A circularly polarizing plate and an OLED display device

Abstract

The application discloses a circular polarizer and an OLED display device, the circular polarizer comprises a linear polarizing plate, a phase compensation film and a cholesteric liquid crystal film structure which are stacked, the linear polarizing plate is used for absorbing light whose vibration direction is perpendicular to the transmission axis and for transmitting light whose vibration direction is parallel to the transmission axis in ambient light and converting the light into linearly polarized light, the phase compensation film is used for converting the linearly polarized light into circularly polarized light; the cholesteric liquid crystal film structure is used for reflecting ultraviolet light and infrared light in ambient light, the cholesteric liquid crystal film structure is composed of one layer of left-handed cholesteric liquid crystal film and one layer of right-handed cholesteric liquid crystal film, or is composed of two layers of left-handed cholesteric liquid crystal film with a half-wave plate in between, or is composed of two layers of right-handed cholesteric liquid crystal film with a half-wave plate in between. The application can effectively shield ultraviolet light and infrared light in ambient light, thereby improving the operation efficiency and service life of the OLED display device.

Description

Technical Field

[0001] This invention belongs to the field of electroluminescent display technology, and specifically relates to a circular polarizer and an OLED display device. Background Technology

[0002] Since the beginning of the 21st century, 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 great strides. OLED and LCD have advantages such as simple structure, self-illumination without backlight, high contrast, thinness, wide viewing angle, fast response speed, applicability to flexible panels, and wide operating temperature range.

[0003] OLED displays are now widely used in mobile phones, computers, televisions, and other display applications. An OLED display typically consists of organic light-emitting diodes (OLEDs), a phase compensation film, and a linear polarizer. In current OLED display technology, when ambient light shines on the outer surface of the linear polarizer, approximately 50% of the ambient light is absorbed by the linear polarizer. The remaining 50% of the ambient light, with its vibration direction parallel to the transmission axis of the linear polarizer, is converted into linearly polarized light by the linear polarizer. This linearly polarized light is then converted into right-handed or left-handed circularly polarized light by the phase compensation film. After being reflected by the emitting electrodes of the light-emitting panel, the rotation direction of this portion of ambient light changes, from right-handed (left-handed) circularly polarized light to left-handed (right-handed) circularly polarized light. This circularly polarized light with its changed rotation direction is then converted into linearly polarized light with its vibration direction perpendicular to the transmission axis of the linear polarizer by the phase compensation film and absorbed by the linear polarizer. This process effectively shields against ambient light. However, a problem arises when ultraviolet light from the ambient light shines on the organic layer of the OLED light-emitting panel, causing partial failure of the organic materials and affecting the lifespan of the OLED light-emitting panel. Furthermore, in existing OLED display devices, the aperture ratio is approximately 40%-50%, with the portion outside the aperture being a light-absorbing structure. This light-absorbing structure absorbs the infrared and ultraviolet portions of ambient light, causing the internal temperature of the OLED display device to rise. This not only reduces the operating efficiency of the OLED display device but also affects its lifespan. Therefore, there is an urgent need for a new technology that can effectively shield the ultraviolet and infrared portions of ambient light before it reaches the light-emitting panel. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a circular polarizer and an OLED display device that can effectively shield ultraviolet and infrared light from ambient light, thereby improving the operating efficiency and lifespan of the OLED display device.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A circular polarizer includes a linear polarizing plate, a phase compensation film, and a cholesteric liquid crystal film structure stacked together. The linear polarizing plate is used to absorb light whose vibration direction is perpendicular to its transmission axis and to allow light in ambient light whose vibration direction is parallel to its transmission axis to pass through and be converted into linearly polarized light. The phase compensation film is used to convert the linearly polarized light into circularly polarized light.

[0007] The cholesteric liquid crystal film structure is used to reflect ultraviolet and infrared light in ambient light. The cholesteric liquid crystal film structure includes at least one cholesteric liquid crystal film structure A layer that reflects ultraviolet light with a wavelength range of 100nm-380nm and at least one cholesteric liquid crystal film structure B layer that reflects infrared light with a wavelength range of 760nm-2500nm. Both the cholesteric liquid crystal film structure A layer and the cholesteric liquid crystal film structure B layer are composed of one layer of levorotatory cholesteric liquid crystal film and one layer of dextrorotatory cholesteric liquid crystal film.

