Liquid crystal composition and application thereof
Technical Field
The present invention relates to a liquid crystal composition used for a liquid crystal display element, and more particularly to a liquid crystal composition used for a liquid crystal display element driven by an active matrix system.
Background
Liquid crystal devices operate by utilizing optical anisotropy and dielectric anisotropy of liquid crystal materials themselves, and are now widely used. The device can be designed into various operation modes by utilizing different characteristics and operation modes of the liquid crystal material, wherein the conventional display commonly uses a TN mode (i.e. a twisted nematic mode-a liquid crystal mixture has a nematic structure twisted by about 90 degrees), an STN mode (i.e. a super twisted nematic mode), an SBE mode (i.e. a super twisted birefringence mode), an ECB mode (i.e. an electrically controlled birefringence mode), a VA mode (i.e. a vertical alignment mode), an IPS mode (i.e. an in-plane switching mode), and the like, and contains a plurality of improved modes according to the modes.
In low information content, a passive mode is generally adopted for driving, but with the increase of information content, the phenomena of crosstalk and contrast reduction become serious, so an Active Matrix (AM) mode is generally adopted for driving, and at present, a Thin Film Transistor (TFT) is frequently adopted for driving.
In the early 70 s of the last century, experimental studies have been carried out on the basic electro-optical characteristics of the IPS mode of nematic liquid crystals, both uniformly and twisted, characterized in that a pair of electrodes is made on the same substrate, while the other substrate has no electrode, and the arrangement of the liquid crystal molecules is controlled by a transverse electric field applied between the electrodes, so this mode can also be called transverse field mode. In the IPS mode, nematic liquid crystal molecules are uniformly arranged in parallel between two substrates, and two polarizing plates are orthogonally arranged. In the IPS mode, when no electric field is applied, incident light is blocked by two orthogonal polarizing plates to be in a dark state, and when an electric field is applied, liquid crystal molecules rotate to cause retardation, so that light leaks from the two orthogonal polarizing plates.
Since the IPS modes are simple to fabricate and have a wide viewing angle, they become the most attractive approach capable of improving viewing angle characteristics and realizing large-area display.
The IPS mode requires only a linear polarizer and no compensation film, but its response speed is too slow to display a fast moving picture. Therefore, the IPS type display liquid crystal is required to have a faster response speed than the conventional TN-TFT type display mode. But based on the complexity of the liquid crystal mixed crystal modulation: from the viewpoint of the preparation of the liquid crystal composition material, the properties of the material (low optical birefringence value, high dielectric anisotropy value, high resistivity, low rotational viscosity, low melting point, good thermal stability and ultraviolet stability, etc.) are mutually hampered, and the improvement of some properties is accompanied by the deterioration of the other properties, and it is very difficult to prepare a liquid crystal composition having suitable properties in all respects.
Therefore, a liquid crystal composition having properties such as low optical birefringence, high dielectric anisotropy, high resistivity, low rotational viscosity, low melting point, good thermal stability and uv stability is needed to solve the problems of the existing liquid crystal compositions.
Disclosure of Invention
The purpose of the invention is as follows: the object of the present invention is to provide a liquid crystal composition having a low optical birefringence value, a high dielectric anisotropy value, a low rotational viscosity and a wide nematic phase temperature range.
The invention also provides a liquid crystal display device comprising the liquid crystal composition.
The technical scheme is as follows: in order to accomplish the above object of the invention, the present invention provides a liquid crystal composition comprising:
40-70% by weight of the total weight of the liquid crystal composition of a compound of formula I
2-10% of one or more compounds of general formula II-1 and/or general formula II-2 based on the total weight of the liquid crystal composition
10-20% of one or more compounds of general formula III based on the total weight of the liquid crystal composition
10-30% of the total weight of the liquid crystal composition, and one or more compounds in the general formula IV
Wherein,
r represents H or CH3;
The R is1、R2And R3The alkyl or alkoxy with 1 to 12 carbon atoms and the alkenyl or alkenyloxy with 2 to 12 carbon atoms are the same or different and respectively and independently represent H, the alkyl or alkoxy with 1 to 12 carbon atoms and the alkenyl or alkenyloxy with 2 to 12 carbon atoms, wherein one or more H can be substituted by F;
the R is5And R6The alkyl or alkoxy with 1 to 12 carbon atoms and the alkenyl or alkenyloxy with 2 to 12 carbon atoms are the same or different and respectively and independently represent H, the alkyl or alkoxy with 1 to 12 carbon atoms and the alkenyl or alkenyloxy with 2 to 12 carbon atoms, wherein one or more H can be substituted by F;
said Y is13And R4The same or different, each independently represent-F or-OCF3;
Z is1、Z2And Z3The same or different, each independently represent a single bond, -CH2O-、-OCH2-、-CF2O-, -COO-or-OCO-;
z is4And Z5The same or different, each independently represent a single bond, -CH2O-or-COO-;
said Y is11、Y12、Y21、Y22、Y23、Y24、Y25And Y26Are identical or different and each independently represents H or F, wherein Y21And Y22Not simultaneously being F and Y24And Y25F is not simultaneously obtained;
the ringIdentical or different, each independently of the other Wherein, theH in (1) may be substituted by F, andat least one selected from
The ringIdentical or different, each independently of the otherWherein, theH in (a) may be substituted by F;
m, n, q, p and d are the same or different and each independently represents 0 or 1.
