WO 2005/017613
PCT/KR2004/002032

COMPLEX LIGHT-COMPENSATION C PLATK WITH TWO OR MORE OF C
PLATES DIFFERENT IN DISPERSION RATIO VALUE AND LIQUID CRYSTAL
DISPLAY USING THE SAME
Technical Field
The present invention relates to a viewing angle
compensation film for an LCD, and more particularly to a
viewing angle compensation film for an LCD such as a VA-LCD
(vertically aligned liquid crystal display, see U.S. Patent
number 4,889,412) filled with liquid crystal having negative
dielectric anisotropy (< 0), an IPS-LCD (in-plane switching
liquid crystal display) and a TN-LCD (twisted nematic liquid
crystal display), capable of achieving a superior contrast
characteristic at various viewing angles, and capable of
minimizing color variation depending on various viewing
angles in a black state.
Background Art
Generally, liquid crystal has a birefringence
characteristic, that is, a refractive index, of light in a
longitudinal axis direction of molecules of the liquid
crystal is different from a refractive index of light in a
transverse axis direction of molecules of the liquid crystal.
Due to such a birefringence characteristic of the liquid
crystal, persons may feel different refractive indexes of
light depending on their positions with respect to an LCD.
Accordingly, when linearly polarized light passes through the
liquid crystal, a polarizing state of the light is changed
with various ratios, so an amount of light and the color
characteristic perceived by the persons may vary depending on

WO 2005/017613 PCT/KR20O4/002032
positions of the persons with respect to the LCD. Therefore,
a liquid crystal display device having a twisted nematic
structure may represent various contrast ratios, color
shifts, and a gray inversion phenomenon according to viewing
angles.
In order to compensate for a phase difference created in
a liquid crystal cell, a TN LCD technique using a phase
difference compensation film has been developed. According to
the TN LCD technique, the phase difference of light created
in the liquid crystal cell is compensated for by means of the
phase difference compensation film, so that the above-
mentioned problems derived from the viewing angles can be
solved. However, a TN LCD using a negative phase difference
compensation film can improve a gray characteristic only when
a viewing angle forms an angle of 45° with respect to a
transmission axis of a polarizing plate, while representing
uneven image quality and a halftone gray inversion
phenomenon. Meanwhile, a VATN-LCD (vertically aligned TN-LCD)
using liquid crystal having a negative dielectric anisotropy
property has been developed. The VATN-LCD can be fabricated
with low costs and simple processes as compared with the TN-
LCD, while representing a superior contrast ratio, low
threshold voltage and fast response time.
In a case of the TN-LCD, if voltage is not applied to
the liquid crystal, a longitudinal axis of liquid crystal
molecules is spirally twisted in parallel to a substrate. In
this state, if voltage is applied to the liquid crystal, the
longitudinal axis of liquid crystal molecules is aligned
vertically to the substrate. In contrast, at an initial stage
of the VATN-LCD, liquid crystal molecules of the VATN-LCD are
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WO 2005/017613 PCT/KR2004/002032
aligned similar to an alignment of the liquid crystal
molecules of the TN-LCD to which voltage has been applied. In
this state, if voltage is applied to the liquid crystal of
the VATN-LCD, liquid crystal molecules of the VATN-LCD are
twisted.
In an off-state of the VATN-LCD, liquid crystal
molecules are vertically aligned and retardation of light
does not occur if a viewing angle matches with an alignment
direction of the liquid crystal molecules. Therefore, a
superior contrast ratio may be achieved at the above viewing
angle. However, if the viewing angle does not match with the
alignment direction of the liquid crystal molecules,
retardation of light may occur due to the birefringence of
the liquid crystal, causing inferior contrast ratio. In
particular, the contrast ratio is extremely lowered when the
viewing angle forms an angle of 45° with respect to a
transmission axis of a polarizing plate.
Liquid crystal having vertically aligned molecules has a
characteristic identical to that of a C plate having a
positive birefringence. Accordingly, the above birefringence
of the liquid crystal can be compensated for by means of a
compensation film made from a C plate having a negative
birefringence. Preferably, an optimum retardation value of
the compensation film made from C plate is substantially
identical to a retardation value created due to the
birefringence of the liquid crystal cell.
U.S Patent No. 4,889,412 discloses a technique regarding
a negative (-) C plate. A main function of the negative C
plate is to compensate for a black state of a VA-LCD at a no-
voltage state or a low-voltage state. However, a conventional
3

