Patent Application
20150125631
The present invention relates to an optical film and a display device using the same. More particularly, the present invention relates to an optical film with excellent liquid crystal arrangement and improved photoreaction rate, and a display device using the same.
With a recent advent of large-sized LCDs and a gradual expansion of their usage from portable devices, such as mobile phones, lap-top computers, etc., to home appliances, such as wall mounted flat panel TVs, there is a demand for LCDs with high definition and wide viewing angle. In particular, TFT-driven thin film transistor LCDs (TFT-LCDs) of which the individual pixels are independently driven are much superior in response speed of liquid crystals, realizing high-definition motion pictures, and thus increasingly used in a wider range of applications.
To be used as an optical switch in the TFT-LCDs, liquid crystals are required to initially align in a defined direction on a layer including innermost TFT of the display cell. For this, a liquid crystal alignment layer is used.
For the liquid crystal alignment to occur, a heat-resistant polymer such as polyimide is applied on a transparent glass to form a polymer alignment layer, which is then subjected to a rubbing process using a rotary roller wound with a rubbing cloth of nylon or rayon fabrics at a high rotation speed to align liquid crystals.
However, the rubbing process remains mechanical scratches on the surface of the liquid crystal alignment layer or generates strong static electricity, possibly destroying the TFTs. Moreover, fine fibers coming from the rubbing cloth may cause defectives, imposing an obstacle to acquiring a higher production yield.
To overcome the problems with the rubbing process and achieve innovation in the aspect of production yield, there has been derived a liquid crystal alignment (hereinafter, referred to as “photo-alignment”) method using a light such as UV radiation.
Photo-alignment refers to the mechanism using a linearly polarized UV radiation to cause the photoreactive groups of a defined photoreactive polymer to participate in a photoreaction, ending up with the main chain of the polymer aligned in a defined direction to form a photo-polymerized liquid crystal alignment layer with aligned liquid crystals.
The representative example of the photo-alignment is photopolymerization-based photo-alignment as disclosed by M. Schadt et al. (Jpn. J. Appl. Phys., Vol 31., 1992, 2155), Dae S. Kang et al. (U.S. Pat. No. 5,464,669), and Yuriy Reznikov (Jpn. J. Appl. Phys. Vol. 34, 1995, L1000). The photo-aligned polymers used in these patent and research papers are mostly polycinnamate-based polymers, such as poly(vinylcinnamate) (PVCN) or poly(vinyl methoxycinnamate) (PVMC). For photo-alignment of polymers, the double bond of cinnamate exposed to UV radiation participates in a [2+2] cycloaddition reaction to form cyclobutane, which provides anisotropy to cause liquid crystal molecules aligned in one direction, inducing liquid crystal alignment.
Besides, JP11-181127 discloses a polymer and an alignment layer including the same in which the polymer has a side chain including photoreactive groups such as cinnamate on a main chain such as acrylate, methacrylate, etc. Korean Patent Laid-Open Publication No. 2002-0006819 also discloses the use of an alignment layer comprising a polymethacryl-based polymer.
Such conventional photoreactive polymers for alignment layer, however, have their polymer main chain with low thermal stability and thus undesirably contribute to deterioration in the stability of the alignment layer or poor characteristics regarding photoreactivity, liquid crystal alignment, or alignment rate. For example, polymers with an acryl-based main chain have low thermal stability, which contributes to a great deterioration in the stability of the alignment layer, while polymers with photosensitive groups belonging in the main chain cannot rapidly react to the polarized light irradiated on the alignment layer and thus deteriorate liquid crystal alignment or alignment rate. Such deterioration in liquid crystal alignment or alignment rate causes reduced process efficiency or contributes to insufficient liquid crystal alignment of the LCDs, leading to lower dichroic ratio and poor contrast.
On the other hand, Bull. Korean Chem. Soc. 2002, Vol. 23, 957 discloses a photoreactive polymer containing a repeating unit bound to an azo group as a part of the repeating units. However, such a photoreactive polymer also has poor alignment and low photoreaction rate and still results in low process efficiency and poor contrast of the LCDs.
To solve the problems with the prior art, it is an object of the present invention to provide an optical film with excellent liquid crystal alignment and improved photoreaction rate.
It is another object of the present invention to provide a display device including the liquid crystal film.
