JPS6381668A - Manufacture of rotary disk of discoid recording medium - Google Patents

Abstract

PURPOSE:To reduce the weight to enhance the flatness and to considerably improve vibration proofing of a substrate by forming substrate by a thermoplastic resin complex of high rigidity and forming a concentric ring rib by injection-molding elastomer to the substrate. CONSTITUTION:By using the thermoplastic resin complex of high rigidity, the substrate 2 in which many through holes 7 and 9 are pierced concentrically on the periperal part and at the a central part. As for the thermoplastic resin complex, material in which carbon fiber or the like is mixed with amorphous thermoplastic resin of polycarbonate or the like by 19-70vol% is used for example. The substrate 2 is packed in an injection mold, heat reversible elastomer is injection-molded in the part of through holes 7 and 9, and concentric ring ribs 3 and 4 are formed. Such a rotary disk is light and has less warping and high levelness, and it can considerably improve the vibration proofing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for manufacturing a novel rotary disk for mounting a disk in audio and video equipment such as a video disk player and a compact disk player.

(Prior Art) Conventionally, metal products such as aluminum, reinforced thermosetting resin products such as BMC, etc. have been used as turntables for audio and video equipment. Rotating discs made of metal or reinforced thermosetting resin have the advantage of good dimensional accuracy and little rotational vibration during high-speed rotation, but because of their heavy weight, the access time until the picture 1 sound starts is reduced. One disadvantage is that it is long and has poor vibration isolation properties when vibration is applied to the equipment.
It was desired to develop a rotary disk with higher performance.

In response to such development issues, the present inventors attempted to develop a high-performance rotary disk using a thermoplastic resin molded body.

Compared to thermosetting resins, thermoplastic resins make it easier to manufacture products with thinner walls, making it easier to manufacture lightweight rotary discs, and also to manufacture products with complex shapes such as ribs and holes. It is considered to be suitable for obtaining high-performance rotary disks because it can be manufactured without secondary processing.

However, when conventional thermoplastic resins are molded into a disk shape with a wall thickness of 3 mm or less, internal distortion of the molded product causes "glue".
0 Also, in order to reduce the unevenness of the rotary disk to obtain levelness and to improve the stability of the recording medium, the recording medium of the rotary disk was It is possible to cover the impact part with an elastomer, but
For videos, etc., extremely high precision is required for the horizontality of the recording medium, so it is not possible to obtain a rotary disk that can produce high-quality images by attaching a separately molded elastomer with adhesive.

(Summary of the Invention) In view of the above circumstances, the inventors of the present invention have conducted extensive studies, and as a result, they have formed a base using a highly rigid thermoplastic resin composite, and have injection molded an elastomer onto the base. By forming concentric annular lips, it was possible to successfully obtain a rotary disk with excellent dimensional accuracy and excellent levelness, thereby achieving the present invention.

More specifically, the present invention involves molding a base with a large number of concentric through holes in the periphery and center using a resin composite with excellent specific rigidity, and molding the base in an injection mold. The present invention provides a method for manufacturing a rotary disc for a disc-shaped recording medium, characterized in that a concentric annular lip is formed by injection molding a thermoplastic elastomer into the through-hole forming portion.

(Detailed description of the invention) The contents of the present invention will be explained in detail below based on the drawings.

As shown in FIGS. 1 and 2, the rotary disk 1 of the present invention has a base 2 made of thermoplastic resin with high specific rigidity.

The thermoplastic resin composite used in the present invention is -4
The dynamic shear modulus G' measured at a frequency of 11 Hz from 0°C to 100°C is 1.5 x 1010°dyne
/- or more thermoplastic resin composite.

In addition, the thermoplastic resin composite has a dynamic shear modulus G□' at -40°C and a dynamic shear modulus G at 100°C.
The ratio G1'/a; with z' is 1.5 or less, and the density is 2.0
Preferably, it is less than f/ad.

A thermoplastic resin molded body with d less than 1.5 lacks rigidity as a base for a rotary disk, resulting in insufficient stability of the recording medium.

Even if G' is 1.5 or more, a material whose G□'/a exceeds 1.5 is not preferable as a base for a rotary disk because the characteristics change depending on the temperature.

Specifically, for example, a non-grade thermoplastic resin with a glass transition point of 100°C or higher, such as polycarbonate, styrene-modified polycarbonate, polysulfone, or polyetherketone, is reinforced with carbon fiber, silicon carbide fiber, glass fiber, boron fiber, etc. Blending fibers, the amount of reinforcing fibers is 19% by volume or more with respect to the total amount of non-grade resin and reinforcing fibers.70
Examples include thermoplastic resin composites having a volume of less than or equal to 0.0 Composites in which the blending amount of reinforcing fibers is 22 or more and less than or equal to 50 volume are preferred, and in particular, glass fibers having an average diameter of 9 μ or less are preferred. A composite containing 25 volume thick or more and 50 volume thick or less is preferred.

