Preparation method of peep-proof double faced adhesive tape for ultrasonic fingerprint unlocking screen

Abstract

The invention discloses a preparation method of a peep-proof double faced adhesive tape for an ultrasonic fingerprint unlocking screen. The preparation method comprises the following steps: S1, preparing a surface-treated base film; s2, coating a silica gel liquid on one surface of a base film, curing to form a silica gel layer, and covering with a first release film; s3, arranging a peep-proof layer on the other surface of the base film; s4, the surface, away from the base film, of the peep-proof layer is coated with the OCA glue solution, an OCA glue layer is formed through curing, and a second release film covers the OCA glue layer; s5, rolling and curing; and the base film is a PET (Polyethylene Terephthalate) film of 23-27 microns. The thin base film is firstly coated with the silica gel layer, then the peep-proof layer and the OCA layer are compounded, bubbles generated by the OCA layer due to high-temperature curing in preparation of the silica gel layer are prevented, and the optical performance and quality of the OCA layer are optimized in combination with a curing process; the selection of the thin base film is combined with the layer thickness adjustment of the silica gel layer and the OCA layer, so that the use of a fingerprint unlocking screen and a curved screen is met, and the structural stability is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of double-sided adhesive tapes, and in particular to a method for preparing an anti-peeping double-sided adhesive tape for an ultrasonic fingerprint unlocking screen. Background Art

[0002] With the development of under-screen fingerprint technology, its application in the full-screen of smart devices has become a trend. Applications can be divided into three major methods: under-screen capacitive fingerprint recognition, under-screen ultrasonic fingerprint recognition, and under-screen optical fingerprint recognition. Tempered glass film is usually used to protect the screen. Tempered glass film is adhered to the screen surface with double-sided tape. If the double-sided tape has low light transmittance, applying it to the smart device screen will significantly reduce the fingerprint unlocking signal, resulting in fingerprint unlocking delays, seriously affecting the normal user experience.

[0003] Therefore, it is necessary to improve the preparation method of the anti-peep double-sided tape for ultrasonic fingerprint unlocking screen in the prior art. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects existing in the prior art and provide a method for preparing an anti-peeping double-sided tape for an ultrasonic fingerprint unlocking screen. By first coating a silicone layer on a thin base film and then compounding an anti-peeping layer and an OCA adhesive layer, bubbles are prevented in the OCA adhesive layer caused by high-temperature curing during the preparation of the silicone layer. The optical performance and quality of the OCA adhesive layer are optimized in combination with the aging process. The selection of a thin base film ensures the sensitivity of screen fingerprint unlocking, and also helps to flexibly adjust the layer thickness of the silicone layer and the OCA adhesive layer, thereby improving the connection firmness with the adhered object, and conforming to the use of curved screens and improving structural stability.

[0005] To achieve the above technical effects, the technical solution of the present invention is: a method for preparing an anti-peep double-sided tape for an ultrasonic fingerprint unlocking screen, comprising the following steps: S1: configure the surface treated base film; S2: applying a silicone liquid on one surface of the base film, curing it to form a silicone layer, and covering it with a first release film; S3: providing an anti-peep layer on the other surface of the base film; S4: applying the OCA adhesive solution to the surface of the privacy protection layer away from the base film, curing it to form an OCA adhesive layer, and covering it with a second release film; S5: winding and maturation; The base film is a PET film with a thickness of 23 to 27 microns.

[0006] The anti-peeping layer is processed externally, with a thickness of 70-80 microns. The surface treatment of the base film can be chemical treatment or corona treatment, meeting the dyne value ≥52dyn / cm, and double-sided treatment.

[0007] The preferred technical solution is that, by weight, the silicone liquid includes 32 to 38 parts of low-viscosity silicone rubber, 15 to 20 parts of high-viscosity silicone rubber, 0.5 to 0.7 parts of silane coupling agent, 0.7 to 0.9 parts of catalyst and 43 to 50 parts of solvent.

[0008] The preferred technical solution is that the low-viscosity silicone rubber is one or more of double-ended vinyl silicone oil, single-ended vinyl silicone oil and side-chain vinyl silicone oil, the high-viscosity silicone rubber is one or more of double-ended vinyl silicone oil, single-ended vinyl silicone oil and side-chain vinyl silicone oil, the silane coupling agent is vinyltriethoxysilane, the catalyst is a platinum catalyst, and the solvent is toluene and ethyl acetate in a mass ratio of 1: (1.5~2).

