A composite buffer film and preparation method thereof

Abstract

The present invention discloses a composite buffer film, which comprises a first buffer rubber layer, a substrate layer and a second buffer rubber layer in sequence; the first buffer rubber layer and the second buffer rubber layer comprise the following raw materials in percentage by mass: 30% to 70% of silicone pressure-sensitive adhesive, 0.01% to 10% of cross-linking agent, 0.01% to 10% of catalyst, 0.01% to 10% of inhibitor, and 20% to 60% of solvent; the substrate layer is made of PET, silicone rubber or PE. The present invention also discloses a method for preparing the composite buffer film. The composite buffer film of the present invention not only has stable adhesion, but also has a higher buffering effect than a single buffer rubber layer, has the advantages of small falling ball buffering force and unobvious back pressure imprint, and is suitable for application in the protection of flexible screens.

Description

Technical Field

[0001] The present invention relates to the technical field of buffer films, and in particular to a composite buffer film and a preparation method thereof. Background Art

[0002] At present, AMOLED is the mainstream product of OLED technology and is widely used in small-size flat-panel displays such as mobile phones. As a new display technology, OLED has developed rapidly and has great potential, representing a new application direction. The shipment area of ​​AMOLED panels increased from 1.5505 million square meters in 2014 to 8.0762 million square meters in 2019, with a compound growth rate of 39.11%. The growth of the downstream OLED panel market has also driven the development of the upstream OLED material market. Foam is one of the indispensable materials. Foam is a high-molecular polymer with many small pores. The solid phase is a polymer matrix, and the small pores are filled with other gases. Foam has a certain buffering effect. When a force is applied to the outside of the flexible screen, the force can be transmitted along the flexible screen to the foam. The foam releases the force through deformation to avoid large deformation of the flexible screen caused by the force, thereby protecting the flexible screen and reducing the damage to the flexible screen caused by the force; however, the conductivity of the foam is poor and the cost is high. At the same thickness, the buffering performance is not as good as the buffer film, resulting in the foam being gradually replaced by the buffer film. However, the existing buffer film has limited buffering effect and insufficient protection for the display screen, especially when the display screen is pressed or hit hard, it is easy to form obvious back pressure imprint, which is not easy to restore to its original state, affecting the visual effect of the screen, and needs further improvement. Summary of the invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes a composite buffer film and a preparation method thereof.

[0004] The composite buffer film provided by the present invention comprises a first buffer adhesive layer, a substrate layer and a second buffer adhesive layer in sequence;

[0005] The first buffer adhesive layer and the second buffer adhesive layer include the following raw materials in percentage by weight: 30% to 70% of organic silicone pressure-sensitive adhesive, 0.01% to 10% of cross-linking agent, 0.01% to 10% of catalyst, 0.01% to 10% of inhibitor, and 20% to 60% of solvent;

[0006] The material of the substrate layer is PET, silicone rubber or PE;

[0007] According to the test standard of ASTM D4440-15, the loss modulus of the composite buffer film is 30 to 150 kPa, and the storage modulus is 50 to 200 kPa.

[0008] If the loss modulus and storage modulus of the composite buffer film are too large, the buffering effect of the composite buffer film is not good; if the loss modulus and storage modulus of the composite buffer film are too small, the improvement effect of the composite buffer film on back pressure imprint is not obvious.

[0009] The raw materials of the first buffer rubber layer and the second buffer rubber layer can be the same or different.

[0010] Silicone pressure-sensitive adhesive refers to a pressure-sensitive adhesive with silicone polymer as the main body, or acrylic and silicone-modified rubber pressure-sensitive adhesive modified by silicone polymer.

[0011] Preferably, the viscosity of the silicone pressure-sensitive adhesive is 50 CPS to 20,000 CPS.

[0012] Preferably, the solid content of the organic silicone pressure-sensitive adhesive is 10% to 100%.

[0013] In the present invention, the role of the crosslinking agent is to improve the curing degree of the silicone adhesive layer. The present invention does not particularly limit the crosslinking agent, and is preferably DCP, BPO, DTBP, DBHP, TAIC, KISCO H-165, Dow 7560 or Bis-25.

[0014] In the present invention, the role of the catalyst is to increase the curing degree and curing speed of the silicone adhesive layer. The present invention does not particularly limit the catalyst, and is preferably Shanghai Sibao PT-50, Beiteli F50040, Beiteli F50050, Dow 4500 or Dow 4000.

[0015] In the present invention, the inhibitor is used to control the curing speed and time. The present invention does not impose any particular restrictions on the inhibitor, and KISCO I-224 is preferred.

[0016] The present invention does not impose any particular limitation on the solvent, but it is preferably at least one of toluene, xylene, ethyl acetate, butanone, and 100-200 solvent oil.

[0017] The thickness of the first buffer rubber layer is 15 to 60 μm; the thickness of the second buffer rubber layer is 15 to 100 μm; and the thickness of the substrate layer is 5 to 50 μm.

[0018] The thickness of the first buffer rubber layer and the second buffer rubber layer may be the same or different.

[0019] Preferably, the composite buffer film further comprises a first release film located outside the first buffer adhesive layer and a second release film located outside the second buffer adhesive layer.

[0020] A method for preparing the composite buffer film comprises the following steps:

[0021] The raw materials of the first buffer adhesive layer are mixed evenly, coated on the surface of the first release film, and formed on the surface of the first release film after high-temperature curing; the raw materials of the second buffer adhesive layer are mixed evenly, coated on the surface of the second release film, and formed on the surface of the second release film after high-temperature curing; the first buffer adhesive layer and the second buffer adhesive layer are respectively bonded to the two surfaces of the substrate layer to obtain a composite buffer film.

[0022] Preferably, the high temperature curing temperature is 100°C to 200°C.

[0023] The beneficial effects of the present invention are as follows:

[0024] The composite buffer film of the present invention uses a substrate of PET, silicone rubber or PE material as an intermediate layer, and composites the first buffer rubber layer and the second buffer rubber layer on both sides of the substrate. It not only has stable adhesion ability, but also the intermediate layer can absorb and disperse the force, thereby significantly reducing the back pressure imprint. The buffering effect of the obtained composite buffer film is higher than that of a single buffer rubber layer, and it has the advantages of small falling ball buffering force and unobvious back pressure imprint, and is suitable for application in the protection of flexible screens. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the back pressure test result of the composite buffer membrane prepared in Example 1 of the present invention.

[0026] Figure 2 This is the back pressure test result of the buffer membrane prepared in Comparative Example 1.

[0027] Figure 3 This is the back pressure test result of the foam.

[0028] Figure 4 It is a schematic diagram of the structure of the composite buffer film of the present invention. Figure 4 Middle: 1-first buffer layer; 2-substrate layer; 3-second buffer layer. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is described in detail below through specific embodiments.

[0030] In the following examples and comparative examples, the silicone pressure-sensitive adhesive is Dow Corning 7666 with a viscosity of 20,000 CPS; the crosslinking agent is triallyl cyanurate (TAIC) with a brand name of Shanghai Pande 1025-15-6; the catalyst is a platinum complex with a brand name of Dow 4000; and the inhibitor is Kisco I-224.

[0031] Example 1

[0032] A composite buffer film comprises a first buffer adhesive layer, a substrate layer and a second buffer adhesive layer in sequence;

[0033] The first buffer adhesive layer and the second buffer adhesive layer include the following raw materials in percentage by weight: 50% organic silicon pressure-sensitive adhesive, 5% cross-linking agent, 5% catalyst, 5% inhibitor, and 35% solvent; the material of the substrate layer is PE.

[0034] The thickness of the first buffer rubber layer is 40 μm, the thickness of the second buffer rubber layer is 60 μm, and the thickness of the base material layer is 25 μm.

[0035] The preparation method of the composite buffer film comprises the following steps:

[0036] After the raw materials of the first buffer adhesive layer are mixed evenly, they are coated on the surface of the first release film, and the first buffer adhesive layer is formed on the surface of the first release film after high-temperature curing at 150°C; after the raw materials of the second buffer adhesive layer are mixed evenly, they are coated on the surface of the second release film, and the second buffer adhesive layer is formed on the surface of the second release film after high-temperature curing at 150°C; the first buffer adhesive layer and the second buffer adhesive layer are respectively adhered to the two surfaces of the substrate layer to obtain.

[0037] The first release film is a light release film, and the second release film is a heavy release film.

[0038] Example 2

[0039] A composite buffer film comprises a first buffer adhesive layer, a substrate layer and a second buffer adhesive layer in sequence;

[0040] The first buffer adhesive layer and the second buffer adhesive layer include the following raw materials in percentage by weight: 40% organic silicon pressure-sensitive adhesive, 6% cross-linking agent, 6% catalyst, 6% inhibitor, and 42% solvent; the material of the substrate layer is PET.

[0041] The thickness of the first buffer rubber layer is 15 μm, the thickness of the second buffer rubber layer is 50 μm, and the thickness of the base material layer is 5 μm.

[0042] The preparation method of the composite buffer film comprises the following steps:

[0043] After the raw materials of the first buffer adhesive layer are mixed evenly, they are coated on the surface of the first release film, and the first buffer adhesive layer is formed on the surface of the first release film after high-temperature curing at 200°C; after the raw materials of the second buffer adhesive layer are mixed evenly, they are coated on the surface of the second release film, and the second buffer adhesive layer is formed on the surface of the second release film after high-temperature curing at 200°C; the first buffer adhesive layer and the second buffer adhesive layer are respectively adhered to the two surfaces of the substrate layer to obtain.

[0044] The first release film is a light release film, and the second release film is a heavy release film.

[0045] Example 3

[0046] A composite buffer film comprises a first buffer adhesive layer, a substrate layer and a second buffer adhesive layer in sequence;

[0047] The first buffer adhesive layer and the second buffer adhesive layer include the following raw materials in percentage by weight: 70% organic silicon pressure-sensitive adhesive, 1% cross-linking agent, 1% catalyst, 1% inhibitor, and 27% solvent; the material of the substrate layer is silicone rubber.

[0048] The thickness of the first buffer rubber layer is 60 μm, the thickness of the second buffer rubber layer is 100 μm, and the thickness of the base material layer is 50 μm.

[0049] The preparation method of the composite buffer film comprises the following steps:

[0050] After the raw materials of the first buffer adhesive layer are mixed evenly, they are coated on the surface of the first release film, and the first buffer adhesive layer is formed on the surface of the first release film after high-temperature curing at 100°C; after the raw materials of the second buffer adhesive layer are mixed evenly, they are coated on the surface of the second release film, and the second buffer adhesive layer is formed on the surface of the second release film after high-temperature curing at 100°C; the first buffer adhesive layer and the second buffer adhesive layer are respectively adhered to the two surfaces of the substrate layer to obtain.

[0051] The first release film is a light release film, and the second release film is a heavy release film.

[0052] According to the test standard of ASTM D4440-15, the loss modulus of the composite buffer films of the above-mentioned embodiments 1 to 3 is 30 to 150 kPa, and the storage modulus is 50 to 200 kPa.

[0053] Comparative Example 1

[0054] A buffer film comprises a buffer adhesive layer, wherein the buffer adhesive layer comprises the following raw materials in percentage by weight: 50% of organic silicon pressure-sensitive adhesive, 5% of cross-linking agent, 5% of catalyst, 5% of inhibitor, and 35% of solvent;

[0055] The thickness of the buffer rubber layer is 125 μm.

[0056] The method for preparing the buffer film comprises the following steps:

[0057] After the raw materials of the buffer adhesive layer are evenly mixed, they are coated on the surface of the first release film, and after high-temperature curing at 150° C., a buffer adhesive layer is formed on the surface of the first release film, and then a second release film is attached to the surface of the buffer adhesive layer that is not attached to the release film.

[0058] The first release film is a light release film, and the second release film is a heavy release film.

[0059] Test example

[0060] The buffer films and foams of Example 1 and Comparative Example 1 were respectively subjected to buffering performance tests and back pressure tests, and the test methods and conditions were as follows:

[0061] Ball drop test conditions: 55MM height, 1.2g steel ball;

[0062] Drop ball test method: tear off the release film of the buffer film, stick one side to the copper foil, and stick the other side to the sensor of the drop ball drop system, start the drop ball tester, and measure the drop ball buffer force;

[0063] Back pressure test conditions: FPC, height 55MM, 1.2g steel ball;

[0064] Back pressure test method: tear off the release film of the buffer film, stick one side to the copper foil and the other side to the FPC. After starting the instrument, let the steel ball fall on the copper foil to test the pit diameter.

[0065] The test results are shown in Table 1 and Figures 1 to 3 As shown:

[0066] Table 1

[0067]

[0068] From Table 1 and Figures 1 to 3 The test results show that under the same test conditions, the composite buffer film of the present invention has less ball-falling buffering force than foam and existing buffer films; and the diameter of the pit formed by the back pressure test is significantly smaller, the depth of the pit is significantly shallower, the back pressure imprint is greatly reduced, and it has a better buffering protection effect.

[0069] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A composite buffer film, characterized in that: It comprises a first buffer rubber layer, a base material layer and a second buffer rubber layer in sequence; The first buffer adhesive layer and the second buffer adhesive layer include the following raw materials in percentage by weight: 30% to 70% of organic silicon pressure-sensitive adhesive, 0.01% to 10% of cross-linking agent, 0.01% to 10% of catalyst, 0.01% to 10% of inhibitor, and 20% to 60% of solvent; the viscosity of the organic silicon pressure-sensitive adhesive is 50CPS to 20000CPS; the cross-linking agent is DCP, BPO, DTBP, DBHP, TAIC, KISCO H-165, Dow 7560 or Double 25; The material of the substrate layer is PET, silicone rubber or PE; The loss modulus of the composite buffer film is 30-150 kPa, and the storage modulus is 50-200 kPa; The thickness of the first buffer rubber layer is 15-60 μm; the thickness of the second buffer rubber layer is 15-100 μm; and the thickness of the substrate layer is 5-50 μm.

2. The composite buffer film according to claim 1, characterized in that: The solid content of the organic silicone pressure-sensitive adhesive is 10% to 100%.

3. The composite buffer film according to claim 1, characterized in that: The catalyst is Shanghai Sibao PT-50, Beite F50040, Beite F50050, Dow 4500 or Dow 4000; the inhibitor is Kisko I-224; the solvent is at least one of toluene, xylene, ethyl acetate, butanone, and 100-200# solvent oil.

4. The composite buffer film according to claim 1, characterized in that: The composite buffer film further includes a first release film located outside the first buffer adhesive layer and a second release film located outside the second buffer adhesive layer.

5. A method for preparing a composite buffer film according to any one of claims 1 to 4, characterized in that: The steps include: The raw materials of the first buffer adhesive layer are mixed evenly, coated on the surface of the first release film, and formed on the surface of the first release film after high-temperature curing; the raw materials of the second buffer adhesive layer are mixed evenly, coated on the surface of the second release film, and formed on the surface of the second release film after high-temperature curing; the first buffer adhesive layer and the second buffer adhesive layer are respectively bonded to the two surfaces of the substrate layer to obtain a composite buffer film.

6. The method for preparing a composite buffer film according to claim 5, characterized in that: The high temperature curing temperature is 100°C to 200°C.

Images