U.S. patent application number 15/747368 was filed with the patent office on 2018-08-02 for antireflection film.
The applicant listed for this patent is LG CHEM, LTD.. Invention is credited to Jin Seok BYUN, Yeong Rae CHANG, Seok Hoon JANG, Boo Kyung KIM.
Application Number | 20180217297 15/747368 |
Document ID | / |
Family ID | 59274263 |
Filed Date | 2018-08-02 |
United States Patent
Application |
20180217297 |
Kind Code |
A1 |
KIM; Boo Kyung ; et
al. |
August 2, 2018 |
ANTIREFLECTION FILM
Abstract
The present invention relates to an antireflection film. The
antireflection film includes a low refractive index layer having
excellent alkali resistance and exhibiting remarkably improved
mechanical properties such as scratch resistance and impact
resistance as well as reduction of a glare phenomenon, and a base
film exhibiting excellent mechanical strength and water resistance
in spite of a thin thickness and having no fear of interference
fringes occurring. Therefore, such antireflection film can be used
as a protective film of a polarizing plate or used as any other
component so as to provide a thin display device, and furthermore,
can effectively prevent the glare phenomenon of the display device,
and can more improve the durability and lifespan thereof.
Inventors: |
KIM; Boo Kyung; (Daejeon,
KR) ; CHANG; Yeong Rae; (Daejeon, KR) ; JANG;
Seok Hoon; (Daejeon, KR) ; BYUN; Jin Seok;
(Daejeon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG CHEM, LTD. |
Seoul |
|
KR |
|
|
Family ID: |
59274263 |
Appl. No.: |
15/747368 |
Filed: |
December 27, 2016 |
PCT Filed: |
December 27, 2016 |
PCT NO: |
PCT/KR2016/015340 |
371 Date: |
January 24, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09D 4/00 20130101; B32B
27/36 20130101; C09D 7/65 20180101; C08J 2483/04 20130101; C09D
5/006 20130101; C08J 2367/02 20130101; C08J 2367/00 20130101; C09D
7/63 20180101; C08J 7/042 20130101; B32B 27/08 20130101; G02B 1/111
20130101; C08J 2435/02 20130101; C09D 5/00 20130101; C08K 3/36
20130101; C08K 7/26 20130101; C08K 3/36 20130101; C08L 83/00
20130101; C08K 7/26 20130101; C08L 83/00 20130101 |
International
Class: |
G02B 1/111 20060101
G02B001/111; C08J 7/04 20060101 C08J007/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 7, 2016 |
KR |
10-2016-0002242 |
Claims
1. An antireflection film comprising: a polyester film having an
in-plane retardation value (Rin) of 3000 nm to 30,000 nm in which a
ratio (Rin/Rth) of an in-plane retardation value (Rin) to an
thickness-direction retardation value (Rth) is 0.2 to 1.2; and a
low refractive index layer which is disposed on the polyester film
and which is a crosslinked polymer comprising a photopolymerizable
compound, an inorganic particle, and a polysilsesquioxane in which
at least one reactive functional group is substituted.
2. The antireflection film of claim 1, wherein the polyester film
is a uniaxially stretched film or a biaxially stretched film of
polyethylene terephthalate or polyethylene naphthalate.
3. The antireflection film of claim 1, wherein the photocurable
coating composition includes a monomer or an oligomer containing a
(meth)acryloyl group or a vinyl group as a photopolymerizable
compound.
4. The antireflection film of claim 1, wherein the photocurable
coating composition contains a polysilsesquioxane in which at least
one reactive functional group is substituted in an amount of 0.5 to
30 parts by weight based on 100 parts by weight of the
photopolymerizable compound.
5. The antireflection film of claim 1, wherein the reactive
functional group substituted in the polysilsesquioxane includes at
least one functional group selected from the group consisting of an
alcohols, amines, carboxylic acids, epoxides, imides,
(meth)acrylates, nitriles, norbornenes, olefins, polyethylene
glycol, thiols, and vinyl groups.
6. The antireflection film of claim 1, wherein the
polysilsesquioxane in which at least one reactive functional group
is substituted includes the polyhedral oligomeric silsesquioxane
(POSS) having a cage structure in which at least one reactive
functional group is substituted.
7. The antireflection film of claim 1, wherein the photocurable
coating composition further includes a fluorine-based compound
containing a photoreactive functional group.
8. The antireflection film of claim 7, wherein the photoreactive
functional group contained in the fluorine-based compound is at
least one functional group selected from the group consisting of a
(meth)acryloyl group, an epoxy group, a vinyl group, and a mercapto
group.
9. The antireflection film of claim 7, wherein the fluorine-based
compound containing the photoreactive functional group has a weight
average molecular weight of 2,000 to 200,000 g/mol.
10. The antireflection film of claim 7, wherein the photocurable
coating composition includes 1 to 75 parts by weight of the
fluorine-based compound containing the photoreactive functional
group based on 100 parts by weight of the photopolymerizable
compound.
11. The antireflection film of claim 1, wherein the inorganic fine
particle includes a hollow silica particle having a number average
particle diameter of 10 nm to 100 nm.
12. The antireflection film of claim 11, wherein the photocurable
coating composition includes 10 to 350 parts by weight of the
hollow silica nanoparticle based on 100 parts by weight of the
photopolymerizable compound.
13. The antireflection film of claim 1, wherein the hard coating
layer is interposed between the polyester film and the low
refraction index layer.
14. The antireflection film of claim 13, wherein the hard coating
layer realizes an antiglare function, a scratch prevention
function, an antistatic function, or a combination of two or more
of these functions.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application claims priority to and the benefit of
Korean Patent Application No. 10-2016-0002242 filed on Jan. 7, 2016
with the Korean Intellectual Property Office, the entire content of
which is incorporated herein by reference.
[0002] The present invention relates to an antireflection film.
TECHNICAL FIELD
Background Art
[0003] In general, a flat panel display device such as a PDP or a
LCD is equipped with an antireflection film for minimizing
reflection of light incident from the outside.
[0004] As methods for minimizing the reflection of light, a method
(anti-glare: AG coating) in which a filler such as an inorganic
fine particle is dispersed in a resin and coated onto a base film
to impart irregularities; a method (anti-reflection: AR coating) of
using the interference of light by forming a plurality of layers
having different refractive indexes on a base film; a method for
mixing them; etc., exist.
[0005] Among them, in the case of the AG coating, the absolute
amount of reflected light is equivalent to that of a general hard
coating, but a low reflection effect can be obtained by reducing
the amount of light entering the eye using light scattering through
irregularities. However, since the AG coating has poor screen
sharpness due to the surface irregularities, many studies on AR
coating have recently been conducted.
[0006] On the other hand, a cellulose film is mainly used as a
protective film of a polarizing plate which is essentially provided
in a display device. However, the cellulose film is expensive, and
with the recent tendency of a thin design for the display device,
when produced with a thin thickness, the mechanical strength and
permeability become poor, which causes problems such as the
occurrence of light leakage phenomenon. In addition, polyester
films are inexpensive and are known to exhibit excellent mechanical
strength and water resistance even when produced with a thin
thickness, but they have birefringence property, and thus, when
used as a polarizing plate protective film, they cause a problem
that image quality is deteriorated due to optical distortion.
