U.S. patent application number 12/093190 was filed with the patent office on 2009-06-25 for system and method for manufacturing optical display.
This patent application is currently assigned to NITTO DENKO CORPORATION. Invention is credited to Hideo Abe, Yasushi Nakahira.
Application Number | 20090159175 12/093190 |
Document ID | / |
Family ID | 38048415 |
Filed Date | 2009-06-25 |
United States Patent
Application |
20090159175 |
Kind Code |
A1 |
Nakahira; Yasushi ; et
al. |
June 25, 2009 |
SYSTEM AND METHOD FOR MANUFACTURING OPTICAL DISPLAY
Abstract
An object of the invention is to provide an optical display
manufacturing system or method that allows an increase in the yield
of an optical film, a reduction in cost and an improvement in
inventory control. An optical display manufacturing system includes
feeding means (11, 14) that feeds a belt and sheet-shaped product
(3) having an optical film from a roll (4) of the belt and
sheet-shaped product, detection means (12) that detects a defect of
the belt and sheet-shaped product fed by the feeding means, cutting
means (13) that cuts the belt and sheet-shaped product into
individual sheet-shaped products based on the result of the
detection, transfer means (16) that transports each of the
sheet-shaped products from the cutting process to a sticking
process, and sticking means (17) that sticks the transported
sheet-shaped product to an optical display unit.
Inventors: |
Nakahira; Yasushi; (Osaka,
JP) ; Abe; Hideo; (Osaka, JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW, SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
NITTO DENKO CORPORATION
Ibaraki-shi, Osaka
JP
|
Family ID: |
38048415 |
Appl. No.: |
12/093190 |
Filed: |
October 2, 2006 |
PCT Filed: |
October 2, 2006 |
PCT NO: |
PCT/JP2006/319660 |
371 Date: |
May 9, 2008 |
Current U.S.
Class: |
156/64 |
Current CPC
Class: |
Y10T 156/1062 20150115;
Y10T 156/1052 20150115; B32B 38/0004 20130101; Y10T 156/1084
20150115; Y10T 156/12 20150115; B32B 37/182 20130101; G02F 1/1303
20130101; Y10T 156/1057 20150115; B32B 2038/042 20130101; Y10T
156/1056 20150115; B32B 2457/202 20130101; G02F 1/133528 20130101;
B32B 41/00 20130101 |
Class at
Publication: |
156/64 |
International
Class: |
B32B 37/00 20060101
B32B037/00; B32B 38/00 20060101 B32B038/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 17, 2005 |
JP |
2005-332740 |
Claims
1. An optical display manufacturing system, comprising: feeding
means that feeds a belt and sheet-shaped product comprising at
least an optical film as a component of the optical display from a
roll of the belt and sheet-shaped product; detection means that
detects a defect of the belt and sheet-shaped product fed by the
feeding means; cutting means that cuts the belt and sheet-shaped
product into individual sheet-shaped products based on a result of
the detection by the detection means; transfer means that
transports each of the sheet-shaped products from the cutting means
to a sticking process; and sticking means that sticks the
sheet-shaped product transported by the transfer means to an
optical display unit as another component of the optical display,
wherein all of the means are placed on a continuous manufacturing
line.
2. The optical display manufacturing system according to claim 1,
wherein the belt and sheet-shaped product has a pressure-sensitive
adhesive for sticking to the optical display unit and a release
film for protecting the pressure-sensitive adhesive, and the system
further comprises separating means that separates the release film
from the belt and sheet-shaped product before the detection of a
defect by the detection means and cleaning means that cleans the
belt and sheet-shaped product from which the release film has been
separated, before the detection of a defect by the detection
means.
3. The optical display manufacturing system according to claim 1 or
2, further comprising second detection means that detects a defect
after the sticking by the sticking means.
4. A method for manufacturing an optical display, comprising the
steps of: feeding a belt and sheet-shaped product comprising an
optical film as a component of the optical display from a roll of
the belt and sheet-shaped product; detecting a defect of the belt
and sheet-shaped product supplied by the feeding step; cutting the
belt and sheet-shaped product into individual sheet-shaped products
based on a result of the detection in the detecting step;
transferring each of the sheet-shaped products from the cutting
step; and sticking the sheet-shaped product transported by the
transferring step to an optical display unit as another component
of the optical display, wherein all of the steps are performed on a
continuous manufacturing line.
Description
TECHNICAL FIELD
[0001] The invention relates to systems and methods for
manufacturing optical displays. More specifically, the invention
relates to a system and method for manufacturing an optical display
including a laminate of a belt- or sheet-shaped product and an
optical display unit.
BACKGROUND ART
[0002] According to conventional techniques, optical film makers
manufacture a roll of a belt and sheet-shaped product having an
optical film component in a continuous manner. Examples of the
"belt and sheet-shaped product" include a raw polarizing plate, a
raw retardation plate, and a raw laminated film of a polarizing
plate and a retardation plate each for use in liquid crystal
displays. The optical film component is supplied to panel makers
who assemble the optical film component (such as a polarizing plate
and a retardation plate) and an optical display unit (such as a
sealed glass substrate unit containing a liquid crystal cell) from
the optical film makers. The optical film makers punch a desired
size pieces, which is desired by the panel makers, from the belt
and sheet-shaped product and pack a pile of several punched
sheet-shaped product pieces for delivery.
[0003] A pressure-sensitive adhesive is used to stick the
sheet-shaped product to the optical display unit. The
pressure-sensitive adhesive is previously provided as a layer on
the sheet-shaped product, and a release film is further provided to
protect the pressure-sensitive adhesive layer. In the process of
punching pieces from the sheet-shaped product, therefore, the
pressure-sensitive adhesive layer can be squeezed out of the
punched section. When a pile of several pieces is packed, the
squeezing out of the pressure-sensitive adhesive layer
(pressure-sensitive adhesive) can cause sticking of the layered
sheet-shaped products and can further cause scratches or stains on
the surface of the sheet-shaped products to degrade the quality.
Against the problem, it is proposed that the end face of the
sheet-shaped product should be worked after the punching so that
the influence of the squeezing out of the pressure-sensitive
adhesive layer can be reduced (see Patent Literature 1 listed
below).
[0004] Patent Literature 1: Japanese Patent Application Laid-Open
(JP-A) No. 2004-167673
DISCLOSURE OF INVENTION
Problems to be Solved by the Invention
[0005] The processes of piling several punched sheet-shaped
products and packing the resulting pile require a high-cleanliness
working environment such that dust, soil and so on can be
prevented. In order to prevent scratches, cracks and so on during
transportation, the packing material is carefully selected, and the
packing process is also carefully performed.
[0006] On the other hand, panel makers use the carefully packed
sheet-shaped products for assembling. However, unpacking of the
carefully packed products is laboring and must be carefully
conducted so as not to cause scratches or cracks, which is a
significant work load.
