Liquid crystal composition and liquid crystal display device using the liquid crystal composition

Abstract

A liquid crystal composition and a liquid crystal display device having a rotational viscosity lower than that of conventional liquid crystal compositions. [Solution] The liquid crystal display device includes at least 5 to 50% of a first composition and 40 to 80% of a second composition, and has a dielectric anisotropy at 25°C of -2.0 to -3.9, the first composition including one or more compounds represented by structural formulas (1-1) and (1-2), JPEG0007671095000018.jpg2568 (In the formula, R 1 represents an alkyl group (C=1-5) or an alkenyl group (C=2-5), R 2 represents an alkyl group (C=1 to 4) or an alkenyl group (C=2 to 4). The second composition is, for example, a liquid crystal composition containing one or more compounds having the following structural formula: JPEG0007671095000019.jpg29113

Description

[Technical field]

[0001] The present invention relates to a liquid crystal composition having negative dielectric anisotropy, and a liquid crystal display device using the liquid crystal composition. [Background technology]

[0002] Liquid crystal display elements are used in automobile panels, word processors, electronic organizers, printers, computers, mobile phones, televisions, advertising display boards, etc. Representative liquid crystal display methods include TN (twisted nematic) type, STN (super twisted nematic) type, MVA (multi-domain vertical alignment) type using TFT (thin film transistor), PSA (polymer sustained alignment) type, IPS (in-plane switching) type, FFS (fringe field switching) type, etc. Liquid crystal compositions used in these liquid crystal display elements are required to be stable against external factors such as moisture, air, heat, and light, to exhibit a liquid crystal phase in as wide a temperature range as possible centered on room temperature, and to have low viscosity. Furthermore, liquid crystal compositions are composed of several to about twenty types of compounds, as shown in the following Patent Document 1, from the viewpoint of setting the dielectric anisotropy (Δε) or refractive index anisotropy (Δn) to the required value for each display element.

[0003] In particular, in recent years, there has been a demand for liquid crystal compositions with high speed response. There are various methods for achieving the desired physical properties, but an effective method is to reduce the viscosity of the liquid crystal composition. To reduce the viscosity of the liquid crystal composition, it is extremely effective to add a compound with low viscosity (η). In particular, it is effective to add a compound with low rotational viscosity (γ1). However, most of the conventional compounds with very low viscosity are non-polar compounds with a dielectric anisotropy of around 0, and if a large amount of these are used, the dielectric anisotropy decreases. Therefore, in order to achieve the desired dielectric anisotropy, it was not possible to use a large amount of them. This has been a problem, especially when preparing a liquid crystal composition with low viscosity and negative dielectric anisotropy.

[0004] For this reason, in order to further improve the liquid crystal properties, there is a demand for the development of a low-viscosity liquid crystal composition having the desired negative dielectric anisotropy by using a compound with a relatively low viscosity and strong negative dielectric anisotropy and using a large amount of a low-viscosity non-polar compound. The following Patent Document 2 shows a compound with a strong negative dielectric anisotropy developed for the same purpose, but the compound has the drawback of being insufficiently compatible with conventional liquid crystal compounds and difficult to increase in content, and does not fully achieve the required cutting-edge properties.

[0005] Furthermore, although Patent Document 3 is a prior art related to the present invention, there is no description whatsoever of a liquid crystal composition using the compound used in the present invention or of the characteristics thereof. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2006-99038 A [Patent Document 2] Patent No. 7297269 [Patent Document 3] Patent No. 4562827 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above circumstances, and has an objective of providing a liquid crystal composition designed to have a low rotational viscosity using a selected compound that has strong negative dielectric anisotropy, relatively low viscosity, and excellent compatibility with other liquid crystal compounds, and a liquid crystal display element using the liquid crystal composition. [Means for solving the problem]

[0008] In order to solve the above problems, the liquid crystal composition of the present invention contains 5% to 50% of one or more compounds selected from the compounds represented by the following structural formula (1-1): [ka] (In the formula, R 1 represents an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 5 carbon atoms; S, R 2 represents an alkyl group having 1 to 4 carbon atoms or an alkenyl group having 2 to 4 carbon atoms. ) Contains 40% to 80% of one or more compounds selected from the compounds represented by the following structural formulas (2-1) to (2-6), [ka] (In the formula, R 3 represents an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 5 carbon atoms; R 4 represents an alkyl group or an alkoxy group having 1 to 5 carbon atoms, or an alkenyl group having 3 to 5 carbon atoms. The dielectric anisotropy shown at 25°C is -2.0 to -3.9.