DISCLOSURE
Technical Problem
[0007] It is one object of the present invention to provide an
antireflection film including a low refractive index layer capable
of remarkably improving a glare phenomenon resulting from
reflection of light incident on the outside, and a base film having
a birefringence property but not generating interference fringes
due to optical distortion.
Technical Solution
[0008] The antireflection film or the like according to specific
embodiments of the present invention will be described in more
detail below.
[0009] In one embodiment of the present invention, an
antireflection film is provided, including: a polyester film having
an in-plane retardation value (Rin) of 3,000 nm to 30,000 nm in
which a ratio (Rin/Rth) of an in-plane retardation value (Rin) to
an thickness-direction retardation value (Rth) is 0.2 to 1.2; and a
low refractive index layer which is disposed on the polyester film
and which is a crosslinked polymer comprising a photopolymerizable
compound, an inorganic particle, and a polysilsesquioxane in which
at least one reactive functional group is substituted.
[0010] As an existing polarizing plate protective film, a cellulose
film has been mainly used. However, the cellulose film is
expensive, and with the recent tendency of a thin design for the
display device, when produced with a thin thickness, the mechanical
strength and water resistance become poor, which causes problems
such as the occurrence of a light leakage phenomenon. Meanwhile,
polyester films are inexpensive and have an advantage of exhibiting
excellent mechanical strength and water resistance even when
produced with a thin thickness, but they have a birefringence
property, and thus, when used as a polarizing plate protective
film, they cause a problem that image quality is deteriorated due
to optical distortion.
[0011] Thus, the antireflection film according to one embodiment of
the present invention includes a polyester film as a base film, and
particularly includes a polyester film of which a retardation value
is adjusted to a specific range, thereby effectively suppressing
the occurrence of interference fringes and the like.
[0012] Specifically, the in-plane retardation value (Rin) of the
polyester film may be adjusted to be within the range of 3,000 nm
to 30,000 nm. More specifically, the lower limit of the in-plane
retardation value (Rin) may be adjusted to be 4500 nm or more,
5,000 nm or more, 6,000 nm or more, or 7,000 nm or more, and the
upper limit may be adjusted to be 30,000 nm or less. Within these
ranges, the antireflection film can effectively suppress the
occurrence of interference fringes, and it is formed with an
appropriate thickness, thereby ensuring ease of handling, and
further providing a thin polarizing plate and/or display
device.
[0013] The in-plane retardation value (Rin) is a value calculated
by measuring the biaxial refractive indexes (nx, ny) orthogonal to
each other in the polyester film plane and the thickness (d) of the
polyester film, and substituting the measured values into
|nx-ny|*d. The refractive index and the thickness of the polyester
film can be measured by various methods known in the technical
field to which the present invention belongs, and for details of
the measurement method, reference may be made to the methods
described in test examples described later. The in-plane
retardation value (Rin) can also be confirmed through a
commercially available automatic birefringence measuring
apparatus.
[0014] In addition, the polyester film has a ratio (Rin/Rth) of the
in-plane retardation value (Rin) to the thickness-direction
retardation value (Rth) in the range of 0.2 to 1.2 in order to
prevent the occurrence of interference fringes while maintaining
sufficient mechanical strength and water resistance. As the ratio
(Rin/Rth) of the in-plane retardation value (Rin) to the
thickness-direction retardation value (Rth) is larger, the isotropy
of the polyester film is increased and thus the occurrence of
interference fringes can be remarkably improved. However, in the
case of a complete uniaxial film in which the ratio (Rin/Rth) of
the in-plane retardation value (Rin) to the thickness-direction
retardation value (Rth) is 2.0, there is a problem that the
mechanical strength in the direction orthogonal to the direction of
the orientation is lowered. Thus, it is possible to prevent the
occurrence of interference fringes while maintaining sufficient
mechanical strength and water resistance by adjusting the ratio
(Rin/Rth) of the in-plane retardation value (Rin) to the
thickness-direction retardation value (Rth) within the
above-mentioned range.
[0015] The thickness-direction retardation value (Rth) is a value
calculated by measuring the biaxial refractive indexes (nx, ny)
orthogonal to each other in the polyester film plane, the
refractive index (nz) in the thickness direction, and the thickness
(d) of the polyester film, and substituting the measured values
into [(nx+ny)/2-nz]d. The refractive index and the thickness of the
polyester film can be measured by various methods known in the
technical field to which the present invention belongs, and for
details of the measurement method, reference may be made to the
methods described in test examples described later. The
thickness-direction retardation value (Rth) can also be confirmed
through a commercially available automatic birefringence measuring
apparatus.
[0016] The polyester film having the retardation value as described
above can be obtained by stretch-processing various polyester
resins which are known to have excellent transparency and thermal
and mechanical properties in the technical field to which the
present invention belongs. Specifically, a polyester resin such as
polyethylene terephthalate or polyethylene naphthalate can be
subjected to stretch processing under appropriate conditions to
produce a polyester film exhibiting the above-mentioned properties.
The polyester film may be provided either as a uniaxially stretched
film or as a biaxially stretched film. The uniaxially stretched
film is advantageous from the viewpoint of preventing the
occurrence of interference fringes, but the uniaxially stretched
film has a problem that the mechanical strength in a direction
orthogonal to the direction of the orientation is poor. Therefore,
it is advantageous for the polyester film to be provided as a
biaxially stretched film. Such a biaxially stretched film can be
provided by stretching various known polyester resins to a range of
1.0 to 3.5 times the longitudinal stretching magnification and a
range of 2.5 to 6.0 times the transverse stretching magnification
at a temperature of 80 to 130.degree. C.
[0017] The thickness of the polyester film having the specific
retardation value can be suitably adjusted within the range of 15
to 300 .mu.m. Within these ranges, the antireflection film can be
handled with ease while exhibiting sufficient mechanical strength
and water resistance, and can further provide a thin polarizing
plate and/or display device.
[0018] A low refractive index layer which is a crosslinked polymer
of a photocurable coating composition including a
photopolymerizable compound, an inorganic particle, and a
polysilsesquioxane in which at least one reactive functional group
is substituted is present on the polyester film having the specific
retardation value. As used herein, the term "low refractive index
layer" may refer to a layer having a low refractive index, for
example, a layer exhibiting a refractive index of about 1.2 to 1.6.
Hereinafter, the photocurable coating composition and the method of
forming the low refractive index layer through the photocurable
coating composition will be described in detail.
[0019] The photocurable coating composition may include a monomer
or an oligomer containing a (meth)acryloyl group or a vinyl group
as a photopolymerizable compound. The monomer or oligomer may
include one or more, two or more, or three or more of
(meth)acryloyl groups or vinyl groups. In the present
specification, the (meth)acryl refers to including both acryl and
methacryl.
