A low-stress optical transparent pressure-sensitive adhesive composition suitable for full-lamination of large-size display modules and a preparation method thereof

Abstract

The present application relates to a kind of low stress optical transparent pressure sensitive adhesive composition suitable for large size display module full bonding and preparation method thereof.A kind of low stress optical transparent pressure sensitive adhesive composition suitable for large size display module full bonding, comprising: partially acrylate-terminated polyurethane prepolymer 30-50 parts, low glass transition temperature acrylate monomer 15-40 parts, high glass transition temperature acrylate monomer 5~30 parts, functional acrylate monomer 5-30 parts, photoinitiator 0.5~2 parts, thiol chain transfer agent 0.1~1 parts, antioxidant 2~5 parts.The present application also provides the preparation method of low stress optical transparent pressure sensitive adhesive of large size display module full bonding.The pressure sensitive adhesive composition described in the present application has very low bonding stress and suitable peel strength, after adding thiol chain transfer agent, bonding stress is further reduced while peel strength is significantly increased, suitable for stress sensitive large size display module full bonding process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of large-size display module optical transparent adhesive, in particular to a low-stress optical transparent pressure-sensitive adhesive composition suitable for full bonding of large-size display modules and a preparation method thereof. BACKGROUND

[0002] With the further development of the 5G era, display technology has a huge impact on human life, and the demand for high-quality ultra-high-definition display is increasing. At present, super large size display modules (> 80 inches) have quite a number of application scenarios and target customer groups.

[0003] Chinese patent application No. CN202410505460.3 "Aging-resistant hot melt pressure-sensitive adhesive and its preparation method and preparation device" suggests an aging-resistant hot melt pressure-sensitive adhesive and its preparation method and preparation device, which belong to the technical field of pressure-sensitive adhesive. The aging-resistant hot melt pressure-sensitive adhesive comprises the following components: 50-60 parts by weight of SIS / SI composition, 60-70 parts by weight of tackifier, 45-55 parts by weight of plasticizer, 1-2 parts by weight of aging-resistant agent, 1-2 parts by weight of modified sepiolite, and 3-5 parts by weight of pre-capped polyurethane acrylate microcapsules. The glue applicator in the preparation device is composed of multiple parallel arranged glue applicators, and each glue applicator has three glue outlets. The polyurethane acrylate is pre-capped, and the polyurethane acrylate is used as an auxiliary functional resin, which can increase the flexibility of the hot melt pressure-sensitive adhesive, reduce stress shrinkage, and improve adhesion.

[0004] PCT / EP2019 / 063595 "Removable pressure-sensitive adhesive strip" suggests a pressure-sensitive adhesive strip which can be removed again without residue and non-destructively by extensive stretching essentially in the adhesive plane, comprising a pressure-sensitive adhesive layer HK1, characterized in that the at least one surface pressure-sensitive adhesive layer HK1 has one or more, preferably a plurality of pressure-sensitive adhesive structural elements which result in a structured surface profile of the pressure-sensitive adhesive strip, wherein preferably the pressure-sensitive adhesive layer HK1 and the structural elements together represent a single-layer structure. The PSA layer and the structural elements are independently of each other based on vinyl aromatic block copolymer, poly(meth)acrylate, poly(meth)acrylate block copolymer, silicone, nitrile rubber, or mixtures thereof, more particularly on vinyl aromatic block copolymer, and the carrier uses polyurethane.

[0005] PCT / KR2018 / 009396《Adhesive film, adhesive composition therefor anddisplay member comprising same》suggests an adhesive film, an adhesive composition therefor, and a display member comprising the same. The adhesive film is formed from an adhesive composition including urethane resin, isocyanate curing agent, polyfunctional (meth)acrylate monomer, photoinitiator, and thermal initiator. The adhesive film has a peel strength ratio of 0.1 or less than 0.1, an initial peel strength of 30 g / 25 mm or greater than 30 g / 25 mm, and a maximum load of 1 kg or greater, while at the maximum load, the adhesive film does not generate particles or burrs due to scattering when evaluated in the scattering property. It has high peel strength against an OLED panel or an inorganic layer stacked on the OLED panel before ultraviolet irradiation to protect the OLED panel, and low peel strength against the OLED or the inorganic layer after ultraviolet irradiation to ensure good re-peeling properties.

