Circular polarizer based on visual angle compensation and display device

Abstract

The invention discloses a circular polarizer based on visual angle compensation and a display device, and belongs to the technical field of display. The circular polarizer comprises a cholesteric liquid crystal layer, a phase difference layer, a linear polarization layer and a visual angle compensation layer, the display device comprises a display substrate and the circular polarizer. The cholesteric liquid crystal layer is located between the display substrate and the phase difference layer, the linear polarization layer is located on the side, away from the cholesteric liquid crystal layer, of the phase difference layer, the visual angle compensation layer is located between the cholesteric liquid crystal layer and the display substrate, and a cholesteric liquid crystal regulation and control light wave band at least comprises partial wavelengths ranging from 440 nm to 680 nm. The visual angle compensation layer is used for converting part of small visual angle (0-30 degrees) light emitted by the display substrate into large visual angle (31-80 degrees) emitting angle light, the problem that the cholesteric liquid crystal brightening efficiency is low under the large visual angle is solved, and the display effect of the display device is improved.

Description

Technical Field

[0001] The invention belongs to the field of display technology and relates to a circular polarizer and a display device based on viewing angle compensation. Background Art

[0002] The circular polarizer consists of a linear polarizer and a quarter wave plate. It converts natural light into linear polarized light through the linear polarizer, and then generates phase delay through the quarter wave plate to form left-handed (right-handed) circularly polarized light, which is reflected by the reflective layer of the display substrate and converted into right-handed (left-handed circularly polarized light). The polarization direction of the linear polarized light after passing through the quarter wave plate again is perpendicular to the transmission axis of the linear polarizer, and is absorbed by the linear polarizer to achieve the effect of shielding the reflection of ambient light. However, the above circular polarizer will also cause about 50% of the light emitted by the display substrate to be absorbed by the linear polarizer, resulting in reduced light output efficiency.

[0003] In order to improve the light extraction efficiency, the existing technology often introduces a cholesteric liquid crystal layer, which achieves brightness enhancement by selectively reflecting light of a specific wavelength. However, at a wide viewing angle, the spiral structure of the cholesteric liquid crystal is sensitive to the incident angle, resulting in a shift in the reflected wavelength and the emitted light being elliptically polarized light. The brightness enhancement efficiency decreases sharply with the increase in the angle of the emitted light. Therefore, there is an urgent need for a circular polarizer that can compensate for the low brightness enhancement efficiency of the cholesteric liquid crystal layer at a wide viewing angle to improve the display effect. Summary of the invention

[0004] In view of the above-mentioned technical problems and defects, the present invention provides a circular polarizer and a display device based on viewing angle compensation. The present invention adds a viewing angle compensation layer between the cholesteric liquid crystal layer and the display substrate, thereby widening the angle of the light emitted from the display substrate, and redistributing the light energy originally concentrated in a small viewing angle range to a larger viewing angle range, thereby compensating for the brightness attenuation of the cholesteric liquid crystal layer at a large viewing angle, thereby improving the display effect of the display device at a large viewing angle.

[0005] In a first aspect, the present invention provides a circular polarizer based on viewing angle compensation, wherein the circular polarizer is placed on a display substrate, and the circular polarizer comprises a viewing angle compensation layer, a cholesteric liquid crystal layer, a phase difference layer and a linear polarizer layer; The cholesteric liquid crystal layer is located between the display substrate and the phase difference layer, the linear polarizing layer is located on the side of the phase difference layer away from the cholesteric liquid crystal layer, and the viewing angle compensation layer is located between the cholesteric liquid crystal layer and the display substrate.

[0006] Furthermore, in the circular polarizer based on viewing angle compensation provided by the present invention, the viewing angle compensation layer is selected from any one of a microstructure viewing angle compensation layer, a non-liquid crystal polymer coating with added viewing angle compensation particles, a liquid crystal polymer coating with added viewing angle compensation particles, and a polymerizable liquid crystal coating.

[0007] Furthermore, in the circular polarizer based on viewing angle compensation provided by the present invention, the surface roughness Ra of the microstructure viewing angle compensation layer is 10 nm to 2 μm.

[0008] Furthermore, in the circular polarizer based on viewing angle compensation provided by the present invention, the viewing angle compensation particles in the non-liquid crystal polymer coating to which viewing angle compensation particles are added are inorganic substances with a diameter of 10 nm to 30 μm and / or organic substances with a diameter of 1 μm to 50 μm.

[0009] Furthermore, in the circular polarizer based on viewing angle compensation provided by the present invention, the inorganic substance is selected from at least one of titanium dioxide, calcium carbonate, barium sulfate and silicon dioxide; The organic matter is selected from at least one of polymethyl methacrylate, polybutyl methacrylate, polystyrene, polymerizable liquid crystal monomers, and siloxane resin.

[0010] Furthermore, in the circular polarizer based on viewing angle compensation provided by the present invention, the non-liquid crystal polymer coating added with viewing angle compensation particles is prepared by mixing and curing the viewing angle compensation particles and the non-liquid crystal polymer, and the mass ratio of the viewing angle compensation particles to the organic colloid is 0.1-1.2:1; the non-liquid crystal polymerizable colloid is a mixture of one or more of methyl methacrylate, butyl methacrylate, and styrene; Furthermore, in the circular polarizer based on viewing angle compensation provided by the present invention, the polymerizable liquid crystal coating is a liquid crystal polymer layer with focal conic texture containing chiral compounds.