[0020] Specific examples of the monomer or oligomer containing a
(meth)acryloyl group include pentaerythritol tri(meth)acrylate,
pentaerythritol tetra(meth)acrylate, dipentaerythritol
penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate,
tripentaerythritol hepta(meth)acrylate, trimethylolpropane
tri(meth)acrylate, trimethylolpropane polyethoxy tri(meth)acrylate,
ethylene glycol di(meth)acrylate, butanediol di(meth)acrylate,
ethylhexyl (meth)acrylate, butyl (meth)acrylate, or a mixture of
two or more thereof, or a urethane-modified acrylate oligomer,
epoxide acrylate oligomer, ether acrylate oligomer, dendritic
acrylate oligomer, or a mixture of two or more thereof.
[0021] Specific examples of the monomer or oligomer containing a
vinyl group may include oligomers or the like obtained by
polymerizing divinylbenzene, styrene, para-methyl styrene, or more
than one type thereof. The molecular weight of the oligomer may be
adjusted to be 1,000 to 10,000 g/mol.
[0022] The content of the photopolymerizable compound in the
photocurable coating composition is not particularly limited, but
may be adjusted to be 10% by weight to 80% by weight with respect
to the solid content of the photocurable coating composition in
consideration of the mechanical properties and the like of the
finally produced low refractive index layer. The solid content of
the photocurable coating composition means only a solid component,
excluding a liquid component in the photocurable coating
composition, for example, a component such as an organic solvent
which may be optionally included as described below.
[0023] Since the photocurable coating composition includes a
polysilsesquioxane in which at least one reactive functional group
is substituted, it is possible to provide a low refractive index
layer capable of realizing low reflectivity and high light
transmittance, and simultaneously ensuring excellent wear
resistance and scratch resistance while improving alkali
resistance.
[0024] Such polysilsesquioxane in which at least one reactive
functional group is substituted may contained in an amount of 0.5
to 30 parts by weight, 1 to 30 parts by weight, or 2 to 27 parts by
weight based on 100 parts by weight of the photopolymerizable
compound.
[0025] When the content of the polysilsesquioxane in which at least
one reactive functional group is substituted is lower than the
above-mentioned range, it may be difficult to ensure sufficient
alkali resistance and scratch resistance of the coating film or the
polymer resin formed during photocuring of the photocurable coating
composition. In contrast, when the content of the
polysilsesquioxane in which at least one reactive functional group
is substituted is higher than the above-mentioned range, the
transparency of the low refractive index layer produced from the
photocurable coating composition may be decreased, and the scratch
resistance may rather be decreased.
[0026] The reactive functional group that can be substituted in the
polysilsesquioxane may include at least one functional group
selected from the group consisting of alcohols, amines, carboxylic
acids, epoxides, imides, (meth)acrylates, nitriles, norbornenes,
olefins [ally, cycloalkenyl, vinyldimethylsilyl, etc.],
polyethylene glycol, thiols, and vinyls, and may preferably be an
epoxide or (meth)acrylate.
[0027] More specifically, when the reactive functional group is an
epoxide, a 2-[3,4-epoxycyclohexyl]ethyl group or a
3-glycidoxypropyl group may be introduced as a reactive functional
group, and when the reactive functional group is a (meth)acrylate,
a (meth)acryloyloxyalkyl group (in which the alkyl group may have 1
to 6 carbon atoms) may be introduced as a reactive functional
group.
[0028] Even if polysilsesquioxane employs the same functional group
as the photopolymerizable compound as a reactive functional group,
polysilsesquioxane having a skeleton of a siloxane bond (--Si--O--)
is defined as not being included in the photopolymerizable
compound.
[0029] Meanwhile, the polysilsesquioxane in which at least one
reactive functional group is substituted may be additionally
substituted with at least one non-reactive functional group
selected from the group consisting of a linear or branched alkyl
group having 1 to 20 carbon atoms, a cyclohexyl group having 6 to
20 carbon atoms, and an aryl group having 6 to 20 carbon atoms, in
addition to the above-mentioned reactive functional group. As the
surface of the polysilsesquioxane is substituted with a reactive
functional group and an non-reactive functional group as described
above, the siloxane bond (--Si--O--) in the polysilsesquioxane in
which at least one reactive functional group is substituted is not
exposed to the outside while being located inside the molecule,
thereby further enhancing the alkali resistance of the coating film
or the polymer resin formed during photocuring of the photocurable
coating composition.
[0030] The polysilsesquioxane may be represented by
(RSiO.sub.1.5).sub.n (where n is 4 to 30 or 8 to 20, and R is a
linear or branched alkyl group having 1 to 20 carbon atoms, a
cycloalkyl group having 6 to 20 carbon atoms, or an aryl group
having 6 to 20 carbon atoms), and may have various structures such
as random, ladder-type, cage-type, partial cage-type, etc.
[0031] Among them, in order to further enhance the above-mentioned
properties, a polyhedral oligomeric silsesquioxane having a cage
structure, in which at least one reactive functional group is
substituted, may be used as the polysilsesquioxane in which at
least one reactive group is substituted.
[0032] More specifically, the polyhedral oligomeric silsesquioxane
may include 8 to 20 silicon atoms in a molecule.
[0033] Further, the reactive functional groups may be introduced
into at least one of the silicon atoms of the polyhedral oligomeric
silsesquioxane, and the silicon atoms in which no reactive
functional groups are introduced may be substituted with the
non-reactive functional groups described above.
[0034] When the reactive functional groups are introduced into at
least one of the silicon atoms of the polyhedral oligomeric
silsesquioxane, the mechanical properties of the coating film or
the polymer resin formed during photocuring of the photocurable
coating composition may be greatly enhanced. Further, when a
nonreactive functional group is introduced into the remaining
silicon atoms, steric hindrance appears in the molecular structure
and the probability of exposure of the siloxane bond (--Si O--) to
the outside can be greatly lowered. Consequently, it is possible to
greatly improve the alkali resistance of the coating film and the
polymer resin formed during photocuring of the photocurable coating
composition.