To achieve the objects of the present invention, there is provided an optical film comprising: a first optically anisotropic layer comprising at least one liquid crystal compound represented by the following formula 1; and a second optically anisotropic layer comprising a photoreactive polymer including a repeating unit represented by the following Formula 2:
A1-Ar1-E1-Ar2-E2-Ar3-A2 [Formula 1]
wherein Ar1, Ar2 and Ar3 are the same as or different from one another and independently an arylene having 6 to 40 carbon atoms, wherein the arylene can be substituted by a C1-C10 alkyl or halogen substituent;
E1 and E2 are the same as or different from each other and independently a chemical bond, —C(═O)—, —OC(═O)—, —C(═O)O—, or C1-C10 alkylene; and
A1 and A2 are the same as or different from each other and independently represented by the following formula 1a:
-Gm-Jm-Lm-Mm-Nm-Qm [Formula 1a]
wherein Gm, Lm and Nm are the same as or different from one another and independently a chemical bond, —O—, —S—, —C(═O)—, —C(═O)O—, —OC(═O)—, —OC(═O)O—, —C(═O)NR—, —NRC(═O)—, —NRC(═O)NR—, —OCH2—, —CH2O—, —SCH2—, —CH2S—, —CF2O—, —OCF2—, —CF2S—, —SCF2—, —CH2—(CH2)2—, —(CH2)3—, —(CH2)4—, —CF2CH2—, —CH2CF2—, or —CF2CF2—, wherein R is hydrogen or C1-C10 alkylene;
Jm and Mm are the same as or different from each other and independently a chemical bond, C1-C10 alkylene, or C3-C10 cycloalkylene; and
Qm is a C1-C10 alkyl, acrylate, methacrylate, or epoxy group;
The substituents of the Formula 2 are as described below in detail.
The present invention also provides a display device comprising the optical film.
According to the present invention, it is possible to provide an optical film with excellent liquid crystal alignment and improved photoreaction rate and a display device comprising the same.
It will be understood that, although the terms “first”, “second”, etc. may be used herein to describe various elements, they are only used to distinguish one element from another.
It will also be understood that when a layer or an element is referred to as being “on” another layer or element, it can be directly on the other layer or element, or intervening layers or elements may be present therebetween.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments of the invention. As used herein, the singular forms 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”, “including”, and/or “have/has/having”, when used herein, specify the presence of stated features, steps, components, and/or groups thereof but do not preclude the presence or addition of one or more other features, steps, components, and/or groups thereof.
While example embodiments of the present invention are susceptible to various modifications and alternative forms, specific embodiments thereof will be described in detail. It should be understood, however, that there is no intent to limit example embodiments of the invention to the particular forms disclosed, but conversely, example embodiments of the invention are to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.
Hereinafter, a detailed description will be given as to an optical film and a display device according to the present invention.
Optical Film
The optical film of the present invention comprises: a first optically anisotropic layer comprising at least one liquid crystal compound represented by the following formula 1; and a second optically anisotropic layer comprising a photoreactive polymer including a repeating unit represented by the following Formula 2:
Ar1—Ar1-E1-Ar2-E2-Ar3-A2 [Formula 1]
In the formula 1, Ar1, Ar2 and Ar3 are the same as or different from one another and independently an arylene having 6 to 40 carbon atoms, where the arylene can be substituted by a C1-C10 alkyl or halogen substituent;
E1 and E2 are the same as or different from each other and independently a chemical bond, —C(═O)—, —OC(═O)—, —C(═O)O—, or C1-C10 alkylene; and
A1 and A2 are the same as or different from each other and independently represented by the following formula 1a:
-Gm-Jm-Lm-Mm-Nm-Qm [Formula 1a]
In the formula 1a, Gm, Lm and Nm are the same as or different from one another and independently a chemical bond, —O—, —S—, —C(═O)—, —C(═O)O—, —OC(═O)—, —OC(═O)O—, —C(═O)NR—, —NRC(═O)—, —NRC(═O)NR—, —OCH2—, —CH2O—, —SCH2—, —CH2S—, —CF2O—, —OCF2—, —CF2S—, —SCF2—, —CH2— (CH2)2—, —(CH2)3—, —(CH2)4—, —CF2CH2—, —CH2CF2—, or —CF2CF2—, where R is hydrogen or C1-C10 alkylene;
Jm and Mm are the same as or different from each other and independently a chemical bond, C1-C10 alkylene, or C3-C10 cycloalkylene; and
Qm is a C1-C10 alkyl, acrylate, methacrylate, or epoxy group;
In the Formula 2, n is an integer from 50 to 5,000;
p is an integer from 0 to 4; and
at least one of R1, R2, R3 and R4 is a radical selected from the group consisting of the following formulas 2a, 2b and 2c.
Among the R1, R2, R3, and R4, the remainders other than the radical of the formula 2a, 2b or 2c are the same as or different from one another and independently selected from the group consisting of hydrogen; halogen; substituted or unsubstituted alkyl having 1 to 20 carbon atoms; substituted or unsubstituted alkenyl having 2 to 20 carbon atoms; substituted or unsubstituted cycloalkyl having 3 to 12 carbon atoms; substituted or unsubstituted aryl having 6 to 40 carbon atoms; substituted or unsubstituted arylalkyl having 7 to 15 carbon atoms; substituted or unsubstituted alkynyl 2 to 20 carbon atoms; and a non-hydrocarbonaceous polar group comprising at least one of oxygen, nitrogen, phosphor, sulfur, silicon, and boron.
