A semi-interpenetrating double network organic gel OCA optical adhesive applied to a folding display device, a preparation method thereof and a folding display device

Abstract

The application discloses a semi-interpenetrating double network organic gel OCA optical adhesive applied to a folding display device and a preparation method and a folding display device thereof. The preparation method is as follows: after a crosslinking network component, a non-crosslinking network component and a polar small molecule are uniformly mixed, the mixture is coated on a release film and is placed into an oven for drying. The OCA optical adhesive has the crosslinking network component as a skeleton in the colloid, the cohesive energy is enhanced, and the creep resistance is enhanced; the non-crosslinking network component improves the wettability of the colloid, and the peeling strength of the optical adhesive is improved; and the polar small molecule enhances the energy dissipation of the colloid, is favorable to the stress generated during bending, and further enhances the flexibility of the colloid. The OCA optical adhesive has a light transmittance greater than 99%, a haze value not more than 0.1%, excellent optical performance, moderate initial adhesion and peeling force, and a continuous bending resistance of more than 200,000 times, and can be widely applied to the device bonding of the folding display device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical adhesive, in particular to a semi-interpenetrating double network organic gel OCA optical adhesive applied to a foldable display device, a preparation method thereof and a foldable display device. BACKGROUND

[0002] With the development of the hyperlink society, people interact with each other in the network, and people and objects interact through display services. Display technology continues to evolve and improve to consider user convenience. Organic light-emitting diode technology has driven the application of new foldable and flexible screens. Compared with rigid flat displays, these innovative displays are suitable for wearable devices, foldable smartphones, and medical sensors.

[0003] Pressure-sensitive adhesives are used to effectively combine high-transparency and viscoelasticity cover layers (such as cover glass and touch sensors) with various display layers. With the continuous progress of display technology, display layers gradually exhibit foldable characteristics, so pressure-sensitive adhesives also need to have corresponding properties. When the display layer is folded, it will be subjected to both tensile and compressive stresses. If the strain cannot recover quickly, the adhesive may sag and swell, and this residual strain will cause the adhesive to fail and peel off. Pressure-sensitive adhesives can adjust the neutral plane during folding and connect various foldable display layers. Flexible adhesives can form a partition between brittle substrates, thereby reducing the stress applied to the material during deformation and effectively preventing problems such as warping, delamination, and failure. In addition, residual stress relaxation performance helps to protect the adhesive from cracking and rapid fatigue failure.

[0004] Due to the low cohesive strength of the traditional linear polymer structure of polyacrylate (PSA), the polymer chains cannot be reversed and fully recovered. Although cross-linking can improve the recoverability of the polymer, it also needs to balance the relationship between its recovery ability and adhesion strength. Cross-linking can increase the internal connectivity and recyclability of polyacrylate, but it reduces the mobility of the polymer chains, thereby affecting the adhesion strength. In addition, cross-linking also limits the rearrangement ability of the polymer chains, further reducing the stress relaxation performance.

[0005] In order to maintain a certain peeling strength, traditional optical pressure-sensitive adhesives often have a low cross-linking density, which causes the optical adhesive to be unable to cope with the multiple folding or long-time bending state of the foldable display device, and prone to irreversible creep, thereby causing the phenomenon of debonding and opening of the adhesive.

[0006] Chinese invention patent CN110776855B discloses a UV light-cured high-transmittance optical adhesive and a preparation method thereof. In terms of weight parts, the raw material formula of the high-transmittance optical adhesive includes 20-50 parts of (meth) acrylate alkyl ester, 15-40 parts of (meth) acrylate hydroxyalkyl ester, 10-15 parts of N atom-containing polar monomer, 10-20 parts of active diluent, 0.1-2 parts of chain transfer agent, 0.5-1 part of thermal initiator, 0.5-1 part of photoinitiator, and 0.6-1.8 parts of other auxiliaries. The obtained product has the advantages of high transmittance and low haze. However, its modulus is relatively high, the anti-creep performance is poor, and irreversible deformation is prone to occur after multiple folding, thereby leading to bonding failure.

