U.S. patent application number 09/315404 was filed with the patent office on 2002-04-18 for composite polyester film and magnetic recording medium.
Invention is credited to OSAWA, TOSHIFUMI, TOJO, MITSUO, UCHIDA, TOSHIKAZU.
Application Number | 20020045068 09/315404 |
Document ID | / |
Family ID | 26472486 |
Filed Date | 2002-04-18 |
United States Patent
Application |
20020045068 |
Kind Code |
A1 |
TOJO, MITSUO ; et
al. |
April 18, 2002 |
COMPOSITE POLYESTER FILM AND MAGNETIC RECORDING MEDIUM
Abstract
A composite polyester film comprising (1) a base film C of an
aromatic polyester which does not contain or contains inert
particles having an average particle diameter of 5 to 2,000 nm in
an amount of 0.001 to 5.0 wt % based on the aromatic polyester; (2)
a coating layer A on one side of the base film C, which comprises a
binder resin, inert particles, a surfactant and a siloxane
copolymeried acrylic resin, the outer surface of the coating layer
A being not a surface for forming a magnetic layer thereon, and the
siloxane copolymerized acrylic resin being contained in an amount
of 1 to 50 wt % based on the coating layer A; and, (3) a coating
layer B on the other side where the coating layer A is not existent
of the base file C, which comprises one member selected from the
group consisting of a siloxane copolymerized polyester resin,
siloxane copolymerized acrylic resin, silicone and wax, a binder
resin, inert particles and a surfactant, the outer surface of the
coating layer B being a surface for forming a magnetic layer
thereon, and the above member being contained in an amount of 5 to
90 wt % based on the coating layer B when the member is a siloxane
copolymerized polyester resin or 1 to 50 wt % based on the coating
layer B when the member is other than the siloxane copolymerized
polyester resin.
Inventors: |
TOJO, MITSUO;
(SAGAMIHARA-SHI, JP) ; UCHIDA, TOSHIKAZU;
(SAGAMIHARA-SHI, JP) ; OSAWA, TOSHIFUMI;
(SAGAMIHARA-SHI, JP) |
Correspondence
Address: |
SUGHRUE MION ZINN MACPEAK & SEAS
2100 PENNSYLVANIA AVENUE NW
WASHINGTON
DC
20037
|
Family ID: |
26472486 |
Appl. No.: |
09/315404 |
Filed: |
May 20, 1999 |
Current U.S.
Class: |
428/847.2 ;
G9B/5.284 |
Current CPC
Class: |
G11B 5/73935 20190501;
Y10T 428/24355 20150115; G11B 5/73931 20190501; Y10T 428/2998
20150115; Y10T 428/25 20150115; Y10T 428/31797 20150401; C08J
2483/00 20130101; Y10T 428/254 20150115; Y10T 428/31663 20150401;
C08J 2467/00 20130101; C08J 7/043 20200101; C08J 2367/02 20130101;
C08J 7/0427 20200101; C08J 7/046 20200101; C08J 2433/00 20130101;
Y10S 428/90 20130101; Y10T 428/31786 20150401 |
Class at
Publication: |
428/694.0SL |
International
Class: |
G11B 005/78 |
Foreign Application Data
Date |
Code |
Application Number |
May 21, 1998 |
JP |
10-139782 |
Sep 28, 1998 |
JP |
10-273142 |
Claims
What is claimed is:
1. A composite polyester film comprising: (1) a base film C of an
aromatic polyester which does not contain or contains inert
particles having an average particle diameter of 5 to 2,000 nm in
an amount of 0.001 to 5.0 wt % based on the aromatic polyester; and
(2) a coating layer A on one side of the base film C, which
comprises a binder resin, inert particles, a surfactant and a
siloxane copolymerized acrylic resin, the outer surface of the
coating layer A being not a surface for forming a magnetic layer
thereon, and the siloxane copolymerized acrylic resin being
contained in an amount of 1 to 50 wt % based on the coating layer
A.
2. The composite polyester film of claim 1, wherein the binder
resin contained in the coating layer A is at least one
water-soluble or water-dispersible resin selected from the group
consisting of water-soluble or water-dispersible acrylic resins,
polyester resins and acryl-polyester resins.
3. The composite polyester film of claim 1, wherein the outer
surface of the coating layer A has a center line average roughness
Ra.sup.A of 1 to 30 nm.
4. The composite polyester film of claim 1, wherein the average
particle diameter of the inert particles contained in the coating
layer A is 10 to 200 nm.
5. The composite polyester film of claim 1, wherein the content of
the inert particles in the coating layer A is 5 to 40 wt %.
6. The composite polyester film of claim 1, wherein the surfactant
contained in the coating layer A is a nonionic surfactant.
7. A composite polyester film comprising: (1) a base film C of an
aromatic polyester which does not contain or contains inert
particles having an average particle diameter of 5 to 2,000 nm in
an amount of 0.001 to 5.0 wt % based on the aromatic polyester; and
(2) a coating layer B on one side of the base film C, which
comprises one member selected from the group consisting of a
siloxane copolymerized polyester resin, siloxane copolymerized
acrylic resin, silicone and wax, a binder resin, inert particles
and a surfactant, the outer surface of the coating layer B being a
surface for forming a magnetic layer thereon, and the above member
being contained in an amount of 5 to 90 wt % based on the coating
layer B when the member is a siloxane copolymerized polyester resin
or 1 to 50 wt % based on the coating layer B when the member is
other than the siloxane copolymerized polyester resin.
8. The composite polyester film of claim 7, wherein peel strength
between the outer surface of the coating layer B and the corona
treated exposed surface of the base film C is 15 g/10 cm or
less.
9. The composite polyester film of claim 7, wherein the binder
resin contained in the coating layer B is at least one
water-soluble or water-dispersible resin selected from the group
consisting of water-soluble or water-dispersible acrylic resins,
polyester resins and acryl-polyester resins.
10. The composite polyester film of claim 7, wherein the outer
surface of the coating layer B has a center line average roughness
Ra.sup.B of 0.1 to 2 nm.
11. The composite polyester film of claim 7, wherein protrusions
derived from the inert particles contained in the coating layer B
are existent on the outer surface of the coating layer B at a
density of 1 to 100/.mu.m.sup.2.
12. The composite polyester film of claim 7, wherein the average
particle diameter of the inert particles contained in the coating
layer B is 5 to 100 nm.
13. The composite polyester film of claim 7, wherein the
agglomeration rate of the inert particles contained in the coating
layer B is 20% or less.
14. The composite polyester film of claim 7, wherein the content of
the inert particles contained in the coating layer B is 0.5 to 30
wt %.
15. The composite polyester film of claim 7, wherein large
protrusions having a height of 4 nm or more are existent on the
outer surface of the coating layer B at a maximum density of
200/mm.sup.2.
16. The composite polyester film of claim 7, wherein the surfactant
contained in the coating layer B is a nonionic surfactant.
17. A composite polyester film comprising: (1) a base film C of an
aromatic polyester which does not contain or contains inert
particles having an average particle diameter of 5 to 2,000 nm in
an amount of 0.001 to 5.0 wt % based on the aromatic polyester; (2)
a coating layer A on one side of the base film C, which comprises a
binder resin, inert particles, a surfactant and a siloxane
copolymerized acrylic resin, the outer surface of the coating layer
A being not a surface for forming a magnetic layer thereon, and the
siloxane copolymerized acrylic resin being contained in an amount
of 1 to 50 wt % based on the coating layer A; and (3) a coating
layer B on the other side where the coating layer A is not existent
of the base film C, which comprises one member selected from the
group consisting of a siloxane copolymerized polyester resin,
siloxane copolymerized acrylic resin, silicone and wax, a binder
resin, inert particles and a surfactant, the outer surface of the
coating layer B being a surface for forming a magnetic layer
thereon, and the above member being contained in an amount of 5 to
90 wt % based on the coating layer B when the member is a siloxane
copolymerized polyester resin or 1 to 50 wt % based on the coating
layer B when the member is other than the siloxane copolymerized
polyester resin.
18. A base film for a magnetic recording medium, which comprises
the composite polyester film of claim 1.
19. A base film for a magnetic recording medium, which comprises
the composite polyester film of claim 7.
20. A base film for a magnetic recording medium, which comprises
the composite polyester film of claim 17.
21. A magnetic recording medium comprising the composite polyester
film of claim 1 and a magnetic recording layer on the surface where
the coating layer A of the composite polyester film is not existent
of the base film C.
22. A magnetic recording medium comprising the composite polyester
film of claim 7 and a magnetic recording layer on the outer surface
of the coating layer B of the composite polyester film.
23. A magnetic recording medium comprising the composite polyester
film of claim 17 and a magnetic recording layer on the outer
surface of the coating layer B of the composite polyester film.
