JPH0146640B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing a conductive film used as a product packaging film for electronic parts, an in-process dustproof film, or an electromagnetic shielding film for electronic equipment. Specifically, the present invention relates to a method for producing a conductive film that is relatively thin and can be manufactured continuously, and has sufficient conductivity and excellent strength even if it is a low basis weight product. [Conventional technology] Electronic components such as semiconductor ICs and LSIs, printed circuit boards,
Magnetic tape and other products need to be protected from problems caused by static electricity that attracts dust and electrostatic charges during the packaging and shipping process.In particular, MOS type ICs are susceptible to dielectric breakdown due to static electricity, so anti-static is essential. ing. In order to protect products from these electrostatic disturbances, packaging them with a conductive film with low surface resistivity may be considered. In addition, it is desirable for products such as the above-mentioned ICs to be able to see through and judge the packaged contents for transactions, so when packaging with conductive film, the conductive film itself is required to have a certain degree of transparency. be done. In order to manufacture the above-mentioned conductive film, in addition to meeting the demands for conductivity and transparency, it is also important to make the film as thin as possible in order to maintain superior transparency and make the film flexible. It is necessary that the film can be obtained, and that it has sufficient strength so that the film does not break during the manufacturing process, and that sheet-like products can be manufactured continuously. Furthermore, in the field of electronic equipment industry such as computers and measuring instruments, conductive films that have functions of electrostatic shielding and electromagnetic shielding in addition to assembly processes are required. Although transparency is not necessarily required for these uses, sufficient conductivity and product strength are required, and continuous production of sheet-like products is desired. Conventionally, a method for producing conductive polyolefin materials has been proposed in which paper stock is made by mixing carbon fibers into polyolefin-based synthetic pulp, and the resulting paper-like material is thermally fused at a temperature higher than the melting point of the polyolefin component. Publication No. 52-13214). A manufacturing method using stainless steel fibers instead of carbon fibers has also been proposed (Special Publication No. 41760/1983). However, according to the inventor's experiments, when producing a conductive film made only of polyolefin-based synthetic pulp and carbon fibers or stainless steel fibers, it is difficult to produce a conductive film because the polyolefin-based synthetic pulp has almost no physical or chemical bonding properties. The tensile strength, tear strength, and surface strength of the paper-like products produced are weak, and the film may tear during the process before heat fusing the polyolefin, making it impossible to continuously manufacture sheet-like products while winding them up. In practice, it has been difficult and impossible to manufacture a thin film with a small basis weight and sufficient electrical conductivity and strength. To compensate for the lack of strength, it is possible to use a single-component binder such as a hot water-soluble polyvinyl alcohol fibrous binder in combination with synthetic pulp, but the melting point is too low and the molten binder will stick to the dryer of the paper machine. This is undesirable as it may cause lees to adhere to the sheet, create holes, or cause paper breakage. Although it is possible to obtain strength by melting polyolefin synthetic pulp in a dry part without using reinforcing materials, there are many problems. For example, synthetic pulp has problems such as blistering just before it melts, uneven heating and melting, partial elongation, and wrinkles, making it impossible to obtain a highly accurate film with a low basis weight. be. [Problems to be Solved by the Invention] The present invention provides a method for continuously manufacturing a thin conductive film that has high strength and excellent paper formability and does not tear during the manufacturing and processing steps. At the same time, it is possible to obtain a film with sufficient conductivity even if it is a low basis weight product, and to obtain a conductive film with excellent transparency by adjusting the material as necessary, and it is possible to obtain a conductive film with excellent transparency even if it is a low basis weight product. This was done to solve problems in the method. [Means for solving the problem] In the present invention, thermoplastic conjugate fibers described later are blended into paper stock, utilizing the properties of this conjugate fiber, and by controlling the heating temperature in the manufacturing process,
In addition to making it possible to continuously manufacture a conductive film with excellent strength, we also discovered the optimal manufacturing conditions through experiments. That is, the present invention uses thermoplastic synthetic pulp 94.5 to 40
5 to 30% by volume of thermoplastic composite fibers consisting of a first component having a melting point lower than the melting point of the thermoplastic synthetic pulp and a second component having a melting point higher than the melting point of the thermoplastic synthetic pulp; After forming a wet paper using a paper stock made by mixing 0.5 to 30% by volume of conductive fibers (excluding those consisting only of carbon fibers), the temperature is higher than the melting point of the first component and lower than the melting point of the thermoplastic synthetic pulp. The first one is heated and dried at a low temperature.
