U.S. patent application number 11/964625 was filed with the patent office on 2008-04-24 for optical film and fabrication method thereof.
This patent application is currently assigned to DAXON TECHNOLOGY INC.. Invention is credited to Po-Tau Liu.
Application Number | 20080096006 11/964625 |
Document ID | / |
Family ID | 38041193 |
Filed Date | 2008-04-24 |
United States Patent
Application |
20080096006 |
Kind Code |
A1 |
Liu; Po-Tau |
April 24, 2008 |
OPTICAL FILM AND FABRICATION METHOD THEREOF
Abstract
An optical film and fabrication method thereof are disclosed.
The optical film comprises a substrate and an anti-static layer
disposed thereon. The anti-static layer comprises a resin layer and
a plurality of anti-static particles *wherein the bottom half
portion of the anti-static layer contains more than 60 wt % of tile
anti-static particles.
Inventors: |
Liu; Po-Tau; (Taipei City,
TW) |
Correspondence
Address: |
QUINTERO LAW OFFICE, PC
2210 MAIN STREET, SUITE 200
SANTA MONICA
CA
90405
US
|
Assignee: |
DAXON TECHNOLOGY INC.
TAOYUAN
TW
|
Family ID: |
38041193 |
Appl. No.: |
11/964625 |
Filed: |
December 26, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11388271 |
Mar 24, 2006 |
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11964625 |
Dec 26, 2007 |
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Current U.S.
Class: |
428/323 ;
427/162 |
Current CPC
Class: |
G02F 2202/22 20130101;
G02B 1/10 20130101; Y10T 428/31855 20150401; C03C 2217/475
20130101; C08J 7/0427 20200101; G02B 1/14 20150115; Y10T 428/31938
20150401; Y10T 428/31504 20150401; C08J 7/046 20200101; C08J 7/044
20200101; Y10T 428/257 20150115; Y10T 428/256 20150115; C03C
2217/476 20130101; Y10T 428/25 20150115; C03C 17/007 20130101; Y10T
428/31507 20150401; Y10T 428/31971 20150401; Y10T 428/31786
20150401; G02B 1/16 20150115 |
Class at
Publication: |
428/323 ;
427/162 |
International
Class: |
B32B 5/16 20060101
B32B005/16; B05D 5/06 20060101 B05D005/06 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 16, 2005 |
TW |
TW94140235 |
Claims
1-10. (canceled)
11. A method of fabricating an optical film, comprising: providing
a substrate; coating an anti-static solution on the substrate to
form an anti-static wet layer thereon, wherein the anti-static
solution comprises a plurality of anti-static particles and a resin
material; providing the anti-static particles an external force or
an inter-particle force; drying the anti-static wet layer; and
curing the anti-static wet layer to form an anti-static layer,
comprising the anti-static particles and a resin layer, and having
a top half portion and a bottom half portion containing more than
60 wt % of the anti-static particles.
12. The optical film of claim 11, wherein the anti-static particles
have a primary diameter of 5 to 100 nm.
13. The optical film of claim 11, wherein the anti-static particles
have a primary diameter of 10 to 40 nm.
14. The method of claim 11, wherein the anti-static particles have
a zeta potential of +70 to -70 eV in the anti-static solution.
15. The method of claim 11, wherein the anti-static particles have
a zeta potential of -10 to -50 eV in the anti-static solution.
16. The method of claim 11, wherein the inter-particle force is
provided by adding an electrolyte or a polymeric flocculant to the
anti-static solution.
17. The method of claim 16, wherein the electrolyte has a
concentration of 10.sup.-6 to 10.sup.-1 M in the anti-static
solution.
18. The method of claim 11, wherein the external force is provided
by applying an electric field or a magnetic field to the
anti-static particles in the anti-static wet layer.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a thin film and fabrication method
thereof and in particular to an optical film and fabrication method
thereof.
[0003] Liquid crystal display (LCD) and liquid crystal display
television (LCD TV) are currently popular in display technology. An
optical film having good transmittance is an important component. A
hard coat layer is usually coated on an optical film, preventing
outside damage. The hard coat layer is mostly insulation and
comprises resin materials. such that static electricity is easily
accumulated, producing electrostatic discharge (ESD). and dust is
readily attracted to its surface. Therefore, an anti-static layer
is usually coated on the hard coat layer surface to prevent the
static issues.
[0004] A conventional anti-static hard coat layer can be formed by
coating once or twice. Two-step coating is more problematic than
one-step coating, since some defects appear as a bottom layer
coated on a substrate, and other defects appear as a top layer then
coated on the bottom layer, so that the defective fraction of
two-step coating is higher.