Description
DETAILED DESCRIPTION OF THE INVENTION
[0001] The present invention relates to a composite polyester film
and to a magnetic recording medium. More specifically, it relates
to a composite polyester film whose amount of electrostatic charge
is small and which is free from blocking, rarely chipped and
suitable for use as a base film for a high-density magnetic
recording medium having excellent electromagnetic conversion
characteristics, adhesion to a magnetic layer and adhesion to a
back coat and to a magnetic recording medium comprising the same as
a base film.
[0002] A magnetic recording medium such as a video tape, audio
tape, memory tape, magnetic sheet or magnetic disk comprises a base
film and a magnetic layer formed on the surface of the base film.
On a surface opposite to the magnetic layer, a slippery back coat
layer is formed in many cases to achieve slipperiness. As the base
film of the magnetic recording medium is mainly used a polyester
film. The adhesion of the polyester film to the magnetic layer and
the adhesion of the polyester film to the slippery back coat layer
are important properties. If these adhesion properties are
unsatisfactory, the magnetic layer and the back coat layer peel off
and magnetic characteristics are completely lost in the sound
recording, image recording or reproduction step of the magnetic
recording medium.
[0003] Polyester films having improved adhesion include one whose
surface is subjected to corona discharge, one whose surface is
coated with an adhesive resin, and the like. In order to provide a
marked adhesion effect, it is said that the surface of a polyester
base film is desirably coated with an adhesive resin.
[0004] In recent years, along with an increase in magnetic
recording density, the surface of a polyester film used has been
made less rough and more smooth. In this case, blocking readily
occurs when a conventional polyester film coated with an adhesive
resin is rolled and the film is easily broken or torn when it is
unrolled in the production process of a magnetic medium.
[0005] Particularly, in a deposited tape having a magnetic metal
thin film formed on the surface of a polyester film by vacuum
deposition, such as a deposited video tape, the base film used has
a low surface roughness and hence, the slipperiness of the tape
traveling surface must be improved by forming a back coat layer on
a side opposite to a magnetic side. When the surface of the
polyester film is coated with an adhesive resin by a conventional
technology to improve the adhesion of the back coat layer to the
polyester film, blocking readily occurs because the surface
roughness of the base film is extremely low.
[0006] It is considered that this blocking is caused by the fact
that moisture contained in the air permeates into the surface of
the film or penetrates between the contact surfaces of films and
the contact surfaces of the films become a state that they are
adhered to each other by pressure between the films. Film rolls
after film production or before using to base films are kept at low
humidity at a plant. Although it is possible to prevent blocking to
a certain degree by strictly controlling storage conditions, there
is no radical solution to this problem. Particularly, in the case
of a polyester film for a deposited magnetic recording medium, it
is impossible to prevent blocking of an adhesive film by the
control of humidity alone during storage.
[0007] A polyester film which is readily blocked is easily
electrified with electricity and a high electrostatic film involves
such problems that the handling properties of the film greatly
deteriorate at the time of film formation and tape formation,
sparks generated by electrostatic charge may ignite an organic
solvent used for the formation of a tape, and the film easily
adsorbs suspending dust in the air electrically, thereby causing a
drop out in a deposited tape and the like which require
high-density recording.
[0008] JP-A 61-5941 (the term "JP-A" as used herein means an
"unexamined published Japanese patent application") discloses an
adhesive polyester film for use as a base film for a magnetic metal
thin film deposited magnetic recording medium, which comprises a
smooth polyester film having an Ra value of 0.002 to 0.030 .mu.m
and a polymer layer formed on both sides of the polyester film,
wherein at least one of the polymer layers is essentially composed
of an adhesive resin and 0.1 to 30 wt % of silicone based on the
adhesive resin and a magnetic layer is formed on the other polymer
layer. Polyurethanes, polyester ether copolymers, water-soluble
polyester copolymers and polyester copolymers containing a
polyethylene glycol-sulfonic acid alkali metal salt are enumerated
as the adhesive resin. It is disclosed that the silicone compound
usable is a compound having a chain component represented by the
following formula: 1
[0009] wherein R.sub.1 is CH.sub.3, C.sub.6H.sub.5 or H, R.sub.2 is
CH.sub.3, C.sub.6H.sub.5, H or functional group (such as an epoxy
group, amino group or hydroxyl group), and n is an integer of 100
to 7,000.
[0010] JP-A 10-261215 discloses a polyester film for a magnetic
recording medium which comprises a polyester film having a surface
A with an SRa value of 2 to 4 nm and an SRz value of 10 to 40 nm
and a coating layer formed on the other surface B of the polyester
film, the coating layer comprising 20 to 80 wt % of an adhesive
polymer prepared by copolymerizing a fluorine compound or a silicon
compound and fine particles existent in the coating film and/or on
the surface of the coating film, a ferromagnetic metal thin layer
being formed on outside of the surface A, and a back coat layer
being formed on outside of the coating layer.
[0011] JP-A 10-261216 discloses a polyester film for a magnetic
recording medium which comprises a polyester film having a surface
A with an SRa value of 2 to 4 nm and an SRz value of 10 to 40 nm
and a polymer layer essentially composed of an adhesive resin
formed on the other surface B of the polyester film, the adhesive
resin being prepared by copolymerizing 0.1 to 30 wt % of a fluorine
compound or silicon compound, a ferromagnetic metal thin film layer
being formed on outside of the surface A and a back coat layer
being formed on outside of the polymer layer.
[0012] WO98/49008 discloses a low electrostatic composite polyester
film which is a composite film comprising a base film C, a coating
layer A on one side of the base film C and a coating layer B on the
other side of the base film C, wherein
[0013] (1) the coating layer A is made from a water-soluble resin
or water-dispersible resin containing inert particles having an
average particle diameter of 5 to 100 nm and has protrusions on the
surface at a density of 1.times.10.sup.6 to
1.times.10.sup.8/mm.sup.2 and a center line average surface
roughness (Ra-A) of 0.1 to 2 nm;
[0014] (2) the coating layer B comprises 1 to 40 wt % of inert
particles having an average particle diameter of 20 to 100 nm and
60 to 99 wt % of a water-soluble resin- or water-dispersible
resin-containing composition which contains 5 to 85 wt % of a
silicone-modified polyester resin or 1 to 30 wt % of silicone or
wax based on the layer B; and
[0015] (3) the base film C is an aromatic polyester film which does
not contain inert particles or contains inert particles having an
average particle diameter of 5 to 2,000 nm in an amount of 0.001 to
5.0 wt %.
[0016] This composite polyester film is used as a base film for
producing a magnetic recording medium having a magnetic recording
layer on outside of the coating layer A.
[0017] It is an object of the present invention to provide a
composite polyester film whose amount of electrostatic charge is
small and which is free from blocking, rarely chipped and suitable
for use as a base film for a high-density magnetic recording medium
having excellent electromagnetic conversion characteristics,
adhesion to a magnetic layer and adhesion to a back coat.
[0018] It is another object of the present invention to provide a
composite polyester film having a back coat layer having new
composition and the above characteristic properties.
[0019] It is a further object of the present invention to provide a
composite polyester film having a coating layer having new
composition for forming a magnetic layer thereon and the above
characteristic properties.
[0020] It is a still further object of the present invention to
provide a composite polyester film having a back coat layer having
new composition, a coating layer for forming a magnetic layer
thereon and the above characteristic properties.
[0021] It is a still further object of the present invention to
provide a magnetic recording medium comprising the above composite
polyester film of the present invention as a base film.
[0022] Other objects and advantages of the present invention will
become apparent from the following description.
[0023] According to the present invention, firstly, the above
objects and advantages of the present invention are attained by a
composite polyester film (may be referred to as "first composite
polyester film of the present invention" hereinafter)
comprising:
[0024] (1) a base film C of an aromatic polyester which does not
contain inert particles or contains inert particles having an
average particle diameter of 5 to 2,000 nm in an amount of 0.001 to
5.0 wt % based on the aromatic polyester; and
[0025] (2) a coating layer A on one side of the base film C, which
comprises a binder resin, inert particles, a surfactant and a
siloxane copolymerized acrylic resin, the outer surface of the
coating layer A being not a surface for forming a magnetic layer
thereon, and the siloxane copolymerized acrylic resin being
contained in an amount of 1 to 50 wt % based on the coating layer
A.
[0026] Secondly, the above objects and advantages of the present
invention are attained by a composite polyester film (may be
referred to as "second composite polyester film of the present
invention" hereinafter) comprising:
[0027] (1) a base film C of an aromatic polyester which does not
contain inert particles or contains inert particles having an
average particle diameter of 5 to 2,000 nm in an amount of 0.001 to
5.0 wt % based on the aromatic polyester; and
[0028] (2) a coating layer B on one side of the base film C, which
comprises one member selected from the group consisting of a
siloxane copolymerized polyester resin, siloxane copolymerized
acrylic resin, silicone and wax, a binder resin, inert particles
and a surfactant, the outer surface of the coating layer B being a
surface for a forming a magnetic layer thereon, and the above
member being contained in an amount of 5 to 90 wt % based on the
coating layer B when the member is a siloxane copolymerized
polyester resin or 1 to 50 wt % based on the coating layer B when
the member is other than the siloxane copolymerized polyester
resin.
