JP2009280746A - Composite material member with uniform surface resistivity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily obtain an injection-molded molding having a good and unifrom electroconductivity. <P>SOLUTION: The composite material comprises carbon fibers dispersed in the matrix as a filler. In the carbon fiber-containing composite material member, the number density of the carbon fibers is uniform in the depth direction and the carbon fibers are not extremely orientated along the flow direction on the surface of the composite member. Preferably, the carbon fibers are carbon nanotubes or gas phase-grown carbon fibers. For example, when a molding material containing the filers and the matrix is flown into the mold, the orientation and density of the carbon fibers are controlled by carrying out the molding as the fountain flow phenomenon on the free surface of the tip of the flow is covered with another resin. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a composite material containing nanocarbon fibers and a member using the same.

  The composite material of the present invention can be used without particular limitation in a technical field where predetermined characteristics (for example, conductivity, thermal conductivity, mechanical strength, etc.) are required. Therefore, the background art related to “conductivity”, which is mainly required in the field of semiconductors, will be described.

  2. Description of the Related Art Conventionally, transport containers made of a conductive material-resin composite material in which a conductive material is mixed with a resin have been used for the purpose of preventing damage to electronic equipment due to electrostatic discharge or the like in the semiconductor manufacturing industry. Currently, for the purpose of providing such a composite material, a composite material in which metal powder, carbon black, carbon fiber, or the like is mixed is used as a conductive substance.

  In particular, a composite material in which nano carbon fibers are mixed as a conductive substance can be made conductive with a small amount of mass because the fibers are nano-sized, and because it is fine, the fine shape of the molded product It has attracted attention because it has the characteristics of providing a composite material suitable for use in a clean room or the like because it has a low dust generation from a molded product due to the fine shape of the filler.

  However, the antistatic materials obtained by injection molding these nanocarbon fiber-containing composite materials are about 2 to 3 orders of magnitude larger than the resistivity of the molding material itself, and further antistatic in the molded product. The surface resistivity that has an important effect on the effect becomes non-uniform, and static electricity cannot be removed well, affecting the electronic equipment. That is, a molded product produced by injection molding of a nanocarbon fiber-containing composite material has a drawback that the surface resistivity is non-uniform depending on the location within the molded product.

This increase in resistivity and non-uniformity greatly depends on the molding conditions during injection molding, and in particular, when the material flow rate during molding increases, the surface resistivity tends to increase. As the demand for weight reduction of members increases in the future, the thickness of the members will become thinner, and it will be impossible to mold unless the injection speed is increased. Along with this, these problems are expected to increase.
A technology for producing a highly conductive molded product by injection molding of a composite material of a thermoplastic resin and fine carbon fibers has already been reported (Patent Document 2). Since it is necessary to hold at temperature for 10 seconds or more, productivity is a problem.
With regard to (Patent Document 1), the technology of controlling the electrical resistance by making the molded product into a two-layer structure has already been reported, but since this patent is molded by wrapping molding, it forms the surface layer part to be injected in advance. Since the resin to be accompanied also flows, the filler may be non-uniform.

Japanese Patent Publication No. 2005-81827 Japanese Patent Publication No. 2004-35826

  An object of the present invention is to eliminate the above-described drawbacks of the prior art and provide a composite material having good conductivity.

  As a result of intensive studies, the present inventor has found that the filler concentration in the resin can be controlled by suppressing the chaotic movement of the filler.

  The composite material of the present invention is based on the above findings. More specifically, the composite material includes at least a matrix and a filler (for example, 0.05 to 50 wt.%) Dispersed in the matrix. When the filler concentration (number density) in the region (a region) from the surface of the composite material to a depth of 5 μm or less is Fa and the filler concentration in the region (b region) at a depth of 20 μm or more from the surface is Fb The ratio (Fa / Fb) is 0.7 or more.

  In the present invention, the reason why the above-described effects can be obtained is estimated according to the inventor as follows.

Generally, the surface resistivity of a molded product varies greatly depending on molding conditions. For example, when a nanocarbon fiber composite material having a surface resistivity of 10 ³ Ω / sq is injection-molded, the surface resistivity of the filler on the surface of the molded product changes from 10 ³ to 10 ⁷ Ω / sq when the resin flow rate in the cavity changes. It varies in the range. When the cavity has a complicated shape, the resin flow rate varies within the cavity when the resin is filled. As a result, there is a problem that the surface resistivity also varies based on the resin flow rate.

  In the present invention, by suppressing the fountain flow phenomenon that occurs at the flow front portion of the resin flowing into the cavity, it becomes possible to produce a molded product having a uniform surface resistivity within the molded product.

  In the present invention, the cause of the change in the surface resistivity of the molded product is that the carbon fiber existing in the vicinity of the molded product surface layer has an orientation phenomenon in the flow direction and a layer having a low number density in the surface layer. It became clear from observation. When the carbon fibers are uniformly oriented in the flow direction, the contact points between the fillers are drastically reduced and the resistance tends to increase. Moreover, when the number density of the filler in the surface layer portion of the molded product changes, the contact points between the fillers are drastically reduced and the resistance tends to increase.

  In the present invention, it is possible to suppress the filler orientation phenomenon and the number density reduction phenomenon in the surface layer portion of the molded article during injection molding.

  As described above, according to the present invention, it is possible to easily obtain an antistatic material such as a transport container having excellent conductivity uniformity and good conductivity with a small amount of fine carbon fiber added.

  Hereinafter, the present invention will be described more specifically with reference to the drawings as necessary. In the following description, “parts” and “%” representing the quantity ratio are based on mass unless otherwise specified.

(Composite material)
The composite material of the present invention includes at least a matrix and a filler dispersed in the matrix. In the composite material of the present invention, the filler concentration (number density) of the region (a region) from the surface of the composite material to a depth of 5 μm or less is Fa, and the region (b region) of a depth of 20 μm or more from the surface (b region). Their ratio (Fa / Fb) is characteristic when the filler concentration is Fb. That is, the number density of fillers in the depth direction from one or more randomly selected points in the vicinity of the surface resistivity measurement point is 0.7 or more. This (Fa / Fb) ratio is preferably 0.8 or more, and more preferably 0.9 or more.

(Normal injection molding)
In a similar composite material obtained by ordinary injection molding, the ratio of (Fa / Fb) is usually about 0.5 or less (for example, about 0.1 to 0.5).

(Fa / Fb measurement method)
The ratio of (Fa / Fb) can be obtained according to the measurement method described in Examples described later.

