A high-coverage controllable photochromic black adhesive and its preparation method

Abstract

This invention relates to the field of adhesive technology, specifically to a high-opacity controllable photochromic blackening adhesive, comprising the following components: 60 parts acrylic resin, 35-50 parts acrylic monomer, 1-3 parts cationic photoinitiator, 10-20 parts free radical photoinitiator, 1-2 parts color-changing dye, 0.2-0.5 parts chain transfer agent, and 1-2 parts high-opacity photochromic dye. Before photo-initiated polymerization, the adhesive is transparent. After photo-initiated acryloyloxy groups undergo free radical chain polymerization to form a transparent solid of a certain thickness, the color of the color-changing dye rapidly changes from transparent to uniform black upon ultraviolet radiation. Simultaneously, the high-opacity photochromic dye undergoes an oxidation reaction and turns black, significantly increasing the absorbance of the colloid. The tertiary amine chain transfer agent controls the curing speed and achieves a greater curing depth. This solves the problem of black photocurable adhesives blocking curing light, affecting the cured thickness and bulk strength.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, specifically to a high-opacity controllable photochromic black adhesive and its preparation method. Background Technology

[0002] With the development of electronic information technology, OLED displays, with their numerous advantages such as self-illumination, fast response speed, and wide viewing angle, have been widely used. Among these applications, epoxy resin, due to its excellent mechanical properties, adhesive properties, chemical stability, and low shrinkage during curing, is traditionally used as an encapsulant for OLEDs, preventing contamination of the devices. However, cured epoxy resin products exhibit problems such as increased brittleness, cracking, and high internal stress during long-term use, which can affect the normal operation of OLED displays. Furthermore, the presence of coatings in OLED displays still presents light leakage issues in practical applications; the current solution is to use UV black adhesive for encapsulation.

[0003] For example, Chinese patent application (publication number CN109957369A) discloses a UV-curable black adhesive and its preparation method, which involves mixing black pigment into a transparent resin, the main component of which is carbon powder. During preparation, a simple free radical photoinitiator is selected, and black pigment carbon black is used as the color developer. However, carbon black blocks the curing light, affecting the cured thickness and surface dryness, thus affecting the light-blocking rate and bulk strength. Therefore, this UV black adhesive faces the technical problem of a contradiction between light-blocking performance and curing depth, achieving only a basic light-blocking effect, with an OD value of only 0.6–1.2, making it only suitable for traditional bezel applications. With the technological upgrade in consumer applications, the application areas of narrow and ultra-narrow bezel screens are constantly expanding, especially in mobile phones and televisions, which places higher demands on light-blocking performance. Moreover, some display applications require high insulation, so this type of UV black adhesive is no longer suitable for these occasions.

[0004] Later, a new type of UV-sensitive color-changing black adhesive was introduced, such as the Chinese patent application (publication number CN).

[0005] (113683998A). This formulation system utilizes color-changing dyes, free radical photoinitiators, and chain transfer agents. By adding a specific amount of chain transfer agent, the curing reaction rate is controlled, thereby reducing the temperature during UV curing and preventing discoloration of the composition due to excessively high curing temperatures. This UV color-changing black adhesive not only meets the requirements for high insulation but also possesses a higher curing depth and more uniform curing than the aforementioned UV black adhesives. However, due to the limited hiding power of the color-changing dye after color change, the final OD value of the UV color-changing black adhesive is relatively low, restricting its application in certain situations.

[0006] Chinese patent (authorization announcement number CN 108841345B) discloses a hybrid-cured photochromic black acrylate adhesive that introduces pyrrole rings into acrylic resin. Acryloyloxy groups are initiated by a free radical photoinitiator, and after free radical chain polymerization, a transparent solid of a certain thickness is rapidly formed. Then, the pyrrole rings are gradually polymerized by a cationic initiator to slowly form a uniform black color. This acrylate adhesive solves the problem of ordinary black UV-cured adhesives blocking the curing light, affecting the cured thickness and light-blocking rate. However, this acrylate adhesive cannot quickly form a black cover after UV curing, and the measurement of the light-blocking degree requires several hours to obtain a stable value, causing inconvenience for large-scale production. Furthermore, the photochromic black adhesive obtained by this method cannot control the polymerization rate, thus affecting the cured thickness.