[0007] After the unpacking, dust or soil must be cleaned from each
individual sheet-shaped product, which is a complicated task.
[0008] The punched sheet-shaped product with a scratch or crack
formed during the process of packing, transferring or unpacking is
determined as a defective product. Therefore, there has been
demanded for a solution to the problem of a reduction in the
product yield or high cost, which is caused by a relatively large
number of processes or a complicated process. Since optical
displays as final products vary widely in terms of type and size, a
wide variety of sheet-shaped products are produced by cutting and
punching. For example, if there are 50 types of optical displays,
individual makers should manufacture, stock and manage 50 types of
sheet-shaped products corresponding thereto. However, properly
stocking and managing all types of sheet-shaped products is a very
complicated task, and inventory control under proper conditions
requires an adequate warehouse space (in a clean room
environment).
[0009] The invention has been made under the circumstances
described above, and it is an object of the invention to provide a
system and a method for manufacturing an optical display which
allow an improvement in the yield of optical film components, a
reduction in cost and an improvement in inventory control.
Means for Solving the Problems
[0010] As a result of investigations for solving the problems, the
invention described below has been completed.
[0011] The invention is directed to an optical display
manufacturing system, including: feeding means that feeds a belt
and sheet-shaped product including an optical film as a component
of the optical display from a roll of the belt and sheet-shaped
product; detection means that detects a defect of the belt and
sheet-shaped product fed by the feeding means; cutting means that
cuts the belt and sheet-shaped product into individual sheet-shaped
products based on a result of the detection by the detection means;
transfer means that transports each of the sheet-shaped products
from the cutting means to a sticking process; and sticking means
that sticks the sheet-shaped product transported by the transfer
means to an optical display unit as another component of the
optical display, wherein all of the means are placed on a
continuous manufacturing line.
[0012] The effects of the invention are described below. The
optical display includes at least the optical film and the optical
display unit. The belt and sheet-shaped product includes at least
an optical film layer and optionally, for example, a protective
film layer. The belt and sheet-shaped product is long and provided
in the form of a roll. The belt and sheet-shaped product is fed
from the roll, when whether or not defects such as stains,
scratches and cracks are present is detected by the detection
means.
[0013] According to the result of the detection, the belt and
sheet-shaped product is cut into specific size pieces. The
"specific size" depends on the size of the optical display product.
When a certain defect is found as a result of the detection, for
example, the cutting means is controlled such that the defect can
be removed while specific size cut pieces can be produced. The
sheet-shaped product obtained by cutting is then transferred to a
sticking process. The transferred sheet-shaped product is stuck to
the optical display unit by the sticking means. All of these means
are placed on a continuous manufacturing line.
[0014] In the above manufacturing system, desired size pieces can
be directly obtained by cutting from the belt and sheet-shaped
product having the optical film and each stuck to the optical
display unit. Therefore, a roll of the belt and sheet-shaped
product can be directly packed and delivered to panel makers in
contrast to the conventional technique where the belt and
sheet-shaped product is subjected to punching, and punched
sheet-shaped products are carefully packed and supplied to panel
makers. Packing the roll allows easy selection of the packing
material, allows simple packing operation with no need of a
conventional packing tool or instrument for piling and packing
sheet-shaped cut products and allows a reduction in the work load.
There is also no need to perform the conventional end face working,
which is also significantly advantageous for optical film component
makers because of a reduction in the number of working
processes.
[0015] Panel makers to which the products are supplied can easily
perform the unpacking so that the work load can be reduced.
Transferring the roll can also reduce the occurrence of scratches,
cracks and so on and can prevent quality degradation.
[0016] In addition, the packing material can be simple, and the
packing material cost and the occurrence of scratches, cracks and
so on during the transportation can be reduced, so that the cost
performance of the whole of the product can be significantly
increased. It is also unnecessary for optical film component makers
to cut sheet-shaped products depending on the type and size of the
final optical display product or to stock and manage individual
sheet-shaped products. The belt and sheet-shaped product itself (in
the form of a raw roll) can be stored and managed so that inventory
control can be simplified and that control management can be
significantly improved. This is also advantageous for panel makers,
because it is possible to stock and manage only a single type or
few types of row rolls of the belt and sheet-shaped product and to
cut a necessary portion (size) in a necessary form for use in
manufacture so that expensive optical film stocks can be
significantly reduced. According to the invention, therefore, both
makers can significantly increase the productivity.
[0017] In a preferred embodiment of the invention, the belt and
sheet-shaped product has a pressure-sensitive adhesive for sticking
to the optical display unit and a release film for protecting the
pressure-sensitive adhesive, and the system further includes
separating means that separates the release film from the belt and
sheet-shaped product before the detection of a defect by the
detection means and cleaning means that cleans the belt and
sheet-shaped product from which the release film has been
separated, before the detection of a defect by the detection
means.
[0018] In this embodiment, the belt and sheet-shaped product
further includes a pressure-sensitive adhesive for sticking the
optical display unit and a release film for protecting the
pressure-sensitive adhesive. Before a defect is detected by the
detection means, the release film is separated from the belt and
sheet-shaped product, and the resulting belt and sheet-shaped
product is cleaned by the cleaning means so that dust and soil can
be removed. According to these features, the detection means can
precisely detect scratches, cracks, stains and so on of the optical
film component, while scratches, stains and so on of the release
film are not detected.
[0019] In another preferred embodiment of the invention, the system
further includes second detection means that detects a defect after
the sticking by the sticking means.
[0020] According to this feature, any defect of a laminate of the
optical display unit and the sheet-shaped product can be
immediately detected after the sticking. As a result of the
detection, for example, when a defect is detected on the
sheet-shaped product side (the optical film component), the
sheet-shaped product (the optical film component) may be separated
from the optical display unit, and the separated optical display
unit may be recycled (hereinafter this process is referred to as
"reworking").
[0021] The invention is also directed to a method for manufacturing
an optical display, including the steps of: feeding a belt and
sheet-shaped product including an optical film as a component of
the optical display from a roll of the belt and sheet-shaped
product; detecting a defect of the belt and sheet-shaped product
supplied by the feeding step; cutting the belt and sheet-shaped
product into individual sheet-shaped products based on a result of
the detection in the detecting step; transferring each of the
sheet-shaped products from the cutting step; and sticking the
sheet-shaped product transported by the transferring step to an
optical display unit as another component of the optical display,
wherein all of the steps are performed on a continuous
manufacturing line. The effects of this aspect are the same as
those described above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a schematic diagram of the entire configuration of
a manufacturing system;
[0023] FIG. 2 is a diagram showing an example of sticking means;
and
[0024] FIG. 3 is a flowchart of a manufacturing method.