[0007] Chinese invention patent application CN113025240A provides a UV solvent-free optical adhesive and a preparation method thereof, which includes 50-95 parts of acrylic alkyl ester, 1-30 parts of acrylic ester with a fatty cyclic side chain, 1-30 parts of acrylic ester with a polar cyclic side chain, 1-30 parts of acrylic ester containing a polar group, 0.01-5 parts of multifunctional acrylic ester, and 0.02-2.0 parts of photoinitiator. Through the introduction of polar cyclic structure and non-polar cyclic structure for molecular design, the compatibility of the polar part and the non-polar part in the high molecular chain segment is strengthened while the glass transition temperature of the material is controlled, so that the optical performance, high temperature and humidity resistance, and water boiling whitening characteristics of the optical transparent adhesive film can be improved, and the optical adhesive film has good ink filling performance and easy reworkability. However, the patent cannot effectively cope with the stress generated during multiple folding, so its folding performance is lacking, and its transmittance is only 92%, which is poor in transmittance. SUMMARY

[0008] In order to overcome the above-mentioned defects and shortcomings of the prior art, the purpose of the present application is to provide a preparation method of a semi-interpenetrating double network organic gel OCA optical adhesive applied to a folding display device, which effectively solves the problem that the conventional optical pressure-sensitive adhesive cannot balance the bonding performance and folding resistance.

[0009] Another purpose of the present application is to provide a semi-interpenetrating double network organic gel OCA optical adhesive applied to a folding display device.

[0010] Still another purpose of the present application is to provide a folding display device.

[0011] The purpose of the present application is achieved by the following technical solutions:

[0012] The present application provides a preparation method of a semi-interpenetrating double network organic gel OCA optical adhesive applied to a folding display device, which includes the following steps:

[0013] Preparation of crosslinked network component: 20-80 parts of alkyl acrylate monomer, 5-20 parts of carboxyl-containing acrylic monomer, 0.05-1 part of crosslinking agent, 0.1-2 parts of thermal initiator, 90-240 parts of solvent are added into a reaction vessel, heated to 70-75℃, and reacted for 6-8h under the condition of 70-80r / min of rotation speed; after the reaction is completed, it is cooled to room temperature to discharge, to obtain the crosslinked network component;

[0014] Preparation of non-crosslinked network component: 20-80 parts of alkyl acrylate monomer, 5-20 parts of hydroxy acrylate monomer, 0.1-2 parts of thermal initiator, 0.5-1 part of chain transfer agent are added into a reaction vessel, heated to 70-75℃, and reacted for 6-8h under the condition of 70-80r / min of rotation speed; after the reaction is completed, it is cooled to room temperature to discharge, to obtain the non-crosslinked network component;

[0015] Preparation of semi-interpenetrating double network organic gel: 20-40 parts of crosslinked network component, 20-40 parts of non-crosslinked network component and 1-40 parts of polar small molecule are mixed uniformly and coated on a release film, and placed in an oven for drying at 60-80℃, to obtain a semi-interpenetrating double network organic gel OCA optical adhesive;

[0016] The polar small molecule is at least one of ethanol, n-propanol, isopropanol, n-butanol, isobutyl alcohol, n-pentanol, isopentanol, n-hexanol, heptanol, octanol, isooctanol, ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, glycerol, pentaerythritol, polyethylene glycol, and polypropylene glycol.

[0017] Preferably, the alkyl acrylate is at least one of methyl acrylate, ethyl acrylate, isopropyl acrylate, isoamyl acrylate, sec-butyl acrylate, n-butyl acrylate, isobornyl acrylate, 2-methylbutyl acrylate, 4-methyl-2-pentyl acrylate, 2-ethylhexyl acrylate, and isooctyl acrylate.

[0018] Preferably, the carboxyl-containing acrylic monomer is at least one of acrylic acid, methacrylic acid, and 2-carboxyethyl acrylate.

[0019] Preferably, the crosslinking agent is at least one of acetylacetone aluminum, aziridine, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, cyclohexanedimethanol di(meth)acrylate, alkoxylated cyclohexanedimethanol diacrylate, ethoxylated bisphenol A di(meth)acrylate, neopentyl glycol diacrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and urethane di(meth)acrylate.

[0020] Preferably, the thermal initiator is at least one of benzoyl peroxide or azobisisobutyronitrile.

[0021] Preferably, the hydroxy acrylate is at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.

[0022] Preferably, the chain transfer agent is at least one of dodecyl mercaptan or tertiary dodecyl mercaptan.

[0023] Preferably, the solvent is at least one of acetone, ethyl acetate, n-butyl acetate, n-hexane, n-heptane, benzene, toluene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane, methylcyclohexane, and anhydrous ethanol.