negative C plate represents a limited phase difference

conventional negative C plate cannot properly compensate for
the black state and color variation of RGB at various viewing
angles.
For instance, a wavelength dispersion ratio value of an
LCD panel has a normal wavelength dispersion characteristic,
and a C plate having a super-high wavelength dispersion
characteristic is required in order to compensate for the
black state and color variation of RGB created in the LCD
panel. However, it is difficult to achieve such a super-high
wavelength dispersion characteristic by using one
conventional phase difference film.
In the black state, the VA-LCD represents
characteristics identical to those of a positive (+) C plate.
In order to completely compensate for the positive C plate by
using the negative C plate, the negative and positive C
plates must have the same wavelength dispersion
characteristic. Liquid crystal used for an LCD has a normal
wavelength dispersion characteristic, and the wavelength

difficult to fabricate a phase difference film adaptable for
the wavelength dispersion characteristic of liquid crystal of
the VA-LCD by using the conventional negative C plate having
the limited phase difference wavelength dispersion ratio
value.
The positive C plate has been used for minimizing color
variation of a CLC polarizing plate (for a brightness
4

enhancement) at various viewing angles. However, the positive
C plate also has a limited phase difference wavelength


dispersion ratio value
so the positive C plate
represents problems identical to those of the negative C
plate.
For instance, the positive C plate must have a super-
high wavelength dispersion characteristic in order to
minimize color variation of the CLC polarizing plate, but the
conventional C plate phase difference film cannot provide the
positive C plate having the super-high wavelength dispersion
characteristic.
In a case of the CLC polarizing plate, it is necessary
to provide the positive C plate representing the wavelength
dispersion characteristic identical to that of the CLC.
However, since the wavelength dispersion ratio value of the
CLC is very large, it is difficult to fabricate the phase
difference film adaptable for the wavelength dispersion
characteristic of the CLC by using the conventional positive
C plate.
Brief Description of the Drawings
FIG. 1 is a schematic view showing an example of a
position of a complex light compensation C plate of the
present invention in a liquid crystal display device, in
which reference numerals 1 to 4 represent an upper polarizing
plate (1), a lower polarizing plate (2), an LCD panel (3), and a
backlight (4), respectively, reference numerals 5 and 6
represent a uniaxial A plate or a biaxial A plate, and
reference numerals 7 and 8 represent complex light
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WO 2005/017613 PCT/KR2004/002032
compensation C plates, wherein the position of the A plates
can be interchanged with the position of the complex light
compensation C plates.
FIG. 2 is a view showing a refractive index of a
positive C plate.
FIG. 3 is a view showing a refractive index of a
negative C plate.
FIG. 4 is a view showing a wavelength dispersion
characteristic (an absolute phase difference value in a
thickness direction as a function of wavelengths) of a
conventional C plate.
FIG. 5 is a view showing a super-high wavelength
dispersion characteristic of a complex positive C plate
consisting of a positive C plate and a negative C plate.
FIG. 6 is a view showing a super-high wavelength
dispersion characteristic of a complex negative C plate
consisting of a positive C plate and a negative C plate.
FIG 7 is a view showing an inverse wavelength
dispersion characteristic of a complex positive C plate
consisting of a positive C plate and a negative C plate.
FIG 8 is a view showing an inverse wavelength
dispersion characteristic of a complex negative C plate
consisting of a positive C plate and a negative C plate.
FIG. 9 is a view showing an intermediate wavelength
dispersion characteristic of a complex positive C plate
consisting of two positive C plates.
FIG. 10 is a view showing an intermediate wavelength
dispersion characteristic of a complex negative C plate
consisting of two negative C plates.
FIG. 11 is a view showing a mixed wavelength dispersion
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WO 2005/017613 PCT/KR2004/002032
characteristic of a complex C plate having a variable mark
and consisting of a positive C plate and a negative C plate,
wherein, if a wavelength having a phase difference value of
zero is a reference wavelength, a negative C plate having an
inverse wavelength dispersion characteristic belongs to an
area having a wavelength longer than the reference wavelength
and a positive C plate having a normal wavelength dispersion
characteristic belongs to an area having a wavelength shorter
than the reference wavelength.
FIG. 12 is a view showing a mixed wavelength dispersion
characteristic of a C plate having a complex variable mark
and consisting of a negative C plate and a positive C plate,
wherein, if a wavelength having a phase difference value of
zero is a reference wavelength, a negative C plate having a
normal wavelength dispersion characteristic belongs to an
area having a wavelength shorter than the reference
wavelength and a positive C plate having an inverse
wavelength dispersion characteristic belongs to an area
having a wavelength longer than the reference wavelength.
FIG. 13 is a view showing an inverse wavelength
dispersion characteristic of a coinplex C plate consisting of
two positive C plates and one negative C plate.
Disclosure of the Invention
Technical Problem
Therefore, in order to completely compensate for
variation of a phase difference value in a cell of an LCD, it
is necessary to provide a C plate having broadband wavelength
dispersion characteristics including a super-high wavelength
dispersion characteristic, an inverse wavelength dispersion
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WO 2005/017613 PC T/KR2 004/002032
characteristic, an intermediate wavelength dispersion
characteristic, and a mixed wavelength dispersion
characteristic.
The present invention is based on the findings that in
case of using a complex light-compensation C plate including
at least two C plates representing different dispersion ratio
values, phase difference values, that is, retardation values
of the C plates in the thickness direction can be summed up
at the same wavelengths and then differently from the
conventional C plate consisting of only one sheet of C plate
with the limited phase difference dispersion ratio value