[0035] Examples of the polyhedral oligomeric silsesquioxane (POSS)
having a cage structure in which at least one reactive functional
group is substituted include POSS in which at least one alcohol is
substituted, such as TMP diolisobutyl POSS, cyclohexanediol
isobutyl POSS, 1,2-propanediolisobutyl POSS, octa(3-hydroxy-3
methylbutyldimethylsiloxy) POSS, etc.; POSS in which at least one
amine is substituted, such as aminopropylisobutyl POSS,
aminopropylisooctyl POSS, aminoethylaminopropyl isobutyl POSS,
N-phenylaminopropyl POSS, N-methylaminopropyl isobutyl POSS,
octaammonium POSS, aminophenylcyclohexyl POSS, aminophenylisobutyl
POSS, etc.; POSS in which at least one carboxylic acid is
substituted, such as maleamic acid-cyclohexyl POSS, maleamic
acid-isobutyl POSS, octamaleamic acid POSS, etc; POSS in which at
least one epoxide is substituted, such as epoxycyclohexylisobutyl
POSS, epoxycyclohexyl POSS, glycidyl POSS, glycidylethyl POSS,
glycidylisobutyl POSS, glycidylisooctyl POSS, etc.; POSS in which
at least one imide is substituted, such as POSS maleimide
cyclohexyl, POSS maleimide isobutyl, etc.; POSS in which at least
one (meth)acrylate is substituted, such as acryloisobutyl POSS,
(meth)acrylisobutyl POSS, (meth)acrylate cyclohexyl POSS,
(meth)acrylate isobutyl POSS, (meth)acrylate ethyl POSS,
(meth)acrylethyl POSS, (meth)acrylate isooctyl POSS,
(meth)acrylisooctyl POSS, (meth)acrylphenyl POSS, (meth)acryl POSS,
acrylo POSS, etc.; POSS in which at least one nitrile group is
substituted, such as cyanopropylisobutyl POSS, etc.; POSS in which
at least one norbornene group is substituted, such as
norbornenylethylethyl POSS, norbornenylethylisobutyl POSS,
norbornenylethyl disilanoisobutyl POSS, trisnorbornenyl isobutyl
POSS, etc.; POSS in which at least one vinyl group is substituted,
such as allylisobutyl POSS, monovinylisobutyl POSS,
octacyclohexenyldimethylsilyl POSS, octavinyldimethylsilyl POSS,
octavinyl POSS, etc.; POSS in which at least one olefin is
substituted, such as allylisobutyl POSS, monovinylisobutyl POSS,
octacyclohexenyldimethylsilyl POSS, octavinyldimethylsilyl POSS,
octavinyl POSS, etc.; POSS in which PEG having 5 to 30 carbon atoms
is substituted; or POSS in which at least one thiol group is
substituted, such as mercaptopropylisobutyl POSS,
mercaptopropylisooctyl POSS, etc.
[0036] On the other hand, the photocurable coating composition may
further include a fluorine-based compound containing a
photoreactive functional group. In the present specification, a
fluorine-based compound containing a photoreactive functional group
means a compound having a weight average molecular weight of 2,000
g/mol or more and substituted with fluorine, and such a compound is
defined as not being included in the definition of the
photopolymerizable compound described above.
[0037] As the fluorine-based compound containing the photoreactive
functional group is included, the low refractive index layer
produced from the photocurable coating composition includes a
polymer resin containing a crosslinked polymer between a
photopolymerizable compound, a polysilsesquioxane in which at least
one reactive functional group is substituted, and a
fluorine-containing compound containing a photoreactive functional
group, and an inorganic particle dispersed therein. An
antireflection film including such a low refractive index layer can
have lower reflectivity and improved light transmittance, and can
further exhibit more improved alkali resistance and scratch
resistance.
[0038] At least one photoreactive functional group is introduced
into the fluorine-based compound, and the photoreactive functional
group refers to a functional group which can participate in a
polymerization reaction by irradiation of light, for example, by
irradiation of visible light or ultraviolet light. The
photoreactive functional group may include various functional
groups known to be able to participate in a polymerization reaction
by irradiation of light. Specific examples thereof include a
(meth)acrylate group, an epoxy group, a vinyl group, a mercapto
group, or the like. The at least one photoreactive functional group
may be composed of any one of the functional groups listed or at
least two selected from the functional groups listed.
[0039] The fluorine-based compound containing the photoreactive
functional group may have a fluorine content of 1% by weight to 25%
by weight. When the content of fluorine in the fluorine-based
compound containing the photoreactive functional group is lower
than the above-mentioned range, the fluorine component cannot be
sufficiently arranged on the surface of the final product obtained
from the photocurable coating composition, and thus it may be
difficult to sufficiently secure the physical properties such as
alkali resistance. Further, when the content of fluorine in the
fluorine-based compound containing the photoreactive functional
group is higher than the above-mentioned range, the surface
properties of the final product obtained from the photocurable
coating composition may be decreased, or the incidence rate of
defective products may be increased in the subsequent process for
obtaining the final product.
[0040] On the other hand, the fluorine-based compound containing a
photoreactive functional group may further contain silicon, or a
side chain or a repeating unit derived from a silicon compound.
When the fluorine-based compound contains silicon, or a side chain
or a repeating unit derived from a silicon compound, the content of
silicon can be 0.1% by weight to 20% by weight based on the
fluorine-based compound. The silicon contained in the
fluorine-based compound containing the photoreactive functional
group has a role of preventing the occurrence of haze in the low
refractive index layer obtained from the photocurable coating
composition of the embodiment, thereby serving to enhance
transparency. On the other hand, when the content of silicon in the
fluorine-based compound containing the photoreactive functional
group exceeds the above-mentioned range, the alkali resistance of
the low refractive layer obtained from the photocurable coating
composition can be lowered.
[0041] The fluorine-based compound containing the photoreactive
functional group may have a weight average molecular weight of
2,000 to 200,000 g/mol. If the weight average molecular weight of
the fluorine-based compound containing the photoreactive functional
group is too small, the low refractive index layer obtained from
the photocurable coating composition may not have sufficient alkali
resistance. Further, if the weight average molecular weight of the
fluorine-based compound containing the photoreactive functional
group is too large, the low refractive index layer obtained from
the photocurable coating composition may not have sufficient
durability and scratch resistance. In the present specification,
the weight average molecular weight refers to a converted value
with respect to standard polystyrene, as measured by gel permeation
chromatography (GPC).
[0042] Specifically, the fluorine-based compound containing the
photoreactive functional group may be: i) an aliphatic compound or
an aliphatic cyclic compound in which at least one photoreactive
functional group is substituted and at least one hydrogen is
substituted with fluorine; ii) a silicone-based compound in which
at least one carbon of the aliphatic compound or aliphatic cyclic
compound is substituted with silicon; iii) a siloxane-based
compound in which at least one carbon of the aliphatic compound or
aliphatic cyclic compound is substituted with silicon and at least
one --CH.sub.2-- is substituted with oxygen; iv) a fluoropolyether
in which at least one --CH.sub.2-- of the aliphatic compound or
aliphatic cyclic compound is substituted with oxygen; or a mixture
or copolymer of two or more thereof.
[0043] The photocurable coating composition may include 1 to 75
parts by weight of the fluorine-based compound containing the
photoreactive functional group based on 100 parts by weight of the
photopolymerizable compound. When the fluorine-based compound
containing the photoreactive functional group is added in an excess
amount relative to the photopolymerizable compound, the coating
properties of the photocurable coating composition may be reduced,
or the low refractive index layer obtained from the photocurable
coating composition may not have sufficient durability or scratch
resistance. Further, when the amount of the fluorine-based compound
containing the photoreactive functional group is too small relative
to the photopolymerizable compound, the low refractive index layer
obtained from the photocurable coating composition may not have
sufficient alkali resistance.
[0044] On the other hand, the photocurable coating composition
includes an inorganic particle having a diameter of nanometer or
micrometer units.
[0045] Specifically, the inorganic fine particle may include a
hollow silica particle having a number average particle diameter of
10 nm to 100 nm. The hollow silica particle refers to a silica
particle derived from a silicon compound or an organosilicon
compound, in which voids are present on the surface and/or inside
of the silica particle. The hollow silica particle has a low
refractive index compared to the particle filled inside, thereby
exhibiting an excellent antiglare property.
