Liquid crystal display device for color display

Abstract

The invention provides a liquid crystal display device for color display. The liquid crystal display device is used for color display. The array substrate sequentially comprises a first substrate, a first conducting layer, a first orientation layer, a first guest-host liquid crystal composition layer, a second orientation layer, a second conducting layer, a second substrate, a third substrate, a third conducting layer, a third orientation layer, a second guest-host liquid crystal composition layer, a fourth orientation layer, a fourth conducting layer and a fourth substrate. Wherein the components of the first guest-host liquid crystal composition layer and the second guest-host liquid crystal composition layer can be the same or different, each of the first guest-host liquid crystal composition layer and the second guest-host liquid crystal composition layer independently comprises at least one liquid crystal composition with negative dielectric anisotropy, at least one dichroic dye and at least one chiral agent, and the dichroic ratio of the dichroic dye is greater than 10. The liquid crystal display device can achieve display of different colors such as black, orange red, blue, red, cyan, yellow and transparency, has a good display effect, and keeps a normally white state under the condition that driving voltage is not applied.

Description

Technical Field

[0001] The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device for color display. Background Art

[0002] Liquid crystal display has become the mainstream display technology in the 21st century. Compared with other display technologies, it has the characteristics of thin appearance, low power consumption and low driving voltage, and is easy to achieve the effects of being thin and light, and large-size flat panel display. A liquid crystal display panel is a passive device that does not emit light by itself. Its working principle is to sandwich a liquid crystal medium between two parallel glass substrates. There are many fine vertical and horizontal wires in the two glass substrates. By controlling the voltage, the arrangement direction of liquid crystal molecules can be changed, and the light emitted by the backlight module is refracted to generate corresponding images. Most of the current liquid crystal elements are mainly the twisted nematic (TN) type suitable for low-line driving and the super-twisted nematic (STN) type suitable for high-line driving. However, since these elements use polarizing plates, there is a disadvantage of low light utilization efficiency.

[0003] The guest-host liquid crystal display element is currently a type of display element that can achieve high light utilization efficiency without a polarizing plate. Especially in the case of a reflective display device without a backlight, light-emitting display can be achieved. The so-called guest-host liquid crystal is to dissolve a dichroic dye (guest) in a liquid crystal (host). The dye can absorb visible light of different wavelengths, making the liquid crystal device present different colors, thereby realizing color display. Generally, the dichroic dye has anisotropy in the absorption of visible light along the long axis and short axis directions of the molecule. When the vibration direction of the incident light is consistent with the long axis direction of the dye, the light is absorbed; when the vibration direction of the incident light is perpendicular to the long axis direction of the dye, the light can pass through, so that the dye has two states of absorption state and non-absorption state during the use of the device. The dye molecules can be oriented parallel to the arrangement of the liquid crystal molecules. When an electric field acts, the dye molecules will change with the change of the orientation of the liquid crystal molecules, so that the absorption of visible light by the dye changes.

[0004] Chinese Patent CN103744211A discloses a technical solution including a three-layer liquid crystal cell. It uses a dichroic dye to absorb light of some colors, and then realizes color display. It does not need to set a polarizing plate and a color filter, which reduces the manufacturing cost of the liquid crystal display panel to a certain extent, reduces the requirement for backlight brightness, and improves the light transmittance and light efficiency. However, the superposition use of the three-layer liquid crystal cell will weaken the light passing through it to a certain extent, resulting in a decrease in light efficiency and an increase in manufacturing cost. The dichroism of the dye used is generally less than 10, and the solubility of the dye molecules in the liquid crystal is generally less than 5%, which makes the transmittance of the dark state still relatively high and the contrast relatively low, and cannot meet the requirements of high-contrast color display today.

[0005] Chinese patent CN103235445A discloses a reflective liquid crystal display device, which includes a dye liquid crystal composition layer, a reflective material is arranged between the dye liquid crystal composition layer and the lower substrate, and the color of the dye in the liquid crystal composition and the color of the reflective material form a complementary relationship, so that the reflective liquid crystal display device has a higher reflectivity and a higher contrast, and has a simple structure and low cost. However, this display mode can only realize the display of a single color, and the reflective brightness and transmittance cannot be adjusted, and the application scenarios are limited.

[0006] In the application of liquid crystal display devices, the contrast has a critical impact on the visual effect. Generally speaking, the greater the contrast, the clearer and more eye-catching the image, and the brighter the color; on the contrary, if the contrast is small, the whole picture will be gray. High contrast can greatly improve the clarity, detail and grayscale performance of the image. High-contrast products have advantages in black and white contrast, clarity, integrity and other aspects. Contrast also has a great impact on the display effect of dynamic video. Since the light and dark conversion in dynamic images is relatively fast, the higher the contrast, the easier it is for the human eye to distinguish such a conversion process.

[0007] Normally white mode and normally black mode are two commonly used display modes in LCD monitors. In normally white mode, the display screen background is white, and the text and images are black, while in normally black mode, the display screen background is black, and the text and images are white. In normally white mode, the white background can provide more light and reflect more light, so the text and images are clearer against the background. In addition, the display background brightness is higher in normally white mode, which can reduce visual fatigue of the eyes, especially when used in brighter environments, which can reduce eye rotation and reflection, and is suitable for use in scenarios such as text processing and web browsing.

[0008] Therefore, how to obtain a high-contrast normally white color display liquid crystal display device is a technical problem to be solved urgently in the art. Summary of the invention

[0009] Purpose of the invention: The purpose of the present invention is to provide a double-layered liquid crystal display device for color display, which can realize different color changes (black, orange-red, blue, red, cyan, yellow and transparent, etc.) by driving voltage or the selection and deployment of dyes, and has a smaller dark state transmittance in the dark state and a higher bright state transmittance in the bright state, that is, it has a better display effect while realizing the display of multiple different colors, and maintains a normally white state without applying a driving voltage, which is suitable for use in scenarios such as text processing and web browsing.

