JPS63275796A - Conductive paper and laminate thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a conductive paper and a conductive laminate, and more particularly to a conductive paper containing conductive synthetic fibers having a two-layer coating of copper and nickel. The present invention also relates to a conductive laminate in which this conductive paper and a sheet-like member are laminated.

Since the conductive paper and conductive laminate of the present invention have conductivity, they are suitable as static electricity generation prevention materials and electromagnetic wave shielding materials.

[Conventional technology]

In recent years, composites of metal powder, metal fibers, inorganic fillers having metal coatings, such as mica, glass beads, etc., and resins have been known as materials for electromagnetic shielding.

(Japanese Patent Application Laid-Open No. 57-65754.

JP-A-58-161205, JP-A-58-192
On the other hand, conductive paper made by mixing carbon fibers or fibrous metals with fibrous substances such as pulp has been known for some time (see Publication No. 202, etc.).
Special Publication No. 45-32766, Special Publication No. 49-2124
(see Publication No. 2, etc.) and is commercially available as an antistatic material.

In addition, many composites consisting of conductive fibers and fibrous binders of polymeric substances have recently been proposed (
JP-A-61-127199, JP-A-61-225
(See Publication No. 398, etc.).

[Problem that the invention seeks to solve]

In recent years, as electronic devices have become smaller and more dense, malfunctions and noise caused by electromagnetic waves that pass through their packages and housing materials have become major problems. Also, IC
Destruction occurs in semiconductor devices such as LSIs and LSIs due to electrostatic discharge. Furthermore, accidents have also occurred in magnetic recording media such as magnetic tapes, ID cards, floppy disks, and hard disks in which records are lost due to electrostatic discharge or electromagnetic waves.

In order to solve these problems, composites of conductive fillers and resins have been proposed and are being adopted for packages and casings of new electronic devices. However, it is not only extremely difficult to uniformly disperse metal powder, metal fibers, fillers with metal coatings, etc. in resin, but also because electromagnetic shielding properties deteriorate due to oxidation of the metal, making it difficult to obtain products with stable performance. It is either difficult to obtain, or even if it is available, it is quite expensive. Furthermore, it is extremely difficult to apply these composites to electronic devices that have already been manufactured.

On the other hand, it is possible to improve the performance of conductive paper, which has been commercially available for preventing static electricity generation, and to attach it to the packages and casings of electronic devices, but carbon fiber It is thought that conductive fibers with a large aspect ratio, such as stainless steel fibers, are required. However, since carbon fibers and fibrous metals are extremely expensive, conductive paper using them is also extremely expensive and difficult to employ.

In addition, instead of these conductive fibers, it is also possible to coat natural fibers (bulbs) or synthetic fibers with metal to give them conductivity, and add them to paper stock to make conductive paper. In the case of fibers with a large fiber length, that is, a large aspect ratio, they tend to pill when handled, making it difficult to form a uniform metal coating by plating.
In addition, during paper making, the dispersibility is poor and it is not uniformly dispersed in the paper layer, making it impossible to obtain conductive paper with high static electricity generation prevention properties and electromagnetic shielding properties. In addition, in the recently proposed conductive sheet using a fibrous binder,
Long fibers are used as conductive fibers, and a fibrous binder is used to improve their adhesion, but it is extremely expensive as it requires a large amount of conductive fibers and uses expensive fibers. Become something.

An object of the present invention is to provide an economical conductive paper and a laminate thereof that are excellent in static electricity generation prevention properties and electromagnetic wave shielding properties.

[Means for solving problems]

As a result of intensive research to achieve the above object, the present inventors have discovered that a paper material containing conductive fibers made of synthetic fibers with a relatively short fiber length plated with two layers of copper and nickel, and natural fibers such as bulbs, etc. It was discovered that the conductive paper obtained by paper-making has extremely excellent electromagnetic shielding properties, and the present invention was completed.

The present invention provides a conductive paper characterized by containing synthetic fibers having a two-layer coating of copper and nickel and an average fiber length of 2 mm or less, and a sheet-like member laminated on at least one side of the conductive paper. This is a characteristic conductive laminate.

In the present invention, synthetic fibers mean fibers with an average fiber length of 2 mm.
Below, the fiber diameter is 1 to 3 deniers, the aspect (fiber length/
Synthetic fibers such as nylon fibers, polyester fibers, vinylon fibers, acrylonitrile fibers, etc. with relatively short fiber lengths with a diameter) ratio of 20 to 200 have a uniform wire diameter and a small specific surface area. Those having a specific surface area of 0.2 nf/g or less are particularly preferred.

The conductive fiber is a fiber with an aspect ratio of 20 to 200 and has a two-layer coating of copper and nickel, which is obtained by plating the synthetic fiber with copper and further plating nickel on the copper coating.Copper coverage with respect to synthetic fiber 0 is 20 to 50% by weight,
Preferably it is 25% by weight or more, more preferably 35% by weight or more.

