U.S. patent application number 12/854472 was filed with the patent office on 2011-02-10 for magnetic sheet composition, magnetic sheet, and method for producing magnetic sheet.
This patent application is currently assigned to Sony Chemical & Information Device Corporation. Invention is credited to Keisuke Aramaki, Katsuhiko Komuro, Yoshihisa Shinya.
Application Number | 20110033732 12/854472 |
Document ID | / |
Family ID | 40985495 |
Filed Date | 2011-02-10 |
United States Patent
Application |
20110033732 |
Kind Code |
A1 |
Aramaki; Keisuke ; et
al. |
February 10, 2011 |
MAGNETIC SHEET COMPOSITION, MAGNETIC SHEET, AND METHOD FOR
PRODUCING MAGNETIC SHEET
Abstract
To provide a magnetic sheet composition, which contains: a
binder; magnetic powder; and a curing agent, wherein the binder
contains a thermosetting organic resin, and the curing agent
contains a sulfonium borate complex expressed by General Formula 1:
##STR00001## where R.sub.1 is an aralkyl group, R.sub.2 is a lower
alkyl group, X is a halogen atom, and n is an integer of 0 to
3.
Inventors: |
Aramaki; Keisuke; (Tochigi,
JP) ; Shinya; Yoshihisa; (Tochigi, JP) ;
Komuro; Katsuhiko; (Tochigi, JP) |
Correspondence
Address: |
BUCHANAN, INGERSOLL & ROONEY PC
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
Sony Chemical & Information
Device Corporation
Shinagawa-ku
JP
|
Family ID: |
40985495 |
Appl. No.: |
12/854472 |
Filed: |
August 11, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2009/052720 |
Feb 17, 2009 |
|
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12854472 |
|
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Current U.S.
Class: |
428/704 ;
156/224; 252/62.54; 427/130 |
Current CPC
Class: |
Y10T 156/10 20150115;
H01F 1/37 20130101; C08G 59/687 20130101; H01F 1/26 20130101; H05K
9/0081 20130101; H05K 9/0075 20130101; C08K 5/372 20130101; C08K
5/34924 20130101; Y10T 156/1048 20150115; C08K 5/20 20130101; C08K
5/50 20130101; C08L 63/00 20130101 |
Class at
Publication: |
428/704 ;
252/62.54; 427/130; 156/224 |
International
Class: |
H01F 1/42 20060101
H01F001/42; B05D 5/00 20060101 B05D005/00; B29C 51/14 20060101
B29C051/14; B32B 27/00 20060101 B32B027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 18, 2008 |
JP |
2008-036349 |
Claims
1. A magnetic sheet composition, comprising: a binder; magnetic
powder; and a curing agent, wherein the binder contains a
thermosetting organic resin, and the curing agent contains a
sulfonium borate complex expressed by General Formula 1:
##STR00009## where R.sub.1 is an aralkyl group, R.sub.2 is a lower
alkyl group, X is a halogen atom, and n is an integer of 0 to
3.
2. The magnetic sheet composition according to claim 1, wherein
R.sub.1 is a benzyl group, an o-methyl benzyl group, or a
(1-naphthyl)methyl group.
3. The magnetic sheet composition according to claim 1, wherein
R.sub.2 is a methyl group.
4. The magnetic sheet composition according to claim 1, wherein the
sulfonium borate complex is contained in an amount of 2 parts by
mass to 15 parts by mass relative to 106.1 parts by mass of the
binder.
5. The magnetic sheet composition according to claim 1, further
comprising a flame retardant, wherein the flame retardant contains
carboxylic acid amide-containing melamine cyanurate.
6. A method for producing a magnetic sheet, comprising: applying a
magnetic sheet composition onto a substrate; drying the magnetic
sheet composition applied onto the substrate; and thermosetting the
dried magnetic sheet composition, wherein the magnetic sheet
composition comprises: a binder; magnetic powder; and a curing
agent, wherein the binder contains a thermosetting organic resin,
and the curing agent contains a sulfonium borate complex expressed
by General Formula 1: ##STR00010## where R.sub.1 is an aralkyl
group, R.sub.2 is a lower alkyl group, X is a halogen atom, and n
is an integer of 0 to 3.
7. The method for producing a magnetic sheet according to claim 6,
further comprising: stacking a convex-concave forming layer and a
pattern transferring layer on a surface of a magnetic layer, which
is formed by thermosetting the magnetic sheet composition, in this
order from the side of the magnetic layer so as to form a stacked
body; and hot-pressing the stacked body so as to transfer a surface
configuration of the pattern transferring layer to surfaces of the
convex-concave forming layer and the magnetic layer, as well as
bonding the convex-concave forming layer and the magnetic layer
together.
8. A magnetic sheet, obtained by the method comprising: applying a
magnetic sheet composition onto a substrate; drying the magnetic
sheet composition applied onto the substrate; and thermosetting the
dried magnetic sheet composition, wherein the magnetic sheet
composition comprises: a binder; magnetic powder; and a curing
agent, wherein the binder contains a thermosetting organic resin,
and the curing agent contains a sulfonium borate complex expressed
by General Formula 1: ##STR00011## where R.sub.1 is an aralkyl
group, R.sub.2 is a lower alkyl group, X is a halogen atom, and n
is an integer of 0 to 3.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuation of Application No. PCT/JP2009/052720,
filed on Feb. 17, 2009.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a magnetic sheet, which is
capable of suppressing undesirable electromagnetic waves emitted
from an electronic equipment, and inhibiting electromagnetic
disorders caused due to the interference of the undesirable
electromagnetic waves, and also relates to a production method
thereof which is efficient and low cost.
[0004] 2. Description of the Related Art
[0005] The magnetic sheets are used for depression of noise, or for
RFID. For the purpose of depression of noise, along with rapid
developments of electronic equipments, e.g. personal computers and
mobile phones, such as down sizing and higher frequency, these
electronic equipments suffer from a noise interference due to outer
electromagnetic waves and interference of noises occurred within
the electronic equipment. In order to suppress such interferences,
various countermeasures have been taken for the noises. For
example, a magnetic sheet (noise depressing sheet) is disposed
adjacent to a noise emitting source or a noise receiving
source.
[0006] The magnetic sheet is formed by adding alloy (magnetic
powder) such as Fe--Si--Al to an epoxy resin, acrylic resin, or the
like, and then being cured to form into a sheet by hot pressing.
The magnetic powder inhibits noise, and functions as a so-called
noise depressor. The better the effect of inhibiting the noise of
the magnetic sheet is, the larger an imaginary part .mu.'' of the
magnetic permeability of the magnetic sheet is.
[0007] On the other hand, in the case where the magnetic sheets are
used for RFID, as a recent trend in the art, radio communication
using a coil antenna in an electromagnetic induction method, which
is represented as mobile information terminals having IC tags
referred as Radio Frequency Identification (RFID), has been widely
used. For example, in the mobile information terminal, various
conductors (metals) such as a metal casing or metal parts are
disposed adjacent to an antenna element for transmitting and
receiving due to downsizing of the mobile information terminal. In
this case, a magnetic field usable for the transmission is largely
attenuated because of the metal present adjacent to the antenna
element, and as a result, a communication distance for RFID
transmission in an electromagnetic induction system may be
shortened, or transmission or receiving of a radio frequency may
become difficult because a resonance frequency is shifted. To
prevent these electromagnetic disorders, a magnetic sheet is placed
between the antenna element and the conductor. As for a function of
RFID, it is preferred that the magnetic sheet has a large real part
.mu.' of the magnetic permeability, and a small imaginary part
.mu.'' of the magnetic permeability.
[0008] A curing agent (i.e. a crosslinking agent) for curing a
thermosetting organic resin is generally added to a magnetic sheet
composition that is a material of the magnetic sheet. The magnetic
sheet is hardened by adding the curing agent to the magnetic sheet
composition. Especially in the case where a polymer material for
use in the magnetic sheet easily absorbs moisture, however, the
thickness of the magnetic sheet undesirably changes depending on
the fluctuations in the environment such as temperature and
humidity. In order to sufficiently cure the magnetic sheet in such
environment, the curing temperature is set high and the curing
duration is set long. In this case, a large volume of water is
consumed as the cooling duration becomes long according to the long
and high temperature curing, and moreover the production efficiency
decreases. If the curing temperature is set high and the curing
duration is set short to solve the aforementioned problem, a
problem occurs in the heat resistance of an insulating support.
[0009] Moreover, a sulfonium-based cationic curing agent has been
commonly used as the conventional curing agent, but the
sulfonium-based cationic curing agent contains antimony that is
toxic. Therefore, use of such curing agent gives an adverse
influence to the environment. Furthermore, as in this
antimony-containing sulfonium-based cationic curing agent, a
counter ion has a Sb--F bond, which has weak bonding force, a
F.sup.-1 ion tends to be free. For this reason, in the case where
the magnetic sheet containing the antimony-containing cationic
curing agent is used around a wiring, the free F.sup.-1 ion reacts
with water to form hydrofluoric acid, which causes corrosion of the
wiring.
[0010] For example, Japanese Patent Application Laid-Open (JP-A)
No. 2007-95829 describes photocuring of a magnetic binder
containing a photocuring cationic curing agent, and discloses an
electromagnetic-wave-absorbing sheet having a concentration
distribution of magnetic filler from the surface of the sheet
towards the depth direction thereof. The curing of this
electromagnetic-wave-absorbing sheet is performed by a drum
device.
BRIEF SUMMARY OF THE INVENTION
[0011] The present invention aims at solving the problems in the
art, and achieving the following objects. Namely, an object of the
present invention is to provide a magnetic sheet composition, which
is a material of a magnetic sheet, capable of reducing unnecessary
electromagnetic waves released from an electronic equipment, is
capable of inhibiting electromagnetic disorders caused by an
interference of unnecessary electromagnetic waves within an
electronic equipment, prevents liberation of halogen ions to
thereby prevent corrosion of wirings when it is used around the
wirings, and does not give any adverse influence to the
environment. Another object of the present invention is to provide
a method for producing a magnetic sheet using such magnetic sheet
composition, and a magnetic sheet produced by such method for
producing a magnetic sheet.