[0024] The application also provides a semi-interpenetrating polymer network organic gel OCA optical adhesive applied to a foldable display device, comprising a mixed material coated on a release film; the mixed material comprises 20-40 parts of a crosslinking network component, 20-40 parts of a non-crosslinking network component, and 1-40 parts of a polar small molecule;

[0025] The crosslinking network component is prepared after reaction of 20-80 parts of an alkyl acrylate monomer, 5-20 parts of a carboxyl-containing acrylic monomer, 0.05-1 part of a crosslinking agent, 0.1-2 parts of a thermal initiator, and 90-240 parts of a solvent;

[0026] The non-crosslinking network component is prepared after reaction of 20-80 parts of an alkyl acrylate monomer, 5-20 parts of a hydroxy acrylate monomer, 0.1-2 parts of a thermal initiator, and 0.5-1 part of a chain transfer agent;

[0027] The polar small molecule is at least one of ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, isopentanol, n-hexanol, heptanol, octanol, isooctanol, ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, glycerol, pentaerythritol, polyethylene glycol, and polypropylene glycol.

[0028] The application also provides a folding display device comprising the semi-interpenetrating double network organic gel OCA optical adhesive.

[0029] Compared with the prior art, the application has the following advantages and beneficial effects:

[0030] (1) The semi-interpenetrating double network organic gel OCA optical adhesive applied to the folding display device can improve the cohesive energy of the optical adhesive and thus enhance the creep resistance, can provide effective skeleton support to prevent irreversible deformation of the adhesive during folding, and can ensure good resilience of the adhesive and excellent fatigue resistance during folding.

[0031] (2) The semi-interpenetrating double network organic gel OCA optical adhesive applied to the folding display device of the application introduces polar small molecules, enhances the polarity of the substrate, and forms a large number of reversible hydrogen bonds between the molecules. These reversible hydrogen bonds can absorb a large amount of energy during the process of being destroyed and reconstructed, thereby providing good energy dissipation capacity for the adhesive and further reducing the generation of folding stress, thereby greatly improving the bending resistance of the optical adhesive.

[0032] (3) The semi-interpenetrating double network organic gel OCA optical adhesive applied to the folding display device of the application has a light transmittance of greater than 99% and a haze value of not more than 0.1%, has excellent optical properties, moderate initial adhesion and peeling force, and has a continuous bending resistance of more than 200,000 times, and can be widely applied to the device bonding of folding display devices. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a preparation schematic diagram of the A component in Example 1 of the application.

[0034] Figure 2 is a preparation schematic diagram of the B component in Example 1 of the application.

[0035] Figure 3 is a schematic diagram of the optical adhesive structure of the semi-interpenetrating double network organic gel in Example 1 of the application.

[0036] Figure 4 is a loss modulus-frequency curve diagram of Comparative Examples 1 and 2 and Example 1 of the application. DETAILED DESCRIPTION

[0037] The application will be further described in detail below with reference to examples, but the embodiments of the application are not limited thereto.

[0038] The thickness of the adhesive films prepared from Examples 1-3 and Comparative Examples 1-2 after photocuring was 25 μm before the mechanical and optical performance tests. In the mechanical performance tests, the initial tack was tested according to the national standard GB / T4852-2002, the holding power was tested according to the national standard GB / T4851-1998, and the peeling force was tested according to the national standard GB / T2792-1998. In the optical performance tests, the adhesive film was first transferred to optical glass, and then the transmittance and haze were tested using a Lambda950 UV-visible spectrophotometer and a haze meter, respectively. In the optical adhesive room temperature rheological performance tests, a DHR-2 rotary rheometer was used for the tests, the sample size was 8 mm in diameter x (0.8-1 mm) in thickness, the temperature was 25°C, the frequency was 1 Hz, and the test mode was shear. In the bending energy tests, the optical adhesive was coated on a PET film, the coating thickness was 120 μm, the coated film was placed in an oven at 50°C for 3 h, and then a clean PET film was pasted on the adhesive layer to form an ABA type sandwich (the upper and lower A layers were PET films, and the middle B layer was the optical adhesive). Then the sandwich was tested for folding using a flexibility tester (folding number 100000 times, folding angle 180°, speed 80 times / min), and then the PET film was observed for adhesive opening. In the test results, excellent indicated no opening, good indicated slight opening, and poor indicated opening.

[0039] Comparative Example 1

[0040] (1) 64 parts of isooctyl acrylate, 16 parts of 2-carboxyethyl acrylate, 0.4 parts of azobisisobutyronitrile, and 160 parts of ethyl acetate were added into a four-necked flask, heated to 75°C, and reacted at a rotation speed of 80 r / min for 6 h. Then 0.4 parts of aluminum acetylacetone was added and stirred for 15 min. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain component A (crosslinked network component).

