Liquid crystal composition containing dibenzo derivatives and liquid crystal display device

Abstract

A liquid crystal composition containing dibenzo derivatives for use in a liquid crystal display device includes at least one compound of general formula I and at least one compound of general formula II.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of International Application No. PCT/CN2021/102328, filed Jun. 25, 2021, which claims the benefit of Netherlands Application No. 202010596444.1, filed Jun. 28, 2020, the contents of which is incorporated by reference herein.

TECHNICAL FIELD

The present application belongs to the technical field of liquid crystal display materials, and relates to a liquid crystal composition containing a dibenzo derivative and a liquid crystal display device.

BACKGROUND ARTS

The liquid crystal display (LCD) has been rapidly developed because of its small size, light weight, low power consumption, and excellent display quality, and thus has been widely applied especially in portable electronic information products. According to the type of display mode, liquid crystal displays can be divided into the following types: PC (phase change PC), TN (twist nematic), STN (super twisted nematic), ECB (electrically controlled birefringence), OCB (optically compensated bend), IPS (in plane switching), FFS (fringe field switching), VA (vertical alignment), and PSA (polymer stable alignment), etc.

Among these modes, it is known that the IPS mode, FFS mode, and VA mode can improve the shortcoming of narrow viewing angle of action modes for the TN mode, STN mode and the like. Liquid crystal displays of these display modes mainly use liquid crystal compositions having negative dielectric anisotropy. In order to further improve the characteristics of the liquid crystal display, the composition optionally has the following physical properties (1) to (8):

• • (1) high stability to heat, light, etc.;
  • (2) high clearing point;
  • (3) low lower limit temperature of liquid crystal phase;
  • (4) low viscosity;
  • (5) appropriate optical anisotropy;
  • (6) large negative dielectric anisotropy;
  • (7) appropriate elastic constant;
  • (8) good compatibility of liquid crystal compound.

The physical properties of liquid crystal compositions have an important influence on the display effect of liquid crystal displays. For example, the liquid crystal composition with high stability to heat, light, and the like can increase the voltage retention rate of the liquid crystal display, thereby prolonging the service life of the liquid crystal display; the liquid crystal composition with a high clearing point and low lower limit temperature of the liquid crystal phase can expand the usable temperature range of the liquid crystal display; the liquid crystal composition with low viscosity can shorten the response time of the liquid crystal display; the liquid crystal composition having appropriate optical anisotropy can improve the contrast of the liquid crystal display, and the liquid crystal composition having large optical anisotropy is more appropriate when the liquid crystal display has been gradually developing thinner; the liquid crystal composition having large negative dielectric anisotropy can reduce the threshold voltage of the liquid crystal display element, thereby reducing the power consumption; the liquid crystal composition with a large elastic constant can shorten the response time of the liquid crystal display, and the liquid crystal composition with a small elastic constant can reduce the threshold voltage of the liquid crystal display; and good compatibility of the liquid crystal compound is beneficial to mixing liquid crystal compounds with different physical properties to adjust the physical properties of the liquid crystal composition.

In addition, improving the contrast of the liquid crystal display is also one of the goals sought to be achieved by the industry through continuous researches. The research shows that the most important factor affecting the contrast of the liquid crystal display element is the light leakage of the liquid crystal material, and the main factor affecting the light leakage is LC Scattering of the liquid crystal material, and the LC Scattering and the average elastic constant K_ave have the following relationship:

$LC\mathrm{Scattering}\propto \frac{d·\Delta n^2·{\left(n_e+n_o\right)}^2}{K_{\mathrm{ave}}}$

• • wherein d represents the distance between liquid crystal cells, n_e represents the refractive index of extraordinary light, and n_o represents the refractive index of ordinary light. It can be seen from this relationship that LC Scattering is inversely proportional to K_ave, and the light leakage of the liquid crystal material can be reduced by increasing K_ave.

In addition, the relationship between the contrast rate (CR) and the luminance (L) is as follows:CR=L₂₅₅/L₀×100%,

• • wherein L₂₅₅ is the On-state luminance, and L₀ is the Off-state luminance. It can be seen that CR is significantly affected by the change of L₀. In the Off state, L₀ has nothing to do with the dielectric of the liquid crystal molecule but is related to the LC Scattering of the liquid crystal material. The smaller the LC Scattering, the smaller the L₀, and the more significantly CR will be increased.

In addition, the current liquid crystal display device still has the problem of high power consumption, which is because only about 5% of the backlight can penetrate the display device and then be captured by human eyes while most of the light is “wasted”. If the liquid crystal with high transmittance can be developed, the backlight intensity can be reduced, thus achieving the purpose of saving energy consumption and prolonging the service time of the device.

Chinese Patent Announcement No. CN107973766A discloses a liquid crystal compound of cycloalkyl-containing dibenzofuran derivative, and the structure thereof is shown as follows:

• • in which, H represents one of cyclopropyl, cyclobutyl, cyclopentyl or 2-tetrahydrofuranyl; Z represents one of a single bond, —CH₂—, —O—, —CH₂CH₂— or —CH₂O—; and X represents a hydrogen atom, a fluorine atom, an alkyl group having 1-7 carbon atoms or an alkoxy group having 1-7 carbon atoms.

