CN116940153A

CN116940153A - Flexible optical stack and organic light emitting diode display containing the same

Info

Publication number: CN116940153A
Application number: CN202210344584.9A
Authority: CN
Inventors: 萧博友; 刘胜发; 杨宜龙; 陈威州; 刘明宗; 张雅菁; 颜哲伟; 吴和虔
Original assignee: TPK Advanced Solutions Inc
Current assignee: TPK Advanced Solutions Inc
Priority date: 2022-03-31
Filing date: 2022-03-31
Publication date: 2023-10-24
Also published as: JP2023152248A; KR20230141381A

Abstract

The invention relates to a flexible optical stack and an organic light-emitting diode display containing the same, wherein the adhesive layer is arranged between a cover plate and a circular deflection component, between the circular deflection component and a touch component or between the touch component and the display component, wherein the storage modulus of the adhesive layer at 60 ℃ is between 15 and 30kPa, and the ratio of the storage modulus of the adhesive layer at-30 ℃ to the storage modulus at 60 ℃ is between 6 and 16. The organic light emitting diode display includes the optical stack.

Description

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

Technical Field

The present invention relates to a flexible optical stack and an organic light emitting diode display including the same, and more particularly, to a stable and flexible ultra-thin optical stack and an organic light emitting diode display including the same.

Background

Currently, circular polarizers (Circular Polarizer, CPOLs) are mainly formed by combining a phase retardation layer (polarizer) with a linear polarizer, however, in the display field, a display device must combine an electrical signal processing element (e.g. a touch electrode) with an optical element (e.g. an optical film such as a polarizing film, a phase retardation film, etc.) to meet the application requirements of the terminal customer, and the electrical signal processing element and the optical element are usually combined by an optical transparent adhesive. However, as the use environment, storage environment, and/or manufacturing environment of the display device have become severe recently, and the application of the display device to the flexible display device has become mature, the characteristics of each film layer on the display device need to be matched. In particular, in order to apply the display device in a flexible context, the optically transparent adhesive plays an important role, for example, the optically transparent adhesive can absorb stress in a bent state of the display device to avoid the failure of the electrical signal processing element or the optical element.

Taiwan patent No. I590119 (hereinafter referred to as patent I590119) discloses a flexible display device, which utilizes a first adhesive film to assemble a photoelectric portion and a touch functional portion; and the touch control function part and the window film are assembled by using the second adhesive film.

Patent I590119 discloses adhesive films for flexible display devices and is discussed with respect to their storage modulus, for example, by analyzing the storage modulus of adhesive films to have an average slope of-9.9 to 0 at-20 ℃ to 80 ℃ and to have a storage modulus of 10KPa to 1000KPa at 80 ℃. However, the patent I590119 only performs a stretching experiment, which cannot effectively verify the state of the adhesive film in a bending situation, that is, the patent I590119 cannot provide an adhesive material suitable for a bendable/flexible/crimpable product at a low temperature (e.g., -30 ℃ to-20 ℃). Therefore, how to find a preferred specification rule to make the adhesive film applicable in high and low temperature environments (e.g., -30 ℃ to 60 ℃) is a problem to be solved.

Therefore, the present invention has been made in view of the above-described drawbacks.

Disclosure of Invention

The invention aims to provide a flexible optical stack, wherein the optical stack comprises at least one bonding layer, and the optical stack is formed by integrating an electric signal processing element and an optical element, so that the two elements with different characteristics/functions can not damage respective characteristics when being matched through the bonding layer, and meanwhile, products can be thinned to meet the integration requirement, thereby realizing the bendable and ultrathin optical stack and products thereof.

Another object of the present invention is to provide a flexible optical stack, wherein the adhesive layer has a storage modulus at 60 ℃ between 15kPa and 30 kPa; the ratio of the storage modulus at-30 ℃ to the storage modulus at 60 ℃ of the adhesive layer is between 6 and 16, whereby an adhesive layer that maintains viscoelastic properties over a wide temperature range and can have excellent recovery properties can be achieved.

The flexible optical stack of the present invention comprises: at least one bonding layer arranged between a cover plate and a circular deflection component, between the circular deflection component and a touch component or between the touch component and the display component; wherein the adhesive layer has a storage modulus at 60 ℃ of between 15kPa and 30 kPa; the ratio of the storage modulus at-30 ℃ to the storage modulus at 60 ℃ of the adhesive layer is between 6 and 16.