[0007] Therefore, it is essential to study the formulation and process of controllable photochromic black adhesives with high opacity. Summary of the Invention

[0008] In order to overcome the problems of existing black light-curing adhesives where it is impossible to achieve both light-blocking rate and curing thickness, and the slow color change rate of high-light-blocking adhesives, this invention provides a new formulation of a high-opacity controllable photochromic blackening adhesive that can completely solve the above-mentioned technical problems.

[0009] The technical solutions to the above technical problems are as follows:

[0010] By weight, the high-opacity controllable photochromic blackening adhesive comprises the following components:

[0011] 60 parts acrylic resin, 35-50 parts acrylic monomer, 1-3 parts cationic photoinitiator, 10-20 parts free radical photoinitiator, 1-2 parts color-changing dye, 0.2-0.5 parts chain transfer agent, and 1-2 parts high-opacity photochromic dye.

[0012] The cationic photoinitiator is a diaryliodonium salt or a triarylthionium salt, including but not limited to one or more of p-(octoxyphenyl)phenyliodonium hexafluoroantimonate (Ph2ISbF6), phenylthiophenyl-diphenylthionium hexafluorophosphate, and triarylthionium hexafluorophosphate.

[0013] The color-changing dye is 3-dibutylamino-6-methyl-7-aniline fluorane;

[0014] The chain transfer agent is one or more of triethanolamine, morpholine, and acrylomorpholine;

[0015] High-opacity photochromic dyes are one or more of pyrrole, pyrrole-2-carboxylic acid, and tannic acid.

[0016] Furthermore, the acrylic resin is selected from one or more of epoxy-modified acrylates, polyurethane-modified acrylates, and aliphatic-modified acrylates.

[0017] The epoxy-modified acrylate refers to a macromolecular polymer containing both methacryloxy and epoxy groups in its molecular chain, and its molecular structure is as follows:

[0018]

[0019] Where R is

[0020]

[0021] n is a positive integer between 0 and 100;

[0022] The polyurethane-modified acrylate refers to a macromolecular polymer containing both methacryloxy and amide groups in its molecular chain, and its molecular structure is as follows:

[0023]

[0024] Where R1 is

[0025]

[0026] m is a positive integer between 0 and 50;

[0027] R2 is

[0028]

[0029] R3 is

[0030]

[0031] z is a positive integer between 0 and 50;

[0032] The aliphatic modified acrylate refers to an acrylic resin obtained by modifying with aliphatic polyurethane, and its molecular structure is as follows:

[0033]

[0034] Where R1 is

[0035]

[0036] x is a positive integer between 0 and 50;

[0037] R2 is

[0038]

[0039] R3 is

[0040]

[0041] y is a positive integer between 0 and 50;

[0042] Furthermore, the acrylic monomer is selected from one or more of isobornyl acrylate (IBOA), hydroxypropyl methacrylate (HPMA), cyclotrimethylolpropane methyl acetal acrylate (CTFA), dihydroxytricyclodecane diacrylate, and urethane (meth) acrylate.

[0043] Furthermore, the free radical photoinitiator is selected from one or more of 2,4,6-trimethylbenzoyl diphenylphosphine oxide (TPO), 1-hydroxycyclohexylphenyl ketone (brand name 184), 2-methyl-1-[4-methylthiophenyl]-2-morpholino-1-propanone (brand name 907), and 2-methoxy-2-phenylacetophenone (BZME).

[0044] Another object of the present invention is to provide a method for preparing the above-mentioned high-opacity controllable photochromic black adhesive, comprising the following steps:

[0045] S1: According to the above component ratio, acrylic resin and acrylic monomer are placed in a brown reaction vessel, high-purity nitrogen is introduced into the reaction vessel, free radical photoinitiator and cationic photoinitiator are added respectively, the temperature is raised to 80-100℃, and the mixture is stirred for 1 hour to obtain intermediate product A.

