Flexible optical stack and organic light emitting diode display containing the same

Abstract

The present application relates to a flexible optical stack and an organic light emitting diode display comprising the optical stack, the adhesive layer is disposed between a cover plate and a circular polarizer assembly, between the circular polarizer assembly and a touch assembly, or between the touch assembly and the display assembly, wherein the adhesive layer has a storage modulus between 15 kPa and 30 kPa at 60 DEG C, and the ratio of the storage modulus at -30 DEG C to the storage modulus at 60 DEG C is between 6 and 16. The organic light emitting diode display comprises the optical stack.

Description

Technical Field

[0001] The present invention relates to a flexible optical stack and an organic light-emitting diode display containing the optical stack, and more particularly to an ultra-thin optical stack with stable flexibility and an organic light-emitting diode display containing the optical stack. Background Technology

[0002] Currently, circular polarizers (CPOLs) are mainly composed of a phase retardation layer and a linear polarizer. However, in the display field, display devices must combine electrical signal processing components (such as touch electrodes) and optical components (such as polarizing films, phase retardation films, etc.) to meet the application requirements of end customers. These electrical signal processing components and optical components are typically bonded together using optically transparent adhesives. However, due to the increasingly demanding operating, storage, and / or manufacturing environments of display devices, and the growing maturity of flexible display devices, the properties of each film layer in a display device must be well-matched. In particular, to enable flexible applications of display devices, the aforementioned optically transparent adhesives play a crucial role. For example, optically transparent adhesives can absorb stress during bending of the display device, thereby preventing the failure of the aforementioned electrical signal processing components or optical components.

[0003] Taiwan Patent No. I590119 (hereinafter referred to as Patent I590119) discloses a flexible display device, which uses a first adhesive film to assemble the photoelectric part and the touch function part; and uses a second adhesive film to assemble the touch function part and the window film.

[0004] Patent I590119 discloses an adhesive film for flexible display devices and discusses its storage modulus, for example, analyzing that the storage modulus of the adhesive film has an average slope of -9.9 to 0 at -20°C to 80°C, and a storage modulus of 10 kPa to 1000 kPa at 80°C. However, Patent I590119 only conducts tensile tests, which cannot effectively verify the state of the adhesive film under bending conditions. In other words, Patent I590119 cannot provide an adhesive material suitable for bendable / flexible / rollable products at low temperatures (e.g., -30°C to -20°C). Therefore, finding a preferred specification criterion that makes the adhesive film suitable for both high and low temperature environments (e.g., -30°C to 60°C) is an urgent problem to be solved.

[0005] Therefore, in view of the above-mentioned deficiencies, the present invention was developed. Summary of the Invention

[0006] The purpose of this invention is to provide a flexible optical stack, wherein the optical stack includes at least one adhesive layer and the optical stack is integrated with an electrical signal processing element and an optical element. The adhesive layer enables two elements with different characteristics / functions to be combined without compromising their respective characteristics, while also making the product thinner and meeting the integration requirements, thereby realizing a bendable and ultra-thin optical stack and its product.

[0007] Another object of the present invention is to provide a flexible optical stack, wherein the storage modulus of the adhesive layer at 60°C is between 15 kPa and 30 kPa; the ratio of the storage modulus of the adhesive layer at -30°C to the storage modulus at 60°C is between 6 and 16, thereby achieving an adhesive layer that maintains viscoelastic properties over a wide temperature range and has excellent recovery properties.

[0008] The flexible optical stack of the present invention includes: at least one adhesive layer disposed between a cover plate and a circular offset component, between the circular offset component and a touch component, or between the touch component and the display component; wherein the energy storage modulus of the adhesive layer at 60°C is between 15 kPa and 30 kPa; and the ratio of the energy storage modulus of the adhesive layer at -30°C to the energy storage modulus at 60°C is between 6 and 16.

[0009] Preferably, in the optical stack according to the present invention, the energy storage modulus of the adhesive layer at 60°C is 27, and the ratio of the energy storage modulus of the adhesive layer at -30°C to the energy storage modulus at 60°C is 6.6; or the energy storage modulus of the adhesive layer at 60°C is 17, and the ratio of the energy storage modulus of the adhesive layer at -30°C to the energy storage modulus at 60°C is 15.8; or the energy storage modulus of the adhesive layer at 60°C is 28, and the ratio of the energy storage modulus of the adhesive layer at -30°C to the energy storage modulus at 60°C is 13.3.

[0010] Preferably, in the optical stack according to the invention, the glass transition temperature of the adhesive layer is less than -30°C.

