TWI568839B - Polymerizable liquid crystal composition - Google Patents

Description

Polymeric liquid crystal composition

The present invention relates to a polymerizable liquid crystal composition, and more particularly to a polymerizable liquid crystal composition which is characterized in that it has thermal stability and a wide temperature range of a liquid crystal phase region when used in an optical film, and is cost-effective.

Recently, with the rapid development of the information communication field, the importance of displays for displaying various information is increasing. The cathode ray tube of one of the existing display devices has certain limitations and cannot correspond to the recent trend of thinning. Therefore, in order to meet the requirements, a liquid crystal display, a plasma display panel (PDP), an ELD (Electro Luminescence Display), and the like have been developed, and active research and activities are being conducted.

In the above display device, the liquid crystal display device is a display device which is advantageous in terms of weight reduction, thinning, and low power. With these advantages, the liquid crystal display can be used not only for displays of mobile terminals, notebook computers, etc., but also for desktop computers and large televisions, and the demand for this is increasing.

The driving principle of the liquid crystal display device utilizes the optical anisotropy and polarization properties of the liquid crystal. Since the liquid crystal has a long and thin structure, the molecular arrangement has an orientation, and an electric field applied to the liquid crystal can be artificially Control the orientation of the molecular arrangement. This characteristic becomes a factor that changes the polarization of light passing through the liquid crystal.

Therefore, if the molecular alignment direction of the liquid crystal is arbitrarily adjusted, the molecular arrangement of the liquid crystal can be changed, and due to the optical anisotropy, the light is refracted toward the molecular arrangement direction of the liquid crystal, whereby the image information can be displayed.

Further, the liquid crystal display device is composed of a color filter film substrate on which a common electrode is formed, an array substrate on which a pixel electrode is formed, and a liquid crystal filled between the two substrates, which is applied to the common electrode and the pixel. The vertical electric field between the electrodes drives the liquid crystal, which has good light transmittance and aperture ratio characteristics, but also has the disadvantage of poor viewing angle characteristics.

On the other hand, the liquid crystal cell of the liquid crystal display device has been proposed to be able to indicate ON or OFF depending on the alignment state of the liquid crystal molecules, and is applicable to any transmissive or reflective TN (Twist Nematic) or IPS (In-Plane Switching). Display devices such as OCB (Optically Compensatory Bend), VA (Vertically Aligned), and ECB (Electrically Controlled Birefingence).

Since the liquid crystal is an anisotropic substance having a birefringence of the above-described driving form, that is, an ordinary refractive index and an extraordinary refractive index, a contrast ratio is generated according to an incident angle of incident light ( Contrast Ratio: CR) changes and gray scale inversion. In particular, twisted nematic (TN) liquid crystals have a narrow viewing angle and a contrast ratio (CR) characteristic due to a large phase delay variation with respect to the direction in which light is conducted. In order to improve this disadvantage, a compensation film is used for phase difference compensation in order to improve viewing angle performance.

Such a liquid crystal optical film is required to have a wide range of operating temperature ranges, polymerizable group reactivity, coating properties, good orientation, and chemical stability. The liquid crystal element uses a material which can exhibit a liquid crystal phase, and it is currently impossible to satisfy such a characteristic with a single compound, so one or two kinds will be used. Many of the above reactive liquid crystal compounds or reactive non-liquid crystalline compounds having excellent characteristics are used in combination to satisfy the performance required as a liquid crystal composition.

In the field of liquid crystal optical films, how to provide good compatibility with different reactive liquid crystal materials or reactive non-liquid crystal materials among chemical properties required for compounds for liquid crystal compositions, and A liquid crystal phase can be maintained in a wide temperature range, and a compound having a good orientation and chemical stability or a polymerizable liquid crystal composition when used in a liquid crystal optical film is an important subject.