DESCRIPTION OF REFERENCE MARKS
[0025] In the drawings, reference mark 3 represents a row
polarizing plate, 3a a polarizing plate, 4 a roll, 5 an optical
display unit, 11 feeding rollers (feeding means), 12 detection
means, 13 cutting means, 14 suction means (feeding means), 16
suction means (transfer means), 17 a roller component (sticking
means), and 18 second detection means.
BEST MODE FOR CARRYING OUT THE INVENTION
[0026] Preferred embodiments of the invention are described below.
Sheet-Shaped Product, Optical Display Unit and Optical Display
[0027] A description is given of some embodiments using a raw
polarizing plate as an example of the sheet-shaped product to be
handled according to the invention. The raw polarizing plate is in
the form of a long film, and polarizing plates each with a specific
size are punched (or cut) from the film-shaped raw polarizing
plate. For example, the raw polarizing plate may be produced by
sticking a triacetylcellulose film (transparent protective film) to
both the front and back sides of a previously prepared polyvinyl
alcohol film (polarizer). It is necessary to detect whether or not
defects (such as scratches and foreign matter) are present on the
surface of or in the interior of the raw polarizing plate with such
a multilayer structure. The defects are detected by the detection
means described later.
[0028] The raw polarizing plate may be produced by a manufacturing
method including the steps of: (A) dyeing, crosslinking,
stretching, and drying a polyvinyl alcohol film to form a
polarizer; (B) sticking a protective layer to one or both sides of
the polarizer; and (C) heating the resulting laminate.
[0029] The processes of dyeing, crosslinking and stretching the
polyvinyl alcohol film are not necessarily independently performed
and may be performed at the same time or in any order. The
polyvinyl alcohol film may be subjected to a swelling process
before use. A general process may include the steps of immersing
the polyvinyl alcohol film in a solution containing iodine or a
dichroic dye so that the film is dyed with the iodine or the
dichroic dye being adsorbed thereon, then washing the film,
uniaxially stretching the film at a stretching ratio of 3 to 7
times in a solution containing boric acid, borax or the like, and
then drying the film. It is particularly preferred that the step of
stretching the film in a solution containing iodine or a dichroic
dye should be followed by the steps of stretching the film in a
solution containing boric acid, borax or the like (two-stage
stretching) and then drying the film, so that the iodine can be
highly oriented to provide good polarizing properties.
[0030] For example, the polyvinyl alcohol polymer may be a polymer
produced by polymerizing vinyl acetate and then saponifying the
polymer or a copolymer produced by copolymerizing vinyl acetate
with a small amount of a copolymerizable monomer such as an
unsaturated carboxylic acid, an unsaturated sulfonic acid, or a
cationic monomer. The average polymerization degree of the
polyvinyl alcohol polymer is preferably, but not limited to, 1,000
or more, more preferably from 2,000 to 5,000. The saponification
degree of the polyvinyl alcohol polymer is preferably 85% by mole
or more, more preferably from 98 to 100% by mole.
[0031] The thickness of the prepared polarizer is generally, but
not limited to, from 5 to 80 .mu.m. The thickness of the polarizer
may be controlled by any conventional method such as tentering,
roll stretching, and rolling.
[0032] No limitation is set on the process of boding the polarizer
to the transparent protective film as the protective layer. For
example, it may be performed using an adhesive comprising a vinyl
alcohol polymer or an adhesive comprising a vinyl alcohol polymer
and a water-soluble crosslinking agent therefor such as boracic
acid, borax, glutaraldehyde, melamine, and oxalic acid. The
adhesive layer may be formed by applying and drying an aqueous
solution layer. In the process of preparing the aqueous solution,
if necessary, any other additive or a catalyst such as an acid may
also be added.
[0033] Any appropriate transparent film may be used as the
protective film to be placed on one or both sides of the polarizer.
In particular, a film comprising a polymer with a high level of
transparency, mechanical strength, thermal stability, or
water-blocking performance is preferably used. Examples of such a
polymer include acetate resins such as triacetylcellulose,
polycarbonate resins, polyester resins such as polyarylate and
polyethylene terephthalate, polyimide resins, polysulfone resins,
polyethersulfone resins, polystyrene resins, polyolefin resins such
as polyethylene and polypropylene, polyvinyl alcohol resins,
polyvinyl chloride resins, polynorbornene resins, poly(methyl
methacrylate) resins, and liquid crystal polymers. The film may be
produced by any of a casting method, a calender method and an
extrusion method.
[0034] The polymer film disclosed in JP-A No. 2001-343529
(WO01/37007) may also be used, for example, which comprises a resin
composition containing (A) a thermoplastic resin having a
substituted and/or unsubstituted imide group in the side chain and
(B) a thermoplastic resin having a substituted and/or unsubstituted
phenyl and nitrile groups in the side chain. Specifically, the film
comprises a resin composition containing an alternating copolymer
of isobutylene and N-methylmaleimide and an acrylonitrile-styrene
copolymer. The film may be produced by mixing-extrusion of the
resin composition. These films have a low level of retardation and
photoelastic coefficient and thus can prevent polarizing plates
from having defects such as strain-induced unevenness. They also
have low water-vapor permeability and thus have good humidity
durability.
[0035] The protective film is preferably as colorless as possible.
Therefore, the protective film to be used preferably has a
retardation of -90 nm to +75 nm in its thickness direction, wherein
the retardation (Rth) in the thickness direction is expressed by
the formula Rth=[(nx+ny)/2-nz]d, wherein nx and ny are each the
principal in-plane refractive index of the film, nz is the
refractive index of the film in its thickness direction, and d is
the thickness of the film. If the protective film used has a
retardation (Rth) of -90 nm to +75 nm in its thickness direction,
protective film-induced coloration of polarizing plates (optical
coloration) can be substantially avoided. The retardation (Rth) in
the thickness direction is more preferably from -80 nm to +60 nm,
particularly preferably from -70 nm to +45 nm.
[0036] In view of polarizing properties and durability, acetate
resins such as triacetylcellulose are preferred, and a
triacetylcellulose film whose surface has been saponified with an
alkali is particularly preferred. When a transparent protective
film is provided on both sides of the polarizing film, the front
and back transparent protective films may comprise different
polymers.
[0037] While the protective film may have any thickness, it
generally has a thickness of 500 .mu.m or less, preferably of 1 to
300 .mu.m, particularly preferably of 5 to 200 .mu.m, in order to
form a relatively thin polarizing plate. When a transparent
protective film is provided on both sides of the polarizing film,
the front and back transparent protective films may comprise
different polymers.