[0005] Two-step coating involves two types, anti-static layer upon
hard coat layer and hard coat layer upon anti-static layer.
[0006] FIG. 1a shows an anti-static hard coat film 10a, comprising
substrate 12, hard coat layer 14 and anti-static layer 16
respectively disposed on the substrate 12, and anti-static
particles 18 dispersed in the anti-static layer 16. In this case,
electric conductivity is increased due to the anti-static layer 16
disposed as the surface layer of the anti-static hard coat film 10a
but anti-scratch properties are reduced because the hardness and
abrasion of the anti-static layer 16 is usually poorer than that of
the hard coat layer 14.
[0007] FIG. 1b shows an anti-static hard coat film 10b, comprising
substrate 12, hard coat layer 14 and anti-static layer 16
respectively disposed on the substrate 12, and anti-static
particles 18 dispersed in the anti-static layer 16. In this case,
anti-scratch properties are increased due to the hard coat layer 14
disposed as the surface layer of tile anti-static hard coat film
10b, but electric conductivity is reduced.
[0008] If the refractive index of the anti-static particles 18 is
high, the anti-static layer 16 as shown in FIGS. 1a and 1b will
results in interference and high reflection, especially the
anti-static particles 18 are collected in a thin layer (the
anti-static layer 16).
[0009] One-step coating can also be used. Referring to FIG. 1c, an
anti-static hard coat film 10c is provided, comprising a substrate
12 and an anti-static layer 15 disposed thereon. The anti-static
layer 15 comprises a resin layer 19 and dispersed anti-static
particles 18. The process of one-step coating is simpler than
two-step coating, but the anti-static effects of the anti-static
hard coat film 10c are less than the anti-static hard coat film 10a
and 10b due to more separated particles.
BRIEF SUMMARY OF THE INVENTION
[0010] A detailed description is given in the following embodiments
with reference to the accompanying drawings.
[0011] In an embodiment, an optical film is provided. The optical
film comprises a substrate and an anti-static layer disposed
thereon. The anti-static layer comprises a resin layer and a
plurality of anti-static particles, wherein the bottom half portion
of the anti-static layer contains more than 60 wt % of the
anti-static particles.
[0012] A method for fabricating an optical film is also provided. A
substrate is provided. An anti-static solution is coated on the
substrate to form an anti-static wet layer thereon. The anti-static
solution comprises a plurality of anti-static particles and a resin
material. The anti-static particles are interacted by an external
force or an inter-particle force. The anti-static wet layer is
dried and cured to form an anti-static layer. Which comprises the
anti-static particles and a resin layer. The anti-static layer has
a top half portion and a bottom half portion containing more than
60 wt % of the anti-static particles.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The invention can be more fully understood by reading the
subsequent detailed description and examples with references made
to the accompanying drawings, wherein:
[0014] FIGS. 1a to 1c are cross-sections of conventional
anti-static hard coat films.
[0015] FIG. 2a is a cross section of an anti-static solution coated
on a substrate in an embodiment of the invention.
[0016] FIG. 2b is a cross section of an optical film in an
embodiment of the invention.
[0017] FIGS. 2c to 2d are devices for fabricating an optical film
according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The following description is of the best-contemplated mode
of carrying out the invention. This description is made for the
purpose of illustrating the general principles of the invention and
should not be taken in a limiting sense. The scope of the invention
is best determined by reference to the appended claims.
[0019] An optical film and fabrication method thereof are provided,
with, when a bottom half portion of an anti-static layer contains
more than 60 wt % of anti-static particles. properties including
anti-scratch anti-static, low reflection or low interference.
[0020] FIG. 2a shows anti-static wet layer 206 being coated on a
substrate 201 in an embodiment of the invention. The anti-static
wet layer 206 comprises solvent and anti-static particles 205
dispersed therein.
[0021] FIG. 2b is a cross-section of an optical film 200 in an
embodiment of the invention. The optical film 200 comprises a
substrate 201 and an anti-static layer 207 disposed thereon. The
anti-static layer 207 comprises a resin layer 203 and anti-static
particles 205. A virtual plane 209c, parallel to the substrate 201,
is in the position of half thickness of the anti-static layer 207.
The portions of anti-static layer 207 above and below the virtual
plane 209c are respectively referred to as top half portion 209a
and bottom half portion 209b. In an embodiment of the invention,
the bottom half portion 209b contains more than 60 wt % of the
anti-static particles 205, and in another, between about 60 and 90
wt %, and yet another, between about 70 and 90 wt %.
