Note: Descriptions are shown in the official language in which they were submitted.
CA 02029190 1998-07-31
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Electrically conductive decorative material
The present invention relates to electrically
conductive decorative materials, such as conductive deco-
rative sheets or tiles, suitable as floor materials for use
in factories handling ICs, LSIs and like electronic parts,
laboratories or operating rooms, various clean rooms etc.
In order to avoid electrostatic troubles, plastics or
rubber floor materials filled with a large quantity of
electrically conductive carbon black have heretofore been
used in factories handling ICs, LSIs and like electronic
parts, laboratories, operating rooms, etc. However, these
floor materials, although producing an antistatic effect,
have a black surface and are therefore low in decorative
effect as interior finishing materials. To overcome this
problem, JP-B No. 60-6429 published February 18, 1985,
proposes an interior finishing material comprising
electrically non-conductive colored pellets and electrically
conductive pellets. This material has a decorative effect
and exhibits a considerable antistatic effect, whereas the
conductive pellets used are black pellets incorporating
conductive carbon black, giving a dark color to the material
in its entirety. Further when this floor material is used
in electronic part factories handling ICs, LSIs or the like,
the material is subjected for example, to a voltage of at
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least 300 V for 10 K V as measured by the Honest Meter
method, causing a voltage breakdown of electronic parts.
T he term, "voltage breakdown" refers to the phenomenon
t(tat a I ectr i c charge stored i n the human body, wIt i ch can
he viewed as a capacitor, flows out into an electronic
part to break down the part. T he voltage breakdown
invariably occurs when the charge voltage is not lower
than 100 V . T o preclude this, the charge voltage. is
preferably up to 50V, more preferably up to 30V, The
known floor material nevertheless has the problem that the -
charge on the nonconductive pellets is not readily
removable but induces a voltage breakdown. Further with
the above floor finishing materials wherein conductive
carbon black is used, fine particles of carbon black
become suspended in the air owing to the wear of the
surface to degrade the clean atmosphere of factories
handling E L S I s, precision electronic parts or the like,
laboratories or clean rooms.
A n object of the present invention is to
provide an electrically conductive decorative material
having an excellent conductive properties along with a
decorative effect acrd a light - colored appearance,
Another object of the present invention is to
provide an electrically conductive decorative material free
of the problem of dust and like particles,
T he present invention provides an electrically
conductive decorative rnaterial characterized in that the
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material comprises:
(a) a layer of an electrically conductive resin containing
an electrically conductive fiber, and
(b) a layer of collection of pattern pieces formed over
the resin layer and containing an antistatic agent,
(c) the fiber - containing conductive resin penetrating into
and filling the interstices between the pattern pieces,
T he present invention will be described below
w i th ref erence to the accornpany i ng draw i ngs, i n wh i ch:
F I G . 1 is a sectional view showing a
decorative material of the invention;
F I G . 2 is a fragmentary enlarged view of the
surface layer of the material;
F I G. 3 is a fragmentary enlarged view of a
surface layer having arranged therein pellets containing an
electrically conductive fiber; and
F I G . 4 is a rear view of the decorative
material of the invention.
I n the drawings, 1 is an electrical ly _
conductive backing which is optionally provided, 2 is
conductive resin layer containing an electrically conductive
fiber 3 , 4 is pattern piece containing an antistatic
agent, 5 is layer of collection of pattern pieces 4 ,
6 is electrically conductive resin layer which penetrates
into and f i l l the interstices between the pattern pieces
4 , and '~ is pellet containing an electrically conductive
fiber.
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T he electrically conductive decorative material of
the present invention is prepared, for example, by coating
an electrically conductive Lacking 1 with a thermoplastic
resin 2 in the forrn of a paste and containing an
electrically conductive filer 3 , scattering a predetermined
quantity of pattern pieces 4 over the resin coating, and
subjecting the resulting sheet to an increased pressure
with heating preferably at 1G0 to 220 C to thereby cause
the thermoplastic resin 2 containing the conductive filer
3 to penetrate into and fill the interstices Letween the
pattern pieces 4 and form a layer 5 of collection of
the pattern pieces 4.
Examples of conductive filers for use in the
present invention are carbon filer, metal fiber, fiber of
vacuurn- evaporated rnetal and the like, These conductive
fibers are preferably 0.1 to lOmm, more preferably 0.5 to
5 mrrt, i n average 1 ength and pref crab I y 5 to 50 ~ m, more
preferably 10 to 20 a m, in average diameter. T he
thermoplastic resin serving as a matrix resin for the
conductive filer is, for example, polyvinyl chloride
( P V C ) or copolymer thereof, ethylene - vinyl acetate
copolymer ( E V A ), polyethylene ( P E ), polypropylene ( P P ),
amorphous poly a ° olefin ( A P A O ) or the like. T he
matrix resin contains the conductive fiber preferably in
an arnount of 0,5 to 5 wt%. Pel lets '7 containing an
electrically conductive fiber can be incorporated into the
conductive resin layer along with the conductive filer.