[0006] US16 / 729099《Pressure sensitive adhesive composition and protective filmemploying the same》suggests a pressure sensitive adhesive composition and a protective film employing the same. The pressure sensitive adhesive composition includes 30-45 parts by weight of a tackifier; and 55-70 parts by weight of a polymer. The polymer includes at least one block copolymer. The total weight of the tackifier and the polymer is 100 parts by weight. The block copolymer includes an ethylene aromatic block polymerized from an ethylene aromatic monomer and a conjugated diene block polymerized from a conjugated diene monomer, and the block copolymer satisfies one of the following conditions: (1) the content of the ethylene aromatic monomer is 15 wt% to 25 wt% based on the total weight of the block copolymer, and the content of vinyl groups in the conjugated diene block is less than or equal to 45 wt% based on the weight of the conjugated diene block; or (2) the content of the ethylene aromatic monomer is 10 wt% to 15 wt% based on the total weight of the block copolymer, and the content of vinyl groups in the conjugated diene block is less than or equal to 45 wt% or greater than or equal to 60 wt% based on the weight of the conjugated diene block.

[0007] However, the existing optical transparent pressure sensitive adhesive for full lamination of large size display module still has practical problems such as the use of multiple volatile substances to regulate the viscosity, low bonding strength, uncontrolled stress after lamination leading to display defects, etc. SUMMARY

[0008] To solve the above technical problems, the present application aims at: providing a low-stress optical transparent pressure-sensitive adhesive composition suitable for full-lamination of large-size display modules.

[0009] The present application further aims at: providing a preparation method of the above low-stress optical transparent pressure-sensitive adhesive composition suitable for full-lamination of large-size display modules.

[0010] In the first aspect, the present application provides a low-stress optical transparent pressure-sensitive adhesive composition suitable for full-lamination of large-size display modules, which adopts the following technical solution:

[0011] The low-stress optical transparent pressure-sensitive adhesive composition suitable for full-lamination of large-size display modules, the raw materials of the pressure-sensitive composition include the following components by weight: 30-50 parts of partially acrylate-terminated polyurethane prepolymer, 15-40 parts of low glass transition temperature acrylate monomer, 5-30 parts of high glass transition temperature acrylate monomer, 5-30 parts of functional acrylate monomer, 0.5-2 parts of photoinitiator, 0.1-1 part of thiol chain transfer agent, and 2-5 parts of antioxidant; wherein the partially acrylate-terminated polyurethane prepolymer includes polyurethane prepolymer terminated with both partial isocyanate groups and partial acrylate groups; and the thiol chain transfer agent includes one or a combination of n-dodecanethiol, n-octadecanethiol, 1,4-butanediol bis(3-mercaptobutyrate), and pentaerythritol tetra(3-sec-mercaptopropionate).

[0012] By adopting the above technical solution, the pressure-sensitive adhesive composition obtained from the formula system of partially acrylate-terminated polyurethane prepolymer, low glass transition temperature acrylate monomer, high glass transition temperature acrylate monomer, and functional acrylate monomer has extremely low lamination stress and appropriate peel strength, and the lamination stress is further reduced and the peel strength is significantly increased after adding the thiol chain transfer agent, which is suitable for full-lamination process of large-size display modules sensitive to stress.

[0013] On the basis of the above solution, the photoinitiator includes one of 2,4,6-trimethylbenzoyl phenyl ethyl phosphonate, photoinitiator 184, photoinitiator 1173, and (2,4,6-trimethylbenzoyl) diphenyl phosphine oxide.

[0014] On the basis of the above solution, the antioxidant is one of antioxidant 264 and antioxidant 1135.

