U.S. patent application number 15/074391 was filed with the patent office on 2017-04-13 for liquid crystal composition and liquid crystal display comprising the same.
The applicant listed for this patent is Samsung Display Co. Ltd.. Invention is credited to Sun Young KWON, Keun Chan OH.
Application Number | 20170101580 15/074391 |
Document ID | / |
Family ID | 58460523 |
Filed Date | 2017-04-13 |
United States Patent
Application |
20170101580 |
Kind Code |
A1 |
KWON; Sun Young ; et
al. |
April 13, 2017 |
LIQUID CRYSTAL COMPOSITION AND LIQUID CRYSTAL DISPLAY COMPRISING
THE SAME
Abstract
A liquid crystal composition includes at least one first
compound represented by Formula I: ##STR00001## wherein each of L1
to L8 are independently a hydrogen or a fluorine; ##STR00002## is a
cyclohexyl group, a phenyl group, tetrahydropyran, 1,3-dioxane, a
fluorocyclohexyl group, a fluorophenyl group,
fluorotetrahydropyran, or fluoro-1,3-dioxane; n is 0 to 2, and when
n=2, each ##STR00003## is independently a cyclohexyl group, a
phenyl group, tetrahydropyran, 1,3-dioxane, a fluorocyclohexyl
group, a fluorophenyl group, fluorotetrahydropyran, or
fluoro-1,3-dioxane; each of R.sub.1 and R.sub.2 is independently a
C.sub.1.about..sub.2 alkyl group; and R' is hydrogen, a
C.sub.1.about..sub.5 alkyl group, a C.sub.2.about..sub.5 alkenyl
group, or a C.sub.1.about..sub.5 alkoxy group.
Inventors: |
KWON; Sun Young; (Seoul,
KR) ; OH; Keun Chan; (Cheonan-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Display Co. Ltd. |
Yongin-city |
|
KR |
|
|
Family ID: |
58460523 |
Appl. No.: |
15/074391 |
Filed: |
March 18, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07C 43/225 20130101;
C07C 25/24 20130101; C07C 25/13 20130101; C09K 2019/301 20130101;
C09K 19/0403 20130101; C09K 2019/3027 20130101; C09K 2019/3021
20130101; C09K 19/062 20130101; C09K 2019/3004 20130101; C09K
2019/3009 20130101; C09K 2019/124 20130101; C09K 19/3003 20130101;
C09K 19/3066 20130101; C07C 2601/14 20170501; C09K 2019/3016
20130101; G02F 1/0045 20130101; C09K 2019/3422 20130101; C09K
2019/123 20130101; C09K 19/063 20130101 |
International
Class: |
C09K 19/30 20060101
C09K019/30; G02F 1/1368 20060101 G02F001/1368; C07C 25/24 20060101
C07C025/24; C07C 43/225 20060101 C07C043/225; C07C 25/13 20060101
C07C025/13 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 7, 2015 |
KR |
10-2015-0140867 |
Claims
1. A liquid crystal composition, comprising: at least one first
compound represented by Formula I: ##STR00039## wherein each of L1
to L8 is a hydrogen or a fluorine; ##STR00040## is a cyclohexyl
group, a phenyl group, tetrahydropyran, 1,3-dioxane, a
fluorocyclohexyl group, a fluorophenyl group,
fluorotetrahydropyran, or fluoro-1,3-dioxane; ##STR00041## n is 0
to 2, and when n=2, each is independently a cyclohexyl group, a
phenyl group, tetrahydropyran, 1,3-dioxane, a fluorocyclohexyl
group, a fluorophenyl group, fluorotetrahydropyran, or
fluoro-1,3-dioxane; each of R.sub.1 and R.sub.2 are independently a
C.sub.1.about..sub.2 alkyl group; and R' is hydrogen, a
C.sub.1.about..sub.5 alkyl group, a C.sub.2.about..sub.5 alkenyl
group, or a C.sub.1.about..sub.5 alkoxy group.
