JPH10168315A - Polyarylene sulfide resin composition for optical actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain polyarylene sulfide resin composition that contain specific carbon fibers and calcium carbonate whiskers, has improved resonance frequency response, lowers the resonance peak value, and is durable for long-term use. SOLUTION: This polyarylene sulfide resin composition contains (A) 10-40wt.% of carbon fibers having fiber diameter of 20μm or smaller, for example, PAN-based carbon fibers obtained by carbonization/graphitization of polyacrylonitrile used as the starting material, and (B) 40-70wt.% of calcium carbonate whiskers of average fiber diameter of 0.5-1.0μm, and average fiber length of 10-30μm, and by melting and mixing both the fibers and the whiskers with a Henschel mixer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a resin composition used for an actuator of an optical pickup mounted on an optical disk device such as a CD-ROM, a video disk player and a digital audio player.

[0002]

2. Description of the Related Art An optical pickup is an apparatus for reading information of a signal track of a disk by a light receiving element from reflected light of a semiconductor laser beam applied to a disk surface via a reflection mirror and an objective lens. Above all, an actuator on which an objective lens is mounted requires accurate and quick movement for tracking. The specific characteristics required are a high resonance frequency and a low resonance peak. To achieve this, the material must have low specific gravity, high dimensional stability, and linear expansion coefficient (longitudinal and lateral directions). Is not required. In recent years, as disclosed in JP-A-3-66756, combinations of reinforcing materials and fillers based on polyphenylene sulfide (PPS) have been studied. However, since an actuator using this resin composition uses barium sulfate, it has a high specific gravity, and cannot respond to high-speed tracking.

An actuator made of a resin composition disclosed in Japanese Patent Application Laid-Open No. 5-262982 is lightweight, has a high specific elastic modulus, has an improved resonance frequency, and can withstand a high reading speed. In Although,
Aluminum borate whiskers have a very small expansion coefficient in the fiber axis direction, so depending on the structure of the actuator, the linear expansion coefficient of the resin composition exhibits directionality, and the optical axis shifts with the temperature rise during long-term use, Tracking cannot be maintained. As described above, the conventional resin composition was insufficient as a resin composition for an optical actuator.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a resin composition most suitable for an optical actuator capable of improving resonance frequency characteristics, reducing a resonance peak value and enduring long-term use. is there.

[0005]

Means for Solving the Problems The present inventors have proposed that the fiber diameter 2
By using a polyarylene sulfide resin composition containing 10 to 40% by weight of carbon fibers of 0 μm or less, 40 to 70% by weight of calcium carbonate whiskers having an average fiber diameter of 0.5 to 1.0 μm and an average fiber length of 10 to 30 μm. The present inventors have found that the object can be achieved and completed the present invention.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical polyarylene sulfide resin used in the present invention is polyphenylene sulfide and a copolymer thereof. These resins are relatively low molecular weight and low viscosity cross-linked or
High-viscosity, high-linear type products are known, and commercially available products of various grades can be easily obtained, and these can be used alone or in combination. Polyphenylene sulfide (PPS) is available in Japanese Patent Publication No. 44-276.
No. 71, No. 45-3368 and No. 45-27255, and a polymer synthesized by the method described in U.S. Pat. No. 3,274,165.
A polymer comprising a repeating unit represented by the following general formula and containing the repeating unit in an amount of 80 mol or more is preferable.

[0007]

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In the practice of the present invention, a polyphenylene sulfide copolymer component consisting of a repeating unit represented by the following general formula (2) may have an adverse effect on the crystallinity of the polymer of less than 20 mol%. It may be used in a mixing ratio that does not give.

[0009]

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The carbon fiber used in the resin composition of the present invention is limited to a fiber diameter of 20 μm or less. If the fiber diameter exceeds the fiber diameter, the wettability to the resin is deteriorated, high-density filling cannot be performed, and problems such as roughening of the molding surface occur. Examples of the type of carbon fiber include a PAN type and a pitch type. PAN-based carbon fiber is made from polyacrylonitrile as a starting material, carbonized,
Obtained by graphitization. The pitch-based carbon fiber can be obtained by using tar pitch as a starting material and carbonizing and graphitizing the same as in the PAN-based carbon fiber. In the former, a high-strength material is easily obtained, and in the latter, a high-elasticity material is easily obtained.