Preferably, the optical stack according to the invention, wherein the storage modulus of the adhesive layer at 60 ℃ is 27 and the ratio of the storage modulus of the adhesive layer at-30 ℃ to the storage modulus at 60 ℃ is 6.6; or the adhesive layer has a storage modulus at 60 ℃ of 17 and the ratio of the storage modulus at-30 ℃ to the storage modulus at 60 ℃ of 15.8; the storage modulus of the adhesive layer at 60 ℃ was 28, and the ratio of the storage modulus of the adhesive layer at-30 ℃ to the storage modulus at 60 ℃ was 13.3.

Preferably, the optical stack according to the invention, wherein the glass transition temperature of the adhesive layer is less than-30 ℃.

Preferably, the optical stack according to the invention, wherein the material of the adhesive layer is a hydroxyl group containing acrylic polymer.

Preferably, the optical stack according to the invention, wherein the interfacial adhesion between the adhesive layer and the circularly polarized component is greater than 500g/inch in the range of-30 ℃ to 60 ℃.

The present invention further provides an organic light emitting diode with stable flexibility, which is applied to the optical stacking structure, and the organic light emitting diode comprises: the first bonding layer is arranged between a cover plate and a circular deflection assembly; the method comprises the steps of carrying out a first treatment on the surface of the The second bonding layer is arranged between the circular deflection component and a touch component; the third bonding layer is arranged between the touch control component and a display component; the cover plate is arranged on the uppermost layer of the organic light-emitting diode display, the storage modulus of the first, second and third adhesive layers at 60 ℃ is between 15 and 30kPa, and the ratio of the storage modulus of the first, second and third adhesive layers at-30 ℃ to the storage modulus at 60 ℃ is between 6 and 16.

The flexible optical stack structure provided by the invention comprises at least one bonding layer, and the optical stack structure is formed by integrating the electric signal processing element and the optical element, so that the two elements with different characteristics/functions can not damage the respective characteristics when being matched through the bonding layer, and meanwhile, the product can be thinned, and the integrated requirement is met, thereby realizing the bendable and ultrathin optical stack structure and the product thereof. And the adhesive layer has a storage modulus at 60 ℃ of between 15 and 30 kPa; the ratio of the storage modulus at-30 ℃ to the storage modulus at 60 ℃ of the adhesive layer is between 6 and 16, whereby the adhesive layer 11 can be ensured to have an excellent balance of cohesive strength and adhesive strength, an adhesive layer which maintains a viscoelastic property over a wide temperature range and can have excellent recovery properties can be realized, and excellent reliability and durability can be provided.

The present invention will be described in detail with reference to the following specific examples, which are included to provide a person skilled in the art with an understanding of the objects, features and effects of the present invention.

Drawings

FIG. 1 is a schematic illustration of an exemplary optical stack according to the present invention;

FIG. 2 is an exemplary schematic diagram illustrating a lamination of peel strength tests; and

fig. 3 is an exemplary schematic diagram illustrating the folding of a bending test.

Detailed Description

Advantages, features and methods of achieving the present invention according to exemplary embodiments thereof will be described in more detail below with reference to the accompanying drawings. It should be noted, however, that the present invention is not limited to the following exemplary embodiments, but may be embodied in various forms.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.

Furthermore, it will be understood that when an element is referred to as being "on" another element, it can be directly on the other element or intervening elements may be present. In addition, the thickness values referred to herein are not absolute, and those of skill in the art will appreciate that the thicknesses referred to may include manufacturing tolerances, measurement errors, and the like, and preferably the thicknesses recited herein may have a range of 10%, 20%.

It will also be understood that, although the terms "first," "second," etc. may be used herein to describe various elements, these elements should not be limited by these terms. The term is used merely to distinguish between individual elements. Thus, a first element could be termed a second element in other embodiments without departing from the teachings of the present invention. In the present specification, the same reference numerals denote the same elements. In addition, optical elements are used interchangeably herein with "plate," "layer," "film," or other similar terms, and unless specifically indicated otherwise, are merely by differences in name.

Referring to FIG. 1, an exemplary optical stack 100 according to the present invention is shown. The flexible optical stack 100 includes at least one adhesive layer 11. The adhesive layer 11 may be disposed between the substrates 12 and 13, and in the present invention, the substrates 12 and 13 may be at least a cover plate, a circular deflection component, a touch component, a display component, etc., for example, the adhesive layer 11 may be disposed between the cover plate (i.e. the substrate 13) and the circular deflection component (i.e. the substrate 12); alternatively, in another embodiment, the adhesive layer 11 may be disposed between the circular offset component (i.e. the substrate 13) and the touch component (i.e. the substrate 12); or in another embodiment, the adhesive layer 11 may be disposed between the touch component (i.e., the substrate 13) and the display component (i.e., the substrate 12), which is only for example and not for limiting the present invention. According to the characteristics of the adhesive layer 11 of the present invention, two or more layers of the assembly can realize a flexible and ultra-thin integrated touch module and its product at a wide operating temperature (e.g., -30 ℃ to 60 ℃).

