U.S. patent application number 09/816377 was filed with the patent office on 2001-08-30 for thermoplastic resin film and label paper employing the same.
This patent application is currently assigned to YUPO CORPORATION. Invention is credited to Ohkawachi, Ichiro, Shibuya, Nobuhiro.
Application Number | 20010018125 09/816377 |
Document ID | / |
Family ID | 26556693 |
Filed Date | 2001-08-30 |
United States Patent
Application |
20010018125 |
Kind Code |
A1 |
Shibuya, Nobuhiro ; et
al. |
August 30, 2001 |
Thermoplastic resin film and label paper employing the same
Abstract
A thermoplastic resin film (i) which has a degree of dimensional
change through heating and cooling (.alpha.) in the range of from
-2% to 2% as measured by thermomechanical analysis in the range of
from room temperature to 135.degree. C., or which has a degree of
thermal shrinkage of 1.8% or lower upon heating at 130.degree. C.
for 30 minutes or longer; and a label paper employing the same. The
label paper has suitability for heated-roll fixing type
electrophotographic printers and is satisfactory in curling after
printing.
Inventors: |
Shibuya, Nobuhiro;
(Kashima-gun, JP) ; Ohkawachi, Ichiro;
(Kashima-gun, JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Assignee: |
YUPO CORPORATION
Chiyoda-ku
JP
|
Family ID: |
26556693 |
Appl. No.: |
09/816377 |
Filed: |
March 26, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09816377 |
Mar 26, 2001 |
|
|
|
PCT/JP99/05161 |
Sep 21, 1999 |
|
|
|
Current U.S.
Class: |
428/352 ;
428/343; 428/355R; 428/41.8 |
Current CPC
Class: |
Y10T 428/2839 20150115;
Y10T 428/2848 20150115; Y10T 428/24998 20150401; Y10T 428/249986
20150401; Y10T 428/1476 20150115; Y10T 428/2852 20150115; C08J 5/18
20130101; G09F 3/10 20130101; Y10T 428/28 20150115; Y10T 428/249982
20150401; Y10T 428/249976 20150401 |
Class at
Publication: |
428/352 ;
428/343; 428/355.00R; 428/41.8 |
International
Class: |
B32B 009/00; B32B
033/00; B32B 007/12; B32B 015/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 25, 1998 |
JP |
10-287373 |
Dec 16, 1998 |
JP |
10-357231 |
Claims
1. A thermoplastic resin film (i) comprising a stretched
thermoplastic resin sheet comprising a thermoplastic resin, wherein
the thermoplastic resin film has a degree of dimensional change
after heating and cooling (.alpha.) in the range of from -2% to 2%
as measured by thermomechanical analysis in the range of from room
temperature to 135.degree. C. or which has a degree of thermal
shrinkage of 1.8% or lower upon heating at 130.degree. C. for 30
minutes or longer.
2. The thermoplastic resin film (i) according to claim 1, having a
degree of dimensional change after heating and cooling (.alpha.) in
the range of from -2% to 2% as measured by thermomechanical
analysis in the range of from room temperature to 135.degree.
C.
3. The thermoplastic resin film (i) according to claim 1, having a
degree of thermal shrinkage of 1.8% or lower upon heating at
130.degree. C. for 30 minutes or longer.
4. The thermoplastic resin film (i) according to claim 1, having a
degree of dimensional change after heating and cooling (.alpha.) in
the range of from -2% to 2% as measured by thermomechanical
analysis in the range of from room temperature to 135.degree. C.,
and having a degree of thermal shrinkage of 1.8% or lower upon
heating at 130.degree. C. for 30 minutes or longer.
5. The thermoplastic resin film (i) according to any one of claims
1 to 4, comprising from 35 to 100 wt % of a thermoplastic resin and
from 65 to 0 wt % of inorganic and/or organic fine particles.
6. The thermoplastic resin film (i) according to any one of claims
1 to 5, wherein the thermoplastic resin is a porosity as shown by
the following equation of from 8 to 60%: 2 Porosity ( % ) = 0 - 0
.times. 100 .rho..sub.0: density of the resin film before
stretching .rho.: density of the resin film after stretching.
7. The thermoplastic resin film (i) according to any one of claims
1 to 6, wherein the thermoplastic polyolefin resin is a
polyolefin-based resin.
8. The thermoplastic resin film (i) according to claim 7, wherein
the polyolefin-based resin is a polypropylene-based resin.
9. The thermoplastic resin film (i) according to any one of claims
6 to 8, which has an opacity as measured in accordance with
JIS-P8138-1976 of from 20% to 100%.
10. The thermoplastic resin film (i) according to any one of claims
1 to 9, which is one obtained through a heat treatment.
11. The thermoplastic resin film (i) according to claim 10, wherein
the heat treatment is carried out at 90.degree. C. to 250.degree.
C.
12. The thermoplastic resin film (i) according to claim 10 or 11,
wherein the heat treatment is carried out in an oven.
13. The thermoplastic resin film according to any one of claims 1
to 12, which comprises a toner receiving layer on one side
thereof.
14. The thermoplastic resin film according to any one of claims 1
to 13, which comprises a toner receiving layer on at least the side
thereof opposite to the side in contact with a pressure-sensitive
adhesive layer.
15. A label paper which comprises a thermoplastic resin film (i), a
pressure-sensitive adhesive layer (ii), and a release payer (iii),
in this order on the thermoplastic resin film (i), wherein the
thermoplastic resin film (i) is the thermoplastic resin film (i)
according to any one of claims 1 to 14.
16. The label paper according to claim 15, wherein a A-4 size (210
mm.times.297 mm) paper has an average curl height at the four
corners of 50 mm or smaller, measured 2 minutes after printing the
label paper with a heated-roll fixing type electrophotographic
printer.
17. The label paper according to claim 15 or 16, wherein the
thermoplastic resin film (i) has a degree of dimensional change
after heating and cooling (.alpha.) in the range of from -2% to 2%
as measured by thermomechanical analysis in the range of from room
temperature to 135.degree. C., and the difference (.alpha.-.beta.)
between the degree of dimensional change (.alpha.) of the film and
the degree of dimensional change after heating and cooling (.beta.)
of the release paper (iii), as measured by thermomechanical
analysis in the range of from room temperature to 135.degree. C.,
is in the range of from -1.5% to 1.5%.
Description
TECHNICAL FIELD
[0001] The present invention relates to a thermoplastic resin film
which has a degree of dimensional change through heating and
cooling (.alpha.) in the range of from -2% to 2% as measured by
thermomechanical analysis in the range of from room temperature to
135.degree. C., or which has reduced thermal shrinkage upon heating
at 130.degree. C. for 30 minutes or longer. The invention further
relates to a label paper which employs the film and which has
reduced curling after being printed with a printing method in which
thermal energy is applied, in particular, printing with a
heated-roll fixing type electrophotographic printer.
BACKGROUND ART
[0002] Thermoplastic resin films which have satisfactory water
resistance, in particular, polyolefin-based synthetic papers, may
be used, for example, as stickers for outdoor advertising or as
labels which may be applied to containers for frozen foods, because
the conventional stickers, and the coated paper used in such
labels, have poor water resistance.
[0003] Resin films for use in water resistant labels are known.
With respect to details thereof, reference may be made to, for
example, such films are described in Examined Japanese Patent
Publications Nos. 46-40794 and 49-1782, Unexamined Published
Japanese Patent Applications Nos.56-118437, 57-12642, and 57-56224,
etc.
[0004] However, such polyolefin-based synthetic papers, when used
as labels and printed with a heated-roll fixing type
electrophotographic printer, in which the heated roll has a surface
treatment as high as 140 to 190.degree. C., have a higher degree of
thermal shrinkage than the release paper adhered thereto, which
causes the label to curling considerably after printing. In extreme
cases, the label paper may roll up into a cylinder, making it
difficult to peel the printed synthetic paper from the release
paper. Because of this curling problem, polyolefin-based synthetic
papers cannot be satisfactorily printed using a heated-roll fixing
type electrophotographic printer.
[0005] An object of the present invention is to provide a
thermoplastic resin film, and a label papers comprising such a
film, which has reduced thermal curling compared with conventional
papers, and can be easily peeled from the release paper when used
as a label printed with a heated-roll fixing type
electrophotographic printer.
DISCLOSURE OF THE INVENTION
[0006] The thermoplastic resin film (i) of the present invention
may be used as a base paper for labels, and has a degree of
dimensional change upon heating and cooling (.alpha.) in the range
of from -2% to 2%, as measured by thermomechanical analysis in the
range of from room temperature to 135.degree. C., or which has a
degree of thermal shrinkage of 1.8% or lower upon heating at
130.degree. C. for 30 minutes or longer. A label prepared from this
film comprises a label paper comprising the thermoplastic resin
film of the present invention, a pressure-sensitive adhesive, and a
release paper. The label of the present invention has reduced curl
height after printing with a heated-roll fixing type
electrophotographic printer, and is therefore suitable for use with
this printing method.
