JPH0366756A - Resin composition for part of optical pick-up and optical pick-up part - Google Patents

Abstract

PURPOSE:To provide a composition having a specific density, containing a polyarylene sulfide resin, a fibrous filler and a powdery filler having a specific density, and capable of providing a part of optical pick-up generating little resonance and having excellent dimensional stability. CONSTITUTION:The objective resin composition for an optical pick-up part has a density of >=2g/cm<3> (preferably >=2.1g/cm<3>) and contains (A) 20-40wt.% (preferably 25-38wt.%) of a polyarylene sulfide resin. preferably polyphenylene sulfide containing >=80mol% of the recurring unit of formula, (B) 10-40wt.% (preferably 13-35wt.%) of a fibrous filler, preferably glass fiber having a length of 2-5mm and fiber diameter of 5-20mum and (C) 20-70wt.% (preferably 30-60wt.%) of a powdery filler having a specific gravity of >=3.5, preferably precipitated barium sulfate having particle diameter of 0.2-20mum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a resin composition for parts of an optical pickup and to parts of an optical pickup.

[Prior Art] Optical pickups are installed in optical disc devices such as video disc players, digital audio players, and optical disc file devices. This optical pickup is a device that irradiates a disk surface with semiconductor laser light through a reflecting mirror and an objective lens, and reads the reflected light with a light receiving element through a half mirror. Therefore, the optical pickup must not cause optical axis misalignment due to dimensional changes or distortions of the main body and optical path system.

For example, it is necessary to suppress the relative positional accuracy of each component such as a reflecting mirror and a light receiving element to within a few gm.

Traditionally, aluminum guid cast products and threads have been used as materials that meet these requirements, but they have problems with weight and weight.
, machining accuracy on the order of m is not available, so parts that require precision must be post-processed by cutting, and tool management and inspection are time-consuming and costly.For these reasons, high-performance engineering plastics have recently been developed. has come into practical use. For example, polyetherimide (PH1)
, liquid crystal polymer (LCP), polyphenyl/nsulfide (PPS), etc. have been tried.

・Required performance is strict in terms of accuracy, heat resistance, rigidity, low coefficient of thermal expansion, etc. 2 Research and development is being carried out, such as devising reinforcing agents and fillers, or devising the arrangement with resins with the same value as epoxy resin. (For example, Japanese Patent Application Laid-Open No. 52-723275
No., JP-A No. 63-288433).

Particularly recently, in order to meet the demand for lighter optical pickups, efforts have been made to make molded parts such as the main body and lens holder thinner.

The characteristics required of the materials used in these materials are that although they are thin-walled molded products, they have a high resonance frequency, excellent t8 dynamic damping properties, and good moldability without flashes or sink marks. The resonant frequency of the lens holder etc. needs to be higher than the servo band of the optical pickup ~3k)lz. In order to increase the resonance frequency, it is necessary to use a material with a high bending modulus.

The above-mentioned LCP is a material that meets these requirements, but when this resin is molded into a thin wall, the orientation progresses, and the elastic modulus and linear expansion coefficient become highly anisotropic in the direction of flow during molding and in the direction perpendicular thereto. Economic problems also remain. Glass fiber again! Some attempts have been made to increase the flexural modulus by mixing I(GF) with PPS, but this is not sufficient as the fluidity during molding is reduced and the amount added is limited.

An object of the present invention is to solve the above problems. That is, the object of this invention is to have high elastic modulus and high specific gravity,
The objective is to provide a resin composition that has excellent fluidity and good moldability, and is ideal for parts for optical pick amplifiers. Our goal is to provide parts for optical pickups.

[Means for Solving the Problems] This invention for solving the above-mentioned problems includes adding 40% by weight of fibrous filler l to polyarylene sulfide resin 20.
It contains 20-70% by weight of a powder filler with a density of 0~40% by weight and a ratio of 3.5 or more -1m, and a density of 7!
, Og/c- or more, preferably 2.11/c- or more, a resin composition for optical big top parts, wherein the powdery filler is! The present invention is preferably made of barium acid, and is a part of an optical pickup characterized in that it is molded from the resin composition.

The present invention will be explained in detail below.

There are no particular limitations on the poly7-arylene sulfur f-dos resin in this invention, but polyquenylene sulfide is preferred.

