CN1369093A - Tray for transporting magnetoresistance effect head for magnetic disk - Google Patents

Abstract

A tray for transporting a magnetoresistance effect head for magnetic disks produced by modling a resin composition containing 100 parts by weight of thermoplastic resin material and 0.1 to 8 parts by weight of carbon fibrils whose fibril diameter is less than 100 nm and whose ratio of the fibril length to the fibril diameter is 5 or more, wherein the surface resistivity is stably 104 to 1012 Ω/□, the surface is uniform, and few particles are produced because of scratching, friction, and cleaning.

Description

Magneto-resistive effect head transport tray for magnetic disk

technical field

The present invention relates to a transport tray for transporting magnetoresistive effect heads for magnetic disks (hereinafter sometimes referred to as MR heads).

current technology

Trays used to transport films, IC chips, and other electronic components are required to have antistatic properties. In this regard, people used to add antistatic agents, carbon black and other conductive components to resins such as ABS resins as molding materials, so that the transport tray has antistatic properties.

However, such a shipping tray molded from a conductive resin composition containing an antistatic agent and carbon black has the following problems. That is to say, after adding the antistatic agent, since the conduction mode is ion conduction, it is easily affected by the ambient temperature; after cleaning and long-term use, the antistatic performance will decrease due to the loss of the antistatic agent; Antistatic agents, which impair heat resistance, etc. In addition, in the case of carbon black, although carbon black is not affected by humidity and cleaning, etc., in order to produce electrical conductivity, a large amount of carbon black must be added. As a result, the scratch resistance and scratch resistance of the surface of the final molded product The wear resistance will decrease, and it is easy to generate wear dust and carbon particles to fall off.

In order to solve the above problems, carbon fiber is sometimes added to polycarbonate as the material for the delivery tray of the hard disk head.

However, in recent years, with the continuous improvement of the recording density of the magnetic head, the MR magnetic head has replaced the previous thin-film magnetic head and become the mainstream product. The MR magnetic head generally consists of a support arm component, an MR element installed at the front end of the support arm, and a lead wire connected to the MR element.

The traditional thin-film element detects the signal based on the current generated when the signal magnetic field approaches the coil, while the MR element makes a certain weak sensing current flow, and detects the signal magnetic field according to the current resistance. This structure can greatly improve the detection sensitivity of the MR head, reduce the track pitch of the recording medium, and increase the capacity. In recent years, GMR heads with larger capacity have been released.

As mentioned above, since the MR head detects the magnetism based on the resistance change of the weak current (sensing current) flowing through the MR element, there is a great risk that the MR element will be damaged even if there is a weak noise current. . Therefore, compared with conventional integrated heads and integrated circuits, MR heads are more sensitive to electrostatic discharge due to potential differences with the shipping tray and touch currents due to contact with the head and shipping tray.

During the assembly process of the MR magnetic head, it is necessary to connect a lead wire to the MR element, and then install the MR element connected with the lead wire to the front end of the arm member. Although the lead wire is a metal wire coated with polyimide, due to the contact potential difference between the polyimide and the metal wire, the contact part is always in a state of charge separation, so it is also in a state of current instability. state. As a result, when the tip of the lead wire comes into contact with the shipping tray, charge transfer is prone to occur at the contact point, thereby further aggravating the risk of damage.

Based on the above reasons, there is an electrostatic discharge or excessive contact current between the MR element and the transport tray or between the surrounding components and the transport tray due to the low surface resistance of the transport tray. serious problem of damage.

In addition, during the assembly of the MR heads, in many cases the MR heads are washed and heat dried together with the shipping tray. In this way, it is necessary to require the delivery tray not to contaminate and damage the magnetic head during cleaning and heating and drying. Especially in the drying process, since it is dried at a temperature above 120°C, it is required that the transport tray must have heat resistance that can fully withstand this drying temperature.