Specifically, according to some embodiments, the adhesive layer 11 may be an Optically Clear Adhesive (OCA), and the material thereof may be a hydroxyl group-containing acrylic polymer. Specifically, in some embodiments, the material of the adhesive layer 11 may include at least one of an alkyl (meth) acrylate monomer, a monomer having ethylene oxide (ethylene oxide), a monomer having propylene oxide (propylene oxide), a monomer having an amine group, a monomer having an amide group, a monomer having an alkoxy group, a monomer having a phosphate group, a monomer having a sulfonate group (sulfonic acid group), a monomer having a phenyl group, and a monomer having a silane group. More specifically, the adhesive layer 11 may have a glass transition temperature of less than or equal to-30 ℃.

Additionally, in some embodiments of the present disclosure, the circularly polarized component may be an anti-reflective optical element formed by a combination of at least one phase retardation layer and a linearly polarized layer. For the purpose of pre-integration and product thinning, in one embodiment of the present invention, the retarder layer may be a 45 μm thick cycloolefin polymer (COP) which can be used as a quarter-phase compensation layer (also called 1/4 wave plate or 1/4 wavelength retarder). In addition, in some embodiments of the present disclosure, the linear polarizing layer may be a generally commercially available polarizing plate having a degree of polarization (degree of polarization, DOP) of greater than 98%, but is not limited thereto. The linear polarizing layer may be two protective films (such as cellulose triacetate, TAC) to fix a polyvinyl alcohol (PVA) material in the middle (hereinafter abbreviated as a type-a polarizing layer), or a combination of a single protective film (such as TAC) and a polyvinyl alcohol (PVA) material (hereinafter abbreviated as B type polarizing layer), both of which are applicable to the present invention, or any other type of polarizing layer, and is not limited to the embodiment. 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 called 1/2 wave plate or 1/2 wave retarder). In one embodiment of the present invention, the phase retardation layer may be one half of the phase compensation layer. The embodiment of the invention provides the phase retardation value measured by the plane perpendicular to the thickness direction of the object to be measured, namely, the in-plane phase retardation value (in plane retardance/retardation (R0)) to describe the characteristics of the optical film. The in-plane retardation value of the object to be measured in the visible wavelength range is measured using a commercial device model AxScan (manufacturer Axometrics, inc.).

It should be further noted that since the present invention relates to the storage modulus of the adhesive layer 11, the measurement method is described below. The storage modulus can be measured by dynamic load testing/Dynamic Mechanical Analysis (DMA) of the adhesive layer 11, and the basic principle is to apply periodic stress with a certain frequency to the adhesive layer 11, and analyze the magnitude of strain and the phase difference between the applied dynamic force and the deformation of the adhesive layer 11, thereby obtaining dynamic properties of the material, such as stiffness (i.e., storage modulus) and damping (i.e., loss modulus). In order to simulate the stress mode of the material under the actual working condition, the dynamic stress can be sine wave, triangular wave, square wave and the like. For example, applying stress to a material, the ratio of stress to strain is complex modulus, and the phase difference between the two can be defined as the phase angle delta, which is the hysteresis level that represents the deformation of the material. It should be further noted that, in the complex coordinates, the included angle between the complex modulus and the x-axis is the phase angle δ, the storage modulus and the loss modulus are projections of the complex modulus on the real axis and the imaginary axis, respectively, and the loss characteristic of the adhesive layer 11 is represented by defining tan δ as the loss factor.

It should be noted that, since the present invention relates to the peel strength (also referred to as interface adhesion) between the adhesive layer 11 and the different components, the measurement method is described below. Referring to fig. 2, fig. 2 is an exemplary schematic diagram illustrating a stack of peel strength tests. First, an adhesive composition to be measured is coated on a tape 22 (a material is a polyethylene terephthalate (PET) film), and after the adhesive composition is cured, a first adhesive film 21 is formed, which is combined with the tape 22 to form an adhesive sheet 200, wherein the thickness of the tape 22 is 50 μm; then, the other surface of the first adhesive film 21 is combined with the component 23 to be tested to form an adhesive interface, wherein the component 23 to be tested can be a cover plate, a circular deflection component, a touch component, a display component and the like, a user can replace different components according to the requirements for testing, and the component 23 to be tested can be fixed on the glass 25 through the second adhesive film 24; finally, one side of the adhesive sheet 200 was folded back 180 ° and a pulling force was applied under different temperature environments to pull the adhesive sheet 200 at a rate of 300mm/min, thereby measuring peel strength of an adhesive interface formed by the adhesive composition to be tested and the component to be tested 23 under different temperature environments. It should be noted that, since the first adhesive film 21 and the second adhesive film 24 are formed by the same adhesive composition, the peeling strength between the adhesive composition to be tested and the component to be tested 23 can be considered no matter the peeling interface 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.

