U.S. patent application number 14/695973 was filed with the patent office on 2015-08-13 for method of manufacturing polarizing plate.
This patent application is currently assigned to NITTO DENKO CORPORATION. The applicant listed for this patent is NITTO DENKO CORPORATION. Invention is credited to Shusaku Goto, Nobuyuki Haida, Kentaro Ikeshima, Osamu Kaneko, Minoru Miyatake, Yuuki Nakano.
Application Number | 20150226894 14/695973 |
Document ID | / |
Family ID | 50727698 |
Filed Date | 2015-08-13 |
United States Patent
Application |
20150226894 |
Kind Code |
A1 |
Goto; Shusaku ; et
al. |
August 13, 2015 |
METHOD OF MANUFACTURING POLARIZING PLATE
Abstract
A method of manufacturing a polarizing plate according to an
embodiment of the present invention includes: stretching and dyeing
a laminate having a resin substrate and a polyvinyl alcohol-based
resin layer formed on at least one side of the resin substrate to
produce a polarizing film on the resin substrate; laminating an
optically functional film on the laminate on a polarizing film side
to produce an optically functional film laminate; and peeling the
resin substrate from the optically functional film laminate. The
peeling is performed so that an angle .alpha. formed between a
surface of the optically functional film laminate immediately
before the peeling and a peeling direction of the resin substrate
is smaller than an angle .beta. formed between the surface of the
optically functional film laminate immediately before the peeling
and a peeling direction of the polarizing film.
Inventors: |
Goto; Shusaku; (Ibaraki-shi,
JP) ; Nakano; Yuuki; (Ibaraki-shi, JP) ;
Ikeshima; Kentaro; (Ibaraki-shi, JP) ; Haida;
Nobuyuki; (Ibaraki-shi, JP) ; Miyatake; Minoru;
(Ibaraki-shi, JP) ; Kaneko; Osamu; (Ibaraki-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NITTO DENKO CORPORATION |
Osaka |
|
JP |
|
|
Assignee: |
NITTO DENKO CORPORATION
Osaka
JP
|
Family ID: |
50727698 |
Appl. No.: |
14/695973 |
Filed: |
April 24, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14056178 |
Oct 17, 2013 |
9046655 |
|
|
14695973 |
|
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|
|
Current U.S.
Class: |
156/229 |
Current CPC
Class: |
G02B 5/3033 20130101;
G02B 5/30 20130101; B32B 2307/42 20130101; B32B 2457/202 20130101;
G02B 5/305 20130101; B32B 2038/0028 20130101; B32B 38/0012
20130101; G02B 1/08 20130101; B32B 38/10 20130101; B32B 2037/243
20130101; B32B 37/24 20130101; B32B 2551/00 20130101; B29D 11/00644
20130101; G02B 1/14 20150115 |
International
Class: |
G02B 5/30 20060101
G02B005/30; G02B 1/08 20060101 G02B001/08; B32B 37/24 20060101
B32B037/24; G02B 1/14 20060101 G02B001/14; B32B 38/00 20060101
B32B038/00; B32B 38/10 20060101 B32B038/10 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 16, 2012 |
JP |
2012-251784 |
Jul 8, 2013 |
JP |
2013-142375 |
Claims
1.-16. (canceled)
17. A method of manufacturing a polarizing plate, comprising:
forming a laminate having a resin substrate and a polyvinyl
alcohol-based resin layer formed on one side of the resin
substrate; stretching and dyeing the laminate to produce a
polarizing film on the resin substrate; laminating an optically
functional film on the polarizing film on the resin substrate to
produce an optically functional film laminate; and peeling the
resin substrate from the optically functional film laminate,
wherein the peeling is performed so that an angle .alpha. is
smaller than an angle .beta.; wherein the angle .alpha. is formed
between a surface of the optically functional film laminate
immediately before the peeling and a peeling direction of the resin
substrate, and wherein the angle .beta. is formed between the
surface of the optically functional film laminate immediately
before the peeling and a peeling direction of the polarizing
film.
18. The method of manufacturing the polarizing plate according to
claim 17, wherein a difference between the angle .alpha. and the
angle .beta. is 60.degree. or more.
19. The method of manufacturing the polarizing plate according to
claim 18, wherein the difference between the angle .alpha. and the
angle .beta. is 90.degree. to 180.degree..
20. The method of manufacturing the polarizing plate according to
claim 17, wherein a tension needed for the peeling is 3.0 N/mm or
less.
21. The method of manufacturing the polarizing plate according to
claim 17, wherein the resin substrate has a modulus of elasticity
at a time of the peeling of 2 GPa to 3 GPa.
22. The method of manufacturing the polarizing plate according to
claim 17, wherein the resin substrate has a radius of curvature at
a time of the peeling of 1 mm to 10 mm.
23. The method of manufacturing the polarizing plate according to
claim 17, wherein, in the peeling, a peeling roll is arranged on
the optically functional film laminate on an optically functional
film side, and the peeling is performed with an aid of the peeling
roll.
24. The method of manufacturing the polarizing plate according to
claim 23, wherein the peeling roll has a diameter of 10 mm to 30
mm.
25. The method of manufacturing the polarizing plate according to
claim 17, wherein, in the peeling, a peeling bar is arranged on the
optically functional film laminate on an optically functional film
side, and the peeling is performed with an aid of the peeling
bar.
26. The method of manufacturing the polarizing plate according to
claim 25, wherein the peeling bar has a diameter of a tip portion
of 5 mm to 30 mm.
27. The method of manufacturing the polarizing plate according to
claim 23, wherein a surface of the optically functional film
laminate on the optically functional film side has a surface
protective film attached thereto.
28. The method of manufacturing the polarizing plate according to
claim 25, wherein a surface of the optically functional film
laminate on the optically functional film side has a surface
protective film attached thereto.
Description
[0001] This application is a Divisional of U.S. application Ser.
No. 14/056,178, filed Oct. 17, 2015, which claims priority under 35
U.S.C. Section 119 to Japanese Patent Application Nos. 2012-251784
and 2013-142375 each filed on Nov. 16, 2012, and Jul. 8, 2013,
which are herein incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method of manufacturing a
polarizing plate.
[0004] 2. Description of the Related Art
[0005] Polarizing films are placed on both sides of a liquid
crystal cell of a liquid crystal display apparatus as a typical
image display apparatus, the placement being attributable to an
image-forming mode of the apparatus. For example, the following
method has been proposed as a method of manufacturing the
polarizing film (for example, Japanese Patent Application Laid-open
No. 2000-338329). A laminate having a resin substrate and a
polyvinyl alcohol (PVA)-based resin layer is stretched, and is then
subjected to a dyeing treatment so that the polarizing film may be
formed on the resin substrate. According to such method, a
polarizing film having a small thickness is formed. Accordingly,
the method has been attracting attention because of its potential
to contribute to thinning of an image display apparatus in recent
years.
[0006] By the way, the polarizing film is typically laminated on
another optically functional film (e.g., a protective film) and is
used as a polarizing plate. However, the polarizing plate using the
polarizing film produced by using the resin substrate involves the
following problem. A wrinkle, foreign matter, or the like is liable
to occur, and hence the polarizing plate is poor in external
appearance.
