WO2002008334A1

WO2002008334A1 - Composition of cellular phone case for shielding electromagnetic wave and method of manufacturing cellular phone case using the same

Info

Publication number: WO2002008334A1
Application number: PCT/KR2001/001199
Authority: WO
Inventors: Jong-Young Lee; Yang-Seok Jeon; Yong-Sung Choi; Do-Sung Hwang
Original assignee: Msbk Co., Ltd.
Priority date: 2000-07-12
Filing date: 2001-07-12
Publication date: 2002-01-31
Also published as: KR20020006317A; CN1436212A; AU2001269596A1

Abstract

The composition of a cellular phone case for shielding electromagnetic wave in order to prevent any malfunction of the cellular phone due to the electromagnetic wave interference and minimize radiation of the electromagnetic wave into a human body, includes 90 to 70 w% of synthetic resins selected in a group consisting of polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS) and blend of PC and ABS, and 10 to 30w% of electromagnetic wave absorber with a particle size of 0.1 to 30νm.

Description

COMPOSITION OF CELLULAR PHONE CASE FOR SHIELDING

ELECTROMAGNETIC WAVE AND METHOD OF MANUFACTURING

CELLULAR PHONE CASE USING THE SAME

TECHNICAL FIELD

The present invention relates to a cellular phone composition and

method for manufacturing a case of the cellular phone using the

composition which prevents malfunction of the cellular phone due to an

electromagnetic wave thereof and minimizes penetration of the

electromagnetic wave from the cellular phone into the body.

BACKGROUND ART

Typically, cellular phone cases for shielding an electromagnetic

wave generating therein were developed by a method in which a case

was made by projecting PC/ ABS blending and ABS material in

thermoplastic resin and metal of high-conductivity was coated inside

the case to shield the electromagnetic wave. In this method, materials

with high conductivity should be developed to fully shield the

electromagnetic wave for preventing malfunction of the cellular phone.

Also, as the cellular phone is getting smaller and driving voltages

applied to devices in the cellular phone are getting lower, the more

shielding materials should be coated to obtain shielding effect. Moreover, the method generates manufacturing errors in the process of

coating the conductive materials on the cellular phone, which makes

the price of product relatively high.

Also, since secondary electromagnetic wave interference occurs

between adjacent devices due to electromagnetic wave shield, a

shielding means may be additionally installed therebetween with

additional work and time. Also, an element in a type of a metal can is

inserted in the projectile as the additional shielding means, which

increases the manufacturing cost and errors.

Almost, conductive material such as silver (Ag) is used as the

electromagnetic wave shielding materials. As the cellular phone is

getting smaller and driving voltages applied to devices in the cellular

phone are getting lower, the shielding means should have higher

conductivity, which makes the price of product high and improvement

of quality of devices difficult.

Also, typical cellular phones focus prevention of malfunction of

the devices while disregarding the shield of electromagnetic wave that

may be harmful to a user with long-term use thereof.

Conventionally, products made by adding inorganic or organic

antibacterial agent to plastic such as polyethylene, polypropylene and

polyvinyl chloride, epoxy or tiles are applied to various goods such as

water containers, sheets, fiber and paint. However, since the antibacterial agent is relatively expensive, the price of products is high,

and color may fade with long-term use.

DISCLOSURE OF INVENTION

The present invention is designed to overcome the problems of the

prior art. An object of the invention is to provide a composition of

cellular phone case made by adding electromagnetic wave absorbents

into a resin of case to thereby increase the shielding effect of

electromagnetic wave and prevent malfunction of the device together

with the simplification of manufacturing process and lower-cost of

products, and a manufacturing method of the cellular phone using the

composition.

To achieve the above object, there is provided a composition of a

cellular phone case comprising: synthetic resin of 90~70wt% selected

from the group consisting of polycarbonate, polymer blend of

polycarbonate and acrylonitrile-butadiene-styrene and ABS resin; and

an electromagnetic wave absorbent of 10 ~ 30wt% having the particle

size of 0. 1 — 30/tm.