[0015] The present application further provides a preparation method of the low-stress optical transparent pressure-sensitive adhesive composition suitable for full-lamination of large-size display modules as described in any one of the above, which includes the following steps:

[0016] The anti-aging agent, the photoinitiator, the high glass transition temperature acrylate monomer, the low glass transition temperature acrylate monomer and the functional acrylate monomer are mixed under a yellow light source to be fully dissolved, and then the partial acrylate-terminated polyurethane prepolymer and the thiol chain transfer agent are continuously stirred and mixed to be uniform, so that a transparent pressure-sensitive adhesive composition is obtained.

[0017] In a specific embodiment, the partial acrylate-terminated polyurethane prepolymer is prepared from a raw material including a polyurethane prepolymer terminated by partial isocyanate groups and partial acrylate groups, and a monofunctional small molecule alcohol.

[0018] Preferably, the monofunctional small molecule alcohol includes one of methanol, ethanol and n-butanol.

[0019] Preferably, the polyurethane prepolymer terminated by partial isocyanate groups and partial acrylate groups is prepared from a monohydroxy acrylate, an aliphatic diisocyanate and a polyether diol, the monohydroxy acrylate is one of hydroxyethyl acrylate, hydroxypropyl acrylate and hydroxybutyl acrylate, the aliphatic diisocyanate is one of hexamethylene diisocyanate, isophorone diisocyanate and 4,4'-dicyclohexyl methane diisocyanate, and the isocyanate index (R value) is 1.2-2.0, and the polyether diol is a polypropylene oxide diol with a molecular weight of 200-8000 or a polytetrahydrofuran diol with a molecular weight of 1000-3000.

[0020] The application also provides a preparation method of the partial acrylate-terminated polyurethane prepolymer, including the following steps:

[0021] 1) Preparation of the polyurethane prepolymer terminated by partial isocyanate groups and partial acrylate groups

[0022] The polyether diol is first dehydrated at 110 °C for 2 h, then cooled to 70 °C, and then the aliphatic diisocyanate is reacted under catalysis of a catalyst for 3-6 h to obtain the polyurethane prepolymer terminated by isocyanate groups; then cooled to 60 °C, and the monohydroxy acrylate is further reacted for 1-2 h to obtain the polyurethane prepolymer terminated by partial isocyanate groups and partial acrylate groups;

[0023] 2) Preparation of the partial acrylate-terminated polyurethane prepolymer

[0024] The polyurethane prepolymer terminated by partial isocyanate groups and partial acrylate groups and the monofunctional small molecule alcohol are reacted at 60 °C for 1-2 h to obtain the partial acrylate-terminated polyurethane prepolymer.

[0025] The mechanism is: polyether diol is dehydrated to obtain an isocyanate-terminated polyurethane prepolymer by reacting with aliphatic diisocyanate under the action of a catalyst, further adding a hydroxy acrylate monomer to obtain a partially isocyanate-terminated and partially acrylate-terminated polyurethane prepolymer, and finally adding the partially isocyanate-terminated and partially acrylate-terminated polyurethane prepolymer and a monofunctional small molecule alcohol to obtain a stable partially acrylate-terminated polyurethane prepolymer.

[0026] In a specific embodiment, the average acrylate number of the partially acrylate-terminated polyurethane prepolymer is 1.2.

[0027] In a specific embodiment, the weight average molecular weight of the partially acrylate-terminated polyurethane prepolymer is between 5-25 kg / mol. -1

[0028] The present application has the following beneficial technical effects:

[0029] The pressure-sensitive adhesive composition has extremely low bonding stress and suitable peeling strength, and after the addition of a thiol chain transfer agent, the bonding stress is further reduced and the peeling strength is significantly increased, which is suitable for the full bonding process of large-size display modules sensitive to stress. BRIEF DESCRIPTION OF DRAWINGS

[0030] Fig. 1 The GPC curve of a partially acrylate-terminated polyurethane prepolymer obtained from Preparation Example 1;

[0031] Fig. 2 The GPC curve of a partially acrylate-terminated polyurethane prepolymer obtained from Preparation Example 2;

[0032] Fig. 3 The GPC curve of a partially acrylate-terminated polyurethane prepolymer obtained from Preparation Example 3. DETAILED DESCRIPTION

[0033] All raw materials in the examples can be obtained by market purchase. Among them,

[0034] The low glass transition temperature acrylate monomer is preferably isooctyl acrylate.