In addition, the primary requirement for the performance of traditional antistatic or static charge dissipative materials is to quickly dissipate static charges generated by friction and contact. Therefore, general documents do not specify the lower limit of the resistance value (for example, JP-A-8-288266, JP-A-8-508534, etc.). In addition, when there is a high requirement for static charge dissipation on integrated circuit chip transport trays, etc., the surface resistance should preferably be above 103Ω/□ (for example, JP-A-8-283584).

As mentioned above, although polycarbonate/carbon fiber series materials are used in conventional MR head shipping trays, these materials have the following defects, so it is difficult to be used in MR head shipping trays that are particularly sensitive to electrostatic charges.

(1) Although incorporation of a small amount of carbon fiber can significantly improve electrical conductivity compared with carbon black, there is a possibility that the surface resistance value of the molded body thus formed may decrease. This fails to meet the requirement that the MR head transport tray should have a high surface resistance. If the resistance value is increased by reducing the doping amount, the contact state between the carbon fibers inside the molded body will be unstable, making it difficult to obtain a uniform resistance value.

(2) The diameter of carbon fibers dispersed in the resin is generally 7-12 μm, and the fiber length is 50-300 μm. This size is relatively large, so carbon fibers will be exposed on the surface of the obtained molded body. As a result, an extremely low-resistance region formed by exposed carbon fibers and an electrically insulating region composed of resin will appear on the surface of the molded body. These two regions are dispersed in units of about 10 μm to 1 mm. In this way, to a large extent, there is a risk of damage caused by overcurrent due to the direct contact between the sharp front end of the MR magnetic head connecting lead and the exposed part of the carbon fiber on the surface. On the other hand, because the charge generated in the resin region is difficult to be discharged, it will appear in a charged state microscopically.

(3) During the process of putting the MR head forming device in pure water for ultrasonic cleaning, etc., the carbon fiber itself will fall off from the surface of the transport tray, and the resin component between the carbon fibers will also peel off. These shed particles will not only contaminate the magnetic head and cause damage to the magnetic head, but also have the danger of being a foreign matter that enters the gap between the magnetic head and the hard disk during the operation of the hard disk drive system and squeezes the magnetic head.

(4) In the case where carbon fibers are dispersed evenly in the resin, adhesives for bonding carbon fibers together and surface treatment agents for improving the dispersion of carbon fibers and resin and increasing the strength of the contact surface are generally used. The use of such treatment agents may cause problems such as ions being dissolved in the cleaning solution during pure water cleaning (ion contamination) and organic compounds with lower molecular weights deposited on the device during heating (non-volatile organic contamination) .

The magnetoresistive effect head delivery tray for magnetic disks provided by the present invention can solve the long-standing problems mentioned above. Its surface resistance value can be stabilized in the range of 10 ⁴ to 10 ¹² Ω/□, and the surface state is uniform, and rarely occurs due to Particle shedding due to scratching, rubbing and washing.

Contents of the invention

The feature of the magnetoresistance effect head conveying tray for magnetic disk of the present invention is: it is molded by adding carbon fibril resin composition in thermoplastic resin material, and the fiber diameter of this carbon fibril is below 100nm, and the fiber length and The fiber diameter ratio is above 5, and the blending amount is 0.1-8 parts by weight of carbon fibrils per 100 parts by weight of the above-mentioned thermoplastic resin material.

Description of drawings

FIG. 1 is an explanatory diagram of a method for measuring surface resistance in Example 1. FIG.

FIG. 2 is a graph showing the measurement results of surface resistance values of Example 1 and Comparative Examples 1 to 5. FIG.

FIG. 3 is a graph showing the measurement results of surface resistance values of microscopic parts in Example 1 and Comparative Example 2. FIG.

Implementation

The carbon fibrils have a graphite outer layer deposited substantially concentrically along the cylindrical axis of the fibrils, and the central axis of the fibrils is not a straight line but a curved tubular form. Because the present invention uses this carbon fibril as a kind of conductive medium, its fiber diameter is 100nm or less, and the ratio of fiber length to fiber diameter (hereinafter referred to as "aspect ratio") is more than 5, thereby having the following effects.