The components are melted to form a base paper in which the paper stocks are mutually bonded, and then the base paper is heated and pressurized at a temperature higher than the melting point of the thermoplastic synthetic pulp and lower than the melting point of the second component to make it thermoplastic. Melt synthetic pulp,
The in-plane specific resistance 1× is characterized in that the second component and the conductive fibers form a dispersed film.
This invention relates to a method for manufacturing a conductive film having a resistance of 10 ⁶ Ω-cm or less. (Thermoplastic synthetic pulp) The thermoplastic synthetic pulp used in the present invention refers to a fibrous material that can be made into paper, such as pulp made of a thermoplastic synthetic resin. In addition, thermoplastic synthetic resins include polyolefin, polyacrylonitrile, polyester, polyamide, etc., which become transparent when melted by heating.
Any material may be used as long as it maintains its transparency even when it returns to a solid polymer upon cooling. Among these, particularly preferred are polyolefins that have a low melting point and are relatively inexpensive. Polyolefins include polyethylene, polypropylene, copolymers of ethylene and propylene, copolymers of ethylene or propylene and α-olefin, ethylene or and vinyl acetate, acrylic acid, etc., a mixture thereof, or a polymer obtained by further chemically treating these. In addition, when considering the heat sealability of the conductive film, it is preferable that the melting point is 200°C or lower, particularly 170°C or lower. (Conductive fiber) The conductive fiber used in the present invention is mainly a variety of metal fibers or metal-coated fibers made by coating the surface of inorganic fibers such as carbon fibers or glass fibers with metal. In addition, materials that can be made into short fibers and have a small specific resistance value in the planar direction,
For example, metal-deposited films cut into fibers, organic conductive fibers such as polyacetylene, etc. can also be used. Examples of metal fibers include steel fibers, stainless steel fibers, aluminum fibers, cinched fibers, copper fibers, bronze fibers, etc., but stainless steel fibers, aluminum fibers, cinched fibers, etc. whose surfaces are resistant to oxidation are preferred because they are easy to handle. These metal fibers are generally produced in various diameters by a drawing method, etc., but for use in the present invention, fibers with a diameter of 1 to 100 μm, preferably 20 μm or less, and a fiber length of 1 to 40 mm, preferably 3 to 25 mm is best. If the diameter exceeds 100 μm, the resulting film will have a thickness of 100 μm or more, which is undesirable, and due to the weight of the fibers, the fibers tend to settle on one side of the film, which may result in non-uniform blending. Further, the thicker the fibers, the easier it is to reduce the opacity of the film, but in order to ensure uniform dispersion in papermaking, it is desirable that the diameter be 20 μm or less. If the fiber length is short, 1 mm or less, it becomes difficult to construct a network of fibers within the film, which is undesirable. On the other hand, if the fiber length is 40 mm or more, there may be relatively wide areas where fibers are absent or large fiber agglomerates within the conductive film. This is not preferable because it makes it easier to create. Even when using metal-coated fibers in which carbon fibers or glass fibers are coated with metal, it is desirable that the coated metal be oxidizable, such as aluminum or nickel. As the carbon fiber serving as the core material, it is possible to use carbon fibers ranging from those fired at a relatively low temperature of about 1400° C. or less to graphitic fibers fired at higher temperatures. The form of carbon fiber has a fiber length of 1 to 40
Chopped fibers with a thread diameter of 5 to 30 μm are preferable, and the surface of these fibers is coated with metal such as aluminum or nickel to a thickness of about 0.5 to 30 μm by electroless plating or vacuum deposition. The obtained fibers can be used as conductive fibers. When glass fiber is used as the core material, aluminum, nickel, etc. are applied to chopped glass strands with a cut length of 7 to 10 mm and a diameter of 10 to 15 μm by vacuum deposition or immersion in a metal bath. A commercially available product coated with metal to a thickness of 305 μm can be used. If the amount of conductive fibers added to the paper stock is too small, the contact between the fibers will be insufficient, making it impossible to obtain a conductive film with low in-plane resistivity, and if the amount of conductive fibers is too large, the strength of the product will decrease. In addition to being inferior, it becomes difficult to obtain a uniform film.