[0010] Technical solution: The present invention provides a double-layer stacked liquid crystal display device, which sequentially includes a first substrate, a first conductive layer, a first alignment layer, a first guest-host liquid crystal composition layer, a second alignment layer, a second conductive layer, a second substrate, a third substrate, a third conductive layer, a third alignment layer, a second guest-host liquid crystal composition layer, a fourth alignment layer, a fourth conductive layer, and a fourth substrate from the direction of light entry to light exit; wherein, the components of the first guest-host liquid crystal composition layer and the second guest-host liquid crystal composition layer may be the same or different, and each independently contains at least one liquid crystal composition with negative dielectric anisotropy, at least one (for example, two, three or more) dichroic dyes, and at least one (for example, two, three or more) chiral agent, and the dichroic ratio of the dichroic dye is greater than 10 (for example, 10, 10.2, 10.4, 10.5, 10.6, 10.8, 11, 11.2, 11.4, 11.5, 11.6, 11.8, 12, 12.2, 12.4, 12.5, 12.6, 12.8, 13, 13.2, 13.4, 13.5, 13.6, 13.8, 14, 14.2, 14.4, 14.5, 14.6, 14.8, 15, 15.2, 15.4, 15.5, 15.6, 15.8, 16, 16.2, 16.4, 16.5, 16.6, 16.8, 17, 17.2, 17.4, 17.6, 17.8, 18, 18.2, 18.4, 18.6, 18.8, 19, 19.2, 19.4, 19.6, 19.8, 20, 20.2, 20.4, 20.6, 20.8, 21, 21.2, 21.4, 21.6, 21.8, 22, 22.2, 22.4, 22.6, 22.8, 23, 23.2, 23.4, 23.6, 23.8, 24, 24.2, 24.4, 24.6, 24.8, 25, 25.2, 25.4, 25.6, 25.8, 26, 26.2, 26.4, 26.6, 26.8, 27, 27.2, 27.4, 27.6, 27.8, 28, 28.2, 28.4, 28.6, 28.8, 29, 29.2, 29.4, 29.6, 29.8, 30).

[0011] In some embodiments of the present invention, the liquid crystal composition with negative dielectric anisotropy of the present invention contains at least one compound of general formula N:

[0012]

[0013] Wherein,

[0014] R N1 and R N2Each independently represents a straight-chain alkyl group having 1 to 12 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12) carbon atoms, a branched-chain alkyl group having 3 to 12 (e.g., 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12) carbon atoms, wherein one or more non-adjacent -CH2- groups in the straight-chain alkyl group having 1 to 12 carbon atoms or the branched-chain alkyl group having 3 to 12 carbon atoms may be independently replaced by -CH=CH-, -C≡C-, -O-, -CO-, -CO-O-, or -O-CO-;

[0015] Ring and Ring Each independently represents wherein one or more -CH2- groups therein may be replaced by -O-, and one or at most two single bonds in the ring may be replaced by double bonds, and wherein one or more -H groups therein may be independently replaced by -F, -Cl, or -CN, and one or more -CH= in the ring may be replaced by -N=;

[0016] Z N1 and Z N2 Each independently represents a single bond, -CO-O-, -O-CO-, -CH2O-, -OCH2-, -CH=CH-, -C≡C-, -CH2CH2-, -CF2CF2-, -(CH2)4-, -CF2O-, or -OCF2-;

[0017] L N1 and L N2 Each independently represents -H, an alkyl group having 1 to 3 (e.g., 1, 2, or 3) carbon atoms, or a halogen; and

[0018] n N1 represents 0, 1, 2, or 3, n N2 represents 0 or 1, and 0 ≤ n N1 +n N2 ≤ 3,, where when n N1 = 2 or 3, Ring may be the same or different, Z N1 may be the same or different.

[0019] In some embodiments of the present invention, L N1 and L N2 both represent -H.

[0020] In some embodiments of the present invention, the compounds of formula N are selected from the group consisting of the following compounds:

[0021]

[0022]

[0023]

[0024]

[0025] and

[0026]

[0027] In some embodiments of the present invention, preferably, R N1 and R N2 each independently represents a straight-chain alkyl group having 1-10 carbon atoms, a branched-chain alkyl group having 3-10 carbon atoms, a straight-chain alkoxy group having 1-9 carbon atoms, a branched-chain alkoxy group having 3-9 carbon atoms, a straight-chain alkenyl group having 2-10 carbon atoms, or a branched-chain alkenyl group having 3-10 carbon atoms; more preferably, R N1 and R N2 each independently represents a straight-chain alkyl group having 1-8 carbon atoms, a straight-chain alkoxy group having 1-7 carbon atoms, or a straight-chain alkenyl group having 2-8 carbon atoms.

[0028] In some embodiments of the present invention, the weight percentage of the compound of formula N in the negative dielectric anisotropy liquid crystal composition is 0.1%-95% (including any value or sub-range within this range), for example, 0.1%, 0.5%, 1%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 47%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 77%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 95%, or the range between any two of these values; preferably, in order to obtain a smaller Tmin, a larger Tmax, and taking into account a larger CRmax, the weight percentage of the compound of formula N in the negative dielectric anisotropy liquid crystal composition is 80%-95%.

[0029] In some embodiments of the present invention, the compound of general formula N, which accounts for 1% - 94% (including any value or sub-range within this range, e.g., 1%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 47%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 77%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%) of the weight of the liquid crystal composition having negative dielectric anisotropy, contains at least one (e.g., it can be two, three, four, five, six, seven, eight, nine, ten) compound selected from the group consisting of the compounds of general formula N-2, the compounds of general formula N-7, the compounds of general formula N-9, the compounds of general formula N-12, the compounds of general formula N-15, the compounds of general formula N-21, the compounds of general formula N-23, and the compounds of general formula N-32.

[0030] In some embodiments of the present invention, the compound of general formula N, which accounts for 1% - 80% (including any value or sub-range within this range, e.g., 1%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%) of the weight of the liquid crystal composition having negative dielectric anisotropy, contains at least one (e.g., it can be two, three, four, five, six, seven) compound selected from the group consisting of the compounds of general formula N-2 and the compounds of general formula N-9. Preferably, in order to obtain a smaller Tmin, a larger Tmax, and taking into account a larger CRmax, the compounds selected from the group consisting of the compounds of general formula N-2 and the compounds of general formula N-9 account for 60% - 80% of the weight of the liquid crystal composition having negative dielectric anisotropy.

[0031] In some embodiments of the present invention, the liquid crystal composition having negative dielectric anisotropy of the present invention further contains at least one compound of general formula M:

[0032]

[0033] Wherein,

[0034] R M1 and R M2Each independently represents a straight-chain alkyl group having 1 to 12 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12) carbon atoms, a branched-chain alkyl group having 3 to 12 (e.g., 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12) carbon atoms, One or more than two non-adjacent -CH2- in the straight-chain alkyl group having 1 to 12 carbon atoms and the branched-chain alkyl group having 3 to 12 carbon atoms can be independently replaced by -CH=CH-, -C≡C-, -O-, -CO-, -CO-O-, or -O-CO- respectively;

[0035] ring ring and ring Each independently represents wherein One or more -CH2- therein can be replaced by -O-, and one or at most two single bonds in the ring can be replaced by double bonds, At most one -H therein can be substituted by a halogen;

[0036] Z M1 and Z M2 Each independently represents a single bond, -CO-O-, -O-CO-, -CH2O-, -OCH2-, -CH=CH-, -CH2CH2-, or -(CH2)4-; and

[0037] n M represents 0, 1, or 2, where when n M = 2, the rings can be the same or different, and Z M2 can be the same or different.