[0007] The invention directed attention to the relationship between
the thermal dimension change of label papers and the curling
thereof in order to solve the problems described above, and the
above object is accomplished by regulating the thermal dimensional
change of label papers comprised of the thermoplastic resin film of
the present invention, to a specific value. Namely, a reduction in
curl height and satisfactory printing properties have been achieved
by using a thermoplastic resin film as a label paper which has a
degree of dimensional change (.alpha.) in a specific range, and/or
a specific degree of thermal shrinkage.
BEST MODE FOR CARRYING OUT THE INVENTION
[0008] The thermoplastic resin film (i) of the present invention
has a reduced degree of dimensional change upon heating and cooling
(.alpha.) as measured by thermomechanical analysis in the range of
from room temperature to 135.degree. C., and/or a reduced degree of
thermal shrinkage upon heating at 130.degree. C. for 30 minutes or
longer. The present invention further relates to a label paper
comprising the film and, bonded thereto, a pressure-sensitive
adhesive layer (ii) and a release paper (iii). The present
invention will be explained below in detail.
[0009] (1) Thermoplastic Resin Film (i)
[0010] The thermoplastic resin used in the thermoplastic resin film
(i) of the present invention may include, for example, polyolefin
resins such as ethylene-based resins, e.g., high-density
polyethylene and medium-density polyethylene, and propylene-based
resins, poly (4-methyl-1-pentene), ethylene/cycloolefin copolymers,
polyamide resins such as nylon-6, nylon-6,6, nylon-6,10,
nylon-6,12, and nylon-6,T, thermoplastic polyester resins such as
poly(ethylene terephthalate) and copolymers thereof, poly (ethylene
naphthalate), and aliphatic polyesters, and thermoplastic resins
such as polycarbonates, atactic polystyrene, syndiotactic
polystyrene, and poly (phenylene sulfide). These resins may be used
as a mixture of two or more thereof. Polyolefin resins are the
preferred resin. Propylene-based resins are the preferred
polyolefin resin, based, for example, on their good chemical
resistance,- and low cost.
[0011] The propylene-based resin may include an isotactic or
syndiotactic propylene homopolymer or a propylene homopolymer
having any of various degrees of stereoregularity, or a copolymer
having propylene as the main component, with one or more
.alpha.-olefin comonomers such as ethylene, butene-1, hexene-1,
heptene-1, and 4-methyl-1-pentene. This copolymer may be a binary
system, ternary system, or quaternary system, and may be a random
copolymer or block copolymer.
[0012] The thermoplastic resin may also be blended with fine
inorganic particles to form the thermoplastic resin film (i). The
fine inorganic particles may include, for example, particles of
calcium carbonate, calcined clay, silica, diatomaceous earth, talc,
titanium oxide, barium sulfate, alumina or the like, which have an
average particle diameter of from 0.01 to 15 .mu.m.
[0013] If the thermoplastic resin film is a polyolefin resin film,
the polyolefin may be blended with fine organic particles. The fine
organic particles may have a melting point of from 170 to
300.degree. C. higher than the melting point of the polyolefin
resin, or a glass transition temperature of from 170.degree. C. to
280.degree. C. higher than the melting point of the polyolefin
resin.
[0014] For example, the fine organic particles may include
particles of poly (ethylene terephthalate), poly(butylene
terephthalate), a polycarbonate, nylon-6, nylon-6,6, nylon-6,T, a
polymer of a cycloolefin, or the like.
[0015] Fine inorganic particles are preferred to organic fine
particles because of their lower cost. Calcium carbonate, calcined
clay, and talc are especially preferred inorganic fine
particles.
[0016] As needed, the thermoplastic resin film may also include a
stabilizer, light stabilizer, dispersant, lubricant, and the like.
The amount of stabilizer incorporated into the thermoplastic resin
film may be from 0.001 to 1% by weight, based on the total weight
of the thermoplastic resin. The stabilizer may include, for
example, a sterically hindered phenol, phosphorus, or amine
compound or the like. The amount of light stabilizer incorporated
into the thermoplastic resin film may be from 0.001 to 1% by
weight, based on the total weight of the thermoplastic resin. The
light stabilizer may include, for example, a sterically hindered
amine, benzotriazole, or benzophenone compound or the like. In
addition, a dispersant for the fine inorganic particles may also be
added, including for example a silane coupling agent, a higher
fatty acid such as oleic acid or stearic acid, a metal soap,
poly(acrylic acid), poly(methacrylic acid), salts thereof, or the
like. The amount of dispersant may be from 0.01 to 4% by weight,
based on the total weight of the thermoplastic resin.
[0017] The thermoplastic resin film (i) may have one or more
layers. For example, the thermoplastic resin film (i) may be a
single layer film, or may have a two-layer structure composed of a
base layer and a surface layer, a three-layer structure having a
surface layer on each of the front and back sides of a base layer,
or a multilayer structure comprising a base layer, a surface layer,
and one or more other resin film layers interposed therebetween.
The film may comprises from 35 to 100% by weight thermoplastic
resin and from 65 to 0% by weight inorganic and/or organic fine
particles.
[0018] If the thermoplastic resin film (i) is a single-layer
polyolefin resin film and contains inorganic and/or organic fine
particles, it may comprise from 35 to 99.5% by weight of a
polyolefin resin and from 65 to 0.5% by weight of the inorganic
and/or organic fine particles, and preferably comprises from 50 to
97% by weight polyolefin resin and from 50 to 3% by weight of the
inorganic and/or organic fine particles. If the thermoplastic resin
film has a multilayer structure comprising a base layer and a
surface layer each containing inorganic and/or organic fine
particles, the base layer of the thermoplastic resin film may
comprise from 35 to 99.5% by weight of a polyolefin resin aid from
65 to 0.5% by weight of the inorganic and/or organic fine particles
and the surface layer may comprise from 25 to 100% by weight of a
polyolefin resin and from 75 to 0% by weight of the inorganic
and/or organic fine particles. In this case, the base layer
preferably comprises from 50 to 97% by weight of a polyolefin resin
and from 50 to 3% by weight of the inorganic and/or organic fine
particles and the surface layer preferably comprises from 30 to 97%
by weight of a polyolefin resin and from 70 to 3% by weight of the
inorganic and/or organic fine particles.
[0019] In order to improve the flexibility of the film, the amount
of the inorganic and/or organic fine particles incorporated into
the base layer in a single-layer film or a multilayer film
structure is preferably 65% by weight or smaller. If the film is to
be made by a process which includes stretching the film, described
below, the amount of the inorganic and/or organic fine particles in
the surface layer is preferably 75% by weight or less, in order
that the stretched film have a higher level of surface
strength.
[0020] Formation of the Resin Film
[0021] The method of making the thermoplastic resin film (i) of the
present invention is not particularly limited, and any of various
known techniques may be used. For example, the thermoplastic resin
film may be made by extruding a molten resin into a sheet form with
a single-layer or multilayered T-die or I-die, connected to a screw
type extruder, or by calendering, rolling, inflation, by casting or
calendering a mixture of a thermoplastic resin and an organic
solvent or oil and subsequent removing the solvent or oil, casting
a solution of a thermoplastic resin and removing the solvent, and
the like. In order to efficiently obtain a film having a large
area, a combination of any of the above film forming methods with
the stretching treatment described below, is preferred.
[0022] Stretching
[0023] Various known methods may be used for stretching, and may be
carried out in a temperature range known to be suitable for the
thermoplastic resin used. If the resin is a noncrystalline resin,
the stretching temperature is not lower than the glass transition
point of the thermoplastic resin. If the resin is crystalline, the
stretching temperature range may be from the glass transition point
of the noncrystalline portions of the resin to the melting point of
the crystalline portions. Examples of methods for stretching films
include, for example, machine-direction stretching utilizing a
difference in peripheral speed between rolls. transverse-direction
stretching with a tenter oven, calendering, simultaneous biaxial
stretching with a combination of a tenter oven and a linear motor,
and the like.
[0024] The stretch ratio is defined as the area of the film after
stretching, divided by the area of the film prior to stretching.
The stretch ratio is not limited to any particular value, and is
selected based on the desired properties of the thermoplastic
resin. For example, if the thermoplastic resin is polypropylene or
a copolymer thereof, the unidirectional stretch ratio may be from
about 1.2 to about 12, preferably from 2 to 10, and the biaxial
stretch ratio may be from about 1.5 to about 60, preferably from 10
to 50. If other thermoplastic resins are used, the unidirectional
stretch ratio may be from 1.2 to 10, preferably from 2 to 5, and
that in biaxial stretch ratio is from 1.5 to 20, preferably from 4
to 12. If desired, the film may also be heat treated at a high
temperature.