[0029] Thirdly, the above objects and advantages of the present
invention are attained by a composite polyester film (may be
referred to as "third composite polyester film of the present
invention" hereinafter) comprising:
[0030] (1) a base film C of an aromatic polyester which does not
contain inert particles or contains inert particles having an
average particle diameter of 5 to 2,000 nm in an amount of 0.001 to
5.0 wt % based on the aromatic polyester;
[0031] (2) a coating layer A on one side of the base film C, which
comprises a binder resin, inert particles, a surfactant and a
siloxane copolymerized acrylic resin, the outer surface of the
coating layer A being not a surface for forming a magnetic layer
thereon, and the siloxane copolymerized acrylic resin being
contained in an amount of 1 to 50 wt % based on the coating layer
A; and
[0032] (3) a coating layer B on the other side of the base film C
where the coating layer A is not existent, which comprises one
member selected from the group consisting of a siloxane
copolymerized polyester resin, siloxane copolymerized acrylic
resin, silicone and wax, a binder resin, inert particles and a
surfactant, the outer surface of the coating layer B being a
surface for forming a magnetic layer thereon, and the above member
being contained in an amount of 5 to 90 wt % based on the coating
layer B when the member is a siloxane copolymerized polyester resin
or 1 to 50 wt % based on the coating layer B when the member is
other than the siloxane copolymerized polyester resin.
[0033] Further detail description is as follows:
[0034] The first composite polyester film of the present invention
will first be described hereinafter.
[0035] The base film C is made from an aromatic polyester. The
aromatic polyester may contain inert particles. When it contains
inert particles, it contains 0.001 to 5.0 wt % of inert particles
having an average particle diameter of 5 to 2,000 nm.
[0036] The aromatic polyester is selected from polyethylene
terephthalate, polyethylene isophthalate, polytetramethylene
terephthalate, poly-1,4-cyclohexylene dimethylene terephthalate,
polyethylene-2,6-naphth- alene dicarboxylate and the like. Out of
these, polyethylene terephthalate and polyethylene-2,6-naphthalene
dicarboxylate are preferred.
[0037] The aromatic polyester may be either a homopolyester or a
copolyester. In the case of a copolyester, components to be
copolymerizable with polyethylene terephthalate and
polyethylene-2,6-naphthalene dicarboxylate include diol components
such as diethylene glycol, propylene glycol, neopentyl glycol,
polyoxyethylene glycol, p-xylene glycol and
1,4-cyclohexanedimethanol; other dicarboxylic acid components such
as adipic acid, sebacic acid, phthalic acid, isophthalic acid,
terephthalic acid (for polyethylene-2,6-naphthalene dicarboxylate),
2,6-naphthalenedicarboxylic acid (for polyethylene terephthalate)
and 5-sodium sulfoisophthalic acid; oxycarboxylic acid components
such as p-oxyethoxybenzoic acid; and the like. The amount of the
copolymerizable component is 20 mol % or less, preferably 10 mol %
or less.
[0038] Further, a polyfunctional compound having a functionality of
3 or more, such as trimellitic acid or pyromellitic acid, may be
copolymerized. In this case, it is preferably copolymerized in such
an amount that the polymer is substantially linear, for example, 2
mol % or less.
[0039] The thickness of the base film C is preferably 1 to 20
.mu.m, more preferably 2 to 10 .mu.m.
[0040] The base film C in the present invention may or may not
contain inert particles as described above. When it contains inert
particles, the inert particles may be either organic particles or
inorganic particles. The inert particles contained in the base film
C may be the same or different from inert particles contained in
the coating layer A and the coating layer B which will be described
hereinafter in type and average particle diameter. Illustrative
examples of the inert particles include core-shell structured
organic particles such as polystyrene, polystyrene-divinylbenzene,
polymethyl methacrylate, methyl methacrylate copolymer, methyl
methacrylate copolymer crosslinked material,
polytetrafluoroethylene, polyvinylidene fluoride,
polyacrylonitrile, benzoguanamine resin and graft copolymers
comprising these polymers; and inorganic particles such as silica,
alumina, titanium dioxide, feldspar, kaolin, talc, graphite,
calcium carbonate, molybdenum disulfide, carbon black and barium
sulfate. These particles are added to a reaction system preferably
as a slurry contained in glycol during the production of a
polyester, for example, at any time during an ester exchange
reaction or polycondensation reaction when it is produced by an
ester exchange method, or at any time when it is produced by a
direct polymerization method. The average particle diameter of the
inert particles is preferably 5 to 2,000 nm, more preferably 10 to
1,800 nm. The amount of the inert particles is 0.001 to 5.0 wt %,
preferably 0.001 to 2.0 wt %, more preferably 0.01 to 1.5 wt %.
[0041] The volume shape coefficient of the inert particles is
preferably 0.1 to .pi./6, more preferably 0.4 to .pi./6.
[0042] The volume shape coefficient (f) is defined by the following
equation.
f=V/R.sup.3
[0043] wherein f is a volume shape coefficient, V is the volume
(.mu.m.sup.3) of the inert particles and R is the average particle
diameter (.mu.m) of the inert particles.
[0044] When the coefficient (f) is .pi./6, the inert particle is
globular (spherical). When the coefficient is 0.4 to .pi./6, the
inert particle is substantially globular (spherical) or elliptical
like a rugby ball. It is difficult for a particle having a volume
shape coefficient (f) of less than 0.1, for example, a flake-like
particle to achieve sufficient traveling durability.
[0045] The base film C may be a single-layer film or a multi-layer
film consisting of aromatic polyester films having different
compositions of the each layers.
[0046] The first composite polyester film of the present invention
has a coating layer A on one side of the base film C. The coating
layer A comprises a binder resin, inert particles, a surfactant and
a siloxane copolymerized acrylic resin.
[0047] Illustrative examples of the binder resin include alkyd
resins, phenol resins, epoxy resins, amino resins, polyurethane
resins, cellulose resins, vinyl acetate resins, vinyl
chloride-vinyl acetate copolymer, acrylic resins, polyester resins
and acryl-polyester resins.
[0048] Out of these, acrylic resins, polyester resins and
acryl-polyester resins which are water-soluble or water-dispersible
resins are preferred from the viewpoints of adhesion to a polyester
film as a base film, protrusion retention properties and
slipperiness. These resins may be either a homopolymer, copolymer
or mixture. The content of the binder resin is preferably 20 to 90
wt %.
[0049] The above water-soluble and water-dispersible acrylic resins
include, for example, acrylic acid esters (residual alcohol groups
include a methyl group, ethyl group, n-propyl group, isopropyl
group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl
group, cyclohexyl group, phenyl group, benzyl group, phenylethyl
group and the like); methacrylic acid esters (residual alcohol
group are the same as above); hydroxy-containing monomers such as
2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,
2-hydroxypropyl acrylate and 2-hydroxypropyl methacrylate; amide
group-containing monomers such as acrylamide, methacrylamide,
N-methyl methacrylamide, N-methyl acrylamide, N-methylol
acrylamide, N-methylol methacrylamide, N,N-dimethylol acrylamide,
N-methoxymethyl acrylamide, N-methoxymethyl methacrylamide and
N-phenyl acrylamide; amino group-containing monomers such as
N,N-diethyl aminoethyl acrylate and N,N-diethyl aminoethyl
methacrylate; epoxy group-containing monomers such as glycidyl
acrylate, glycidyl methacrylate and allyl glycidyl ether; monomers
containing a sulfonic acid group or salt thereof, such as
styrenesulfonic acid, vinylsulfonic acid and salts thereof (such as
sodium salts, potassium salts and ammonium salts thereof); monomers
containing a carboxyl group or salt thereof such as crotonic acid,
itaconic acid, acrylic acid, maleic acid, fumaric acid and salts
thereof (such as sodium salts, potassium salts and ammonium salts
thereof); monomers containing an anhydride such as maleic anhydride
and itaconic anhydride; and combinations of monomers such as vinyl
isocyanate, allyl isocyanate, styrene, vinyl methyl ether, vinyl
ethyl ether, vinyl trisalkoxysilane, alkyl maleic acid monoester,
alkyl fumaric acid monoester, acrylonitrile, methacrylonitrile,
alkyl itaconic acid monoester, vinylidene chloride, vinyl acetate
and vinyl chloride. What contain 50 mol % or more of a (meth)acryl
monomer such as an acrylic acid derivative or methacrylic acid
derivative are preferred and what contain methyl methacrylate are
particularly preferred.
[0050] The water-soluble or water-dispersible acrylic resins can be
self-crosslinked with a functional group in the molecule or can be
crosslinked using a crosslinking agent such as a melamine resin or
epoxy compound.
[0051] The above water-soluble or water-dispersible polyester
resins comprise a polycarboxylic acid and a polyhydroxy compound.