[0038] In some embodiments of the present invention, the compounds of general formula M are selected from the group consisting of the following compounds:

[0039]

[0040]

[0041]

[0042]

[0043] and

[0044]

[0045] wherein, R M1 and R M2Each independently represents a straight-chain alkyl group having 1 to 12 carbon atoms, a branched-chain alkyl group having 3 to 12 carbon atoms, a straight-chain alkyl group having 1 to 12 carbon atoms, or one or two or more non-adjacent -CH2- in the branched-chain alkyl group having 3 to 12 carbon atoms may be independently replaced by -CH=CH-, -C≡C-, -O-, -CO-, -CO-O- or -O-CO-.

[0046] In some embodiments of the present invention, the compound of general formula M accounts for 0.1% - 50% (including any value or sub-range within this range) of the weight of the negative dielectric anisotropy liquid crystal composition, such as 0.1%, 0.5%, 1%, 2%, 4%, 6%, 8%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 20%, 22%, 23%, 24%, 25%, 26%, 28%, 30%, 32%, 34%, 35%, 36%, 38%, 40%, 42%, 44%, 45%, 46%, 48%, 50%, or the range between any two of these values.

[0047] In some embodiments of the present invention, R M1 and R M2 are preferably each independently a straight-chain alkyl group having 1 to 8 carbon atoms, a straight-chain alkoxy group having 1 to 8 carbon atoms, or a straight-chain alkenyl group having 2 to 8 carbon atoms; R M1 and R M2 are further preferably each independently a straight-chain alkyl group having 1 to 5 carbon atoms, a straight-chain alkoxy group having 1 to 5 carbon atoms, or a straight-chain alkenyl group having 2 to 5 carbon atoms.

[0048] In some embodiments of the present invention, any one of R M1 and R M2 is a straight-chain alkenyl group having 2 to 5 carbon atoms, and the other is a straight-chain alkyl group having 1 to 5 carbon atoms.

[0049] In some embodiments of the present invention, the compound of general formula M comprises at least one (for example, it can be two, three, four, five, six) compound selected from the group consisting of the compound of general formula M-1, the compound of general formula M-14, the compound of general formula M-22, the compound of general formula M-49, and the compound of general formula M-51.

[0050] In some embodiments of the present invention, the compound of general formula M is selected from the group consisting of the following compounds:

[0051]

[0052] and

[0053]

[0054] Among them, R M1 and R M2 are each independently a straight-chain alkyl group having 1-8 (for example, 1, 2, 3, 4, 5, 6, 7, 8) carbon atoms;

[0055] R M1 ” and R M2 ” are each independently a straight-chain alkenyl group having 2-8 (for example, 2, 3, 4, 5, 6, 7, 8) carbon atoms.

[0056] In some embodiments of the present invention, the weight percentage of the compound of general formula M in the liquid crystal composition having negative dielectric anisotropy is 0.1%-48% (including any value or sub-range within this range), for example, 0.1%, 0.5%, 1%, 2%, 4%, 6%, 8%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 20%, 22%, 24%, 25%, 26%, 28%, 30%, 32%, 34%, 35%, 36%, 37%, 38%, 40%, 42%, 44%, 45%, 46%, 48%, and the compound of general formula M includes at least one (for example, two, three, four, five, six) selected from the group consisting of the compounds of general formula M-1-2, the compounds of general formula M-14-2, the compounds of general formula M-22-2, the compounds of general formula M-49-1, and the compounds of general formula M-51-1.

[0057] In some embodiments of the present invention, the liquid crystal composition having negative dielectric anisotropy of the present invention further includes at least one compound of general formula F:

[0058]

[0059] Among them,

[0060] R F1 and R F2 each independently represent -H, halogen, a straight-chain or branched-chain alkyl group having 1-12 (for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12) carbon atoms, wherein the straight-chain or branched-chain alkyl group having 1-12 carbon atoms, One or more non-adjacent -CH2- groups can be independently replaced by -CH=CH-, -C≡C-, -O-, -S-, -CO-, -CO-O- or -O-CO-, and one or more -H atoms in a straight-chain or branched alkyl group containing 1-12 carbon atoms can be independently replaced by -F or -Cl;

[0061] Ring and Ring each independently represents wherein one or more non-adjacent -CH2- groups can be replaced by -O-, and one or up to two non-adjacent single bonds in the ring can be replaced by double bonds, wherein one or more -H atoms can be independently replaced by -CN, -F or -Cl, and one or more -CH= groups in the ring can be replaced by -N=;

[0062] X F represents -O-, -S- or -CO-;

[0063] L F1 and L F2 each independently represents -H, -F, -Cl, -CF3 or -OCF3;

[0064] Z F1 and Z F2 each independently represents a single bond, -O-, -CO-O-, -O-CO-, -CH2O-, -OCH2-, -(CH2)2O-, -O(CH2)2-, -CH=CH-, -C≡C-, -CH2CH2-, -CF2CF2-, -(CH2)3-, -(CH2)4-, -CF2O- or -OCF2-;

[0065] n F1 and n F2 each independently represents 0, 1 or 2, where when n F1 represents 2, Ring can be the same or different, where when n F2 represents 2, Ring can be the same or different, Z F2 can be the same or different; and

[0066] n F4 represents an integer from 0 to 4 (e.g., 0, 1, 2, 3 or 4).

[0067] In some embodiments of the present invention, the compound of general formula F accounts for 1% - 30% (including any value or sub-range within this range) of the weight of the negative dielectric anisotropy liquid crystal composition, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30%, etc., preferably 5% - 20%, and more preferably 7 - 16%.

