CN117304817A - OCA adhesive for inkjet printing - Google Patents

Abstract

The invention relates to the technical field of adhesives, and discloses an OCA adhesive for inkjet printing, which comprises, by weight, 5-40 parts of an acrylic ester oligomer, 10-90 parts of a reactive diluent, 0.1-5 parts of a photoinitiator, 0.1-5 parts of a molecular structure regulator and 0-5 parts of an auxiliary agent, wherein the weight average molecular weight range of the acrylic ester oligomer is 500-100000Da, the functionality is 0.5-4, and the reactive diluent takes an acrylic ester monomer as a main component. The adhesive meets the requirement of ink-jet printing in liquid state, and after curing, the optical performance of the adhesive meets the requirement of OCA.

Description

OCA adhesive for inkjet printing

Technical Field

The invention relates to the technical field of low-viscosity adhesives, in particular to an OCA adhesive for inkjet printing, which is mainly applied to flexible equipment.

Background

As is well known, all electronic devices having a display UI must use a transparent optical adhesive material, generally referred to as an optically transparent adhesive, which must meet corresponding requirements in terms of light evening, antireflection, filling, weather resistance, appearance, and the like, in addition to maintaining transparency and adhesion. Traditionally, such materials are classified into OCR (optical resin) and OCA (optical film). OCA is used for the occasion of convenient laminating glued membrane, generally uses in the surface level and evenly, and the level difference is in the design below tens microns, for example most tablet equipment and cell-phone. The OCA has the advantages that the finished product degree of the material is high, and the material can be finished only by simple lamination and post-curing, so that the assembly line assembly efficiency is conveniently improved. The method has the defects of high requirements on material manufacturing process and cleanliness, need of cutting and multiple processing, and low yield. In addition, OCAs are difficult to use in irregular surfaces and high level difference designs, which can cause various problems due to the lack of tightness of fit. In this case, OCR is used instead of OCA to fill the level differences in liquid form or to bite-fill the opposite surface. For example, in an in-vehicle visual UI electronic device, and a portion of a special packaged display module. However, with the development of electronic products, a new class of applications has emerged that are neither convenient for the attachment of OCAs nor suitable for the filling or dispensing of OCR: for example, on an optical module of VR equipment, the requirements of ultra-thin and uniform are simultaneously met, and the design of the overall high-radian curved surface is adapted, so that the bonding of OCA and spot-coating OCR are very difficult, because OCA is difficult to achieve uniform wettability and warp resistance on the high-radian curved surface, so that the problems generated when different materials shrink and deform are difficult to resist, and the high fluidity of OCR is difficult to maintain uniform thickness on the curved surface; for example, when the MiniLED/MicroLED is assembled, the tiny light-emitting units are difficult to bear the bonding pressure of the pressure-sensitive adhesive, the matrix of the micro-light-emitting units is large in specific surface area, so that OCA (optical character recognition) cannot form good wetting and bonding strength on the surface of the micro-light-emitting units, and the OCR dispensing and diffusion process is used for exhausting air between the micro-light-emitting units and the light-emitting units with high specific surface areas, so that bubble defects are extremely easy to form.

Thus, a new type of high precision OCA construction scheme by inkjet printing and corresponding material scheme are increasingly being given high attention: in terms of equipment, the ink jet printing OCA equipment integrates the most advanced piezoelectric ink jet printer, rotary jet, program editing system, and nitrogen protection, lamination, curing system specifically prepared for OCA. Unlike common inks and OCAs, inkjet OCAs need to consider the properties of three states of deposition on the material surface, curing into a film during printing: the special viscosity, material/spray gun/air surface tension and other requirements are met in the printing process; during surface deposition, thixotropic properties and material/interface/air surface tension are observed; all properties of the OCA are to be met after curing to form a film.

