An optical film assembly and an OLED display device

Abstract

This invention discloses an optical film assembly and an OLED display device. The OLED display device includes a light-emitting panel and an optical film assembly, which comprises a brightness enhancement layer, a phase retardation layer, and a linear polarizing layer. The composite film layer formed by the brightness enhancement layer and the phase retardation layer in the optical film assembly exhibits better reverse wavelength dispersion, improving the light extraction efficiency of the display device. Simultaneously, the thickness of the optical film assembly is smaller. The optical film assembly prepared by this invention exhibits high circular polarization rate for single-color light wavelengths or multiple-color light wavelengths, specifically 0.98–0.99, which is significantly improved compared to the comparative example. The haze is 0.3%, and the transmittance is better than the comparative example. The thickness of the optical film assembly is less than 20 μm, significantly smaller than that of the comparative example. The linear polarizing layer, brightness enhancement layer, and phase retardation layer in the optical film assembly of this invention can be polymerized into a single film in a simple process, improving the yield of the optical film assembly.

Description

Technical Field

[0001] This invention belongs to the field of organic electroluminescence technology and relates to an optical film assembly and an OLED display device. Background Technology

[0002] With the continuous improvement of social informatization, new display technologies such as liquid crystal display (LCD), organic light-emitting diode (OLED), Mini-LED, and Micro-LED have made significant progress. OLED display technology is a self-emissive display technology that does not require backlighting. It has advantages such as simple structure, high contrast, thinness, wide viewing angle, fast response speed, low driving voltage, low power consumption, applicability to flexible panels, and wide operating temperature range. OLED display devices are widely used in mobile phones, media players, and televisions. To shield ambient light, OLED displays add a circular polarizer layer composed of a linear polarizer and a phase retardation layer to the outside of the light-emitting panel. Due to its structure, the linear polarizer can only utilize up to 50% of the light emitted by the light-emitting panel, with the remainder being absorbed, resulting in a light utilization efficiency of less than 50% for the light-emitting panel.

[0003] Existing technologies typically use phase retardation layers to correct the phase difference of light to improve the display effect of optical displays. However, existing phase retardation layers can only provide relatively accurate phase retardation values ​​for a single wavelength of light, exhibiting poor inverse wavelength dispersion. Patent CN114755750A discloses a display device and a method for manufacturing an optical film. The display device includes a display panel and a polarization layer and a phase retardation layer disposed on the display panel. The phase retardation layer has two layers and can transmit polarized ultraviolet light in the wavelength range of 254–365 nm. Since existing phase retardation layers only address the phase retardation of a single wavelength of light, providing an optical film assembly with better inverse wavelength dispersion and higher light utilization efficiency is of great significance. Summary of the Invention

[0004] To address the problems of poor light inverse wavelength dispersion and low light utilization efficiency in existing technologies, this invention proposes an optical film assembly comprising a brightness enhancement layer, a phase retardation layer, and a linear polarizing layer. The brightness enhancement layer includes at least one cholesteric liquid crystal layer. The phase retardation layer is a quarter-phase retardation layer corresponding to the modulated wavelength light of the cholesteric liquid crystal layer with the largest pitch in the brightness enhancement layer.

[0005] On the one hand, in order to achieve the technical objective of the present invention, the present invention proposes an optical film assembly, including a brightness enhancement layer, a phase retardation layer and a linear polarizing layer. The brightness enhancement layer includes at least one cholesteric liquid crystal layer, and any two cholesteric liquid crystal layers have different pitches. The phase retardation layer is a quarter-phase retardation layer corresponding to the wavelength of the modulated light in the cholesteric liquid crystal layer with the largest pitch in the brightness enhancement layer.

[0006] Furthermore, in the optical film assembly provided by this invention, any cholesteric liquid crystal layer is selected from one of a red light enhancement layer, a green light enhancement layer, and a blue light enhancement layer. The blue light wavelength range is 430–480 nm, the green light wavelength range is 500–580 nm, and the red light wavelength range is 590–680 nm.

[0007] Furthermore, in the optical film assembly provided by the present invention, the cholesteric liquid crystal layer can selectively transmit one of the left-handed and right-handed circularly polarized light in a specific wavelength band and reflect the other circularly polarized light, depending on its pitch and direction of rotation. After the reflected circularly polarized light is reflected again by the reflective electrode of the light-emitting panel, the direction of rotation of the circularly polarized light changes, thereby passing through the brightening layer.

[0008] Cholesteric liquid crystal layers with different pitch sizes can be used to control the reflection of light of different wavelengths. The cholesteric liquid crystal layer in this invention has a uniform pitch structure within this layer. The relationship between the reflected wavelength λ and the pitch P is as follows:

[0009] λ=n×P×cosθ

[0010] In the formula, n is the refractive index of the cholesteric liquid crystal layer, and θ is the angle between the incident ray and the helical axis of the cholesteric liquid crystal layer.

[0011] Furthermore, to enhance brightness across all visible light bands, the brightening layer has multiple pitches or a continuous pitch gradient distribution, where the bandwidth Δλ of the reflection wavelength for a single pitch is:

[0012] Δλ=Δn×P×cosθ

[0013] In the formula, Δn is the in-plane birefringence of the cholesteric liquid crystal layer.