[0011] Preferably, in the optical stack according to the present invention, the material of the adhesive layer is a hydroxyl-containing acrylic polymer.

[0012] Preferably, in the optical stack according to the invention, the interfacial adhesion between the adhesive layer and the circular offset component is greater than 500 g / inch in the range of -30°C to 60°C.

[0013] Furthermore, the present invention provides a stable and flexible organic light-emitting diode (OLED) that utilizes the optical stacking structure described above. The OLED includes: a first adhesive layer disposed between a cover plate and a circular offset component; a second adhesive layer disposed between the circular offset component and a touch component; and a third adhesive layer disposed between the touch component and a display component. The cover plate is disposed on the top layer of the OLED display. The energy storage modulus of the first, second, and third adhesive layers at 60°C is between 15 kPa and 30 kPa, and the ratio of the energy storage modulus of the first, second, and third adhesive layers at -30°C to the energy storage modulus at 60°C is between 6 and 16.

[0014] The flexible optical stack provided by this invention includes at least one adhesive layer and is integrated from electrical signal processing elements and optical elements. The adhesive layer allows two elements with different characteristics / functions to be combined without compromising their respective properties, while also enabling a thinner product that meets integration requirements. This achieves a bendable and ultra-thin optical stack and its products. Furthermore, the storage modulus of the adhesive layer at 60°C is between 15 kPa and 30 kPa; the ratio of the storage modulus of the adhesive layer at -30°C to its storage modulus at 60°C is between 6 and 16. This ensures an excellent balance between cohesive strength and adhesive strength in the adhesive layer, achieving a viscoelastic property that is maintained over a wide temperature range and possesses excellent recovery properties, resulting in excellent reliability and durability.

[0015] To enable those skilled in the art to understand the purpose, features and effects of the present invention, the present invention will be described in detail through the following specific embodiments and in conjunction with the accompanying drawings. Attached Figure Description

[0016] Figure 1 This is an illustrative optical overlay diagram according to the present invention;

[0017] Figure 2 An exemplary schematic diagram illustrating the stack for peel strength testing; and

[0018] Figure 3 An exemplary schematic diagram illustrating the stacked structure for bending tests. Detailed Implementation

[0019] The advantages, features, and methods of achieving the present invention will become apparent from the following detailed description of exemplary embodiments according to the accompanying drawings. However, it should be noted that the present invention is not limited to the following exemplary embodiments, but can be implemented in various forms.

[0020] The terminology used herein is for illustrating specific embodiments only and is not intended to limit the invention. Unless the context clearly indicates otherwise, the singular forms of the terms "a" and "the" as used herein also include the plural forms.

[0021] Furthermore, it should be understood that when one element is referred to as being "on" another element, the element may be directly on the other element, or there may be an intermediate element. Additionally, the thickness values ​​referred to herein are not absolute, and those skilled in the art will understand that the thickness may include manufacturing tolerances, measurement errors, etc. Preferably, the thicknesses listed herein may have a range of 10% or 20%.

[0022] It should also be understood that although terms such as "first," "second," etc., may be used herein to describe various elements, the elements should not be limited to these terms. These terms are used only to distinguish individual elements. Therefore, a first element in some embodiments may be referred to as a second element in other embodiments without departing from the teachings of the invention. In this specification, the same reference numerals denote the same elements. Furthermore, optical elements will be used interchangeably herein with terms such as "plate," "layer," "film," or other similar terms, unless otherwise specified, and these are merely differences in name.

[0023] Please refer to Figure 1 This illustrates an exemplary optical stack 100 according to the present invention. The flexible optical stack 100 includes at least one adhesive layer 11. The adhesive layer 11 may be disposed between substrates 12 and 13. In the present invention, substrates 12 and 13 may be at least a cover plate, a circular offset assembly, a touch assembly, a display assembly, etc. For example, the adhesive layer 11 may be disposed between the cover plate (i.e., substrate 13) and the circular offset assembly (i.e., substrate 12); or in another embodiment, the adhesive layer 11 may be disposed between the circular offset assembly (i.e., substrate 13) and the touch assembly (i.e., substrate 12); or in another embodiment, the adhesive layer 11 may be disposed between the touch assembly (i.e., substrate 13) and the display assembly (i.e., substrate 12). The above are merely examples and are not intended to limit the present invention. According to the characteristics of the adhesive layer 11 of the present invention, two or more layers of components can realize a flexible and ultra-thin integrated touch module and its products within a wide operating temperature range (e.g., -30°C to 60°C).