The present inventors have continually diligently studied in order to solve the above problems, and as a result, have found a ring-like structure in which a liquid crystalline compound having a core structure having one or more or no linking groups and having a single bond or a polycyclic structure is attached. When the polymerizable liquid crystal composition is mixed with a polymerizable mesogenic compound, the compatibility can be improved, the chemical stability is maintained, and the characteristics of the liquid crystal phase are maintained over a wide temperature range, and thus the present invention has been completed.

An object of the present invention is to provide a polymerizable liquid crystal composition and an optical film comprising the same, which have good compatibility between two or more liquid crystal materials, chemical stability, and can maintain liquid crystal over a wide temperature range. Phase, and has good orientation and chemical stability when used in liquid crystal optical films.

In order to achieve the above object, the present invention provides a polymerizable liquid crystal composition comprising at least one polymerizable mesogen compound and one or more liquid crystal compounds of the following Chemical Formula 1: [Chemical Formula 1] P1-AL-P2, In the formula, P1 and P2 are a polymerizable group, and AL is a core structure having one or more ring groups which are connected by a single bond or have a polycyclic structure.

The present invention also provides an optical film, a liquid crystal panel, and a liquid crystal display device including the polymerizable liquid crystal composition.

In the present invention, a liquid crystalline compound having a core structure having one or more or no linking groups and having a single bond or a polycyclic structure is bonded to the polymerizable mesogenic compound to form a polymerizable liquid crystal composition. Thereby, it is possible to produce a good compatibility between the liquid crystal materials, chemical stability, to maintain the liquid crystal phase over a wide temperature range, and to have good orientation and chemical stability when used in a liquid crystal optical film. The optical film is simple in its manufacturing method and therefore economical.

All technical or scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains, unless otherwise defined. In general, the nomenclature used in the present specification and the experimental methods described below are well known in the art and are also commonly used.

The present invention relates, in one aspect, to a polymerizable liquid crystal composition comprising at least one polymerizable mesogen compound and at least one liquid crystal compound of the following Chemical Formula 1.

[Chemical Formula 1] P ₁ -A _L -P ₂ , wherein P ₁ and P ₂ are polymerizable groups, and A _L is a core structure having more than one or no linking group Bonds are connected, or ring structures connected by a multi-ring structure. In the present invention, the polymerizable group refers to a group capable of cross-linking by light irradiation, such as acryloyl, methacryloyl, etc., which can form a three-dimensional polymer network. The role. As for one or more ring structures which are linked by a single bond without a linking group, a structure in which a single bond is bonded, such as a biphenyl group, a terphenyl group or the like, and one or more are connected by a polycyclic structure. The ring structure refers to a structure in which more than one carbon-carbon bond is shared in the ring structure, such as napthalene, anthracene, and fluorene. In the present invention, it has been found that when the core structure is composed of more than one ring structure which does not contain a linking group and is linked by a single bond or a polycyclic structure, the occurrence of a carboxyl linking group structure such as an ester group linking group can be reduced. Thermal and chemical instability. When a liquid crystalline compound having a polymerizable group at both ends of the core structure is included in the polymerizable liquid crystal composition, the temperature range of the liquid crystal phase can be enlarged.

Specifically, according to the present invention, the A _{L is} selected from the group consisting of: as well as In the formula, L, L1, and L2 may each independently be a substituent selected from the group consisting of H, F, Cl, Br, CH ₃ , OCH ₃ and OCF ₃ .

In a preferred embodiment, the liquid crystalline compound is a compound represented by the following Chemical Formula 3: [Chemical Formula 3]

In the formula, L1 and L2 are each independently a substituent selected from the group consisting of H, F, Cl, Br, CH ₃ , OCH ₃ and OCF ₃ . In one embodiment of the present invention, when a liquid crystalline compound represented by the above Chemical Formula 3 and a polymerizable mesogen compound are mixed to obtain a polymerizable liquid crystal composition, the temperature range of the liquid crystal phase can be enlarged. More preferably, the liquid crystalline compound is 4,4'-bis(acryloyloxy)biphenyl. The compound represented by the above Chemical Formula 3 is obtained by adding acrylic acid to dichloromethane, DMF and oxalic chloride to form acrylic chloride, and adding 4 to the formed chlorinated acrylic acid. After 4' biphenyl (4,4'-biphenyl) and triethylamine are reacted, the solvent is evaporated to obtain a separation.