Illustrative examples of the polycarboxylic acid include
terephthalic acid, isophthalic acid, phthalic acid,
1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid,
4,4'-diphenyldicarboxylic acid, adipic acid, sebacic acid,
dodecanedicarboxylic acid, succinic acid, 5-sodium sulfoisophthalic
acid, 2-potassium sulfoterephthalic acid, trimellitic acid,
trimesic acid, trimellitic anhydride, phthalic anhydride,
p-hydroxybenzoic acid, monopotassium trimellitate and the like.
Illustrative examples of the polyhydroxyl compound include ethylene
glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol,
1,6-hexanediol, neopentyl glycol, 1,4-cyclohexane dimethanol,
p-xylylene glycol, adduct of bisphenol A with ethylene oxide,
diethylene glycol, triethylene glycol, polyethylene oxide glycol,
polytetramethylene oxide glycol, dimethylolpropionic acid,
glycerin, trimethylol propane, sodium dimethylol ethyl sulfonate,
potassium dimethylol propionate and the like. Polyester resins can
be produced from these compounds in accordance with a commonly used
method. To produce an water-soluble or water-dispersible polyester
resin, an aqueous polyester resin containing a 5-sodium
sulfoisophthalic acid component or carboxylate group is preferably
used. The polyester resin can be self-crosslinked with a functional
group in the molecule or can be crosslinked using a curing agent
such as a melamine resin or epoxy resin.
[0052] The above water-soluble or water-dispersible acryl-polyester
resins comprehend both acryl modified polyester resins and
polyester modified acrylic resins in which an acrylic resin
component and a polyester resin component are bonded together, such
as graft type and block type resins. The acryl-polyester resins can
be produced, for example, by adding a radical initiator to both
ends of a polyester resin to polymerize an acrylic monomer, by
adding a radical initiator to the side chain of a polyester resin
to polymerize an acrylic monomer, or by adding a hydroxyl group to
the side chain of an acrylic resin to react it with a polyester
having an isocyanate group or carboxyl group at a terminal so as to
form a comb-like polymer.
[0053] The inert particles contained in the coating layer A may be
an organic particle such as polystyrene,
polystyrene-divinylbenzene, polymethyl methacrylate, methyl
methacrylate copolymer, methyl methacrylate crosslinked copolymer,
polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile
or benzoguanamine resin, or an inorganic particle such as silica,
alumina, titanium dioxide, kaolin, talc, graphite, calcium
carbonate, feldspar, molybdenum disulfide, carbon black or barium
sulfate. A multi-layer structured core-shell type particle whose
core and shell are made from materials having different properties
may be used.
[0054] The inert particles preferably have an average particle
diameter of 10 to 200 nm, more preferably 20 to 100 nm. The content
of the inert particles in the coating layer A is preferably 5 to 40
wt %, more preferably 5 to 20 wt %. Further, the inert particles
preferably have a uniform particle size distribution. When the
average particle diameter of the inert particles is smaller than 5
nm or the content thereof is smaller than 5 wt %, winding
properties and conveyance properties in the film formation process
become unsatisfactory or blocking readily occurs. When the average
particle diameter is larger than 200 nm or the content is larger
than 40 wt %, the coating layer A is easily chipped.
[0055] Ra.sup.A of the outer surface of the coating layer A is
preferably 1 to 30 nm, more preferably 2 to 20 nm. When Ra.sup.A is
less than 1 nm, winding properties and conveyance properties in the
film formation process become unsatisfactory or blocking readily
occurs. When Ra.sup.A is more than 30 nm, the coating layer A is
easily chipped and shape transfer to the other surface readily
occurs at the time of rolling the film. This roughness may be
provided by the coating layer A, the polyester film or a
combination of the coating layer A and the polyester film.
[0056] A siloxane copolymerized acrylic resin is further contained
in the coating layer A in an amount of 1 to 50 wt %. The siloxane
copolymerized acrylic resin of the present invention is such that a
siloxane component and an acrylic resin component are bonded
together, and comprehends graft type and block type resins. The
copolymer can be produced, for example, by adding a radical
initiator to both ends of an acrylic resin to carry out the
polymerization of a siloxane or by adding a hydroxyl group to the
side chain of a siloxane to react it with an acrylic compound
having an isocyanate group or carboxyl group at a terminal to form
a comb-like polymer.
[0057] The acrylic resin preferably comprises the same monomer
components as those enumerated for the acrylic resin used in the
coating layer A.
[0058] The siloxane component is preferably a polymer having a
chain component represented by the following formula: 2
[0059] wherein R.sub.3 is a hydrogen atom, methyl group or phenyl
group, R.sub.4 is a hydrogen atom, methyl group, phenyl group or
functional group (such as an epoxy group, amino group or hydroxy
group), and m is an integer of 100 to 7,000.
[0060] Out of these, a polymer having an epoxy group, amino group,
hydroxyl group or other functional terminal group at a terminal is
preferred. In the present invention, the siloxane compound does not
have to be a homopolymer and may be a copolymer or a mixture of
several homopolymers.
[0061] The weight ratio of the acrylic resin component to the
siloxane component is preferably 98:2 to 50:50, more preferably
95:5 to 60:40. The content of the siloxane copolymerized acrylic
resin in the coating layer A is preferably 1 to 50 wt %, more
preferably 1 to 30 wt %. When the content is smaller than 1 wt %,
the effect becomes unsatisfactory, thereby readily causing blocking
and an increase in the amount of electrostatic charge. When the
content is larger than 50 wt %, adhesion of a back coat
deteriorates, transfer to the contact surface occurs at the time of
rolling the film, or the contact roll is readily stained at the
time of traveling the film.
[0062] The surfactant is not particularly limited but preferably a
nonionic surfactant, anionic surfactant or cationic surfactant. Out
of these, a nonionic surfactant is particularly preferred. The
content of the surfactant is preferably 5 to 40 wt %.
[0063] A component other than the binder resin, inert particles,
surfactant and siloxane copolymerized acrylic resin may be added to
the coating layer A in limits that do not influence the present
invention. For example, a cellulose-based resin is preferably added
to improve slipperiness. The thickness of the coating layer A is
preferably 1 to 100 nm, more preferably 2 to 20 nm.
[0064] The outer surface of the coating layer A is not a surface
for forming a magnetic layer thereon. A magnetic layer is formed on
the outer surface of the base film C or the outer surface of an
intermediate layer formed on the outer surface of the base film
C.
[0065] A description is subsequently given of the second composite
polyester film of the present invention.
[0066] The base film C is identical to the base film C which has
been described for the first composite polyester film.
[0067] The second composite polyester film of the present invention
has a coating layer B on one side of the base film C. The coating
film B comprises one member selected from the group consisting of a
siloxane copolymerized polyester resin, siloxane copolymerized
acrylic resin, silicone and wax, a binder resin, inert particles
and a surfactant.
[0068] The siloxane copolymerized polyester resin is preferably
water-soluble or water-dispersible. The resin can be produced by
carrying out the polymerization of a siloxane, by adding a radical
initiator to both ends of a polyester resin to carry out the
polymerization of a siloxane or by adding a hydroxyl group to the
side chain of a siloxane to react it with a polyester having an
isocyanate group or carboxyl group at a terminal to form a
comb-like polymer. Examples of the polyester resin component used
for polymerization are the same resins as those enumerated for the
polyester resin used in the coating layer A of the first composite
polyester film of the present invention. The siloxane is the same
compound having a chain component represented by the above formula
1 or a compound having an epoxy group, amino group, hydroxyl group
or other functional terminal group. In the present invention, the
silicone compound does not have to be a homopolymer and may be a
copolymer or a mixture of several homopolymers. The weight ratio of
the polyester resin component to the siloxane component is
preferably 98:2 to 60:40, more preferably 95:5 to 80:20.
[0069] Examples of the siloxane copolymerized acrylic resin are the
same as those enumerated for the siloxane copolymerized acrylic
resin which has been described for the coating layer A of the first
composite polyester film of the present invention. Examples of the
silicone are the same polymers as those enumerated as the siloxane
component for the above siloxane copolymerized acrylic resin.
[0070] The wax may be petroleum wax, vegetable wax, mineral wax,
animal wax, low molecular weight polyolefin or the like and not
particularly limited. Examples of the petroleum wax include
paraffin wax, microcrystalline wax, oxide wax and the like.
Examples of the vegetable wax include candelilla wax, carnauba wax,
Japan wax, oricurie wax, cane wax, rosin modified wax and the
like.
[0071] The content of the siloxane copolymerized acrylic resin,
silicone or wax in the coating layer B is 1 to 50 wt %, preferably
1 to 30 wt %. When the content is smaller than 1 wt %, blocking
occurs and the amount of electrostatic charge increases and when
the content is larger than 50 wt %, adhesion of a magnetic layer
degrades or the contact roll is stained at the time of traveling
the film. The content of the siloxane copolymerized polyester resin
in the coating layer B is 5 to 90 wt %, preferably 20 to 80 wt %.