[0025] The stretching temperature is lower than the melting point
of the thermoplastic resin by from 2 to 150.degree. C., preferably
from 2 to 60.degree. C., and is selected based on the stretching
process used. For example, if the thermoplastic resin is a
propylene homopolymer or copolymer (melting point, 155 to
167.degree. C.), high-density polyethylene (melting point, 121 to
134.degree. C.), or poly (ethylene terephthalate) (melting point,
246 to 252.degree. C.), the stretching temperature may be in the
range of from 110 to 164.degree. C., from 110 to 120.degree. C., or
from 104 to 115.degree. C., respectively.
[0026] Furthermore, the stretching speed may be from 20 to 350
m/min.
[0027] If the thermoplastic resin film is made from a polypropylene
homopolymer using a process comprising a transverse-direction
stretching step using a tenter oven, an effective technique for
reducing the degree of thermal shrinkage is to dispose a
heat-setting zone in the latter half of the process and heat the
stretched and formed polypropylene film to a temperature which is
at most close to its melting temperature. The temperature of the
heat-setting zone can any of a wide range of temperatures, which
depends on the line speed of the film during the stretching step,
the flow speed and flow rate of the high-temperature air blown in
the heat-setting zone, the structure of the heat-setting zone, etc.
For example, the temperature of the heat setting zone may be in the
range of from 158 to 175.degree. C.
[0028] If the thermoplastic resin film contains fine inorganic
particles or an organic filler, the film surfaces may also develop
microcracks and inner portions of the film may develop
microvoids.
[0029] After the stretching, the thermoplastic resin film may have
a thickness in the range of from 30 to 350 .mu.m, preferably from
50 to 300 .mu.m.
[0030] Heat Treatment
[0031] Usually, a combination of the forming and stretching process
described above, together with high-temperature setting in a
heat-setting zone or a heat treatment after the forming, provides a
means for regulating the thermoplastic resin film (i) of the
invention so that the degree of dimensional change through heating
and cooling (.alpha.) of the film, as measured by thermomechanical
analysis in the range of from room temperature to 135.degree. C.,
is from -2% to 2%, preferably from -1.5% to 1.5%, more preferably
from -1.2% to 1.2%, and/or the degree of thermal shrinkage of the
film upon heating at 130.degree. C. for 30 minutes is 1.8% or
lower, preferably 1.5% or lower, more preferably 1.2% or lower.
[0032] The heating temperature of the heating zone or the heat
treatment is preferably lower than the melting point of the
thermoplastic resin, and may be, for example, in the range of from
90.degree. C. to 250.degree. C., preferably from 95.degree. C. to
250.degree. C., more preferably from 105.degree. C. to 160.degree.
C. At temperatures lower than 90.degree. C., the heat treatment
tends to have an insufficient effect on the degree of dimensional
change or thermal shrinkage. At temperatures exceeding 250.degree.
C., the film may deform or becomes wavy. Furthermore, if the
thermoplastic resin is a polypropylene resin, the heating
temperature is preferably in the range of from 90 to 175.degree.
C., more preferably from 95 to 158.degree. C. even more preferably
from 105 to 140.degree. C. At temperatures lower than 90.degree.
C., either the effect of the heat treatment is insufficient, or a
long heating time is necessary in order to obtain a sufficient
effect, thereby making it difficult to efficiently produce the film
on an industrial scale. The temperature of a heat conducting medium
used for the heating the film is selected so that the film has a
temperature within the range shown above.
[0033] The heating time may be selected over a wide range of times,
preferably not shorter than 0.1 second. However. it may be in the
range of from 2 seconds to 30 days, more preferably from 4 seconds
to 7 days, even more preferably from 4 seconds to 2 days. Heating
times longer than 30 days are apt to result in film deterioration,
while heating times shorter than 0.1 second may provide
insufficient treatment. The heat treatment may be carried out after
the film itself is formed, or after the film is surface treated,
discussed below.
[0034] Examples of methods for heat treating the film of the
present invention include a heat treatment conducted in a
high-temperature heat-setting zone after stretching the film in a
tenter oven, as described above, a heat treating the film in sheet
or roll form in an oven, heating with high-temperature air, steam,
or other heating conducting media, etc. The heat treatment may be
carried out in such a manner that the ends of the film are kept
unconstrained so as to allow the film to gradually shrink upon
heating. If the ends of the film are fixed, the heat treatment may
be conducted by arranging the devices used to fixing two opposed
ends or for fixing the two pairs of opposed ends, so that the
distance therebetween may be reduced in conjunction with the
thermal shrinkage of the film. Alternatively, the treatment may be
conducted in such a manner that at least two opposed ends of the
film are kept fixed so as not to follow the film shrinkage.
Specific examples include a method in which the film in a roll form
is heated in a forced-air oven, a method in which the film in the
form of either single sheet or in the form of stacked sheets is
heated, a method in which the film is heated by contact with at
least one high-temperature roll, etc.
[0035] Surface Treatment
[0036] The thermoplastic resin film (i) is preferably subjected to
a surface treatment on at least the side of the film which is
intended to be printed, or on both sides, for the purpose of
improving toner adhesion, improving the adhesion of a
toner-receiving layer on the thermoplastic resin film (i), or
imparting antistatic properties.
[0037] Such surface treatments may include, for example, a surface
oxidation treatment, a combination of a surface oxidation treatment
and a coating of a surface-treating agent, etc. Conventional
treatments for films, either alone or in combination, such as
corona discharge treatment, flame treatment, plasma treatment, glow
discharge treatment, and ozone treatment may be used as the surface
oxidation treatment. Corona treatment and flame treatment are
preferred. If corona treatment is used, the amount of treatment
should be from 600 to 12,000 J/m.sup.2 (from 10 to 200
W-min/m.sup.2), preferably from 1,200 to 9,000 J/m.sup.2 (from 20
to 180 W-min/m.sup.2), and if flame treatment is used, the amount
of treatment should be from 8,000 to 200,000 J/m.sup.2, preferably
from 20,000 to 100,000 J/m.sup.2.
[0038] A surface-treating agent may consists mainly of one
ingredient or a mixture of two or more ingredients selected from
the following primers and antistatic polymers. In order to obtain
good toner adhesion and antistatic properties, the preferred
surface-treating agents are primers and combinations of one or more
primers with one or more antistatic polymers.
[0039] (1) Primers
[0040] The primer may be, for example, polyethyleneimine type
polymers such as polyethyleneimine, polyethyleneimines modified
with an alkyl group having 1 to 12 carbon atoms,
poly(ethyleneimine-urea) ethyleneimine adducts of
polyamine-polyamides, and
[0041] epichlorohydrin adducts of polyamine-polyamides, acrylic
ester polymers such as acrylamide/acrylic ester copolymers,
acrylamide/acrylic ester/methacrylic ester copolymers,
polyacrylamide derivatives, acrylic ester polymers containing
oxazoline groups, and poly(acrylic esters), water-soluble resins
such as polyvinylpyrrolidone, polyethylene glycol, poly(vinyl
alcohol); water-dispersible resins such as poly (vinyl acetate),
polyurethanes, ethylene/vinyl acetate copolymers, poly(vinylidene
chloride), chlorinated polypropylene, and acrylonitrile/butadiene
copolymers, and the like.
[0042] Polyethyleneimine type polymers, urethane resins,
poly(acrylic esters), and the like are preferred primers.
Polyethyleneimine type polymers are more preferred, and
polyethyleneimine having a degree of polymerization of from 20 to
3,000, ethyleneimine adducts of polyamine-polyamides, and modified
polyethyleneimines obtained by modifying these polymers with
halogenoalkyl, halogenoalkenyl, halogenocycloalkyl, or
halogenobenzyl groups having 1 to 24 carbon atoms, are most
preferred.
[0043] (2) Antistatic Polymers
[0044] Examples of antistatic polymers include cationic, anionic,
amphoteric, and other polymers. Examples of cationic polymers
include polymers having a quaternary ammonium salt structure or a
phosphonium salt structure, nitrogen-containing acrylic polymers,
and acrylic or methacrylic polymers having nitrogen as a quaternary
ammonium salt structure. Examples of the amphoteric polymers
include nitrogen-containing acrylic or methacrylic polymers having
a betaine structure. Examples of the anionic polymers include
styrene/maleic anhydride copolymers or alkali metal salts thereof,
alkali metal salts of ethylene/acrylic acid copolymers, alkali
metal salts of ethylene/methacrylic acid copolymers, and the like.
Acrylic or methacrylic polymers having nitrogen as a quaternary
ammonium salt structurc are especially preferred.
[0045] An antistatic polymer having any desired molecular weight
may be obtained by regulating the polymerization conditions under
which it is made, for example, the polymerization temperature, the
kind and amount of a polymerization initiator, the amount of a
solvent used, and the presence of a chain transfer agent. In
general, the antistatic polymer should have a molecular weight
(M.sub.w) of from 1,000 to 1,000,000 preferably 1,000 to
500,000.
[0046] The surface-treating agent described above for use in the
present invention may contain the following optional ingredients,
as needed.