It should be noted that, since the present invention relates to the bending test of the adhesive layer 11, the test method is described below. The term "pass bending test" as used herein means that the following failure behavior is not produced by the following procedure. Referring to fig. 3, fig. 3 is an exemplary schematic diagram illustrating a folding structure of a bending test. The bending test of the present invention is mainly directed to the to-be-tested stack of fig. 3, where the to-be-tested stack is mainly used to simulate whether an actual touch display device can pass the bending test, so when the bending test is performed, bending feasibility is mainly evaluated in different temperature environments for replacing different optical adhesive materials in the to-be-tested stack, and detailed description will be given below for each layer of structure. The bending test method comprises the steps of carrying out bending test for at least 20 ten thousand times on the to-be-tested structure under different temperature environments; then, confirming whether the to-be-tested stacking structure generates failure behaviors such as fracture, buckling, delamination and the like; finally, when the to-be-tested stacking structure is confirmed to not generate failure, the optical adhesive material can be judged to pass the bending test.

The following description of fig. 3 shows an exemplary touch display device 1 according to the present invention. The touch display device 1 includes: the touch panel comprises a cover plate 131, a first adhesive layer 111, a circular bias component composed of a linear bias sheet 132 and a 1/2 wavelength delay sheet 133, a second adhesive layer 112, a touch component 121 composed of a 1/4 wavelength delay sheet 135 and touch electrodes 134 and 136 positioned on the upper and lower surfaces thereof, a third adhesive layer 113 and a display component 122. Wherein for testing cost considerations, the display assembly 122 is replaced with a 50 μm transparent polyimide film (CPI) for an organic light emitting diode display (OLED).

The cover 131 may be used as an outermost member of the touch display device 1, or may be defined as a member that can be touched by a user. The cap plate 131 may be a single layer of an inorganic encapsulation material, a multi-layer stack of an inorganic encapsulation material, or a stack of a pair of an inorganic encapsulation material and an organic encapsulation material, for example, but not limited to, silicon nitride (SiNx), silicon oxide (SiOx), silicon oxynitride (SiONx), aluminum oxide (AlOx), or titanium oxide (TiOx), glass, a resin layer, or the like. In this embodiment, the cover plate 131 is a 50 μm transparent polyimide film (CPI).

The circular polarization component is generally composed of a linear polarizer and a phase retarder, and the function of the circular polarization component is often used as an anti-reflection sheet to solve the problem of reflection light generated by incident light from the external environment and reduce the disturbance of display, wherein the phase retarder can be a 1/4 wave plate (quarter wave plate, QWP) or a 1/2 wave plate (HWP). Theoretically, when the external incident light passes through the outermost linear polarizer, the linear polarizer converts the incident light into linear polarized incident light, the polarization direction of the linear polarized incident light is vertical, and then the linear polarized incident light enters a 1/4 wave plate serving as a phase retarder to generate phase retardation, so that the linear polarized incident light is converted into left-handed polarized light; then, after the light is reflected by the display panel, reverse right-handed polarized light is formed and then passes through the 1/4 wave plate serving as the phase delay layer, so that the polarization direction of the linearly polarized incident light is orthogonal with that of the linearly polarized incident light, and the incident light in the external environment cannot pass through the linear polarizer, so that the light cannot be observed by human eyes, and the anti-reflection effect is achieved. That is, the combination of the line polarizer 132 and the 1/2 wavelength retarder 133 of the present embodiment can constitute an anti-reflection optical element. The line bias sheet 132 is coupled to the cover plate 131 through the first adhesive layer 111, and the 1/2 wavelength delay sheet 133 is coupled to the touch device 121 through the second adhesive layer 112. More specifically, the 1/2 wavelength retarder 133 is a liquid crystal phase retarder layer, which may be a single layer liquid crystal coating, having a phase retardation value R0 (550) at 550nm of between 230nm and 310nm, preferably at least 250nm, for example, using commercially available products: the Reactive Mesogen (RM) Reactive liquid crystal is made to have a thickness of about 2 μm and a slow axis of about 15 degrees, and has a retardation value of 260nm at 550nm, but the present invention is not limited thereto. The linear polarization sheet 132 is the type B polarizing layer, which is commercially available as SPN32-1805M (supplier: SAPO), and the liquid crystal type 1/2 wavelength retarder 133 is attached to the linear polarization sheet 132 by a glue of polyvinyl alcohol (PVA).