SUMMARY OF THE INVENTION
[0007] According to an embodiment of the present invention, there
is provided a method of manufacturing a polarizing plate excellent
in external appearance.
[0008] A method of manufacturing a polarizing plate according to an
embodiment of the present invention includes: stretching and dyeing
a laminate having a resin substrate and a polyvinyl alcohol-based
resin layer formed on one side of the resin substrate to produce a
polarizing film on the resin substrate; laminating an optically
functional film on the laminate on a polarizing film side to
produce an optically functional film laminate; and peeling the
resin substrate from the optically functional film laminate. The
peeling is performed so that an angle .alpha. formed between a
surface of the optically functional film laminate immediately
before the peeling and a peeling direction of the resin substrate
is smaller than an angle .beta. formed between the surface of the
optically functional film laminate immediately before the peeling
and a peeling direction of the polarizing film.
[0009] In one embodiment of the present invention, a difference
between the angle .alpha. and the angle .beta. is 60.degree. or
more. In one embodiment of the present invention, the difference
between the angle .alpha. and the angle .beta. is 90.degree. to
180.degree..
[0010] In one embodiment of the present invention, a tension needed
for the peeling is 3.0 N/15 mm or less.
[0011] In one embodiment of the present invention, the resin
substrate has a modulus of elasticity at a time of the peeling of 2
GPa to 3 GPa.
[0012] In one embodiment of the present invention, the resin
substrate has a radius of curvature at a time of the peeling of 1
mm to 10 mm.
[0013] In one embodiment of the present invention, in the peeling,
a peeling roll is arranged on the optically functional film
laminate on an optically functional film side, and the peeling is
performed with an aid of the peeling roll. In one embodiment of the
present invention, the peeling roll has a diameter of 10 mm to 30
mm.
[0014] In one embodiment of the present invention, in the peeling,
a peeling bar is arranged on the optically functional film laminate
on an optically functional film side, and the peeling is performed
with an aid of the peeling bar. In one embodiment of the present
invention, the peeling bar has a diameter of a tip portion of 5 mm
to 30 mm.
[0015] In one embodiment of the present invention, a surface of the
optically functional film laminate on the optically functional film
side has a surface protective film attached thereto.
[0016] According to another aspect of the present invention, a
polarizing plate is provided. The polarizing plate is obtained by
the manufacturing method as described above.
[0017] According to an embodiment of the present invention, an
optically functional film is laminated on a polarizing film formed
on a resin substrate to produce an optically functional film
laminate, and upon peeling of the resin substrate from the
optically functional film laminate, an angle .alpha. formed between
the surface of the optically functional film laminate immediately
before the peeling and the peeling direction of the resin substrate
is set to be smaller than an angle .beta. formed between the
surface of the optically functional film laminate immediately
before the peeling and the peeling direction of the polarizing
film, whereby the resin substrate can be satisfactorily peeled
while the occurrence of a wrinkle, foreign matter (such as a
substrate residue), or the like is suppressed. As a result, a
polarizing plate extremely excellent in external appearance can be
obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In the accompanying drawings:
[0019] FIG. 1 is a partial sectional view of a laminate according
to an embodiment of the present invention;
[0020] FIG. 2 is an explanatory diagram of a method of measuring a
radius of curvature R;
[0021] FIG. 3 is a schematic view illustrating an example of a
peeling step in the present invention;
[0022] FIG. 4 is a schematic view illustrating another example of
the peeling step in the present invention;
[0023] FIG. 5A is a schematic view illustrating still another
example of the peeling step in the present invention; and
[0024] FIG. 5B is a schematic view illustrating still another
example of the peeling step in the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] Hereinafter, embodiments of the present invention are
described. However, the present invention is not limited to these
embodiments.
[0026] A method of manufacturing a polarizing plate according to an
embodiment of the present invention includes: stretching and dyeing
a laminate having a resin substrate and a polyvinyl alcohol-based
resin layer formed on one side of the resin substrate to produce a
polarizing film on the resin substrate; laminating an optically
functional film on a polarizing film side of the laminate to
produce an optically functional film laminate; and peeling the
resin substrate from the optically functional film laminate.
Hereinafter, the respective steps are described.
A. Step of Producing Polarizing Film
A-1. Laminate
[0027] FIG. 1 is a partial sectional view of a laminate according
to an embodiment of the present invention. A laminate 10 has a
resin substrate 11 and a polyvinyl alcohol-based resin layer 12.
The laminate 10 is produced by forming the polyvinyl alcohol-based
resin layer 12 on the resin substrate 11 having a long shape. Any
appropriate method may be adopted as a method of forming the
polyvinyl alcohol-based resin layer 12. The polyvinyl alcohol-based
resin (hereinafter referred to as "PVA-based resin") layer 12 is
preferably formed by applying an application liquid containing a
PVA-based resin onto the resin substrate 11 and drying the
liquid.
[0028] As a formation material for the resin substrate, any
appropriate thermoplastic resin may be adopted. Examples of the
thermoplastic resin include: an ester-based resin such as a
polyethylene terephthalate-based resin; a cycloolefin-based resin
such as a norbornene-based resin; an olefin-based resin such as
polypropylene; a polyamide-based resin; a polycarbonate-based
resin; and a copolymer resin thereof. Of those, a norbornene-based
resin and an amorphous polyethylene terephthalate-based resin are
preferred.
[0029] In one embodiment, an amorphous (uncrystallized)
polyethylene terephthalate-based resin is preferably used. In
particular, a noncrystalline (hard-to-crystallize) polyethylene
terephthalate-based resin is particularly preferably used. Specific
examples of the noncrystalline polyethylene terephthalate-based
resin include a copolymer further containing isophthalic acid as a
dicarboxylic acid component and a copolymer further containing
cyclohexane dimethanol as a glycol component.
[0030] When an underwater stretching mode is adopted in a
stretching treatment to be described later, the resin substrate can
absorb water and the water acts as like a plasticizer so that the
substrate can plasticize. As a result, a stretching stress can be
significantly reduced. Accordingly, the stretching can be performed
at a high ratio and the stretchability of the resin substrate can
be more excellent than that at the time of in-air stretching. As a
result, a polarizing film having excellent optical characteristics
can be produced. In one embodiment, the percentage of water
absorption of the resin substrate is preferably 0.2% or more, more
preferably 0.3% or more. Meanwhile, the percentage of water
absorption of the resin substrate is preferably 3.0% or less, more
preferably 1.0% or less. The use of such resin substrate can
prevent, for example, the following inconvenience: the dimensional
stability of the resin substrate remarkably reduces at the time of
the production and hence the external appearance of the polarizing
film to be obtained deteriorates. In addition, the use of such
resin substrate can prevent the rupture of the substrate at the
time of the underwater stretching and the peeling of the PVA-based
resin layer from the resin substrate. It should be noted that the
percentage of water absorption of the resin substrate can be
adjusted by, for example, introducing a modification group into the
constituent material. The percentage of water absorption is a value
determined in conformity with JIS K 7209.