In some embodiments of the present invention, the liquid crystal composition further comprises 0-25% by total weight of the liquid crystal composition of one or more of the compounds of formula v:
the R is7Represents H, alkyl or alkoxy of 1 to 12 carbon atoms, alkenyl or alkenyloxy of 2 to 12 carbon atoms, wherein one or more H in the alkyl or alkoxy of 1 to 12 carbon atoms, alkenyl or alkenyloxy of 2 to 12 carbon atoms can be substituted by F;
the ringTo represent
Said X12Represents H or F;
the a represents 0 or 1.
In some embodiments of the present invention, the liquid crystal composition further comprises 0-15% by weight of the total weight of the liquid crystal composition of one or more compounds of formula VI
Wherein,
the R is8And R9The same or different, each independently represents H, alkyl or alkoxy of 1-12 carbon atoms, alkenyl or alkenyloxy of 2-12 carbon atoms, wherein one or more H in the alkyl or alkoxy of 1-12 carbon atoms, alkenyl or alkenyloxy of 2-12 carbon atoms can be substituted by F.
In some embodiments of the invention, the compound of formula II-1 is selected from one or more of:
and
in some embodiments of the invention, the compound of formula II-2 is selected from one or more of:
and
wherein,
the R is2Represents H, alkyl or alkoxy of 1 to 5 carbon atoms, alkenyl or alkenyloxy of 2 to 6 carbon atoms, wherein one or more H in the alkyl or alkoxy of 1 to 5 carbon atoms, alkenyl or alkenyloxy of 2 to 6 carbon atoms can be substituted by F.
In some embodiments of the present invention, the compound of formula II-2 is preferably selected from one or more of:
and
wherein,
the R is2Represents an alkyl or alkoxy group of 1 to 5 carbon atoms, an alkenyl or alkenyloxy group of 2 to 6 carbon atoms.
In some embodiments of the invention, the compound of formula iii is selected from one or more of:
and
wherein,
the R is3Represents H, alkyl or alkoxy of 1 to 5 carbon atoms, alkenyl or alkenyloxy of 2 to 6 carbon atoms, wherein one or more H in the alkyl or alkoxy of 1 to 5 carbon atoms, alkenyl or alkenyloxy of 2 to 6 carbon atoms can be substituted by F.
In some embodiments of the invention, the compound of formula iv is selected from one or more of:
and
wherein,
the R is5And R6The alkyl or alkoxy with 1 to 5 carbon atoms, the alkenyl or alkenyloxy with 2 to 6 carbon atoms and the like or different, independently represent, wherein one or more H in the alkyl or alkoxy with 1 to 12 carbon atoms, the alkenyl or alkenyloxy with 2 to 12 carbon atoms can be substituted by F;
in some embodiments of the invention, the compound of formula IV-1 is selected from one or more of the following compounds:
and
in some embodiments of the invention, the compound of formula IV-2 is selected from one or more of the following compounds:
and
in some embodiments of the invention, the compound of formula v is selected from one or more of the following compounds:
and
wherein,
the R is7Represents an alkyl or alkoxy group of 1 to 5 carbon atoms, an alkenyl or alkenyloxy group of 2 to 6 carbon atoms, wherein one or more H of the alkyl or alkoxy group of 1 to 5 carbon atoms, the alkenyl or alkenyloxy group of 2 to 6 carbon atoms may be substituted by F.