Preferably, the electromagnetic wave absorbent is one or more

selected from the group onsisting of Mn-Zn-, Ni-Zn-, Mg-Zn-, and

Mg-Zn-Cu-ferrite.

According to another aspect of the present invention, there is provided a cellular phone case which is made by ejaculation using the

above composition.

Preferably, the cellular phone case may be coated with a

conductive material on over inner and outer surfaces thereof.

Alternatively, the conductive material is coated only on separation walls

which are formed inside the case.

According to another aspect of the present invention, there is

provided a method for manufacturing a cellular phone case comprising

the following steps of:

extruding synthetic resin of 90~70wt% selected from the group

consisting of polycarbonate, polymer blend of polycarbonate and

acrylonitrile-butadiene-styrene and ABS resin, and one or more

electromagnetic wave absorbents of 10 ~ 30wt% having the particle size

of 0.1 ~ 30μm selected from the group consisting of Mn-Zn-, Ni-Zn-,

Mg-Zn-, and Mg-Zn-Cu-ferrite at the temperature of 180 ~315^°C to

manufacture pallet resin; and

ejaculating the pellet resin into a mold at the temperature of

180 ~ 315 ^°C to form the case .

Preferably, the method further comprises the step of coating a

conductive material on at least a portion of the surface of the case.

Also, the conductive material is coated by spray coating, sputtering or

non-electrolytic plating. Also, the method further comprises the step of attaching a

conductive sheet inside the case.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of preferred

embodiments of the present invention will be more fully described in the

following detailed description, taken accompanying drawings. In the

drawings:

FIG. 1 shows a cellular phone case provided with electromagnetic

shield composition according to the present invention;

FIGs. 2 and 3 show a cellular phone case on which conductive

coating layer is formed according to the present invention; and

FIG. 4 is a diagram for illustrating a cellular phone case whose

separating walls are coated with coating layer.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will

be described in detail with reference to the accompanying drawings.

FIG. 1 exemplarily shows a cellular phone adopting a composition

of the present invention. Generally, the cellular phone comprises a

case 12 and separating walls 14 to separate a plurality elements each other in the case 12. The case 12 and separating walls 14 are made of

an electromagnetic wave shield composition of the invention as

described below.

In order to manufacture the electromagnetic wave shield

composition, an electromagnetic wave absorbent 10 — 30wt%, one or

more selected from the group consisting of Mn-Zn-, Ni-Zn-, Mg-Zn-, and

Mg-Zn-Cu-ferrite, having the particle size of 0. 1 — 30/ffli is mixed with

polycarbonate (hereinafter 'PC), polymer blend of polycarbonate and

acrylonitrile-butadiene-styrene (hereinafter 'ABS'), or ABS resin

90~70wt%, and then extruded by an extruder at the temperature of

180 — 315 ^°C . Here, the extrudate is manufactured as electromagnetic

wave shield pellet resin suitable for mass production using a pelletizer.

After that, the cellular phone case 12 is manufactured by

injecting the electromagnetic wave shield resin containing the

electromagnetic absorbent of 10wt% or 20wt% into a mold utilizing a

catapult. Here, the resin is ejaculated to the cellular phone case under

the condition of the temperature of 180 ~ 315^°C in the catapult, the

mold temperature of 60 — 125^°C , the screw speed of 30 — l lOrpm, the

ejaculating pressure of 400- 1200kg/ mπf.

A cellular phone case by the above method turned out to have an

absorption capacity over the broad band enough to fully shield

electromagnetic wave generating from the local oscillation frequency of 19.6MHz, the RX intermediate frequency of 85.38MHz, the TX

intermediate frequency of 130.38MHz and the communication

frequency of 800 ~900MHz for CDMA, and the RX intermediate

frequency of 130.38MHz, the TX intermediate frequency of 260.76MHz

and the communication frequency of 1500 — 2000MHz for PCS

The inner sides of the cellular phone case 12 may be coated with

a conductive material in order to increase an electromagnetic wave

shielding ratio thereof. FIG. 2 shows a cellular phone case 12 whose

inner surfaces are formed with a coating layer 20 by coating a

conductive material thereon. Such a coating layer 20 increases the

electromagnetic wave shielding ratio to thereby efficiently prevent the

emission of electromagnetic wave.