[0012] The inventors of the present invention have intensively
studied to solve the problems, and come to the following insights.
Namely, the inventors have found a magnetic sheet composition
containing at least a binder which contains a thermosetting organic
resin, a magnetic powder, and a curing agent which contains a
sulfonium borate complex expressed by General Formula 1 can produce
a magnetic sheet which realizes low-temperature-high-speed curing,
prevents libration of halogen ions so as to prevent corrosion of
wirings when it is used around the wirings, gives less
environmental load.
##STR00002##
[0013] In General Formula 1, R.sub.1 is an aralkyl group, R.sub.2
is a lower alkyl group, X is a halogen atom, and n is an integer of
0 to 3.
[0014] The present invention has been made based upon the insight
of the present inventors, and means for solving the aforementioned
problems are as follows.
<1> A magnetic sheet composition, containing:
[0015] a binder;
[0016] magnetic powder; and
[0017] a curing agent,
[0018] wherein the binder contains a thermosetting organic resin,
and the curing agent contains a sulfonium borate complex expressed
by General Formula 1:
##STR00003##
[0019] where R.sub.1 is an aralkyl group, R.sub.2 is a lower alkyl
group, X is a halogen atom, and n is an integer of 0 to 3.
[0020] Since the magnetic sheet composition according to <1>
contains the curing agent, which does not contain antimony, it will
provide a less load to the environment. Moreover, as the bonding
energy of X (halogen atom) and a phenyl group in the sulfonium
borate complex expressed by General Formula 1, the bond between X
(halogen atom) and the phenyl group is unlikely broken, and thus
the isolation of X (halogen atom) ions is prevented. Therefore, the
generation of acid such as hydrofluoric acid as a result of the
reaction between free X (halogen atom) ions and water or the like
is prevented. For this reason, corrosion of wirings can be
prevented even when a magnetic sheet formed using the magnetic
sheet composition is used around the wirings. Furthermore, a
cationic curing magnetic sheet curable at low temperature and at
high speed can be provided.
<2> The magnetic sheet composition according to <1>,
wherein R.sub.1 is a benzyl group, an o-methyl benzyl group, or a
(1-naphthyl)methyl group. <3> The magnetic sheet composition
according to any of <1> or <2>, wherein R.sub.2 is a
methyl group. <4> The magnetic sheet composition according to
any one of <1> to <3>, wherein the sulfonium borate
complex is contained in an amount of 2 parts by mass to 15 parts by
mass relative to 106.1 parts by mass of the binder. <5> The
magnetic sheet composition according to any one of <1> to
<4>, further containing a flame retardant, wherein the flame
retardant contains carboxylic acid amide-containing melamine
cyanurate. <6> A method for producing a magnetic sheet,
containing:
[0021] applying the magnetic sheet composition as defined in any
one of <1> to <5> onto a substrate;
[0022] drying the magnetic sheet composition applied onto the
substrate; and
[0023] thermosetting the dried magnetic sheet composition.
<7> The method for producing a magnetic sheet according to
<6>, further containing:
[0024] stacking a convex-concave forming layer and a pattern
transferring layer on a surface of a magnetic layer, which is
formed by thermosetting the magnetic sheet composition, in this
order from the side of the magnetic layer so as to form a stacked
body; and
[0025] hot-pressing the stacked body so as to transfer a surface
configuration of the pattern transferring layer to surfaces of the
convex-concave forming layer and the magnetic layer, as well as
bonding the convex-concave forming layer and the magnetic layer
together.
<8> A magnetic sheet, obtained by the method as defined in
any of <6> or <7>.
[0026] In accordance with the present invention, the various
problems in the art can be solved, and there can be provided a
magnetic sheet composition, which is a material of a magnetic
sheet, capable of reducing unnecessary electromagnetic waves
released from an electronic equipment, is capable of inhibiting
electromagnetic disorders caused by an interference of unnecessary
electromagnetic waves within an electronic equipment, prevents
libration of halogen ions to thereby prevent corrosion of wirings
when it is used around the wirings, and does not give any adverse
influence to the environment, as well as providing a method for
producing a magnetic sheet using such magnetic sheet composition,
and a magnetic sheet produced by such method for producing a
magnetic sheet.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a .sup.1H-NMR chart of the sulfonium borate
complex expressed by the formula 1a.
[0028] FIG. 2 is a .sup.1H-NMR chart of the sulfonium borate
complex expressed by the formula 1b.
[0029] FIG. 3A is a photograph showing a cross-section of the
magnetic sheet sample (Example 1) after the corrosion test.
[0030] FIG. 3B is a photograph showing a cross-section of the
magnetic sheet sample (Comparative Example 8) after the corrosion
test.
[0031] FIG. 4 is a diagram for explaining the method for measuring
the transmission loss.
DETAILED DESCRIPTION OF THE INVENTION
Magnetic Sheet Composition
[0032] The magnetic sheet composition of the present invention
contains at least a binder, a magnetic powder, and a curing agent,
and may further contain other components, if necessary.
[0033] Curing Agent--
[0034] The curing agent is suitably selected depending on the
intended purpose without any restriction, provided that it contains
the sulfonium borate complex expressed by General Formula 1:
##STR00004##
[0035] In General Formula 1, R.sub.1 is an aralkyl group, R.sub.2
is a lower alkyl group, X is a halogen atom, and n is an integer of
0 to 3.
[0036] Examples of the aralkyl group expressed as R.sub.1 include a
benzyl group, an o-methyl benzyl group, a (1-naphthyl)methyl group,
a pyridyl methyl group, and an anthracenyl methyl group. Among
them, the (1-naphthyl)methyl group is preferable as it provides the
curing agent with excellent and fast curing ability, and it is
readily available.
[0037] Examples of the lower alkyl group expressed as R.sub.2
include a methyl group, an ethyl group, a propyl group, and a butyl
group. Among them, the methyl group is preferable as it provides
the curing agent with excellent and fast curing ability, and it is
readily available.
[0038] "n" is an integer of 0 to 3, where n denotes a number of
hydroxyl group(s) contained in phenyl group(s) bonded to the
sulfonium residue. In the case where n is 1, examples of such
phenyl group include a 4-hydroxyl phenyl group, a 2-hydroxyl phenyl
group, and a 3-hydroxyl phenyl group. In the case where n is 2,
examples of such phenyl group include a 2,4-dihydroxyl phenyl
group, a 2,6-dihydroxyl phenyl group, a 3,5-dihydroxyl phenyl
group, and a 2,3-dihydroxyl phenyl group. In the case where n is 3,
examples of such phenyl group include a 2,4,6-trihydroxy phenyl
group, a 2,4,5-trihydroxy phenyl group, and a 2,3,4-trihydroxy
phenyl group. Among them, the 4-hydroxy phenyl group is preferable,
as it provides the curing agent with excellent and fast curing
ability, and it is readily available.
[0039] Examples of the halogen atom expressed as X include a
fluorine atom, chlorine atom, bromine atom, and iodine atom. Among
them, the fluorine atom having high electron-withdrawing properties
is preferable for improving the reactivity.
[0040] The sulfonium borate complex expressed by General Formula 1
can be produced in accordance with the following reaction formula.
In General Formulae 1 to 3, R.sub.1 is an aralkyl group, R.sub.2 is
a lower alkyl group, X is a halogen atom, and n is an integer of 0
to 3.
<Reaction Formula>
##STR00005##
[0042] Namely, the sulfonium antimonate complex (see JP-A No.
10-245378 for a synthesis method thereof) expressed by General
Formula 2 is made dissolved in an organic solvent such as ethyl
acetate, and a solution of sodium borate (see JP-A No. 10-310587
for a synthesis method thereof) expressed by General Formula 3 is
mixed to the aforementioned solution in the equimolecular amount.
The obtained two-layered mixture is stirred at the temperature of
20.degree. C. to 80.degree. C. for 1 hour to 3 hours so as to allow
the sulfonium antimonate complex expressed by General Formula 2 to
react with the sodium borate expressed by General Formula 3 to
thereby obtain a sulfonium borate complex expressed by General
Formula 1. The isolation of the sulfonium borate complex expressed
by General Formula 1 can be performed in the following manner.
Specifically, the organic solvent layer is separated and dried, and
the organic solvent is evaporated to remove under the reduced
pressure so that the specified substance can be obtained as the
evaporated residue.
[0043] The sulfonium borate complex expressed by General Formula 1
can be used as a thermal cationic polymerization initiator for a
common epoxy resin. In this case, an epoxy resin composition (in
the form of a paste or film) containing 100 parts by mass of an
epoxy resin and 0.1 parts by mass to 10 parts by mass of the
sulfonium borate complex expressed by General Formula 1 as the
thermal cationic polymerization initiator is heated at 50.degree.
C. to 150.degree. C. so as to provide a cured product which is
excellent in electrolytic corrosion resistance, and is cured at
high speed and low temperature.
[0044] Binder--
[0045] The binder is suitably selected depending on the intended
purpose without any restriction. Examples thereof include acrylic
rubber containing a thermosetting organic resin, which will be
mentioned later.
[0046] The acrylic rubber preferably contains epoxy groups. In this
case, the epoxy groups are reacted with a curing agent, so as to
improve reliability. Moreover, the acrylic rubber preferably
further contains hydroxyl groups. The hydroxyl groups are contained
in the acrylic rubber, so as to improve adhesion.
[0047] The mass average molecular mass of the acrylic rubber is
10,000 to 450,000 in terms of excellent coating ability.
