JP5479055B2 - Thermally conductive resin composition and molded article using the same - Google Patents

Description

  The present invention relates to a thermally conductive resin composition and a molded article using the same, and more specifically, a thermally conductive resin composition that provides a molded article having excellent moldability and excellent thermal conductivity and mechanical properties. And a molded article using the same.

  As the integration density of semiconductor elements such as LSIs increases, the operation speed increases, and the electronic components are mounted with high density, heat dissipation measures for electronic components serving as heat sources have become a major problem. For example, metal and ceramics with high thermal conductivity have been conventionally used for housings of electronic components, but in recent years, resin-based materials that have a large degree of freedom in shape selection and are easy to reduce in size and weight have been used. .

  Conventionally, resin-based materials are usually used for the purpose of dispersing a thermally conductive filler such as carbon fiber (CF), graphite powder, metal powder or ceramic powder in a matrix resin, and simultaneously improving mechanical properties. A resin composition containing glass fiber is used (for example, Patent Document 1).

JP 2005-89652 A

  However, in a resin composition in which glass fibers are blended for the purpose of improving mechanical properties, anisotropy of the linear expansion coefficient accompanying the orientation of the glass fibers during molding appears. That is, there is a problem that the linear expansion coefficient is different between the flow direction and the direction perpendicular to the flow direction, and the molded product obtained by molding is warped and deformed, and cannot be applied to electronic components that require high accuracy. It was.

  Accordingly, the present inventors have solved the above-mentioned problems, and have a heat conductive resin composition that gives a molded product having excellent heat processability and excellent mechanical properties while being excellent in molding processability, and molding using the same. The purpose was to provide goods.

In order to solve the above problems, the thermally conductive resin composition of the present invention comprises at least a liquid crystal polymer of 40 vol% or more, a thermal conductive filler of 10 to 40 vol % having a flat shape and an average aspect ratio of 2 or less, and glass. and a fiber 5 to 20 vol%, the volume ratio of the thermally conductive filler and the glass fibers are thermally conductive filler / glass fiber = 2 / 1-8 / 1, thermally conductive injection molding for the optical pickup base It is a resin composition.

  In the resin composition of the present invention, the thermally conductive filler is preferably one or more selected from the group consisting of scaly graphite, copper flakes, aluminum flakes, silver flakes, and boron nitride.

The molded article of the present invention is an optical pickup base formed by molding the above-described thermally conductive resin composition of the present invention.

  The molded article of the present invention preferably has a thermal conductivity of 2 W / (m · k) or more and a linear expansion coefficient anisotropy (TD-MD) of ± 10 ppm / ° C. or less.

  Here, the anisotropy of the linear expansion coefficient (TD-MD) means that when the linear expansion coefficient in the flow direction of the molded product is MD and the linear expansion coefficient in the direction orthogonal to the flow direction is TD, (TD- MD) is defined as an index representing the anisotropy of a molded article.

  According to the present invention, together with the glass fiber, the heat conductive filler that is flat and has an average aspect ratio of 2 or less, the volume ratio of the heat conductive filler to the glass fiber is the heat conductive filler / glass fiber = 2/1 to 1. By using the resin composition blended so as to be 10/1, it becomes possible to suppress the anisotropy of the linear expansion coefficient of the molded product, and provide a thermally conductive resin composition excellent in molding processability. It becomes possible. In addition, it is possible to provide a molded product having excellent mechanical properties and thermal conductivity. In addition, the molded product has excellent dimensional stability because thermal deformation is suppressed by the influence of changes in environmental temperature, heat generation of peripheral components, and the like.

It is an example of the scanning electron micrograph which shows the shape of the scaly graphite used for the heat conductive resin composition of this invention. It is a schematic diagram which shows an example of the structure of the optical disk drive device using the optical pick-up base produced using the heat conductive resin composition of this invention. It is a model perspective view which shows an example of the structure of the optical pick-up base produced using the heat conductive resin composition of this invention.