[0038] The transparent protective film may be subjected to hard
coat treatment, anti-reflection treatment, anti-sticking treatment,
diffusion or antiglare treatment, or the like, as long as the
effects of the invention are not reduced. Hard coat treatment may
be performed in order to prevent scratches on the polarizing plate
surface and the like. The hard coat may be formed by a method
including making a cured film with a high level of hardness and
smoothness on the surface of the transparent protective film from
an appropriate ultraviolet-curable resin such as a silicone
resin.
[0039] Anti-reflection treatment may be performed in order to
prevent reflection of external light on the polarizing plate
surface. It may be achieved by forming an anti-reflection film or
the like according to conventional techniques. Anti-sticking
treatment may be performed in order to prevent sticking to the
adjacent layer, and antiglare treatment may be performed in order
to prevent interference from reflection of external light on the
polarizing plate surface to visibility of light transmitted through
the polarizing plate. The anti-sticking or antiglare part may be
formed by providing fine irregularities on the surface of the
transparent protective film by any appropriate method such as a
surface roughening method such as sand blasting and embossing or a
method of mixing transparent fine particles.
[0040] For example, the transparent fine particles may be silica,
alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide,
antimony oxide, or the like with an average particle size of 0.5 to
20 .mu.m. Electrically-conductive inorganic fine particles or
organic fine particles of a crosslinked or uncrosslinked
particulate polymer may also be used. The transparent fine
particles are generally used in an amount of 2 to 70 parts by mass,
particularly in an amount of 5 to 50 parts by mass, based on 100
parts by mass of the transparent resin.
[0041] The transparent fine particles-containing antiglare layer
may also be formed as the transparent protective layer itself or as
a coating layer on the surface of the transparent protective layer.
The antiglare layer may also serves as a diffusion layer (with a
viewing angle compensation function or the like) to diffuse light
being transmitted through the polarizing plate and to expand the
viewing angle. The anti-reflection layer, the anti-sticking layer,
the diffusion layer, the antiglare layer, or the like may be
provided as an optical layer of a sheet having such a functional
layer independent of the transparent protective layer.
[0042] In an embodiment of the invention, the sheet-shaped product
may be a laminate including any of various optical layers and may
be used as an optical film for practical use. Examples of the
optical layers for such a laminate include, but are not limited to,
layers formed by hard coat treatment, anti-reflection treatment, or
surface treatment for an anti-sticking, diffusion or antiglare
purpose, on the transparent protective film surface to which no
polarizer is stuck (the surface on which the adhesive coating layer
is not provided) and oriented liquid crystal layers for viewing
angle compensation or the like. The sheet-shaped product may also
be a laminate including one or more layers of an optical film or
films for use in forming liquid crystal displays or the like, and
examples of such an optical film include a reflector, a
transflector (or a semitransparent reflector), a retardation plate
(including a wave plate (.lamda. plate) such as a half-wave plate
(.lamda./2 plate) and a quarter wavelength plate (.lamda./4
plate)), and a viewing angle compensation film. In particular, the
sheet-shaped product for use as a polarizing plate is preferably a
reflector- or transflector-laminated reflective or transflective
polarizing plate, a retardation plate-laminated elliptically or
circularly polarizing plate, a viewing angle compensation layer- or
film-laminated, wide-viewing-angle, polarizing plate, or a
brightness enhancement film-laminated polarizing plate.
[0043] The reflective polarizing plate includes a polarizing plate
and a reflective layer formed thereon and may be used to form a
certain type liquid crystal display in which light incident on the
viewer side (display side) is reflected and displayed. It has the
advantage that a built-in light source such as a backlight can be
omitted so that a thin liquid crystal display can be easily
produced. The reflective polarizing plate may be formed by any
appropriate method such as a method including forming a reflective
layer of metal or the like on one side of a polarizing plate with
an optional transparent protective layer or the like interposed
therebetween.
[0044] In the reflective polarizing plate, for example, the
reflective layer is formed by providing a foil or vapor-deposited
film of a reflective metal such as aluminum on one side of the
transparent protective film that is optionally matte-finished.
Alternatively, the transparent protective film may contain fine
particles so as to form a fine irregular surface structure, and the
reflective layer formed thereon may have fine irregularities. The
reflective layer with fine irregularities has the advantage that
incident light can be diffused by irregular reflection so that
directional bias or glare can be prevented and that uneven
brightness or darkness can be reduced. The fine
particles-containing transparent protective film also has the
advantage that when transmitted therethrough, incident light and
reflected light therefrom can be diffused so that uneven brightness
or darkness can be further reduced. The reflective layer having
fine irregularities corresponding to the fine irregular surface
structure of the transparent protective film may be formed by a
method including directly depositing a metal on the surface of the
transparent protective layer by a vapor deposition method such as
vacuum deposition, ion plating and sputtering, a plating method or
any other appropriate method.
[0045] Instead of the method of direct deposition on the
transparent protective film of the polarizing plate, the reflector
may be used in the form of a reflective sheet including an
appropriate film corresponding to the transparent film and a
reflective layer formed thereon. The reflective layer is generally
made of a metal. In order to prevent an oxidation-induced reduction
in reflectance and to keep the initial reflectance for a long time
or in order to avoid the formation of an additional protective
layer, therefore, the reflective surface is preferably covered with
the transparent protective film, the polarizing plate or the like,
when used.
[0046] The transflective polarizing plate may be produced by the
method described above, except that a transflective layer capable
of reflecting and transmitting light such as a half mirror is used
in place of the reflective layer. The transflective polarizing
plate is generally placed on the back side of a liquid crystal cell
to form a certain type liquid crystal display in which an image is
displayed by reflecting light incident on the viewer side (display
side) during operation in a relatively bright place, and an image
is displayed using a built-in light source, such as a backlight,
placed on the back side of the transflective polarizing plate
during operation in a relatively dark place. Therefore, the
transflective polarizing plate is useful for forming a certain type
liquid crystal display that uses a built-in light source such as a
backlight in a relatively dark place, while saving the energy of
the available light source in a relatively bright place.
[0047] A description is given of the elliptically or circularly
polarizing plate including a polarizing plate and a retardation
plate placed thereon. Retardation plates or the like are used to
convert linearly polarized light into elliptically or circularly
polarized light, to convert elliptically or circularly polarized
light into linearly polarized light or to change the direction of
polarization of linearly polarized light. Specifically, so-called
quarter wavelength plates (also referred to as .lamda./4 plates)
are used as retardation plates for converting linearly polarized
light into circularly polarized light or converting circularly
polarized light into linearly polarized light. Half-wave plates
(also referred to as .lamda./2 plates) are generally used to change
the direction of polarization of linearly polarized light.
[0048] The elliptically polarizing plate is effectively used in
cases where coloration (blue or yellow) caused by the birefringence
of a liquid crystal layer in a super-twisted nematic (STN) liquid
crystal display should be compensated for (canceled) such that
white and black can be displayed without the coloration. The
elliptically polarizing plate with controlled three-dimensional
refractive indices is also preferred, because it can also
compensate for (cancel) coloration that occurs when the screen of a
liquid crystal display is obliquely viewed. For example, the
circularly polarizing plate is effectively used in cases where the
tone of color images displayed by a reflective liquid crystal
display should be adjusted. The circularly polarizing plate can
also have an anti-reflection function.