[0041] (2) The adhesive solution containing only component A was coated on a release film. Then it was placed in an oven for 2 h, and dried at 60-80°C. Finally, an optical adhesive sample was obtained. The optical adhesive sample contained only a crosslinked single network.

[0042] Comparative Example 2

[0043] (1) 64 parts of isooctyl acrylate, 16 parts of 2-carboxyethyl acrylate, 0.4 parts of azobisisobutyronitrile, and 160 parts of ethyl acetate were added into a four-necked flask, heated to 75°C, and reacted at a rotation speed of 80 r / min for 6 h. Then 0.4 parts of aluminum acetylacetone was added and stirred for 15 min. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain component A (crosslinked network component).

[0044] (2) In weight parts, 64 parts of isooctyl acrylate, 16 parts of hydroxyethyl acrylate, 0.4 parts of azobisisobutyronitrile, 160 parts of ethyl acetate, 0.4 parts of dodecyl mercaptan were added to a four-necked flask, and the temperature was raised to 75°C, and the reaction was carried out at a rotation speed of 80 r / min for 6 h. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain the B component (non-crosslinked network component).

[0045] (3) In weight parts, 40 parts of the A component, 40 parts of the B component, and 5 parts of pentanediol (C component) were mixed uniformly and coated on a release film. Then, it was put into an oven for 2 h, and dried at 60-80°C. Finally, an optical adhesive sample was obtained. The optical adhesive sample was a semi-interpenetrating double network optical adhesive, and its structure is shown in

[0046] Example 1

[0047] (1) In weight parts, 64 parts of isooctyl acrylate, 16 parts of 2-carboxyethyl acrylate, 0.4 parts of azobisisobutyronitrile, and 160 parts of ethyl acetate were added to a four-necked flask, and the temperature was raised to 75°C, and the reaction was carried out at a rotation speed of 80 r / min for 6 h. Then, 0.4 parts of aluminum acetylacetone was added and stirred for 15 min. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain the A component (crosslinked network component), and its preparation process is shown in Figure 1 .

[0048] (2) In weight parts, 64 parts of isooctyl acrylate, 16 parts of hydroxyethyl acrylate, 0.4 parts of azobisisobutyronitrile, 160 parts of ethyl acetate, and 0.4 parts of dodecyl mercaptan were added to a four-necked flask, and the temperature was raised to 75°C, and the reaction was carried out at a rotation speed of 80 r / min for 6 h. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain the B component (non-crosslinked network component), and its preparation process is shown in Figure 2 .

[0049] (3) In weight parts, 40 parts of the A component, 40 parts of the B component, and 5 parts of pentanediol (C component) were mixed uniformly and coated on a release film. Then, it was put into an oven for 2 h, and dried at 60-80°C. Finally, an optical adhesive sample was obtained. The optical adhesive sample was a semi-interpenetrating double network optical adhesive, and its structure is shown in Figure 3 .

[0050] Example 2

[0051] (1) In weight parts, 64 parts of isooctyl acrylate, 16 parts of 2-carboxyethyl acrylate, 0.4 parts of azobisisobutyronitrile, and 160 parts of ethyl acetate were added to a four-necked flask, and the temperature was raised to 75°C, and the reaction was carried out at a rotation speed of 80 r / min for 6 h. Then, 0.4 parts of aluminum acetylacetone was added and stirred for 15 min. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain the A component.

[0052] (2) In weight parts, 64 parts of isooctyl acrylate, 16 parts of hydroxyethyl acrylate, 0.4 parts of azobisisobutyronitrile, 160 parts of ethyl acetate, 0.4 parts of dodecyl mercaptan were added into a four-necked flask, and the temperature was raised to 75°C, and the reaction was carried out at a rotation speed of 80 r / min for 6 h. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain component B.

[0053] (3) In weight parts, 40 parts of component A, 40 parts of component B, and 10 parts of pentanediol (component C) were mixed uniformly and coated on a release film. Then, it was put into an oven for 2 h, and dried at 60-80°C. Finally, an optical adhesive sample was obtained. The optical adhesive sample was a semi-interpenetrating polymer network organic gel optical adhesive.