[0009] The preferred technical solution is that, by weight, the raw materials for preparing the OCA glue include 58-63 parts of isooctyl acrylate, 8-12 parts of isooctyl methacrylate, 3-6 parts of isobornyl acrylate, 7-10 parts of methyl methacrylate, 8-12 parts of acrylic acid, 4-8 parts of hydroxyethyl acrylate and 0.7-0.9 parts of photoinitiator.

[0010] The preferred technical solution is that the system viscosity of the OCA glue is 100-200 cps. In order to balance the coating adaptability, leveling, bubble control and comprehensive performance of the adhesive layer, the system viscosity of the OCA glue is further 120-180 cps.

[0011] The preferred technical solution is that the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone, and in the preparation of the OCA glue, the ultraviolet irradiation intensity of the photoinitiator is 2-3 mW / cm 2 The photoinitiation time is controlled within 1~1.5h, thereby controlling the system viscosity of the OCA glue.

[0012] The preferred technical solution is that in S2, the curing temperature of the silicone layer is set to 45±5°C, 85±5°C, 130±5°C, 145±5°C, 145±5°C, 130±5°C, and 120±5°C in sequence.

[0013] The preferred technical solution is that in S4, the UV irradiation intensity of the OCA adhesive layer is 2-3 mW / cm 2 ; UV energy density is 400~600mJ / cm 2 .

[0014] A preferred technical solution is that in S5, the aging temperature is 43±5°C and the time is 72±2h.

[0015] A preferred technical solution is that the thickness of the silica gel layer is 40-45 microns, and the thickness of the OCA layer is 40-50 microns.

[0016] The advantages and beneficial effects of the present invention are: The present invention provides a method for preparing an anti-peeping double-sided tape for an ultrasonic fingerprint unlocking screen. By first coating a silicone layer on a thin base film, and then compounding the anti-peeping layer and the OCA adhesive layer, bubbles in the OCA adhesive layer caused by high-temperature curing during the preparation of the silicone layer are prevented. The optical performance and quality of the OCA adhesive layer are optimized in combination with a curing process. The thickness of the base film must ensure the sensitivity of screen fingerprint unlocking and the flatness of thermal processing. It also helps to flexibly adjust the thickness of the silicone layer and the OCA layer, improve the connection firmness with the object being adhered, and match the use of curved screens and improve structural stability. DETAILED DESCRIPTION

[0017] The following examples are only used to illustrate the technical solution of the present invention more clearly, and are not intended to limit the scope of protection of the present invention.

[0018] Selection of raw materials for the preparation of OCA glue Isooctyl acrylate (2-EHA), the primary long-chain flexible monomer, provides excellent flexibility, low-temperature compliance, high initial tack (wettability), and good optical properties. This ensures the adhesive layer possesses a pleasant tactile feel, low modulus, excellent conformability (rapid wetting of the bonded surface), and adaptability to curved or irregular surfaces. A higher addition of isooctyl acrylate results in a softer adhesive and better initial tack, but may also result in insufficient cohesive strength. A lower addition results in a stiffer adhesive and poor initial tack.

[0019] Isooctyl methacrylate (EHMA) is a long-chain flexible monomer with a similar structure to 2-EHA, but with a methyl group (methacrylate). This monomer provides excellent flexibility, low surface energy, and excellent weather resistance (particularly resistance to UV yellowing and hydrolysis). Compared to 2-EHA, its homopolymer exhibits a slightly higher glass transition temperature and improved cohesive strength. This significantly improves the adhesive layer's yellowing stability and resistance to wet heat aging. It also improves the adhesive layer's cohesive strength without becoming too rigid. It also exhibits better adhesion to low-surface-energy materials (tempered glass film). However, increasing the amount of isooctyl methacrylate added decreases initial tack.

