Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
3~
The present invention relates to a light~polarizing
film having good heat stability and humidity resistance.
A conventional light-polarizing film is produced by
impregnating a film of polyvinyl alcohol (hereinafter
referred to as PVA) or a derivative thereof with an
aqueous solution of iodine or a dichromic dye, and then
stretching the film by dry or wet heating so that high
molecular micelles are unidirectionally oriented. How-
ever, since PVA used as the base material is a hydrophilic
polymer, the light-polarizing film thus obtained lacks
humidity resistance.
We have previously developed a process ~or producing
a hydrophobic light-polari~ing film (e.g. as described in
our United States Patent No. 3,621,085 issued on November
16, 1971). In this process, a halogenated vinyl polymer
or a halogenated vinylidene polymer is reacted with a
dehydrohalogenating agent to form polyene chains (con-
jugated double bonds) in the molecule and the polyene
chains are unidirectionally orientaed in the film of
the pol~mer to obtain a light-polarizin~ film.
However, these conventional light-polarizing films,
including our hydrophobic film mentioned above, are still
somewhat inadequate with respect to heat stability. For
example, a light polarizing Eilm having PVA as the base
material should be used at a temperature of not more than
~0C over long periods of time, and at the most at 60C
for even short periods of time. In the case of our
hydrophobic light-polarizing film mentioned above, the
~ilm changes in color and darkens, thus reducing light
transmittance, when it is continuously used at 60C for
a long period of time (e.g. for several days).
3~
Accordingly, the use of light-polarizing films has
hltherto been limited by such drawbacks and it would be
desirable in various fields of use to improve the heat
resistance of light-polarizing films. This is particu-
larly true in the case of liquid crystal display devices
in which light-polarizing films are expected to play an
expanding role. It is required that light-polarizing
films for this use have a sufficiently high stability to
dry and wet heating to be continuously used at 60 to 70 C
for a long period of time.
We have made intensive studies of the improvement of
light-polarizing films in an attempt to satisfy these
requirements and have found that the heat stability of
a light-polarizing film can be remarkably improved while
maintaining excellent humidity resistance and polariza-
tion efficiency by homogeneously distributing an acrylate
and/or methacrylate polymer in a conventional polyene-
containing light-polarizing film.
The main object of the present invention is to provide
a light-polarizing film having improved heat resistance
and stability as ~ell as good humidity resistance and good
polarization efficiency. `~
According to the present invention there is provided
a light-polarizing film comprising a polymer mixture of a
polymer having polyene chains formed by partial dehydro-
halogenation of a halogenated vinyl polymer or a halogen-
ated vinylidene polymer and one or more of the polymers
selected from the group consisting of acrylate polymers
and methacrylate polymers.
The light-polarizing film of the present invention can ; ,
be produced by various processes.
.
- .
. . .
~.23~
For example, the light-polarizing film can be pro-
duced by substantlally the same processes as employed for
producing known polyene-containing light-polarizing film.
In the light-polarizing film of the present invention,
an acrylate and/or methacrylate polymer is merely homo-
geneously distributed in the conventional film which
displays the polarization effect by unidirectional
orientation of a polymer having polyene chains. That is,
the light-polarizing film of the present invention can be
produced by homogeneously admixing an acrylate polymer or
a methacrylate polymer with all the other components of
the film and with any other ~ilm-forming polymers at any
stage of a conventional process for producing polyene-
containing films which comprises partially dehydrohalo-
genating a halogenated vinyl polymer or a halogenated
vinylidene polymer to form polyene chains in the molecule
thereof and then unidirectionally orienting the polyene
chains in the film.
The formation of polyene chains can be carried out in
one step or in two steps but, pre~erably, in the present
invention, it is carried out in two steps. Firstly, a
halogenated vinyl polymer or a halogenated vinylidene
polymer is partially dehydrohalogenated with a dehydro-
halogenating agent to form polyene chains. The polymer
is subjected to the dehydrohalogenation in the ~orm of a
solution or a solid such as a suspension or film. Then,
the dehydrohalogenated product is further dehydrohalo-
genated by heating which causes the polyene chains to
grow in size in the polymer.
For example, the li~ht-polarizing film of the present
invention can be produced by reacting a halogenated vinyl
.
~ ' ,
3~3~
polymer or a halogenated vinylidene polymer with a de-
hydrohalogenating agent in a solvent either after or
before the addition thereto of an acrylate polymer or a
methacrylate polymer and, if necessary, one or more other
polymers, until the dehydrohalogenation degree (i.e. the
ratio of halogen atoms removed as hydrogen halide to the
total halogen atoms in the polymer used~ reaches 0.1 to
20 mol%, casting the solution thus obtained into a film,
heating the film preferably to 70 to 150C to cause the
polyene chains to grow and then unidirectionally orienting
the resulting polyene-containing film.