In the present invention, the polymerizable mesogen compound can be obtained by using a generally known RM (reactive mesogen) which is generally used in combination with the liquid crystalline compound of the present invention to improve the properties of the polymerizable liquid crystal composition. Specifically, the polymerizable mesogen compound is at least one compound represented by the following Chemical Formula 2: [Chemical Formula 2] Or P ₁ -A ₁ -Sp-A ₂ - mesogenic group-P ₂

Wherein P1 is a polymerizable group, and means a group which is crosslinkable by light refraction, such as acryloyl, methacryloyl, etc.; and Sp represents 1 to 20 carbon atoms. The linking group; A1 and A2 are each independently selected from the group consisting of -O-, -S-, -CO-, -COO-, -OCO-, -OCOO- or a group selected from a single bond; H, F, CH ₃ , OCH ₃ , OCF ₃ , one of a halogen group, a cyano group and a polymerizable group, or have the meaning represented by -A ₂ -Sp-A ₁ -P ₁ . The mesogenic group is represented by -(X ₁ -A ₃ ) _n -X ₂ -A ₄ -X ₃ -; A3 and A4 are each independently selected from -O-, -S-, -CO-, -COO-, -OCO-, -OCOO- or a single bond; X1, X2 and X3 each independently represent a 1,4-phenylene group, wherein one or more CH groups may also be substituted by N, 1,4-cyclohexyl, 1 a 4-cyclohexylene group or a naphthalene-2,6-diyl group, wherein one or two non-adjacent CH ₂ groups may also be substituted by O and/or S, and these groups may not be substituted, or Monosubstituted or polysubstituted by halogen, cyano, nitro, or alkyl, alkoxy or alkanoyl, wherein the alkyl, alkoxy or alkano group has from 1 to 7 carbon atoms, of which more than one The hydrogen atom is replaced by F or Cl, and n represents 0, 1 or 2.

The polymerizable mesogenic compounds in which the structure of the chemical formula 2 P ₂ can be divided in accordance with a single or a double reactive compound reactive compound. In general, when P _{2 is} represented by -A ₂ -Sp-A ₁ -P ₁ or has a polymerizable group, since the both ends of the polymerizable mesogen compound have a polymerizable group, the compound It may be referred to as a bireactive polymeric mesogenic compound. When the double-reactive polymerizable mesogen compound is contained in a polymerizable liquid crystal composition, it plays a major role in the formation of a polymer photocrosslinking network. Further, the polymerizable mesogen compound, if P ₂ does not include a polymerizable group, may be referred to as a monoreactive polymerizable mesogen compound. Since the monoreactive polymeric mesogen compound has a polymerizable group only at one end, the other end may include a group such as H, F, CH ₃ , OCH ₃ , OCF ₃ , a halogen group, a cyano group or the like. Such a monoreactive polymerizable mesogen compound, when included in a polymerizable liquid crystal composition, can function to adjust viscosity, crystallization temperature, birefringence, and the like. The monoreactive polymerizable mesogenic compound may introduce a functional group having a different electronegativity at the non-polymerizable terminal, and if it is F, OCF ₃ , a halogen group or a cyano group, it exhibits a polarity, and if it is H, an alkyl group or an alkoxy group The base time is non-polar. The polar compound is contained in the polymerizable liquid crystal composition to lower the viscosity and enhance the birefringence. The non-polar compound contained in the polymerizable liquid crystal composition can function to adjust the crystallization temperature.

In the present invention, the polymerizable liquid crystal composition is characterized by comprising at least one 55 to 50% by weight of a bireactive compound, at least one 20 to 35% by weight of a monoreactive compound, and 1 to 20% by weight of Chemical Formula 1 Compounds, but this is only one specific embodiment, and it will be apparent to those skilled in the art that the composition ratio can be adjusted for different optical devices.