[0047] (3) Optional Ingredient 1: Crosslinking Agent
[0048] Coating film strength and water resistance can be further
improved by adding a crosslinking agent. Examples of the
crosslinking agent may include, for example, epoxy compounds such
as a glycidyl ether and a glycidyl ester, and aqueous dispersion
type resins such as epoxy resins and isocyanate, oxazoline,
formalin, and hydrazide compounds. The amount of the crosslinking
agent added to the surface-treating agent may be in the range of up
to 100 parts by weight per 100 parts by weight of the effective
ingredients of the surface-treating agent, which exclude the
solvent.
[0049] (4) Optional Ingredient 2: Alkali Metal Salt or Alkaline
Earth Metal Salt
[0050] Examples of the alkali metal salt or alkaline earth metal
salt may include water-soluble inorganic salts such as, e.g.,
sodium carbonate, sodium hydrogen carbonate, potassium carbonate,
sodium sulfite, and other alkaline salts, and further may include
sodium chloride, sodium sulfate, sodium nitrate, sodium
tripolyphosphate, sodium pyrophosphate, and ammonium alum.
[0051] The amount of optional ingredient 2 may be 50 parts by
weight or smaller per 100 parts by weight of the effective
ingredients of the surface-treating agent, which exclude the
solvent.
[0052] (5) Optional Ingredients 3
[0053] The surface-treating agent may further contain a surfactant,
an antifoamer, a water-soluble or water-dispersible, finely
particulate substance, and other processing aids.
[0054] The amount of optional ingredients 3 may be 20 parts by
weight or smaller per 100 parts by weight of the effective
ingredients of the surface-treating agent, which exclude the
solvent.
[0055] Formation of Surface Treatment Layer
[0056] The ingredients for the surface treatment layer described
above are typically as a solution, for example by dissolving them
in water or a hydrophilic solvent such as methyl alcohol, ethyl
alcohol, or isopropyl alcohol. Preferably, the ingredients are used
in the form of an aqueous solution. The total concentration of
these ingredients in the solution is, for example, about from 0.1
to 20% by weight, preferably about from 0. to 10% by weight, based
on the total weight of the solution.
[0057] The surface treatment layer is coated onto the thermoplastic
resin film (i) by coating the solution with a roll coater, blade
coater, bar coater, air-knife coater, size press coater, gravure
coater, reverse coater, die coater, lip coater, spray coater, or
the like. Smoothing of the surface treatment layer is carried out
as needed, and any excess water or hydrophilic solvent is removed
by a drying step.
[0058] The solution may be applied in an amount of from 0.005 to 5
g/m.sup.2, preferably from 0.01 to 2 g/m.sup.2, based on the weight
of the dried film.
[0059] If the thermoplastic resin film (i) is a stretched film, the
surface treatment layer may be provided by a single-stage coating
or multistage coating process, either before or after the machine-
or transverse-direction stretching.
[0060] Properties of Thermoplastic Resin Film (i)
[0061] If the thermoplastic resin film has been stretched, the
thermoplastic resin film has a porosity, as shown by the following
equation, of from 5 to 60%, preferably from 8 to 35%, more
preferably from 8 to 30%. If the porosity of the film is lower than
5%, it is difficult to reduce the weight of the film. Porosities
exceeding 60% are apt to result in poor label strength. 1 Porosity
( % ) = 0 - 0 .times. 100
[0062] .rho..sub.0: density of the resin film before stretching
[0063] .rho.: density of the resin film after stretching
[0064] The density of the film as measured in accordance with
JIS-P8118-1976, and may be in the range of from 0.65 to 1.3
g/cm.sup.3, preferably from 0.8 to 1.1 g/cm.sup.3. Films with
densities lower than 0.65 g/cm.sup.3 tend to have poor base
strength. If the density of the film exceeds 1.3 g/cm.sup.3, a
stack of many sheets may be too heavy to carry.
[0065] Furthermore, the film should have the following properties:
the opacity as measured in accordance with JIS-P8138-1976 should be
from 20 to 100%, preferably from 60 to 100, and the Bekk's surface
smoothness should be from 50 to 25,000 seconds.
[0066] Thermomechanical Analysis
[0067] The degree of dimensional change after heating and cooling
(.alpha.) as measured by thermomechanical analysis (hereinafter
abbreviated as "TMA") in the range of from room temperature to
135.degree. C. (hereinafter abbreviated as "degree of dimensional
change (.alpha.)") of the thermoplastic resin film (i) of the
present invention should be in the range of from -2 to 2%.
[0068] The thermomechanical analysis of the films of the present
invention may be conducted with a commercial thermomechanical
analyzer. Typical examples of the apparatus, principle, features,
and uses are described in documents including "1997 Bunseki Kiki
Soran", edited and published by Japan Analytical Instruments
Association, Chap. IV, p. 92 (Sep. 1, 1997) and Bernhard
Wunderlich, "Thernal Analysis", Chap. 6, pp. 311-312, Academic
Press, Inc., 1990, herewith incorporated by reference.
[0069] Specific examples of the TMA apparatus include a "TMA120C"
manufactured by Seiko Instruments Inc., a "TMA7" manufactured by
Perkin-Elmer Corp., a "TMA-50" manufactured by Shimadzu Corp., a
"TM-9200" manufactured by Shinku Riko, and the like.
[0070] An example of a method for measuring the degree of
dimensional change after heating and cooling by TMA of a film
according to the present invention is as follows. A TMA apparatus,
e.g., "TMA120C" manufactured by Seiko Instruments Inc., was used in
the tension mode. A fixed load selected in the range of from about
1 to 20 g was used. A film sample having a width of 4 mm and a
length of 10 mm (excluding the portions fixed to the upper and
lower clamps of the TMA) was prepared and affixed to the TMA. The
rate of heating and that of cooling during each measurement was
2.degree. C./min. The samples were heated in a measuring
temperature range, i.e. from room temperature. e.g., 25.degree. C.
to 50.degree. C. to a set temperature of 150.degree. C. (actual
temperature, 135.degree. C.) and then cooled back to room
temperature. The degree of shrinkage or expansion of the sample
piece is expressed as a percent of the initial sample length of 10
mm, and is referred to as the degree of dimensional change.
[0071] The degree of dimensional change (.alpha.) of the
thermoplastic resin film (i) of the present invention means the
larger of the degrees of machine-direction (MD) and
transverse-direction (TD) dimensional changes after heating and
cooling (.alpha.) as measured by thermomechanical analysis in the
range of from room temperature to 135.degree. C. The degree of
dimensional change may be in the range of from -2% (elongation) to
2% (shrinkage) , preferably from -1.5% (elongation) to 1.5%
(shrinkage), more preferably from -1.25% (elongation) to 1.25%
(shrinkage), even more preferably from -1% (elongation) to 1%
(shrinkage). If the degree of dimensional change of the film is
outside the range of -2% to 2%, the label paper curls considerably
when printed on a heated-roll fixing type electrophotographic
printer, which is likely to result in printing trouble or leads to
poor efficiency in peeling the label from the release paper.
[0072] Degree of Thermal Shrinkage
[0073] The degree of thermal shrinkage after heating at 130.degree.
C. for 30 minutes of the thermoplastic resin film (i) of the
present invention is the average of the machine-direction and
transverse-direction thermal shrinkage values. The degree of
thermal shrinkage may be 1.8% or lower, preferably 1.5% or lower,
more preferably 1.2% or lower. If the degree of thermal shrinkage
of the film exceeds 1.8%, the label curls considerably when printed
on a heated-roll fixing type electrophotographic printer.
[0074] The degree of thermal shrinkage may be determined by cutting
the film into a square shape of a given size, e.g., 100 mm in both
length and width, measuring the dimensions of the square sample
after holding it in a thermo-hygrostatic chamber having a
temperature of 23.degree. C. and a relative humidity of 50%,
subsequently heat treating the sample in a 130.degree. C.
forced-air oven for 30 minutes, taking the film out of the
forced-air oven, allowing the film to cool in the same
thermo-hygrostatic chamber for 1 hour, and then measuring the
dimensions of the sample.
[0075] Formation of Toner-Receiving Layer
[0076] In order to improve the reception of a toner on the film
after printing, a toner-receiving layer comprising an inorganic
and/or organic pigment and a binder may be formed on the side of
the thermoplastic resin film (i) which is to be printed. Any
conventional inorganic pigment may be used, such as lightweight or
heavy calcium carbonate, clay, titanium oxide, silica, alumina, or
the like. In order to improve the toner reception properties of the
film, the thickness of the toner reception layer may be from 0.1 to
20 .mu.m, preferably in the range of from 0.5 to 15 .mu.m. The
binder may be a polymeric binder such as an acrylic, styrene, or
acrylic/styrene polymer, natural rubber, a synthetic rubber, an
ethylene/acrylic or ethylene/methacrylic polymer, or a urethane
polymer. The binder may have the form of particles dispersed in
water, such as a dispersion or emulsion.