[0068] In some embodiments of the present invention, the compound of general formula F is selected from the group consisting of the following compounds:

[0069]

[0070]

[0071]

[0072]

[0073] and

[0074]

[0075] wherein, R F1 and R F2 each independently represents -H, halogen, a straight-chain or branched-chain alkyl group containing 1 - 10 (such as 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10) carbon atoms, wherein one or more non-adjacent -CH2- in the straight-chain or branched-chain alkyl group containing 1 - 10 carbon atoms can be independently replaced by -C≡C-, -O-, -S-, -CO-, -CO-O- or -O-CO-, and one or more -H in the straight-chain or branched-chain alkyl group containing 1 - 10 carbon atoms can be independently replaced by -F or -Cl;

[0076] Z F1 represents a single bond, -O-, -CO-O-, -O-CO-, -CH2O-, -OCH2-, -CH=CH-, -C≡C-, -CH2CH2-, -CF2CF2-, -(CH2)4-, -CF2O- or -OCF2-;

[0077] R F2 ' represents a straight-chain or branched-chain alkoxy group containing 1 - 11 (such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11) carbon atoms;

[0078] R F2 ” represents a straight-chain or branched alkyl group having 1 to 10 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10) carbon atoms;

[0079] X F1 and X F2 each independently represents -CH2- or -O-;

[0080] n F3 represents an integer from 1 to 5; and

[0081] R F3 represents a straight-chain or branched alkyl group having 1 to 5 (e.g., 1, 2, 3, 4, or 5) carbon atoms, a straight-chain or branched alkoxy group having 1 to 4 (e.g., 1, 2, 3, or 4) carbon atoms, or a straight-chain or branched alkenyl group having 2 to 5 (e.g., 2, 3, 4, or 5) carbon atoms.

[0082] In some embodiments of the present invention, the compound of formula F comprises at least one (e.g., one, two, three, or more) compound selected from the group consisting of the compounds of formula F-3 and the compounds of formula F-32.

[0083] In some embodiments of the present invention, the dichroic dye is selected from the group consisting of azo dichroic dyes, anthraquinone dichroic dyes, phthalocyanine dichroic dyes, cyanine dichroic dyes, indigoid dichroic dyes, arylmethane dichroic dyes, nitro dichroic dyes, and nitroso dichroic dyes.

[0084] In some embodiments of the present invention, the dichroic dye is selected from one or at least two (e.g., three, four, or five) combinations of the group consisting of the following compounds:

[0085]

[0086]

[0087]

[0088] In some embodiments of the present invention, the addition amount of the dichroic dye accounts for 0.01% - 10% (including any value or sub-range within this range) of the weight percentage of the guest-host liquid crystal composition layer. For example, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.2%, 1.3%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 1.95%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6%, 6.2%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 7.8%, 8%, 8.2%, 8.5%, 8.8%, 9%, 9.2%, 9.5%, 9.8%, 10%, or the range between any two of these values; preferably 0.2% - 6%, and more preferably 0.2% - 4%.

[0089] In some embodiments of the present invention, the dichroic dye is selected from one or a combination of at least two of the group consisting of the following compounds, and the addition amount of the dichroic dye accounts for 0.01% - 5% (for example, it can be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.2%, 1.3%, 1.5%, 1.7%, 1.8%, 1.95%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%) of the weight percentage of the guest-host liquid crystal composition layer:

[0090]

[0091] In some embodiments of the present invention, the dichroic dye in the first guest-host liquid crystal composition layer and the dichroic dye in the second guest-host liquid crystal composition layer are complementary colors to each other. After the dichroic dye in the first guest-host liquid crystal composition layer and the dichroic dye in the second guest-host liquid crystal composition layer are superimposed, they can absorb all visible light bands and present black.

[0092] In some embodiments of the present invention, the dichroic dye in the first guest-host liquid crystal composition layer is selected from the group consisting of Dye 14 and Dye 15, and the dichroic dye in the second guest-host liquid crystal composition layer is selected from Dye 23.

[0093] In some embodiments of the present invention, the dichroic dye in the first guest-host liquid crystal composition layer is selected from Dye 14, and the dichroic dye in the second guest-host liquid crystal composition layer is selected from the group consisting of Dye 15 and Dye 23.

[0094] In some embodiments of the present invention, the chiral agent of the present invention may be any one or a combination of at least two selected from the group consisting of the following compounds:

[0095]

[0096]

[0097] and

[0098]

[0099] wherein, * represents a chiral site.

[0100] In some embodiments of the present invention, the weight percentage of the chiral agent in the guest-host liquid crystal composition layer is 0.01% - 10% (including any value or sub-range within this range), for example, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, 3%, 3.1%, 3.2%, 3.4%, 3.5%, 3.6%, 3.8%, 3.9%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, 5%, 5.2%, 5.4%, 5.6%, 5.8%, 6%, 6.2%, 6.4%, 6.6%, 6.8%, 7%, 7.2%, 7.4%, 7.6%, 7.8%, 8%, 8.2%, 8.4%, 8.6%, 8.8%, 9%, 9.2%, 9.4%, 9.6%, 9.8%, 10%, or the range between any two of these values.

[0101] In some embodiments of the present invention, the chiral agent is:

[0102]

[0103] wherein, * represents a chiral site.

[0104] In some embodiments of the present invention, the helix direction of the chiral agent in the first guest-host liquid crystal composition layer is opposite to that of the chiral agent in the second guest-host liquid crystal composition layer. Exemplarily, when the chiral agent in the first guest-host liquid crystal composition layer is S811, the chiral agent in the second guest-host liquid crystal composition layer is R811.

[0105] In some embodiments of the present invention, the first substrate, the second substrate, the third substrate, and the fourth substrate are each independently glass or a hard film layer, wherein the hard film layer can be a transparent plastic film or a transparent plastic plate.

[0106] In some embodiments of the present invention, the alignment directions between the first alignment layer and the second alignment layer are anti-parallel alignment or parallel alignment, preferably anti-parallel alignment.

[0107] In some embodiments of the present invention, the alignment directions between the third alignment layer and the fourth alignment layer are anti-parallel alignment or parallel alignment, preferably anti-parallel alignment.

[0108] In some embodiments of the present invention, the thickness of the first guest-host liquid crystal composition layer is 1 μm to 8 μm, and for example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, or 8 μm.

[0109] In some embodiments of the present invention, the thickness of the second guest-host liquid crystal composition layer is 1 μm to 8 μm, and for example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, or 8 μm.

[0110] In some embodiments of the present invention, the thickness of the first guest-host liquid crystal composition layer and the thickness of the second guest-host liquid crystal composition layer can be the same or different. Preferably, the thickness of the first guest-host liquid crystal composition layer is the same as the thickness of the second guest-host liquid crystal composition layer.