Further, the coverage rate of nickel may be as long as it can prevent oxidation of copper, and is usually 5 to 20% by weight.

Chemical copper plating is usually used for copper plating of synthetic fibers, and electroplating or chemical plating can be used for nickel plating, and they can also be used together. 0 Usually, electroplating is preferably used. .

The conductive paper contains the conductive fibers and a fibrous substance,
A paper stock with various additives added as desired has a basis weight of 50 g/g or more, preferably 80-1
20 glrd paper.

The content of conductive fibers in conductive paper varies depending on the aspect ratio and metal coverage of the conductive fibers, but on a dry basis it is 1.
It is 0% by weight or more. In particular, in order to obtain high electromagnetic shielding properties, the content is preferably 20% by weight or more, more preferably 30% by weight or more.

As fibrous substances, wood valve, bast fiber 1, hair fiber 2
Plant natural fibers such as leaf fibers, nylon fibers.

Vinylon IT polyester fiber, polyethylene fiber,
Synthetic fibers such as polypropylene fibers, inorganic fibers such as glass fibers, asbestos fibers, and alumina fibers, carbon fibers, and mixtures thereof can be used. In particular, conductive paper that uses thermoplastic resin fibers such as polyethylene or polypropylene as the fibrous material and heat-fuses the resin fibers using a calender after papermaking has high strength and the conductive fibers are strong. Because it is fixed, it has excellent electromagnetic shielding properties and is extremely useful.

As additives, surface treatment agents such as surfactants and camping agents to improve the dispersibility of conductive fibers during paper making,
Binding agents such as modified starch, vegetable gum, carboxymethyl cellulose, polyacrylamide, urea resin, and melamine resin to improve the bonding properties of paper stock components, as well as aluminum sulfate, calcium carbonate, etc. commonly used in paper making.
Examples include fillers such as clay, coloring agents, and the like.

In the present invention, the conductive laminate is obtained by laminating a sheet-like member on at least one side of the conductive paper to improve the strength of the conductive paper.

As a sheet-like member, for example, natural valve paper.

Examples include synthetic paper, plastic film, nonwoven fabric, etc., and from the viewpoint of reinforcing the conductive paper, a sheet-like member having a higher tensile strength than the conductive paper is preferably employed.

There is no particular restriction on the method of laminating the conductive paper and the sheet-like member, and for example, a paper making method, an adhesion method, etc. can be employed. In addition, plastic films such as polyvinyl chloride, polyethylene, polypropylene, polyester, and polyamide can be laminated using the lamination method, and these laminated papers can be used as conductive papers that can be heat-sealed by utilizing the thermal adhesive properties of plastic films. can be used.

[For production]

As described above, the conductive paper of the present invention is characterized in that it contains conductive fibers, which are synthetic fibers having a relatively short fiber length and coated with copper-nickel in two layers, as a paper stock component.

In general, conductive paper exhibits higher conductivity as the conductive fiber content and basis weight increase, but in the present invention, when the conductive fiber content is 30 to 40% by weight and the basis weight is 80 g / - Shows electromagnetic shielding characteristics of 40 dB or more in all frequency ranges specified in ES-7-83. This electromagnetic shielding property is comparable to that of a conductive paper containing 60% by weight of the same basis weight when compared with conductive paper containing stainless steel fibers, which was conventionally considered to be very good.

These effects are due to the fact that the specific gravity of conductive fibers with a uniform copper-nickel double-layer coating formed on synthetic fibers is less than 1/3 of that of metal fibers, which is close to the specific gravity of natural and synthetic bulbs. It is presumed that good electromagnetic shielding properties are developed due to improved dispersibility of the conductive fibers in the paper stock component and improved adhesion between the conductive fibers and the bulb.

The conductivity of the conductive paper improves as the aspect ratio of the conductive fibers increases, i.e., it is preferable to use long fibers as the base fiber rather than short fibers, but when long fibers are used, a uniform metal coating can be obtained. Moreover, it is difficult to uniformly disperse it into other paper stock components during paper making.

Therefore, in consideration of the ability to form a metal film and the dispersibility into paper stock components, it is preferable to use synthetic fibers with a high aspect ratio and an average fiber length of 2 mm or less, and more preferably, an average fiber length of 0 mm or less. 3-1. 0mm, use one with an aspect ratio of 20 or more.

The adhesion rate of metal to synthetic fibers (hereinafter referred to as "metallization rate") also affects the conductivity of conductive paper.

If the copper metallization rate is too low, a uniform copper film will not be formed and the conductivity will decrease; if it is too high, the density as a filler will increase and the dispersibility in paper stock components will decrease. It is difficult to obtain conductive paper that exhibits homogeneous conductivity. Therefore, the metallization rate by copper is 20 to 50% by weight, preferably 25 to 45% by weight, more preferably 35 to 40% by weight.
It is. On the other hand, the metallization rate with nickel is 5 to 20% by weight, preferably 8 to 13% by weight, which can prevent oxidation of the copper coating.
Weight % is used.