[0014] The bandwidth of the brightness enhancement layer's reflection wavelength is the union of the reflection wavelength bandwidths of each pitch:

[0015] Δλ=Δn1×P1×cosθ1∪Δn2×P2×cosθ2∪···Δn m ×P m ×cosθ m

[0016] The optical film module can control the wavelength range of light from 430 to 680 nm; the thickness of the optical film module is less than 20 μm.

[0017] Furthermore, in the optical film assembly provided by the present invention, any two cholesteric liquid crystal layers have different pitches, wherein the cholesteric liquid crystal layer with the smaller pitch is located on the light-emitting side of the light-emitting panel, and the cholesteric liquid crystal layer with the larger pitch is located on the side of the cholesteric liquid crystal layer with the smaller pitch away from the light-emitting panel; preferably, the cholesteric liquid crystal layer with the smallest pitch is located on the light-emitting side of the light-emitting panel, the cholesteric liquid crystal layer with the largest pitch is located on the outermost side of the cholesteric liquid crystal layer away from the light-emitting panel, and the cholesteric liquid crystal layers with the remaining pitches are arranged sequentially in order of pitch size.

[0018] Furthermore, in the optical film assembly provided by the present invention, cholesteric liquid crystal layers with different pitches are arranged sequentially according to the pitch size, and the thickness of each cholesteric liquid crystal layer is different. The liquid crystal materials in each cholesteric liquid crystal layer may be the same or different; preferably, the liquid crystal materials in each cholesteric liquid crystal layer are the same.

[0019] Furthermore, in the optical film assembly provided by the present invention, the phase retardation layer is prepared by a liquid crystal material, which may be the same as or different from the liquid crystal material used to prepare the cholesteric phase liquid crystal brightening layer; preferably, the liquid crystal material is the same as the liquid crystal material used to prepare the cholesteric phase liquid crystal brightening layer.

[0020] This invention does not specifically limit the material of the linear polarizing layer in the optical film assembly. Linear polarizing layers prepared by those skilled in the art using liquid crystal compounds and linear dichroic light-absorbing materials or polyvinyl alcohol iodine-based polarizers have similar effects.

[0021] This invention does not specifically limit the linear dichroic light-absorbing materials in linear polarizing materials; examples are as follows:

[0022]

[0023]

[0024] Furthermore, in the optical film assembly provided by the present invention, the liquid crystal material is prepared by liquid crystal monomers, photoinitiators, chiral compounds, and solvents in proportion.

[0025] This invention does not specifically limit the liquid crystal material used in the preparation of optical film modules. Those skilled in the art can use nematic liquid crystals, disk-shaped liquid crystals, and disc-shaped liquid crystals; the liquid crystal materials are shown below.

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035] Exemplarily, the present invention provides an optical film assembly comprising a brightness enhancement layer, a phase retardation layer, and a linear polarizing layer sequentially stacked on the light-emitting side of a light-emitting panel. The brightness enhancement layer consists of three cholesteric liquid crystal layers with different pitches: a red brightness enhancement layer, a green brightness enhancement layer, and a blue brightness enhancement layer, which are sequentially stacked on the light-emitting side of the light-emitting panel. In this optical film assembly, the phase retardation layer is a quarter-phase retardation layer corresponding to the wavelength of the light controlled by the red brightness enhancement layer; the phase retardation layer and the red brightness enhancement layer together constitute a quarter-phase retardation layer corresponding to the wavelength of the light controlled by the green brightness enhancement layer; and the phase retardation layer, the red brightness enhancement layer, and the green brightness enhancement layer together constitute a quarter-phase retardation layer corresponding to the wavelength of the light controlled by the blue brightness enhancement layer.

[0036] Exemplarily, the present invention provides an optical film assembly comprising a brightness enhancement layer, a phase retardation layer, and a linear polarizing layer sequentially stacked on the light-emitting side of a light-emitting panel. The brightness enhancement layer consists of three cholesteric liquid crystal layers with different pitches: a red brightness enhancement layer, a green brightness enhancement layer, and a blue brightness enhancement layer, which are sequentially stacked on the light-emitting side of the light-emitting panel. In this optical film assembly, the phase retardation layer is a quarter-phase retardation layer corresponding to the wavelength of the controlled light from the red brightness enhancement layer; the phase retardation layer and the red brightness enhancement layer together constitute a quarter-phase retardation layer corresponding to the wavelength of the controlled light from the blue brightness enhancement layer; and the phase retardation layer and the red brightness enhancement layer together constitute a quarter-phase retardation layer corresponding to the wavelength of the controlled light from the green brightness enhancement layer.

[0037] Exemplarily, the present invention provides an optical film assembly comprising a brightness enhancement layer, a phase retardation layer, and a linear polarizing layer sequentially stacked on the light-emitting side of a light-emitting panel. The brightness enhancement layer consists of two cholesteric liquid crystal layers with different pitches, namely a red brightness enhancement layer and a blue brightness enhancement layer, which are sequentially stacked on the light-emitting side of the light-emitting panel. In this optical film assembly, the phase retardation layer is a quarter-phase retardation layer corresponding to the wavelength of the controlled light from the red brightness enhancement layer; the phase retardation layer and the red brightness enhancement layer together constitute a quarter-phase retardation layer corresponding to the wavelength of the controlled light from the blue brightness enhancement layer.