[0046] S2: Cool the intermediate product A obtained in step S1 to below 40°C, add the color-changing dye and stir evenly to obtain intermediate product B;

[0047] S3: Add a high-opacity photochromic dye to intermediate product B obtained in step S2, stir at 40°C for 30 min to obtain intermediate product C;

[0048] S4: Add chain transfer agent to intermediate product C obtained in step S3, stir evenly for 30 minutes, and store the final product in a dark, airtight container.

[0049] The beneficial effects of this invention are:

[0050] The high-opacity controllable photochromic blackening adhesive prepared by this invention, under ultraviolet light irradiation, the transparent acrylate adhesive is rapidly polymerized and cured by a free radical photoinitiator. After ultraviolet radiation, the color-changing dye changes from transparent to uniform black rapidly. The tertiary amine chain transfer agent can control the rate at which the system generates acidic substances, thereby controlling the curing depth and time of the resin. The high-opacity photochromic blackening dye enhances the light-blocking rate of the system under the influence of free radicals.

[0051] The invention prepares a high-opacity, controllable photochromic black adhesive, the curing process of which is controlled by free radical chain polymerization and cationic stepwise polymerization respectively. The polymerization reactions involved are divided into the following parts:

[0052] 1. Acrylic monomers and acrylic resins polymerize under ultraviolet light irradiation via a free radical photoinitiator;

[0053] 2. When cationic photoinitiators are exposed to ultraviolet light, they produce acidic compounds that react with color-changing dyes in the system that were originally colorless, causing the colloid to turn black.

[0054] 3. High-opacity photochromic dyes undergo an oxidation reaction under ultraviolet light irradiation, generating black quinone groups or polypyrrole substances, thus enhancing opacity.

[0055] Therefore, the high-opacity controllable photochromic black adhesive prepared by this invention is transparent before photo-initiated polymerization. After photo-initiated acryloyloxy groups undergo free radical chain polymerization, they are rapidly positioned to form a transparent solid of a certain thickness. Then, after ultraviolet radiation, the color of the color-changing dye rapidly changes from transparent to uniform black. At the same time, the high-opacity photochromic black dye undergoes an oxidation reaction and turns black, thereby greatly improving its colloidal absorbance. In addition, the addition of tertiary amine chain transfer agents can control the curing speed and achieve a greater curing depth. This solves the problem that ordinary black photocurable adhesives block the curing light, affecting the cured thickness and bulk strength. Attached Figure Description

[0056] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0057] Figure 1 This is a flowchart illustrating the curing process of the high-opacity controllable photochromic black adhesive of the present invention. Detailed Implementation

[0058] Example 1:

[0059] High-purity nitrogen gas was introduced into a brown reaction vessel. 60 grams of epoxy-modified acrylate (in this embodiment, an epoxy-modified acrylate with n=36 was used; using this molecular weight is merely a preferred technical solution and not a limitation of the invention; as an extension, n can be any positive integer from 0 to 100), 15 grams of hydroxypropyl methacrylate (HPMA), 18 grams of cyclotrimethylolpropane methyl acetal acrylate (CTFA), 8 grams of 2,4,6-trimethylbenzoyl diphenylphosphine oxide (TPO), and 10 grams of 2 2.5 g of methyl-1-[4-methylthiophenyl]-2-morpholino-1-propanone (907) and phenylthiophenyl-diphenylthionium hexafluorophosphate were added to the reaction vessel, and stirring was started simultaneously. The mixture was heated to 80°C and stirred for 1 h. The temperature was then lowered to 40°C, and 2 g of 3-dibutylamino-6-methyl-7-aniline fluorane was added. The mixture was stirred until homogeneous, and then 1.5 g of pyrrole-2-carboxylic acid was added. The mixture was stirred at 40°C for 30 min. Then 0.2 g of triethanolamine was added and stirred for 30 min until homogeneous. The mixture was then stored in a light-proof, sealed container.