The optimal blending ratio of the conductive fibers may vary depending on the type and thickness of the conductive fibers used, but in order to obtain a conductive film with an in-plane specific resistance of 1×10 ⁶ Ω-cm or less,
It should be blended at least 0.5% by volume, but not more than 30% by volume from the viewpoint of product strength and film uniformity. For electromagnetic shielding, it is desirable to incorporate a relatively large amount of conductive fiber. Furthermore, since the amount of conductive fibers to be blended is related to the transparency of the resulting conductive film, when used for applications that require transparency, the amount to be blended is adjusted depending on the application. If you want to keep the opacity below 30%, mix the amount of conductive fibers according to their thickness.
7% by volume if the diameter of the conductive fiber is 5 to 10 μm
Below, in case of 10~15μm, 12% by volume or less, 15~
In the case of 20 μm, it is desirable to set it to 30% by volume or less. (Thermoplastic composite fiber) In addition to the above raw materials, the present invention comprises a first component having a melting point lower than the melting point of the thermoplastic synthetic pulp and a second component having a melting point higher than the melting point of the thermoplastic synthetic pulp. Blending thermoplastic composite fibers. Thermoplastic composite fibers are fibers composed of two or more types of thermoplastic resins having different melting points, and are generally produced by a composite spinning method or the like. 1
An example is the one disclosed in Japanese Patent Publication No. 48-15684. The first component and the second component of the composite are appropriately selected depending on the melting point of the synthetic pulp used among the thermoplastic synthetic pulps described above. For example, when using polyethylene-based synthetic pulp with a melting point of about 120° C. as the synthetic pulp, a composite fiber containing low-density polyethylene having a lower melting point as the first component and polypropylene as the second component can be used. Other examples of the first component include those having relatively low melting points such as ethylene vinyl acetate copolymer and polyvinyl alcohol, and examples of the second component include polyester. Even if the first component and the second component are similar to synthetic pulp, they can be used as long as they have different melting points. Also, conversely,
Once the composite fiber is determined, a thermoplastic synthetic pulp may be selected as having a melting point higher than the first component of the composite fiber and lower than the second component. Composite fibers have a concentric or eccentric structure in which the second component with a high melting point is the core and the first component with the low melting point is the sheath, or the core part is exposed on the surface of the fiber. The second component and the second component may be continuously and irregularly combined, and the first component mutually binds the other paper materials in the blended raw materials of the base paper at a temperature before the high melting point second component melts. There is no particular restriction as long as it is in a form that can be eluted to the outside of the composite fiber so that it can be bonded to the composite fiber. In addition, composite fibers have a fiber length of 2 to prevent them from falling off during the papermaking process and to enable uniform blending.
It is desirable to have a diameter of about 40mm, particularly preferably 3mm.