[0022] The anti-static wet layer 206 as shown in FIG. 2a is a wet
layer (having solvent), after the process described the following,
the anti-static wet layer 206 is dryer and the structure of the
anti-static layer 207 as shown in FIG. 2b is formed.
[0023] Referring to FIG. 2c, electrolyte in tank 211 is added into
anti-static solution placed in tank 213, and the solution is mixed
well by stirring: Added amount of electrolyte depends on its
charge. Substrate 201 is transported by unwinder 217 and winder
223, anti-static solution is supplied to the surface of the
substrate 201 through coater head 215, and then a structure as
shown in FIG. 2a is formed.
[0024] After that, the coated substrate is transported by the
unwinder 217 and winder 223 to the oven 219 and the following
curing device 221, so that solvent is evaporated. resin is
hardened, such that the anti-static wet layer 206 (as shown in FIG.
2a) is converted into anti-static layer 207 (as shown in FIG. 2b).
and then the optical film 200 as shown in FIG. 2b is formed.
[0025] An acceptable added amount of electrolyte depends on its
charge, too high or too low electrolyte concentration is not
applicable in the invention. For example. concentration of
monovalent electrolyte in anti-static solution is between about
10.sup.-6 to 10.sup.-1 M. Aggregation of particles are not obvious
when electrolyte concentration is too low, normally lower than
10.sup.-6 M. Larger than 1 um particles are dramatically formed
such that transmittance of the film is negatively affected when
electrolyte concentration is too high, normally higher than
10.sup.-1 M.
[0026] In an embodiment of the invention, electrolyte can be acid
electrolyte, alkali electrolyte, salts, or other ionic compound,
such as NaCl, KCl, KNO.sub.3, Na.sub.2CO.sub.3. Mg(NO.sub.3).sub.2.
K.sub.2SO.sub.4. H.sub.2CO.sub.3, CH.sub.3COOH, or
KAl(SO.sub.4).sub.2. By addition of electrolyte, anti-static
particles become unstable, so that collision probability between
particles is increased and sedimentation of the aggregated
particles becomes easier.
[0027] Electrolyte is used in an embodiment of the invention
causing aggregations, while polymeric flocculant (also referred to
as polymeric flocculating agent) can also be used. The polymeric
flocculent can be inorganic polymeric flocculant such as poly
aluminum chloride, or organic polymeric flocculant such as
polyacrylamide. While utilizing polymeric flocculant, anti-static
particles are bridged by polymer chains, resulting
aggregations.
[0028] A stirring apparatus can optionally be used in the tank 213
as shown in FIG. 2c, so that electrolyte (or polymeric flocculant)
is dissolved (or dispersed) well, and sedimentation of anti-static
particles in the tank 213 can be prevented.
[0029] Referring to FIG. 2b, the resin layer 203 can be of
ultraviolet-cured resin. thermal-cured resin, or
electron-beam-cured resin, so that the curing device 221 as shown
in FIGS. 2c and 2d can be an ultraviolet curing device, a thermal
curing device, or a electron beam curing device.
[0030] Referring to FIG. 2c, the coating method for coating a
solution on the substrate 201 by coater head 215 can be slot die
coating, extrusion coating, gravure coating, co-extrusion coating,
slide coating, or curtain coating.
[0031] FIG. 2d shows another device for fabricating an optical
layer in another embodiment of the invention, wherein, as shown,
substrate 201 is transported by the unwinder 217 and winder 223,
anti-static solution placed in tank 213 is supplied to the
substrate 201 through coating die 215, and then a structure as
shown in FIG. 2a is formed.
[0032] After that, the coated substrate is transported by the
unwinder 217 and winder 223 to an electric field generator 225, the
anti-static particles 205 in anti-static wet layer 206 as shown in
FIG. 2a are attracted and move to the substrate direction by
electric force (referred to as electrophoresis) due to tile charged
particles, and then the coated substrate is transported to the oven
219 and the curing device 221, so that solvent is evaporated, resin
is hardened, such that the anti-static wet layer 206 (as shown in
FIG. 2a) is converted to the anti-static layer 207 (as shown in
FIG. 2b), and then the optical film 200 as shown in FIG. 2b is
formed.
[0033] An magnetic field generator (not shown) can also be used to
replace the electric field generator 225 to attract and aggregate
particles if the particles may also be ferromagnetic.