[0038] Exemplarily, the present invention provides an optical film assembly comprising a brightness enhancement layer, a phase retardation layer, and a linear polarizing layer sequentially stacked on the light-emitting side of a light-emitting panel. The brightness enhancement layer consists of two cholesteric liquid crystal layers with different pitches, namely a red brightness enhancement layer and a green brightness enhancement layer, which are sequentially stacked on the light-emitting side of the light-emitting panel. In this optical film assembly, the phase retardation layer is a quarter-phase retardation layer corresponding to the wavelength of the controlled light from the red brightness enhancement layer; the phase retardation layer and the red brightness enhancement layer together constitute a quarter-phase retardation layer corresponding to the wavelength of the controlled light from the green brightness enhancement layer.

[0039] Exemplarily, the present invention provides an optical film assembly comprising a brightness enhancement layer, a phase retardation layer, and a linear polarizing layer sequentially stacked on the light-emitting side of a light-emitting panel. The brightness enhancement layer consists of two cholesteric liquid crystal layers with different pitches, namely a blue brightness enhancement layer and a green brightness enhancement layer, which are sequentially stacked on the light-emitting side of the light-emitting panel. In this optical film assembly, the phase retardation layer is a quarter-phase retardation layer corresponding to the wavelength of the light controlled by the green brightness enhancement layer; the phase retardation layer and the green brightness enhancement layer together constitute a quarter-phase retardation layer corresponding to the wavelength of the light controlled by the blue brightness enhancement layer.

[0040] Exemplarily, the present invention provides an optical film assembly comprising a brightness enhancement layer, a phase retardation layer, and a linear polarizing layer sequentially stacked on the light-emitting side of a light-emitting panel. The brightness enhancement layer is a single-pitch cholesteric liquid crystal layer, selected from a red light brightness enhancement layer, a green light brightness enhancement layer, a blue light brightness enhancement layer, or a brightness enhancement layer for other wavelengths of light. In this optical film assembly, the phase retardation layer is a quarter-phase retardation layer corresponding to the wavelength of the controlled light from the cholesteric liquid crystal layer.

[0041] On the other hand, the present invention provides a method for preparing an optical film assembly, specifically a first process, which includes the following steps:

[0042] Step 1: Coat the phase retardation layer liquid crystal mixture onto the linear polarizing layer, and remove the solvent from the phase retardation layer liquid crystal mixture by heating and ventilation.

[0043] Step 2: Coat the cholesteric liquid crystal layer with the maximum pitch onto the phase retardation layer liquid crystal mixture with a liquid crystal mixture, and remove the solvent from the liquid crystal mixture by heating and ventilation to obtain the cholesteric liquid crystal layer with the maximum pitch.

[0044] Step 3: Repeat Step 2 until all cholesteric liquid crystal layers with different pitches have been coated. Preferably, the coating order is arranged from largest to smallest.

[0045] Step 4: At a certain temperature, the phase retardation layer and brightness enhancement layer prepared by the above coating are irradiated with ultraviolet light and cured to prepare the required optical film assembly.

[0046] The optical film assembly obtained through the first process may have a mixed layer thickness of 10–500 nm caused by the infiltration between the phase retardation liquid crystal layer and adjacent cholesteric liquid crystal layers or cholesteric liquid crystal layers with different pitches in the thickness direction.

[0047] For example, the present invention provides a method for preparing an optical film assembly, specifically a second process, which includes the following steps:

[0048] Step 1: The phase retardation layer liquid crystal mixture is coated onto the linear polarizing layer, and the solvent in the liquid crystal mixture is removed by heating and ventilation. At a certain temperature, the phase retardation layer liquid crystal mixture is irradiated with an ultraviolet lamp to cure it, thus preparing the desired phase retardation layer.

[0049] Step 2: The cholesteric liquid crystal layer with the largest pitch is coated onto the phase retardation layer using a liquid crystal mixture. The solvent in the liquid crystal mixture is removed by heating and ventilation. At a certain temperature, the cholesteric liquid crystal layer with the largest pitch is cured by irradiation with an ultraviolet lamp to prepare the desired cholesteric liquid crystal layer with the largest pitch.

[0050] Step 3: Repeat Step 2 until all cholesteric liquid crystal layers with different pitches have been prepared. Preferably, the above preparation order is arranged in descending order of pitch.

[0051] For example, the present invention provides a method for preparing an optical film assembly, specifically a third process, which includes the following steps:

[0052] Step 1: The phase retardation layer liquid crystal mixture is coated onto a substrate, and the solvent in the liquid crystal mixture is removed by heating and ventilation. At a certain temperature, the phase retardation layer liquid crystal mixture is irradiated with an ultraviolet lamp to cure, thus preparing the desired phase retardation layer.

[0053] Step 2: The cholesteric phase liquid crystal layer with the largest pitch is coated onto the substrate with a liquid crystal mixture. After heating and ventilation, the solvent in the liquid crystal mixture is removed to obtain the cholesteric phase liquid crystal layer with the largest pitch.

[0054] Step 3: Repeat Step 2 until all cholesteric liquid crystal layers with different pitches have been coated. The above preparation sequence is arranged from largest to smallest pitch.