[0054] Example 3

[0055] (1) In weight parts, 64 parts of isooctyl acrylate, 16 parts of 2-carboxyethyl acrylate, 0.4 parts of azobisisobutyronitrile, 160 parts of ethyl acetate were added into a four-necked flask, and the temperature was raised to 75°C, and the reaction was carried out at a rotation speed of 80 r / min for 6 h, and then 0.4 parts of aluminum acetylacetate was added and stirred for 15 min. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain component A.

[0056] (2) In weight parts, 64 parts of isooctyl acrylate, 16 parts of hydroxyethyl acrylate, 0.4 parts of azobisisobutyronitrile, 160 parts of ethyl acetate, 0.4 parts of dodecyl mercaptan were added into a four-necked flask, and the temperature was raised to 75°C, and the reaction was carried out at a rotation speed of 80 r / min for 6 h. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain component B.

[0057] (3) In weight parts, 40 parts of component A, 40 parts of component B, and 15 parts of pentanediol (component C) were mixed uniformly and coated on a release film. Then, it was put into an oven for 2 h, and dried at 60-80°C. Finally, an optical adhesive sample was obtained. The optical adhesive sample was a semi-interpenetrating polymer network organic gel optical adhesive.

[0058] Example 4

[0059] (1) Preparation of component A: In weight parts, 64 parts of butyl acrylate, 16 parts of acrylic acid, 0.4 parts of azobisisobutyronitrile, 160 parts of ethyl acetate were added into a four-necked flask, and the temperature was raised to 75°C, and the reaction was carried out at a rotation speed of 80 r / min for 6 h, and then 0.4 parts of aluminum acetylacetate was added and stirred for 15 min. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain component A.

[0060] (2) Preparation of B component: 64 parts of butyl acrylate, 16 parts of hydroxypropyl acrylate, 0.4 parts of azobisisobutyronitrile, 160 parts of ethyl acetate, and 0.4 parts of dodecyl mercaptan were added into a four-necked flask, and the temperature was raised to 75°C. The reaction was carried out at a rotation speed of 80 r / min for 6 h. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain the B component.

[0061] (3) Preparation of OCA optical adhesive: 50 parts of the A component, 30 parts of the B component, and 5 parts of 1,4-butanediol (C component) were uniformly mixed and coated on a release film. Then, the mixture was placed in an oven for 2 h, and dried at 60-80°C. Finally, an optical adhesive sample was obtained. The optical adhesive sample was a semi-interpenetrating double network organic gel optical adhesive.

[0062] Example 5

[0063] (1) Preparation of A component: 64 parts of butyl acrylate, 16 parts of acrylic acid, 0.4 parts of azobisisobutyronitrile, and 160 parts of ethyl acetate were added into a four-necked flask, and the temperature was raised to 75°C. The reaction was carried out at a rotation speed of 80 r / min for 6 h. Then, 0.4 parts of aluminum acetylacetate was added and stirred for 15 min. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain the A component.

[0064] (2) Preparation of B component: 64 parts of butyl acrylate, 16 parts of hydroxypropyl acrylate, 0.4 parts of azobisisobutyronitrile, 160 parts of ethyl acetate, and 0.4 parts of dodecyl mercaptan were added into a four-necked flask, and the temperature was raised to 75°C. The reaction was carried out at a rotation speed of 80 r / min for 6 h. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain the B component.

[0065] (3) Preparation of OCA optical adhesive: 50 parts of the A component, 30 parts of the B component, and 20 parts of polypropylene glycol (Mn = 200) (C component) were uniformly mixed and coated on a release film. Then, the mixture was placed in an oven for 2 h, and dried at 60-80°C. Finally, an optical adhesive sample was obtained. The optical adhesive sample was a semi-interpenetrating double network organic gel optical adhesive.

[0066] Example 6

[0067] (1) Preparation of A component: 64 parts of isooctyl acrylate, 16 parts of 2-carboxyethyl acrylate, 0.4 parts of azobisisobutyronitrile, and 160 parts of ethyl acetate were added into a four-necked flask, and the temperature was raised to 75°C. The reaction was carried out at a rotation speed of 80 r / min for 6 h. Then, 0.4 parts of aluminum acetylacetate was added and stirred for 15 min. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain the A component.

[0068] (2) Preparation of B component: 64 parts of isooctyl acrylate, 16 parts of hydroxybutyl acrylate, 0.4 parts of azobisisobutyronitrile, 160 parts of ethyl acetate, and 0.4 parts of dodecyl mercaptan were added into a four-necked flask, and the temperature was raised to 75°C. The reaction was carried out at a rotation speed of 80 r / min for 6 h. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain the B component.

[0069] (3) Preparation of OCA optical adhesive: 30 parts of the A component, 50 parts of the B component, and 10 parts of amyl alcohol (C component) were uniformly mixed and coated on a release film. Then, the mixture was placed in an oven for 2 h, and dried at 60-80°C. Finally, an optical adhesive sample was obtained. The optical adhesive sample was a semi-interpenetrating double network organic gel optical adhesive.

[0070] Example 7

[0071] (1) Preparation of A component: 48 parts of isooctyl acrylate, 16 parts of methyl acrylate, 16 parts of 2-carboxyethyl acrylate, 0.4 parts of azobisisobutyronitrile, and 160 parts of ethyl acetate were added into a four-necked flask, and the temperature was raised to 75°C. The reaction was carried out at a rotation speed of 80 r / min for 6 h. Then, 0.4 parts of aluminum acetylacetate was added and stirred for 15 min. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain the A component.

[0072] (2) Preparation of B component: 48 parts of isooctyl acrylate, 16 parts of methyl acrylate, 16 parts of hydroxypropyl acrylate, 0.4 parts of azobisisobutyronitrile, 160 parts of ethyl acetate, and 0.4 parts of dodecyl mercaptan were added into a four-necked flask, and the temperature was raised to 75°C. The reaction was carried out at a rotation speed of 80 r / min for 6 h. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain the B component.

[0073] (3) Preparation of OCA optical adhesive: 40 parts of the A component, 40 parts of the B component, and 5 parts of isooctyl alcohol (C component) were uniformly mixed and coated on a release film. Then, the mixture was placed in an oven for 2 h, and dried at 60-80°C. Finally, an optical adhesive sample was obtained. The optical adhesive sample was a semi-interpenetrating double network organic gel optical adhesive.

[0074] Example 8

[0075] (1) Preparation of A component: 64 parts of isooctyl acrylate, 16 parts of 2-carboxyethyl acrylate, 0.4 parts of azobisisobutyronitrile, and 160 parts of ethyl acetate were added into a four-necked flask, and the temperature was raised to 75°C. The reaction was carried out at a rotation speed of 80 r / min for 6 h. Then, 0.4 parts of aluminum acetylacetate was added and stirred for 15 min. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain the A component.

[0076] (2) Preparation of B component: 64 parts of isooctyl acrylate, 16 parts of hydroxybutyl acrylate, 0.4 parts of azobisisobutyronitrile, 160 parts of ethanol, and 0.4 parts of dodecyl mercaptan were added into a four-necked flask, and the temperature was raised to 75°C. The reaction was carried out at a rotation speed of 80 r / min for 6 h. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain the B component.

[0077] (3) Preparation of OCA optical adhesive: 40 parts of A component, 40 parts of B component, and 10 parts of propylene glycol (C component) were uniformly mixed and coated on a release film. Then, the mixture was placed in an oven for 2 h, and dried at 60-80°C. Finally, an optical adhesive sample was obtained. The optical adhesive sample was a semi-interpenetrating double network organic gel optical adhesive.

[0078] Example 9

[0079] (1) Preparation of A component: 64 parts of isooctyl acrylate, 16 parts of 2-carboxyethyl acrylate, 0.4 parts of azobisisobutyronitrile, and 160 parts of ethanol were added into a four-necked flask, and the temperature was raised to 75°C. The reaction was carried out at a rotation speed of 80 r / min for 6 h, and then 0.4 parts of aluminum acetylacetone was added and stirred for 15 min. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain the A component.

[0080] (2) Preparation of B component: 60 parts of isooctyl acrylate, 20 parts of hydroxyethyl acrylate, 0.4 parts of azobisisobutyronitrile, 160 parts of ethyl acetate, and 0.4 parts of dodecyl mercaptan were added into a four-necked flask, and the temperature was raised to 75°C. The reaction was carried out at a rotation speed of 80 r / min for 6 h. After the reaction was completed, the temperature was lowered to room temperature, and the product was discharged to obtain the B component.

[0081] (3) Preparation of OCA optical adhesive: 50 parts of A component, 50 parts of B component, and 15 parts of octanediol (C component) were uniformly mixed and coated on a release film. Then, the mixture was placed in an oven for 2 h, and dried at 60-80°C. Finally, an optical adhesive sample was obtained. The optical adhesive sample was a semi-interpenetrating double network organic gel optical adhesive.

[0082] Optical adhesive transmittance, bonding, mechanical, and folding resistance performance analysis

[0083] According to the above test methods, the comprehensive performance of the samples of Examples 1-9 and Comparative Examples 1-2 was analyzed, and the results are shown in Table 1.

[0084] Table 1. Performance test table of samples of Examples 1-9 and Comparative Examples 1-2

[0085]

[0086]

[0087] From the data in Table 1, first, the silicone-modified acrylate OCA optical adhesive prepared by the application examples 1-9 has moderate soft and hard monomer ratio, moderate initial adhesion (6-8 ball), which meets the ideal value of international high-end OCA optical adhesive film and meets the industry requirements. In examples 1-9, due to the addition of small polar molecules, the cohesive energy between molecular chains is reduced, which plays a similar role to plasticizers, so the holding adhesion of examples 1-9 is relatively lower than that of comparative examples 1 and 2, but still greater than 100h, fully meeting the requirements. And the peeling force is enhanced due to the introduction of small polar molecules, so with the increase of the content of small polar molecules, the peeling strength shows an upward trend.

[0088] The transmittance of the OCA optical adhesive film prepared by examples 1-9 is greater than 99%, and the haze value is not more than 0.2%; this is mainly because all the raw materials are colorless and do not contain color groups, and these monomers will not discolor after free radical polymerization. In addition, since the raw materials used basically do not contain water molecules, the water vapor in the film is very little; and because the formula contains hydroxyl-containing acrylate monomers, the little water vapor will be uniformly dispersed and will not cause the formation of turbidity points. Compared with Chinese invention patent application CN113025240A, the optical adhesive of the application has more excellent light transmission efficiency and lower haze, and has better display effect.

[0089] Examples 1-9 prepared by the application examples 1-9 are semi-interpenetrating double network organic gel systems, while comparative example 1 is a single network system, and comparative example 2 is a semi-interpenetrating double network system, and the folding performance of examples 1-9 is better than that of comparative examples 1 and 2. This is because the crosslinked network in the semi-interpenetrating double network organic gel system can provide effective skeleton support, prevent irreversible deformation of the adhesive during folding, ensure good resilience of the adhesive, and provide excellent fatigue resistance during folding; and the uncrosslinked network is almost a linear macromolecule, which can provide certain wetting ability for the adhesive and enhance the bonding with the substrate; the small polar molecules further enhance the polarity of the substrate, so that a large number of reversible hydrogen bonds are formed between the molecules, and these reversible hydrogen bonds can absorb a large amount of energy during the destruction and reconstruction process, providing good energy dissipation capacity for the adhesive, thereby further reducing the generation of folding stress. Figure 4is the loss modulus-frequency curve diagram of Comparative Example 1, 2 and Example 1, the loss modulus of Example 1 is the largest, that of Comparative Example 2 is the second, and that of Comparative Example 1 is the smallest, which indicates that Example 1 has the best energy dissipation capacity, and can effectively convert the stress and energy generated in the folding process into heat dissipation, thereby preventing the phenomenon of colloid damage in the folding process, which further proves that the optical adhesive of the application has better folding resistance. Compared with Chinese Invention Patent CN110776855B, the patent has only a single network system and less reversible structure, and cannot effectively absorb stress in the folding process, so it cannot cope with the folding process of more than 100,000 times in the long-term use of the folding display device.

[0090] In summary, compared with the optical pressure-sensitive adhesive for display devices in the prior art, the application first effectively improves the folding resistance of the optical adhesive by constructing a semi-interpenetrating double network system and an organic gel system. The optical adhesive of the application has the advantages of good bonding performance and folding resistance, which makes it have a broad application prospect in foldable flexible electronic display devices.

[0091] The above examples are the preferred embodiments of the application, but the embodiments of the application are not limited by the examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the application shall be equivalent replacement methods, and are all included in the protection scope of the application.