[0020] Isobornyl acrylate (IBOA) is a monomer with a large, rigid alicyclic structure. It significantly improves the hardness, modulus, heat resistance, solvent resistance, cohesive strength, and weather resistance of the adhesive layer, while maintaining good transparency and low shrinkage. It is a key component in enhancing the adhesive layer's "support" and "collapse resistance." It imparts excellent high-temperature retention and creep resistance to the adhesive layer, and also helps improve scratch resistance. If the addition level of IBOA is too low, the adhesive layer will lack cohesion and heat resistance. If the addition level is too high, the adhesive layer will become brittle and hard, with a significant decrease in initial adhesion and poor low-temperature performance.

[0021] Methyl methacrylate (MMA) improves the hardness, modulus, strength, heat resistance, solvent resistance, and weather resistance of the adhesive layer. Excessive addition of MMA can increase the adhesive layer's brittleness, reduce its flexibility, increase its shrinkage, and weaken its initial adhesion.

[0022] Acrylic acid (AA) is highly polar and provides carboxyl groups (-COOH), significantly improving the adhesive layer's adhesion (ultimate bonding strength) to various substrates (particularly metal, glass, and polar plastics). It also participates in cross-linking reactions, enhancing cohesive strength and resistance to moisture and heat aging. Even a small amount of acrylic acid can significantly improve adhesion, but excessive amounts can cause the adhesive layer to become hard and brittle, and reduce storage stability (prone to self-polymerization).

[0023] Hydroxyethyl acrylate (HEA) provides hydroxyl groups (-OH) that react with the curing system (active groups in UV curing systems) to form a crosslinking network, significantly improving the adhesive layer's cohesive strength, heat resistance, solvent resistance, and creep resistance (endurance). It also provides a certain degree of polarity, improving adhesion to the substrate. If the addition level of hydroxyethyl acrylate is too low, the crosslinking density will be insufficient, resulting in poor cohesion and heat resistance. If the addition level is too high, the crosslinking density will be too high, making the adhesive layer hard and brittle, and reducing flexibility and initial tack.

[0024] Example 1

[0025] The preparation method of the anti-peep double-sided tape for ultrasonic fingerprint unlocking screen includes the following steps: S1: Configure the surface treated base film, the base film is 25 micron PET film (Hengli HB023); S2: applying silicone liquid to one surface of the base film and curing it to form a silicone layer, and then covering it with a first release film, wherein the curing temperature of the silicone layer is sequentially set to 45°C, 85°C, 130°C, 145°C, 145°C, 130°C, and 120°C; S3: An anti-peeping layer is provided on the other surface of the base film, with a thickness of 72 microns; S4: applying the OCA adhesive to the surface of the privacy protection layer away from the base film, curing it to form an OCA adhesive layer, and covering it with a second release film; Among them, the UV radiation intensity of the OCA adhesive layer is 2.6mW / cm2 ; UV energy density is 500mJ / cm 2 ; The height settings of the ultraviolet UV lamps are 188, 188, 188, 218, 225, 188, 239, 176, 191, 196 at the top, and 188, 180, 195, 197, 181, 207, 228, 259, 275, 246 at the bottom.

[0026] S5: Winding and aging, the aging temperature is 43°C and the time is 72h; The first release film and the second release film are both 50 micron PET original films.

[0027] Calculated by mass, the silicone liquid includes 35 parts of low-viscosity silicone rubber, 18 parts of high-viscosity silicone rubber, 0.6 parts of silane coupling agent, 0.8 parts of catalyst and 45.6 parts of solvent.

[0028] The low-viscosity silicone rubber is Shengquan SC-8-2018, the high-viscosity silicone rubber is Dow Corning 7657, the silane coupling agent is vinyltriethoxysilane, the catalyst is a platinum catalyst (Dow Corning 4000), and the solvent is toluene and ethyl acetate with a mass ratio of 1:1.83.

[0029] The raw materials for the preparation of OCA glue include 60 parts of isooctyl acrylate, 10 parts of isooctyl methacrylate, 5 parts of isobornyl acrylate, 9 parts of methyl methacrylate, 10 parts of acrylic acid, 6 parts of hydroxyethyl acrylate and 0.8 parts of photoinitiator. Among them, the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173). In the preparation of OCA glue, the ultraviolet irradiation intensity of the photoinitiator is 2.5mW / cm 2 The initiation time was 1.5 h. The viscosity of the OCA adhesive was 150 cps.

[0030] The thickness of the silicone layer is 43 microns, and the thickness of the OCA layer is 45 microns.

