U.S. patent application number 10/919377 was filed with the patent office on 2005-01-27 for optical compensatory sheet producing method and apparatus, thermal treating method and apparatus, and dust removing method and apparatus.
This patent application is currently assigned to FUJI PHOTO FILM CO., LTD.. Invention is credited to Fujiwara, Kazuhiko, Ishizuka, Seiji, Kawanishi, Naoyuki, Nakajima, Kenji, Sugiyama, Tadashi, Ura, Munehiro.
Application Number | 20050018116 10/919377 |
Document ID | / |
Family ID | 27343357 |
Filed Date | 2005-01-27 |
United States Patent
Application |
20050018116 |
Kind Code |
A1 |
Ishizuka, Seiji ; et
al. |
January 27, 2005 |
Optical compensatory sheet producing method and apparatus, thermal
treating method and apparatus, and dust removing method and
apparatus
Abstract
An optical compensatory sheet producing apparatus produces an
optical compensatory sheet having a liquid crystal layer. In the
apparatus, a rubbing unit is supplied with resin film having a
first layer including resin, and subjects the first layer to a
rubbing process, so as to form an orientation layer. A dust remover
removes dust from the orientation layer by use of liquid such as
perfluorocarbon, to which the orientation layer is insoluble. A
liquid crystal layer coater is disposed downstream from the dust
remover, for coating the orientation layer with coating liquid
including liquid crystalline compound, so that the liquid crystal
layer is formed.
Inventors: |
Ishizuka, Seiji; (Kanagawa,
JP) ; Ura, Munehiro; (Kanagawa, JP) ;
Sugiyama, Tadashi; (Kanagawa, JP) ; Nakajima,
Kenji; (Kanagawa, JP) ; Fujiwara, Kazuhiko;
(Kanagawa, JP) ; Kawanishi, Naoyuki; (Kanagawa,
JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
FUJI PHOTO FILM CO., LTD.
|
Family ID: |
27343357 |
Appl. No.: |
10/919377 |
Filed: |
August 17, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10919377 |
Aug 17, 2004 |
|
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|
09851416 |
May 9, 2001 |
|
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6812982 |
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Current U.S.
Class: |
349/117 |
Current CPC
Class: |
B05D 3/0413 20130101;
G02B 5/3016 20130101; B05D 7/04 20130101; G02B 5/3083 20130101;
G02F 1/13363 20130101; G02F 1/133633 20210101 |
Class at
Publication: |
349/117 |
International
Class: |
A61F 013/15; A61F
013/20; G02F 001/1335 |
Foreign Application Data
Date |
Code |
Application Number |
May 12, 2000 |
JP |
2000-140023 |
Jul 6, 2000 |
JP |
2000-204557 |
Jul 21, 2000 |
JP |
2000-220330 |
Claims
What is claimed is:
1. A thermal treating apparatus for a coating layer formed by
coating traveling web with coating liquid, comprising: at least one
hot air supply unit for blowing said coating layer with hot air;
and at least one exhaust unit, disposed upstream or downstream from
said hot air supply unit in a traveling direction of said web, for
sucking said hot air from said coating layer.
2. A thermal treating apparatus as defined in claim 1, further
comprising a controller for adjusting a first flow speed at which
said hot air is supplied by said hot air supply unit, and a second
flow speed at which said hot air is sucked by said exhaust
unit.
3. A thermal treating apparatus as defined in claim 2, wherein said
hot air supply unit includes: a hot air generator for generating
said hot air; an air blow opening disposed to face said coating
layer; a supply fan or blower, controlled by said controller, for
sending said hot air from said hot air generator through said air
blow opening; said exhaust unit includes: an exhaust opening
disposed to face said coating layer; an exhaust fan or blower,
controlled by said controller, for sending said hot air from said
exhaust opening.
4. A thermal treating apparatus as defined in claim 3, wherein said
controller controls said supply fan or blower and said exhaust fan
or blower, to keep a flow speed of said hot air equal to or lower
than 1 m/sec with reference to a web width direction crosswise to
said traveling direction.
5. A thermal treating apparatus as defined in claim 4, wherein as
viewed in said web width direction, said air blow opening has
1.05-2 times as great a size as a width of said web.
6. A thermal treating apparatus as defined in claim 5, further
comprising a flow speed sensor for detecting said flow speed of
said hot air on said coating layer; wherein said controller
controls said supply fan or blower and said exhaust fan or Lower
according to said flow speed.
7. A thermal treating apparatus as defined in claim 6, wherein said
air blow opening includes plural air blow nozzles arranged in said
traveling direction.
8. A thermal treating apparatus as defined in claim 7, wherein said
air blow nozzles are arranged in a matrix manner.
9. A thermal treating apparatus as defined in claim 7, wherein said
air blow nozzles are slit-shaped and extend crosswise to said
traveling direction.
10. A thermal treating apparatus as defined in claim 9, wherein
said air blow nozzles are disposed in a zigzag manner.
11. A thermal treating apparatus as defined in claim 7, wherein
said hot air supply unit is disposed 3-300 mm distant from said
coating layer.
12. A thermal treating apparatus as defined in claim 11, wherein
said at least one hot air supply unit comprises plural hot air
supply units; said at least one exhaust unit comprises plural
exhaust units disposed alternately with said plural hot air supply
units in said traveling direction.
13. A thermal treating apparatus as defined in claim 11, further
comprising a far infrared heater for applying heat energy to said
coating layer in addition to said hot air from said hot air supply
unit.
14. A thermal treating apparatus as defined in claim 13, wherein
said coating liquid includes liquid crystalline compound, and said
coating layer is a liquid crystal layer of an optical compensatory
sheet.
15. A sheet producing apparatus for producing a sheet from web,
comprising: a coater for coating said web being traveled with
coating liquid to form a coating layer; at least one hot air supply
unit for blowing said coating layer with hot air; at least one
exhaust unit, disposed upstream or downstream from said hot air
supply unit in a traveling direction of said web, for sucking said
hot air from said coating layer; and a controller for adjusting a
first flow speed at which said hot air is supplied by said hot air
supply unit, and a second flow speed at which said hot air is
sucked by said exhaust unit.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an optical compensatory
sheet producing method and apparatus, thermal treating method and
apparatus, and dust removing method and apparatus. More
particularly, the present invention relates to an optical
compensatory sheet producing method and apparatus in which an
optical compensatory sheet can be obtained with high quality for
good contrast and color in a liquid crystal display unit, and
thermal treating method and apparatus, and dust removing method and
apparatus for the optical compensatory sheet.
[0003] 2. Description Related to the Prior Art
[0004] A liquid crystal display unit (LCD) is characterized in
having a shape with a small thickness, being lightweight and using
low electric power in comparison with a cathode ray tube (CRT) to
display an image. LCD is used widely as a component incorporated in
a portable type of word processor and a desk-top type of personal
computer. In LCD, twisted nematic liquid crystal is used. In
general, LCD include a liquid crystal cell and a pair or polarizing
plates between which the liquid crystal cell is disposed. The
liquid crystal cell is constituted by a liquid crystal panel and an
electrode for applying voltage to the liquid crystal panel.
Furthermore, the liquid crystal panel includes transparent
orientation layers and a liquid crystal layer sandwiched between
the orientation layers. To display an image in LCD, there are two
modes include a birefringence mode and an optically rotary
mode.
[0005] A super twisted nematic LCD (hereinafter referred to as
STN-LCD) utilizing the birefringence mode uses a super twisted
nematic liquid crystal showing a twisted angle more than 90 degrees
and having steep electro-optical characteristics. Such STN-LCD,
therefore, has an advantage of giving display data of a large size
by driving in time-sharing mode. However, the STN-LCD has
disadvantages in providing good contrast only when set in the
yellow mode (yellowish green/deep blue) or blue mode (blue/pale
yellow). A phase difference plate (uniaxial stretched polymer film
or compensatory liquid crystal cell) is required to give
black-and-white display.
[0006] TN-LCD, when set in an optically rotary mode, shows quick
response (as quick as several tens of milliseconds) and high
display contrast. Hence, the optical rotary mode has a number of
advantages compared with the birefringence mode or other modes.
However, TN-LCD has disadvantages that color or contrast on display
varies with changes in viewing angle to LCD, and its display
characteristics are not comparable to display characteristics of
CRT.
[0007] In order to improve the viewing angle characteristics (i.e.,
to enlarge the viewable angle), arrangement of a phase difference
film (optical compensatory sheet) between a pair of polarizing
plates and the liquid crystal cell has been known. The optical
compensatory sheets show no optical effect when an LCD is seen in
the direction vertical to the screen of the display because phase
difference in the direction perpendicular to the surface of LCD is
almost zero. However, the optical compensatory sheet serves to
compensate for phase difference (depending upon wavelengths of
light) that occurs when LCD is viewed in an oblique direction.
[0008] JP-A 6-075115, U.S. Pat. No. 5,506,706 (corresponding to
JP-A 6-075116), and JP-A 4-276076 disclose an optical compensatory
sheet having the negative birefringence and inclined optical axis.
In more detail, the disclosed sheet is produced by stretching
polymer such as polycarbonate or polyester, and has the directions
of the main refractive indices which are inclined from the normal
of the sheet. To prepare the above sheet by the stretching
treatment, extremely complicated treatments are required.
Therefore, an optical compensatory sheet of a large surface are
cannot be easily produced according to the disclosed process.
[0009] Also, an optical compensatory sheet comprising liquid
crystalline polymer is known. For instance, U.S. Pat. No. 5,064,697
(corresponding to JP-A 3-009326) and JP-A 3-291601 disclose an
optical compensatory sheet for LCD which is prepared by applying a
coating of polymer showing liquid crystal property on an
orientation layer provided on a support film. However, polymers
having a liquid crystalline property have a shortcoming in low
productivity and are unsuitable for mass production, because it
needs orientation by ripening for a long time at high temperature.
JP-A 5-215921 discloses the use of a birefringence plate (optical
compensatory sheet) comprising a support and a polymerizable
rod-like compound showing liquid crystal property and positive
birefringence. The birefringence plate is prepared by applying a
coating of solution of the rod-like compound to the support and
curing the compound with heat. The cured layer of the prior
document, however, does not show negative birefringence. Hence, the
resulting compensatory sheet cannot enlarge satisfactorily the
viewing angle in all directions.
[0010] U.S. Pat. No. 5,646,703 (corresponding to EP-A 0 646 829)
discloses an optical compensatory sheet greatly enlarging the
viewing angle in all directions. The optical compensatory sheet has
a representative structure comprising a transparent support, an
orientation layer thereon, and a layer of discotic liquid
crystalline compound provided on the orientation layer.
[0011] To produce an optical compensatory sheet with a large area,
a transparent resin film with a large area must be coated with a
discotic liquid crystal compound in a state substantially free from
defects. So it has been conceived to reduce the number of the
defects in consideration of enlarging LCD.
[0012] To produce the optical compensatory sheet, a rubbing process
rubs a surface of a resin layer overlaid on the resin film for
forming an orientation layer by use of a rubbing sheet (of fabric).
This creates dust such as minute particles of resin. The dust
becomes collectively stuck on a surface of the orientation layer,
to create the defects (uneven orientation or local failure in
orientation) in an oriented state of a liquid crystal layer of the
optical compensatory sheet. When LCD is provided with the optical
compensatory sheet, the defects occur in a display state. To avoid
failure in removal of dust, the rubbing sheet about a rubbing
roller should be exchanged and renewed frequently. However, there
is a problem in that occurrence of the defects gradually becomes
frequent according to dust. Furthermore, renewal of the rubbing
sheet must be periodical, and inconsistent to continuous operation
of the manufacture.
[0013] JP-A 9-073081 discloses a producing method of an optical
compensatory sheet. Transparent resin film in a continuous shape is
coated with solution including resin for forming an orientation
layer, then is subjected to a rubbing process. So the orientation
layer is formed, then is coated with solution including discotic
liquid crystalline compound. Then the coating is dried. The resin
film is thermally treated next. The resin film is heated to
discotic nematic forming temperature, to form a liquid crystal
layer oriented at a predetermined angle of an orientation axis.
[0014] In FIG. 18, an example of thermal treating apparatus is
depicted. There are plural air blow openings 102 disposed above and
below resin film 101 as web, and arranged in an alternate manner
with one another. The air blow openings 102 supply hot air, blow
both surface of the resin film 101, and apply heat thereto. Exhaust
openings 103 are opposed to respectively the air blow openings 102,
and ejects the hot air from the resin film 101.
[0015] In the optical compensatory sheet, the liquid crystal layer
must be oriented according to an orientation axis previously
intended.
[0016] In the thermal treating apparatus according to the prior
art, it is likely that offsetting of an orientation axis occurs in
a width direction of the discotic liquid crystal layer. If the
offsetting of the orientation axis is over a tolerable range,
portions of the resin film must be discarded. There are problems in
that yield of products of the optical compensatory sheet decreases
to increase the manufacturing cost, and that efficiency in
manufacturing operation becomes lower according to inspection of
the offsetting of the orientation axis and the discarding
operation.
[0017] In manufacturing the optical compensatory sheet, dust must
be removed from the resin film by a dust removing apparatus. U.S.
Pat. No. 4,577,362 (corresponding to JP-A 59-150571) discloses an
example of dust removal in a dry type. A non-woven fabric or blade
is pressed against a surface of the resin film. Also, JP-A
10-309553 discloses dust removal in which compressed air with high
cleanness is supplied to blow the resin film and separate dust from
the same. An exhaust opening sucks the dust by ejecting the air.
Also, there is an apparatus characterized in that an ultrasonic
vibrator is used to vibrate an air flow, which separates dust with
higher shearing force for the purpose of efficient cleaning.
[0018] Also, JP-A 10-290964 discloses a dry type of dust removal in
which electrostatic charge is used. Positive and negative ions of
air are injected to neutralize the charge. Dust is separated and
then eliminated by use of another flow or air.
[0019] Also, a wet type of dust removal is also known. There is a
method in which the resin film is traveled through a cleaning
liquid in a cleaning liquid bath, and an ultrasonic vibrator is
driven to separate dust from the resin film in the cleaning liquid
bath. Furthermore, U.S. Pat. No. 3,956,790 (corresponding to JP-B
49-013020) discloses a method in which the resin film is supplied
with cleaning liquid, and then compressed air blows the resin film
to such the dust.
[0020] Those cleaning methods are effective to dust of particles of
at least 10 .mu.m or tens of .mu.m, or dust stuck weakly. However,
it is experimentally found that the known cleaning methods are
nearly ineffective to dust of particles of 10 .mu.m or less, or
dust stuck with strong adhesion.
[0021] To solve such problems, JP-B 5-050419 (corresponding to JP-A
62-060749) proposes a method in which a cleaning rod is pressed
against the resin film to remove dust. For the cleaning rod, the
resin film immediately after being coated with solvent is supplied.
The cleaning rod is caused to rotate in reverse to the traveling to
clear the dust while the solvent remains. According to the
document, a space is formed between the resin film and the cleaning
rod with a small thickness. Dust having a size over the space is
stopped from passing the rod. Also, more minute dust is separated
by transmission of shearing force in the solvent liquid, so that
dust of a small size or strongly stuck dust can be removed
effectively.
[0022] Also, JP-A 62-065872 discloses a dust removing method in
which a blade with a sharp edge is used to contact the resin
film.