[0049] The retardation plate may also be used. Examples of the
retardation plate include birefringent films produced by uniaxially
or biaxially stretching polymer materials, oriented liquid crystal
polymer films, and oriented liquid crystal polymer layers supported
on films. The stretching process may be typically performed by roll
stretching, long-gap stretching, tenter stretching, or tubular
stretching. Uniaxial stretching is generally performed at a
stretching ratio of about 1.1 to about 3 times. The thickness of
the retardation plate is generally, but not limited to, from 10 to
200 .mu.m, preferably from 20 to 100 .mu.m.
[0050] Examples of the polymer materials include polyvinyl alcohol,
polyvinyl butyral, poly(methyl vinyl ether), poly(hydroxyethyl
acrylate), hydroxyethyl cellulose, hydroxypropyl cellulose,
methylcellulose, polycarbonate, polyarylate, polysulfone,
polyethylene terephthalate, polyethylene naphthalate,
polyethersulfone, polyphenylene sulfide, polyphenylene oxide,
polyallylsulfone, polyvinyl alcohol, polyamide, polyimide,
polyolefin, polyvinyl chloride, cellulose polymers, and various
types of binary or ternary copolymers thereof, graft copolymers
thereof, and any blend thereof. Any of these polymer materials may
be formed into an oriented product (a stretched film) by stretching
or the like.
[0051] Examples of the liquid crystal polymer include various
main-chain or side-chain types having a conjugated linear atomic
group (mesogen) that is introduced in the main or side chain of the
polymer to impart liquid crystal molecular orientation. Examples of
the main chain type liquid crystal polymer include polymers having
a mesogen group bounded thereto through a flexibility-imparting
spacer moiety, such as nematically ordered polyester
liquid-crystalline polymers, discotic polymers, and cholesteric
polymers. For example, the side-chain type liquid crystal polymer
may be a polymer comprising: a main chain skeleton of polysiloxane,
polyacrylate, polymethacrylate, or polymalonate; and a side chain
having a mesogen moiety that comprises a nematic
orientation-imparting para-substituted cyclic compound unit and is
bonded thereto through a spacer moiety comprising a conjugated
atomic group. For example, any of these liquid crystal polymers may
be applied by a process that includes: spreading a solution of the
liquid crystalline polymer on an alignment surface, such as a
rubbed surface of a thin film of polyimide, polyvinyl alcohol or
the like or an obliquely vapor-deposited silicon oxide surface,
formed on a glass plate; and heat-treating the solution.
[0052] The retardation plate may have any appropriate retardation
depending on the intended use such as compensation for coloration,
viewing angle, or the like associated with the birefringence of
various wave plates or liquid crystal layers. Two or more types of
retardation plates may also be laminated to provide controlled
optical properties such as controlled retardation.
[0053] The viewing angle compensation film is for expanding the
viewing angle such that images can be relatively clearly viewed
even when the screen of a liquid crystal display is viewed from
directions not perpendicular but somewhat oblique to the screen.
Examples of such a viewing angle compensation retardation plate
include a retardation film, an oriented film of a liquid crystal
polymer or the like, and an oriented layer of a liquid crystal
polymer or the like supported on a transparent substrate. General
retardation plates are produced with a polymer film that is
uniaxially stretched in the in-plane direction and has
birefringence. On the other hand, retardation plates for use as the
viewing angle compensation film are produced with a
bi-directionally stretched film such as a polymer film that is
biaxially stretched in the in-plane direction and has
birefringence, a polymer film that is uniaxially stretched in the
in-plane direction and also stretched in the thickness direction so
that it has a controlled refractive index in the thickness
direction and has birefringence, and an obliquely oriented film.
Examples of the obliquely oriented film include a film produced by
a process including sticking a heat-shrinkable film to a polymer
film and stretching and/or shrinking the polymer film under the
action of the heat-shrinkage force, and an obliquely-oriented
liquid crystal polymer film. The raw material polymer for the
retardation plate may be the same as the polymer described above
for the retardation plate, and any appropriate polymer may be used
depending on the purpose such as prevention of coloration caused by
changes in viewing angle based on the retardation of a liquid
crystal cell and expansion of the viewing angle at which good
visibility is achieved.
[0054] In order to expand the viewing angle at which good
visibility is achieved, an optical compensation retardation plate
is preferably used that includes a triacetylcellulose film and an
optically-anisotropic layer of an oriented liquid crystal polymer,
specifically an obliquely-oriented discotic liquid crystal polymer
layer, supported on the film.
[0055] A laminate of the polarizing plate and the brightness
enhancement film is generally placed on the back side of a liquid
crystal cell, when used. The brightness enhancement film exhibits
the property that when light is incident on it from a backlight of
a liquid crystal display or the like or when natural light is
reflected on the back side and incident on it, it reflects linearly
polarized light with a specific polarization axis or reflects
circularly polarized light in a specific direction and transmits
the other part of the light. When light from a light source such as
a backlight is incident on the laminate of the polarizing plate and
the brightness enhancement film, transmitted light in a specific
polarization state is produced, and light in the state other than
the specific polarization sate is not transmitted but reflected.
The light reflected from the surface of the brightness enhancement
film may be reversed by a reflective layer or the like provided
behind the brightness enhancement film and allowed to reenter the
brightness enhancement film so that the light can be entirely or
partially transmitted in the specific polarization state.
Therefore, the quantity of the light transmitted through the
brightness enhancement film can be increased, and polarized light,
which is less likely to be absorbed by the polarizer, can be
supplied so that the brightness can be enhanced by increasing the
quantity of the light available at a liquid crystal display or the
like. If the brightness enhancement film is not used when the light
of a backlight or the like is allowed to enter from the back side
of a liquid cell through a polarizer, light whose polarization
direction does not coincides with the polarization axis of the
polarizer will be almost absorbed (not transmitted) by the
polarizer. Therefore, about 50% of the light can be absorbed by the
polarizer, depending on the characteristics of the polarizer, so
that the quantity of the light available for image display on a
liquid crystal display or the like can be reduced and that the
brightness of the image can be lowered. Light that has a
polarization direction such that it can be absorbed by the
polarizer is not allowed to enter but temporarily reflected by the
brightness enhancement film and then reversed by a reflective layer
or the like placed behind the brightness enhancement film and
allowed to reenter the brightness enhancement film. This process is
repeated so that the brightness enhancement film can transmit
polarized light to the polarizer only when the polarized light
reflected and reversed by them has a polarization direction such
that it can pass through the polarizer. Therefore, the brightness
enhancement film allows efficient use of light from a backlight or
the like for image display on a liquid crystal display and thus
allows an increase in the brightness of the screen.
