JPS6316418A - Magnetic disk substrate - Google Patents

Abstract

PURPOSE:To permit formation of an extremely flat surface by coating a polyamic ester oligomer which yields a soln. of a high resin component and low viscosity on a substrate and drying the coating. CONSTITUTION:The polyamic ester oligomer obtd. by bringing an arom. diamine and/or diaminosiloxane into reaction with the arom. tetracarboxylate obtd. by bringing an arom. tetracarboxylic anhydride and alcohol and/or alcohol deriv. or arom. tetracarboxylate and arom. arom. tetracarboxylic anhydride into reaction is coated on the aluminum substrate and is cured, by which this disk substrate is formed. The polyamic ester oligomer used here is the oligomer having the mol.wt. lower than the mol.wt. of the conventional polyimide resin. Such oligomer has the high solubility, yields the soln. of the high resin component and low viscosity and permits the formation of the substantially flat surface on the substrate even with <=5mum film thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic disk substrate, and more particularly to a magnetic disk substrate with a flat surface.

(Prior Art) Aluminum or aluminum alloy is used as a magnetic disk substrate conventionally used. In order to use these materials as disk substrates, it is required to make the substrate surface highly flat by various polishing methods and surface treatment methods. However, these polishing methods and surface treatments are quite difficult processes because aluminum, which is essentially soft, is used as the substrate. Therefore, a method of forming a resin layer on a substrate without performing these steps and flattening the surface by filling holes with a fluid resin is attracting attention. On the other hand, since heat treatment is involved in the process of forming a magnetic material on a substrate and manufacturing a magnetic disk, the resin used for these purposes is required to be a heat-resistant resin, and polyimide is a resin that satisfies this condition. resin is known. However, in order to form a resin layer on a substrate and make the surface flat, it is necessary to have a high resin concentration and a relatively low viscosity, but conventional polyimide resins have a high resin content and a relatively low viscosity.
It is very difficult to satisfy the two conditions of low viscosity and low viscosity at the same time, and therefore it is very difficult to obtain good flatness with conventional polyimide resins.

(Problems to be Solved by the Invention) An object of the present invention is to eliminate the drawbacks of the prior art and form a flat surface on an aluminum substrate using a compound that provides a solution with a high resin content and low viscosity. It is an object of the present invention to provide a magnetic disk substrate with improved performance.

(Means for Solving the Problems) The present invention provides an aromatic tetracarboxylic acid ester obtained by reacting an aromatic tetracarboxylic dianhydride with an alcohol and/or an alcohol derivative, or The present invention relates to a magnetic disk substrate obtained by applying a polyamic acid ester oligomer obtained by reacting an ester and an aromatic tetracarboxylic dianhydride with an aromatic diamine and/or a diaminosiloxane onto an aluminum substrate and hardening the same.

The polyamic acid ester oligomer used in the present invention is an aromatic tetracarboxylic acid dianhydride obtained by reacting an aromatic tetracarboxylic dianhydride with an alcohol and/or an alcohol derivative, optionally in the presence of a solvent. It is obtained by reacting an acid ester, or the aromatic tetracarboxylic acid ester and an aromatic tetracarboxylic dianhydride with an aromatic diamine and/or a diaminosiloxane. Examples of the solvent in this case include ether glycol solvents such as butyl cellosolve, N-methyl-2-pyrrolidone, N,N-diethylformamide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, One or more types of toluene, xylene, etc. are used.

Aromatic tetracarboxylic dianhydride has the general formula (in the formula R1
means a tetravalent aromatic hydrocarbon group), for example, 3.3', 4.4'-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, 3.3', 4
．． 4'-diphenyltetracarboxylic dianhydride, cyclopenkune tetracarboxylic dianhydride, 1.2.5.6-
Naphthalenetetracarboxylic dianhydride, 2.3,6.7
-Naphthalenetetracarboxylic dianhydride, 2,3°5.
6-pyridinetetracarboxylic dianhydride, 1°4.5.
8-Naphthalenetetracarboxylic dianhydride, 3.4,9
．． 10-perylenetetracarboxylic dianhydride, 4.41
- One or more types of sulfonyl siphthalic dianhydride and the like are used.