[0048] When the mass average molecular mass is less than 10,000,
the viscosity of the magnetic sheet composition decreases, and it
becomes hard to apply the magnetic sheet composition containing the
magnetic powder having a large mass. When the mass average
molecular mass is more than 450,000, the viscosity of the magnetic
sheet composition becomes large, and it becomes hard to apply the
magnetic sheet composition having a large viscosity.
[0049] The glass transition temperature of the acrylic rubber is
preferably -50.degree. C. to +15.degree. C.
[0050] When the glass transition temperature is lower than
-50.degree. C., the reliability at a high temperature or in a high
temperature and high humidity environment may become poor. When the
glass transition temperature is higher than +15.degree. C., the
magnetic sheet tends to be hard.
[0051] Moreover, one or more acrylic rubbers may be used in
combination.
[0052] Thermosetting Organic Resin--
[0053] Examples of the thermosetting organic resin include an epoxy
resin. When an epoxy resin having a small molecular mass is added,
the melt viscosity of the binder is further decreased upon
compressing (forming) the magnetic sheet. Thus, the magnetic
properties can be increased. Moreover, for example, by using a
polyfunctional epoxy resin, the reliability of the magnetic sheet
after curing can be further improved.
[0054] Examples of the epoxy resin include a cation-curing epoxy
resin. The epoxy resin may be used independently, or in
combination.
[0055] Magnetic Powder--
[0056] The magnetic powder is suitably selected depending on the
intended purpose without any restriction. Examples of the shape of
the magnetic powder include a flat, lump, fiber, sphere, and
irregular shape. Of these, the flat shape is preferable as the
magnetic powder of such shape can be easily orientated in a
predetermined direction and high magnetic permeability can be
attained.
[0057] Examples of the magnetic powder include soft magnetic metal,
ferrite, and pure iron particles.
[0058] Examples of the soft magnetic metal include magnetic
stainless steel (i.e., Fe--Cr--Al--Si alloy), Sendust (i.e.,
Fe--Si--Al alloy), permalloy (i.e., Fe--Ni alloy), silicon copper
(i.e., Fe--Cu--Si alloy), Fe--Si alloy, Fe--Si--B(--Cu--Nb) alloy,
Fe--Ni--Cr--Si alloy, Fe--Si--Cr alloy, Fe--Si--Al--Ni--Cr alloy,
and amorphous metal.
[0059] The magnetic powder may be used independently, or in
combination.
[0060] The amounts of the binder, magnetic powder, and curing agent
are each suitably selected depending on the intended purpose
without any restriction. It is preferred that the amount of the
magnetic powder be 400 parts by mass to 1,400 parts by mass and the
amount of the sulfonium borate complex as the curing agent be 2
parts by mass to 15 parts by mass, both relative to 106.1 parts by
mass of the binder. Note that, the proportion of the magnetic
powder in the magnetic sheet is preferably 60% by weight to 95% by
weight.
[0061] When the amount of the magnetic powder is less than 400
parts by mass relative to 106.1 parts by mass of the binder,
excellent magnetic properties may not be obtained. When the amount
thereof is more than 1,400 parts by mass relative to 106.1 parts by
mass of the binder, it becomes hard to bind the magnetic powder
with the binder. Consequently, the thickness variation of the
magnetic sheet becomes large in a high temperature and high
humidity environment, and the flame retardant may bleed out on the
surface of the magnetic sheet. Moreover, the magnetic sheet becomes
brittle, and the magnetic powder falls off (powder falling) not
only from an edge face of the magnetic sheet but also from a
surface of the magnetic sheet.
[0062] Other Components--
[0063] The other components are suitably selected from various
known additives depending on the intended purpose without any
restriction, as long as the effect of the present invention is not
impaired. For the purpose of improving the coating ability (i.e.
adjusting the viscosity) of a magnetic composition, which is
prepared by adding the magnetic powder and the flame retardant to
the binder, a solvent may be added. Examples of the solvent
include: ketenes such as acetone, methylethyl ketone,
methylisobutyl ketone, and cyclohexanone; alcohols such as
methanol, ethanol, propanol, butanol, isopropyl alcohol; esters
such as methyl acetate, ethyl acetate, propyl acetate, butyl
acetate, ethyl lactate, and ethyl glycol acetate; ethers such as
diethylene glycol dimethyl ether, 2-ethoxy ethanol,
tetrahydrofurane, and dioxane; aromatic hydrocarbon compounds such
as benzene, toluene, and xylene; and halogenated hydrocarbon
compounds such as methylene chloride, ethylene chloride, carbon
tetrachloride, chloroform, chlorobenzene. These may be used
independently or in combination.
[0064] If necessary, various additives, such as a flame retardant
(e.g. melamine cyanurate, and red phosphorous), a dispersant,
stabilizer, lubricant, silane or titanate coupling agent, filler,
plasticizer, and antioxidant may be added.
[0065] The amounts of the other components are suitably selected
depending on the amounts of the binder, the magnetic powder and the
curing agent, without any restriction.
[0066] Carboxylic Acid Amide-Containing Melamine Cyanurate--
[0067] The presence of the carboxylic acid amide in the carboxylic
acid amide-containing melamine cyanurate can be confirmed, for
example, by pyrolysis gas chromatography analysis (Py-GC-MS).
[0068] The number average particle size of the carboxylic acid
amide-containing melamine cyanurate is suitably selected depending
on the intended purpose without any restriction. It is preferably 1
.mu.m or less.
[0069] When the number average particle size is more than 1 .mu.m,
the close alignment of the magnetic powder is blocked, and the
magnetic properties of the magnetic sheet may be degraded, and the
thickness variation of the magnetic sheet may become large at high
temperature or in a high temperature and high humidity
environment.
[0070] The number average particle size of the carboxylic acid
amide-containing melamine cyanurate can be obtained, for example,
from a particle size distribution thereof measured by laser
diffraction.
[0071] The carboxylic acid amide-containing melamine cyanurate may
be a commercially available product or arbitrarily prepared
product.
[0072] Examples of the commercially available product include MC-5F
(manufactured by SAKAI CHEMICAL INDUSTRY, CO., LTD.).
[0073] A method for producing the carboxylic acid amide-containing
melamine cyanurate is suitably selected depending on the intended
purpose without any restriction. For example, a method for treating
a surface of the melamine cyanurate using fatty acid is preferably
used.
[0074] A surface treatment method is suitably selected from known
methods depending on the intended purpose without any restriction.
For example, a method of mixing and stirring the melamine cyanurate
and the fatty acid is used.
[0075] When the surface of the melamine cyanurate is treated with
the fatty acid, it is considered that an amino group in the
melamine cyanurate is reacted with the fatty acid, and as a result,
an amide compound is formed, as represented by the following
reaction formula 1. Thus, an analysis is performed by pyrolysis gas
chromatography (Py-GC-MS), so as to confirm the presence of the
carboxylic acid amide.
--NH.sub.2+R--COOH.fwdarw.R--CONH-- Reaction Formula 1
[0076] The fatty acid is suitably selected depending on the
intended purpose without any restriction. Examples thereof include
lauric acid, isostearic acid, stearic acid, palmitic acid, oleic
acid, and linolenic acid. These may be used independently, or in
combination. Among these, lauric acid is preferred, in terms of
high hydrophobicity and favorable dispersibility.
[0077] Red Phosphorus--
[0078] The flame retardant preferably contains red phosphorus, in
addition to the silicon atom-containing melamine cyanurate and the
carboxylic acid amide-containing melamine cyanurate. This is
advantageous in terms of further improving the flame retardant of
the magnetic sheet.
[0079] The red phosphorus is suitably selected depending on the
intended purpose without any restriction, and may be a commercially
available product or arbitrarily prepared product. It is preferred
that the surface of the red phosphorus be coated for providing
excellent humidity resistance, and favorable stability owing to no
spontaneous combustion upon mixing.
[0080] As the red phosphorus whose surface is coated, red
phosphorus whose surface is treated with aluminum hydroxide is
exemplified.
[0081] The amount of the red phosphorus is suitably selected
depending on the intended purpose without any restriction. It is
preferably 6 parts by mass to 19 parts by mass, relative to the 100
parts by mass of the binder.
[0082] When the amount is less than 6 parts by mass, the obtainable
effect of improving the flame resistance cannot be obtained. When
the amount is more than 19 parts by mass, the total amount of the
magnetic powder and the flame retardant increases relative to the
binder. This makes difficult to keep binding the magnetic powder
and the flame retardant together with the binder, the proportion of
the magnetic powder in the magnetic sheet is decreased, causing
decrease in the magnetic permeability.
[0083] The method for producing a magnetic sheet of the present
invention is suitably selected from those known in the art
depending on the intended purpose without any restriction, but the
magnetic sheet is suitably produced by the following method.
<Production Method>
[0084] The method for producing a magnetic sheet contains at least
applying the magnetic sheet composition on a substrate, drying the
magnetic sheet composition applied on the substrate, and
thermosetting the dried magnetic sheet composition, and may further
contain other steps, if necessary.
[0085] Magnetic Sheet Composition--
[0086] The magnetic sheet composition contains at least a binder, a
magnetic powder, and a curing agent, and may further contain other
components. In the magnetic sheet composition, the binder contains
a thermosetting organic resin, and the curing agent contains a
sulfonium borate complex expressed by General Formula 1.
[0087] Note that, the details of the binder, magnetic powder,
curing agent, and other components are as mentioned above.
[0088] Substrate--
[0089] The substrate is suitably selected depending on the intended
purpose without any restriction, but it is preferably a polyester
film a surface of which is lubrication processed (a release PET) as
the formed magnetic layer can be easily peeled from the
substrate.
[0090] Coating--
[0091] A method for coating is suitably selected depending on the
intended purpose without any restriction. Examples thereof include
spin coating, dip coating, kneader coating, curtain coating, blade
coating, and doctor blade coating. Of these, the blade coating, and
the doctor blade coating are preferable, in terms of excellent
coating efficiency.