When the R1, R2, R3, and R4 are not hydrogen, halogen, or the non-hydrocarbonaceous polar group, a R1 and R2 coordination or a R3 and R4 coordination is bonded together to form an alkylidene group having 1 to 10 carbon atoms; or R1 or R2 is bonded to either R3 or R4 to form a saturated or unsaturated aliphatic ring having 4 to 12 carbon atoms or an aromatic ring having 6 to 24 carbon atoms.
In the formula 2a, 2b or 2c, A is selected from the group consisting of chemical bond, substituted or unsubstituted alkylene having 1 to 20 carbon atoms, carbonyl, carboxy, ester, substituted or unsubstituted arylene having 6 to 40 carbon atoms, and substituted or unsubstituted heteroarylene having 6 to 40 carbon atoms;
B is chemical bond, oxygen, sulfur, or —NH—;
X is oxygen or sulfur;
R9 is selected from the group consisting of chemical bond, substituted or unsubstituted alkylene having 1 to 20 carbon atoms, substituted or unsubstituted alkenylene having 2 to 20 carbon atoms, substituted or unsubstituted cycloalkylene having 3 to 12 carbon atoms, substituted or unsubstituted arylene having 6 to 40 carbon atoms, substituted or unsubstituted arylalkylene having 7 to 15 carbon atoms, and substituted or unsubstituted alkynylene having 2 to 20 carbon atoms; and
at least one of R10, R11, R12, R13, and R14 is halogen (F, Cl, Br, or I).
Among the R10, R11, R12, R13, and R14, the remainders other than halogen are the same as or different from one another and independently selected from the group consisting of substituted or unsubstituted alkyl having 1 to 20 carbon atoms, substituted or unsubstituted alkoxy having 1 to 20 carbon atoms, substituted or unsubstituted aryloxy having 6 to 30 carbon atoms, substituted or unsubstituted aryl having 6 to 40 carbon atoms, heteroaryl having 6 to 40 carbon atoms with a hetero element in Group 14, 15 or 16, substituted or unsubstituted alkoxyaryl having 6 to 40 carbon atoms, and halogen.
According to one embodiment of the present invention, the non-hydrocarbonaceous polar group may be selected from the group consisting of the following functional groups:
—OR6, —R5OR6, —OC(O)OR6, —R5OC(O)OR6, —C(O)OR6, —R5C(O)OR6, —C(O)R6, —R5C(O)R6, —OC(O)R6, —R5OC(O)R6, —(R50)p—OR6, —(OR5)p—OR6, —C(O)—O—C(O)R6, —R5C(O)—O—C(O)R6, —SR6, —R5SR6, —SSR6, —R5SSR6, —S(═O))R6, —R5S(═O)R6, —R5C(═S)R6—, —R5C(═S)SR6, —R5SO3R6, —SO3R6, —R5N═C═S, —N═C═S, —NCO, —R5—NCO, —CN, —R5CN, —NNC(═S)R6, —R5NNC(═S)R6, —NO2, —R5NO2,
In the non-hydrocarbonaceous polar group, p is independently an integer from 1 to 10.
R5 is the same as or different from one another and is independently linear or branched alkylene having 1 to 20 carbon atoms and being substituted or unsubstituted with at least one substituent selected from halogen, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl, haloaryl, arylalkyl, haloarylalkyl, alkoxy, haloalkoxy, carbonyloxy, halocarbonyloxy, aryloxy, haloaryloxy, silyl, and siloxy;
linear or branched alkenylene having 2 to 20 carbon atoms and being substituted or unsubstituted with at least one substituent selected from halogen, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl, haloaryl, arylalkyl, haloarylalkyl, alkoxy, haloalkoxy, carbonyloxy, halocarbonyloxy, aryloxy, haloaryloxy, silyl, and siloxy;
linear or branched alkynylene having 3 to 20 carbon atoms and being substituted or unsubstituted with at least one substituent selected from halogen, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl, haloaryl, arylalkyl, haloarylalkyl, alkoxy, haloalkoxy, carbonyloxy, halocarbonyloxy, aryloxy, haloaryloxy, silyl, and siloxy;
cycloalkylene having 3 to 12 carbon atoms and being substituted or unsubstituted with at least one substituent selected from halogen, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl, haloaryl, arylalkyl, haloarylalkyl, alkoxy, haloalkoxy, carbonyloxy, halocarbonyloxy, aryloxy, haloaryloxy, silyl, and siloxy;
arylene having 6 to 40 carbon atoms and being substituted or unsubstituted with at least one substituent selected from halogen, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl, haloaryl, arylalkyl, haloarylalkyl, alkoxy, haloalkoxy, carbonyloxy, halocarbonyloxy, aryloxy, haloaryloxy, silyl, and siloxy;
alkoxylene having 1 to 20 carbon atoms and being substituted or unsubstituted with at least one substituent selected from halogen, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl, haloaryl, arylalkyl, haloarylalkyl, alkoxy, haloalkoxy, carbonyloxy, halocarbonyloxy, aryloxy, haloaryloxy, silyl, and siloxy; or
carbonyloxylene having 1 to 20 carbon atoms and being substituted or unsubstituted with at least one substituent selected from halogen, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl, haloaryl, arylalkyl, haloarylalkyl, alkoxy, haloalkoxy, carbonyloxy, halocarbonyloxy, aryloxy, haloaryloxy, silyl, and siloxy.