Alternatively, the light-polarizing film of the
present invention can be produced by admixing an acrylate
polymer or a methacrylate polymer with a halogenated vinyl
polymer or a halogenated vinylidene polymer, forming the
mixture into a film of 5 to 500 ~in thickness by a normal
method, such as calendering, extruding or casting, react-
ing the film with a dehydrohalogenating agent in a non-
solvent or a swelling agent for the film to obtain a
yellowish film, removing the dehydrohalogenating agent
by washing, heating the film at 70 to 150C to cause the
polyene chains formed therein to grow and then stretching
the film in one direction.
The light-polarizing film of the present invention
preferably has an average light transmittance of 10 to
70 %, more preferably 20 to 70 ~, at wavelengths in the
range of 450 to 700 m ~ ti.e. the average of light trans-
mittance measured within the wavelength range at intervals
of 10 m~), and a ratio of the average percent of light
transmitted with the polari2ation axes parallel (Ho)
to the average percent of light transmitted with the
- 4 -
- ~ . .
: ' ~
3~
polarization axes crossed (Hgo) of Ho/Hgo_2r more
preferably, Ho/Hgo_4~
When the above light transmittance is too low, the
brightness of the film is insufficient. On the other
hand, when the above light transmittance is too high,
the polarization efficiency of the film is insufficient.
Further, when the Ho/Hgo ratio is too low, a good
contrast cannot be obtained and there is insuEficient
difference between a bright part and a dark part when
the film is used in a liquid crystal display device.
Generally, when the value of percent light transmitted
with the polarization axes parallel (i.e. the light
transmittance of two films overlapping in the parallel
position with respect to the polarization axes) and
the value of percent light transmitted with the polar
ization axes crossed (i.e. the light transmittance of
` two films overlapping at right angles with respect to the
; polarization axes) are used as a measure of polarization
efficiency of a light-polarizing f.ilm and the ratio or
difference of these two values is large, the difference in
contrast of bright-and dark between two films overlapping
in the parallel position and at right angles with respect
to the polarization axes is large. Usually, corresponding
to the above average light transmittance, Ho and Hgo
at the wave-length of 450 to 700 m~ of the light-polarizing
film of the present invention are l0 to 55 %, preferably
25 to 45 %, and 0.01 to 45 %, preferably 0.01 to 20 ~,
; respectively.
The thickness of the light-polarizing film of the
present invention is not critical but is usually in the
- 5 -
.
.
, ' '
.
3~
range of 1 to 200 ~, preferably 5 to 50~.
The acrylate or methacrylate polymer used in the
present invention may be a homopolymer or a copolymer
of a monomer of the formula:
Rl
CH2 = C - COOR2 (I)
in which Rl is hydrogen or an alkyl group having 1 to 10
carbon atoms (preferably hydrogen or methyl); and R2 is
an alkyl group having 1 to 10 carbon atoms, a cycloalkyl
or bicycloalkyl group having 5 to 10 carbon atoms (e.q.
cyclohexyl, isomenthyl, isobornyl, etc.), an aryl group
having 6 to 10 carbon atoms (e.g. phenyl, naphthyl, etc.),
an aralkyl group having 7 to 10 carbon atoms (e.g. benzyl,
p-isopropylbenzyl etc.) or a heterocyclic group containing
one or more hetero atoms selected from O, N and S (e.g.
furfuryl, thienyl etc.) and the alkyl chain of the group
R2 may be interrupted with O, N or S and the alkyl or
aryl group may be substituted with one or more halogens
(e.g. bromine, etc.). Further, the acrylate or meth- `
acrylate polymer may include a copolymer of the above
monomer (I) and up to 50 mol % (based on all the struc~
tural units of the polymer) of another copolymerizable
monomer of the formula:
' .
2 = C \ (II)
in whch R3 is hydrogen or an alkyl group having 1 to 10
carbon atoms (preferably, hydrogen or methyl); and R4 is
a hydrocarbon group having 1 to 10 carbon atoms such as an
alkyl group ha~7ing 1 to 10 carbon atoms, an aryl group
having 6 to 10 carbon atoms (e.g. phenyl, naphthyl, etc.l,
- 6 -
3~
or a cycloalkyl ~ro-lp or bicycloalkyl group having ~ to 10
carbon atoms (e.g. cyclohexyl, etc.), a heterocyclic group
having one or more hetero a~oms selected grom O, N and S
(e.g. furfuryl, thienyl etc.), -CN, -OH or -OOCR5; R5
is an alkyl group having 1 to 10 carbon atoms and the
alkyl chain of the groups R4 and R5 may be interrupted
with O, N, S, or -COO- and the group R4 may be substi-
tuted with one or more OH or halogens (e.g. bromine, etc.).