When the content is smaller than 5 wt %, the effect becomes
unsatisfactory, thereby causing blocking and an increase in the
amount of electrostatic charge and when the content is larger than
90 wt %, adhesion of a magnetic layer degrades or the contact roll
is stained at the time of traveling the film.
[0072] The coating layer B further contains a binder resin, inert
particles and a surfactant. As for what is not described herein for
each of the above components, it should be understood that what has
been described for the coating layer A of the first composite
polyester film of the present invention is applied directly.
[0073] The binder resin preferably has a softening point measured
in accordance with JIS-K7206 (for a dried binder resin) of
50.degree. C. or more to improve corona treatment blocking
resistance. However, the surface of the coating layer B is apt to
be roughened according to coating conditions or the like if Tg of
the resin of the coating layer B is too high. Accordingly, when a
binder resin having a high glass transition temperature Tg is used,
it is important not to roughen the surface of the coating layer B
by controlling coating conditions in order to prevent that
electromagnetic conversion characteristics are deteriorated by the
roughened surface. The term "roughness" in this case means square
average roughness obtained when a 10 .mu.m.sup.2 area is measured
with a contact surface roughness meter. The roughness is preferably
2.0 nm or less, more preferably 1.8 nm or less, much more
preferably 1.5 nm or less.
[0074] The inert particles preferably have an average particle
diameter of 5 to 100 nm, more preferably 10 to 50 nm. Further, the
inert particles preferably have a uniform particle size
distribution. When the average particle diameter is smaller than 5
nm, slipperiness and chipping resistance are liable to deteriorate.
When the average particle diameter is larger than 100 nm, the
particles readily fall off and chipping resistance is apt to
degrade. Since spacing between the magnetic head and the film
becomes large, it is difficult to provide a high-density magnetic
recording medium.
[0075] The inert particles are contained in the coating layer B to
ensure that the surface protrusion density of the coating layer B
should be 1 to 100/.mu.m.sup.2. When the surface protrusion density
is lower than 1/.mu.m.sup.2, the traveling durability of the
resulting magnetic recording medium tends to become unsatisfactory.
When the surface protrusion density is higher than 100/.mu.m.sup.2,
electromagnetic conversion characteristics are adversely affected.
The surface protrusion density is preferably 2 to 50/.mu.m.sup.2,
more preferably 3 to 30/.mu.m.sup.2. The agglomeration rate of the
inert particles contained in the coating layer B is preferably 20%
or less. When the agglomeration rate is higher than 20%, the
particles are easily chipped off or the electromagnetic conversion
characteristics of the resulting magnetic recording medium may be
adversely affected.
[0076] Large protrusions having a height of 4 nm or more calculated
from a surface roughness profile obtained by a non-contact 3-D
roughness meter are existent on the surface not in contact with the
base film C of the coating layer B preferably at a maximum density
of 200/mm.sup.2 or less, more preferably 100/mm.sup.2 or less.
Excellent traveling durability can be obtained by the existence of
the above protrusions.
[0077] The content of the inert particles is preferably 0.5 to 30
wt %, particularly preferably 1 to 20 wt %. The thickness of the
coating layer B is preferably 1 to 100 nm, more preferably 2 to 20
nm.
[0078] Ra.sup.B of the outer surface of the coating layer B is
preferably 0.1 to 2 nm, more preferably 0.5 to 1.5 nm. When
Ra.sup.B is more than 2 nm, the electromagnetic conversion
characteristics of the resulting metal thin film magnetic recording
medium may degrade and when Ra.sup.B is smaller than 0.1 nm,
slipperiness may markedly deteriorate, traveling durability may
become unsatisfactory, and the film may stick to the magnetic head,
making sound from the tape. Therefore, the tape may not be able to
be put to practical use.
[0079] The surfactant is preferably used in the coating layer B in
an amount of 10 to 50 wt %, more preferably 12 to 40 wt %,
particularly preferably 15 to 30 wt %. When the amount of the
surfactant is smaller than 10 wt % (based on the total solid
content), defects such as cissing are apt to occur at the time of
coating and when the amount is larger than 50 wt %, stripe coating
defects are formed by foaming. The surfactant preferably has a
softening point measured by JIS-K7206 (for a dried surfactant) of
30.degree. C. or more to improve corona treatment blocking
resistance.
[0080] The surfactant is preferably a nonionic surfactant,
particularly preferably a surfactant prepared by adding or binding
(poly)ethylene oxide to an alkyl alcohol, alkyl phenyl alcohol or
higher fatty acid.
[0081] Illustrative examples of the nonionic surfactant include
polyoxyethylene alkylphenyl ether-based compounds such as Nonion
NS-230, NS-240, HS-220 and HS-240 of NOF Corporation, Nonipole 200,
Nonipole 400, Nonipole 500 and Octapole 400 of Sanyo Chemical
Industries, Ltd., polyoxyethylene alkylether-based compounds such
as Nonion E-230, K-220 and K-230 of NOF Corporation,
polyoxyethylene ester-based compounds of higher fatty acids such as
Nonion S-15.4 and S-40 of NOF Corporation and the like.
[0082] A surfactant other than the above may be used in combination
in an amount of less than 10 wt % (based on the total solid
content) to reduce the surface tension of a coating solution in
order to prevent the generation of uncoated portions when the
coating solution for the coating layer B is applied.
[0083] The coating layer B preferably has properties to ensure that
peel strength between its outer surface and the corona treated
exposed surface of the base film C should be 15 g/10 cm or less.
When this peel strength is higher than 15 g/10 cm, the film is
easily broken by blocking at the time of use. This peel strength is
preferably 10 g/10 cm or less.
[0084] The thickness of the coating layer B is preferably 1 to 100
nm, more preferably 2 to 50 nm, much more preferably 3 to 10 nm,
particularly preferably 3 to 8 nm.
[0085] The outer surface of the coating layer B is a surface for
foaming a magnetic layer thereon.
[0086] Finally, the third composite polyester film of the present
invention will be described hereinafter.
[0087] The third composite polyester film comprises the base film
C, the coating layer B and the coating layer A.
[0088] As for what is not described herein for the base film C and
the coating layer A, it should be understood that what has been
described for the first composite polyester film is directly
applied. As for what is not described herein for the coating layer
B, it should be understood that what has been described for the
second composite polyester film is directly applied.
[0089] The total thickness of the third composite polyester film is
preferably 2.5 to 20 .mu.m, more preferably 3.0 to 10 .mu.m, much
more preferably 4.0 to 10 .mu.m. The thickness of the coating layer
A is preferably 1 to 100 nm, more preferably 2 to 20 nm. The
thickness of the coating layer B is preferably 1 to 100 nm, more
preferably 2 to 50 nm, much more preferably 3 to 10 nm,
particularly preferably 3 to 8 nm.
[0090] A description which is applied to all of the first, second
and third composite polyester films of the present invention will
be given below.
[0091] The base film C of the present invention can be produced by
conventionally known methods.
[0092] For example, when the polyester film is a single-layer film,
the above polyester resin is extruded into a film from a die at a
temperature of Tm to (Tm+70).degree. C. (Tm: melting point of
polyester) and solidified by quenching at 40 to 90.degree. C. to
obtain an unstretched film. Thereafter, the unstretched film is
stretched to 2.5 to 8.0 times, preferably 3.0 to 7.5 times,
uniaxially (longitudinal or transverse direction) at a temperature
of (Tg-10) to (Tg+70).degree. C. (Tg: glass transition temperature
of polyester), a coating solution for forming the coating layer A
and/or the coating layer B is then applied to both surfaces of the
film, the film is stretched to 2.5 to 8.0 times, preferably 3.0 to
7.5 times in a direction perpendicular to the above direction at a
temperature of Tg to (Tg+70).degree. C. The film may be stretched
again in a longitudinal direction and/or transverse direction as
required.
[0093] That is, 2-stage, 3-stage, 4-stage or multi-stage stretching
may be carried out. The total draw ratio is generally 9 times or
more, preferably 12 to 35 times, more preferably 15 to 32 times in
terms of area draw ratio. Subsequently, the obtained biaxially
oriented film is heat set and crystallized at a temperature of
(Tg+70) to (Tm-10).degree. C., for example, 180 to 250.degree. C.
to provide excellent dimensional stability. The heat setting time
is preferably 1 to 60 sec.
[0094] In the above method, the coating solution for the coating
layers A and B is applied to the surface of the polyester base film
C before final stretching. After coating, the film is preferably
stretched at least uniaxially. The coating film is dried before or
during this stretching. Coating is preferably carried out on an
unstretched laminate film or uniaxially (longitudinal direction)
stretched laminate film, particularly preferably on an uniaxially
(longitudinal direction) stretched laminate film. Coating is not
particularly limited but may be roll coating, die coating or the
like.