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These pellets can be obtained by incorporating
the carne conductive fiber as rnentioned aGove into pellets
of a resin similar to the matrix resin for the fiber,
T he presence of pellets gives irnproved conductivity to
the material. Such pellets are used preferably in a
quantity of 1 to lOwt~o based on the matrix resin,
T he con ductive backing to be used in the
invention is preferably a sheet or the like which is
prepared, for example, from the carne matrix resin as
above and electrically conductive carbon black kneaded
therewith. W hen the backing 1 is not provided, it is
desirable to forrn the conductive resin layer over release
paper ar the like. T he conductive resin containing the
conductive fiber is applied to the hacking 1 or release
paper to a thickness preferably of 0.1 to 2 mm, more
preferably 0.2 to 0.7mm.
According to the present invention, the
conductive resin layer has formed thereon the layer 5 of
collection of pattern pieces 4 prepared from a
thermoplastic resin which contains no conductive fiber and
is given an antistatic property by an antistatic agent.
T he th errnaplastic resin serving as a matrix resin for
the antistatic agent can be the same as the rnatrix resin
for the conductive fiber.
T he antistatic agent to be used in the
invention is, for example, any of various surfactants,
which include, for exarnple, anionic, nonionic, cationic and
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ampholytie surfactants as given below,
Anionic surfactants
Higher alcohol - sulfuric acid ester salts,
alkylbenzenesulfonic acid salts, alkylnaphthalenesulfonic
acid salts, phosphoric acid ester salts, fatty acid
ethylsulfonic acid salts and fatty acid salts,
Cationic surfactants
Alkylamine salts, polyoxyethylene alkylarnine salts
and quaternary arnrnoniurn salts,
Nonionic surfactants
Partial esters of fatty acid with polyvalent
alcohols, polyoxyethylene alkyl ethers, polyoxyethylene alkyl
phenyl ethers, polyoxyethylene acyl esters, polyethylene
glycols and polyoxyethylene alkylamines.,
Amphalytic surfactants
A ikylbetaines and irnidazoline sulfuric acid esters,
U4'hen required, surfactants can be used in
combination with an electrically conductive plasticizers of
the phosphoric acid ester type, such as cresyldiphenyl
phosphate, tricresyl phosphate, dioctyl phosphate, triamyl
phosphate, 2 - butoxyethyl phosphate and 2 - chloroethyl
phosphate, T he antistatic agent is used preferably in an
amount of 1 to 5 wt% based on the matrix resin.
Preferably, the pattern pieces 4 are 0,5 to 5 mm in
diarneter,
A ccordin g to the present invention, the
conductive resin layer 1 having pattern pieces 4
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arranged thereon is pressed with heating to thereby cause
the conductive resin to penetrate into and fill the
interstices between the pattern pieces 4 , whereby the
contemplated conductive decorative material can be formed,
Consequently, the conductive fiber ~ is partly present
in the penetrating resin portions . 6 to give greatly
unproved conductivity to the rnaterial vertically thereof.
I~4oreover, the conductive fiber, which is present in the
above - mentioned arnount, is difficult to recognize with the
unaided eye, so that the material appears to contain no
conductive fiber, has nothing which impairs its decorative
appearance and can be colored light as desired,
A ecordingly, it is not likely that the material is solid
black or only dark - colored like the conventional
conductive floor material, but the present material is
available with an optional design, Additionally, the,
pieces of conductive fiber which are virtually difficult
to recognize with the unaided eye are dispersed as
entangled with one another in the thermoplastic resin and
electrically connected to the conductive backing. T his
gives very satisfactory conductivity to the decorative
. material, facilitating release of charge from the material
itself or frorn the human body in contact with the
material. Thus, the decorative material has remarkable
conductivity in its entirety,
A ccarding to the invention, the pieces of
conductive fiber are spread in the conductive resin layer
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as entangled with one another horizontally as shown in
F I ~ . 1 and as entangled also vertically as seen in
F I G . 2 , T he conductive fiber thus entangled three -
dirnensionally effectively affords electric conductivity.