[0056] The diffusion plate may be placed between the brightness
enhancement film and the reflective layer or the like. When the
polarized light reflected from the brightness enhancement film goes
to the reflective layer or the like, the diffusion plate placed
therebetween can uniformly diffuse the light passing therethrough
and simultaneously cancel the polarization state to produce an
unpolarized state. Namely, the diffusion plate can convert
polarized light back into natural light in the initial state. The
light in the unpolarized state, namely in the natural light state,
goes to the reflective layer or the like and is reflected therefrom
and passes through the diffusion plate again and reenter the
brightness enhancement film. This process is repeated. Therefore,
the diffusion plate that is placed between the brightness
enhancement film and the reflective layer or the like to convert
the polarization state back into the initial natural light state
can reduce unevenness of the brightness of the display screen,
while maintaining the brightness of the display screen, so that the
resulting screen can be uniform and bright. When the diffusion
plate is provided as described above, the number of times of
repeated reflection of the initial incident light can be properly
increased so that a bright uniform display screen can be provided
together with the diffusion function of the diffusion plate.
[0057] Examples of the brightness enhancement film that may be used
include a film having the property of transmitting linearly
polarized light with a specific polarization axis and reflecting
the other type of light, such as a dielectric multilayer thin film
and a multilayer laminate of thin films different in refractive
index anisotropy, and a film having the property of reflecting one
of clockwise circularly polarized light and counterclockwise
circularly polarized light and transmitting the other, such as an
oriented cholesteric liquid crystal polymer film and an oriented
cholesteric liquid crystal layer supported on a film substrate.
[0058] When the brightness enhancement film having the property of
transmitting linearly polarized light with a specific polarization
axis is used, the light transmitted therethrough may be allowed to
directly enter the polarizing plate, while the polarization axis is
aligned, so that the light can be efficiently transmitted, while
the absorption loss of the polarizing plate can be reduced. When
the brightness enhancement film having the property of transmitting
circularly polarized light, such as the cholesteric liquid crystal
layer, is used, the transmitted circularly polarized light may be
allowed to directly enter the polarizer. In order to reduce the
absorption loss, however, it is preferred that the transmitted
circularly polarized light should be converted into linearly
polarized light through a retardation plate and then allowed to
enter the polarizing plate. Using a quarter wavelength plate as the
retardation plate, circularly polarized light can be converted into
linearly polarized light.
[0059] A retardation plate functioning as a quarter wavelength
plate in a wide wavelength range such as the visible light range
may be produced by laminating a retardation layer functioning as a
quarter wavelength plate for monochromatic light such as light with
a wavelength of 550 nm and another retardation layer exhibiting
other retardation properties, such as a retardation layer
functioning as a half-wave plate. Therefore, the retardation plate
placed between the polarizing plate and the brightness enhancement
film may include one or more retardation layers.
[0060] Two or more cholesteric liquid crystal layers with different
reflection wavelengths may also be laminated so that the resulting
combined structure can reflect circularly polarized light in a wide
wavelength range such as the visible light range, and as a result,
circularly polarized light in a wide wavelength range can be
transmitted.
[0061] In an embodiment of the invention, the sheet-shaped product
(such as a polarizing plate) may comprise a laminate of a
polarizing plate and two or more optical layers, like the polarized
light-separating polarizing plate described above. Therefore, the
sheet-shaped product may also be a reflective or transflective
elliptically polarizing plate that is a combination of the
reflective or transflective polarizing plate and a retardation
plate.
[0062] An optical film comprising a laminate of the polarizing
plate and the optical layer may be formed by a method of stacking
them one by one in the process of manufacturing a liquid crystal
display or the like. However, an optical film formed by previous
lamination is stable in quality and has the advantage that it can
facilitate the process of manufacturing a liquid crystal display or
the like, because of its good assembling workability. In the
lamination, any appropriate sticking means such as adhesive layers
may be used. When the polarizing plate and other optical layers are
stuck to one another, their optical axes may be each aligned at an
appropriate angle, depending on the desired retardation properties
or the like.
[0063] In an embodiment of the invention, the polarizing plate or
the laminated optical component may also have a pressure-sensitive
adhesive layer for sticking it to another component such as a
liquid crystal cell. The pressure-sensitive adhesive layer may be
formed of any appropriate pressure-sensitive adhesive such as an
acrylic pressure-sensitive adhesive according to conventional
techniques. The pressure-sensitive adhesive layer preferably has
low moisture absorption coefficient and high heat resistance, in
order to prevent moisture absorption-induced foaming or peeling, to
prevent optical property degradation due to a thermal expansion
difference or the like, to prevent warping of a liquid crystal
cell, and to form an image display with high quality and high
durability. The pressure-sensitive adhesive layer may also contain
fine particles so as to have light diffusing properties. The
pressure-sensitive adhesive layer may be provided as needed on a
necessary surface. Concerning the polarizing plate comprising the
polarizer and the protective film, for example, a
pressure-sensitive adhesive layer may be provided as needed on one
or both sides of the protective film.
[0064] The exposed surface of the pressure-sensitive adhesive layer
may be temporarily covered with a separator (corresponding to the
release film) for antifouling or the like until it is put to use.
This can prevent contact with the pressure-sensitive adhesive layer
during usual handling. Except for the thickness conditions
described above, conventional appropriate separators may be used
such as appropriate thin leaves including plastic films, rubber
sheets, paper, cloth, nonwoven fabric, net, foam sheets, metal
leafs, and laminates thereof, which are optionally coated with any
appropriate release agent such as a silicone, long-chain alkyl or
fluoride release agent and molybdenum sulfide.
[0065] In an embodiment of the invention, an ultraviolet absorbing
capability may be imparted to the polarizer, the protective film,
or the optical film for the polarizing plate or to each layer such
as the pressure-sensitive adhesive layer, for example, by treatment
with an ultraviolet-absorbing agent such as salicylate ester
compounds, benzophenol compounds, benzotriazole compounds,
cyanoacrylate compounds, and nickel complex salt compounds.
[0066] The sheet-shaped product according to the invention is
preferably used to form an image display (corresponding to the
optical display) such as a liquid crystal display, an organic
electroluminescence display (organic EL display) and a plasma
display panel (PDP).
[0067] The polarizing plate or the optical film according to the
invention is preferably used to form any of various devices such as
liquid crystal displays. Liquid crystal displays may be formed
according to conventional techniques. Specifically, a liquid
crystal display may be typically formed by assembling a liquid
crystal cell (corresponding to the optical display unit) and
polarizing plates or optical films, and optional components such as
a lighting system and incorporating a driving circuit, according to
conventional techniques, except that the polarizing plate or the
optical film is used according to the invention. The liquid crystal
cell to be used may also be of any type such as TN type, STN type
and .pi. type.