Embodiments of the present invention will be described below.
The thermoplastic resin used in the present invention is not particularly limited as long as it is a heat resistant resin having a deflection temperature under load defined by JIS K 7191 of 100 ° C. or higher. Specifically, liquid crystal polymer (LCP), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyimide, polyetherimide, polyacetal, polyethersulfone, polysulfone, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene Examples thereof include oxides, polyphthalamides, and polyamides, and liquid crystal polymers (LCP) are preferable. Liquid crystal polymer has high heat resistance, high fluidity, good thin-wall filling, and excellent shock absorption, etc., housing of electronic parts, heat sinks and fans for releasing heat from electronic parts to the outside, etc. This is because it is suitable for heat dissipation measures.

  Here, the liquid crystal polymer is a polymer having a property of forming a melt phase having optical anisotropy. A melt phase having optical anisotropy can be confirmed by a polarization inspection method using a polarizing microscope using a crossed polarizer. Although the kind of liquid crystal polymer is not particularly limited, aromatic polyester or aromatic polyester amide is preferable.

  The volume content of the thermoplastic resin is 40 vol% or more, preferably 40 to 85 vol% with respect to the resin composition in order to ensure moldability.

The thermally conductive filler used in the present invention is flat and has an average aspect ratio of 2 or less, preferably 1.1 to 1.9. This is because if the average aspect ratio of the thermally conductive filler is larger than 2, the anisotropy of the linear expansion coefficient of the molded product increases, and warpage and thermal deformation occur. Compared with bulky particles such as spherical particles, the thermally conductive filler used in the present invention can be filled in the molded body at a higher concentration, and can reduce the anisotropy of the linear expansion coefficient of the molded product. .
Here, the flat heat conductive filler in the present invention is a heat conductive filler having a shape having a major axis and a minor axis, which is not a perfect sphere, for example, a scale shape, a part of a lump shape. Shape etc. are included. The aspect ratio is defined by the major axis length / minor axis length. The average aspect ratio is determined by observing the thermally conductive filler with a scanning electron microscope, measuring the major axis length and minor axis length of each flat filler in the field of view, and averaging the aspect ratios of 50 fillers. Average aspect ratio. Moreover, it is preferable that the major axis length of a heat conductive filler exists in the range of 20-100 micrometers, and a minor axis length exists in the range of 10-90 micrometers.

  The thermal conductivity of the thermally conductive filler used in the present invention is 100 W / (m · k) or more, preferably 200 W / (m · k) or more.

  Specific examples of the thermally conductive filler used in the present invention include scaly graphite, copper flakes, aluminum flakes, silver flakes, and boron nitride. These can be used alone or in combination of two or more. Preferably, at least one of scaly graphite, copper flakes or aluminum flakes, more preferably scaly graphite.

  FIG. 1 is a scanning electron micrograph showing an example of scaly graphite used in the present invention. The average aspect ratio of the scaly graphite is about 1.6.

  The volume content of the heat conductive filler is 10 vol% or more, preferably 10 to 40 vol% with respect to the resin composition. This is because if it is less than 10 vol%, the thermal conductivity decreases, and if it exceeds 40 vol%, the molding processability of the resin composition decreases and the mechanical strength also decreases.

  Thermally conductive fillers are processed and sieved using a jet mill, a Henschel mixer, or a tumbler so that the average aspect ratio is 2 or less, as well as those manufactured to have an average aspect ratio of 2 or less. Things can also be used.

  Although the glass fiber used for this invention will not be specifically limited if it is normally used as a filler for thermoplastic resins, a cut length is 3-6 mm, a fiber diameter is 10-13 micrometers, average aspect-ratio (cut length) (Fiber diameter) is preferably 230 to 600.

  The volume content of the glass fiber is 5 vol% or more, preferably 5 to 20 vol% with respect to the resin composition in order to ensure mechanical strength.

  In the present invention, the volume ratio of the thermally conductive filler and glass fiber is thermally conductive filler / glass fiber = 2/1 to 10/1, preferably 5/2 to 10/1. When the volume ratio is less than 2/1, the heat conductive filler is small and the effect of suppressing the anisotropy of the linear expansion coefficient is not sufficient. When the volume ratio is greater than 10/1, the resin has a large amount of heat conductive filler. This is because the moldability of the composition is significantly reduced.