The touch assembly 121 of the present invention may form a touch electrode on a substrate through a patterning process using 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). In the embodiment shown in fig. 3, the touch device 121 is composed of a 1/4 wavelength retardation plate 135 and touch electrodes 134 and 136 disposed on the upper and lower surfaces thereof, in other words, the 1/4 wavelength retardation plate 135 can be used as a carrier substrate for the touch electrodes 134 and 136, and the phase retardation value R0 (550) of the 1/4 wavelength retardation plate 135 at 550nm can be between 100nm and 160nm, preferably at least 130nm. Specifically, the 1/4 wavelength retarder 135 is a cyclic olefin copolymer (Cyclo Olefin Polymer; COP) material (vendor: KONICA MINOLTA) having a thickness of 25 μm and a phase retardation value at 550nm of 131nm at 550 nm. The touch control component 121 of the present embodiment is made of nano silver, and the method used may be to apply a dispersion liquid containing nano silver wires on the upper and lower surfaces of the 1/4 wavelength retardation plate 135, for example, mixing nano silver wires into a solvent, for example: water, alcohols, ketones, ethers, hydrocarbons or aromatic solvents (benzene, toluene, xylene, etc.) to form a coating/slurry; the above-described coating/slurry may also contain additives, surfactants or binders, such as: carboxymethyl cellulose (carboxymethyl cellulose, CMC), 2-hydroxyethyl cellulose (hydroxyethyl Cellulose, HEC), hydroxypropyl methyl cellulose (hydroxypropyl methylcellulose, HPMC), sulfonate, sulfate, disulfonate, sulfosuccinate, phosphate, or fluorosurfactant, and the like. After the coating is completed, a nano silver wire layer is formed by a curing step, and the nano silver wire layer can be formed into the touch electrodes 134 and 136 by patterning methods known to those skilled in the art (for example, a photolithography process using a photoresist and an etching process).

Preferably, the nano silver wires are fixed on the surface of the polymer phase delay layer 20 without falling off to form the nano silver wire layer, and the nano silver wires can contact each other to provide a continuous current path, thereby forming a conductive network (conductive network), in other words, the nano silver wires contact each other at the crossing position to form a path for transferring electrons. That is, one nano silver wire layer and the other nano silver wire layer form a direct contact state at the crossing position, so that a low-resistance transmission electron path is formed. In one embodiment, a region or structure may be considered electrically insulating when sheet resistance is above 108 ohms/square (ohm/square), preferably above 104 ohms/square, 3000 ohms/square, 1000 ohms/square, 350 ohms/square, or 100 ohms/square. In one embodiment, the sheet resistance of the nano-silver wire layer comprised of nano-silver wires is less than 100 ohms/square. The nano-silver wire electrode has a high transmittance, for example, a light transmittance (Transmission) in the visible light range of greater than about 88%, 90%, 91%, 92%, 93% or more.

In an embodiment, a polymer layer may be further disposed to cover the nano silver wire. In a specific embodiment, a proper polymer/polymer is coated on the nano silver wires, the polymer with flowing state/property can permeate between the nano silver wires to form a filler, the nano silver wires can be embedded into the polymer/polymer, and the composite structure is formed after the polymer is solidified. That is, in this step, a polymer layer is applied to the nano silver wires by coating the polymer/polymer, and the nano silver wires 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 may be a non-conductive resin or other organic material such as polyacrylate, epoxy, polyurethane, polysilane, polysilicone, poly (silicon-acrylic), polyethylene (PE), polypropylene (PP), polyvinylbutyral (Polyvinyl butyral; PVB), polycarbonate (PC), acrylonitrile-butadiene-styrene copolymer (Acrylonitrile butadiene styrene; ABS), and the like. In some embodiments of the present invention, the polymer layer may be formed by spin coating, spray coating, printing, or the like. In some embodiments, the thickness of the polymer layer is about 20nm to 10mm, or 50nm to 200nm, or 30nm to 100nm, for example, the thickness of the polymer layer may be about 90nm or 100nm. The above specific method can be referred to and incorporated in the document of US20190227650A, CN101292362, etc., and both the nano silver wire paste and the polymer coating are provided by Cambrios.