2. The liquid crystal composition of claim 1, wherein the first
compound is at least one of compounds represented by Formulas I-1
to I-42: ##STR00042## ##STR00043## ##STR00044## ##STR00045##
##STR00046##
3. The liquid crystal composition of claim 1, further comprising at
least one second compound represented by Formulas II-1 to II-8:
##STR00047## wherein each X and Y are independently hydrogen, a
C.sub.1.about..sub.5 alkyl group, a C.sub.2.about..sub.5 alkenyl
group, a C.sub.1.about..sub.5 alkoxy group, a C.sub.1.about..sub.5
fluoroalkyl group, a C.sub.2.about..sub.5 fluoroalkenyl group, or a
C.sub.1.about..sub.5 fluoroalkoxy group.
4. The liquid crystal composition of claim 1, further comprising at
least one third compound represented by Formulas III-1 to III-12:
##STR00048## ##STR00049## wherein each X and Y are independently
hydrogen, a C.sub.1.about..sub.6 alkyl group, a
C.sub.2.about..sub.6 alkenyl group, a C.sub.1.about..sub.6 alkoxy
group, a C.sub.1.about..sub.6 fluoroalkyl group, a
C.sub.2.about..sub.6 fluoroalkenyl group, or a C.sub.1.about..sub.6
fluoroalkoxy group.
5. A liquid crystal display (LCD), comprising: a first display
substrate comprising one or more thin-film transistor (TFT); a
second display substrate facing the first display substrate; and a
liquid crystal layer comprising at least one first compound
represented by Formula I: ##STR00050## wherein each of L1 to L8 is
a hydrogen or a fluorine; ##STR00051## is a cyclohexyl group, a
phenyl group, tetrahydropyran, 1,3-dioxane, a fluorocyclohexyl
group, a fluorophenyl group, fluorotetrahydropyran, or
fluoro-1,3-dioxane; n is 0 to 2, and when n=2, each ##STR00052## is
independently a cyclohexyl group, a phenyl group, tetrahydropyran,
1,3-dioxane, a fluorocyclohexyl group, a fluorophenyl group,
fluorotetrahydropyran, or fluoro-1,3-dioxane; each of R.sub.1 and
R.sub.2 are independently a C.sub.1.about..sub.2 alkyl group; and
R' is hydrogen, a C.sub.1.about..sub.5 alkyl group, a
C.sub.2.about..sub.5 alkenyl group, or a C.sub.1.about..sub.5
alkoxy group.
6. The LCD of claim 5, wherein the first compound is at least one
of compounds represented by Formulas I-1 to I-42: ##STR00053##
##STR00054## ##STR00055## ##STR00056## ##STR00057##
7. The LCD of claim 5, wherein the liquid crystal layer further
comprises at least one second compound represented by Formulas II-1
to II-8: ##STR00058## wherein each X and Y are independently
hydrogen, a C.sub.1.about..sub.5 alkyl group, a
C.sub.2.about..sub.5 alkenyl group, a C.sub.1.about..sub.5 alkoxy
group, a C.sub.1.about..sub.5 fluoroalkyl group, a
C.sub.2.about..sub.5 fluoroalkenyl group, or a C.sub.1.about..sub.5
fluoroalkoxy group.
8. The LCD of claim 5, wherein the liquid crystal layer further
comprises at least one third compound represented by Formulas III-1
to III-12: ##STR00059## ##STR00060## wherein each X and Y are
independently hydrogen, a C.sub.1.about..sub.6 alkyl group, a
C.sub.2.about..sub.6 alkenyl group, a C.sub.1.about..sub.6 alkoxy
group, a C.sub.1.about..sub.6 fluoroalkyl group, a
C.sub.2.about..sub.6 fluoroalkenyl group, or a C.sub.1.about..sub.6
fluoroalkoxy group.
Description
[0001] This application claims priority to Korean Patent
Application No. 10-2015-0140867, filed on Oct. 7, 2015, and all the
benefits accruing therefrom under 35 U.S.C. .sctn.119, the content
of which in its entirety is herein incorporated by reference.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The invention relates to a liquid crystal composition and a
liquid crystal display (LCD) comprising the same.
[0004] 2. Description of the Related Art
[0005] A liquid crystal display (LCD), is one of the most
widely-used flat panel displays. The LCD includes two substrates on
which field-generating electrodes such as pixel electrodes and a
common electrode are formed and a liquid crystal layer interposed
between the two substrates.
[0006] As the field of application of LCDs has widened,
improvements in the properties of LCDs, such as response speed,
contrast ratio, and driving voltage characteristics, have improved.