[0010] Moreover, the liquid crystal composition according to the present invention preferably further contains a UV-curable monomer at a ratio of 0.2% to 0.5%, depending on the liquid crystal display device in which it is used.

[0011] Furthermore, there is provided a liquid crystal display device using the liquid crystal composition of the present invention. The liquid crystal display device of the present invention is preferably of MVA type, PSA type, IPS type, or FFS type. Effect of the Invention

[0012] The liquid crystal composition of the present invention has a strong negative dielectric anisotropy and excellent compatibility with other liquid crystal compounds, and by using a larger amount of a compound exhibiting a relatively low rotational viscosity and a compound having a low viscosity and low rotational viscosity with a dielectric anisotropy of about 0, the required dielectric anisotropy and low rotational viscosity of the liquid crystal composition are achieved. Furthermore, a liquid crystal display element using the liquid crystal composition of the present invention is particularly suitable for providing a liquid crystal display element for liquid crystal televisions and liquid crystal monitors which require high-speed response. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will be described in detail below, but the present invention is not limited thereto. The liquid crystal composition of the present invention may contain 5% to 50% of one or more compounds selected from the compounds represented by the above structural formula (1-1). Alternatively, the liquid crystal composition of the present invention may contain 15% to 50% of one or more compounds selected from the compounds represented by the above structural formula (1-1) or structural formula (1-2). Furthermore, the liquid crystal composition of the present invention may contain 40% to 80% of one or more compounds selected from the compounds represented by the above structural formula (2-1) to structural formula (2-6). The one or more compounds selected from the compounds represented by the above structural formula (2-1) to structural formula (2-6) are Dielectric anisotropy (hereinafter also referred to simply as "Δε") is around 0 (approximately -2 to +2) To be Further, the liquid crystal composition of the present invention is preferably One or more compounds selected from the compounds represented by the above structural formulas (2-1) to (2-6) The content is preferably 50% to 80%. One or more compounds selected from the compounds represented by the above structural formulas (2-1) to (2-6) A content of 60% to 80% is preferred since a low rotational viscosity can be achieved.

[0014] moreover, The above The compound of structural formula (1-1) includes one or more compounds represented by the following structural formulas (1-1-1), (1-1-2), (1-1-3), and (1-1-4), The above When the compound of structural formula (1-2) is included, it is more preferable that the compound of structural formula (1-2) is a liquid crystal compound containing one or more of the compounds represented by the following structural formulas (1-2-1), (1-2-2), (1-2-3), and (1-2-4). In addition, in the compound of structural formula (1-1), one of the structural formulas (1-1-1) to (1-1-4) may be used, or two or more of the structural formulas may be selected and used. In the compound of structural formula (1-2), one of the structural formulas (1-2-1) to (1-2-4) may be used, or two or more of the structural formulas may be selected and used. [ka]

[0015] In addition, R in structural formula (2-1) to structural formula (2-6) 3 represents an ethyl group, a propyl group, an ethenyl group, or a propenyl group; R 4 preferably represents an alkyl or alkoxy group having 1 to 5 carbon atoms.

[0016] moreover, The above In the case where the liquid crystal compound of structural formula (2-1) is contained, the liquid crystal compound of structural formula (2-1) contains one or more compounds represented by the following structural formulas (2-1-1), (2-1-2), (2-1-3), (2-1-4), and (2-1-5), The above In the case where the liquid crystal compound represented by the structural formula (2-2) is contained, the liquid crystal compound represented by the structural formula (2-2) contains one or more compounds represented by the structural formula (2-2-1) and the structural formula (2-2-2), The above In the case where the liquid crystal compound represented by the structural formula (2-3) is contained, the liquid crystal compound represented by the structural formula (2-3) contains one or more compounds represented by the structural formulas (2-3-1) and (2-3-2), The above When the liquid crystal compound of structural formula (2-4) is contained, the liquid crystal compound of structural formula (2-4) includes one or more compounds represented by structural formula (2-4-1), structural formula (2-4-2), structural formula (2-4-3), and structural formula (2-4-4); The above In the case where the liquid crystal compound represented by the structural formula (2-5) is contained, the liquid crystal compound represented by the structural formula (2-5) contains a compound represented by the structural formula (2-5-1), The aboveIn the case where the liquid crystal compound of structural formula (2-6) is included, it is more preferable that the liquid crystal compound of structural formula (2-6) is a liquid crystal compound containing one or more of the compounds represented by structural formula (2-6-1) and structural formula (2-6-2). In addition, in the compound of structural formula (2-1), one structural formula may be used from structural formula (2-1-1) to structural formula (2-1-5), or two or more structural formulas may be selected and used. In the compound of structural formula (2-2), one structural formula may be used from structural formula (2-2-1) to structural formula (2-2-2), or two or more structural formulas may be selected and used. In the compound of structural formula (2-3), one structural formula may be used from structural formula (2-3-1) to structural formula (2-3-2), or two or more structural formulas may be selected and used. In the compound of formula (2-4), one of the formulae (2-4-1) to (2-4-4) may be used, or two or more of the formulae may be selected and used. In the compound of formula (2-6), one of the formulae (2-6-1) to (2-6-2) may be used, or two or more of the formulae may be selected and used. [ka] JPEG0007671095000005.jpg43170