The invention is also characterized by comprising at least one 45 to 70% by weight of a bireactive compound, at least one 10 to 25% by weight of a negative dielectric monoreactive compound, at least one 5 to 20% by weight of a positive dielectric single a reactive compound and 1 to 20% by weight of a compound of Chemical Formula 1, but It is merely a specific embodiment, and it will be apparent to those skilled in the art that the composition ratio can be adjusted according to different optical devices.

In a preferred embodiment of the invention, it is found that one embodiment of the invention includes: as well as

In the formula, n is an integer of 0 to 10, and when the polymerizable liquid crystal composition is used, the temperature range of the liquid crystal phase can be enlarged.

In the present invention, the polymerizable liquid crystal composition may further include a photoinitiator. In the present invention, the photoinitiator acts to initiate photocrosslinking. Photopolymerization is preferably carried out by UV irradiation, and when polymerization is carried out by UV, a photoinitiator which is decomposed under UV irradiation and which generates a radical or ion (Ion) which initiates polymerization can be used. UV photoinitiators, especially radical UV photoinitiators, are preferably used. A radical type UV photoinitiator is a standard type photoinitiator for performing radical polymerization, and includes, for example, a-carbonyl compound (U.S. Patent No. 2,276,661, U.S. Patent No. 2,367,670), (acyloin ethers) (US Patent Publication No. 248828), a-hydrogen-substituted aromatic auxin compounds (US Patent Publication No. 27722212), polynuclear hydrazine compounds (US Patent Publication No. 2951758), triaryl imidazole dimerization a combination of a substance and p-aminopropionone (U.S. Patent No. 4,239,850), acridine and phenazine (Japanese Patent Publication No. Sho 60-105667, U.S. Patent No. 4,239,850 And oxadiazole (oxadiazole) compound (US Patent Publication No. 4212970). For example, a commercial preparation such as IrgacureR or Darocure R (all manufactured by Ciba Geigy AG) or the like can be used, and a known photoinitiator which can be included in the liquid crystal composition can be used.

The polymerizable liquid crystal composition of the present invention is suitably used for an optical film on a liquid crystal display device such as a TN, STN, AMD-TN or other type of display. More specifically, it can be used for a viewing angle compensation film such as a polarizing film which is polymerized by a liquid crystal, a color filter film which uses a pitch of a liquid crystal molecule, and an optical film for compensating for a change in luminance caused by a viewing angle of the LCD panel. An optical film which is also used for a three-dimensional portrait, such as a patterned retardation film for binocular parallax, an optical film for generating optical axis change, an optical film for converting linearly polarized light into circularly polarized light, and the like, And an optical film for the BLU portion to increase the light efficiency of the LCD or to utilize the refractive index of the film to adjust the direction of light travel.

Hereinafter, the present invention will be described in more detail by way of examples. It will be apparent to those skilled in the art that the present invention is not limited to the scope of the invention.

[Example 1]

Preparation of 4,4'-bis(acryloyloxy)biphenyl

Acrylic acid (23.2 g, 0.321 mol), dichloromethane (200 ml) was added to a 500 mL round bottom flask equipped with an ice bath, and two drops of DMF were added dropwise. Then, oxalic chloride (40.8 g, 0.321 mol) was slowly added, followed by stirring at room temperature for 6 hours. Further, triethylamine (40 g, 0.327 mol) and 4,4'-biphenyl (10 g, 0.053 mol) were added, and the mixture was reacted at room temperature for 24 hours. The solvent of the reaction mixture was evaporated and purified by column chromatography (n-hexene: ethyl acetate = 10:1) to afford white solid.

[Example 2]

This embodiment will understand the characteristics of the polymerizable liquid crystal composition according to the present invention when it is used for an optical film.

In this embodiment, a polymerizable liquid crystal composition is mixed, including the following composition:

The following polymerizable mesogen compound (1) is 60.0% by weight;

The following polymerizable mesogen compound (2) 30.0 wt%;

The following liquid crystalline compound (3) prepared in Example 1 was 5.0 wt%;

A photoinitiator (Irgacure 907, available from Ciba Geigy AG) 5.0 wt%.