To improve the properties of LCDs, it is desirable for the a liquid
crystal compound contained in a liquid crystal composition to have
low rotational viscosity, high chemical and physical stability, a
high liquid phase-to-isotrophic phase transition temperature, a low
liquid-phase lower limit temperature, and an appropriate elastic
modulus. In particular, a low-rotational viscosity liquid crystal
material is desired to provide high-speed response
characteristics.
SUMMARY
[0007] Exemplary embodiments of the invention provide a liquid
crystal composition comprising a novel low-viscosity polar liquid
crystal compound.
[0008] Exemplary embodiments of the invention also provide a liquid
crystal display comprising a liquid crystal layer comprising a
novel low-viscosity polar liquid crystal compound.
[0009] According to an exemplary embodiment, a liquid crystal
composition includes a novel low-viscosity polar liquid crystal
compound. In another exemplary embodiment, an LCD including the
liquid crystal composition is provided.
[0010] According to an exemplary embodiment, a liquid crystal
composition includes at least one first compound represented by
Formula I.
[0011] According to another exemplary embodiment, a liquid crystal
display (LCD) includes a first display substrate including
thin-film transistors (TFTs), a second display substrate facing the
first display substrate and a liquid crystal layer comprising at
least one first compound represented by Formula I.
##STR00004##
[0012] In Formula I, each of L1 to L8 is a hydrogen or a
fluorine;
##STR00005##
is a cyclohexyl group, a phenyl group, tetrahydropyran,
1,3-dioxane, a fluorocyclohexyl group, a fluorophenyl group,
fluorotetrahydropyran, or fluoro-1,3-dioxane; n is 0 to 2, and when
n=2, each
##STR00006##
is independently a cyclohexyl group, a phenyl group,
tetrahydropyran, 1,3-dioxane, a fluorocyclohexyl group, a
fluorophenyl group, fluorotetrahydropyran, or fluoro-1,3-dioxane;
each of R.sub.1 and R.sub.2 is independently a C.sub.1.about..sub.2
alkyl group; and R' is hydrogen, a C.sub.1.about..sub.5 alkyl
group, a C.sub.2.about..sub.5 alkenyl group, or a
C.sub.1.about..sub.5 alkoxy group.
[0013] Other features and exemplary embodiments will be apparent
from the following detailed description, the drawings, and the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] A more complete appreciation of the present disclosure, and
many of the attendant advantages thereof, will be readily apparent
when the following detailed description is considered in
conjunction with the accompanying drawings, in which:
[0015] FIG. 1 is a schematic exploded perspective view of an
exemplary embodiment of a liquid crystal display (LCD); and
[0016] FIG. 2 is a schematic cross-sectional view of the exemplary
LCD of FIG. 1.
DETAILED DESCRIPTION
[0017] Features of the inventive concept and methods of
accomplishing the same may be understood more readily by
referencing the following detailed description and the accompanying
drawings. The inventive concept may, however, be embodied in many
different forms and are not limited to the embodiments set forth
herein. Rather, these embodiments are provided to help illustrate
the scope of the invention to those of ordinary skill in the
art.
[0018] In the drawings, the thickness of layers and regions are
exaggerated for clarity. It will be understood that when an element
or layer is referred to as being "on", "connected to" or "coupled
to" another element or layer, the element or layer may be directly
on, connected or coupled to another element or layer, or
intervening elements or layers. In contrast, when an element is
referred to as being "directly on", "directly connected to" or
"directly coupled to" another element or layer, there are no
intervening elements or layers present. As used herein, connected
may refer to elements being physically, electrically and/or fluidly
connected to each other.
[0019] Like numbers refer to like elements throughout. As used
herein, the term "and/or" includes any and all combinations of one
or more of the associated listed items.
[0020] It will be understood that, although the terms first,
second, third, etc., may be used herein to describe various
elements, components, regions, layers and/or sections, these
elements, components, regions, layers and/or sections are not
limited by these terms. These terms are only used to distinguish
one element, component, region, layer or section from another
element, component, region, layer or section. Thus, a first
element, component, region, layer or section discussed below could
be termed a second element, component, region, layer or section
without departing from the teachings of the present disclosure.