The above liquid crystal compound of cycloalkyl-containing dibenzofuran derivative has a good intersolubility with other liquid crystal compounds, and the low temperature stability is improved accordingly. However, the transmittance of the liquid crystal composition including this type of compounds needs to be further improved.

Therefore, on the basis of the existing art, it is expected to develop a liquid crystal composition with higher transmittance and higher contrast, so as to meet the increasing requirements of visual effects and low power consumption of the liquid crystal display.

SUMMARY OF THE INVENTION

The objective of the present application is to provide a liquid crystal composition containing a dibenzo derivative and a liquid crystal display device, the liquid crystal composition has a high clearing point, a large optical anisotropy, a large dielectric anisotropy, a larger dielectric constant perpendicular to the molecular axis ε_⊥, a larger ratio of perpendicular dielectric to a absolute value of dielectric ε_⊥/|Δε|, and a larger average elastic constant K_ave.

In order to achieve the above objective, the present application utilizes the following technical solutions:

In the first aspect, the present application provides a liquid crystal composition containing a dibenzo derivative, the liquid crystal composition includes at least one compound of general formula I and at least one compound of general formula II:

• • in which,
  • R represents —H, halogen, —CN, C_1-12 linear or branched alkyl,

one or at least two nonadjacent —CH₂— in the C_1-12 linear or branched alkyl may be respectively and independently replaced by —CH═CH—, —C≡C—, —O—, —S—, —CO—, —CO—O— or —O—CO—, one or at least two —H in the aforesaid groups may be respectively and independently substituted by —F or —Cl;

• • R_x represents —H, C_1-12 linear or branched alkyl, one or at least two nonadjacent —CH₂— in the C_1-12 linear or branched alkyl may be respectively and independently replaced by —CH═CH—, —C≡C—, —O—, —S—, —CO—, —CO—O— or —O—CO—, one or at least two —H in the C_1-12 linear or branched alkyl may be respectively and independently substituted by —F or —Cl, R_x is attached to an arbitrary carbon atom in ring

• • R₁ and R₂ each independently represents C_1-12 linear or branched alkyl,

one or at least two nonadjacent —CH₂— in the C_1-12 linear or branched alkyl may be respectively and independently replaced by —CH═CH—, —C≡C—, —O—, —CO—, —CO—O— or —O—CO—, ring

represents

one or at least two single bond within the ring of the aforesaid groups may be replaced by double bond; ring

represents

one or at least two —CH₂— in

may be replaced by —O—, one or at most two single bond within the ring may be replaced by double bond; one or at least two —H in

may be substituted by —F or —Cl, one or at least two —CH═ within the ring may be replaced by —N═; “one or at least two” in “one or at least two —CH═ within the ring may be replaced by —N═” refers to the number of —CH═ replaced by —N═, the same expressions involved in the present application all have the same meaning; ring

represents

one or at least two —CH₂— in

may be replaced by —O—, one or at most two single bond within the if may be replaced by double bond; one or at least two —H in

may be substituted by —F or —Cl, one or at least two —CH═ within the ring may be replaced by —N═;

• • Z₁ represents —(CH₂)_aO— or —(CH₂)_aS—, wherein a represents an integer of 0 to 7, for example, a may be 0, 1, 2, 3, 4, 5, 6 or 7;
  • Z₂ represents —O—, —S—, —CO—O—, —O—CO—, —CF₂O—, —OCF₂—, —CH₂O—, —CH₂S—, —OCH₂—, —SCH₂—, —CH₂—, —CH₂CH₂—, —(CH₂)₄—, —CH═CH—CH₂O—, —C₂F₄—, —CH₂CF₂—, —CF₂CH₂—, —CF═CF—, —CH═CF—, —CF═CH—, —CH═CH—, —C≡C— or single bond;
  • Z₃ represents single bond, —CO—O—, —O—CO—, —CH₂O—, —OCH₂—, —CH═CH—, —C≡C—, —CH₂CH₂—, —(CH₂)₄—, —CF₂O—, —OCF₂— or —CF₂CF₂—;
  • L₁ and L₂ each independently represents —F, —Cl, —CF₃ or —CHF₂;
  • X represents —CO—, —S— or —O—;
  • n represents 0, 1 or 2, wherein when n represents 2, ring

is same or different, Z₂ is same or different;

• • m represents 0, 1 or 2, wherein when m represents 2, ring

is same or different, Z₃ is same or different; and

• • at least one group of the following three groups: R₁, ring

and Z₃, contains at least one of —CH═CH— or —C≡C—, i.e., at least one of R₁, ring

and Z₃ contains carbon-carbon unsaturated bond other than aryl unsaturated bond.

In the present application, C_1-12 may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 carbon atoms.

The carbon-carbon unsaturated bond of the present application is —CH═CH— or —C ≡C—, for example, R₁ represents CH₂═CH—, or ring

represents

or Z₃ represents —CH═CH—, etc.

When n=2, there are two

in the compound, these two

may have the same structure or different structures. For example, one may be

and the other is

when the expressions of “same or different” involved in the present application, they all have the same meaning.

