JP2001179791A - Method and apparatus for manufacturing conductive resin molded object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a conductive resin molded object markedly reduced in its surface in the vicinity of a gate. SOLUTION: In a method for manufacturing a conductive resin molded object by injecting a conductive resin in an injection mold, the inner surface of the injection mold is heated to temperature higher than the peripheral temperature in the vicinity of a gate and the conductive resin is injected to mold a tray main body 1 as the carrier of a magnetic head 4. In this case, the regions (a), (b), (c) in the vicinity of the gate 8 of the inner surface of the mold is heated to temperature higher than the peripheral temperature by 10 deg.C or higher by high frequency induction heating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a conductive resin molded article. More specifically, the present invention relates to a method and an apparatus for manufacturing a conductive resin molded article suitable for manufacturing trays for handling electronic components such as semiconductor devices and elements that are vulnerable to electric shock such as static electricity.

[0002]

2. Description of the Related Art With the spread of personal computers and the like, mass production of semiconductor devices, semiconductor elements, magnetic elements, and the like has been performed. These devices and devices are becoming finer and finer devices and devices in order to respond to the miniaturization, which is a development direction of personal computers, and the sensitivity thereof is becoming very sensitive. In particular, many are very vulnerable to electric shock such as static electricity.

Conventional trays for handling such devices and elements are manufactured by molding a resin composition comprising a polycarbonate resin and a conductive filler such as carbon black.

[0004] By the way, recently manufactured devices and elements which are very sensitive to electric shock have a great risk of being damaged even by a weak noise current. For this reason, electrostatic discharge due to the potential difference between the element and the like and the tray, and contact current generated by contact between the element and the like and the tray are serious problems.

[0005]

A molded article produced by injection molding a conductive resin containing a conductive filler such as carbon black as a conductive filler has a surface resistance value near the gate higher than that of other parts. It was found that

SUMMARY OF THE INVENTION An object of the present invention is to solve such a problem and to provide a method and an apparatus for manufacturing a conductive resin molded article having a surface resistance near the gate equal to that of other surfaces. I do.

[0007]

According to the present invention, there is provided a method for producing a conductive resin molded article, wherein the conductive resin is injected into an injection mold. Injection is performed after heating the vicinity of the gate on the inner surface of the mold to a temperature higher than the surroundings.

[0008] The apparatus for producing a conductive resin molded article of the present invention comprises:
It comprises an injection mold and heating means for heating only the vicinity of the gate on the inner surface of the mold.

According to the method and apparatus of the present invention, it has been recognized that the surface resistance becomes equal to that of other surfaces even in the vicinity of the gate.

This is probably because if the temperature of the inner surface of the mold near the gate is increased, the orientation or dispersion of the conductive filler inside the resin near the gate is canceled, and the resistance value of the conductive resin decreases. It is likely.

That is, when the resin is injected into the mold, the flow velocity of the resin is large near the gate, so that fibrous filler is oriented in the resin flow direction, and carbon black is finely dispersed in the case of carbon black. However, this increases the resistance value of the resin. During this injection molding, if the vicinity of the gate is heated in the inner surface of the mold, the heat increases the temperature of the resin near the gate, thereby lowering the viscosity of the resin. Or the carbon black is re-agglomerated and the fine dispersion is eliminated, and the surface resistance of the resin becomes as low as the other surface even near the gate.

It is well known that a mold of an injection molding apparatus is heated, thereby improving the surface transferability and surface smoothness of a molded product. However, the conventional mold heating heats the entire mold, and does not heat only the vicinity of the gate.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention can be applied to the production of molded articles of various kinds of conductive resins, but includes assembling tools, parts for picking up electronic parts, petri dishes, head bearings, wafers, hard disks, IC chips, liquid crystal filters, etc. A wide range of applications are conceivable, such as transfer trays and cases, storage, antistatic applications, and electromagnetic wave shielding applications. In particular, it is very suitable to be applied to the production of a molded article for handling electronic components. PC (polycarbonate) is preferable as the conductive resin constituting such a molded article for handling electronic parts, but polystyrene, polyphenylene ether, A
BS, polyamide, polyethylene, polypropylene, polyacetal, polyester, polyvinyl chloride, polymethyl methacrylate, polyetherimide, and the like can also be used. A plurality of these resins may be blended.