[0021] Spatially related terms, such as "below", "lower", "under",
"above", "upper" and the like, may be used herein for ease of
description to describe the relationship of one element or feature
to another element(s) or feature(s) as illustrated in the figures.
It will be understood that the spatially related terms are intended
to encompass different orientations of the device in use or
operation, in addition to the orientation depicted in the figures.
For example, if the device in the figures is turned over, elements
described as "below" or "beneath" relative to other elements or
features would then be oriented "above" relative to the other
elements or features. Thus, the exemplary term "below" can
encompass both an orientation of above and below. The device may be
otherwise oriented (rotated 90 degrees or at other orientations)
and the spatially related descriptors used herein may be
interpreted accordingly.
[0022] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the present disclosure. As used herein, the singular forms "a",
"an" and "the" are intended to include the plural forms as well,
unless the context clearly indicates otherwise. It will be further
understood that the terms "comprises", "comprising", "includes"
and/or "including", when used in this specification, specify the
presence of stated features, integers, operations, elements, and/or
components, but do not preclude the presence or addition of one or
more other features, integers, steps, operations, elements,
components, and/or groups thereof.
[0023] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
disclosure belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and the present
disclosure, and will not be interpreted in an idealized or overly
formal sense unless expressly so defined herein.
[0024] Exemplary embodiments are described herein with reference to
cross section illustrations that are schematic illustrations of
idealized embodiments. As such, variations from the shapes of the
illustrations as a result, for example, of manufacturing techniques
and/or tolerances, are to be expected. Thus, embodiments described
herein should not be construed as limited to the particular shapes
of regions as illustrated herein but are to include deviations in
shapes that result, for example, from manufacturing. For example, a
region illustrated or described as flat may, typically, have rough
and/or nonlinear features. Moreover, sharp angles that are
illustrated may be rounded. Thus, the regions illustrated in the
figures are schematic in nature and their shapes are not intended
to illustrate the precise shape of a region and are not intended to
limit the scope of the present claims.
[0025] The term "C.sub.A.about..sub.B", as used herein, refers to a
carbon number of A to B. For example, the term
"C.sub.1.about..sub.5" refers to a carbon number of one to
five.
[0026] FIG. 1 is a schematic exploded perspective view of an
exemplary embodiment of a liquid crystal display 500. FIG. 2 is a
schematic cross-sectional view of the LCD 500 of FIG. 1.
[0027] Referring to FIGS. 1 and 2, the LCD 500 may include a first
display substrate 100, a second display substrate 200, which is
spaced from, and faces, the first display substrate 100, and a
liquid crystal layer 300, which is interposed between the first and
second display substrates 100 and 200. Each of the first and second
display substrates 100 and 200 includes a display area I and a
non-display area II. In the display area I, a plurality of pixels
PX, which are arranged in a matrix form, may be defined.
[0028] In the display area I of the first display substrate 100, a
plurality of gate lines GL, which extend in a first direction, and
a plurality of data lines DL, which extend in a second direction
that is perpendicular to the first direction, may be formed. A
pixel electrode 180 may be disposed in each of the pixels PX, which
are defined by the gate lines GL and the data lines DL.
[0029] The pixel electrode 180 may be provided with a data voltage
via a thin-film transistor (TFT), which is a switching device. A
gate electrode 125, which is the control terminal of the TFT, may
be connected to a gate line GL, a source electrode 152, which is
the input terminal of the TFT, may be connected to a data line DL,
and a drain electrode 155, which is the output terminal of the TFT,
may be electrically connected to the pixel electrode 180 via a
contact hole 172.
[0030] A channel of the TFT may be formed in a semiconductor layer
140. The semiconductor layer 140 may be disposed to overlap the
gate electrode 125. The source and drain electrodes 152 and 155 may
be spaced a distance apart from each other with the semiconductor
layer 140 interposed therebetween. The pixel electrode 180 may form
an electric field with a common electrode 250 and may control the
alignment direction of a liquid crystal compound 301 in the liquid
crystal layer 300, which is interposed between the pixel electrode
180 and the common electrode 250.
[0031] The non-display area II may be an area surrounding the
display area I. Driving units (not illustrated) providing a gate
driving signal and a data driving signal to each of the pixels PX
in the display area I may be disposed in the non-display area II of
the first display substrate 100.