~15mm, single fineness 1~30 denier,
Preferably it has a denier of 1.5 to 8. The above composite fibers are blended in a proportion of 5 to 30% by volume. If it is less than 5% by volume, the reinforcing effect that gives strength to the base paper is insufficient, and as the blending ratio increases, the tear strength of the base paper will increase, but if it is more than 20% by volume, the degree of strength improvement will be somewhat gradual. Become. On the other hand, if the blending ratio exceeds 30% by volume, there will be many voids in the conductive film obtained after heating and pressure treatment, making it impossible to produce a uniform film, and the strength of the product will be poor. Considering the characteristics of both the base paper and the conductive film, a particularly desirable blending ratio is 10 to 20% by volume. (Manufacturing process) In the method of the present invention, first, thermoplastic synthetic pulp, conductive fibers, and thermoplastic composite fibers are mixed. When mixing, the thermoplastic synthetic pulp is placed in hot water or the like in advance and stirred to disintegrate it, and the conductive fibers and composite fibers are also dispersed in water or the like, and then these are mixed. Furthermore, if necessary, when blending chemical pulp or the like, the beaten pulp is mixed with the above raw materials. The mixed paper stock is sufficiently stirred to make it homogeneous and sent to the paper making process. In papermaking, a papermaking machine that is used in normal papermaking technology and is composed of a screen section, a pressing section, a drying section, etc. can be used. Wet paper formed from the above paper stock is heated and dried in a drying section at a temperature higher than the melting point of the first component of the thermoplastic composite fiber and lower than the melting point of the thermoplastic synthetic pulp,
Only the first component is melted to produce a base paper in which paper stock is bonded to each other. The base paper obtained by drying is heated and pressurized. Heating and pressure can be done by calendering or hot press treatment, which makes the paper glossy and smooth the surface in the normal papermaking process, and the pressure conditions are 40 to 200 kg/kg by normal calendering.
cm linear pressure or hot press: 60~
Select appropriately under a pressure of 200Kg/cm ² . Further, under similar conditions, treatment using a plastic calendar can also be carried out. The temperature conditions for heating and pressurizing were set to a temperature higher than the melting point of the thermoplastic synthetic pulp and lower than the melting point of the second component of the thermoplastic composite fiber, and the second component and conductive fibers were dispersed in the obtained conductive film. A network is formed. It should be noted that there is no problem in adding a high-strength material or a high-melting point material to the extent that it does not impair the inventive idea of the present invention. Further, papermaking pulp such as chemical pulp may be added. Depending on the type of conductive fiber, those containing paper-making pulp such as chemical pulp have the effect of significantly increasing the dissipation rate of static electricity. [Function] In the method of the present invention, composite fibers composed of components with different melting points are blended into the paper stock, and as a first step, the fibers are heated and dried at a temperature at which only the first component with a low melting point melts. , the first component with a low melting point melts and plays the role of a binder that binds other paper stocks, and even if this first component melts, the second component with a high melting point maintains the fiber shape and strengthens it. It is effective and increases the tensile strength and tear strength of the base paper. Further, the conductive film produced after the second stage of heating and pressure treatment is formed by suitably adhering the respective paper materials and has excellent strength due to the reinforcing effect of the second component. Experimental Example 1 The following was used as paper stock. As a thermoplastic synthetic pulp, SWP UL-410 (manufactured by Mitsui Petrochemicals, polyethylene resin, melting point 123℃, specific gravity 0.94, average fiber length 0.9)
mm, whiteness of 94% or more) This is hereinafter abbreviated as SWP. The conductive fiber is stainless steel fiber (manufactured by Nippon Yakin, average fiber length 3 mm, diameter 8 μm), hereinafter abbreviated as SSF. The composite fiber is NBF-E (manufactured by Daiwabo Co., Ltd.) The first component is ethylene vinyl acetate copolymer (melting point 96-100℃) and the second component polypropylene (melting point 165-170℃).The first component is a sheath and the second component is a sheath. Core sheath-core type, fiber length 5 mm, fineness 2 denier] This is hereinafter abbreviated as NBF. Only SSF is a constant amount of 0.6% by volume, and SWP is
The rice (meter) basis weight was determined by varying the blending ratio in the range of 69.4 to 99.4 volume% and NBF from 0 to 30 volume%.
Various sheets of 50 g/m ² were produced. SWP, NBF, and SSF were each dispersed in water and then mixed to make paper stock. Drying is performed at a temperature of 100 to 115, above the melting point of the first component with a low melting point of NBF and below the melting point of SWP.
