JPH063673B2 - Method for manufacturing optical memory disk hub - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method of manufacturing a hub attached to an optical memory disk for clamping by a magnet.

[Conventional technology]

In recent years, optical memory disks have been put to practical use as large-capacity memory as document files, educational materials, image processing files, and the like. In this optical memory disk, two recording material coated substrates are bonded to each other with the recording surface facing in, or
An optical disk with a hub, in which a hub for magnet clamp is attached to both sides outside the central portion of the substrate, is attached as a cartridge, which is housed in a dedicated case, is generally supplied.

By the way, such a hub is usually a metal plate having a diameter of 40 mm or less and a thickness of 3 mm or less with a hole in the center or a diameter of 35 mm.
Hereafter, a thin metal plate with a thickness of 1.5 mm or less is attached to the thermoplastic resin by adhesive or integral injection molding, but in order not to contaminate the optical memory disk due to rust,
The metal is made of non-rust steel such as stainless steel alloy.
The hub can be attached to the board by directly adhering the board and the metal plate, by sandwiching the metal plate from both sides of the board and then tightening it with screws, or by adhering the metal plate or attaching it to the thermoplastic resin by insert injection molding. A method of attaching the attached hub to the disk using ultrasonic waves or an adhesive has been put into practical use.

On the other hand, Japanese Patent Laid-Open No. 62-129985 discloses that a hub formed by mixing ferromagnetic metal powder such as iron oxide, permalloy, sendust into a plastic having the same coefficient of thermal expansion as the disk substrate is fixed to the disk substrate. A magnetic clamp type information recording disk has been proposed.

Further, Japanese Patent Application Laid-Open No. 62-129985 also describes that thermal distortion does not occur in the disk substrate even when the hub and the disk substrate have the same coefficient of thermal expansion and the ambient temperature changes.

[Problems to be Solved by the Invention]

However, a large amount of magnetic metal powder must be mixed in order to obtain a hub that has a sufficient suction force during magnet clamping. However, as the amount of magnetic metal powder mixed increases, the coefficient of thermal expansion of the hub and the disk substrate It was revealed by the study of the present inventor that the difference from the coefficient of thermal expansion becomes large.

Also, in an attempt to keep the amount of magnetic powder mixed in a small amount and to slightly reduce the decrease in the thermal expansion coefficient, it is unavoidable to strengthen the magnetic force of the drive in order to compensate for the decrease in the adsorption force, increasing the impossibility of drive and increasing the drive inability. It is not preferable in terms of the circuit and structure. In particular, in the case of a magneto-optical disk, it must be avoided, and it has been difficult to obtain a hub having a sufficient adsorption force by making the coefficient of thermal expansion of the hub equal to the coefficient of thermal expansion of the disk substrate.

[Means for Solving the Problems]

The present inventor has arrived at the present invention as a result of extensive studies on a method of manufacturing a hub which has a sufficient clamping force for a magnet clamp device and which does not increase the distortion of a disk substrate due to temperature and humidity changes. .

That is, the present invention is a method for producing an optical memory disk by injection molding a mixture of 15 to 55% by weight of a thermoplastic resin and 45 to 85% by weight of magnetic fibers, in which a magnetic field is applied in the cavity of an injection molding die. And a method for manufacturing an optical memory disk hub.

If the optical memory disk obtained by the manufacturing method of the present invention is used, it can be easily bonded to a disk substrate without substantially increasing the birefringence of the disk substrate, and the adhesive surface is cracked by a thermal cycle test. Since it does not show defects such as etc., it withstands repeated rotating tests well, and does not generate rust even under severe environmental conditions,
The increase in bit error rate due to hub mounting can be minimized.

Examples of the thermoplastic resin used in the present invention include polyester resin, polyamide resin, ABS resin, polycarbonate resin, polyphenylene oxide resin, polyacetal resin, polyphenylene sulfide resin, polysulfone resin, polyether sulfone resin, polyolefin resin,
Examples of the polystyrene resin include polyester resin, polyamide resin, ABS resin, polycarbonate resin, and polyolefin resin.