[0055] Step 4: At a certain temperature, the above-mentioned multilayer cholesteric liquid crystal coatings with different pitches are irradiated with ultraviolet light and cured to prepare the desired brightening layer.

[0056] Step 5: The linear polarizing layer, phase retardation layer and brightness enhancement layer are bonded together with optical adhesive to prepare the required optical film assembly.

[0057] For example, the present invention provides a method for preparing an optical film assembly, specifically a fourth process, which includes the following steps:

[0058] Step 1: The linear polarizing layer is coated onto the substrate with a liquid crystal mixture. After heating and ventilation, the solvent in the liquid crystal mixture is removed to obtain the linear polarizing liquid crystal layer.

[0059] Step 2: Repeat steps 1 to 3 in process 1 to prepare the required optical film assembly.

[0060] This invention does not specifically limit the substrate, and those skilled in the art can use organic materials such as polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polymethyl methacrylate (PMMA).

[0061] Furthermore, this invention does not specifically limit the orientation method of the initial liquid crystal molecules in the first step of the optical film assembly coating process. Those skilled in the art can use bilayer film extrusion orientation, blade coating orientation, electric field orientation, magnetic field orientation, light-controlled orientation, molecular bonding orientation of the substrate surface layer, and triboelectric orientation of the substrate layer, etc. The orientation of the initial liquid crystal molecule layer in the Nth step coating is determined by the termination liquid crystal molecule layer in the (N-1)th step coating.

[0062] The optical adhesive is a non-birefringent and photocurable optical adhesive. Furthermore, the photocuring conditions of the optical adhesive are the same as those of the brightness enhancement layer.

[0063] This invention does not specifically limit the coating process used in the preparation of optical film modules. Those skilled in the art can employ coating processes such as gravure coating, slot coating, reverse roller coating, rotator coating, inkjet coating, printing coating, knife roller coating, metering rod coating, grooved die coating, curtain coating, air knife coating, extrusion die coating, closed-loop doctor blade coating, offset gravure coating, single-roller matching coating, reverse matching coating using a small-diameter gravure roller, three-reverse roller coating, four-reverse roller coating, forward roller coating, doctor blade coating, blade coating, impregnation coating, MB coating, and MB reverse coating.

[0064] This invention does not specifically limit the polymerization process of the liquid crystal mixture in the preparation of the optical film assembly. Those skilled in the art can use thermal polymerization, photopolymerization, or other common polymerization methods. Photopolymerization is preferred, where the light source is ultraviolet or visible light with a wavelength of 150–800 nm; more preferably, the light source is ultraviolet light with a wavelength of 300–400 nm. The light source is emitted by one of the following: a low-pressure mercury lamp, a high-pressure mercury lamp, a deuterium lamp, a metal halide lamp, an argon resonance lamp, a xenon lamp, or an excimer laser. The irradiation dose is 1000 J / m². 2 ~200000J / m 2.

[0065] In the preparation of the optical film assembly, after coating the liquid crystal mixture, the temperature of the liquid crystal mixture before and during curing is greater than or equal to the critical temperature at which each liquid crystal molecule in the liquid crystal mixture is in a liquid crystal state. To ensure the liquid crystal state, a lower liquid crystal mixture temperature is preferred, as lower temperatures result in better order parameters of the liquid crystal molecules.

[0066] This invention provides an OLED display device, including an optical film assembly stacked on a light-emitting panel, wherein the optical film assembly includes a brightness enhancement layer, a phase retardation layer, and a linear polarizing layer. The light-emitting panel and the optical film assembly are bonded together with optical adhesive. The light emitted by the light-emitting panel has a wavelength of 380–760 nm.

[0067] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0068] The optical film assembly prepared by this invention exhibits better reverse wavelength dispersion and higher light extraction efficiency in the display device. When the optical film assembly consists of a linear polarizing layer, a phase retardation layer, a red light enhancement layer, a green light enhancement layer, and a blue light enhancement layer in sequence, the phase retardation layer serves as a quarter-phase retardation layer for the wavelength of light controlled by the red light enhancement layer. The phase retardation layer and the red light enhancement layer together serve as a quarter-phase retardation layer for the wavelength of light controlled by the corresponding green light enhancement layer. The phase retardation layer, the red light enhancement layer, and the green light enhancement layer together serve as a quarter-phase retardation layer for the wavelength of light controlled by the corresponding blue light enhancement layer. The optical film assembly provided by this invention not only has a good circular polarization effect for a single color wavelength but also a high circular polarization rate for multiple color wavelengths. The circular polarization rates of the optical film assembly prepared by this invention for red, green, and blue light are all 0.98–0.99, which is a significant increase compared to the 0.93 of the comparative example.

[0069] The optical film assembly prepared by this invention has a smaller thickness and lower haze, resulting in better light transmittance and higher quality. This invention enables the linear polarizing layer, phase retardation layer, and brightness enhancement layer to be polymerized into a single film in one step, eliminating the need for photoresist bonding of the layers. This simplifies the fabrication process, significantly improves the yield of the optical film assembly, and substantially reduces its thickness. The thickness of the optical film assembly prepared by this invention is less than 20 μm, while in Comparative Example 1, where the layers are connected by optical adhesive, the thickness is 160 μm. This invention's fabrication method significantly reduces the thickness of the optical film assembly. The haze of the optical film assembly prepared by this invention is 0.3%, compared to 1.0% in the Comparative Example, demonstrating a better haze reduction effect. The linear polarizing layer, phase retardation layer, and brightness enhancement layer in this invention can be polymerized into a single film in one step, simplifying the fabrication process and significantly improving the yield of the optical film assembly. Attached Figure Description

[0070] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention.