As polyphenylene sulfide, for example,
4-27871 and 45-3368, and the reaction of an aromatic compound with an alkali sulfide as disclosed in Japanese Patent Publication No. 45-27255. Acid-catalyzed condensation reaction of sulfur chloride, or U.S. Pat. No. 3.2
A polymer synthesized by a condensation reaction of thiophenols in the presence of an alkali catalyst or a copper salt, etc. as shown in Japanese Patent No. 74,185, and is composed of repeating units represented by the general formula. Those containing 80 mol% or more of units can be suitably used. The copolymerization component 1 includes a meta bond, an ether bond, a sulfone bond, a biphenyl bond, a substituted phenyl sulfide bond (where R is a substituent such as an alkyl group, a nitro group, a phenyl group, an alkoxy group), a trifunctional phenyl sulfide bond, etc. It can also be used in an amount of less than 20 mol % within a range that does not adversely affect the crystallinity of the polymer.

These resins are nearly white immediately after the above-mentioned condensation reaction, and some have low molecular weight and low viscosity, but they can be oxidized, branched, or cross-linked by heating below their melting point in air. It is used by increasing the molecular weight by mono-branching or crosslinking with a branching agent in the condensation reaction step, and changing the melt viscosity to be suitable for injection molding. In some cases, a linear resin having a sufficiently high molecular weight and high viscosity is obtained in the condensation reaction step, and this can also be used. Polyphenylene sulfide is commercially available in various grades, so it is easy to obtain, and it is suitable both economically and in terms of performance, and these can be used alone or in combination.

Next, the fibrous fillers used in this invention include glass fibers, carbon fibers, graphite fibers, wollastonite, various whiskers such as potassium titanate whiskers, silicon carbide whiskers, sapphire whiskers, silicon carbide whiskers, and metals. Fibers, ceramic fibers, or metal wires such as copper wires, steel wires, stainless steel wires, etc. can also be applied. Also, carbon! Heat-resistant inorganic composite fibers such as boron or silicon carbide m fibers, aromatic aramid mta etc.
It is also possible to use heat-resistant organic fibers such as .

Among these, glass fiber is a suitable fibrous filler in terms of economy and performance.

As the glass fiber, any of alkali-containing glass fiber, low-alkali glass fiber, alkali-free glass fiber, etc. can be used.

The length of the glass fiber in the polyarylene sulfide resin composition is preferably 0.1-1 mm, particularly preferably 0.2-0.5 mm. Glass fibers often break when kneaded with resin, and the length of glass fibers used for kneading is usually preferably 2 to 5 cm. The m#1 diameter of glass fibers is usually 5 cm. ~2
0 uLm, especially preferably 7 to 15 μm, am diameter 20
If it exceeds pm, crosstalk with the resin becomes difficult and the performance of the composition is also unfavorable.

The form of this glass fiber is not particularly limited, and may be, for example, roving, chopped strand, milled fiber, or the like.

In addition, when using glass fibers, it is also good to subject the glass fibers to surface treatment such as poran treatment, silane treatment, titanate treatment, and epoxy treatment.

The powder filler used in the present invention needs to have a specific gravity of 3.5 or more. If the specific gravity is 3.5 or less, a molded article with a high elastic modulus and a high resonance frequency band, which is the object of the present invention, cannot be obtained.

Examples of the powdery filler having a specific gravity of 3.5 or more include precipitated barium sulfate, titanium oxide, zinc oxide, lead oxide, alumina, iron oxide, molybdenum disulfide, etc. Particularly suitable is precipitated barium sulfate.

This is because the use of precipitated barium sulfate has the advantages of good properties during molding, surface gloss of the molded product, and high dimensional accuracy.

It is also important that the particle size of precipitated barium sulfate is within the range of 0.22-20p.If the particle size is smaller than 0.2jLm, the effect will be small;
When the size becomes larger, dispersion in the resin composition, surface smoothness, glossiness, etc. of the molded product deteriorate.

In this invention, the content ratio of each component in the resin composition for parts of an optical pickup is 20 to 40% by amount of polyarylene sulfide resin, especially 2% by weight.
5 to 38% by weight, the fibrous filler is 10 to 40% by weight, especially 12 to 35% by weight, and the powdery filler with a specific gravity of 3.5 or more is 20 to 701%, especially 30 to 60%. Heavy stitching%
It is. When the content ratio of each component is outside the range,
It becomes difficult to form the resin composition into an optical bead or cup, or the desired performance cannot be obtained.

Also, it is important to note that the content ratio of each component is within the above range, and the weight ratio is 2.0 g/cm3 or more, preferably 2.1 g. /cm3 or more.