(1) Since the carbon fibrils dispersed in the matrix resin can form a fine conductive network, the surface of the molded body is uniform and smooth, so that the surface resistance value can be stabilized within the specified range, and the microscopic parts have excellent Reproducibility of resistance values.

(2) Since the carbon fibrils are not in a straight line but in a curved state, good positioning effect can be produced in the matrix resin, and the fibrils themselves rarely fall off during scratching, friction and cleaning. In addition, the resin hardly peeled off from the fibers. Therefore, particle shedding rarely occurs during abrasion and cleaning.

(3) Carbon fibrils rarely produce ion pollution and pollution caused by non-volatile organic compounds.

In the measurement when the probe diameter is 2 mm and the probe distance is 20 mm, the surface resistance value of the transport tray of the present invention should be 10 ⁴ -10 ¹² Ω/□, preferably 10 ⁶ -10 ¹² Ω/□.

In addition, as mentioned above, since the transport tray is exposed to a drying temperature of 100-120° C. during the cleaning and drying process of the magnetic head, considering the heat resistance during drying, the transport tray of the present invention The heat distortion temperature (ASTM D684, 4.6Kg load) should preferably be above 110°C.

The thermoplastic resin material used as the matrix resin in the present invention is preferably at least one of polycarbonate, polybutylene terephthalate, polyethylene terephthalate and polypropylene.

Embodiments of the present invention will be described in detail below.

The carbon fibrils used in the present invention have a diameter of 100 nm or less and an aspect ratio of 5 or more. For example, those described in JP-A-8-508534 can be used.

If the fiber diameter of the carbon fibrils exceeds 100 nm, the contact between the carbon fibrils in the matrix resin will be insufficient, making it difficult to obtain a stable resistance value. The fiber diameter of the carbon fibrils is preferably less than 20nm. That is to say, if the carbon fibrils can be so thin, even if there are carbon fibrils falling off, since the gap between the MR element and the hard disk is generally 50nm, the risk of the hard disk being crushed by the falling carbon fibrils will be reduced. very low. However, because the fiber diameter is too small, it is difficult to produce, so the fiber diameter of the carbon fibrils can be 0.1 nm or more, preferably 0.5 nm or more.

Also, if the aspect ratio of the carbon fibrils is less than 5, it is difficult to secure a good positioning effect in the matrix resin, and abrasion powder and particles are generated. Therefore, the aspect ratio of the carbon fibrils used should be more than 5, preferably more than 100, and more preferably more than 1000.

Also, as mentioned above, although the carbon fibrils have a tubular shape, their wall thickness (thickness) is preferably about 0.1 to 0.4 times the outer diameter of the carbon fibrils generally in the range of 3.5 to 75 nm.

Such carbon fibrils can be purchased from the market, for example, "BN" (fiber diameter 10-20nm, aspect ratio 500-2000) produced by Hyperion Catalysis International, Inc. can be used.

In addition, if at least a part of the carbon fibrils in the matrix resin are in an aggregated state, it is desirable that the resin composition does not contain fibril aggregates with a diameter of about 50 μm, preferably more than 10 μm, according to the area measurement.

In the present invention, 0.1 to 8 parts by weight of such carbon fibrils are incorporated into 100 parts by weight of the thermoplastic resin material. If the doping amount of the carbon fibrils does not reach 0.1 parts by weight, the resistance value will be too high, the conductivity will be lost, and the antistatic performance will be deteriorated. On the other hand, if the incorporation of carbon fibrils exceeds 8 parts by weight, not only the surface resistance value of the obtained molded body tends to decrease, but also problems such as an increase in the amount of dust and a significant decrease in moldability will occur. question. The blending amount is preferably 1 to 4 parts by weight of carbon fibrils per 100 parts by weight of thermoplastic resin material.