it is possible to provide the complex light-
compensation C plate having broadband wavelength dispersion
characteristics.
Accordingly, an object of the present invention is to
provide a design condition and a fabricating method for a
complex light-compensation C plate having broadband
wavelength dispersion characteristics.
Technical solution.
In order to accomplish the above objects, there is
provided a complex light compensation C plate comprising at
least two C plates representing different dispersion ratio
values, respectively.
In detail, the present invention provides the complex
light compensation C plate consisting of an m-number of
positive C plates and an n-number of negative C plates,


wherein dispersion ratio values

of at least two C

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WO 2005/017613 PCT/KR20O4/002032
plates are different from each other. Herein, m = 0 or a
positive integer, n = 0 or a positive integer, m+n2;
R=(nz-ny)d representing a phase difference value in a
thickness direction, nx and ny are surface refractive indexes
of a film, nz is a refractive index in a thickness direction
of a film, d is a thickness of a film; R450C is a phase
difference value of a C plate at a wavelength of 450nm, and
R550c is a phase difference value of a C plate at a wavelength
of 550nm.
In this case, when the m-number of positive C plates are
stacked together with the n-number of negative C plates,
regardless of the stacking order thereof, the total phase
different value (Rtot) of the stacked C plates can be achieved
by adding a value R obtained by summing up the phase
difference values of the m-number of positive C plates to a
value R' obtained by summing up the phase difference values
of the n-number of negative C plates. That is, Rtot = R + R'.
Herein, the R has a positive value and the R' has a negative
value.
Advanced Effect
The compensation film made from the complex C plate
according to the present invention can improve a contrast
characteristic of a liquid crystal display device at various
viewing angles and has a broadband wavelength dispersion
characteristic capable of minimizing color variation in a
black state of an LCD depending on various viewing angles.
Mode for Invention
Reference will now be made in detail to the preferred
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WO 2005/017613 PCT/KR2004/002032
embodiments of the present invention.
Hereinafter, a preferred embodiment of the present
invention will be described with reference to accompanying
drawings.
FIGS. 2 and 3 show refractive indexes of a positive (+)
C plate and a negative (-) C plate, respectively. The C plate
signifies a phase difference film having a phase difference
value in a thickness direction thereof. The phase difference
value in a thickness direction of the phase difference film
is defined as follows:
R = (nz-ny)d
R > 0 : positive C plate
R < 0 : negative C plate
Wherein, ny is a smallest refractive index value among
surface refractive index values of a film, nz is a refractive
index in a thickness direction of a film, and d is a
thickness of a film.
The positive C plate can be made from polymer having a
positive birefringence, biaxial stretched polymer or UV-
curable nematic liquid crystal polymer. The negative C plate
can be made from TAC (triacetate cellulose), a cyclo-olefin
based copolymer film, a biaxial stretched polymer film, or a
UV-curable short pitch cholesteric liquid crystal film.
The phase difference value as a function of the
wavelength of the C plate is called "wavelength dispersion
characteristic of a phase difference film" and is defined as
follows:

wherein, A and B represent a Cauchy coefficient
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WO 2005/017613 PCT/KR2004/002032
determined according to materials and  represents an
absorption wavelength.
FIG. 4 is a view showing a phase difference absolute
value in a thickness direction of conventional positive and
negative C plates as a function of wavelengths. As shown in
FIG. 4 as a graph, a film having a phase difference absolute
value decreased as the wavelength is increased is called a
phase difference film having a normal wavelength dispersion
characteristic.


of the C plate is
The dispersion characteristic
a specific characteristic determined by a material of a film.
The wavelength dispersion characteristic of the C plate
can be described by using dispersion ratio values in two


wavelengths
as parameters. Herein, R450,R550,R650
represent phase difference values at wavelengths of 450nm,
550nm and 650nm, respectively.
In a case of a general C plate, a phase difference
ratio value in wavelengths of 450nm and 550nm is limited


within a range of

and a phase difference ratio

value in wavelengths of 550nm and 650nm is limited within a


range of
In a case of a transparent material, a great phase
difference dispersion is represented in visible light area
having a short wavelength because great light absorption may
occur at the short wavelength. Thus, the wavelength
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WO 2005/017613 PCT/KR2004/002032
larger than the wavelength dispersion ratio value at a long

at the short wavelength as described above, the wavelength
dispersion ratio value of the C plate is limited.
For instance, when the light absorption occurs at the
short wavelength, a denominator value of a last term, which
includes a coefficient B, in the Cauchy equation becomes
reduced and variation of the phase difference value according
to the wavelength becomes large, so a difference between the
phase difference value at the short wavelength and the phase
difference value at the long wavelength is more increased.
Because almost materials represent light absorption at
a short wavelength area (UV area}, materials have a normal
wavelength dispersion ratio value. In order to represent a
super-high wavelength dispersion characteristic, light
absorption must be represented at a wavelength of 400nm.
However, if an absorption wavelength exists in visible light
area, the material cannot be adaptable for the phase
difference film. Accordingly, the wavelength dispersion ratio
value is limited. In addition, it is also impossible to
fabricate the phase difference film having an inverse
wavelength dispersion characteristic, in which a phase
difference value is increased as the wavelength in the
visible light area becomes increased.
The limitation of the wavelength dispersion ratio value
in the C plate can be solved by using two C plates (first C
plate C1 and second C plate C2 ) representing different
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WO 2005/017613 PCT/KR2004/002032
dispersion ratio values, respectively.
Accordingly, the present invention is characterized in
adjusting the wavelength dispersion characteristic of the C
plates to any level by using two C plates ( C1 and C2 )
representing different dispersion ratio values.
According to a first embodiment of the present
invention, there is provided a complex C plate having a
broadband wavelength dispersion characteristic by consisting
of two C plates f C1 and C2 ) satisfying the following
equation.

wherein, R=(nz-ny)d is a phase difference value in a
thickness direction, {R45O)c1 is a phase difference value of a C
plate C1 at 450nm, (R550)c1 is a phase difference value of a C
plate C1 at 550nm, (R450)c2 is a phase difference value of a C
plate C2 at 450nm, and (R550)c2 is a phase difference value of
a C plate C2 at 550nm. In addition, each film must satisfy
the following equation:
nznx=ny
wherein, nx and ny represent a surface refractive index
of a film, nz represents a refractive index in a thickness
direction of a film, and d represents a thickness of a film.
According to a second embodiment of the present
invention, there is provided a complex light compensation
positive C plate having a super-high wavelength dispersion
characteristic (the complex positive C plate having a large


wavelength dispersion ratio

value) by consisting of

positive and negative C plates.
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WO 2005/017613 PCT/KR2004/0 02032
On the assumption that two films forming the complex
light compensation positive C plate having a super-high
wavelength dispersion characteristic are C1 and C2, in which
C, is the positive C plate (nz>nx=ny) and C2 is the negative
C plate ( nznx=ny), the complex light compensation negative
C plate having two films stacked on each other must satisfy
the following equations in order to achieve the super-high
dispersion characteristic.

