JPH07233276A - Thermoplastic resin composition for turntable molding - Google Patents

Abstract

PURPOSE:To obtain a compsn. which, when molded, gives a turntable with a good surface flatness and firmly fixed to a drive shaft by compounding an amorphous thermoplastic resin and an inorg. platy filler. CONSTITUTION:This compsn. contains an amorphous thermoplastic resin and an inorg. platy filler. An amorphous resin having low shrinkability is used to obtain a high molding accuracy. Examples of such a resin are a polycarbonate, an ABS resin, polyphenylene oxide, polyphenylene ether, and alloys of these resins. Pref. examples of the filler area mica chips, kaolin clay, and glass flakes and have aspect ratios of 5-50. An aspect ratio lower than 5 gives a turntable which is not well fixed to a drive shaft through it has a good surface flatness while the ratio higher than 50 degrades the surface flatness.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a thermoplastic resin composition for molding a turntable for an information recording medium such as an optical disk.

[0002]

2. Description of the Related Art Optical pickups used for compact discs (CDs), laser discs (LDs), etc., record information on recording tracks formed on an optical disc surface as an information recording medium. Information is read by irradiating a reading light beam and reflecting light from the recording surface of the optical disk. In order to rotate the optical disc accurately, the optical disc is fixed on a member usually called a turntable. An example of this turntable is shown in FIGS. The turntable 1 has a boss portion 11 for fixing it to the rotary drive shaft 2, an outer peripheral annular fixing portion 12 for fixing the optical disc 3, and a recess 13 in which a pin gate is located during injection molding. The optical disc 3 is placed on the turntable 1 and then fixed to the turntable 1 by a clamper 4.

In order to reliably focus the light beam on the recording track on the optical disk surface, surface wobbling of the optical disk must be minimized. Although the objective lens for focusing the light beam of the optical pickup is designed to track the movement and change due to the eccentricity of the optical disk, in order to accurately track the recording track, the surface wobbling of the optical disk surface should be minimized. Is essential.

In addition to the above requirements, the turntable 1
It is necessary to satisfy the requirement that the fixation to the rotary drive shaft 2 is exactly right and is strong. Normally, in order to attach the turntable 1 to the drive shaft 2 at a right angle, a method of press-fitting the drive shaft 2 into the turntable 1 is adopted, but in order that the press-fitted turntable 1 is securely fixed, The deformation resistance and strength of the turntable 1 must be sufficiently large.

As described above, in order to reduce the surface runout of the optical disk surface, (a) improve the flatness of the turntable 1, and (b) ensure that the turntable 1 and the rotary drive shaft 2 are at right angles. It is necessary to be able to fix it so that (c) its angle can be maintained for a long time.

As materials for forming turntables satisfying the above requirements, nylon 12, polycarbonate and ABS resin (acrylonitrile-butadiene-) have hitherto been used.
A composition obtained by blending a thermoplastic resin such as a styrene copolymer resin) with an inorganic filler is used. Ferrite powder, glass fiber, talc, calcium carbonate, wollastonite, etc. are used as the inorganic filler.

In particular, in the case of ferrite powder, a large amount is mixed in nylon, and rather nylon is used as a binder. Such a material is suitable for a turntable because it is easy to secure deformation resistance and flatness, but there is a problem that the extruder for blending and the die for injection molding are heavily worn.

In the case of glass fiber, there are problems that the surface of the molded product is likely to have irregularities and the shrinkage ratio is anisotropic, so that the dimensional accuracy of the molded product is low.

[0009] Therefore, an object of the present invention is to provide a thermoplastic resin composition for molding a turntable which has good flatness and is capable of maintaining a strong fixation to a rotary drive shaft.

[0010]

As a result of earnest research to solve the above problems, the present inventors have found that a substantially amorphous thermoplastic resin is used as a base polymer and a plate-like inorganic filler is added thereto. It was discovered that a kneaded thermoplastic resin composition can be used to form a turntable having good flatness and capable of maintaining a strong fixation to a rotary drive shaft, and completed the present invention.

That is, the turntable molding thermoplastic resin composition of the present invention is characterized by containing a substantially amorphous thermoplastic resin and a plate-like inorganic filler.

The components of the turntable molding thermoplastic resin composition of the present invention will be described in detail below. Base Polymer In order to obtain good molding accuracy, a substantially amorphous thermoplastic resin having a small shrinkage rate is used. Preferred examples of such a thermoplastic resin include polycarbonate, ABS resin, polyphenylene oxide, polyphenylene ether, and polymer alloys thereof.

Inorganic Filler A plate-like inorganic filler is used as a filler for reinforcing the base polymer. Specifically, mica pieces, kaolin clay,
Glass flakes and the like are preferable, and mica flakes are particularly preferable.
As the shape of the inorganic filler, the aspect ratio is 5 to 5
0, preferably 20 to 40, and the average particle diameter (average of major axis) is 1 to 100 μm, preferably 2 to 50 μm. If the aspect ratio is less than 5, the flatness of the turntable is good, but the adhesion to the drive shaft is poor, and if it exceeds 50, the flatness of the surface is poor. The average particle size is 1μ
If it is less than m, the appearance is glossy and good, but the adhesion to the drive shaft is inferior.