[0092] Drying--
[0093] A method for drying is suitably selected depending on the
intended purpose without any restriction. Examples thereof include
methods using a dry oven, a drier, a hot press, and a heating
automation. Among them, the method using the dry oven is
particularly preferable as the process thereof is easy, and it is
advantageous in terms of the cost for the facilities.
[0094] Thermosetting (Formation)--
[0095] A method of thermosetting (forming) the magnetic sheet is
suitably selected depending on the intended purpose without any
restriction. For example, the magnetic sheet can be formed by hot
pressing.
[0096] A method of hot pressing is suitably selected depending on
the intended purpose without any restriction. For example, both
sides of a layer, which is formed by applying the magnetic
composition onto the substrate, are sandwiched with press plates
respectively via buffer materials, and heated and pressed.
[0097] The conditions for the hot pressing are suitably adjusted
depending on the intended purpose without any restriction. For
example, the temperature is preferably 80.degree. C. to 190.degree.
C., the pressure is preferably 5 MPa to 20 MPa, and the duration is
preferably 1 minute to 20 minutes.
[0098] The structure, thickness, and material of the buffer
material are suitably selected depending on the indented purpose
without any restriction.
[0099] The buffer material may be a commercially available product
or arbitrarily prepared product. Examples of the commercially
available product include a high quality paper (product name: OK
Prince High Quality 70, manufacturer: Oji Paper Co., Ltd., Bekk
smoothness: 6.2 sec/mL), a cushioned paper (product name: TF190,
manufacturer: THE TOYO FIBRE CO., LTD., Bekk smoothness: 1.7
sec/mL), nylon mesh (product name: N-NO. 110S, manufacturer: TOKYO
SCREEN CO., LTD., Bekk smoothness: less than 0.1 sec/mL), cotton
cloth (product name: Kanakin No. 3, manufacturer: Japanese
Standards Association, Bekk smoothness: less than 0.1 sec/mL), a
base paper for an adhesive (product name: SO base paper 18G,
manufacturer: DAIFUKU PAPER MFG CO., LTD., Bekk smoothness: less
than 0.1 sec/mL), a double sided release paper (product name:
100GVW (High lubricity surfaces), manufacturer: Oji Paper Co.,
Ltd., Bekk smoothness: 146 sec/mL), and a double sided release
paper (product name: 100GVW (Low lubricity surfaces), manufacturer:
Oji Paper Co., Ltd., Bekk smoothness: 66 sec/mL).
[0100] Bekk smoothness expresses the time required for a certain
amount of air to pass through the surface having some
irregularities of a sheet member such as paper and a cloth. The
larger the degree of the irregularities on the surface of the sheet
member, the smaller the value of Bekk smoothness is, namely meaning
excellent "lubricity".
[0101] Bekk smoothness is measured, for example, by Bekk Smoothness
Tester (manufactured by TESTER SANGYO CO., LTD.).
[0102] As mentioned above, the magnetic sheet composition is
applied onto the substrate, the applied magnetic sheet composition
on the substrate is dried, and the dried magnetic sheet composition
is thermoset, to thereby produce a magnetic sheet. Here, the
magnetic sheet is obtained in such a state that the magnetic sheet
is laminated on the substrate (release PET), but the magnetic sheet
can be peeled from the substrate and used.
[0103] Other Steps--
[0104] Other steps are suitably selected depending on the intended
purpose without any restriction. Examples thereof include a
pattern-transferring step.
[0105] Pattern-Transferring Step--
[0106] The pattern transferring step is stacking a convex-concave
forming layer and a pattern transferring material on a surface of
the magnetic layer, which has been formed by thermosetting the
magnetic sheet composition, in this order, and hot pressing the
stacked layers so as to bond the convex-concave forming layer with
the magnetic layer to form a stacked body, as well as to transfer a
surface configuration of the pattern transferring material to a
surface of the laminate of the convex-concave forming layer and the
magnetic layer.
[0107] Convex-Concave Forming Layer--
[0108] The structure, thickness, and material of the convex-concave
forming layer are suitably selected depending on the intended
purpose without any restriction. The details thereof are as
mentioned earlier.
[0109] The surface configuration of the convex-concave forming
layer is not particularly limited, and one surface thereof may be
surface-treated, or no surface treatment may be performed. As a
surface treatment, a matte processing, lubrication processing
without using a silicone resin and the like are preferable. In the
case a surface thereof is treated with any of the aforementioned
processes, a lubricity of the surface is improved compared to the
surface without any surface treatment. Moreover, in these processes
of the surface treatment, as the silicone resin is not used,
silicone oligomers do not bleed out under the condition of high
temperature and/or high humidity, and thus it is suitably used
inside of an electronic equipment.
[0110] The matte processing is suitably selected depending on the
intended purpose without any restriction. Examples thereof include
a sand matte processing, chemical matte processing, surface emboss
processing and the like. By these processing, the convex-concave
pattern is formed on the convex-concave forming layer and as a
result, a lubricity thereof is improved.
[0111] The convex-concave forming layer preferably has Bekk
smoothness of 200 sec/mL or less before hot pressing.
[0112] When Bekk smoothness thereof is more than 200 sec/mL before
hot pressing, it adversely affects Bekk smoothness after hot
pressing.
[0113] Pattern-Transferring Material--
[0114] The structure, thickness and material of the
pattern-transferring material are suitably selected depending on
the intended purpose without any restriction. For example, those
having a convex-concave pattern on the surface thereof and
excellent air permeability are preferable. In this case, once the
convex-concave pattern convex-concave forming layer on the surface
of the pattern transferring material is transferred to the
convex-concave forming layer, the convex-concave pattern is formed
on the surface of the convex-concave forming layer, and as a
result, Bekk smoothness of the convex-concave forming layer is
lowered and lubricity of the convex-concave forming layer is
improved.
[0115] The surface irregularities of the pattern transferring
material can be evaluated by the value of Bekk smoothness. The
smaller the value of Bekk smoothness is the larger the
irregularities are.
[0116] The structure of the pattern transferring material may be a
monolayered structure or laminate structure.
[0117] The thickness of the pattern transferring material is
preferably 25 .mu.m to 200 .mu.m.
[0118] When the thickness thereof is less than 25 .mu.m, it may not
be able to attain a magnetic sheet of low Bekk smoothness. When the
thickness thereof is more than 200 .mu.m, heat does not easily
transfer to the magnetic layer at the time of hot pressing, and
thus the reliability may be lowered.
[0119] The material of the pattern transferring material is, for
example, paper, synthetic fibers, or natural fibers.
[0120] The pattern-transferring material may be a commercially
available product or arbitrarily prepared product. Examples of the
commercially available product include a high quality paper
(product name: OK Prince High Quality 70, manufacturer: Oji Paper
Co., Ltd., Bekk smoothness: 6.2 sec/mL), a cushioned paper (product
name: TF190, manufacturer: THE TOYO FIBER CO., LTD., Bekk
smoothness: 1.7 sec/mL), nylon mesh (product name: N-No. 110S,
manufacturer: TOKYO SCREEN CO., LTD., Bekk smoothness: less than
0.1 sec/mL), cotton cloth (product name: Kanakin No. 3,
manufacturer: Japanese Standards Association, Bekk smoothness: less
than 0.1 sec/mL), a base paper for an adhesive (product name: SO
base paper 18G, manufacturer: DAIFUKU PAPER MFG CO., LTD., Bekk
smoothness: less than 0.1 sec/mL), a double sided release paper
(product name: 100GVW (High lubricity surfaces), manufacturer: Oji
Paper Co., Ltd., Bekk smoothness: 146 sec/mL), and a double sided
release paper (product name: 100GVW (Low lubricity surfaces),
manufacturer: Oji Paper Co., Ltd., Bekk smoothness: 66 sec/mL).
[0121] Arrangement of Stacked Layers--
[0122] The method for an arrangement of stacked layers is suitably
selected depending on the purpose without any restriction, provided
that the convex-concave forming layer and the pattern transferring
material are stacked on at least one surface of the magnetic layer
in this order. It is preferred that a release layer and the pattern
transferring material are further stacked on the other surface of
the magnetic layer in this order. As the pattern transferring
material are stacked on the other surface of the magnetic layer
with the release layer being placed in between, the other surface
of the magnetic layer is protected and prevented from closely
attaching to the pattern transferring material at the time of hot
pressing mentioned later, and the pattern transferring layer is
easily peeled from the magnetic layer along with the release layer
after hot pressing. Moreover, the surface configuration of the
pattern transferring material is transfer to the surface of the
magnetic layer which is present at the side of the releasing layer,
and at this time, air bubbles present in the resin composition of
the magnetic layer are easily released, and thus the reliability of
the obtained magnetic sheet is improved. In the case where the
pattern transferring material is not used at the side of the
release layer, magnetic permeability of the magnetic sheet is
improved.
[0123] The release layer is suitably selected depending on the
intended purpose without any restriction, provided that it
functions to prevent the close attachment between the other surface
of the magnetic layer and the pattern transferring material at the
time of hot pressing. The release layer is preferably a polyester
film a surface of which is lubrication processed (lubrication
processed PET), as it is easily peeled from the magnetic layer
after hot pressing.
[0124] Hot Press--
[0125] The method for hot pressing is suitably selected depending
on the intended purpose without any restriction. For example, it is
performed by sandwiching stacked layers of the magnetic layer, the
convex-concave forming layer and the pattern transferring layer
with a laminator or press the stacked layers from the both sides
thereof, then heating and pressing the same.
[0126] As a result of hot pressing, the surface configuration
(convex-concave pattern) of the pattern transferring material is
transferred to surfaces of the convex-concave forming layer and
magnetic layer, and also the convex-concave forming layer and the
magnetic layer are directly bonded to each other without using an
adhesive or the like.
[0127] The conditions for hot pressing are suitably adjusted
depending on the intended purpose without any restriction. For
example, the temperature is preferably 80.degree. C. to 190.degree.
