JPS5944709A - Electromagnetic wave shield paper - 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 The present invention involves making paper by mixing water-dispersible fibers and conductive materials.
This paper relates to paper that has electromagnetic shielding properties.

The rapid development of high-density integrated circuit technology has led to the widespread use of digital devices, such as in computers, electronic cash registers, digital clocks, calculators, word processors, video games, etc.

The problem of electromagnetic interference has been pointed out as plastics have been used as housing cases for these devices in place of the sheet metal and aluminum die-casting that were conventionally used due to the need for miniaturization and mass demand. ing.

Plastic itself has a high electrical insulation property (as it is, electromagnetic waves pass through it, so it is not effective in shielding the electromagnetic waves that are generated by digital devices and cause noise that interferes with the reception function of radios, televisions, etc.). A common method for shielding is to form a conductive layer on the surface, but this method involves molding the case, applying a surface treatment, and then applying a conductive agent, which is expensive. However, there was a problem with the durability of the surface coating layer.

In addition, the method of kneading conductive filler into plastic to form a shield has poor dispersion of the conductive filler, and when the kneaded material is injection molded, the conductive filler tends to stay in the nozzle or bent part. Therefore, it is difficult to obtain a uniform sheet (furthermore, since contact between the conductive fillers is likely to be inhibited by the plastic, the shielding effect is often insufficient).

The present invention provides a novel electromagnetic shielding paper that can be used as an alternative to slanted plastic materials. The electromagnetic shielding paper according to the present invention has a volume resistivity of 103 to 10-39 cm by blending water-dispersible fibers with conductive fibers or powder.
It is characterized by being made into paper.

Conventionally, there have been cases in which conductive fillers are added to discharge breakdown recording paper and electrostatic recording paper, but in this case, the volume resistivity is adjusted to about 104 to 107 Ω-cs, It has almost no electromagnetic wave shielding properties and is C free. Furthermore, antistatic paper only removes static electricity and does not have an electromagnetic shielding effect.

The electromagnetic shielding paper according to the present invention is produced by preparing a uniform slurry containing water-dispersible fibers and conductive fibers or powder,
This slurry is obtained by making paper using a conventional method.

The water-dispersible fibers used in the present invention include tree fibers such as ice-phase pulp (softwood pulp, hardwood pulp), cotton pulp, straw pulp, bamboo bulb, bagasse pulp, Manila hemp pulp, flax pulp, jute pulp, and waste paper pulp;
Also mineral #! Asbestos fiber, glass 7 aiba,
Examples include p-tsuku wool, silica fiber, and synthetic pulps such as polyethylene pulp, polypropylene pulp, polyester pulp, and polyamide pulp.

Examples of conductive fibers include aluminum, aluminum alloy, copper, copper alloy, iron, stainless steel, zinc, lead, nickel, tin, carbon fiber, etc., and the fiber length is 10077~
60 and a fiber diameter of about 5 to 100 μm is sufficient.

Further, examples of the conductive powder include aluminum, aluminum alloy, copper, copper alloy, iron, stainless steel, zinc, lead, nickel, tin, and carbon. The size of the powder is 1
It is preferable to use a powder of about μ to 3 fins, and it is particularly desirable to use flaky powder.

The blending ratio is preferably about 85 to 10% by weight of water-dispersible fibers to 15 to 90% by weight of conductive fibers or powder; if the content of water-dispersible fibers is less than 10% by weight, the strength will be insufficient. On the other hand, conductive fibers or powders can improve uniformity from 15% by weight.

In the present invention, water-dispersible fibers are blended and formed into a sheet in a wet process, so that the water-dispersible fibers and conductive fibers or conductive powder are completely mixed, and they are diluted with a large amount of water to form a slurry. Therefore, the sheet forming process from the flow box to the wire part is improved, and a uniform sheet can be obtained in both the width direction and the direction of travel. Furthermore, by passing through a press process or a calender process after forming the sheet, the contact state between the conductive substances becomes good, and accordingly, the volume resistivity is low and stable, and the electromagnetic shielding effect is improved.

In addition, when producing the electromagnetic shielding paper of the present invention, magnetic powder such as ferrite, spinel type ferrite, nickel-zinc ferrite, magnetic iron oxide, etc. is added to the paper stock slurry containing the above-mentioned water-dispersible fibers and conductive fibers or conductive powder. Combining these is particularly effective in enhancing the performance as an electromagnetic wave absorbing material. In addition, binders can be added for the purpose of improving strength, chemical resistance, or flexibility. Examples include synthetic polymeric substances such as chloroprene, emulsion dispersion, starch/gelatin, and natural polymeric substances such as natural rubber. Furthermore, the use of flocculants is effective in increasing productivity and improving drainage.

The electromagnetic shielding paper obtained by the present invention can be effectively used not only for electromagnetic shielding of cases for electronic devices, cables and connectors, but also for interior decoration of rooms in which electronic devices are installed.

The present invention will be explained below according to examples. Furthermore, during the explanation,
Parts indicate parts by weight of solid content.

[Example 1] Aluminum fiber #e with an average fiber diameter of 25 μm and an average length of 6 μm
20 parts of aluminum powder with an average particle size of 200μ were previously dispersed in water, 60 parts of softwood unbleached sulfate pulp (Canadian standard f water content 450cc) was added to this dispersion, and the mixture was mixed in a lab mixer for 5 minutes. After stirring, add 5 88R latex
part was added and stirring continued. Furthermore, 2 parts of 5-minute diameter sulfuric acid band were added to prepare a paper stock slurry having a concentration of 0.5%.