The test was carried out at ℃ to obtain various base papers. The relationship between the NBF blending ratio, tear length, and specific tear strength is shown in Figures 1 and 2. From FIG. 1, even if NBF is added at a blending rate of 5% by volume or less, the breaking length does not improve much. An improvement in the breaking length appears when adding 5% by volume or more, and a significant improvement in the breaking length is seen when adding 10% by volume or more. At 20% by volume or more, the degree of improvement in fracture length becomes somewhat gradual, and at 30% by volume,
At this point, it has almost reached a plateau. From FIG. 2, it can be seen that the specific tear strength improves as the NBF content increases. Next, these base papers were heated and pressurized using a test supercalender to obtain a transparent sheet. Super calendar conditions are linear pressure 60Kg/cm, speed 4.5m/
The treatment was carried out at a roll surface temperature of 130°C. The relationship between the properties of the film sheet and the NBF blending ratio is shown below. From FIG. 3, it can be seen that the fracture length increases as the NBF content increases up to 20% by volume, but remains almost constant above that. According to Figure 4, the opacity of the film is NBF
Regardless of the blending ratio, it is 10% or less, and a highly transparent film can be obtained. In addition, although the in-plane specific resistance complies with SRIS2301,
Regardless of the presence or absence of NBF, no difference was observed in the in-plane resistivity, charging voltage, or half-life, indicating that NBF does not adversely affect the electrical properties of the sheet. From the above experimental results, the tearing length and specific tear strength required for paper making and heating and pressure treatment of the base paper are satisfied when the NBF blending ratio is 5% by volume or more. Also, regarding the strength of the film sheet,
It is recognized that NBF works effectively and does not have a negative effect on electrical characteristics. but,
Since NBF is in the form of rigid fibers, if the blending ratio exceeds 30% by volume, voids will appear in the film obtained after heating and pressing, making it difficult to obtain the desired film. Therefore, the blending ratio of NBF needs to be 30% by volume or less, and from the viewpoint of strength related to workability, it should be 5% by volume or more, preferably 10% by volume or more. Experimental example 2 The blending ratio of SWP/NBF/SSF is volume %,
Using paper stocks of 62.8/26.9/10.3 (weight ratio 35/15/50), target basis weights are 30g/m ² , 50g/m ² , 100g/m ² ,
Four types of sheet-like films of 200 g/m ² were produced. The properties of each film were as shown in Table 1.
Planar resistivity was based on SRIS2301 (the same applies to measurements of planar resistivity below).

[Table] From the results in Table 1, the target basis weight is 30g/m ² and 50g/m2.
It can be seen that even with a low basis weight product such as m ² , a product with in-plane specific resistance comparable to that of a high basis weight product can be obtained. In addition, the lower the basis weight, the lower the opacity.
It can be used in fields where transparency is required. Next, using a plastic shielding material evaluation device (Takeda Riken Kogyo Co., Ltd., TR17301), the shielding effect (electric field) for each frequency (MHz) was measured for the ^two 50g/m conductive films shown in Table 1, and the results are shown in Figure 5. Indicated. 30dB in the region up to 100MHz as shown
From the above, it was found that it has an electromagnetic shielding effect. In addition, almost the same effect was observed regarding the shielding effect (magnetic field). Example 1 A certain amount of SWP was 50% as thermoplastic synthetic pulp.
The mixture was poured into warm water at ℃ to give a concentration of 3%, and disintegrated with a stirrer. In addition, a certain amount of NBF as a thermoplastic composite fiber was dispersed in water at room temperature. Furthermore, SSF was prepared as a conductive fiber by dispersing it in water at room temperature to a concentration of 1%, and adding a small amount of an antifoaming agent to this. The mixing ratio of SWP/NBF/SSF in volume %,
82.2/16.5/1.3 (weight ratio 75/15/10), put it in a mixing tank and stir for more than 20 minutes, then add a small amount of dispersant to the raw material, and measure the basis weight in meters using a test machine. The base paper was manufactured with a target of 50 g/m ² . The drying of the base paper is at the melting point of the NBF sheath component, 96
~100~ above 100℃, SWP melting point below 123℃
It was carried out at 115℃. The production speed was 30 m/min, and even without any special mold release treatment on the dryer, the film could be easily released continuously from the dryer and there was no paper breakage. This base paper was supercalendered under the conditions of a linear pressure of 60 Kg/cm and a roll surface temperature of 130°C, which is above the melting point of SWP, 123°C, and below the melting point of the core component of NBF, 165-170°C. The paper passing speed was 4.5 m/min. For comparison, the base paper was prepared with the SWP/NBF/SSF blending ratio of 98.7/0/1.3 in volume% (weight ratio 90/0/10), that is, the same amount of SSF as in the example but without NBF. And a conductive film was manufactured. However, because the paper strength was weak, paper breakage occurred and continuous production was extremely difficult. Table 2 shows the physical properties of the base paper and conductive film for this example and comparative example.