[0031] The glass transition temperature (Tg) of the resin substrate
is preferably 170.degree. C. or less. The use of such resin
substrate can sufficiently secure the stretchability of the
laminate while suppressing the crystallization of the PVA-based
resin layer. Further, the glass transition temperature is more
preferably 120.degree. C. or less in consideration of the
plasticization of the resin substrate by water and favorable
performance of the underwater stretching. In one embodiment, the
glass transition temperature of the resin substrate is preferably
60.degree. C. or more. The use of such resin substrate prevents an
inconvenience such as the deformation of the resin substrate (e.g.,
the occurrence of unevenness, a slack, or a wrinkle) during the
application and drying of the application liquid containing the
PVA-based resin, thereby enabling favorable production of the
laminate. In addition, the use enables favorable stretching of the
PVA-based resin layer at a suitable temperature (e.g., about
60.degree. C.). In another embodiment, a glass transition
temperature of less than 60.degree. C. is permitted as long as the
resin substrate does not deform during the application and drying
of the application liquid containing the PVA-based resin. It should
be noted that the glass transition temperature of the resin
substrate can be adjusted by, for example, introducing a
modification group into the formation material or heating the
substrate constituted of a crystallization material. The glass
transition temperature (Tg) is a value determined in conformity
with JIS K 7121.
[0032] The thickness of the resin substrate before the stretching
is preferably 20 .mu.m to 300 .mu.m, more preferably 50 .mu.m to
200 .mu.m. When the thickness is less than 20 .mu.m, it may be
difficult to form the PVA-based resin layer. When the thickness
exceeds 300 .mu.m, in, for example, underwater stretching, it may
take a long time for the resin substrate to absorb water, and an
excessively large load may be needed in the stretching.
[0033] Any appropriate resin may be adopted as the PVA-based resin
for forming the PVA-based resin layer. Examples of the resin
include polyvinyl alcohol and an ethylene-vinyl alcohol copolymer.
The polyvinyl alcohol is obtained by saponifying polyvinyl acetate.
The ethylene-vinyl alcohol copolymer is obtained by saponifying an
ethylene-vinyl acetate copolymer. The saponification degree of the
PVA-based resin is typically 85 mol % to 100 mol %, preferably 95.0
mol % to 99.95 mol %, more preferably 99.0 mol % to 99.93 mol %.
The saponification degree can be determined in conformity with JIS
K 6726-1994. The use of the PVA-based resin having such
saponification degree can provide a polarizing film excellent in
durability. When the saponification degree is excessively high, the
resin may gel.
[0034] The average polymerization degree of the PVA-based resin may
be appropriately selected depending on purposes. The average
polymerization degree is typically 1,000 to 10,000, preferably
1,200 to 5,000, more preferably 1,500 to 4,500. It should be noted
that the average polymerization degree can be determined in
conformity with JIS K 6726-1994.
[0035] The application liquid is typically a solution prepared by
dissolving the PVA-based resin in a solvent. Examples of the
solvent include water, dimethylsulfoxide, dimethylformamide,
dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric
alcohols such as trimethylolpropane, and amines such as
ethylenediamine and diethylenetriamine. They may be used alone or
in combination. Of those, water is preferred. The concentration of
the PVA-based resin of the solution is preferably 3 parts by weight
to 20 parts by weight with respect to 100 parts by weight of the
solvent. At such resin concentration, a uniform coating film in
close contact with the resin substrate can be formed.
[0036] The application liquid may be compounded with an additive.
Examples of the additive include a plasticizer and a surfactant.
Examples of the plasticizer include polyhydric alcohols such as
ethylene glycol and glycerin. Examples of the surfactant include
nonionic surfactants. Such additive can be used for the purpose of
additionally improving the uniformity, dyeing property, or
stretchability of the PVA-based resin layer to be obtained. In
addition, examples of the additive include an easy-adhesion
component. The use of the easy-adhesion component can improve
adhesiveness between the resin substrate and the PVA-based resin
layer. As a result, an inconvenience such as peeling of the
PVA-based resin layer from the substrate is suppressed, and dyeing
and underwater stretching to be described later can be
satisfactorily performed.
[0037] Examples of the easy-adhesion component include a modified
PVA such as acetoacetyl modified PVA. A polymer having at least a
repeating unit represented by the below-indicated general formula
(I) is preferably used as the acetoacetyl modified PVA.
##STR00001##
[0038] In the formula (I), the ratio of "n" to "l+m+n"
(modification degree) is preferably 1% to 10%.
[0039] The saponification degree of the acetoacetyl modified PVA is
preferably 97 mol % or more. In addition, the pH of a 4-wt %
aqueous solution of the acetoacetyl modified PVA is preferably 3.5
to 5.5.
[0040] The modified PVA is added so that the amount of the modified
PVA is preferably 3 wt % or more, more preferably 5 wt % or more
with respect to the total weight of the PVA-based resins in the
application liquid. On the other hand, the amount of the modified
PVA added is preferably 30 wt % or less.
[0041] Any appropriate method may be adopted as a method of
applying the application liquid. Examples of the method include a
roll coating method, a spin coating method, a wire bar coating
method, a dip coating method, a die coating method, a curtain
coating method, a spray coating method, and a knife coating method
(comma coating method or the like).
[0042] The application liquid is preferably applied and dried at a
temperature of 50.degree. C. or more.
[0043] The thickness of the PVA-based resin layer before the
stretching is preferably 3 .mu.m to 40 .mu.m, more preferably 5
.mu.m to 20 .mu.m.
[0044] The resin substrate may be subjected to a surface treatment
(such as a corona treatment) before the formation of the PVA-based
resin layer. Alternatively, an easy-adhesion layer may be formed on
the resin substrate. Of those, the formation of an easy-adhesion
layer (a coating treatment) is preferably performed. For example,
an acrylic resin or a polyvinyl alcohol-based resin is used as a
material for forming the easy-adhesion layer. Of those, a polyvinyl
alcohol-based resin is particularly preferred. Examples of the
polyvinyl alcohol-based resin include a polyvinyl alcohol resin and
a modified product thereof. Examples of the modified product of the
polyvinyl alcohol resin include the acetoacetyl modified PVA. It
should be noted that the thickness of the easy-adhesion layer is
preferably about 0.05 .mu.m to 1 .mu.m. Such treatment can improve
adhesiveness between the resin substrate and the PVA-based resin
layer. As a result, for example, an inconvenience such as peeling
of the PVA-based resin layer from the substrate is suppressed, and
dyeing and underwater stretching to be described later can be
satisfactorily performed.
A-2. Stretching of Laminate
[0045] Any appropriate method may be adopted as a method of
stretching the laminate. Specifically, fixed-end stretching may be
adopted or free-end stretching (such as a method involving passing
the laminate through rolls having different peripheral speeds to
uniaxially stretch the laminate) maybe adopted. Of those, free-end
stretching is preferred.
[0046] The stretching direction of the laminate maybe appropriately
set. In one embodiment, the laminate having a long shape is
stretched in its lengthwise direction. In this case, there may be
typically adopted a method involving passing the laminate between
rolls having different peripheral speeds to stretch the laminate.