A hub using a polyester resin has a glossy appearance, excellent sliding properties, light resistance and environmental resistance properties, and has a polyester-forming ability. For example, dicarboxylic acid and diol, hydroxycarboxylic acid. Suitable are homopolyesters and copolyesters produced by a known method. Examples of dicarboxylic acid components include aliphatic acids such as malonic acid, succinic acid, adipic acid, and sebacic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid. Aromatic dicarboxylic acids such as cyclic dicarboxylic acid, terephthalic acid, isophthalic acid, 2,5-dipromterephthalic acid, 2,6-naphthalene dicarboxylic acid, 4,4-sulfone-diphenyldicarboxylic acid and their dicarboxylic acids. Alkyl-substituted esters, etc., diol components such as ethylene glycol, polyethylene glycol, polypropylene glycol, dipropylene glycol, 1,4-butanediol, 1,4-dihydroxyhexane, 1,4-dihydroxymethyl-cyclohexane, etc. The carboxylic acid may be p-hydroxymethyl-cyclohexyl. San carboxylic acid, can be used p- hydroxyphenyl acetate.

Among these polyester resins, polyethylene terephthalate, polybutylene terephthalate, and a copolymer or blend composition containing at least 50% by weight thereof are particularly preferably used.

As the polyamide resin, nylon 66, nylon 61
No. 0, nylon 12, and a copolymer or blend composition thereof can be used, but nylon 6 and nylon 4 easily absorb moisture, and cause dimensional change due to rusting of magnetic fiber and environmental change. It has an easy defect. Further, in order to improve the hygroscopicity and dimensional stability of the polyamide resin, it is preferable to use it by mixing it with polyphenylene sulfide.

The ABS resin is an acrylonitrile-butadiene-styrene resin containing polybutadiene or a polybutadiene copolymer as a rubber component, and generally commercially available products can be used. The ABS resin has a short molding cycle, a low molding temperature, and is excellent in dimensional stability. Therefore, the molding loss is small, the molding advantage is large, and the adhesion to the disk substrate is excellent.

Further, the polycarbonate resin is obtained by reacting bisphenols and phosgene, or a carbonate precursor such as diaryl carbonate,
The bisphenols include bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4 -Hydroxyphenyl) butane, 2,2
-Bis (4-hydroxyphenyl) octane, bis (4
-Hydroxyphenyl) phenylmethane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 1,
1-bis (4-hydroxyphenyl) cyclopentane,
Examples thereof include 1,1-bis (4-hydroxyphenyl) cyclohexane and 4,4-dihydroxydiphenyl ether. Among these polycarbonate resins, the polycarbonate resin produced from 2,2-bis (4-hydroxyphenyl) propane (so-called bisphenol A) is particularly preferable.

Polycarbonate resin has few troubles during molding, and the obtained hub is excellent in heat resistance, dimensional stability, environment resistance, and adhesiveness, and is particularly preferable for a polycarbonate optical disk substrate.

Further, as the polyolefin resin, a resin obtained by polymerizing one or more of ethylene, propylene, butene-1,4-methylbutene-1,4-methylpentene-1, or acrylic acid, methacrylic acid, maleic acid, Examples thereof include unsaturated carboxylic acids such as fumaric acid and the like, and polyolefin copolymers obtained by copolymerizing or graft-polymerizing anhydrides or esters of these acids.

A polyolefin resin is excellent in moisture resistance and is preferable as a hub for a polyolefin optical disc substrate.

The magnetic fiber used in the present invention has a small coercive force and a low residual magnetic flux density, is preferably a material having a high saturation magnetic flux density and a high magnetic permeability. Examples of these include Fe fibers having a purity of 98% or more and 1 to 4% by weight of Si.
Si-Fe alloy fiber Al-Fe alloy fiber containing 10 to 16% by weight of Al, Ni-Fe alloy fiber, Ni-Fe-Co alloy fiber, or Fe, N
Alloy fibers containing 80% by weight or more of one or more of i and Co and containing Cr, Mn, W, and the like, for example, SUS 400-series alloy defined in JIS can be used.

The average fiber length of these magnetic fibers is preferably 10 mm or less, and when the average fiber length is 10 mm or more, they are mixed with a thermoplastic resin and friction between the screen and the barrel during injection molding increases, so that the screen and the barrel are It is not preferable because it is easily damaged. The fiber diameter is preferably 0.002 to 0.2 mm.
If it is 0.002 mm or less, it is easy to form a lump of fibers and the mixing operation with the thermoplastic resin becomes difficult, and the saturation magnetic flux density of the obtained hub molded product becomes small, and the magnetic permeability becomes small, which is also preferable. None, of which 0.005-
0.15 mm is a particularly preferable range.

These fibers can be manufactured by a so-called chatter vibration method in which a lump of metal is scraped off by a vibrating blade, or by a method in which metal is pulled out to form long fibers, and if necessary, they are bundled and then cut.