Examples of the acrylate or methacrylate polymer
are homopolymers such as polymethyl methacrylate,
polyethy methacrylate, polypropyl methacrylate, polymethyl
acrylate, polyethyl acrylate and the like; bipolymers such
as methyl methacrylate-ethyl methacrylate copolymer, methyl
methacrylate-propyl methacrylate copolymer, methyl methacry-
late-butyl methacrylate copolymer, ethyl methacrylate-propyl
methacrylate copolymer, methyl methacrylate-methyl acrylate
copolymer, ethyl methacrylate-methyl acrylate copolymer,
; methyl methacrylate-ethyl acrylate copolymer, methyl acrylate-
methyltri~lycol acrylate copolymer, methyl methacrylate-
methyltriglycol acrylate copolymer, methyl methacrylate-
stearyl acrylate copolymer, methyl methacrylate-stearyl
methacrylate copolymer, ethyl methacrylate-ethy acrylate
copolymer, methyl methacryla-te-butyl acrylate copolymer,
methyl methacrylate-propyl acrylate copolymer, methyl
methacrylate-2-hydroxyethyl methacrylate copolymer, methyl
methacrylate-2-hydroxypropyl methacrylate copolymer, ethyl
methacrylate-2-hydroxyethyl methacrylate copolymer, ethyl
methacrylate-2-hydroxypropyl methacrylate copolymer,methyl
-- 7 --
- " ~h~.~;3~3~
ethacrylate-2-hydroxyethyl acrylate copolymer, methyl
methacrylate-2-hydroxypropyl acrylate copolymer, ethyl
methacrylate-2-hydroxyethyl acrylate copolymer, ethyl meth-
acrylate-2-hydro~ypropyl acrylate copolymer, methyl meth-
acrylate-tetrahydrofurfuryl acrylate copolymer, methyl
methacrylate-tetrahydro~urfuryl methacrylate copolymer,
ethyl methacrylate-tetrahydrofurfuryl acrylate copolymer,
ethyl me~hacrylate tetrahydrofurfuryl methacrylate copolymer,
methyl methacrylate-benzyl acrylate copolymer, methyl
methacrylate-benzyl methacrylate copolymer, methyl meth-
acrylate-benzyl acrylate copolymer, methyl methacrylate- : ;
phenoxyethyl acrylate copolymer, methyl methacrylate-phenoxy-
ethyl methacrylate copolymer, methyl methacrylate-cyclohexyl
acrylate copolymer, methyl methacrylate-cyclohexyl meth-
acrylate copolymer, methyl methacrylate-glycidyl acrylate
copolymer, methyl methacrylate-ylycidyl methacrylate copolymer,
ethyl methacrylate-tribromophenyl acrylate copolymer methyl
methacrylate-dibromopropyl acrylate copolymer, methyl
methacrylate-tropine acrylate copolyme~, methyl methacry-
late-tropine methacrylate copolymer, methyl acrylate-tropine
methacrylate copolymer, ethyl methacrylate-tropine acrylate
copolymer, methyl methacrylate-isobornyl methacrylate co-
polymer, methyl methacrylate-isobornyl acrylate copolymer,
ethyl methacrylate-isobornyl methacrylate copolymer, propyl
methacrylate-isobornyl methacrylate copolymer, methyl
methacrylate-lsomenthyl acrylate copolymer, metyl meth-
acrylate~isomenthyl methacrylate copolymer, ethyl meth-
acrylate~isomenthyl methacrylate copolymer,methyl acrylate~
:~ acrylonitrile copolymer, butyl acrylate-acrylonitrile copolymer,
n~propyl acrylate~acrylonitrile copolymer and the like; and
terpolymers such as methy methacrylate~ethyl methacrylate~
~ 8 ~
3~
butyl Methacrylate copolymer, methyl methacrylate-ethyl
methacrylate-methyl acrylate copolymer, methyl methacrylate-
ethyl methacrylate methyltriglycol acrylate copolymer,
methyl methacrylate-ethyl methacrylate-stearyl acrylate co-
polymer, methyl methacrylate-ethyl methacrylate-stearyl
methacrylate copolymer, methyl methacrylate-ethyl meth-
acrylate-tetrahydrofurfuryl acrylate copolymer, methyl
methacrylate-ethyl methacrylate-tetrahydrofurfuryl meth-
acrylate copolymer, methyl methacrylate-ethyl methacrylate-
benzyl acrylate copolymer, methyl methacrylate-ethyl meth-
acrylate-benzyl methacrylate copolymer, methyl methacrylate-
ethyl methacrylate-phenoxyethyl acrylate copolymer, methyl
methacrylate-ethyl methacrylate-phenoxyethyl methacrylate
copolymer, methyl methacrylate-ethyl methacrylate-cyclo-
hexyl acrylate copolymer, methyl methacrylate-ethyl meth-
acrylate-cyclohexyl methacrylate copolymer, methyl meth-
acrylate-ethyl methacrylate-glycidyl acrylate copolymer,
methyl methacrylate-ethyl methacrylate-glycidyl methacrylate
copolymer, methy methacrylate-ethyl me~thacrylate-tribromo-
phenyl acrylate copolymer, methyl methacrylate-ethyl meth-
acrylate-tribromophenyl methacrylate copolymer, ~ethyl
methacrylate-ethyl methacrylate-dibromophenyl methacrylate
copolymer, methyl methacryla-te-methyl acrylate-benzyl meth- :
acrylate copolymer, methyl methacrylate~methyl acrylate-
cyclohexyl acrylate copolymer, methyl methacrylate-methyl
acrylate-~lycidyl methacrylate copolymer, methyl methacry-
late-methyl acrylate-tribromophenyl methacrylate copolymer
and the like. These polymers can be used alone or in any
combination thereof.