In another embodiment, the laminate having a long shape is
stretched in its widthwise direction. In this case, there may be
typically adopted a method involving stretching the laminate using
a tenter stretching apparatus.
[0047] A stretching mode is not particularly limited and may be an
in-air stretching mode or an underwater stretching mode. Of those,
an underwater stretching mode is preferred. According to the
underwater stretching mode, the stretching can be performed at a
temperature lower than the glass transition temperature (typically
about 80.degree. C.) of each of the resin substrate and the
PVA-based resin layer, and hence the PVA-based resin layer can be
stretched at a high ratio while its crystallization is suppressed.
As a result, a polarizing film having excellent optical
characteristics can be produced.
[0048] The stretching of the laminate maybe performed in one stage,
or may be performed in a plurality of stages. When the stretching
is performed in a plurality of stages, for example, the free-end
stretching and the fix-end stretching may be performed in
combination, or the underwater stretching mode and the in-air
stretching mode maybe performed in combination. When the stretching
is performed in a plurality of stages, the stretching ratio
(maximum stretching ratio) of the laminate to be described later is
the product of stretching ratios in the respective stages.
[0049] The stretching temperature of the laminate may be set to any
appropriate value depending on, for example, a formation material
for the resin substrate and the stretching mode. When the in-air
stretching mode is adopted, the stretching temperature is
preferably equal to or higher than the glass transition temperature
(Tg) of the resin substrate, more preferably Tg+10.degree. C. or
more, particularly preferably Tg+15.degree. C. or more. Meanwhile,
the stretching temperature of the laminate is preferably
170.degree. C. or less. Performing the stretching at such
temperature suppresses rapid progress of the crystallization of the
PVA-based resin, thereby enabling the suppression of an
inconvenience due to the crystallization (such as the inhibition of
the orientation of the PVA-based resin layer by the
stretching).
[0050] When the underwater stretching mode is adopted as a
stretching mode, the liquid temperature of a stretching bath is
preferably 40.degree. C. to 85.degree. C., more preferably
50.degree. C. to 85.degree. C. At such temperature, the PVA-based
resin layer can be stretched at a high ratio while its dissolution
is suppressed. Specifically, as described above, the glass
transition temperature (Tg) of the resin substrate is preferably
60.degree. C. or more in relation to the formation of the PVA-based
resin layer. In this case, when the stretching temperature falls
short of 40.degree. C., there is a possibility that the stretching
cannot be satisfactorily performed even in consideration of the
plasticization of the resin substrate by water. On the other hand,
as the temperature of the stretching bath increases, the solubility
of the PVA-based resin layer is raised and hence excellent optical
characteristics may not be obtained. The laminate is preferably
immersed in the stretching bath for a time of 15 seconds to 5
minutes.
[0051] When the underwater stretching mode is adopted, the laminate
is preferably stretched while being immersed in an aqueous solution
of boric acid (in-boric-acid-solution stretching). The use of the
aqueous solution of boric acid as the stretching bath can impart,
to the PVA-based resin layer, rigidity enough to withstand a
tension to be applied at the time of the stretching and such water
resistance that the layer does not dissolve in water. Specifically,
boric acid can produce a tetrahydroxyborate anion in the aqueous
solution to cross-link with the PVA-based resin through a hydrogen
bond. As a result, the PVA-based resin layer can be satisfactorily
stretched with the aid of the rigidity and the water resistance
imparted thereto, and hence a polarizing film having excellent
optical characteristics can be produced.
[0052] The aqueous solution of boric acid is preferably obtained by
dissolving boric acid and/or a borate in water as a solvent. The
concentration of boric acid is preferably 1 part by weight to 10
parts by weight with respect to 100 parts by weight of water.
Setting the concentration of boric acid to 1 part by weight or more
can effectively suppress the dissolution of the PVA-based resin
layer, thereby enabling the production of a polarizing film having
additionally high characteristics. It should be noted that an
aqueous solution obtained by dissolving a boron compound such as
borax, glyoxal, glutaric aldehyde, or the like as well as boric
acid or the borate in the solvent may also be used.
[0053] When the PVA-based resin layer has been caused to adsorb a
dichromatic substance (typically iodine) in advance by dyeing to be
described later, the stretching bath (aqueous solution of boric
acid) is preferably compounded with an iodide. Compounding the bath
with the iodide can suppress the elution of iodine that the
PVA-based resin layer has been caused to adsorb. Examples of the
iodide include potassium iodide, lithium iodide, sodium iodide,
zinc iodide, aluminum iodide, lead iodide, copper iodide, barium
iodide, calcium iodide, tin iodide, and titanium iodide. Of those,
potassium iodide is preferred. The concentration of the iodide is
preferably 0.05 part by weight to 15 parts by weight, more
preferably 0.5 part by weight to 8 parts by weight with respect to
100 parts by weight of water.
[0054] The stretching ratio (maximum stretching ratio) of the
laminate is preferably 5.0 times or more with respect to the
original length of the laminate. Such high stretching ratio can be
achieved by adopting, for example, the underwater stretching mode
(in-boric-acid-solution stretching). It should be noted that the
term "maximum stretching ratio" as used in this specification
refers to a stretching ratio immediately before the rupture of the
laminate. The stretching ratio at which the laminate ruptures is
separately identified and a value lower than the value by 0.2 is
the maximum stretching ratio.
[0055] In one embodiment, the laminate is subjected to in-air
stretching at high temperature (e.g., 95.degree. C. or more), and
then subjected to the in-boric-acid-solution stretching, and dyeing
to be described later. Such in-air stretching is hereinafter
referred to as "preliminary in-air stretching" because the
stretching can be ranked as stretching preliminary or auxiliary to
the in-boric-acid-solution stretching.
[0056] When the preliminary in-air stretching is combined with the
in-boric-acid-solution stretching, the laminate can be stretched at
an additionally high ratio in some cases. As a result, a polarizing
film having additionally excellent optical characteristics (such as
a polarization degree) can be produced. For example, when a
polyethylene terephthalate-based resin is used as the resin
substrate, the resin substrate can be stretched satisfactorily,
while its orientation is suppressed, by a combination of the
preliminary in-air stretching and the in-boric-acid-solution
stretching than that in the case of the in-boric-acid-solution
stretching alone. As the orientation property of the resin
substrate is raised, its stretching tension increases and hence it
becomes difficult to stably stretch the substrate or the resin
substrate ruptures. Accordingly, the laminate can be stretched at
an additionally high ratio by stretching the resin substrate while
suppressing its orientation.
[0057] In addition, when the preliminary in-air stretching is
combined with the in-boric-acid-solution stretching, the
orientation property of the PVA-based resin is improved and hence
the orientation property of the PVA-based resin can be improved
even after the in-boric-acid-solution stretching. Specifically, the
orientation property of the PVA-based resin is improved in advance
by the preliminary in-air stretching so that the PVA-based resin
may easily cross-link with boric acid during the
in-boric-acid-solution stretching. Then, the stretching is
performed in a state where boric acid serves as a junction, and
hence the orientation property of the PVA-based resin is assumed to
be high even after the in-boric-acid-solution stretching. As a
result, a polarizing film having excellent optical characteristics
(such as a polarization degree) can be produced.