[0023] However, problems arise in the method of JP-B 5-050419
(corresponding to JP-A 62-060749) and JP-A 62-065872. The cleaning
rod or the like directly contact the surface of the resin film. The
cleaning rod or the like is formed from super hard alloy resistant
to abrasion, and has a very smooth surface. Damages or scratches
may occur in the resin film if hard foreign matter or dust becomes
squeezed between the cleaning rod and the resin film.
SUMMARY OF THE INVENTION
[0024] In view of the foregoing problems, an object of the present
invention is to provide an optical compensatory sheet producing
method and apparatus in which an optical compensatory sheet can be
easily and efficiently obtained with high quality for good contrast
and color in a liquid crystal display unit.
[0025] Another object of the present invention is to provide a
thermal treating method and apparatus in which sheet material can
be heated without irregularity.
[0026] Still another object of the present invention is to provide
a dust removing method and apparatus capable of removing dust from
sheet material without scratching or damaging its surface.
[0027] In order to achieve the above and other objects and
advantages of this invention, an optical compensatory sheet
producing method for producing an optical compensatory sheet having
a liquid crystal layer is provided. A first layer of support
material is subjected to a rubbing process, so as to form an
orientation layer, the first layer including resin. Dust is removed
from the orientation layer by use of liquid to which the
orientation layer is insoluble. After the removing step, the
orientation layer is coated with coating liquid including liquid
crystalline compound, thereby the liquid crystal layer being
formed.
[0028] In a preferred embodiment, the removing step includes
polishing the orientation layer with the liquid in a direction
equal to a direction of the rubbing process.
[0029] An optical compensatory sheet producing apparatus produces
an optical compensatory sheet having a liquid crystal layer. In the
apparatus, a rubbing unit is supplied with support material having
a first layer including resin, for subjecting the first layer to a
rubbing process, so as to form an orientation layer. A dust remover
removes dust from the orientation layer by use of liquid to which
the orientation layer is insoluble. A liquid crystal layer coater
is disposed downstream from the dust remover, for coating the
orientation layer with coating liquid including liquid crystalline
compound, thereby the liquid crystal layer being formed.
[0030] Furthermore, a liquid bath contains the liquid. The dust
remover includes a cleaning roller, dipped in the liquid at least
partially, for contacting the orientation layer, to polish the
orientation layer with the liquid in the direction of the rubbing
process.
[0031] Furthermore, a resin layer coater is disposed upstream from
the rubbing unit, for coating the support material with first
coating liquid including the resin, to obtain the first layer. A
thermal treating unit is disposed downstream from the liquid
crystal layer coater, for heating the liquid crystalline compound
at phase forming temperature, to form the liquid crystal layer. A
curing unit cures the liquid crystal layer to obtain the optical
compensatory sheet.
[0032] The liquid is perfluorocarbon having 6-12 carbon atoms.
[0033] In another preferred embodiment, the liquid is straight
chain siloxane having 2-4 silicon atoms.
[0034] Furthermore, a dry-type dust remover is disposed upstream
from the dust remover, for removing dust from the orientation layer
by blow of compressed air.
[0035] Consequently, an optical compensatory sheet can be easily
and efficiently obtained with high quality for good contrast and
color in a liquid crystal display unit, because the dust remover
removes dust from the orientation layer by use of liquid to which
the orientation layer is insoluble, and because the orientation
layer is polished with the liquid in a direction equal to a
direction of the rubbing process.
[0036] According to one aspect of the invention, a thermal treating
apparatus for a coating layer formed by coating traveling web with
coating liquid is provided. At least one hot air supply unit blows
the coating layer with hot air. At least one exhaust unit is
disposed upstream or downstream from the hot air supply unit in a
traveling direction of the web, for sucking the hot air from the
coating layer.
[0037] Furthermore, a controller adjusts a first flow speed at
which the hot air is supplied by the hot air supply unit, and a
second flow speed at which the hot air is sucked by the exhaust
unit.
[0038] The hot air supply unit includes a hot air generator for
generating the hot air. An air blow opening is disposed to face the
coating layer. A supply fan or blower is controlled by the
controller, for sending the hot air from the hot air generator
through the air blow opening. The exhaust unit includes an exhaust
opening disposed to face the coating layer. An exhaust fan or
blower is controlled by the controller, for sending the hot air
from the exhaust opening.
[0039] The controller controls the supply fan or blower and the
exhaust fan or blower, to keep a flow speed of the hot air equal to
or lower than 1 m/sec with reference to a web width direction
crosswise to the traveling direction.
[0040] As viewed in the web width direction, the air blow opening
has 1.05-2 times as great a size as a width of the web.
[0041] Furthermore, a flow speed sensor detects the flow speed of
the hot air on the coating layer. The controller controls the
supply fan or blower and the exhaust fan or blower according to the
flow speed.
[0042] The air blow opening includes plural air blow nozzles
arranged in the traveling direction.
[0043] In another preferred embodiment, the air blow nozzles are
arranged in a matrix manner.
[0044] In still another preferred embodiment, the air blow nozzles
are slit-shaped and extend crosswise to the traveling
direction.
[0045] In an additional preferred embodiment, the air blow nozzles
are disposed in a zigzag manner.
[0046] The hot air supply unit is disposed 3-300 mm distant from
the coating layer.
[0047] The at least one hot air supply unit comprises plural hot
air supply units. The at least one exhaust unit comprises plural
exhaust units disposed alternately with the plural hot air supply
units in the traveling direction.
[0048] Furthermore, a far infrared heater applies heat energy to
the coating layer in addition to the hot air from the hot air
supply unit.
[0049] The coating liquid includes liquid crystalline compound, and
the coating layer is a liquid crystal layer of an optical
compensatory sheet.
[0050] Consequently, web can be heated without irregularity,
because the exhaust unit is disposed upstream or downstream from
the hot air supply unit in a traveling direction of the web.
[0051] According to another aspect of the invention, a dust
removing apparatus for web is provided. A first dust remover
removes dust from the web by blowing a first surface of the web
with compressed air. A rinsing unit is disposed downstream from the
first dust remover with reference to the web being traveled, for
removing dust from the web by rinsing the first surface with
liquid. A second dust remover is disposed between the first dust
remover and the rinsing unit, including a cleaning member and a
pinch member for contacting respectively the first surface and a
second surface of the web, to nip the web, wherein the cleaning
member polishes the first surface with liquid, to remove dust from
the web.
[0052] The cleaning member and the pinch member are a cleaning
roller and a rotatable pinch roller. Furthermore, a liquid bath
contains the liquid in which the cleaning roller is dipped at least
partially.
[0053] Each of the cleaning roller and the pinch roller includes a
roller body, and a resilient roll fitted about the roller body.
[0054] Furthermore, a feeder travels the web at one traveling
speed. A motor rotates the cleaning roller at one peripheral speed
different from the traveling speed.
[0055] The first dust remover includes at least one air blow
opening for blowing the first surface with the compressed air to
separate the dust from the web. At least one exhaust opening for
sucking the compressed air to eject the dust.
[0056] The at least one air blow opening and the at least one
exhaust opening are slit-shaped and extend in a web width direction
crosswise to a traveling direction of the web.
[0057] The first dust remover includes an ultrasonic vibrator for
ultrasonically vibrating the compressed air to be supplied from the
air blow opening.
[0058] The second dust remover further includes an ultrasonic
vibrator, disposed in the liquid bath, for applying ultrasonic
waves to the cleaning roller dipped in the liquid, to remove dust
from the cleaning roller.
[0059] Furthermore, a drier is disposed downstream from the rinsing
unit, for blowing the web with air to dry the liquid.
[0060] The drier includes at least one air blow opening for blowing
the first surface with the air to separate the liquid from the web.
At least one exhaust opening for sucking the air to eject the
liquid.
[0061] The at least one air blow opening and the at least one
exhaust opening are slit-shaped and extend in a web width direction
crosswise to a traveling direction of the web.
[0062] The drier includes an ultrasonic oscillator for
ultrasonically vibrating the air to be supplied from the air blow
opening.
[0063] Furthermore, at least one pair of rotatable edge rollers
support first and second edges of the first or second surface, to
guide the web in a non-contact state from a central portion of the
web.
[0064] In another preferred embodiment, furthermore, a hovering
roller is opposed to the first or second surface, for guiding the
web. Plural holes or slits are formed in a peripheral wall of the
hovering roll. A fan or blower blows the web through the plural
holes or slits with compressed air, to keep the web in a
non-contact state from the web.
[0065] Consequently, it is possible to remove dust from sheet
material without scratching or damaging its surface, because the
cleaning member and pinch member nip the web, and the cleaning
member polishes the first surface with liquid.
BRIEF DESCRIPTION OF THE DRAWINGS
[0066] The above objects and advantages of the present invention
will become more apparent from the following detailed description
when read in connection with the accompanying drawings, in
which:
[0067] FIG. 1A is an explanatory view in elevation, illustrating an
optical compensatory sheet producing apparatus of the
invention;
[0068] FIG. 1B is an explanatory view in section, illustrating an
optical compensatory sheet;
[0069] FIG. 2 is an explanatory view in elevation, illustrating
another optical compensatory sheet producing apparatus supplied
with a roll of support material web with a resin layer;
[0070] FIG. 3A is a plan illustrating a rubbing unit in the optical
compensatory sheet producing apparatus;
[0071] FIG. 3B is a side elevation illustrating the same as FIG.
3A;
[0072] FIG. 4 is an explanatory view illustrating a dust remover
units;
[0073] FIG. 5 is an explanatory view in elevation, illustrating
another preferred optical compensatory sheet producing apparatus
having an additional dust remover;
[0074] FIG. 6 is an explanatory view in elevation, illustrating the
dust remover in the apparatus of FIG. 5;
[0075] FIG. 7 illustrates a structure of anionic polymer;
[0076] FIG. 8 illustrates a structure of alkyl modified polyvinyl
alcohol;
[0077] FIG. 9 illustrates a structure of a discotic liquid crystal
compound;
[0078] FIG. 10 is an explanatory view in section, illustrating a
thermal treating apparatus of the invention;
[0079] FIG. 11 is an explanatory view in plan, illustrating a hot
air supply unit together with resin film;
[0080] FIG. 12 is an explanatory view in plan, illustrating one
preferred hot air supply unit having nozzles arranged in a
zigzag;
[0081] FIG. 13 is an explanatory view in plan, illustrating another
preferred hot air supply unit having hole-shaped nozzles;
[0082] FIG. 14 is an explanatory view in elevation, illustrating an
overall arrangement of a sheet producing system having the thermal
treating apparatus;
[0083] FIG. 15A is an explanatory view illustrating a dust removing
apparatus of the invention;
[0084] FIG. 15B is a cross section illustrating a hovering roller
in the dust removing apparatus together with a fan;
[0085] FIG. 15C is a cross section illustrating a first dust
remover unit of a dry type;
[0086] FIG. 15D is a plan illustrating a pair of edge rollers in
combination;
[0087] FIG. 16 is a block diagram illustrating an overall
arrangement of a sheet producing system having the dust removing
apparatus;
[0088] FIG. 17A is a table illustrating results of experiments
according to comparative examples;
[0089] FIG. 17B is a table illustrating results of experiments
according to samples of the invention; and
[0090] FIG. 18 is an explanatory view illustrating a thermal
treating apparatus according to the prior art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) OF THE PRESENT
INVENTION
[0091] A method of manufacturing an optical compensatory sheet of
the invention is characterized in dust removal in a wet type after
a rubbing process of an orientation layer laminated on a
transparent resin film.
[0092] The manufacturing method includes plural steps as
follows:
[0093] 1. Step of supplying transparent resin film;
[0094] 2. Step of forming a preliminary resin layer by coating a
surface of the resin film with solution having resin to form an
orientation layer, and by drying;
[0095] 3. Step of rubbing for forming the orientation layer on the
resin film according to a rubbing treatment of the surface of the
preliminary resin layer on the resin film;
[0096] 4. Step of dust removal, either by eliminating dust from the
surface of the orientation layer according to a wet type, or by
eliminating dust from the surface of the orientation layer
according to a dry type and then a wet type;
[0097] 5. Step of coating the orientation layer with a coating
layer including a liquid crystalline compound;
[0098] 6. Step of drying the coating layer to evaporate solvent in
the coating layer;
[0099] 7. Step of forming a liquid crystal layer by heating the
coating layer to a phase forming temperature;
[0100] 8. Step of hardening the liquid crystal layer, either by
forcibly cooling the liquid crystal layer, or by cross linking of
the liquid crystal layer photochemically or with heat typically if
the liquid crystalline compound has a cross linking functional
group;
[0101] 9. Step of winding the resin film with the orientation layer
and the liquid crystal layer.
[0102] In FIGS. 1A and 1B, a web supply device 1a is loaded with a
film roll 2a, from which the web supply device 1a supplies
transparent resin film 3a as web or support material. Feeder
rollers feed the resin film 3a. A dust removing device 4 eliminates
dust from a surface of the resin film 3a. A resin layer coater 5
coats the resin film 3a with coating liquid which contains resin
for forming an orientation layer. A heater/drier zone 6 dries the
coating liquid on the resin film 3a so as to form the orientation
layer overlaid on the resin film 3a. See the above steps Nos. 1 and
2.
[0103] Then resin film 3b including a preliminary resin layer is
obtained. A rubbing unit 9 is constituted by rubbing rollers 7,
dust removing sections 8 for removing dust from the rubbing rollers
7, and the like. The resin film 3b is subjected to rubbing
operation in the rubbing unit 9, so that the preliminary resin
layer is processed and becomes an orientation layer 52. See the
above step No. 3.
[0104] Resin film 3c having the orientation layer 52 after the
rubbing process is transferred from the rubbing unit 9 into a dust
removing device 10, which eliminates dust from a surface of the
orientation layer 52. See the above step No. 4.
[0105] After the orientation layer 52 is cleaned, the resin film 3c
is fed by feeder rollers. A liquid crystal layer coater 11 coats
the orientation layer 52 with coating solution including a liquid
crystalline compound. See the above step No. 5. Then solvent is
evaporated according to the above step No. 6. The resin film 3c
travels into a thermal treating zone 12. The coating solution is
heated by the thermal treating zone 12 to a phase forming
temperature, to form a liquid crystal layer 50. See the above step
No. 7. Note that the thermal treating zone 12 also evaporates
remainder of the solvent included in the coating solution.
[0106] Then an ultraviolet lamp 13 as curing unit is driven to
apply ultraviolet rays to the liquid crystal layer 50 for cross
linking of the liquid crystal layer 50. See the step No. 8 above.
For the purpose of the cross linking, the liquid crystalline
compound to be used must have a cross linking functional group. If
a liquid crystalline compound without the cross linking functional
group is used, there is no step of applying ultraviolet rays. The
liquid crystal layer 50 is cooled down immediately. It is necessary
to cool the liquid crystal layer 50 in a very short time, for the
purpose of avoiding changes in liquid crystalline phase. This being
so, an optical compensatory sheet 3d is obtained in a form with the
orientation layer 52 and the liquid crystal layer 50. An inspector
14 inspects the surface of the optical compensatory sheet 3d by
measuring optical characteristics of the optical compensatory sheet
3d. After the inspection, a laminator 15 laminates protector film
16 on the surface of the liquid crystal layer 50. A winder 17 winds
the optical compensatory sheet 3d with the protector film 16.