[0071] Figure 1 This is a schematic diagram of the structure of the OLED display device of the present invention.

[0072] The reference numerals in the attached figures are explained as follows: S100—Emitting panel; S200—Brightening layer; S300—Phase delay layer; S400—Linear polarizing layer. Detailed Implementation

[0073] The technical solution of the present invention will now be described with reference to the embodiments. However, the present invention is not limited to the following embodiments. Unless otherwise specified, the experimental methods and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0074] Example 1

[0075] This embodiment provides an optical film assembly and its preparation method, specifically including the following steps:

[0076] Preparation of orientation layer

[0077] An orientation layer was coated on a PET substrate. By weight, the orientation layer consisted of 10 parts modified polyvinyl alcohol, 200 parts water, 50 parts methanol, 20 parts isopropanol, and 1 part BASF photoinitiator IRGACURE 2959. The layer was dried at 65℃ for 1 minute followed by 100℃ for 2 minutes, resulting in a cured orientation layer thickness of 0.8 μm. The orientation layer was then rubbed to create grooves with a depth of 50–200 nm on its surface, facilitating orientation. Film thickness, groove shape, and depth were measured using a reflective film thickness gauge SR-C (Wuhan Yiguang Technology). Haze was measured using a haze meter TH-100 (Hangzhou Caipu Technology Co., Ltd.). The saponification degree of the modified polyvinyl alcohol was 97.5%, and its structure is as follows:

[0078]

[0079] Linear polarizing layer fabrication

[0080] A linear polarizing liquid crystal compound was applied to the alignment layer using a slit coating method. The mixture was heated at 120°C for 2 minutes to ensure uniform liquid crystal alignment and remove the solvent. After cooling to 90°C, the mixture was subjected to nitrogen protection using a metal halide lamp at 90°C and 1000 J / m². 2The liquid crystal layer is cured into a linear polarizing layer by ultraviolet irradiation, and the thickness of the linear polarizing layer is 5 μm. The liquid crystal mixture of the linear polarizing layer is prepared by liquid crystal monomers, linear dichroic light-absorbing materials, photoinitiators, and solvents in a certain proportion. Specifically, by mass, the contents of each component are as follows: liquid crystal compound (1) 23 parts, liquid crystal compound (2) 28 parts, liquid crystal compound (3) 15 parts, liquid crystal compound (4) 22 parts, liquid crystal compound (5) 9 parts, liquid crystal compound (6) 32 parts, Z2 24 parts, Z5 17 parts, 4-tert-butylphenyliodonium diphenyliodonium tetrafluoroborate 3 parts, propylene glycol monomethyl ether acetate 240 parts, and ethylene glycol dimethyl ether 85 parts.

[0081] Phase delay layer fabrication

[0082] A phase retardation layer liquid crystal mixture was coated onto the linear polarizing layer and heated at 120°C for 2 min to homogenize the liquid crystal and remove the solvent. After cooling to 90°C, the mixture was subjected to nitrogen protection using a metal halide lamp at 90°C and 1000 J / m². 2 The liquid crystal layer is cured into a phase retardation layer under ultraviolet light. The phase retardation layer has a thickness of 0.8 μm. The phase retardation layer liquid crystal mixture is prepared by liquid crystal monomers, photoinitiators, chiral compounds, and solvents in a specified ratio. Specifically, the contents of each component by mass are as follows: 20 parts of liquid crystal compound (6), 21 parts of liquid crystal compound (9), 25 parts of liquid crystal compound (12), 7 parts of liquid crystal compound (4), 14 parts of liquid crystal compound (5), 19 parts of liquid crystal compound (22), 3 parts of 4-tert-butylphenyliodonium diphenyliodonium tetrafluoroborate, 0.5 parts of chiral compound (1), 240 parts of propylene glycol monomethyl ether acetate, and 85 parts of ethylene glycol dimethyl ether.

[0083]

[0084] Preparation of brightening layer

[0085] A red-light enhancement layer liquid crystal mixture was coated onto the phase retardation layer and heated at 120°C for 2 minutes to homogenize the liquid crystal and remove the solvent. After cooling to 90°C, the mixture was heated under nitrogen protection using a metal halide lamp at 90°C and 1000 J / m². 2The liquid crystal layer was cured into a red light enhancement layer by ultraviolet irradiation. The red light enhancement layer had a thickness of 4 μm, a birefringence of 0.22, an average refractive index of 1.63, and a pitch of 387 nm. The liquid crystal mixture of the red light enhancement layer was prepared by liquid crystal monomers, photoinitiators, chiral compounds, and solvents in a specified ratio. Specifically, by mass, the contents of each component were as follows: 20 parts of liquid crystal compound (6), 21 parts of liquid crystal compound (9), 25 parts of liquid crystal compound (12), 7 parts of liquid crystal compound (4), 14 parts of liquid crystal compound (5), 19 parts of liquid crystal compound (22), 3 parts of 4-tert-butylphenyliodonium diphenyliodonium tetrafluoroborate, 4.74 parts of chiral compound (1), 240 parts of propylene glycol monomethyl ether acetate, and 85 parts of ethylene glycol dimethyl ether.