Referring to table 1 and fig. 3, table 1 is a graph illustrating the storage modulus and bending test results measured by applying the adhesive layers 111, 112, 113 made of the adhesive materials according to the first and second comparative examples of the present invention to the structure of fig. 3 and performing dynamic load test at different temperatures, specifically, as shown in table 1, the storage modulus at 60 ℃ of the adhesive materials according to the first and second comparative examples of the present invention is more than 30kPa, and the ratio of the storage modulus at-30 ℃ to the storage modulus at 60 ℃ of the adhesive materials according to the first and second comparative examples is more than 16. More specifically, the storage modulus of the adhesive material of the first comparative example at-30 ℃ was 4000kPa, the storage modulus of the adhesive layer 11 of the first comparative example at 60 ℃ was 100kPa, and the ratio of the storage modulus of the adhesive layer 11 of the first comparative example at-30 ℃ to the storage modulus at 60 ℃ was as high as 40. More specifically, the storage modulus of the adhesive material of the second comparative example at-30℃was 3800kPa, the storage modulus of the adhesive material of the second comparative example at 60℃was 40kPa, and the ratio of the storage modulus of the adhesive material of the second comparative example at-30℃to the storage modulus at 60℃was as high as 95.

TABLE 1

It can be understood that, according to the storage modulus of the adhesive layer of the first comparative example and the second comparative example at high temperature (e.g. 60 ℃), it is obvious that the storage modulus of the adhesive material of the first comparative example and the second comparative example is too high at high temperature, and the excessive storage modulus represents that the property of the adhesive material is hard and poor in viscosity, so that the sample can be delaminated/foamed under the test of high Wen Wanshe, that is, the product flexibility requirement cannot be satisfied. However, the temperature varies greatly, and in terms of stability, the optical stack is often more fragile under high and low temperature conditions due to the large variation of storage modulus, and the stability is poor. According to the first and second comparative examples, it was found that when the storage modulus is too large, for example, the ratio of the storage modulus at-30 ℃ to the storage modulus at 60 ℃ of the adhesive material in the first comparative example is as high as 40, and thus the adhesive material cannot deform in response to bending at low temperature (for example, -30 ℃ to-20 ℃) to cause the risk of breakage due to stress concentration, which may lead to the risk of mechanical damage or optical distortion (Mura) caused by breakage of the optical stack 100. Therefore, from the bending results of the first comparative example and the second comparative example, the present invention considers that the application range of the storage modulus of the adhesive material at 60 ℃ and the ratio range of the storage modulus at-30 ℃ to the storage modulus at 60 ℃ must be found, so that the product (such as the touch product shown in the simulation of fig. 3) can meet the flexible requirement under the conditions of high and low temperature ranges.

Referring to table 2 and fig. 2, table 2 is a graph illustrating peel strengths measured for adhesive materials according to the first and second comparative examples of the present invention at different temperatures for different interfaces. Specifically, as shown in Table 2, the adhesive materials according to the first comparative example and the second comparative example of the present invention had peel strengths of less than 500g/in at-20 ℃. More specifically, the adhesive layer 11 of the first comparative example had peel strengths of only 175g/inch, 127g/inch and 124g/inch for the optical element 13 (polarizing layer and phase retardation layer) and the electric signal processing element 12 (touch device) at-20 ℃, and the adhesive layer 11 of the second comparative example had peel strengths of only 122g/inch, 349g/inch and 241g/inch for the optical element 13 (polarizing layer and phase retardation layer) and the electric signal processing element 12 (touch device) at-20 ℃. It is apparent that the adhesive layer 11 of the first comparative example and the second comparative example cannot deform in response to bending in a low temperature environment, and the stress concentration affects the adhesive strength of the adhesive layer 11 in a continuous manner, and the long-term reliable adhesion function cannot be maintained, and the data of the peel strength can explain the reason why the adhesive materials of the first comparative example and the second comparative example cannot pass the bending test at a low temperature.

TABLE 2

Interface (I)	Temperature (temperature)	First comparative example	Second comparative example
				Polarizing layer	-20℃	175	122
Phase delay layer	-20℃	127	349
				Touch control assembly	-20℃	124	241