Examples of alcohols and/or alcohol derivatives for esterifying aromatic tetracarboxylic dianhydrides include monohydric alcohols such as methanol, ethanol, propatool, isopropyl alcohol, and butanol, ethylene glycol, propylene glycol, glycerin, and trimethylolpropane. One or more types of alcohol derivatives such as polyhydric alcohols such as cellosolves, carpitols, etc. are used. Alcohol and alcohol derivatives may be used in combination. Aromatic tetracarboxylic esters are reacted alone or together with aromatic tetracarboxylic dianhydrides with aromatic diamines and/or diaminosiloxanes.

The aromatic diamine used in the present invention is represented by the general formula % (in the formula, R2 means a divalent aromatic hydrocarbon group), such as 4,4"-diaminodiphenyl ether, 4.4"- One or two of diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 4,41-diaminodiphenyl sulfide, benzidine, metaphenylenediamine, paraphenylenediamine, 1,5-naphthalenediamine, 2゜6-naphthalenediamine, etc. The above is used.

The diaminosiloxane used in the present invention has the general formula (where n is an integer of 1 to 10, R is 2 with a carbon number of 1 to 10).
R4, R3, R6 or R7 means a monovalent hydrocarbon group having 1 to 10 carbon atoms, which may be the same or different; for example, 1 such as □. A species or two or more species may be used.

Aromatic diamine and diaminosiloxane may be used together.

The esterification of the aromatic tetracarboxylic dianhydride in the present invention can be carried out using alcohol and/or alcohol derivatives in a ratio of 4 moles or less per 1 mole of the aromatic tetracarboxylic dianhydride. Preferably.The reaction temperature varies depending on the solvent, alcohol, alcohol derivative, etc. used, and is not limited to Part 3.
3', 4. When 4'-benzophenonetetracarboxylic dianhydride is esterified using ethanol in N-methyl-2-pyrrolidone, a reaction temperature of 80 to 150°C is preferred. Furthermore, after esterification, excess alcohol or alcohol derivative can be removed in order to adjust the concentration, but in this case, the temperature is preferably higher than the boiling point of the alcohol or alcohol derivative.

-Nl The reaction of the aromatic tetracarboxylic acid ester thus obtained (or the aromatic tetracarboxylic acid ester and aromatic tetracarboxylic dianhydride, hereinafter the same) with the aromatic diamine and/or diaminosiloxane is as follows: In order to maximize the heat resistance of the polyimide compound obtained by curing the resulting polyamic acid ester oligomer, it is preferred that the aromatic tetracarboxylic acid ester and the aromatic diamine and/or diaminosiloxane be used in approximately equimolar amounts. In addition, the reaction between aromatic tetracarboxylic acid ester and aromatic diamine and/or diaminosiloxane is difficult because if the reaction temperature is too high, the resulting polyamic acid ester oligomer will be imidized, its solubility will decrease, and it will precipitate. (Both reactions are preferably carried out at a reaction temperature of up to 90°C.

For the polyamic acid ester oligomer thus produced, 200 to 400°C, preferably 250 to 3
If heat treatment is performed at 50°C, a polyimide resin with excellent heat resistance will be produced.

The magnetic disk substrate of the present invention is obtained by applying the polyamic acid ester oligomer as a solution onto an aluminum substrate or an aluminum alloy substrate to a thickness of preferably 5 μm or less and curing. Polyamic acid ester oligomers of the type, already known polyamic acids and/or already known polyimides may be mixed. As the solvent used at this time, the solvent used in the production of the polyamic acid ester oligomer may be used, or other solvents may be used.