[0060] Example 2:

[0061] High-purity nitrogen gas was introduced into a brown reaction vessel. 50 grams of epoxy-modified acrylate, 10 grams of polyurethane-modified acrylate (in this embodiment, an epoxy-modified acrylate with n=46 and a polyurethane-modified acrylate with m=25 and z=25 are used; similarly, the selection of epoxy-modified acrylate and polyurethane-modified acrylate with these molecular weights is only a preferred technical solution and is not a limitation of the invention. As an extension, n can be any positive integer from 0 to 100, m can be any positive integer from 0 to 50, and z can be any positive integer from 0 to 50), 20 grams of isobornyl acrylate (IBOA), and 21 grams of cyclotriazine... 20 g of hydroxymethyl propane acetal acrylate (CTFA), 20 g of 2-methoxy-2-phenylacetophenone (BZME), and 2.2 g of p-(octoxyphenyl)phenyliodonium hexafluoroantimonate (Ph2ISbF6) were added to a reaction vessel, and stirring was started simultaneously. The mixture was heated to 90 °C and stirred for 1 h. The temperature was then lowered to 40 °C, and 1.5 g of 3-dibutylamino-6-methyl-7-aniline fluorane was added and stirred until homogeneous. Then, 1 g of pyrrole was added, and the mixture was stirred at 40 °C for 30 min. Finally, 0.2 g of morpholine and 0.1 g of triethanolamine were added, and the mixture was stirred for 30 min until homogeneous. The mixture was then stored in a light-proof, sealed container.

[0062] Example 3:

[0063] High-purity nitrogen gas was introduced into a brown reaction vessel. 60 grams of aliphatic modified acrylate (in this embodiment, an aliphatic modified acrylate with x=47 and y=38 was used; using this molecular weight aliphatic modified acrylate is merely a preferred technical solution and not a limitation of the invention; as an extension, x and y can be any positive integer from 0 to 50), 13 grams of hydroxypropyl methacrylate (HPMA), 22 grams of cyclotrimethylolpropane methyl acetal acrylate (CTFA), 5 grams of dihydroxytricyclodecane diacrylate, and 5 grams of carbamate (methyl... In an acrylate container, 10 g of 1-hydroxycyclohexylphenyl ketone (184), 0.7 g of triaryl hexafluorophosphate thioonium salt, and 0.3 g of phenylthiophenyl-diphenylthioonium hexafluorophosphate were added to the container. The mixture was stirred and heated to 100°C for 1 h. The mixture was then cooled to 40°C, and 1 g of 3-dibutylamino-6-methyl-7-aniline fluorane was added and stirred until homogeneous. 1 g of tannic acid and 1 g of pyrrole were added and stirred at 40°C for 30 min. Then, 0.5 g of acryloylmorpholine was added and stirred for 30 min until homogeneous.

[0064] Comparative Example 1:

[0065] Referring to the formulation of Example 3 of the ultraviolet-curable black adhesive disclosed in the Chinese patent application (publication number CN109957369A) described in the background art, a light-curable edge-sealing insulation material was prepared.

[0066] Comparative Example 2:

[0067] The formulation of Example 1 of the controllable color-changing ultraviolet curable adhesive composition disclosed in the Chinese patent application (publication number CN 113683998A) described in the background art is as follows.

[0068] Comparative Example 3:

[0069] Referring to the formulation of Example 1 of the hybrid curing photochromic black acrylate adhesive disclosed in the background art (authorization announcement number CN 108841345B).

[0070] The performance testing method is as follows:

[0071] (1) Curing thickness: The photocurable resin composition was placed into a metal cylinder with a depth of 5 mm and cured using a UV irradiator (365 nm) at 100 mW / cm². 2 The material was cured by UV irradiation for 120 seconds to obtain a cured product. The uncured part was removed with a solvent, and the remaining part was measured with vernier calipers.

[0072] (2) Surface dryness: Irradiate with 365nm wavelength ultraviolet light for 15s, cool to 25℃, and test with rubber finger cots.