Referring to table 3 and fig. 3, table 3 is a graph illustrating the storage modulus and bending test results of the adhesive layers 111, 112, 113 made of the adhesive materials according to the first to third embodiments of the present invention, which are applied to the structure of fig. 3, and are measured by dynamic load test at different temperatures. Specifically, as shown in table 3, the storage modulus at 60 ℃ of the adhesive materials according to the first to third embodiments of the present invention is between 15kPa and 30kPa, and the ratio of the storage modulus at-30 ℃ to the storage modulus at 60 ℃ of the adhesive materials according to the first to third embodiments is between 6 and 16. More specifically, the storage modulus at-30 ℃ of the adhesive material of the first embodiment was 270kPa and passed the bending test, the storage modulus at 60 ℃ of the adhesive material of the first embodiment was 17kPa and passed the bending test, and the ratio of the storage modulus at-30 ℃ to the storage modulus at 60 ℃ of the adhesive material of the first embodiment was 15.8. More specifically, the adhesive material of the second embodiment has a storage modulus at-30 ℃ of 371kPa and passes the bending test, the adhesive material of the second embodiment has a storage modulus at 60 ℃ of 28kPa and passes the bending test, and the ratio of the storage modulus at-30 ℃ to the storage modulus at 60 ℃ of the adhesive material of the second embodiment is 13.3. More specifically, the adhesive material of the third embodiment had a storage modulus at-30℃of 177kPa and passed the bending test, the adhesive material of the third embodiment had a storage modulus at 60℃of 27kPa and passed the bending test, and the ratio of the storage modulus at-30℃to the storage modulus at 60℃of the adhesive material of the third embodiment was 6.6.

TABLE 3 Table 3

It can be understood that, according to the ratio of the storage moduli of the adhesive materials of the first to third embodiments under the test range, it is apparent that the storage moduli of the adhesive materials of the first to third embodiments do not significantly vary with temperature under the test condition range, and the adhesive layers 11 of the first to third embodiments maintain the viscoelastic properties over a wide temperature range and can have excellent recovery properties with excellent stability in terms of stability. If G '(-30 ℃ C.)/G' (60 ℃ C.) is greater than 16, it is shown that the storage modulus of the adhesive material at-30 ℃ C. Is too large, resulting in the adhesive material having harder properties and poor tackiness; on the other hand, the ratio of G '(-30 ℃) to G' (60 ℃) is not smaller and better, and although the adhesive material has small storage modulus at-30 ℃ and contributes to bending of the product, in practice, too low storage modulus also represents small cohesion of molecules inside the adhesive material and degree of polymerization of molecules, so that the strength of the adhesive material is too low to be beneficial to processing, that is, too low strength of the material is not beneficial to practical production and manufacturing processes. Patent I590119 discloses the average slope of the storage modulus at-20 ℃ to 80 ℃ and the storage modulus at each temperature, but does not disclose the storage modulus at-30 ℃, so the invention adopts the interpolation method/extrapolation method which is common in general experimental study for analysis, and the G '(-30 ℃) and G' (60 ℃) of 9 groups of specific embodiments disclosed in patent I590119 have values between 2 and 4, and the bonding material of patent I590119 has the defect of too low material strength and adverse processing according to the previous discussion.

Further, since the first comparative example did not pass the bending test at 60 ℃, we judged that the storage modulus of the adhesive layer at 60 ℃ could not be greater than 40kPa, and further according to the first to third examples, we found that when the storage modulus of the adhesive layer at 60 ℃ was less than 30kPa, it was possible to sufficiently ensure that the storage modulus of the adhesive material was still sufficiently small under the high temperature environment, so that the optical stack 100 of the first to third examples passed the bending test under the high temperature condition, ensuring that the adhesive material could still achieve reliable adhesion for a long period of time under the high temperature environment. It should be further noted that, although the low storage modulus ensures deformation of the adhesive material in response to bending and prevents the risk of breakage and breakage, when the storage modulus is too low, the adhesive material cannot maintain the cohesive strength necessary for processing, handling, maintaining the shape and the like, which causes difficulty in the process of the adhesive material. Thus, according to the summary of the data of the first to third embodiments, the present invention provides a specification of a preferable adhesive material, in which a balance of cohesive strength and adhesive strength can be ensured when the storage modulus of the adhesive material at 60 ℃ is between 15kPa and 30 kPa.

Referring to table 4 and fig. 2, table 4 is a graph illustrating the peel strengths measured at different temperatures for different interfaces of the adhesive layer 11 according to the first to third embodiments of the present invention. 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 different interfaces at-20℃was higher than 500g/inch. More specifically, the adhesive material of the first embodiment has peel strengths of 2812g/inch, 2132g/inch and 1531g/inch at-20 ℃ for the optical element 13 (polarizing layer and phase retardation layer) and the electrical signal processing element 12 (touch device), and other data can be read accordingly. When the peel strength between the adhesive and other interfaces is higher than 500g/inch, the adhesive maintains excellent reliability and durability in the use temperature range, as is evident from the combination of the bending test and the peel strength of table 4.