On the other hand, the thermoplastic resin material used in the present invention as the matrix resin includes polyethylene, polypropylene, polybutene, and aliphatic polyolefins such as polymethylpentene or alicyclic polyolefins, and non-olefins. Resins, such as: aromatic polycarbonate, polybutylene terephthalate, polyethylene terephthalate, polyphenylene sulfide, various polyamides (such as nylon 6, 66, nylon 610 and nylon MXD6, etc.), polyetherimide, polysulfones, polyethersulfone, polyether ether ketone, acrylic resin, styrene resin, modified polyphenylene ether, and liquid crystalline polyester.

As mentioned above, since the MR magnetic head transport tray will be exposed to a drying temperature of 100-120°C during the cleaning and drying process of the magnetic head, so considering the heat resistance during drying, the transport tray of the present invention preferably adopts its The heat distortion temperature (ASTM D684 4.6Kg load) can guarantee the matrix resin above 110°C. From the consideration of heat resistance and cost, it is best to use polypropylene, polycarbonate, polybutylene terephthalate, polyparaphthalate Ethylene glycol phthalate, and modified polyphenylene ether. From the viewpoint of dimensional accuracy, it is desirable to also use polycarbonate, polybutylene terephthalate, and polyethylene terephthalate.

If necessary, other components can be added to the resin composition used in the present invention, such as glass fiber, silica fiber, silicon-aluminum fiber, potassium titanate fiber, aluminum borate fiber, inorganic fiber-shaped reinforcement materials such as aluminum fiber; aromatic Organic fibrous reinforcements such as polyamide fiber, polyimide fiber, and fluororesin fiber; inorganic fillers such as talc, calcium carbonate, mica, glass beads, glass powder, and glass bubbles; fluororesin powder, di Solid lubricants such as molybdenum sulfide; plasticizers such as paraffin oil; antioxidants; heat stabilizers; light stabilizers; ultraviolet absorbers; neutralizers; lubricants; compatibilizers; antifogging agents; anticondensation agent; slip agent; dispersant; colorant; antibacterial agent and fluorescent whitening agent, etc.

In addition, in the resin composition used in the present invention, it is also possible to add conductive fillers other than carbon fibrils, such as metal fillers such as aluminum, silver, copper, zinc, nickel, stainless steel, brass, and titanium. Various carbon blacks, graphite (artificial graphite and natural graphite), glassy carbon particles, pitch-based carbon fibers, PAN (peroxyacetyl nitrate)-based carbon fibers, carbon-based fillers such as graphite whiskers; zinc oxide, oxide Metal oxide-based fillers such as tin and indium oxide. In addition, if the metal oxide-based filler generates excess electrons due to lattice defects and conducts electricity, other dopants can be added to enhance the conductivity. For example, aluminum, antimony, and tin can be added as dopants in zinc oxide, tin oxide, and indium oxide, respectively. It is also possible to use a composite conductive filler in which a metal coating is applied to carbon fibers or the like, or a conductive tin oxide is formed on the surface of potassium titanate whiskers.

As long as it is suitable for the production method of the matrix resin used, the production method of the resin composition involved in the present invention is not limited. For example, after the thermoplastic resin material is pre-mixed with carbon fibrils, a closed mixer, a rolling machine, a Brabender machine, a single-screw mixing extruder, a double-screw mixing extruder, and a mixer can be used. etc. for melt processing production.

The resin composition of the present invention is preferably produced by, for example, the method described in JP-A-8-508534. That is, the carbon fibrils are dispersed in the matrix resin using, for example, a high-speed mixer manufactured by Henschel. This is followed by a co-rotating twin-screw extruder such as available from Werner-Pfleiderer, a counter-rotating twin-screw extruder from Leistritz, or A synchronous mixer (Ko-Kneader) produced by Buss Corporation applied shear force to reduce the aggregate size of carbon fibrils. The shear force is applied until substantially all of the existing aggregates have a diameter measured by area less than about 50 μm, ideally at least 90% of the existing aggregates have a diameter measured by area less than 25 μm. More desirably, the shear force is applied until substantially all of the aggregates present are less than 5 μm in diameter as measured by area, especially if 98% of the aggregates are less than 3 μm in diameter as measured by area .