wherein, (R450)Cl represents a phase difference value of
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WO 2005/017613 PCT/KR2004/002032
C plate C1 in a thiclcness direction of a film at a wavelength
of 450nm, (R55O)C1 represents a phase difference value of C
plate C1 in a thickness direction of a film at a wavelength of
550nm, (R450)c2 represents a phase difference value of C plate
C2 in a thiclcness direction of a film at a wavelength of
450nm, and (R550)C2 represents a phase difference value of C
plate C2 in a thickness direction of a film at a wavelength
of 550nm.
FIG. 6 is a view showing an absolute phase difference
values of a negative C plate C1, a positive C plate C2 and a
complex: negative C plate in the thickness direction as a
function of wavelengths, respectively, in which the complex
negative C plate has a super-high wavelength dispersion
characteristic.
For instance, if the negative C plate C1 has a phase
difference value of -400nm in the thickness direction thereof
at the wavelength of 550nm and a phase difference value of -
500nm in the thickness direction thereof at the wavelength of
450nm, the dispersion ratio value of the negative C plate C1


is represented as
In addition, if the
positive C plate C2 has a phase difference value of 300nm in
the thickness direction thereof at the wavelength of 550nm
with a flat type wavelength dispersion characteristic
representing almost similar phase difference values in the
thickness direction of the positive C plate within a range of
visible light, the dispersion ratio value of the positive C


plate C2 is represented as

At this time, the complex C plate has a phase
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WO 2005/017613 PCT/KR2004/002032
difference value of (R550)=-400nm + 300nm = -100nm at the
wavelength of 550nm, and a phase difference value of (R450) =
-500nm + 300nm = -200nm at the wavelength of 450nm.
Therefore, the complex light compensation negative C plate of
the present invention is a negative C plate having a super-


high dispersion ratio value of


A value of
for the complex light compensation
negative C plate having a super-high wavelength dispersion
characteristic can be identical to or more than 1.2, which
can be achieved by using one film.
The complex light compensation negative C plate having
the super-high dispersion characteristic is adaptable for an
IPS-LCD, and a brightness enhancement film, such as a CLC
polarizing plate.
Meanwhile, the C plate having a low wavelength
dispersion characteristic, a flat wavelength dispersion
characteristic, or an inverse wavelength dispersion
characteristic, depending on wavelength dispersion
characteristic of the A plate shown in FIG. 1, can be
combined with the A plate so as to be used as a viewing angle
compensation film for an IPS-LCD.
According to a fourth embodiment of the present
invention, there is provided a complex light compensation
positive C plate having a low wavelength dispersion


characteristic

, a flat wavelength

dispersion characteristic

or an inverse

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WO 2005/017613 PCT/KR2004/002032


wavelength dispersion characteristic

by

consisting of positive and negative C plates.
On the assumption that two films forming the complex
light compensation positive C plate having the low wavelength
dispersion characteristic, the flat wavelength dispersion
characteristic or the inverse wavelength dispersion
characteristic are C1 and C2 , in which C1 is a positive C
plate (nz > nx = ny ) and C2 is a negative C plate (nznx=ny),
the complex light compensation negative C plate having two
films stacked on each other must satisfy the following
equations in order to achieve the low wavelength dispersion
characteristic, the flat wavelength dispersion characteristic
or the inverse wavelength dispersion characteristic.