[0077] The toner-receiving layer may be coated on the surface of
the thermoplastic resin film (i), for example using a roll coater,
blade coater, bar coater, air-knife coater, gravure coater, reverse
coater, die coater, lip coater, spray coater, or the like. The
toner-receiving layer may also be smoothed, as needed. The
toner-receiving layer may also be dried after coating.
[0078] Pressure-Sensitive Adhesive Layer (ii)
[0079] The type, thickness, and amount of pressure-sensitive
adhesive layer (ii) formed on one side of the thermoplastic resin
film (i) may be selected based on the type of adhesive used, the
environment in which the label paper is expected to be used, the
adhesive strength desired, etc.
[0080] A general purpose water- or solvent-based pressure-sensitive
adhesive may be applied and dried to form a pressure-sensitive
adhesive layer. Any pressure-sensitive adhesive, for example those
based on natural rubber, a synthetic rubber, an acrylic, or the
like, may be used. Pressure-sensitive adhesives based on a
synthetic polymer may be used in the form of a solution in an
organic solvent, or in the form of particles dispersed in water,
such as a dispersion or emulsion.
[0081] A pressure-sensitive adhesive containing a pigment such as
titanium white can be used in order to improve the opacity of the
label.
[0082] Formation of Pressure-Sensitive Adhesive Layer (ii)
[0083] The pressure-sensitive adhesive layer (ii) may be formed by
applying a solution of a pressure-sensitive adhesive on the
silicone-treated side of a release paper (iii) . The coating may be
carried out with a roll coater, blade coater, bar coater, air-knife
coater, gravure coater, reverse coater, die coater, lip coater,
spray coater, or the like. The pressure-sensitive adhesive layer
(ii) may also be smoothed if needed, and be dried after
coating.
[0084] The pressure-sensitive adhesive layer (ii) may also be
coated directly on the thermoplastic resin film (i).
[0085] Although the pressure-sensitive adhesive layer (ii) may have
any suitable thickness, depending on the intended use of the label,
it is usually in the range of from 2 to 30 .mu.m, preferably from 5
to 20 .mu.m.
[0086] Release Paper (iii)
[0087] The release paper (iii) contacts the pressure-sensitive
adhesive layer formed on the thermoplastic resin layer (i), and is
generally treated, on the side in contact with the
pressure-sensitive adhesive layer (ii), with a silicone in order
that the release paper may be readily removed from the
pressure-sensitive adhesive layer (ii).
[0088] Any conventional release paper may be used as release paper
(iii). For example, the release paper may be silicone-treating
wood-free or kraft paper which has not been pretreated or
calendered. In addition, resin coated, film laminated, or
silicone-treated glassine paper, coated paper, plastic film, or the
like, may be used. Paper or film laminated on both sides with a
polymer is effective in reducing curling, because it is less
influenced by ambient humidity.
[0089] The degree of dimensional change (.beta.) of a release paper
may be measured under the same conditions as the degree of
dimensional change of the thermoplastic resin film (i) of the
present invention, as determined by TMA. The degree of dimensional
change (.beta.) of a release paper means the degree of dimensional
change in the machine direction, i.e., the direction (MD) in which
the release paper has been wound into a roll.
[0090] Difference in Degree of Dimensional Change Between
Thermoplastic Resin Film (i) and Release Paper
[0091] In order to further reduce curling caused by printing on a
printer, the difference (.alpha.-.beta.) between the degree of
dimensional change (.alpha.) of the thermoplastic resin film (i) of
the present invention, and the degree of dimensional change
(.beta.) of the release paper as measured under the same
conditions, may be in the range of from -1.5% to 1.5%, preferably
from -1.2% to 1.2%, more preferably from -0.5% to 1%, even more
preferably from 0% to 0.8%.
[0092] Curling
[0093] The label paper of the present invention is suitable for
printing using a heated-roll fixing type electrophotographic
printer. In order to provide improved the ease of stripping the
printed film from the release paper, printed A4 label paper (210
mm.times.297 mm) should have an average curl height at the four
comers of 50 mm or smaller, preferably 45 mm or smaller, as
measured 2 minutes after the printing.
[0094] Printing
[0095] The thermoplastic resin film (i) of the present invention
may be used for any printing method in which heat energy is applied
to the printed surface, such as, e.g., thermal transfer,
sublimation transfer, and heat-sensitive printing, and in
letterpress printing, gravure printing, flexography, solvent-based
offset printing, and ultraviolet-curable offset printing, as well
as the base film of a label printed using a heated-roll fixing type
electrophotographic printing process. The thermoplastic resin film
(i) or a label paper comprising such a film may be used in the form
of a sheet, or in the form of a roll when printing with a rotary
press. Furthermore, a laminate of the thermoplastic resin film (i)
with a release paper may be form printed and then printed on an
electrophotographic printer.
[0096] The present invention will be explained in more detail by
means of the following Examples.
[0097] The raw materials and evaluation methods used in the
Examples are as follows. The term "parts" in an ingredient blending
ratio means "parts by weight".
EXAMPLE 1
[0098] Thermoplastic Resin Film (i)
[0099] A composition (C) was prepared by compounding polypropylene
having a melt flow rate (MFR) of 4 g/10 min with 15 wt % heavy
calcium carbonate having an average particle diameter of 1.3 .mu.m,
0.7 wt % titanium white, and 5.5 wt % high-density polyethylene
having an MFR of 11 g/10 min and was kneaded in an extruder set at
250.degree. C., subsequently extruded into a sheet form through a
T-die connected to an extruder set at 230.degree. C., and cooled
with a cooler to obtain an unstretched sheet.
[0100] Into the above-described composition, and into the resin
compositions described in the following Examples and Comparative
Examples, phenolic stabilizers, i.e., 0.05 parts of
3-methyl-2,6-di-t-butylphenol and 0.08 parts of Irganox 1010 (trade
name; manufactured by Ciba-Geigy Corp.), and 0.05 parts of Weston
618 (trade name; manufactured by G. E. Plastics), a phosphorus
compound stabilizer, per 100 parts of the sum of the polypropylene
and calcium carbonate used, were also incorporated. These same
stabilizers were also used in the compositions of Examples 2 to
4.
[0101] This unstretched sheet was then heated to a temperature of
142.degree. C. and stretched 4.6-fold in the machine direction with
a machine-direction stretching machine comprising rolls having
different peripheral speeds.
[0102] A composition (A) was prepared by mixing 43 wt %
polypropylene having an MFR of 8 g/10 min, 4 wt %
maleic-acid-modified polypropylene, and 5% high-density
polyethylene (MFR, 10 g/10 min) with 47.5 wt % calcium carbonate
having an average particle diameter of 1.3 .mu.m, and 0 .5 wt %
titanium white and was melt-kneaded in an extruder set at
240.degree. C. A composition (B) was prepared by mixing 47 wt %
polypropylene having an MFR of 11 g/10 min with 47.5 wt % calcium
carbonate having an average particle diameter of 1.3 .mu.m, 5%
high-density polyethylene (MFR, 10 g/10 min), and 0.5 wt % titanium
white and was melt-kneaded in another extruder set at 240.degree.
C. The two melts (i.e., compositions (A) and (B)) were superimposed
in a multilayer coextrusion die, laminated on either side of the
stretched sheet of composition (C), described above, in such a
manner that the layer of composition (A) faced outward. Thus, a
five-layer laminate having the structure A/B/C/B/A was
obtained.
[0103] Stretching
[0104] Using a tenter oven, the five-layer laminate described above
was heated to 157.degree. C. and then stretched 9.5-fold in the
transverse direction. Subsequently, the laminate was passed through
a heat-setting zone (set temperature, 163.degree. C.) placed after
the tenter oven to obtain a five-layer laminated film having a
thickness of 84 .mu.m (thicknesses of the individual layers: 5
.mu.m/16 .mu.m/42 .mu.m/16 .mu.m/5 .mu.m)
[0105] Formation of Surface Treatment Layers
[0106] Both sides of this film were subjected to corona discharge
treatment at an applied-energy density of 90 W-min/m.sup.2.
[0107] Subsequently, an aqueous solution containing a 1:1:1 mixture
of a butyl-modified polyethyleneimine, an ethyleneimine adduct of a
polyamine-polyamide, and an alkyl acrylate polymer having groups
containing a quaternary ammonium salt structure was applied to each
side of the film in an amount of about 0.1 g/m.sup.2 (based on the
weight of the dry film), and the coating was dried to form surface
treatment layers on either side of the multilayer thermoplastic
resin film.
[0108] Heat Treatment
[0109] The film (i), obtained as described above, was heat-treated
for 2 days in a forced-air oven set at 110.degree. C.