TABLE 4 Table 4

It will be appreciated that those skilled in the art can make various changes and modifications based on the above examples, which are not explicitly recited herein. The following focuses on the application of the organic light emitting diode display having stable flexibility according to the embodiment to more clearly understand possible variations by those skilled in the art of the present invention. Elements denoted by the same reference numerals as the above-described embodiments are substantially the same as those described above with reference to fig. 1 to 3. The same elements, features, and advantages as the optical stack 11 will not be described in detail.

It is further noted that in the present embodiment, the thicknesses of the first adhesive layer 111, the second adhesive layer 112, and the third adhesive layer 113 may be 25 micrometers to 50 micrometers, and further, the first adhesive layer 111, the second adhesive layer 112, and the third adhesive layer 113 may include an adhesive film having a haze of 5% or less, specifically 3% or less, and more specifically 1% or less at a thickness of 25 micrometers to 50 micrometers. Within this range, the adhesive layer 11 exhibits excellent transparency when used for display, however, the present invention is not limited thereto.

In this embodiment, the first adhesive layer 111, the second adhesive layer 112, and the third adhesive layer 113 may be made of the same material. In the present invention, "the same material" means that the composition (component) and physical properties are the same. In another embodiment, the first adhesive layer 111, the second adhesive layer 112, and the third adhesive layer 113 may be made of different materials. In another embodiment, the thickness of the second adhesive layer 112 may be thicker than the thicknesses of the first adhesive layer 111 and the third adhesive layer 113. Accordingly, the second adhesive layer 112 may have higher adhesion than the first adhesive layer 111 and the third adhesive layer 113. Therefore, the reliability of the organic light emitting diode display can be increased by adjusting the thickness of the adhesive layer 11, while achieving the effects of planarization of the optical element, etc.

Finally, the technical features and the technical effects that can be achieved by the invention are summarized as follows:

1. according to the optical stack 100 of the present invention, the adhesive material has a storage modulus at 60 ℃ of 15kPa to 30kPa and a ratio of the storage modulus at-30 ℃ to the storage modulus at 60 ℃ of 6 to 16, whereby the adhesive layer 11 can be ensured to have an excellent balance of cohesive strength and adhesive strength, and an optical stack and a product thereof according to practical application requirements.

2. The adhesive material of the optical stack 100 according to the present invention has a peel strength with different interfaces of more than 500g/inch at the use temperature, and it is apparent that the adhesive layer 11 according to the present invention maintains excellent reliability and durability even in severe use environments, storage environments and/or manufacturing environments, which meet practical application requirements.

The foregoing describes embodiments of the present invention in terms of specific examples, and further features, advantages, and effects of the present invention will be readily apparent to those skilled in the art from the disclosure herein.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the scope of the present invention. Other equivalent changes and modifications can be made without departing from the spirit of the present disclosure, and are intended to be included within the scope of the following claims.

Claims

1. An optical stack, comprising:

at least one bonding layer arranged between the cover plate and the circular deflection component, between the circular deflection component and the touch component, or between the touch component and the display component;

wherein the adhesive layer has a storage modulus at 60 ℃ of between 15 and 30kPa, and the adhesive layer has a ratio of storage modulus at-30 ℃ to storage modulus at 60 ℃ of between 6 and 16.

2. The optical stack according to claim 1, wherein the adhesive layer has a storage modulus at 60 ℃ of 27 and the ratio of the storage modulus at-30 ℃ to the storage modulus at 60 ℃ of the adhesive layer is 6.6; or the adhesive layer has a storage modulus at 60 ℃ of 17 and the ratio of the storage modulus at-30 ℃ to the storage modulus at 60 ℃ of 15.8; the storage modulus of the adhesive layer at 60 ℃ was 28, and the ratio of the storage modulus of the adhesive layer at-30 ℃ to the storage modulus at 60 ℃ was 13.3.

3. The optical stack according to claim 1, wherein the glass transition temperature of the adhesive layer is less than-30 ℃.

4. The optical stack of claim 1 wherein the material of the adhesive layer is a hydroxyl-containing acrylic polymer.

5. The optical stack of claim 1, wherein the interfacial adhesion between the adhesive layer and the circularly polarized component is greater than 500g/inch in the range of-30 ℃ to 60 ℃.

6. An organic light emitting diode display, comprising:

the first bonding layer is arranged between the cover plate and the circular deflection assembly;

the second bonding layer is arranged between the circular deflection component and the touch component;

the third bonding layer is arranged between the touch control component and the display component;

the cover plate is arranged on the uppermost layer of the organic light-emitting diode display, the storage modulus of the first, second and third bonding layers at 60 ℃ is between 15 and 30kPa, and the ratio of the storage modulus of the first, second and third bonding layers at-30 ℃ to the storage modulus at 60 ℃ is between 6 and 16.