[0107] In the present embodiment, the steps from the forming of the
preliminary resin layer to the sheet winding are consecutive after
one another. Alternatively, the resin film 3b including the
preliminary resin layer may be previously prepared in a roll form,
and used for producing an optical compensatory sheet. In FIG. 2, a
film roll 5b is loaded in a web supply device 1b, which supplies
the resin film 3b including the preliminary resin layer. The steps
including the rubbing step and those succeeding thereto are the
same as those according to FIGS. 1A and 1B.
[0108] The steps Nos. 1-9 are carried out in series by the
construction of FIGS. 1A and 1B. Also, it is possible to define two
series, one including an earlier part of the steps Nos. 1-9 and the
other including a later part of the steps Nos. 1-9 as illustrated
in FIG. 2. Furthermore, the step of forming the orientation layer
may be separate. The rubbing step and the liquid crystal layer
forming step may be separate. Of course, the steps Nos. 1-9 may be
totally separate from one another.
[0109] In FIGS. 3A and 3B, the rubbing unit 9 is illustrated. FIG.
3A is a top plan of the rubbing unit 9. FIG. 3B is a front
elevation. A guide roller 22 in FIG. 3B is not depicted in FIG.
3A.
[0110] A rubbing sheet 7a is provided in a periphery of the rubbing
rollers 7, and may be formed from velvet, and rubs the surface of
the preliminary resin layer to form the orientation layer 52. A
motor 21 rotates the rubbing rollers 7a and is controlled in a
speed of at most 1,000 rotations per minute. The rubbing rollers 7
are adjustable in an angle of its inclination with respect to the
resin film 3b. To this end, the rubbing rollers 7 are supported in
a pivotally movable manner about an axis that is defined vertical
to the surface of the resin film 3b at its center line. Thus, a
pivot about which the rubbing rollers 7 rotate or roll can be
adjusted in its angle with respect to feeding of the resin film
3b.
[0111] A roller stage 23 supports the guide roller 22, which
contacts an upper back surface of the resin film 3b, and keeps a
lower front surface of the resin film 3b pressed on the rubbing
rollers 7.
[0112] For a rubbing operation, the rubbing rollers 7 are moved
pivotally about the axis being vertical to the resin film 3b. The
resin film 3b is fed by a feeder at regular tension and a regular
speed of at least 5 meters per minute. The rubbing rollers 7 are
rotated at a regular speed in a direction against the feeding of
the resin film 3b. Thus the rubbing rollers 7 operate continuously.
The resin film 3b is fed in a hovering manner according to air foil
effect. There occurs no shift of the resin film 3b in its width
direction. The resin film 3b can be rubbed stably in a continuous
manner.
[0113] During the rubbing, the resin film 3b is caused to travel at
a speed of 10-50 m/min. A diameter of the rubbing rollers 7 is
100-500 mm, and preferably 80-200 mm. A rotational speed of the
rubbing rollers 7 is 500-1,500 r.p.m. An angle of lap of the
rubbing rollers 7 relative to the resin film 3b is 4-20 degrees.
Tension of the rubbing rollers 7 applied to the resin film 3b is
1-2 N per 1 cm of the film width. The number of the rubbing rollers
7 is 2-4. A rotational axis of the rubbing rollers 7 is adjustable
in a range of 0-45 degrees on a horizontal plane. To set and remove
the rubbing rollers 7, it is desired to dispose a roller moving
mechanism to keep the rubbing rollers 7 removable at a connection
portion. Note that the angle of lap of the rubbing rollers 7 and
tension of the rubbing rollers 7 to the resin film 3b is kept
adjustable by the guide roller 22 moved up and down.
[0114] Examples of materials for the rubbing sheet 7a are sheets of
rubber, nylon, polyester, a velvet sheet or other sheets of nylon
fiber, rayon fiber, polyester fiber, sheets of paper, gauze and
felt, and the like. A relative speed between the orientation layer
52 and the rubbing sheet 7a is 50-1,000 m/min, preferably 100-500
m/min.
[0115] While the rubbing rollers 7 rub the resin film 3c, the dust
removing sections 8 near to the rubbing rollers 7 clean the surface
of the rubbing sheet 7a. An example of the dust removing sections 8
is an ultrasonic dust remover, which has a fan or blower for blow
of compressed air being ultrasonically vibrated, and an exhaust
opening for sucking and ejecting the air and dust.
[0116] Also, it is possible to use other structures for the rubbing
unit 9 according to known techniques.
[0117] In FIG. 4, the dust removing device 10 of the invention is
illustrated. The resin film 3c after being rubbed travels toward
the right in the drawing. Travel of the resin film 3c depends on
feeder rollers suitably disposed in the dust removing device 10. It
is necessary that a cleaning roller 24 contacts the surface of the
orientation layer 52 with a positive angle of lap. Also, a rinsing
nozzle 25 should be so positioned that the polished surface of the
orientation layer 52 comes near thereto.
[0118] In the dust removing device 10, guide rollers 27 and 28
guide the resin film 3c at the cleaning roller 24. A surface of the
orientation layer 52 is kept in contact with an upper portion of
the cleaning roller 24. A cleaning liquid bath 30 contains cleaning
liquid 31, in which the resin film 3c is dipped by the guide roller
27. Rotation of the cleaning roller 24 cleans the surface of the
orientation layer 52. There is another guide roller 29 toward which
the resin film 3c moves with an inclination. The cleaning liquid 31
is sprayed or jetted by the rinsing nozzle 25 to the same surface
of the resin film 3c, to rinse and clarify the orientation layer
52.
[0119] A motor 26 rotates the cleaning roller 24 in one direction.
Approximately a lower half of the cleaning roller 24 is dipped in
the cleaning liquid 31. When the cleaning roller 24 rotates, a thin
layer of the cleaning liquid 31 occurs between the cleaning roller
24 and the orientation layer 52. The cleaning roller 24 polishes
the orientation layer 52 without direct contact with the
orientation layer 52. A circulating pump 32 sends the cleaning
liquid 31 from the cleaning liquid bath 30. A filtration equipment
33 filters the cleaning liquid 31 from the circulating pump 32
before the rinsing nozzle 25 is supplied with the cleaning liquid
31. The rinsing nozzle 25 jets or sprays the cleaning liquid 31 to
the orientation layer 52 at a suitable hydraulic pressure of
liquid. Foreign matter deposited on the orientation layer 52, which
is dust created in the course of the rubbing operation, is washed
away.
[0120] The filtration equipment 33 clarifies the cleaning liquid 31
contaminated by dust or foreign matter eliminated from the resin
film 3c. The cleaning liquid 31 after being filtered is sent to the
rinsing nozzle 25.
[0121] Note that the cleaning roller 24 can rotate forwards or
backwards relative to traveling of the resin film 3c. However, a
diameter and rotational speed of the cleaning roller 24 should be
preferably so determined that a difference between a speed of the
resin film 3c and a peripheral speed of the cleaning roller 24 is 5
m/min or more.
[0122] Furthermore, it is possible that the cleaning roller 24 is
stationary without rotation if the resin film 3c travels at a
sufficiently high speed, which may be 5 m/min or more.
[0123] In a manner similar to the rubbing rollers 7, the cleaning
roller 24 is movable pivotally about an axis that is perpendicular
to the resin film 3c, and thus is adjustable in its inclination
relative to the resin film 3c. To control the cleaning roller 24,
it is desirable that an inclination of the cleaning roller 24
should be equal to that of the rubbing rollers 7 for the purpose of
keeping the orientation of the orientation layer 52. A difference
between the angles of the cleaning roller 24 and of the rubbing
rollers 7 with reference to the resin film 3b is in a range of
preferably .+-.15 degrees, desirably .+-.10 degrees, and most
desirably .+-.5 degrees.
[0124] In FIG. 4, a resilient roll 24a covers a roller body of the
cleaning roller 24 to project the orientation layer 52 from being
scratched. In the cleaning roller 24, the resilient roll 24a has a
thickness equal to or more than 0.5 mm, preferably 0.5-100 mm, and
desirably 1.0-50 mm. Any suitable material may be used to produce
the resilient roll 24a. Examples of the material for the resilient
roll 24a are polyamides (such as 6-nylon, 66-nylon, and copolymer
nylon), polyesters (such as polyethylene terephthalate,
polybutylene terephthalate, and copolymer polyester), polyolefins
(such as polyethylene and polypropylene), polyvinyl halide (such as
polyvinyl chloride, poly vinylidene fluoride, and Teflon), natural
rubber, neoprene rubber, nitrile rubber, Nordel, Viton rubber,
Hypalon, polyurethane, rayon, cellulose, and the like.
[0125] Examples of materials for the resilient roll 24a may have a
structure formed from a single material, mixed structure, layered
structure, a structure of woven fabric with fibers, and a non-woven
structure as a non-woven fabric. Conditions of preferable materials
include a characteristic not being softened or dissolved by the
cleaning liquid 31, and also a lower hardness than that of the
surface of the resin film 3c with the orientation layer 52.
[0126] An angle of lap of the resin film 3c to the cleaning roller
24 is determined according to disposition of the guide rollers 27a
and 28. If the angle of lap is determined greater, this is
effective in efficient polishing because of longer time for passage
of the resin film 3c at the cleaning roller 24. However, the angle
of lap should be not too great in view of preventing wrinkles,
scratches and zigzag movement. It is concluded that the angle of
lap is determined equal to or less than 180 degrees, preferably
1-135 degrees and desirably 5-90 degrees. Also, if a diameter of
the cleaning roller 24 is determined greater, this also prolongs
time for passage of the resin film 3c at the cleaning roller 24.
According to the preferred embodiment, the diameter of the cleaning
roller 24 is equal to or less than 200 cm, preferably 5-100 cm and
desirably 10-50 cm in view of a size of its space and a
manufacturing cost.
[0127] A pressure of the cleaning roller 24 to the resin film 3c
per unit area depends upon tension applied by a film feeding
mechanism and a roll diameter of the cleaning roller 24. It is
preferable to control the tension of the feeding mechanism because
the roll diameter changes according to the above-mentioned
contacting time. To eliminate foreign matter, it is preferable to
keep the pressure high. If the pressure is too high, a thin layer
of the cleaning liquid 31 between the orientation layer 52 and the
cleaning roller 24 is likely to be interrupted partially. This
causes scratches to occur in the resin film 3c due to a direct
contact between the resilient roll 24a and the resin film 3c. Thus,
the pressure of the cleaning roller 24 to the resin film 3c is
preferably equal to or less than 100 kgf/m per unit width,
desirably in a range of 5-100 kgf/m per unit width, and most
desirably in a range of 5-50 kgf/m per unit width.
[0128] Furthermore, a plurality of cleaning rollers 24 may be used
specifically when the resin film 3c is considerably contaminated.
The rinsing nozzles 25 may be disposed in an alternate manner with
the cleaning rollers 24. Alternatively, a series of the plural
cleaning rollers 24 can be arranged upstream from one or more
rinsing nozzles 25.
[0129] In the structure of FIG. 4, the cleaning liquid 31 is sent
from the cleaning liquid bath 30 to the rinsing nozzle 25 and
poured again to the cleaning liquid bath 30 in a circulating
manner. Alternatively, a filtration equipment may be associated
with the cleaning liquid bath 30 for clarifying the cleaning liquid
31 contaminated by dust in a separate manner from the structure
including the rinsing nozzle 25. The filtration equipment
preferably includes a filter of which a great number of regularly
arranged minute openings have a size determined in consideration of
a size of foreign matter to be eliminated. A nominal size of the
minute openings is preferably at most a half as great as that of
foreign matter, and desirably from 10/1 to {fraction (1/2 )} of
that of foreign matter. As a filter, a cartridge filter of a pleat
folded type can be used because of its long life and great ease in
handling.
[0130] A filtering circulated flow rate should be determined so as
not to increase dust in the cleaning liquid bath 30 due to cleaning
of the resin film 3c. To measure a quantity of the dust flowing in
the cleaning liquid 31, it is effective and easy to use HIAC/ROYCO
liquid fine particle counter Model 4100 (trade name) manufactured
by Nozaki Industry Inc. A size of minute openings in the filtration
equipment 33 and the circulated flow rate can be adjusted so as not
to increase the size of particles to be removed with time in
operation of circulation.
[0131] An ultrasonic vibrator 35 is disposed in the cleaning liquid
bath 30 and directed to the cleaning roller 24. The ultrasonic
vibrator 35 applies ultrasonic waves to the cleaning roller 24, and
ultrasonically eliminates dust from the cleaning roller 24
efficiently.
[0132] As viewed in the axial direction of the cleaning roller 24,
a size of the ultrasonic vibrator 35 is greater than that of the
cleaning roller 24. As viewed in a traveling direction of the resin
film 3c, an area of projection of the ultrasonic vibrator 35 is
preferably at least 50% as large as a diameter of the cleaning
roller 24. Instead, it is possible to use a small size of the
ultrasonic vibrator 35 under this condition. Plural ultrasonic
vibrators of such a small type can be used desirably, to cover the
same area of projection. An interval between the plural ultrasonic
vibrators should determined so as to overlap wave zones on one
another in a regularized manner.
[0133] Frequency of the ultrasonic vibrator 35 may be from 20 kHz
to 1 MHZ or more. If the material of the resilient roll 24a of the
cleaning roller 24 has a characteristic weak to cavitation or
erosion, damages are likely to occur in a surface of the resilient
roll 24a when the frequency is 500 kHz or less. So it is desirable
to use a high-quality type of ultrasonic vibrator 35 of which
frequency is 1 MHZ or more. In general, a particle size of foreign
matter to which ultrasonic waves are effective change according to
changes in the frequency. If the frequency is high, the ultrasonic
waves are effective to relatively small foreign matter.
Accordingly, it is preferable in the invention to use plural
ultrasonic vibrators for ultrasonic waves of different frequencies.
Also, the ultrasonic vibrator 35 may be a frequency variable
type.
[0134] Preferably, an output of the ultrasonic waves per unit area
is 0.1-2 W/cm.sup.2. There is an optimum distance between the
ultrasonic vibrator 35 and the cleaning roller 24 because of
existence of standing waves. The optimum distance is preferably a
product of .lambda. and an integer, where .lambda. is a wavelength
of the ultrasonic wave transmitted in the cleaning liquid 31. Note
that the wavelength .lambda. is obtained according to the equation
indicated below, where C is a speed of transmission of the
ultrasonic waves in the cleaning liquid 31, and f is frequency of
the ultrasonic vibrator 35.
.lambda.=C/f
[0135] Temperature of the cleaning liquid 31 in the cleaning liquid
bath 30 becomes higher because of generation of heat from the
ultrasonic vibrator 35 or the circulating pump 32. Thus, the
cleaning liquid bath 30 should have a device for keeping the
temperature unchanged in the cleaning liquid 31. For example, the
cleaning liquid bath 30 can have a jacket structure for circulating
heating medium or suitable fluid. Also, a heat exchanger can be
disposed in the cleaning liquid 31 for circulating heating medium
or fluid.
[0136] In FIG. 5, another preferred embodiment is depicted, in
which a dry type of dust removal is added. There is a dry type of
dust removing device 40 disposed between the rubbing unit 9 and the
dust removing device 10 for removing foreign matter from the
surface of the resin film 3c in a dry manner. Elements in FIG. 5
similar to those of FIGS. 1A and 1B are designated with identical
reference numerals.