R6, R7 and R8 are the same as or different from one another and are independently selected from the group consisting of hydrogen; halogen; linear or branched alkyl having 1 to 20 carbon atoms and being substituted or unsubstituted with at least one substituent selected from halogen, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl, haloaryl, arylalkyl, haloarylalkyl, alkoxy, haloalkoxy, carbonyloxy, halocarbonyloxy, aryloxy, haloaryloxy, silyl, and siloxy;
linear or branched alkenyl having 2 to 20 carbon atoms and being substituted or unsubstituted with at least one substituent selected from halogen, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl, haloaryl, arylalkyl, haloarylalkyl, alkoxy, haloalkoxy, carbonyloxy, halocarbonyloxy, aryloxy, haloaryloxy, silyl, and siloxy;
linear or branched alkynyl having 3 to 20 carbon atoms and being substituted or unsubstituted with at least one substituent selected from halogen, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl, haloaryl, arylalkyl, haloarylalkyl, alkoxy, haloalkoxy, carbonyloxy, halocarbonyloxy, aryloxy, haloaryloxy, silyl, and siloxy;
cycloalkyl having 3 to 12 carbon atoms and being substituted or unsubstituted with at least one substituent selected from halogen, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl, haloaryl, arylalkyl, haloarylalkyl, alkoxy, haloalkoxy, carbonyloxy, halocarbonyloxy, aryloxy, haloaryloxy, silyl, and siloxy;
aryl having 6 to 40 carbon atoms and being substituted or unsubstituted with at least one substituent selected from halogen, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl, haloaryl, arylalkyl, haloarylalkyl, alkoxy, haloalkoxy, carbonyloxy, halocarbonyloxy, aryloxy, haloaryloxy, silyl, and siloxy;
alkoxy having 1 to 20 carbon atoms and being substituted or unsubstituted with at least one substituent selected from halogen, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl, haloaryl, arylalkyl, haloarylalkyl, alkoxy, haloalkoxy, carbonyloxy, halocarbonyloxy, aryloxy, haloaryloxy, silyl, and siloxy; or carbonyloxy having 1 to 20 carbon atoms and being substituted or unsubstituted with at least one substituent selected from halogen, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkynyl, aryl, haloaryl, arylalkyl, haloarylalkyl, alkoxy, haloalkoxy, carbonyloxy, halocarbonyloxy, aryloxy, haloaryloxy, silyl, and siloxy.
On the other hand, the heteroaryl having 6 to 40 carbon atoms with a hetero element in Group 14, 15 or 16, or the aryl having 6 to 40 carbon atoms may be at least one selected from the group consisting of the compounds represented by the following formulas:
In these formulas, at least one of R′10, R′11, R′12, R′13, R′14, R′15, R′16, R′17, and R′18 is substituted or unsubstituted alkoxy having 1 to 20 carbon atoms, or substituted or unsubstituted aryloxy having 6 to 30 carbon atoms; and the remainders other than the substituted or unsubstituted alkoxy having 1 to 20 carbon atoms or the substituted or unsubstituted aryloxy having 6 to 30 carbon atoms are independently substituted or unsubstituted alkyl having 1 to 20 carbon atoms, substituted or unsubstituted alkoxy having 1 to 20 carbon atoms, substituted or unsubstituted aryloxy having 6 to 30 carbon atoms, or substituted or unsubstituted aryl having 6 to 40 carbon atoms.
In the above-described formulas, the individual substituents may be specifically defined as follows:
The term “alkyl” as used herein refers to a monovalent linear or branched saturated hydrocarbon portion having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms. The alkyl group may be arbitrarily substituted by at least one halogen substituent. The examples of the alkyl group may include methyl, ethyl, propyl, 2-propyl, n-butyl, iso-butyl, tert-butyl, pentyl, hexyl, dodecyl, fluoromethyl, difluoromethyl, trifluoromethyl, chloromethyl, dichloromethyl, trichloromethyl, iodomethyl, bromomethyl, etc.
The term “alkenyl” as used herein refers to a monovalent linear or branched hydrocarbon portion having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 6 carbon atoms with at least one carbon-carbon double bond. The alkenyl group may form a bonding through carbon atoms including a carbon-carbon double bond or through saturated carbon atoms. The alkenyl group may be arbitrarily substituted by at least one halogen substituent. The examples of the alkenyl group may include ethenyl, 1-propenyl, 2-propenyl, 2-butenyl, 3-butenyl, pentenyl, 5-hexenyl, dodecenyl, etc.