As the conductive filler, carbon black (including acetylene black) is preferable. Carbon black is thermal black, furnace black,
Any of acetylene black may be used. Note that carbon black having a dibutyl phthalate (DBP) oil absorption of 100 ml / 100 g or more is particularly preferable. DBP oil absorption is 1
If the carbon black is less than 00 ml / 100 g, the surface resistance may not be sufficiently reduced.

The conductive resin may contain other fillers, solid lubricants, plasticizers, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, neutralizers, lubricants, compatibilizers, Various additives such as a fogging agent, an anti-blocking agent, a slip agent, a dispersant, a colorant, a bactericide, and a fluorescent whitening agent can be blended.

The injection mold is provided with a heating means for heating the inner surface of the mold near the gate. As the heating means, an induction heating device is preferable, but a semiconductor heat pump element, a heating element such as an electric heater provided near the gate, a heating element such as an electric heater close to or in contact with the vicinity of the gate, or the like is used. You may. However, an induction heating device that can rapidly heat the vicinity of the gate, but also quickly reduces the temperature of the mold near the gate after injection is preferable. As the induction heating device, it is preferable to use an induction heating device that is separate from the mold and that can move the induction heating coil close to the inner surface of the mold near the gate.

In order to produce a conductive resin molded product, for example, a resin such as polycarbonate is mixed in advance with a conductive filler, and then a Banbury mixer, a roll, a Brabender, a single-screw kneading extruder, a twin-screw kneading extruder is used. The resin composition is manufactured by melt-kneading with a kneader or the like, and then injection molding.

As the injection molding method, in addition to a general injection molding method, integral molding with metal parts and other parts by insert injection molding method, two-color injection molding method, core back injection molding method, sandwich injection molding And various molding methods such as an injection press molding method.

When the present invention is applied to a molded polycarbonate article for handling electronic parts, the surface resistance of the molded article measured by using a two-probe is 10 ³ to 10 ¹² Ω, particularly 10 ⁴ to 10 ¹¹ Ω, particularly 10 10 Ω. It is preferably ⁵ to 10 ¹⁰ Ω. If the surface resistance is within this range,
Not only is it excellent in antistatic properties, but also because it can prevent excessive contact current in contact with the polycarbonate molded body,
Less damage to electronic components.

In general, the surface resistance value considers the current wrap around in the thickness and width directions of the measurement sample. However, in the case of a complicated shape such as a molded body for handling electronic parts, the shape factor is taken into consideration. Is extremely difficult. On the other hand, in practical use, the apparent resistance value including the shape is important, and in the present invention, this is used as the surface resistance value.

[0021]

EXAMPLES Examples and comparative examples will be described below.

(Production method of conductive resin A) 82 parts by weight of polycarbonate (Iupilon S2000F, manufactured by Mitsubishi Engineering-Plastics Co., Ltd.) and carbon black (Denka Black, manufactured by Denki Kagaku KK, DBP oil absorption 190)
18 parts by weight (ml / 100 g) were extruded at a discharge rate of 30 Kg / h using a twin-screw kneader (PCM45, screw length / screw diameter = 32, manufactured by Ikegai Iron Works Co., Ltd.).

(Method of Forming Molded Body for Handling Electronic Parts)
A magnetic head tray for a hard disk drive shown in FIGS. 1 and 2 was injection molded as a molded body for handling electronic components. The shape and dimensions of this tray are as shown in FIG. 1 (perspective view), FIG. 2 (a) (plan view), and (b) (cross-sectional view along line BB in FIG. 2 (a)). In the figure, 1 is a tray main body, 2 is a positioning rib, 3 is a positioning boss, and 4 is a magnetic head. The injection / injection gate is located at the location indicated by reference numeral 8. The hatched areas a, b, and c in the figure are resistance measurement areas near the gate.

As a method for making a temperature difference between the vicinity of the mold gate and the surrounding temperature of the mold, that is, a portion controlled by a mold temperature controller, a high-frequency induction mold heating device (BSM manufactured by Asahi Engineering Co., Ltd .; Device (60KW type). The size of the heating coil is 60 x 152m
m, and one heating coil was heated to face three regions a, b, and c in FIG. The temperature difference was controlled by the heating time of the heating device. The set temperature of the mold temperature controller was 60 ° C.