The amount of the inorganic filler added is 5 to 50, with the total amount of the base polymer and the inorganic filler being 100% by weight.
Weight% It is preferably 10 to 40% by weight, more preferably 20 to 30% by weight. When the content of the inorganic filler is less than 5% by weight, sink marks are significantly generated on the inner surface of the drive shaft press-fitting hole 14 and the adherence to the drive shaft is poor. On the other hand, if it exceeds 50% by weight, the melt viscosity of the resin composition composed of the base polymer and the inorganic filler becomes high, and the resin pressure at the time of injection molding must be increased, so that the molded product is distorted and the flatness is deteriorated. Results inferior.

Further, glass fiber may be added if necessary. The size of the glass fiber is preferably 1 to 20 μm in diameter and 1 to 10 mm in length, more preferably 5 in diameter.
It has a length of 2 to 4 mm and a length of 15 μm. The amount of glass fiber added is preferably 20% by weight or less, more preferably 5 to 10% by weight, based on 100% by weight of the total amount of the base polymer and the filler. When the glass fiber content exceeds 20% by weight, the flatness of the turntable deteriorates.

[0016]

A turntable molded using the thermoplastic resin composition for molding having such a structure exhibits excellent flatness, and the rotary drive shaft is simply press-fitted into the boss opening of the turntable. The squareness with can be reliably maintained. It is considered that this is because when the plate-like inorganic filler is used, there is little disturbance during injection molding, and most plate-like inorganic fillers are arranged substantially parallel to the turntable surface.

[0017]

EXAMPLES The present invention will now be described in more detail with reference to specific examples, but the present invention is not limited thereto.

Examples 1 to 5 and Comparative Examples 1 to 5 Using the thermoplastic resin compositions according to Examples and Comparative Examples having the formulations shown in Table 1, turntables having a shape shown in FIGS. 1 and 2 (diameter 35 mm, Thickness of the outer peripheral annular fixing portion 12 is 2.0 mm)
Was produced by injection molding.

Table 1 Average particle size of inorganic filler Addition amount NO. Base polymer type Aspect ratio (μm) (wt%) Example 1 Polycarbonate muscovite 20-40 6 20 Example 2 ABS muscovite 20-40 40 20 Example 3 ABS muscovite 20 to 40 6 30 Example 4 Polymer alloy ⁽¹⁾ muscovite 20 to 40 6 20 Example 5 Polymer alloy ⁽¹⁾ muscovite 20 to 40 6 30 Comparative example 1 Polycarbonate glass fiber 190 to 270 13 ⁽²⁾ 30 Comparative Example 2 Polymer Alloy ⁽¹⁾ Talc 5 to 20 5 10 Comparative Example 3 PBT ⁽³⁾ Glass Fiber 190 to 270 13 ⁽²⁾ 30 Comparative Example 4 PBT ⁽³⁾ Glass Fiber + 270> 13 ^{( 2)} 20 glass beads-30 20 Comparative Example 5 PHT ⁽⁴⁾ Glass fiber 190 to 270 13 ⁽²⁾ 30 Note) (1): Polymer alloy of polycarbonate and ABS. (2): For glass fiber, the diameter of the cross section. (3): Polybutylene terephthalate. (4): Polycyclohexane dimethylene terephthalate.

Using the obtained turntable, measurement of pressure input and surface wobbling test were conducted. The press-fitting was performed by measuring the value when the drive shaft 2 was press-fitted into the turntable a plurality of times, and the surface runout was measured by measuring the distance that the outer peripheral annular fixing portion 12 moves up and down when the turntable rotates. Table 2 shows the measurement results of the pressure input and the surface runout.

Table 2 Rotary Drive Axial Pressure Input Surface Runout Example NO. (Kg weight) (μm) Example 1 20-23 20-30 Example 2 20-24 20-30 Example 3 22-25 20-30 Implementation Example 4 24-27 15-25 Example 5 25-28 20-30 Comparative Example 1 18-20 25-35 Comparative Example 2 12-15 25-35 Comparative Example 3 16-18 30-50 Comparative Example 4 15-17 30-40 Comparative Example 5 15-17 30-40

As is clear from Table 2, the amorphous thermoplastic resin was used as the base polymer and was molded using the thermoplastic resin in which the plate-like inorganic filler was kneaded. The surface wobbling performance has been greatly improved.

[0023]

As described in detail above, the thermoplastic resin for turntable molding of the present invention is excellent because it is obtained by kneading a plate-like inorganic filler with an amorphous thermoplastic resin as a base polymer. It is possible to mold a turntable which has a high degree of flatness, can be securely fixed to the rotary drive shaft at a right angle, and can maintain the angle for a long period of time.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing a turntable in a state where an optical disc is mounted.

FIG. 2 is a plan view showing a turntable.

[Explanation of symbols]

 1 turntable 11 boss portion 12 outer peripheral annular fixing portion 14 drive shaft press-fitting hole 2 rotation drive shaft 3 optical disk 4 clamper

Claims (3)

[Claims] 1. A thermoplastic resin composition for turntable molding, which comprises a substantially amorphous thermoplastic resin and a plate-like inorganic filler. 2. The turntable molding thermoplastic resin according to claim 1, wherein the plate-like inorganic filler has an aspect ratio of 5 to 50. 3. The turntable molding thermoplastic resin according to claim 1 or 2, wherein the plate-like inorganic filler is at least one selected from mica flakes, kaolin clay and glass flakes. A characteristic thermoplastic resin for turntable molding.