[0011] Furthermore, in the circular polarizer based on viewing angle compensation provided by the present invention, the liquid crystal polymer coating with viewing angle compensation particles added thereto is prepared by mixing the viewing angle compensation particles and a liquid crystal mixture, coating the mixture on a substrate layer, and then curing the mixture; The mass ratio of the viewing angle compensation particles to the liquid crystal mixture is 0.1-1.2:1; The liquid crystal mixture comprises, by weight, 100 to 980 parts of a polymerizable liquid crystal monomer, 5 to 300 parts of a chiral compound, 1 to 50 parts of a photoinitiator, and 5 to 800 parts of an organic solvent.

[0012] The substrate layer is an organic film with a thickness of 5 to 300 μm.

[0013] Furthermore, in the circular polarizer based on viewing angle compensation provided by the present invention, the polymerizable liquid crystal monomer is selected from one or more of nematic liquid crystal, discotic liquid crystal, and disk-shaped liquid crystal; The polymerizable liquid crystal monomer contains n polymerizable groups, wherein n≥1; The polymerizable group is one of an alkenyl group, an alkynyl group, an epoxy group, and a mercapto group.

[0014] In a second aspect, the present invention provides a display device, comprising the circular polarizer and a display substrate, and the display device may be an organic light emitting diode (OLED) or a liquid crystal display (LCD).

[0015] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages: (1) The present invention introduces a viewing angle compensation layer between the cholesteric liquid crystal layer and the display substrate, thereby expanding the light emission angle and improving the display effect of the display device. The mixture of inorganic and organic particles of different particle sizes is used as viewing angle compensation particles, which utilizes the synergistic effect of the flexibility of organic matter and the rigidity of inorganic matter, optimizes the particle dispersion, and makes the brightness reach 95nit at a viewing angle of 80°, which is better than the pure inorganic coating, and compensates for the low brightness enhancement efficiency of the cholesteric liquid crystal layer at a large viewing angle.

[0016] (2) When the viewing angle compensation layer of the viewing angle compensation particles is combined with the focal conic texture layer of the liquid crystal polymer, the brightness decay is the most gentle at full viewing angle (0°~80°), especially at a wide viewing angle of 31°~80°. This achieves a balance between the efficiency of the normal viewing angle and the performance of the wide viewing angle. The present invention solves the problems of low light efficiency and severe color deviation at wide viewing angles in the prior art by optimizing both materials and structures, and provides a new path for high-performance display technology.

[0017] (3) By arranging the viewing angle compensation layer between the display substrate and the cholesteric liquid crystal layer, the brightening efficiency of the cholesteric liquid crystal layer can be further improved, and part of the lost light reflected by the cholesteric liquid crystal layer to the edge of the display device can be scattered back to the display substrate, thereby improving the light extraction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The schematic diagram of the brightening principle of the cholesteric liquid crystal layer is shown in FIG. 1 , where L is left-handed circularly polarized light; R is right-handed circularly polarized light; S00 is the display substrate; and S100 is the cholesteric liquid crystal layer.

[0019] Figure 2 The schematic diagram of the structure of a non-liquid crystal polymer coating with viewing angle compensation particles of different diameters is shown in the figure. D is a glue layer; D1 is a viewing angle compensation particle with a particle size greater than 5μm; D2 is a viewing angle compensation particle with a particle size between 500nm and 5μm; and D3 is a viewing angle compensation particle with a particle size less than 500nm.

[0020] Figure 3 The schematic diagram of the low light path caused by the cholesteric liquid crystal layer under a wide viewing angle is shown in FIG. 1 , where L is left-handed circularly polarized light; L' is the lost left-handed circularly polarized light; R is right-handed circularly polarized light; R' is the lost right-handed circularly polarized light; S00 is the display substrate; and S100 is the cholesteric liquid crystal layer.

[0021] Figure 4Schematic diagram of compensation of high viewing angle light efficiency by adding non-liquid crystal polymer coating with viewing angle compensation particles. Among them, L is left-handed circularly polarized light; R is right-handed circularly polarized light; P is linearly polarized light; S00 is display substrate; S400 is viewing angle compensation layer; S100 is cholesteric liquid crystal layer; S200 is phase difference layer; S300 is linear polarization layer.

[0022] Figure 5 Schematic diagram of the compensation of the light output efficiency at a large viewing angle by the microstructure viewing angle compensation layer. Among them, L is left-handed circularly polarized light; R is right-handed circularly polarized light; P is linearly polarized light; S00 is the display substrate; S400 is the viewing angle compensation layer; S100 is the cholesteric liquid crystal layer; S200 is the phase difference layer; S300 is the linear polarizing layer. DETAILED DESCRIPTION

[0023] The technical scheme of the present invention is described below in conjunction with the embodiments, but the present invention is not limited to the following embodiments. The experimental methods and detection methods described in each embodiment are conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0024] The invention provides a circular polarizer, which comprises a cholesteric liquid crystal layer, a phase difference layer, a linear polarizer layer and a viewing angle compensation layer.

[0025] The present invention also provides a display device, comprising a display substrate and the above circular polarizer. The cholesteric liquid crystal layer is located between the display substrate and the phase difference layer, the linear polarizing layer is located on the side of the phase difference away from the cholesteric liquid crystal layer, and the viewing angle compensation layer is located between the cholesteric liquid crystal layer and the display substrate.

[0026] 1. Viewing angle compensation layer: The light emitted from the display substrate has a small divergence angle. When it is directly incident on the cholesteric liquid crystal layer, its inherent spiral structure and selective reflection characteristics will cause the large-angle light to be significantly attenuated. In this case, the present invention can expand the angle of the light emitted from the display substrate in advance by inserting a viewing angle compensation layer between the substrate and the liquid crystal layer, so that the light energy originally concentrated in a small viewing angle range is redistributed to a larger viewing angle range, thereby compensating for the light efficiency loss of the cholesteric liquid crystal layer at a large viewing angle, and improving the display effect of the display device at a large viewing angle.