Preferably, the acrylate or methacrylate polymer is
used in an amount of 5 to 95 % by weight, more preferably
3~3:~
5 to 35 ~ by weight, based on the total weight of the
halogenated vinyl or vinylidene polymer used for the
formation of polyene chains. When the amount of the
polymer is less than 5 ~ by weight, the improvement in
heat stability of the resulting light-polarizing film is
low. On the other hand, when the amount of the polymer is
more than 95 ~ by weight, the polyene concentration in the
molecule is insufficient and the polarization efficiency
is lowered.
The halogenated vinyl or vinylidene polymer used for
the formation of polyene chains is preferably a homo- ~ ;
polymer or a copolymer of a monomer of the formula:
/R6 `~ ~ ~
CH2 = C \ (III)
X
in which X is halogen (preferably, chlorine or bromine);
R6 is hydrogen, -CN, -COOR7, -OOCR8 or an aryl group
having 6 to 10 carbon atoms (e.g phenyl, naphthyl, etc.);
R7 is an alkyl group having 1 to 10 carbon atoms; and
R8 is an alkyl group having 1 to 10 carbon atoms,
an aryl group having 6 to 10 carbon atoms (e.g. phenyl,
naphthyl, etc.) or a cycloalkyl ~roup having 5 to 10
carbon atoms (e.g. cyclohexyl, etc.).
Typical examples of these polymers are a homopolymer
; or a copolymer of a vinyl halide and/or a vinylidene
haIide such as vinyl chloride, vinyl bromide, vinylidene
chloride and the like.
Further, the halogenated vinyl or vinylidene polymer
-:
may include a copolymer of the above monomer (III) and
up to 90 mol % (based on all the structural units of the
polymer) of another copolymerizable monomer, preferably,
-- 10 --
.
3~
a monomer of the formula:
/
C~2 = C (IV)
in ~hich Rg is hydrogen or an alkyl group having 1 to
10 carbon atoms; Rlo is hydrogen, a hydrocarbon group
having 1 to 10 carbon atoms such as an alkyl group having
1 to 10 carbon atoms, an aryl group having 6 to 10 carbon
atoms (e.g. phenyl, naphthyl, etc.) or a cycloalkyl groùp
having 5 to 10 carbon atoms (e.g. cyclohexyl, etc.), a
heterocyclic group having one or more hetero atoms sel-
ected from O, N and S (e.g. furfuryl, thienyl etc.), -CN,
-COORll, -OOCR12 or -OH; Rll is hydrogen or an alkyl
group having 1 to 10 carbon atoms; R12 is an alkyl group
having 1 to lQ carbon atoms, an aryl group having 6 to 10
carbon atoms (e.g. phenyl, naphthyl, etc.), or a cyclo-
alkyl group having 5 to 10 carbon atoms (e.g. cyclohexyl
etc.) and the alkyl chain of the groups Rll and R12
may be interrupted with O, N or S and the hydrocarbon
group of Rlo may be substituted with one or more
halogens.
When using a copolymer of a vinyl halide and a vinyli-
dene halide and/or one or more other copolymerizable
monomers, the copolymer must be in the form of a block
copolymer or a graft copolymer so as to form polyene
chains having suffisient chain length and it is preferable
that the average chain length (polymeriæation degree) of a
polyv~nyl halide block or a polyvinylidene halide block in
the copolymer is more than 20. When the chain length is
less than 20, it is difficult to obtain light-polarizing
elements having sufficient activity within the visible ;~
:
.. :
light range. Further, it is preferable that the molar
ratio of a vinyl halide or a vinylidene halide to all
structural units of the polymer is 0.1/1 to 1/1, more
preferably 0.5/1 to 1/1.