[0086] A green brightness enhancement layer liquid crystal mixture was coated onto the red brightness enhancement layer and heated at 120°C for 2 minutes to ensure uniform liquid crystal alignment and remove the solvent. After cooling to 90°C, the mixture was then heated under nitrogen protection using a metal halide lamp at 90°C and 1000 J / m². 2 The liquid crystal layer was cured into a green brightness enhancement layer under ultraviolet light irradiation. The thickness of the green brightness enhancement layer was 3.5 μm, the birefringence was 0.23, the average refractive index was 1.63, and the pitch was 325 nm. The difference between the content of each component in the green brightness enhancement layer liquid crystal mixture and the red brightness enhancement layer liquid crystal mixture is that the chiral compound (1) contains 5.69 parts.

[0087] A blue light enhancement layer liquid crystal mixture was coated onto the green light enhancement layer and heated at 120°C for 2 minutes to ensure uniform liquid crystal alignment and remove the solvent. After cooling to 90°C, the mixture was then heated under nitrogen protection using a metal halide lamp at 90°C and 1000 J / m². 2 The liquid crystal layer was cured into a blue light enhancement layer by ultraviolet irradiation. The blue light enhancement layer had a thickness of 3.5 μm, a birefringence of 0.24, an average refractive index of 1.63, and a pitch of 282 nm. The difference between the content of each component in the blue light enhancement layer liquid crystal mixture and the red light enhancement layer liquid crystal mixture is that the chiral compound (1) contains 6.61 parts.

[0088] In the aforementioned optical film assembly preparation process, the alignment layer determines the initial liquid crystal molecule orientation of the linear polarizing layer liquid crystal mixture; the alignment of the linear polarizing layer termination layer liquid crystal molecule orientation determines the initial liquid crystal molecule orientation of the phase retardation layer; the alignment of the phase retardation layer termination layer liquid crystal molecule orientation determines the initial liquid crystal molecule orientation of the red light enhancement layer liquid crystal mixture; the alignment of the red light enhancement layer termination layer liquid crystal molecule orientation determines the initial liquid crystal molecule orientation of the green light enhancement layer liquid crystal mixture; and the green light enhancement layer termination layer liquid crystal molecule orientation determines the initial liquid crystal molecule orientation of the blue light enhancement layer liquid crystal mixture. The phase retardation layer is a quarter-phase retardation layer corresponding to the wavelength of the controlled light from the red light enhancement layer; the phase retardation layer and the red light enhancement layer together serve as a quarter-phase retardation layer corresponding to the wavelength of the controlled light from the green light enhancement layer; and the phase retardation layer, the red light enhancement layer, and the green light enhancement layer together serve as a quarter-phase retardation layer corresponding to the wavelength of the controlled light from the blue light enhancement layer. This optical film assembly exhibits excellent control effects for incident light with an angle of less than 30° to the direction perpendicular to the optical film assembly surface.

[0089] Example 2

[0090] The preparation method of the optical film group in this embodiment is the same as that in embodiment 1, except that: in the preparation process of the brightening layer, the red light brightening layer, the green light brightening layer and the blue light brightening layer are coated and the solvent is removed, and then the brightening layer is cured in one step.

[0091] Example 3

[0092] The preparation method of the optical film group in this embodiment is the same as that in embodiment 1, except that: in this embodiment, the linear polarizing layer, the phase delay layer and the multi-layer brightness enhancement layer are coated and the solvent is removed before the optical film group is photocured in one step.

[0093] Example 4

[0094] The optical film assembly in this embodiment is prepared in the same way as in embodiment 1, except that the linear polarizing layer in this embodiment was purchased from Sugon Optoelectronics Co., Ltd. and has a thickness of 50 μm. A phase retardation layer and a brightness enhancement layer are prepared on it.

[0095] Example 5

[0096] The fabrication method of the optical film assembly in this embodiment is the same as that in Embodiment 1, except that the brightness enhancement layer prepared in this embodiment includes a red brightness enhancement layer and a green brightness enhancement layer. The phase retardation layer is a quarter-phase retardation layer corresponding to the wavelength of the controlled light in the red brightness enhancement layer, and the phase retardation layer and the red brightness enhancement layer together serve as a quarter-phase retardation layer corresponding to the wavelength of the controlled light in the green brightness enhancement layer.

[0097] Example 6

[0098] The fabrication method of the optical film assembly in this embodiment is the same as in Embodiment 1, except that the brightness enhancement layer prepared in this embodiment includes a red light brightness enhancement layer and a blue light brightness enhancement layer. The thickness of the red light brightness enhancement layer is 5.2 μm. The phase retardation layer is a quarter-phase retardation layer corresponding to the wavelength of the controlled light in the red light brightness enhancement layer, and the phase retardation layer and the red light brightness enhancement layer together serve as a quarter-phase retardation layer corresponding to the wavelength of the controlled light in the blue light brightness enhancement layer.