[0137] The dust removing device 40 is preferably an ultrasonic dust
remover which supplies compressed air vibrated ultrasonically, and
also sucks dust or foreign matter. An example of the ultrasonic
dust remover is New Ultra Cleaner (trade name) type UVU-W
manufactured by Shinko Co., Ltd.
[0138] In FIG. 6, a structure of the dust removing device 40 is
depicted. The dust removing device 40 includes a static eliminator
41, a front surface dust removing section 42, a rear surface dust
removing section 43 and backup rollers 44 and 45. The backup
rollers 44 and 45 are opposed respectively to the dust removing
sections 42 and 43, and support and guide the resin film 3c. The
static eliminator 41 eliminates static charge from the resin film
3c after the rubbing operation, and makes it easy to remove dust
from the resin film 3c.
[0139] The dust removing sections 42 and 43 blow the resin film 3c
with compressed air vibrated ultrasonically, and suck dust. The
front surface dust removing section 42 is directed to the
orientation layer 52 or the front surface of the resin film 3c
opposite to the backup roller 44, and cleans the orientation layer
52 in a manner of a dry type by blowing of the compressed air and
suction.
[0140] The rear surface dust removing section 43 is directed to the
back surface of the resin film 3c opposite to the orientation layer
52 in a position at the backup roller 45, and cleans the back
surface of the resin film 3c in a manner of a dry type by blowing
of the compressed air and suction.
[0141] A flow rate of the compressed air from the dust removing
sections 42 and 43 is in a range of 10-50 m/sec, and preferably in
a range of 10-30 m/sec. A distance from the backup rollers 44 and
45 to an end of the dust removing sections 42 and 43 is preferably
2-5 mm. A diameter of the backup rollers 44 and 45 is preferably
50-150 mm.
[0142] In FIG. 6, the dust removing device 40 effects dry removal
of dust to both the orientation layer 52 and the back surface of
the resin film 3c. However, the dust removing device 40 may clean
only the orientation layer 52 without cleaning the back surface of
the resin film 3c.
[0143] Any suitable transparent material may be used for the resin
film 3a on which the orientation layer 52 is formed. The resin film
3a desirably has transmittance of 80% or more for visible light,
and should have optical isotropy as viewed vertically. So the
material for the resin film 3a should have a small index of
birefringence. A preferable example of the material is cellulose
triacetate. Also, material having a great index of birefringence
may be used by suitably determining a condition in flow casting of
solution, a condition in melt extrusion, a condition in stretch in
vertical or horizontal directions, or the like. Examples of such
materials are polycarbonate, polyarylate, polysulfone, polyether
sulfone and the like.
[0144] To form synthetic resin into a sheet, it is general to add
plasticizer to the resin to improve physical characteristics of the
resin, for example, to facilitate the forming, and to increase
flexibility and resistance to heat. It is well-known that preferred
examples of plasticizers have similarity in chemical structure, and
have high compatibility. In combination with cellulose triacetate,
preferable examples of plasticizers are phthalate ester, phosphate
ester, ester of glycol, and the like.
[0145] It is further preferable to provide an undercoat layer on
the resin film 3a for the purpose of increasing strength in
adhesion between the resin film 3a and the preliminary resin layer.
An example of method of forming the undercoat layer is disclosed in
U.S. Pat. No. 5,583,679 (corresponding to JP-B 2,587,398, JP-A
8-050206), which also discloses examples of material for the
undercoat layer. Furthermore, the optical compensatory sheet can be
used as a protector film for a polarizing plate as disclosed in
EP-A 0 911 656.
[0146] The preliminary resin layer for forming the orientation
layer may be formed from any suitable material that is transparent
and can be oriented when processed for orientation. Examples of
materials for the preliminary resin layer are polymethyl
methacrylate, acrylic acid/methacrylic acid copolymer,
styrene/maleinimide copolymer, polyvinyl alcohol, denatured
polyvinyl alcohol, poly(N-methylolacrylamide), styrene/vinyl
toluene copolymer, chlorosulfonated polyethylene, nitrocellulose,
polyvinyl chloride, chlorinated polyolefin, polyester, polyimide,
vinyl acetate/vinyl chloride copolymer, ethylene/vinyl acetate
copolymer, carboxymethyl cellulose, polyethylene, polypropylene,
and polycarbonate. Organic substances such as silane coupling
agents may be employed together with the polymer. Particularly
preferable examples of polymers for the preliminary resin layer are
polyimide, polystyrene, styrene derivative polymer, gelatine,
polyvinyl alcohol, denatured polyvinyl alcohol, and polyvinyl
alcohol derivative. Specifically, the preliminary resin layer can
be formed from material having polymerizable groups for the purpose
of strengthening the joining with the liquid crystal layer, as
disclosed in JP-A 9-152509.
[0147] Among those polymers, polyvinyl alcohol and denatured
polyvinyl alcohol are preferred. The polyvinyl alcohol generally
has saponification degree in the range of 70-100%, preferably in
the range of 80-100%, and especially in the range of 85-95%. A
polymerization degree of this is preferably in the range of
100-3,000.
[0148] Examples of the denatured polyvinyl alcohols include
polyvinyl alcohols denatured by copolymerization having a group
such as --COONa, --Si(OX).sub.3 [X: hydrogen or halogen],
--N(CH.sub.3).sub.3Cl, C.sub.9H.sub.19COO--, --SO.sub.3Na or
--C.sub.12H.sub.25, polyvinyl alcohols denatured by incorporation
of chain transfer agent employed in copolymerization having a
terminated group such as --COONa, --SH or --C.sub.12H.sub.25, and
polyvinyl alcohols denatured by block-copolymerization having a
group such as --COOH, --CONH.sub.2, --COOR [R: alkyl] or
--C.sub.6H.sub.5. A polymerization degree of those is preferably in
the range of 100-3,000.
[0149] Among those, preferable examples are non-denatured polyvinyl
alcohol and denatured polyvinyl alcohol with a saponification
degree in the range of 80-100%. Desirable examples are
non-denatured polyvinyl alcohol and denatured polyvinyl alcohol
having alkylthio group (C.sub.12H.sub.25S--) with a saponification
degree in the range of 85-95%. Available examples of this polyvinyl
alcohol having an alkyl group at a side chain are MP 103, MP 203, R
1130 (trade names) and the like manufactured by Kuraray Co., Ltd.
Also, cross linking agents disclosed in U.S. Pat. No. 5,631,051
(corresponding to JP-A 8-338913) can be added preferably.
[0150] In view of reliable quality in an optical compensatory
sheet, it is important that the cleaning liquid 31 should have
characteristics not to dissolve any substance in the resin film 3c,
extract any substance from the resin film 3c, or permeate into the
resin film 3c, the substance being any one of the orientation layer
overlaid on the resin film 3a, the resin in the resin film 3a, and
the undercoat layer of the resin film 3c.
[0151] If water-soluble polymer such as gelatine and polyvinyl
alcohol is used to form the undercoat layer or orientation layer,
it is necessary to use non-aqueous solvent with low polarity. To
control microscopic corrugation of a surface of the orientation
layer after the rubbing treatment is essential to operation of
regularly orienting a liquid crystalline compound overlaid thereon.
It is necessary to consider mobility of polymer chains on the
surface and glass transition in a state of coexistence of molecules
of the solvent, which are not explicable as macroscopic phenomena
of dissolution, swell or the like. Thus, it is not always possible
to use water or other solvent with high polarity even when the
preliminary resin layer is non-aqueous polymer, such as polymethyl
methacrylate, styrene/maleinimide copolymer, styrene/vinyl toluene
copolymer, polyvinyl chloride, polyester, polyimide, polyethylene,
polypropylene and polycarbonate.
[0152] As materials for forming the preliminary resin layer
includes hydrocarbons at backbone chains and side chains, it is
effective to use fluorine type solvent or siloxane type solvent as
the cleaning liquid 31. This is because those are not compatible
with hydrocarbon, and are not harmful to an orderly structure of
molecules of the surface to be processed by the rubbing operation.
Examples of fluorine types include perfluorocarbon, of which the
number of carbon atoms is 6-12, preferably 7-10. Should the number
of carbon atoms of perfluorocarbon be too small, there is
permeation of the cleaning liquid 31 to the orientation layer. In
contrast, should the number of carbon atoms be too great, the
cleaning liquid 31 has a very high boiling point inconsistent to
quick drying after cleaning. Available examples of perfluorocarbons
are PF-5060 (6 carbon atoms), PF-5070 (7 carbon atoms), and PF-5080
(8 carbon atoms) which are manufactured by Sumitomo 3M Co.,
Ltd.
[0153] Among fluorine types of solvents, perfluorocarbon can
provide the most stable rubbed surface, as all the hydrogen atoms
have been replaced by fluorine. It is likely that hydro
fluorocarbon and chlorofluorocarbon does not obtain desired
orientation of the liquid crystalline compound. The hydro
fluorocarbon has hydrogen groups in a partial manner. The
chlorofluorocarbon has chlorine by partial substitution. Those are
likely to lower regularity in microscopic orderly corrugation on
the surface of the orientation layer according to contact time with
the cleaning liquid 31 or the temperature of the cleaning liquid
31.
[0154] Also, the cleaning liquid 31 of the invention can be a
siloxane type solvent. In consideration of a higher boiling point
of the siloxane type solvent than that of perfluorocarbon,
preferred examples of siloxane type solvents should have 2-4
silicon atoms. Preferred examples of substituent groups include
methyl group, ethyl group and propyl group. The most preferable
example has a structure produced by substituting methyl groups for
all the hydrogen atoms. Available examples of siloxane type of
cleaning liquid 31 are FRD-10 and FRD-20 which are manufactured by
Toshiba Corporation.
[0155] The liquid crystal layer, formed on the orientation layer
after the dust removal of the wet type, is a layer which has a
negative birefringence, and which is obtained by cooling and
hardening a discotic liquid crystalline compound after orientation
of the same, or by polymerizing (curing) a discotic liquid
crystalline compound which is polymerizable. Examples of the
discotic compounds include:
[0156] benzene derivatives described in C. Destrade et al., Mol.
Cryst., vol.71, p.111, 1981;
[0157] truxene derivatives described in C. Destrade et al., Mol.
Cryst., vol.122, p.141. 1985 and Physics lett. A, vol.78, p.82,
1990;
[0158] cyclohexane derivatives described in B. Kohne et al., Angew.
Chem., vol.96, p.70, 1984;
[0159] macrocyclic compounds of azacrown-type or
phenylacetylene-type described in J. M. Lehn et al., J. Chem.
Commun., p.1794, 1985, and in J. Zhang et al., J. Am. Chem. Soc.,
vol.116, p.2655, 1994.
[0160] The discotic liquid crystal generally has a structure that
the above compound is located at a center of the crystal as a
parent core and further straight chain groups such as alkyl, alkoxy
and benzoyl having a substituent are radially bonded to the
compound. Also, the discotic liquid crystal has a crystalline
characteristic. Furthermore, it is possible to use a compound of
which a molecule has a negative uniaxial property (negative
birefringence) and which can be provided with regular orientation.
In the present specification, forming by use of the discotic
compound does not mean that a final product is discotic. For
example, the discotic liquid crystal of a low molecular weight may
have groups reacting in response to application of heat or light.
Reaction of the groups may cause polymerization or cross linking to
lose a liquid crystalline characteristic.
[0161] In a process of producing the liquid crystal layer 50 of a
discotic nematic phase, at first a discotic compound and other
compounds are dissolved in solvent to obtain solution. The
orientation layer 52 is coated with the solution and dried, and
then heated to temperature of forming the discotic nematic phase.
After this, the dried solution is cooled in keeping the discotic
nematic phase or the oriented state, before the liquid crystal
layer 50 can be obtained. In a variant process of producing the
liquid crystal layer 50, the discotic compound and other compounds
(and also polymerizable monomer and photo polymerization initiator)
are dissolved in solvent to obtain solution. The orientation layer
52 is coated with the solution and dried, and then heated to
temperature of forming the discotic nematic phase, and polymerized
by ultraviolet rays or the like. After this, the dried solution is
cooled to obtain the liquid crystal layer 50. A temperature of
transfer between the discotic nematic liquid crystalline phase and
solid phase of the discotic compound is 70-300.degree. C., and
preferably 70-170.degree. C. according to the invention.
Orientation of the discotic compound is the bend-hybrid orientation
disclosed in U.S. Pat. No. 5,583,679 (corresponding to JP-B
2,587,398, JP-A 8-050206).
[0162] A tilt angle at the time of orientation of a discotic
compound on the side of the support can be determined by
designation of a material for the discotic compound or orientation
layer, or by determining the method of the rubbing treatment. An
angle of an inclination of a discotic unit on the side of an outer
surface (air) can be determined by designation of a discotic
compound or additional compounds used together with the discotic
compound, the additional compounds including plasticizers, surface
active agents, polymerizable monomers, polymers and the like.
[0163] The plasticizers, surface active agents and polymerizable
monomers may be any suitable compounds that are compatible with a
discotic compound, and can provide the tilt angle of the discotic
liquid crystalline compound, or is not harmful to orientation.
Among those, polymerizable monomers are preferable in particular,
including compounds having a vinyl group, vinyl oxy group, acryloyl
group and methacryloyl group Each of those compounds is used at
1-50 wt. %, preferably 5-30 wt. % relative to the discotic
compound.
[0164] For the above polymers, any type may be used if it has a
compatibility with the discotic compound, and can provide a tilt
angle for the discotic liquid crystalline compound. A preferable
example of the polymer is cellulose ester. Examples of cellulose
esters are cellulose acetate, cellulose acetate propionate, hydroxy
propyl cellulose, cellulose acetate butylate, and the like. Those
polymers are used at a ratio of 0.1-10 wt. %, preferably 0.1-8 wt.
%, desirably 0.1-5 wt. % to an amount of the discotic compound so
as not to block orientation of the discotic liquid crystalline
compound.
[0165] Coating solution for forming the liquid crystal layer of the
discotic nematic phase can be produced by dissolving the discotic
compound and above-mentioned other compounds in solvent. Examples
of the organic solvents are polar solvents (such as
N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and
pyridine), non-polar solvents (such as benzene and hexane), alkyl
halides (such as chloroform and dichloromethane), esters (such as
methyl acetate and butyl acetate), ketones (such as acetone and
methyl ethyl ketone), and ethers (such as tetrahydrofuran and
1,2-dimethoxyethane). Specifically, alkyl halides and ketones are
preferable. Each of those types of solvents may be used in a single
manner, or may be used in combination with others.
[0166] The optical compensatory sheet obtained by the above method
can be free from defects in a liquid crystal layer due to dust
(existence of an excessively large particle in the liquid crystal
layer, and irregularity in the orientation). When the optical
compensatory sheet is mounted in a liquid crystal display unit
(LCD), an angle of view according to the liquid crystal layer can
be enlarged. There occurs no defects in the image.
EXAMPLES
[0167] Samples of optical compensatory sheets were produced
according to the present invention, and evaluated in comparison
with comparative examples, as described hereinafter. Of course, the
present invention is also applicable to constructions other than
the samples herein described.
Comparative Example 1 (Prior Art)
[0168] 1. Production of the transparent resin film
[0169] [Forming of a transparent support material] Substances
indicated below were poured into a mixing tank, and stirred and
heated to produce cellulose acetate solution.