[0027] The viewing angle compensation layer in the present invention is selected from any one of a microstructure viewing angle compensation layer, a non-liquid crystal polymer coating with viewing angle compensation particles added, a liquid crystal polymer coating with viewing angle compensation particles added, and a polymerizable liquid crystal coating. The viewing angle compensation layer of the present invention can diffusely reflect the light emitted from the display substrate multiple times, and redistribute part of the light originally concentrated at a viewing angle of 0°~30° to a range of 0°~80°, thereby reducing the brightness attenuation under a large viewing angle. At the same time, the viewing angle compensation layer can scatter part of the light reflected by the cholesteric liquid crystal layer to the edge of the display device back into the display device and reuse it, thereby improving the light extraction efficiency of the display device.

[0028] The preparation methods of the above different types of viewing angle compensation layers are as follows: (1) Microstructure viewing angle compensation layer The microstructure viewing angle compensation layer is formed on the surface of PET (polyethylene terephthalate), COP (cycloolefin polymer), PC (polycarbonate), PMMA (polymethyl methacrylate) and other film layers through nanoimprinting process with a roughness ranging from 10nm to 2μm.

[0029] (2) Non-liquid crystal polymer coating with viewing angle compensation particles The non-liquid crystal polymer coating with added viewing angle compensation particles is prepared by mixing the viewing angle compensation particles and the non-liquid crystal polymer, and then coating the mixture on the surface of the substrate and forming it by thermal curing or photocuring. The core function of the viewing angle compensation particles is to adjust the phase and angle of light, so they must have specific optical anisotropy. Therefore, the viewing angle compensation particles are selected from any one of inorganic substances, organic substances, and inorganic-organic mixtures. Among them, the inorganic substance is one or more of titanium dioxide, calcium carbonate, barium sulfate, and silicon dioxide with a diameter between 10nm and 30μm; the organic substance is one or more of polymethyl methacrylate, polybutyl methacrylate, polystyrene, and silicone resin with a diameter between 1μm and 50μm; the non-liquid crystal polymer is a mixture of one or more of methyl methacrylate, butyl methacrylate, and styrene. Such as Figure 2 As shown, the viewing angle compensation particles in the viewing angle compensation layer preferably have a distribution combination of particles with different diameters.

[0030] (3) Liquid crystal polymer coating with viewing angle compensation particles The liquid crystal polymer coating with viewing angle compensation particles added thereto is prepared by mixing viewing angle compensation particles and a liquid crystal mixture, coating the mixture on a substrate layer, and then curing the mixture; the liquid crystal mixture is a liquid crystal polymer with a focal conic texture containing a chiral compound; the mass ratio of the viewing angle compensation particles to the liquid crystal mixture is 0.1-1.2:1; The liquid crystal mixture comprises, by weight, 100 to 980 parts of a polymerizable liquid crystal monomer, 5 to 300 parts of a chiral compound, 1 to 50 parts of a photoinitiator, and 5 to 800 parts of an organic solvent.

[0031] The substrate layer is an organic film with a thickness of 5 to 300 μm.

[0032] The polymerizable liquid crystal monomer is selected from one or more of nematic liquid crystal, discotic liquid crystal, and disk-shaped liquid crystal; the polymerizable liquid crystal monomer contains n polymerizable groups, wherein n≥1; the polymerizable group is one of alkenyl, alkynyl, epoxy, and mercapto.

[0033] (4) Polymerizable liquid crystal coating The polymerizable liquid crystal coating is a liquid crystal polymer layer with focal conic texture containing chiral compounds.

[0034] 2. Cholesteric liquid crystal layer: (1) Principle of light wave control in cholesteric liquid crystal layer: The light band regulated by the cholesteric liquid crystal layer at least includes some wavelengths between 440 and 680 nm. The light band regulated by the cholesteric liquid crystal layer includes at least one of the bands of 440 to 480 nm, 500 to 580 nm and 600 to 680 nm. For example, the cholesteric liquid crystal layer can regulate the light band of 440 to 480 nm; the cholesteric liquid crystal layer can regulate the light band of 440 to 480 nm and 500 to 580 nm; the cholesteric liquid crystal layer can regulate the light band of 440 to 480 nm, 500 to 580 nm and 600 to 680 nm.

[0035] The cholesteric liquid crystal layer may have a single pitch structure or multiple pitch structures. When the cholesteric liquid crystal layer contains multiple pitch structures, the cholesteric liquid crystal structures with different pitch sizes can be arranged in any order in the thickness direction. For example, the cholesteric liquid crystal layer has a pitch in the thickness direction, such as 291nm (denoted as P1). Assuming that the average refractive index of the cholesteric liquid crystal layer is 1.58, the cholesteric liquid crystal layer regulates the central wavelength to 460nm; the cholesteric liquid crystal layer has two pitches in the thickness direction, such as a cholesteric liquid crystal polymer layer with a pitch of 291nm and a pitch of 335nm (denoted as P2). Assuming that the average refractive index of the cholesteric liquid crystal layer is 1.58, the cholesteric liquid crystal layer regulates two central wavelengths, which are 4 60nm and 530nm; the cholesteric liquid crystal layer has three pitches in the thickness direction, such as three cholesteric liquid crystal polymer layers with pitch sizes of 291nm, 335nm and 392nm (denoted as P3). Assuming that the average refractive index of the cholesteric liquid crystal layer is 1.58, the cholesteric liquid crystal layer regulates three central wavelengths of 460nm, 530nm and 620nm; the three cholesteric liquid crystal polymer layers P1, P2 and P3 can be arranged in any order in the thickness direction, such as P1 P2 P3, P2 P3 P1, P3 P2 P1, P3P1 P2, P1 P3 P2, P2 P1 P3.