[0111] In the present invention, a liquid crystal composition with negative dielectric anisotropy, at least one (for example, two or three) dichroic dyes, and at least one (for example, two or three) chiral agents are formulated into a guest-host liquid crystal composition containing chiral agents according to a weight ratio, and are independently filled into the first guest-host liquid crystal composition layer and the second guest-host liquid crystal composition layer respectively to form the double-layer stacked liquid crystal display device of the present invention. When the liquid crystal display device formed by the first substrate, the second substrate and the intermediate layer therein (hereinafter simply referred to as the first-layer display device) and the liquid crystal display device formed by the third substrate, the fourth substrate and the intermediate layer therein (hereinafter simply referred to as the second-layer display device) are not applied with a driving voltage, the double-layer stacked liquid crystal display device of the present invention presents a bright state (i.e., white) display; when only the first-layer display device is applied with a driving voltage and the second-layer display device is not applied with a driving voltage, the double-layer stacked liquid crystal display device of the present invention presents the color corresponding to the dye in the first guest-host liquid crystal composition layer; when only the second-layer display device is applied with a driving voltage and the first-layer display device is not applied with a driving voltage, the double-layer stacked liquid crystal display device of the present invention presents the color corresponding to the dye in the second guest-host liquid crystal composition layer; and when the first-layer display device and the second-layer display device are simultaneously applied with a driving voltage, the double-layer stacked liquid crystal display device of the present invention presents a dark state (i.e., black) display. Therefore, the double-layer stacked liquid crystal display device of the present invention can achieve displays of multiple colors, and in the case of non-energization, the double-layer stacked liquid crystal display device of the present invention presents a normally white state.

[0112] In addition to the above compounds, the liquid crystal composition of the present invention may also contain common additives, such as antioxidants, ultraviolet absorbers, infrared absorbers, photoinitiators, polymerizable monomers, or light stabilizers, etc.

[0113] In addition, additives such as antioxidants and light stabilizers used in the liquid crystal composition of the present invention are preferably the following substances:

[0114]

[0115]

[0116]

[0117] Among them, n represents a positive integer from 1 to 12, n2 represents a positive integer from 3 to 15, and + represents a free radical.

[0118] Preferably, the antioxidant is selected from the light stabilizers shown below:

[0119]

[0120] Among them, n represents a positive integer from 1 to 12.

[0121] In some embodiments of the present invention, the additive accounts for 0% - 5% of the total weight of the liquid crystal composition; preferably, the additive accounts for 0.01% - 1% of the total weight of the liquid crystal composition.

[0122] Advantageous effects: Compared with the prior art, the double-layer stacked liquid crystal display device for color display of the present invention can achieve different color changes (such as black, orange-red, blue, red, cyan, yellow, and transparent, etc.) through the driving voltage or the selection and formulation of dyes, and has a small dark state transmittance in the dark state and a high bright state transmittance in the bright state, that is, while achieving a variety of different color displays, it also has a good display effect, and when no driving voltage is applied, it maintains a normally white state, which is suitable for use in scenarios such as text processing and web browsing. Detailed embodiments

[0123] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following examples are examples of the present invention, only used to illustrate the present invention, and not used to limit the present invention. Other combinations and various improvements within the concept of the present invention can be made without departing from the main idea or scope of the present invention.

[0124] Unless otherwise specified, the performance parameters of the examples and comparative examples in the present invention are measured at room temperature.

[0125] For the sake of convenience of expression, in the following embodiments, the group structures of the compounds are represented by the codes listed in Table 1:

[0126] Table 1. Group Structure Codes of Compounds

[0127]

[0128]

[0129] Taking the compound with the following structural formula as an example:

[0130]

[0131] If this structural formula is represented by the codes listed in Table 1, it can be expressed as: nCCGF. In the code, n represents the number of C atoms of the alkyl group at the left end. For example, when n is "3", it means the alkyl group is -C3H7; C in the code represents 1,4-cyclohexylene, G represents 2-fluoro-1,4-phenylene, and F represents a fluorine substituent.

[0132] The abbreviated codes for the test items in the following embodiments are as follows:

[0133] Cp Clearing point of the liquid crystal composition (transition temperature from nematic phase to isotropic phase, °C)

[0134] Δn Optical anisotropy (589 nm, 25 °C)

[0135] Δε Dielectric anisotropy (1 kHz, 25 °C)

[0136] CRmax Contrast ratio (transmittance in bright state / transmittance in dark state, 25 °C)

[0137] HTP Liquid crystal helical twisting power constant

[0138] T -40℃ Low-temperature storage stability of the liquid crystal composition with negative dielectric anisotropy (days, d)

[0139] t -40℃ Low-temperature storage stability of the guest-host liquid crystal composition containing a chiral agent (days, d)

[0140] D Dye dichroic ratio

[0141] Tmax Transmittance in bright state (%)

[0142] Tmin Transmittance in dark state (%)

[0143] Among them,

[0144] Cp: Obtained by testing with a melting point instrument.

[0145] Δn: Δn = n e -no , measured using an Abbe refractometer under a sodium lamp (589 nm) light source at 25 °C.

[0146] Δε: Δε = ε ∥ - ε ⊥ , where ε ∥ is the dielectric constant parallel to the molecular axis, and ε ⊥ is the dielectric constant perpendicular to the molecular axis; test conditions: VA type test cell at 25 °C, 1 KHz, and cell thickness of 6 μm.

[0147] CRmax: The ratio of the maximum Tmax to Tmin.

[0148] HTP = 1 / (c × Pitch), where c is the chiral dopant content and Pitch is the liquid crystal pitch value, measured using a reading microscope, wedge cell at 25 °C.

[0149] T -40℃ : The time recorded when a liquid crystal composition with negative dielectric anisotropy is placed in a glass bottle, stored at a constant temperature of -40 °C, and crystals are observed to precipitate.

[0150] t -40℃ : The time recorded when a guest-host liquid crystal composition containing a chiral dopant is placed in a glass bottle, stored at a constant temperature of -40 °C, and crystals are observed to precipitate.

[0151] Tmax: The maximum value of the transmittance on the V-T curve of a dimming device is measured using an LS182 optical transmittance meter and taken as the liquid crystal transmittance. The test cell is a negative FFS type.

[0152] Tmin: The minimum value of the transmittance on the V-T curve of a dimming device is measured using an LS182 optical transmittance meter and taken as the liquid crystal transmittance. The test cell is a negative FFS type.

[0153] D: The dichroic dye component is dissolved in the liquid crystal matrix at a ratio of 1% by weight and filled into a 7 μm positive anti-parallel rubbed cell. The transmittance spectra parallel and perpendicular to the polarizer of the liquid crystal cell are measured using a comprehensive liquid crystal optoelectronic property tester. Select the lowest point T ∥min of the parallel transmittance and the perpendicular transmittance T ⊥min at the corresponding wavelength. According to the formula A = Log(100 / T), calculate A ∥min and A ⊥min , D = A ∥min / A ⊥min .

