Phase delay film and compensation film

Abstract

A phase retardation film suitable for use in an organic light emitting diode display device includes a polymer substrate and a liquid crystal layer. The polymer substrate has a positive wavelength dispersion characteristic and a thickness between 5 micrometers and 100 micrometers. The liquid crystal layer is directly coated on the polymer substrate in a full coating process. One of the polymer substrate and the liquid crystal layer has a phase retardation amount of one-half wavelength, and the other has a phase retardation amount of one-quarter wavelength. The phase retardation film has a thin profile and can be laminated with a linear polarizer in a roll-to-roll process. A compensation film using the phase retardation film is also provided.

Description

Technical Field

[0001] This invention relates to a phase delay film and a compensation film, and more particularly to a phase delay film and a compensation film for use in organic light-emitting diode display devices. Background Technology

[0002] In optical displays, phase retardation films are typically used to correct the phase difference of light to improve the display effect. For example, in organic light-emitting diode (OLED) displays, metal electrodes easily reflect ambient light, leading to a decrease in contrast. Therefore, a circular polarizer consisting of a linear polarizer and a phase retardation film is usually attached to the light-emitting surface to correct the phase difference of the reflected ambient light, preventing the ambient light from escaping from the light-emitting surface and thus improving the problem of ambient light reflection.

[0003] However, conventional phase retardation films can usually only provide ideal phase difference correction for a single wavelength and typically have positive wavelength dispersion characteristics, which greatly limit their application range and performance. Conventional reverse wavelength dispersion products are made by laminating two polymer layers, which is complex and relatively thick, limiting their application range under the current trend of thinner and lighter films. In addition, they cannot be directly laminated with polarizer roll-to-roll, making the process cumbersome and costly.

[0004] In addition, another existing product with known reverse wavelength dispersion is made of two liquid crystal layers bonded together. It is too thin, making it difficult to process in subsequent processes, and has color shift problems with light leakage at a wide viewing angle, as well as poor weather resistance. Summary of the Invention

[0005] This invention provides a phase retardation film that is thin and can be bonded to a linear polarizer using a roll-to-roll process.

[0006] This invention provides a compensation membrane that simplifies the manufacturing process and reduces production costs.

[0007] The phase retardation film provided by this invention is suitable for use in organic light-emitting diode (OLED) display devices. The phase retardation film includes a biaxially extended polymer substrate and a liquid crystal layer. The polymer substrate has positive wavelength dispersion characteristics, and its thickness is between 5 micrometers and 100 micrometers. The liquid crystal layer is directly coated onto the polymer substrate using a full coating process. There is no adhesive layer between the liquid crystal layer and the polymer substrate, and the thickness of the liquid crystal layer is between 0.4 micrometers and 5 micrometers. One of the polymer substrate and the liquid crystal layer has a phase retardation of half a wavelength, and the other has a phase retardation of one-quarter of a wavelength.

[0008] In one embodiment of the present invention, one of the polymer substrate and the liquid crystal layer has an optical axis angle between 10 degrees and 20 degrees, and the other has an optical axis angle between 70 degrees and 80 degrees.

[0009] In one embodiment of the present invention, the polymer substrate and liquid crystal layer constitute a quarter-wave plate with reverse wavelength dispersion characteristics.

[0010] In one embodiment of the present invention, the phase retardation film described above is adapted to be directly bonded to a linear polarizer in a roll-to-roll process, and one of the liquid crystal layer and the polymer substrate having a phase retardation of half a wavelength is located between the other of the liquid crystal layer and the polymer substrate having a phase retardation of a quarter wavelength and the linear polarizer.

[0011] In one embodiment of the present invention, the polymer substrate may be polyester carbonate (PC), cycloolefin polymer (COP), cycloolefin polymer, polyethylene terephthalate (PET), or other polymer materials.