[0036] When the cholesteric liquid crystal layer contains a plurality of pitch structures, the cholesteric liquid crystal polymer layer has a continuous pitch gradient in the thickness direction. For example, the pitch of the cholesteric liquid crystal layer in the thickness direction includes part or all of the pitch sizes between 291 and 392 nm.

[0037] The relationship between the wavelength and pitch of light regulated by the cholesteric liquid crystal layer is as follows:

[0038] In the above formula, λ is the wavelength of light modulated by the cholesteric liquid crystal layer, n is the average refractive index of the cholesteric liquid crystal layer, P is the helical pitch of the cholesteric liquid crystal layer, and θ is the angle between the incident light and the helical axis of the cholesteric liquid crystal layer.

[0039] like Figure 1As shown, when the incident angle is 0, the cholesteric liquid crystal layer brightens the optical path as follows: the cholesteric liquid crystal layer converts the light emitted from the display substrate into about 50% left-handed polarized light and about 50% right-handed polarized light. When the optical rotation selectivity of the cholesteric liquid crystal layer allows the left-handed polarized light (right-handed polarized light) to pass through, this part is recorded as Y1, and the right-handed polarized light (left-handed polarized light) (recorded as Y2) is reflected back to the reflective layer of the display substrate. After being reflected again by the reflective layer, the polarization direction of the light changes, that is, the left-handed polarized light (right-handed polarized light) becomes right-handed polarized light (left-handed polarized light). The circularly polarized light with changed polarization direction can pass through the cholesteric liquid crystal layer, and after passing through the phase difference layer, it is converted into linearly polarized light. The linearly polarized light then passes through the linear polarizing layer to reach the surface of the display device. It can be seen from the above optical path that the cholesteric liquid crystal layer can greatly improve the light output efficiency of the display device.

[0040] like Figure 3 As shown in the figure, when the incident angle is not 0, the cholesteric liquid crystal layer brightening light path is as follows: when the Y2 part is reflected by the cholesteric liquid crystal layer back to the display substrate reflective layer, part of the light will be reflected to the edge of the display device, causing partial light loss; or when the Y2 part is reflected by the cholesteric liquid crystal layer back to the display substrate reflective layer, part of the light will be reflected to the edge of the display device after being reflected by the reflective layer, causing partial light loss. The larger the viewing angle, the lower the brightening efficiency of the cholesteric liquid crystal layer, which leads to poor display effect under large viewing angle.

[0041] like Figure 4 As shown, a viewing angle compensation layer is added between the cholesteric liquid crystal layer and the display substrate to convert part of the small viewing angle light emitted from the display substrate into large viewing angle light, thereby compensating the light extraction efficiency under large viewing angle. At the same time, part of the large-angle light reflected back to the display substrate by the cholesteric liquid crystal layer changes its light path after passing through the viewing angle compensation layer, from the edge of the display device to the inside of the display device, thereby reducing light loss and improving light extraction efficiency.

[0042] (2) Preparation of cholesteric liquid crystal layer: The first step is to pre-treat the substrate layer to improve the adhesion of the cholesteric liquid crystal coating. The pre-treatment method can be corona or plasma pre-treatment, such as corona treatment of the substrate layer, with a corona power of 100V*2A and a corona speed of 2m / min. The substrate layer is preferably an organic film layer that is easy to roll up, such as PMMA film, TAC (triacetyl cellulose) film, COP film, etc., without specific limitation. The thickness of the substrate layer is 5~300μm, preferably 5~100μm.

[0043] The second step is to prepare a liquid crystal mixture for coating and preparing a cholesteric liquid crystal layer. The raw materials for preparing the liquid crystal mixture are measured in proportion. In terms of mass fraction, the liquid crystal mixture includes: 10-98% of polymerizable liquid crystal monomers, 0.5-30% of chiral compounds, 0.1-5% of photoinitiators, and 0.5-80% of organic solvents. In some applications, other functional additives such as surfactants and cross-linking agents can also be added as required. Heat the measured liquid crystal mixture to above the phase transition temperature of all polymerizable liquid crystal monomers, stir while heating until the mixture is evenly mixed, and cool to 10-50°C for coating.

[0044] The polymerizable liquid crystal monomer is selected from one or more of nematic liquid crystal, discotic liquid crystal, and disk-shaped liquid crystal. The polymerizable liquid crystal monomer contains at least one polymerizable group, preferably two or more polymerizable groups. The polymerizable group is one of alkenyl, alkynyl, epoxy, and mercapto.

[0045] For example, polymerizable liquid crystal monomers containing two or more polymerizable groups include: L1: ; L2: ; L3: ; L4: ; L5: ; L6: ; L7: ; L8: .

[0046] The chiral compound is selected from one or more of X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12, X13, X14, X15, X16, X17, X18, X19, X20, and X21.

[0047] The structure of X1 is: ; The structure of X2 is: ; The structure of X3 is: ; The structure of X4 is: ; The structure of X5 is: ; The structure of X6 is: ; The structure of X7 is: ; The structure of X8 is: ; The structure of X9 is: ; The structure of X10 is: ; The structure of X11 is: ; The structure of X12 is: ; The structure of X13 is: ; The structure of X14 is: ; The structure of X15 is: ; The structure of X16 is: ; The structure of X17 is: ; The structure of X18 is: ; The structure of X19 is: ; The structure of X20 is: ; The structure of X21 is: .