[0024] Specifically, according to some embodiments, the adhesive layer 11 may be an optically transparent adhesive (OCA), the material of which may be a hydroxyl-containing acrylic polymer. Specifically, in some embodiments, the material of the adhesive layer 11 may contain at least one of the following: (meth)acrylate monomers, monomers containing ethylene oxide, monomers containing propylene oxide, monomers containing amino groups, monomers containing amide groups, monomers containing alkoxy groups, monomers containing phosphate groups, monomers containing sulfonic acid groups, monomers containing phenyl groups, and monomers containing silane groups. More specifically, the adhesive layer 11 may have a glass transition temperature of less than or equal to -30°C.

[0025] In some embodiments of this disclosure, the circular polarizer can be an anti-reflective optical element constructed by combining at least one phase retardation layer and a linear polarizing layer. To achieve front integration and product thinning, in one embodiment of the invention, the phase retardation layer can be a 45 μm thick cyclic olefin polymer (COP), which can serve as a quarter-wave compensation layer (also known as a quarter-wave plate or quarter-wave delay plate). In some embodiments of this disclosure, the linear polarizing layer can be a commercially available polarizing plate with a degree of polarization (DOP) greater than 98%, but is not limited thereto. The linear polarizing layer can be two protective films (such as cellulose triacetate, TAC) fixing polyvinyl alcohol (PVA) material in the middle (hereinafter referred to as Type A polarizing layer), or a combination of a single protective film (such as TAC) and polyvinyl alcohol (PVA) material (hereinafter referred to as Type B polarizing layer). Both types of polarizing layers or any other form of polarizing layer are applicable to this invention and are not limited to specific embodiments. In one embodiment of the present invention, the phase retardation layer may be a combination of a quarter-phase compensation layer and a half-phase compensation layer (also known as a half-wave plate or half-wavelength retardation plate). In another embodiment of the present invention, the phase retardation layer may be a half-phase compensation layer. The embodiments of the present invention will present the phase retardation value measured in a plane perpendicular to the thickness direction of the test object, i.e., the in-plane phase retardance / retardation (R0) value, to illustrate the characteristics of the optical film. The embodiments of the present invention use a commercially available device, model AxoScan (manufacturer Axometrics, Inc.), to measure the in-plane phase retardation value of the test object in the visible light wavelength range.

[0026] It should be further explained that, since this invention relates to the storage modulus of the adhesive layer 11, the measurement method will be described first. The storage modulus can be measured by dynamic load testing / dynamic mechanical analysis (DMA) of the adhesive layer 11. The basic principle is to apply a periodic stress of a certain frequency to the adhesive layer 11, analyze the strain magnitude and the phase difference between the applied dynamic force and the deformation of the adhesive layer 11, thereby obtaining the dynamic properties of the material, such as stiffness (i.e., storage modulus) and damping (i.e., loss modulus). To simulate the stress mode of the material under actual working conditions, the dynamic stress can be a sine wave, a triangular wave, or a square wave, etc. For example, when stress is applied to the material, the ratio of stress to strain is the complex modulus, and the phase difference between the two can be defined as the phase angle δ, which represents the degree of hysteresis of the material deformation. It should be further explained that the complex modulus is in the complex coordinate system, and the angle between the complex modulus and the x-axis is the phase angle δ. The energy storage modulus and the loss modulus are the projections of the complex modulus onto the real axis and the imaginary axis, respectively. Furthermore, tanδ is defined as the loss factor to represent the loss characteristics of the adhesive layer 11.

[0027] It is worth mentioning that, since this invention relates to the peel strength (also known as interfacial adhesion) between the adhesive layer 11 and the aforementioned different components, the measurement method will be described below first. Please refer to... Figure 2 , Figure 2 This is an exemplary schematic diagram illustrating the stack for peel strength testing. First, the adhesive composition to be tested is coated onto a guide strip 22 (made of polyethylene terephthalate (PET) film). After the adhesive composition cures, a first adhesive film 21 is formed, which, together with the guide strip 22, forms an adhesive sheet 200. The guide strip 22 has a thickness of 50 μm. Then, the other side of the first adhesive film 21 is bonded to the component to be tested 23 to form an adhesive interface. The component to be tested 23 can be a cover plate, a round-off component, a touch component, or a display component, etc. Users can replace different components as needed for testing. The component to be tested 23 can be fixed to glass 25 by a second adhesive film 24. Finally, one side of the adhesive sheet 200 is folded back 180° and a tensile force is applied at a rate of 300 mm / min under different temperature environments. The peel strength of the adhesive interface formed between the adhesive composition to be tested and the component to be tested 23 is measured under different temperature environments. It is worth mentioning that since the first adhesive film 21 and the second adhesive film 24 are formed from the same adhesive composition, the peeling interface can be regarded as the peel strength between the adhesive composition to be tested and the component to be tested 23, regardless of whether the peeling occurs between the first adhesive film 21 and the component to be tested 23 or between the component to be tested 23 and the second adhesive film 24.