wherein, (R450)c1 represents a phase difference value of
C plate C1 in a thickness direction of a film at a wavelength
of 450nm, (R550)c1 represents a phase difference value of C
plate C1 in a thickness direction of a film at a wavelength of
550nm, (R450)c2 represents a phase difference value of C plate
C2 in a thickness direction of a film at a wavelength of
450nm, and (R550)c2 represents a phase difference value of C
plate C2 in a thickness direction of a film at a wavelength
of 550nm.
FIG. 8 is a view showing an absolute phase difference
values of a negative C plate C1, a positive C plate C2 and a
complex negative C plate in the thickness direction as a
function of wavelengths, respectively, in which the complex
negative C plate has an inverse wavelength dispersion
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WO 2005/017613 PCT/KR2004/O02032


characteristic
For instance, if the negative C plate C1 has a phase
difference value of -500nm in the thickness direction thereof
at the wavelength of 550nm with a flat type wavelength
dispersion characteristic representing almost similar phase
difference values in the thickness direction thereof within a
range of visible light, a wavelength dispersion ratio value
for the negative C plate C1 is represented as


In addition, if the positive C plate C2
has a phase difference value of 350nm in the thickness
direction thereof at the wavelength of 550nm, and a phase
difference value of 400nm in the thickness direction thereof
at the wavelength of 450nm, the dispersion ratio value of the


positive C plate C2 is represented as
At this time, the complex C plate has a phase
difference value of (R550)=-500nm+350nm=-l50nm at the
wavelength of 550nm, and a phase difference value of
(R450)=-500nm+400nm=-100nm at the wavelength of 450nm.
Therefore, the complex light compensation negative C plate is
a negative C plate having an inverse dispersion


characteristic of

The complex light compensation C plate can be combined
with the A plate shown in FIG. 1 so as to be used in an LCD.
In addition, the complex light compensation negative C plate
can be selected according to the wavelength dispersion
characteristic of liquid crystal used in an LCD panel and the
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A plate. The complex light compensation negative C plate
having the flat wavelength dispersion characteristic or the
low wavelength dispersion characteristic may be used when the
wavelength dispersion characteristics of the liquid crystal
used in the LCD panel and the A plate represent the flat
wavelength dispersion characteristic or the low wavelength
dispersion characteristic. The complex light compensation
negative C plate having the inverse wavelength dispersion
characteristic may be used when the liquid crystal used in
the LCD panel has a normal wavelength dispersion
characteristic and the A plate has a normal wavelength
dispersion characteristic.
According to a sixth embodiment of the present
invention, there is provided a complex light compensation
positive C plate having an intermediate wavelength dispersion
characteristic by consisting of two positive C plates
representing different wavelength dispersion characteristics.
On the assumption that two films forming the complex
light compensation positive C plate having the intermediate
wavelength dispersion characteristic are C1 and C2, in which
C1 is a first positive C plate ( nz>nx=ny), C2 is a second
positive C plate (nz>nx=ny), and C1 and C2 represent
different wavelength dispersion characteristics, FIG. 9 shows
an absolute phase difference values of two films and the
complex positive C plate in the thickness direction as a
function of wavelengths, respectively.
For instance, if the first positive C plate C1 has a
phase difference value of 200nm in the thickness direction
thereof at the wavelength of 550nm and a phase difference
value of 240nm in the thickness direction thereof at the
24

wavelength of 450nm, the wavelength dispersion characteristic
for the first positive C plate C1 is represented as


In addition, if the second positive C
plate C2 has a phase difference value of 300nm in the
thickness direction thereof at the wavelength of 550nm and a
phase difference value of 330nm in the thickness direction
thereof at the wavelength of 450nm, the dispersion ratio
value of the second positive C plate C2 is represented as

At this time, the complex light compensation C plate
has a phase difference value of (R55O)=200nm+300nm=500nm at
the wavelength of 550nm, and a phase difference value of
(R450)=240nm+330nm=570nm at the wavelength of 450nm.
Therefore, the complex light compensation positive C plate
according to the present invention is a positive C plate
having an intermediate dispersion characteristic of