Furthermore, it is also possible to prepare a stock batch pre-loaded with carbon fibrils in large quantities and then to dilute it. The reason why this raw batch method is adopted is that the concentration of carbon fibrils in the raw batch is relatively high, and the dispersing shear force is relatively large, so that the carbon fibrils are easier to disperse.

In the production of the magnetoresistive effect head transport tray for magnetic disks of the present invention, the resin composition chips prepared as above are molded into desired shapes. The forming methods include extrusion molding, blow molding, injection molding and vacuum forming. Although the injection molding method is the most advantageous from the cost point of view, due to the structure of the mold, the surface resistance value of the product will change with the resin temperature, mold temperature and molding pressure, so it is necessary to set appropriate conditions.

In addition, if the volatile gas emitted from the molded body produced in this way becomes a problem during use, it can be annealed under normal pressure or reduced pressure conditions below the thermal deformation temperature of the molded body material.

When the magnetoresistive effect head transport tray for magnetic disks of the present invention is measured under the conditions of a probe diameter of 2 mm and a probe spacing of 20 mm, its surface resistance value can reach 10 ⁴ to 10 ¹² Ω/□, especially 10 ⁶ to 10 ¹² Ω/□ range, the surface resistance value on the microscopic area can show excellent uniformity.

In the existing measurement of surface resistance value, electrodes with larger areas are generally used for measurement. For example, under the ASTM D257 standard, a peripheral electrode of about 830mm ² and a center electrode of about 490mm ² are used even for a small area.

Since the surface resistance value measured using such a large-area electrode is measured based on the average contact resistance within the contact range with the electrode, the unevenness of the resistance value within the electrode area cannot be detected.

On the other hand, in injection molded products, the thickness of the outer layer on the surface of the molded body is susceptible to unevenness due to the influence of mold pressure and unevenness in concentration. What's more, the resistance value of the flow part under the strong shear force near the injection port will increase due to the directionality of the fiber or structure, and conversely, the resistance value will increase near the end or welding part. likely to be lowered. Especially for filling materials such as carbon fiber with a large fiber diameter, the resistance value tends to fluctuate based on the presence or absence of a skin and the change of the contact state depending on the directionality.

Although this slight fluctuation in resistance value is not a problem in existing shipping trays for electronic components, in equipment trays that are sensitive to electrostatic charges, such as MR head shipping trays, the resistance on microscopic areas is greatly affected. There are certain requirements for the uniformity of the value.

Therefore, in the present invention, since the measured value of the surface resistance on the microscopic area measured under the condition of the probe diameter of 2 mm and the probe spacing of 20 mm is used as an index value, the uniformity of the surface resistance value can be highly controlled.

The present invention will be described in more detail below in conjunction with examples and comparative examples.

Example 1

Disperse carbon fibrils (fiber diameter is about 10nm, length-diameter ratio is 500～2000) in polycarbonate with the addition of 15% by weight in advance to form the raw material (by the product "BN type" of Super Catalyst International Co., Ltd. ), and then diluted with polycarbonate (Mitsubishi Engineering Plastics product "NOVAREX 7025A") to obtain a resin composition containing 4.5 parts by weight of carbon fibrils per 100 parts by weight of resin. The compounding process is carried out with a twin-screw compounding extruder, and the composition is then sliced.

Thin slices with a thickness of 1 μm were cut out from the processed slices with a microtome, and the cross-sections were observed under an optical microscope. The slices cut out from arbitrary ten locations could be observed, but aggregates of carbon fibrils of 50 μm or more were not seen. In addition, when observed with a transmission electron microscope, carbon fibrils with a fiber diameter of about 10 nm were uniformly dispersed, and each fiber was not straight but curved.

Next, the resin chip was processed into a plate-shaped shipping tray sample (hereinafter referred to as a plate-shaped sample) having a thickness of 100 mm x 100 mm x 2 mm using an injection molding machine.