[0068] Any appropriate liquid crystal display may be formed such as
a liquid crystal display including a liquid crystal cell and the
polarizing plate or the optical film placed one or both sides of
the liquid crystal cell and a liquid crystal display using a
backlight or a reflector in a lighting system. In this case, the
polarizing plate or the optical film according to the invention may
be placed one or both sides of the liquid crystal cell. The
polarizing plates or the optical films placed on both sides may be
the same or different. In the process of forming the liquid crystal
display, one or more layers of an additional appropriate component
or components such as a diffusion plate, an antiglare layer, an
anti-reflection film, a protective plate, a prism array, a lens
array sheet, a light diffusion plate, and a backlight may also be
placed at an appropriate position or positions.
[0069] Next, a description is given below of an organic
electroluminescence device (organic EL display). An organic EL
display generally includes a transparent substrate and a
light-emitting element (an organic electroluminescence
light-emitting element corresponding to the optical display unit)
that is formed on the substrate by laminating a transparent
electrode, an organic light-emitting layer and a metal electrode in
this order. In this structure, the organic light-emitting layer is
a laminate of different organic thin films. Known laminate
structures have various combinations, including a laminate of a
hole injection layer comprising a triphenylamine derivative or the
like and a light-emitting layer comprising a fluorescent organic
solid material such as anthracene, a laminate of such a
light-emitting layer and an electron injection layer comprising a
perylene derivative or the like, and a laminate of the hole
injection layer, the light-emitting layer and the electron
injection layer.
[0070] The organic EL display emits light based on the mechanism
that holes and electrons are injected into the organic
light-emitting layer upon application of a voltage between the
transparent electrode and the metal electrode so that the energy
generated by the recombination of the holes and the electrons
excites the fluorescent substance, and light is emitted when the
excited fluorescent substance goes back to the ground state. The
mechanism of the recombination during the process is similar to
that in general diodes. As expected from this feature, current and
emission intensity exhibit strong nonlinearity accompanied by
rectification with respect to applied voltages.
[0071] In the organic EL display, at least one of the electrodes
must be transparent for the output of the emission from the organic
light-emitting layer, and a transparent electrode made of a
transparent electrical conductor such as indium tin oxide (ITO) is
generally used as an anode. On the other hand, for the purpose of
facilitating the electron injection and increasing the luminous
efficiency, it is important to use a low-work-function substance
for the cathode, and an electrode of a metal such as Mg--Ag and
Al--Li is generally used.
[0072] In the organic EL display with such a configuration, the
organic light-emitting layer is formed of a very thin film with a
thickness of about 10 nm. Therefore, light is almost entirely
transmitted through the organic light-emitting layer, as well as
through the transparent electrode. In the off-state, therefore,
light incident on the surface of the transparent substrate is
transmitted through the transparent electrode and the organic
light-emitting layer and reflected from the metal electrode to
return to and exit from the surface of the transparent substrate,
so that the screen of the organic EL display looks like a mirror
surface when it is viewed from the outside.
[0073] An organic EL display including an organic
electroluminescence light-emitting element comprising an organic
light-emitting layer for emitting light upon voltage application, a
transparent electrode provided on the front side of the
light-emitting layer and a metal electrode provided on the back
side of the light-emitting layer may also include a polarizing
plate provided on the front side of the transparent electrode and a
retardation plate provided between the transparent electrode and
the polarizing plate.
[0074] The retardation plate and the polarizing plate act to
polarize light that enters from the outside and is reflected from
the metal electrode. Therefore, their polarization action is
effective in preventing the mirror surface of the metal electrode
from being visible from the outside. Specifically, the retardation
plate may comprise a quarter wavelength plate, and the angle
between the polarization directions of the polarizing plate and the
retardation plate may be set at .pi./4, so that the mirror surface
of the metal electrode can be completely shielded.
[0075] Of external light incident on the organic EL display,
therefore, only a linearly polarized light component is transmitted
by the polarizing plate. The linearly polarized light is generally
turned into elliptically polarized light by the retardation plate.
Particularly when the retardation plate is a quarter wavelength
plate and the angle between the polarization directions of the
polarizing plate and the retardation plate is .pi./4, the linearly
polarized light is turned into circularly polarized light.
[0076] The circularly polarized light is transmitted through the
transparent substrate, the transparent electrode and the organic
thin film, reflected from the metal electrode, transmitted through
the organic thin film, the transparent electrode and the
transparent substrate again, and turned into linearly polarized
light again by the retardation plate. The linearly polarized light
has a polarization direction orthogonal to that of the polarizing
plate and therefore cannot pass through the polarizing plate. As a
result, the mirror surface of the metal electrode can be completely
shielded.
[0077] The sheet-shaped product (such as the polarizing plate)
according to the invention is preferably used to form various
devices such as liquid crystal displays. The sheet-shaped product
(such as the polarizing plate) according to the invention may be
placed on one or both sides of a liquid crystal cell to form a
liquid crystal display having an appropriate structure according to
conventional techniques, such as a transmissive, reflective or
transflective liquid crystal display. The liquid crystal cell for
forming the liquid crystal display may be of any type. Any
appropriate type of liquid crystal cell such as a simple matrix
driving type typified by a thin film transistor type may be
used.
[0078] The polarizing plates or the optical components provided on
both sides of a liquid crystal cell may be the same or different.
In the process of forming a liquid crystal display, one or more
layers of an additional appropriate component or components such as
a prism array sheet, a lens array sheet, a light diffusion plate,
and a backlight may be placed at an appropriate position or
positions.
[0079] Configuration of the System for Manufacturing Optical
Displays
[0080] FIG. 1 is a diagram illustrating the configuration of a
system for manufacturing optical displays according to the
invention. For the sake of illustration, a description is given
below of a case where a raw polarizing plate is used as the belt
and sheet-shaped product.
[0081] Transfer means (corresponding to the feeding means) allows
the placement of a roll 4 of a raw polarizing plate 3 and is
configured such that the raw polarizing plate 3 is fed from the
roll 4. The transfer means comprises feeding rollers 11 and so on,
while it may be of any type as long as it has the transferring
function.
[0082] Separating means (not shown) separates a release film (not
shown) from the raw polarizing plate 3 before or after the
detection of defects by detection means 12 as described later. The
separation is preferably performed before the detection of defects
by the detection means 12. Cleaning means cleans the raw polarizing
plate 3 from which the release film has been separated. Known
techniques may be used for the separating means 14 and the cleaning
means 15.