The term “cycloalkyl” as used herein refers to a monovalent saturated or unsaturated mono-, bi- or tri-cyclic non-aromatic hydrocarbon portion having 3 to 12 ring-carbon atoms. The cycloalkyl group may be arbitrarily substituted by at least one halogen substituent. The examples of the cycloalkyl group may include cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl, cycloheptyl, cyclooctyl, decahydronaphthalenyl, adamantyl, norbornyl (i.e., bicyclo[2,2,1]hept-5-enyl), etc.
The term “aryl” as used herein refers to a monovalent mono-, bi- or tri-cyclic aromatic hydrocarbon portion having 6 to 40 ring-carbon atoms, preferably 6 to 12 ring-carbon atoms. The aryl group may be arbitrarily substituted by at least one halogen substituent. The examples of the aryl group may include phenyl, naphthalenyl, fluorenyl, etc.
The term “alkoxyaryl” as used herein refers to a radical in which an alkoxy group is substituted for at least one hydrogen atom of the above-defined aryl group. The examples of the alkoxyaryl group may include methoxyphenyl, ethoxyphenyl, propoxyphenyl, butoxyphenyl, pentoxyphenyl, hextoxyphenyl, heptoxy, octoxy, nanoxy, methoxybiphenyl, methoxynaphthalenyl, methoxyfluorenyl, methoxyanthracenyl, ethoxyanthracenyl, propoxyanthracenyl, methoxyfluorenyl, etc.
The term “arylalkyl” as used herein refers to a radical in which an aryl group is substituted for at least one hydrogen atom of the above-defined alkyl group. The arylalkyl group may be arbitrarily substituted by at least one halogen substituent. The examples of the arylalkyl group may include benzyl, benzhydryl, trityl, etc.
The term “alkynyl” as used herein refers to a monovalent linear or branched hydrocarbon portion having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 6 carbon atoms with at least one carbon-carbon triple bond. The alkynyl group may form a bonding through carbon atoms including a carbon-carbon triple bond or through saturated carbon atoms. The alkynyl group may be arbitrarily substituted by at least one halogen substituent. The examples of the alkynyl group may include ethynyl, propynyl, etc.
The term “alkylene” as used herein refers to a divalent linear or branched saturated hydrocarbon portion having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms. The alkylene group may be arbitrarily substituted by at least one halogen substituent. The examples of the alkylene group may include methylene, ethylene, propylene, butylene, hexylene, etc.
The term “alkenylene” as used herein refers to a divalent linear or branched hydrocarbon portion having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 6 carbon atoms with at least one carbon-carbon double bond. The alkenylene group may form a bonding through carbon atoms including a carbon-carbon double bond and/or through saturated carbon atoms. The alkenylene group may be arbitrarily substituted by at least one halogen substituent.
The term “cycloalkylene” as used herein refers to a divalent saturated or unsaturated mono-, bi- or tri-cyclic non-aromatic hydrocarbon portion having 3 to 12 ring-carbon atoms. The cycloalkylene group may be arbitrarily substituted by at least one halogen substituent. The examples of the cycloalkylene group may include cyclopropylene, cyclobutylene, etc.
The term “arylene” as used herein refers to a divalent mono-, bi- or tri-cyclic aromatic hydrocarbon portion having 6 to 20 ring-carbon atoms, preferably 6 to 12 ring-carbon atoms. The arylene group may be arbitrarily substituted by at least one halogen substituent. The aromatic portion of the arylene group includes carbon atoms only. The examples of the arylene group may include phenylene, etc.
The term “arylalkylene” as used herein refers to a divalent radical in which an aryl group is substituted for at least one hydrogen atom of the above-defined alkyl group. The arylalkylene group may be arbitrarily substituted by at least one halogen substituent. The examples of the arylalkylene group may include benzylene, etc.
The term “alkynylene” as used herein refers to a divalent linear or branched hydrocarbon portion having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 6 carbon atoms with at least one carbon-carbon triple bond. The alkynylene group may form a bonding through carbon atoms including a carbon-carbon triple bond or through saturated carbon atoms. The alkynylene group may be arbitrarily substituted by at least one halogen substituent. The examples of the alkynylene group may include ethynylene, propynylene, etc.
According to one exemplary embodiment of the present invention, the photoreactive polymer including a repeating unit represented by the Formula 2 may further comprise a photoactivator, a (meth)acrylate-based compound, and a photoinitiator.
The addition of the photoactivator to the photoreactive polymer may promote the reactivity of the photoreactive groups. The examples of the photoactivator as used herein may include 2,4-ethyl-9H-thioxanthen-9-one, 1-isopropyl-9H-thioxanthen-9-one, 1,3-difluoro-9H-thioxanthen-9-one, 2-trifluoromethyl-9H-thioxanthen-9-one, etc.