[0035] The high glass transition temperature acrylate monomer is preferably isobornyl acrylate.

[0036] The functional acrylate monomer is preferably hydroxyethyl acrylate.

[0037] The monofunctional small molecule alcohol includes but is not limited to one of methanol, ethanol, and n-butanol, and methanol is preferred in the present application.

[0038] ​The acrylic monomers containing hydroxyl groups include, but are not limited to, one of hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxybutyl acrylate, with hydroxyethyl acrylate being preferred in this application.

[0039] Aliphatic diisocyanates include, but are not limited to, one of hexamethylene diisocyanate, isophorone diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate, and have an isocyanate index (R value) of 1.2-2.0. In this application, isophorone diisocyanate with an isocyanate index (R value) of 1.6 is preferred.

[0040] Polyether diols include, but are not limited to, polypropylene oxide diols with a molecular weight of 1000-4000 or polytetrahydrofuran diols with a molecular weight of 1000-2000. In this application, polypropylene glycol 1000, polypropylene glycol 2000 and polypropylene glycol 4000 are preferred.

[0041] Photoinitiators include, but are not limited to, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, photoinitiator 184, photoinitiator 1173, and (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, with (2,4,6-trimethylbenzoyl)diphenylphosphine oxide being the preferred choice in this application.

[0042] Thiol chain transfer agents include, but are not limited to, one or a combination of n-dodecyl mercaptan, n-octadecyl mercaptan, 1,4-butanediol bis(3-mercaptobutyrate), and pentaerythritol tetra(3-secondary mercaptopropionate), with n-dodecyl mercaptan being preferred in this application.

[0043] Antioxidants include, but are not limited to, one of antioxidant 264 and antioxidant 1135, with antioxidant 264 being preferred in this application.

[0044] Preparation Example 1

[0045] A partially acrylate-terminated polyurethane prepolymer is provided, prepared according to the following steps:

[0046] 0.1 mol of polypropylene glycol 1000 was first dehydrated at 110°C for 2 h and then added to a three-necked flask. The temperature was then lowered to 70°C, and 0.05 wt% of organotin catalyst was added. 0.16 mol of isophorone diisocyanate was then slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Subsequently, the temperature was lowered to 60°C, and 0.072 mol of hydroxyethyl acrylate was added and reacted for another 2 h to obtain a polyurethane prepolymer containing both isocyanate-terminated and acrylate-terminated groups.

[0047] A polyurethane prepolymer containing partially isocyanate-terminated and partially acrylate-terminated groups was reacted with 0.048 mol of methanol for 2 h to obtain a polyurethane prepolymer with partially acrylate-terminated groups.

[0048] The number-average molecular weight of the acrylate-terminated polyurethane prepolymer is 3.8 kg mol. -1 The weight-average molecular weight is 5.7 kg mol. -1 The dispersion is 1.5, and the GPC curve is as follows: Fig. 1 .

[0049] Preparation Example 2

[0050] A partially acrylate-terminated polyurethane prepolymer is provided, prepared according to the following steps:

[0051] 0.1 mol of polypropylene glycol 2000 was first dehydrated at 110°C for 2 h and then added to a three-necked flask. The temperature was then lowered to 70°C, and 0.05 wt% of organotin catalyst was added. 0.16 mol of isophorone diisocyanate was then slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Subsequently, the temperature was lowered to 60°C, and 0.072 mol of hydroxyethyl acrylate was added and reacted further for 2 h to obtain a polyurethane prepolymer containing both isocyanate-terminated and acrylate-terminated groups.