Examples of suitable block copolymers are as follows
(they are shown by monomer structural units wherein "VC"
and "VB" stand for vinyl chloride and vinyl bromide,
respectively):
VC-vinyl acetate, VC-acrylonitrile, VC-ethylene, VC-pro-
pylene, VC-styrene, VC-butadiene, VC-isoprene, VC-vinyli-
dene chloride, VC-acrylic acid, VC-methyl acrylate, VC-
methyl methacrylate, VC-ethylene trifluoride, VB-vinyl
acetate, VB-acrylonitrile, VB-ethylene, VB-propylene, VB-
vinylidene chl~ride, VB-styrene, VB-acrylic acid, VB-methyl
acrylate, VB-methyl methacrylate, VC-vinyl acetate-vinyl
alcohol, VC-vinylidene chloride-methyl acrylate, VC-vinyl
~luoride-ethylene tetrafluoride, VB-styrene-methyl
acrylate, ~-chlorovinylbenzene-vinylbenæene, ~-chloro-
acrylonitrile-acrylonitrile, ~-chloroacrylonitrile-meth-
acrylic acid. Suitable examples of the graft copolymerare polyvinyl chloride graft-copolymerized with methyl
methacrylate or styrene, polyvinyl bromide graft-copoly-
merized wlth styrene and the like.
These polymers or copolymers capable of formation of
polyene chains can be used alone or in any combination
thereof.
The light-polarizing film of the present invention
preferably contains 5 to 95 ~ by weight of the acrylate
or methacrylate polymer and 5 to 95 ~ by weight of the
partially dehydrohalogenated halogenated vinyl or vinyli-
dene polymer.
- 12 -
' '
If desired, one or more other film-forming polymers
can be present in the light-polarizing film of the present
invention together with the polymer having polyene chains
and the acrylate or methacrylate polymer. Examples of
these polymers are polyvinyl chloride, vinyl chloride-
vinyl acetate copolymer, vinyl chloride-vinyl aceta-te-
vinyl alcohol copolymer, vinyl acetate-vinyl alcohol
copolymer.
As described above, the formation of polyene chains
can be carried out in one step with a dehydrohalogenating
agent alone, or in two steps with a dehydydrohalogenating
agent and then a heat treatment.
The dehydrohalogenating agent used in the present
invention is, for example, a secondary or tertiary amine
such as triethylamine, tri-n-propylamine, tri-n-butyl-
amine, tri~n-amylamine, triethylened;aminediethylamine,
di-n-propylamine and di-n-butylamine; an alkali metal
alcoholate such as sodium methylate and sodium ethylate;
an amidine compound such as 1,8-diazabicyclol5.4.0]un-
decene-7 and 1,5-diazabicyclo[4.3.0]nonene-5 and the like.
Although the preferred amount of the dehydrohalogen-
ating agent depends upon the content of the partially
dehydrohalogenated halogenated vinyl or vinylidene polymer
and other polymer in the film, it is desirable to use more
than 0.1 part by weight of the dehydrohalogenating agent
per lO0 parts by weight of the halogenated vinyl or vinyli-
dene polymer. When the amount of the dehydrohalogenating
agent is less than 0.1 part by weight, the reaction rate
is extremely low.
The dehydrogenation can be carried out in respect of
3~;3~
the polymer in the form of a solution or solid as
described above.
The solvent which dissolves the polymer to be used
and the dehydrohalogenating agent and is suitable for
carrying out the dehydrohalogenation is, for example,
dimethylformamide, diethylformamide, dimethyl sulfoxide,
tetrahydrofuran, dioxane, methyl ethyl ketone, a mixture
thereof and the like.
When the dehydrohalogenation is carried out in the
form of a solution, the dehydrohalogenating agent is
desirably added to the polymer dissolved in the above
solvent in an amount of 0.00001 to 1 mol ~, preferably
0.00002 to 0.4 mol %, based on the amount of the vinyl
halide or vinylidene halide units in the polymer to be
used.
When the dehydrohalogenation is carried out in the
form of solid such as a film, the material to be dehydro-
halogenated is treated with a solution o~ the dehydro-
halogenating agent (concentration: 1 to 50 % by weight)
in a good solvent thereof which does not dissolve the
material (usually, n-hexane, n-heptane, isopropyl ether
and the like can be used).
When forming the polyene chains in two steps, the
treatment with the dehydrohalogenating agent is usually
carried out at 5 to 150C, preferably at 20 to 100C,
until the dehydrohalogenation degree reaches 0.1 to 20
mol ~, preEerably 0.2 to 10 mol %. The dehydrohalogen-
ation degree can be calculated by the change of halogen
content of the polymer used but the progress of the
dehydrohalogenation can also be fairly exactly checked by
the color change of the polymer or a solution thereof.
- 14 -
3~
That is, when the dehydrohalogenation is adequately
carried out, the product has a yellow color whereas the
product becomes orange, red or black when excess dehydro-
halogenation takes place. Accordingly, the time when the
reaction should be stopped can usually be decided by mon-
itoring the change of the visible light transmittance curve
of the reaction mixture to check the progress of the reac-
tion (light absorption is initially observed in the near UV
range and gradually appears in a longer wavelength range).
In the molecule of the polymer thus partially dehydro-
halogenated by the dehydrohalogenating agent, double bonds
are distributed at random and polyene chains having short
chain length are also partially formed. When the polymer
is subsequently treated by heating, the growth of the
polyene chains is initiated at these double bonds.