The mixing ratio of the thermoplastic resin and the magnetic fiber is determined from the magnetic properties and reliability of the obtained optical memory disk hub and the workability of extrusion. The mixing ratio of the magnetic fiber is 45 to 8
It is 5% by weight. If it is 45% by weight or less, the force required to clamp the optical memory disk cannot be obtained, which is not preferable. On the other hand, if it exceeds 85% by weight, extrusion workability and injection moldability are significantly impaired, and mixing of the thermoplastic resin and the magnetic fibers becomes insufficient, resulting in low strength and cracking even by a slight impact. However, it is not preferable because reliability is deteriorated.

As a device for mixing the thermoplastic resin and the magnetic fiber,
A commonly used apparatus such as a Henschel mixer, a mixing roll, a single screw extruder, or a twin screw extruder can be used. When mixed, the thermoplastic resin has an average particle size of 1.5 m
Particularly good mixing operation can be performed by supplying the powder as m or less.

The method of previously treating the magnetic fibers with an epoxy-based treating agent or a silane-based treating agent and then mixing them brings preferable results such as improving the appearance of the molded article and improving the mechanical strength. There is no hindrance to the implementation of. Also,
Addition of a colorant, an antioxidant, a release agent, etc. at the time of mixing does not hinder the practice of the present invention.

The mixing ratio greatly affects the linear expansion coefficient of the mixed composition, and generally, the higher the mixing ratio of the magnetic fibers, the smaller the linear expansion coefficient. On the other hand, since the linear expansion coefficient of the molded product is greatly influenced by the orientation direction of the fibers, the dependence of the linear expansion coefficient on the direction can be controlled by controlling the orientation of the fibers. In the hub, the coefficient of linear expansion in the thickness direction may be far away from the coefficient of linear expansion of the substrate, but the coefficient of linear expansion in the radial or circumferential direction must be close to that of the substrate. If the linear expansion coefficient in the radial direction is greatly different between the substrate and the hub, distortion is likely to occur on the signal surface due to thermal cycles or the like, and peeling or cracking is likely to occur on the adhesive surface.

Next, in the method of the present invention, by using a mold incorporating a solenoid coil so that the magnetic flux lines penetrate the cavity, the magnetic fibers are formed in a state in which a magnetic field is formed by energization, and You can also line them up. At this time, the same effect was observed when a permanent magnet was used instead of the solenoid coil. The degree of orientation of the fibers is influenced by the magnetic flux density, the saturation magnetic flux density of the magnetic substance, the magnetic permeability, the resin temperature, the filling speed, and the like.

During this injection molding, by turning the magnetic field on and off in synchronization with the injection cycle, a hub having a higher degree of orientation of the magnetic fibers and less distortion can be obtained. The magnetic field is preferably turned on before the filling is completed and turned off during the cooling process.

The injection molding temperature is set to be 10 to 20 ° C higher than the molding temperature of the thermoplastic resin used as the raw material at the time of injection molding, or the injection pressure is increased to 50 to 100 kg / cm ² for molding, and the surface has gloss and sink marks. From this point, preferable results can be obtained.

Since the material used in the present invention is more likely to wear the mold than unfilled thermoplastic resin, the material of the injection molding mold is hard steel or hard chrome plating treatment, the life of the mold is significantly increased. It can be postponed.

In the present invention, the number of gates, the position, and the method have little influence on the orientation degree of the magnetic fiber.

The hub of the present invention thus molded has a stronger clamping force than the hub made of the same amount of the magnetic powder filling material as compared with the same filling amount, and has a linear expansion coefficient in the radial direction. Get closer to the board.

Furthermore, it does not rust even under severe salt spray test or thermal cycle test, and it is stable for a long time. Epoxy adhesives, dianoacrylate adhesives, acrylic adhesives, urethane adhesives are used for disk substrates. It can be attached by adhesion or ultrasonic bonding.
When these are bonded, alignment is very important, and it is necessary to perform alignment after sufficient alignment so that the inclination and eccentricity of the disk are minimized.

The optical memory disk hub of the present invention gives particularly good results when applied to a thermoplastic resin disk substrate, but also gives good results when applied to a glass disk substrate.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to examples. In addition,
Evaluation of the hub and the optical memory disk in the examples was performed according to the following method.

(1) Evaluation of Hub Salt Water Test A salt water spray test was carried out for 48 hours by the method of JIS Z2371 to observe the occurrence of rust on the hub surface.