The conductive materials used in the conductive coating layer 20

may be one of a copper (Cu) ion, a nickel (Ni) ion, an iron (Fe) ion, a

silver (Ag) ion, or a mixture thereof, or conductive polyethylene.

For example, the coating layer 20 may be formed by

manufacturing two cellular phone cases with two resin containing the

electromagnetic wave absorbent of 10wt% and 20wt% respectively

under the same ejaculating condition as the above and coating

conductive materials on the inner sides of the cellular phone cases.

In the above embodiment, a cellular phone case made of the

resin containing the electromagnetic wave absorbent of 10wt% had the electromagnetic wave shielding ratio of 90%, while the electromagnetic

wave shielding ratio of a cellular phone case whose inner surfaces are

formed with the conductive coating layer 20 amount to more than 95%.

In case that the conductive coating layer 20 was formed on the

inner surfaces of a cellular phone case containing the electromagnetic

wave absorbent of 20wt% having a superior shielding ratio, malfunction

of the cellular phone due to the electromagnetic wave absolutely did not

occur and attenuated the electromagnetic wave to thereby minimize the

penetration of electromagnetic wave into body without any interferences

to telephone conversation.

In a cellular phone case made of pellet resin containing the

electromagnetic wave absorbent of more than 20wt%, additional effect

by the conductive layer was not so much. Accordingly, in the

manufacture of cellular phone case made of pellet resin containing the

electromagnetic wave absorbent of 20~30wt%, the coating process can

be omitted to reduce the manufacture cost.

Also, when a cellular phone case ejaculated from a pellet resin

containing the electromagnetic wave absorbent of more than 10wt% is

coated with the conductive materials, a manufacturing error, if it occurs,

in the coating process never influence the quality of products, which

reduce inferior products and manufacturing cost.

Such a coating layer may be formed on the outer surface of the cellular phone case 12. As shown in FIG. 3, coating layers 20 and 22

are formed on both inner and outer surfaces of the cellular phone case

12, which enhances the efficiency of the electromagnetic wave shield.

The coating may be accomplished by spay process, sputtering or

non-electrolytic plating.

Alternatively, a sheet having conductivity may be inserted into

the cellular phone case treated to shield the electromagnetic wave,

instead of forming the conductive coating layer as described above. In

this case, the conductive sheet provides the same effect for shielding the

electromagnetic wave as the coating layer.

Also, the conductive sheets may be additionally attached after

the conductive coating layers are formed on inner surface or on both

inner and outer surfaces of the cellular phone case. At this time, the

conductive sheets are preferably inserted in the cellular phone case 12.

According to another embodiment, two cellular phone cases

containing the electromagnetic wave absorbents of 10wt% and 20wt%

respectively are manufactured, and then conductive materials may be

coated on separating walls 14 which are formed in the manufactured

cellular phone case 12. Referring to FIG. 4, even separating walls 14

are formed to separate electric devices in the cellular phone case 12, the

electromagnetic wave may interfere the devices to bring malfunction of

operation. Accordingly, interference of electromagnetic wave with each other can be prevented by forming the conductive coating layer 24 on

the separating walls 14.

Since such a configuration can relatively reduce area to be

coated, cost for coating process may be saved and manufacturing

process may be simplified.

As described above, the cellular phone case of the present

invention undergoes the electromagnetic interference treatment in order

to minimize the exposure of the body to the electromagnetic wave as

well as to prevent malfunction of the cellular phone, which enables

manufacture of product with complete electromagnetic compatibility

effect.

Also, as a result of application of the present invention to the

cellular phone, it was found that the electromagnetic wave shield effect

is superior on the broad band of electromagnetic wave from low

frequency wave of 10MHz through microwave of 20GHz. Particularly,

electromagnetic wave shield ratio amounts to from 90% minimum to

99% maximum in the range of 10- 300MHz, 800-900MHz and

1500 - 2600MHz.

Also, antibacterial effect may enhance by increasing the ions of

electromagnetic wave absorbents in manufacturing the cellular phone

case. Generally, since the cellular phone is used in contact with a

user's body, antibacterial activity is important to provide sanitary conditions to the user.