The thermoplastic resin and reinforcing fibers are kneaded and pelletized using a kneading machine such as an l-screw extruder or a twin-screw extruder, and the pellets are molded into a disk shape using an injection molding machine to form the base 2.

In injection molding, a molding machine with high mold clamping pressure is used, and an appropriate mold is used at a high molding temperature and an injection pressure of 1,000 to 2.000 ky/ad, preferably 1,500 to 2.000 ky/cd. A favorable base can be obtained by molding at a temperature of 0.The thermoplastic resin composite can also be modified to contain inorganic fillers such as calcium carbonate, Merck, mica, clay, titanium white, zinc oxide, Additives such as pigments such as carbon black can be used.

Further, at the position where the annular lip 4 is attached at the center, an annular groove 8 is recessed and a large number of minute through holes 9.9 are formed.

Further, minute through holes 11.11 for forming protrusions 10 are formed at intervals in the circumferential direction between the annular rib 3 at the peripheral edge and the annular rib 4 at the center, and the annular rib at the center It is desirable to form holes 12, 12 at intervals in the circumferential direction on the outer periphery of rotary disk 1 to adjust the self-vibration system of rotary disk 1.

In addition, 13 is a mounting hole to the main body of the device, and 14 is a tightening hole.

The thermoplastic elastomer forming the annular rib 3 at the peripheral edge of the base 2 and the annular rib 4 at the center has a hardness of 5 to 40 as determined by JIS K6301 "Spring Type Hardness Test".
Preferably it is a thermoplastic elastomer having a molecular weight of 10 to 30.

There are many types of thermoplastic elastomers, including copolymer types of polystyrene, polyolefin, and polyester, or composite types in which one thermoplastic resin and one rubber are blended, and among these, those with a hardness of 5 to 40 are used in the present invention. used for.

Among these, hydrogenated derivatives obtained by hydrogenating a block copolymer having the general formula A-(B-A)n can be used, where A is a hydrogenated derivative of a monovinyl-substituted aromatic hydrocarbon such as styrene. The combined block B is an elastomeric polymer block of a conjugated diene, preferably a thermoplastic elastomer using as one of the components n an integer of 1 to 5 and having a hardness of 5 to 40.

The annular ribs 3 and 4 are formed concentrically around the peripheral edge of the base and the center of the base, and their tops are at the same height.

In the present invention, it is desirable that the annular ribs 3 and 4 be formed continuously over the entire circumference, but they may be formed into a discontinuous annular shape by cutting out a part of the annular ribs.

Further, between the annular rib 3 at the peripheral edge and the annular rib 4 at the center, it is preferable to form protrusions 10 at intervals in the circumferential direction using the same thermoplastic elastomer as the annular ribs 3 and 4.

The base plate 2 is loaded into an injection mold 15, 16, as shown in FIG.

C in order to accurately and firmly connect the annular ribs 3 and 4 to the base.
Second, the base 2 must be accurately loaded into the injection mold cavity and firmly fixed and held. For this purpose, it is necessary to uniformly suppress the entire mold parting surface, and it is necessary to optimize the clamping force in order to eliminate the influence on the surface accuracy due to the distortion C2 caused by the suppression.

Specifically, the pressing force of the indoor surface of the mold against the base is 300 square meters/
- or more, 5ookf/- or less, preferably 400kf
/d or more and 5ooh/crI or less.0 The molded product obtained under these conditions has little warp, just like the base, and the base 2, the annular ribs 3, 4, and the protrusion 10. It is possible to obtain an excellent base l with less occurrence of cracks at the joint interface, high dimensional accuracy, and high bonding strength.The rotary disk obtained in this way has less "warpage", good surface accuracy, and is lightweight. It is extremely suitable for turntables in video and audio equipment such as video disc players and compact disc players.

In particular, the rotary disc of the present invention exhibits the effect of dramatically improving the vibration-proofing properties and is extremely suitable for VHD video discs, for which improvement in vibration-proofing properties is strongly desired.

In the present invention, the dynamic shear modulus G' is a value measured by the following method.

Method for measuring dynamic shear modulus G' The method for measuring dynamic mechanical properties of plastics described in ASTM D4065-82 is followed.

In the present invention, the dynamic shear modulus G' is measured using a forced torsional vibration method under conditions of constant strain (i, os or less) and constant frequency (11 Hz). Usually, a device having a forced torsional vibration mode, such as a mechanical spectrometer model 605M or 7osM (manufactured by Rheometrics, Inc., USA) is used.