[0095] The solid content of the above coating solution,
particularly aqueous coating solution, is preferably 0.2 to 8 wt %,
more preferably 0.3 to 6 wt %, particularly preferably 0.5 to 4 wt
%. This coating solution (preferably aqueous coating solution) may
contain other components such as other surfactant, a stabilizer,
dispersant, UV absorber, thickener and the like in limits that do
not impair the effect of the present invention.
[0096] In the present invention, to improve the characteristic
properties such as head touch and traveling durability of the
resulting magnetic recording medium and reduce the thickness of the
medium at the same time, the Young's moduli in longitudinal and
transverse directions of the composite film are preferably
controlled to 450 kg/mm.sup.2 or more and 600 kg/mm.sup.2 or more,
more preferably 480 kg/mm.sup.2 or more and 680 kg/mm.sup.2 or
more, much more preferably 550 kg/mm.sup.2 or more and 800
kg/mm.sup.2 or more, particularly preferably 550 kg/mm.sup.2 or
more and 1,000 kg/mm.sup.2 or more, respectively. When the base
film C is a polyethylene terephthalate layer, the crystallinity of
the layer is preferably 30 to 50% and when the base film C is a
polyethylene-2,6-naphthalene dicarboxylate layer, the crystallinity
is preferably 28 to 38%. When the crystallinity falls below the
above lower limits, thermal shrinkage tends to grow and when the
crystallinity exceeds the above upper limits, the abrasion
resistance of the film is apt to deteriorate and white powders are
readily produced by sliding contact between the film and the
surface of the roll or the guide pin.
[0097] According to the present invention, there is also provided a
magnetic recording medium which comprises the composite film of the
present invention as a base film, that is, a magnetic recording
medium which comprises a magnetic layer formed on the base film C
of the first composite film of the present invention or the coating
layer B of the second or third composite film of the present
invention.
[0098] The magnetic recording medium is produced using the
composite film of the present invention as follows.
[0099] A deposited magnetic recording medium for high-density
recording which has excellent electromagnetic conversion
characteristics such as output at a short-wavelength range, S/N and
C/N, few drop outs and a small error rate can be obtained by
forming a ferromagnetic metal thin film layer made from iron,
cobalt, chromium or an alloy or oxide essentially composed thereof
on the surface of the base film C of the first composite film or
the coating layer B of the second or third composite film by vacuum
deposition, sputtering, ion plating or the like, a protective layer
made from diamond-like carbon (DLC) and a fluorine-containing
carboxylic acid-based lubricant layer on the surface of the
ferromagnetic metal thin film layer according to purpose or
application, or as required, and a known back coat layer on a
surface opposite to the magnetic layer as required. This deposited
magnetic recording medium is extremely useful as a tape medium for
Hi8 for analog signal recording, and digital video cassette
recorder (DVC), data 8 mm and DDSIV for digital signal
recording.
[0100] A metal coated magnetic recording medium for high-density
recording which has excellent electromagnetic conversion
characteristics such as output at a short-wavelength range, SIN and
C/N, few drop outs and a small error rate can be obtained by
uniformly dispersing iron or needle-like magnetic fine powders
(metal powder) essentially composed of iron into a binder such as
polyvinyl chloride or vinyl chloride-vinyl acetate copolymer,
applying the obtained binder to the surface of the base film C of
the first composite film of the present invention or the coating
layer B of the second or third composite film of the present
invention to ensure that the thickness of a magnetic layer should
be 1 .mu.m or less, preferably 0.1 to 1 .mu.m, and further forming
a back coat layer on a surface opposite to the magnetic layer as
required by a known method. A non-magnetic layer containing
titanium oxide fine particles may be dispersed into the same
organic binder as that for the magnetic layer and be formed on the
base film C as a primary coat for the metal power containing
magnetic layer as required. This metal coated magnetic recording
medium is extremely useful as a tape medium for 8 mm video, Hi8,
.beta.-cam SP and W-VHS for analog signal recording and digital
video cassette recorder (DVC), data 8 mm, DDSIV, digital
.beta.-cam, D2, D3 and SX and the like for digital signal
recording.
[0101] Further, a coated magnetic recording medium for high-density
recording which has excellent electromagnetic conversion
characteristics such as output at a short-wavelength range, S/N and
C/N, few drop outs and a small error rate can be obtained by
uniformly dispersing needle-like magnetic fine powders such as iron
oxide or chromium oxide or lamellar magnetic fine powders such as
barium ferrite into a binder such as polyvinyl chloride or vinyl
chloride-vinyl acetate copolymer, applying the obtained binder to
the surface of the base film C of the first composite film of the
present invention or the coating layer B of the second or third
composite film of the present invention to ensure that the
thickness of a magnetic layer should be 1 .mu.m or less, preferably
0.1 to 1 .mu.m and further forming a back coat layer on a surface
opposite to the magnetic layer as required by a known method. A
non-magnetic layer containing titanium oxide fine particles may be
dispersed into the same organic binder as that for the magnetic
layer and be formed on the base film C as a primary coat for the
magnetic power containing magnetic layer as required. This oxide
coated magnetic recording medium is useful as a high-density oxide
coated magnetic recording medium for data streamer QIC for digital
signal recording.
[0102] The above W-VHS is an VTR for analog HDTV signal recording
and DVC can be used to record digital HDTV signals. It can be said
that the film of the present invention is extremely useful as a
base film for a magnetic recording medium for VTRs applying to
HDTV.
[0103] The following examples are given to further illustrate the
present invention. In Examples 1 to 3 and Comparative Examples 1 to
7, the following measurement methods (1) to (10) were used.
[0104] (1) average particle diameter of particles (average particle
diameter: 0.06 .mu.m or more)
[0105] This is measured using the CP-50 Centrifugal Particle Size
Analyzer of Shimadzu Corporation. A particle diameter, "equivalent
spherical diameter" equivalent to 50 mass percent, is read from a
cumulative curve of the particles of each diameter and the amount
thereof calculated based on the obtained centrifugal sedimentation
curve and taken as the above average particle diameter (refer to
"Particle Size Measurement Technology" issued by Nikkan Kogyo
Press, pp. 242-247, 1975).
[0106] (2) average particle diameter of super fine particles
(average particle diameter: less than 0.06 .mu.m)
[0107] Particles having an average particle diameter smaller than
0.06 .mu.m which form small protrusions are measured by a light
scattering method. That is, the average particle diameter of the
particles is expressed by the "equivalent spherical diameter" of
the particles which account for 50 wt % of the total of all
particles obtained by the NICOMP MODEL 270 SUBMICRON PARTICLES
SIZER of Nicomp Instruments Inc.
[0108] (3) surface roughness of film (center line average
roughness: Ra)
[0109] The center line average roughness (Ra) is measured in
accordance with JIS-B601. In the present invention, a probe type
surface roughness meter (SURFCORDER SE,30C) of Kosaka Kenkyusho
Co., Ltd. is used to measure it under the following conditions.
[0110] (a) radius of tip of probe: 2 .mu.m
[0111] (b) measurement pressure: 30 mg
[0112] (c) cut off: 0.08 mm
[0113] (d) measurement length: 8.0 mm
[0114] (e) collection of data: The surface roughness of a single
sample is measured 6 times, and five measurement values excluding
the largest value are used to obtain an average value as a center
line average roughness (Ra).
[0115] (4) number of particle protrusions
[0116] Using a SEM (the T-300 scanning electron microscope of JEOL
Corp.), 20 photos of the surface of a laminate film are taken at a
magnification of 30,000.times. at an angle of 0.degree. to count
the number of granular protrusions and an average value thereof is
calculated as the number of protrusions per 1 mm.sup.2.
[0117] (5) agglomeration rate of particles
[0118] The number of protrusions A is counted from 20 photos taken
in (4) when each of the particles forming a protrusion is an
agglomerate of two or more particles and the agglomeration rate is
calculated from (number of protrusions A derived from
agglomerates)/(number of all protrusions derived from
particles).times.100 (%).
[0119] (6) layer thickness
[0120] The total thickness of a film is measured at 10 random
locations of the film by a micrometer and the average value of the
measurement values is taken as the total thickness of the film. The
thickness of a thin layer is measured by the following method while
the thickness of a thick layer is obtained by subtracting the
thickness of the thin layer from the total thickness. That is,
using a secondary ion mass spectrometer (SIMS), the concentration
ratio (M.sup.+/C.sup.+) of an element derived from particles having
the highest concentration out of the particles contained in an area
of the film from the surface layer to a depth of 5,000 nm to the
carbon element of a polyester is taken as a particle concentration,
and a portion from the surface up to a depth of 5,000 nm is
analyzed in the thickness direction. The particle concentration is
low in the surface layer but becomes higher as the distance from
the surface increases. In the case of the present invention, there
are two cases. That is, one is a case where after the particle
concentration becomes a stable value 1, it increases or decreases
to a stable value 2, and the other is a case where after the
particle concentration becomes a stable value 1, it decreases
continuously. Based on this distribution curve, in the former case,
a depth which provides a particle concentration of (stable value
1+stable value 2)/2 is taken as the thickness of the layer whereas,
in the latter case, a depth that provides a particle concentration
of one-half of the stable value 1 (deeper than the depth that gives
a stable value 1) is taken as the thickness of the layer.