The compound (1) is obtained by the method described in WO93/22397; the compound (2) is obtained by the method described in European Patent Application No. EP 0331233 B1; the photoinitiator Irgacure 907 has the following chemical formula:

In order to prepare an optical film using the polymerizable liquid crystal composition, a 30% by weight solution containing the polymerizable liquid crystal composition in toluene was applied onto a TAC film, wherein the TAC film was unidirectionally wiped with a velvet coated rod at a length of 500 mm. it is good. The toluene was then evaporated off and a 1 μm thick layer of the initiated polymerizable mixture was obtained. Next, the layer was polymerized by irradiation with an illuminance of 10 mW/cm ² and UV light of 365 nm.

In order to confirm the coating and orientation of the polymerizable liquid crystal composition prepared in Example 2 on the film, the change in the area was observed by a polarizing microscope, and the results are shown in Table 1 below:

As shown in Table 1, the brightness exhibited by the polarizing microscope was significantly different depending on the polarization direction of the light, and therefore it was confirmed that the orientation state was good.

[Comparative example]

In order to compare with the reactive liquid crystal composition according to the present invention, a reactive liquid crystal composition not containing the liquid crystalline compound of the present invention is mixed as follows:

The following polymerizable mesogen compound (1) 65.0 wt%;

The following polymerizable mesogen compound (2) is 30.0% by weight;

A photoinitiator (Irgacure 907, available from Ciba Geigy AG) 5.0 wt%.

The compound (1) is obtained by the method described in WO93/22397; the compound (2) is obtained by the method described in European Patent Application No. EP 0331233 B1; the photoinitiator Irgacure 907 has the following chemical formula:

In order to prepare an optical film using the polymerizable liquid crystal composition, a 30% by weight solution containing the polymerizable liquid crystal composition in toluene was applied onto a TAC film, wherein the TAC film was unidirectionally wiped with a velvet coated rod at a length of 500 mm. it is good. The toluene was then evaporated off and a 1 μm thick layer of the initiated polymerizable mixture was obtained. Next, the layer was polymerized by irradiation with an illuminance of 10 mW/cm ² and UV light of 365 nm.

In order to investigate the temperature range of the nematic liquid crystal phase of the polymerizable liquid crystal composition of the examples and the comparative examples, the nematic phase was investigated in the range of 70 to 100 °C. The phase exhibited by the polymerizable liquid crystal composition according to the embodiment of the present invention at 93 ° C was compared with the phase exhibited by the comparative example at 80 ° C, and the photographs thereof are shown in Table 2 below: From the above Table 2, it was confirmed that the polymerizable mixture prepared according to the examples of the present invention can maintain the nematic liquid crystal phase at 93 ° C, and the polymerizable liquid crystal composition of the comparative example which does not contain the liquid crystalline compound of the present invention. The material did not exhibit a nematic liquid crystal phase at 80 °C. From this, it is understood that the polymerizable liquid crystal composition according to the present invention can maintain a nematic phase in a range from about room temperature to about 95 ° C, and the polymerizable liquid crystal composition according to the comparative example can be in a range from room temperature to about 75 ° C. The nematic phase was maintained, and therefore, it was confirmed that the polymerizable liquid crystal composition including the liquid crystalline compound according to the present invention has a wide nematic liquid crystal phase temperature range.

Claims (5)

A polymerizable liquid crystal composition comprising: as well as In the formula, n is an integer of 1 to 10. The polymerizable liquid crystal composition according to claim 1, which further comprises a photoinitiator. An optical film comprising the polymerizable liquid crystal composition according to item 1 or 2 of the patent application. A liquid crystal panel comprising the polymerizable liquid crystal composition as described in claim 1 or 2. A liquid crystal display device comprising the polymerizable liquid crystal composition according to the first or second aspect of the invention.