Depending on the shape and size of the test piece, constant strain (1.0%
It is also possible to use the forced tensile vibration method under conditions of (below) and constant frequency (11 Hz). However, one-third of the dynamic tensile modulus E' determined by the tensile vibration method is defined as the dynamic shear modulus G'. In this case, a device having a forced tensile vibration mode, such as a Rheopipron model ■ or ■ (manufactured by Toyo Boldwine Co., Ltd.), a high frequency viscoelastic spectrometer YES-HC (manufactured by Nippon Roki Seisakusho), is used. Furthermore, it is also possible to use a forced compression vibration method or a forced bending vibration method, and in this case as well, one-third of the required dynamic elastic modulus is defined as the dynamic shear modulus G'.

The measurement temperature is in the range of -40°C to 100°C, and the heating speed is set so that the temperature of the test piece is in equilibrium. The temperature increase speed is step-like but linear.

It may be a target. Usually holding time is 3-5 in 2-5℃ steps.
min or 1~b Among the values measured in this manner, the values at -40°C and 100°C are adopted.

The test piece used is a rod-shaped or rectangular piece cut out from the molded body. Although the size of the test piece is not particularly limited, it is easier to measure if it is cut out as large as possible. If it is rod-shaped, measure the diameter and length, and if it is rectangular, measure the width, thickness, and length in advance.

Select clamps and other equipment that are appropriate for the shape and size of the test piece.For example, a standard clamp for torsional vibration of a mechanical spectrometer is! 12.7 m, thickness 0.5~
A test piece with a size of 6.4 m and a length of 40 to 63.5 meters is suitable. Furthermore, with a special clamp, it is possible to measure even smaller size test pieces.

Standard clamps for high frequency viscoelastic spectrometers include:
For tension vibration, width 2cm, thickness 1cm, length 1.5m (maximum dimensions above), for compression vibration, width 10cm, thickness 1cm,
A test piece having a length of 15 cm (maximum dimension) is suitable.

The test piece cut out from the molded body was heated at 23°C ± 2°C and 50°C.
Adjust for 40 hours or more at 5% relative humidity. After adjustment, be careful not to give any heat history other than during zero molding, which should be measured immediately.

Example 1 Polycarbonate modified by styrene impregnation polymerization (glass transition point 149°C, styrene content 5x1 ml) 65
After mixing with 35 volumetric glass fibers having an average particle diameter of 8 μm based on body volume, the mixture was kneaded using a single screw extruder to form pellets. The pellets were molded using a precision injection molding machine with a clamping pressure of 350 tons at a cylinder temperature of 320°C, a mold temperature of 100°C, and an injection pressure of 1.
Injection molded under the conditions of 800ky/, -j and diameter 260m
A doughnut-shaped molded body having a thickness of 2 m and a cavity with a diameter of about 70 cm at the center was obtained. The density of this compact is 160f/
It was 7.

In addition, from this molded body, the length is 63.5 m and the width is 12.7 n1.
Cut out a test piece with a thickness of 2 cm, and
After adjusting for 48 hours under the conditions of 3°C ± 2°C and 50% ± 5 chronic relative humidity, the dynamic shear modulus at a frequency of 11 Hz was measured using a mechanical spectrometer manufactured by Rheometrics. G; (-40°C) = 2.
2 X 10!0dyne/i, GJ (100℃)
= 2. OX 10” dyne / (4, c, ',
ic;=1.1.

A hydrogenated derivative obtained by loading a mold with the molded product thus obtained, and hydrogenating a block copolymer represented by A-f-B-n on the outer and inner peripheries. A is a styrene polymer block, B is a butadiene elastomeric polymer block, and the hardness is 2, which is a blend of non-aromatic mineral oil and polypropylene.
0 thermoplastic elastomer at a cylinder temperature of 190℃,
Mold temperature 40℃, primary injection pressure 250kii/cnl,
Secondary injection pressure 47okg/al, injection time 3.0 seconds,
The clamping force was set so that the pressing force of the inner surface of the mold against the base was 4ooky/aA, and injection molding was performed to obtain a molded product having the shape shown in FIG.

When this molded product was used as a rotary disk for a VHD video disk player, the image output time was short and the vibration-proofing properties were extremely excellent.

[Brief explanation of the drawing]

Fig. 1 is a partial cross-sectional view (A-A' cross section in Fig. 2) of a rotary disk showing an embodiment of the present invention, Fig. 2 is a partial perspective view thereof, and Fig. 3
The figure is a cross-sectional view of the mold part explaining the method of forming an annular lip.

Claims (1)

[Claims] A base with many concentric holes drilled in the periphery and center is molded using a thermoplastic resin composite with high specific rigidity.
A rotary disk for a disk-shaped recording medium, characterized in that the obtained substrate is loaded into an injection mold and a thermoplastic elastomer is injection-molded into the through-hole forming portion to form concentric annular ribs. Manufacturing method.