[0028] It is worth mentioning again that, since this invention relates to a bending test of the adhesive layer 11, the test method will be described first. The term "passes the bending test" as used herein means that the following process does not produce the failure behavior described below. Please refer to... Figure 3 , Figure 3 This is an exemplary schematic diagram illustrating the stacked structure for a bending test. The bending test described in this invention is primarily aimed at... Figure 3 The test stack was used to simulate the bending test of a real touch display device. Therefore, the bending test primarily focused on evaluating the bending feasibility of the test stack by replacing different optical adhesive materials under different temperature environments. A detailed explanation of each layer will follow later. The bending test method involved subjecting the test stack to at least 200,000 bending cycles under different temperature environments. Afterward, it was confirmed whether the test stack exhibited failure behaviors such as breakage, buckling, or delamination. Finally, if the test stack did not exhibit any failure behaviors, the optical adhesive material was deemed to have passed the bending test.

[0029] The following explanation Figure 3 This illustrates an exemplary touch display device 1 according to the present invention. The touch display device 1 includes: a cover plate 131, a first adhesive layer 111, a circular bias assembly composed of a line bias sheet 132 and a half-wavelength retardation sheet 133, a second adhesive layer 112, a touch assembly 121 composed of a quarter-wavelength retardation sheet 135 and touch electrodes 134 and 136 located on its upper and lower surfaces, a third adhesive layer 113, and a display assembly 122. For cost considerations during testing, the display assembly 122 uses a 50 μm transparent polyimide film (Colorless PI, CPI) instead of an organic light-emitting diode display (OLED).

[0030] The cover plate 131 can serve as the outermost component of the touch display device 1, or it can be defined as a component that can be touched by the user. The cover plate 131 can be a single layer of inorganic encapsulation material, a multi-layer stack of inorganic encapsulation materials, or a stack of pairs of inorganic and organic encapsulation materials. The inorganic encapsulation materials used are, but are not limited to, silicon nitride (SiNx), silicon oxide (SiOx), silicon oxynitride (SiONx), aluminum oxide (AlOx), titanium oxide (TiOx), glass, resin layers, etc. In this specific embodiment, the cover plate 131 is a 50μm transparent polyimide film (Colorless PI, CPI).

[0031] A circular polarizer generally consists of a linear polarizer and a phase delay plate. Its function is often used as an anti-reflective film to solve the problem of reflected light generated by incident light from the external environment and reduce display problems. The phase delay plate used can be a quarter wave plate (QWP) or a half wave plate (HWP). In theory, when incident light from the outside passes through the outermost linear polarizer, the linear polarizer converts the incident light into linearly polarized incident light with a perpendicular polarization direction. Then, the linearly polarized incident light enters the quarter-wave plate, which acts as a phase retardation layer, causing a phase delay and converting the linearly polarized incident light into left-handed circularly polarized light. Next, when the light is reflected by the display panel, it forms right-handed circularly polarized light, which then passes through the quarter-wave plate again, ultimately making the polarization direction of the linearly polarized incident light orthogonal to its own polarization direction. This prevents incident light from the external environment from passing through the linear polarizer and thus becomes invisible to the human eye, achieving an anti-reflection effect. In other words, the combination of the linear polarizer 132 and the half-wave retardation plate 133 in this embodiment constitutes an anti-reflection optical element. The line polarizer 132 is coupled to the cover plate 131 via a first adhesive layer 111, and the half-wavelength retardation film 133 is coupled to the touch component 121 via a second adhesive layer 112. More specifically, the half-wavelength retardation film 133 is a liquid crystal phase retardation layer, which can be a single-layer liquid crystal coating. Its phase retardation value R0 (550) at 550 nm can be between 230 nm and 310 nm, preferably at least 250 nm. For example, it can be made using commercially available Reactive Mesogen (RM) reactive liquid crystal, with a thickness of about 2 μm and a slow axis of about 15 degrees. Its phase retardation value at 550 nm is 260 nm, but the present invention is not limited to this. In addition, the line polarizer 132 is the aforementioned type B polarizing layer, which is a commercially available product SPN32-1805M (supplier: SAPO), and the liquid crystal type half-wavelength retardation film 133 is bonded to the line polarizer 132 with polyvinyl alcohol (PVA) water-based adhesive.