[0048] The photoinitiator is selected from the group consisting of benzoyl peroxide, azobisisobutyronitrile, benzoin ethers, benzophenones, acetophenones, benzil ketals, diaryliodonium salts, triarylsulfonium salts, diphenyliodonium tetrafluoroborate, diphenyliodonium hexafluorophosphate, diphenyliodonium arsenate, diphenyliodonium tetraborate, 4-methoxyphenyliodonium tetrafluoroborate, 4-methoxyphenyliodonium hexafluorophosphate, 4-methoxyphenyliodonium hexafluoroarsenate, 4-tert-butylphenyliodonium diphenyliodonium tetrafluoroborate, 4-tert-butylphenyliodonium diphenyliodonium hexafluorophosphate, 4- One or more of tert-butylphenyliodonium diphenyliodonium trifluoromethanesulfonate, triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroarsenate, triphenylsulfonium tetraborate, 4-methoxyphenyldiphenylsulfonium tetrahydroborate, 4-methoxyphenyldiphenylsulfonium tetrahydrogenphosphate, 4-methoxyphenyldiphenylsulfonium tetrahydroarsenate, 4-methoxyphenyldiphenylsulfonium trifluoromethanesulfonate, 4-methoxyphenyldiphenylsulfonium triphenylsulfonium tetraborate, 4-phenylphenylthiodiphenylsulfonium hexafluoroarsenate, benzil dimethyl ketal and bis-phenylphosphine oxide.

[0049] The solvent is selected from the group consisting of benzene, toluene, xylene, mesitylene, n-butylbenzene, diethylbenzene, tetralin, methoxybenzene, 1,2-dimethoxybenzene, cyclohexanone, ethyl acetate, methyl lactate, ethyl lactate, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, 2-pyrrolidone, chloroform, methylene chloride, methyl chloride, ethylene dichloride, trichloroethylene, tetrachloroethylene, chlorobenzene, tert-butyl alcohol, diacetone alcohol, glycerol, monoacetin, triethylene glycol, and ethyl cellosolve. and one or more of butyl cellosolve, N-methyl-2-pyrrolidone, γ-butyrolactone, N,N-dimethylformamide, N,N-dimethylacetamide, diethylene glycol monomethyl ether ethyl ester, methanol, ethanol, isopropanol, cyclohexanol, ethylene glycol, tetrahydrofuran, dichloromethane, chlorobenzene, 1,2-dichloroethane, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclobutanone, methyl acetate, ethyl acetate, ethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol methyl ethyl ether, and ethylene glycol dimethyl ether.

[0050] The third step is to coat the liquid crystal mixture of the second step on the pre-treated substrate layer with a coating thickness of 100-5000nm, and heat to remove the organic solvent at a temperature of 30-150°C for 5-1000s. Then, the mixture is cured by irradiation with a wavelength of 300-400nm and an irradiation dose of 1000-200000J / m 2 When the cholesteric liquid crystal layer is composed of multiple liquid crystal layers with a single pitch structure, after the first layer of cholesteric liquid crystal coating is coated and cured, the remaining cholesteric liquid crystal mixtures with different pitch sizes are coated in turn until all the liquid crystal mixtures are coated.

[0051] 3. Phase difference layer: The phase difference layer is a stretched phase difference layer or a coated phase difference layer. The stretched phase difference layer can be made of PC or PET material, and the coated phase difference layer can be a liquid crystal coated phase difference layer.

[0052] The phase difference layer is preferably a material or structure with reverse wavelength dispersion performance, for example, it is prepared by compounding multiple layers of nematic liquid crystal polymer coatings, and there is a certain angle between the optical axes of each nematic liquid crystal polymer layer, or the liquid crystal polymer coating is a phase difference layer prepared by adding a chiral compound, forming an optical axis change in the thickness direction, thereby achieving reverse wavelength dispersion. The coating type liquid crystal phase difference layer is a reverse wavelength dispersion phase difference layer prepared in CN117844494A.

[0053] 4. Linear polarizing layer: The linear polarizing layer can be an iodine polarizing layer or a dye polarizing layer, without specific limitation. The iodine polarizer is a commercially available linear polarizing layer of Shengbo Optoelectronics model SMV-TDA, and the dye polarizer is a linear polarizing layer prepared in CN117844494A.

[0054] The cholesteric liquid crystal layer, the phase difference layer, the linear polarizing layer and the viewing angle compensation layer can be bonded together by optical adhesive.

[0055] The light-emitting side of the circular polarizer of the present invention may further include other functional layers, such as an anti-fingerprint layer, an anti-scratch layer, etc. In some possible applications, the viewing angle compensation layer may be used as an optical adhesive layer.

[0056] Example 1 This embodiment provides a non-liquid crystal polymer coating with viewing angle compensation particles added thereto.

[0057] (1) Viewing angle compensation particle design The viewing angle compensation particles in this embodiment are inorganic, that is, silicon dioxide of different particle sizes is mixed, and the mass percentage of silicon dioxide of each particle size is shown in Table 1: Table 1 Mass percentage of each component in inorganic matter

[0058] 2. Construction of composite colloids The above inorganic substances were dispersed in a methyl methacrylate matrix (non-liquid crystal polymer), and dibenzoyl peroxide (BPO) was added as a thermal initiator, and the mixture was stirred and mixed to obtain a composite colloid. The mass percentages of the components in the composite colloid are shown in Table 2. The composite colloid was coated on the surface of a PET substrate, heated to 80°C, and maintained for 5 minutes to obtain a non-liquid crystal polymer coating with viewing angle compensation particles added thereto.