[0083] The detection means 12 detects defects on one or both sides
of the raw polarizing plate 3 being fed from the roll 4. Examples
of "defects" include scratches, stains and cracks. For example, the
detection means 12 includes a lighting system and a plurality of
CCD (charge-coupled device) cameras arranged in a single line along
the direction of the width of the raw polarizing plate 3 (see JP-A
No. 2005-62165, Page 13).
[0084] In order to detect surface defects of the raw polarizing
plate 3, for example, a first camera line 12a includes four CCD
cameras placed along the direction of the width of the raw
polarizing plate 3, and a second camera line 12b also includes four
CCD cameras placed along the same width direction. The second
camera line 12b is placed downstream from the first camera line
12a, and two lines are provided in order to ensure the detection of
defects. A third camera line 12c and a fourth camera line 12d are
also placed in the same manner for the back side. In addition, a
fifth camera line 12e is preferably placed such that defects formed
during the transferring process and other defects missed by the
first to fourth camera lines can be detected immediately before the
cutting process described later.
[0085] The images taken with the first to fifth camera lines 12a to
12e are sent to an image processing unit (not shown) which detects
defects on the surface of and in the interior of the raw polarizing
plate 3 based on an image processing technique. The image
processing unit may be implemented by a kind of software such as an
image processing program. Of course, the image processing unit may
comprise a kind of hardware. The image processing unit determines
whether or not and where defects exist. As described above, the
first to fifth camera lines 12a to 12e and the image processing
unit function as the detection means 12 to detect defects of the
raw polarizing plate 3. A known defect-judging algorithm may be
used when the process is implemented by the image processing
program.
[0086] Based on the result of the detection by the detection means
12, the cutting means 13 cut the raw polarizing plate 3 into
individual sheet-shaped products (polarizing plates 3a) each with a
specific size. For example, "cutting" may be performed by a
guillotine method, a punching method, a laser cutting method, or
the like. A laser cutting method is preferably used, because the
cut section is smooth and because squeezing out of a
pressure-sensitive adhesive can be prevented when the belt and
sheet-shaped product is a raw laminated film having a
pressure-sensitive adhesive layer. The raw polarizing plate 3 is
sucked under a negative pressure by suction means 14, and a part of
a specific size is transported and cut by the cutting means 13.
[0087] In the cutting process, specific size pieces are produced.
The size data may be stored in a memory before hand or input or
selected as appropriate by the system operator.
[0088] A description is given below of the cutting process in the
case where defects are detected. After defects are detected, the
raw polarizing plate 3 is successively transported by the feeding
means including the feeding rollers 11 and the suction means 14.
The cutting means 13 cuts the defect-containing portion of the raw
polarizing plate 3. In this process, for example, when the defect
is located 20 cm from the last cut section, the raw polarizing
plate 3 is fed and cut at a position located 21 cm from the cut
section. The cut piece of the polarizing plate 3a is determined as
a defective and transported and rejected along defective transfer
means 15. When the specific size is 50 cm from the cut section,
this cutting process can significantly increase the yield of the
polarizing plate 3a. For example, the transfer means 15 may be
implemented by a belt conveyor to transport defectives.
[0089] When a punching method is used for the cutting means 13,
different punching dies may be used to punch polarizing plates 3a
of different sizes. Namely, polarizing plates 3a of different sizes
may be obtained from the same raw polarizing plate 3. When a laser
cutting method is used, the cutting region setting may be changed
so that polarizing plates 3a of different sizes can be obtained by
cutting.
[0090] When no defect is detected, the cut piece of the polarizing
plate 3a with a specific size is transported to a sticking process.
The polarizing plate 3a is sucked under negative pressure by
suction means 16 (corresponding to the transfer means) and
transported thereby without being damaged. As shown in FIG. 2, a
liquid crystal cell substrate 5 (an optical display unit) is
previously placed, and the polarizing plate 3a is placed on the
liquid crystal cell substrate 5 by the suction means 16. In this
process, a roller component 17 (corresponding to the laminating
means) works together with the suction means 16 to press and stick
the polarizing plate 3a onto the liquid crystal cell substrate 5,
while rolling. This process can suppress air-bubble contamination
so that the defoaming or degassing process described later can be
eliminated or reduced in time. The sticking process using the
roller component 17 may be replaced by any other method such as a
sticking process using a roller component not mechanically coupled
to the suction means 16. The transfer means is not limited to the
suction system, and a belt conveyor system may be used instead.
[0091] Suction means 19 then transports, to the next process, the
liquid crystal display (corresponding to the optical display)
comprising a laminate of the polarizing plate 3a and the liquid
crystal cell substrate 5. The suction means 19 has the same
function as the suction means 14 or 16.
[0092] Second detection means 18 then detects defects on the
transported liquid crystal display. The detection may be performed
by the same method as described for the detection means 12. When
any defect is detected, reworking is performed. When no defect is
detected, defoaming is performed. The other surface to which no
polarizing plate 3a is stuck may be turned upside down such that
another polarizing plate 3a can be stuck thereto in the same
manner. The defoaming process may be performed before the detection
of defects by the second detection means 18.
Flow Chart of Manufacturing Process
[0093] A method for manufacturing an optical display according to
the invention is described below with reference to the flow chart
of FIG. 3.
[0094] First, a belt and sheet-shaped product (for example, a raw
polarizing plate) is placed in a manufacturing system (S1). The
belt and sheet-shaped product is supplied in the form of a roll
from an optical film maker. An assembling manufacturer unpacks the
roll product, cleans the surface of the roll and places the roll in
a manufacturing system.
[0095] A release film is then separated (S2). Thereafter, the belt
and sheet-shaped product is cleaned (S3). The cleaning is
preferably performed on the product with a weak pressure-sensitive
adhesive.
[0096] The process of detecting defects is then performed (S4), and
based on the result of the detection, a non-defective piece or
pieces of a specific size are cut, or a defect-containing portion
or portions are cut (S5). The cut piece determined as having a
defect portion (S6) is rejected as a defective (S7). The cut piece
determined as a non-defective (S6) is subjected to a laminating
process (S8). The detection process may be performed several
steps.
[0097] The detection of defects is then performed on an optical
display (S9). As a result of the detection, the product determined
as a defective (S10) is subjected to reworking (S11). The product
determined as a non-defective (S10) is subjected to the next
process (S12). An example of the next process is defoaming. In an
illustrative process, the other surface where no sheet-shaped
product is stuck may be turned upside down such that it can be
subjected to the process of sticking another sheet-shaped product
thereto.
Other Embodiments
[0098] The invention is not limited to manufacturing systems and
methods in which only a polarizing plate or plates are stuck to an
optical display unit. The invention may also be applied to cases
where a retardation plate is stuck to an optical display unit or to
cases where a polarizing plate and a retardation plate is
integrally stuck to an optical display unit. The optical unit may
also be other than the liquid crystal cell substrate.
* * * * *