C., the pressure is preferably 5 MPa to 20 MPa, and the duration is
preferably 1 minute to 20 minutes.
[0128] Bekk smoothness of the convex-concave forming layer after
hot pressing is preferably 70 sec/mL or less, more preferably 1
sec/mL to 60 sec/mL.
[0129] When Bekk smoothness thereof is more than 70 sec/mL, the
surface lubricity of the convex-concave forming layer may be
insufficient, and as a result, the magnetic sheet and a member
which is brought into contact with the magnetic sheet may be
adhered.
[0130] According to the aforementioned step, the surface
configuration of the pattern transferring material is transferred
to the surfaces of the convex-concave forming layer and magnetic
layer at the same time as the convex-concave forming layer and the
magnetic layer are bonded to each other. As a result, a magnetic
sheet containing the magnetic layer and the convex-concave forming
layer is obtained.
[0131] The magnetic sheet obtained in the aforementioned manner has
the convex-concave forming layer a surface of which has the surface
configuration transferred from the surface configuration
(convex-concave surface pattern) of the pattern transferring
material and is roughened, and thus Bekk smoothness thereof is low
and the lubricity thereof is excellent.
[0132] According to the method for producing the magnetic sheet of
the present invention, a surface configuration of the pattern
transferring material is transferred to surfaces of the
convex-concave forming layer and magnetic layer by hot pressing,
and thus a surface of the convex-concave forming layer is
roughened, Bekk smoothness thereof is reduced, and the lubricity is
improved.
[0133] Therefore, Bekk smoothness of the convex-concave forming
layer can be suitably controlled in the desirable range regardless
of the original value of Bekk smoothness of the convex-concave
forming layer, and thus the selection of the material used for the
convex-concave forming layer is widened. In addition, the control
of Bekk smoothness can be performed easily.
[0134] Moreover, as the convex-concave forming layer and the
magnetic layer are directly bonded to each other by hot pressing,
an adhesive layer is unnecessary, and thus a magnetic sheet can be
easily and efficiently produced at low cost.
(Magnetic Sheet)
[0135] The magnetic sheet is suitably selected depending on the
intended purpose without any restriction, provided that it is
produced by the method for producing a magnetic sheet mentioned
earlier.
[0136] Use--
[0137] The method for using the magnetic sheet of the present
invention is suitably selected depending on the intended purpose
without any restriction. For example, the magnetic sheet may be cut
into a desirable size, and disposed in an electronic equipment so
that the magnetic sheet is placed adjacent to a noise source of the
electronic equipment.
[0138] Application--
[0139] The magnetic sheet of the present invention can be suitably
applied for electromagnetic noise depressors, electromagnetic wave
absorbers, magnetic shielding, electronic equipments having IC tag
functions such as Radio Frequency Identification (RFID), and
non-contact IC cards. Particularly, the magnetic sheet can be
suitably used for RFID functioned mobile phones.
EXAMPLES
[0140] Examples of the present invention will be explained
hereinafter, but these examples shall not be construed as limiting
the scope of the present invention.
Example 1
Preparation of Curing Agent
[0141] Sulfonium anthimonate complexes respectively expressed by
the formula 1d, 1e and 1f (see JP-A No. 10-245378 for synthesis
methods thereof) were each made dissolved in ethyl acetate to
prepare a 10% by mass ethyl acetate solution of each complex. A 10%
solution of sodium borate expressed by the formula 3 (see JP-A No.
10-310587 for a synthesis method thereof) was prepared separately
to above.
[0142] The 10% by mass solution of the sodium borate expressed by
the formula 3 was mixed in the 10% by mass ethyl acetate solution
of the complex in an equimolecular amount at room temperature, and
the mixture was stirred for 30 minutes. Thereafter, the ethyl
acetate layer was separated from the reacted mixed solution, and
dried. The ethyl acetate was then removed under the reduced
pressure. As a result, the sulfonium borate complex
(4-hydroxyphenyl-methyl-1-naphthylmethyl sulfonium
tetrakis(pentafluorophenyl) borate) expressed by the formula 1a,
the sulfornium borate complex
(4-hydroxyphenyl-methyl-(2-methylbenzyl)sulfonium
tetrakis(pentafluorophenyl) borate) expressed by the formula 1b,
and the sulfonium borate complex
(4-hydroxyphenyl-methyl-benzylsulfonium
tetrakis(pentafluorophenyl)borate) expressed by the formula 1c were
each obtained as an evaporated residue.
##STR00006##
[0143] The sulfonium borate complexes 1a and 1b were each subjected
to mass spectrometry (measuring device: AQUITY HPLC System,
manufacturer: Nihon Waters K.K.), an elemental analysis (measuring
device: PHOENIX, manufacturer: EDAX Inc.), an IR analysis
(measuring device: 7000e FT-IR, manufacturer: Varian Technologies
Japan Limited), and .sup.1H-NMR analysis (measuring device: MERCURY
PLUS, manufacturer: Varian Technologies Japan Limited). As a
result, these complexes found to be targeted compounds.
Analysis Result of Sulfonium Borate Complex
[0144] (4-hydroxyphenyl-methyl-1-naphthylmethyl sulfonium
tetrakis(pentafluorophenyl) borate) of Formula 1a
<Result of MS Analysis>
[0145] M.sup.+=281 (sulfonium residue)
[0146] M.sup.+=679 (borate residue)
<Result of Element Analysis>
[0147] Actual Value: C, 52.51; H, 1.89
[0148] Theoretical Value: C, 52.52; H, 1.78
<Result of IR Analysis (cm.sup.-1)>
[0149] 662 (C--S), 776, 980, 1088, 1276 (Ar--F), 1300, 1374, 1464,
1514, 1583, 1643, 2881 (C--H), 2981 (C--H), 3107 (O--H)
<Result of .sup.1H-NMR Analysis (.delta.), see FIG. 1 (using
THF)>
[0150] 2.6 (1H, (d)), 3.3 (3H, (a)), 5.3 (2H, (e)), 6.9 (2H, (c)),
7.6 (2H, (b)), 7.2 to 8.1 (7H, (f), (g), (h), (i), (j), (k),
(l))
<Assignment of Proton>
##STR00007##
[0151] Analysis Result of Sulfonium Borate Complex
[0152] (4-hydroxyphenyl-methyl-(2-methylbenzyl)sulfonium
tetrakis(pentafluorophenyl) borate) of Formula 1b
<Result of MS Analysis>
[0153] M.sup.+=245 (sulfonium residue)
[0154] M.sup.+=679 (borate residue)
<Result of Element Analysis>
[0155] Actual Value: C, 50.39; H, 1.77
[0156] Theoretical Value: C, 50.60; H, 1.80
<Result of IR Analysis (cm.sup.-1)>
[0157] 662 (C--S), 773, 980, 1088, 1276 (Ar--F), 1463, 1514, 1583,
1644, 2882 (C--H), 2983 (C--H), 3109 (O--H)
<Result of .sup.1H-NMR Analysis (.delta.), see FIG. 2 (using
THF)>
[0158] 2.3 (3H, (j)), 2.4 (1H, (d)), 3.3 (3H, (a)), 4.8 (2H, (e)),
7.0 (2H, (c)), 7.6 (2H, (b)), 7.0 to 7.4 (4H, (0, (g), (h),
(i))
##STR00008##
[0159] Evaluation of Properties--
[0160] The sulfonium borate complexes 1a to 1c and sulfonium
antimonate complexes 1d to 1f were each subjected to the
measurement of the fluorine-ion concentration under the same
temperature condition to that of thermal cationic polymerization in
the manner described below. Moreover, a thermal cationic
polymerization composition was prepared using each complex, and the
prepared composition was subjected to a differential thermal
analysis (DSC) at the temperature rising rate of 10.degree.
C./min.
[0161] Measurement of Fluorine Ion Concentration--
[0162] To 10 mL of pure water, 0.2 g of each complex was added, and
the mixture was heated at 100.degree. C. for 10 hours. Then, an
amount of fluorine ions contained in the supernatant was measured
by an ion chromatography system (manufactured by Dionex
Corporation). The results are shown in Table 1. It is preferred
that the result be less than 10 ppm for the practical use.
[0163] DSC--
[0164] In 100 parts by mass of a fluid epoxy resin (Epikote 828,
manufactured by Japan Epoxy Resins Co., Ltd.) the complexes of
Examples 1 and 2, and Comparative Examples 1 to 4 were each mixed
to prepare a thermal cationic polymerization composition. Here, the
complexes of Examples 1 and 2 were each mixed in an amount of 1
part by mass, the complex of Comparative Example 1 was mixed in an
amount of 3 parts by mass, and the complexes of Comparative
Examples 2 to 4 were each mixed in an amount of 5 parts by mass.
Each thermal cationic polymerization composition was subjected to a
differential thermal analysis (heating onset temperature, peak
temperature, calorific value) by means of a thermal analysis
equipment (DSC 5100, manufactured by Seiko Instruments Inc.). The
results are shown in Table 1.
[0165] Note that, the heating onset temperature is temperature at
which protons are generated from the complex to initiate cationic
polymerization. The low-temperature curing ability is more enhanced
as the heat onset temperature is lower. However, in this case, the
storage stability tends to decrease. Therefore, it is preferably
80.degree. C. to 110.degree. C. Moreover, when the thermal peak
temperature is excessively low, the storage stability reduced. When
it is excessively high, curing failures tend to occur. Therefore,
the thermal peak temperature is preferably 100.degree. C. to
140.degree. C. The calorific value is corresponded to heat of the
reaction, and is preferably 200 J/g or larger as curing failures
tend to occur with the excessively small calorific value.