The injection molding machine used had a mold clamping force of 220 tons (manufactured by Nissei Plastic Industries Co., Ltd.).

(Method of Measuring Surface Resistance) Measurement was carried out using a two-probe probe at the tip of the probe: 2 mmφ, the distance between the centers of the probes: 20 mm, and the applied voltage between the following probes.

When the surface resistance value is 10 ⁴ Ω or more and less than 10 ⁹ : 10 V When the surface resistance value is 10 ⁹ Ω or more: 100 V However, when measuring the surface resistance value of 10 ⁸ Ω or more, the tip of the probe is set to 5 mmφ. Furthermore, thickness 2mmt, diameter 15
The conductive silicon rubber having a diameter of 100 mm or less was assembled, and the measurement was performed so that the adhesion to the sample surface was stabilized.

As a measuring instrument, Hiresta AP manufactured by Dia Instruments was used.

Example 1 Using a conductive resin A, the vicinity of the gate was heated by a high-frequency induction mold heating device for 7 seconds and then molded. At this time, the mold surface (inner surface) temperature near the gate was 158 ° C., and the temperature difference from the periphery was 98 ° C. The filling time was 1.5 seconds. Table 1 shows the surface resistance value of each part.

Example 2 The same operation as in Example 1 was performed except that the heating time of the high-frequency induction mold heating device was 10 seconds. The mold surface temperature near the gate is 188 ° C.,
The temperature difference from the surroundings is 128 ° C., and the filling time is 1.4.
Seconds. Table 1 shows the surface resistance value of each part.

Comparative Example 1 A conductive resin A was molded at a mold temperature of 60 ° C. without using a high-frequency induction mold heating apparatus. The filling time was 1.3 seconds. Table 1 shows the surface resistance value of each part.

[0032]

[Table 1]

[0033]

As is clear from the above Examples and Comparative Examples, according to the present invention, it is possible to manufacture a conductive resin molded article whose surface has a resistance almost equal to that of its surroundings in the vicinity of the gate.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a tray of a magnetic head manufactured in an example and a comparative example.

FIG. 2A is a plan view of the tray shown in FIG. 1, and FIG.
FIG. 2B is a sectional view taken along the line BB of FIG.

[Explanation of symbols]

 Reference Signs List 1 tray body 2 positioning rib 3 positioning boss 4 magnetic head

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichi Sagisaka 1 Tohocho, Yokkaichi City, Mie Prefecture Inside the Yokkaichi Office of Mitsubishi Chemical Corporation (72) Inventor Ikuo Mizuno 3-17, Ojida, Yokkaichi City, Mie Prefecture No.F-term in Yukaichi Factory of Yukaichi Electronics Co., Ltd. (Reference) 4F202 AB13 AB18 AE03 AH58 AK11 AR06 CA11 CB01 CK06 CN01 CN20 4F206 AB13 AB18 AE03 AH58 AK11 AR066 JA07 JF02 JL02 JN43 JQ81 4J002 AA011 BB031 001 CL001 CM041 DA036 FD116 GQ00 GQ02

Claims (6)

[Claims] 1. A method of manufacturing a conductive resin molded body by injecting a conductive resin into an injection molding die, wherein the vicinity of the gate on the inner surface of the injection molding die is heated to a height higher than the surroundings. A method for producing a conductive resin molded body, comprising injecting after setting the temperature. 2. The method according to claim 1, wherein the temperature is reduced to 1 by heating.
A method for producing a conductive resin molded body, wherein the temperature is raised to 0 ° C. or higher. 3. The method according to claim 1, wherein the heating is performed by induction heating. 4. The method for producing a conductive resin molded product according to claim 1, wherein the conductive resin contains carbon black. 5. The method for producing a conductive resin molded article according to claim 1, wherein the conductive resin molded article is a molded article for handling electronic components. 6. An apparatus for producing a conductive resin molded article, comprising: an injection molding die; and a heating means for heating only the vicinity of the gate on the inner surface of the die.