In addition, the heat distortion temperature of this resin composition measured according to ASTM D684 standard (4.6Kg load) is 145°C.

The characteristics of the obtained plate samples were evaluated according to the following methods, and the evaluation results are shown in Table 1 and Figures 2 and 3. In addition, before performing the following particle pollution, ion pollution, and non-volatile organic compound pollution assessments, as a pre-treatment of the assessment, the plate-shaped sample was cleaned with pure water for 8 minutes, and then dried in a 100°C oven Internal drying, time is 30 minutes. This operation is carried out in a clean room. Furthermore, all containers used for immersion of plate samples are glass containers.

(Surface State Observation)

Place the surface of the plate sample under an optical microscope for imaging and observation. The results are shown in Table 1.

(surface resistance value)

The Hiresta IP (manufactured by Dia Instrument Co.: Dia Instrument Co., Ltd.) of the surface resistance value of the plate-shaped sample was measured at 10 volts using a double-probe (2 mm in probe diameter and 20 mm in probe spacing) probe. Also, if the surface resistance value is less than 10 ⁴ Ω/□, it is measured at Loresta (manufactured by Dia Instrument Co., Ltd.) with four probes (probe diameter 1 mm, probe pitch 10 mm).

The measurement position is shown in Figure 1. Probes 2A and 2B respectively touch two points across the center of the plate-shaped sample 1 and perpendicular to the flow direction of the resin. The distance between the injection port and the opposite side edge is 10mm during measurement. The measured value line graph is shown in FIG. 2 (■-■ in the figure). Furthermore, Table 1 also shows the maximum and minimum values.

(Surface resistance value of microscopic part)

The tips of the microelectrodes used had a shape of 0.5mmR, and were pressed against the surface of the plate-like sample with a pitch of 2mm and a load of 20g, and a voltage of 10V was applied to measure the resistance value between the electrodes. To measure this resistance value, a high resistance measuring instrument R8340A manufactured by Advantest Co., Ltd. was used. The results are shown in Fig. 3 (■-■ in the figure).

(scratch friction wear amount)

When evaluating the generation of scraping friction dust on a plate-shaped sample, it is measured in a T-type wear tester using a friction wheel H18 with a load of 500gf and a rotation speed of 500 revolutions to obtain the amount of wear . The results are shown in Table 1.

(particle pollution)

A plate-like sample is immersed in 500ml of pure water, and ultrasonic waves (40KHz, 0.5W/cm ² ) are applied for up to 60 seconds. Then use the particle counter in the liquid to extract the pure water extract, and measure the particle size (dust particle diameter) and quantity. The results are shown in Table 1.

(ion pollution)

One of the above-mentioned plate samples was immersed in 50 ml of pure water, stirred at 60° C. for 60 minutes, and then the ions dissolved in the pure water were analyzed by an ion chromatography analyzer. The results are shown in Table 1.

(non-volatile organic compound pollution)

One of the above-mentioned plate samples was immersed in 50 ml of "Asahi Krin AK-225EC" (manufactured by Sumitomo 3M Co., Ltd.), ultrasonic waves (40KHz, 0.5W/cm ² ) were applied for 60 seconds, and the extract was then heated at 100 Volatilize on an aluminum pan at a temperature of ℃, and measure the weight of the residue. The results are shown in Table 1.

Comparative example 1

For every 100 parts by weight of polycarbonate ("NOVAREX7025A" produced by Mitsubishi Engineering Plastics Co., Ltd.), 15 parts by weight of PAN-based carbon fiber ("HTA-C6-SR" produced by Toho Rayon Co., Ltd., with a fiber diameter of 7 μm and a length of Diameter ratio is 1000), with the same method as Example 1 to make the same shape of the plate sample. Obtained plate-shaped sample is carried out same as embodiment 1 and carries out the evaluation of surface state, surface resistance value and various pollutions, and its result is as shown in Table 1 and Fig. 2 (indicated by ◇-◇ in the figure).