TABLE-US-00001 TABLE 1 Exothermic F-ion Reaction onset peak
Calorific concentration temperature temperature value Complex (ppm)
(.degree. C.) (.degree. C.) (J/g) 1a 2.1 85 114 250 1b 2.3 105 134
320 1c 2.3 115 147 270 1d 160,000 83 118 290 1e 170,000 106 135 300
1f 172,000 116 146 280
[0166] Preparation of Magnetic Sheet--
[0167] At first, in a mixture of 270 parts by mass of toluene and
120 parts by mass of ethyl acetate, 83 parts by mass of acrylic
rubber having epoxy groups (SG80H-3, manufactured by Nagase ChemteX
Corporation, a number average molecular mass of 150,000, a mass
average molecular mass of 350,000) serving as a binder, 23.1 parts
by mass of an epoxy resin (Epikote 1031S, manufactured by Japan
Epoxy Resins Co., Ltd.) serving as a binder, and 6.9 parts by mass
of a cationic curing agent A
(4-hydroxyphenyl-methyl-1-naphthylsulfoniumtetrakis(pentafluorophenyl)bor-
ate; Formula 1a) serving as a curing agent were made dissolved to
prepare a resin composition. To the resin composition, 550 parts by
mass of a flat magnetic powder (JEM-S, manufactured by Mitsubishi
Materials Corporation) serving as a magnetic powder was added, and
mixed to prepare a magnetic sheet composition.
[0168] Next, the obtained magnetic sheet composition was applied
onto a polyester film a surface of which had been lubricated
processed (a release PET) (38GS manufactured by Lintec Corporation,
thickness of 38 .mu.m) as a substrate using a bar coater (i.e., the
magnetic sheet composition was applied on the surface which had
been lubricated processed), to form a layer having a thickness of
100 .mu.m to 200 .mu.m.
[0169] Next, the applied coat was dried at room temperature for 10
minutes, and then dried at 60.degree. C. for 10 minutes. The
release PET on the lubrication-processed surface of which a layer
formed of the magnetic sheet composition (a magnetic layer) had
been formed was cut into the size of 250 mm.times.250 mm, to
thereby obtain 4 pieces of the release PET on the
lubrication-processed surface of which the magnetic layer had been
formed in the size of 250 mm.times.250 mm. Regarding two pieces of
the release PET on the lubrication-processed surface of which the
magnetic layer in the size of 250 mm.times.250 mm had been formed,
the release PET was removed from the magnetic layer, to thereby
obtain two pieces of the 250 mm.times.250 mm magnetic layer. The
two magnetic layers (each in the size of 250 mm.times.250 mm) were
placed and stacked on the magnetic layer side of the release PET on
the lubrication-processed surface of which the magnetic sheet in
the size of 250 mm.times.250 mm had been formed. Moreover, to the
side of the lubrication-processed surface of this release PET, one
piece of the release PET on the lubrication-processed surface of
which the magnetic layer in the size of 250 mm.times.250 mm had
been formed was placed and stacked (so that the magnetic layers
were facing each other), to thereby obtain a release PET in which
four magnetic layers were stacked and both surfaces of the stacked
layers were both held with a pair of the release PETs (i.e. the
lubrication-processed surfaces of the two release PET were arranged
so as to be in contact with the magnetic layers).
[0170] Next, on both surfaces of the stacked layers, which
consisted of the release PET, and the four magnetic layers stacked
on another release PET, two pieces of high quality paper (product
name: OK Prince High Quality 70, manufacturer: Oji Paper Co., Ltd.,
thickness: 100 .mu.m, Bekk smoothness: 6.2 sec/mL) used as buffer
materials were respectively stacked. Then, the stacked buffer
materials were hot-pressed by means of press plates using a vacuum
press (manufactured by KITAGAWA SEIKI Co., Ltd.) under the
conditions of the press-retaining temperature of 170.degree. C.,
press-retaining duration (i.e. the time-period during which the
press-retaining temperature was maintained) of 5 minutes, press
duration (i.e., the time required to come drown to 90.degree. C.
after reaching the press-retaining temperature from 90.degree. C.)
of 38 minutes, and press-pressure of 9 MPa. Thereafter, the two
release PET were removed from the magnetic layer formed by curing
the laminated four magnetic layers, to thereby obtain a magnetic
sheet.
Examples 2 to 7
Preparation of Magnetic Sheet--
[0171] Magnetic sheets of Examples 2 to 7 were each prepared in the
same manner as in Example 1, provided that at least one of the
formulated amount of the cationic curing agent A, the press
retaining temperature, and the press retaining duration were
changed as presented in Table 2.
Example 8
Preparation of Magnetic Sheet
[0172] A magnetic sheet of Example 8 was prepared in the same
manner as in Example 1, provided that as the curing agent, a
cationic curing agent C (4-hydroxyphenyl-methyl-benzyl sulfonium
tetrakis(pentafluorophenyl)borate; the formula (1c)) was used
instead of the cationic curing agent A
(4-hydroxyphenyl-methyl-1-naphthylmethyl sulfonium
tetrakis(pentafluorophenyl) borate; the formula (1a)).
Examples 9 and 10
Preparation of Magnetic Sheet
[0173] Magnetic sheets of Examples 9 and 10 were each prepared in
the same manner as in Example 8, provided that at least one of the
formulated amount of the cationic curing agent C, the
press-retaining temperature, and the press-duration were changed as
presented in Table 3.
Example 11
Preparation of Magnetic Sheet
[0174] A magnetic sheet of Example 11 was prepared in the same
manner as in Example 2, provided that as the curing agent, the
cationic curing agent B (4-hydroxyphenyl-methyl-(2-methylbenzyl)
sulfonium tetrakis(pentafluorophenyl) borate; the formula (1b)) was
used instead of the cationic curing agent A
(4-hydroxyphenyl-methyl-1-naphthyl sulfonium
tetrakis(pentafluorophenyl)borate; the formula (1a)).
Example 12
Preparation of Magnetic Sheet
[0175] A magnetic sheet of Example 12 was prepared in the same
manner as in Example 2, provided that as the magnetic powder, a
flat magnetic powder (SP-1, manufactured by MATE CO., LTD.) was
used instead of the flat magnetic powder (JEM-S, manufactured by
Mitsubishi Materials Corporation).
Example 13
Preparation of Magnetic Sheet
[0176] A magnetic sheet of Example 13 was prepared in the same
manner as in Example 1, provided that as the magnetic powder, a
flat magnetic powder (SP-1, manufactured by MATE CO., LTD.) was
used instead of the flat magnetic powder (JEM-S, manufactured by
Mitsubishi Materials Corporation).
Example 14
Preparation of Magnetic Sheet
[0177] A magnetic sheet of Example 14 was prepared in the same
manner as in Example 1, provided that as the magnetic powder, 900
parts by mass of a flat magnetic powder (EMS10, manufactured by
Mitsubishi Materials Corporation) was used instead of 550 parts by
mass of the flat magnetic powder (JEM-S, manufactured by Mitsubishi
Materials Corporation), and the formulated amount of the cationic
curing agent A was changed from 6.9 parts by mass to 8 parts by
mass.
Example 15
Preparation of Magnetic Sheet
[0178] A magnetic sheet of Example 15 was prepared in the same
manner as in Example 1, provided that the formulated amount of the
flat magnetic powder (JEM-S, manufactured by Mitsubishi Materials
Corporation) was changed from 550 parts by mass to 1,600 parts by
mass, the formulated amount of the cationic curing agent A was
changed from 6.9 parts by mass to 10 parts by mass, and a
convex-concave forming layer and a pattern-transferring material
were stacked in this order on one plane of the magnetic layer,
which had bee formed by thermosetting the magnetic sheet
composition, followed by hot-pressing to transfer the pattern.
[0179] Pattern Transferring--
[0180] A matte-surface treated polyester film (matte-processed PET)
(product name: LUMIRRORX44-#25, manufacturer: Toray Industries,
Inc., thickness: 25 .mu.m, Bekk smoothness: 101.8 sec/mL) serving
as a convex-concave forming layer, and a high quality paper
(product name: OK Prince High Quality 70, manufacturer: Oji Paper
Co., Ltd., thickness: 100 .mu.m, Bekk smoothness: 6.2 sec/mL)
serving as a pattern transferring material were stacked on a
surface of the magnetic layer so that the convex-concave forming
layer and the pattern transferring material were stacked in this
order from the side of the magnetic layer.
[0181] Moreover, on the other surface of the magnetic layer, a
surface-lubrication-processed polyester film (manufactured by
Lintec Corporation) serving as a release layer, and a high quality
paper (product name: OK Prince High Quality 70, manufacturer: Oji
Paper Co., Ltd., thickness: 100 .mu.m, Bekk smoothness: 6.2 sec/mL)
serving as a pattern transferring material were stacked, to thereby
form a stacked body.
[0182] Thereafter, the stacked body was subjected to hot pressing
using a vacuum press (manufactured by KITAGAWA SEIKI CO., LTD.) at
temperature of 170.degree. C., and pressure of 9 MPa, for 10
minutes, by sandwiching the stacked body from both sides thereof
with press plates to form the magnetic layer having a thickness of
80 .mu.m. As a result, the convex-concave forming layer and the
magnetic layer were bonded, and at the same time, the surface
configuration of the pattern transferring material was transferred
to a surface of the laminate of the convex-concave forming layer
and the magnetic layer. The processes mentioned above were
corresponded to the pattern transferring step.
[0183] The laminate, which had been hot-pressed, was cut into a
sample size of 250 mm.times.250 mm.
[0184] Then, the pattern transferring material and the release
layer were released from the convex-concave forming layer and the
magnetic layer to thereby obtain a magnetic sheet having a
thickness of 105 .mu.m.
[0185] Note that, the Bekk smoothness thereof after the
hot-pressing was 26.3 sec./mL.