[0154] In the following embodiments, each component used can be synthesized by methods well known in the art or obtained through commercial channels. These synthesis techniques are conventional, and each of the obtained liquid crystal compounds meets the standards for electronic compounds after testing.

[0155] Prepare a liquid crystal composition according to the ratio of each liquid crystal compound specified in the following embodiments. The preparation of the liquid crystal composition is carried out according to the conventional methods in the art, such as by heating, ultrasonic waves, suspension, etc., and mixing in proportion.

[0156] LC1

[0157] Prepare a liquid crystal composition LC1 with negative dielectric anisotropy according to the compounds and their weight percentages listed in Table 2, and fill it between the two substrates of the liquid crystal display for performance testing.

[0158] Table 2 Formulation of liquid crystal composition LC1 and test results of performance parameters

[0159]

[0160] LC2

[0161] Prepare a liquid crystal composition LC2 with negative dielectric anisotropy according to the compounds and their weight percentages listed in Table 3, and fill it between the two substrates of the liquid crystal display for performance testing.

[0162] Table 3 Formulation of liquid crystal composition LC2 and test results of performance parameters

[0163]

[0164] LC3

[0165] Prepare a liquid crystal composition LC3 with negative dielectric anisotropy according to the compounds and their weight percentages listed in Table 4, and fill it between the two substrates of the liquid crystal display for performance testing.

[0166] Table 4 Formulation of liquid crystal composition LC3 and test results of performance parameters

[0167]

[0168] LC4

[0169] Prepare a liquid crystal composition LC4 with negative dielectric anisotropy according to the compounds and their weight percentages listed in Table 5, and fill it between the two substrates of the liquid crystal display for performance testing.

[0170] Table 5 Formulation of liquid crystal composition LC4 and test results of performance parameters

[0171]

[0172] Example 1

[0173] A double-layer stacked liquid crystal display device for color display, in the direction from light entry to light exit, successively includes a first substrate, a first conductive layer, a first alignment layer, a first guest-host liquid crystal composition layer, a second alignment layer, a second conductive layer, a second substrate, a third substrate, a third conductive layer, a third alignment layer, a second guest-host liquid crystal composition layer, a fourth alignment layer, a fourth conductive layer, and a fourth substrate; wherein, the first alignment layer and the second alignment layer are in antiparallel alignment, the third alignment layer and the fourth alignment layer are in antiparallel alignment, the liquid crystal composition of component A in Table 1-1 is filled in the first guest-host liquid crystal composition layer (cell thickness is 4 μm), the liquid crystal composition of component B in Table 1-1 is filled in the second guest-host liquid crystal composition layer (cell thickness is 4 μm), and the first substrate, the second substrate, the third substrate, and the fourth substrate are ITO glasses.

[0174] Formulation of liquid crystal composition in Table 1-1

[0175]

[0176] Among them, dye 14 represents the dye with dye number 14, dye 15 represents the dye with dye number 15, dye 23 represents the dye with dye number 23, and among them, the D value of dye 14 in component A is 10.8, the D value of dye 15 in component A is 11.5, and the D value of dye 23 in component B is 14.2.

[0177] Among them, the twist angle of the liquid crystal composition of component A is 480°, and the twist angle of the liquid crystal composition of component B is 480°.

[0178] The color display and related performance parameters of the liquid crystal display device under different power-on conditions are summarized in Table 1-2 below.

[0179] Test results of performance parameters of liquid crystal display device in Table 1-2

[0180]

[0181] From the above performance parameter test data, it can be seen that the display device of the present invention can achieve various different color changes such as black, orange-red, blue, and transparent through the regulation of whether to apply a driving voltage, and has a small dark-state transmittance in the dark state and a high bright-state transmittance in the bright state, that is, it has a good display effect while realizing various different color displays.

[0182] Example 2

[0183] A double-layer stacked liquid crystal display device for color display, in the direction from light entry to light exit, sequentially includes a first substrate, a first conductive layer, a first alignment layer, a first guest-host liquid crystal composition layer, a second alignment layer, a second conductive layer, a second substrate, a third substrate, a third conductive layer, a third alignment layer, a second guest-host liquid crystal composition layer, a fourth alignment layer, a fourth conductive layer, and a fourth substrate; wherein, the first alignment layer and the second alignment layer are in anti-parallel alignment, the third alignment layer and the fourth alignment layer are in anti-parallel alignment, the liquid crystal composition of component C in Table 2-1 is filled in the first guest-host liquid crystal composition layer (cell thickness is 6 μm), the liquid crystal composition of component D in Table 2-1 is filled in the second guest-host liquid crystal composition layer (cell thickness is 6 μm), and the first substrate, the second substrate, the third substrate, and the fourth substrate are ITO glasses.

[0184] Formulation of Liquid Crystal Composition in Table 2-1

[0185]

[0186] Among them, Dye 14 represents the dye with dye number 14, Dye 15 represents the dye with dye number 15, Dye 23 represents the dye with dye number 23. Among them, the D value of Dye 14 in Component C is 10.8, the D value of Dye 15 is 11.5, and the D value of Dye 23 in Component D is 14.2.

[0187] Among them, the twist angle of the liquid crystal composition of Component C is 480°, and the twist angle of the liquid crystal composition of Component D is 480°.

[0188] The color display and related performance parameters of the liquid crystal display device under different power-on conditions are summarized in Table 2-2 below.

[0189] Test Results of Performance Parameters of Liquid Crystal Display Device in Table 2-2

[0190]

[0191] From the above performance parameter test data, it can be seen that the display device of the present invention can achieve various different color changes such as black, orange-red, blue, and transparent through the regulation of whether to apply a driving voltage, and has a small dark-state transmittance in the dark state and a high bright-state transmittance in the bright state, that is, it has a good display effect while achieving various different color displays.

[0192] Example 3

[0193] A double-layer stacked liquid crystal display device for color display, in the direction from light entry to light exit, sequentially includes a first substrate, a first conductive layer, a first alignment layer, a first guest-host liquid crystal composition layer, a second alignment layer, a second conductive layer, a second substrate, a third substrate, a third conductive layer, a third alignment layer, a second guest-host liquid crystal composition layer, a fourth alignment layer, a fourth conductive layer, and a fourth substrate; wherein, the first alignment layer and the second alignment layer are in anti-parallel alignment, the third alignment layer and the fourth alignment layer are in anti-parallel alignment, the liquid crystal composition of component E in Table 3-1 is filled in the first guest-host liquid crystal composition layer (cell thickness is 4 μm), the liquid crystal composition of component F in Table 3-1 is filled in the second guest-host liquid crystal composition layer (cell thickness is 4 μm), and the first substrate, the second substrate, the third substrate, and the fourth substrate are ITO glasses.