[0059] Table 2 Mass percentage of each component in the composite colloid

[0060] Example 2 This embodiment is the same as Embodiment 1, except that the composition of the viewing angle compensation particles is different. The viewing angle compensation particles in this embodiment are an inorganic and organic mixture. The composition of the inorganic and organic mixture is shown in Table 3, and the composition of the composite colloid is shown in Table 4.

[0061] Table 3 Mass percentage of each component in inorganic and organic mixtures

[0062] Table 4 Mass percentage of each component in the composite colloid

[0063] Example 3 This embodiment is the same as Embodiment 1, except that the composition of the viewing angle compensation particles is different. The viewing angle compensation particles in this embodiment are inorganic substances, the composition of the inorganic substances is shown in Table 5, and the composition of the composite colloid is shown in Table 6.

[0064] Table 5 Mass percentage of each component in inorganic matter

[0065] Table 6 Mass percentage of each component in the composite colloid

[0066] Example 4 This embodiment is the same as Embodiment 1, except that the composition of the viewing angle compensation particles is different. The viewing angle compensation particles in this embodiment are organic matter, the composition of the organic matter is shown in Table 7, and the composition of the composite colloid is shown in Table 8.

[0067] Table 5 Mass percentage of each component in organic matter

[0068] Table 6 Mass percentage of each component in the composite colloid

[0069] Example 5 This embodiment provides a microstructure viewing angle compensation layer.

[0070] In this embodiment, a nanoimprint process is used to form a roughness of Ra of 0.5 μm on the surface of polyethylene terephthalate (PET). The nanoimprint machine uses a commercially available Stensborg roll-to-roll type to form a microstructure with an average roughness of 0.5 μm on the surface of PET. Figure 5 As shown in S400.

[0071] Example 6 This embodiment provides a liquid crystal polymer coating with added viewing angle compensation particles.

[0072] The preparation method of the liquid crystal polymer coating with viewing angle compensation particles added is similar to the preparation method of the cholesteric liquid crystal layer, except that the viewing angle compensation particles and the liquid crystal mixture are mixed evenly before the liquid crystal mixture is applied, and the coating mixture is applied to the surface of the substrate and cured to obtain the liquid crystal mixture, wherein the liquid crystal mixture is a focal conic textured liquid crystal polymer containing a chiral compound. The specific preparation method is as follows: The method for preparing the viewing angle compensation particles of this embodiment is the same as that of embodiment 1. On the basis of embodiment 1, the method for preparing the liquid crystal polymer coating with viewing angle compensation particles added is as follows: One side of the TAC (triacetylcellulose) film of the substrate was subjected to corona treatment, with a corona power of 100V*2A and a corona speed of 2m / min. The polymerizable liquid crystal monomer, chiral compound, photoinitiator, and solvent were measured in proportion to obtain a liquid crystal mixture, and the mass percentage of the liquid crystal mixture is shown in Table 7. The measured liquid crystal mixture was heated to 180°C, stirred while heating until the liquid crystal mixture was evenly mixed, cooled to 50°C, and the viewing angle compensation particles were mixed with the liquid crystal mixture, with a mass ratio of the viewing angle compensation particles to the liquid crystal mixture of 0.3:1, to form a coating mixture for later use.

[0073] Table 7 Mass percentage of each component of liquid crystal mixture

[0074] The coating mixture was coated on the corona treated substrate layer by slit coating process. The coating thickness was 3 μm, heated to 80°C and maintained for 1 min to remove the solvent. The temperature was lowered to 20°C and then cured by ultraviolet light with a wavelength of 365 nm and an irradiation dose of 5000 J / m 2 , a liquid crystal polymer coating with viewing angle compensation particles added thereto is obtained.

[0075] Example 7 This embodiment provides a polymerizable liquid crystal coating.

[0076] The polymerizable liquid crystal coating described in this embodiment is a liquid crystal polymer layer with focal conic texture containing chiral compounds.

[0077] One side of the TAC (triacetylcellulose) film of the substrate was subjected to corona treatment, with a corona power of 100V*2A and a corona speed of 2m / min. The polymerizable liquid crystal monomer, the chiral compound, the photoinitiator, and the solvent were weighed in proportion to obtain a liquid crystal mixture, and the mass percentage of the liquid crystal mixture is shown in Table 7. The weighed liquid crystal mixture was heated to 180°C, stirred while heating, until the liquid crystal mixture was evenly mixed, and cooled to 20°C to form a coating mixture for later use.

[0078] The coating mixture was coated on the corona treated substrate layer by slit coating process. The coating thickness was 3 μm, heated to 80°C and maintained for 1 min to remove the solvent. The temperature was lowered to 20°C and then cured by ultraviolet light with a wavelength of 365 nm and an irradiation dose of 5000 J / m 2 , a polymerizable liquid crystal coating is obtained.

[0079] Example 8 This embodiment provides a method for preparing a cholesteric liquid crystal layer.

[0080] The cholesteric liquid crystal layer has a single-size pitch structure in the thickness direction, the pitch is 291nm, the control center wavelength is 460nm, the control light band is 440~480nm, and the thickness of the cholesteric liquid crystal layer is 3μm.