That is, this method includes the following steps.
(1) Freezing and breaking along the flow direction.
(2) Gold coating is performed on the observation surface by about 10 nm.
(3) Enlarge the obtained cross section up to 5000 times using an electron microscope.
(4) The number of fillers pulled out from the resin is measured every 15 μm width × 5 μm in the depth direction.

(5) A graph obtained by averaging the obtained measurement results with a cross-sectional area (15 × 5 μm 2) is plotted as a depth direction on the horizontal axis and a filler concentration (number density) on the vertical axis.

  According to the above measurement, in the composite material (or composite member) of the present invention, the filler is dispersed in the matrix, and the number density of the filler is uniform in the depth direction on the surface of the composite material (in addition, For example, it is possible to confirm that the orientation in the flow direction is suppressed).

(Filler)
The filler that can be used in the present invention is not particularly limited as long as it does not contradict the gist of the present invention. From the viewpoint of improvement in mechanical properties and low dust generation, the filler preferably has a fibrous shape.

(Carbon fiber)
From the viewpoint of improving mechanical properties, imparting and improving conductivity, and imparting and improving thermal conductivity, carbon fibers can be used particularly suitably as the filler. Among these, carbon nanotubes (CNT) or vapor grown carbon fibers are preferable from the viewpoint of expressing the above-described properties with a small addition amount.

  As the carbon fiber, carbon nanotubes and vapor-grown carbon fibers, which are fine carbon fibers of 0.1 mm or less, are suitable, but PAN-based or pitch-based carbon fibers obtained by firing after melt spinning or centrifugal spinning. Can also be used. As for the length of the carbon fibers, any of long fibers to short fibers that do not impose a burden on the injection molding machine can be used depending on the purpose.

(matrix)
In the composite material of the present invention, it is preferable to select a resin suitable for injection molding as the matrix. As such a resin, a thermoplastic resin and a conductive resin are suitable. More specifically, for example, general-purpose resins such as polyester, polystyrene, polycarbonate, polyacetal, polyacetylene, and polypropylene are also included.

<Thermoplastic resin>
The thermoplastic resin used in the present invention is, for example, polycarbonate, polybutylene terephthalate, polyamide, ABS resin, AS resin, polyethylene, polypropylene, polyacetal, polyamideimide, polyethersulfone, polyethylene terephthalate, polyimide, polyphenylene oxide, polyphenylene sulfide, poly Examples thereof include thermoplastic resins such as phenyl sulfone, polystyrene, thermoplastic polyurethane, polyvinyl chloride, fluororesin, and liquid crystalline polyester, or a mixture thereof. These include mechanical strength, moldability, etc. according to the intended use of the molded product. It is possible to appropriately select from these characteristics.

  Among these, examples of the amorphous thermoplastic resin include polycarbonate, polyarylate, polysulfone, polyethersulfone, polyetherimide, modified polyoxymethylene, ABS resin, AS resin, polystyrene, and alicyclic polyolefin.

  Examples of the crystalline thermoplastic resin include polyethylene, polypropylene, polymethylpentene, polyethylene terephthalate, polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyamide, polyether ether ketone, syndiotactic (crystalline) polystyrene, and the like. Is mentioned.

  In addition, a liquid crystalline resin such as liquid crystalline polyester can also be used.

  In particular, when used as a fuel cell separator, water resistance, acid resistance, and heat resistance are required. Therefore, among the above crystalline thermoplastics, polyphenylene sulfide (PPS), polyether ether ketone, syndiotactic (crystalline) ) It is preferable to use polystyrene or the like. Further, it is also preferable to use an amorphous resin excellent in heat resistance and hydrolysis resistance such as liquid crystal resin, polysulfone, polyetherimide, or polyethersulfone.

(Orientation angle)
In the composite material of the present invention, it is preferable that the orientation angle of the filler (for example, carbon fiber) is about 15 ° or more with the flow direction as 0 °. The orientation angle is preferably about 30 ° or more in the vertical direction, and more preferably about 45 ° or more in the vertical direction. This filler (for example, carbon fiber) preferably has a number density of about 1.2 to 1.4 / μm ⁻² .

(Filler orientation)
The present inventor has found that the filler (for example, carbon fiber) is oriented in the flow direction and the shear strain that the filler receives from the flow resin when the resin is filled in the cavity. Further, it has been clarified by the present inventors that the phenomenon in which the number density of the filler decreases is caused by phantom flow at the flow front end when the resin is filled in the cavity. In the present invention, according to the knowledge of the present inventors, by suppressing the fountain flow occurring on the free surface of the flow front portion of the resin during filling, in the present invention, the filler orientation phenomenon and the number density reduction phenomenon (Furthermore, it is easy to obtain a molded product having good conductivity and uniform surface resistivity).

As will be described later, in the present invention, 5 wt. %, The surface resistivity was 10 ⁷ to 10 ⁶ Ω / sq in the case of a molded product produced by a normal injection molding method when melt-kneaded at a ratio of%. On the other hand, when the present invention was applied to the same composite material system, the surface resistivity was improved to about 10 ³ to 10 ⁴ Ω / sq under the same injection molding conditions. As will be described later, when the inside of the molded product obtained by such an experiment is observed with a scanning electron microscope, the orientation of the carbon fibers in the vicinity of the surface layer of the molded product in the flow direction is relaxed, and a uniform number density is maintained. It was confirmed that

(Electromagnetic shield)
The present invention can also be applied to electromagnetic shielding. In this field of electromagnetic shielding, electrical characteristics are often evaluated not by surface resistivity but by volume resistivity, and usually a conductivity of about 10 ⁻¹ to several Ω · cm is often required.

With respect to this electromagnetic shield, due to the rapid improvement in performance of semiconductors and hard disks, the ESD damage of the device in the manufacturing process is large, but it is becoming a big problem. Until now, in order to avoid ESD destruction, we have dealt with using ionizers and using conductive plastics with a surface resistivity of 10 ⁵ Q / sq or less. There is an increasing demand for a material that is in contact with the device and has a surface resistivity that is strictly controlled in the range of 10 ⁶ to 10 ¹⁰ Ω / sq and that has a high degree of cleanness. The reason why the surface resistivity of 10 ⁶ to 10 ¹⁰ Ω / sq is required is mainly due to the following reason.