[0194] Table 3-1 Formulation of Liquid Crystal Composition

[0195]

[0196] Wherein, Dye 14 represents the dye with dye number 14, Dye 15 represents the dye with dye number 15, Dye 23 represents the dye with dye number 23, wherein, the D value of Dye 14 in component E is 10.8, the D value of Dye 23 in component F is 14.2, and the D value of Dye 15 is 11.5.

[0197] Wherein, the twist angle of the liquid crystal composition of component E is 100°, and the twist angle of the liquid crystal composition of component F is 100.

[0198] The color display and related performance parameters of the liquid crystal display device under different power-on conditions are summarized in Table 3-2 below.

[0199] Table 3-2 Test Results of Performance Parameters of Liquid Crystal Display Device

[0200]

[0201] From the above test data of performance parameters, it can be seen that the display device of the present invention can achieve various different color changes such as black, red, cyan, and transparent through the regulation of whether to apply a driving voltage, and has a small dark state transmittance in the dark state and a high bright state transmittance in the bright state, that is, it has a good display effect while achieving various different color displays.

[0202] Example 4

[0203] A double-layer stacked liquid crystal display device for color display, in the direction from light entry to light exit, sequentially includes a first substrate, a first conductive layer, a first alignment layer, a first guest-host liquid crystal composition layer, a second alignment layer, a second conductive layer, a second substrate, a third substrate, a third conductive layer, a third alignment layer, a second guest-host liquid crystal composition layer, a fourth alignment layer, a fourth conductive layer, and a fourth substrate; wherein, the first alignment layer and the second alignment layer are in anti-parallel alignment, the third alignment layer and the fourth alignment layer are in anti-parallel alignment, the liquid crystal composition of component G in Table 4-1 is filled in the first guest-host liquid crystal composition layer (cell thickness is 7 μm), the liquid crystal composition of component H in Table 4-1 is filled in the second guest-host liquid crystal composition layer (cell thickness is 7 μm), and the first substrate, the second substrate, the third substrate, and the fourth substrate are ITO glasses.

[0204] Formulation of Liquid Crystal Composition in Table 4-1

[0205]

[0206] Wherein, Dye 14 represents the dye with dye number 14, Dye 15 represents the dye with dye number 15, Dye 23 represents the dye with dye number 23. Among them, the D value of Dye 14 in component G is 10.8, the D value of Dye 23 in component H is 14.2, and the D value of Dye 15 is 11.5.

[0207] Wherein, the twist angle of the liquid crystal composition of component G is 100°, and the twist angle of the liquid crystal composition of component H is 205°.

[0208] The color display and related performance parameters of the liquid crystal display device under different power-on conditions are summarized in Table 4-2 below.

[0209] Test Results of Performance Parameters of Liquid Crystal Display Device in Table 4-2

[0210]

[0211] From the above test data of performance parameters, it can be seen that the display device of the present invention can achieve various different color changes such as black, red, cyan, and transparent through the regulation of whether to apply a driving voltage, and has a small dark state transmittance in the dark state and a high bright state transmittance in the bright state, that is, it has a good display effect while realizing various different color displays.

[0212] Example 5

[0213] A double-layer stacked liquid crystal display device for color display, in the direction from light entry to light exit, sequentially includes a first substrate, a first conductive layer, a first alignment layer, a first guest-host liquid crystal composition layer, a second alignment layer, a second conductive layer, a second substrate, a third substrate, a third conductive layer, a third alignment layer, a second guest-host liquid crystal composition layer, a fourth alignment layer, a fourth conductive layer, and a fourth substrate; wherein, the first alignment layer and the second alignment layer are in anti-parallel alignment, the third alignment layer and the fourth alignment layer are in anti-parallel alignment, the liquid crystal composition of Component I in Table 5-1 is filled in the first guest-host liquid crystal composition layer (cell thickness is 6 μm), the liquid crystal composition of Component J in Table 5-1 is filled in the second guest-host liquid crystal composition layer (cell thickness is 6 μm), and the first substrate, the second substrate, the third substrate, and the fourth substrate are ITO glasses.

[0214] Formulation of Liquid Crystal Composition in Table 5-1

[0215]

[0216] Among them, Dye 14 represents the dye with dye number 14, Dye 15 represents the dye with dye number 15, Dye 23 represents the dye with dye number 23. Among them, the D value of Dye 14 in Component I is 10.8, the D value of Dye 15 is 11.5, and the D value of Dye 23 in Component J is 14.2.

[0217] Among them, the twist angle of the liquid crystal composition of Component I is 610°, and the twist angle of the liquid crystal composition of Component J is 610°.

[0218] The color display and related performance parameters of the liquid crystal display device under different power-on conditions are summarized in Table 5-2 below.

[0219] Test Results of Performance Parameters of Liquid Crystal Display Device in Table 5-2

[0220]

[0221] From the above test data of performance parameters, it can be seen that the display device of the present invention can achieve various different color changes such as black, orange-red, blue, and transparent through the regulation of whether to apply a driving voltage, and has a small dark-state transmittance in the dark state and a high bright-state transmittance in the bright state, that is, it has a good display effect while achieving various different color displays.

[0222] In summary, the double-layer stacked liquid crystal display device of the present invention can achieve different color changes (such as black, orange-red, blue, red, cyan, yellow, and transparent) through the driving voltage or the selection and preparation of dyes, and has a small dark state transmittance in the dark state and a high bright state transmittance in the bright state. That is, while achieving a variety of different color displays, it also has a good display effect, and when no driving voltage is applied, it maintains the normally white state, which is suitable for use in scenarios such as text processing and web browsing.

[0223] The above embodiments are only for illustrating the technical concept and characteristics of the present invention, and their purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it, and cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A double-layer stacked liquid crystal display device for color display, characterized in that, In the direction from the entry of light to the exit of light, the liquid crystal display device sequentially includes a first substrate, a first conductive layer, a first alignment layer, a first guest-host liquid crystal composition layer, a second alignment layer, a second conductive layer, a second substrate, a third substrate, a third conductive layer, a third alignment layer, a second guest-host liquid crystal composition layer, a fourth alignment layer, a fourth conductive layer, and a fourth substrate; wherein, the components of the first guest-host liquid crystal composition layer and the second guest-host liquid crystal composition layer may be the same or different, and each independently contains at least one liquid crystal composition with negative dielectric anisotropy, at least one dichroic dye, and at least one chiral agent, and the dichroic ratio of the dichroic dye is greater than 10.