Comparative example 2

Every 100 parts of weight polycarbonate (" NOVAREX7025A " produced by Mitsubishi Engineering Plastics Co., Ltd.) adds 30 parts of weight of PAN series carbon fiber (" HTA-C6-SR " produced by Dongbang Rayon Co., Ltd.), with embodiment 1 Plate samples of the same shape are made by the same method. Carry out surface resistance value, microscopic region surface resistance value and various pollution evaluations to the plate sample that obtains identically with embodiment 1, its result is as shown in table 1 and Fig. 2, Fig. 3 (respectively in the figure with △-△ express).

Comparative example 3

The raw material of carbon fibrils made by dispersing carbon fibrils in the same polycarbonate as in Example 1 was diluted with polycarbonate ("NOVAREX7025A" produced by Mitsubishi Engineering Plastics Co., Ltd.) to make 100 A plate-shaped sample of the same shape was produced as in Example 1 except that the resin composition contained 10 parts by weight of carbon fibrils in one part by weight of resin. The obtained plate sample was evaluated for surface resistance value, abrasion amount of scratching and particle contamination in the same manner as in Example 1, and the results are shown in Table 1 and Fig. 2 (port-port in the figure).

Comparative example 4

Synthesized using a resin in which 100 parts by weight of polycarbonate ("NOVAREX7025A" manufactured by Mitsubishi Engineering Plastics) was added as conductive carbon black to 16 parts by weight of acetylene black ("Denka Black" manufactured by Denka Corporation) Except for this, the other methods are the same as in Example 1, and a plate-shaped sample of the same shape is made. The surface resistance value, the wear amount of scratching and friction, and the particle contamination were evaluated on the obtained plate sample in the same manner as in Example 1. The results are shown in Table 1 and Figure 2 (- in the figure).

Comparative example 5

The raw material of carbon fibrils made by dispersing carbon fibrils in the same polycarbonate as in Example 1 was diluted with polycarbonate ("NOVAREX7025A" produced by Mitsubishi Engineering Plastics Co., Ltd.) to make 100 Except for the resin composition containing 0.05 parts by weight of carbon fibrils in one part by weight of resin, other methods were the same as in Example 1, and a plate-shaped sample of the same shape as in Example 1 was produced. The surface resistance value of the obtained plate sample was evaluated in the same manner as in Example 1, and the results are shown in Table 1 and Figure 2 (○-○ in the figure).

Table 1 example Example 1 Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative Example 5 Surface State Observation very even and smooth surface Exposed carbon fiber, the degree of exposure varies by location Surface resistance ^* (Ω/□) maximum value 5×10 ⁹ >10 ¹² ＜10 ⁴ (8×10 ¹ ) 6×10 ⁵ 5×10 ⁹ >10 ¹² minimum value 2×10 ⁷ ＜10 ⁴ (8×10 ¹ ) ＜10 ⁴ (1×10 ¹ ) ＜10 ⁴ (2×10 ² ) 1×10 ⁵ Scratch abrasion amount (mg) 95 140 160 Particle pollution (pcs/cm ² ) particle size 0.3μm 6160 34400 56700 20290 89530 0.5μm 1200 13380 26330 8960 37300 0.7μm 600 7950 11000 2580 14380 1.0μm 310 4110 6820 1020 3430 2.0μm 60 1060 1770 750 960 Ion pollution (μg/cm ² ) Ion species ^F- not detected 0.0055 0.0098 ^Cl- 0.0015 0.0158 0.0220 NO ₃ ^- 0.0020 0.0026 0.0032 Non-volatile organic compound pollution (μg/cm ² ) 0.31 0.67 0.82 *The value in ( ) is measured by Loresta 4 probe instrument. Other values are measured with a Hiresta instrument at a voltage of 100V.

The contents of Table 1 are explained as follows.