[0012] In one embodiment of the present invention, one of the polymer substrate and the liquid crystal layer has a phase retardation of one-quarter wavelength and an in-plane retardation (Ro) between 120 nanometers and 138 nanometers.

[0013] In one embodiment of the present invention, one of the polymer substrate and the liquid crystal layer has a phase retardation of half a wavelength, and the in-plane phase difference (Ro) is between 240 nm and 270 nm.

[0014] In one embodiment of the present invention, the in-plane phase difference (Ro) of the phase retardation film is between 150 nm and 170 nm.

[0015] In one embodiment of the present invention, the polymer substrate described above has a positive wavelength dispersion characteristic in which the phase difference decreases as the wavelength of light increases, or a flat wavelength dispersion characteristic in which the phase difference does not change.

[0016] In one embodiment of the present invention, the thickness of the phase retardation film is between 5 micrometers and 105 micrometers, and the optical axis angle is between 40 degrees and 50 degrees.

[0017] The compensation film provided by this invention is suitable for use in organic light-emitting diode (OLED) display devices. The compensation film includes a phase retardation film and a linear polarizer. The phase retardation film includes a polymer substrate and a liquid crystal layer. The polymer substrate has positive wavelength dispersion characteristics and is a biaxially extended polyester carbonate with an optical axis angle between 10 and 20 degrees or between 70 and 80 degrees. The thickness of the polymer substrate is between 5 micrometers and 100 micrometers. The liquid crystal layer is directly coated onto the polymer substrate using a full-coating process. One of the polymer substrate and the liquid crystal layer has a phase retardation of half a wavelength, and the other has a phase retardation of one-quarter of a wavelength. One of the polymer substrate and the liquid crystal layer has an optical axis angle between 10 and 20 degrees, and the other has an optical axis angle between 70 and 80 degrees. The in-plane phase difference Ro of the phase retardation film is between 150 nanometers and 170 nanometers, and the optical axis angle is between 40 and 50 degrees. The linear polarizer is bonded to the phase retardation film via a roll-to-roll process, wherein one of the liquid crystal layer and the polymer substrate having a half wavelength is located between the other of the liquid crystal layer and the polymer substrate having a quarter wavelength phase retardation film and the linear polarizer.

[0018] The phase retardation film in this embodiment of the invention adopts the direct and comprehensive coating of the liquid crystal layer on the biaxially extended polymer substrate, thus meeting the trend of thinning of the phase retardation film. Furthermore, by adjusting the appropriate thickness of the polymer plate, the phase retardation film can meet the optimal thickness requirements of different displays. Moreover, the phase retardation film can be bonded to the linear polarizer in a roll-to-roll process, thereby effectively simplifying the process, reducing production costs and improving production efficiency.

[0019] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a phase retardation film according to an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the structure of a compensation membrane according to an embodiment of the present invention.

[0022] Figure 3 This is a schematic diagram of the structure of the compensation membrane in another embodiment of the present invention. Detailed Implementation

[0023] Figure 1 This is a schematic diagram of the structure of a phase retardation film according to an embodiment of the present invention, as shown below. Figure 1As shown, the phase retardation film 10 includes a polymer substrate 12 and a liquid crystal layer 14. The thickness of the polymer substrate 12 is between 5 micrometers (μm) and 100 micrometers. In one embodiment, the polymer substrate 12 has positive wavelength dispersion characteristics, that is, the polymer substrate 12 can exhibit positive wavelength dispersion characteristics where the phase difference value decreases as the wavelength of light increases, or the polymer substrate 12 can exhibit flat wavelength dispersion characteristics where the phase difference value hardly changes as the wavelength of light increases. The liquid crystal layer 14 is directly coated on the polymer substrate 12 using a full coating process. There is no adhesive layer between the liquid crystal layer 14 and the polymer substrate 12. The thickness of the liquid crystal layer 14 is between 0.4 micrometers and 5 micrometers. One of the polymer substrate 12 and the liquid crystal layer 14 has a phase retardation amount of half a wavelength (λ / 2), and the other has a phase retardation amount of one-quarter of a wavelength (λ / 4).