  In addition, the resin composition of the present invention is mixed with a predetermined amount of raw material powder and kneaded and molded into a desired shape using an injection molding machine, a compression molding machine, an extrusion molding machine or the like having a predetermined mold. be able to. In particular, an injection molding method with a short molding cycle and excellent productivity is preferable.

  The molded article of the present invention has a thermal conductivity of 2 W / (m · k) or more, preferably 6 W / (m · k) or more, and a difference in linear expansion coefficient (TD-MD) of 15 ppm / ° C. or less. Preferably it is 10 ppm / ° C. or less.

  Examples of the molded article of the present invention include a housing for an electronic component, a heat sink and a fan for releasing heat from the electronic component to the outside, and the like. Specific examples include an optical pickup base that is a heat radiating body for housing a semiconductor laser in an optical pickup, a package material or heat sink material for a semiconductor element, a casing for a fan motor, a housing for a motor core, a case for a secondary battery, and And the case of a personal computer or a mobile phone.

  FIG. 2 is a schematic diagram showing an example of the structure of an optical disc driving apparatus using the optical pickup base of the present invention. The optical disk drive device includes a chassis 10, a main shaft 11 and a sub shaft 12 attached to the chassis 10, and an optical pickup 13 slidably attached to the main shaft 11 and the sub shaft 12. The optical pickup 13 moves in the radial direction of the optical disc D along the main shaft 11 and the sub shaft 12 by the driving force of a driving motor (not shown) controlled by a control system (not shown), and records and reproduces information. Do.

  Here, the optical pickup 13 comprises an optical pickup base 14 of the present embodiment shown in FIG. 3 and a laser diode (not shown) attached via a laser diode holder (not shown). The optical pickup base 14 has a base 14a and two main bearings 14b and 14b which are arranged at a predetermined interval at one end of the base 14a and are integrally formed with the base 14a. And a sub-bearing 14c molded integrally therewith. The main bearings 14b and 14b and the auxiliary bearing 14c are loosely inserted into the main shaft 11 and the auxiliary shaft 12, respectively. The laser diode holder is attached to the laser diode holder attachment portion 14d. Light emitted from the laser diode is emitted toward the optical disk D by an optical element (not shown).

  The optical pickup base of the present invention is lighter than the conventional metal optical pickup base, and can not only increase the access speed to the optical disc, but also has a high thermal conductivity of 2 W / (m · k) or more. Therefore, it has a heat dissipation property that can release heat generated from the laser diode.

(Sample preparation)
The thermoplastic resin is a liquid crystal polymer (Zenite 7000, manufactured by DuPont), and the thermally conductive filler is a scaly graphite (average aspect ratio: about 1.6), copper flakes (average aspect ratio: about 1.7), or aluminum. Flakes (average aspect ratio: about 1.9) and glass fibers having an average diameter of 13 μm and an average fiber length of 3 mm were used.

  The raw material mixed powder blended in the composition shown in Table 1 was put into a kneading extruder, kneaded at a temperature of 310 to 340 ° C., and extruded to produce a pellet for molding. This pellet for molding was molded by hot pressing and cut to obtain a cylindrical molded sample for evaluation having a diameter of 10 mm and a thickness of 1.5 mm. Further, as a comparison, a heat conductive filler using spherical graphite powder (average aspect ratio: about 1.1) (sample 9) and a carbon fiber (average aspect ratio: about 600) (sample) 10) and a combination of two types of thermally conductive fillers (sample 11) were prepared in the same manner as described above to produce evaluation molded samples.

(Thermal conductivity measurement)
Thermal conductivity was calculated using the Xe flash method. The thermal diffusivity is measured using a Xe flash analyzer (model LFA447) manufactured by NETZSCH, the specific heat is measured using a heat flux differential scanning heat flow meter (model DSC-50) manufactured by Shimadzu Corporation, and the density is substituted in water. The thermal conductivity was calculated by measuring by the method and multiplying them. Table 2 shows the measurement results of thermal conductivity.

