Method for manufacturing a foldable backsheet film

Abstract

The present application relates to a method for manufacturing a foldable backsheet film, and according to one aspect of the present application, there is provided a method for manufacturing a foldable backsheet film by cutting the foldable backsheet film in a direction from a release film to a protective film at a half-cut, and then changing the release film from a release film, whereby the foldable backsheet does not fall off at the time of release film peeling by improving the half-cut process.

Description

Technical Field

[0001] This application relates to a method for manufacturing a foldable backsheet membrane.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0025029, filed on February 24, 2021, the disclosure of which is incorporated herein by reference in its entirety. Background Technology

[0003] Recently, with the development of display-related technologies, display devices that can deform during use (e.g., fold, roll up, or stretch like a rubber band) have been researched and developed.

[0004] Deformable display devices can not only transform into preset shapes, but also into various shapes according to user requirements or the circumstances under which the display device is used. Therefore, it is necessary to identify the deformable shape of the display and control the display device in response to the identified shape.

[0005] Meanwhile, deformable display devices have the problem that various components of the display device can be damaged due to deformation, and each component of the display device must meet the requirements of folding reliability and stability.

[0006] In particular, recently, flexible substrates have been mainly used to make displays thinner. Since the display panels using flexible substrates are too thin, a foldable backsheet film that can support the display panel is attached to the bottom of the flexible substrate and used.

[0007] Figure 1 This is a vertical cross-sectional view showing an existing foldable backsheet membrane; Figure 2 This is a plan view of an existing foldable backsheet membrane; and Figure 3 This is an exemplary diagram illustrating a method for manufacturing an existing foldable backsheet membrane.

[0008] The existing foldable backsheet film has a structure of release film 1 / pressure-sensitive adhesive layer 2 / foldable backsheet 3 / protective film 4, and in the process of manufacturing the foldable backsheet film, a cutting process is carried out to cut the foldable backsheet film along the cutting line S2 into two unit sizes, so that it consists of a main body part S1 attached to the screen part of the panel and a base part S3 attached to the lower part for DI bonding.

[0009] Reference Figure 3 The conventional cutting process involves making a half-cut in the direction from the foldable backplate 3 to the release film 1 and then attaching the protective film 4. As described above, in the conventional foldable backplate film manufactured by the half-cutting, a groove H1 is formed in the release film.

[0010] However, a problem exists in foldable backsheet films manufactured through such a cutting process: the main body or base portion of the foldable backsheet film is attached during the release film peeling process. Summary of the Invention

[0011] Technical issues

[0012] This application relates to a method for manufacturing a foldable backsheet film, which can prevent the problem of backsheet attachment during the release film peeling process by improving the half-cutting process.

[0013] Technical solution

[0014] According to one embodiment of this application, a method for manufacturing a foldable backsheet film is provided, the method comprising the steps of: preparing a foldable backsheet, the foldable backsheet comprising a base film and a pressure-sensitive adhesive layer disposed on one side of the base film; attaching a first release film to the side of the pressure-sensitive adhesive layer opposite to the side in contact with the base film; attaching a protective film to the side of the base film opposite to the side in contact with the pressure-sensitive adhesive layer; half-cutting the foldable backsheet along a cutting line dividing a body portion and a base portion in a direction from the first release film to the protective film; peeling off the first release film after the half-cutting step; and attaching an uncut second release film to the position where the first release film has been peeled off to manufacture the foldable backsheet film.

[0015] Beneficial effects

[0016] In a method for manufacturing a foldable backsheet film according to one embodiment of this application, the foldable backsheet film is manufactured by cutting the foldable backsheet film in the direction from the release film to the protective film during half-cutting, and then releasing the release film to change the release film, thereby preventing the problem of the backsheet being attached when the release film is peeled off. Attached Figure Description

[0017] Figure 1 This is a vertical cross-sectional view showing an existing foldable backsheet membrane.

[0018] Figure 2 This is a plan view of an existing foldable backsheet membrane.

[0019] Figure 3 This is an exemplary diagram illustrating a method for manufacturing an existing foldable backsheet membrane.

[0020] Figure 4 The figure illustrates, by way of example, a method for manufacturing a foldable backsheet film according to the present invention.

[0021] Figure 5 It shows through Figure 4 A diagram of a foldable backsheet membrane manufactured using the method shown. Detailed Implementation

[0022] This instruction manual will be described in more detail below.

[0023] In this specification, unless otherwise stated, when any part “includes” a component, it means that other components may also be included, rather than excluding other components.

[0024] Examples of the invention will be described in detail with reference to the accompanying drawings, enabling those skilled in the art to readily practice the invention. However, the invention may be presented in several different forms and is not limited to the examples described herein.

[0025] Figure 4 The figure illustrates, by way of example, a method for manufacturing a foldable backsheet film according to the present invention. Figure 5 It shows through Figure 4 A diagram of a foldable backsheet membrane manufactured using the method shown.

[0026] A method for manufacturing a foldable backsheet film according to one embodiment of this application includes the following steps: preparing a foldable backsheet, the foldable backsheet including a base film 100 and a pressure-sensitive adhesive layer 200 disposed on one side of the base film 100; attaching a first release film 300 to the side of the pressure-sensitive adhesive layer 200 opposite to the side that contacts the base film 100; attaching a protective film 400 to the side of the base film 100 opposite to the side that contacts the pressure-sensitive adhesive layer 200; half-cutting the foldable backsheet along a cutting line dividing the body portion and the base portion in a direction from the first release film 300 to the protective film 400; peeling off the first release film 300 after the half-cutting step; and attaching an uncut second release film 500 to the position where the first release film 300 has been peeled off to manufacture the foldable backsheet film.

[0027] Existing manufacturing methods involve halving a foldable backsheet in the direction from the backsheet to the release film and then attaching a protective film thereto. In contrast, the manufacturing method according to the present invention involves halving the foldable backsheet in the direction from the release film to the protective film, and then releasing the first release film 300 (which has been cut) into a non-cut release film (a second release film). This prevents the problem of the backsheet being attached when peeling off the release film for product application. The difference lies in that the foldable backsheet film manufactured according to the existing method has a groove H1 formed on the release film 1 by halving, while the foldable backsheet film manufactured according to the method of the present invention has a groove H2 formed on the protective film 400 by halving.

[0028] Then, the foldable backsheet film according to the manufacturing method of the present invention exhibits the following structural features during the manufacturing process.

[0029] In one example, in the half-cut state, the first release film 300, the base film 100, and the pressure-sensitive adhesive layer 200 may include a through region extending along the cut line, and the protective film 400 may have a groove H2 formed along the cut line.

[0030] Furthermore, the foldable backsheet film that has undergone the cutting process has a structure in which a second release film 500, a pressure-sensitive adhesive layer 200, a base film 100 and a protective film 400 are sequentially laminated, wherein the second release film may not form any through areas and grooves, and the pressure-sensitive adhesive layer and the base film may include through areas along the cutting line and the protective film 400 may include grooves along the cutting line.

[0031] That is, the foldable backsheet film includes a protective film 400 having a groove H2, a base film 100 laminated to surround the groove H2 and having a first through region communicating with the groove H2, a pressure-sensitive adhesive layer 200 laminated on the base film and having a second through region communicating with the first through region, and a second release film 500 laminated on the pressure-sensitive adhesive layer 200. Furthermore, the second release film does not form any through region or groove communicating with the second through region.

[0032] Furthermore, as described below, this application can provide a foldable backsheet membrane with excellent reliability and stability through the selection of materials and control of physical properties of each component.

[0033] The energy storage modulus of the base film at 20°C can be from 1 GPa to 5 GPa, for example, from 1.5 GPa to 4 GPa or from 2 GPa to 4 GPa. The base film according to this application satisfies the aforementioned energy storage modulus range, thereby maintaining reliability even after repeated folding when subsequently applied to the back panel of a foldable display, minimizing the stress generated during folding, and possessing characteristics sufficient to support the rigidity of the display panel.

[0034] In one embodiment of this application, a foldable backsheet is provided in which the base membrane has an elongation at break of 20% or greater and 200% or less at 20°C.

[0035] In another embodiment, the elongation at break of the base membrane at 20°C can be 20% or more and 200% or less, preferably 40% or more and 180% or less, more preferably 70% or more and 150% or less.

[0036] When the initial length of the base film is L1 and the length at which it breaks due to stretching is L2, the elongation at break of the polyimide substrate is expressed as (L2-L1) / L1×100 (%).

[0037] Storage modulus and elongation at break were measured using Zwick's UTM according to the KS M ISO527 method. By cutting the membrane to be measured into pieces with a width of 5 mm and a length of 60 mm or more, and then setting the gap between the clamps to 40 mm, the storage modulus and elongation at break can be measured individually as values ​​when the sample membrane is pulled at a speed of 20 mm / min.

[0038] In one embodiment of this application, a foldable backsheet film is provided in which the base film has a heat shrinkage rate of 0.1% or less at 200°C.

[0039] In another embodiment, the base film may have a thermal shrinkage rate of 0.03% or greater at 200°C.

[0040] Heat shrinkage rate refers to the degree of shrinkage in the direction of maximum shrinkage force when heat is applied to the base film. When the initial length of the base film is M1 and the length of shrinkage in the shrinkage direction is M2 after heating at 200°C for 2 hours, it means the value of (M1-M2) / M1×100%.

[0041] Because the base film has thermal shrinkage force within the above range, it has the characteristic of not deforming, since the shrinkage force is low even when heat is applied during the backing coating process.

[0042] In one example, the base film may be a polyimide base film. For instance, the base film may be a polyimide base film that satisfies at least one or more of the energy storage modulus, elongation at break, and heat shrinkage as described above.

[0043] In the case of the foldable backsheet film according to this application, a polyimide base film that meets the above conditions is used, thereby having excellent durability because no plastic deformation occurs in the backsheet even when the folding and unfolding operation of the foldable display is repeated, and it has the characteristic that the strain generated during folding can be recovered during unfolding without permanent deformation.

[0044] Furthermore, the thickness of the base film can be 20 μm or greater and 120 μm or less; for example, it can be 30 μm or greater and 100 μm or less, or 40 μm or greater and 80 μm or less. Because the base film has these thickness ranges, it performs excellently as a support when subsequently used as a back panel for foldable displays, without causing handling problems during roll coating, and it features minimized stress values ​​due to suitable curvature radius deviation.

[0045] The peel force of the first release film from the pressure-sensitive adhesive layer at 23°C can be 12 gf / inch or less, for example, it can be 11 gf / inch or less, or 10 gf / inch or less. The peel force of the first release film from the pressure-sensitive adhesive layer was measured using a Stable MicroSystems texture analyzer at a peel angle of 180° and a peel rate of 2400 mm / min, respectively, by measuring the foldable backsheet film manufactured according to the present invention at 23°C.

[0046] The first and second release films can be silicone-based.

[0047] The first and second release films are layers used to protect very thin first and second pressure-sensitive adhesive layers. The first and second release films are transparent layers attached to one side of the first and second adhesive layers, and can be films with excellent mechanical strength, thermal stability, moisture barrier properties, isotropy, etc. For example, films based on acetate, polyester, polyethersulfone, polycarbonate, polyamide, polyimide, polyolefin, cycloolefin, polyurethane, silicone, and acrylic resins such as triacetyl cellulose (TAC) can be used; however, they are not limited to these, as long as they are commercially available silicone-based release films.

[0048] In one embodiment of this application, the first release film and the second release film may further include an antistatic treatment to prevent damage to the display panel due to static electricity when they are attached to the lower part of the display panel.

[0049] In one embodiment of this application, as a pressure-sensitive adhesive layer, one or more selected from acrylic pressure-sensitive adhesive layers, rubber-based pressure-sensitive adhesive layers, and silicone-based pressure-sensitive adhesive layers can be used.

[0050] In another embodiment, an acrylic pressure-sensitive adhesive layer can be used as the pressure-sensitive adhesive layer.

[0051] In one example, the surface resistivity of the first and second release films can be 10 Ω under conditions of 500V or lower. 10 Ω / square or less, and can be 3×10 9 Ω / square or less, or 1×10 9 Ω / square or less. The surface resistance of the first and second release films can be measured using concentric electrodes on the back of the PET of the test piece, and can be measured in an MCT-HT800 (Mitsubishi Corporation) with an applied voltage of 500V, an applied time of 10 seconds, 25°C and 55%RH.

[0052] The first and second release films have surface resistance values ​​within the above range due to antistatic treatment, and have the characteristic that when the first release film is subsequently peeled off and attached to the lower part of the display panel, damage to the display panel due to static electricity can be prevented.

[0053] In one embodiment of this application, the first release film and the second release film may further include an antistatic treatment to prevent damage to the display panel due to static electricity when they are attached to the lower part of the display panel.

[0054] The protective film can be attached through processes such as lamination, where there are no particular restrictions on the type of protective film, and conventional products can be used. For example, products such as EPDC and LCFP made of PET / PSA can be used as protective films.

[0055] In one embodiment, the protective film may have a groove formed along the cutting line. The difference is that, since the manufacturing method according to this application performs a half-cut in the direction from the first release film to the protective film, a groove is formed in the protective film; however, since the existing cutting process performs a half-cut in the direction from the backing plate to the release film, a groove is formed in the release film.

[0056] Hereinafter, embodiments of the invention will be described in detail so that those skilled in the art can readily practice the invention. However, the invention may be presented in several different forms and is not limited to the embodiments described herein.

[0057] Example

[0058] according to Figure 4 The manufacturing method shown herein is used to manufacture a foldable backsheet membrane.

[0059] Comparative example

[0060] according to Figure 3 The manufacturing method shown manufactures a foldable backsheet membrane.

[0061] Experimental Example

[0062] Evaluation experiments were conducted to improve the reverse peeling of the foldable backsheet film manufactured in the above embodiments and comparative examples.

[0063] First, attach double-sided tape to the SUS board and then attach release film to the double-sided tape to form the top surface. Next, attach the tape to the bottom right corner and peel it off.

[0064] The evaluation was good when only the release film was peeled off, and poor when the release film and the foldable backing were peeled off together. A total of 60 tests were performed, and the results are shown in Table 1.

[0065] [Table 1]

[0066] good Difference Failure rate Example 60 0 0％ Comparative example 43 17 28％

[0067] Industrial applicability

[0068] In a method for manufacturing a foldable backsheet film according to one embodiment of this application, the foldable backsheet film is manufactured by cutting the foldable backsheet film in the direction from the release film to the protective film during half-cutting, and then releasing the release film to change the release film, thereby preventing the problem of the backsheet being attached when the release film is peeled off.

Claims

1. A method for manufacturing a foldable backsheet film, comprising the following steps: Prepare a foldable back panel, the foldable back panel comprising a base film and a pressure-sensitive adhesive layer disposed on one side of the base film; A first release film is attached to the side opposite to the side of the pressure-sensitive adhesive layer that is in contact with the base film; A protective film is attached to the side of the base film opposite to the side that contacts the pressure-sensitive adhesive layer; The foldable back panel is half-cut along the cutting line dividing the main body and the base portion in the direction from the first release film to the protective film, wherein in the half-cut state, The first release film, the base film, and the pressure-sensitive adhesive layer include a through region extending along the cut line, and the protective film has a groove formed along the cut line; The first release film is peeled off after the semi-cutting step; And attaching a non-cut second release film to the location where the first release film has been peeled off to manufacture a foldable backsheet film; The foldable backsheet film has a structure in which the second release film, the pressure-sensitive adhesive layer, the base film and the protective film are sequentially laminated. The second release film does not form any through areas or grooves, the pressure-sensitive adhesive layer and the base film include through areas along the cut line, and the protective film includes grooves along the cut line; The first release film and the second release film are made of silicone. The protective film is made of PET / PSA.

2. The method for manufacturing a foldable backsheet membrane according to claim 1, wherein the base membrane has an elongation at break of 20% or greater and 200% or less at 20°C.

3. The method for manufacturing a foldable backsheet film according to claim 1, wherein the base film has a heat shrinkage rate of 0.1% or less at 200°C.

4. The method for manufacturing a foldable backsheet film according to claim 1, wherein the base film is a polyimide base film.

5. The method for manufacturing a foldable backsheet membrane according to claim 1, wherein the thickness of the base membrane is 20 μm or greater and 120 μm or less.

6. The method for manufacturing a foldable backsheet film according to claim 1, wherein the peel force of the first release film from the pressure-sensitive adhesive layer is 12 gf / inch or less at 23°C.

7. The method for manufacturing a foldable backsheet film according to claim 1, wherein the surface resistivity of the first release film and the second release film is 10 Ω under conditions of 500V or lower. 10 Ω / square or less.

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