If the density of the molded product is less than 2.0 g/em3, the resonant frequency will fall between 1 and 3 KHz and will be affected by the servo mechanism, making it impossible to achieve the object of the present invention.

The resin composition for parts of an optical big 7 according to the present invention includes the polyarylene sulfide, a fibrous filler, and a powdery filler having a specific gravity of 3.5 or more, and a density of 2.5 or more.
0 g/am3 or more, preferably 2.1 g/am3 or more J
yJ can be manufactured by selecting and mixing or cross-connecting each of the above-mentioned components so that:

The mixing and crossing can be performed according to known methods. For example, mixing may be performed using a mixer such as a ribbon blender, tumbler mixer, or Henschel mixer, followed by melt mixing, or mixing using a panburi mixer or screw t11. Mixing can also be carried out simultaneously using a machine or the like.

A pellet is formed by kneading, and the pellet is used to form a molded article using various molding methods, usually injection molding.

Here, the resin composition for the closure of an optical pickup of the present invention has a high bending elastic modulus and bending strength,
It has good formability as it does not produce any cracks or sink marks even when formed into thin-walled and shaped products.It has low resonance, has excellent vibration lIf and damping properties, and is resistant to changes in temperature and humidity. Since it is an excellent resin composition that does not change in size, it is best to mold it into parts of optical pickups.

Examples of the parts of the optical pickup of the present invention include various parts constituting the optical pickup, such as an optical pickup body, a lens holder, and an actuator body. The raw materials used are listed below.

■Polyphelene sulfite F4 & 4 resin (pps) melt viscosity 1500 poise (320℃, shear rate 1000 seconds)
: Thermal crosslinking type ■ Precipitated barium sulfate, (true specific gravity 4.499, particle size 2.5-4.5 m)] ■ Calcium carbonate, (true north t2.7) ] ■ Glass fiber, Chi! l-/butostrand (ia miscellaneous diameter 1
(Examples 1 to 3) The PPS and barium ADft acid were mixed using a Henschel mixer at the mixing ratio shown in the table, and then mixed using a two-wheel extruder (manufactured by Toshiba Machinery Co., Ltd., TEM35). Glass fibers were added by side feed, and the mixture was melt-extruded at 330°C to form pellets.

The ratio of glass fibers is shown in the table.

Using an injection molding machine with a mold clamping pressure of 30 mm, this pellet was used to measure the resonance of a test piece for flexural modulus measurement in accordance with ASTM D-790 and a rectangular shape of 40X IOX O, 5 (thickness) (■). A test piece was prepared.

Bending test in accordance with ASTM D790, AST
Specific gravity was measured in accordance with MD792. The results are shown in the table.

Further, using these pellets, seven cutuators for an optical pickup were molded by injection molding.

(Comparative Examples 1 to 4) Comparative Example 1 was carried out in the same manner as in Example 1 except that calcium carbonate was used as the powdery filler. Comparative Examples 2 to 4 were carried out in the same manner as in Example 1 except that the amounts shown in the table were blended.

The results are shown in the table.

Comparative Example 1 has a resonance point at 1 to 3k)Iz. Comparative Example 2 is 8!, which has less PPS than filler and is stable in the extruder.
I couldn't do 1. Comparative Example 3 had low bending strength, was extremely brittle, and had low weld strength, and Comparative Example 4 had extremely poor fluidity, and the composition did not fill into a 0.5 mm thick mold, resulting in poor moldability.

(Hereinafter, blank spaces) C Effect of the Invention 1 As explained above, the resin composition for parts of an optical pickup of the present invention has excellent resin fluidity during molding, and the molded product has no directionality. .

In addition, there are no cracks or sink marks, and it can be molded into molded products with high dimensional accuracy.Also, there is no dimensional change, so when this resin set is molded into optical pickup parts, optical misalignment may occur. It is possible to construct an optical pickup with low vibration and low resonance, and it can be manufactured with high productivity and at low cost.

Claims (3)

[Claims] (1) 20 to 40% by weight of polyarylene sulfide resin, 10 to 40% by weight of fibrous filler, and a specific gravity of 3.
A resin composition for parts of an optical pickup, characterized in that it contains 20 to 70% by weight of a powdery filler of 5 or more and has a density of 2.0 g/cm^3 or more. (2) The resin composition for parts of an optical pickup according to claim 1, wherein the powdery filler is barium sulfate. (3) A part for an optical pickup characterized by being molded from the resin composition.