[0031] Example 2

[0032] Example 2 is based on Example 1, except that, by weight, the silicone liquid includes 38 parts of low-viscosity silicone rubber, 15 parts of high-viscosity silicone rubber, 0.6 parts of silane coupling agent, 0.8 parts of catalyst and 45.6 parts of solvent.

[0033] Example 3

[0034] Example 3 is based on Example 1, except that, by weight, the silicone liquid includes 30 parts of low-viscosity silicone rubber, 23 parts of high-viscosity silicone rubber, 0.6 parts of silane coupling agent, 0.8 parts of catalyst and 45.6 parts of solvent.

[0035] Example 4

[0036] Example 4 is based on Example 1, except that the solvent is toluene and ethyl acetate in a mass ratio of 1:3.

[0037] Example 5

[0038] Example 5 is based on Example 1, except that the solvent included in the silica gel liquid is cyclohexane.

[0039] Example 6

[0040] Example 6 is based on Example 1, except that, by mass, the raw materials for preparing the OCA glue include 65 parts of isooctyl acrylate, 5 parts of isooctyl methacrylate, 5 parts of isobornyl acrylate, 9 parts of methyl methacrylate, 10 parts of acrylic acid, 6 parts of hydroxyethyl acrylate and 0.8 parts of photoinitiator.

[0041] Example 7

[0042] Example 7 is based on Example 1, except that, by mass, the raw materials for preparing the OCA glue include 70 parts of isooctyl acrylate, 5 parts of isobornyl acrylate, 9 parts of methyl methacrylate, 10 parts of acrylic acid, 6 parts of hydroxyethyl acrylate and 0.8 parts of photoinitiator.

[0043] Example 8

[0044] Example 8 is based on Example 1, except that the raw materials for preparing the OCA glue include 60 parts of isooctyl acrylate, 10 parts of isooctyl methacrylate, 14 parts of methyl methacrylate, 10 parts of acrylic acid, 6 parts of hydroxyethyl acrylate and 0.8 parts of photoinitiator.

[0045] Example 9

[0046] Example 9 is based on Example 1, except that the coil is rolled up in S5 and then aged at room temperature.

[0047] Comparative Example 1 Comparative Example 1 is based on Example 1, except that the base film is a 50 μm PET film, the silicone layer has a thickness of 32 μm, the OCA layer has a thickness of 31 μm, the thickness of other layers remains unchanged, and the total thickness of the double-sided tape remains unchanged.

[0048] Comparative Example 2 Comparative Example 2 is based on Example 1, except that the surface of the base film is not surface treated.

[0049] Performance Testing 1. Transmittance and haze: measured using Ultra Scan PRO instrument.

[0050] 2. Peel strength test: According to GB / T 2792-1998 standard, 180° peel strength test, where the object to be adhered is SUS304 steel plate.

[0051] 3. Evaluate the fit of the curved screen: Attach the OCA side of the double-sided privacy tape to the tempered glass, and the silicone side to the curved screen. Place the tape in an 80°C oven for 24 hours and observe for any abnormalities such as bubbles, difficulty in tearing, or warping.

[0052] 4. Adhesion: According to GB / T4851-2014 standard, cut the protective film into standard tape (25mm wide, 100mm long), attach it to the glass, align the upper end with the standard line, cut off the excess part at the lower end, press back and forth three times with a 2kg roller, and place it at 100℃ for 30 minutes. Hang the glass with the sample vertically on the test frame and keep it still. Hang a 1kg weight underneath. The time it takes for the tape to fall represents the adhesion of the protective film.

[0053] The performance test results of the embodiments and comparative examples are as follows:

[0054] In Example 2 compared with Example 1, if the amount of low-viscosity silicone rubber added is too high and the amount of high-viscosity silicone rubber added is reduced, the double-sided tape may easily shift or fall off on the device surface during use.

[0055] Compared with Example 1, in Example 3, if the amount of low-viscosity silicone rubber added is too small and the amount of high-viscosity silicone rubber added is increased, the peeling force of the silicone surface of the double-sided tape increases, which makes it difficult to peel the double-sided tape from the device surface during use.

[0056] In Example 4, compared with Example 1, the content of ethyl acetate in the solvent system is increased, which may easily lead to an uneven surface of the silicone rubber layer and slight orange peel texture on the rubber surface.