【table】

[Table] The heat seal strength in the table is based on Tatsupi Standard T517-69, and the sheet conditions are crimping pressure 2
Kg/cm ² , crimping time 1 second, temperature 150℃, seal width 10
mm, the strength test was performed using a universal tensile tester Tensilon (manufactured by Toyo Baldwin Co., Ltd.) at a T-type peeling rate of 50
mm/min, the grip interval was 10 cm, and the width of the test piece was 2.5 cm. Table 2 shows that a conductive film with low opacity and high heat seal strength can be obtained. In comparison with the comparative example, a significant improvement in strength can be seen by replacing part of SWP with NBF. In particular, in base paper, the strength of the paper is more than doubled in terms of tearing length and more than three times as strong in terms of specific tear strength by adding NBF. This shows that this is a factor that allows the base paper to be easily continuous. Opacity is 5.5
%, which was comparable to ordinary transparent plastic film. Moreover, the obtained conductive film could be suitably used for preventing electrostatic damage. Example 2 Mixing ratio of SWP/NBF/SSF in volume %,
83.7/15.7/0.6 (weight ratio 80/15/5), target basis weight
A base paper and a conductive film were obtained in the same manner as in Example 1 using 25 g/m ² and 50 g/m ² . The physical properties are shown in Table 3.

[Table] The strength of the base paper is improved and the basis weight is reduced by adding NBF.
Similarly to Example 1, 25 g/m ² products could be easily and continuously manufactured. Due to the low content of SSF, the opacity is low, and the in-plane resistivity is sufficiently low. The obtained conductive film could be used satisfactorily as a bag for preventing dust from adhering to electronic components. Example 3 Mixing ratio of SWP/NBF/SSF in volume %,
A conductive film was obtained in the same manner as in Example 1, with a target weight of 62.8/26.9/10.3 and a target basis weight of 70 g/m ² . As in Example 1, continuous production could be easily carried out. The obtained conductive film has a basis weight of 69.5 g/m ² and an opacity.
39.5%, in-plane resistivity 1.5×10 ^-2 Ω-cm, breaking length
It was 2.43km. If the SSF compounding ratio is increased and the basis weight is 70g/m ² , transparency becomes inferior, but on the other hand, it has a shielding effect of 43dB against electromagnetic waves at a frequency of 500MHz, and a shielding effect of 43dB at 1GHz.
It had a shielding effect of 30 dB against electromagnetic waves at a frequency of , making it suitable for use as an electromagnetic shielding material. Example 4 Mixing ratio of SWP/NBF/SSF in volume %,
A conductive film was obtained in the same manner as in Example 1, with a sample weight of 87.2/10/2.8 and a target basis weight of 50 g/m ² . Example 1
could easily be serially produced. The obtained conductive film has a basis weight of 51.2 g/m ² and an opacity of 6.5.
%, surface direction specific resistance 7.5×10 ^-1 Ω−cm, fracture length 1.95Km
It was hot. Example 5 ES-Chop − instead of NBF as composite fiber
EA (manufactured by Chitsuso Co., Ltd., composite fiber of polyethylene and polypropylene, low melting point 100-110℃, high melting point 165
~170℃, fiber length 5mm, fineness 3 denier) (below)
(abbreviated as ES), the mixing ratio of SWP/ES/SSF is set to 77.2/20/2.8 in volume%, and the target basis weight is 50g/
m ² , base paper and conductive film were produced according to Example 1. The drying temperature of the base paper was set above the melting point of the low melting point portion of ES, 100 to 110°C, and below the melting point of SWP, 123°C, and continuous production was easy due to the fusing effect. The obtained conductive film has a basis weight of 49.5 g/m ² , an opacity of 6.8%, a tearing length of 2.38 km, and a specific resistance in the plane direction of 6.7×
It was 10 ^-1 Ω-cm. Example 6 Carbon fiber (pitch carbon fiber manufactured by Kureha Chemical Industry Co., Ltd., average fiber length 6 mm, single yarn diameter 12.5 μm) was used as the conductive fiber.