The solid content of this paper stock slurry was 4.8P, and TAPP
The paper was made using an I-type hand sheet machine. At this time, the slurry white water that had passed through the wire was circulated to bring the yield close to 100%. The obtained sheet was sandwiched between two pieces of 60 mesh plastic wire and pressed for 5 minutes at a load of 3.5 t/- to dehydrate it.The sheet was then attached to a stainless metal plate and dried at 50°C for 1 hour, then the load was removed. It was pressed at 10 kg/cd for 5 minutes to obtain electromagnetic shielding paper.

[Example 2] Bagasse sulfate pulp (Canadian Standard T) Suisan 300 was added to a dispersion of 50 parts of copper fibers with an average fiber diameter of 40 μm and an average length of 3 fibers.
ω) After adding 50 parts and stirring with a lab mixer for 5 minutes, SB
5 parts of R latex was added, and while stirring, 2 parts of 5-minute diameter sulfuric acid band were added to prepare a stock slurry having a concentration of 0.5%. The solid content of this paper stock slurry was taken as IOJ' and an electromagnetic shielding paper was prepared under the same conditions as in Example 1.

[Example 3] 30 parts of copper fibers with an average length of m, a fiber diameter of 40 μm, and an average length of 6 corners and 50 parts of aluminum powder with an average particle size of 1.5 fi were dispersed in water in advance, and 20 parts of polyethylene pulp was added. A paper stock slurry of grade 2 was prepared by stirring with a lab mixer.

The solid content of this paper-sized slurry was 481, and electromagnetic shielding paper was prepared in the same manner as in Example 1.

[Example 4] 40 parts of copper powder with an average particle size of 150 μm was washed and dispersed in advance, and softwood unbleached sulfate pulp (Canadian standard 1 water strength 450
c1! ) and 10 parts of 8BR latex were sequentially added, and while stirring was continued, 2 parts of 5-minute diameter sulfuric acid band were further added to prepare a paper stock slurry having a concentration of 0.5%. The solid content of this paper stock slurry was taken at 4Xp, and as in Example 1, KL-
Ctt magnetic sheeted paper was prepared.

[Example 5] 30 parts of stainless steel fibers with an average fiber diameter of 401' and an average length of 3 and 20 parts of turite powder with an average particle size of 2 μm were dispersed in water in advance, and asbestos (Quebec Standard 6, Canada) was dispersed in water. After adding 50 parts of NBR latex and stirring for 5 minutes with a lab mixer, add 10 parts of NBR latex.
While stirring, 2 parts of 5-minute diameter sulfuric acid band were further added to obtain a paper stock slurry having a concentration of 0.5%. 11f of this paper stock slurry was sampled in terms of solid content, and an electromagnetic shielding paper was prepared in the same manner as in Example 1.

[Example 6] 20 parts of aluminum fibers with an average fiber diameter of 25 μm and an average length of 6 fl and 30 parts of brass powder with an average particle size of 100 μm were previously dispersed in water, 50 parts of polypropylene pulp was added, and the mixture was mixed in a lab mixer for 5 minutes. After ffl stirring, SBR latex 5
After 5 minutes of stirring, 0.5 part of cationic polyacrylic amide was added to prepare a paper stock slurry having a concentration of 2%. This paper stock slurry was collected in solid form at 482 TA
The paper was made using a PPI type hand sheet machine. The paper forming conditions were the same as in Example 1 except that the load after drying was 5 Ky/cl.

[Examples 7 and 8] Electromagnetic shielding papers were prepared in the same manner except that the strength was increased to 100 kF/-.

[Example 9] Aluminum fiber 7 with an average fiber diameter of 15μ and an average length of 3 fins
15 parts of zinc powder with an average particle size of 1 fin was previously dispersed in water, 10 parts of cotton lint was added thereto, and after stirring, 5 parts of 88R latex was added, and while stirring, cations were added. A paper stock slurry having a concentration of 2% was prepared by adding 0.5 part of polyacrylamide, and this slurry was made using a Fourdrinier paper machine to obtain electromagnetic shielding paper.

/ [To Comparative Example] 10 parts of carbon fiber with an average fiber diameter of 20 μm and an average length of 6 fins was dispersed in water in advance, and 90 parts of unbleached sulfate Norkurup was added and stirred with a lab mixer to adjust the concentration. A 0.5 inch paper stock slurry was prepared. The solid content of this paper stock slurry was 4.41, and a paper was obtained in the same manner as in Example 1.

[Comparative example Atsushi]

31/- 100 parts of aluminum fibers with an average fiber diameter of 25 μm and an average length of 6 are divided into water, to which 5 parts of 1C8BR latex is added, and while stirring, 2 parts of sulfuric acid band with a 5-minute diameter is added to the solution to give a concentration. A 0.5% stock slurry was prepared. This paper stock slurry was sampled in a solid content of 8 f, and a paper was obtained in the same manner as in Example 1.

The following quality evaluations were performed on the products obtained in each of the above Examples and Comparative Examples.

(C for 11 thickness, basis weight, and tensile strength are each JI8P
8118, JI8P8124, and Jt8P8113 were trapped, and an antenna was placed 20C1l away from them and measured using a field strength measuring device.

The results are summarized in Table 1.

1N Kaisho 59-44709 (Age) As is clear from Table 1, Comparative Example 1 with a volume resistivity of 10Ω-(up to) has almost no electromagnetic shielding effect. In Comparative Example 2, which did not contain electromagnetic wave shielding properties, the strength was low and the handling workability was poor.On the other hand, the electromagnetic wave shielding papers according to each example had good shielding effects. In addition to this, the handling and workability are also good.

Patent applicant Jujo Paper Co., Ltd. 39-

Claims (1)

[Claims] (1) An electromagnetic shielding paper made by blending water-dispersible fibers with conductive fibers or powder and having a specific resistance of 103 to 10-30.