[0032] In the display area I of the second display substrate 200, a
color filter 230 may be formed for each of the pixels PX. Examples
of the color filter 230 include red R, green G, and blue B color
filters. The red R, green G, and blue B color filters may be
alternately arranged. A light-blocking pattern 220 may be disposed
along a boundary between the color filter 230 and a neighboring
color filter 230 and thus the light-blocking pattern 220 may be
disposed in the display area I and the non-display area II of the
second display substrate 200. The light-blocking pattern 220 may
have a larger width in the non-display area II than a
light-blocking pattern 220 disposed along the boundary between the
color filter 230 and the neighboring color filter 230. The common
electrode 250, which is formed in one continuous piece, may be
disposed on the entire surface of the display area I regardless of
the pixels PX.
[0033] The first and second display substrates 100 and 200 may be
bonded together by a seal line 310, which is formed of a sealant.
The seal line 310 may account for the periphery of the first and
second display substrates 100 and 200 and may be disposed in the
non-display area II. The seal line 310 is formed along the
periphery of the display area I and thus surrounds the display area
I. The seal line 310 bonds the first and second display substrates
100 and 200 together and also defines a predetermined space
therebetween. The liquid crystal layer 300 is inserted in the space
defined by the seal line 310, and thus the seal line 310 may
prevent the liquid crystal compound 301 from leaking.
[0034] The LCD 500 will hereinafter be described in detail. The
first display substrate 100 may have a first substrate 110 as a
base substrate. The first substrate 110 may include the display
area I and the non-display area II. The first substrate 110 may be
provided as a transparent insulating substrate formed of glass or a
transparent plastic material.
[0035] The gate line GL, which is formed of a conductive material,
and the gate electrode 125, which protrudes from the gate line GL,
may be disposed on the first substrate 110 in the display area I.
Although not specifically illustrated, the gate line GL may extend
into the non-display area II and may form a gate pad (not
illustrated) in the non-display area II. The gate line GL and the
gate electrode 125 may be covered by a gate insulating layer 130.
The gate insulating layer 130 may also be formed in the non-display
area II.
[0036] The semiconductor layer 140 and an ohmic contact layer (not
illustrated) may be formed on the gate insulating layer 130 in the
display area I. The source electrode 152, which is branched off
from the data line DL, and the drain electrode 155, which is spaced
from the source electrode 152, may be formed on the semiconductor
layer 140 and the ohmic contact layer. Although not specifically
illustrated, the data line DL may extend into the non-display area
II and may form a data pad (not illustrated) in the non-display
area II.
[0037] A passivation layer 160, which is a type of insulating
layer, may be formed on the source and drain electrodes 152 and
155, and an organic layer 170 may be formed on the passivation
layer 160 using an organic material. The passivation layer 160 may
be formed of an insulating material, such as a silicon nitride
layer, a silicon oxide layer, or a silicon oxynitride layer. The
passivation layer 160 and the organic layer 170 may be formed in
the display area I and in the non-display area II. Optionally, the
passivation layer 160 may not be present.
[0038] The pixel electrode 180 may be formed on the organic layer
170 in the display area I for each of the pixels PX, and may be
formed using a conductive material. The pixel electrode 180 may be
electrically connected to the drain electrode 155 via a contact
hole 172 defined in the organic layer 170 and the passivation layer
160 and which exposes the drain electrode 155 therethrough. The
pixel electrode 180 may be formed of at least one of indium tin
oxide (ITO), indium zinc oxide (IZO), indium oxide, zinc oxide, tin
oxide, gallium oxide, titanium oxide, aluminum (Al), silver (Ag),
platinum (Pt), chromium (Cr), molybdenum (Mo), tantalum (Ta),
niobium (Nb), zinc (Zn), magnesium (Mg), an alloy thereof, and a
deposition layer thereof.
[0039] The second display substrate 200 will hereinafter be
described. The second display substrate 200 has a second substrate
210 as a base substrate. The second substrate 210 may be provided
as a transparent insulating substrate formed of glass or a
transparent plastic material.