(Measurement of linear expansion coefficient)
The linear expansion coefficient (MD) in the flow direction of the molded product and the linear expansion coefficient (TD) in the direction orthogonal to the flow direction are obtained by using ISO 3167 (JIS K7139) from a molding pellet obtained in the same manner as described above from an injection molding machine. A multi-purpose test piece conforming to) was molded and cut into a flow direction and a direction perpendicular to the flow direction by cutting to obtain a measurement sample. Each sample was measured for the amount of change in sample length with respect to temperature change using a thermomechanical analyzer (TMA, model CN8098F1) manufactured by Rigaku Corporation in accordance with JIS K7197. The measured value was expressed as 10 ⁻⁶ / ° C. = ppm / ° C., and the difference (TD-MD) was defined as the anisotropy of the linear expansion coefficient.

(Bending strength measurement)
The bending strength was determined by carrying out the test according to ISO 178 (JIS K7171) using a large-scale universal testing machine (Tensilon, model UTM-5T) manufactured by Toyo Baldwin Co., Ltd. As the test piece, a multipurpose test piece based on ISO 3167 (JIS K7139) was used. The results are shown in Table 2.

  As shown in Table 2, Samples 3, 4, 5, 6, 8, and 11 produced using the resin composition of the present invention had a thermal conductivity of 2 W / (m · k) or more and a linear expansion coefficient. Anisotropy (TD-MD) of 15 ppm / ° C. or less. Also, the bending strength was sufficient for practical use. On the other hand, when no thermally conductive filler is added (sample 1), or when spherical particles or a filler having an average aspect ratio greater than 2 is used as the thermally conductive filler (samples 9 and 10), the linear expansion coefficient Anisotropy (TD-MD) of 20 or more.

(Production of optical pickup base)
The raw material mixed powder blended in the composition of Sample 4 in Table 1 was put into a kneading extruder, kneaded at a temperature of 310 to 340 ° C. and extruded to produce a molding pellet. The molding pellets were put into an injection molding machine and injection molded at a temperature of 310 to 340 ° C. to produce an optical pickup base having the shape shown in FIG.
This optical pickup base has a thermal conductivity of 2 W / (m · k) or more and a linear expansion coefficient anisotropy (TD-MD) of 15 ppm / ° C. or less. It has sufficient heat dissipation that can escape the heat generation.

  As described above, according to the present invention, it is possible to provide a thermally conductive resin composition excellent in molding processability capable of suppressing the anisotropy of the linear expansion coefficient of a molded product. Thereby, it is possible to provide a molded article having excellent mechanical properties and thermal conductivity. For example, when used in an optical pickup base, it has sufficient heat dissipation to maintain the light emission characteristics of a light emitting element such as a laser. Furthermore, it is lighter than a metal one and can move at high speed, and the access speed to the optical disk can be greatly improved.

DESCRIPTION OF SYMBOLS 10 Chassis 11 Main axis | shaft 12 Sub axis | shaft 13 Optical pick-up 14 Optical pick-up base 14a Base 14b Main bearing 14c Main bearing 14d Laser diode holder attaching part D Optical disk

Claims (4)

At least, a liquid crystal polymer 40 vol% or more, and 10 to 40 vol% thermally conductive filler average aspect ratio of 2 or less flat, and a 5 to 20 vol% of glass fibers, the thermally conductive filler and the glass fibers volume ratio of the thermally conductive filler / glass fiber = 2 / 1-8 / 1, for injection molding a thermally conductive resin composition for the optical pick-up base.   The resin composition according to claim 1, wherein the thermally conductive filler is at least one selected from the group consisting of scaly graphite, copper flakes, aluminum flakes, silver flakes, and boron nitride. Claims 1 to 2 of the molded article is an optical pickup base made of a thermally conductive resin composition of any one. The molded article according to claim 3 , wherein the thermal conductivity is 2 W / (m · k) or more and the anisotropy of linear expansion coefficient (TD-MD) is ± 10 ppm / ° C or less.