[0121] The measurement conditions of a secondary ion mass
spectrometer (SIMS: 6300 of PERKIN ELMER Co., Ltd.) are as
follows.
[0122] species of primary ion: O.sup.2+
[0123] primary ion acceleration voltage: 12 kV
[0124] primary ion current: 200 mA
[0125] luster area: 400 .mu.m .quadrature.
[0126] analysis area: gate 30%
[0127] measurement degree of vacuum: 6.0.times.10.sup.-9 Torr
[0128] E-GUNN: 0.5 kV-3.0 A
[0129] In the case where most of the particles contained in an area
of from the surface layer to a depth of 5,000 nm are organic
polymer particles other than a silicone resin, it is difficult to
measure them with SIMS. Therefore, a concentration distribution
curve similar to the above is measured by FT-IR (Fourier transform
infrared spectrometry) or XPS (X-ray photo-electron spectrometry)
depending on a parallel to obtain the thickness of the layer while
the film is etched little by little from the surface.
[0130] The above measurement method is very effective in the case
of a coextruded layer. In the case of a coating layer, a piece of a
film is fixed with an epoxy resin and molded to prepare a very thin
piece having a thickness of about 60 nm with a microtome (by
cutting the film in parallel with a flow direction). This sample is
observed by a transmission electron microscope (H-800 of Hitachi,
Ltd.) to obtain the thickness of the layer from the interface of
the layer.
[0131] (7) electrostatic properties
[0132] A polyester film (500 mm in width.times.3,000 m in length)
is rewound at a speed of 150 m/min at 23.degree. C. and 75% RH and
the amount of electrostatic charge generated on reviewing of the
roll is measured using the Model-203 digital test electric
measuring instrument of Hugle Electronics Co., Ltd.
[0133] .largecircle.: less than 2.5 kV
[0134] .DELTA.: 2.5 to less than 5.0 kV
[0135] X: 5.0 kV or more
[0136] (8) blocking
[0137] Tow films are superposed in such a manner that a treated
surface of one film and an untreated surface of the other film come
into contact with each other, a pressure of 150 kg/cm.sup.2 is
applied to the resulting laminate at 60.degree. C. and 80% RH for
65 hours, these films are separated from each other, and blocking
resistance is evaluated based on peel strength (g per 5 cm).
[0138] Evaluation is made from peel strength based on the following
criteria.
[0139] .largecircle.: 0 to less than 10 g/cm
[0140] .DELTA.: 10 to less than 15 g/cm
[0141] X: 15 g/cm or more to break
[0142] (9) chipping resistance
[0143] A film is cut to a length of 25 to 30 cm and a width of 1/2
inch, the edge of a razor blade is applied to the coating layer of
the film at an angle of 90.degree. and a depth of 0.5 mm, and the
width in a depth direction of chippings adhered to the razor blade
is obtained from photomicrography (magnification of 160.times.)
when the film is caused to run at a speed of 6.7 cm/sec under a
load of 500 g/0.5 inch. Chipping resistance is evaluated according
to the width in a depth direction of chippings. The smaller the
width in a depth direction of the chippings the higher the chipping
resistance becomes.
[0144] .largecircle.: less than 3 nm
[0145] .DELTA.: 3 nm to less than 5 nm
[0146] X>: 5 nm or more
[0147] (10) production of magnetic tape and evaluation of
characteristic properties
[0148] Two 100% cobalt ferromagnetic thin film layers are formed on
the surface of the coating layer B of a laminate film to a total
thickness of 0.02 .mu.m (each layer has a thickness of about 0.1
.mu.m) by a vapor deposition method. A diamond-like carbon (DLC)
film layer and a fluorine-containing carboxylic acid-based
lubricant layer are formed sequentially on the surface of the thin
film layers, and a back coat layer having the following composition
is further formed on the surface of the coating layer B and
dried.
[0149] The thickness of the back coat layer after drying is 0.8
.mu.m.
1 composition of back coat layer: carbon black 100 parts by weight
thermoplastic polyurethane 60 parts by weight isocyanate compound
18 parts by weight (Colonate L of Nippon Polyurethane Kogyo Co.,
Ltd.) silicone oil 0.5 part by weight methyl ethyl ketone 250 parts
by weight
[0150] Thereafter, the film is slit to a width of 8 mm and loaded
into a trade 8 mm video cassette. The following trade devices are
used to measure the characteristic properties of the tape used
device:
[0151] 8 mm video tape recorder: EDV-6000 of Sony Corporation C/N
measurement: noise meter of Shibasoku Co., Ltd.
[0152] {circumflex over (1)} C/N measurement
[0153] A signal having a recording wavelength of 0.5 .mu.m
(frequency of about 7.4 MHz) is recorded on a tape, and the ratio
of 6.4 MHz and 7.4 MHz values of its reproduction signal is taken
as a relative value of C/N of the tape when C/N of a commercial 8
mm video deposited tape is 0 dB.
[0154] .largecircle.: more than 0 dB
[0155] .DELTA.: -3 to 0 dB
[0156] X: less than -3 dB
[0157] {circumflex over (2)} traveling durability
[0158] C/N of a tape is measured after recording and reproduction
are repeated 500 times at a traveling speed of 85 cm/min and at
40.degree. C. and 80% RH and the traveling durability of the tape
is judged based on a deviation from the initial value.
[0159] .largecircle.: +0.0 dB or more from initial value
[0160] .DELTA.: -1.0 to less than +0.0 dB from initial value
[0161] X: less than -1.0 dB from initial value
[0162] {circumflex over (3)} adhesion of magnetic layer
[0163] Scotch Tape No. 600 (of 3M Co., Ltd.) is affixed to a
magnetic layer which has been cross cut into 2 mm square pieces in
such a manner that an air bubble is not included between them, the
tape is rolled by a manual load roll specified in JIS C. 2701
(1975), a 5 cm laminated portion of this sample is peeled in the
perpendicular direction at a head speed of 100 mm/min using the
UM-11 Tensilon of Toyo Baldwin Co., Ltd., and the adhesion of the
magnetic layer is obtained from (number of peeled cross-cutting
magnetic layer pieces)/(total number of cross-cutting magnetic
layer pieces).times.100 (%).
[0164] .largecircle.: 0 to less than 3%
[0165] .DELTA.: 3 to less than 10%
[0166] X: 10% or more
[0167] {circumflex over (4)} adhesion of back coat Scotch Tape No.
600 (of 3M Co., Ltd.) having a width of 19.4 mm and a length of 8
cm is affixed to a back coat in such a manner that an air bubble is
not included between them, the tape is rolled by a manual load roll
specified in JIS. C2701 (1975), a 5 cm laminated portion of this
sample is peeled in the perpendicular direction at a head speed of
300 mm/min using the UM-11 Tensilon of Toyo Baldwin Co., Ltd., and
the peel strength at this point is obtained and divided by the
width of the tape to obtain the adhesion of the back coat in unit
of g/cm. In the peeling in the perpendicular direction, the
laminate is separated with the tape facing down at a chuck interval
of 5 cm.
[0168] The adhesion of the back coat is evaluated from peel
strength based on the following criteria.
[0169] .largecircle.: 50 g/cm.sup.2 or more
[0170] .DELTA.: 20 g/cm.sup.2 or more to less than 50
g/cm.sup.2
[0171] X: less than 20 g/cm.sup.2
[0172] (11) deaeration index
[0173] 40 films are first placed one upon another using the Beck
smoothness tester of Toyo Seiki Co., Ltd., a 5 mm-diameter hole is
formed in 39 films excluding the topmost film, and this set of
films is set on a sample table. The center of the hole is located
at the center of the sample table. In this state, a load of 0.5
kg/cm.sup.2 is applied to the set of films and the ultimate vacuum
is set to 550 mmHg. After 550 mmHg is reached, air flows into the
gaps between the films because the pressure tends to return to
normal level. At this point, the falling vacuum degree (mmHg) is
measured at intervals of 30 sec for 1 hour and the inclination
(=mmHg/hr) of a straight line approximating the degree of vacuum
with respect to the measurement time (hr) is taken as deaeration
index G.
[0174] (12) peel strength after corona treatment
[0175] A 100 mm long, 200 mm wide rectangular sample is cut away
from a rolled film and the base film C of the sample is subjected
to a corona treatment at a temperature of 25.degree.
C..+-.5.degree. C. and a humidity of 50%.+-.5%.
[0176] The treatment is carried out under the following conditions
using the CG-102 high-frequency power source of Kasuga Denki Co.,
Ltd.
[0177] current: 4.5 A
[0178] distance between electrodes: 1.0 mm
[0179] treatment time: passing between electrodes at a speed of 1.2
m/min
[0180] After the treated film is contacted to the surface opposite
to the base film C of the sample and aged for 17 hours at a
pressure of 100 kg/cm.sup.2, a temperature of 60.degree. C. and a
humidity of 80%, peel strength per 100 mm in width under tension is
obtained.