In the present application, “may be respectively and independently replaced by . . . ” refers that it may be replaced or may not be replaced, that is, “replaced” or “not replaced”, both of which fall within the protection scope of the present application. The same applies to the expression of “may be respectively and independently substituted by”, and the “replacement” and “substitution” may occur at arbitrary position(s).

In the present application, the short straight line(s) on one side or both sides of the group structure represent the access bond and do not represent methyl, for example, the short straight line on the right side of

and the short straight lines on both sides of

In the present application, halogen comprises fluorine, chlorine, bromine, iodine and the like.

In the compound of general formula I of the present application, ring

is of the five-numbered O-containing heterocycle structure or five-numbered S-containing heterocycle structure. Compared with the existing art in which ring

is five-membered carbocycle, the compound of general formula I of the present application has a larger dielectric constant perpendicular to the molecular axis ε_⊥, which is more beneficial to improve the ratio of perpendicular dielectric to the absolute value of dielectric ε_⊥/|Δε| of the liquid crystal composition, while maintaining the dielectric anisotropy constant, thus achieving the technical effect of improving the transmittance of the liquid crystal composition. In addition, the compound of the general formula I of the present application also has a larger average elastic constant K_ave, such that the liquid crystal display device including the liquid crystal composition of the present application has a smaller amount of light leakage and a higher contract in the Off state.

It is also surprisingly discovered in the present application that, in the compound of general formula I, Z₁ is of alkoxyene or thioalkylene structure, as compared with the technical solution in which Z₁ represents linear alkylene, the compound of general formula I exhibits a stronger overall conjugation effect, and both the ratio of perpendicular dielectric to the absolute value of dielectric ε_⊥/|Δε| and average elastic constant K_ave are significantly improved after the synergistic interaction between the intramolecular groups, which is more beneficial to achieving the effects of high transmittance and high contrast of the present application.

In an optional embodiment of the present application, n represents 0.

In an optional embodiment of the present application, both L₁ and L₂ represent —F.

In an optional embodiment of the present application, X represents —O— or —S—.

In an optional embodiment of the present application, the liquid crystal composition contains at least one compound of general formula I in which X represents —O—; optionally, the liquid crystal composition contains at least one compound of general formula I in which X represents —O— and at least one compound of general formula I in which X represents —S—.

In an optional embodiment of the present application, a represents an integer from 0 to 3, for example, 0, 1, 2 or 3; further optionally, a represents an integer from 1 to 3; optionally, a represents 1.

In an optional embodiment of the present application, R represents C_1-12 (for example, C₁, C₂, C₃, C₄, C₅, C₆, C₈, C₁₀ or C₁₁, etc.) linear or branched alkyl, or one or at least two nonadjacent —CH₂— in the C_1-12 (for example, C₁, C₂, C₃, C₄, C₅, C₆, C₈, C₁₀ or C₁₁, etc.) linear or branched alkyl may be respectively and independently replaced by —O— or —S—.

In an optional embodiment of the present application, R represents C_1-12 (for example, C₁, C₂, C₃, C₄, C₅, C₆, C₈, C₁₀ or C₁₁, etc.) linear alkyl or alkoxy.

In an optional embodiment of the present application, R_x represents —H, C_1-12 (for example, C₁, C₂, C₃, C₄, C₅, C₆, C₈, C₁₀ or C₁₁, etc.) linear or branched alkyl.

In an optional embodiment of the present application, R_x represents —H or C_1-6 linear alkyl.

In an optional embodiment of the present application, the compound of general formula I comprises 0.1-40%, for example 0.2%, 0.5%, 0.8%, 1%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 37% or 39%, etc., of the total weigh of the liquid crystal composition; optionally, the compound of general formula I comprises 1-30% of the total weight of the liquid crystal composition.

In an optional embodiment of the present, the compound of general formula II meets at least one of the following conditions a)˜c):

• • a) R₁ represents C_2-10 (for example, C₂, C₃, C₄, C₅, C₆, C₈, C₉ or C₁₀) alkenyl or alkenoxy;
  • b) when m represents 1 or 2, at least one ring

represents

• • c) when m represents 1 or 2, at least one Z₃ represents —CH═CH— or —C≡C—.

The alkenyl in the present application is optionally a group represented by any one of formula (V1) to formula (V9), optionally formula (V1), formula (V2), formula (V8) or formula (V9). The groups represented by formula (V1) to formula (V9) are as follows:

• • in which, * represents the site through which the above-mentioned group is attached to the compound.

The alkenoxy group in the present application is optionally a group represented by any one of formula (OV1) to formula (OV9), optionally formula (OV1), formula (OV2), formula (OV8) or formula (OV9). The groups represented by formula (OV1) to formula (OV9) are as follows:

• • in which, * represents the site through which the above-mentioned group is attached to the compound.

In an optional embodiment of the present application, the compound of general formula II is selected from a group consisting of the following compounds:

• • in which,
  • R_alkenyl represents C_2-7 (for example, C₂, C₃, C₄, C₅, C₆ or C₇) alkenyl;
  • R₁ and R₂ each independently represents C_1-10 (for example, C₁, C₂, C₃, C₄, C₅, C₆, C₇, C₈, C₉ or C₁₀) linear alkyl or alkoxy, or C_2-10 (for example, C₂, C₃, C₄, C₅, C₆, C₇, C₈, C₉ or C₁₀) linear alkenyl or alkenoxy.

