CN115926646A - Adhesive film for foldable display screen - Google Patents
Adhesive film for foldable display screen Download PDFInfo
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- CN115926646A CN115926646A CN202210641830.7A CN202210641830A CN115926646A CN 115926646 A CN115926646 A CN 115926646A CN 202210641830 A CN202210641830 A CN 202210641830A CN 115926646 A CN115926646 A CN 115926646A
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Abstract
The present invention relates to an adhesive film for a foldable display panel, and more particularly, to an adhesive film for a foldable display panel which has excellent bend recovery characteristics without crease or bulge between adherends when repeatedly bent, and can minimize the generation of bubbles between adherends.
Description
[ technical field ] A method for producing a semiconductor device
The present invention relates to an adhesive film for a foldable display panel, and more particularly, to an adhesive film for a foldable display panel which has excellent bend recovery characteristics without crease or bulge between adherends when repeatedly bent, and can minimize the generation of bubbles between adherends.
[ background of the invention ]
A pressure sensitive adhesive (pressure sensitive adhesive) is a substance that can permanently maintain its viscosity unless its surface is contaminated, and can easily adhere to an adherend at room temperature in a short time with a very small pressure such as finger pressure.
Such pressure-sensitive adhesives are widely used in a wide variety of fields such as consumer goods, automobiles, aviation, and the IT industry, and are used in the IT industry for transportation of semiconductors, mobile phones, display devices, precision products, and the like, and for fixing and protecting materials.
Recently, with the development of display screen related technologies, research and development are being conducted on a deformable display screen that can be folded, rolled (Roll) or stretched like a rubber band during use. These displays can be deformed into various forms, and thus, the enlargement of the display and the miniaturization of the display required for portability can be satisfied simultaneously during the use. The deformable display device can be deformed into a preset shape, and can be deformed into various shapes according to the requirements of users or the use conditions of the display device. Therefore, it is necessary to recognize a deformed form of the display screen and control the display device corresponding to the recognized form.
On the other hand, the deformable display device has a problem that each component of the display device is damaged by deformation, and thus each component of such a display device needs to satisfy Folding (Folding) reliability and stability.
Therefore, the adhesives used for the deformable display device also satisfy the aforementioned Folding (Folding) reliability and stability, and the adhesives used for the deformable display devices currently on the market have a problem that they do not satisfy all of the physical properties such as adhesive force, heat resistance, and recovery rate in addition to the Folding (Folding) characteristics.
[ Prior art documents ]
[ patent document ]
(patent document 0001) Korean laid-open patent No. 2015-0011230 (published: 2015.01.30)
[ summary of the invention ]
[ technical problem to be solved ]
The present invention has been made in view of the above problems, and an object thereof is to provide an adhesive film for a foldable display panel which has not only excellent bend recovery characteristics without crease or bulging between adherends when repeatedly bent, but also can minimize the occurrence of bubbles between the adherends.
[ technical solution ] A
In order to solve the above problems, an adhesive film for a foldable display panel of the present invention includes an adhesive layer formed by curing an adhesive composition for a foldable display panel.
As a preferred embodiment of the present invention, the adhesive composition for a foldable display screen may include an acrylic polymer and a curing agent.
As a preferred embodiment of the present invention, the adhesive film for a foldable display screen of the present invention may have a creep rate at 25 ℃ of 30 to 60% measured according to the following relation 1.
[ relational expression 1]
In the above relation 1, σ represents Stress (Stress), E represents elastic modulus (elastic modulus), t represents creep (creep) deformation time, λ represents η/E, and η represents viscosity ratio (viscocity rate).
As a preferred embodiment of the present invention, the adhesive film for a foldable display panel of the present invention may have a recovery rate at 25 ℃ of 60% or more, measured according to the following relational expression 2.
[ relational expression 2]
In the above relation 2, σ represents Stress (Stress), E represents elastic modulus (elastic modulus), t represents creep (creep) deformation time, tr represents creep recovery time after creep deformation, λ represents η/E, and η represents viscosity ratio (viscocity rate).
As a preferred embodiment of the present invention, the adhesive film for a foldable display screen of the present invention may have a loss factor (tan δ) at-20 ℃ of 1.0 to 2.0.
As a preferred embodiment of the present invention, the adhesive film for a foldable display screen of the present invention may have a creep rate at 60 ℃ measured according to the relation 1 of 20% to 50%.
As a preferred embodiment of the present invention, the adhesive film for a foldable display screen of the present invention may have a recovery rate at 60 ℃ measured according to the relational expression 2 of 80% or more.
As a preferred embodiment of the present invention, the adhesive film for a foldable display screen of the present invention may have a loss factor (tan δ) at 25 ℃ of 0.4 to 1.0.
As a preferred embodiment of the present invention, the adhesive film for a foldable display screen of the present invention may have a loss factor (tan δ) at 60 ℃ of 0.05 to 0.5.
As a preferred embodiment of the present invention, the adhesive film for a foldable display panel of the present invention may have a loss factor (tan δ) of 0.1 to 0.8 at 100 ℃.
As a preferred embodiment of the present invention, the Acrylic polymer may be a polymer polymerized by including a monomer mixture including three or more selected from the group consisting of a monomer represented by the following chemical formula 1, a monomer represented by the following chemical formula 2, a monomer represented by the following chemical formula 3, a monomer represented by the following chemical formula 4, a monomer represented by the following chemical formula 5, an Isobornyl acrylate monomer, a 2-hydroxypropyl acrylate (2-hydroxypropyl acrylate) monomer, an Acrylic acid monomer, and an acrylonitrile monomer.
[ chemical formula 1]
In the above chemical formula 1, B 1 is-CH 2 -、-CH 2 CH 2 -、-CH 2 CH 2 CH 2 -、-CH 2 CH 2 CH 2 CH 2 -or-CH 2 CH 2 CH 2 CH 2 CH 2 -，R 1 And R 2 Are respectively and independently C1-C12 straight-chain alkyl, C3-C12 branched-chain alkyl, phenyl or alkyl phenyl.
[ chemical formula 2]
In the above chemical formula 2, B 2 is-CH 2 -、-CH 2 CH 2 -、-CH 2 CH 2 CH 2 -、-CH 2 CH 2 CH 2 CH 2 -or-CH 2 CH 2 CH 2 CH 2 CH 2 -，R 3 Is C1-C12 straight-chain alkyl, C3-C12 branched-chain alkyl, phenyl or alkyl phenyl.
[ chemical formula 3]
In the above chemical formula 3, R 4 Is straight-chain alkyl of C1 to C12, branched-chain alkyl of C3 to C12, phenyl or alkyl phenyl.
[ chemical formula 4]
In the above chemical formula 4, B 2 is-CH 2 CH 2 -、-CH 2 CH 2 CH 2 -、-CH 2 CH 2 CH 2 CH 2 -、-CH 2 CH 2 CH 2 CH 2 CH 2 -or-CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 -。
[ chemical formula 5]
In the above chemical formula 5, R 5 And R 6 Are respectively and independently C1-C12 straight-chain alkyl, C3-C12 branched-chain alkyl, phenyl or alkyl phenyl.
As a preferred embodiment of the present invention, the acrylic polymer may include a compound represented by the following chemical formula 1-1 as a main agent resin.
[ chemical formula 1-1]
In the above chemical formula 1-1, B 1 is-CH 2 -，R 1 Is ethyl, R 2 Is butyl.
In a preferred embodiment of the present invention, the acrylic polymer may include 3 to 25 parts by weight of a compound represented by the following chemical formula 3-1, based on 100 parts by weight of the main resin.
[ chemical formula 3-1]
In the above chemical formula 3-1, R 4 Is methyl.
As a preferred embodiment of the present invention, the acrylic polymer may have a glass transition temperature (Tg) of-70 ℃ to-90 ℃.
As a preferred embodiment of the present invention, the acrylic polymer may have a weight average molecular weight of 100000 to 2000000.
In a preferred embodiment of the present invention, the curing agent may include one or more selected from isocyanate-based curing agents and epoxy resin-based curing agents.
In a preferred embodiment of the present invention, the adhesive layer may have a thickness of 20 to 200 μm.
[ Effect of the invention ]
The adhesive film for a foldable display panel of the present invention not only has excellent bend recovery characteristics without crease or bulging between adherends when repeatedly bent, but also can minimize the occurrence of bubbles between adherends.
[ detailed description ] embodiments
The following detailed description of the embodiments of the present invention is provided to enable those skilled in the art to easily practice the embodiments of the present invention. The present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly describe the present invention, portions irrelevant to the description are omitted.
The adhesive film for a foldable display panel of the present invention is an adhesive film including an adhesive layer formed by curing an adhesive composition for a foldable display panel, and the adhesive layer may be included in an adhesive film for a foldable display panel for use in attaching a display panel and a cover glass or the like.
In addition, the "foldable display screen" defined in the present invention may mean a flexible display screen designed to be unfolded like paper after being repeatedly folded, and the radius of curvature of the folded portion is within 5 mm.
In addition, the adhesive film for a foldable display screen of the present invention applied to the foldable display screen needs to realize folding (folding) characteristics that can satisfy specific ranges of creep rate, recovery rate and loss factor (tan δ, loss tangent), unlike the adhesive for other applications.
In addition, other specific configurations of foldable display screens are known, for example, through korean laid-open patent No. 2015-0138450 and the like, and the adhesive composition for foldable display screens of the present invention may be included in such known configurations of foldable display screens without limitation.
The adhesive composition for a foldable display screen of the present invention may include an acrylic polymer and a curing agent.
The acrylic polymer of the present invention can be prepared in various ways. As an example, the acrylic polymer of the present invention may be prepared by selecting the following monomers required for preparing the acrylic polymer, then compounding the selected monomers in a desired ratio, and preparing the obtained monomer mixture by Solution polymerization (Solution polymerization), bulk polymerization (Bulk polymerization), suspension polymerization (suspension polymerization), or emulsion polymerization (emulsion polymerization), preferably, by Solution polymerization. The manner of preparing the polymer by solution polymerization is not particularly limited.
In addition, the solution polymerization method may be carried out at a polymerization temperature of 30 to 140 ℃ for 3 to 15 hours by mixing a radical polymerization initiator and a solvent in a state where the monomer components selected for the preparation of the acrylic polymer of the present invention are mixed at an appropriate weight ratio.
The radical polymerization initiator used for the production of the acrylic polymer of the present invention may be any known one, and for example, an azo polymerization initiator such as azobisisobutyronitrile or azobiscyclohexanecarbonitrile, or an oxide such as benzoyl peroxide or acetyl peroxide may be used.
The radical polymerization initiator may be used alone or in combination of two or more, and may be used in an amount of 0.01 to 1 part by weight based on 100 parts by weight of the acrylic polymer.
The solvent used for the production of the acrylic polymer of the present invention may be any known solvent, and for example, ethyl acetate, toluene or the like may be used, but is not limited thereto.
The Acrylic polymer of the present invention may be a polymer obtained by polymerizing a monomer mixture including three or more selected from the group consisting of a monomer represented by the following chemical formula 1, a monomer represented by the following chemical formula 2, a monomer represented by the following chemical formula 3, a monomer represented by the following chemical formula 4, a monomer represented by the following chemical formula 5, an Isobornyl acrylate (Isobornyl acrylate) monomer, a 2-hydroxypropyl acrylate (2-hydroxypropyl acrylate) monomer, an Acrylic acid (Acrylic acid) monomer, and an acrylonitrile (acrylonitrile) monomer. If the acrylic polymer of the present invention is a polymer polymerized by including less than three kinds of the above-listed monomers, there is a problem that the physical properties required in the present invention cannot be satisfied.
[ chemical formula 1]
In the above chemical formula 1, B 1 is-CH 2 -、-CH 2 CH 2 -、-CH 2 CH 2 CH 2 -、-CH 2 CH 2 CH 2 CH 2 -or-CH 2 CH 2 CH 2 CH 2 CH 2 -, preferably, -CH 2 -、-CH 2 CH 2 -or-CH 2 CH 2 CH 2 -。
In the above chemical formula 1, R 1 And R 2 Each independently is a C1-C12 straight chain alkyl, C3-C12 branched alkyl, phenyl or alkylphenyl, preferably a C1-C5 straight chain alkyl, more preferably R 1 Is a linear alkyl of C1 to C3, R 2 Is straight-chain alkyl of C3-C5.
[ chemical formula 2]
In the above chemical formula 2, B 2 is-CH 2 -、-CH 2 CH 2 -、-CH 2 CH 2 CH 2 -、-CH 2 CH 2 CH 2 CH 2 -or-CH 2 CH 2 CH 2 CH 2 CH 2 -, preferably, is CH 2 -、-CH 2 CH 2 -or-CH 2 CH 2 CH 2 -。
In the above chemical formula 2, R 3 Is a C1-C12 linear alkyl group, a C3-C12 branched alkyl group, a phenyl group or an alkylphenyl group, preferably a C1-C5 linear alkyl group, more preferably a C1-C3 linear alkyl group.
[ chemical formula 3]
In the above chemical formula 3, R 4 Is a C1-C12 straight-chain alkyl group, a C3-C12 branched-chain alkyl group, a phenyl group or an alkylphenyl group, preferably a C1-C5 straight-chain alkyl group, more preferably a C1-C3 straight-chain alkyl group.
[ chemical formula 4]
In the above chemical formula 4, B 2 is-CH 2 CH 2 -、-CH 2 CH 2 CH 2 -、-CH 2 CH 2 CH 2 CH 2 -、-CH 2 CH 2 CH 2 CH 2 CH 2 -or-CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 -, preferably, -CH 2 CH 2 CH 2 CH 2 -、-CH 2 CH 2 CH 2 CH 2 CH 2 -or-CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 -。
[ chemical formula 5]
In the above chemical formula 5, R 5 And R 6 Are respectively and independently C1-C12 straight-chain alkyl, C3-C12 branched-chain alkyl, phenyl or alkyl phenyl, preferably C1-C5 straight-chain alkyl.
Specifically, the acrylic polymer of the present invention may include a compound represented by the following chemical formula 1-1 as a main agent resin.
[ chemical formula 1-1]
In the above chemical formula 1-1, B 1 is-CH 2 -，R 1 Is ethyl, R 2 Is butyl.
The main agent resin is a monomer that accounts for 50% by weight or more of the total weight of the monomers used in the production of the acrylic polymer, and the acrylic polymer of the present invention contains the compound represented by the above chemical formula 1-1 as the main agent resin in 50% by weight or more of the total weight of the monomers used in the production of the acrylic polymer, thereby making it possible to produce an adhesive film that not only has excellent bending recovery characteristics without crease or bulge between adherends when repeatedly bent, but also can minimize the generation of bubbles between adherends.
Further, the acrylic polymer of the present invention may include 3 to 25 parts by weight, preferably 4 to 10 parts by weight, of the compound represented by the following chemical formula 3-1, with respect to 100 parts by weight of the main agent resin.
[ chemical formula 3-1]
In the above chemical formula 3-1, R 4 Is methyl.
On the other hand, the acrylic polymer of the present invention may have a glass transition temperature (Tg) of-70 to-90 ℃, preferably, may have a glass transition temperature (Tg) of-72 to-80 ℃, more preferably, may have a glass transition temperature (Tg) of-74 to-76 ℃, and if it is out of such a glass transition temperature range, there is a problem that the physical property characteristics required in the present invention cannot be satisfied.
As a preferred embodiment of the present invention, the acrylic polymer may have a weight average molecular weight of 100000 to 2000000, preferably 100000 to 1000000, more preferably 200000 to 800000, and even more preferably 300000 to 600000, and if it is out of such a range of weight average molecular weight, there is a problem that the physical property characteristics required by the present invention cannot be satisfied.
The curing agent of the present invention may include one or more selected from isocyanate (isocyanate) type curing agents and epoxy (epoxy) type curing agents, and preferably, may include isocyanate type curing agents.
In addition, the adhesive composition for a foldable display screen may include a curing agent in an amount of 0.01 to 1 part by weight, preferably 0.1 to 0.4 part by weight, based on 100 parts by weight of the acrylic polymer.
The adhesive layer may have a thickness of 20 to 200. Mu.m, preferably 20 to 50 μm, and more preferably 25 to 45 μm.
On the other hand, the adhesive film for a foldable display screen of the present invention may have a creep rate (creep rate) at 25 ℃ measured according to the following relational expression 1 of 30 to 60%, preferably, 30 to 55%, more preferably, 30 to 40%. If the creep rate at 25 ℃ is less than 30%, there is a problem that folding lines are generated when repeated bending is performed, and if it exceeds 60%, there is a problem that bulging between adherends is generated when repeated bending is performed.
[ relational expression 1]
In the above relation 1, σ represents Stress (Stress), E represents elastic modulus (elastic modulus), t represents creep (creep) deformation time, λ represents η/E, and η represents viscosity ratio (viscocity rate).
Creep (creep) is a phenomenon in which a material is continuously deformed with time in a state in which a predetermined load is applied to the material, and t represents a time in which creep deformation occurs in a state in which a predetermined load is applied to the adhesive film for a folding screen of the present invention.
In addition, the adhesive film for a foldable display screen of the present invention may have a creep rate (rate) at 60 ℃ measured according to the relational expression 1 of 20 to 50%, preferably, 20 to 40%, more preferably, 20 to 30%. If the creep rate at 60 ℃ is less than 20%, there is a problem that folding occurs when bending is repeated, and if it exceeds 50%, there is a problem that bulging occurs between adherends when bending is repeated.
Further, the adhesive film for a foldable display screen of the present invention may have a recovery rate at 25 ℃ measured according to the following relation 2 of 60% or more, preferably 80% or more, more preferably 90% or more, and even more preferably 95 to 99.9%. If the recovery rate at 25 ℃ is less than 60%, there is a problem that the adherend becomes swollen when repeated bending is performed.
[ relational expression 2]
In the above relation 2, σ represents Stress (Stress), E represents elastic modulus (elastic modulus), t represents creep (creep) deformation time, tr represents creep recovery time after creep deformation, λ represents η/E, and η represents viscosity ratio (viscocity rate).
Creep (creep) refers to a phenomenon in which a material is continuously deformed with time in a state in which a predetermined load is applied to the material, t represents a time in which creep deformation occurs in a state in which a predetermined load is applied to the adhesive film for a foldable display panel of the present invention, and tr represents a time in which the deformation is partially recovered after creep deformation occurs in the adhesive film for a foldable display panel of the present invention.
In addition, the adhesive film for a foldable display screen of the present invention may have a recovery rate (recovery rate) at 60 ℃ measured according to the relationship 2 of 80% or more, preferably, 90% or more, more preferably, 95% or more, and even more preferably, 95 to 99%. If the recovery rate at 60 ℃ is less than 80%, there is a problem that the adherend tends to bulge when the sheet is repeatedly bent.
On the other hand, the adhesive film for a foldable display screen of the present invention may have a loss tangent (tan δ) at-20 ℃ of 1.0 to 2.0, preferably, 1.4 to 2.0, more preferably, 1.7 to 1.95. The loss factor refers to the ratio of storage modulus (strain modulus) to loss modulus (loss modulus), and if the loss factor at-20 ℃ is less than 1.0, there is a problem of occurrence of creases when bending is repeated, and if it exceeds 2.0, there is a problem of occurrence of bulging between adherends when bending is repeated.
In addition, the adhesive film for a foldable display panel of the present invention may have a loss factor at 25 ℃ of 0.4 to 1.0, preferably 0.5 to 1.5, more preferably 0.6 to 0.8, and if the loss factor at 25 ℃ is less than 0.4, there is a problem of occurrence of creases when repeatedly bent, and if it exceeds 1.0, there is a problem of occurrence of bulging between adherends when repeatedly bent.
In addition, the adhesive film for a foldable display screen of the present invention may have a loss factor at 60 ℃ of 0.05 to 0.5, preferably 0.1 to 0.3, more preferably 0.1 to 0.2, and if the loss factor at 25 ℃ is less than 0.05, there is a problem of occurrence of creases when repeatedly bent, and if it exceeds 0.5, there is a problem of occurrence of bulging between adherends when repeatedly bent.
In addition, the adhesive film for a foldable display panel of the present invention may have a loss factor at 100 ℃ of 0.1 to 0.8, preferably 0.1 to 0.6, more preferably 0.2 to 0.4, and if the loss factor at 25 ℃ is less than 0.1, there is a problem of occurrence of creases when repeatedly bent, and if it exceeds 0.8, there is a problem of occurrence of bulging between adherends when repeatedly bent.
Further, the adhesive film for a foldable display screen of the present invention may have an adhesive force of 600gf/inch or more, preferably 650 to 1200gf/inch, more preferably 680 to 1000gf/inch, measured when peeled at 180 ° at a speed of 300mm per minute after being attached to an Alkali-free Glass plate (Non Alkali Glass).
On the other hand, the adhesive film for a foldable display panel of the present invention, after attaching the adhesive film to the PET film, was evaluated by 200000 folds (folding) with a curvature radius of 1.5mm, and not only no cracks occurred, but also no swelling occurred between the adhesive film and the PET film.
Further, the adhesive film for a foldable display screen of the present invention may include an amount of bubbles generated in an area of 50mm × 50mm (length × width) may be less than 5, preferably, may be 1 to 3, observed by a microscope, after being autoclaved for 5 to 20 minutes, preferably, 6 to 10 minutes, and then maintained for 5 to 20 minutes, preferably, 6 to 10 minutes, after being autoclaved for 6 to 10 minutes, after the adhesive film is attached to the polyimide film. The size of the bubbles may be less than 200. Mu.m, and preferably 80 to 120 μm. The penetration distance may be less than 400. Mu.m, and preferably 300 to 380. Mu.m.
The present invention has been described above mainly in terms of the embodiments, but these embodiments are merely examples and do not limit the embodiments of the present invention, and it will be understood by those skilled in the art that various modifications and applications not listed above can be implemented without departing from the essential characteristics of the present invention. For example, the constituent elements specifically shown in the embodiment of the present invention may be modified. Moreover, it is to be understood that variations and modifications related to such variations and applications are intended to be included within the scope of the invention as defined in the appended claims.
Example 1: preparation of adhesive composition for foldable display screen
An acrylic polymer having a weight average molecular weight of 450000 and a glass transition temperature of-74.9 c was mixed with an isocyanate-based curing agent to prepare an adhesive composition for a foldable display panel. In this case, 0.2 parts by weight of an isocyanate-based curing agent was mixed with 100 parts by weight of the acrylic polymer.
Further, as the acrylic polymer, a polymer obtained by polymerizing 20 parts by weight of the monomer represented by the following chemical formula 2-1, 6.67 parts by weight of the monomer represented by the following chemical formula 3-1 and 6.67 parts by weight of the monomer represented by the following chemical formula 4-1 with respect to 100 parts by weight of the monomer represented by the following chemical formula 1-1 was used.
[ chemical formula 1-1]
In the above chemical formula 1-1, B 1 is-CH 2 -，R 1 Is ethyl, R 2 Is butyl.
[ chemical formula 2-1]
In the above chemical formula 2-1, B 2 is-CH 2 CH 2 -，R 3 Is a methyl group.
[ chemical formula 3-1]
In the above chemical formula 3-1, R 4 Is methyl.
[ chemical formula 4-1]
In the above chemical formula 4-1, B 2 is-CH 2 CH 2 CH 2 CH 2 -。
Example 2: preparation of adhesive composition for foldable display screen
In the same manner as in example 1, an adhesive composition for a foldable display screen was prepared. However, unlike example 1, an acrylic polymer having a weight average molecular weight of 1600000 and a glass transition temperature of-73.7 ℃ was used, and as the acrylic polymer, a polymer obtained by polymerizing 23.08 parts by weight of the monomer represented by the following chemical formula 3-2, 7.69 parts by weight of the monomer represented by the following chemical formula 5-1, 23.08 parts by weight of the monomer represented by the following chemical formula 3-1 and 7.69 parts by weight of the monomer represented by the following chemical formula 4-2 was used, based on 100 parts by weight of the monomer represented by the above chemical formula 1-1.
[ chemical formula 3-2]
In the above chemical formula 3-2, R 4 Is butyl.
[ chemical formula 5-1]
In the above chemical formula 5-1, R 5 Is ethyl, R 6 Is methyl.
[ chemical formula 4-2]
In the above chemical formula 4-2, B 2 is-CH 2 CH 2 -。
Comparative example 1: preparation of adhesive composition for foldable display screen
In the same manner as in example 1, an adhesive composition for a foldable display screen was prepared. However, unlike example 1, an acrylic polymer having a weight average molecular weight of 1200000 and a glass transition temperature of-64.0 ℃ was used, and as the acrylic polymer, a polymer obtained by polymerizing 20 parts by weight of Isobornyl acrylate monomer and 13.33 parts by weight of monomer represented by the above chemical formula 4-2 with respect to 100 parts by weight of monomer represented by the above chemical formula 1-1 was used.
Comparative example 2: preparation of adhesive composition for foldable display screen
In the same manner as in example 1, an adhesive composition for a foldable display screen was prepared. However, unlike example 1, an acrylic polymer having a weight average molecular weight of 1700000 and a glass transition temperature of-65.8 ℃ was used, and as the acrylic polymer, a polymer obtained by polymerizing 23.08 parts by weight of the monomer represented by chemical formula 3-2, 15.38 parts by weight of the monomer represented by chemical formula 5-1, and 15.38 parts by weight of the monomer represented by chemical formula 4-2 with respect to 100 parts by weight of the monomer represented by chemical formula 1-1 was used.
Comparative example 3: preparation of adhesive composition for foldable display screen
In the same manner as in example 1, an adhesive composition for a foldable display screen was prepared. However, unlike example 1, an acrylic polymer having a weight average molecular weight of 870000 and a glass transition temperature of-53.0 ℃ was used, and a polymer obtained by polymerizing 95 wt% of the monomer represented by the above chemical formula 3-2 and 5 wt% of the monomer represented by the above chemical formula 4-1 with respect to the total weight of the monomers was used as the acrylic polymer.
Comparative example 4: preparation of adhesive composition for foldable display screen
(1) An acrylic polymer having a weight average molecular weight of 760000 and a glass transition temperature of-34.5 ℃ and an epoxy resin curing agent were mixed to prepare an adhesive composition for a foldable display panel. In this case, 0.5 part by weight of an epoxy resin curing agent was mixed with 100 parts by weight of the acrylic polymer.
Further, as the Acrylic polymer, a polymer obtained by polymerizing 12.5 parts by weight of a monomer represented by the following chemical formula 5-2, 6.25 parts by weight of an Isobornyl acrylate monomer and 6.25 parts by weight of an Acrylic acid monomer with respect to 100 parts by weight of a monomer represented by the above chemical formula 3-2 was used.
[ chemical formula 5-2]
In the above chemical formula 5-2, R 5 And R 6 Is methyl.
Experimental example 1
The adhesive compositions prepared in examples 1 to 2 and comparative examples 1 to 4 were evaluated based on the following physical property evaluation methods, and the results are shown in table 1.
(1) Adhesion measurement
The adhesive compositions prepared in examples 1 to 2 and comparative examples 1 to 4 were cured to a thickness of 35 μm, respectively, and then transferred to a polyimide film (SKC Kolon Co., GF 200) having a thickness of 50 μm to prepare samples. The prepared sample was cut into a size of 25mm wide by 150mm long. After 3 washes with MEK (methyl ethyl ketone), an alkali-free glass plate having no surface mark was prepared, and then the cured adhesive composition side of the cut sample was attached to the prepared alkali-free glass plate using a 2kg hand roller. After the application, the film was left at room temperature (25 ℃) for 24 hours and then peeled at 180 ℃ at a speed of 300mm per minute, and the adhesion was measured by UTM (WL 2100) (the adhesion was calculated as an average value of the stable interval).
(2) Measuring whether or not bubbles occur
The adhesive compositions prepared in examples 1 to 2 and comparative examples 1 to 4 were cured to a thickness of 150 μm, respectively, and then attached between a polyimide film (SKC Kolon Co., GF 200) having a thickness of 50 μm and a glass plate (glass) to prepare samples. After the prepared specimen was cut into a size of 25mm wide × 150mm long, the cut specimen was autoclaved for 8 minutes (autoclave condition: use of pressurized steam of 15psi at 121 ℃) by an autoclave (Auto focus), then kept for 7 minutes and 30 seconds, and then decompressed for 8 minutes, and the number of bubbles generated, the size of bubbles, and the permeation distance included in an area of 50mm × 50mm (length × width) were measured under a microscope of 5 times magnification.
(3) Folding test
The adhesive compositions prepared in examples 1 to 2 and comparative examples 1 to 4 were respectively bonded between a PET film (TORAY U48) having a thickness of 50 μm and a release film having a thickness of 50 μm at a thickness of 35 μm, and then cut into 50mm × 100mm (length × width) to prepare samples. The prepared sample was subjected to 200000 bending evaluations with a curvature radius of 1.5mm using bending evaluation equipment (F1-2SV, forehu).
After the bending evaluation was performed at 10000 cycles, the samples were checked for cracking and non-cracking, and it was confirmed whether cracks (Crack) occurred in the prepared samples or whether the adhesion surface was bulged. The evaluation was OK when no change occurred, and NG when deformation such as peeling, cracking, thickness change occurred.
(4) Creep rate and recovery rate measurements
The adhesive compositions prepared in examples 1 to 2 and comparative examples 1 to 4 were respectively laminated between polyimide films (GF 200 by SKC Kolon Co., ltd.) having a thickness of 50 μm at a thickness of 35 μm and cured to prepare samples. For the prepared samples, data required for calculating the creep rate and the recovery rate were measured by the following measuring apparatus and measuring conditions, and the creep rate at 25 ℃ and 60 ℃ measured according to the following relational expression 1, and the recovery rate at 25 ℃ and 60 ℃ measured according to the following relational expression 2 were calculated.
* Measuring device and measuring conditions
(1) The measuring equipment comprises: ARES-G2, TA instruments Inc
(2) Measuring the temperature interval: 20-70 DEG C
(3) Temperature rise rate: 10 ℃/min
(4) Axial Force (Axial Force): 0.5N
(5) Stress (Stress): 2kPa
(6) Creep (creep) deformation time (t): 10 minutes
(7) Creep recovery time after creep deformation (tr): 10 minutes
[ relational expression 1]
In the above relation 1, σ represents Stress (Stress), E represents elastic modulus (elastic modulus), t represents creep (creep) deformation time, λ represents η/E, and η represents viscosity ratio (viscocity rate).
[ relational expression 2]
In the above relation 2, σ represents Stress (Stress), E represents elastic modulus (elastic modulus), t represents creep (creep) deformation time, tr represents creep recovery time after creep deformation, λ represents η/E, and η represents viscosity ratio (viscocity rate).
(5) Loss factor (tan delta) measurement
The adhesive compositions prepared in examples 1 to 2 and comparative examples 1 to 4 were bonded between release films at a thickness of 35 μm and cured so that no air bubbles were generated, to prepare samples. After the prepared sample was placed on one surface of a parallel plate (parallel plate) and the opening (gap) was adjusted, the moment (Torque) zero point was set, and after the stability of the force (force) was confirmed, the storage modulus (strain modulus) at-20 ℃, 25 ℃, 60 ℃, 100 ℃ and the loss modulus (loss modulus) at-20 ℃, 25 ℃, 60 ℃, 100 ℃ were measured with the following measurement equipment and measurement conditions, and the loss factor (Tan δ) was calculated from the following relational expression 3.
[ relational expression 3]
Loss factor (Tan delta) = loss modulus (loss module)/storage modulus (storage module)
* Measuring device and measuring conditions
(1) The measuring equipment comprises: ARES-G2, TA instruments Inc
(2) Deformation (strain): 1 percent of
(3) Measuring the temperature interval: -55 to 250 DEG C
(4) Temperature rise rate: 10 ℃/min
(5) Measuring frequency: 6.28rad/s
[ TABLE 1]
As shown in table 1, it was confirmed that the adhesive composition prepared in example 1 has not only excellent bending recovery characteristics without crease or bulging between adherends when repeatedly bent, but also minimized generation of bubbles between adherends.
Those skilled in the art can easily implement the simple modification or modification of the present invention, and such modification or modification can be considered as included in the present invention.
Claims (10)
1. An adhesive film for a foldable display panel, the adhesive film comprising an adhesive layer formed by curing an adhesive composition for a foldable display panel,
the adhesive composition for a foldable display screen includes an acrylic polymer and a curing agent,
the adhesive film has a creep rate at 25 ℃ of 30 to 60% as measured by the following relational expression 1, a recovery rate at 25 ℃ of 60% or more as measured by the following relational expression 2, and a loss factor (tan δ) at-20 ℃ of 1.0 to 2.0;
[ relational expression 1]
[ relational expression 2]
In the relation 1, σ represents Stress (Stress), E represents elastic modulus (elastic modulus), t represents creep (creep) deformation time, λ represents η/E, η represents viscosity ratio (viscocity rate),
in the relation 2, σ represents Stress (Stress), E represents elastic modulus (elastic modulus), t represents creep (creep) deformation time, tr represents creep recovery time after creep deformation, λ represents η/E, and η represents viscosity ratio (viscocity rate).
2. The adhesive film for a foldable display screen according to claim 1,
the adhesive film has a creep rate at 60 ℃ of 20 to 50% as measured according to the relational expression 1, and a recovery rate at 60 ℃ of 80% or more as measured according to the relational expression 2.
3. The adhesive film for a foldable display screen of claim 1,
the adhesive film has a loss factor (tan delta) of 0.4 to 1.0 at 25 ℃,
a loss factor (tan delta) at 60 ℃ of 0.05 to 0.5,
a loss factor (tan delta) at 100 ℃ of 0.1 to 0.8.
4. The adhesive film for a foldable display screen according to claim 1,
the Acrylic polymer is a polymer obtained by polymerizing a monomer mixture, wherein the monomer mixture includes three or more selected from the group consisting of a monomer represented by the following chemical formula 1, a monomer represented by the following chemical formula 2, a monomer represented by the following chemical formula 3, a monomer represented by the following chemical formula 4, a monomer represented by the following chemical formula 5, an Isobornyl acrylate (Isobornyl acrylate) monomer, a 2-hydroxypropyl acrylate (2-hydroxypropyl acrylate) monomer, an Acrylic acid (Acrylic acid) monomer, and an acrylonitrile (acrylonitrile) monomer.
[ chemical formula 1]
[ chemical formula 2]
[ chemical formula 3]
[ chemical formula 4]
[ chemical formula 5]
In the chemical formula 1, B 1 is-CH 2 -、-CH 2 CH 2 -、-CH 2 CH 2 CH 2 -、-CH 2 CH 2 CH 2 CH 2 -or-CH 2 CH 2 CH 2 CH 2 CH 2 -，R 1 And R 2 Are respectively and independently C1-C12 straight-chain alkyl, C3-C12 branched-chain alkyl, phenyl or alkyl phenyl,
in the chemical formula 2, B 2 is-CH 2 -、-CH 2 CH 2 -、-CH 2 CH 2 CH 2 -、-CH 2 CH 2 CH 2 CH 2 -or-CH 2 CH 2 CH 2 CH 2 CH 2 -，R 3 Is C1-C12 straight-chain alkyl, C3-C12 branched-chain alkyl, phenyl or alkyl phenyl,
in the chemical formula 3, R 4 Is straight-chain alkyl of C1 to C12, branched-chain alkyl of C3 to C12, benzeneA radical or an alkylphenyl radical,
in the chemical formula 4, B 2 is-CH 2 CH 2 -、-CH 2 CH 2 CH 2 -、-CH 2 CH 2 CH 2 CH 2 -、-CH 2 CH 2 CH 2 CH 2 CH 2 -or-CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 -，
In the chemical formula 5, R 5 And R 6 Are respectively and independently C1-C12 straight-chain alkyl, C3-C12 branched-chain alkyl, phenyl or alkyl phenyl.
5. The adhesive film for a foldable display screen of claim 1,
the acrylic polymer includes a compound represented by the following chemical formula 1-1 as a main agent resin.
[ chemical formula 1-1]
In the chemical formula 1-1, B 1 is-CH 2 -，R 1 Is ethyl, R 2 Is a butyl group.
6. The adhesive film for a foldable display screen according to claim 5,
the acrylic polymer contains 3 to 25 parts by weight of a compound represented by the following chemical formula 3-1, per 100 parts by weight of a main agent resin.
[ chemical formula 3-1]
In the chemical formula 3-1, R 4 Is a methyl group.
7. The adhesive film for a foldable display screen of claim 1,
the acrylic polymer has a glass transition temperature (Tg) of-70 to-90 ℃.
8. The adhesive film for a foldable display screen of claim 7,
the acrylic polymer has a weight average molecular weight of 100000 to 2000000.
9. The adhesive film for a foldable display screen according to claim 1,
the curing agent comprises more than one selected from isocyanate curing agents and epoxy resin curing agents.
10. The adhesive film for a foldable display screen according to claim 1,
the adhesive layer has a thickness of 20 to 200 [ mu ] m.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1020210073838A KR102444641B1 (en) | 2021-06-08 | 2021-06-08 | adhesive film using foldable display |
| KR10-2021-0073838 | 2021-06-08 |
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| Publication Number | Publication Date |
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| CN115926646A true CN115926646A (en) | 2023-04-07 |
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| CN202210641830.7A Pending CN115926646A (en) | 2021-06-08 | 2022-06-07 | Adhesive film for foldable display screen |
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| KR (1) | KR102444641B1 (en) |
| CN (1) | CN115926646A (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR102097031B1 (en) | 2013-07-22 | 2020-04-06 | 삼성디스플레이 주식회사 | Foldable display and method of manufacturing the same |
| JP7291475B2 (en) * | 2018-12-04 | 2023-06-15 | 三星エスディアイ株式会社 | OPTICAL FILM ADHESIVE, ADHESIVE LAYER, OPTICAL MEMBER, AND IMAGE DISPLAY DEVICE |
| KR102609849B1 (en) * | 2019-02-28 | 2023-12-04 | 동우 화인켐 주식회사 | Adhesive Sheet |
| KR20210075246A (en) * | 2019-12-12 | 2021-06-23 | 삼성디스플레이 주식회사 | Display device |
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