[0099] Example 7

[0100] The fabrication method of the optical film in this embodiment is the same as in Embodiment 1, except that: the brightness enhancement layer prepared in this embodiment includes a green brightness enhancement layer and a blue brightness enhancement layer, and the phase retardation layer is a one-quarter phase retardation layer for the wavelength of light corresponding to the green brightness enhancement layer. The phase retardation layer and the green brightness enhancement layer together serve as a one-quarter phase retardation layer for the wavelength of light corresponding to the blue brightness enhancement layer. The thickness of the phase retardation layer is 0.72 μm.

[0101] Example 8

[0102] The optical film assembly in this embodiment is prepared in the same way as in Embodiment 1, except that: the brightening layer is a blue light brightening layer, the phase retardation layer is a quarter-phase retardation layer for the blue light corresponding to the controlled wavelength, and the thickness of the phase retardation layer is 0.68 μm.

[0103] Example 9

[0104] The preparation method of the optical film group in this embodiment is the same as that in Example 1, except that: by mass, the content of each component of the liquid crystal mixture in the linear polarizing layer is as follows: 23 parts of liquid crystal compound (12), 28 parts of liquid crystal compound (21), 15 parts of liquid crystal compound (25), 22 parts of liquid crystal compound (36), 9 parts of liquid crystal compound (41), 32 parts of liquid crystal compound (40), 24 parts of Z2, 17 parts of Z5, 3 parts of 4-tert-butylphenyliodonium diphenyliodonium tetrafluoroborate, 240 parts of propylene glycol monomethyl ether acetate, and 85 parts of ethylene glycol dimethyl ether. The contents of each component of the liquid crystal mixture in the phase retardation layer are as follows: 20 parts of liquid crystal compound (13), 21 parts of liquid crystal compound (16), 25 parts of liquid crystal compound (17), 7 parts of liquid crystal compound (25), 14 parts of liquid crystal compound (35), 19 parts of liquid crystal compound (42), 3 parts of 4-tert-butylphenyliodonium diphenyliodonium tetrafluoroborate, 0.5 parts of chiral compound (1), 240 parts of propylene glycol monomethyl ether acetate, and 85 parts of ethylene glycol dimethyl ether. The contents of each component in the liquid crystal mixture in the red light brightening layer are as follows: 20 parts of liquid crystal compound (14), 21 parts of liquid crystal compound (16), 25 parts of liquid crystal compound (24), 7 parts of liquid crystal compound (36), 14 parts of liquid crystal compound (41), 19 parts of liquid crystal compound (4), 3 parts of 4-tert-butylphenyliodonium diphenyliodonium tetrafluoroborate, 4.74 parts of chiral compound (1), 240 parts of propylene glycol monomethyl ether acetate, and 85 parts of ethylene glycol dimethyl ether. The contents of each component in the liquid crystal mixture in the green light enhancement layer are as follows: 20 parts of liquid crystal compound (16), 21 parts of liquid crystal compound (17), 25 parts of liquid crystal compound (23), 7 parts of liquid crystal compound (35), 14 parts of liquid crystal compound (37), 19 parts of liquid crystal compound (40), 3 parts of 4-tert-butylphenyliodonium diphenyliodonium tetrafluoroborate, 5.69 parts of chiral compound (1), 240 parts of propylene glycol monomethyl ether acetate, and 85 parts of ethylene glycol dimethyl ether. The components of the liquid crystal mixture in the blue light enhancement layer are as follows: 20 parts of liquid crystal compound (11), 21 parts of liquid crystal compound (18), 25 parts of liquid crystal compound (25), 7 parts of liquid crystal compound (36), 14 parts of liquid crystal compound (37), 19 parts of liquid crystal compound (38), 3 parts of 4-tert-butylphenyliodonium diphenyliodonium tetrafluoroborate, 6.61 parts of chiral compound (1), 240 parts of propylene glycol monomethyl ether acetate, and 85 parts of ethylene glycol dimethyl ether. Nitrogen protection is not required during curing. The thickness of each film layer in this embodiment is the same as in Example 1.

[0105] Comparative Example 1

[0106] In this comparative example, the optical film assembly includes a linear polarizing layer, a phase retardation layer, and a brightness enhancement layer bonded together with optical adhesive. The brightness enhancement layer is selected from patent CN217181267U and has a thickness of 10 μm; the phase retardation layer is purchased from Teijin GT-138 and has a thickness of 40 μm; the linear polarizing film is purchased from Sugin Optoelectronics Co., Ltd. and has a thickness of 50 μm; the optical adhesive has a thickness of 30 μm.

[0107] Table 1: Brightening wavelength, thickness, circular polarization index, and haze of optical films

[0108] Example 1 R+G+B 17.6μm 0.98 0.3％ Example 2 R+G+B 17.6μm 0.98 0.3％ Example 3 R+G+B 17.6μm 0.99 0.3％ Example 4 R+G+B 61.8μm 0.95 0.5％ Example 5 R+G 14.1μm 0.99 0.3％ Example 6 R+B 15.3μm 0.99 0.3％ Example 7 G+B 13.52μm 0.99 0.3％ Example 8 B 9.98μm 0.99 0.3％ Example 9 R+G+B 17.6μm 0.98 0.3％ Comparative Example 1 R+G+B 160μm 0.93 1.0％

[0109] In the table above, the wavelength of the brightening light R refers to red light with a wavelength between 590 and 680 nm, G refers to green light with a wavelength between 500 and 580 nm, B refers to blue light with a wavelength between 430 and 480 nm, the circular polarization rate refers to the ratio of the minor axis to the major axis of the light that converts linearly polarized light into circularly polarized or elliptical polarized light, and the haze refers to the percentage of transmitted light intensity that deviates from the direction of the incident light by more than 2.5° to the total transmitted light intensity.