[0058] The stretching ratio in the preliminary in-air stretching is
preferably 3.5 times or less. A stretching temperature in the
preliminary in-air stretching is preferably equal to or higher than
the glass transition temperature of the PVA-based resin. The
stretching temperature is preferably 95.degree. C. to 150.degree.
C. It should be noted that the maximum stretching ratio when the
preliminary in-air stretching and the in-boric-acid-solution
stretching are combined with each other is preferably 5.0 times or
more, more preferably 5.5 times or more, still more preferably 6.0
times or more with respect to the original length of the
laminate.
A-3. Dyeing
[0059] The dyeing of the laminate is typically performed by causing
the PVA-based resin layer to adsorb a dichromatic substance
(preferably iodine). A method for the adsorption is, for example, a
method involving immersing the PVA-based resin layer (laminate) in
a dyeing liquid containing iodine, a method involving applying the
dyeing liquid to the PVA-based resin layer, or a method involving
spraying the dyeing liquid on the PVA-based resin layer. Of those,
a method involving immersing the laminate in the dyeing liquid is
preferred. This is because iodine can satisfactorily adsorb to the
layer.
[0060] The dyeing liquid is preferably an aqueous solution of
iodine. The compounding amount of iodine is preferably 0.1 part by
weight to 0.5 part by weight with respect to 100 parts by weight of
water. The aqueous solution of iodine is preferably compounded with
an iodide so that the solubility of iodine in water may be
increased. Specific examples of the iodide are as described above.
The compounding amount of the iodide is preferably 0.02 part by
weight to 20 parts by weight, more preferably 0.1 part by weight to
10 parts by weight with respect to 100 parts by weight of water.
The liquid temperature of the dyeing liquid at the time of the
dyeing is preferably 20.degree. C. to 50.degree. C. so that the
dissolution of the PVA-based resin may be suppressed. When the
PVA-based resin layer is immersed in the dyeing liquid, an
immersion time is preferably 5 seconds to 5 minutes so that the
transmittance of the PVA-based resin layer may be secured. In
addition, the dyeing conditions (the concentration, the liquid
temperature, and the immersion time) can be set so that the
polarization degree or single axis transmittance of the polarizing
film to be finally obtained may fall within a predetermined range.
In one embodiment, the immersion time is set so that the
polarization degree of the polarizing film to be obtained may be
99.98% or more. In another embodiment, the immersion time is set so
that the single axis transmittance of the polarizing film to be
obtained may be 40% to 44%.
[0061] The dyeing treatment can be performed at any appropriate
timing. When the underwater stretching is performed, the dyeing
treatment is preferably performed before the underwater
stretching.
A-4. Any Other Treatment
[0062] The laminate may be appropriately subjected to a treatment
for forming the PVA-based resin layer into a polarizing film in
addition to the stretching and dyeing. Examples of the treatment
for forming the PVA-based resin layer into the polarizing film
include an insolubilizing treatment, a cross-linking treatment, a
washing treatment, and a drying treatment. It should be noted that
the number of times, order, and the like of these treatments are
not particularly limited.
[0063] The insolubilizing treatment is typically performed by
immersing the PVA-based resin layer in an aqueous solution of boric
acid. Water resistance can be imparted to the PVA-based resin layer
by subjecting the layer to the insolubilizing treatment. The
concentration of the aqueous solution of boric acid is preferably 1
part by weight to 4 parts by weight with respect to 100 parts by
weight of water. The liquid temperature of an insolubilizing bath
(the aqueous solution of boric acid) is preferably 20.degree. C. to
50.degree. C. The insolubilizing treatment is preferably performed
before the underwater stretching treatment or the dyeing
treatment.
[0064] The cross-linking treatment is typically performed by
immersing the PVA-based resin layer in an aqueous solution of boric
acid. Water resistance can be imparted to the PVA-based resin layer
by subjecting the layer to the cross-linking treatment. The
concentration of the aqueous solution of boric acid is preferably 1
part by weight to 5 parts by weight with respect to 100 parts by
weight of water. In addition, when the cross-linking treatment is
performed after the dyeing treatment, the solution is preferably
further compounded with an iodide. Compounding the solution with
the iodide can suppress the elution of iodine which the PVA-based
resin layer has been caused to adsorb. The compounding amount of
the iodide is preferably 1 part by weight to 5 parts by weight with
respect to 100 parts by weight of water. Specific examples of the
iodide are as described above. The liquid temperature of a
cross-linking bath (the aqueous solution of boric acid) is
preferably 20.degree. C. to 60.degree. C. The cross-linking
treatment is preferably performed before the underwater stretching
treatment. In a preferred embodiment, the dyeing treatment, the
cross-linking treatment, and the underwater stretching treatment
are performed in the stated order.
[0065] The washing treatment is typically performed by immersing
the PVA-based resin layer in an aqueous solution of potassium
iodide. The drying temperature in the drying treatment is
preferably 30.degree. C. to 100.degree. C.
A-5. Polarizing Film
[0066] The polarizing film is substantially a PVA-based resin layer
that adsorbs and orients a dichromatic substance. The thickness of
the polarizing film is typically 25 .mu.m or less, preferably 15
.mu.m or less, more preferably 10 .mu.m or less, still more
preferably 7 .mu.m or less, particularly preferably 5 .mu.m or
less. Meanwhile, the thickness of the polarizing film is preferably
0.5 .mu.m or more, more preferably 1.5 .mu.m or more. The
polarizing film preferably shows absorption dichroism at any
wavelength in the wavelength range of 380 nm to 780 nm. The single
axis transmittance of the polarizing film is preferably 40.0% or
more, more preferably 41.0% or more, still more preferably 42.0% or
more, particularly preferably 43.0% or more. The polarization
degree of the polarizing film is preferably 99.8% or more, more
preferably 99.9% or more, still more preferably 99.95% or more.
B. Step of Producing Optically Functional Film Laminate
[0067] After the laminate (PVA-based resin layer) has been
subjected to the respective treatments, an optically functional
film is laminated on the laminate on the polarizing film (PVA-based
resin layer) side. An optically functional film having a long shape
is typically laminated on the laminate having a long shape so that
their lengthwise directions are aligned.
[0068] The optically functional film can function as, for example,
a protective film for a polarizing film or a retardation film.
[0069] Any appropriate resin film may be adopted as the optically
functional film. As a formation material for the optically
functional film, there are given, for example: a cellulose-based
resin such as triacetyl cellulose (TAC); a cycloolefin-based resin
such as a norbornene-based resin; an olefin-based resin such as
polyethylene or polypropylene; a polyester-based resin; and a
(meth)acrylic resin. It should be noted that the term
"(meth)acrylic resin" refers to an acrylic resin and/or a
methacrylic resin.
[0070] The thickness of the optically functional film is typically
10 .mu.m to 100 .mu.m, preferably 20 .mu.m to 60 .mu.m. It should
be noted that the optically functional film may be subjected to
various surface treatments.