That is, when two conductive materials having different charge levels come into contact with each other, charge transfer occurs instantaneously, the charge levels become equal, and a current flows. The ESD breakdown of the device is considered to be caused by the current generated by the movement of the charge. Therefore, in order to protect the device from ESD destruction, it is necessary to control the speed of movement of this charge and suppress the generated current level. In other words, ESD damage can be avoided by using a material that contacts the device with a material that has a relatively low charge transfer rate and that is not charged. The charge transfer rate depends on the surface resistance of the material, and the surface resistivity generally required for an ESD-compatible material is 10 ⁶ to 10 ¹⁰ Ω / sq. When the surface resistivity of the material is higher than 10 ¹¹ Ω / sq, not only charging due to friction but also a tendency to cause other problems due to adsorption of dust, dust and the like due to charging.

(Other ingredients)
Other compounding agents that can be used in the present invention are as follows.
(1) Flame retardant compounding agent Used to ensure fire safety.
For example, in the case of aluminum hydroxide, the principle is that aluminum hydroxide is dehydrated at 300 ° C. to 350 ° C. to take advantage of the endothermic action when it becomes aluminum oxide, suppressing the temperature rise and ignition of the resin, and burning. It is to delay and prevent.

  Examples of inorganic compounding agents include aluminum hydroxide and magnesium hydroxide. Examples of the halogen compounding agent include bromine compounds and chlorine compounds. Examples of the phosphorus-based compounding agent include phosphoric acid compounds.

  Examples of the antibacterial compounding agent include various organic compounds, food additives, and inorganic compounds. This is mainly made by binding metal ions with antibacterial functions such as silver, copper and zinc to various compounds (Reference: http://www.aichi-inst.jp/htmJ/news/news98/ news98084.html).

  As a compounding agent for high specific gravity materials, a high specific gravity compounding agent such as tungsten-based material can be mentioned.

  Due to its high specific gravity, vibration absorption is good and sound insulation is excellent. Furthermore, since it is a metal, it is also conductive.

(Filler lowering phenomenon in the surface layer of the flow front)
According to the knowledge of the present inventor, the resin flow accompanied by the fountain flow at the flow front portion is not caused by the shear rate inside the fluid resin, and is cited as a main factor that promotes the decrease in the concentration of nanocarbon fibers that are fillers. It is done. Further, according to the numerical analysis, it is predicted that there is a region where the purchase of the resin flow rate is small at the flow front end, and a phenomenon in which the molten resin stays is occurring. Here, when the phenomenon occurring in the flow front free surface portion is considered, it is expected that a tensile stress unrelated to the resin flow from the flow front top portion to the mold wall surface is applied. It was hypothesized that the tensile stress would cause the free surface to be extremely tensed, which would cause the filler to move inwardly, leading to a decrease in the filler concentration list price.

(Lapping molding)
When injection molding is performed, the molding material advances in the mold while accompanying the fountain flow, so that a phenomenon in which a free surface appears at the flow front end portion always occurs.
As a flow without fountain flow, there is a phenomenon called plug flow, but this occurs due to slippage at the interface between the mold wall surface and the molten resin, which may damage the surface of the molded product. There is usually a tendency to avoid molding by plug flow.

Therefore, in order to prevent the formation of a free surface of the resin accompanied by fountain flow at the flow front end, it was considered to suppress the exposure of the free surface by covering the flow front end with the same or different material. This method will be called lapping molding. Specifically, it can be easily carried out by sandwiching a device for accumulating molten material resin between a nozzle of a normal injection molding machine and a resin injection port of a mold.
According to this method, the material for forming the surface layer portion is not accompanied by a fountain flow, and the molded product surface layer portion is formed while being stretched to the material forming the interior, so that the phenomenon of lowering the filler concentration of the molded product surface layer portion does not occur.

  When the same kind of material is used in the surface layer part and the inside when performing the lapping molding method in the present invention, the same kind of material is automatically replenished in the surface layer part material reservoir so that it is continuously produced in terms of productivity. Is possible.

  The thickness of the material forming the surface layer part after molding is desirably 5 μm or more indicated by the a region.

  In the present invention, the nanofiber-containing composite material is used as the surface layer material and the same material or transparent polycarbonate (PC) is used as the internal material, and lapping molding is performed, and the filler concentration in the composite material member that is not affected by the fountain flow. Observe changes. As the injection conditions, in particular, the injection speed that greatly changed the surface resistivity was changed, and the flow velocity in the cavity was changed.

  If this molding method is used, a molded product having a surface resistivity substantially equal to that of the pellet can be obtained. Therefore, a pellet having a surface resistivity according to need may be used as the surface layer material.

  Hereinafter, the present invention will be described more specifically with reference to examples.

Example A-1
Multi-walled carbon nanotubes (MWCNT) (diameter 80 nm, length 15-20 μm) grown in a vapor phase are used as a filler in 5 wt. % Was used as pellets (commercially available), and a molded product having a thickness of 1 mm was obtained by injection molding.

  Observation was performed with a scanning electron microscope (SEM) to confirm whether or not the filler in the test piece formed by injection molding was oriented. FIG. 1 shows an SEM photograph of the surface layer portion in the plate thickness direction of a test piece produced at an injection pressure of 45 MPa, a plate thickness of 1.0 mm, a resin temperature of 300 ° C., a mold temperature of 100 ° C., and an in-cavity speed of 325 mm / s. . By observing the inside of the resin with this SEM, it was confirmed that the filler inside the test piece molded by the injection molding method was oriented in the direction of resin flow during molding.

  As shown in FIG. 2 (a), it was confirmed that the number density of the filler was extremely reduced by about 70% in the region of the depth of 0 to 15 μm near the surface layer portion of the test piece.

  The phenomenon in which the number density of the filler decreases near the surface layer of the specimen molded by injection molding is observed with a scanning electron microscope to confirm whether the resin occurs at the flow front end during the filling process into the cavity. went. In order to observe the flow front part in the middle of the flow, the mold was held at an extremely low temperature using liquid nitrogen or the like, and injection molding was performed to produce a short shot molding defective product. The SEM photograph which expanded on the flow front-end | tip front surface of the test piece produced by injection pressure-several MPa, mold temperature -150 degreeC, and resin temperature 300 degreeC is shown in FIG. From this, it was confirmed that there is a region where the number density of the filler is extremely low in the depth direction of 0 to 15 μm from the free surface of the flow tip.

  From the above, when the carbon fiber-containing composite material is injection-molded, the number density of the carbon fibers as the filler is reduced on the free surface of the flow front end, and the orientation in the flow direction is caused by the shear strain caused by the difference in the flow rate of the resin. appear. In order to suppress these phenomena, it is necessary to prevent the influence of the resin flow at the flow front end from reaching the surface layer of the molded product. As a method for this, it is conceivable to control the influence of the resin flow on the surface layer portion of the molded product by selectively solidifying the free surface portion of the flow tip portion.