In some embodiments of the invention, the compound of formula vi is selected from one or more of the following compounds:
and
in some embodiments of the invention, the compound of formula I comprises 45-60% by weight of the total liquid crystal composition; the compound of the general formula II accounts for 3-10% of the total weight of the liquid crystal composition; the compound of the general formula III accounts for 10-15% of the total weight of the liquid crystal composition; the compound of the general formula IV accounts for 10-25% of the total weight of the liquid crystal composition; the compound of the general formula V accounts for 0-10% of the total weight of the liquid crystal composition; and the compound of the general formula VI accounts for 0-15% of the total weight of the liquid crystal composition.
Preferably, the compound of the general formula I accounts for 45-60% of the total weight of the liquid crystal composition; the compound of the general formula II accounts for 3-10% of the total weight of the liquid crystal composition; the compound of the general formula III accounts for 10-15% of the total weight of the liquid crystal composition; the compound of the general formula IV accounts for 10-25% of the total weight of the liquid crystal composition; the compound of the general formula V accounts for 1-10% of the total weight of the liquid crystal composition; and the compound of the general formula VI accounts for 1-15% of the total weight of the liquid crystal composition.
The present invention also provides an application of the liquid crystal composition in an IPS mode liquid crystal display device.
Has the advantages that: in the prior art, the skeleton structure of the liquid crystal monomer used in the liquid crystal composition mostly adopts cyclohexane and benzene ring as skeletons, wherein, oxygen atoms and N atoms can be used to selectively replace individual carbon atoms in the cyclohexane ring and the benzene ring, but when the structure corresponds to the following dielectric with low dielectric below 4.5 and the refractive index range is required to be between 0.095 and 0.125, the response speed and the temperature width of nematic phase are contradictory, and the wide nematic phase temperature is either too low in clearing point or too high in low-temperature Tcn, so that the liquid crystal is easy to crystallize under the low-temperature storage condition. The main reason is that the nematic phase temperature of the liquid crystal is generally only selectively biased to a clearing point or a low-temperature phase transition point under the molecular design that the traditional benzene cyclohexane is a skeleton structure. The naphthalene ring is the only molecular framework structure which is found in the molecules of the prior annular framework structure and can simultaneously widen the high-temperature phase change point and the low-temperature phase change point of the liquid crystal, and simultaneously, the fluorine substitution design of the H of the naphthalene ring is optimized, so that the fat solubility of the liquid crystal is enhanced. But naphthalene ring also has the disadvantage of slow response speed, and the invention can compensate the disadvantage of slow response speed and difficult use of naphthalene ring through the preferable combination of neutral monomer structure and strong polarity and medium polarity structure. The liquid crystal composition containing the naphthalene ring structure has the advantages of wide nematic phase temperature range, high response speed, lower rotary viscosity and the like in the positive liquid crystal composition with the dielectric property of 2-4.5. Meanwhile, as a heterocyclic structure with poor reliability is not adopted, the composition has better reliability and obtains very good technical effect.
In the present invention, unless otherwise specified, the proportions are weight ratios, all temperatures are in degrees centigrade, and the thickness of the box selected for the response time data test is 7 μm.
Detailed Description
The invention will be illustrated below with reference to specific embodiments. It should be noted that the following examples are illustrative of the present invention, and are not intended to limit the present invention. Other combinations and various modifications within the spirit or scope of the present invention may be made without departing from the spirit or scope of the present invention.
For convenience of expression, in the following examples, the group structure of the liquid crystal composition is represented by the code listed in Table 1:
TABLE 1 radical structural code of liquid crystal compounds
Compounds of the following formula are exemplified:
the structural formula is represented by the code listed in Table 1, and can be expressed as: nCGUF, wherein n in the code represents the number of carbon atoms of the left alkyl group, for example, n is "2", that is, the alkyl group is-C2H5(ii) a C in the code represents "cyclohexane group", G in the code represents "2-fluoro-1, 4-phenylene group", U in the code represents "2, 5-difluoro-1, 4-phenylene group", and F in the code represents "fluorine substituent".
The abbreviated codes of the test items in the following examples are as follows:
Δ n: optical anisotropy (589nm, 25 ℃ C.)
Δ ε: dielectric anisotropy (1KHz, 25 ℃ C.)
Vth: threshold voltage (1KHZ, 25 ℃, TN90)
Tni: clearing Point (nematic-isotropic phase transition temperature, degree C.)
