in 100 ml of methylene chloride has a specific viscosity in the range of 0.2 to 0.5 measured at 20 ° C and (B) a water absorption of 0.18% by weight as defined in the text. A hard disk substrate formed of a resin satisfying the following.

20. The aromatic polycarbonate resin is:

(a) 1,1-bis (4-hydroxyphenyl) -1,3,3,5-trimethylcycline hexane (component a) and

(b) 4,4,-(m-phenylenediisopropylidene) diphenol and Z or 2,2-bis (3-methyl-1-hydroxyphenyl) propane (component b) as a wholly aromatic dihydroxy component 20. The hard disk substrate according to claim 19, wherein at least 90 mol% of the component (a) and component (b) are in a molar ratio of 30:70 to 70:30.

21. The hard disk substrate according to claim 20, wherein the component is 4,4,-(m-phenylenediisopropylidene) diphenol.

22. The hard disk substrate according to claim 20, wherein the ratio of component a: component b is 40:60 to 60:40 in molar ratio.

23. The aromatic polycarbonate resin according to claim 19, wherein (A) the specific gravity is 0.95 to 1.25 and (B) the flexural modulus is 2,200 to 3,500 MPa. Hard disk board.

24. The hard disk substrate according to claim 19, wherein the center line average roughness (Ra) on the surface on which the magnetic film is formed is 2 nm or less.

25. The hard disk substrate according to claim 19, wherein a flatness in a circumferential direction on a magnetic film forming surface is 10 m or less.

26. The hard disk substrate according to claim 19, wherein substantially no coarse protrusions having a height of 25 nm or more are present on the surface on which the magnetic film is formed.

27. The hard disk substrate according to claim 19, wherein the resin has a linear expansion coefficient of 6.5 × 10 ⁵ deg ¹ or less.

28. The hard disk substrate according to claim 19, wherein the resin has a chlorine content of 10 ppm or less.

29. A hard disk having a magnetic film formed on a surface of the hard disk substrate according to claim 19.

30. A video hard disk in which a magnetic film is formed on the surface of the hard disk substrate according to claim 19.