[0032] The touch component 121 of the present invention can form touch electrodes on a substrate using a patterning process on transparent conductive materials such as indium tin oxide (ITO), metal mesh, silver nanowire (SNW), carbon nanotube (CNT), graphene, and conductive polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT). Figure 3In the illustrated embodiment, the touch component 121 is composed of a quarter-wavelength delay film 135 and touch electrodes 134 and 136 located on its upper and lower surfaces. In other words, the quarter-wavelength delay film 135 can serve as a carrier substrate for the touch electrodes 134 and 136. The phase retardation value R0 (550) of the quarter-wavelength delay film 135 at 550 nm can be between 100 nm and 160 nm, preferably at least 130 nm. Specifically, the quarter-wavelength delay film 135 is a 25 μm thick cyclic olefin copolymer (COP) material (supplier: KONICA MINOLTA), and its phase retardation value at 550 nm is 131 nm. The touch component 121 in this embodiment is made of silver nanowires. The method used can be to coat the upper and lower surfaces of the quarter-wavelength retardation film 135 with a dispersion containing silver nanowires. For example, the silver nanowires can be mixed with a solvent, such as water, alcohol, ketone, ether, hydrocarbon, or aromatic solvent (benzene, toluene, xylene, etc.) to form a coating / slurry. The coating / slurry may also contain additives, surfactants, or binders, such as carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxypropyl methylcellulose (HPMC), sulfonates, sulfates, disulfonates, sulfosuccinates, phosphates, or fluorinated surfactants. After coating, a silver nanowire layer is formed through a curing step. This silver nanowire layer can then be used to form the touch electrodes 134 and 136 using patterning methods known to those skilled in the art (e.g., using photoresist photolithography combined with etching processes, etc.).

[0033] Preferably, the silver nanowires are fixed to the surface of the polymer phase retardation layer 20 without detaching, forming the aforementioned silver nanowire layer. The silver nanowires can contact each other to provide a continuous current path, thereby forming a conductive network. In other words, the silver nanowires contact each other at their intersections to form a path for electron transfer. That is, one silver nanowire layer and another silver nanowire layer will form direct contact at their intersections, thus forming a low-resistance electron transfer path. In one embodiment, a region or structure is considered electrically insulating when its sheet resistance is higher than 10⁸ ohms / square, preferably higher than 10⁴ ohms / square, 3000 ohms / square, 1000 ohms / square, 350 ohms / square, or 100 ohms / square. In one embodiment, the sheet resistance of the silver nanowire layer is less than 100 ohms / square. The silver nanowire electrode has high transmittance, for example, a light transmittance of more than about 88%, 90%, 91%, 92%, 93% or above in the visible light range.

[0034] In one embodiment, a polymer layer may be further provided to cover the silver nanowires. In a specific embodiment, a suitable polymer is coated onto the silver nanowires. The polymer, having a flowable state / property, can penetrate between the silver nanowires to form a filler, and the silver nanowires are embedded in the polymer. After the polymer cures, a composite structure is formed. That is, in this step, a polymer layer is added to the silver nanowires after coating them with the polymer, and the silver nanowires are embedded in the polymer layer to form a composite structure. In some embodiments of the present invention, the polymer layer is formed of an insulating material. For example, the material of the polymer layer can be a non-conductive resin or other organic material, such as polyacrylate, epoxy resin, polyurethane, polysilane, polysiloxane, poly(silicon-acrylic acid), polyethylene (PE), polypropylene (PP), polyvinyl butyral (PVB), polycarbonate (PC), acrylonitrile butadiene styrene (ABS), etc. In some embodiments of the present invention, the polymer layer can be formed by spin coating, spraying, printing, or other methods. In some embodiments, the thickness of the polymer layer is approximately 20 nm to 10 mm, or 50 nm to 200 nm, or 30 nm to 100 nm. For example, the thickness of the polymer layer can be approximately 90 nm or 100 nm. Specific methods described above can be referred to and incorporated in their entirety by reference to documents such as US20190227650A and CN101292362, while the silver nanowire paste and polymer coating are both provided by the supplier Cambrios.

[0035] Please refer to Table 1 and Figure 3 As shown, Table 1 illustrates the application of adhesive layers 111, 112, and 113 made from the adhesive materials of the first and second comparative examples according to the present invention. Figure 3The storage modulus and bending test results were measured in the structure under dynamic load tests at different temperatures. Specifically, as shown in Table 1, the storage modulus of the adhesive materials of the first and second comparative examples according to the present invention exceeds 30 kPa at 60°C, and the ratio of the storage modulus of the adhesive materials of the first and second comparative examples at -30°C to the storage modulus at 60°C is greater than 16. More specifically, the storage modulus of the adhesive material of the first comparative example is 4000 kPa at -30°C, the storage modulus of the adhesive layer 11 of the first comparative example is 100 kPa at 60°C, and the ratio of the storage modulus of the adhesive layer 11 of the first comparative example at -30°C to the storage modulus at 60°C is as high as 40. More specifically, the adhesive material of the second comparative example has a storage modulus of 3800 kPa at -30°C, and the adhesive material of the second comparative example has a storage modulus of 40 kPa at 60°C. The ratio of the storage modulus of the adhesive material of the second comparative example at -30°C to the storage modulus at 60°C is as high as 95.

[0036] Table 1

[0037]

[0038] Understandably, based on the storage modulus of the adhesive layers in the first and second comparative examples at high temperatures (e.g., 60°C), it is clear that the storage modulus of the adhesive materials in the first and second comparative examples is excessively high at high temperatures. An excessively high storage modulus indicates that the adhesive material is too hard and its adhesion is poor. Therefore, under high-temperature bending tests, the samples will exhibit the aforementioned delamination / bubbling phenomena, meaning they cannot meet the product's flexibility requirements. Furthermore, with significant temperature variations, in terms of stability, large variations in the storage modulus often make the optical stack more brittle and unstable under high and low temperature conditions. Based on the first and second comparative examples, we found that when the storage modulus varies too much—for example, in the first comparative example, the ratio of the storage modulus of the adhesive material at -30°C to that at 60°C is as high as 40—the adhesive material will be unable to deform under bending conditions at low temperatures (e.g., -30°C to -20°C), leading to stress concentration and the risk of breakage. This could result in the optical stack 100 breaking, causing mechanical damage or optical distortion (Mura). Therefore, based on the bending results of the first and second comparative examples, this invention believes that it is necessary to find the applicable range of the storage modulus of the adhesive material at 60°C and the range of the ratio of the storage modulus at -30°C to that at 60°C in order to ensure that the product (e.g., Figure 3 The simulated display touch products meet the flexibility requirements under high and low temperature conditions.

[0039] Please refer to Table 2 and Figure 2As shown in Table 2, the peel strength of the adhesive materials of the first and second comparative examples according to the present invention for different interfaces measured at different temperatures is illustrated. Specifically, as shown in Table 2, the peel strength of the adhesive materials of the first and second comparative examples according to the present invention at -20°C is less than 500 g / inch. More specifically, the peel strength of the adhesive layer 11 of the first comparative example for the optical element 13 (polarizing layer and phase retardation layer) and the electrical signal processing element 12 (touch component) at -20°C is only 175 g / inch, 127 g / inch, and 124 g / inch, respectively, while the peel strength of the adhesive layer 11 of the second comparative example for the optical element 13 (polarizing layer and phase retardation layer) and the electrical signal processing element 12 (touch component) at -20°C is only 122 g / inch, 349 g / inch, and 241 g / inch, respectively. It is evident that the adhesive layer 11 of the first and second comparative examples cannot deform under bending conditions in low-temperature environments, resulting in stress concentration that affects the adhesive strength of the adhesive layer 11 and makes it impossible to maintain long-term reliable adhesive function. This peel strength data can explain why the adhesive materials of the first and second comparative examples cannot pass the aforementioned bending test at low temperatures.

[0040] Table 2

[0041] polarizing layer -20℃ 175 122 Phase Delay Layer -20℃ 127 349 Touch components -20℃ 124 241

[0042] Please refer to Table 3 and Figure 3 As shown, Table 3 illustrates the application of adhesive layers 111, 112, and 113 made from the adhesive materials of the first to third embodiments of the present invention. Figure 3The storage modulus and bending test results were measured in the structure under dynamic load tests at different temperatures. Specifically, as shown in Table 3, the storage modulus of the adhesive materials according to the first to third embodiments of the present invention at 60°C is between 15 kPa and 30 kPa, and the ratio of the storage modulus of the adhesive materials of the first to third embodiments at -30°C to the storage modulus at 60°C is between 6 and 16. More specifically, the storage modulus of the adhesive material of the first embodiment at -30°C is 270 kPa and passes the bending test, the storage modulus of the adhesive material of the first embodiment at 60°C is 17 kPa and passes the bending test, and the ratio of the storage modulus of the adhesive material of the first embodiment at -30°C to the storage modulus at 60°C is 15.8. More specifically, the adhesive material of the second embodiment has a storage modulus of 371 kPa at -30°C and passes the bending test; the adhesive material of the second embodiment has a storage modulus of 28 kPa at 60°C and passes the bending test; the ratio of the storage modulus of the adhesive material of the second embodiment at -30°C to the storage modulus at 60°C is 13.3. More specifically, the adhesive material of the third embodiment has a storage modulus of 177 kPa at -30°C and passes the bending test; the adhesive material of the third embodiment has a storage modulus of 27 kPa at 60°C and passes the bending test; the ratio of the storage modulus of the adhesive material of the third embodiment at -30°C to the storage modulus at 60°C is 6.6.

[0043] Table 3

[0044]

[0045] It is understandable that, based on the ratio of the storage modulus of the adhesive materials in the first to third embodiments within the test range, it is evident that the storage modulus of the adhesive materials in the first to third embodiments does not exhibit significant variation with temperature under the test conditions. In terms of stability, the adhesive layer 11 in the first to third embodiments maintains viscoelastic properties and exhibits excellent recovery properties over a wide temperature range, demonstrating excellent stability. If G'(-30℃) / G'(60℃) is greater than 16, it indicates that the storage modulus of the adhesive material at -30℃ is too large, resulting in a harder adhesive material and poorer adhesion. On the other hand, this invention believes that the ratio of G'(-30℃) / G'(60℃) is not necessarily better the smaller it is. Although the adhesive material has a small storage modulus at -30℃, which helps with product bending, in reality, an excessively low storage modulus also indicates that the cohesive force and degree of polymerization of the molecules within the adhesive material are very small, resulting in excessively low strength of the adhesive material, which is not conducive to processing. In other words, excessively low material strength is not beneficial to the actual manufacturing process. Patent I590119 discloses the average slope of the energy storage modulus from -20℃ to 80℃ and the energy storage modulus at each temperature, but does not disclose the energy storage modulus at -30℃. Therefore, this invention uses the interpolation / extrapolation method commonly used in general experimental research. The G'(-30℃) / G'(60℃) values ​​of the nine specific embodiments disclosed in Patent I590119 are between 2 and 4. According to the previous discussion, the adhesive material of Patent I590119 should have defects such as low material strength and difficulty in processing.

[0046] Furthermore, since the first comparative example failed the 60°C bending test, we determined that the storage modulus of the adhesive layer at 60°C should not exceed 40 kPa. Further, based on the first to third embodiments, we found that when the storage modulus of the adhesive layer at 60°C is below 30 kPa, it sufficiently ensures that the storage modulus of the adhesive material remains sufficiently small under high-temperature conditions. This allows the optical stack 100 of the first to third embodiments to pass the bending test under high-temperature conditions, ensuring that the adhesive material can still achieve long-term reliable adhesion under high-temperature conditions. It should be further noted that although a low storage modulus ensures that the adhesive material deforms under bending, preventing the risk of breakage and fracture, when the storage modulus is too low, the adhesive material cannot maintain the cohesive strength necessary for processing, handling, shape retention, and similar operations, causing difficulties in the manufacturing process. Therefore, based on the data from the first to the third embodiments, the present invention provides a preferred specification for an adhesive material. When the storage modulus of the adhesive material at 60°C is between 15 kPa and 30 kPa, within this range, the adhesive material can ensure a balance between cohesive strength and adhesive strength.

[0047] Please refer to Table 4 and Figure 2As shown in Table 4, the peel strength of the adhesive layer 11 according to the first to third embodiments of the present invention is measured at different temperatures for different interfaces. Specifically, as shown in Table 4, the peel strength of the adhesive layer 11 according to the first to third embodiments of the present invention at -20°C is higher than 500 g / inch for different interfaces. More specifically, the peel strength of the adhesive material of the first embodiment for optical element 13 (polarizing layer and phase retardation layer) and electrical signal processing element 12 (touch component) at -20°C is 2812 g / inch, 2132 g / inch, and 1531 g / inch, respectively, and other data can be interpreted accordingly. Combined with the aforementioned bending test and the peel strength in Table 4, it is evident that within the operating temperature range, when the peel strength between the adhesive material and other interfaces is higher than 500 g / inch, excellent reliability and durability are maintained.

[0048] Table 4

[0049]

[0050] It is understood that those skilled in the art can make various changes and adjustments based on the above examples, which will not be listed here. The focus here will be on the application of stable and flexible organic light-emitting diode displays according to the embodiments, so that those skilled in the art can more clearly understand the possible variations. Elements indicated by the same element symbols as in the above embodiments are substantially the same as those referenced above. Figures 1-3 The components, features, and advantages that are the same as those described in optical stack 11 will not be repeated.

[0051] It should be further noted that, in this embodiment, the thicknesses of the first adhesive layer 111, the second adhesive layer 112, and the third adhesive layer 113 can be between 25 micrometers and 50 micrometers. Furthermore, the first adhesive layer 111, the second adhesive layer 112, and the third adhesive layer 113 can comprise an adhesive film with a haze of 5% or less when the thickness is between 25 and 50 micrometers, specifically 3% or less, and more specifically 1% or less. Within this range, when the adhesive layer 11 is used for display, it exhibits excellent transparency; however, the invention is not limited thereto.

[0052] In this embodiment, the first adhesive layer 111, the second adhesive layer 112, and the third adhesive layer 113 can be made of the same material. In this invention, "the same material" means that they have the same composition and physical properties. In another embodiment, the first adhesive layer 111, the second adhesive layer 112, and the third adhesive layer 113 can be made of different materials. In yet another embodiment, the thickness of the second adhesive layer 112 can be greater than the thickness of the first adhesive layer 111 and the third adhesive layer 113. Therefore, the second adhesive layer 112 can have a higher degree of adhesion than the first adhesive layer 111 and the third adhesive layer 113. Therefore, by adjusting the thickness of the adhesive layer 11, the reliability of the organic light-emitting diode display can be increased, while simultaneously achieving effects such as planarization of optical elements.

[0053] Finally, the technical features of the present invention and the technical effects it can achieve are summarized as follows:

[0054] 1. According to the optical stack 100 of the present invention, the energy storage modulus of the adhesive material at 60°C is between 15 kPa and 30 kPa, and the ratio of the energy storage modulus at -30°C to the energy storage modulus at 60°C is between 6 and 16. In this way, the adhesive layer 11 can be ensured to have an excellent balance between cohesive strength and adhesive strength, which meets the requirements of practical applications for optical stacks and their products.

[0055] 2. The adhesive material of the optical stack 100 according to the present invention has a peel strength of more than 500 g / inch at different interfaces under the operating temperature. It is evident that the adhesive layer 11 according to the present invention maintains excellent reliability and durability even in harsh operating, storage and / or manufacturing environments, which meets the requirements of practical applications.

[0056] The above description illustrates the implementation of the present invention through specific embodiments. Those skilled in the art can easily understand the technical features, advantages, and effects of the present invention from the content disclosed in this specification.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Any equivalent changes or modifications made without departing from the spirit of the invention should be included within the scope of the following claims.

Claims

1. An optical stack, characterized in that, include: At least one adhesive layer is disposed between the cover plate and the rounded component, between the rounded component and the touch component, or between the touch component and the display component; The energy storage modulus of the adhesive layer at 60°C is between 15 kPa and 30 kPa, and the ratio of the energy storage modulus of the adhesive layer at -30°C to the energy storage modulus at 60°C is between 6 and 16.

2. The optical stack according to claim 1, characterized in that, The energy storage modulus of the adhesive layer at 60°C is 27 kPa, and the ratio of the energy storage modulus of the adhesive layer at -30°C to the energy storage modulus at 60°C is 6.6; or the energy storage modulus of the adhesive layer at 60°C is 17 kPa, and the ratio of the energy storage modulus of the adhesive layer at -30°C to the energy storage modulus at 60°C is 15.8; or the energy storage modulus of the adhesive layer at 60°C is 28 kPa, and the ratio of the energy storage modulus of the adhesive layer at -30°C to the energy storage modulus at 60°C is 13.

3.

3. The optical stack according to claim 1, characterized in that, The glass transition temperature of the adhesive layer is less than -30°C.

4. The optical stack according to claim 1, characterized in that, The adhesive layer is made of hydroxyl-containing acrylic polymer.

5. The optical stack according to claim 1, characterized in that, The interfacial adhesion between the adhesive layer and the rounded component is greater than 500 g / inch in the range of -30°C to 60°C.

6. An organic light-emitting diode display, characterized in that, include: The first adhesive layer is disposed between the cover plate and the rounded component; The second adhesive layer is disposed between the rounded component and the touch component; The third adhesive layer is disposed between the touch component and the display component; The cover plate is disposed on the topmost layer of the organic light-emitting diode display. The energy storage modulus of the first, second, and third adhesive layers at 60°C is between 15 kPa and 30 kPa. The ratio of the energy storage modulus of the first, second, and third adhesive layers at -30°C to the energy storage modulus at 60°C is between 6 and 16.

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