[0057] Compared with Example 1, the OCA adhesive layer in Example 9 is not fully cured at room temperature, which has a negative impact on the performance.

[0058] Compared with Example 1, the thickness of the base film in Comparative Example 1 is increased, and the thickness of the silicone layer and the OCA layer are reduced. During lamination, bubbles will be generated on both adhesive surfaces, and the lamination is incomplete. The increased thickness of the PET base film makes the fingerprint unlocking of the screen less sensitive.

[0059] During the preparation of the product of Comparative Example 2, the silicone layer had bubbles, was not firmly bonded to the substrate, and fell off.

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing an anti-peep double-sided tape for an ultrasonic fingerprint unlocking screen, characterized in that: The following steps are involved: S1: configure the surface treated base film; S2: applying a silicone liquid on one surface of the base film, curing it to form a silicone layer, and covering it with a first release film; S3: providing an anti-peep layer on the other surface of the base film; S4: applying the OCA adhesive solution to the surface of the privacy protection layer away from the base film, curing it to form an OCA adhesive layer, and covering it with a second release film; S5: winding and maturation; The base film is a PET film with a thickness of 23 to 27 microns.

2. The method for preparing the anti-peep double-sided tape for ultrasonic fingerprint unlocking screen according to claim 1, characterized in that: Calculated by mass, the silicone liquid includes 32 to 38 parts of low-viscosity silicone rubber, 15 to 20 parts of high-viscosity silicone rubber, 0.5 to 0.7 parts of silane coupling agent, 0.7 to 0.9 parts of catalyst and 43 to 50 parts of solvent.

3. The method for preparing the anti-peep double-sided tape for ultrasonic fingerprint unlocking screen according to claim 2, characterized in that: The low-viscosity silicone rubber is one or more of double-ended vinyl silicone oil, single-ended vinyl silicone oil and side-chain vinyl silicone oil; the high-viscosity silicone rubber is one or more of double-ended vinyl silicone oil, single-ended vinyl silicone oil and side-chain vinyl silicone oil; the silane coupling agent is vinyltriethoxysilane; the catalyst is a platinum catalyst; and the solvent is toluene and ethyl acetate in a mass ratio of 1:(1.5~2).

4. The method for preparing the anti-peep double-sided tape for ultrasonic fingerprint unlocking screen according to claim 1 or 2, characterized in that: The raw materials for preparing the OCA glue include, by mass, 58-63 parts of isooctyl acrylate, 8-12 parts of isooctyl methacrylate, 3-6 parts of isobornyl acrylate, 7-10 parts of methyl methacrylate, 8-12 parts of acrylic acid, 4-8 parts of hydroxyethyl acrylate and 0.7-0.9 parts of a photoinitiator.

5. The method for preparing the anti-peep double-sided tape for ultrasonic fingerprint unlocking screen according to claim 4, characterized in that: The system viscosity of the OCA glue is 100-200 cps.

6. The method for preparing the anti-peep double-sided tape for ultrasonic fingerprint unlocking screen according to claim 4, characterized in that: The photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone. In the preparation of the OCA glue, the ultraviolet irradiation intensity of the photoinitiator is 2-3 mW / cm 2 .

7. The method for preparing the anti-peep double-sided tape for ultrasonic fingerprint unlocking screen according to claim 1, characterized in that: In S2, the curing temperature of the silicone layer is set to 45±5°C, 85±5°C, 130±5°C, 145±5°C, 145±5°C, 130±5°C, and 120±5°C in sequence.

8. The method for preparing the anti-peeping double-sided tape for ultrasonic fingerprint unlocking screen according to claim 1, characterized in that: In S4, the UV radiation intensity of the OCA adhesive layer is 2-3 mW / cm 2 ; UV energy density is 400~600mJ / cm 2 .

9. The method for preparing the anti-peeping double-sided tape for ultrasonic fingerprint unlocking screen according to claim 1, characterized in that: In S5, the aging temperature is 43±5° C. and the aging time is 72±2 h.

10. The method for preparing the anti-peep double-sided tape for ultrasonic fingerprint unlocking screen according to claim 1, characterized in that: The thickness of the silica gel layer is 40-45 microns, and the thickness of the OCA layer is 40-50 microns.

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