[0046] The hollow silica particles may be those having a number
average particle diameter of 10 nm to 100 nm, 20 nm to 70 nm, or 30
nm to 70 nm, and the shape of the particles is preferably
spherical, but they may be amorphous.
[0047] In addition, the hollow silica nanoparticles include hollow
silica nanoparticles of which the surface is coated with a
photoreactive functional group, hollow silica particles of which
the surface is coated with a fluorine-containing compound, and
hollow silica particles of which the surface is not treated (hollow
silica particles of which the surface is not substituted with a
photoreactive functional group and of which the surface is not
coated with the fluorine-containing compound), and these particles
can be used alone, or in combination of two or more. Alternatively,
a reaction product obtained by reacting two or more particles can
be used. The photoreactive functional group may be a (meth)acrylate
group, a vinyl group, a hydroxy group, an amine group, an allyl
group, an epoxide group, a hydroxy group, an isocyanate group, an
amine group, and a thiol group. When the surface of the hollow
silica nanoparticles is coated with a fluorine-based compound, the
surface energy may be further reduced. Thus, the hollow inorganic
nanoparticles may be more uniformly distributed in the photocurable
coating composition. Consequently, the film obtained from the
photocurable coating composition containing the hollow silica
nanoparticles can exhibit more improved durability and scratch
resistance.
[0048] As a method of coating the fluorine-based compound onto the
surface of the hollow inorganic nanoparticles, a conventionally
known particle coating method or polymerization method and the like
may be used without particular limitation. As a non-limiting
example, a method by which the fluorine-based compound may be
bonded to the surface of the hollow inorganic nanoparticles via
hydrolysis and a condensation reaction by subjecting the hollow
silica nanoparticles and the fluorine-based compound to a sol-gel
reaction in the presence of water and a catalyst and the like can
be used.
[0049] The hollow silica particles may be contained in the
composition as a colloidal phase dispersed in a predetermined
dispersion medium. The colloidal phase including the hollow silica
particles may include an organic solvent as a dispersion
medium.
[0050] The solid content of the hollow silica nanoparticles in the
colloidal phase of the hollow silica particles can be determined in
consideration of the content range of the hollow silica
nanoparticles in the photocurable coating composition, the
viscosity of the photocurable coating composition, and the like.
For example, the solid content of the hollow silica nanoparticles
in the colloidal phase may be 5% by weight to 60% by weight.
[0051] Herein, examples of the organic solvent in the dispersion
medium include alcohols such as methanol, isopropyl alcohol,
ethylene glycol, butanol, and the like; ketones such as methyl
ethyl ketone, methyl isobutyl ketone, and the like; aromatic
hydrocarbons such as toluene, xylene, and the like; amides such as
dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and the
like; esters such as ethyl acetate, butyl acetate,
gamma-butyrolactone, and the like; ethers such as tetrahydrofuran,
1,4-dioxane, and the like; or a mixture thereof.
[0052] The photocurable coating composition may include 10 to 350
parts by weight of the hollow silica nanoparticles based on 100
parts by weight of the photopolymerizable compound. If the hollow
silica nanoparticles are added in an excess amount, the scratch
resistance and wear resistance of the coating film may be lowered
due to reduction of the content of the polymer resin.
[0053] As the photopolymerization initiator, any compound known to
be usable in a photocurable resin composition may be used without
particular limitation. Specifically, a benzophenone-based compound,
an acetophenone-based based compound, a nonimidazole-based
compound, a triazine-based compound, an oxime-based compound, or a
mixture of two or more thereof may be used.
[0054] The photopolymerization initiator may be used in an amount
of 1 to 100 parts by weight, 1 to 50 parts by weight, or 1 to 25
parts by weight based on 100 parts by weight of the
photopolymerizable compound. If the amount of the
photopolymerization initiator is too small, some of the
photocurable coating composition can be uncured in the photocuring
step to generate a residual material. If the amount of the
photopolymerization initiator is too large, the unreacted initiator
may remain as impurities or the crosslinking density may be
lowered, and thus the mechanical properties of the resulting film
may be deteriorated, or the reflectivity may be greatly
increased.
[0055] Meanwhile, the photocurable coating composition may further
include an inorganic solvent. Non-limiting examples of the organic
solvent include ketones, alcohols, acetates, and ethers, or a
mixture of two or more thereof. Specific examples of such organic
solvent include ketones such as methyl ethyl ketone, methyl
isobutyl ketone, acetylacetone, and isobutyl ketone; alcohols such
as methanol, ethanol, n-propanol, iso-propanol, n-butanol,
iso-butanol, and t-butanol; acetates such as ethyl acetate,
iso-propyl acetate, and polyethylene glycol monomethyl ether
acetate; ethers such as tetrahydrofuran and propylene glycol
monomethyl ether; and a mixture of two or more thereof.
[0056] The organic solvent may be added at the time of mixing the
respective components contained in the photocurable coating
composition, or may be contained in the photocurable coating
composition while the respective components are added in a state of
being dispersed or mixed in the organic solvent. If the content of
the organic solvent in the photocurable coating composition is too
small, the flowability of the photocurable coating composition may
be reduced, resulting in defects such as the occurrence of stripes
in the finally produced film, or the like. Further, if the organic
solvent is added in an excess amount, the solid content is lowered,
and the physical properties and surface properties of the film may
be deteriorated due to insufficient coating and film formation, and
defects may occur during the drying and curing processes.
Accordingly, the photocurable coating composition may include an
organic solvent such that the concentration of the total solids of
the components contained becomes 1% to 50% by weight, or 2% to 20%
by weight.
[0057] Such photocurable coating composition can be coated and
photocured according to methods known in the technical field to
which the present invention pertains to provide the low refractive
index layer described above.
[0058] First, the photocurable coating composition can be coated
onto the polyester film having the specific retardation value
described above. In this case, the photocurable coating composition
can be coated directly onto the polyester film or can be coated on
a separate layer previously formed on the polyester film. The
separate layer can be a hard coat layer having various functions
described later.
[0059] The photocurable coating composition can be coated using
methods and apparatuses known in the technical field to which the
present invention belongs, and for example, it can be coated
through a bar coating method such as with a Meyer bar or the like,
a gravure coating method, a 2-roll reverse coating method, a vacuum
slot die coating method, a 2-roll coating method, or the like.
[0060] The low refractive index layer may have a thickness of 1 nm
to 300 nm, or 50 nm to 200 nm. Accordingly, the thickness of the
photocurable coating composition coated onto the polyester film can
be adjusted to be about 1 nm to 300 nm, or 50 nm to 200 nm.
[0061] After coating the photocurable coating composition on the
base as described above, the photocurable coating composition can
be photocured by irradiation with ultraviolet light or visible
light in the wavelength region of 200 nm to 400 nm. At this time,
the exposure amount of the irradiated light can be adjusted to be
in the range of 100 mJ/cm.sup.2 to 4,000 mJ/cm.sup.2, and the
exposure time can be appropriately adjusted depending on the
exposure apparatus used, the wavelength of the irradiated light, or
the amount of exposure.
[0062] The photocuring step may be performed under a nitrogen
atmosphere. Accordingly, nitrogen purging can be performed before
the photocuring step or during the photocuring step.