The calcium carbonate whiskers used in the present invention are characterized in that they have a small specific gravity and do not easily exhibit the directionality of the linear expansion coefficient, and have a fiber diameter of 0.5 to 1 μm and a fiber length of 10 μm.
Those having a size of ３０30 μm are preferable because they can enter the gaps between the carbon fibers and can be finely packed.

In the practice of the present invention, additives such as a nucleating agent and a lubricant other than a stabilizer such as an antioxidant may be added to the resin composition as long as the performance of the optical pickup is not deteriorated.

In the present invention, the mixing ratio of the above components is such that calcium carbonate whisker is added to 20 to 40% by weight, preferably 20 to 30% by weight of a polyarylene sulfide resin.
0 to 70% by weight and 10 to 40% by weight of carbon fiber are blended. If the amount of the calcium carbonate whisker and the carbon fiber exceeds the above range, it becomes difficult to fill the resin, and if the amount falls below the range, the resonance peak becomes high, and the desired performance as an actuator cannot be obtained.

The resin composition of the present invention comprises a ribbon blender,
A method of mixing and kneading using a mixer such as a tumbler mixer and a Henschel mixer, or a method of simultaneously mixing and kneading using a Banbury mixer and a screw kneader, etc. good. Using the pellets, a resin molded product of an optical actuator component can be obtained by various molding methods such as an injection molding method.

[0015]

The present invention will be described below in more detail with reference to examples and comparative examples. The raw materials used are as follows. (1) Polyphenylene sulfide resin [melt viscosity 15
Thermal cross-linking type of 00 poise (320 ° C., shear rate 1000 seconds)] (2) Carbon fiber [PAN type, 6 mm chopped strand, fiber diameter 7 μm] (3) Calcium carbonate whisker [true specific gravity 2.8, diameter 0.
5-1 μm, length 20-30 μm] (4) Aluminum borate whisker [true specific gravity 3.0, diameter 0.5-1 μm, length 10-30 μm] (5) Potassium titanate whisker [true specific gravity 3.3, Diameter 0.1-1.5 μm, length 10-100 μm)

[Examples 1 to 3] Polyphenylene sulfide resin and calcium carbonate whisker were mixed at the mixing ratio (% by weight) shown in Table 1 using a Henschel mixer, and then a twin screw extruder (TEM, manufactured by Toshiba Machine Co., Ltd.) -35)
The mixture was kneaded, and carbon fibers were charged through a side feed port, and melt-extruded at a temperature of 320 ° C. to form pellets. Using an injection molding machine having a mold clamping pressure of 30 tons, a test piece and a pickup component were produced from the obtained pellet. The physical properties of the test piece were examined to confirm that the test piece had high elasticity, and the pickup component was measured for its resonance property and the like using a mounting test and a resonance frequency measuring device. These test results were as shown in Table 1. The bending test using a test piece was performed using ASTM D-790, the specific gravity was measured using ASTM D-792, and the coefficient of linear expansion was measured using ASTM D-6.
96.

[Comparative Examples 1 to 3] The same polyphenylene sulfide resin and carbon fiber as in the above example were used except that aluminum borate whiskers and potassium titanate whiskers were used instead of calcium carbonate whiskers. The mixture was mixed at a ratio (% by weight), and the same treatment was performed to produce a test piece and a pickup part. The same evaluation test as in the example was performed using these, and the results were as shown in Table 1.

Both the examples and comparative examples had good moldability and high elasticity, and did not cause any problems at resonance points and resonance peaks. However, the resin composition of Comparative Example 1 was anisotropic. Due to the excessively high performance, the optical axis shift occurred along with the temperature rise of the CD pickup component itself, resulting in malfunction. In addition, some of the resin compositions of Comparative Example 2 took a long time to adjust the optical axis during operation, or could not adjust the optical axis. On the other hand, in the case of using the resin composition of the present invention, the operation was performed without any trouble for a long time.

[0019]

[Table 1]

[0020]

The actuator of the optical pickup using the resin composition of the present invention has excellent resonance frequency characteristics and excellent dimensionality without directivity, so that it can sufficiently withstand long-time use. Can be.

Claims (1)

[Claims] 1. A method in which carbon fibers having a fiber diameter of 20 μm or less
0 to 40% by weight, an average fiber diameter of 0.5 to 1.0 μm, and an average fiber length of 10 to 30 μm
A polyarylene sulfide resin composition for an optical activator, characterized in that the composition comprises from 70 to 70% by weight.