The (meth)acrylate-based compound as used herein may comprise, for example, at least one selected from the group consisting of pentaerythritol triacrylate, tris(2-acrylolyloxyethyl)isocynurate, trimethylolpropane triacrylate, and dipentaerythritol hexaacrylate.
The photoinitiator as used herein may include, but are not limited to, Irgacure 907 or 819.
According to one exemplary embodiment of the present invention, the optical film may comprise, based on the total weight of the composition, 50 to 70 wt % of the photoreactive polymer including a repeating unit represented by the Formula 2; 1 to 20 wt % of the photoactivator; 20 to 40 wt % of the (meth)acrylate-based compound; and 1 to 15 wt % of the photoinitiator.
In the optical film of the present invention, the first optically anisotropic layer comprises at least one liquid crystal compound represented by the following formula 1:
A1-Ar1E1-Ar2-E2-Ar3-A2 [Formula 1]
In the formula 1, Ar1, Ar2 and Ar3 are the same as or different from one another and independently an arylene having 6 to 40 carbon atoms, where the arylene can be substituted by a C1-C10 alkyl or halogen substituent;
E1 and E2 are the same as or different from each other and independently a chemical bond, —C(═O)—, —OC(═O)—, —C(═O)O—, or C1-C10 alkylene; and
A1 and A2 are the same as or different from each other and independently represented by the following formula 1a:
-Gm-Jm-Lm-Mm-Nm-Qm [Formula 1a]
In the formula 1a, Gm, Lm and Nm are the same as or different from one another and independently a chemical bond, —O—, —S—, —C(═O)—, —C(═O)O—, —OC(═O)—, —OC(═O)O—, —C(═O)NR—, —NRC(═O)—, —NRC(═O)NR—, —OCH2—, —CH2O—, —SCH2—, —CH2S—, —CF2O—, —OCF2—, —CF2S—, —SCF2—, —CH2—(CH2)2—, —(CH2)3—, —(CH2)4—, —CF2CH2—, —CH2CF2—, or —CF2CF2—, wherein R is hydrogen or C1-C10 alkylene;
Jm and Mm are the same as or different from each other and independently a chemical bond, C1-C10 alkylene, or C3-C10 cycloalkylene; and
Qm is a C1-C10 alkyl, acrylate, methacrylate, or epoxy group.
According to one embodiment of the present invention, the first optically anisotropic layer may further comprise at least one monoacrylate-based compound in addition to the liquid crystal compound of the formula 1.
According to one exemplary embodiment of the present invention, the monoacrylate-based compound may be at least one selected from the group consisting of the following compounds, where z is an integer from 2 to 12:
The physical characteristics, such as alignment, photoreactivity, or the like, that are required for optical films are determined by the interaction between the liquid crystal compound included in the first optically anisotropic layer and the photoreactive polymer included in the second optically anisotropic layer. Therefore, such an interaction may be dependent upon the structural characteristics of the liquid crystal compound and the photoreactive polymer.
The optical film of the present invention comprises, as individual layers, the liquid crystal compound represented by the formula 1 and the photoreactive polymer including a repeating unit represented by the formula 2. Hence, the liquid crystal compound and the photoreactive polymer are combined together without unnecessary interactions occurring in the case that they are included in a single layer, thereby securing excellent alignment and high photoreactivity by way of an appropriate binding force. This leads to providing an optical film with improved liquid crystal alignment and photoreaction rate.
The optical film of the present invention may be fabricated according to a typical method as known to those skilled in the art. For fabrication of the optical film, a composition comprising a photoreactive polymer including a repeating unit represented by the Formula 2, a photoactivator, a (meth)acrylate-based compound as a binder, and a photoinitiator is dissolved in a proper organic solvent to prepare a solution. The organic solvent as used herein may include, but are not limited to, toluene, anisole, chlorobenzene, dichloroethane, cyclohexane, cyclopentane, propylene glycol methyl ether acetate, etc.
In this regard, the solid proportion of the solution may be about 1 wt % to about 15 wt % with respect to the weight of the solution. For casting the solution into a film, for example, the solid portion is preferably about 10 wt % to about 15 wt %; for casting the solution into a thin film, the solid portion is preferably about 1 wt % to about 5 wt %.
The solution thus prepared is applied dropwise onto a substrate or a glass, subjected to spin coating, bar coating, solvent casting, or the like and then dried out in an oven or on a hot plate. Subsequently, the solution is exposed to a polarized UV radiation so that the double bond of the photoreactive groups form a dimer in defined direction to form the second optically anisotropic layer.
A solution containing the liquid crystal compound represented by the formula 1 may be applied onto the second optically anisotropic layer by coating and dried out to form a first optically anisotropic layer.
In this regard, the solution may be prepared by dissolving the liquid crystal compound and the photoinitiator in an organic solvent. The content of the liquid crystal compound in the liquid crystal compound solution is not specifically limited and may be, based on 100 parts by weight of the liquid crystal compound solution, about 5 parts by weight to about 70 parts by weight, preferably about 5 parts by weight to about 50 parts by weight.