EXAMPLE 1
[0181] Dimethyl 2,6-naphthalene dicarboxylate and ethylene glycol
were polymerized in the presence of manganese acetate as an ester
exchange catalyst, antimony trioxide as a polymerization catalyst
and phosphorous acid as a stabilizer in accordance with a commonly
used method to give polyethylene-2,6-naphthalate (PEN) containing
substantially no inert particles.
[0182] This polyethylene-2,6-naphthalate was dried at 170.degree.
C. for 6 hours, supplied to an extruder, molten at a temperature of
280 to 300.degree. C., extruded into a sheet from a die and
quenched to give a 82 .mu.m-thick unstretched film.
[0183] The obtained unstretched film was preheated, stretched to
3.5 times in a longitudinal direction between high-speed and
low-speed rolls at a film temperature of 95.degree. C. and
quenched. A water-soluble coating solution for the coating layer B
shown in Table 1 was applied to one side of this stretched film to
a thickness of 0.009 .mu.m (after stretching and drying) and a
water-soluble coating solution for the coating layer A was applied
to the other side of the film to a thickness of 0.035 .mu.m.
Thereafter, the film was supplied to a stenter to be stretched to
5.6 times in a transverse direction at 150.degree. C. The obtained
biaxially oriented film was heat set with hot air heated at
200.degree. C. for 4 sec to give a 4.9 .mu.m-thick biaxially
oriented polyester film.
2 {circle over (1)} coating layer A binder resin SH551A acryl
modified polyester of 43.3 parts Takamatsu Yushi Co., Ltd. SM15
methyl cellulose of 21.7 parts Shin-Etsu Chemical Co., Ltd.
siloxane copolymerized acrylic resin 5 parts X-22-8053 of Shin-Etsu
Chemical Co., Ltd. inert particles acryl particles 10 parts
(average particle diameter of 40 nm) surfactant Nonion NS-240 of
NOF Corporation 20 parts
[0184]
3 {circle over (2)} coating layer B binder resin 70 parts IN-170-6
acryl modified polyester of Takamatsu Yushi Co., Ltd. inert
particles acryl particles 10 parts (average particle diameter of 40
nm) surfactant Nonion NS-240 of NOF Corporation 20 parts
COMPARATIVE EXAMPLES 1, 2 AND 7
[0185] Polyester films were obtained in the same manner as in
Example 1 except that the compositions of the coating layer A and
the coating layer B were changed as shown in Table 1.
EXAMPLE 2 AND COMPARATIVE EXAMPLES 3 TO 6
[0186] Dimethyl terephthalate and ethylene glycol were polymerized
in the presence of manganese acetate as an ester exchange catalyst,
antimony trioxide as a polymerization catalyst and phosphorous acid
as a stabilizer in accordance with a commonly used method to give
polyethylene terephthalate (PET) containing substantially no inert
particles.
[0187] This polyethylene terephthalate was dried at 170.degree. C.
for 3 hours, supplied to an extruder, molten at a temperature of
280 to 300.degree. C., extruded into a sheet from a die and
quenched to give a 82 .mu.m-thick unstretched film.
[0188] The obtained unstretched film was preheated, stretched to
3.2 times in a longitudinal direction between high-speed and
low-speed rolls at a film temperature of 95.degree. C. and
quenched. A water-soluble coating solution for the coating layer B
was applied to one side of this stretched film to a thickness of
0.009 .mu.m (after stretching and drying) and a water-soluble
coating solution for the coating layer A was applied to the other
side of the film to a thickness of 0.035 .mu.m. Thereafter, the
film was supplied to a stenter to be stretched to 4.1 times in a
transverse direction at 110.degree. C. The obtained biaxially
oriented film was heat set with hot air heated at 220.degree. C.
for 4 sec to give a 6.0 .mu.m-thick biaxially oriented polyester
film.
EXAMPLE 3
[0189] A polyester film was obtained in the same manner as in
Example 1 except that polyethylene-2,6-naphthalate containing
substantially no inert particles and polyethylene-2,6-naphthalate
containing 0.2 wt % of silica particles having an average particle
diameter of 200 nm were dried at 170.degree. C. for 6 hours, molten
at 310.degree. C. using two extruders and laminated together using
a multi-manifold coextrusion die to ensure that the thickness ratio
of polyethylene-2,6-naphthalate containing no particles to
polyethylene-2,6-naphthalate containing particles should be 2:1,
and the coating layer A shown in Table 1 was formed on the
particle-containing layer and the coating layer B was formed on the
other side.
[0190] As is obvious from Table 1 and Table 2, the composite
polyester films of the present invention have a small amount of
electrostatic charge, are free from blocking and rarely chipped and
have excellent electromagnetic conversion characteristics, adhesion
to a magnetic layer and adhesion to a back coat. In contrast to
this, composite polyester films which do not meet the requirements
of the present invention do not achieve the above characteristic
properties at the same time.
4 TABLE 1 coating layer B coating layer A siloxane siloxane
copolymerized inert particles copolymerized inert particles acrylic
resin other average particle acrylic resin other average particle
content resin diameter base content resin diameter content type (wt
%) type material (nm) film type (wt %) type material (nm) (wt %)
Ex. 1 -- -- a acrylic copolymer 40 {circle over (1)} e 5 d acrylic
copolymer 40 10 Ex. 2 e 3 a acrylic copolymer 40 {circle over (2)}
e 10 d acrylic copolymer 40 10 Ex. 3 -- -- a silica 25 {circle over
(3)} f 25 c silica 30 20 C. Ex. 1 -- -- a acrylic copolymer 40
{circle over (1)} -- -- d acrylic copolymer 40 10 C. Ex. 2 e 60 a
acrylic copolymer 40 {circle over (1)} e 5 d acrylic copolymer 40
10 C. Ex. 3 -- -- b silica 25 {circle over (2)} f 70 d acrylic
copolymer 40 10 C. Ex. 4 -- -- a acrylic copolymer 40 {circle over
(2)} e 20 d -- C. Ex. 5 -- -- b silica 25 {circle over (2)} f 10 d
acrylic copolymer 40 10 C. Ex. 6 -- -- b silica 20 {circle over
(2)} f 10 d acrylic copolymer 40 10 C. Ex. 7 -- -- a acrylic
copolymer 40 {circle over (1)} e 5 d silica 300 5 Ex.: Example C.
Ex.: Comparative Example
[0191] (Notes) type of resin of coating layer
[0192] a; acrylmodified polyester(IN-170-6 of Takamatsu Yushi Co.,
Ltd.)
[0193] b; copolyester (2,6-naphthalenedicarboxylic acid/isophthalic
acid/5-sodium sulfoisophthalic acid//ethylene glycol/adduct of
bisphenol A with two moles of propylene oxide)
[0194] c; acryl modified polyester (SH551A of Takamatsu Yushi Co.,
Ltd.)
[0195] d; acryl modified polyester SH551A/methyl cellulose (SM15 of
Shin-Etsu Chemical Co., Ltd.)=2/1
[0196] e; siloxane copolymerized acryl (X-22-8053 of Shin-Etsu
Chemical Co., Ltd.)
[0197] f; siloxane copolymerized acryl (X-22-8053EM of Shin-Etsu
Chemical Co., Ltd.)
[0198] base film
[0199] {circumflex over (1)} single-layer PEN
[0200] {circumflex over (1)} single-layer PET
[0201] {circumflex over (1)} double-layer coextruded PEN
5TABLE 2 characteristic properties of magnetic characteristic
properties of film recording medium electro- coating layer B
chipping chipping magnetic agglo- density of Ra.sup.A of resis-
resis- conversion meration protrusions coating electro- tance tance
character- adhesion of adhesion rate (unit: Ra.sup.B layer A static
of coating of coating istics traveling magnetic of back (%)
10.sup.6/mm.sup.2) (nm) (nm) properties blocking layer B layer A
C/N durability layer coat Ex. 1 8 20 0.7 2.5 .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. Ex. 2 12 21 0.8 2.3
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. Ex. 3 18 8
0.6 5.7 .largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. C. Ex. 1 10
20 0.7 2.4 X X .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. C. Ex. 2 9 21 0.8 2.7
.largecircle. .largecircle. X .largecircle. X .largecircle. X
.largecircle. C. Ex. 3 15 32 0.9 2.6 .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. X C. Ex. 4 10 10 0.6 1.9 .largecircle. X
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. C. Ex. 5 13 0.5 0.6 2.5 .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. X
.largecircle. .largecircle. C. Ex. 6 40 130 1.5 2.5 .largecircle.
.largecircle. X .largecircle. X .largecircle. .largecircle.
.largecircle. C. Ex. 7 11 18 0.8 4 .largecircle. .largecircle.
.largecircle. X .largecircle. .largecircle. .largecircle.
.largecircle. Ex.: Example C. Ex.: Comparative Example
* * * * *