In an optional embodiment of the present application, the compound of general formula II comprises 0.1-50%, for example 0.2%, 0.5%, 0.8%, 1%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 37%, 39%, 40%, 42%, 45%, 47% or 49%, etc., of the total weight of the liquid crystal composition; optionally, the compound of general formula II comprises 1-45% of the total weight of the liquid crystal composition, optionally, the compound of general formula II comprises 5-43% of the total weight of the liquid crystal composition.

In an optional embodiment of the present application, the liquid crystal composition further includes one or at least two compound of general formula M

• • in which,
  • R_M1 and R_M2 each independently represents C_1-12 (for example, C₁, C₂, C₃, C₄, C₅, C₆, C₈, C₁₀ or C₁₁, etc.) linear or branched alkyl,

one or at least two nonadjacent —CH₂— in the C_1-12 linear or branched alkyl may be respectively and independently replaced by —CH═CH—, —C≡C—, —O—, —CO—, —CO—O— or —O—CO—;

ring

ring

and ring

each independently represents

one or at least two —CH₂— in

may be replaced by —O—, at most one —H in

may be substituted by halogen;

• • Z_M1 and Z_M2 each independently represents single bond, —CO—O—, —O—CO—, —CH₂O—, —OCH₂—, —CH═CH—, —C≡C—, —CH₂CH₂—, —(CH₂)₄—, —CF₂O—, —OCF₂— or —CF₂CF₂—;
  • n_M1 represents 0, 1, 2 or 3, wherein when n_M1=2 or 3, ring

is same or different, Z_M2 is same or different.

In an optional embodiment of the present application, R_M1 and R_M2 each independently represents C_1-10 (for example, C₁, C₂, C₃, C₄, C₅, C₆, C₈, C₉ or C₁₀) linear alkyl, C_1-9 (for example, C₁, C₂, C₃, C₄, C₅, C₆, C₈ or C₉) linear alkoxy or C_2-10 (for example, C₂, C₃, C₄, C₅, C₆, C₈, C₉ or C₁₀) linear alkenyl.

Optionally, R_M1 and R_M2 each independently represents C_1-8 linear alkyl, C_1-7 linear alkoxy or C_2-8 linear alkenyl.

Optionally, R_M1 and R_M2 each independently represents C_1-5 linear alkyl, C_1-4 linear alkoxy or C_2-5 linear alkenyl.

In an optional embodiment of the present application, any one of R_M1 and R_M2 is C_2-5 linear alkenyl, and the other is C_1-5 linear alkyl.

In an optional embodiment of the present application, any one of R_M1 and R_M2 is C_1-5 linear alkyl, and the other is C_1-5 linear alkyl or C_1-4 linear alkoxy; optionally, both R_M1 and R_M2 are each independently C_1-5 linear alkyl.

In an optional embodiment of the present application, the compound of general formula M is selected from a group consisting of the following compounds:

Wherein, R_M1 and R_M2 each independently represents C_1-12 (for example, C₁, C₂, C₃, C₄, C₅, C₆, C₈, C₁₀ or C₁₁, etc.) linear or branched alkyl, or one or at least two nonadjacent —CH₂— in the C_1-12 linear or branched alkyl may be respectively and independently replaced by —CH═CH— or —O—.

Optionally, R_M1 and R_M2 each independently represents C_1-10 (for example, C₁, C₂, C₃, C₄, C₅, C₆, C₈, C₉ or C₁₀) linear alkyl, C_2-10 (for example, C₂, C₃, C₄, C₅, C₆, C₈, C₉ or C₁₀) linear alkenyl or C_1-9 (for example, C₁, C₂, C₃, C₄, C₅, C₆, C₈ or C₉) linear alkoxy.

Optionally, the compound of general formula M comprises 1-70%, for example, 2%, 4%, 6%, 8%, 10%, 13%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 67% or 69%, etc., of the total weight of the liquid crystal composition.

In order to adjust the properties of the liquid crystal composition in terms of clearing point, viscosity, and low-temperature storage stability and the like to enable the obtained liquid crystal display device to have great application value in addition to excellent performance in terms of transmittance and color performance, the components of the liquid crystal composition need to be adjusted. Specifically, the content of the compound of general formula M in which ring

represents

is 10% to 50%; optionally, the content of the compound in general formula M in which ring

represents

is 20% to 45%, relative to the total weight of the liquid crystal composition of the present application.

As for the content of the compound of general formula M, a high lower limit value and a high upper limit value may be selected when it is necessary to keep the viscosity of the liquid crystal composition of the present application lower and the response time thereof shorter; further, a high lower limit value and a high upper limit value may be selected when it is necessary to keep the clearing point of the liquid crystal composition of the present application higher and the temperature stability good; and, when in order to keep the driving voltage lower and make the absolute value of the dielectric anisotropy become large, it is optional to make the lower limit value become low and the upper limit value become low.

In the case where reliability is a priority, optionally, R_M1 and R_M2 are each independently alkyl; in the case where reducing the volatility of the compound is a priority, optionally, R_M1 and R_M2 are each independently alkoxy; and in the case where reducing viscosity is a priority, optionally, at least one of R_M1 and R_M2 is alkenyl.