The heat treatment o~ the above deh~drohalogenated
product is carried out in air or in an inert gas such as
nitrogen at 50 to 150C, preferably at 60 to 130C, under
atmospheric pressure or a reduced pressure.
During the heat treatment, the polyene chains grow
with the progress of the treatment since the reaction is
a chain reaction initiated at the double bonds which are ~ ;
already present in the molecule of the polymer. With the
growth of the polyene chains, the light absorption of the
reaction product within the visible light range increases
and the color thereof changes to blue via violet.
~hen the reaction mixture is a blue color, its visible
light transmittance curve shows a maximum absorption at
wavelengths of 565 to 600 m~. Therefore, the heat treat-
ment is preferably terminated when a maximum absorption of
the reaction mixture is observed within or at least around
- 15 -
~ ~;3~3~
the abo~e wavelength and the light transmittance thereof
at the wavelength of the maximum absorption reaches 0.001
to 60 ~, preferably 0.01 to 45 %. At this stage, 10 to 25
double bonds are linked in the polyene chains.
The heat treatment time necessary for the formation of
polyene chains having sufficient length varies with the
dehydrohalogenation degree (in the above treatment with
the dehydrohalogenating agent) and other conditions but,
usually, it is in the range of 2 minutes to 20 hours.
In any process, the polymer is dehydrohalogenated
until the dehydrohalogenation degree finally reaches 0.1
to 30 mol %, usually 0.5 to 20 mol %.
After the dehydrohalogenation, the polyene chains
formed in the polyvinyl or vinylidene halide are uni-
directionally orientated by stretching a film formed from
a polymer mi~ture comprising, as the main compounds, the
polymer having polyene chains and the acrylate or meth-
acrylate polymer. The stretching is carried out, for
example, at 80 to 150C, preferably at 85 to 1~0C, when
polyvinyl chloride is used as the halogenated vinyl
polymer. The film is stretched in a stretching ratio
of more than 1.2 times the length without break, pre-
ferably 2 to 8.5 times. Optionally, the film may be also
stretched in a direction at right angle to the above
stretching direction in a stretching rat~o of about 1.1
to 2 times the length after, before or at the same time as
the above stretching in order to improve the mechanical
properties of the film.
The light-polarizing film of the present invention
thus obtained has very good heat stahility compared to a
conventional polyene-containing light-polarizing film
- 16 -
~.23~3~
containing no acrylate or methacrylate polymer. That is,
the light-polarizing film of the present invention can be
used for a long time under dry or wet heating conditions,
such as at 40 to 30C, with minimum change of polarization
efficiency and color ~hue and density). Accordingly, the
`light-polarizing film of the present invention can be used
without any trouble even in those applications where a
light-polarizing film (or a device using a light-polarizing
film) hitherto could not be used due to high temperature
and humidity.
Moreover, the light-polarizing film of the present
invention is superior in transparency and physical pro-
perties to conventional light-polarizing film composed
only of a polyene-containing halogenated vinyl or
vinylidene polymer since the film of the present invention
contains an acrylate or methacrylate polymer having good
transparency.
In view of the above characteristics, the light-
polarizing film of the present invention can be used in
various fields, such as liquid crystal display devices,
various optical devices or apparatuses, light-filters in
photography, sun glasses, sunvisors and the like.
In practice, the light-polarizlng film of the present
invention may be laminated with a protective transparent
plastic or glass in order to protect the film from light.
In particular, when the film is used in the open air or in
a liquid crystal device, it is preferable to laminate a
filter thereto which cuts off the light of under 430 m~
since specific superior light resistance is re~uired.
Provided optical uniformity can be maintained, the
filter to be laminated may be any layer or film which can
.. . . .. ,:, ... . .
3~o~
be formed on the surface of the light-polarizing film of
the present invention, for example, a protective plastic
plate or film which is formed on the light-polarizing
film, a coating layer which is coated on the light-
polarizing film or an adhesive layer which is provided
between a protective film and the light-polarizing film.
As a base material of the layer or film, various general
purpose polymers, preferably, those having superior
transparency, such as cellulose acetate, cellulose
butyrate, cellulose acetate butyrate, polycarbonate and
polyvinyl acrylate, can be used. Also, a urethane resin,
an epoxy resin, polybutyl acrylate or polybutyl meth-
acrylate can be used as the adhesive for the lamination.
Such a protective filter can be prepared from the
above polymer in the following manner. A film or sheet
formed from the base polymer is treated in a mixture of a
yellow dye having a maximum light absorption around 400 m~
and a UV àbsorber at a temperature of from room tempera-
ture to the softening point of the polymer for several
seconds to several tens of minutes, washed with water (or
the solvent is removed), and then air-dried. Alterna-
tiv~ly, a mixture of the polymer, the above yellow dye and
~the UV absorber may be formed into a film or a sheet, or
the mixture may be coated on the surface of the light-
polarizing film to form a coating film. Further, the
yellow dye and the UV absorber may be admixed in the
above adhesive between the light-polarizing film and a
protective film thereon. Examples of a yellow dye having
a maximum light absorption around 400 m~ are a disperse
dye such as C.I. Disperse Yellow 5, C.I. Disperse Yellow
8 and the like and an acidic dye such as C~I. Direct
.