1 cellulose acetate at an acetylation ratio 100 parts by weight of
60.9%: triphenyl phosphate: 7.8 parts by weight biphenyl diphyenyl
phosphate: 3.9 parts by weight methylene chloride: 300 parts by
weight methanol: 54 parts by weight 1-butanol: 11 parts by
weight
[0170] One other mixing tank was used, and supplied with the
following compounds, which were heated and stirred to produce
retardation booster agent solution.
2 2-hydroxy-4-benzyl oxy benzophenone: 12 parts by weight
2,4-benzyl oxy benzophenone: 4 parts by weight methylene chloride:
80 parts by weight methanol: 20 parts by weight
[0171] 474 parts by weight of cellulose acetate solution was mixed
with 22 parts by weight of retardation booster agent solution, and
was stirred sufficiently to obtain dope. Note that 100 parts by
weight of cellulose acetate was mixed with 3 parts by weight of
retardation booster agent. The dope was ejected through a flow
opening, and extended on a drum cooled at 0.degree. C., then was
peeled in a state of including the solvent at 70 wt. %. Lateral
portions of the film as viewed crosswise to the feeding were fixed
by a bin tenter machine. The film was dried in keeping such an
interval as to set an extension proportion of 3% as viewed
crosswise to the feeding direction in a range where the solvent is
included at 3-5 wt. %. The film was dried further by feeding
between rollers in the thermal treating device, and was so treated
to have an extension proportion of substantially 0% in the feeding
direction, and a ratio 0.75 between extension proportions in the
feeding direction and in a direction crosswise to the same in a
zone where the glass transition temperature is 120.degree. C. or
higher. (The ratio 0.75 was determined in consideration of 4%
extension in the feeding direction upon a peeling operation.) Thus,
the cellulose acetate film with a thickness of 107 .mu.m was
obtained. Retardation of the film was measured. The film had a
retardation Rth=80 nm in the thickness direction, and a retardation
Re=11 nm as viewed in a surface.
[0172] [Forming of 1.sup.st undercoat layer] The cellulose acetate
film obtained above was used as transparent support material, which
was coated with coating solution having composition indicated below
at 28 ml/m.sup.2, so that a first undercoat layer was formed by
drying the coating solution.
3 Gelatine: 5.42 parts by weight formaldehyde: 1.36 parts by weight
salicylic acid: 1.6 parts by weight acetone: 391 parts by weight
methanol: 158 parts by weight methylene chloride: 406 parts by
weight water: 12 parts by weight
[0173] [Forming of 2.sup.nd undercoat layer] The first undercoat
layer was coated with coating solution having composition indicated
below at 7 ml/m.sup.2, so that a second undercoat layer was formed
by drying the coating solution.
4 anionic polymer having a structure 0.79 part by weight of FIG. 7:
mono ethyl citrate ester: 10.1 parts by weight acetone: 200 parts
by weight methanol: 877 parts by weight water: 40.5 parts by
weight
[0174] [Forming of back layer] A surface of the transparent support
material opposite to the above coating was coated with coating
solution having composition indicated below at 25 ml/m.sup.2, so
that a back layer was formed by drying the coating solution. The
transparent resin film or resin film 3a was finally obtained.
5 Cellulose diacetate at an acetylation ratio of 55%: 6.56 parts by
weight silica type of mat agent (particles with average 0.65 part
by weight diameter of 1 .mu.m): acetone: 679 parts by weight
methanol: 104 parts by weight
[0175] 2. Production of orientation layer and liquid crystal
layer
[0176] [Forming of preliminary resin layer for forming orientation
layer] In using the above-described transparent resin film 3a, the
second undercoat layer was coated with aqueous solution of alkyl
modified polyvinyl alcohol, of which a structure is depicted in
FIG. 8. A preliminary resin layer was formed on the transparent
resin film by drying the solution with hot air at 60 .degree. C.
for 90 seconds.
[0177] [Rubbing process] After the preliminary resin layer is
formed, there was a rubbing process to form the orientation layer
52 by use of the rubbing unit 9 illustrated in FIGS. 3A and 3B. The
resin film 3b with the preliminary resin layer is traveled
continuously at a speed of 20 m/min. The guide roller 22 was 65 mm
across. The rubbing rollers 7 were 150 mm across. The resin film 3b
was guided by the guide roller 22. The rubbing rollers 7 were
caused to rotate at 600 r.p.m. in reverse to traveling of the resin
film 3b. During the rotation, the rubbing sheet 7a of velvet about
the rubbing rollers 7 was in contact with the preliminary resin
layer, and rubbed the same. In the rubbing, an angle of lap at the
base was 6 degrees. Tension applied to the resin film 3b was 1.8
N/cm per unit width. An angle of a rotational axis of the rubbing
rollers 7 was 0 degree with reference to the crosswise direction of
traveling of the resin film 3b.
[0178] In the rubbing process, a surface of the rubbing sheet 7a in
the rubbing rollers 7 was cleaned by the dust removing sections 8.
Each of the dust removing sections 8 was New Ultra Cleaner (trade
name) type UVU-W manufactured by Shinko Co., Ltd., and had a head
pressure of 300 mmAq, a flow speed of 20 m/sec to blow with air,
and a distance of 3 mm between a roll surface and an end of the
cleaner.
[0179] [Dust removal in a dry manner] After the rubbing, the resin
film 3c was subjected to dust removal in the dust removing device
40 depicted in FIG. 6. The static eliminator 41 eliminated static
charge from the resin film 3c, before the dust removing sections 42
and 43 cleaned the orientation layer 52 and a back surface of the
resin film 3c opposite to the orientation layer 52. Each of the
dust removing sections 42 and 43 was provided with a New Ultra
Cleaner (trade name) type UVU-W manufactured by Shinko Co., Ltd.,
and had a head pressure of 300 mmAq, a flow speed of 20 m/sec to
blow with air, and a distance of 2 mm between an end of the cleaner
and a surface of the backup rollers 44 and 45. The backup rollers
44 and 45 were 50 mm across.
[0180] [Forming of liquid crystal layer] After the dust removal of
the dry type, the liquid crystal layer was formed on the
orientation layer. Coating solution which was used for this had
composition as follows:
6 methyl ethyl ketone: 20.67 grams discotic liquid crystal DLC-A of
FIG. 9: 9.1 grams ethylene oxide modified trimethylol propane
acrylate 0.9 gram V#360 manufactured by Osaka Organic Chemical Ind.
Co., Ltd.: Cellulose acetate butylate CAB 551-0.2 manufactured by
0.2 gram Eastman Chemical Co.: Cellulose acetate butylate CAB 531-1
manufactured by 0.05 gram Eastman Chemical Co.: Irgacure 907 (trade
name) manufactured by Japan Ciba- 3.0 grams Geigy: Kayacure DETX
(trade name) manufactured by Nippon 0.1 gram Kayaku Co., Ltd.:
[0181] The orientation layer was coated with the coating solution
by a wire bar (#3 bar). The resin film was attached on a frame of
metal, and heated for three minutes in a high temperature bath at
120.degree. C. to orient the discotic liquid crystal. Then the
discotic liquid crystal was subjected to ultraviolet rays for one
minute by a high pressure mercury lamp still under 120.degree. C.
The resin film was left to stand and cooled down to the room
temperature, to obtain a continuous type of optical compensatory
sheet 3d in which the liquid crystal layer 50 was overlaid on the
transparent resin film 3c.
[0182] The liquid crystal layer 50 was 1.4 .mu.m thick. Retardation
of the optical compensatory sheet 3d was measured in a direction of
rubbing of the orientation layer. Average angle of the inclination
of the optical axis was 15.5 degrees. The optical compensatory
sheet had a retardation Rth=137 nm in the thickness direction, and
a retardation Re =25 nm as viewed in a surface.
[0183] Sample 1
[0184] An optical compensatory sheet of the invention was produced
in the same manner as Comparative Example 1 except for the dust
removal. In the dust removal for Sample 1, a process at the dry
type of dust removing device 40 was followed by a wet type of dust
removal for the orientation layer 52 by use of the dust removing
device 10 in FIG. 4. The cleaning roller 24 included an aluminum
roller body and a resilient roll 24a of velvet disposed thereabout.
The roller body was 550 mm long and 20 cm across. The resilient
roll 24a was the same as the rubbing sheet 7a. Guide rollers were
adjusted to set the angle of lap of the cleaning roller 24 at 0
degrees to a crosswise direction of the resin film 3c.
[0185] Also, positions of the guide rollers 27 and 28 were adjusted
to have the angle of lap of 50 degrees to the resin film. The
cleaning liquid 31 was perfluorocarbon PF-5080 (8 carbon atoms)
manufactured by Sumitomo 3M Co., Ltd. The cleaning roller 24 was
dipped in the cleaning liquid 31 at a depth of 10 cm, and caused to
rotate in reverse to the traveling direction. The rinsing nozzle 25
had a clearance which was 500 mm long as viewed in the film width
direction and 1 mm wide as viewed in the traveling direction, and
suppled the cleaning liquid 31 at a flow speed of 30 liters per
minute. The filtration equipment 33 included Astro Pore Filter
(trade name) manufactured by Fuji Photo Film, Co., Ltd. The filter
had a nominal size of the minute openings of 0.2 .mu.m.
[0186] The single ultrasonic vibrator 35 manufactured by Japan Alex
Corporation was used, disposed to extend crosswise to the traveling
direction of the resin film 3c, and caused to emit ultrasonic waves
to the whole range of the cleaning roller 24. The ultrasonic
vibrator 35 was 50 cm long and 30 cm across, and emitted the
ultrasonic waves of 100 kHz at the power of 1,000 W.
Comparative Example 2
[0187] An optical compensatory sheet was produced by the same
processes as Sample 1 except for the type of the cleaning liquid 31
used in the dust removal of the wet type. The cleaning liquid 31
was perfluorocarbon PF-5050 (5 carbon atoms) manufactured by
Sumitomo 3M Co., Ltd., instead of PF-5080 (8 carbon atoms).
[0188] Sample 2
[0189] An optical compensatory sheet of the invention was produced
by the same processes as Sample 1 except for the type of the
cleaning liquid 31 used in the dust removal of the wet type. The
cleaning liquid 31 was a silicone type FRD-20 that is octamethyl
trisiloxane manufactured by Toshiba Corporation, instead of
PF-5080.
[0190] Comparative Example 3
[0191] The optical compensatory sheet was produced by the same
processes as Sample 1 except for the inclination of the cleaning
roller 24. A rotational axis of the cleaning roller 24 was inclined
at 20 degrees relative to the width direction of the resin
film.
[0192] To evaluate the samples and comparative examples, optical
compensatory sheets were left to stand for one (1) hour. Then each
sheet was observed through a microscope. If there are point-shaped
defects being at least 10 .mu.m across, then the number of the
detects per unit area of 1 m.sup.2 was counted and evaluated.
Furthermore, each optical compensatory sheet was mounted in a
liquid crystal display unit (LCD) of the TN type. In the LCD, a
product, which was obtained by multiplying a gap size of liquid
crystal cells by a difference in the refractive index between
liquid crystal extraordinary light and normal light, was 370 nm. A
twisted angle was 90 degrees. Then existence of defects in a
visible state of display, was evaluated, as well as quality of
display of an image with evenness without degradation in
indication. Results are indicated in the table.
[0193] In the following table, the angle represents that defined by
the rotational axis of the cleaning roller 24 relative to the width
direction of the resin film.
7 Dust Evaluation Cleaning Angle Particles of Evenness Liquid
(.degree.) (/m.sup.2) in Display Comparative None 0 35 Good Example
1 Sample 1 PF-5080 0 7 Good Comparative PF-5050 0 3 Very Uneven
Example 2 Sample 2 FRD-20 0 8 Good Comparative PF-5080 20 5 Locally
Example 3 Uneven
[0194] Another preferred embodiment is described next, according to
which a process of thermal treatment is capable of avoiding
unevenness in application of heat.
[0195] In FIG. 10, the thermal treatment is depicted. In FIG. 11, a
station for blowing with air and a station for exhaust of air are
depicted.
[0196] In FIGS. 10 and 11, a thermal treating apparatus 110 is
constituted by pass rollers 112, a hot air supply unit 118 and an
exhaust unit 120. The pass rollers 112 guide traveling of resin
film 114 as web. The resin film 114 includes a liquid crystal layer
116 as a coating. The hot air supply unit 118 blows the liquid
crystal layer 116 with hot air. The exhaust unit 120 sucks and
ejects the hot air from the liquid crystal layer 116. A casing 122
in a quadrilateral shape constitutes a body of the thermal treating
apparatus 110, and has upper and lower openings. A partition plate
124 separates the exhaust unit 120 from the hot air supply unit 118
in a direction crosswise to travel of the resin film 114.
[0197] A plurality of air blow openings 126 are formed in a lower
wall of the hot air supply unit 118 facing the liquid crystal layer
116. A hot air generator 164 is connected to a supply duct 128,
where a fan 130 or blower is disposed. The fan 130 is changeable in
rotational speed. An exhaust opening 132 is formed in a lower side
of the exhaust unit 120. A fan 134 or blower is disposed over the
exhaust opening 132 in the exhaust unit 120, and changeable in
rotational speed. A controller 136 is connected with the fans 130
and 134 and the hot air generator 164, and controls those elements
in the thermal treating apparatus 110. When the fans 130 and 134
rotate, hot air flowing from the hot air generator 164 to the hot
air supply unit 118 is caused to blow the liquid crystal layer 116
of the resin film 114 through the air blow openings 126 while the
resin film 114 travels. The hot air is sent into the exhaust unit
120 through the exhaust opening 132 and ejected from the apparatus.
The hot air flows as a form of an air flow in a direction of
traveling of the resin film 114 because the hot air flows from the
air blow openings 126 toward the exhaust opening 132 and is
influenced by traveling of the resin film 114. It is preferable
that a component flow speed of the hot air as viewed in a direction
perpendicular to traveling of the resin film 114 is 1 m/sec or
less, preferably 0.8 m/sec, and most preferably 0.7 m/sec or
less.
[0198] The air blow openings 126 are constituted by slit-shaped
nozzles, a slit-formed plate, a plate of punched metal, and the
like. In FIG. 11, slit-shaped nozzles 126 A extend crosswise to
traveling of the resin film 114, and are arranged along the
traveling of the resin film 114. In FIG. 12, the air blow openings
126 are slit-shaped nozzles 126B formed in a plate of punched
metal. In FIG. 13, nozzles 126C are circular holes.
[0199] A size L1 of the air blow openings 126 as viewed crosswise
to traveling of the resin film 114 is longer than a web width L2 of
the resin film 114, is 1.05-2 times as long as the web width L2,
and preferably 1.1-1.5 times as long. It is preferable that a size
of the exhaust opening 132 as viewed crosswise to the feeding
should be equal to the size Li of the air blow openings 126. In the
construction with the slit-shaped nozzles 126B or the nozzles 126C
formed in the air blow openings 126, the size of each of the
slit-shaped nozzles 126B or the nozzles 126C is shorter than web
width L2 of the resin film 114. However, the size L1 of a region of
a combination of the slit-shaped nozzles 126B or the nozzles 126C
as viewed crosswise to traveling of the resin film 114 should be
longer than a web width L2. See FIGS. 12 and 13. Also, it is
necessary to suppress differences with reference to the direction
crosswise to traveling of the resin film 114 in heat quantity
applied to the resin film 114 by arrangement of the slit-shaped
nozzles 126B or the nozzles 126C in a chain manner. A size D of the
air blow openings 126 as viewed in a traveling direction of the
resin film 114 is 1-100 mm, and preferably 3-10 mm.