Example A-2
In this experiment, in order to selectively solidify the flow front end free surface, a method of separating the resin flowing in the cavity into a core layer and a skin layer is used, and is shown in FIG. 4 between the vertical injection molding machine and the cavity. A vessel (skin layer melting device) having the function of heating and melting a resin such as A was designed and manufactured.

  The skin layer melter (symbol A in FIG. 4) can be heated to 370 ° C. by a heater. In this container, a carbon fiber-containing composite material that becomes a skin material is put and heated and melted to the injection conditions. Then, by injecting the core material from above with a cylinder of an injection molding machine, the carbon fiber-containing composite material is filled into the cavity while forming a skin layer and a core layer. At this time, the resin flow affecting the orientation and number density of the filler is limited to the core material.

  The molding conditions when skin / core molding is performed are described below.

(Table 1)

  The inside of the test piece after molding was observed with a scanning electron microscope, and the number density in the depth direction from the surface of the molded article of the filler and the orientation angle were measured. It was confirmed that the number density of the filler did not decrease even in the region of 0 to 15 μm in the depth direction in the surface layer of the test piece (FIG. 2A). Further, it was confirmed that the orientation in the flow direction was relaxed as compared with normal injection molding (FIG. 5).

The surface resistivity of this test piece was 10 ³ to 10 ⁴ Ω / sq, and a value about 1/100 of a test piece produced under the same molding conditions by a normal injection molding method was confirmed (FIG. 6).

Example B-1
(Lapping molding)
Lapping molding was performed using the apparatus shown in FIG.
(1) Test material polycarbonate (PC)
In this experiment, polycarbonate was used as a core material in lapping molding. Panlite L-1225Y manufactured by Teijin Chemicals Ltd. was used. Since the same material as the matrix resin of the composite material of the skin material is used, there is an advantage that a sandwich structure is easily formed.

(2) Resin-based CNT composite material (PCcArr)
In the examples, polycarbonate was used as a matrix resin and MWCNT was used as a filler at 5 wt. % MWCNT / PC composite pellets were used.

(3) Experimental apparatus Originally, the lapping molding method requires the preparation of an apparatus having two cylinders for melting and injecting each of the skin material and the core material. However, in this experiment, a new device was added to the normal vertical injection molding machine described above, and the design and production were modified to enable lapping molding.

  An outline from the skin material melting part to the cavity of this experimental apparatus is shown in FIG. This experimental apparatus is composed of three units: a vertical injection molding machine, a heating pan, and a cavity.

  First, a dish-shaped device capable of heating a small amount of resin to the melting temperature is installed between a sprue bush and a cylinder of a normal vertical injection molding machine (A in FIG. 7). This is called a heating dish. Next, at the lower part of the sprue, a mold having a test piece molding cavity incorporating two pressure sensors is installed (B in FIG. 7).

(4) Heating dish The heating dish can be heated up to 360 ° C with a cartridge heater. After a small amount of resin serving as a skin material has been put into the pocket part of this heating dish (the region of the pocket of composite matrix in Fig. 7) Heat to injection temperature and melt. Further, by injecting a resin that becomes a core material melted in a cylinder, the same function as that of a lapping molding machine can be expressed.

(5) Pressure sensor In this experiment, when a new mold was produced, the pressure sensor was changed to an indirect in-mold pressure sensor ISA446-2.25C (Dynisco). In the conventional mold apparatus for preparing test pieces, when the molten resin flows in the cavity, the shape of the pressure measuring element (diameter 6 mm) is transferred to the molded product, and the flow condition in the cavity is affected. was there. Therefore, in order to make the pressure element trace as small as possible, a method of measuring pressure via an ejector pin having a diameter of 1.5 mm was adopted. When the molten resin flowing in the cavity passes over the pin and pressure is generated, the load is applied to the load cell via the injector pin, and the voltage is output to the logger (PCD-300: manufactured by Kyowa Denki Co., Ltd.). The This indirectly measures the pressure in the mold.

(6) Mold In this experiment, in order to avoid unnecessary disturbance of the fluid resin, the cavity shape was designed so that the cylinder, sprue, and cavity were aligned. In the cavity, pins of ¢ 1.5 mm are built with an interval of 25 mm, which are designated as S3 and S4, respectively. This is the pressure measurement interface described above, and measures the pressure in the cavity and calculates the resin flow rate in the cavity from the time difference between the pressure rises between the two points.

  A mold having another test piece preparation cavity is put together with the first mold as shown in FIG. The shape of the cavity was a cylindrical shape of ¢ 5 x 60 mm so that a sandwich shape could be easily established. Since the shape of the molded product is a cylindrical shape, a cavity block is provided, so that the molded product after injection is easily taken out. A cavity block is aligned with mold A and fitted into Mold A, and combined with the above-described mold with a built-in pressure sensor, so that it is incorporated into the experimental apparatus as a cavity.

  To this, heating is performed up to the injection temperature condition using a cartridge type heater and a plate type heater as shown in the figure.

(7) Injection conditions Although the resin used this time is the same polycarbonate, the thermal conductivity is improved by using CNT as a filler. Therefore, the thermal properties and viscosity of the skin material and the core material are different. Since the skin material has a high thermal conductivity, the mold is easily deprived of heat, so the viscosity is likely to increase, and short shots are likely to occur. Therefore, in this experiment, the short shot was prevented by setting the skin material temperature about 50 ° C. higher than the injection temperature of the core material and lowering the viscosity of the skin material.

  Similarly, the mold temperature was set higher than the normal molding conditions. Table 2 shows the molding conditions.

(Table 2)

(Cross section observation)
(injection molding)
FIG. 9 shows the relationship between the flow velocity in the cavity and the pressure waveform measured in S3 and S4. The maximum value of the pressure measured with the flow velocity in the cavity increased. This is presumably because the energy of the fluid resin increases as the resin flow rate in the cavity increases. It can also be seen that the pressure drop between the two points measured in the cavities S1 and S2 used in the above-described experiment is slightly smaller. This is probably because the pressure loss received by the fluid resin is reduced because the cavity shape has been changed from the T shape to the linear shape.

(Optical microscope observation)
Each test piece was cut perpendicularly in the axial direction every 10 mm from the vicinity of the gate, and the cross section was observed with an optical microscope. 9 and 10 show optical micrographs of the vicinity of 20 mm and 50 mm from the vicinity of the gate. From these, the composite material (in the photo: black layer) and the PC (in the photo: white layer) form a layered structure, which indicates that lapping molding is established. Also, the shadow in the center of FIG. 9 is a mixture of bubbles in the injection process.