[0052] A polyurethane prepolymer containing partially isocyanate-terminated and partially acrylate-terminated groups was reacted with 0.048 mol of methanol for 2 h to obtain a polyurethane prepolymer with partially acrylate-terminated groups.

[0053] The number-average molecular weight of the partially acrylate-terminated polyurethane prepolymer is 6.8 kg mol. -1 The weight-average molecular weight is 10.5 kg mol. -1 The dispersion is 1.5, and the GPC curve is as follows: Fig. 2 .

[0054] Preparation Example 3

[0055] A partially acrylate-terminated polyurethane prepolymer is provided, prepared according to the following steps:

[0056] 0.1 mol of polypropylene glycol 4000 was first dehydrated at 110℃ for 2 h and then added to a three-necked flask. The temperature was then lowered to 70℃, and 0.05 wt% of organotin catalyst was added. 0.16 mol of isophorone diisocyanate was then slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Subsequently, the temperature was lowered to 60℃, and 0.072 mol of hydroxyethyl acrylate was added and reacted further for 2 h to obtain a polyurethane prepolymer containing both isocyanate-terminated and acrylate-terminated groups.

[0057] A polyurethane prepolymer containing partially isocyanate-terminated and partially acrylate-terminated groups was reacted with 0.048 mol of methanol for 2 h to obtain a polyurethane prepolymer with partially acrylate-terminated groups. The number average molecular weight was 14.6 kgmol. -1 The weight-average molecular weight is 24.3 kg mol. -1 The dispersion is 1.7, and the GPC curve is as follows: Fig. 3 .

[0058] Example 1

[0059] A low-stress optically transparent pressure-sensitive adhesive composition suitable for full lamination of large-size display modules is provided, which is prepared according to the following steps:

[0060] 30 g of isooctyl acrylate with a low glass transition temperature, 30 g of functional acrylate monomer hydroxyethyl acrylate, 1 g of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, and 5 g of antioxidant 264 were added to a mixing tank and stirred to remove bubbles until completely dissolved. The stirring speed was 300 r / min for 10 min. Then, 40 g of the partially acrylate-terminated polyurethane prepolymer from Preparation Example 1 and 0.5 g of n-dodecyl mercaptan were added to the mixing tank and stirred at 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0061] The peel strength of the transparent pressure-sensitive adhesive composition is 796 gf / 25 mm and the stress is 19 kPa, as shown in Table 1.

[0062] Example 2

[0063] A low-stress optically transparent pressure-sensitive adhesive composition suitable for full lamination of large-size display modules is provided, which is prepared according to the following steps:

[0064] 30 g of isooctyl acrylate with a low glass transition temperature, 30 g of isobornyl acrylate with a high glass transition temperature, 1 g of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, and 5 g of antioxidant 264 were added to a mixing tank and mixed and stirred until completely dissolved at a stirring speed of 300 r / min for 10 min. Then, 40 g of the partially acrylate-terminated polyurethane prepolymer from Preparation Example 1 and 0.5 g of n-dodecyl mercaptan were added to the mixing tank and mixed at a stirring speed of 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0065] The peel strength of the transparent pressure-sensitive adhesive composition is 2066 gf / 25 mm and the stress is 35 kPa, as shown in Table 1.

[0066] Example 3

[0067] A low-stress optically transparent pressure-sensitive adhesive composition suitable for full lamination of large-size display modules is provided, which is prepared according to the following steps:

[0068] 30 g of isooctyl acrylate, 15 g of isobornyl acrylate with a high glass transition temperature, 15 g of functional acrylate monomer hydroxyethyl acrylate, 1 g of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, and 5 g of antioxidant 264 were added to a mixing tank and mixed and stirred until completely dissolved to remove bubbles. The stirring speed was 300 r / min for 10 min. Then, 40 g of the partially acrylate-terminated polyurethane prepolymer from Preparation Example 1 and 0.5 g of n-dodecyl mercaptan were added to the mixing tank and mixed at 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0069] The peel strength of the transparent pressure-sensitive adhesive composition is 1704 gf / 25 mm and the stress is 21 kPa, as shown in Table 1.

[0070] In Examples 1 to 3, the addition amounts of high glass transition temperature acrylate monomers and functional acrylate monomers were different, and the test performance showed significant differences.

[0071] Example 4

[0072] A low-stress optically transparent pressure-sensitive adhesive composition suitable for full lamination of large-size display modules is provided. This composition differs from the polyurethane prepolymer with partially acrylate-terminated groups added in Example 3, and is prepared according to the following steps:

[0073] 30 g of isooctyl acrylate, 15 g of isobornyl acrylate, 15 g of hydroxyethyl acrylate, 1 g of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, and 5 g of antioxidant 264 were added to a mixing tank and mixed and stirred until completely dissolved at a stirring speed of 300 r / min for 10 min. Then, 40 g of the partially acrylate-terminated polyurethane prepolymer from Preparation Example 2 and 0.5 g of n-dodecyl mercaptan were added to the mixing tank and mixed at a stirring speed of 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0074] The peel strength of the transparent pressure-sensitive adhesive composition is 1075 gf / 25 mm and the stress is 15 kPa, as shown in Table 1.

[0075] Example 5

[0076] A method for preparing a low-stress optically transparent pressure-sensitive adhesive composition suitable for full lamination of large-size display modules is provided, which differs from the polyurethane prepolymer with partially acrylate-terminated groups added in Example 3, and includes the following steps;

[0077] 30 g of isooctyl acrylate, 15 g of isobornyl acrylate, 15 g of hydroxyethyl acrylate, 1 g of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, and 5 g of antioxidant 264 were added to a mixing tank and mixed and stirred until completely dissolved at a stirring speed of 300 r / min for 10 min. Then, 40 g of the partially acrylate-terminated polyurethane prepolymer from Preparation Example 3 and 0.5 g of n-dodecyl mercaptan were added to the mixing tank and mixed at a stirring speed of 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0078] The peel strength of the transparent pressure-sensitive adhesive composition is 1849 gf / 25 mm and the stress is 31 kPa, as shown in Table 1.

[0079] Comparative Example 1

[0080] A low-stress optically transparent pressure-sensitive adhesive composition suitable for full lamination of large-size display modules is provided, which differs from Example 1 in that it does not contain n-dodecyl mercaptan, and is carried out according to the following steps;

[0081] 30 g of isooctyl acrylate, 30 g of hydroxyethyl acrylate, 1 g of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, and 5 g of antioxidant 264 were added to a mixing tank and stirred to remove bubbles until completely dissolved. The stirring speed was 300 r / min for 10 min. Then, 40 g of the partially acrylate-terminated polyurethane prepolymer from Preparation Example 1 was added to the mixing tank and stirred at 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0082] The peel strength of the transparent pressure-sensitive adhesive composition is 587 gf / 25 mm and the stress is 31 kPa, as shown in Table 1.

[0083] Comparative Example 2

[0084] A low-stress optically transparent pressure-sensitive adhesive composition suitable for full lamination of large-size display modules is provided. Unlike Example 2, it does not contain n-dodecyl mercaptan and is prepared according to the following steps:

[0085] 30 g of isooctyl acrylate, 30 g of isobornyl acrylate, 1 g of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, and 5 g of antioxidant 264 were added to a mixing tank and stirred to remove bubbles until completely dissolved. The stirring speed was 300 r / min for 10 min. Then, 40 g of the partially acrylate-terminated polyurethane prepolymer from Preparation Example 1 was added to the mixing tank and stirred at 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0086] The peel strength of the transparent pressure-sensitive adhesive composition is 967 gf / 25 mm and the stress is 50 kPa, as shown in Table 1.

[0087] Comparative Example 3

[0088] A low-stress optically transparent pressure-sensitive adhesive composition suitable for full lamination of large-size display modules is provided. Unlike Example 3, it does not contain n-dodecyl mercaptan and is prepared according to the following steps:

[0089] 30 g of isooctyl acrylate, 15 g of isobornyl acrylate, 15 g of hydroxyethyl acrylate, 1 g of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, and 5 g of antioxidant 264 were added to a mixing tank and stirred to remove bubbles until completely dissolved. The stirring speed was 300 r / min for 10 min. Then, 40 g of the partially acrylate-terminated polyurethane prepolymer from Preparation Example 1 was added to the mixing tank and stirred at 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0090] The peel strength of the transparent pressure-sensitive adhesive composition is 928 gf / 25 mm and the stress is 33 kPa, as shown in Table 1.

[0091] Comparative Example 4

[0092] A low-stress optically transparent pressure-sensitive adhesive composition suitable for full lamination of large-size display modules is provided. Unlike Example 4, it does not contain n-dodecyl mercaptan and is prepared according to the following steps:

[0093] 30 g of isooctyl acrylate, 15 g of isobornyl acrylate, 15 g of hydroxyethyl acrylate, 1 g of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, and 5 g of antioxidant 264 were added to a mixing tank and stirred to remove bubbles until completely dissolved. The stirring speed was 300 r / min for 10 min. Then, 40 g of the partially acrylate-terminated polyurethane prepolymer from Preparation Example 2 was added to the mixing tank and stirred at 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0094] The peel strength of the transparent pressure-sensitive adhesive composition is 547 gf / 25 mm and the stress is 30 kPa, as shown in Table 1.

[0095] Comparative Example 5

[0096] A low-stress optically transparent pressure-sensitive adhesive composition suitable for full lamination of large-size display modules is provided. Unlike Example 5, it does not contain n-dodecyl mercaptan and is prepared according to the following steps:

[0097] 30 g of isooctyl acrylate, 15 g of isobornyl acrylate, 15 g of hydroxyethyl acrylate, 1 g of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, and 5 g of antioxidant 264 were added to a mixing tank and stirred to remove bubbles until completely dissolved. The stirring speed was 300 r / min for 10 min. Then, 40 g of the partially acrylate-terminated polyurethane prepolymer from Preparation Example 3 was added to the mixing tank and stirred at 100 r / min for 10 min to obtain a transparent pressure-sensitive adhesive composition.

[0098] The peel strength of the transparent pressure-sensitive adhesive composition is 920 gf / 25 mm and the stress is 15 kPa, as shown in Table 1.

[0099] Performance testing

[0100] Adhesion performance test: The transparent pressure-sensitive adhesive compositions in each example and comparative example were coated on a PET film containing silicone oil and cured using a 365 nm LED cold light source. After curing for 2 minutes, an adhesive film was obtained. The peel strength of the adhesive film was tested. The higher the peel strength, the better the adhesion performance of the transparent pressure-sensitive adhesive composition.

[0101] Bonding stress test: The stress relaxation of the cured transparent pressure-sensitive adhesive compositions in each embodiment and comparative example was tested using a rotational rheometer. Lower stress is more beneficial in reducing display defects in large-size display modules during the full bonding process.

[0102]

[0103] refer to Figs. 1-3 As the chain length of polypropylene glycol increases, the effluent time of partially acrylate-terminated polyurethane prepolymer also increases.

[0104] Combining Table 1 with the optically transparent pressure-sensitive adhesives in Examples 1-5 and Comparative Examples 1-5, all examples exhibited excellent adhesion performance and low bonding stress. Examples 1-5, which incorporated thiol chain transfer agents, showed stronger peel strength and lower bonding stress, indicating that thiol chain transfer agents have good performance control capabilities for partially acrylate-terminated polyurethane prepolymers, high glass transition temperature, low glass transition temperature, and functional acrylate monomer mixtures.

[0105] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A low-stress optically transparent pressure-sensitive adhesive composition, characterized in that... By weight, it includes: 30-50 parts of partially acrylate-terminated polyurethane prepolymer, 15-40 parts of low glass transition temperature acrylate monomers, 5-30 parts of high glass transition temperature acrylate monomers, 5-30 parts of functional acrylate monomers, 0.5-2 parts of photoinitiator, 0.1-1 parts of thiol chain transfer agent, and 2-5 parts of antioxidant. The acrylate monomer with the low glass transition temperature is isooctyl acrylate; The acrylate monomer with a high glass transition temperature is isobornyl acrylate; The functional acrylate monomer is hydroxyethyl acrylate; Preparation of the partially acrylate-terminated polyurethane prepolymer: 1) The polyether diol was first dehydrated at 110 °C for 2 h, then cooled to 70 °C, and then the aliphatic diisocyanate was reacted under the catalysis of a catalyst for 3-6 h to obtain a polyurethane prepolymer with isocyanate groups at the end; then cooled to 60 °C, and monohydroxy acrylate was added and reacted for 1-2 h to obtain a polyurethane prepolymer containing some isocyanate groups at the end and some acrylate groups at the end; 2) The polyurethane prepolymer containing partially isocyanate-terminated and partially acrylate-terminated groups obtained in step 1) is reacted with a monofunctional small-molecule alcohol at 60°C for 1-2 h to obtain a partially acrylate-terminated polyurethane prepolymer. The partially acrylate-terminated polyurethane prepolymer has an average number of acrylates of 1.2 and a weight-average molecular weight of 5-25 kgmol. -1 between.

2. The low-stress optically transparent pressure-sensitive adhesive composition according to claim 1, characterized in that... The photoinitiator includes one of ethyl 2,4,6-trimethylbenzoylphenylphosphonate, photoinitiator 184, photoinitiator 1173, and (2,4,6-trimethylbenzoyl)diphenylphosphine oxide.

3. The low-stress optically transparent pressure-sensitive adhesive composition according to claim 1, characterized in that... The antioxidant mentioned is one of antioxidant 264 and antioxidant 1135.

4. The low-stress optically transparent pressure-sensitive adhesive composition according to claim 1, characterized in that... : The monohydroxy acrylate is one of hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxybutyl acrylate; The aliphatic diisocyanate includes one of hexamethylene diisocyanate, isophorone diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate, and the isocyanate index (R value) is 1.2-2.0; The polyether diol is a polypropylene oxide diol with a molecular weight of 200-8000 or a polytetrahydrofuran diol with a molecular weight of 1000-3000.

5. The low-stress optically transparent pressure-sensitive adhesive composition according to claim 1, characterized in that... The monofunctional small molecule alcohols include one of methanol, ethanol, and n-butanol.

6. The low-stress optically transparent pressure-sensitive adhesive composition according to claim 1, characterized in that, Step 1), prepare according to the following steps: 0.1 mol of polypropylene glycol with a molecular weight of 1000-4000 was first dehydrated at 110℃ for 2 h and then added to a three-necked flask. The temperature was then lowered to 70℃, and 0.05 wt% of organotin catalyst was added. 0.16 mol of isophorone diisocyanate was slowly added through a feeding funnel. After reacting for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Subsequently, the temperature was lowered to 60℃, and 0.072 mol of hydroxyethyl acrylate was added and reacted for another 2 h to obtain a polyurethane prepolymer containing both isocyanate-terminated and acrylate-terminated groups.

7. A method for preparing a low-stress optically transparent pressure-sensitive adhesive composition as described in any one of claims 1-6, characterized in that it comprises the following steps: Under a yellow light source, antioxidants, photoinitiators, acrylate monomers with high glass transition temperature, acrylate monomers with low glass transition temperature, and functional acrylate monomers are stirred and degassed until completely dissolved. Then, a portion of acrylate-terminated polyurethane prepolymer and thiol chain transfer agent are stirred and mixed evenly to obtain a transparent pressure-sensitive adhesive composition.

8. The application of a low-stress optically transparent pressure-sensitive adhesive composition according to any one of claims 1 to 6 in the full lamination of large-size display modules.

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