γ1: rotational viscosity (mpa.s, 25 ℃ C. unless otherwise stated)
TcnLow temperature storage phase transition point (i.e. lower temperature limit of nematic phase, ° C)
△ T nematic temperature Range (. degree.C.)
Wherein the optical anisotropy is measured by an Abbe refractometer under a sodium lamp (589nm) light source at 25 ℃; the dielectric test cell was of the type TN90, the cell thickness being 7 μm.
VHR (initial) was tested using the TOY06254 type liquid crystal physical property evaluation system; pulse voltage: 5V 6HZ, the testing temperature is 60 ℃, and the testing unit period is 166.7 ms.
Vth test conditions: c/1KHZ, JTSB 7.0.
Nematic phase temperature range (△ T) nematic phase upper limit temperature (T)ni) Lower temperature limit of nematic phase (T)cn)。
The components used in the following examples can be synthesized by a known method or obtained commercially. These synthesis techniques are conventional, and the resulting liquid crystal compounds were tested to meet the standards for electronic compounds.
Liquid crystal compositions were prepared according to the compounding ratios of the liquid crystal compositions specified in the following examples. The liquid crystal composition is prepared according to the conventional method in the field, such as heating, ultrasonic wave, suspension and the like, and is mixed according to the specified proportion.
Liquid crystal compositions given in the following examples were prepared and studied. The composition of each liquid crystal composition and the results of the performance parameter test thereof are shown below.
Comparative example 1
The liquid crystal composition of comparative example 1, which was filled between two substrates of a liquid crystal display and subjected to a performance test, was prepared with each compound and weight percentage as listed in table 2, and the test data are shown in the following table:
TABLE 2 liquid crystal composition formulations and their test properties
Comparative example 2
The liquid crystal composition of comparative example 2, which was filled between two substrates of a liquid crystal display and subjected to a performance test, was prepared with each compound and weight percentage as listed in table 3, and the test data are shown in the following table:
TABLE 3 liquid crystal composition formula and its test performance
Example 1
The liquid crystal composition of example 1 was prepared according to the compounds and weight percentages listed in table 4, and filled between two substrates of a liquid crystal display for performance testing, and the test data are shown in the following table:
TABLE 4 liquid crystal composition formula and its test performance
Example 2
The liquid crystal composition of example 2 was prepared according to the compounds and weight percentages listed in table 5, and filled between two substrates of a liquid crystal display for performance testing, and the test data are shown in the following table:
TABLE 5 liquid crystal composition formulations and their test properties
Example 3
The liquid crystal composition of example 3 was prepared according to the compounds and weight percentages listed in table 6, and filled between two substrates of a liquid crystal display for performance testing, and the test data are shown in the following table:
TABLE 6 liquid crystal composition formula and its test performance
Example 4
The liquid crystal composition of example 4 was prepared according to the compounds and weight percentages listed in table 7, and filled between two substrates of a liquid crystal display for performance testing, and the test data are shown in the following table:
TABLE 7 liquid crystal composition formulations and their test properties
As can be seen from the above comparative examples and examples, the optical anisotropy (△ n) of the four formulation examples of the present invention listed in examples 1 to 4 can range from 0.1 to about 0.12, and △ n in the range can substantially cover the current mainstream liquid crystal applications.
The examples 1 and 2 correspond to △ n of about 0.1, and the advantages can be found from the comparison of the parameters with the comparative example 1, that the liquid crystal phase width of the examples 1 and 2 is obviously higher than that of the comparative example 1 under the similar △ n, and particularly, the cooling point (T) is larger under the condition of larger phase widthni) At higher, the rotational viscosity (γ) of the examples1) Is obviously lower than that of the comparative example 1, can realize quick response, overcomes the technical defect of slow response speed of the liquid crystal composition containing naphthalene ring in the prior art, and obtains very good technical effect.
The embodiments 3 and 4 of the present invention are typical large △ n liquid crystal compositions, the large △ n liquid crystal can reduce the cell thickness of the liquid crystal application, thereby achieving faster response, the conventional large △ n liquid crystal composition is generally stored at a low temperature of-20 ℃, the liquid crystal compositions of the embodiments 3 and 4 can be stored at a low temperature of-35 ℃, and meanwhile, under the condition of having larger △ n and Tni, and wide phase, especially having larger dielectric, can achieve lower voltage driving, reduce the power consumption of the liquid crystal composition, and make a very good technical progress, thereby overcoming the defects of the prior art.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.