[0034] Referring to FIG. 2a, tile anti-static wet layer 206 is
coated from a solution containing photo initiators and at least one
of monomers and oligomers dissolved il a solvent.
[0035] Photo initiators can be of benzophenone,
1-hydroxy-cyclohexyl-phenyl-ketone.
2-hydroxy-2-methyl-1-phenyl-1-propanone, or
methylbenzoylformate.
[0036] Monomers can be of isobutyl acrylate, 2-ethylhexyl acrylate,
1,6-hexanediol diacrylate, tripropylene glycol diacrylate,
trimethylolpropane diacrylate, dipentaerythritol pentaacrylate,
pentaerythritol triacrylate, or dipentaerythritol hexaacrylate.
[0037] Oligomers can be of urethane (meth)acrylate oligomer,
polyester (meth)acrylate oligomer, or epoxy (meth)acrylate
oligomer.
[0038] Solvents can be of Isopropanol (IPA), methyl ethyl ketone
(MEK), methyl isobutyl ketone,(MIBK), ethyl acetate(EAC), butyl
acetate (BAC), toluene, cyclohexanone. methanol, or propylene
glycol monoethyl esther.
[0039] Inorganic nanoparticles can be added to the anti-static wet
layer 206 as shown in FIG. 2a to reduce the curl level of the
anti-static layer 207 as shown in FIG. 2b due to volume contraction
during drying. Inorganic nanoparticles can be of silica, alumina,
zirconia, titania, zinc oxide, germanium oxide, indium oxide, or
tin oxide.
[0040] The anti-static particles 205 as shown in FIG. 2a and 2b can
be of antimony-doped tin oxide, tin oxide, zinc antimonite,
antimony pentoxide, indium tin oxide, or aluminum-doped zinc oxide.
The radius of the anti-static particles 205 is between about 5 and
100 nm, preferably between about 10 and 40 nm.
[0041] As shown in FIG. 2a, the zeta potential of the anti-static
particles 205 in the anti-static wet layer 206 is between about +70
and -70 eV, preferably between about -10 and -50 eV. The
anti-static particles 205 can stably suspend in the anti-static
solution before adding electrolyte or polymeric flocculant, such
that the anti-static solution is suitable for storage.
[0042] As shown in FIG. 2b, the anti-static particles 205 are 20 to
80(wt % of the anti-static layer 207, preferably 30 to 70 wt %.
Anti-static layer 207 comprises resin layer 203 and anti-static
particles 205.
[0043] Substrate 201 can be of glass, poly(meth)acrylate,
polycarbonate, polyethylene (PE), polyethylene terephthalate (PET),
or triacetyl cellulose (TAC).
[0044] The invention will be better understood by reference to
Tables 1 and 3 showing compositions of each comparison and
embodiment, and Tables 2 and 4 showing their experimental results.
TABLE-US-00001 TABLE 1 compari- embodi- Name composition son 1 ment
1 photo initiator Irgacure 184(Ciba-Geigy) 3 g 3 g monomer
pentaerythritol triacrylate 100 g 100 g anti-static CX-Z210IP
(Nissan 200 g 200 g particles chemical) solvent methyl ethyl
ketone(MEK) 100 g 100 g electrolyte sodium chloride 0 M 0.001 M
[0045] The solutions of comparison 1 and embodiment 1 were
respectively coated on 80 um thick triacetyl cellulose (TAC, Fuji
corporation) films by RDS no. 5 coating rod, placed in an oven at
70.degree. C. for 3 minutes, radiated by H-type mercury lamp(300
mJ/Cm.sup.2 dose). and anti-static hard coat films were
respectively formed. After that, anti-scratch properties of the two
anti-static hard coat films were tested 10 times by steel wire rope
(no. 0000), transmittance was measured by transmittance measuring
instrument (type: ND112000. NIPON DESHOKU corporation), and surface
resistance was measured at 100 V by surface resistance measuring
instrument (type: model 65, Keithley corporation). The experimental
results are shown in Table 2. TABLE-US-00002 TABLE 2 experimental
result comparison 1 embodiment 1 transmittance 89.04% 88.74%
surface resistance 2.3*10.sup.9.OMEGA./cm.sup.2
2.5*10.sup.9.OMEGA./cm.sup.2 anti-scratch property with scratch
under without scratch under 200 g/cm.sup.2 pressure 300 g/cm.sup.2
pressure
[0046] As shown in Table 2, the anti-static hard coat film of
embodiment 1 was not scratched due to sedimentation of anti-static
particles result from addition of electrolyte. TABLE-US-00003 TABLE
3 compari- embodi- name composition son 2 ment 2 photo initiator
Irgacurc 184(Cita-Geigy) 3 g 3 g monomer dipentaerythritol 50 g 50
g hexaacrylate oligomer CN7295(Sartomer) 50 g 50 g anti-static
CX-Z210IP(Nissan 200 g 200 g particles chemical) solvent 1 methyl
ethyl ketone(MEK) 50 g 50 g solvent 2 Isopropanol(IPA) 50 g 50 g