Example 16
Preparation of Magnetic Sheet
[0186] A magnetic sheet of Example 16 was prepared in the same
manner as in Example 1, provided that the formulated amount of the
flat magnetic powder (JEM-S, manufactured by Mitsubishi Materials
Corporation) as the magnetic powder was changed from 550 parts by
mass to 1,200 parts by mass, the formulated amount of the cationic
curing agent A was changed from 6.9 parts by mass to 10 parts by
mass, and 10 parts by mass of red phosphorous (manufactured by
Rinkagaku Kogyo Co., Ltd.) and 90 parts by mass of carboxylic acid
amide-containing melamine cyanurate (MC-5F, manufactured by Sakai
Chemical Industry Co., Ltd.) were further added.
Example 17
Preparation of Magnetic Sheet
[0187] A magnetic sheet of Example 17 was prepared in the same
manner as in Example 1, provided that as the magnetic powder, 900
parts by mass of a flat magnetic powder (EMS 10, manufactured by
Mitsubishi Materials Corporation) was used instead of 550 parts by
mass of the flat magnetic powder (JEM-S, manufactured by Mitsubishi
Materials Corporation), the formulated amount of the cationic
curing agent A was changed from 6.9 parts by mass to 8 parts by
mass, and 10 parts by mass of red phosphorous (manufactured by
Rinkagaku Kogyo Co., Ltd.) and 90 parts by mass of carboxylic acid
amide-containing melamine cyanurate (MC-5F, manufactured by Sakai
Chemical Industry Co., Ltd.) were further added.
Comparative Example 1
Preparation of Magnetic Sheet
[0188] A magnetic sheet of Comparative Example 1 was prepared in
the same manner as in Example 1, provided that as the curing agent,
an imidazole-based curing agent (HX3748, manufactured by Asahi
Kasei Chemicals Corporation) was used instead of the cationic
curing agent A (4-hydroxyphenyl-methyl-1-naphthyl sulfonium
tetrakis(pentafluorophenyl)borate; the formula (1a)).
Comparative Example 2
Preparation of Magnetic Sheet
[0189] A magnetic sheet of Comparative Example 2 was prepared in
the same manner as in Example 2, provided that as the curing agent,
an imidazole-based curing agent (HX3748, manufactured by Asahi
Kasei Chemicals Corporation) was used instead of the cationic
curing agent A (4-hydroxyphenyl-methyl-1-naphthyl sulfonium
tetrakis(pentafluorophenyl)borate; the formula (1a)).
Comparative Example 3
Preparation of Magnetic Sheet
[0190] A magnetic sheet of Comparative Example 3 was prepared in
the same manner as in Example 3, provided that as the curing agent,
an imidazole-based curing agent (HX3748, manufactured by Asahi
Kasei Chemicals Corporation) was used instead of the cationic
curing agent A (4-hydroxyphenyl-methyl-1-naphthyl sulfonium
tetrakis(pentafluorophenyl) borate; the formula (1a)).
Comparative Example 4
Preparation of Magnetic Sheet
[0191] A magnetic sheet of Comparative Example 4 was prepared in
the same manner as in Example 4, provided that as the curing agent,
an imidazole-based curing agent (HX3748, manufactured by Asahi
Kasei Chemicals Corporation) was used instead of the cationic
curing agent A (4-hydroxyphenyl-methyl-1-naphthyl sulfonium
tetrakis(pentafluorophenyl) borate; the formula (1a)).
Comparative Example 5
Preparation of Magnetic Sheet
[0192] A magnetic sheet of Comparative Example 5 was prepared in
the same manner as in Example 5, provided that as the curing agent,
an imidazole-based curing agent (HX3748, manufactured by Asahi
Kasei Chemicals Corporation) was used instead of the cationic
curing agent A (4-hydroxyphenyl-methyl-1-naphthyl sulfonium
tetrakis(pentafluorophenyl) borate; the formula (1a)).
Comparative Example 6
Preparation of Magnetic Sheet
[0193] A magnetic sheet of Comparative Example 6 was prepared in
the same manner as in Example 6, provided that as the curing agent,
an imidazole-based curing agent (HX3748, manufactured by Asahi
Kasei Chemicals Corporation) was used instead of the cationic
curing agent A (4-hydroxyphenyl-methyl-1-naphthyl sulfonium
tetrakis(pentafluorophenyl) borate; the formula (1a)).
Comparative Example 7
Preparation of Magnetic Sheet
[0194] A magnetic sheet of Comparative Example 7 was prepared in
the same manner as in Comparative Example 1, provided that the
press-retaining duration and the press duration were both changed
as presented in Table 6.
Comparative Example 8
Preparation of Magnetic Sheet
[0195] A magnetic sheet of Comparative Example 8 was prepared in
the same manner as in Example 1, provided that as the curing agent,
an antimony-based cationic curing agent (San-Aid SI-60L,
manufactured by Sanshin Chemical Industry Co., Ltd.) was used
instead of the cationic curing agent A
(4-hydroxyphenyl-methyl-1-naphthyl sulfonium
tetrakis(pentafluorophenyl)borate; the formula (1a).
[Magnetic Permeability]
[0196] At first, a ring sample, which had been cut out so as to
have an outer diameter of 7.05 mm, and an inner diameter of 2.945
mm, was prepared. A lead-wire was then wound around the ring sample
5 times, and then it was soldered to a terminal. Here, the length
between the bottom of the terminal and the bottom of the ring
sample was set 20 mm. Then, the inductance and resistance thereof
at 1 MHz were measured using an impedance analyzer (4294A,
manufactured by Agilent Technologies, Inc.), and the obtained
values were converted into magnetic permeability.
[0197] Note that, .mu.' denotes a real part of complex magnetic
permeability.
[0198] The properties of .mu.' are different depending on the
intended use of a magnetic sheet. For example, in the case where it
is used for improving a correspondence of a RFID device, it is
preferred that the value of is high and the value of .mu.'' (an
imaginary part of complex magnetic permeability) is low at the
frequency of 20 MHz or lower.
[0199] Moreover, the magnetic sheet of the present invention is
usable in the frequency range of KHz to GHz.
[Reliability Test]
[0200] Change in Thickness--
[0201] At first, a thickness of the magnetic sheet was measured.
Then, the magnetic sheet was placed in an oven, and heated at
85.degree. C., and 60% RH for 96 hours. After taking the magnetic
sheet out from the oven, the thickness of the magnetic sheet was
measured again, and a rate of the change in the thickness of the
magnetic sheet before and after heating was measured.
[Fluorine (F.sup.-1) Ion Elution Test]
[0202] A magnetic sheet sample (about 0.2 g) of Example 1 and a
magnetic sheet sample (about 0.2 g) of Comparative Example 8 were
each separately added to a PP container having 10 mL of ultrapure
water. The container was then placed in an oven set at 100.degree.
C., and was left there for 10 hours. Thereafter, 10 mL of an
extract was taken out from the container, and was subjected to the
measurement of a fluorine (F.sup.-1) ion concentration (.mu.g/mL).
Based on the obtained fluorine (F.sup.-1) ion concentration
(.mu.g/mL) of the extract, a fluorine (F.sup.-1) ion concentration
(.mu.g/g) per g of the magnetic sheet sample was calculated using
the following formula (1). The results are shown in Table 7.
(Fluorine (F.sup.-1) ion concentration (.mu.g/mL)-blank average
value (.mu.g/mL)).times.10 (mL)/(weight of magnetic sheet sample
(g)) <Formula (1)>
[Corrosion Test]
[0203] A magnetic sheet sample (about 0.2 g) of Example 1 and a
magnetic sheet sample (about 0.2 g) of Comparative Example 8 were
each separately added to a plastic container (DESCUP) containing 50
mL of tap water. Then, the container was placed in an oven set at
85.degree. C. and 85% RH, and was left there for 16 hours.
Thereafter, the magnetic sheet sample was taken out from the
plastic container containing 50 mL of tap water, and the
cross-sectional plane of the magnetic sheet was observed under a
microscope. The results are shown in FIGS. 3A and 3B, and Table
7.
[Combustion Test]
[0204] Magnetic sheet samples of Example 16 and Example 17 were
both subjected to the combustion test in the following manner.
[0205] As the combustion test, a UL94V test (a combustion test for
a plastic material of machinery parts) was carried out. The UL94V
test was a method for evaluating flame resistance based on the
afterflame time, after placing a certain size of a sample directly
in a flame of a burner for 10 seconds with the sample held
vertically. The results were evaluated based on the following
criteria.
[0206] Evaluation Criteria--
[0207] V-0: The afterflame time of each sample was 10 seconds or
shorter, and the total afterflame time of 5 samples was 50 seconds
or shorter.
[0208] V-1: The afterflame time of each sample was 30 seconds or
shorter but longer than 10 seconds, and the total afterflame time
of 5 samples was 250 seconds or shorter but longer than 50
seconds.
[0209] V-2: The combustion time (afterflame time?) was the same as
V-1, but there were flame-droppings.
[0210] NG: The flame resistance was low, and it did not comply with
the standard of UL94V.
[0211] Here, "afterflame time" means a length of time showing how
long flame combustion of the test sample continues after an
ignition source is moved away.
[Method of Measuring LOSS Properties (Transmission Loss)]
[0212] Magnetic sheets of Examples 16 and 17 were each subjected to
the measurement of LOSS properties (transmission loss) in the
following manner.
[0213] For measurement of transmission loss, a microstripline
having an impedance Z of 50.OMEGA. was used. The use of the
microstripline line was a commonly used method for measuring
transmission loss of adjacent noise, because of its structure
suitable for mounting a surface-mounting component and production
easiness. The shape of the microstripline 2 used is shown in FIG.
4. The transmission loss was measured in such a manner that a
linear conductor path was provided on a surface of an insulator
substrate, and a magnetic sheet was placed on the conductor path
for measurement. Both ends of the conductor path were connected to
a network analyzer 1. Then, a reflection amount (dB) and a
permeation amount (dB) from the part where an electromagnetic wave
absorption material was mounted, was measured with respect to
incident wave shown by an arrow, and the difference between the
reflection amount (dB) and the permeation amount (dB) was obtained
as a loss amount, and thus a transmission loss (absorptance) was
obtained (incident amount=reflection S11+loss+permeation S21).