In an optional embodiment of the present application, in order to further reduce the viscosity of the liquid crystal composition, the liquid crystal composition optionally includes one or more compound of general formula M1 in which R_M1 and/or R_M2 is n-propyl:

In an optional embodiment of the present application, the liquid crystal composition further includes one or at least two compound of general formula N

• • in which,
  • R_N1 and R_N2 each independently represents C_1-12 (for example, C₁, C₂, C₃, C₄, C₅, C₆, C₈, C₁₀ or C₁₁, etc.) linear or branched alkyl,

one or at least two nonadjacent —CH₂— in the C_1-12 linear or branched alkyl may be respectively and independently replaced by —O—, —CO—, —CO—O— or —O—CO—, one or least two —H in the C_1-12 linear or branched alkyl,

or may be respectively and independently substituted by —F or —Cl;

ring

or ring

each independently represents

one or more —CH₂— in

may be replaced by —O—; one or at least two —H in

may be substituted by —F or —Cl, one or at least two —CH═ within the ring may be replaced by —N═;

• • Z_N1 and Z_N2 each independently represents single bond, —CO—O—, —O—CO—, —CH₂O—, —OCH₂—, —CH₂CH₂—, —(CH₂)₄—, —CF₂O—, —OCF₂— or —CF₂CF₂—;
  • L_N1 and L_N2 each independently represents —H or methyl;
  • n_N1 represents 0, 1, 2 or 3, n_N2 represents 0 or 1, and 0≤n_N1+n_N2≤3, wherein when n_N1=2 or 3, ring

is same or different, Z_N1 is same or different;

In an optional embodiment of the present application, R_N1 and R_N2 each independently represents C_1-8 (for example, C₁, C₂, C₃, C₄, C₅, C₆, C₇ or C₈) linear or branched alkyl or alkoxy, further optionally, R_N1 and R_N2 are each independently C_1-5 linear or branched alkyl or alkoxy.

In an optional embodiment of the present application, ring

and ring

each independently represents

In an optional embodiment of the present application, the compound of general formula N is selected by a group consisting of the following compounds:

• • in which,
  • R_N1 represents C_1-5 (for example, C₁, C₂, C₃, C₄ or C₅) linear or branched alkyl, and R_N2 represents C_1-4 (for example, C₁, C₂, C₃ or C₄) linear or branched alkoxy.

In an optional embodiment of the present application, the compound of general formula N may be selected from a group consisting of the compounds of general formula N2, general formula N5 and general formula N13.

Optionally, the compound of general formula N comprises 1-75%, for example 2%, 4%, 6%, 8%, 10%, 13%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 67%, 70%, 72% or 74%, etc., of the total weight of the liquid crystal composition.

As for the content of the compound of general formula N, a low lower limit value and a low upper limit value may be selected when it is necessary to keep the response time of the liquid crystal display device of the present application shorter; further, a low lower limit value and a low upper limit value may be selected when it is necessary to keep the operating temperature range of the liquid crystal display device of the present application wider; in addition, when in order to keep the driving voltage of the liquid crystal composition of the present application low and make the absolute value of the dielectric anisotropy become large, it is optional to make the lower limit value of the content become high and the upper limit value become high.

In an optional embodiment of the present application, one or more other additives known to those skilled in the art and described in literature may be added to the liquid crystal composition.

In addition, additives such as antioxidants, light stabilizers and the like used in the liquid crystal composition of the present application may be selected from the following substances:

• • in which, n represents a positive integer of 1-12.

Optionally, the stabilizer is selected from the stabilizers as shown below.

In an optional embodiment of the present application, the stabilizer comprises 0-5% of the total weight of the liquid crystal composition; optionally, the stabilizer comprises 0-1% of the total weight of the liquid crystal composition; more optionally, the stabilizer comprises 0.01-0.1% of the total weight of the liquid crystal composition.

In another aspect, the present application provides a liquid crystal display device comprising the liquid crystal composition described above.

Optionally, the liquid crystal display device is an IPS mode liquid crystal display device, an FFS mode liquid crystal display device or a VA mode liquid crystal display device.

The present application has the following beneficial effects relative to the existing art:

As compared with the existing art, through the structure optimization of the compound of general formula I and the synergistic interaction with the compound of general formula II containing a carbon-carbon unsaturated bond in the liquid crystal compositions provided by the present application, the liquid crystal composition of the present application has a larger dielectric constant perpendicular to the molecular axis ε_⊥, a larger ratio of perpendicular dielectric to a absolute value of dielectric ε_⊥ε_⊥/|Δε| and a larger average elastic constant K_ave, while maintaining substantially equivalent clearing point, optical anisotropy and dielectric anisotropy, such that the liquid crystal display device including such liquid crystal composition has a higher transmittance and a higher contrast, exhibits a better display effect, and has high application value in liquid crystal displays of IPS mode, FFS mode, and VA mode.

DETAILED EMBODIMENTS

The technical solutions of the present application will be further described below in conjunction with specific embodiments. Those skilled in the art should understand that the following examples are exemplary embodiments of the present application, which are only used to illustrate and help understand the present application and should not be construed as limitations to the present application. Other combinations and various modifications within the conception of the present application are possible without departing from the subject matter or scope of the present application.