[0008] Furthermore, the cholesteric liquid crystal film structure is used to reflect ultraviolet light with a wavelength range of 100nm-380nm and infrared light with a wavelength range of 760nm-2500nm.

[0009] Furthermore, both the L-cholesterol phase liquid crystal film and the D-cholesterol phase liquid crystal film are cholesterol derivatives, or cholesterol phase liquid crystal materials polymerized from small molecule nematic liquid crystal monomers, chiral compounds, ultraviolet light absorbers and photoinitiators under 360nm ultraviolet irradiation, and the temperature gradient along the thickness direction during the preparation process is 0.5℃~1℃.

[0010] Furthermore, the thickness of the cholesteric liquid crystal film structure is 1μm-100μm.

[0011] Furthermore, the phase compensation film is formed by bonding a quarter-phase retardation film and a quarter-phase compensation film together.

[0012] Furthermore, the quarter-phase retardation film is one or more of the following: polymer stretched anti-dispersion quarter-phase retardation film, polymer stretched A-plate quarter-phase retardation film, liquid crystal anti-dispersion composite quarter-phase retardation film, liquid crystal A-plate quarter-phase retardation film, liquid crystal O-plate quarter-phase retardation film, or liquid crystal biaxial quarter-phase retardation film.

[0013] Furthermore, the linear polarizing plate is formed by bonding two layers of cellulose triacetate with a layer of polyvinyl alcohol sandwiched in between.

[0014] Furthermore, the outer surface of the triacetate cellulose is sequentially coated with pressure-sensitive adhesive, release film, and protective film.

[0015] Furthermore, the linear polarizing plate is located above the phase compensation film, and the cholesteric liquid crystal film is pasted on top of or below the phase compensation film or on top of the linear polarizing plate.

[0016] An OLED display device includes a light-emitting panel, on the surface of which a circular polarizer is attached.

[0017] Compared with the prior art, the present invention has the following technical effects:

[0018] This invention utilizes the principle that cholesteric liquid crystals exhibit Bragg reflection of corresponding light. A cholesteric liquid crystal film structure, which reflects ultraviolet and infrared light from ambient light but does not reflect visible light, is stacked together with a linear polarizer and a phase compensation film to form a circular polarizer that shields against ultraviolet and infrared light from ambient light. This prevents the organic layer in the light-emitting panel of the OLED display device assembled from the circular polarizer from failing due to ultraviolet radiation, and prevents the internal temperature of the OLED display device from rising due to the absorption of infrared and ultraviolet light, thus preventing a decrease in operating efficiency. Therefore, when the circular polarizer of this invention is applied to an OLED display device, it can effectively shield more than 98% of infrared and ultraviolet light from ambient light, thereby improving the operating efficiency and lifespan of the OLED display device.

[0019] This invention allows for the selective attachment of the cholesteric liquid crystal film structure to the top or bottom of the phase compensation film, or to the top of the linear polarizer. As long as the cholesteric liquid crystal film is present above the light-emitting panel to prevent infrared and ultraviolet light from reaching the light-emitting panel, the linear polarizer, phase compensation film, cholesteric liquid crystal film, and light-emitting panel are all connected by adhesive bonding, making the assembly of the OLED display device more convenient and easier to operate. Attached Figure Description

[0020] Figure 1 Schematic diagram of the OLED display device of the present invention Figure 1 ;

[0021] Figure 2 Schematic diagram of the OLED display device of the present invention Figure 2 ;

[0022] Figure 3 Schematic diagram of the OLED display device of the present invention Figure 3 ;

[0023] In the figure: 1. Linear polarizing plate; 2. Phase compensation film; 3. Cholesteric liquid crystal film structure; 4. Light-emitting panel. Detailed Implementation

[0024] The specific content of the present invention will be further explained in detail below with reference to the embodiments.