Dimensional change The average dimensional change rate (% / ° C) of the outer diameter of the hub was measured when the ambient temperature was raised from -20 ° C to 55 ° C.

(2) Evaluation of optical memory disk Birefringence index The double-bus birefringence index of the optical memory disk with a diameter of 60 mm is 830 nm at the wavelength of 830 nm, before and after hub bonding, and from -30 ° C to 60 ° C.
90% RH was measured for each sample after 10 cycles of a so-called thermal cycle test in which one cycle was 24 hours.

Load-in test Visual inspection was carried out after loading the recording / playback drive device 5,000 times.

Clamping force The clamping force (g) was measured by measuring the force required to separate the optical memory disk clamped by the drive device in the axial direction.

Adhesive Strength of Hub The adhesive strength required to peel the hub from the optical memory disk was measured.

Example 1 Polybutylene terephthalate powder having an intrinsic viscosity of 0.85 measured in a 50/50 solution of phenol and tetrachloroethane, an average particle diameter of 0.4 mm, and a chatter vibration of an average fiber diameter of 0.02 mm and an average fiber length of 1.5 mm. The magnetic fibers produced by the method are mixed in the proportions shown in Table 1, and carbon black 0.3% as a colorant and B-220 (manufactured by Ciba-Geigy) 0.2% as an antioxidant with respect to the amount of thermoplastic resin powder, OP-WAX (Hoechst) 0.2% was added as a release agent and V was added.
The mixture was placed in a mold tumbler and stirred and mixed at 30 rpm for 30 minutes, and then extruded with a pent type single-screw extruder having a screw with a dullage having a diameter of 45 mm, and the strand was cut to obtain a pellet-shaped thermoplastic resin filled with a magnetic material.

These pellets were attached to an injection molding machine having an injection capacity of 1 ounce, with a mold in which a solenoid coil was arranged in a movable plate so that the magnetic flux lines of a single 3-point pin gate crossed the cavity, and the cylinder temperature was 250 ° C. Mold temperature 50
Under the conditions of ℃, maximum injection pressure of 500 kg / cm ² and molding cycle of 22 seconds, a hub-molded product having an outer diameter of 25.00 mm, a thickness of 2.15 mm and a square hole with a side of 4.00 mm at the center was obtained.

At this time, 1 second after the start of injection, the DC voltage and current shown in Table 1 were applied to the solenoid coil to form a magnetic field, and the solenoid was turned off 13 seconds after injection.

The obtained hub was coated separately with a cyanine dye-based recording material on which the outer diameter of 130 mm was recorded.
Bonded to a polycarbonate disk substrate with an inner diameter of 15 mm and a thickness of 1.2 mm using an epoxy adhesive, and then two disk substrates with hubs, with the recording surface inside, and a thickness of 0.6 m.
An m-thin polycarbonate thin plate was sandwiched between the outermost circumference and the innermost circumference, and these were bonded with an adhesive to obtain an optical memory disk having a sandwitch structure. The evaluation results are shown in Table 1.

Examples 2-5. Comparative Examples 1 to 3 An experiment was performed in the same manner as in Example 1 except that the type of magnetic substance fiber and the mixing ratio (weight ratio) of the thermoplastic resin and the magnetic substance fiber were changed as shown in Table 1. The results are also shown in Table 1.

According to the method of the present invention, the birefringence of the optical memory disk is hardly increased due to the adhesion of the hub or the change in the environmental conditions, and the highly reliable optical memory disk with less warpage is industrially produced. It can be obtained at low cost and has excellent industrial effects.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an example of an injection molding die used in the present invention. (1) Fixing mold (2) Moving mold (3) Solenoid coil (4) Wiring (5) Runway (6) Cavity

Claims (3)

[Claims] 1. A method for producing an optical memory disk hub by injection molding a mixture of 15 to 55% by weight of a thermoplastic resin and 45 to 85% by weight of magnetic fibers, wherein a magnetic field is provided in the cavity of an injection molding die. A method for manufacturing an optical memory disk hub, which comprises: 2. The optical memory according to claim 1, wherein the injection molding is performed so that the magnetic flux lines in the cavity of the injection molding die coincide with the thickness direction of the optical memory disk hub being molded. Disk hub manufacturing method. 3. A magnetic field in a cavity of an injection molding die,
The method of manufacturing an optical memory disk hub according to claim 1, wherein the method is turned on / off in synchronization with an injection molding cycle.