[0200] Preferably, a distance from the air blow openings 126 to the
liquid crystal layer 116 of the resin film 114 is 3-300 mm.
[0201] A flow speed of hot air through the air blow openings 126
can be determined suitably in consideration of characteristics of
the liquid crystal layer 116 and in combination with temperature.
In the present embodiment, the flow speed is 0.5-50 m/sec, and
preferably 1-20 m/sec because of great ease in creating of an air
flow in the feeding direction of the resin film 114. The
temperature of the hot air is preferably 70-300.degree. C.
Furthermore, a far infrared heater 166 may be additionally provided
in the dust removing device 10 for a combined use with the hot air
to heat the liquid crystal layer 116.
[0202] A temperature sensor 138 is disposed in the casing 122 of
the hot air supply unit 118, and monitors temperature of hot air
blowing the liquid crystal layer 116 through the air blow openings
126. A three-dimensional flow speed sensor 140 is disposed very
near to the liquid crystal layer 116, and monitors flow speed of
the hot air from the air blow openings 126. Signals of detection of
the temperature sensor 138 and the flow speed sensor 140 are sent
to the controller 136. According to the detection signals, the
controller 136 controls a rotational speeds of the fans 130 and
134, and temperature of heating air in the hot air generator 164 in
a manner of feedback control so as to optimize a flow speed of blow
of the hot air, a flow speed of the hot air in a direction
crosswise of the resin film 114, and the hot air temperature for
the above-described conditions.
[0203] If desired, a filter 142 can be disposed in the hot air
supply unit 118 with the fan 130 to eliminate dust from hot air. A
low molecular weight polymer remover 144 may be positioned
downstream from the fan 134 of the exhaust unit 120, utilize
oxidizing catalyst, and eliminate low molecular weight polymer
volatilizing from the liquid crystal layer 116. Furthermore, a
moisture adjustor (not shown) may be used to adjust to moisture
component included in the hot air.
[0204] In the present embodiment, hot air is used as gas or heating
medium in thermal treatment. However, other kinds of gas may be
used. Examples of gases are nitrogen, noble gas (argon and the
like), carbon dioxide, and the like, and a mixture of some of
those, and a mixture of air with some of those.
[0205] Examples of the resin film 114 are polyethylene
terephthalate (PET), polyethylene naphthalate (PEN) and the like.
Alternatively, web to be treated thermally may be paper, metal
foil, and other continuous material. For the purpose of producing
an optical compensatory sheet, the resin film 114 can preferably be
cellulose acetate film. The resin film 114 can have a preferable
width of 300-5,000 mm, and a preferable thickness of 3-1,000
.mu.m.
[0206] Operation of the thermal treating apparatus 110 for thermal
treatment of the liquid crystal layer 116 is hereinafter
described.
[0207] In the thermal treating apparatus 110, the fans 130 and 134
are actuated for hot air to flow out of the air blow openings 126
and blow the liquid crystal layer 116 of the resin film 114 being
traveled. The hot air is sucked through the exhaust opening 132
positioned downstream from the air blow openings 126. The hot air
flows in an air flow from the air blow openings 126 toward the
exhaust opening 132, and follows traveling of the resin film 114.
The air flow occurs reliably in a direction equal to the traveling
direction of the resin film 114.
[0208] It has been found that, when the liquid crystal layer 116 on
the resin film 114 being traveled is blown with hot air, a flow of
air in the traveling direction does not cause unevenness in
heating, but that a flow of air crosswise to the traveling is very
likely to cause unevenness in heating in a seriously influencing
manner to the finished condition of the liquid crystal layer 116.
It is concluded that the liquid crystal layer 116 can be heated
effectively with hot air flowing at a high speed in the traveling
direction and at a low speed in the crosswise direction.
[0209] In the thermal treatment, a component flow speed of the hot
air as viewed in a direction perpendicular to traveling of the
resin film 114 is 1 m/sec or less, preferably 0.8 m/sec or less,
and most preferably 0.7 m/sec or less. If it is desired in general
to reduce the component flow speed of the hot air, the flow speed
of blow through the air blow openings 126 can be reduced. However,
this causes a problem of insufficiency in heating the liquid
crystal layer 116. If the flow speed of exhaust is excessively
smaller than the flow speed of blow, then a flow in a direction
along traveling of the resin film 114 may not occur stably. The
component flow speed of the hot air as viewed in a direction
perpendicular to traveling of the resin film 114 is likely to
become too high. Therefore, a rotational speed of the fan 130.
should be maintained to obtain a flow speed of blow through the air
blow openings 126 suitably for heating the liquid crystal layer
116. Also, the rotational speeds of the fans 130 and 134 should be
so determined as to keep the component flow speed of the hot air as
viewed crosswise to traveling of the resin film 114 equal to or
less than 1 m/sec.
[0210] It follows that the liquid crystal layer 116 of the resin
film 114 can be heated by hot air with heat quantity regularized in
a direction crosswise to traveling of the resin film 114.
Distribution of heat in the thermal treatment is kept even
two-dimensionally.
[0211] In the present invention, the size L1 of the air blow
openings 126 as viewed crosswise to traveling of the resin film 114
is 1.05-2 times as long as the web width L2. Thus, the flow speed
of the hot air in the film traveling direction can be regularized
with reference to a direction crosswise to the traveling direction.
Specifically, the hot air is likely to flow slower in positions
near to lateral walls of the casing 122. Should the size L1 of the
air blow openings 126 crosswise to the traveling direction be
smaller than 1.05 times of the web width L2, then efficiency in
thermal treatment becomes extremely lower in the position near to
the lateral walls than central positions. In contrast, should the
size L1 of the air blow openings 126 crosswise to the traveling
direction be greater than two times of the web width L2, then there
occur flows in positions near to the lateral walls beside the resin
film 114 and from a film upper surface to a film lower surface
without blowing the resin film 114. This is undesirable, because
considerable flows are likely to occur beside the resin film 114 in
directions crosswise to traveling of the resin film 114.
[0212] The size L1 of the air blow openings 126 is 1.05-2 times as
long as the web width L2. Local unevenness in the thermal treatment
can be suppressed specially at the end positions of the air blow
openings 126.
[0213] The prior art is illustrated in FIG. 18. Hot air is supplied
through air blow openings 102 on the side of the liquid crystal
layer 116, and sucked through exhaust openings 103 on the side
opposite to the air blow openings 102. Portions of the liquid
crystal layer 116 at ends in the web width direction are provided
with the highest flow speed among plural portions of the liquid
crystal layer 116. Also, considerable flows are likely to occur
beside resin film 101 in directions crosswise to traveling of the
resin film 101. Therefore, it is impossible in the prior art to
accomplish the object of the invention. Unevenness in thermal
treatment occurs in the liquid crystal layer 116. Furthermore,
another prior type of thermal treatment has a problem. In this
type, the exhaust openings are positioned opposite to the air blow
openings with reference to the web width direction. The flow speed
becomes the highest in a position of the liquid crystal layer the
nearest to the exhaust openings. Unevenness in thermal treatment
occurs in an unwanted manner.
[0214] In the present embodiment, the exhaust unit 120 is
positioned downstream from the hot air supply unit 118. In
contrast, it is possible to position the exhaust unit 120 upstream
from the hot air supply unit 118, to create a flow of hot air that
is countercurrent to traveling of the resin film 114. Furthermore,
it is possible that there are two exhaust units 120 between which
the hot air supply unit 118 is disposed. Alternatively, the thermal
treating apparatus 110 can have the plural air blow openings 126
and plural exhaust openings 132 alternate with the air blow
openings 126. In any of those constructions, the hot air supply
unit 118 and the exhaust unit 120 are arranged in the traveling
direction to create the flow of hot air along traveling of the
resin film 114. The air flow in the traveling direction should have
a speed sufficiently high for thermally treating the liquid crystal
layer 116. The air flow in the crosswise direction should have as
low a speed as possible.
[0215] In the present embodiment, the thermal treating apparatus
110 is single. However, a plurality of thermal treating apparatuses
110 may be arranged in the traveling direction of the resin film
114. Also, temperature and flow speed of blow of air may be
determined individually in the plural thermal treating apparatuses
110. It is possible to effect the control of the present invention
in all the plural thermal treating apparatuses 110, or in part of
the plural thermal treating apparatuses 110. Specifically, it is
preferable to effect the control of the present invention in a
downstream part of the plural thermal treating apparatuses 110.
[0216] The thermal treatment according to the invention may be used
for photosensitive material, thermosensitive material,
pressure-sensitive recording material, magnetic recording tape, and
other types of recording materials. In particular, the thermal
treatment herein can be used effectively in a process of liquid
crystal layer forming in manufacturing an optical compensatory
sheet.
[0217] An example of the thermal treating apparatus 110 for use in
producing an optical compensatory sheet is described next.
EXAMPLES
[0218] In FIG. 14, a sheet producing line including the thermal
treating apparatus 110 is illustrated. A web supply device 150
supplies the resin film 114. Plural guide rollers 152 guide the
resin film 114 while the resin film 114 is traveled past a rubbing
unit 154, a liquid crystal layer coater 156, a preliminary drier
158, a main drier 160, the thermal treating apparatus 110 of the
invention, and an ultraviolet ray emitter 162 as curing unit. Then
a winder 168 winds the resin film 114 finally. There is a rubbing
roller 154A in the rubbing unit 154 for rubbing operation of the
resin film 114.
[0219] Sample 3
[0220] According to the invention, the resin film 114 was triacetyl
cellulose film Fujitac (trade name, manufactured by Fuji Photo film
Co., Ltd.), and was 1,000 mm wide and 100 .mu.m thick. Then a
surface of the resin film 114 was coated with solution at an amount
of 25 ml per 1 m.sup.2, the solution including 2 wt. % of
long-chain alkyl modified polyvinyl alcohol MP-203(trade name)
manufactured by Kuraray Co., Ltd. After the coating operation, the
resin film 114 was dried for 1 minute at 60.degree. C. to form a
preliminary resin layer, and was traveled at 18 m/min. During the
travel, a surface of the preliminary resin layer was subjected to
rubbing treatment to obtain an orientation layer. Pressure of the
rubbing roller 154A was 98 Pa per 1 cm of the preliminary resin
layer (1 kgf/cm.sup.2). A rotational speed of the periphery of the
rubbing roller 154A was 5.0 m/sec. The orientation layer, which was
obtained by rubbing of the preliminary resin layer, was coated with
liquid crystal coating solution while the resin film 114 was
traveled at a traveling speed of 18 m/min. For the liquid crystal
coating solution, discotic compounds
2,3,6,7,10,11-hexa(4-n-octyloxybenzoyloxy)triphenylene and
2,3,6,7,10,11-hexa(3-n-pentyloxybenzoyloxy)triphenylene were mixed
at a weight ratio of 4:1. Photo polymerization initiator Irgacure
907 (trade name) manufactured by Japan Ciba-Geigy was added to the
mixture of the compounds at 1 wt. %. Then the mixture was dissolved
in methyl ethyl ketone at 40 wt. %, to obtain the liquid crystal
coating solution. In the coating operation, a wire bar was used to
control the coating amount at 5 ml per 1 m.sup.2 of the resin film
114. Then the resin film 114 was dried at 100.degree. C., and
subjected to thermal treatment by the thermal treating apparatus of
the invention, to form a discotic nematic phase.
[0221] The thermal treating apparatus 110 had the slit-shaped
nozzles 126A of which the size L1 is 1,200 mm. The thermal treating
apparatus 110 supplied hot air to the resin film 114 at a flow
speed of 5 m/sec for blow, at temperature of 130.degree. C. for
three (3) minutes. A speed of the air crosswise to the traveling of
the resin film 114 was measured to be 0.5 m/sec. To obtain this, a
zone 50 mm long in the resin film 114 was measured at 11 points
every 100 mm in the crosswise direction. The maximum of the speeds
obtained from 11 points was determined as the measured speed of the
air in the crosswise direction. The three-dimensional flow speed
sensor 140 for the measurement was constituted by a
three-dimensional ultrasonic gas flow meter WA-390 manufactured by
Kaijo Corporation. After the thermal treatment, the liquid crystal
layer 116 received ultraviolet rays from the ultraviolet ray
emitter 162, and cured by cross linking, before the resin film 114
becomes wound by the winder 168.
[0222] The resin film 114 was unwound from the winder 168, and cut
into 10 sample pieces of optical compensatory sheets.
[0223] Sample 4
[0224] Sample 4 was the same as Sample 3 except for the flow of hot
air in the thermal treating apparatus 110, where a flow speed in
the direction crosswise to the traveling was set 1.0 m/sec. 10
sample pieces of optical compensatory sheets were cut from the
resin film 114 in a manner similar to Sample 3.
[0225] Comparative Example 4(Prior Art)
[0226] For Comparative Example 4, a thermal treating apparatus of
the prior art was used, and provided with an air blow opening and
an exhaust opening. The air blow opening is disposed in a position
associated with one lateral edge of the resin film 114. The exhaust
opening is so disposed that a center line of the resin film 114
lies between the air blow opening and the exhaust opening. A flow
speed in the direction crosswise to the traveling was set 2.0
m/sec. Other conditions of the thermal treating apparatus were the
same as those of Sample 3. 10 sample pieces of optical compensatory
sheets were cut from the resin film 114 in a manner similar to
Sample 3.
Comparative Example 5 (Prior Art)
[0227] Comparative Example 5 was the same as Comparative Example 4
except for the flow of hot air in the thermal treating apparatus,
where a flow speed in the direction crosswise to the traveling was
set 4 m/sec. 10 sample pieces of optical compensatory sheets were
cut from the resin film 114 in a manner similar to Sample 3.
[0228] Results of experiments from Samples 3 and 4 and Comparative
Examples 4 and 5 were evaluated in view of the flow speed of the
air in the direction crosswise to traveling, an angular difference
of an orienting angle from the intended orientation axis, and
quality of the product as an optical compensatory sheet. See the
table below. Note that the angular difference from orientation axis
in the table is an average of 10 samples for each example. To
estimate the quality, three grades of good, passing and failure
were used.
8 Angular Flow Speed of Air Difference in Crosswise (.degree.) From
Direction (m/sec) Orientation Axis Quality Sample 3 0.5 0.4 Good
Sample 4 1.0 1.0 Passing Comparative 2.0 2.3 Failure Example 4
Comparative 4.0 3.8 Failure Example 5
[0229] It is concluded from the table that Samples 3 and 4 obtained
according to the thermal treating apparatus 110 of the invention
had a very small angular difference of the orientation from the
orientation axis, and had high quality as a product of the optical
compensatory sheet. In particular, Sample 3, obtained after setting
the flow speed in the crosswise direction as 0.5 m/sec, had an
extremely small angular difference of the orientation from the
orientation axis. The entire surface of the liquid crystal layer
116 can be used as a product, to increase yield in producing the
optical compensatory sheet.
[0230] In contrast, poor results were obtained from Comparative
Examples 4 and 5 where the flow speed in the crosswise direction
was higher than 1 m/sec in a manner different from the invention.
There occurred a considerably great angular difference of the
orientation from the orientation axis. Quality was low as a product
of the optical compensatory sheet.
[0231] In view of those results, the thermal treating apparatus 110
of the invention is effective in minimizing the angular difference
of the orientation from the orientation axis for use in producing
the liquid crystal layer. The yield of the product can be high.