[0040] The light-blocking pattern 220 is formed on the second
substrate 210. The light-blocking pattern 220 may be formed in the
display area I and in the non-display area II. The color filter 230
may be formed on the light-blocking pattern 220 in the display area
I. An overcoat layer 240 may be formed on the color filter 230 and
the light-blocking pattern 220. The overcoat layer 240 may be
formed in the display area I and in the non-display area II.
[0041] The common electrode 250 may be disposed on the overcoat
layer 240. The common electrode 250 may be formed of at least one
of ITO, IZO, indium oxide, zinc oxide, tin oxide, gallium oxide,
titanium oxide, Al, Ag, Pt, Cr, Mo, Ta, Nb, Zn, Mg, an alloy
thereof, and deposition layer thereof.
[0042] The common electrode 250 may be formed to cover the entire
display area I. The common electrode 250 may include slits (not
illustrated) or openings (not illustrated) in the display area I.
The common electrode 250 may also be formed in the non-display area
II, however, the common electrode 250 is not formed along, or near,
the edges of the second display substrate 200, so that the overcoat
layer 240 may be exposed. The pixel electrode 180 of the first
display substrate 100 and the common electrode 250 of the second
display substrate 200 may be disposed to face each other and may
form an electric field in the liquid crystal layer 300.
[0043] The first and second display substrates 100 and 200 may be
disposed to face each other while maintaining a predetermined cell
gap therebetween. The liquid crystal layer 300 may be interposed
between the first and second display substrates 100 and 200 in the
display area I.
[0044] A liquid crystal alignment layer 190 may be formed on the
first display substrate 100 and liquid a crystal alignment layer
270 may be formed on the second display substrate 200. The liquid
crystal alignment layer 190 may be disposed between the first
display substrate 100 and the liquid crystal layer 300 and between
the first display substrate 100 and the seal line 310. The liquid
crystal alignment layer 270 may be disposed between the second
display substrate 200 and the liquid crystal layer 300 and between
the second display substrate 200 and the seal line 310. In a
non-limiting example, the liquid crystal alignment layers 190 and
270 may be polyimide-based liquid crystal alignment layers.
[0045] FIGS. 1 and 2 illustrate a color filter array in which the
second display substrate 200 includes the color filter 230.
Alternatively, the color filter 230 may be included in the first
display substrate 100, in which case, the first display substrate
100 has a color filter-on-array (COA) structure in which a color
filter is formed on a transparent insulating substrate where a TFT
is formed.
[0046] Although not specifically illustrated, the LCD 500 may also
include a backlight unit (not illustrated), which is disposed below
the first display substrate 100, and an upper polarizing plate (not
illustrated), which is disposed on the second display substrate
200.
[0047] The backlight unit may include, for example, a light guide
plate (LGP), a light source unit, a reflection member, and one or
more optical sheets.
[0048] The LGP changes the path of light generated by the light
source unit so the light travels toward the liquid crystal layer
300. The LGP may include an incidence surface, which receives the
light generated by the light source unit, and an emission surface,
which faces the liquid crystal layer 300. The LGP may be formed of
a material having a uniform refractive index, such as poly(methyl
methacrylate) (PMMA) or polycarbonate (PC), but is not limited
thereto. Light incident upon one or both sides of the LGP having a
smaller incidence angle than the critical angle of the LGP, may
thus enter the LGP. On the other hand, light incident upon the top
or bottom surface of the LGP having a greater incidence angle than
the critical angle of the LGP, may thus be evenly distributed
throughout the LGP instead of being emitted out of the LGP.
[0049] A diffusion pattern may be formed on one of the top and
bottom surfaces of the LGP to enable guided light to be emitted
upwards. For example, the diffusion pattern may be formed on the
bottom surface of the LGP that is opposite to the emission surface
of the LGP. More specifically, in order for light transmitted
within the LGP to be emitted upward, the diffusion pattern may be
printed on one surface of the LGP with ink, but is not limited
thereto. That is, the diffusion pattern may also be an array of
fine grooves or protrusions formed on the surface of the LGP.
Alternatively, various other modifications may be made to the
diffusion pattern without departing from the scope of the
invention.
[0050] The reflective member (not illustrated) may be additionally
provided between the LGP and a lower receiving member (not
illustrated). The reflective member reflects light emitted from the
bottom surface of the LGP, which is opposite to, and faces, the
emission surface of the LGP, and thus applies the light back to the
LGP. The reflective member may be formed as a film, but is not
limited thereto.