[0071] The modulus of elasticity of the optically functional film
is preferably 2 GPa or more, more preferably 2 GPa to 6 GPa. When
one end portion of an optically functional film 20 is held in a
state where the other end portion thereof is bonded to a substrate
110, and is then bent in a 180.degree. direction with respect to
the bonding surface as illustrated in FIG. 2, a radius of curvature
R of the bent portion is preferably 3 mm or more, more preferably 5
mm or more. A peeling step to be described later can be performed
more satisfactorily by using such optically functional film.
[0072] The lamination of the optically functional film is performed
using any appropriate adhesive or pressure-sensitive adhesive. In
one embodiment, the adhesive is applied onto the surface of the
polarizing film before the optically functional film is attached.
The adhesive may be an aqueous adhesive, or may be a solvent-based
adhesive. Of those, an aqueous adhesive is preferably used.
[0073] Any appropriate aqueous adhesive may be adopted as the
aqueous adhesive. An aqueous adhesive containing a PVA-based resin
is preferably used. The average polymerization degree of the
PVA-based resin in the aqueous adhesive is preferably about 100 to
5,000, more preferably 1,000 to 4,000 in terms of adhesion. Its
average saponification degree is preferably about 85 mol % to 100
mol %, more preferably 90 mol % to 100 mol % in terms of
adhesion.
[0074] The PVA-based resin in the aqueous adhesive preferably
contains an acetoacetyl group. This is because such resin can be
excellent in adhesiveness between the PVA-based resin layer and the
optically functional film, and in durability. The acetoacetyl
group-containing PVA-based resin is obtained by, for example,
causing a PVA-based resin and diketene to react with each other by
any appropriate method. The acetoacetyl group modification degree
of the acetoacetyl group-containing PVA-based resin is typically
0.1 mol % or more, preferably about 0.1 mol % to 40 mol %, more
preferably 1 mol % to 20 mol %, particularly preferably 2 mol % to
7 mol %. It should be noted that the acetoacetyl group modification
degree is a value measured by NMR.
[0075] The resin concentration of the aqueous adhesive is
preferably 0.1 wt % to 15 wt %, more preferably 0.5 wt % to 10 wt
%.
[0076] The thickness of the adhesive at the time of the application
can be set to any appropriate value. For example, the thickness is
set so that an adhesive layer having a desired thickness may be
obtained after heating (drying). The thickness of the adhesive
layer is preferably 10 nm to 300 nm, more preferably 10 nm to 200
nm, particularly preferably 20 nm to 150 nm.
[0077] Heating is preferably performed after lamination of the
optically functional film. A temperature for the heating is
preferably 50.degree. C. or more, more preferably 55.degree. C. or
more, still more preferably 60.degree. C. or more, particularly
preferably 80.degree. C. or more. It should be noted that the
heating performed after lamination of the optically functional film
may also serve as the drying treatment of the laminate. In
addition, the heating may be performed before or after a peeling
step to be described later, and is preferably performed before the
peeling step.
C. Peeling Step
[0078] The resin substrate is peeled from the optically functional
film laminate. At that time, the peeling is performed so that an
angle .alpha. formed between the surface of the optically
functional film laminate immediately before the peeling and the
peeling direction of the resin substrate maybe smaller than an
angle .beta. formed between the surface of the optically functional
film laminate immediately before the peeling and the peeling
direction of the polarizing film. According to such embodiment, the
resin substrate can be satisfactorily peeled while the occurrence
of a wrinkle, foreign matter (such as a substrate residue), or the
like is suppressed. As a result, a polarizing plate extremely
excellent in external appearance can be obtained. In addition, a
tension needed for the peeling can be reduced and hence a load on
facilities can be alleviated.
[0079] A difference between the angle .beta. and the angle .alpha.
is preferably 60.degree. or more, more preferably 90.degree. to
180.degree.. The angle .alpha. is preferably 30.degree. or less,
more preferably 0.degree. to 20.degree.. The angle .beta. is
preferably 60.degree. or more, more preferably 90.degree. to
180.degree..
[0080] A tension (peel tension) needed for the peeling is
preferably 3.0 N/15 mm or less, more preferably 1.0 N/15 mm or
less, particularly preferably 0.5 N/15 mm or less.
[0081] FIG. 3 is a schematic view illustrating an example of the
peeling step. An optically functional film laminate 100 has the
resin substrate 11, a polarizing film 12', and the optically
functional film 20 in the stated order. In the illustrated example,
the resin substrate 11 is peeled from the optically functional film
laminate 100 by pulling, while conveying the optically functional
film laminate 100 in a substantially horizontal direction, a
laminate (polarizing plate) 50 of the polarizing film 12' and the
optically functional film 20 upward with respect to the conveyance
surface of the optically functional film laminate 100. At the time
of the peeling, the peeling direction of the resin substrate 11 is
substantially the same as the conveyance direction of the optically
functional film laminate 100 immediately before the peeling, and
the peeling direction of the polarizing film 12' is the pulling
direction. Therefore, in the illustrated example, the angle .alpha.
is substantially 0.degree..
[0082] FIG. 4 is a schematic view illustrating another example of
the peeling step. In this illustrated example, the resin substrate
11 is peeled from the optically functional film laminate 100 by
pulling, while conveying the optically functional film laminate 100
so that its resin substrate 11 side may be brought into contact
with a roll 120, the laminate (polarizing plate) 50 of the
polarizing film 12' and the optically functional film 20 in a
direction going away from the roll 120 with respect to the
conveyance surface of the optically functional film laminate 100.
In this example, the surface of the optically functional film
laminate immediately before the peeling is a surface including a
tangent at the point at which the polarizing film 12' goes away. At
the time of the peeling, the peeling direction of the resin
substrate 11 is substantially the same as the conveyance direction
of the optically functional film laminate 100 immediately before
the peeling, and the peeling direction of the polarizing film 12'
is the pulling direction. Therefore, in the illustrated example,
such angle .alpha. as illustrated in FIG. 4 is specified and the
angle .alpha. is smaller than the angle .beta..
[0083] The modulus of elasticity of the resin substrate at the time
of the peeling is typically 2 GPa to 3 GPa. The modulus of
elasticity of the resin substrate before the stretching is
typically 2 GPa to 3 GPa. The modulus of elasticity of the laminate
(polarizing plate) of the polarizing film and the optically
functional film is preferably 4 GPa to 7 GPa. In addition, the
radius of curvature R of the resin substrate (at the time of the
peeling) is typically 1 mm to 10 mm. The radius of curvature R of
the laminate (polarizing plate) of the polarizing film and the
optically functional film is preferably 3 mm to 30 mm. When the
PVA-based resin layer is subjected to a treatment such as
stretching or cross-linking, the rigidity of the polarizing film to
be obtained is high and hence the film can sufficiently resist such
peeling as described above.