Furthermore, the quality of the product can be checked reliably
even in reducing the number of products sampled from the
manufacturing line for the purpose of inspecting the orientation
axis after the thermal treatment. The productivity of the optical
compensatory sheet can be high. Also, manual operation of operators
in the factory can be considerably quick and easy in view of the
same check of products as before. This is effective in reducing the
cost of the optical compensatory sheet.
[0232] Still another preferred embodiment is hereinafter described,
in which a dust removing apparatus is capable of operation without
damaging a surface of web.
[0233] In FIG. 15A, the dust removing apparatus is constituted by
guide rollers 214A, 214B, 214C and 214D, hovering rollers 216A,
216B and 216C as feeders, a first dust removing device 212, a
cleaning roller 220, a pinch roller 224, a rinsing unit 226 and a
drier 228. Resin film 210 as web travels while guided by the guide
rollers 214A, 214B, 214C and 214D and the hovering rollers 216A,
216B and 216C. The first dust removing device 212 supplies
compressed air to, and sucks the same from, the surface of the
resin film 210, and removes dust in a dry manner. The cleaning
roller 220 includes a resilient roll 218, which frictionally
contacts the resin film 210 to eliminate dust from the resin film
210. The pinch roller 224 includes a resilient roll 222, which
contacts a back surface of the resin film 210 and presses the resin
film 210 against the resilient roll 218 for efficient elimination
of dust. The rinsing unit 226 rinses and cleans the surface after
being polished by the cleaning roller 220. The drier 228 supplies
and sucks compressed air, and dries the resin film 210 by blowing
remainder of rinsing liquid on the resin film 210. Note that the
cleaning roller 220 and the pinch roller 224 constitute a second
dust removing device.
[0234] The guide rollers 214A-214D and the hovering rollers
216A-216C are suitably positioned to guide traveling of the resin
film 210. The guide rollers 214A-214D contact a back surface of the
resin film 210. The hovering rollers 216A-216C are opposed to a
front surface of the resin film 210 reverse to the back
surface.
[0235] In FIG. 15B, the hovering roller 216A is depicted. The
hovering rollers 216A-216C guide the resin film 210 in a manner
without contact its surface. To this end, holes 250 or slits are
formed in a peripheral wall of the hovering rollers 216A-216C. A
fan 252 or blower is connected with a duct disposed at a pivot of
the hovering rollers 216A-216C to communicate the inside of the
rollers. Compressed air is supplied by the fan 252 to the inside of
the hovering rollers 216A-216C, and ejected through the holes 250
to hover the resin film 210 while the resin film 210 travels. Thus,
deposition of dust to the resin film 210 is prevented effectively
after the dust removal.
[0236] The positions of the guide rollers 214A-214D and the
hovering rollers 216A-216C are conditioned as follows. The resin
film 210 is caused to contact the resilient roll 218 about the
cleaning roller 220 with a positive angle of lap after dust removal
in the first dust removing device 212. Also, the front surface of
the resin film 210 after moving past the cleaning roller 220 is
guided in a path close to the rinsing unit 226 and the drier 228
that are positioned downstream.
[0237] A diameter of the hovering rollers 216A-216C is 3-30 cm,
preferably 10-25 cm in consideration of flexure and weight.
Pressure of compressed air in the hovering rollers 216A-216C is
490-6,865 Pa (50-700 mmAq), and preferably 1,961-4,903 Pa (200-500
mmAq), which is for the purpose of hovering the resin film 210 at a
distance of 0.1-10 mm, preferably 0.5-5 mm in a manner overcoming
film tension. A flow speed of the compressed air is 1-50 m.sup.3
per minute, and preferably 3-30 m.sup.3 per minute.
[0238] The first dust removing device 212 blows the resin film 210
with compressed air with high cleanness, and eliminates foreign
matter from the surface of the resin film 210. The first dust
removing device 212 is disposed close to the resin film 210,
opposed to the guide roller 214A, and provided with a high-pressure
air supply/exhaust machine (not shown) connected therewith. In FIG.
15C, plural air blow openings 254 and plural exhaust openings 256
are formed in the first dust removing device 212, are slit-shaped,
and extend crosswise to the traveling direction of the resin film
210. The air blow openings 254 blow the resin film 210 with the
compressed air. The exhaust openings 256 suck and eject the
compressed air and also dust removed from the resin film 210.
[0239] Furthermore, an ultrasonic oscillator 258 may be disposed
inside the air blow openings 254 for applying ultrasonic waves to
the compressed air to blow the resin film 210. The first dust
removing device 212 can be constituted by an ultrasonic dust
remover which supplies vibrated compressed air, and sucks dust. An
example of the ultrasonic dust remover is New Ultra Cleaner (trade
name) manufactured by Shinko Co., Ltd. This is highly effective in
dust removal, because of a separating operation to subjecting dust
to shearing in boundary layers of air flow that have a thickness
from tens of .mu.m to 100 .mu.m, and because of vibrating operation
with ultrasonic waves.
[0240] A distance from the first dust removing device 212 to the
resin film 210 is 0.1-10 mm, and preferably 0.3-5 mm so as to
obtain effects in dust removal without blocking handling of the
resin film 210. Flow speeds of supply and exhaust of the compressed
air can be set high with advantages in a range not to influence
ease in handling. It is particularly important in dust removal to
balance the flow speeds between the supply and exhaust of the air
with cleanness. The exhaust flow speed is determined higher than
the supply flow speed. The supply and exhaust flow speeds are
determined 1-100 m.sup.3 /min, and preferably 10-40 m /min. The
exhaust flow speed is determined higher than the supply flow speed
by a difference of 0.1-50 m.sup.3 /min, and preferably 1-10
m.sup.3/min. A pressure of supply of compressed air is set 5-100
kPa, preferably 10-50 kPa, and most preferably 20-35 kPa. A
pressure of exhaust of compressed air is set 1-20 kPa, and
preferably 3-10 kPa.
[0241] The cleaning roller 220 polishes the resin film 210
continuously by means of the resilient roll 218, to remove dust
from the resin film 210. The cleaning roller 220 is constituted by
a roller body and the resilient roll 218 disposed about the roller
body. The cleaning roller 220 is disposed between the guide rollers
214B and 214C. A cleaning liquid bath 230 stores cleaning liquid
232, in which a lower half of the cleaning roller 220 is dipped.
The motor 26 of FIG. 4 is associated with the cleaning roller 220,
and rotates the same. The resin film 210 is polished by the
resilient roll 218 which rotates with friction.
[0242] As the lower half of the cleaning roller 220 is dipped in
the cleaning liquid 232, rotation of the cleaning roller 220 makes
the resilient roll 218 incessantly wet with the cleaning liquid
232. Thus, the dust can be removed with at least 1,000 times as
high force of shearing as a dry type of dust remover. It is
possible reliably to remove small dust stuck firmly. In the present
embodiment, at first the dry type of dust removal is effected for
removing weakly stuck dust. Then the wet type of dust removal is
effected for removing strongly stuck dust. In the end, high effects
in removal of dust are obtained.
[0243] In the present embodiment, only a lower half of the cleaning
roller 220 is dipped in the cleaning liquid 232. However, the
entirety of the cleaning roller 220 may be dipped in the cleaning
liquid 232.
[0244] The pinch roller 224 is supported in a rotatable manner. The
resilient roll 222 about the pinch roller 224 is pressed against a
back surface of the resin film 210. So a front surface of the resin
film 210 is pressed against the resilient roll 218 about the
cleaning roller 220 to keep high the pressure locally along one
line. Effects in polishing the resin film 210 with the resilient
roll 218 are increased. The pinch roller 224 is constituted by a
roller body and the resilient roll 222 disposed about the roller
body, and so disposed that the resin film 210 lies between it and
the cleaning roller 220.
[0245] In the pinch roller 224, the resilient roll 222 has a
thickness equal to or more than 0.5 mm, preferably 0.5-100 mm, and
desirably 1.0-50 mm. Any suitable material may be used to produce
the resilient roll 222. Examples of the material for the resilient
roll 222 are polyamides (such as 6-nylon, 66-nylon, and copolymer
nylon), polyesters (such as polyethylene terephthalate,
polybutylene terephthalate, and copolymer polyester), polyolefins
(such as polyethylene and polypropylene), polyvinyl halide (such as
polyvinyl chloride, poly vinylidene fluoride, and Teflon), natural
rubber, neoprene rubber, nitrile rubber, Nordel, Viton rubber,
Hypalon, polyurethane, rayon, cellulose, and the like. The
resilient roll 222 formed from those resilient materials may have a
structure formed from a single material, mixed structure, layered
structure, a structure of woven fabric with fibers, and a non-woven
structure as a non-woven fabric. Conditions of preferable materials
include a characteristic not being softened or dissolved by the
cleaning liquid 232, and also a lower hardness than that of the
surface of the resin film 210.
[0246] Note that, if the resilient roll 222 has too great a size in
a direction crosswise to the film traveling, there occurs a problem
in handling due to a difference in the speed between the resilient
roll 218 and the resin film 210 with both of which the resilient
roll 222 is in contact. If the resilient roll 222 has too small a
size in the crosswise direction, there occurs a problem in effects
in dust removal because lateral edge portions of the resin film 210
are not pressed by the resilient roll 222. It is concluded that the
size of the resilient roll 222 in the crosswise direction is
preferably equal to or more than a size of a product to be taken
from the resin film 210, and equal to or less than a sum of the
size of the resin film 210 and a range of a zigzag shift during the
travel.
[0247] A position of the pinch roller 224 may be determined in any
suitable manner in combination with the cleaning roller 220 to nip
the resin film 210, but is restricted by a space and relative
position for determining the angle of lap of the resin film 210 to
the cleaning roller 220.
[0248] A diameter of the pinch roller 224 is less than 200 cm,
preferably 1-100 cm, and desirably 1-20 cm in consideration of a
space to be occupied, precision in manufacture, and a manufacturing
cost.
[0249] The pressure of the pinch roller 224 to press the resin film
210 against the cleaning roller 220 is determined equal to or less
than 981 N per meter of the width, preferably 0.3-490 N/m, and
desirably 1-245 N/m (equal to or less than 100 kgf per meter of the
width, preferably 0.03-50 kgf/m, and desirably 0.1-25 kgf/m).
[0250] The rinsing unit 226 rinses and cleans the resin film 210 by
jetting or spraying the cleaning liquid 232 to the front surface of
the resin film 210 after being polished by the cleaning roller 220.
The rinsing unit 226 is disposed between the guide rollers 214C and
214D.
[0251] The cleaning liquid to be sprayed by the rinsing unit 226 is
obtained by clarifying the cleaning liquid 232 stored in the
cleaning liquid bath 230. A pipe 234 connects the rinsing unit 226
to the cleaning liquid bath 230. A pressure feed pump 236 is
associated with the pipe 234, and sends the cleaning liquid 232
from the cleaning liquid bath 230. A filtration equipment 238
clarifies the cleaning liquid 232, which is sent to the rinsing
unit 226 and sprayed. The cleaning liquid 232 from the rinsing unit
226 rinses the surface of the resin film 210 having been polished
by the resilient roll 218 of the cleaning roller 220. Dust or
foreign matter, which remains even after polishing with the
resilient roll 218 or has been deposited due to the cleaning liquid
232 in the cleaning liquid bath 230, is washed away. The cleaning
liquid 232 jetted or sprayed by the rinsing unit 226 strikes the
resin film 210 and drops by gravity into the cleaning liquid bath
230. Accordingly, the cleaning liquid 232 is circulated.
[0252] The cleaning liquid 232 from the rinsing unit 226 should be
preferably a material with a characteristic not to dissolve or
extract a substance included in the resin film 210 or an. undercoat
layer with which the resin film 210 is coated, and a characteristic
of not permeating in any of those. If the undercoat layer is formed
from water-soluble material such as gelatine, the cleaning liquid
232 can include non-aqueous solvent with low polarity. Examples of
the solvent used with the present invention are disclosed in
Shimban Yozai Pocket Book (Solvent Pocket Book, New Edition,
Ohmsha, Ltd., 1994). Of course, any suitable solvent may be used. A
boiling point of the solvent is preferably 30-120.degree. C. in
view of quick drying. Viscosity of the solvent or fluid is
preferably 50 mPa.multidot.s or less. Only one type of the cleaning
liquid 232 may be used. Also, plural types of the cleaning liquid
232 can be used in combination.
[0253] In FIG. 15A, there is an ultrasonic vibrator 240, which
applies ultrasonic waves to the resilient roll 218.
[0254] The ultrasonic vibrator 240 and the resilient roll 218 are
suitably disposed so that part of the cleaning liquid 232 is
located between those for the purpose of efficiently transmitting
ultrasonic waves to the surface of the resilient roll 218.
[0255] The drier 228 blows and dries remainder of the cleaning
liquid 232 existing on the resin film 210 after rinsing. The drier
228 is disposed near to the resin film 210 backed up by the guide
roller 214D, and is provided with a fan or blower (not shown) for
supplying and sucking compressed air. In a manner similar to the
first dust removing device 212, the drier 228 includes the air blow
openings 254 and the exhaust openings 256 respectively extending
crosswise to traveling of the resin film 210. The compressed air
with high cleanness is supplied by the fan or blower, and is caused
to flow through the air blow openings 254 to the resin film 210. So
the remainder of the cleaning liquid 232 is blown away from the
resin film 210. Then the remainder is sucked through the exhaust
openings 256, and removed.
[0256] Note that an ultrasonic vibrator may be disposed in the
drier 228 and directed to the fan or blower. The ultrasonic
vibrator applies ultrasonic waves to the compressed air to be
supplied through the air blow openings 254.
[0257] Note that a distance from the drier 228 to the resin film
210 is 0.1-10 mm, and preferably 0.3-5 mm so as to obtain effects
in drying without blocking handling of the resin film 210. Flow
speeds of supply and exhaust of the compressed air can be set high
with advantages in a range not to influence ease in handling. It is
particularly important in drying by blow to balance the flow speeds
between the supply and exhaust of the air with cleanness. The
exhaust flow speed is determined higher than the supply flow speed.
This is to prevent scattering of the cleaning liquid 232 with dust
inside the apparatus, and also for a final process of dust removal
in which final remainder of dust on the resin film 210 is
eliminated with the cleaning liquid 232. The supply and exhaust
flow speeds are determined 1-100 m.sup.3/min, and preferably 10-40
m /min. The exhaust flow speed is determined higher than the supply
flow speed by a difference of 0.1-50 m.sup.3/min, and preferably
1-10 m /min. A pressure of supply of compressed air is set 5-100
kPa, preferably 10-50 kPa, and most preferably 20-35 kPa. A
pressure of exhaust of compressed air is set 1-20 kPa, and
preferably 3-10 kPa. The retrieved remainder of the cleaning liquid
232 is processed by an air/liquid separator device (not shown), and
will be used again.
[0258] The operation of the dust removing apparatus is described
next.
[0259] Examples of the resin film 210 to be cleaned according to
the invention are polyester, polyethylene terephthalate,
polyethylene naphthalate, cellulose nitride, cellulose ester,
polyvinyl acetal, polycarbonate, polyvinyl chloride, polymeric
vinylidene chloride, polyimide, polyamide, and other resins, and
paper, metal, and the like. A typical example with flexibility is
paper partially acetylated, or which is coated with a coating of
barium hydroxide (baryta) and/or .alpha.-olefin polymer, of which
examples are polyethylene, polypropylene, ethylene butene
copolymer, and other polyolefins with a carbon number of 2-10. It
is possible to add agents to the material of the resin film 210 for
various industrial uses. Examples of materials produced by using
the resin film 210 are classified as photosensitive material,
magnetic recording tape, photographic film and the like. To produce
those, the resin film 210 is coated with photosensitive substance,
magnetic substance, photochemically reacting substance and the
like.
[0260] In the dust removing apparatus, the resin film 210 travels
while guided by the guide rollers 214A-214D and the hovering
rollers 216A-216C. The guide rollers 214A-214D contact the back
surface of the resin film 210. The hovering rollers 216A-216C are
opposed to the front surface of the resin film 210, and guide the
resin film 210 in a manner without contacting the resin film 210
for the purpose of preventing depositing of dust to the front
surface. In the travel, at first the first dust removing device 212
removes dust in a dry manner without contact. Thus, the dust with
relatively weak adhesion is removed.
[0261] The resin film 210 subjected to dust removal by the first
dust removing device 212 is then polished continuously by the
resilient roll 218 of the cleaning roller 220 in rotation while
pressed by the resilient roll 222 of the pinch roller 224.
Remainder of foreign matter, if stuck still on the resin film 210
with a somewhat strong adhesion, can be eliminated by the cleaning
roller 220.
[0262] As the cleaning roller 220 rotates, the resilient roll 218
is kept wet with the cleaning liquid 232. Thus, dust can be removed
with at least 1,000 times as high force or stress of shearing as a
dry type of dust remover with air. Even small dust stuck firmly can
be removed. Also, hardness of the resilient roll 218 is much
smaller than a metal rod or blade. Even upon pressure of the
resilient roll 218 to the resin film 210, very few scratches or
damages will occur.
[0263] The resilient roll 218 after polishing the resin film 210
receives ultrasonic waves from the ultrasonic vibrator 240 during
rotation in the cleaning liquid 232. Even if removed dust is still
stuck on the resilient roll 218, the dust can be eliminated from
the resilient roll 218 ultrasonically in the cleaning liquid 232.
So the resilient roll 218 can polish the resin film 210 while kept
clean. It is possible to avoid scratching the resin film 210 with
the remaining dust, and avoid damaging the resin film 210.
[0264] The resin film 210 polished by the resilient roll 218 is
subjected to ejection of the cleaning liquid 232 from the rinsing
unit 226. It is possible to eliminate dust remaining after the
polishing and dust carried from the cleaning liquid 232 and
deposited to the resin film 210. For the cleaning liquid 232
ejected from the rinsing unit 226, the cleaning liquid 232 stored
in the cleaning liquid bath 230 is used. The cleaning liquid 232 is
filtered by the filtration equipment 238 before being sent to the
rinsing unit 226. Thus, no dust is brought from the rinsing unit
226 with the cleaning liquid 232 and deposits on the resin film
210.
[0265] After rinsing, the resin film 210 is subjected to drying by
blow of compressed air in the drier 228 in a non-contact manner.
Finally, remaining small part of the dust or foreign matter can be
eliminated from the resin film 210 with the cleaning liquid
232.
[0266] This being so, the dust removing apparatus of the invention
can remove dust or any foreign matter from the surface of the resin
film 210 without scratches or damages.
[0267] Note that, in the present embodiment, each of the first dust
removing device 212, the cleaning roller 220, the pinch roller 224,
the rinsing unit 226 and the drier 228 is single. However, it is
possible to use two or more first dust removing devices 212, two or
more combinations of the cleaning roller 220 and the pinch roller
224, two or more rinsing units 226 and two or more driers 228. This
is typically effective when the resin film 210 is considerably
contaminated, or if drying operation by blow is not very quick with
the single drier 228.
[0268] Specifically, two or more series of the devices from the
first dust removing device 212 to the drier 228 may be arranged in
parallel. Furthermore, sections or parts in each of those devices
may be disposed in a plural number. Alternatively, two or more
first dust removing devices 212 may be disposed upstream from the
single series from the cleaning roller 220 to the drier 228.
Additionally, two or more first dust removing devices 212 and two
or more combinations of the cleaning roller 220 and the pinch
roller 224 may be disposed upstream from the rinsing unit 226 and
the drier 228 which are single. Also, devices from the first dust
removing devices 212 to the rinsing units 226 may be disposed in
plural numbers upstream from the drier 228 being single.
Furthermore, the first dust removing device 212 may be single
upstream from devices from the cleaning rollers 220 to the driers
228 in plural numbers. Alternatively, the first dust removing
device 212 and the cleaning roller 220 may be single upstream from
the rinsing units 226 and the driers 228 in plural numbers.
Additionally, the first dust removing device 212, the cleaning
roller 220 and the rinsing unit 226 may be single upstream from the
two or more driers 228. Any modification may be used.
[0269] In the above embodiment, the cleaning liquid 232 in the
cleaning liquid bath 230 is cleaned and supplied to the rinsing
unit 226 in circulation. Alternatively, an additional liquid bath
may be disposed for supplying cleaning liquid to the rinsing unit
226 in a separate manner from the cleaning liquid bath 230.
[0270] In FIG. 15D, an alternative roller is depicted to be used
instead of the hovering rollers 216A-216C. The roller includes a
shaft portion and a pair of edge rollers 262 for supporting edge
portions of the resin film 210. Also, a combined structure
including the hovering rollers 216A-216C and the edge rollers 262
may be used.
[0271] Although a diameter of the edge rollers 262 may be great for
the purpose of preventing flexure or looseness, the diameter is
determined 3-30 cm, preferably 5-15 cm in view of a space to be
used and its suitable weight. Portions of the edge rollers 262 may
be formed with a shaft portion as originally one piece, or else may
be previously separate rings and secured to a shaft fixedly. The
sizes of the edge rollers 262 and the shaft are so determined that
the resin film 210 will not contact the shaft when loosened, and
that no wrinkles will occur in the resin film 210 being fed. A
difference between diameters of the edge rollers 262 and the shaft
is 0.4-20 mm, and preferably 1-5 mm. An area of contact of the edge
rollers 262 to the resin film 210 should preferably be small in
view of reducing repeated deposition of dust or foreign matter to
the resin film 210. A width of a zone for contact of the edge
rollers 262 to the resin film 210 on each of the lateral sides is 1
mm or more, preferably 5 mm or more in consideration of preventing
disengagement of the resin film 210 from the edge rollers 262 even
when the resin film 210 travels in a zigzag shifted manner.
EXAMPLES
[0272] Comparative Example 6 (Prior Art)
[0273] In FIG. 16, a web supply device 201 supplied polyethylene
terephthalate film at a speed of 50 m/min. The film was 100 .mu.m
thick and 100 cm wide. A coater head 202 coated the film with
coating solution including particles of latex of which average
diameters were 3 .mu.m and 10 .mu.m. A drier zone 203 evaporated
the coating solution to obtain film in which an amount of deposited
foreign matter was controlled. Composition of the coating solution
including the latex was as follows:
9 3 .mu.m latex stock solution 0.1 ml 10 .mu.m latex stock solution
3.0 ml Methanol 46.9 ml Pure water 50.0 ml
[0274] The latex stock solution includes monodisperse polystyrene
latex at 1 wt. %. The resin film 210 was coated with the solution
at 25 ml/m.sup.2. A surface of the resin film 210 was dried, and
then checked visually through a microscope. It was observed that
latex particles of 3 .mu.m and 10 .mu.m were regularly deposited on
the surface at a density of approximately 1,000 particles per 1
m.sup.2.
[0275] Then a dust removing zone 205 of a wet type in FIG. 16
received the resin film 210 being fed, and removed dust from the
same. The dust removing zone 205 had a fountain coater disclosed in
JP-B 5-050419 (corresponding to JP-A 62-060749), which coated the
resin film 210 with methanol at 20 ml/m.sup.2. Immediately after
this, a rotating wire bar was pressed against the resin film 210
for removing dust. The wire bar was 100 cm long in the width
direction of the resin film 210, and 1 cm across. Sections before
and after the dust removing zone 205 are separate in application of
tension to the resin film 210. The tension was 118 N/m per unit
width (12 kgf/m per unit width).
[0276] After this, traveling of the resin film 210 was stopped. The
resin film 210 was dried, and wound by a winder 206. In the zone
205 disposed upstream from the winder 206, a sample piece being 1
meter long was taken from the resin film 210 for evaluation of the
dust removal. The sample piece was observed through a microscope
set at a power of 100 times, to count the remainder of the latex
particles. In case of existence of scratches in the surface of the
resin film 210, damaged grades of the resin film 210 were recorded.
Those grades were as follows.
10 Scratches (/m) Grade 0 None 1-10 Locally Existing 10-100
Numerous
[0277] Sampling of a piece was effected for two times, one time
after treatment of 50 meters in a continuous manner, and the second
time after treatment of 3,000 meters in a continuous manner.
Reliability related to lapse of time was checked.
[0278] In Comparative Example 6, a wire bar was contacted with the
resin film 210 and caused to rotate at 50 r.p.m. in reverse to the
traveling. In FIG. 17A, results of this are illustrated. The number
of latex particles decreased. In spite of the initially existing
100 particles per 1 meter, the particles of 3 .mu.m became
approximately {fraction (1/5 )} as numerous as before. The
particles of 10 .mu.m became approximately {fraction (1/10 )} as
numerous as before. The number of particles of dust or foreign
matter became increased upon treatment of 3,000 meters in
comparison with treatment of 500 meters. Many visible scratches
occurred in the surface of the resin film 210.
Comparative Example 7 (Prior Art)
[0279] The resin film 210 was subjected to the dust removal of the
wet type by using latex particles in the same manner as Comparative
Example 6 except for a roller in a dust removing zone 204 of a wet
type. See FIG. 16. The cleaning roller, in a manner similar to the
cleaning roller 220 in FIG. 15A, included an aluminum roller body
and a rubber roll disposed thereabout. The roller body was 110 cm
long and 20 cm across. The rubber roll was formed from Viton rubber
and was 1 cm thick. Guide rollers were adjusted to set the angle of
lap of the cleaning roller at 50 degrees to the resin film 210. A
lower portion of the cleaning roller is dipped in methanol or
cleaning liquid at a depth of 10 cm. The cleaning roller was
rotated at 50 r.p.m. in reverse to the traveling direction. The
methanol was circulated and filtrated, treated by the pressure feed
pump 236 and the ultrasonic vibrator 240, and sent to the rinsing
unit 226.
[0280] The rinsing unit 226 had a clearance which was 100 cm long
as viewed in the film width direction of the resin film 210, and 1
mm wide as viewed in the traveling direction, and supplied the
cleaning liquid 232 at a flow speed of 30 liters per minute. The
filtration equipment 238 included Astro Pore Filter (trade name)
manufactured by Fuji Photo Film, Co., Ltd. The filter had a nominal
size of the minute openings of 0.2 .mu.m.
[0281] Two ultrasonic vibrators 240 manufactured by Japan Alex
Corporation were used, arranged crosswise to the traveling
direction of the resin film 210, and caused to emit ultrasonic
waves to the whole range of the cleaning rubber roller. Each of the
ultrasonic vibrators 240 was 50 cm long and 30 cm across, and
emitted the ultrasonic waves of 100 kHz at the power of 1,000
W.
[0282] Results of experiments of Comparative Example 7 are shown in
FIG. 17A. In comparison with Comparative Example 6 according to the
prior art, the number of remaining particles is smaller. There is a
smaller increase in the particles after the treatment of 3,000
meters. In conclusion, those were obtained by effects of the
cleaning roller and application of ultrasonic waves for cleaning. A
surface of the rubber roll of Viton was visually observed after the
treatment of 3,000 meters. No deposition of particles was
discovered.
Comparative Example 8 (Prior Art)
[0283] The resin film 210 was subjected to the dust removal of the
wet type by using the cleaning roller 220 in the same manner as
Comparative Example 7, but except for the dust removing zone 205 of
a wet type in FIG. 16 which was provided with the first dust
removing device 212, the drier 228 and the edge rollers 262 of a
non-contact type. For the first dust removing device 212 and the
drier 228, see FIG. 15A.
[0284] Each of the first dust removing device 212 and the drier 228
was provided with a New Ultra Cleaner (trade name) type UVU-W
manufactured by Shinko Co., Ltd. In the cleaner, a distance to the
resin film 210 was 3 mm. A flow speed for blow of air was 15 m/min.
A pressure for blow of air was 20 kPa. A flow speed for exhaust of
air was 20 m.sup.3/min. A pressure for exhaust of air was 5 kPa. In
the edge rollers 262, the shaft portion was 10 cm across. The
periphery of the edge rollers 262 had a diameter of 10.4 cm. A
range of contact of the edge rollers 262 with the resin film 210
was 1 cm. Note that the resin film 210 was 100 cm wide.
[0285] Results of the experiments are shown in FIG. 17B at
Comparative Examples 8a and 8b. Comparative Example 8a is the same
as Comparative Example 7 except for that the dry type of dust
removal is added to a step before the wet type of dust removal. As
a result, the number of remaining foreign particles decreased even
after treatment of 50 meters. The structure combined with the dry
type of dust removal was found effective. Comparative Example 8b is
the same as Comparative Example 8a except for the addition of the
drier 228 after the wet type of dust removal, and the edge rollers
262 of a non-contact type in relation to the surface after the dust
removal. The numbers of the remaining particles were decreased
considerably. No increase occurred in the number of particles of
dust even after treatment of 3,000 meters. However, it was found
that there was a smaller effect to removal of 3 .mu.m particles
than to that of 10 .mu.m.
[0286] Sample 5
[0287] The resin film 210, according to the invention, was
subjected to the dust removal of the wet type in the same manner as
Comparative Example 8, but except for the dust removing zone 205 of
a wet type in FIG. 16 which is provided with the cleaning roller
220 depicted in FIG. 15A.
[0288] The cleaning roller 220 included the aluminum roller body
and the resilient roll 218 disposed thereabout. The roller body was
110 cm long and 20 cm across. The resilient roll 218 was formed
from Viton rubber, was 0.2 cm thick and 100.2 cm long. The
resilient roll 218 was fitted about the roller body in a
symmetrical manner. The cleaning roller 220 was positioned so that
the resin film 210 passes a position exactly at the top of the
periphery of the cleaning roller 220.
[0289] Results of the experiments are shown in FIG. 17B at Samples
5a and 5b. Sample 5a is the same as Comparative Example 8b except
for that the pinch roller 224 applies pressure of 9.8 N/m per unit
width (1 kgf/m per unit width). As a result, the number of
remaining foreign particles decreased. The structure combined with
the pinch roller 224 was found effective. Sample 5b was the same as
Sample 5a except for that the pinch roller 224 applied pressure of
19.6 N/m per unit width (2 kgf/m per unit width). The numbers of
the particles of 3 .mu.m and 10 .mu.m were decreased to
approximately zero (0). No increase occurred in the number of
particles of dust or foreign matter even after treatment of 3,000
meters. In conclusion, dust was reliably removed from the resin
film 210 according to the dust removal of the invention.
[0290] Although the present invention has been fully described by
way of the preferred embodiments thereof with reference to the
accompanying drawings, various changes and modifications will be
apparent to those having skill in this field. Therefore, unless
otherwise these changes and modifications depart from the scope of
the present invention, they should be construed as included
therein.
* * * * *