electrolyte sodium chloride 0M 0.1M
[0047] The solutions of comparison 2 and embodiment 2 were
respectively coated on 80 um thick triacetyl cellulose (TAC, Fuji
corporation) films by RDS no. 5 coating rod, placed in an oven at
70.degree. C. for 3 minutes, radiated by H-type mercury lamp (300
mJ/cm.sup.2 dose). and then anti-static hard coat films were
respectively formed. After that, anti-scratch properties of the two
anti-static hard coat films were tested 10 times by steel wire rope
(no. 0000), transmittance was measured by transmittance measuring
instrument (type: NDH2000. NIPPON DESHOKU corporation), and surface
resistance was measured at 100 V by surface resistance measuring
instrument (type: model 65, Keithley corporation). The experimental
results were shown in Table 4. TABLE-US-00004 TABLE 4 experimental
result comparison 2 embodiment 2 transminance 89.08% 88.01% surface
resistance 1.7*10.sup.11.OMEGA./cm.sup.2
1.2*10.sup.9.OMEGA./cm.sup.2 anti-scratch property without scratch
under without scratch under 300 g/cm.sup.2 pressure 300 g/cm.sup.2
pressure
[0048] As shown in table 4. the surface resistance was reduced due
to aggregation of anti-static particles result from addition of
electrolyte.
[0049] As shown in above experimental result, an optical film
according to the invention provides anti-static property and/or
anti-scratch property. Its mechanism is described below.
[0050] Referring to FIGS. 2a and 2b, anti-scratch ability is
usually reduced when anti-static particles 205 exist near the
surface of the anti-static layer 207, because the particles 205 and
the resin layer 203 are bonded together by weaker physical bonds
such as van der Waals force. Therefore, the anti-scratch ability of
the anti-static layer 207 is increased while anti-static particles
205 deposited at the bottom, remaining more chemical-bonded resin
material on the surface of the anti-static layer 207.
[0051] Since collision probability between particles as shown in
FIG. 2a is increased resulting from compressed electric double
layer (not shown) of anti-static particles 205 by addition of
electrolyte or polymeric flocculant, the number of particles
dispersed in bottom half portion 209b are more than that in top
half portion 209a. Therefore, the anti-static particles 205 are
more concentrated and surface resistance thereof is reduced.
[0052] The formation of the conductive regions is affected by
dispersed particle concentration, zeta potential of the anti-static
particles, particle size, and electrolyte concentration. The
primary particle size of anti-static particles 205 is between about
5 and 100 nm, preferably 10 and 4 nm. The anti-static particles 205
are 20 to 80 wt % of the anti-static layer 207, preferably 30 to 70
wt %. Zeta potential of the anti-static particles 205 are between
+70 and -70 cV, preferably -10 and -50 eV. Added amount of
electrolyte depends on its charge, for example, the concentration
needed for univalent electrolyte is between about 10.sup.-6 and
10.sup.-1 M.
[0053] In another embodiment of the inventions electric field or
magnetic field is applied, such that conductive regions are also
formed inside the anti-static layer 207. The surface resistance of
the anti-static layer 207 thereof is reduced because the number of
particles dispersed in bottom half portion 209b are more than that
in top half portion 209a. This is because collision probability
between particles as shown in FIG. 2a increases resulting from
anti-static particles 205 inside anti-static wet layer 206 are
attracted and move to bottom portion thereof.
[0054] Referring to FIG. 2b, although more anti-static particles
205 are dispersed in the bottom half portion 209b than top half
portion 209a, anti-static 205 particles are not all dispersed in a
very narrower area (unlike structures as shown in FIGS. 1a and 1b).
Therefore, interference and reflection of the anti-static layer 207
are lower.
[0055] While the invention has been described by way of example and
in terms of preferred embodiment, it is to be understood that the
invention is not limited thereto. To the contrary, it is intended
to cover various modifications and similar arrangements (as would
be apparent to those skilled in the art). Therefore, the scope of
the appended claims should be accorded the broadest interpretation
so as to encompass all such modifications and similar
arrangements.
* * * * *