Because the positioning and thickness precision of the ink-jet printing is far greater than that of the dispensing knife coating, the scheme is not only suitable for surfaces with different thickness and different curvatures, but also enables regional material combination design to be possible, and breaks through the limitation of using a single OCA material on one module. In addition, the ink-jet printing is very suitable for the requirements of ultrathin and lightweight design, and has great application potential in two positions of surface light and backlight. Ink jet printing OCAs have been introduced and attempted at terminals with autonomous design capabilities, such as apples, samsung, hua, OPPO, etc., and head display module designers, such as eastern, starburst photovoltaics, smallpox, etc. Among them, samsung has already disclosed OLED end products based on technology, dirigible also in autumn 2022, formally announced their research results of the OCA product series of inkjet printing. Domestic companies have also begun to invest in basic formulations, such as: CN 111363512A,CN 114574151A,CN 113831848A, etc. are directed to technologies of flat panels, water drop screens, etc., but still are still in laboratory stage, and are not in industrial scale, meanwhile, in the existing products and the disclosed technologies in the market, although the existing products and the disclosed technologies are used for bonding conventional plane or water drop display panels, the requirements of the physical properties of the novel flexible screen during bending cannot be met yet, on one hand, due to the specificity and scarcity of the inkjet printing equipment, it is difficult for a material company to effectively evaluate the materials of the flexible screen; on the other hand, since the development of the material is inseparable from the terminal design, deep project cooperation between the material company and the terminal company is required, and this mode is not yet mature in the related industries at home.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides an OCA adhesive for inkjet printing. Especially, the flexible screen is optimized (such as a folding screen, a curling screen, bendable wearable equipment and the like) in an application scene, has higher elongation at break (more than 500%), generates fewer stress (tensile strength is unchanged) in stretching, and further reduces the possibility of stripping the protective cover plate in stretching deformation, so that the flexible requirement is met, and the stripping force on a glass interface can be ensured to meet the requirement of lamination.

In order to achieve the above purpose, the invention adopts the following technical scheme: the OCA adhesive for ink-jet printing comprises, by weight, 5-40 parts of an acrylic acid ester oligomer, 10-90 parts of a reactive diluent, 0.1-5 parts of a photoinitiator, 0.1-5 parts of a molecular structure regulator and 0-5 parts of an auxiliary agent, wherein the acrylic acid ester oligomer has a weight average molecular weight range of 500-100000Da and a functionality of 0.5-4, and the reactive diluent takes an acrylic acid ester monomer as a main component.

The apparent viscosity of the adhesive prepared from the materials is 1 to 100cPs, preferably 8 to 40cPs, at room temperature. The surface energy at normal temperature and pressure is 20 to 50mN/m, preferably 20 to 40mN/m.

As a specific embodiment, the acrylate oligomer is selected from one or more of acrylate, acrylate polyurethane, acrylate polyol polymer, and acrylate-miscible polyester.

The acrylate oligomer adopts an acrylate modified structure as a main material and is matched with polyurethane: flexibility and film forming property are increased; or in combination with polyol polymers: increasing polarity, etc. The weight average molecular weight of the oligomer ranges from: 500-100000Da, less than 500Da, the required crosslinking density is too high, and effective stress release is difficult to form; above 100000Da, the apparent viscosity of the material is difficult to meet the use requirements. The oligomer has a functionality of 0-N, which refers to units that can be polymerized, optionally in the range of 0.5 to 4, more preferably 1 to 2. When the content reaches 0, the oligomer is completely dissociated from other components, so that the problems of poor compatibility, low crosslinking degree and the like are caused; above 4, the final degree of crosslinking of the product is too high, losing tackiness and cohesiveness. The oligomer may have an apparent viscosity (25 degrees celsius) in the range of 10 to 10000cPs. The proportion of the oligomer is 5-40 parts by 100 parts of the total sum of all materials. Less than 5 parts, the toughening effect is difficult to achieve; above 40, the viscosity of the system is not high and the system can not be sprayed. The oligomers which can be directly used are: sandomax CN8888 NS, CN9021 NS, CN8893 NS, CN8894 NS, CN8899 NS, SR 495 NS, beauty sources M100, M200, etc.