2. The liquid crystal display device according to claim 1, characterized in that, The liquid crystal composition with negative dielectric anisotropy contains at least one compound of general formula N: Wherein, R N1 and R N2 each independently represents a straight-chain alkyl group having 1 to 12 carbon atoms, a branched-chain alkyl group having 3 to 12 carbon atoms, wherein one or two or more non-adjacent -CH2- in the straight-chain alkyl group having 1 to 12 carbon atoms and the branched-chain alkyl group having 3 to 12 carbon atoms may be independently replaced by -CH=CH-, -C≡C-, -O-, -CO-, -CO-O- or -O-CO-; Ring and the ring each independently represents wherein one or more of the -CH2- therein may be replaced by -O-, and one or at most two single bonds in the ring may be replaced by double bonds, and wherein one or more of the -H therein may be independently replaced by -F, -Cl or -CN, and one or more of the -CH= in the ring may be replaced by -N=; Z N1 and Z N2 each independently represents a single bond, -CO-O-, -O-CO-, -CH2O-, -OCH2-, -CH=CH-, -C≡C-, -CH2CH2-, -CF2CF2-, -(CH2)4-, -CF2O- or -OCF2-; L N1 and L N2 each independently represents -H, an alkyl group having 1 to 3 carbon atoms, or a halogen; and n N1 represents 0, 1, 2 or 3, n N2 represents 0 or 1, and 0 ≤ n N1 + n N2 ≤ 3,, where when n N1 = 2 or 3, the rings can be the same or different, Z N1 can be the same or different.

3. The liquid crystal display device according to claim 2, characterized in that, The compound of general formula N is selected from the group consisting of the following compounds: The weight percentage of the compound of general formula N in the liquid crystal composition with negative dielectric anisotropy is 0.1% - 95%.

4. The liquid crystal display device according to claim 1, characterized in that, The liquid crystal composition with negative dielectric anisotropy further contains at least one compound of general formula M: Wherein, R M1 and R M2 each independently represents a straight-chain alkyl group having 1 to 12 carbon atoms, a branched-chain alkyl group having 3 to 12 carbon atoms, in the straight-chain alkyl group having 1 to 12 carbon atoms and the branched-chain alkyl group having 3 to 12 carbon atoms, one or two or more non-adjacent -CH2- may be independently replaced by -CH=CH-, -C≡C-, -O-, -CO-, -CO-O- or -O-CO-; Ring Ring and Ring each independently represents wherein one or more of the -CH2- therein may be replaced by -O-, and the single bonds in one or at most two of the rings may be replaced by double bonds, at most one -H therein may be substituted by a halogen; Z M1 and Z M2 each independently represents a single bond, -CO-O-, -O-CO-, -CH2O-, -OCH2-, -CH=CH-, -CH2CH2- or -(CH2)4-; and n M represents 0, 1 or 2, where when n M = 2, the rings may be the same or different, and Z M2 may be the same or different.

5. The liquid crystal display device according to claim 4, characterized in that, The compound of general formula M is selected from the group consisting of the following compounds: and Among them, R M1 and R M2 each independently represents a straight-chain alkyl group having 1 to 12 carbon atoms or a branched-chain alkyl group having 3 to 12 carbon atoms, and one or two or more non-adjacent -CH2- in the straight-chain alkyl group having 1 to 12 carbon atoms and the branched-chain alkyl group having 3 to 12 carbon atoms may be independently replaced by -CH=CH-, -C≡C-, -O-, -CO-, -CO-O- or -O-CO- respectively; The weight percentage of the compound of general formula M in the liquid crystal composition with negative dielectric anisotropy is 0.1% - 50%.

6. The liquid crystal display device according to claim 1, characterized in that, The liquid crystal composition with negative dielectric anisotropy further contains at least one compound of general formula F: Wherein, R F1 and R F2 Each independently represents -H, halogen, a linear or branched alkyl group containing 1 to 12 carbon atoms, wherein the straight or branched alkyl group containing 1 to 12 carbon atoms, One or more non-adjacent -CH2- in the group may be independently replaced by -CH=CH-, -C≡C-, -O-, -S-, -CO-, -CO-O- or -O-CO-, and one or more -H in the linear or branched alkyl group containing 1 to 12 carbon atoms may be independently replaced by -F or -Cl; Ring and the ring each independently represents wherein one or more non-adjacent -CH2- in may be replaced by -O-, and single bonds in one or two non-adjacent rings may be replaced by double bonds, wherein one or more -H in may be independently replaced by -CN, -F or -Cl respectively, and -CH= in one or more rings may be replaced by -N=; X F represents -O-, -S- or -CO-; L F1 and L F2 each independently represents -H, -F, -Cl, -CF3 or -OCF3; Z F1 and Z F2 each independently represents a single bond, -O-, -CO-O-, -O-CO-, -CH2O-, -OCH2-, -(CH2)2O-, -O(CH2)2-, -CH=CH-, -C≡C-, -CH2CH2-, -CF2CF2-, -(CH2)3-, -(CH2)4-, -CF2O- or -OCF2-; n F1 and n F2 each independently represents 0, 1 or 2, where when n F1 represents 2, the rings can be the same or different, where when n F2 represents 2, the rings can be the same or different, Z F2 can be the same or different; and n F4 represents an integer from 0 to 4, The weight percentage of the compound of general formula F in the liquid crystal composition with negative dielectric anisotropy is 1% - 30%.

7. The liquid crystal display device according to claim 1, wherein, The dichroic dye is selected from the group consisting of azo dichroic dyes, anthraquinone dichroic dyes, phthalocyanine dichroic dyes, cyanine dichroic dyes, indigo dichroic dyes, arylmethane dichroic dyes, nitro dichroic dyes, and nitroso dichroic dyes.

8. The liquid crystal display device according to claim 1, wherein, The chiral agent is selected from any one or a combination of at least two of the following compounds: and Wherein, * represents a chiral site; The weight percentage of the chiral agent in the guest-host liquid crystal composition layer is 0.01% - 10%.

9. The liquid crystal display device according to claim 1, wherein, The first substrate, the second substrate, the third substrate, and the fourth substrate are each independently glass or a hard film layer, wherein the hard film layer can be a transparent plastic film or a transparent plastic plate; The alignment directions between the first alignment layer and the second alignment layer are anti-parallel alignment or parallel alignment; the alignment directions between the third alignment layer and the fourth alignment layer are anti-parallel alignment or parallel alignment.

10. The liquid crystal display device according to claim 1, wherein, The thickness of the first guest-host liquid crystal composition layer is 1 μm to 8 μm; the thickness of the second guest-host liquid crystal composition layer is 1 μm to 8 μm.

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