  In the vicinity of the gate, composite material is observed in the outermost layer and PC is observed in the inner layer, indicating that wrapping molding has been established, but at a point 50 mm away from the gate, a PC layer is formed on the outer side of the composite material. I understand that. This is because when the cavity is filled, the amount of the composite material that becomes the skin layer is small, or the PC that becomes the core material starts from the portion where the skin layer is locally thinned in the vicinity of the tip of the core layer flow. It is thought that it flowed out to the outermost layer and a PC skin layer was formed at the tip of the composite material. This is generally called break through.

  From these observation results, it can be seen that break-through occurs at a point farther from the gate in the molding condition where the flow velocity in the cavity is fast. Moreover, since neither result has a change in the thickness of the skin layer, it can be seen that the influence due to the difference in the flow velocity in the cavity does not contribute to the thickness of the skin layer. From the above, it is considered that the difference in the injection flow rate does not affect the thickness of the free surface layer at the flow front end.

Example B-2
(Proposal of a filler concentration reduction phenomenon model)
From the above experiment, it is considered that this occurs at the flow front end. Therefore, we will finally consider pressure.

  YK. Shen et al. Perform a numerical analysis of the fountain flow phenomenon at the flow front to obtain a pressure distribution. They state that the pressure inside the flow tip is lower than the surroundings.

  In the filler movement model due to the pressure drop, the molten resin that has moved from the central portion in the cavity to the flow front end portion expands toward the free surface. Then, when moving toward the mold wall surface, the flow path of the melted resin becomes narrow and the resin flow rate becomes relatively high. As a result, the pressure slightly decreases along the flow line of the molten resin according to Bernoulli's theorem, and the filler concentration in the free end surface of the flow tip is extremely lowered by pulling the filler inside the resin in the direction of lower internal pressure. Moreover, it is considered that the molten resin in a high temperature state is exposed to the low pressure for a long time, so that the filler promotes the inward movement from the free surface portion.

Example C-3
(Orientation relaxation method by annealing)
When the filler inside a normal injection-molded molded article is subjected to a large shear strain when the molten resin flows while being cooled to the mold wall surface, it is forced to be oriented in the flow direction. Conceivable.

  Therefore, the test piece obtained by injection molding is heated to a temperature above the glass transition point, and the effect of the resin restraining the filler is weakened, and the filler in the molded product is oriented in the flow direction during molding. The purpose is to lower the surface resistivity by releasing.

(1) Test material In this example, 5 wt. 5 using polycarbonate as a matrix resin and MWCNT as a filler as in the previous molding experiments. % MWCNT / PC composite pellets (PCcNT) were used.

(2) Annealing treatment A molded article having a known surface resistivity was put in a high temperature furnace under various conditions for annealing. Table 4 shows the molding conditions of the molded product and the annealing conditions. The temperature was set above the glass transition point of polycarbonate.

(Table 3)

(Evaluation of electrical characteristics)
FIG. 11 shows the change in the surface resistivity of the test piece (sample No. 8) annealed in a furnace at 260 ° C. for 60 minutes before and after annealing. As in Chapter 2, the measurement points were 10 mm, 25 mm, and 40 mm from the gate, and were designated as points A, B, and C, respectively. As a result, the surface resistivity of the test piece could be reduced by about 1/100 to 1/1000 by annealing. This is a value close to the physical property value of PCcArr. This is thought to be caused by the following phenomenon.

  By heating to a temperature equal to or higher than the glass transition point of the matrix resin, the binding force on the filler is eased as the viscosity in the matrix resin decreases. And since the orientation in a molded article was cancelled | released and the direction of the filler changed to the random direction, the contact point of fillers increased. As a result, a conductive path through the filler in the molded product is formed, and this is considered to have reduced the surface resistivity, which is called the Negative Temperature Coefhcient (NTC) effect.

  FIG. 23 shows changes in surface resistivity before and after annealing for each condition, the vertical axis shows the surface resistivity, and the horizontal axis shows the annealing time.

According to this, the sample No. No. 280 ° C. and the annealing time was 15 minutes. 10 and no. The test piece No. 11 had a surface resistivity reduced to about 10 ³ Ω / sq. However, the surface resistivity of samples with other annealing conditions increased without decreasing. In particular, the surface resistivity of the sample produced under the slow injection rate was as low as 10 ⁴ Ω / sq, but the samples N0.2 and N0.9 increased to 10 ⁷ Ω / sq.

  This is thought to be because the positive temperature coefhcient (PTC) phenomenon in which the resistivity is increased by the expansion of the matrix due to the temperature rise and the disconnection of the conductive path through the filler has occurred.

  This indicates that the restriction of the filler in the molded product was not relaxed even when annealing was performed at a temperature higher than the glass transition point of the matrix resin. As in the previous experiment, the surface resistivity was improved only when annealing was performed at a high temperature of 280 ° C. for 15 minutes. In all these annealing conditions, the sample after the test was greatly deformed by heat, and none of the samples remained as a molded product. For this reason, when the annealing method is taken into consideration for industrial application, the step of annealing the injection-molded molded product causes a great deal of damage to the molded product.

(Production of cross-section observation test piece of molded product)
Next, cross-sectional observation of the molded product before and after annealing is performed to compare the orientation and concentration of the filler in the vicinity of the surface layer of the molded product. The purpose is to examine the factors that decrease the surface resistivity.

A 10 × 50 × 1 mm molded product obtained by ordinary injection molding was prepared. The molding conditions of this molded product were an injection speed of 90%, and the other molding conditions were the same as those shown in Table 3. The surface resistivity is about 10 ⁷ Ω / sq.

  One of the two test pieces cut out from the molded article was annealed in a furnace at 260 degrees for 20 minutes. By annealing, it can be seen that the surface of the test piece is slightly glossy and slightly deformed.

  Then, each test piece was frozen and fractured in the flow direction, and the cross section was observed. 13 and 14 show SEM images of the cross section of the test piece before and after annealing. Prior to annealing, the filler is highly linear and oriented in the flow direction. However, the filler inside the molded product after annealing is weak in linearity, and since it is released from the matrix resin, it seems that each turned to a random direction due to the curvilinearity that CNT originally had. It is done.

  FIG. 15 shows the filler concentration distribution from the surface layer of the molded product from the cross section of each test piece. From this result, it was shown that the filler, which was strongly oriented in the flow direction (near 0 °), was subjected to the annealing treatment and turned in the direction of falling apart. Thus, it is considered that the conductive path was formed by increasing the number of contacts between the fillers in the molded product.