[0084] In the peeling step, peeling auxiliary means may be placed
on the optically functional film laminate 100 on the optically
functional film 20 side so that the peeling may be performed more
easily, more satisfactorily, and more stably. Examples of the
peeling auxiliary means include such peeling roll 70 as illustrated
in FIG. 5A and such peeling bar 80 as illustrated in FIG. 5B. The
peeling roll 70 is brought into abutment with the optically
functional film laminate 100 on the optically functional film 20
side and the roll itself aids the peeling while rotating. When the
peeling roll is used, a roll diameter is preferably 5 mm to 80 mm,
more preferably 5 mm to 50 mm, still more preferably 10 mm to 30
mm. When the roll diameter is excessively large, a peel strength
becomes large and hence good peeling cannot be performed in some
cases. When the roll diameter is excessively small, the strength of
the roll becomes insufficient and hence peeling stability becomes
insufficient in some cases. When the peeling bar 80 is used, the
peeling bar typically has a tip portion whose section is of a
semicircular shape, the tip portion is brought into abutment with
the optically functional film laminate 100 on the optically
functional film 20 side, and the bar aids the peeling without
rotating. When the peeling bar is used, the diameter of the tip
portion is preferably 5 mm to 80 mm, more preferably 5 mm to 50 mm,
still more preferably 5 mm to 30 mm. At this time, a surface
protective film may be laminated on a surface of the optically
functional film laminate on the optically functional film side for
preventing the occurrence of a flaw due to the peeling roll or the
peeling bar. Although the surface protective film is not
particularly limited, the surface protective film is typically, for
example, a polyethylene-based film having a pressure-sensitive
adhesive layer provided on its surface, and the film can be
attached to the surface of the optically functional film with the
pressure-sensitive adhesive layer.
EXAMPLES
[0085] Hereinafter, the present invention is specifically described
byway of Examples. However, the present invention is not limited to
Examples shown below. It should be noted that methods of measuring
the respective characteristics are as described below.
1. Thickness
[0086] Measurement was performed with a digital micrometer
(manufactured by ANRITSU CORPORATION, product name: "KC-351C").
2. Glass Transition Temperature (Tg)
[0087] Measurement was performed in conformity with JIS K 7121.
3. Modulus of Elasticity
[0088] A sample was formed into a tensile test dumbbell whose
parallel portion had a width of 10 mm and a length of 40 mm on the
basis of JIS K6734:2000, and then its modulus of elasticity in
tension was determined by performing a tensile test in conformity
with JIS K7161:1994.
4. Radius of Curvature R
[0089] As illustrated in FIG. 2, one end portion in the lengthwise
direction of a test piece having a width of 50 mm was held in a
state where the other end portion thereof was bonded to a
substrate, and was then bent by being pulled in a 180.degree.
direction with respect to the bonding surface with a force of 150
gw. A radius of curvature was determined by measuring the radius of
the bent portion at that time. It should be noted that the test
piece was cut out so that its lengthwise direction corresponded to
a peeling direction.
5. Peel Tension
[0090] One end portion in the lengthwise direction of a test piece
(optically functional film laminate) having a width of 15 mm and a
length of 100 mm was peeled in advance, and then the peeled portion
was held and peeled in a specified angle direction at a rate of 3
m/min. A peel tension was determined by measuring a tension at the
time of the peeling.
Example 1-1
[0091] An amorphous polyethylene terephthalate (A-PET) film
(manufactured by Mitsubishi Chemical Corporation, trade name:
"NOVACLEAR," thickness: 100 .mu.m) having a long shape and having a
percentage of water absorption of 0.60%, a Tg of 80.degree. C., and
a modulus of elasticity of 2.5 GPa was used as a resin
substrate.
[0092] One surface of the resin substrate was subjected to a corona
treatment (treatment condition: 55 Wmim/m.sup.2), and an aqueous
solution containing 90 parts by weight of polyvinyl alcohol
(polymerization degree: 4,200, saponification degree: 99.2 mol %)
and 10 parts by weight of acetoacetyl-modified PVA (polymerization
degree: 1,200, acetoacetyl modification degree: 4.6%,
saponification degree: 99.0 mol % or more, manufactured by The
Nippon Synthetic Chemical Industry Co., Ltd., trade name:
"GOHSEFIMER Z200") was applied onto the surface subjected to the
corona treatment, and was then dried at 60.degree. C. so that a
PVA-based resin layer having a thickness of 10 .mu.m was formed,
thereby producing a laminate.
[0093] The resultant laminate was subjected to free-end uniaxial
stretching in its longitudinal direction (lengthwise direction) at
1.8 times in an oven at 120.degree. C. between rolls having
different peripheral speeds (preliminary in-air stretching).
[0094] Next, the laminate was immersed in an insolubilizing bath
having a liquid temperature of 30.degree. C. (an aqueous solution
of boric acid obtained by compounding 100 parts by weight of water
with 4 parts by weight of boric acid) for 30 seconds
(insolubilizing treatment).
[0095] Next, the laminate was immersed in a dyeing bath having a
liquid temperature of 30.degree. C. (an aqueous solution of iodine
obtained by compounding 100 parts by weight of water with 0.2 part
by weight of iodine and 1.0 part by weight of potassium iodide) for
60 seconds (dyeing treatment).
[0096] Next, the laminate was immersed in a cross-linking bath
having a liquid temperature of 30.degree. C. (an aqueous solution
of boric acid obtained by compounding 100 parts by weight of water
with 3 parts by weight of potassium iodide and 3 parts by weight of
boric acid) for 30 seconds (cross-linking treatment).
[0097] After that, the laminate was uniaxially stretched in its
longitudinal direction (lengthwise direction) between rolls having
different peripheral speeds while being immersed in an aqueous
solution of boric acid having a liquid temperature of 70.degree. C.
(an aqueous solution obtained by compounding 100 parts by weight of
water with 4 parts by weight of boric acid and 5 parts by weight of
potassium iodide) (underwater stretching). In this case, the
laminate was stretched immediately before its rupture (the maximum
stretching ratio was 6.0 times).
[0098] After that, the laminate was immersed in a washing bath
having a liquid temperature of 30.degree. C. (an aqueous solution
obtained by compounding 100 parts by weight of water with 4 parts
by weight of potassium iodide) (washing treatment).
[0099] Subsequently, an aqueous solution of a PVA-based resin
(manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.,
trade name: "GOHSEFIMER (trademark) Z-200," resin concentration: 3
wt %) was applied onto the surface of the PVA-based resin layer of
the laminate. A triacetyl cellulose film having a modulus of
elasticity of 4.0 GPa (manufactured by Konica Minolta, Inc., trade
name: "KC4UY," thickness: 40 .mu.m) was attached to the resultant,
and the whole was heated in an oven maintained at 60.degree. C. for
5 minutes, thereby producing an optically functional film laminate
having a polarizing film with a thickness of 5 .mu.m.
[0100] The resultant optically functional film laminate was mounted
on a flat table so that its resin substrate was on a lower side,
and then peeling was performed in a state where end portions of the
PVA-based resin layer (polarizing film) and the triacetyl cellulose
film were held at 90.degree. with respect to the flat table (peel
angle .beta.: 90.degree.). Thus, a polarizing plate was
obtained.
[0101] The polarizing plate had a modulus of elasticity of 6.0 GPa
and a radius of curvature R of 5 mm, and the peeled resin substrate
had a modulus of elasticity of 2.5 GPa and a radius of curvature R
of 2 mm.
Example 1-2
[0102] A polarizing plate was obtained in the same manner as in
Example 1-1 except that the peel angle .beta. was changed to
150.degree..