[0063] The low refractive index layer prepared from the
photocurable coating composition as described above may include a
polymer resin including a crosslinked polymer between a
photopolymerizable compound and a polysilsesquioxane in which at
least one reactive functional group is substituted, and optionally
a fluorine-based compound containing a photoreactive functional
group, and an inorganic particle dispersed in the polymer
resin.
[0064] Such a low refractive index layer has excellent optical
properties such as reflectivity and color in the visible light
region, and excellent mechanical properties such as scratch
resistance. Accordingly, the low refractive index layer can be used
in a display device to remarkably improve the glare phenomenon
caused by light incident from the outside of the device without
impairing the quality of the image, and to effectively protect the
surface of the device from external impact or stimulation.
[0065] In addition, the low refractive index layer has
characteristics that the above-mentioned change in physical
properties is very small even when exposed to an alkali. Due to
such high alkali resistance, the low refractive index layer does
not require the step of adhering and desorbing the protective film,
which is essentially performed for protecting the low refractive
index layer during the usual production process of the display
device, and thereby the production process of the display device
can be simplified and the production cost can be lowered. In
particular, the low refractive index layer is excellent in alkali
resistance at a high temperature, and thus the production process
of the display device can be performed in more severe conditions.
Thus, it is expected that the production speed and productivity can
be greatly improved without deteriorating the quality of the
device.
[0066] On the other hand, in the antireflection film according to
one embodiment, a hard coating layer may be interposed between the
polyester film having a specific retardation value and the low
refraction index layer. Such a hard coating layer can realize an
antiglare function, a scratch prevention function, an antistatic
function, or a combination of two or more of these functions.
[0067] As an example, the hard coating layer may include a binder
resin containing a photocurable resin and a (co)polymer having a
weight average molecular weight of 10,000 g/mol or more
(hereinafter referred to as a high molecular weight (co)polymer),
and an organic or inorganic fine particle dispersed in the binder
resin. As used herein, the (co)polymer refers to including both a
co-polymer and a homo-polymer.
[0068] The high molecular weight (co)polymer may include at least
one polymer selected from the group consisting of cellulose-based
polymers, acryl-based polymers, styrene-based polymers,
epoxide-based polymers, nylon-based polymers, urethane-based
polymers, and polyolefin-based polymers.
[0069] The photocurable resin contained in the hard coating layer
may be a polymer of a photopolymerizable compound capable of
causing a polymerization reaction when irradiated with light such
as ultraviolet light, and may be one that is commonly used in the
technical field to which the present invention belongs.
Specifically, as the photopolymerizable compound, at least one
selected from a reactive acrylate oligomer group consisting of a
urethane acrylate oligomer, an epoxide acrylate oligomer, a
polyester acrylate, and a polyether acrylate can be used; and a
polyfunctional acrylate monomer group consisting of
dipentaerythritol hexaacrylate, dipentaerythritol pentaacrylate,
pentaerythritol tetraacrylate, pentaerythritol triacrylate,
trimethylene propyl triacrylate, propoxylated glycerol triacrylate,
ethoxylated trimethylpropane triacrylate, 1,6-hexanediol
diacrylate, tripropylene glycol diacrylate, and ethylene glycol
diacrylate can be used.
[0070] The organic or inorganic fine particles may have a particle
diameter of 0.5 .mu.m to 10 .mu.m. The particle diameter of the
organic or inorganic fine particles may be equal to or higher than
0.5 .mu.m to express the surface irregularities and internal haze,
and may be equal to or lower than 10 .mu.m in terms of the haze or
coating thickness. For example, when the particle size of the fine
particles is excessively increased to exceed 10 .mu.m, the coating
thickness must be increased in order to complement the fine surface
irregularities, and accordingly, the crack resistance of the film
may be reduced, which may be problematic.
[0071] The organic or inorganic fine particles may be organic fine
particles selected from the group consisting of an acryl-based
resin, a styrene-based resin, an epoxy-based resin, a nylon resin,
and a copolymer thereof, or may be inorganic fine particles
selected from the group consisting of a silicon oxide, titanium
dioxide, an indium oxide, a tin oxide, a zirconium oxide, and a
zinc oxide.
[0072] The hard coating layer may contain 1 to 20 parts by weight
or 5 to 15 parts by weight, preferably 6 to 10 parts by weight, of
the organic or inorganic fine particles based on 100 parts by
weight of the photocurable resin. When the organic or inorganic
fine particles are contained in an amount of less than 1 part by
weight based on 100 parts by weight of the photocurable resin, the
haze value may not be appropriately implemented due to internal
scattering. Further, when the amount of the organic or inorganic
fine particles exceeds 20 parts by weight based on 100 parts by
weight of the photopolymerizable resin, the viscosity of the
coating composition is increased, which causes a problem that the
coating property becomes poor.
[0073] Further, the refractive index of the organic or inorganic
fine particles is different from the refractive index of a
photocurable resin forming a matrix. An appropriate refractive
index difference is determined according to the content of the
particles, and it is preferable to have a refractive index
difference of 0.01 to 0.08. When the refractive index difference
between the fine particles and the photocurable resin is less than
0.01, it may be difficult to obtain an appropriate haze value.
Also, when the refractive index difference between the fine
particles and the photocurable resin exceeds 0.08, a desired level
of the shape of surface irregularities cannot be obtained because a
very small amount of particles must be used.
[0074] Meanwhile, the hard coating layer may further include
inorganic nanoparticles having a diameter of 1 nm to 120 nm. A
predetermined functional group or compound may be bonded to the
surface of the inorganic nanoparticles.
[0075] As the inorganic nanoparticles are used, the shape of the
surface irregularities of the hard coating layer can be smoothly
adjusted and the mechanical properties of the coating layer can be
improved. In this case, the content of the inorganic nanoparticles
can be adjusted to be 10 parts by weight or less based on 100 parts
by weight of the photocurable resin. Specific examples of the
inorganic nanoparticles include a silicon oxide, alumina, titania,
etc.
[0076] The hard coating layer may be formed from a hard coating
composition including an organic or inorganic fine particle, a
photopolymerizable compound, a photopolymerization initiator, and a
high molecular weight (co)polymer. The antireflection film
including such a hard coating layer is excellent in antiglare
effect.
[0077] Another example of the hard coating layer may include a hard
coating layer including a binder resin containing a photocurable
resin, and an antistatic agent dispersed in the binder resin.
[0078] The photocurable resin contained in the hard coating layer
may be a polymer of a photopolymerizable compound capable of
causing a polymerization reaction when irradiated with light such
as ultraviolet light, and may be one that is commonly used in the
technical field to which the present invention belongs.
Specifically, as the photopolymerizable compound, a polyfunctional
(meth)acrylate-based monomer or oligomer can be used. In this case,
the number of (meth)acrylate-based functional groups is adjusted to
2 to 10, 2 to 8, or 2 to 7, thereby securing the desired physical
properties of the hard coating layer. More specifically, the
photocurable compound may be at least one selected from the group
consisting of pentaerythritol tri(meth)acrylate, pentaerythritol
tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate,
dipentaerythritol hexa(meth)acrylate, tripentaerythritol
hepta(meth)acrylate, toluene diisocyanate, xylene diisocyanate,
hexamethylene diisocyanate, trimethylolpropane tri(meth)acrylate,
and trimethylolpropane polyethoxy tri(meth)acrylate.