In the present application, unless otherwise specified, the proportions mentioned in the present application are weight ratios, and temperatures are Celsius temperatures.

For the convenience of the expression, the group structures of the liquid crystal compositions in the following Examples are represented by the codes listed in Table 1:

TABLE 1
Codes of the group structures of the liquid crystal compounds
Unit structure of group	Code	Name of group
	C	1,4-cyclohexylidene
	L	1,4-cyclohexenylene
	P	1,4-phenylene
	G	2-fluoro-1,4-phenylene
	W	2,3-difluoro-1,4-phenylene
	B(O)	4,6-difluoro-dibenzo[b,d]furan- 3,7-diyl
	B(S)	4,6-difluoro-dibenzo[b,d]thio- phene-3,7-diyl
	THF(2,5)	tetrahydrofuran-2,5-diyl
	THT(2,5)	tetrahydrothiophene-2,5-diyl
	THF	tetrahydrofuran-2-yl
	THF(3)	tetrahydrofuran-3-yl
	DHF(1)	4,5-dihydrofuran-2-yl
	THT	tetrahydrothiophene-2-yl
	THT(3)	tetrahydrothiophene-3-yl
	DHT(1)	4,5-dihydrothiophene-2-yl
—CH2CH2—	2	ethyl bridge bond
—CH2CH2CH2—	3	propyl bridge group
—CH2O—	1O	methyleneoxy
—F—	F	fluorine substituent
—O—	O	oxygen bridge group
—S—	S	sulfur bridge group
—CnH2n+1	n (n represents a	alkyl
	positive integer of
	1-12)
—C≡C— or —C≡CH	T	ethynyl
—CH=CH— or —CH=CH2	V	ethenyl

Take the compound with the following structural formula as an example:

Represented by the codes listed in Table 1, this structural formula can be expressed as nCCGF, n in the code represents the number of the carbon atoms of the alkyl group on the left, for example, n is “3”, meaning that the alkyl is —C₃H₇; C in the code represents 1,4-cyclohexylidene, G represents 2-fluoro-1,4-phenylene, F represents fluorine substituent.

The abbreviated codes of the test items in the following Examples are as follows:

• • Cp clearing point (nematic-isotropy phases transition temperature, ° C.)
  • Δεdielectric anisotropy (1 KHz, 25° C.)
  • ε_⊥ dielectric constant perpendicular to the molecular axis (1 KHz, 25° C.)
  • ε_⊥/|Δε| ratio of perpendicular dielectric constant to the absolute value of dielectric constant
  • Δn optical anisotropy (light wavelength 589 nm, 25° C.)
  • K_ave average elastic constant
  • T (%) Transmittance (DMS 505, cell gap 3.5 m) in which,
  • Cp: measured by using a melting point apparatus;
  • Δε: Δε=ε_|-ε_⊥, wherein ε_| is a dielectric constant parallel to the molecular axis, ε_⊥ is a dielectric constant perpendicular to the molecular axis, and the test conditions are: 25° C., 1 KHz, and a TN90 test cell with a cell gap of 7 μm;
  • Δn: measured by using Abbe refractometer under the light source of sodium lamp (589 nm) and at 25° C.;
  • K_ave=⅓ (K₁₁+K₂₂+K₃₃), and Ki, K₂₂, and K₃₃ were calculated by testing the C—V curve of liquid crystal using the LCR instrument and anti-parallel friction cells with the test conditions: a 7 m anti-parallel friction cell and V=0.1˜20V.

Test conditions of transmittance: the V-T curve of a dimming device, which was a negative IPS-type test cell with a cell gap of 3.5 μm, was tested by using DMS 505 photoelectric comprehensive tester, and the T_max value in the V-T curve was the transmittance of the liquid crystal material.

Each component adopted in the following Examples can be synthesized by well-known methods or can be obtained commercially. These synthesis techniques are conventional, and the obtained liquid crystal compositions have been tested and proved to meet the standards of electronic compounds.

Liquid crystal compositions were prepared according to the proportions of liquid crystal compositions specified in the following Examples. The preparation of the liquid crystal compositions was carried out according to the conventional methods in the art, such as heating, ultrasonic wave, suspension, and the like, and by mixing components according to specified proportions.

Comparative Example 1

A liquid crystal composition, whose components and performance parameters are shown in Table 2.

TABLE 2
Components and performance parameters
of the liquid crystal composition
	Weight	General	Performance
Component code	percentage	formula code	parameters
3CWO2	10.5	N2	Cp	94
3CLWO2	9	II-5	Δn	0.11
3LCWO2	9	II-6	Δ∈	−3.9
5CCWO2	9.5	N5	∈⊥	6.7
5CWO2	10	N2	Kave	12.7
3CWO4	9	N2	T	13.3%
2PWP3	3	N13	∈⊥/|Δ∈|	1.72
2CPWO2	7	N11
3CPWO2	7	N11
THF2B(O)O6	5
3CCV	15	M1
VCCP1	3	M12
3CCP1	3	M12
Total	100

Comparative Example 2

A liquid crystal composition, whose components and performance parameters are shown in Table 3.