[0081] The method for preparing a cholesteric liquid crystal layer comprises: One side of the TAC (triacetyl cellulose) film was subjected to corona treatment, with a corona power of 100V*2A and a corona speed of 2m / min. The polymerizable liquid crystal monomer, chiral compound, photoinitiator, and solvent were weighed in proportion to obtain a liquid crystal mixture, and the mass percentage of the liquid crystal mixture is shown in Table 8. The weighed liquid crystal mixture was heated to 180°C, stirred while heating, until the liquid crystal mixture was evenly mixed, and cooled to 30°C for use.

[0082] Table 8 Mass percentage of each component of liquid crystal mixture

[0083] The liquid crystal mixture was coated on the corona treated substrate layer by slit coating process. The coating thickness was 3 μm, and the mixture was heated to 80°C and maintained for 1 min to remove the solvent. The mixture was then cured by ultraviolet light with a wavelength of 365 nm and an irradiation dose of 5000 J / m 2 , forming a cholesteric liquid crystal layer.

[0084] Example 9 This embodiment provides a method for preparing a cholesteric liquid crystal layer.

[0085] The cholesteric liquid crystal layer has three pitch structures of different sizes in the thickness direction: a P1 liquid crystal polymer layer with a pitch of 291nm and a thickness of 3μm; a P2 liquid crystal polymer layer with a pitch of 335nm and a thickness of 3.5μm; and a P3 liquid crystal polymer layer with a pitch of 392nm and a thickness of 4μm. The total thickness of the cholesteric liquid crystal layer is 10.5μm.

[0086] The method for preparing a cholesteric liquid crystal layer comprises: (1) Pretreatment of the substrate layer, (2) Preparation of the liquid crystal mixture and (3) Coating of the liquid crystal mixture are the same as in Example 9, except that a P1 liquid crystal polymer layer, a P2 liquid crystal polymer layer and a P3 liquid crystal polymer layer are sequentially coated on the corona-treated substrate layer. The P1 liquid crystal polymer layer is the same as the liquid crystal mixture described in Example 9, and the raw materials for preparing the P2 liquid crystal polymer layer differ from the raw materials for preparing the P1 liquid crystal polymer layer in that the content of the X13 compound (chiral compound) is 1.7% and the content of propylene glycol monomethyl ether acetate (organic solvent) is 16.3%. The raw materials for preparing the P3 liquid crystal polymer layer differ from the raw materials for preparing the P1 liquid crystal polymer layer in that the content of the X13 compound (chiral compound) is 1.4% and the content of propylene glycol monomethyl ether acetate (organic solvent) is 16.6%.

[0087] Embodiments 10 to 15 This embodiment provides a circular polarizer, which includes: a cholesteric liquid crystal layer, a phase difference layer, a linear polarizer layer and a viewing angle compensation layer, wherein the cholesteric liquid crystal layer is located between the display substrate and the phase difference layer, the linear polarizer layer is located on the side of the phase difference layer away from the cholesteric liquid crystal layer, and the viewing angle compensation layer is located between the cholesteric liquid crystal layer and the display substrate. The compositions of the circular polarizers of embodiments 10 to 15 are shown in Table 9.

[0088] Comparative Example 1~2 This comparative example provides a circular polarizer, which includes: a cholesteric liquid crystal layer, a phase difference layer, a linear polarizer layer and a viewing angle compensation layer. The compositions of the circular polarizers of comparative examples 1 and 2 are shown in Table 9.

[0089] Table 9 Structural composition of different circular polarizers

[0090] Embodiment 17 This embodiment provides a display device.

[0091] The display device described in this embodiment includes the circular polarizer and the display substrate in Examples 10 to 16 and Comparative Examples 1 to 2.

[0092] When measuring the light output efficiency of the circular polarizer at different viewing angles, the circular polarizer is attached to the display panel, and the wavelength of light emitted by the display substrate includes blue light with a central wavelength of 460nm, green light with a central wavelength of 530nm, and red light with a central wavelength of 620nm. The light output brightness at different viewing angles is measured by optical power and measured in nit. The test results are shown in Table 10.

[0093] Table 10 Light output efficiency of circular polarizer at different viewing angles

[0094] The viewing angle compensation layer is located between the cholesteric liquid crystal layer and the display substrate, and its structural design has significant advantages in improving the wide viewing angle display effect of the liquid crystal display device. As shown in Table 10, the light extraction efficiency of Comparative Example 2 (without viewing angle compensation layer and cholesteric liquid crystal layer) is the lowest at all viewing angles, while the light extraction efficiency of Comparative Example 1 (with cholesteric liquid crystal layer but without viewing angle compensation layer) is greatly improved at normal incident viewing angle and small incident viewing angle (0°~30°), but as the viewing angle increases, the brightening efficiency is greatly attenuated, and the display effect is not good at a wide viewing angle (31°~80°).

[0095] The present invention effectively solves this problem by adding a viewing angle compensation layer between the display substrate and the cholesteric liquid crystal layer. The data comparison of Examples 10 to 16 with Comparative Example 1 shows that no matter whether the added viewing angle compensation layer is a microstructure viewing angle compensation layer (Example 14), a non-liquid crystal polymer coating with viewing angle compensation particles added (Examples 10 to 13), a liquid crystal polymer coating with viewing angle compensation particles added (Example 15) or a polymerizable liquid crystal coating (Example 16), the angle of the light emitted from the display substrate can be expanded, so that the light originally concentrated in a small viewing angle range is redistributed to a larger viewing angle range, thereby compensating for the light efficiency loss of the cholesteric liquid crystal layer at a large viewing angle, and improving the display effect of the display device at a large viewing angle. In particular, the brightness of Example 12 (inorganic organic mixture) at 0° and 80° viewing angles is 114nit and 78nit, respectively, which is significantly improved compared to 112nit and 75nit of Example 10 (inorganic matter). This shows that the inorganic and organic mixtures have a more uniform scattering effect on the emitted light through the synergistic effect of the flexibility of the organic matter and the rigidity of the inorganic matter.