The reactive diluent is mainly some special monomers for regulating the polarity, compatibility and the like of the system, and mainly comprises functional acrylate monomers.

As a specific embodiment, the acrylate monomer is selected from one or more of hydroxyethyl acrylate, hydroxybutyl acrylate, isodecyl acrylate, lauryl acrylate, isobornyl acrylate, 3, 5-trimethylcyclohexyl acrylate.

The photoinitiator is an initiator required by photo-curing after ink-jet printing, and is mainly a common photoinitiator, specifically, the photoinitiator is one or more selected from 1-hydroxycyclohexyl phenyl ketone, methyl benzoate and 2,4, 6-trimethylbenzoyl benzene-diphenyl phosphine oxide.

As a specific embodiment, the raw material of the adhesive further comprises a cross-linking agent, wherein the cross-linking agent is a multifunctional acrylate micromolecule and is used for increasing the cohesive force of a system and adjusting a network structure. Specifically, the cross-linking agent adopts one or a combination of 1, 6-hexanediol diacrylate and trimethylolpropane triacrylate. The weight of the material is 0-1 part in all materials. If the amount exceeds 1 part, the cohesion of the system becomes too high, and the pressure-sensitive material is not suitable.

As a specific embodiment, the acrylate oligomer is selected from one or more of the group consisting of sandy CN8888 NS, sandy CN9021 NS, sandy CN8893 NS, sandy CN8894 NS, sandy CN8899 NS, sandy SR 495 NS, beauty source M100, and beauty source M200. Among them, the sardamac CN9021 NS is a polyurethane acrylate with a special structure customized for the application of the present patent, and is greatly different from the structure and functional group of the conventional aliphatic polyurethane acrylate. The use is prioritized because of the obvious lifting effect. But this structure and characteristics are not known to the business secret.

As a specific embodiment, the molecular structure modifier is selected from one or more of isooctyl thioglycolate, n-dodecyl mercaptan, t-dodecyl mercaptan, 1, 4-bis (3-mercaptobutyryloxy) butane, 2, 4-diphenyl-4-methyl-1-pentene, pentaerythritol tetrakis (3-mercaptobutyrate), 1, 4-bis (3-mercaptobutyryloxy) butane, 1,3, 5-tris (3-mercaptobutyryloxy ethyl) -1,3, 5-triazine-2, 4,6 (1 h,3h,5 h) -trione, trimethylolpropane tris (3-mercaptobutyl).

Wherein pentaerythritol tetra (3-mercaptobutyrate) is supplied by Japanese Showa electrician and has the model of KarenzMT ™ BD1;1, 4-bis (3-mercaptobutyryloxy) butane was obtained from Japanese Showa electrician under the model KarenzMT ™ PE1;1,3, 5-tris (3-mercaptobutyryloxyethyl) -1,3, 5-triazine-2, 4,6 (1H, 3H, 5H) -trione was prepared by Japanese Showa electric under the model KarenzMT ™ NR1; trimethylolpropane tris (3-mercaptobutyl) is supplied by Japanese Showa electric under the model KarenzMT ™ TPMB.

The molecular weight regulator is added in an amount of 0.1 to 5 parts, preferably 0.1 to 2 parts, and less than 0.1 cannot play a structural adjustment role, and more than 5 parts affect the molecular weight distribution and the polymerization degree. In addition, a polyhydric active phenol compound having structural characteristics such as abietic acid is included, and a customized macromolecule having chain transfer effect and molecular structural characteristics such as an organic-inorganic electrolyte such as a metallocene complex which can be dispersed in an acrylic ester can be provided.