G enerally in factories handling electronic parts,
operating rooms of hospitals, ete., the charge voltage on
the human body due to walking on the floor material is
up to 50 V , pref crab I y up to 301~~ , whereas the
corresponding value in the case of the present decorative
material is surprisingly as low as up to 20 V. T he
present material is therefore useful as a floor material
for completely eliminating voltage breakdown failures in
factories handling I C s, L S I s or the like, ignition
due to the discharge of charge on the human body in
operating rooms, and malfunctions.. or like troubles of
electronic devices.
With the conventional conductive floor material,
a large amount of carbon black or conductive fiber is
exposed on the surface and accordingly releases fine
carbon or like particles, so that the material is not
usable in clean roorns or the like, whereas with the
decorative material of the invention, the conductive fiber
appears on the surface only to such an extent that it
is virtually difficult to recognize with the unaided eye.
T bus, the. present material releases alrnost no dust even
in clean rooms and is usable favorably,
T he conductive decorative rnaterial of the present
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invention have the following advantages.
1 , T he pattern pieces of thermoplastic resin
made antistatic by an antistatic agent can be colored as
desired, while the thermoplastic resin penetratins into the
interstices between the pattern pieces can also be colored
as exactly desired, and the conductive fiber incorporated
therein is virtually difficult to recognize with the
unaided eye. T he material is therefore given both a
highly light - colored appearance and electrical conductivity
which can not he realized with any conventional conductive
floor material.
2 . With almost no carbon black or conductive
fiber left exposed on the surface, there is little or no
likelihood of the material releasing dust ar like
particles,
3 , T he material becomes charged to a voltage of
as low as shout 7 V per 10 K V as measured by the
Honest Meter method, while the charge voltage an the
human body on the material is also low, T his eliminates
the voltage breakdown of I C s, L S I s and the like or
malfunctions of electronic devices.
4 . T he conventional antistatic treatment is
generally dependent on humidity, whereas the decorative
material of the invention has excellent conductive
properties without depending on hurnidity.
5 . T he combination of conductive fiber and
conductive pellets affords a further improved conductive
CA 02029190 1998-07-31
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effect.
T he present invention mill be described with
reference to the fallowing example.
E xarep I a
A P V C paste of composition A was colored
light blue with a toner and applied to a thickness of
0.3mm on a conductive backing having carbon black
incorporated therein. Colored antistatic pattern pieces
orere prepared by add i ng p i gments to port i ons of a
compound of eornposition B individually, making the paste
portions into three kinds of sheets, i.e., dark blue,
blue and light blue sheets, and pulverizing the sheets to
a mean particle size of 2 mrn. The pattern pieces were
scattered over the resin layer on the backing, and the
resulting sheet was heated to 200~C and then pressed to
obtain a conductive decorative floor material of the
invention.
I t was virtually difficult to recognize the
conductive carbon fiber on the surface of the floor
~aaterial with the unaided eye, and the material had a
highly light - colored appearance and an excellent decorative
effect.
Composition A
P V C ( KanevinyITMaste P S L -10, product of
K anegaf uch i C hem i ca 1 I ndustry C o. , L td. )
100 parts
F filler (calcium carbonate) 5 parts
CA 02029190 1998-07-31
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P lasticizer (dioctyl phthalate) 40 parts
S tab i l i zer ( B a- Z n type) 2 parts
C arbon f i ber ( 3 mrn i n average 1 ength
and 13 urn in average diameter) 3 parts
C ompos i t i on B
P V C ( S S -g0, product of Denki
K agaku K ogyo K , K . ) 100 parts
Filler (calcium carbonate) 50 parts
E poxy res i n ( O -130 P , produc t of
Adeka Argus Co., Ltd. ) 4 parts
P lasticizer (dioctyl phthalate) 40 parts
S tabi 1 izer ( Ba- Zn type) 4 parts
Antistatic agent (polyoxyethylene
alkylamine salt) 2 parts
T he following properties of the floor material
obtained were measured at 20'C at a relative humidity.
of
20%,
(1) C barge voltage on the material by the Ho nest Meter
method (according to J I S L 1094)
(2) C barge voltage on the human body due to walkin g
( a c c o r d i n g t o J I S (Japanese Industrial
Standard) L 1021 )
(3) Electric resistance between the ground and the surface
of the material in contact with the ground by the
h( F P A (National Fire Protection Association)
method. Table 1 shows the result.
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Table 1
Honest Meter method 7 V
Charge vol tape on human body 11 V
N F P A rnethod ( ~ )
Electric resistance of the
surface of the material in 1,2 X 10'
contact with the ground
Electric resistance between
the ground and the surface 1,1 X 10'
of the material
T able 1 shaves that the decorative material of
the invention had excellent conductive properties. N o
voltage breakdown of I C s, L S I s or the like, or no
malfunction of electronic devices occurred due to the use
of the present material.
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