The polyamic acid ester oligomer used in the present invention has a lower molecular weight than conventional polyimide resins, and can provide a solution with high dissolved carbon, high resin content, and low viscosity, even with a film thickness of 5 μm or less. A sufficiently flat surface can be formed on the substrate.

(Example) Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 322.1 g of 3.3',4.4'-benzophenonetetracarboxylic dianhydride was added to 520 g of N,N-dimethylformamide, and the mixture was heated to 80°C to dissolve it. Next, 64.08 g of methanol was added to this solution and reacted at 100°C for 3 hours, then cooled to 80°C.
After adding 198.0 g of 4.41-diaminodiphenylmethane, the mixture was reacted at 80°C for 3 hours. The resulting polyamic acid ester oligomer solution had a viscosity of 20 poise at 25°C.

This solution was applied to an aluminum substrate with a maximum surface roughness (Rmax) of 0.3 μm and a thickness of 1 fl using a spinner at 250 Orpm/
It was spin-coated for 60 seconds and cured at 380°C. When the maximum surface roughness of the substrate after curing was measured using a Talystep (surface roughness needle made by Rank Taylor Bopson) over a scanning distance of 2H, the maximum surface roughness was 0.03μ at a film thickness of 5μm.
m or less.

Example 2 64.41 g of 3.3',4.4'-benzophenone tetracarboxylic dianhydride was converted into N-methyl-2=pyrrolidone 9
0.65 g and heated to 60°C to dissolve. Next, 13.80 g of ethanol was added to this solution and reacted at 80°C for 20 minutes, then cooled to room temperature and incubated at 40°C.
After adding and dissolving 40.04 g of ,49-diaminodiphenyl ether, the mixture was heated to 80°C, and then heated to 80°C for 20
Allowed to react for minutes.

After the reaction was completed, the mixture was cooled to room temperature and diluted by adding 16.60 g of N-methyl-2-pyrrolidone. The resulting polyamic acid ester oligomer solution had a viscosity of 30 poise at 25°C.

Thereafter, the coating was applied and cured on an aluminum substrate in the same manner as in Example 1, and the maximum surface roughness was measured in the same manner as in Example 1. The maximum surface roughness was 0.02 μm or less at a film thickness of 3.5 μm. Ta.

Reference Example The polyamic acid ester oligomer obtained in Example 2 was spin-coated using a spinner at 150 rpm/60 seconds, and after curing, the maximum surface roughness was measured in the same manner as in Example 1. The film thickness was 8.08 m. The maximum surface roughness is 0.03μm.
It was below.

Comparative Example 1 28.75 g of 4.4'-diaminodiphenyl ether was dissolved in 425 g of N-methyl-2-pyrrolidone, and 46.25 g of 3.3",4.4'-benzophenonetetracarboxylic dianhydride was added to this solution. g was reacted at 50°C or lower for 8 hours, then at 80°C for several hours, and the viscosity was adjusted to 30 poise at 25°C.
The coating was spin-coated under the conditions of Orpm/60 seconds, cured at 380° C., and the maximum surface roughness was measured. The maximum surface roughness was 0.04 μm at a film thickness of 3.5 μm, but the surface waviness was large.

These results show that according to the present invention, a magnetic disk substrate with a flat surface can be easily obtained.

(Effects of the Invention) The magnetic disk substrate of the present invention is obtained by applying and curing a polyamic acid ester oligomer that provides a solution with a high resin content and low viscosity on a substrate, and has an extremely flat surface. It is something.

Claims (1)

[Claims] 1. To aromatic tetracarboxylic acid ester obtained by reacting aromatic tetracarboxylic dianhydride with alcohol and/or alcohol derivative, or to aromatic tetracarboxylic acid ester and aromatic tetracarboxylic dianhydride. A magnetic disk substrate obtained by applying and curing a polyamic acid ester oligomer obtained by reacting aromatic diamine and/or diaminosiloxane onto an aluminum substrate.