Claims

1. A method for preparing a semi-interpenetrating double network organic gel (OCA) optical adhesive applied to a foldable display device, characterized in that, The method comprises the following steps: Preparation of crosslinked network component: 20-80 parts of alkyl acrylate monomer, 5-20 parts of carboxyl-containing acrylic monomer, 0.05-1 part of crosslinking agent, 0.1-2 parts of thermal initiator, 90-240 parts of solvent are added into a reaction container, and the temperature is raised to 70-75 DEG C, and the reaction is carried out at a rotation speed of 70-80 r / min for 6-8 h; after the reaction is completed, the temperature is lowered to room temperature, and the material is discharged, to obtain the crosslinked network component; Preparation of non-crosslinked network component: 20-80 parts of alkyl acrylate monomer, 5-20 parts of hydroxy acrylate monomer, 0.1-2 parts of thermal initiator, 0.5-1 part of chain transfer agent are added into a reaction container, and the temperature is raised to 70-75 DEG C, and the reaction is carried out at a rotation speed of 70-80 r / min for 6-8 h; after the reaction is completed, the temperature is lowered to room temperature, and the material is discharged, to obtain the non-crosslinked network component; Preparation of semi-interpenetrating polymer network organic gel: 20-40 parts of crosslinked network component, 20-40 parts of non-crosslinked network component and 1-40 parts of polar small molecule are mixed uniformly and coated on a release film, and then placed in an oven and dried at 60-80 DEG C, to obtain a semi-interpenetrating polymer network organic gel OCA optical adhesive; The polar small molecule is at least one of ethanol, n-propanol, isopropanol, n-butanol, isobutyl alcohol, n-pentanol, isopentanol, n-hexanol, heptanol, octanol, isooctanol, ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, glycerol, pentaerythritol. 2.The method for preparing a semi-interpenetrating double network organic gel OCA optical adhesive applied to a foldable display device according to claim 1, wherein, The alkyl acrylate is at least one of methyl acrylate, ethyl acrylate, isopropyl acrylate, isoamyl acrylate, sec-butyl acrylate, n-butyl acrylate, isobornyl acrylate, 2-methylbutyl acrylate, 4-methyl-2-pentyl acrylate, and isooctyl acrylate. 3.The method for preparing a semi-interpenetrating double network organic gel OCA optical adhesive applied to a foldable display device according to claim 1, wherein, The carboxyl-containing acrylic monomer is at least one of acrylic acid, methacrylic acid, and 2-carboxyethyl acrylate. 4.The method for preparing a semi-interpenetrating double network organic gel OCA optical adhesive applied to a foldable display device according to claim 1, wherein, The crosslinking agent is at least one of acetylacetone aluminum, aziridine, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, cyclohexanedimethanol di(meth)acrylate, alkoxylated cyclohexanedimethanol diacrylate, ethoxylated bisphenol A di(meth)acrylate, neopentyl glycol diacrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and urethane di(meth)acrylate. 5.The method for preparing a semi-interpenetrating double network organic gel OCA optical adhesive applied to a foldable display device according to claim 1, wherein, The thermal initiator is at least one of benzoyl peroxide or azobisisobutyronitrile. 6.The method for preparing a semi-interpenetrating double network organic gel OCA optical adhesive applied to a foldable display device according to claim 1, wherein, The hydroxy acrylate monomer is at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate. 7.The method for preparing a semi-interpenetrating double network organic gel OCA optical adhesive applied to a foldable display device according to claim 1, wherein, The chain transfer agent is dodecyl mercaptan. 8.The method for preparing a semi-interpenetrating double network organic gel OCA optical adhesive applied to a foldable display device according to claim 1, wherein, The solvent is at least one of acetone, ethyl acetate, n-butyl acetate, n-hexane, n-heptane, benzene, toluene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane, methylcyclohexane, anhydrous ethanol. 9.A semi-interpenetrating double network organic gel (OCA) optical adhesive applied to a foldable display device, characterized in that, The mixed material coated on the release film; the mixed material comprises 20-40 parts of crosslinked network component, 20-40 parts of non-crosslinked network component and 1-40 parts of small polar molecules; The crosslinked network component is prepared after reaction of 20-80 parts of alkyl acrylate monomer, 5-20 parts of carboxyl-containing acrylic monomer, 0.05-1 part of crosslinking agent, 0.1-2 parts of thermal initiator and 90-240 parts of solvent; The non-crosslinked network component is prepared after reaction of 20-80 parts of alkyl acrylate monomer, 5-20 parts of hydroxy acrylate monomer, 0.1-2 parts of thermal initiator and 0.5-1 part of chain transfer agent; The small polar molecules are at least one of ethanol, n-propanol, isopropanol, n-butanol, isobutyl alcohol, n-pentanol, isoamyl alcohol, n-hexanol, heptanol, octanol, isooctanol, ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, glycerol, pentaerythritol.

10. A foldable display device, characterized by, The semi-interpenetrating double network organic gel OCA optical adhesive for the folding display device of claim 9 is provided.

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