[0110] Measurement of Degree of Dimensional Change
[0111] The degree of dimensional change of the film (i), described
above, was measured in the following manner. A "TMA120C" TMA
apparatus, manufactured by Seiko Instruments Inc., was used in the
tension mode. A fixed load of 5.25 g was used (tension per unit
area, 15.625 g/mm.sup.2; the load was selected so as to be
proportional to the film thickness, with the tension constant). A
film sample was prepared so that the portion of the sample examined
had a width of 4 mm and a length of 10 mm (the portions of the
sample clamped to the upper and lower parts of the TMA were each 5
mm long). The rate of both heating and cooling during the
measurement was 2.degree. C./min. The temperature range over which
the sample was measured was from 40.degree. C. to a set temperature
of 150.degree. C. (actual temperature, 135.degree. C.), and then
the sample was cooled to room temperature. The degree of MD
dimensional change (.alpha.) was 0.59%.
[0112] Property Measurement
[0113] The basis weight of the thermoplastic resin film (i) of the
present invention had a basis weight and a density, measured in
accordance with JIS-P8118-1976, of 71 g/m.sup.2 and 0.85 g/m.sup.3,
respectively, and an opacity, measured in accordance with
JIS-P8138-1976, of 91%. In addition, it had a porosity of 31%.
[0114] Formation of Toner-Receiving Layer
[0115] A toner-receiving layer was formed on one side of the film
(i) using about 10 g/m.sup.2 of a coating prepared as described
below.
[0116] To 100 g of water were successively added 40 parts of
Brilliant S-15 (trade name; precipitated calcium carbonate pigment;
50 wt % aqueous dispersion; manufactured by Shiraishi Kogyo Kaisha,
Ltd.), 10 parts of a 50 wt % aqueous dispersion of Ultra White 90
(trade name; clay pigment; manufactured by Engelhard, Ltd.), 45
parts of Mobinyl M735 (trade name; acrylic emulsion; solid content
on dry basis, 43 wt %; manufactured by Hoechst Gosei K. K.), and 5
parts of a 15 wt % aqueous solution of Z-100 (trade name; modified
poly(vinyl alcohol) ; manufactured by The Nippon Synthetic Chemical
Industry Co., Ltd.) and stirred at room temperature for 2 hours to
prepare a coating fluid.
[0117] This coating fluid was applied to one side of the film (i)
with a bar coater in an amount of about 10 g/m.sup.2 on a dry
basis. The coated film was dried for 2 minutes in a 105.degree. C.
forced-air oven, removed, and then allowed to stand at room
temperature for 4 hours. A pressure-sensitive adhesive and a
release paper were subsequently applied to this coated film.
[0118] Formation of Pressure-Sensitive Adhesive Layer and
Application of Release Paper
[0119] 6 g/m.sup.2 (dry basis) of a solvent-based acrylic
pressure-sensitive adhesive was applied to a silicone treated
clay-coated paper release paper (iii) using a comma coater.
Hereinafter, this release paper will be referred to as "release
paper 1". The coating was dried to form a pressure-sensitive
adhesive layer (ii). This release paper was applied to the
thermoplastic resin film (i), having the toner-receiving layer
described above, to obtain a label paper. The pressure-sensitive
adhesive layer (ii) was disposed between the release paper (iii)
and the surface of the thermoplastic resin film (i) which was not
coated with the toner-receiving layer.
[0120] The degree of MD dimensional change (.beta.) of the release
paper used was measured under the same conditions as for the
thermoplastic resin film (i), and was 0.18% (shrinkage).
[0121] Evaluation
[0122] The label, prepared as described above, was cut into A-4
(210 mm in width direction by 297 mm in flow direction). The cut
label was allowed to stand in a thermo-hygrostatic chamber at
temperature of 23.degree. C. and a relative humidity of 50% for 1
day and then printed on a commercial heated-roll fixing type
electrophotographic printer (Laser Shot 404G2; trade name;
manufactured by Canon Inc.). The printing side of the label paper
faced downward.
[0123] After being printed, the label was allowed to stand at room
temperature on a flat table and the average of the curl heights at
the four corners was determined 2 minutes after printing. The
average of the curl heights was 34 mm.
[0124] Test printing of these labels was also carried out, and the
print quality was visually evaluated. If the print quality of the
labels was equivalent to the print quality obtained on a commercial
PPC paper made mainly of a bleached chemical pulp, the print
quality was considered satisfactory (O). If the printing had
noticeable defects such as line width increase or deformation of
printed characters, scumming, and insufficient printing density,
the print quality was considered poor (X). The print quality of the
label prepared as described above in Example 1 was considered
satisfactory. The results of the evaluation of the label of Example
1 are shown in Table 1.
COMPARATIVE EXAMPLE 1
[0125] Labels were prepared according to the procedure of Example
1, except that the heat treatment of the thermoplastic resin film
(i) in a forced-air oven was omitted. The label was evaluated as
described in Example 1, and the results are shown in Table 1
EXAMPLE 2
[0126] A five-layer laminated thermoplastic resin film (i) having a
thickness of 118 .mu.m (thicknesses of the individual layers: 5
.mu.m/25 .mu.m/58 .mu.m/25 .mu.m/5 .mu.m) was prepared using the
procedure of Example 1, except that the thickness of some of the
individual film layers is slightly different. The thermoplastic
resin film obtained was treated for 2 days in a forced-air oven set
at 110.degree. C.
[0127] The same surface treatment and the same pressure-sensitive
adhesive and release paper as in Example 1 were applied to produce
a label paper which was evaluated as described in Example 1. The
results are shown in Table 1.
EXAMPLE 3
[0128] A composition (C') was prepared by compounding polypropylene
having a melt flow rate (MFR) of 4 g/10 min with 15 wt % heavy
calcium carbonate having an average particle diameter of 1.3 .mu.m,
0.7 wt % titanium white, and 5.5 wt % high-density polyethylene
having an MFR of 11 g/10 min was kneaded in an extruder set at
250.degree. C., subsequently extruded in a sheet form using a T-die
connected to an extruder set at 230.degree. C., and cooled with a
cooler to obtain an unstretched sheet.
[0129] This unstretched sheet was heated to a temperature of
148.degree. C. and stretched 4.6-fold in the machine direction with
a machine-direction stretching machine comprising rolls having
different peripheral speeds.
[0130] A composition (A') was prepared by mixing 45 wt %
polypropylene having an MFR of 10 g/10 min, 5 wt %
maleic-acid-modified polypropylene, and 5% high-density
polyethylene (MFR, 10 g/10 min) with 44.5 wt % calcium carbonate
having an average particle diameter of 1.3 .mu.m and 0.5 wt %
titanium white and melt-kneading the mixture in an extruder set at
250.degree. C. A composition (B') was prepared by mixing 47 wt %
polypropylene having an MFR of 11 g/10 min with 47.5 wt % calcium
carbonate having an average particle diameter of 1.3 .mu.m, 5%
high-density polyethylene (MFR, 10 g/10 min), and 0.5 wt % titanium
white and melt-kneaded the mixture in another extruder set at
240.degree. C. The two melts (i.e., compositions (A') and (B'))
were superimposed in a multilayer coextrusion die, laminated on
either side of the stretched sheet of composition (C'), described
above, in such a manner that the layer of composition (A') faced
outward. Thus, a five-layer laminate having the structure
A'/B'/C'/B'/A' was obtained.
[0131] Stretching
[0132] The five-layer laminate described above was heated to
158.degree. C. in a tenter oven, and then stretched 9.5-fold in the
transverse direction. Subsequently, the laminate was passed thlrouh
a heat-setting zone (set temperature, 175.degree. C.) located after
the tenter oven to obtain a five-layer laminated film having a
thickness of 84 .mu.m (thicknesses of the individual layers: 5
.mu.m/17 .mu.m/40 .mu.m/17 .mu.m/5 .mu.m).
[0133] The same procedure was carried out as in Example 1, except
that the treatment of the film in a forced-air oven was
omitted.
[0134] Thus, a pressure-sensitive adhesive and a release paper were
applied to produce a label paper. This label paper was evaluated,
and the results are shown in Table 1.
EXAMPLE 4
[0135] A composition (D') was prepared by compounding polypropylene
having a melt flow rate (MFR) of 4 g/10 min with 15 wt % heavy
calcium carbonate having an average particle diameter of 1.3 .mu.m,
5 wt % high-density polyethylene having an MFR of 10 g/10 min, and
0.7 wt % titanium white, then kneaded the composition in an
extruder set at 250.degree. C., extruding the composition into
strands, then pelletizing the strands.
[0136] A three-layer T-die was connected to two extruders. The
extruder used to provide the polymer melt for the central layer of
the T-die was set at 240.degree. C., and the extruder used to
provide polymer melt for the outside layers of the T-die was set at
250.degree. C. The composition (D') was extruded from the extruder
supplying the central layer of the T-die, and a composition (E')
containing a polypropylene having an MFR of 4 g/10 min, 10 wt %
calcium carbonate with an average particle diameter of 1.3 .mu.m
and 0.7 wt % titanium white was extruded from the extruder
supplying the exterior layers of the T-die, thereby providing an
extruded sheet having a three-layer structure, E'/D'/E'. This
extruded sheet was cooled with a cooler to provide an unstretched
three-layer laminated sheet.