Specifically, a known amount of an electromagnetic wave was
incident, the reflection amount S11 and the permeation amount S21
were measured, and then calculated to obtain a loss amount.
[0214] The thicker the magnetic sheet was, the higher the
transmission loss of the microstripline became. Generally, a
magnetic sheet having a thin thickness and high transmission loss
is desired.
TABLE-US-00002 TABLE 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7
Magnetic Flat magnetic 550 550 550 550 550 550 550 powder powder
(JEM-S) (mass part) Binder Acrylic rubber 83 83 83 83 83 83 83
(mass part) (SG80H-3) Epoxy resin 23.1 23.1 23.1 23.1 23.1 23.1
23.1 (1031S) Curing Cationic curing 6.9 6.9 6.9 4.0 4.0 2.0 2.0
agent agent A Hot press Press-retaining 170 150 130 170 150 170 150
temperature (.degree. C.) Press-retaining 5 5 5 5 5 5 5 duration
(min.) Press duration 38 20 16 38 20 38 20 (min.) Magnetic Initial
magnetic 40.4 38.9 38.2 41.0 40.2 40.9 40.1 permeability
permeability .mu.' (1 MHz) Reliability Thickness before 293 321 322
297 299 300 301 test test (.mu.m) Thickness after 294 325 330 300
303 305 307 test (.mu.m) Thickness 0.34 1.25 2.48 1.01 1.34 1.67
1.99 changing rate (%)
TABLE-US-00003 TABLE 3 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13
Magnetic Flat magnetic 550 550 550 550 NA NA powder powder (JEM-S)
(mass part) Flat magnetic NA NA NA NA 550 550 powder (SP-1) Binder
Acrylic rubber 83 83 83 83 83 83 (mass part) (SG80H-3) Epoxy resin
23.1 23.1 23.1 23.1 23.1 23.1 (1031S) Curing Cationic curing NA NA
NA NA 6.9 6.9 agent agent A Cationic curing NA NA NA 6.9 NA NA
agent B Cationic curing 6.9 6.9 10.0 NA NA NA agent C Hot press
Press-retaining 170 150 150 150 150 170 temperature (.degree. C.)
Press-retaining 5 5 5 5 5 5 duration (min.) Press duration 38 20 20
20 20 38 (min.) Magnetic Initial magnetic 42.0 41.3 38.9 42.0 101.5
103.3 permeability permeability .mu.' (1 MHz) Reliability Thickness
before 295 300 308 298 291 287 test test (.mu.m) Thickness after
296 304 309 302 296 290 test (.mu.m) Thickness 0.34 1.33 0.32 1.34
1.72 1.05 changing rate (%)
TABLE-US-00004 TABLE 4 Ex. 14 Ex. 15 Ex. 16 Ex. 17 Magnetic powder
Flat magnetic 900 NA NA 900 (mass part) powder (EMS10) Flat
magnetic NA 1,600 1,200 NA powder (JEM-S) Binder Acrylic rubber 83
83 83 83 (mass part) (SG80H-3) Epoxy resin 23.1 23.1 23.1 23.1
(1031S) Curing agent Cationic curing 8 10 10 8 agent A Red
phosphorus Red phosphorus NA NA 10 10 Carboxylic acid MC-5F NA NA
90 90 amide-containing melamine cyanurate Hot press Press-retaining
170 170 170 170 temperature (.degree. C.) Press-retaining 5 5 5 5
duration (min.) Press duration 38 38 38 38 (min.) Magnetic Initial
magnetic 115.1 46.2 41.3 93.4 permeability permeability .mu.' (1
MHz) Reliability test Thickness before 99 105 99 108 test (.mu.m)
Thickness after 100 107 100 109 test (.mu.m) Thickness 1.01 1.90
1.01 0.93 changing rate (%) Combustion test result NA NA V-0
V-0
TABLE-US-00005 TABLE 5 Comp. Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3
Ex. 4 Magnetic Flat magnetic 550 550 550 550 powder powder (JEM-S)
(mass part) Binder Acrylic rubber 83 83 83 83 (mass part) (SG80H-3)
Epoxy resin 23.1 23.1 23.1 23.1 (1031S) Curing agent
Imidazole-based 6.9 6.9 6.9 4.0 curing agent (HX3748) Hot press
Press-retaining 170 150 130 170 temperature (.degree. C.)
Press-retaining 5 5 5 5 duration (min.) Press duration 38 20 16 38
(min.) Magnetic Initial magnetic 40.5 39.9 38.9 34.6 permeability
permeability .mu.' (1 MHz) Reliability Thickness before 278 283 294
336 test test (.mu.m) Thickness after 284 293 308 347 test (.mu.m)
Thickness 2.16 3.53 4.76 3.27 changing rate (%)
TABLE-US-00006 TABLE 6 Comp. Comp. Comp. Comp. Ex. 5 Ex. 6 Ex. 7
Ex. 8 Magnetic Flat magnetic 550 550 550 550 powder powder (JEM-S)
(mass part) Binder Acrylic rubber 83 83 83 83 (mass part) (SG80H-3)
Epoxy resin 23.1 23.1 23.1 23.1 (1031S) Curing agent
Imidazole-based 4.0 2.0 6.9 NA curing agent (HX3748) Antimony-based
NA NA NA 6.9 curing agent (San-Aid SI-60L) Hot press
Press-retaining 150 170 170 170 temperature (.degree. C.)
Press-retaining 5 5 10 5 duration (min.) Press duration 20 38 43 38
(min.) Magnetic Initial magnetic 32.3 33.0 41.0 40.8 permeability
permeability .mu.' (1 MHz) Reliability Thickness before 341 340 282
303 test test (.mu.m) Thickness after 359 406 286 307 test (.mu.m)
Thickness 5.28 19.41 1.42 1.32 changing rate (%)
TABLE-US-00007 TABLE 7 Comp. Ex. 1 Ex. 8 Magnetic Flat magnetic 550
550 powder powder (JEM-S) (mass part) Binder Acrylic rubber 83 83
(mass part) (SG80H-3) Epoxy resin 23.1 23.1 (1031S) Curing agent
Cationic curing 6.9 NA agent A Antimony-based NA 6.9 curing agent
(San-Aid SI-60L) Hot press Press-retaining 170 170 temperature
(.degree. C.) Press-retaining 5 5 duration (min.) Press duration 38
38 (min.) Magnetic Initial magnetic 40.4 40.8 permeability
permeability .mu.' (1 MHz) Reliability Thickness before 293 303
test test (.mu.m) Thickness after 294 307 test (.mu.m) Thickness
changing 0.34 1.32 rate (%) Elution test F-ion concentration 1.168
13.195 (.mu.m/mL) F-ion concentration 55.597 626.820 (.mu.g/g)
Corrosion test Cross-section No Corrosion observation corrosion at
the edge
TABLE-US-00008 TABLE 8 Loss properties Example 16 Example 17 100
MHz 2.58 3.25 500 MHz 22.1 28.4 1 GHz 55.48 62.1
[0215] From the results shown in Tables 2 to 6, it was found that
the magnetic sheets of Examples 1 to 13, in which the curing agents
each containing a sulfonium borate complex (the cationic curing
agents A to C) were used, had excellent size-stability in the
high-temperature high-humidity environment compared to the magnetic
sheets of Comparative Examples 1 to 8 in which the imidazole-based
curing agent or antimony-based curing agent was used as the curing
agent. This can be seen from the fact that the rate of the change
in the thickness in the reliability test of Examples is smaller
than that of Comparative Examples, comparing the combination of
Example and Comparative Example where only the used curing agents
are different between them in the preparation condition of the
magnetic sheet (e.g. Example 1 and Comparative Example 1; Example 1
and Comparative Example 8; Example 2 and Comparative Example 2;
Example 3 and Comparative Example 3; Example 4 and Comparative
Example 4; Example 5 and Comparative Example 5; Example 6 and
Comparative Example 6; Example 8 and Comparative Example 1; Example
8 and Comparative Example 8; Example 9 and Comparative Example 2;
Example 11 and Comparative Example 2).
[0216] Moreover, from the results shown in FIGS. 3A and 3B, and
Table 7, it was found that the magnetic sheet of Example 1 could
suppress elution of fluorine ions more than the magnetic sheet of
Comparative Example 8, so that the magnetic sheet of Example 1
could prevent corrosion of the magnetic sheet. Note that, it is
assumed that the corrosion seen on the surface of the magnetic
sheet of FIG. 3B is the magnetic powder corroded by impurity ions
(fluorine ions). As mentioned above, the magnetic sheet of Example
1 can prevent corrosion of wirings even when it is used around the
wirings, as the magnetic sheet of Example 1 prevents elution of
fluorine ions.
[0217] Moreover, it was found that the magnetic sheets of Examples
1 to 17 were suitably applied for RFID functioned mobile
phones.
[0218] Furthermore, it was found that the magnetic sheet of Example
15 was usable even through it contained a large amount of the
magnetic powder, which would easily cause cracking. This is because
the magnetic sheet of Example 15 has a convex-concave forming layer
(PET), and thus the magnetic sheet of Example 15 could maintain the
shape thereof (as it was protected by the convex-concave forming
layer (PET)).
[0219] Examples 16 and 17 showed high flame resistance in the
combustion test (Table 4), and high electromagnetic wave-absorbing
abilities in the measurement of LOSS properties (transmission loss)
(Table 8).
[0220] The magnetic sheet of the present invention is suitably used
for, for example, an electromagnetic noise depressor, an
electromagnetic wave absorber, a magnetic shielding material, an
electronic equipment having an IC tag function such as RFID and
non-contact IC card, and is particularly suitably used for a RFID
functioned mobile phone.
* * * * *