[0110] As shown in Table 1, the optical film group prepared by this invention exhibits good circular polarization rates for both single-color and multi-color light wavelengths, and can tune light wavelengths from 430 to 680 nm. The circular polarization rates of the optical film groups prepared by this invention (Examples 1-3, Examples 5-9) for red, green, and blue light wavelengths are between 0.98 and 0.99, with Example 4 showing a circular polarization rate of 0.95. Compared to Comparative Example 1's 0.93, the circular polarization rates of Examples 1-9 are significantly improved. The thickness of the optical film groups prepared by this invention (Examples 1-3, Examples 5-9) is less than 20 μm, a significant reduction compared to the 160 μm thickness of the optical film in Comparative Example 1. The haze of the optical film groups prepared by this invention is 0.3%, and the transmittance is good, showing a significant improvement compared to the 1.0% of the comparative example. The above data shows that the optical film group prepared by the present invention has better reverse wavelength dispersion, improves the light extraction efficiency of the display device, has lower haze, higher light transmittance, and smaller optical film group thickness.

[0111] As described above, the basic principles, main features, and advantages of the present invention have been well described. The above embodiments and specifications are merely descriptions of preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. Various changes and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit and scope of the present invention should fall within the protection scope defined by the present invention.

Claims

1. An optical film assembly, characterized in that, It includes a brightness enhancement layer, a phase retardation layer, and a linear polarizing layer; the brightness enhancement layer includes at least one cholesteric liquid crystal layer; Any two of the cholesteric liquid crystal layers have different pitches; Any of the cholesteric liquid crystal layers is selected from one of the following: red light enhancement layer, green light enhancement layer, and blue light enhancement layer; The phase retardation layer is a quarter-phase retardation layer corresponding to the wavelength of the modulated light in the cholesteric liquid crystal layer with the largest pitch in the brightness enhancement layer. The thickness of the optical film assembly is less than 20 μm; The optical film assembly comprises, in sequence, a linear polarizing layer, a phase retardation layer, a red light enhancement layer, a green light enhancement layer, and a blue light enhancement layer. The phase retardation layer is a quarter-phase retardation layer corresponding to the wavelength of the light controlled by the red light enhancement layer. The phase retardation layer and the red light enhancement layer together form a quarter-phase retardation layer corresponding to the wavelength of the light controlled by the green light enhancement layer. The phase retardation layer, the red light enhancement layer, and the green light enhancement layer together form a quarter-phase retardation layer corresponding to the wavelength of the light controlled by the blue light enhancement layer. Alternatively, the optical film group may consist of a linear polarizing layer, a phase retardation layer, a red light enhancement layer, and a blue light enhancement layer, wherein the phase retardation layer is a quarter-phase retardation layer corresponding to the wavelength of the controlled light of the red light enhancement layer; the phase retardation layer and the red light enhancement layer together constitute a quarter-phase retardation layer corresponding to the wavelength of the controlled light of the blue light enhancement layer. Alternatively, the optical film group may consist of a linear polarizing layer, a phase retardation layer, a red light brightening layer, and a green light brightening layer, wherein the phase retardation layer is a quarter-phase retardation layer corresponding to the wavelength of the light controlled by the red light brightening layer; the phase retardation layer and the red light brightening layer together constitute a quarter-phase retardation layer corresponding to the wavelength of the light controlled by the green light brightening layer. Alternatively, the optical film group may consist of a linear polarizing layer, a phase retardation layer, a green light enhancement layer, and a blue light enhancement layer, wherein the phase retardation layer is a quarter-phase retardation layer corresponding to the wavelength of the light controlled by the green light enhancement layer; and the phase retardation layer and the green light enhancement layer together are a quarter-phase retardation layer corresponding to the wavelength of the light controlled by the blue light enhancement layer.

2. The optical film assembly according to claim 1, characterized in that, The cholesteric liquid crystal layers have different pitches, with the cholesteric liquid crystal layers with smaller pitches located on the light-emitting side of the light-emitting panel, the cholesteric liquid crystal layers with larger pitches located on the side of the cholesteric liquid crystal layers with smaller pitches away from the light-emitting panel, and the cholesteric liquid crystal layers with the remaining pitches arranged in order of pitch size.

3. The optical film assembly according to claim 1, characterized in that, The phase retardation layer is made of liquid crystal material.

4. The optical film assembly according to claim 3, characterized in that, The liquid crystal material is the same as the liquid crystal material in the cholesteric phase liquid crystal layer.

5. The optical film assembly according to claim 1, characterized in that, The linear polarizing layer is prepared by adding a linear dichroic light-absorbing material to a liquid crystal compound.

6. The optical film assembly according to claim 1, characterized in that, The optical film group can control the wavelength range of light from 430 to 680 nm.

7. An OLED display device, characterized in that, The device includes the optical film assembly as described in any one of claims 1 to 6, and also includes a light-emitting panel.

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