- 18 -
3~;3,~
Yellow 29, C.I. Direct Yellow 69 and the like. Examples
of the UV absorber are 2,2'-dimethoxybenzophenone/
2,2'-414'-tetrahydroxybenzophenone, 2-(2-hydroxy-5-methyl-
phenyl)-benzotriazole and the like. When the above
polymer is treated in the form of a film or a sheet, a
mixture comprising 0.1 to 5 parts by weight of the yellow
dye and 0.1 to 10 parts by weight of the UV absorber
per 100 parts by weight of a solvent (e.g. methyl ethyl
ketone, ethyl acetate etc.) is preferably used for the
treatment. When a mixture of the polymer, the yellow dye
and the UV absorber is formed into a film or is coated on
the light-polarizing film, a suitable amount of the yellow
dye is in the range of 0.05 to 5 parts by weight per 100
parts by weight of the polymer, although the amount varies
with the thickness of the film or coating film to be
formed or the adhesive layer.
The filter thus obtained may be provided on both
surfaces of the light-polarizing film of the present
invention, but, usually, it is sufficient to provide it on
only one surface of the light-polarizing film. The light-
polarizing film laminated with the filter can be used in
such a mariner that incident light can reach the light-
polarizing film only through the filter.
The following Examples illustrate the present inven-
tion wherein the parts are by weight. In the Examples,
the heat stability of the light-polarizing film is eval-
uated by the degree of (1) change in light transmittance
(k) at the wavelength of 590 m~ ) change in the maximum
absorption wavelength (~ max)~ and (3) change in the dif-
ference between ~0 and Hgo (QH - Ho - Hgo) at the
wavelength of 400 to 700 m~ (calculated ~rom EIo and
-- 19 --
~.23~;3~
Hgo measured within the wavelength range at intervals of
10 m~) before and after a continuous use of the film under
dry heating conditions (the degree of these changes is
smaller, the change in polarization efficiency is lesser
and the change i~ color is also lesser).
The light transmittance was measured with respect
to a sheet of the sample film by Beckman DB-G photoelectric
spectrophotometer according to the standard method.
Example 1
A commercially available polyvinyl chloride ~4
parts, average polymerization degree: 1,800) was dissolved
in dimethylformamide (25 parts). To this solution was added
trimethylamine (0.7 part) and reacted at 80C for 200 minutes.
After the completion of the reaction, a commercially avail-
able polymethyl methacrylate (2 parts, average polymerization
degree: 1,800) was added to the reaction mixture. The
resulting solution was cast on a glass plate and treated at
80C for 5 hours to evapolate the solvent to obtain a trans-
parent ~ilm of 30~ in thickness. The film was heated at
90C for 15 hours to obtain a bluish violet transparent
film. The film was stretched 5.5 times the length in one
direction to obtain a light-polarizing film. For a com-
parative purpose, a light-polarizing film was prepared
according to the same procedure except that polyvinyl chlo-
ride (2 parts) was substituted for the polymethyl methacry-
late (comparative example).
These light-polarizing films were treated by dry
heating at 70C for 3 daysO The change in optical pro-
perties of the each film is shown in Table 1.
- 20 -
35~
Table 1
. s . . . . .. . ... . . ....... . :,
Sample Before heat treatment After heat treatment
_~ . . .
k ~max Average k ~max Average
(%) (m~) ~ (%) (%) (m~) ~H (~)
. ___ . . .
Example 1 55 590 12 54 585 12
Compara-
tive 56 590 11 35 555 6
Example
E~
A commercially available polyvinyl chloride (5
parts, average polymerization degree: 2,500) was dissolved
in a mixed solvent of dimethylformamide (15 parts) and
tetrahydrofuran (15 parts). To this solution was added 1,8-
diazabicyclo[5.4.0]undecene~7 (0.05 part) and partially
dehydrohalogenated at 60C for 30 minutes.
Separately, a commercially available polymethyl
methacrylate (5 parts, avera~e polymerization degree: 1,800)
was dissolved in a mixed solvent of dimethylformamide (15
parts) and tetrahydrofuran (15 parts).
The solution of polymethyl methacrylate (PMMA)
and the above prepared reaction mixture was mixed in various
ratios and further added thereto a mixed solvent of di-
methylformamide and tetrabydrofurane (1:1) in such an
amount as the solid content of the mixture is 5 ~.by weight.
The mixture was cast on a glass place and evapolated the
solvent to obtain a yellow transparent film of 40~ in thick-
ness. The film was heated at 90C for 1 hour to obtain a
bluish violet transparent film. The film was then stretched
- 21 -
~.23~
6 times the length in one direction at 110C to obtain
valious light-polarizing films.