[0096] In addition, the structure of the cholesteric liquid crystal layer also has a significant impact on the display performance. The brightness of Example 10 with a single pitch structure is 75nit at a viewing angle of 80°, while Example 11 with a three-pitch structure increases the brightness to 92nit. The cholesteric liquid crystal layer with a multi-pitch structure can be adjusted to display the red, green and blue three-color spectrum, greatly improving the light output efficiency of the display device. The synergistic effect of pitch and thickness also enhances the brightening efficiency at a wide viewing angle. For example, the superposition of different pitch layers in Example 9 makes the total thickness reach 10.5μm, further improving the display performance.

[0097] In summary, Example 15 (using the viewing angle compensation layer of Example 6 and the cholesteric liquid crystal layer of Example 9) exhibits the highest brightness and the most gentle attenuation at the full viewing angle of 0°~80°, especially at the wide angle of 31°~80°. The synergistic effect of the viewing angle compensation particles and the focal conic texture of the liquid crystal achieves efficient light regulation at a wide viewing angle, taking into account both the normal viewing angle efficiency and the wide viewing angle performance, and is very suitable for high-demand wide viewing angle display scenes. The design of the viewing angle compensation layer between the cholesteric liquid crystal layer and the display substrate not only effectively compensates for the optical path difference at a wide viewing angle, but also significantly improves the overall performance of the display device through the optimization of materials and structures.

[0098] The embodiments described above are part of the embodiments of the present invention, rather than all of the embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. All other embodiments obtained without creative work and related deductions and substitutions made by ordinary technicians in the field under the conditions of the concept of the present invention belong to the scope of protection of the present invention.

Claims

1. A circular polarizer based on viewing angle compensation, the circular polarizer is placed on a display substrate, characterized in that: The circular polarizer comprises a viewing angle compensation layer, a cholesteric liquid crystal layer, a phase difference layer and a linear polarization layer; The cholesteric liquid crystal layer is located between the display substrate and the phase difference layer, the linear polarizing layer is located on the side of the phase difference layer away from the cholesteric liquid crystal layer, and the viewing angle compensation layer is located between the cholesteric liquid crystal layer and the display substrate.

2. The circular polarizer based on viewing angle compensation according to claim 1, characterized in that: The viewing angle compensation layer is selected from any one of a microstructure viewing angle compensation layer, a non-liquid crystal polymer coating with viewing angle compensation particles added thereto, a liquid crystal polymer coating with viewing angle compensation particles added thereto, and a polymerizable liquid crystal coating.

3. The circular polarizer based on viewing angle compensation according to claim 2, characterized in that: The surface roughness Ra of the microstructure viewing angle compensation layer is 10nm~2μm.

4. The circular polarizer based on viewing angle compensation according to claim 2, characterized in that: The viewing angle compensation particles in the non-liquid crystal polymer coating layer to which viewing angle compensation particles are added are inorganic substances with a diameter of 10 nm to 30 μm and / or organic substances with a diameter of 1 μm to 50 μm.

5. The circular polarizer based on viewing angle compensation according to claim 4, characterized in that: The inorganic substance is selected from at least one of titanium dioxide, calcium carbonate, barium sulfate and silicon dioxide; The organic matter is selected from at least one of polymethyl methacrylate, polybutyl methacrylate, polystyrene, polymerizable liquid crystal monomers, and siloxane resin.

6. The circular polarizer based on viewing angle compensation according to claim 4, characterized in that: The non-liquid crystal polymerizable coating with added viewing angle compensation particles is prepared by mixing and solidifying the viewing angle compensation particles and a non-liquid crystal polymerizable colloid, and the mass ratio of the viewing angle compensation particles to the non-liquid crystal polymerizable colloid is 0.1~1.2:1; the non-liquid crystal polymerizable colloid is a mixture of one or more of methyl methacrylate, butyl methacrylate, and styrene.

7. The circular polarizer based on viewing angle compensation according to claim 2, characterized in that: The polymerizable liquid crystal coating is a liquid crystal polymer layer with focal conic texture containing a chiral compound.

8. The circular polarizer based on viewing angle compensation according to claim 2, characterized in that: The liquid crystal polymer coating layer with viewing angle compensation particles added thereto is prepared by mixing the viewing angle compensation particles and a liquid crystal mixture, coating the mixture on a substrate layer, and then curing the mixture; The mass ratio of the viewing angle compensation particles to the liquid crystal mixture is 0.1-1.2:1; The liquid crystal mixture comprises, by weight: 100 to 980 parts of a polymerizable liquid crystal monomer, 5 to 300 parts of a chiral compound, 1 to 50 parts of a photoinitiator, and 5 to 800 parts of an organic solvent; The substrate layer is an organic film with a thickness of 5 to 300 μm.

9. The circular polarizer based on viewing angle compensation according to claim 8, characterized in that: The polymerizable liquid crystal monomer is selected from one or more of nematic liquid crystal, discotic liquid crystal, and smectic liquid crystal; The polymerizable liquid crystal monomer contains n polymerizable groups, wherein n≥1; The polymerizable group is one of an alkenyl group, an alkynyl group, an epoxy group, and a mercapto group.

10. A display device, characterized in that: The invention comprises the circular polarizer according to claim 1 and a display substrate.

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