The complex light compensation positive C plate having
the intermediate wavelength dispersion characteristic of two


exceeding 1.
C plates may have a value of
The complex light compensation positive C plate having
the intermediate wavelength dispersion characteristic can be
used for an IPS-LCD panel representing a low wavelength
dispersion characteristic.
According to a seventh embodiment of the present
invention, there is provided a complex light compensation
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WO 2005/017613 PCT/KR2004/002032
negative C plate having an intermediate wavelength dispersion
characteristic by consisting of two negative C plates
representing different wavelength dispersion characteristics.
On the assumption that two films forming the complex
light compensation negative C plate having the intermediate
wavelength dispersion characteristic are C1 and C2, in which
C1 is a first negative C plate (nznx=ny) and C2 is a
negative C plate (nznx=ny), the mixed light compensation C
plate having two films stacked on each other must satisfy the
following equations in order to achieve the above wavelength
dispersion characteristic.
[If only one wavelength in visible light range
satisfies the above equation, 450nx=ny ) and
an n-number of negative C plates (nznx=ny) and a negative C plate C2
(nznx=ny), and satisfies a following wavelength dispersion
characteristic:

wherein, R=(nz-ny)d representing a phase difference
value in a thickness direction, (R450)C1 represents a phase
difference value of the C plate C1 at a wavelength of 450nm,
(R550)C1 represents a phase difference value of the C plate C1
at a wavelength of 550nm, (R450)C1 represents a phase
difference value of the C plate C2 at a wavelength of 450nm,
(R550)C2 represents a phase difference value of the C plate
C2 at a wavelength of 550nm, nx and ny are surface refractive
indexes of a film, nz is a refractive index in a thickness
direction of a film, and d is a thickness of a film.
6. The complex light compensation C plate according
to claim 1, wherein the complex light compensation C plate
is a complex light compensation positive C plate having a
positive C plate C1 (nz>nx=ny) and a negative C plate C2
(nznx=ny), and satisfies a following wavelength dispersion
characteristic:

wherein, R =(nz-ny)d representing a phase difference
value in a thickness direction, (R45O)C1 represents a phase
difference value of the C plate C1 at a wavelength of 450nm,
(R550 )C1 represents a phase difference value of the C plate C1
at a wavelength of 550nm, (R450)C2 represents a phase
difference value of the C plate C2 at a wavelength of 450nm,
(R550)C2 represents a phase difference value of the C plate
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WO 2005/017613 PCT/KR20O4/0O2032
C2 at a wavelength of 550nm, nx and ny are surface refractive
indexes of a film, nz is a refractive index in a thickness
direction of a film, and d is a thickness of a film.
8. The complex light compensation C plate according
to claim 1, wherein the complex light compensation C plate
is a complex light compensation positive C plate having a
first positive C plate C1 (nz>nx=ny) and a second positive
C plate C2 (nz>nx=ny), said C1 and C2 representing
different dispersion ratio values.
9. The complex light compensation C plate according
to claim 1, wherein the complex light compensation C plate
is a complex light compensation negative C plate having a
first negative C plate C1 (nznx=ny), said C1 and C2 representing different
dispersion ratio values.
10. The complex Light compensation C plate according
to claim 1, wherein the complex light compensation C plate
represents a mark inversion characteristic for a phase
difference value at a predetermined wavelength  has a
positive C plate C1 (nz>nx=ny) and a negative C plate C2
(nznx=ny), and satisfies a following wavelength dispersion
characteristic:

wherein, R=(nz-ny)d representing a phase difference
value in a thickness direction, (R)C1 is a phase difference
value of the negative C plate C1 in a thickness direction at
the wavelength of , (R)C2 is a phase difference value of
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WO 2005/017613 PCT/KR2004/002032
the positive C plate C2 in a thickness direction thereof at
the wavelength of , (R450)C1 represents a phase difference
value of the C plate C1 at a wavelength of 450nm, (R550)C1
represents a phase difference value of the C plate C1 at a
wavelength of 550nm, (R450)C2 represents a phase difference
value of the C plate C2 at a wavelength of 450nm, (R550)C2
represents a phase difference value of the C plate C2 at a
wavelength of 550nm, nx and ny are surface refractive indexes
of a film, nz is a refractive index in a thickness direction
of a film, and d is a thickness of a film.
12. The complex light compensation C plate according
to any one of claims 1 to 11, wherein the C plates C1 and
C2 are formed by a plurality of division layers,
respectively.
13. The complex light compensation C plate according
to claim 1, wherein the complex light compensation C plate
has three C plates including a first positive C plate C1
(nz>nx=ny) , a second negative C plate C2 (nznx=ny) or a third negative C
plate (nz