[0051] The light source unit may be disposed to face the incidence
surface of the LGP. The number of light source units provided may
be appropriately varied. In one exemplary embodiment, only one
light source unit may be provided on one side of the LGP. In
another exemplary embodiment, three or more light source units may
be provided to correspond to three or more sides of the LGP. In yet
another exemplary embodiment, a plurality of light source units may
be provided to correspond to only one side of the LGP.
[0052] The backlight unit has been described above, taking as an
example a side light-type backlight unit in which one or more light
source units are provided on one or more sides of an LGP, but is
not limited thereto. That is, the invention is also applicable to a
direct-type backlight unit or another light source device, such as
a surface-type light source device.
[0053] The light source unit may include a white light-emitting
diode (LED), which emits white light, or a plurality of LEDs, which
emit red (R) light, green (G) light and blue (B) light. In response
to the light source unit including a plurality of LEDs, which emit
R light, G light, and B light, white light may be realized by
turning on all the LEDs to mix the R light, G light, and B light
together.
[0054] The liquid crystal layer 300 will hereinafter be described
in detail. The liquid crystal layer 300 may comprise at least one
first compound represented by Formula I:
##STR00007##
where each of L1 to L8 is a hydrogen (H) or a fluorine (F);
##STR00008##
is a cyclohexyl group, a phenyl group, tetrahydropyran,
1,3-dioxane, a fluorocyclohexyl group, a fluorophenyl group,
fluorotetrahydropyran, or fluoro-1,3-dioxane, each of R.sub.1 and
R.sub.2 is independently a C.sub.1.about..sub.2 alkyl group; and R'
is hydrogen, a C.sub.1.about..sub.5 alkyl group, a
C.sub.2.about..sub.5 alkenyl group, or a C.sub.1.about..sub.5alkoxy
group.
[0055] Referring to Formula I, n is 0 to 2. If n is greater than 2,
the long axis of the liquid crystal compound increases, and as a
result, the rotational viscosity of the liquid crystal compound
increases considerably, which is undesirable. Accordingly, n may be
2 or less.
[0056] When n=2, each
##STR00009##
is independently a cyclohexyl group, a phenyl group,
tetrahydropyran, 1,3-dioxane, a fluorocyclohexyl group, a
fluorophenyl group, fluorotetrahydropyran, or
fluoro-1,3-dioxane.
[0057] The first compound may be, but is not limited to, at least
one of the compounds represented by Formulas I-1 through I-42:
##STR00010## ##STR00011## ##STR00012## ##STR00013##
[0058] In a typical polar liquid crystal compound, at least one of
the terminal groups on sides of a mesogen group is a
C.sub.3.about..sub.5 alkyl group, a C.sub.3.about..sub.5 alkoxy
group, or a C.sub.3.about..sub.5 alkenyl group. As the demand for a
fast-response panel has increased, the demand for a low-viscosity
liquid crystal compound has also increased. However, the greater
the carbon number of the terminal groups of a liquid crystal
compound, the higher the viscosity of the liquid crystal
compound.
[0059] Since at least one of the terminal groups of the typical
polar liquid crystal compound is a C.sub.3.about..sub.5 alkyl
group, a C.sub.3.about..sub.5 alkoxy group, or a
C.sub.3.about..sub.5 alkenyl group, the length of the long axis of
the typical polar liquid crystal compound increases, and thus, the
typical polar liquid crystal compound has a higher rotational
viscosity than the first compound described herein.
[0060] Individual structural groups of a liquid crystal compound
will hereinafter be referred to in the abbreviated forms shown in
Table 1 below.
TABLE-US-00001 TABLE 1 Structure Abbreviation ##STR00014## C
##STR00015## P ##STR00016## A ##STR00017## T ##STR00018## B
##STR00019## V ##STR00020## V1 --O-- O ##STR00021## T1 ##STR00022##
L
[0061] Tables 2 and 3 below show molecular weight (grams per mole;
g/mol), dipole moment (D), dielectric anisotropy
(.DELTA..epsilon.), rotational viscosity (.gamma.1) (millipascal
second; mPas), and low-temperature stability measurements for a
typical polar liquid crystal molecule having a structure
represented by Formula A (Table 2) and for an exemplary first
compound represented by Formula I-8 (Table 3).