[0017] The liquid crystal composition of the present invention is Contains 31% to 50% of one or more compounds selected from the compounds represented by the above structural formula (1-1). It is even more preferable that: Alternatively, it is more preferable that the liquid crystal composition of the present invention contains 31% to 50% of one or more compounds selected from the compounds represented by the above structural formula (1-1) and structural formula (1-2).

[0018] The liquid crystal composition of the present invention is The composition may further contain one or more compounds selected from the compounds represented by the following structural formulas (3-1) to (3-6). As examples of the conventionally known and preferred liquid crystal compounds having a negative Δε greater than −3 contained in the liquid crystal composition of the present invention, the following structural formulae (3-1) to (3-6) are given. Compounds of the following structural formulas (3-1) to (3-6) In the above, it is preferable that one or more of these are contained. [ka] (In the formula, R5 represents an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 5 carbon atoms; R 6 represents an alkyl group having 1 to 5 carbon atoms, and more preferably R 5 represents an ethyl group, a propyl group, an ethenyl group, or a propenyl group; R 6 represents a methyl group or an ethyl group.

[0019] The liquid crystal composition of the present invention is One or two compounds selected from the compounds represented by the following structural formula (4-1-1) to (4-1-2) Examples of the conventionally known preferred liquid crystal compounds having a negative Δε of approximately −2 contained in the liquid crystal composition of the present invention include the following structural formula (4-1-1) and structural formula (4-1-2). Compounds represented by the following structural formulas (4-1-1) to (4-1-2) In the above, it is preferable that one or two of these are contained. [ka]

[0020] The liquid crystal display element using the liquid crystal composition of the present invention is preferably an MVA type, a PSA type, an IPS type or an FFS type. In particular, the vertical alignment type MVA type and PSA type are preferred, in which a liquid crystal material is sandwiched between two substrates, the liquid crystal is aligned approximately perpendicular to the substrates, and an electric field is applied approximately perpendicular to the substrates to be used as an optical element or a display element, and the IPS type and FFS type are also preferred, in which the liquid crystal is aligned approximately parallel to the substrates and approximately perpendicular to the electrodes.

[0021] When the liquid crystal composition of the present invention is used in a PSA type liquid crystal display element, it is preferable that the liquid crystal composition of the present invention contains a UV-curable monomer in a ratio of 0.2% to 0.5%. Here, the "ratio of 0.2% to 0.5%" refers to the weight ratio of the UV-curable monomer contained in the liquid crystal composition to the total weight of the liquid crystal composition containing a plurality of compounds. When producing a liquid crystal display element, the liquid crystal composition containing the UV-curable monomer is irradiated with UV while applying a voltage, thereby separating the polymer phase and stabilizing the slight tilt alignment.

[0022] This UV-curable monomer is also called a reactive mesogen, and is preferably a polyfunctional monomer having multiple (two or more) functional groups. In particular, it is more preferable that the UV-curable monomer has two or three functional groups, and the two or three functional groups include at least one of a methacryloyl group, an acryloyl group, and a cinnamoyl group.