In Comparative Examples 1 and 2 in which carbon fibers were incorporated, in the case of a low amount of incorporation (Comparative Example 1), a region of high or low electrical resistance was generated, resulting in an uneven molded product. On the other hand, In the case of a high doping amount, (Comparative Example 2), the resistance value over the entire surface was too low to reach a stable resistance value in the range of 10 ⁴ to 10 ¹² Ω/□. In addition, in the measurement of the resistance value of the microscopic area, the resistance value of some areas is extremely high, such as the area in contact with the sharp front end of the lead wire connected to the MR head, and its safety will be compromised. Moreover, in Comparative Examples 1 and 2, there were many particles falling off, which increased the risk of damage and contamination of the device. Especially for the surface of the molded product where the carbon fiber is exposed, there is a high risk that the product will come into contact with the part and the carbon fiber itself will fall off.

Even if carbon fibrils are incorporated, as shown in Comparative Example 3, if the amount of carbon fibrils incorporated is too large, not only the resistance value will drop too much, but also the amount of wear powder and particulates will increase. Conversely, as shown in Comparative Example 5, if the doping amount of carbon fibrils is too small, the resistance value will rise too much, and the antistatic performance will be impaired.

As shown in Comparative Example 4, for the type containing carbon black, not only the resistance value distribution is not uniform, but also the doping amount has to be increased in order to achieve the necessary resistance value, resulting in a significant increase in wear powder and particles.

In this regard, as shown in Example 1, the thermoplastic resin after adding a specified amount of carbon fibrils has excellent heat resistance, and it is within the range of 10 ⁴ to 10 ¹² Ω/□ required by the M R head transport tray Can exhibit stable resistance value. In addition, the surface of the molded body is uniform and smooth, and the measured resistance value of the corresponding microscopic area can show good repeatability. We believe this is because carbon fibrils dispersed in the resin form a finer conductive network than carbon fibers.

In addition, very little particle shedding occurs during abrasion and cleaning. This is because the shape of carbon fibrils is not a straight line but a curved shape, which can increase the positioning effect in the matrix resin, so that the carbon fibrils themselves rarely fall off during scratching, friction and cleaning. , and the resin hardly peels off from the fibers. In addition, the carbon fibrils used in the present invention are not prone to ion pollution and non-volatile organic pollution.

According to the above detailed description, the magnetoresistive effect head transport tray for magnetic disks of the present invention has good heat resistance, uniform surface state, and stable surface resistance value in the range of 10 ⁴ to 10 ¹² Ω/□, and is rarely caused by Scratching or rubbing, cleaning will produce abrasive powder, and there will be almost no pollution and damage to the magnetic head caused by ions and non-volatile organic compounds.

Claims (5)

1. a magneto-resistance effect head transport tray for a magnetic disk, for transporting a magneto-resistance effect head for a magnetic disc, comprising a support arm part; the MR element installed on the support arm part; the lead wire connected with the MR element, characterized in that: The tray is molded from a resin composition that incorporates carbon fibrils into a thermoplastic resin material. The carbon fibrils have a fiber diameter of 100 nm or less, a ratio of fiber length to fiber diameter of 5 or more, The carbon fibrils are added in an amount of 0.1-8 parts by weight per 100 parts by weight of the above-mentioned thermoplastic resin material. 2. The magnetoresistive effect head transport tray for magnetic disks according to claim 1, wherein The measured surface resistance value is 10 ⁴ -10 ¹² Ω/□ under the condition that the probe diameter is 2 mm and the probe distance is 20 mm. 3. The magnetoresistive effect head transport tray for magnetic disks according to claim 2, wherein The above surface resistance value is 10 ⁶ to 10 ¹² Ω/□. 4. The magnetoresistance effect head transport tray for magnetic disks according to any one of claims 1 to 3, wherein Heat distortion temperature (ASTM D684 standard, 4.6Kg load) is above 110°C. 5. The magnetoresistance effect head transport tray for magnetic disks according to any one of claims 1 to 4, wherein The above thermoplastic resin material contains one or more of polycarbonate, polybutylene terephthalate, polyethylene terephthalate and polypropylene.

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