[0025] A circular polarizer and an OLED display device are disclosed. The OLED display device includes a light-emitting panel 4 and a circular polarizer adhered to its surface. The circular polarizer includes a linear polarizer 1, a phase compensation film 2, and a cholesteric liquid crystal film structure 3 stacked together. The linear polarizer 1 is located above the phase compensation film 2. The cholesteric liquid crystal film structure 3 is adhered above or below the phase compensation film 2, or adhered above the linear polarizer 1, specifically in the following three ways:

[0026] Example 1: When the cholesteric liquid crystal film structure 3 is pasted under the phase compensation film 2, the structure of the OLED display device is as follows. Figure 1 As shown, the cholesteric liquid crystal film structure 3, the phase compensation film 2, and the linear polarizing plate 1 are sequentially stacked and pasted on the top of the light-emitting panel 4;

[0027] Example 2: When the cholesteric liquid crystal film structure 3 is bonded to the phase compensation film 2, the structure of the OLED display device is as follows. Figure 2 As shown, the phase compensation film 2, the cholesteric liquid crystal film structure 3, and the linear polarizing plate 1 are sequentially stacked and pasted on the top of the light-emitting panel 4;

[0028] Example 3: When the cholesteric liquid crystal film structure 3 is bonded to the linear polarizing plate 1, the structure of the OLED display device is as follows. Figure 3 As shown, the phase compensation film 2, the linear polarizing plate 1, and the cholesteric liquid crystal film structure 3 are sequentially stacked and pasted on the top of the light-emitting panel 4.

[0029] The linear polarizer 1 is used to absorb light in the environment whose vibration direction is perpendicular to its transmission axis, and to pass through light in the ambient light whose vibration direction is parallel to its transmission axis and convert it into linearly polarized light. The phase compensation film 2 is used to convert linearly polarized light into right-handed or left-handed circularly polarized light, and at the same time convert the red, green and blue primary color light emitted by the light-emitting panel 4 into right-handed or left-handed circularly polarized light.

[0030] The cholesteric liquid crystal film structure 3 is used to reflect ultraviolet and infrared light in ambient light. However, the cholesteric liquid crystal film structure 3 does not reflect visible light in ambient light. This allows the visible light in ambient light to pass through the linear polarizer 1 and the phase compensation film 2 in sequence, generating right-handed or left-handed circularly polarized light, which then reaches the reflective electrode of the light-emitting panel 4. After being reflected by the light-emitting panel 4, the direction of rotation changes. The circularly polarized light with the changed direction passes through the phase compensation film 2 and is transformed into linearly polarized light with the vibration direction perpendicular to the transmission axis of the linear polarizer 1. Finally, it is absorbed by the linear polarizer 1. This invention utilizes this principle to shield most of the ultraviolet and infrared light in the environment without affecting the display effect of the OLED display device.

[0031] The cholesteric liquid crystal film structure 3 includes at least one cholesteric liquid crystal film structure A layer that reflects ultraviolet light in the wavelength range of 100nm-380nm and at least one cholesteric liquid crystal film structure B layer that reflects infrared light in the wavelength range of 760nm-2500nm. Both the cholesteric liquid crystal film structure A layer and the cholesteric liquid crystal film structure B layer are composed of one layer of levorotatory cholesteric liquid crystal film and one layer of dextrorotatory cholesteric liquid crystal film, or two layers of levorotatory cholesteric liquid crystal film sandwiched with a half-wave plate, or two layers of dextrorotatory cholesteric liquid crystal film sandwiched with a half-wave plate. The pitch of the cholesteric liquid crystal film structure A layer that reflects ultraviolet light is between 40-720nm, and the pitch of the cholesteric liquid crystal film structure B layer that reflects infrared light is between 300-4800nm.

[0032] Cholesteric liquid crystals with a certain pitch will exhibit Bragg reflection of the corresponding light, and the corresponding relationship is expressed as follows: ,in The wavelengths are: ultraviolet light wavelengths in the range of 100-380 nm and infrared light wavelengths in the range of 760-2500 nm; n is the refractive index of the cholesteric liquid crystal, which is between 1.05 and 2.5; θ is the angle between the incident light and the cholesteric liquid crystal film; and P is the pitch of the cholesteric liquid crystal. Using these properties, cholesteric liquid crystal materials are prepared into cholesteric liquid crystal films. The cholesteric liquid crystal material is a cholesterol derivative, or a cholesteric liquid crystal material polymerized from nematic liquid crystals, chiral compounds, ultraviolet absorbers, and photoinitiators under 360 nm ultraviolet irradiation.