[0079] The antistatic agent may be a quaternary ammonium salt
compound, a conductive polymer, or a mixture thereof. Herein, the
quaternary ammonium salt compound may be a compound having at least
one quaternary ammonium salt group in the molecule, and a low
molecule type or a high molecule type can be used without
limitation. Further, as the conductive polymer, a low molecule type
or a high molecule type can be used without limitation, and its
type is not particularly limited as long as it is conventionally
used in the technical field to which the present invention
belongs.
[0080] The hard coating film including a binder resin of the
photocurable resin, and an antistatic agent dispersed in the binder
resin, may further include at least one compound selected from the
group consisting of an alkoxysilane-based oligomer and a metal
alkoxide-based oligomer.
[0081] The alkoxysilane-based compound may be one that is
conventionally used in the relevant art, but preferably, it may be
at least one compound selected from the group consisting of
tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane,
methyltrimethoxysilane, methyltriethoxysilane,
methacryloxypropyltrimethoxysilane, glycidoxypropyl
trimethoxysilane, and glycidoxypropyl triethoxysilane.
[0082] In addition, the metal alkoxide-based oligomer can be
prepared through a sol-gel reaction of a composition including a
metal alkoxide-based compound and water. The sol-gel reaction can
be carried out by a method similar to the above-described method
for preparing an alkoxysilane-based oligomer.
[0083] However, since the metal alkoxide-based compound can rapidly
react with water, the sol-gel reaction can be performed by a method
of diluting the metal alkoxide-based compound in an organic solvent
and then slowly dripping water thereto. At this time, considering
the reaction efficiency or the like, the molar ratio (based on
metal oxide ions) of the metal alkoxide-based compound to water is
preferably adjusted within the range of 3 to 170.
[0084] Herein, the metal alkoxide-based compound may be at least
one compound selected from the group consisting of titanium
tetra-isopropoxide, zirconium isopropoxide, and aluminum
isopropoxide.
[0085] The hard coating composition for forming the hard coating
layer capable of realizing the various functions may further
include a photopolymerization initiator, a solvent, etc., which may
be added to the photocurable coating composition for forming the
low refractive index layer.
[0086] In one embodiment of the invention as described above, the
low refractive index layer having excellent alkali resistance and
exhibiting remarkably improved mechanical properties such as
scratch resistance and impact resistance as well as a reduced glare
phenomenon is formed on a base film exhibiting excellent mechanical
strength and water resistance in spite of a thin thickness, thereby
providing an antireflection film that satisfies various required
properties evenly. Such an antireflection film can be used as a
protective film of a polarizing plate or used as any other
component so as to provide a thin display device, and furthermore,
can effectively prevent the glare phenomenon of the display device,
and can more improve the durability and lifespan thereof.
Advantageous Effects
[0087] The antireflection film according to one embodiment of the
present invention includes a low refractive index layer having
excellent alkali resistance and exhibiting remarkably improved
mechanical properties such as scratch resistance and impact
resistance as well as reduction of a glare phenomenon, and a base
film exhibiting excellent mechanical strength and water resistance
in spite of a thin thickness and having no fear of interference
fringes occurring. Therefore, such antireflection film can be used
as a protective film of a polarizing plate or used as any other
component so as to provide a thin display device, and furthermore,
can effectively prevent the glare phenomenon of the display device,
and can more improve the durability and lifespan thereof.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0088] The action and effect of the invention will be described in
more detail through concrete examples of the invention below.
However, these examples are given for illustrative purposes only,
and these examples are not intended to limit the scope of the
invention in any way.
Examples 1-4 and Comparative Examples 1-4: Preparation of
Antireflection Film
[0089] An antireflection film was prepared by the following method
using the base film, the hard coating composition, and the
photocurable coating composition listed in Table 1 below.
[0090] Specifically, the hard coating composition was coated onto a
base film with a #10 Mayer bar, dried at 90.degree. C. for 1
minute, and then irradiated with ultraviolet light at 150
mJ/cm.sup.2 to form a hard coating layer having a thickness of 5
.mu.m (antistatic hard coating layer or antiglare hard coating
layer).
[0091] Then, the photocurable coating composition was coated onto
the hard coat layer with a #3 Mayer bar and dried at 60.degree. C.
for 1 minute. Then, ultraviolet light at 180 mJ/cm.sup.2 was
irradiated to the dried material under a nitrogen purge to form a
low refractive index layer having a thickness of 110 nm, thereby
preparing an antireflection film.
TABLE-US-00001 TABLE 1 Comparative Comparative Comparative
Comparative Example 1 Example 2 Example 3 Example 4 Example 1
Example 2 Example 3 Example 4 Base TA015 A015 A015 A015 4300 4300 Z
TAC TA015 film (thickness: (thickness: (thickness: (thickness:
(thickness: (thickness: (thickness: (thickness: 80 .mu.m) 80 .mu.m)
80 .mu.m) 80 .mu.m) 75 .mu.m) 100 .mu.m) 60 .mu.m) 80 .mu.m) ard
HD1 HD2 HD1 HD2 HD1 HD1 HD1 HD1 coating composition Photocurable
LR1 LR1 LR2 LR2 LR1 LR1 LR1 LR3 coating composition
[0092] The physical properties such as manufacturer, phase
difference, and water vapor transmission rate of each base film in
Table 1 are listed in Table 2 below. HD1 is a salt type of
antistatic hard coating solution (manufactured by KYOEISHA
Chemical, solid content: 50 wt %, product name: LJD-1000).
[0093] HD2 is an antiglare hard coating composition prepared by
mixing 13 g of pentaerythritol triacrylate (molecular weight: 298
g/mol), 10 g of a urethane acrylate oligomer (3061, KYOEISHA
Chemical), 10 g of a urethane acrylate oligomer (306T, KYOEISHA
Chemical), 20 g of isopropyl alcohol as a solvent, 2 g of a
photoinitiator (Irgacure 184, Ciba), and 0.5 g of a leveling agent
(Tego glide 410) and then adding 2.3 g of an acryl-styrene
copolymer (Techpolymer, Sekisui Plastic) which is spherical organic
fine particles having an average particle diameter of 3 .mu.m and a
refractive index of 1.555, and 0.01 g of a nanosilica dispersion
(MA-ST, Nissan Chemical) having a volume average particle diameter
of 12 nm, to the resulting composition. Specific components and
compositions of LR1, LR2, and LR3 are listed in Table 3 below. LR1,
LR2, and LR3 were used by mixing the components described in Table
3 below with the compositions described herein and diluting in a
solvent in which MIBK (methyl isobutyl ketone) and PGME (propylene
glycol monomethyl ether) were mixed at a weight ratio of 1:1 so
that the solid content concentration became 3 wt %.