[0024] In one embodiment, the polymer substrate 12 is, for example, a biaxially extended polycarbonate (PC) substrate with an optical axis angle between 10 and 20 degrees or between 70 and 80 degrees, and the optical axis angle of the liquid crystal layer 14 is between 10 and 20 degrees or between 70 and 80 degrees. In one embodiment, when the optical axis angle of the polymer substrate 12 is between 10 and 20 degrees, the optical axis angle of the liquid crystal layer 14 is between 70 and 80 degrees; when the optical axis angle of the polymer substrate 12 is between 70 and 80 degrees, the optical axis angle of the liquid crystal layer 14 is between 10 and 20 degrees. The in-plane retardation (Ro) of the polymer substrate 12 is between 120 nanometers (nm) and 138 nanometers, and the in-plane retardation (Ro) of the liquid crystal layer 14 is between 240 and 270 nanometers.

[0025] By coating the entire polymer substrate 12 with the liquid crystal layer 14, a quarter-wave plate (i.e., phase retardation film 10) with reverse wavelength dispersion characteristics is formed. That is, the phase retardation film 10 has the characteristic that the longer the wavelength, the greater the phase difference value. In one embodiment, the in-plane phase difference (Ro) of the phase retardation film 10 is between 150 nanometers and 170 nanometers, the optical axis angle of the phase retardation film 10 is between 40 degrees and 50 degrees, and the thickness of the phase retardation film 10 is between 5 micrometers and 105 micrometers. In addition to polyester carbonate, the polymer substrate 12 can also be made of cyclic olefin polymer (COP), polyethylene terephthalate (PET), or other polymer materials.

[0026] In the phase retardation film 10 of the present invention, a polymer substrate 12 with a large area, thin thickness and a phase retardation amount of λ / 2 or λ / 4 can be formed by stretching the polymer material, and the liquid crystal layer 14 is directly coated on the polymer substrate 12 over a large area, thus completing a large sheet or even a roll of phase retardation film 10. Figure 2 This is a schematic diagram of the structure of a compensation film according to an embodiment of the present invention. The phase retardation film 10 can be bonded to a linear polarizer 16 via a roll-to-roll process in subsequent applications to serve as a compensation film 18 for an organic light-emitting diode display device (not shown in the figure), such as... Figure 2 As shown, when the phase retardation film 10 is bonded to the linear polarizer 16, the liquid crystal layer 14 faces the linear polarizer, such that the liquid crystal layer 14 is positioned between the polymer substrate 12 and the linear polarizer 16. Preferably, the liquid crystal layer 14 having a phase retardation of half a wavelength is positioned between the polymer substrate 12 having a phase retardation of one-quarter wavelength and the linear polarizer 16. However, this is not the only possibility. Figure 3 This is a schematic diagram of the structure of the compensation membrane according to another embodiment of the present invention, as shown below. Figure 3 As shown, in this compensation film 18a, a polymer substrate 12 having a phase retardation of half a wavelength is located between a liquid crystal layer 14 having a phase retardation of a quarter wavelength and a linear polarizer 16.

[0027] Compared to conventional phase retardation films formed by bonding two liquid crystal layers or two polymer layers, the phase retardation film 10 of this embodiment omits the use of an adhesive layer (adhesive layer or bonding layer) between the two liquid crystal layers or two polymer layers. Therefore, it can meet the current demand for thinner designs. Furthermore, the phase retardation film 10 of this embodiment is itself a quarter-wave plate, and no angle adjustment is required relative to the linear polarizer 16 when bonding it with the linear polarizer 16. This facilitates roll-to-roll bonding and achieves a bonding and cutting rate of approximately 99.9%. On the other hand, in the phase retardation film 10 of this embodiment, by adjusting the optical properties of the refractive index of the polymer substrate 12, such as nx, ny, nz, the optical compensation value of the phase retardation film 10 can be effectively adjusted to solve the large viewing angle light leakage problem of the conventional liquid crystal layer 14. Here, nz represents the refractive index in the thickness direction, nx represents the refractive index in the direction where the maximum refractive index is generated in the plane, and ny represents the refractive index in the direction orthogonal to the nx direction in the plane.

[0028] Based on the above, the phase retardation film of the present invention has the advantages of being thin and being able to be bonded to linear polarizers through roll-to-roll processes, effectively simplifying the manufacturing process of the compensation film to reduce production costs. Furthermore, by adjusting the thickness of the appropriate polymer plate, the phase retardation film can meet the optimal thickness requirements of different displays. In addition, the phase retardation film of the present invention can solve the problem of light leakage at wide viewing angles and has better weather resistance.

[0029] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the methods and techniques disclosed above without departing from the scope of the present invention to create equivalent embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A phase retardation film suitable for use in an organic light emitting diode display device, characterized in that, The phase retardation film includes: a polymer substrate having a positive wavelength dispersion characteristic in which a phase difference value becomes smaller as a wavelength of light becomes longer, and a thickness of the polymer substrate is between 5 micrometers and 100 micrometers; and a liquid crystal layer directly coated on the polymer substrate in a full coating process, there is no adhesive layer between the liquid crystal layer and the polymer substrate, and a thickness of the liquid crystal layer is between 0.4 micrometers and 5 micrometers, wherein one of the polymer substrate and the liquid crystal layer has a phase retardation amount of one-half wavelength, and the other has a phase retardation amount of one-quarter wavelength, wherein the polymer substrate and the liquid crystal layer constitute a quarter-wave plate having an inverse wavelength dispersion characteristic.

2. The phase retardation film of claim 1, wherein, The phase retardation film is adapted to be directly laminated with a linear polarizer in a roll-to-roll process, and one of the liquid crystal layer and the polymer substrate having a phase retardation amount of one-half wavelength is between the other of the liquid crystal layer and the polymer substrate having a phase retardation amount of one-quarter wavelength and the linear polarizer.

3. The phase retardation film of claim 1, wherein, The polymer substrate is a polycarbonate, a cyclic olefin polymer, or a polyethylene terephthalate.

4. The phase retardation film of claim 1, wherein, One of the polymer substrate and the liquid crystal layer has a phase retardation amount of one-quarter wavelength, and an in-plane phase difference value is between 120 nanometers and 138 nanometers.

5. The phase retardation film of claim 1, wherein, One of the polymer substrate and the liquid crystal layer has a phase retardation amount of one-half wavelength, and an in-plane phase difference value is between 240 nanometers and 270 nanometers.

6. The phase retardation film of claim 1, wherein, An in-plane phase difference value of the phase retardation film is between 150 nanometers and 170 nanometers.

7. A compensation film, suitable for use in an organic light emitting diode display device, characterized in that, The compensation film includes: a phase retardation film including a polymer substrate having a positive wavelength dispersion characteristic in which a phase difference value becomes smaller as a wavelength of light becomes longer, and a thickness of the polymer substrate is between 5 micrometers and 100 micrometers, and a liquid crystal layer directly coated on the polymer substrate in a full coating process, wherein one of the polymer substrate and the liquid crystal layer has a phase retardation amount of one-half wavelength, and the other has a phase retardation amount of one-quarter wavelength, wherein the polymer substrate and the liquid crystal layer constitute a quarter-wave plate having an inverse wavelength dispersion characteristic; and a linear polarizer laminated with the phase retardation film in a roll-to-roll process, wherein one of the liquid crystal layer and the polymer substrate having a phase retardation amount of one-half wavelength is between the other of the liquid crystal layer and the polymer substrate having a phase retardation amount of one-quarter wavelength and the linear polarizer.

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