  In addition, when annealing is performed on the filler concentration in the vicinity of the molded product surface layer portion, the filler concentration in the molded product surface layer portion is slightly increased. This is considered that CNT which is a filler moved toward the surface layer part of a molded article with a low filler density by heating the resin and decreasing the viscosity of the resin.

  Here, the phenomenon occurs in which the CNT released from the restraint of the matrix resin due to heating / viscosity loss loses orientation and moves to the surface layer. It is presumed that the residual stress was applied.

  As described above, the injection-molded resin-based CNT composite material has a problem that it has a non-uniform surface resistivity due to the presence of filler orientation and concentration in the molded product. However, from these results, it was shown that by using a very simple technique called annealing, the decrease in the orientation and concentration of the filler on the entire surface of the molded article can be alleviated and the surface resistivity can be made uniform.

(Surface resistivity reduction processing by lapping molding method)
In recent years, interest in wrapping molding (Co-idection molding) has been increasing, and much research has been applied to this method, and expectations from the plastics industry have increased.

  The main interest in this technology is the ability to create products that combine different physical and chemical properties of the skin and core layers. For example, by using a fiber reinforced resin for the core material and a normal resin for the skin material with a certain aspect ratio, it is possible to maintain a high decorative property while having mechanical properties.

  In addition, the lapping molding method can reduce costs while maintaining good mechanical strength by using inexpensive recycled resin as the core material and unused unused resin as the skin material. It is said to be an important alternative to the molding method.

  In the examples described above, it has been clarified that the surface resistivity of the molded product is determined by the orientation degree and concentration of the filler existing in the vicinity of the surface layer portion of the molded product. The degree of orientation can be explained by the total shear strain applied to the resin in the vicinity of the mold in the cavity during the injection process. Also, molding is caused by local decrease in filler concentration near the surface of the molded product. It was clarified that the surface resistivity of the product became uneven within the individual. R. S. Bay [79, 80] et al. State that they are caused by the resin fountain flow phenomenon in the process of filling the mold. According to them, numerical analysis is performed on the presence or absence of the fountain flow phenomenon in the condition of the flow front and the orientation of the filler in the molded article when the fountain flow phenomenon occurs at a position away from the free surface. The vertical axis represents the degree of orientation in the flow direction, and the horizontal axis represents the dimensionless number from the center of the molded product to the surface layer. According to this, when the mold is filled in a state where the fountain flow phenomenon occurs to some extent behind the free surface, a skin layer having a low degree of filler orientation is formed in the vicinity of the surface layer portion.

  Based on this knowledge and the relationship between the filler concentration lowering phenomenon and the fountain flow described above, the problems such as the surface resistivity non-uniformity problem caused by the filler concentration lowering phenomenon and the surface resistivity increase caused by filler orientation have been solved. As a means for achieving this, a lapping molding method capable of separating the fountain flow and the free surface at the flow front end can be applied. Thereby, it is considered that a high-quality antistatic material (in this case, the surface resistivity is uniform in the molded product and has high conductivity) can be produced using the resin-based CNT composite material.

(1) Test material VGCF150
Vapor grown carbon fiber (VG150) was used. VG150 is a highly crystalline carbon nanofiber synthesized by a vapor deposition method. VGCF is a fibrous carbon grown in a reducing atmosphere reactor heated to 1100 ° C. by vapor-decomposing hydrocarbons using ultrafine metal particles as a catalyst and growing to a length of several hundred μm using metal particles as nuclei. . Depending on the size of the core metal particles, it has a diameter of 50 mm to 1 μm. Among these, those having a diameter of 50 nm to 200 nm are particularly referred to as vapor grown carbon nanofibers (VGCNF). From these observations, it can be seen that the diameter is 80 to 200 mm (average diameter 150 μm).

(Study on improvement of surface resistivity of molded products)
(Polycarbonate)
Above (PC / MWCNT composite material)
PCcArr that has been used in previous studies is used.
(PC / VG150 composite material (PCvg150)
In this experiment, short carbon fibers different from MWCNT were mixed with PC in order to distinguish it from PCcNT for the purpose of grasping the flow state of the core material, and a new composite material was produced. PC was used for the matrix resin and VG150 was used for the filler. These were prepared by melt kneading with a kneader. This is PCvg150.

(Kneading)
In this experiment, PCvg 150 as a co-test material was prepared by newly kneading.
Normally, when injection molding is performed, the effect of mixing filler and matrix resin is manifested by the screw of the injection molding machine, but when short fiber-containing resin is injection molded, the filler is uniformly dispersed in the matrix resin only by this effect. It is difficult. Therefore, injection molding was performed after the filler and matrix resin were melt-kneaded and pelletized by a laboratory blast mill.

  In this example, a laboratory blast mill (50C150) manufactured by Toyo Seiki Co., Ltd. was used to uniformly disperse the filler in the matrix resin. This apparatus melts and kneads the filler and matrix resin charged in the heated mixer section between two screws rotating at a constant speed and between the screw and the inner wall of the mixer.

(Kneading conditions)
The kneading conditions were determined with reference to the kneading conditions carried out in the laboratory so far.

(injection molding)
In this experiment, the experiment was performed using the lapping molding apparatus described above.

(1) Mold With conventional specimens, a complete sandwich structure cannot be produced because a break-through phenomenon occurs in which the core material precedes the skin material near the center of the cavity. There wasn't. In order to suppress this phenomenon and make it easier to obtain a sandwich structure when preparing a test piece for surface resistivity measurement, a new test piece mold was designed and manufactured.

  By reducing the aspect ratio of the test piece to 16 × 20 × 1 as compared with the conventional test piece, the possibility of breakthrough was reduced. In addition, the gate part from the sprue to the cavity was eliminated, and elements that could hinder the sandwich structure were excluded.

  FIG. 16 shows an outline of the test piece. Moreover, the example (PC / PCcNT) of the molded article of the test piece for lapping molding surface resistivity measurement obtained with this metal mold | die is shown in FIG. In this case, about 10 mm from the vicinity of the gate, a black composite material is formed on the skin layer and the PC layer / core layer is black, and wrapping molding is established. Also, the composite material forms a surface layer portion on the outside.

(Surface resistivity reduction processing by lapping molding method)
In this experiment, three kinds of materials _PC · _PC CNT · PCvg150, was performed by combining a plurality of skin layer / core layer.

  Table 4 shows a summary of test piece numbers and combinations of skin layers and core layers.

(Table 4)

First, the core layer and the skin layer are _subjected to lapping using PC / _PCNT , and the surface resistivity is evaluated (PC / _PCNT and _PCNT / PC). Also tried combinations to fill the _{P CNT} in both the skin layer and the core layer _{(P CNT /} P CNT). Then, the pressure of 20 kg / cm ² and 90 kg / cm ² is set for the normal injection of P _CNT into the same mold (P _CNT ), and the surface resistivity is compared with P _CNT / P _CNT. It was.

  Table 5 shows the molding conditions.

(Table 5)

When filling the PC to the core layer, the viscosity of PC was for the purpose of aligning the viscosity of the skin layer and the core layer is lower than the P _CNT, a resin temperature of PC and 270 ° C. of the molding temperature limit. Further, in the case of conditions, PC _CNT and PC, the mold temperature is set to 100 ° C. for the purpose of adjusting to normal injection conditions.

(Evaluation of electrical characteristics)
In FIG. 18, the surface resistivity of the test piece shape | molded by each condition is shown. For this case PC _{/ PC CNT} and _PC CNT / PC and three specimens of PC, since the surface resistivity showed a value exceeding the measurement range of the measuring instrument ^{(~10 7 Ω / sq),} PC / P CNT And P _CNT PC are described as being incapable of measurement, and reference values from the specs are listed for PC. The reason why PC / P _CNT and P _CNT PC exceeded the measured value is that the surface resistivity of PC is so high as 10 ¹⁶ Ω / sq, so it is insulated by the extremely thin film formed on the surface layer of the molded product. It is thought that.

The value of the surface resistivity of the injection molded product of PC _CNT alone shows the same tendency as the value measured above. The higher the injection pressure, the higher the filler density and, as a result, the surface resistivity appears to have decreased.

In addition, the surface resistivity of the test piece of the same PC _CNT formed by wrapping each other shows a value of about 1/100 compared with the injection molded product of PC _CNT alone performed under the same molding conditions (FIG. 18). ). This is a value approximately equivalent to the resistivity inherent in PC _CNT . This is because the fountain flow phenomenon and the skin layer formation process are separated at the flow front part of the flow in the cavity using the lapping molding method, so that the orientation and concentration reduction phenomenon of the filler near the surface part of the molded product does not occur. It is thought that it was because of it.

(Cross-section observation of molded product)
Next, cross-sectional observation of _PCNT / _PCNT , _PCNT, and PC / _PCNT was performed. Each test piece was fractured in the flow direction by the freeze fracture method, and observed with an electron microscope, and the distribution of filler orientation angle and the filler concentration in the depth direction from the vicinity of the surface layer of the molded product were measured.

  FIG. 19 shows the filler concentration measured from the surface of the molded product in the depth direction. Three points near the surface where the surface resistivity was measured are extracted and measured, and the average value is examined.

Within moldings were injection molded PC _CNT alone in this to the same as in depth 0~10μm area and cross-sectional observation of, could be observed how the filler concentration is significantly reduced.

On the other hand, in the molded article PCCNT _{/ PC CNT,} reduction phenomena of the filler concentration in the region of depth 0~10μm was hardly observed. From this result, as described above, it was shown that the wrapping molding can suppress the filler concentration lowering phenomenon in the vicinity of the surface layer portion of the molded product.

  Moreover, in FIG. 20 and FIG. 21, the orientation angle | corner of the filler which exists in each molded article for every depth from the surface is shown. From now on, the molded product subjected to lapping molding is weakly oriented around 0 ° compared to that molded by single injection molding. In particular, in a region having a depth of 0 to 15 μm, which is considered to have a great influence on the surface resistivity, the filler angle is concentrated between −5 to 5 ° for those molded by ordinary injection molding, and is strong in the flow direction. Although the orientation is shown, the filler angle of one formed by lapping molding is dispersed around −45 to 45 °. Due to these differences, it is considered that the contact points between the fillers increased, and as a result, the surface resistivity decreased due to the formation of the conductive path.

22 and 23 show cross-sectional SEM photographs of each.
Normally, the filler existing angle in a molded product subjected to injection molding has a low dispersion value. This is due to the filler being concentrated in the vicinity of 0 °. On the other hand, lapping molded products such as P _CNT / P _CNT and P _CNT PC show high dispersion. This is thought to be because the filler is not oriented in the flow direction (near 0 °) and the orientation is random, and it was shown that the lapping molding method is effective for suppressing the orientation of the filler.

(Filler state in the core layer of the wrapping molded product)
When PCvg 150 was used for the core layer, the surface resistivity of the molded product exceeded the measurement range (up to 107 Ω / sq) and could not be measured. This is 5 wt. In PCvg150 mixed with VG150 in%, the viscosity is lower than that of PCCNT which is a skin material, and it is considered that a breakthrough occurred in which the core layer broke through the skin layer and the molding progressed at an early stage. In addition, since the bulk density of the filler is small, the fillers in the molded product do not have sufficient contact points, and no conductive path is formed, so that percolation does not occur. Therefore, it is estimated that the resistivity has increased.

  Here, the behavior of the resin in the lapping molding is estimated by examining the presence state of the filler in the core material. In order to examine the state of the filler in the core layer of the molded article of PCCNT / PCvg150, cross-sectional observation was performed.

  The filler present in the skin layer is MWCNT, and the filler present in the core layer is VG150. Although the two fillers are different in thickness, it is obvious, but the number density in the matrix VG150 having a small bulk density is extremely lower than that of MWCNT. Moreover, since the length of the filler itself is shorter than VG150 in the VG150, there is little contact between the fillers, and it can be seen that a conductive path cannot be formed.

  It can be seen that the filler concentration on the core layer side is lowered at the boundary between the skin layer and the core layer on the core material side from the result of the average value of the three points in addition to those measured by randomly selecting three points. Usually, in lapping molding, it is considered that the core material proceeds in the skin layer with a fountain flow phenomenon. It is considered that the filler concentration decrease phenomenon occurs at the boundary between the skin layer and the core layer due to the fountain flow phenomenon. Therefore, it was further confirmed that the fountain flow phenomenon has a profound effect on the filler concentration lowering phenomenon in the vicinity of the surface layer of the molded product.

(Filler orientation / concentration reduction suppression model by lapping molding)
From the above studies, it was found that the lapping molding method can suppress the filler orientation and the concentration reduction phenomenon in the vicinity of the molded product surface.

  A model for suppressing filler orientation / concentration reduction by lapping molding is shown below by integrating the findings so far.

  First, the skin material previously injected into the cavity is cooled by the mold and the viscosity increases. Then, the core material injected from the rear proceeds in the skin material with a fountain flow. During this time, the skin layer and the core layer are formed without mixing the boundary between the skin material and the core material.

  The skin material expands so as to be pushed by the core material from the inside at the flow front end portion. The fountain flow phenomenon does not occur inside the skin material, and the skin layer is simply stretched by applying a tensile stress from the relative velocity between the flow velocity in the cavity and the mold wall surface in the vicinity of the mold wall surface.

  At this time, the flow velocity in the cavity affects the magnitude of the tensile stress, and the filler density of the skin layer changes. For example, if the flow velocity in the cavity is high, the tensile stress increases, and the skin layer is strongly stretched. As a result, the matrix expands, the filler contained around the unit volume decreases, and the filler density decreases. However, looking at the relationship between the flow velocity in the cavity and the surface resistivity described above, it seems that the decrease in density due to this phenomenon does not affect the surface resistivity.

  In addition, since the shear rate due to the difference in flow velocity does not occur inside when being stretched, the filler orientation phenomenon is difficult to occur. At that time, since the filler is formed in the skin layer without being oriented, it is considered that the filler is not oriented in the flow direction in the vicinity of the surface of the molded product (FIG. 42).

  Assuming that the extreme filler concentration reduction phenomenon near the surface of the molded product occurs in the model described above, the core material that has flowed and developed with the fountain flow phenomenon is a pressure drop caused by changes in the resin flow rate. Happens inside. At this time, the filler moves to a lower pressure side, and an extreme filler concentration lowering phenomenon occurs near the boundary between the skin layer and the core layer.

  Further, in the skin layer, since the fountain flow phenomenon does not occur as described above, it is estimated that the pressure inside the resin does not decrease. Therefore, the filler in the vicinity of the skin layer surface layer portion forms the molded product surface layer portion without moving, and therefore, an extreme filler concentration lowering phenomenon does not occur in the vicinity of the molded product surface layer portion. In addition to this, the skin material previously injected continues to exist in the flow front part for a relatively long time based on the knowledge obtained by the above-described annealing. Then, the flow front end free surface is in a state similar to that of being annealed, and the uniform filler concentration and the relaxation of the filler orientation are promoted.

  As a result of these factors, when the lapping molding method is used, the filler concentration near the surface layer of the molded product is uniform, the filler orientation in the flow direction is suppressed, and the surface resistivity is uniform within each molded product. It is thought that the material can be produced.

It is a SEM photograph of the plate | board thickness direction surface layer part of the test piece obtained in Example A-1. Fig.3 (a) is a graph which shows the number density of the filler in the area | region of the depth of 0-60 micrometers in the test piece surface layer vicinity vicinity shown in FIG. FIG.3 (b) is a graph which shows the number density of the filler in the area | region of the depth of 0-60 micrometers near the test piece surface layer part obtained by this invention. It is the SEM photograph which expanded the flow front-end | tip part free surface of the test piece of a short shot molding inferior goods. It is a schematic cross section which shows the structure of the melter for skin layers. It is a graph which shows the orientation angle from the molded article surface of a filler to a depth direction. It is a graph which shows the comparison of the surface resistivity of normal injection molding and skin / core molding. It is a schematic cross section which shows the outline | summary of the experimental apparatus used in the Example. It is a graph which shows an example of the relationship between the flow velocity in a cavity, and the pressure waveform measured with the pressure sensor. FIG. 15 (a) is an optical micrograph of a molded product obtained by molding under a condition where the flow velocity in the cavity is 125 mm / s, on a surface 20 mm from the gate. FIG. 15B is an optical micrograph on a surface 50 mm from the gate. FIG. 16A is an optical micrograph of a molded product obtained by molding under the condition of a flow velocity in the cavity of 625 mm / s on a surface 20 mm from the gate. FIG. 16B is an optical micrograph on a surface 50 mm from the gate. It is a graph which shows an example of the surface resistivity change before and behind annealing. It is a graph which shows an example of the surface resistivity change in each annealing condition. It is a SEM photograph which shows the flow direction cross section of the test piece before annealing. It is a SEM photograph which shows the flow direction cross section of the test piece after annealing. It is a graph which shows an example of a molded article surface layer vicinity filler density change before and behind annealing. It is a schematic diagram which shows the outline | summary of the test piece for surface resistivity measurement of a lapping molded product. It is a photograph which shows an example of a PC / PC _CNT molded product. FIG. 33A is a graph showing an example of the relationship between the skin / core combination and the surface resistivity. FIG. _33B is a graph showing an example of a comparison of surface resistivity between PC _CNT / PC _CNT and PC _CNT . FIG. 34 (a) is a graph showing an example of the relationship between the depth from the surface of the molded product in PC _CNT and the filler concentration. FIG. 34B is a graph showing an example of the relationship between the depth from the surface of the molded product and the filler concentration in PC _CNT / PC _CNT . FIG. 34 (c) is a graph showing an example of the relationship between the depth from the surface of the molded article in PC _CNT / PC and the filler concentration. It is a graph which shows an example of the relationship from the depth from a molded article surface, the orientation angle | corner of a filler, and an abundance ratio. (A) is depth 0-5 micrometers, (b) is depth 5-10 micrometers, (c) is depth 10-15 micrometers, (d) is a graph in each condition of depth 15-20 micrometers. It is a graph which shows an example of the relationship from the depth from a molded article surface, the orientation angle | corner of a filler, and an abundance ratio. (E) is a depth of 20 to 25 μm, (f) is a depth of 25 to 30 μm, (g) is a depth of 30 to 35 μm, and (h) is a graph under the conditions of a depth of 35 to 40 μm. Is a SEM photograph showing a cross-section of the PC _CNT. It is a SEM photograph which shows the cross section of _PCCNT / _PCCNT .

Claims (6)

A composite material comprising at least a matrix and a filler dispersed in the matrix;
When the filler concentration (number density) in the region (a region) from the surface of the composite material to a depth of 5 μm or less is Fa, and the filler concentration in the region (b region) at a depth of 20 μm or more from the surface is Fb. A composite material characterized in that the ratio (Fa / Fb) is 0.7 or more.   The composite material according to claim 1, wherein the filler has a fibrous shape.   The composite material according to claim 2, wherein the filler is carbon fiber.   The composite material according to claim 3, wherein the carbon fiber is a carbon nanotube (CNT) or a vapor-grown carbon fiber.   The composite material according to claim 1, which has a shape of a composite member.   When the molding material containing the filler and matrix flows into the mold, the filler concentration in the resin and A method for producing a composite member, wherein the orientation of the filler is controlled.