Further, a photoinitiator, a chelating agent, a surfactant, a monomer for polymerization, a polymer, etc. may be added to the liquid crystal compound solution unless the addition interferes with the liquid crystal alignment.
In the preparation of the liquid crystal compound solution, the organic solvent may include, but are not limited to, halogenated hydrocarbons, such as chloroform, tetrachloroethane, trichloroethane, tetrachloroethylene, chlorobenzene, etc.; aromatic hydrocarbons, such as benzene, toluene, xylene, methoxy benzene, 1,2-dimethoxy benzene, etc.; ketones, such as acetone, methylethylketone, cyclohexanone, cyclopentanone, etc.; alcohols, such as isopropyl alcohol, n-butanol, etc.; or cellosolves, such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, etc., which organic solvents may be used alone or in a mixture thereof.
Display Device
The present invention also provides a display device comprising the optical film.
The optical film according to the present invention may be used as an optical member for liquid crystal display devices. The examples of the optical member may include phase contrast films for STN (Super Twist Nematic) LCD, TFT-TN (Thin Film Transistor-Twisted Nematic) LCD, VA (Vertical Alignment) LCD, IPS (In-Plane Switching) LCD, etc.; ½ wave plates; ¼ wave plates; reverse wavelength dispersion type films; optical compensation films; color films; laminated films with a polarizing plate; compensation films for polarizing plate, etc.
The display device of the present invention may comprise one or two of the optical film.
In a display device comprising a liquid crystal cell and first and second polarizing plates each provided on either side of the liquid crystal cell, for example, the optical film of the present invention may be provided between the liquid crystal cell and the first polarizing plate and/or the second polarizing plate. In other words, at least one of the optical film may be provided between the first polarizing plate and the liquid crystal cell; between the second polarizing plate and the liquid crystal cell; or both between the first polarizing plate and the liquid crystal cell and between the second polarizing plate and the liquid crystal cell.
The display device of the present invention may be prepared according to a typical method known to those skilled in the related art.
According to one embodiment of the present invention, the display device may be prepared by the steps of: preparing first and second substrates as substrate materials; forming a second optically anisotropic layer on the substrates; drying the second optically anisotropic layer formed on the substrates; exposing the dried second optically anisotropic layer to UV radiation to acquire optical alignment; forming a first optically anisotropic layer on the second optically anisotropic layer; and binding the two substrates together to interpose a liquid crystal layer between the two substrates.
More specifically, a composition comprising a photoreactive polymer including a repeating unit of the Formula 2, a photoactivator, a (meth)acrylate-based compounds as a binder, and a photoinitiator is dissolved in an appropriate organic solvent, and the resultant solution is applied on the substrates and dried out.
After completion of the drying, a UV radiation linearly polarized in a defined direction is applied on the substrate to acquire alignment in an arbitrary direction. This induces the first molecular alignment in the direction (i.e., absorption direction) perpendicular to the transmission axis of the UV polarizing plate (i.e., wire grid polarizing plate) through UV-driven dimerization of the photoreactive polymer constituting the optically anisotropic layer. In this regard, the alignment direction of the optically anisotropic layer can be controlled to a desired angle by adjusting the polarizing direction of the UV radiation applied. Hence, the optical axis of the first optically anisotropic layer that will be formed later on the second optically anisotropic layer can be controlled to a desired angle with respect to the lengthwise direction of the substrates.
A solution comprising a liquid crystal compound is applied onto the first optically anisotropic layer and then dried out to form a first optically anisotropic layer.
After the drying step, the first optically anisotropic layer aligned on the second optically anisotropic layer is subjected to polymerization upon exposure to UV radiation and then set by curing.
Subsequently, a photoreactive adhesive containing a ball spacer is applied on the end of either one of the two substrates having the optical film of the present invention. The substrate is combined with the other substrate, and only the adhesive side is exposed to UV radiation to complete a cell by bonding. Liquid crystal is injected into the cell, which is then subjected to heat treatment to complete a display device.
The display device of the present invention that has the optical film exhibits excellent liquid crystal alignment and high photoreaction rate.
Referring to
In the following are set forth preferred examples of the invention for better understanding of the invention. It is to be understood that the examples are only for illustrative purposes and are not intended to limit the scope of the invention.
5-norbornene-2-ethyl-(4-fluoro cinnamate) polymer (Mw: 159k) was dissolved in c-pentanone solvent at concentration of 2 wt %, and the resultant solution was applied onto a 8 μm-thick polyethylene terephthalate (SH71™, manufactured by SKC Inc., S. Korea) substrate to a dry-film thickness of 1,000 Å by roll coating. Then, the substrate was heated in an oven at 80° C. for 3 minutes to eliminate the solvent from the inside of the coating layer and complete the coating layer.