TABLE-US-00002 TABLE 2 ##STR00023## Classification (Formula
A_3CPAO2) Molecular Weight (g/mol) 358.47 Dipole Moment (D) 3.41
Dielectric anisotropy (.DELTA..epsilon.) -5.8 Rotational Viscosity
(.gamma.1)(mPa .cndot. s) 230 Low-Temperature Stability Average
TABLE-US-00003 TABLE 3 ##STR00024## Classification (Formula
I-8_TPAO2) Molecular Weight (g/mol) 344.45 Dipole Moment (D) 3.41
Dielectric anisotropy (.DELTA..epsilon.) -5.7 Rotational Viscosity
(.gamma.1)(mPa .cndot. s) 150 Low-Temperature Stability
Excellent
[0062] Referring to Tables 2 and 3 above, the polar liquid crystal
compound of Formula I-8 has almost the same level of dielectric
anisotropy as the typical polar liquid crystal compound of Formula
A, but has much better rotational viscosity and low-temperature
stability than the typical polar liquid crystal compound of Formula
A.
[0063] The liquid crystal layer 300 may further comprise at least
one second compound represented by Formulas II-1 to II-8:
##STR00025##
Where each X and Y are independently H, a C.sub.1.about..sub.5
alkyl group, a C.sub.2.sup.-.sub.5 alkenyl group, a
C.sub.1.about..sub.5 alkoxy group, a C.sub.1.about..sub.5
fluoroalkyl group, a C.sub.2.about..sub.5 fluoroalkenyl group, or a
C.sub.1.about..sub.5 fluoroalkoxy group.
[0064] The liquid crystal layer 300 may further comprise at least
one third compound represented by Formulas III-1 to III-12:
##STR00026## ##STR00027##
Where each X and Y are independently H, a C.sub.1.about..sub.6
alkyl group, a C.sub.2.about..sub.6 alkenyl group, a
C.sub.1.about..sub.6 alkoxy group, a C.sub.1.about..sub.6
fluoroalkyl group, a C.sub.2.about..sub.6 fluoroalkenyl group, or a
C.sub.1.about..sub.6 fluoroalkoxy group.
[0065] Tables 4 and 5 below show performance evaluation results for
a liquid crystal composition including the liquid crystal compound
of Formula A (Comparative Example) and for a liquid crystal
composition including the exemplary first compound of Formula I-8
(Example).
TABLE-US-00004 TABLE 4 Liquid Crystal Composition Content
(Comparative Example) (Wt %) Performance Evaluation ##STR00028## 20
VHR (UV 5J): 88.5% .DELTA.n(ne-no): 0.095
.DELTA..epsilon.(.epsilon..parallel. - .epsilon..perp.): -4.9
(V1CC3) .gamma.1: 160 mPa .cndot. s ##STR00029## 14 (3CC4)
##STR00030## 22 (3CAO2) ##STR00031## 22 (3CCAO2) ##STR00032## 22
(3CPAO2)
TABLE-US-00005 TABLE 5 Liquid Crystal Composition Content (Example)
(Wt %) Performance Evaluation ##STR00033## 20 VHR (UV 5J): 88.4%
.DELTA.n(ne-no): 0.092 .DELTA..epsilon.(.epsilon..parallel. -
.epsilon..perp.): -4.8 (V1CC3) .gamma.1: 152 mPa .cndot. s
##STR00034## 14 (3CC4) ##STR00035## 22 (3CAO2) ##STR00036## 22
(3CCAO2) ##STR00037## 12 (3CPAO2) ##STR00038## 10 (TPAO2)
[0066] Referring to Tables 4 and 5 above, the Example liquid
crystal composition has almost the same physical properties as the
Comparative Example liquid crystal composition and yet has a
better, or at least equivalent, rotational viscosity, reliability,
and low-temperature stability than the liquid crystal composition
of the Comparative Example.
[0067] While the present disclosure has been particularly shown and
described with reference to exemplary embodiments thereof, it will
be understood by those of ordinary skill in the art that various
changes in implementation and detail may be made therein without
departing from the spirit and scope of the following claims. The
exemplary embodiments should be considered in a descriptive sense
only and not for purposes of limitation.
* * * * *