TABLE-US-00002 TABLE 2 Product name TA015 4300 4300 Z TAC
(thickness: (thickness: (thickness: (thickness: 80 .mu.m) 75 .mu.m)
100 .mu.m) 60 .mu.m) Manufacturer TOYOBO TOYOBO TOYOBO FUJI Rin
[nm] 8400 2400 3200 3.3 Rth [nm] 9200 12750 17000 48.6 Rin/Rth
0.913 0.188 0.188 0.068 Water vapor 6.38 6.93 5.1 275 transmission
rate [g/m.sup.2*day] Permeability 5.1 5.2 5.1 165
[0094] (1) The thickness of the base film was measured using
ID-C112XBS (Mitutoyo).
[0095] (2) The in-plane retardation value (Rin=|nx-ny|*d) and the
thickness-direction retardation value (Rth=[(nx+ny)/2-nz]d) of the
base film were measured using RETS-100 (OTSUKA ELECTRONICS).
However, the retardation value of the triacetylcellulose film (UZ
TAC, FUJI) was measured using AxoScan (Axometrics). Then, Rin/Rth
was determined by dividing the in-plane retardation value (Rin) by
the thickness-direction retardation value (Rth).
[0096] (3) The water vapor transmission rate (WVTS) of the base
film was measured at a temperature of 40.degree. C. and relative
humidity of 90% using TSY-T3 (Labthink) which is a water vapor
permeability tester. Since the water vapor transmission rate (WVTS)
decreases as the thickness increases, the water vapor transmission
rate per thickness of 100 .mu.m is defined as permeability, and the
permeability is determined by the formula of "thickness (unit:
.mu.m)*water vapor transmission rate/100" and shown in Table 2.
TABLE-US-00003 TABLE 3 LR1 LR2 LR3 Hollow silica dispersion.sup.1)
250 220 250 Dipentaerythritol pentaacrylate 37 39 40
Polysilsesquioxane.sup.2) 3 3 0 Fluorine-containing compound
containing a 13.3 26.7 13.3 photoreactive functional group.sup.3)
Photoinitiator.sup.4) 6 6 6 (unit: g) .sup.1)Hollow silica
dispersion: THRULYA 4320 (manufactured by Catalysts and Chemicals
Ltd.) in which hollow silica particles having a number average
diameter of 50 nm are dispersed to a solid content of 20% by weight
in methyl isobutyl ketone. .sup.2)Polysilsesquioxane: MA0701
manufactured by Hybrid Plastics. .sup.3)Fluorine-based compound
containing a photoreactive functional group: A fluorine compound
containing a photoreactive functional group and containing a trace
amount of silicon, and RS537 (manufactured by DIC) diluted to 30%
by weight in methyl isobutyl ketone .sup.4)Photoinitiator:
Irgacure-127 (manufactured by Ciba)
Experimental Examples: Measurement of Physical Properties of
Antireflection Films
[0097] 1. Measurement of Average Reflectivity
[0098] The average reflectivity of the antireflection films
obtained in the examples and comparative examples was measured
using Solidspec 3700 (SHIMADZU) equipment.
[0099] Specifically, a black tape was attached to the surface of
the base film on which no hard coating layer was formed so that
light would not be transmitted. The measurement conditions were set
as a sampling interval 1 nm, a time constant of 0.1 s, a slit width
20 nm, and a medium scanning speed. Light of a wavelength region of
380 nm to 780 nm was irradiated to the low refractive index layer
of the antireflection film at room temperature.
[0100] When HD2 was used as the hard coating composition, a 100% T
mode was applied, and when HD1 was used as the hard coating
composition, a measure mode was applied. Thereby, the reflectance
in the wavelength region of 380 nm to 780 nm was measured. The
results are shown in Table 4 below.
[0101] 2. Measurement of Scratch Resistance
[0102] The surfaces of the antireflection films obtained in the
examples and comparative examples were rubbed while applying a load
to a steel wool (#0000) and reciprocating ten times at a speed of
24 rpm. When observed with the naked eye under ceiling illumination
by a 50 W LED while increasing the load applied to the steel wool,
the maximum load at which scratches were not generated was
measured. The above load is defined as weight (g) per area (2*2
cm.sup.2) of 2 cm in width and 2 cm in height.
[0103] 3. Evaluation of Occurrence of Interference Fringes
[0104] A black PET film was attached to the surface of the base
film on which the hard coating layer was not formed by using the
antireflection film produced according to the examples and
comparative examples, and it was evaluated with respect to whether
interference fringes were observed with the naked eye. As a result
of the evaluation, when no interference fringes were observed in
the antireflection film, it was described as "good" in Table 4
below, and when interference fringes were clearly observed, it was
described as "severe".
[0105] 4. Evaluation of Water Vapor Transmission Rate and
Permeability
[0106] The water vapor transmission rate (WVTS) of the
antireflection films prepared according to the examples and
comparative examples was measured at a temperature of 40.degree. C.
using TSY-T3 (Labthink), a water vapor permeability tester. At this
time, the antireflection film was loaded so that the base film side
of the antireflection film was placed under a relative humidity of
100%, and the low refractive index layer side was placed under a
relative humidity of 10%. Since the water vapor transmission rate
(WVTS) decreases as the thickness increases, the water vapor
transmission rate per thickness of 100 .mu.m is defined as
permeability, and the permeability is determined by the formula
"thickness (unit: .mu.m)*water vapor transmission rate/100" and is
shown in Table 4 below. Here, the thickness of the antireflection
film was measured in the same manner as the method of measuring the
thickness of the base film.
TABLE-US-00004 TABLE 4 Comparative Comparative Comparative
Comparative Example 1 Example 2 Example 3 Example 4 Example 1
Example 2 Example 3 Example 4 Average ~1.5% ~1.5% ~1.5% ~1.5% ~1.5%
~1.5% ~1.5% ~1.5% reflectivity Scratch 300 300 300 300 300 300 300
100 resistance [g/(2 * 2 cm.sup.2)] Interference Good Good Good
Good Severe Severe Good Good fringes Water vapor 10.18 9.79 10.20
9.56 11.01 8.54 222.77 10.82 transmission rate [g/m.sup.2 * day]
Total thickness 85.1 85.1 85.1 85.1 80.1 105.1 65.1 85.1 of film
[.mu.m] Permeability 8.66 8.33 8.68 8.14 8.82 8.98 145.02 9.21
[0107] Referring to Table 4, it was confirmed that the
antireflection film according to one embodiment of the present
invention exhibited excellent water resistance while showing an
excellent low reflective index and scratch resistance, and hardly
any interference fringe was found. In contrast, when an optically
anisotropic base film of which the phase difference was not
adjusted to a specific range was used as in Comparative Examples 1
and 2, it was confirmed that interference fringes were severely
generated, thereby being unsuitable for the antireflection film of
the display. Moreover, when an existing cellulose base film was
used as in Comparative Example 3, it was confirmed that the
permeability was poor and there was a fear of shortening the
lifespan of the display. In addition, even if an optically
anisotropic base film of which the phase difference was adjusted to
a specific range was used as the base film as in Comparative
Example 3, it was confirmed that, when the low refractive index
layer according to one embodiment of the present invention was not
included, excellent scratch resistance could not be ensured.
* * * * *