The above obtained 6 light-polarizing films of
various P~A contents were treated by dry heating at 70C
for 3 days. The change in optical properties of the each
film is shown in Table 2.
Table 2
PMMA Before heat treatment ¦ After heat treatment
content
(wt %) __ _ _
k ~ max Average k ~max Average
(~5) (m~) ~H (%) (%) (m~) ~H (%)
57 ~ ~ 10-~ ~ 31 555 ~ 4 ~--
56 1 590 1154 580 1 10
1 20 57 1 590 1055 580 1 9
! 30 58 ~ 590 1056 585 10
59 1 590 1157 585 10
56 1 590 _ 55 1 585 _
Example 3
A solution of partially dehydrohalogenated poly~
vinyl chloride prepared by the same procedure in Example 2
was mixed with a solution of various polyalkyl methacrylates
( the concentration and the solvent are the same as those of
PMMA solution in Example 2) in such a ratio as the amount of
the polyalkyl methacrylat~ is 20 % by weight based on the
total amount of the resins in the mixture obtained. The
mixture was cast on a glass plate and evapolated the solvent
to obtain a film of 50ll in thickness. The film was heated
at 90C for 2 hours. The bluish violet film thus obtained
- 22 -
' ~ ~
3~3~
was then stretched 5.5 times the length in one direction at
110C to obtain valious light-polarizing films.
The above obtained light-polarizing films con-
taining various polyalkyl methacrylates and a light-pola-
rizing film prepared for a comparative purpose by the same
procedure without addition of any polyalkyl methacrylate
were treated by dry heating at 70C for 3 days. The change
in optical properties of the each film is shown in Table 3.
The alphabetical numbers of the polymers in Table 3 mean as
follows (the numbers in parenthesis are molar ratios of
copolymerization):
A : polyethyl methacrylate,
B : polybutyl methacrylate,
C : copoly(methyl methacrylate-ethyl methacrylate) (70/30),
D : copoly(methyl methacrylate-methyl acrylate) (80/20), and
E : copoly(methyl methacrylate-ethyl acrylate) (60/40).
Tab3.e 3
..... __ __._ . . . ............. .. _._ __ . 7
Polymer Before heat treatment After heat treatment ¦
added k Amax ¦ Average k ¦ Amax ¦ Average
¦ (%) (m~ H (%) (%) ¦ (m~QH (%)
- -- --- ~ - - . ~, _
Non 52 ¦ 590 1 8 23¦ 555 3
j 1 52 ', 590 1 9 47¦ 585 19
54 ~ 590 ¦11 49¦ 580 10 ~ ,
C1 53 , 590 i10 511 585 9
D¦ 50 590 i 8 47585 8 .
E¦ 51 i 590 ~l9 48585 9
~ ---- t
'~`, '.
- 23 -
'il-- ---- ' - - _ _ . . _ _ _. _
,
-
3~3~
Exam~le 4
A commercially available polyvinyl chloride (5
parts, average polymerization degree: 2,500) was dissolved
in a mixed solvent of dimethylformamide (15 parts) and tetra-
hydrofuran (15 parts). To this solution was added 1.8- -
diazabicyclo[5.4.0]undecene-7 (0.05 part) and partially
dehydrohalogenated at 60C for 30 minutes.
Separately, polyisobornyl methacrylate (5 parts,
average polymerization degree: 1,500) was dissolved in a
mixed solvent of dimethylformamide (15 parts) and tetra-
hydrofuran (15 parts).
The above prepared reaction mixture and the
solution of polyisobornyl methacrylate (PIBA) was mixed in
the weight ratio of solid content of 8/2 and further added
thereto a mixed solvent of dimethylformamide and tetra-
hydrofuran (1 : 1) in such an amount as the solid content o~
the mixture is 1 ~ by weight. The mixture was cast on a
glass plate and evapolated the solvent to obtain a yellow
transparent film of 40~ in thickness. The film was heated
at 90C for 70 minutes to obtain a bluish violet transparent
~ilm. The film was then stretched 6 times the length in one
direction at I10C to obtain a light-polarizing film.
The light-polarizing film was treated by dry
heating at 70C for 5 days. The change in optical pro-
perties of the film is shown in Table 4.
- 24 -
"~, __... . . . .
'
538
Table 4
. ... _ _ .
PIBA Before heat treatment After heat treatment
content
~ (wt %) . . . ---~ - ---r ----- -------------
k ~max Average k ~max IAverage Color
(%) (m~) QH (%) (~) (m~ ~1 (%) differ-
i ence (~E)
_ .. . . __ .. _ !
0 51 590 11 .1 29 1 555 5 8.0
S0 590 ~ 11 1.3 ~:
'' ' '
,
' ~ ~
:
~ ' ,
, -
.
. .
.: .
:
- 25 -
-
.
.~,~_....... .. __ _ _ .. . . . . . . . .. . ___ ~