[0023] Preferred examples of conventionally known UV-curable monomers include those represented by the following structural formulae (5-1) to (5-5), of which it is preferred to contain one or more of them. [ka]

[0024] Furthermore, liquid crystal display elements using this liquid crystal composition are suitable for use in liquid crystal televisions and liquid crystal monitors, which require high-speed response, as well as in-vehicle displays and PIDs (public information displays), which require high-speed response at low temperatures. EXAMPLES

[0025] Example 1 Liquid crystal composition (1) (hereinafter also simply referred to as "composition (1)") in Table 1 was prepared using the compounds of the present invention of formula (1-1-1) having a nematic liquid crystal phase at 65°C to 108°C and formula (1-2-1) having a nematic liquid crystal phase at 99°C to 132°C, which were synthesized using a conventional cross-coupling method. Table 1 shows the composition ratios of the compounds contained in the liquid crystal composition. The composition ratios shown here also correspond to the above-mentioned "content ratios." In this embodiment, the "structural formula" may be simply referred to as "formula," and compounds with the same serial numbers are considered to be equivalent or identical compounds.

[0026] The physical properties of the liquid crystal composition (1) were as follows: the dielectric anisotropy (Δε) and the refractive index anisotropy (Δn) were measured at 25°C, and the rotational viscosity (γ1) was measured at 20°C. Nematic phase upper limit temperature (T n-i): 80.5℃ Dielectric anisotropy (Δε): -3.3 Refractive index anisotropy (Δn): 0.11 Rotational viscosity (γ1): 116 mPa·s

[0027] Example 2 In the same manner as in Example 1, a liquid crystal composition (2) in Table 1 (hereinafter also simply referred to as "composition (2)") was prepared using the compound of formula (1-2-1).

[0028] The physical properties of the liquid crystal composition (2) were as follows. Nematic phase upper limit temperature (T n-i ): 80.3℃ Dielectric anisotropy (Δε): -3.3 Refractive index anisotropy (Δn): 0.11 Rotational viscosity (γ1): 102 mPa·s

[0029] Example 3 In the same manner as in Example 5, liquid crystal composition (3) in Table 1 (hereinafter also simply referred to as “composition (3)”) was prepared using the compounds of the present invention represented by formula (1-1-1), formula (1-2-1), and formula (1-2-2).

[0030] The physical properties of the liquid crystal composition (3) were as follows. Nematic phase upper limit temperature (T n-i ): 79.8℃ Dielectric anisotropy (Δε): -3.3 Refractive index anisotropy (Δn): 0.11 Rotational viscosity (γ1): 94 mPa·s

[0031] Comparative Example 1 As a comparative example for Example 1, liquid crystal composition (4) in Table 1 (hereinafter also simply referred to as "composition (4)") consisting of a conventional liquid crystal compound was prepared.

[0032] The physical properties of the liquid crystal composition (4) were as follows. Nematic phase upper limit temperature (T n-i ): 80.1℃ Dielectric anisotropy (Δε): -3.3 Refractive index anisotropy (Δn): 0.11 Rotational viscosity (γ1): 145 mPa·s

[0033] Comparative Example 2 As a comparative example for Example 2, liquid crystal composition (5) in Table 1 (hereinafter also simply referred to as "composition (5)") consisting of a conventional liquid crystal compound was prepared.

[0034] The physical properties of the liquid crystal composition (5) were as follows. Nematic phase upper limit temperature (T n-i ): 80.3℃ Dielectric anisotropy (Δε): -3.3 Refractive index anisotropy (Δn): 0.11 Rotational viscosity (γ1): 140 mPa·s

[0035] Comparative Example 3 As a comparative example for Example 3, liquid crystal composition (6) in Table 1 (hereinafter also simply referred to as "composition (6)") consisting of a conventional liquid crystal compound was prepared.

[0036] The physical properties of the liquid crystal composition (6) were as follows: Nematic phase upper limit temperature (T n-i ): 80.0℃ Dielectric anisotropy (Δε): -3.3 Refractive index anisotropy (Δn): 0.11 Rotational viscosity (γ1): 114 mPa·s

[0037] The liquid crystal compositions (1) to (6) all satisfy the characteristics typically required for liquid crystal compositions used in PSA-type or MVA-type liquid crystal displays for liquid crystal televisions, namely, the maximum nematic phase temperature (T n-i) = 80°C, dielectric anisotropy (Δε) = -3.3, and refractive index anisotropy (Δn) = 0.11. Furthermore, composition (1) of Example (1) and composition (4) of Comparative Example (1) are composed of the same liquid crystal compounds except for the compounds of the present invention. Similarly, composition (2) of Example (2) and composition (5) of Comparative Example (2), and composition (3) of Example (3) and composition (6) of Comparative Example (3) are composed of the same liquid crystal compounds except for the compounds of the present invention.

[0038] [Table 1]

[0039] The compounds of the formulae (3-1-1), (3-1-2), (3-5-1), (3-5-2), (3-3-1), (3-3-2), (3-4-1), (3-4-2), (3-4-3), (3-6-1), and (3-6-2) in Table 1 represent the following compounds. [ka]

[0040] The compounds of formulae (4-1-1) and (4-1-2) in Table 1 are as follows: [ka]

[0041] The rotational viscosity (γ1) of composition (1) of Example (1) is 116 mPa·s, which is clearly lower than the rotational viscosity (γ1) of 145 mPa·s of composition (4) of Comparative Example (1). Similarly, the rotational viscosity of composition (2) of Example (2) is 102 mPa·s, which is lower than the 140 mPa·s of Comparative Example (2), and the rotational viscosity of composition (3) of Example (3) is also 94 mPa·s, which is lower than the 114 mPa·s of Comparative Example (3). From these facts, it is clear that the liquid crystal compound and its liquid crystal composition of the present invention are effective in achieving high-speed response.

[0042] Example 4 In the same manner as in Example 1, liquid crystal composition (7) in Table 2 (hereinafter also simply referred to as "composition (7)") was prepared using compounds of formula (1-1-1) and formula (1-2-1). Table 2 shows the composition ratios of the compounds contained in the liquid crystal composition. The composition ratios shown here also correspond to the "content ratios" described above.

[0043] The physical properties of the liquid crystal composition (7) were as follows. Nematic phase upper limit temperature (T n-i ): 77.5℃ Dielectric anisotropy (Δε): -3.1 Refractive index anisotropy (Δn): 0.13 Rotational viscosity (γ1): 105 mPa·s

[0044] Example 5 In the same manner as in Example 1, liquid crystal composition (8) in Table 2 (hereinafter also simply referred to as “composition (8)”) was prepared using compounds of formulae (1-1-1), (1-2-1), and (1-2-2).

[0045] The physical properties of the liquid crystal composition (8) were as follows: Nematic phase upper limit temperature (T n-i ): 76.6℃ Dielectric anisotropy (Δε): -2.2 Refractive index anisotropy (Δn): 0.11 Rotational viscosity (γ1): 62 mPa·s

[0046] [Table 2]

[0047] Liquid crystal composition (7) of Example (4) is particularly suitable for PSA-type liquid crystal displays operating at 120 Hz, which require high stability and a thin cell thickness. Liquid crystal composition (8) of Example (5) has a very low rotational viscosity and is suitable for high-speed PSA-type or FFS-type liquid crystal displays. Both compositions are extremely useful for producing cutting-edge liquid crystal displays.

Claims

1. Contains 5% to 50% of one or more compounds selected from the compounds represented by the following structural formula (1-1): 【Chemistry 1】 (In the formula, R １ represents an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 5 carbon atoms, and R 2 represents an alkyl group having 1 to 4 carbon atoms or an alkenyl group having 2 to 4 carbon atoms. Contains 40% to 80% of one or more compounds selected from the compounds represented by the following structural formulas (2-1) to (2-6), 【Chemistry 2】 (In the formula, R ３ represents an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 5 carbon atoms; R ４ represents an alkyl group or an alkoxy group having 1 to 5 carbon atoms, or an alkenyl group having 3 to 5 carbon atoms. The dielectric anisotropy at 25° C. is -2.0 to -3.9 Liquid crystal composition.

2. The compound of the structural formula (1-1) is A liquid crystal compound represented by the following structural formula (1-1-1), structural formula (1-1-2), structural formula (1-1-3), or structural formula (1-1-4): The liquid crystal composition of claim 1. 【Chemistry 5】

3. The composition contains 31% to 50% of one or more compounds selected from the compounds represented by the structural formula (1-1). The liquid crystal composition according to claim 1 or 2.

4. Further containing one or more compounds selected from the compounds represented by the following structural formulas (3-1) to (3-6): The liquid crystal composition of claim 3. 【Chemistry 10】 (In the formula, R 5 represents an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 1 to 5 carbon atoms; R 6 represents an alkyl group having 1 to 5 carbon atoms.

5. Further contains 0.2% to 0.5% of a UV-curable monomer having multiple functional groups. The liquid crystal composition of claim 4.

6. The UV-curable monomer has two or three functional groups, and the two or three functional groups include at least one of a methacryloyl group, an acryloyl group, and a cinnamoyl group. The liquid crystal composition of claim 5 .

7. The UV-curable monomer contains one or more compounds selected from the compounds represented by the following structural formulas (5-1) to (5-5): The liquid crystal composition of claim 6. 【Chemistry 15】

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