Conductive paper (synthetic paper) is produced by using thermoplastic synthetic valves such as polyethylene or polypropylene as the fibrous material to be paper-made together with the conductive fibers, and by heat-sealing the synthetic valves using a calender after paper-making. In addition to improving the strength, the conductive fibers are firmly fixed, so they exhibit superior electromagnetic shielding properties compared to natural fibers used in bulbs, etc. Also, in conductive laminates, they are more effective than conductive paper. By laminating the conductive paper on a sheet-like member that has high strength, the strength is improved and it becomes possible to apply it to a wider range of objects.

〔Example〕

The present invention will be explained in more detail with reference to Examples and Comparative Examples.

However, the scope of the present invention is not limited in any way by the following examples.

(1) Preparation of conductive paper (a) Preparation of conductive fibers Short polyester fibers with an average diameter of 15 μm and an average length of 0.8 mm are chemically copper plated to form a copper film using a conventional method, and then chemically nickel plated. Copper metallization rate 40.8
Weight%, nickel metallization rate 9.4% by weight, density 2.40
conductive fiber with a double-layer coating of copper-nickel of g/-
F-1) was prepared.

In preparing the conductive fiber (F-1), electrolytic nickel plating was performed instead of chemical nickel plating, and the copper metallization rate was 40.5% by weight, the nickel metallization rate was 10.5% by weight, and the density was 2.42g. A conductive fiber (F-2) having a copper-nickel double layer coating of /c+J was prepared.

Furthermore, as a conductive fiber for comparison, an average diameter of 8 μm,
Stainless steel fibers (C-1) with an average length of 5 mm and a density of 7.93 g/cd and polyester long fibers with an average diameter of 15 μm were subjected to chemical copper plating treatment and chemical nickel plating treatment, and then cut to an average length of 3.5 mm. Copper metallization rate 4
A conductive fiber (C-2) having a two-layer copper-nickel coating having a nickel metallization rate of 1.0% by weight, a nickel metallization rate of 10.3% by weight, and a density of 2.44 g/- was prepared.

(2) Preparation of conductive paper Canadian freeness test value 370mj! Using bleached softwood kraft bulbs (NBKP) and the conductive fibers prepared above as paper stock components, changing the mixing ratio and basis weight, conductive paper (NBKP) was prepared using a hand paper machine in accordance with JISP-8209. -1) to (P-8) and conductive paper for comparison (
CP-1) to (CP-4) were prepared.

(3) Preparation of conductive synthetic paper A synthetic valve (polyethylene 5WP-400) and the conductive fiber prepared above were used as paper stock components, and the mixing ratio was changed using a hand paper machine in accordance with JIS P-8209. After paper making, the fibers are thermally fused using a calender (140
℃) to prepare conductive synthetic papers (P-9) to (P-11).

(4) Evaluation test of conductive paper Regarding the conductive paper prepared above, the surface resistance value (Ω/s
q) and a near-field measurement jig (NFC-1000, manufactured by Electrometric) using ASTM ES7
-83 compliant frequency characteristics were measured.

The measurement results are shown in Table 1.

(4) Conductive laminate conductive fiber (F-1) and N used in the above item (2)
A conductive paper layer with a basis weight of 80 g/rrf and a conductive paper layer with a basis weight of 60 g/n
A conductive laminate (P-12) consisting of two layers, f and a paper layer not containing conductive fibers, was prepared.

Regarding the obtained conductive laminate (P-12), the above-mentioned (
The same evaluation test as in section 3) was conducted.

The evaluation test results are shown in Table 1.

〔Effect of the invention〕

In the present invention, the conductive paper obtained in the above example is
As shown in Table 1, this paper exhibits superior surface resistance and frequency characteristics to conductive papers containing stainless steel fibers as conductive fibers (see Comparative Examples 1 and 2). In addition, it has a superior surface resistance value compared to conductive paper (Comparative Examples 3 and 4), which is made by cutting polyester long fibers having a double-layer metal coating similar to the conductive fibers used in the present invention and used as conductive fibers. and frequency characteristics. Furthermore, in the conductive laminate, the conductive paper layer side exhibits excellent conductivity, and the paper layer side exhibits excellent insulating properties and excellent frequency characteristics. Using conductive fibers with a double layer of copper-nickel coating formed on inexpensive synthetic fibers,
The present invention provides a conductive paper and a laminate thereof having conductivity (surface resistance) and electromagnetic shielding properties (frequency characteristics) superior to that of conductive paper containing stainless steel fibers, and its industrial significance is extremely large.

Claims (2)

[Claims] (1) Conductive paper characterized by containing synthetic fibers having a double-layer coating of copper and nickel and having an average fiber length of 2 mm or less (2) A conductive laminate characterized in that a sheet-like member is laminated on at least one side of a conductive paper containing synthetic fibers having a two-layer coating of copper and nickel and an average fiber length of 2 mm or less.