TABLE 3
Components and performance parameters
of the liquid crystal composition
	Weight	General	Performance
Component code	percentage	formula code	parameters
3CWO2	10.5	N2	Cp	94
3CLWO2	9	II-5	Δn	0.109
3LCWO2	9	II-6	Δ∈	−3.9
5CCWO2	9.5	N5	∈⊥	6.6
5CWO2	10	N2	Kave	12.6
3CWO4	9	N2	T	13.2%
2PWP3	3	N13	∈⊥/|Δ∈|	1.69
2CPWO2	7	N11
3CPWO2	7	N11
C(5)1OB(O)O6	5
3CCV	15	M1
VCCP1	3	M12
3CCP1	3	M12
Total	100

Example 1

A liquid crystal composition, whose components and performance parameters are shown in Table 4.

TABLE 4
Components and performance parameters
of the liquid crystal composition
	Weight	General	Performance
Component code	percentage	formula code	parameters
3CWO2	10.5	N2	Cp	94
3CLWO2	9	II-5	Δn	0.111
3LCWO2	9	II-6	Δ∈	−4
5CCWO2	9.5	N5	∈⊥	7
5CWO2	10	N2	Kave	13.2
3CWO4	9	N2	T	14.2%
2PWP3	3	N13	∈⊥/|Δ∈|	1.75
2CPWO2	7	N11
3CPWO2	7	N11
THF1OB(O)O6	5	I
3CCV	15	M1
VCCP1	3	M12
3CCP1	3	M12
Total	100

Example 2

A liquid crystal composition, whose components and performance parameters are shown in Table 5.

TABLE 5
Components and performance parameters
of the liquid crystal composition
	Weight	General	Performance
Component code	percentage	formula code	parameters
3LWO2	10	II-3	Cp	96
3CCWO2	5	N5	Δn	0.112
3LCWO2	9	II-6	Δ∈	−4
3CLWO2	9	II-5	∈⊥	7.3
5LWO2	10	II-3	Kave	13.6
3CWO4	9	N2	T	14.7%
2PWP3	3	N13	∈⊥/|Δ∈|	1.83
2CPWO2	4	N11
3LPWO2	5	II-7
2THF(2,5)1OB(S)O4	6	I
THF1OB(O)O6	5	I
3CCV	17	M1
VCCP1	4	M12
3CCP1	4	M12
Total	100

Example 3

A liquid crystal composition, whose components and performance parameters are shown in Table 6.

TABLE 6
Components and performance parameters
of the liquid crystal composition
	Weight	General	Performance
Component code	percentage	formula code	parameters
3CWO2	10	N2	Cp	95
2CCWO2	9	N5	Δn	0.114
3CCWO2	9	N5	Δ∈	−4
5CCWO2	10	N5	∈⊥	7.2
5CWO2	7	N2	Kave	13.3
3CWO4	7	N2	T	14.3%
VCPWO2	4	II-2	∈⊥/|Δ∈|	1.8
1VCPWO2	5	II-2
3CPWO2	6	N11
THF2SB(S)O6	4	I
THF1OB(O)S4	5	I
DHT(1)1OB(O)O6	3	I
3CCV	15	M1
VCCP1	3	M12
3CCP1	3	M12
Total	100

Example 4

A liquid crystal composition, whose components and performance parameters are shown in Table 7.

TABLE 7
Components and performance parameters
of the liquid crystal composition
	Weight	General	Performance
Component code	percentage	formula code	parameters
3CWO2	10	N2	Cp	95
2CCWO2	8	N5	Δn	0.116
3CCWO2	7	N5	Δ∈	−4.2
5CCWO2	7	N5	∈⊥	7.5
5CWO2	9	N2	Kave	13.5
3CWO4	8	N2	T	14.7%
3PTWO2	5	II-9	∈⊥/|Δ∈|	1.79
3CPTWO2	4	II-10
THF2OB(O)S6	3	I
THF3OB(S)O4	5	I
DHF(1)1OB(O)O6	3	I
THF1OB(O)O4	5	I
THT1OB(O)O6	5	I
3CCV	15	M1
VCCP1	3	M12
3CCP1	3	M12
Total	100

Example 5

A liquid crystal composition, whose components and performance parameters are shown in Table 8.

TABLE 8
Components and performance parameters
of the liquid crystal composition
	Weight	General	Performance
Component code	percentage	formula code	parameters
3CWO2	6	N2	Cp	94
3CCWO2	6	N5	Δn	0.113
3CCWO2	7	N5	Δ∈	−4.3
3LCWO2	5	II-6	∈⊥	7.5
3CWO2	6	N2	Kave	13.5
5CWO2	5	N2	T	14.7%
3CWO4	7	N2	∈⊥/|Δ∈|	1.74
2CPWO2	7	N11
3CPWO2	7	N11
THF2OB(O)S6	5	I
THF3OB(S)O4	5	I
2THT(2,5)1OB(O)O6	3	I
THF(3)1OB(O)O4	3	I
THT1OB(O)O6	5	I
3CCV	15	M1
VCCP1	2	M12
3CCP1	2	M12
3CPO2	4	M2
Total	100

Example 6

A liquid crystal composition, whose components and performance parameters are shown in Table 9.