[0137] This unstretched sheet was heated to a temperature of
142.degree. C. and stretched 4.8-fold in the machine direction with
a machine-direction stretching machine comprising rolls having
different peripheral speeds.
[0138] This five-layer laminate was heated to 157.degree. C. and
then stretched 9.5-fold in the transverse direction using a tenter
oven.
[0139] The stretched laminate was then passed through a
heat-setting zone (set temperature, 170.degree. C.) located after
the tenter oven to provide a three-layer laminated film base (i)
having a thickness of 78 .mu.m (thicknesses of the individual
layers: 8 .mu.m/62 .mu.m/8 .mu.m).
[0140] The thermoplastic resin film then heat-treated for 3 days in
a forced-air oven set at 110.degree. C.
[0141] The thermoplastic resin film was then subjected to the same
surface treatment, application of a pressure-sensitive adhesive and
a release paper as described in Example 1, thereby providing a
label paper. The label paper was evaluated, and the results are
shown in Table 2.
EXAMPLE 5
[0142] The production of a thermoplastic resin film (i), formation
of a toner-receiving layer, formation of a pressure-sensitive
adhesive layer, and application of a release paper were conducted
by conducting the same procedure as in Example 1, except that the
release paper used was a release paper (iii) having a thickness of
120 .mu.m and a density of 1.1 g/m.sup.2 obtained by treating a
clay-coated paper with a silicone (hereinafter abbreviated as
release paper 2). Thus, a label paper was obtained.
[0143] The degree of MD dimensional change (P) of the release paper
used was measured under the same conditions as for the
thermoplastic resin film (i). As a result, it was -0.1%
(elongation).
[0144] The results of evaluation are shown in Table 1.
COMPARATIVE EXAMPLE 2
[0145] The same procedure as in Comparative Example 1 was
conducted, except that the same release paper as in Example 5 was
used. Thus, a label paper to which a pressure-sensitive adhesive
and the release paper had been applied was produced. This label
paper was evaluated. The results are shown in Table 1.
1 TABLE 1 Comparative Comparative Example 1 Example 1 Example 2
Example 3 Example 4 Example 5 Example 2 Thermoplastic resin film
base (i) Thickness (.mu.m) 84 84 118 84 78 84 84 Basis weight
(g/m.sup.2) 71 64 99 83 59 71 64 Density (g/cm.sup.3) 0.85 0.76
0.84 0.99 0.76 0.85 0.76 Porosity (%) 31 33 32 12 30 31 33 Opacity
(%) 91 91 92 72 74 91 91 Degree of dimensional change .alpha. by
0.6 3.1 0.57 -0.3 0.55 0.6 3.1 thermomechanical analysis (%) Degree
of thermal shrinkage (%), 0.82 2.1 0.8 0.7 0.75 0.82 2.1 130 EC, 30
min Kind of release paper used release paper release paper release
paper release paper release paper release paper release paper 1 1 1
1 1 1 1 Degree of dimensional change .beta. of release paper 0.18
0.18 0.18 0.18 0.18 -0.1 -0.1 by thermomechanical analysis (%)
Difference in degree of dimensional 0.42 2.92 0.39 -0.48 0.37 0.7
3.2 change by thermomechanical analysis between base (i) and
release paper, .alpha. - .beta. (%) Results of print evaluation
Curl height (mm), 2 min after printing 35 Cylinder 33 33 32 38
cylinder Print quality .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
[0146] As apparent from Table 1 above, same effect is obtained by
either of the two means specified in the invention, i.e., the
degree of dimensional change (a) and the degree of thermal
shrinkage.
EXAMPLE 6
[0147] Thermoplastic Resin Film (i)
[0148] A composition (C') prepared by compounding 79.4 wt %
propylene homopolymer having a melt flow rate (MFR) of 3.3 g/10 min
with 15 wt % heavy calcium carbonate having an average particle
diameter of 1.5 .mu.m, 0.6 wt % titanium white, and 5 wt %
high-density polyethylene having an MFR of 10 g/10 min was kneaded
with an extruder set at 250.degree. C., subsequently extruded into
a sheet form through a T-die connected to an extruder set at
240.degree. C., and cooled with a cooler to obtain an unstretched
sheet.
[0149] Into the above-described composition to be extruded in sheet
form and into the following compositions to be extruded and
laminated and the compositions used in the following Examples were
incorporated 0.05 parts of 3-methyl-2, 6-di-t-butylphenol, 0.05
parts of Irganox 1010 (trade name; manufactured by Ciba-Geigy
Corp.) as a phenolic stabilizer, and 0.05 parts of Weston 618
(trade name; manufactured by G. E. Plastics) as a phosphorus
compound stabilizer per 100 parts of the sum of the propylene
homopolymer and calcium carbonate used.
[0150] This sheet was heated to a temperature of 142.degree. C. and
stretched 4.5-fold in the machine direction with a
machine-direction stretching machine comprising rolls having
different peripheral speeds.
[0151] A composition (A') prepared by mixing 46 wt % propylene
homopolymer having an MFR of 8 g/10 min, 4 wt %
maleic-acid-modified polypropylene, and 5% high-density
polyethylene (MFR: 10 g/10 min) with 44.4 wt % calcium carbonate
having an average particle diameter of 1.5 .mu.m and 0.6 wt %
titanium white was melt-kneaded with an extruder set at 240.degree.
C. A composition (B') prepared by mixing 49.4 wt % propylene
homopolymer having an MFR of 10 g/10 min with 45 wt % calcium
carbonate having an average particle diameter of 1.5 .mu.m, 5%
high-density polyethylene (MFR: 10 g/10 min), and 0.6 wt % titanium
white was melt-kneaded with another extruder set at 240.degree. C.
The two melts were superposed within a die, and laminated by
coextrusion to each side of the stretched sheet obtained by
extruding the resin composition (C') described above and stretching
the extrudate 4.5 times in the machine direction, in such a manner
that (A') faced outward. Thus, a five-layer laminate
(A'/B'/C'/B'/A') was obtained.
[0152] Stretching
[0153] Using a tenter oven, the five-layer laminate described above
was heated to 157.degree. C. and then stretched 9.4-fold in the
transverse direction. Subsequently, the laminate was passed through
a heat-setting zone (set temperature, 168.degree. C.) located after
the tenter oven to obtain a five-layer laminated film having a
thickness of 80 .mu.m (thicknesses of the individual layers: 5
.mu.m/15 .mu.m/40 .mu.m/15 .mu.m/5 .mu.m).
[0154] Formation of Surface Treatment Layers
[0155] Both sides of this film were subjected to corona discharge
treatment at an applied-energy density of 90 W min/m.sup.2.
[0156] Subsequently, an aqueous solution containing a 1:1:1 mixture
of a butyl-modified polyethyleneimine, an ethyleneimine adduct of a
polyamine-polyamide, and an alkyl acrylate polymer having groups
containing a quaternary ammonium salt structure and represented by
the following structural formula, in the molecular chain was
applied to each side of the film in an amount of about 0.1
g/m.sup.2 on a dry basis, and the coating was dried to form surface
treatment layers. 1
[0157] Heat Treatment
[0158] This film (i) was cut into a B-4 size and heat-treated for 1
hour in a forced-air oven set at 110.degree. C.
[0159] Property Measurement
[0160] This film (i) was cut into a square shape of 100 mm in each
of length and width, and the dimensions thereof were measured with
a cathetometer in a thereto-hygrostatic chamber having a
temperature of 23.degree. C. and a relative humidity of 50%.
Thereafter, the cut film was heat-treated in a 130.degree. C.
forced-air oven for 30 minutes, taken out therefrom, and then
allowed to cool in the same thereto-hygroscopic chamber for 1 hour.
The dimensions thereof were measured. The degree of shrinkage was
calculated by comparison with the dimensions measured before the
oven heat treatment. As a result, the degree of machine-direction
shrinkage was 1.0%, that of transverse-direction shrinkage was 0.
6%, and the average was 0.8%. The film had a basis weight and a
density as measured in accordance with JIS-P8118-1976 of 68.4
g/m.sup.2 and 0.85 g/cm.sup.3, respectively. It further had a
porosity of 31%.
[0161] Formation of Toner-Receiving Layer
[0162] A toner-receiving layer was formed on one side of the film
(i) by coating in an amount of about 10 g/m.sup.2 by conducting the
same procedure as in Example 1.
[0163] This film was used in the subsequent application of a
pressure-sensitive adhesive and a release paper thereto.
[0164] Application of Pressure-Sensitive Adhesive and Release
Paper
[0165] A solvent-based acrylic pressure-sensitive adhesive was
applied to a release paper (iii) having a thickness of 115 .mu.m
and a density of 1.2 g/m.sup.2 obtained by treating a clay-coated
paper with a silicone (hereinafter abbreviated as coat type) on the
silicone-treated side with a bar coater in an amount of 8 g/m.sup.2
on a dry basis. The coating was dried to form a pressure-sensitive
adhesive layer (ii). This release paper was applied to the plastic
resin film (i) having the toner-receiving layer described above to
obtain a label paper.