UV light generated from a high-voltage mercury lamp with an intensity of 200 mW/cm2 and polarized perpendicular to the lengthwise direction of the film using a wire grid polarizer (manufactured by Moxtek Inc.) was irradiated on the substrate for 5 sec. to impose alignment and form a second optically anisotropic layer.
A solid portion comprising 95.0 wt % of RM257 of the following formula and 5.0 wt % of Irgacure 907 (manufactured by Ciba-Geigy, Switzerland) was dissolved in toluene to contain 25 parts by weight of the liquid crystal per 100 parts by weight of the liquid crystal solution, thereby preparing a polymerizable reactive liquid crystal solution.
The liquid crystal solution thus prepared was applied on the second optically anisotropic layer to a dry-film thickness of 1 μm by roll coating and then dried at 80° C. for 2 minutes to acquire alignment of liquid crystal molecules and prepare a first optically anisotropic layer. Non-polarized UV light generated from a high-voltage mercury lamp with an intensity of 200 mW/cm2 was irradiated on the aligned first optically anisotropic layer to set the alignment status of the liquid crystals, thereby completing an optical film including first and second optically anisotropic layers.
The procedures were performed to prepare an optical film in the same manner as described in Example 1, excepting that 5-norbornene-2-ethyl-(4-chloro cinnamate) polymer (Mw: 144k) was used in place of the 5-norbornene-2-ethyl-(4-fluoro cinnamate) polymer.
The procedures were performed to prepare an optical film in the same manner as described in Example 1, excepting that 5-norbornene-2-ethyl-(4-bromo cinnamate) polymer (Mw: 130k) was used in place of the 5-norbornene-2-ethyl-(4-fluoro cinnamate) polymer.
The procedures were performed to prepare an optical film in the same manner as described in Example 1, excepting that 5-norbornene-2-ethyl-(4-methoxy cinnamate) polymer (Mw: 102k) was used in place of the 5-norbornene-2-ethyl-(4-fluoro cinnamate) polymer.
The procedures were performed to prepare an optical film in the same manner as described in Example 1, excepting that RM257-4 of the following formula was used in place of RM257:
The procedures were performed to prepare an optical film in the same manner as described in Example 2, excepting that RM257-4 was used in place of RM257.
The procedures were performed to prepare an optical film in the same manner as described in Example 3, excepting that RM257-4 was used in place of RM257.
The procedures were performed to prepare an optical film in the same manner as described in Example 4, excepting that RM257-4 was used in place of RM257.
The procedures were performed to prepare an optical film in the same manner as described in Example 1, excepting that a mixture of RM 257, RM-T025, RM-T55, and RM-T95 (at weight ratio of 60:10:20:10) was used in place of RM257:
The procedures were performed to prepare an optical film in the same manner as described in Example 1, excepting that RM-T709 of the following formula was used in place of RM257:
The procedures were performed to prepare an optical film in the same manner as described in Example 1, excepting that RM-T813 of the following formula was used in place of RM257:
The procedures were performed to prepare an optical film in the same manner as described in Example 1, excepting that RM-T7861 of the following formula was used in place of RM257:
The procedures were performed to prepare an optical film in the same manner as described in Example 1, excepting that LC1057 of the following formula was used in place of RM257:
The procedures were performed to prepare an optical film in the same manner as described in Example 1, excepting that a compound of the following formula was used in place of the 5-norbornene-2-ethyl-(4-fluoro cinnamate) polymer:
In the formula, CelAc represents cellulose acetate.
The procedures were performed to prepare an optical film in the same manner as described in Example 1, excepting that a compound of the following formula was used in place of the 5-norbornene-2-ethyl-(4-fluoro cinnamate) polymer:
In the formula, Cel represents cellulose.
The procedures were performed to prepare an optical film in the same manner as described in Example 1, excepting that a compound of the following formula was used in place of the 5-norbornene-2-ethyl-(4-fluoro cinnamate) polymer:
In the formula, CelAc represents cellulose acetate.
Between two polarizing plates arranged at right angles to each other was placed each of the optical films of Example 1 and Comparative Examples 3 and 4. Then, ECLIPSE LV100POL (manufactured by NIKON) was used to take an image showing the degree of light leakage.
Referring to
The FT-IR spectra of the respective optical films prepared in Example 1 and to Comparative Examples 3 and 4 were observed. The optical films were evaluated in regards to photoreactivity based on the time t1/2 required to halve the intensity of the C═C bond stretching mode of the cinnamate group in the polymer upon exposure to a mercury lamp with an intensity of 20 my/cm2 and the energy value (E1/2=20 mW/cm2×t1/2) reduced from the time t1/2.
The evaluation results are presented in Table 1.
Referring to Table 1, the optical film prepared according to the present invention is superior in photoreactivity to those of the comparative examples.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2012-0050423 | May 2012 | KR | national |
| 10-2013-0052119 | May 2013 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2013/004092 | 5/9/2013 | WO | 00 |