TABLE 9
Components and performance parameters
of the liquid crystal composition
	Weight	General	Performance
Component code	percentage	formula code	parameters
3CWO2	4	N2	Cp	97
3CWO4	5	N2	Δn	0.121
5CWO2	5	N2	Δ∈	−4.3
5CWO4	5	N2	∈⊥	7.8
VCPWO2	7	II-2	Kave	13.9
1VCPWO2	8	II-2	T	15.3%
1V2CPWO3	8	II-2	∈⊥/|Δ∈|	1.81
V2CPWO2	7	II-2
THF2OB(O)S6	5	I
THF3OB(S)O4	5	I
2THT(2,5)1OB(O)O6	3	I
THF1SB(O)O4	5	I
THT1OB(O)O6	5	I
THT(3)OB(O)O5	3	I
3CCV	19	M1
VCCP1	3	M12
3CPO2	3	M2
Total	100

As can be seen from the comparison between Comparative Examples 1-2 and Example 1 as shown in above tables, through the structure optimization of the compound of general formula I and the synergistic interaction with the compound of general formula II containing a carbon-carbon unsaturated bond in the present application, the liquid crystal composition included in the present application has a larger dielectric constant perpendicular to the molecular axis ε_⊥ a larger ratio of perpendicular dielectric to a absolute value of dielectric ε_⊥/|Δε| and a larger average elastic constant K_ave, while maintaining substantially equivalent clearing point, optical anisotropy and dielectric anisotropy, such that the liquid crystal display device including such liquid crystal composition has a higher transmittance and a higher contrast.

As can be seen from Examples 1-6 described above, the liquid crystal compositions of the present application all have high clearing point, large optical anisotropy, large dielectric anisotropy, larger dielectric constant perpendicular to the molecular axis ε_⊥, larger ratio of perpendicular dielectric to a absolute value of dielectric ε_⊥/|Δε| and larger average elastic constant K_ave, and the liquid crystal display devices including these liquid crystal compositions all have the effects of good transmittance and high contrast. The liquid crystal compositions of the present application can meet the requirements of the liquid crystal display device on low power consumption and good display effect and have high application value in liquid crystal displays of IPS mode, FFS mode, and VA mode.

The applicant has stated that although the liquid crystal composition containing a dibenzo derivative and the liquid crystal display device of the present application are illustrated through the Examples described above in the present application, the present application is not limited to the processes and steps described above, which means that the implementation of the present application does not necessarily depend on the processes and steps described above.

The above embodiments are merely illustrative of the technical concepts and the features of the present application, and the purpose thereof is to enable those familiar with the art to understand the content of the present application and implement the present application, and should not be used to limit the protection scope of the present application.

Claims

1. A liquid crystal composition containing a dibenzo derivative, including at least one compound of general formula I and at least one compound of general formula II:

2. The liquid crystal composition according to claim 1, wherein n represents 0.

3. The liquid crystal composition according to claim 1, wherein both L1 and L2 represent —F.

4. The liquid crystal composition according to claim 1, wherein X represents —O— or —S—; andfurther wherein:a represents an integer of 0-3; orR represents C1-12 linear alkyl, C3-12 branched alkyl, or one or at least two nonadjacent —CH2— in the C1-12 linear alkyl, C3-12 branched alkyl may be respectively and independently replaced by —O— or —S—; orRx represents —H, C1-12 linear alkyl, C3-12 branched alkyl; orthe liquid crystal composition contains at least one compound of general formula I in which X represents —O—; orthe liquid crystal composition contains at least one compound of general formula I in which X represents —O— and at least one compound of general formula I in which X represents —S—.

5. The liquid crystal composition according to claim 1, wherein the compound of general formula I comprises 0.1-40% of the total weight of the liquid crystal composition.

6. The liquid crystal composition according to claim 1, wherein the compound of general formula II meets at least one of following conditions a), b), or c):a) R1 represents C2-10 alkenyl or alkenoxy;b) when m represents 1 or 2, at least one ring

7. The liquid crystal composition according to claim 1, wherein the compound of general formula II comprises 0.1-50% of the total weight of the liquid crystal composition.

8. The liquid crystal composition according to claim 1, wherein the liquid crystal composition further includes one or at least two compound of general formula M

9. The liquid crystal composition according to claim 1, wherein the liquid crystal composition further includes one or at least two compound of general formula N

10. A liquid crystal display device including the liquid crystal composition of claim 1; wherein the liquid crystal display device is an IPS mode liquid crystal display device, an FFS mode liquid crystal display device or a VA mode liquid crystal display device.

11. The liquid crystal composition according to claim 6, wherein the compound of general formula II is selected from a group consisting of the following compounds:

12. The liquid crystal composition according to claim 8, wherein the compound of general formula M is selected from a group consisting of the following compounds:

13. The liquid crystal composition according to claim 12, wherein:RM1 and RM2 each independently represents C1-10 linear alkyl, C2-10 linear alkenyl or C1-9 linear alkoxy; orthe liquid crystal composition includes one or at least two compound of general formula M1 in which RM1 and/or RM2 is n-propyl.

14. The liquid crystal composition according to claim 9, wherein the compound of general formula N is selected from a group consisting of the following compounds: