High-temperature-resistant and high-impedance pressure-sensitive adhesive, supporting film and preparation method of supporting film

Abstract

The invention relates to the technical field of pressure-sensitive adhesives, in particular to a high-temperature-resistant high-impedance pressure-sensitive adhesive, a supporting film and a preparation method of the supporting film. A styrene-butadiene-styrene block copolymer (SBS) is used as a main body material, an acrylic copolymer with high carboxyl content is grafted in a solvent in a thermal initiation mode, the high-temperature-resistant and high-impedance pressure-sensitive adhesive is obtained after the high-temperature-resistant and high-impedance pressure-sensitive adhesive is compounded with tackifying resin, a curing agent and an antioxidant, and after optical-grade PET is coated with the high-temperature-resistant and high-impedance pressure-sensitive adhesive, the high-temperature-resistant and high-impedance pressure-sensitive adhesive is obtained. According to the novel supporting film, the polarity of the SBS main body material is low, the excellent electrical insulation performance is provided, the supporting film body has the characteristic of high impedance, and therefore the requirement for high impedance of the supporting film in a copper bar friction experiment is met; in addition, after the acrylic copolymer with high carboxyl content is grafted, a large number of crosslinking points can be provided, and the overall crosslinking degree is greatly increased after thermocuring, so that the high-temperature modulus of the adhesive layer is improved, and the adhesive layer is endowed with the characteristic of high-temperature deformation resistance.

Description

Technical Field

[0001] The invention relates to the technical field of pressure-sensitive adhesives, in particular to a high-temperature resistant high-impedance pressure-sensitive adhesive, a support film and a preparation method thereof. Background Art

[0002] OLED technology is the third generation display technology after CRT and LCD technology.

[0003] Compared with the previous two generations of display technology, OLED display devices are thinner, have a wider viewing angle, and a wider color gamut. Therefore, they have been applied to various civilian fields and have a broad market space. However, OLED display screens have a certain degree of flexibility. During the production, transportation, and assembly of the module, they are prone to deformation and damage, affecting the use of the entire display screen. The problem can be effectively solved by attaching a support film (BP) containing a pressure-sensitive adhesive layer to the back of the OLED module substrate to play a fixed support role.

[0004] However, the current application of ordinary BP has the following two major pain points: On the one hand, in the OLED module manufacturing process, after the BP is attached, it is necessary to go through the COP bonding packaging process. The process conditions of this process are usually high temperatures exceeding 200°C. The high-temperature modulus of the pressure-sensitive adhesive layer of ordinary BP is low, and it is easy to deform and move, causing production failures. On the other hand, before the OLED module leaves the factory, it is usually necessary to conduct a copper rod friction test. The surface resistivity of the ordinary BP pressure-sensitive adhesive layer currently used is low (usually less than 10 15 The static electricity generated during the friction of the copper rod may cause the thin film transistor characteristics in the display module to shift, causing the transfer output curve to shift and the low grayscale working range to change, resulting in poor image quality in the display module after the copper rod friction experiment.

[0005] At present, there are also support films on the market for solving the above problems. For example, Chinese patent No. CN114550585A discloses a high-resistance support film and a display module. The high-resistance support film is used to support a display screen, and includes: an insulating adhesive layer, a substrate layer, and a functional layer arranged on the substrate layer. The insulating adhesive layer is arranged on the adhesive surface of the substrate layer, and the adhesive surface of the substrate layer is bonded to the non-display surface of the display screen through the insulating adhesive layer. The surface resistivity of the insulating adhesive layer is greater than or equal to 10 13 ohm.

[0006] This invention uses insulating fillers to increase the surface resistivity of the adhesive layer. However, due to the small particle size of the fillers, they are easily agglomerated, resulting in poor appearance of the support film and unstable impedance.

[0007] For another example, Chinese patent with publication number CN214099647U discloses an OLED support film, including a transparent PET film substrate made of polyethylene terephthalate film antistatic material, a PU protective film layer is provided on the lower end surface of the transparent PET film substrate, a safe connection fastening adhesive layer is provided on the upper end of the transparent PET film substrate, the safe connection fastening adhesive layer is an acid-free antistatic protective layer, a light release film is provided on the upper end of the safe connection fastening adhesive layer, the light release film has a thickness of 50 μm and a surface impedance of 109-11; the thickness of the second connection adhesive layer is 13-25 μm and a surface impedance of 10 10-12 Ω, acid value ≤0.5mgKOH / g.

[0008] The surface resistance of the support film produced by the support film is 10 10-12 Ω, this value is relatively low, and there is still a risk of failing to block electrons and breaking through the screen in the copper rod test, causing defects.

[0009] In summary, it is necessary to develop a high-temperature-resistant and high-impedance BP to improve the production yield of OLED modules.

[0010] In order to solve the above problems, the present invention provides a high temperature resistant high impedance pressure sensitive adhesive, a support film and a preparation method thereof. Summary of the invention

[0011] The object of the present invention is to provide a high temperature resistant high impedance pressure sensitive adhesive, a support film and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0012] In order to solve the above technical problems, the present invention provides the following technical solutions: A high temperature resistant high impedance pressure sensitive adhesive, comprising the following substances by weight:

[0013] Acrylic polymer modified SBS 80-120 parts;

[0014] 8-15 parts of terpene phenol tackifying resin;

[0015] Curing agent 0.1~1 part

[0016] 20-40 parts of toluene.

[0017] More optimally, the acrylic polymer modified SBS is synthesized from the following weight components:

[0018] SBS 80~120 copies

[0019] 8-15 parts of butyl acrylate;

[0020] 1-1.5 parts of vinyl acetate;

[0021] Methacrylic acid 0.5-1 part;

[0022] 0.1-0.3 parts of azobisisobutyronitrile;

[0023] Antioxidant 10102~4 parts.

[0024] The present invention provides a high temperature resistant high impedance support film, comprising a protective film layer, a substrate layer, a PSA layer and a release film layer which are arranged in sequence, wherein the substrate layer adopts optical grade PET; wherein the PSA layer is made of any one of the above-mentioned high temperature resistant high impedance pressure sensitive adhesives.

[0025] More optimally, the support film has a storage modulus of >0.05 MPa at 200°C and a surface resistivity of >10 15 Ω·m.

[0026] The present invention also provides a method for preparing a high temperature resistant high impedance support film, which is used to prepare the high temperature resistant high impedance support film, comprising the following steps:

[0027] S1, synthesis of acrylic polymer modified SBS: a certain amount of SBS was dissolved in toluene and stirred for 4-6 hours; a certain amount of butyl acrylate, vinyl acetate and methacrylic acid were added and stirred for 0.5-2 hours; a certain amount of azobisisobutyronitrile was added and reacted at 80-90 degrees for 4-6 hours; after the reaction, an antioxidant 1010 was added, and the sample was collected after stirring for 1 hour to obtain acrylic polymer modified SBS, which was recorded as SBS-AA;

[0028] S2, preparation of support film: take a certain amount of SBS-AA, terpene phenol tackifying resin, curing agent and toluene; after fully stirring, apply them on the surface of optical grade PET and stick a release film on it, with a coating thickness of 10 to 15 μm; the coating process is baking at 100 to 150°C for 2 to 5 minutes and maturing at 60 degrees for 2 to 4 days to obtain the finished product.

[0029] More optimally, step S1 is performed entirely under nitrogen protection.

[0030] More optimally, the curing agent is 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

[0031] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0032] (1) In the present invention, styrene-butadiene-styrene block copolymer (SBS) is used as the main material, and an acrylic copolymer with a high carboxyl content is grafted in a solvent by a thermal initiation method. After compounding with a tackifying resin, a curing agent and an antioxidant, a high-temperature resistant and high-impedance pressure-sensitive adhesive is obtained. After coating on an optical-grade PET, a protective film and a release film are respectively attached to the upper and lower layers to form a new support film. On the one hand, the SBS main material itself has a low polarity and provides excellent electrical insulation properties, so that the support film body has a high impedance characteristic; on the other hand, after grafting with an acrylic copolymer with a high carboxyl content, a large number of cross-linking points can be provided. After thermal curing, the overall cross-linking degree is greatly increased, so that the high-temperature modulus of the adhesive layer is improved, giving it the characteristic of high-temperature deformation resistance.

[0033] (2) In the present invention, the prepared support film has a high storage modulus (> 0.05 MPa) at a high temperature of 200°C and a surface resistivity of more than 10 15 Ω·m, improve the problem that the adhesive layer of ordinary BP will deform at high temperature and the surface resistivity is low, which cannot suppress the static electricity generated in the copper rod friction test.

[0034] (3) In the present invention, the SBS used has a large number of carbon-carbon double bonds, which can provide sufficient reaction sites for the introduction of acrylic polymers. The introduction of acrylic components can increase the crosslinking degree of the SBS main rubber, thereby greatly improving the high-temperature modulus of the rubber layer, thereby achieving the high-temperature resistance requirement while increasing the resistance value. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0036] Figure 1 Schematic diagram of the structure of the support membrane.

[0037] Among them, 1. Protective film layer; 2. Optical grade PET layer; 3. PSA layer; 4. Release film layer. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] In the present invention, the support membrane is prepared by the following steps:

[0040] S1, acrylic polymer modified SBS: The whole reaction was carried out under nitrogen protection; 100 parts of SBS were dissolved in 400 parts of toluene and stirred for 4-6 hours; 10 parts of butyl acrylate, 1.2 parts of vinyl acetate and 0.8 parts of methacrylic acid were added and stirred for 0.5-2 hours; 0.2 parts of azobisisobutyronitrile were added and reacted at 85 degrees for 4-6 hours; after the reaction, 3 parts of antioxidant 1010 were added and the sample was collected after stirring for 1 hour to obtain acrylic polymer modified SBS (denoted as SBS-AA).

[0041] S2, preparation of support film: take 100 parts of SBS-AA, 10 parts of terpene phenol tackifying resin, 0.5 parts of curing agent 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, and 30 parts of toluene; after fully stirring, apply it on the surface of optical grade PET and stick a release film on it. The coating thickness is 10-15 μm, preferably 13 μm; the coating process is 100-150°C, preferably 120°C, baking for 2-5 minutes, and aging at 60 degrees for 2-4 days.

[0042] In order to verify the performance of the prepared support membrane, the present invention prepared several examples and comparative examples and conducted performance tests. In Example 1, an acrylic acid polymer was used to modify SBS, and in the comparative example, an unmodified SBS was used. The formulas of the examples and comparative examples are shown in Table 1:

[0043] Table 1 Formulation of support membrane in various embodiments and comparative examples

[0044]

[0045]

[0046] Next, the supporting films prepared in each embodiment and comparative example were subjected to performance tests, including peeling force, 25°C modulus, 200°C modulus and surface resistivity. The specific results are shown in Table 2:

[0047] Table 2 Performance test table of support membrane in various embodiments and comparative examples

[0048]

[0049] From the data in Table 2, it can be seen that all groups use SBS as the main adhesive of the pressure-sensitive adhesive, so they all show high impedance characteristics (all greater than 10 15 Ω·m).

[0050] Compared with comparative example 1-4, when the acrylic polymer is grafted to provide cross-linkable sites, the Example 1-4 maintains a higher modulus at 200°C, that is, it has high temperature resistance, and as the amount of curing agent increases, the high temperature modulus of the corresponding pressure-sensitive adhesive also increases. This is because the higher the concentration of the curing agent, the greater the cross-linking density of the colloid itself; while the comparative example 1-4 has no cross-linking sites and almost melts at 200°C, and the modulus decreases significantly, which cannot meet the application requirements of the support film in the COP bonding process.

[0051] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0052] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high temperature resistant high impedance pressure sensitive adhesive, characterized in that: The components by weight include the following substances: Acrylic polymer modified SBS 80-120 parts; 8-15 parts of terpene phenol tackifying resin; Curing agent 0.1~1 part 20 to 40 parts of toluene.

2. The high temperature resistant high impedance pressure sensitive adhesive according to claim 1, characterized in that: The acrylic acid polymer modified SBS is synthesized from the following weight components: SBS 80~120 copies 8-15 parts of butyl acrylate; 1-1.5 parts of vinyl acetate; Methacrylic acid 0.5-1 part; 0.1-0.3 parts of azobisisobutyronitrile; Antioxidant 10102~4 parts.

3. A high temperature resistant high impedance support film, characterized in that: It comprises a protective film layer, a substrate layer, a PSA layer and a release film layer arranged in sequence, wherein the substrate layer is made of optical-grade PET; and the PSA layer is made of a high-temperature-resistant and high-impedance pressure-sensitive adhesive as claimed in claim 1 or 2.

4. A high temperature resistant high impedance support film according to claim 3, characterized in that: The support film has a storage modulus of >0.05 MPa at 200°C and a surface resistivity of >10 15 Ω·m.

5. A method for preparing a high temperature resistant high impedance support film, used for preparing a high temperature resistant high impedance support film as claimed in claim 4, characterized in that: The steps include: S1, synthesis of acrylic polymer modified SBS: a certain amount of SBS was dissolved in toluene and stirred for 4-6 hours; a certain amount of butyl acrylate, vinyl acetate and methacrylic acid were added and stirred for 0.5-2 hours; a certain amount of azobisisobutyronitrile was added and reacted at 80-90 degrees for 4-6 hours; after the reaction, an antioxidant 1010 was added, and the sample was collected after stirring for 1 hour to obtain acrylic polymer modified SBS, which was recorded as SBS-AA; S2, preparation of support film: take a certain amount of SBS-AA, terpene phenol tackifying resin, curing agent and toluene; after fully stirring, apply them on the surface of optical grade PET and stick a release film on it, with a coating thickness of 10 to 15 μm; the coating process is baking at 100 to 150°C for 2 to 5 minutes and maturing at 60 degrees for 2 to 4 days to obtain the finished product.

6. The method for preparing a high temperature resistant and high impedance support film according to claim 5, characterized in that: The step S1 is performed under nitrogen protection throughout the process.

7. The method for preparing a high temperature resistant and high impedance support film according to claim 1, characterized in that: The curing agent is 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

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