[0033] Typically, in the preparation of cholesteric liquid crystal films, different pitch gradients can be obtained by controlling the temperature T, photoinitiator, ultraviolet absorber, ultraviolet light intensity, and chiral compound concentration c in the cholesteric liquid crystal film preparation process. During the preparation process, the temperature T is controlled between 30-100℃, preferably between 40-80℃. The pitch P of the cholesteric liquid crystal film increases with increasing temperature, i.e., P∝T. When preparing cholesteric liquid crystal films with a large pitch gradient range, a certain temperature gradient exists in the film thickness direction, ranging from 0.1-10℃. Under different photoinitiators and ultraviolet light intensities, different polymerization rates of the cholesteric liquid crystal film in the thickness direction result in different pitch gradients, increasing the reflection bandwidth. The cholesteric liquid crystal film pitch gradient P∝1 / c. To form a larger pitch gradient in the thickness direction, the concentration gradient of the chiral compound in the thickness direction can be controlled. Different concentrations of ultraviolet absorber and ultraviolet light intensities can control the polymerization rate of the film thickness gradient.

[0034] In this embodiment, a first cholesteric liquid crystal composite system is prepared by mixing 90% of small molecule nematic liquid crystal monomer I, 5% of chiral compound I, 2% of ultraviolet light absorber I, and 3% of photoinitiator III by mass percentage; a second cholesteric liquid crystal composite system is prepared by mixing 90% of small molecule nematic liquid crystal monomer I, 5% of chiral compound II, 2% of ultraviolet light absorber I, and 3% of photoinitiator III by mass percentage; a third cholesteric liquid crystal composite system is prepared by mixing 98% of small molecule nematic liquid crystal monomer I, 0.5% of chiral compound I, 0.5% of ultraviolet light absorber I, and 1% of photoinitiator III by mass percentage; and a third cholesteric liquid crystal composite system is prepared by mixing 98% of small molecule nematic liquid crystal monomer I, 0.5% of chiral compound II, 0.5% of ultraviolet light absorber I, and 1% of photoinitiator III by mass percentage. A fourth cholesteric phase liquid crystal composite system was prepared by mixing 0.5% ultraviolet light absorber I and 1% photoinitiator III. The first, second, third, and fourth cholesteric phase liquid crystal composite systems were sequentially coated onto the substrate surface. The coating thicknesses of the first and second cholesteric phase liquid crystal composite systems were 3.5 μm each, with one side temperature of 30°C and a thickness-direction temperature gradient of 1°C. The coating thicknesses of the third and fourth cholesteric phase liquid crystal composite systems were 3 μm each, with one side temperature of 80°C and a thickness-direction temperature gradient of 0.5°C. Finally, the desired cholesteric phase liquid crystal film was prepared by irradiating the substrate with 360 nm ultraviolet light for one minute.

[0035] Preferably, the cholesteric liquid crystal film structure 3 can be a single-layer or multi-layer structure, and each layer is bonded together with an adhesive. The overall thickness of the cholesteric liquid crystal film structure 3 is 1μm-100μm.

[0036] Preferably, the small-molecule nematic liquid crystal monomer selected in this embodiment is one or more of the following structural formulas I to V:

[0037] Ⅰ

[0038] II

[0039] III

[0040] IV

[0041] V

[0042] In the above molecular formula, m and n are integers between 1 and 15, and R is... , , one of the;

[0043] Preferably, the chiral compound selected in this embodiment is one or more of the following structures I to VIII:

[0044] Ⅰ

[0045] II

[0046] III

[0047] IV

[0048] V

[0049] VI

[0050] VII

[0051] VIII

[0052] Preferably, the ultraviolet light absorber selected in this embodiment is one or more of the following structures I to II:

[0053] Ⅰ

[0054] II

[0055] Preferably, the photoinitiator selected in this embodiment is one or more of the following structures I to III:

[0056] Ⅰ

[0057] II

[0058] III

[0059] The phase compensation film 2 is formed by bonding a quarter-phase retardation film and a quarter-phase compensation film. The quarter-phase retardation film is one or more of the following: polymer stretching anti-dispersion quarter-phase retardation film, polymer stretching A-plate quarter-phase retardation film, liquid crystal anti-dispersion composite quarter-phase retardation film, liquid crystal A-plate quarter-phase retardation film, liquid crystal O-plate quarter-phase retardation film, or liquid crystal biaxial quarter-phase retardation film.

[0060] The linear polarizing plate 1 is formed by bonding two layers of triacetate cellulose with a layer of polyvinyl alcohol sandwiched in between. The outer surface of the triacetate cellulose is coated with pressure-sensitive adhesive, release film and protective film in sequence.

[0061] The linear polarizer 1 is located above the phase compensation film 2, and the cholesteric liquid crystal film 3 is pasted on top of or below the phase compensation film 2 or on top of the linear polarizer 1.

Claims

1. A circular polarizer, characterized in that, The structure includes a linear polarizing plate (1), a phase compensation film (2), and a cholesteric liquid crystal film structure (3) stacked together. The linear polarizing plate (1) is used to absorb light whose vibration direction is perpendicular to its transmission axis and to allow light in the ambient light whose vibration direction is parallel to its transmission axis to pass through and be converted into linearly polarized light. The phase compensation film (2) is used to convert linearly polarized light into circularly polarized light. The cholesteric liquid crystal film structure (3) is used to reflect ultraviolet and infrared light in ambient light. The cholesteric liquid crystal film structure (3) includes at least one cholesteric liquid crystal film structure A layer that reflects ultraviolet light with a wavelength range of 100nm-380nm and at least one cholesteric liquid crystal film structure B layer that reflects infrared light with a wavelength range of 760nm-2500nm. Both the cholesteric liquid crystal film structure A layer and the cholesteric liquid crystal film structure B layer are composed of one layer of levorotatory cholesteric liquid crystal film and one layer of dextrorotatory cholesteric liquid crystal film. Both the levorotatory cholesteric liquid crystal film and the dextrorotatory cholesteric liquid crystal film are cholesteric liquid crystal materials polymerized from small molecule nematic liquid crystal monomers, chiral compounds, ultraviolet light absorbers and photoinitiators under 360nm ultraviolet light irradiation, and the temperature gradient along the thickness direction during the preparation process is 0.5℃~1℃.

2. The circular polarizer according to claim 1, characterized in that, The thickness of the cholesteric phase liquid crystal film structure (3) is 1μm-100μm.

3. The circular polarizer according to claim 1, characterized in that, The phase compensation film (2) is formed by bonding a quarter-phase delay film and a quarter-phase compensation film together.

4. The circular polarizer according to claim 3, characterized in that, The quarter-phase retardation film is one or more of the following: polymer stretched anti-dispersion quarter-phase retardation film, polymer stretched A-plate quarter-phase retardation film, liquid crystal anti-dispersion composite quarter-phase retardation film, liquid crystal A-plate quarter-phase retardation film, liquid crystal O-plate quarter-phase retardation film, or liquid crystal biaxial quarter-phase retardation film.

5. The circular polarizer according to claim 1, characterized in that, The linear polarizing plate (1) is formed by bonding two layers of cellulose triacetate with a layer of polyvinyl alcohol sandwiched in between.

6. The circular polarizer according to claim 5, characterized in that, The outer surface of the cellulose triacetate is sequentially coated with pressure-sensitive adhesive, release film, and protective film.

7. The circular polarizer according to claim 1, characterized in that, The linear polarizer (1) is located above the phase compensation film (2), and the cholesteric liquid crystal film structure (3) is pasted on or below the phase compensation film (2) or on the linear polarizer (1).

8. An OLED display device assembled using the circular polarizer according to any one of claims 1-7, characterized in that, It includes a light-emitting panel (4), and a circular polarizer is attached to the surface of the light-emitting panel (4).

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