The antibacterial activity of the cellular phone case varies with

the amount and a kind of the electromagnetic wave absorbents. That

is, the antibacterial activity is higher as the amount of the

electromagnetic wave absorbents increases. For example, the

suppression ratio of coliform bacilli is 30% at 10wt% of the

electromagnetic wave absorbents, 40% at 20wt%, and 45% at 30wt%,

respectively. Also, the antibacterial activity is better with the

electromagnetic wave absorbents such as Ni-Zn group, particularly

Mg-Zn-Cu group rather than Mn-Zn or Mg-Zn groups.

Such an antibacterial effect was also found with respect to other

bacteria such as staphylococcus aureus and fungus as well as coliform

bacilli.

An impact resistance is important to the cellular phone case

considering careless drop of the cellular phone. The impact resistance

of the cellular phone case containing the electromagnetic wave

absorbents according to the present invention turned out to be the

same as that of conventional case. Also, in case that surfaces of the

electromagnetic wave absorbents was treated with silane-based coating

agent of 0.5 — 3wt% and the cellular phone case was made of the same,

the impact resistance was improved by 10% compared to the typical

case. As described above, the present invention may be applicable to

cases and sheets of cellular phones and electric home appliances to

thereby absorb and remove the electromagnetic wave, suitable to

electromagnetic compatibility.

The present invention is not intended to be limited to the

embodiment herein, but various modifications and changes will be

readily apparent to those skilled in the art within the scope of the

present invention, which is set forth in the appended claims.

Industrial Applicability

The cellular phone case made of electromagnetic shield materials

according to the present invention blocks the electromagnetic wave

emitted from the cellular phone devices to help a user avoid the

interference of the electromagnetic wave.

Further, electromagnetic wave shield ratio can be improved by

forming a conductive coating layer on the cellular phone case, and

malfunction of devices in the cellular phone case due to electromagnetic

wave interference therebetween can be prevented by forming additional

coating layers on the separation walls.

Claims

What is claimed is:

1. A composition of a cellular phone case comprising:

synthetic resin of 90~70wt% selected from the group

consisting of polycarbonate, polymer blend of polycarbonate and

acrylonitrile-butadiene-styrene and ABS resin; and

an electromagnetic wave absorbent of 10 — 30wt% having

the particle size of 0.1 — 30/^πι.

2. The composition as claimed in claim 1 , wherein the

electromagnetic wave absorbent is one or more selected from the

group consisting of Mn-Zn-, Ni-Zn-, Mg-Zn-, and Mg-Zn-Cu-ferrite.

3. A cellular phone case which is made by ejaculation using

the composition as claimed in one of the proceeding claims 1 or 2.

4. The cellular phone case as claimed in claim 3, wherein a

conductive material is coated over inner and outer surfaces of the

case.

5. The cellular phone case as claimed in claim 3, wherein a conductive material is coated over inner surface of the case.

6. The cellular phone case as claimed in claim 3, wherein a

conductive material is coated only on separation walls which are

formed inside the case.

7. A method for manufacturing a cellular phone case

comprising the following steps of:

(1) extruding synthetic resin of 90~70wt% selected from the

group consisting of polycarbonate, polymer blend of

polycarbonate and acrylonitrile-butadiene-styrene and ABS resin,

and one or more electromagnetic wave absorbents of 10 — 30wt%

having the particle size of 0. 1 — 30/i selected from the group

consisting of Mn-Zn-, Ni-Zn-, Mg-Zn-, and Mg-Zn-Cu-ferrite at the

temperature of 180 — 315 °C to manufacture pallet resin; and

(2) ejaculating the pellet resin into a mold at the

temperature of 180 — 315°C to form the case.

8. The method as claimed in claim 7, further comprising the

step of coating a conductive material on at least a portion of the

surface of the case.

9. The method as claimed in claim 8, wherein the conductive

material is coated by spray coating, sputtering or non-electrolytic

plating.

10. The method as claimed in claim 7, further comprising the

step of attaching a conductive sheet inside the case.