SWP, NBF and
Same as Example 1 except that Ni-CF was added.
Three types of conductive films were manufactured. The physical properties of each conductive film were as shown in Table 4.

[Table] [Effects of the Invention] Since the present invention has the above-described effects, the following effects can be obtained. Because the tensile strength and tear strength of the base paper and film are improved, the film can be removed from the dryer at high speed during the papermaking process, making it easy to continuously manufacture and process sheet-like conductive films without breaking the base paper or film. can be done. It is possible to manufacture thinner products than before. 70 again
It is also possible to produce a film with a low basis weight of less than g/m ² , particularly about 50 to 20 g/m ² . As a result of being able to manufacture a thin film, a highly conductive film can be obtained using a small amount of conductive fiber. As a result of being able to produce a thin film with fewer conductive fibers, it is possible to provide a packaging film with better transparency. Due to the improved strength, even if the film has a low basis weight and is thin, it is possible to incorporate a high amount of conductive fiber, and it is possible to provide a film for shielding electromagnetic waves. As a result of the above, by adjusting the basis weight, thickness, etc., it is possible to manufacture films with various characteristics depending on the application. Among the conductive films produced by the method of the present invention, those with a specific resistance in the planar direction of 10 ⁶ to ^{10 0} Ω-cm can be used as bags for preventing dust from adhering to electronic components and for preventing electrostatic damage. Those with a resistance of ⁰ Ω-cm or less are suitable for applications requiring electromagnetic shielding effects.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the breaking length of base paper and the blending amount of thermoplastic conjugate fiber. FIG. 2 is a graph showing the relationship between the specific tear strength of base paper and the amount of thermoplastic conjugate fiber blended. FIG. 3 is a graph showing the relationship between the breaking length of the conductive film and the blending amount of the thermoplastic composite fiber. FIG. 4 is a graph showing the relationship between the opacity of the conductive film and the amount of thermoplastic conjugate fiber blended. Fifth
The figure is a graph showing the electromagnetic shielding effect (electric field) of a conductive film.

Claims (1)

[Scope of Claims] 1 94.5 to 40% by volume of thermoplastic synthetic pulp, a first component having a melting point lower than the melting point of the thermoplastic synthetic pulp, and a second component having a melting point higher than the melting point of the thermoplastic synthetic pulp. After forming a wet paper using a paper stock consisting of a mixture of 5 to 30% by volume of thermoplastic composite fibers consisting of components and 0.5 to 30% by volume of conductive fibers (excluding those consisting only of carbon fibers), The first component is melted by heating and drying at a temperature higher than the melting point of the first component and lower than the melting point of the thermoplastic synthetic pulp, and a base paper in which the paper stocks are mutually bonded is produced, and then,
The base paper is heated and pressurized at a temperature higher than the melting point of the thermoplastic synthetic pulp and lower than the melting point of the second component to melt the thermoplastic synthetic pulp and form a film in which the second component and the conductive fibers are dispersed. A method for producing a conductive film having an in-plane specific resistance of 1×10 ⁶ Ω-cm or less, characterized by: 2. The method for producing a conductive film according to claim 1, wherein the film in which the second component and conductive fibers are dispersed has a transparency of 30% or less in terms of opacity. 3. The method for producing a conductive film according to claim 1, wherein the film in which the second component and conductive fibers are dispersed has a basis weight in meters of 70 g/m ² or less. 4. The method for producing a conductive film according to claim 1, wherein the conductive fiber is a metal fiber or a metal-coated fiber. 5. The method for producing a conductive film according to claim 4, wherein the metal fibers are stainless steel fibers. 6 The thermoplastic composite fiber has the second component as the core and the first component as the core.
The method for producing a conductive film according to claim 1, wherein the conductive film is a composite fiber having a concentric or eccentric structure with the component as a sheath.