[0166] Evaluation
[0167] The label paper obtained was cut into A-4 (210 mm in width
by 297 mm in flow). The cut label was allowed to stand in a
thermo-hygrostatic chamber of 23.degree. C. and a relative humidity
of 50% for 1 day and then printed on a commercial heated-roll
fixing type electrophotographic printer (Laser Shot 404G2; trade
name; manufactured by Canon Inc.), in which paper passed with its
printing side facing upward.
[0168] After having been printed on the printer, the label was
allowed to stand at room temperature on a flat table and the
average of the curl heights at the four comers was determined at 2
minutes after the printing. As a result, the average was found to
be 39 mm.
[0169] Test printing was conducted in a test printing and the print
quality was visually evaluated. The prints which were equal in
print quality to a print obtained by printing a commercial PPC
paper made mainly of a bleached chemical pulp are regarded as
satisfactory (O), while those which had noticeable defects such as
line width increase or deformation of printed characters, scumming,
and printing density insufficiency are regarded as poor (X).
Example 6 was on a satisfactory level. The results of the
evaluation of Example 6 are shown in Table 2.
COMPARATIVE EXAMPLE 3
[0170] The same procedure as in Example 6 was conducted, except
that the heat treatment was omitted. Thus, a pressure-sensitive
adhesive and a release paper were applied to produce a label paper,
and this label paper was evaluated. The results are shown in Table
2.
COMPARATIVE EXAMPLE 4
[0171] The same procedure as in Example 6 was conducted, except
that synthetic paper Yupo FPG-80 (trade name; manufactured by
Oji-Yuka Synthetic Paper Co., Ltd.) was used as a thermoplastic
resin film. Thus, a pressure-sensitive adhesive and a release paper
were applied to produce a label paper, and this label paper was
evaluated. The results are shown in Table 2.
EXAMPLE 7 TO EXAMPLE 9
[0172] The same procedure as in Example 6 was conducted, except
that the heat treatment in the forced-air oven was conducted for
time periods of 0.5 hours, 4 hours, and 168 hours. The results of
evaluation are shown in Table 2.
EXAMPLE 10
[0173] The same procedure as in Example 6 was conducted, except
that the heat treatment in the forced-air oven was conducted at a
temperature of 130.degree. C. The results of evaluation are shown
in Table 2.
EXAMPLE 11
[0174] The same procedure as in Example 6 was conducted, except
that the heat treatment in the forced-air oven was conducted at a
temperature of 105.degree. C. for a time period of 24 hours. The
results of evaluation are shown in Table 2.
EXAMPLE 12
[0175] A composition (C') prepared by compounding 79.4 wt %
propylene homopolymer having a melt flow rate (MFR) of 3.3 g/10 min
with 15 wt % heavy calcium carbonate having an average particle
diameter of 1.5 .mu.m, 0.6 wt % titanium white, and 5 wt %
high-density polyethylene having an MFR of 10 g/10 min was kneaded
with an extruder set at 250.degree. C., subsequently extruded into
a sheet form through a T-die connected to an extruder set at
240.degree. C., and cooled with a cooler to obtain an unstretched
sheet.
[0176] This sheet was heated to a temperature of 147.degree. C. and
stretched 4.4-fold in the machine direction with a
machine-direction stretching machine comprising rolls having
different peripheral speeds.
[0177] A composition (A') prepared by mixing 46 wt % propylene
homopolymer having an MFR of 8 g/10 min, 4 wt %
maleic-acid-modified polypropylene, and 5% high-density
polyethylene (MFR: 10 g/10 min) with 44.4 wt % calcium carbonate
having an average particle diameter of 1.5 .mu.m and 0.6 wt %
titanium white was melt-kneaded with an extruder set at 240.degree.
C. A composition (B') prepared by mixing 49.4 wt % propylene
homopolymer having an MFR of 10 g/10 min with 45 wt % calcium
carbonate having an average particle diameter of 1.5 .mu.m, 5%
high-density polyethylene (MFR: 10 g/10 min), and 0.6 wt % titanium
white was melt-kneaded with another extruder set at 240 EC. The two
melts were superposed within a die, and laminated by coextrision to
each side of the stretched sheet obtained by extruding the resin
composition (C') described above and stretching the extrudate 4.5
times in the machine direction in such a manner that (A') faced
outward. Thus, a five-layer laminate (A'/B'/C'/B'/A') was
obtained.
[0178] Stretching
[0179] Using a tenter oven, the five-layer laminate described above
was heated to 160.degree. C. and then stretched 9-fold in the
transverse direction. Subsequently, the laminate was passed through
a heat-setting zone (set temperature, 168.degree. C.) located after
the tenter oven to obtain a five-layer laminated thermoplastic
resin film (i) having a thickness of 132 .mu.m (thicknesses of the
individual layers: 6 .mu.m/27 .mu.m/66 .mu.m/27 .mu.m/6 .mu.m). The
thermoplastic resin film obtained was cut into a B-4 size and
treated for 2 hours in a forced-air oven set at 110.degree. C.
[0180] The same heat treatment and the same application of a
pressure-sensitive adhesive and a release paper as in Example 6
were conducted to produce a label paper, which was evaluated. The
results are shown in Table 3.
COMPARATIVE EXAMPLE 5
[0181] The same procedure as in Example 13 was conducted, except
that the heat treatment was omitted. Thus, a pressure-sensitive
adhesive and a release paper were applied to produce a label paper,
and this label paper was evaluated. The results are shown in Table
3.
EXAMPLE 14
[0182] The same procedure as in Example 6 was conducted, except
that a heat treatment was conducted in such a manner that the
thermoplastic resin film was wound into a roll and the front and
back sides of the film were successively brought into contact with
four metal rolls set at 120.degree. C. while regulating the contact
time to about 4 minutes. The results of evaluation are shown in
Table 3.
2 TABLE 2 Example Comparative Comparative Example Example Example
Example Example 6 Example 3 Example 4 7 8 9 10 11 Thermoplastic
resin film base (i) Thickness (.mu.m) 80 80 80 80 80 80 80 80 Basis
weight (g/m.sup.2) 68.4 68.4 61.6 68.4 68.4 68.5 68.5 68.5 Density
(g/m.sup.3) 0.85 0.85 0.77 0.85 0.85 0.85 0.85 0.85 Porosity (%) 31
31 33 31 31 31 31 31 Opacity (%) 90 90 90 90 90 90 90 90 Conditions
of heat treatment Temperature (EC) 110 none none 110 110 110 130
105 Time (hr) 1 none none 0.5 4 168 1 24 Degree of thermal
shrinkage of (i) (%), 130 EC, 0.8 2.2 2.3 0.82 0.8 0.79 0.78 0.82
30 mm Thickness after toner-receiving layer formation 88 88 88 88
88 88 88 88 (.mu.m) Opacity after toner-receiving layer formation
(%) 92 92 92 92 92 92 92 92 Kind of release paper used coat type
coat type coat type coat type coat type coat type coat type coat
layer Results of print evaluation Curl height (mm), 2 min after
printing 39 cylinder cylinder 42 40 38 37 42 Print quality (visual
examination) .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle.
[0183]
3 TABLE 3 Example Example Comparative Example 12 13 Example 5 14
Thermoplastic resin film base (i) Thickness 132 80 80 80 (.mu.m)
Basic weight 133 64 64 68.4 (g/m.sup.2) Density (g/cm.sup.3) 1.01
0.8 0.8 0.85 Porosity (%) 12 19 19 31 Opacity (%) 84 82 82 90
Conditions of heat treatments Temperature 110 110 none 120 (EC)
Time (hr) 2 2 none about 4 min Degree of 0.5 0.69 2.1 0.82 thermal
shrinkage of (i) (%), 130EC, 30 min Thickness after 138 88 88 88
toner-receiving layer formation (.mu.m) Opacity after 90 89 89 92
toner-receiving layer formation (%) Kind of release coat type coat
type coat type coat type paper used Results of print evaluation
Curl height 33 35 68 41 (mm), 2 min after printing Print quality O
O O O (visual examination)
[0184] Industrial Applicability of the Invention
[0185] As described above, according to the invention, a
thermoplastic resin film, in particular, a polypropylene-based
film, could be obtained which had suitability for heated-roll
fixing type electrophotographic printers and was especially
satisfactory in curling after printing.
[0186] Furthermore, a label paper employing the same could be
obtained.
[0187] Since the thermoplastic resin film obtained according to the
invention and the label paper employing the same are superior to
plain-paper labels in strength and water resistance, they are
useful as stickers for outdoor advertisement, labels for
frozen-food containers, or namers (labels showing usage or notice)
for industrial products.
* * * * *