Example 1-3
[0103] A polarizing plate was obtained in the same manner as in
Example 1-1 except that: a polyethylene-based surface protective
film (manufactured by Sun A. Kaken Co., Ltd., PAC-3, thickness: 30
.mu.m) was attached to a surface of the optically functional film
laminate on the triacetyl cellulose film side, and such peeling
roll (roll diameter: 20 mm) as illustrated in FIG. 5A was brought
into abutment with the film; and the peel angle .beta. was changed
to 120.degree.. Continuous peeling of the roll-shaped optically
functional film laminate was able to be performed more stably by
using the peeling roll.
Example 1-4
[0104] A polarizing plate was obtained in the same manner as in
Example 1-1 except that: a polyethylene-based surface protective
film (manufactured by Sun A. Kaken Co., Ltd., PAC-3, thickness: 30
.mu.m) was attached to a surface of the optically functional film
laminate on the triacetyl cellulose film side, and such peeling bar
(diameter of tip portion: 5 mm) as illustrated in FIG. 5B was
brought into abutment with the film; and the peel angle .beta. was
changed to 120.degree.. Continuous peeling of the roll-shaped
optically functional film laminate was able to be performed more
stably by using the peeling bar in the same manner as in Example
1-3.
Comparative Example 1-1
[0105] An optically functional film laminate obtained in the same
manner as in Example 1-1 was mounted on a flat table so that its
triacetyl cellulose film was on a lower side, and then peeling was
attempted in a state where an end portion of the resin substrate
was held at 90.degree. with respect to the flat table (peel angle
.alpha.:90.degree.).
Comparative Example 1-2
[0106] Peeling was attempted in the same manner as in Comparative
Example 1-1 except that the peel angle .alpha. was changed to
150.degree..
Example 2
[0107] A norbornene-based resin film (manufactured by JSR
Corporation, trade name: "ARTON," thickness: 150 .mu.m) having a
long shape, a Tg of 130.degree. C., and a modulus of elasticity of
2 GPa was used as a resin substrate.
[0108] An aqueous solution of a polyvinyl alcohol (PVA) resin
(manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.,
trade name: "GOHSENOL (registered trademark) NH-26") having a
polymerization degree of 2,600 and a saponification degree of 99.0
mol % was applied onto one surface of the resin substrate, and was
then dried at 80.degree. C. so that a PVA-based resin layer having
a thickness of 7 .mu.m was formed, thereby producing a
laminate.
[0109] The resultant laminate was stretched in its widthwise
direction at a stretching ratio of up to 4.5 times under heating at
140.degree. C. with a tenter apparatus by free-end uniaxial
stretching. The thickness of the PVA-based resin layer after the
stretching treatment was 3 .mu.m (in-air stretching).
[0110] Next, the laminate was immersed in a dyeing bath having a
liquid temperature of 30.degree. C. (an aqueous solution of iodine
obtained by compounding 100 parts by weight of water with 0.5 part
by weight of iodine and 3.5 parts by weight of potassium iodide)
for 60 seconds (dyeing treatment).
[0111] Next, the laminate was immersed in a cross-linking bath
having a liquid temperature of 60.degree. C. (an aqueous solution
of boric acid obtained by compounding 100 parts by weight of water
with 5 parts by weight of potassium iodide and 5 parts by weight of
boric acid) for 60 seconds (cross-linking treatment).
[0112] After that, the laminate was immersed in a washing bath (an
aqueous solution obtained by compounding 100 parts by weight of
water with 3 parts by weight of potassium iodide), and was then
dried with warm air at 60.degree. C. (washing and drying
treatments).
[0113] Subsequently, an aqueous solution of a PVA-based resin
(manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.,
trade name: "GOHSEFIMER (trademark) Z-200," resin concentration: 3
wt %) was applied onto the surface of the PVA-based resin layer of
the laminate. A norbornene-based resin film having a modulus of
elasticity of 2 GPa (manufactured by JSR Corporation, trade name:
"ARTON," thickness: 35 .mu.m) was attached to the resultant, and
the whole was heated in an oven maintained at 80.degree. C. for 5
minutes, thereby producing an optically functional film laminate
having a polarizing film with a thickness of 3 .mu.m.
[0114] The resultant optically functional film laminate was mounted
on a flat table so that its resin substrate was on a lower side,
and then peeling was performed in a state where end portions of the
PVA-based resin layer (polarizing film) and the norbornene-based
resin film were held at 90.degree. with respect to the flat table
(peel angle .beta.: 90.degree.). Thus, a polarizing plate was
obtained.
[0115] The polarizing plate had a modulus of elasticity of 5.0 GPa
and a radius of curvature R of 5 mm, and the peeled resin substrate
had a modulus of elasticity of 2.5 GPa and a radius of curvature R
of 2 mm.
Comparative Example 2
[0116] An optically functional film laminate obtained in the same
manner as in Example 2 was mounted on a flat table so that its
norbornene-based resin film was on a lower side, and then peeling
was attempted in a state where an end portion of the resin
substrate was held at 90.degree. with respect to the flat table
(peel angle .alpha.:90.degree.).
[0117] The polarizing plates obtained in Examples and Comparative
Examples were evaluated for their external appearances by visual
observation. Table 1 shows the results of the evaluation together
with the results of the measurement of their peel tensions. It
should be noted that evaluation criteria for the external
appearances are as described below.
(Evaluation Criteria for External Appearance)
[0118] Good: The resin substrate was able to be continuously peeled
in a lengthwise direction, and neither a wrinkle nor foreign matter
(such as a substrate residue) was observed in the resultant
polarizing plate. Bad: It was difficult to continuously peeling the
resin substrate, and a wrinkle or foreign matter occurred in the
resultant polarizing plate.
TABLE-US-00001 TABLE 1 External Peel Stretching Peel appear-
tension Peeling mode angle ance (N/15 mm) auxiliary Example 1-1
Underwater .beta.: 90.degree. Good 0.2 -- Example 1-2 Underwater
.beta.: 150.degree. Good 0.2 -- Example 1-3 Underwater .beta.:
120.degree. Good 0.2 Peeling roll Example 1-4 Underwater .beta.:
120.degree. Good 0.2 Peeling bar Comparative Underwater .alpha.:
90.degree. Bad 9.0 -- Example 1-1 Comparative Underwater .alpha.:
150.degree. Bad 12.0 -- Example 1-2 Example 2 In-air .beta.:
90.degree. Good 0.2 -- Comparative In-air .alpha.: 90.degree. Bad
9.0 -- Example 2
[0119] The polarizing plate of the present invention is suitably
used for liquid crystal panels of, for example, liquid crystal
televisions, liquid crystal displays, cellular phones, digital
cameras, video cameras, portable game machines, car navigation
systems, copying machines, printers, facsimile machines, clocks,
and microwave ovens. The polarizing film of the present invention
is also suitably used as an antireflection film for an organic EL
device.
[0120] Many other modifications will be apparent to and be readily
practiced by those skilled in the art without departing from the
scope and spirit of the invention. It should therefore be
understood that the scope of the appended claims is not intended to
be limited by the details of the description but should rather be
broadly construed.
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