[0073] (3) Shear strength test: Tensile strength: Irradiate with 365nm wavelength ultraviolet light for 15s, cool to 25℃, and test according to GB / T528-1998.

[0074] (4) 0.5mm shading rate (%): Irradiate with 365nm wavelength ultraviolet light for 15s, cool to 25℃, and use an ultraviolet-visible spectrophotometer to test the shading rate of the sample at 450nm wavelength.

[0075] (5) Calculation of OD value: OD = lg1 / (1 - shading rate)

[0076] The data obtained from tests conducted according to the above method in Examples 1-3 and Comparative Examples 1-3 are shown in Table 1 below.

[0077]

[0078] As shown in Table 1 above, the high-opacity controllable photochromic black adhesive obtained by this invention exhibits significantly higher maximum cured thickness, surface dryness, and shear strength than the adhesive obtained by the technical solution of Comparative Example 1. Furthermore, in terms of 0.5mm opacity and OD value, the technical solution of this invention far surpasses the technical solutions of Comparative Example 1 and Comparative Example 2. Regarding color-changing time, the technical solution of Comparative Example 3 is not even in the same order of magnitude as the technical solution of this invention. Therefore, the technical solution of this invention overcomes the problem that existing black photocurable adhesives cannot simultaneously achieve high opacity and cured thickness, and that high-opacity adhesives have excessively slow color-changing speeds, thus having a wider range of applications.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A high-opacity, controllable photochromic blackening adhesive, characterized in that, Based on parts by weight, it contains the following components and parts: 60 parts acrylic resin, 35-50 parts acrylic monomer, 1-3 parts cationic photoinitiator, 10-20 parts free radical photoinitiator, 1-2 parts color-changing dye, 0.2-0.5 parts chain transfer agent, and 1-2 parts high-opacity photochromic dye. The cationic photoinitiator is one or more of p-(octoxyphenyl)phenyliodonium hexafluoroantimonate, phenylthiophenyl-diphenylthionium hexafluorophosphate, and triarylhexafluorophosphate thionium salt; The color-changing dye is 3-dibutylamino-6-methyl-7-anilinofluorane; The chain transfer agent is one or more of triethanolamine, morpholine, and acrylomorpholine, used to coordinate the rates of free radical polymerization and cationic polymerization to achieve control of curing depth; The high-opacity photochromic dye is one or more of pyrrole, pyrrole-2-carboxylic acid, and tannic acid.

2. The high-opacity controllable photochromic blackening adhesive according to claim 1, characterized in that, The acrylic resin is one or more of epoxy-modified acrylate, polyurethane-modified acrylate, and aliphatic-modified acrylate.

3. The high-opacity controllable photochromic blackening adhesive according to claim 1, characterized in that, The acrylic monomer is one or more of isobornyl acrylate, hydroxypropyl methacrylate, cyclotrimethylolpropane methyl acetal acrylate, and dihydroxytricyclodecane diacrylate.

4. The high-opacity controllable photochromic blackening adhesive according to claim 1, characterized in that, The free radical photoinitiator is one or more of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-[4-methylthiophenyl]-2-morpholino-1-propanone, and 2-methoxy-2-phenylacetophenone.

5. A method for preparing a high-opacity controllable photochromic blackening adhesive as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1: According to the component ratio of claim 1, acrylic resin and acrylic monomer are placed in a brown reaction container, nitrogen gas is introduced into the reaction container, free radical photoinitiator and cationic photoinitiator are added respectively, the temperature is raised to 80-100°C, and the mixture is stirred for 1 hour to obtain intermediate product A. S2: Cool the intermediate product A obtained in step S1 to below 40°C, add the color-changing dye and stir evenly to obtain intermediate product B; S3: Add a high-opacity photochromic dye to intermediate product B obtained in step S2, stir at 40°C for 30 min to obtain intermediate product C; S4: Add chain transfer agent to intermediate product C obtained in step S3, stir evenly for 30 minutes, and store the final product in a dark, airtight container.

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