As each specific embodiment, the molecular structure regulator is necessary for the invention, the commonly used structure regulator is 1-4 functional mercaptan, the chain length of the monomer part loop is improved by adding the molecular structure regulator, and the defects of excessively short monomer chain segments and excessively high connection density of the photo-external polymer are overcome by the synergistic effect of the molecular structure regulator and the chain length of the polyurethane acrylate oligomer, so that the elongation at break is increased on the premise of not increasing stress and not influencing the cohesive force, and the comprehensive performance requirements of flexible equipment such as bending, recovery, aging and the like are met.

The sardamard CN9021 NS is polyurethane acrylic ester with a special structure customized for the application of the patent, and the sardamard CN9021 NS is adopted as acrylic ester oligomer, so that the performance of the adhesive is improved, and priority is given to the performance.

As a specific embodiment, the auxiliary agent comprises one or more of a light stabilizer, an antioxidant, an antifoaming flatting agent and an accelerator.

1) Light stabilizer, increased acceptable illumination intensity, removal of residual free radicals, adjustment of photoinitiator content, adjustment of reaction rate, etc. The hindered amine is used as the main material, and the proportion of the hindered amine is 0 to 3 parts, such as Tinuvin770, tinuvin 783,Chimassorb 944,Tinuvin 622SF and the like. 2) The defoaming leveling agent is used for inhibiting foam generated by ink jet, promoting leveling and helping construction, and is mainly organic silicon resin, wherein the proportion of parts is 0-3 parts, such as BYK-077, BYK-088, BYK-141, BYK-1707, BYK-1758, BYK-1759, BYK-1790 and the like. 3) An antioxidant for inhibiting oxidative deterioration of a material over a long period of time, the ratio of parts being 0 to 3 parts, such as Chemnox-1010, chemnox-1076, chemnox-1026, chemnox-DLTP,2, 6-di-t-butyl-4-methylphenol (BHT), etc. 4) The adhesion promoter increases the adhesion of resin on the surface of the material, and is mostly a silane coupling agent, and the part ratio is 0-5 parts, such as KH-560, KH-570, solvey PAM-100, PAM-200, saadoma SR9051, SR9050 and the like.

As a specific embodiment, the auxiliary agent comprises a light stabilizer, and the addition amount of the light stabilizer is 0-3 parts.

As a specific embodiment, the auxiliary agent comprises an antioxidant, wherein the antioxidant is selected from one or more of Chemnox-1010, chemnox-1076, chemnox-1026, chemnox-DLTP and 2, 6-di-tert-butyl-4-methylphenol, and the addition amount of the antioxidant is 0-3 parts.

As a specific embodiment, the auxiliary agent comprises an accelerator, wherein the accelerator adopts a silane coupling agent, and the addition amount of the accelerator is 0-5 parts.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages: the OCA adhesive for ink-jet printing has simple components, is obtained by mixing an acrylic acid ester oligomer, a reactive diluent, a photoinitiator and an auxiliary agent, meets the ink-jet printing requirement in a liquid state, and has optical performance meeting the OCA requirement after being solidified.

Detailed Description

The technical scheme of the invention is further described below in conjunction with specific embodiments.

An OCA adhesive for ink-jet printing comprises raw materials of acrylate oligomer, a reactive diluent, a photoinitiator, a crosslinking agent and an auxiliary agent.

1. Preparation of samples

The formulation materials of the adhesive for a plurality of samples are provided in table 1, and the specific components are shown in table 1, and the addition amounts of the components are calculated in parts by weight.

TABLE 1

1.1 preparation of liquid samples

According to the formulation in Table 1, the acrylic acid oligomer in the formulation is dissolved in the monomer dispersion, stirred for 2 hours until the acrylic acid oligomer is completely dissolved, and other monomers and auxiliary agents are added and mixed uniformly.

The weight average molecular weight of the acrylate oligomer of the sandomax CN8894 NS and the CN9021 NS adopted by the sample is between 2000 and 20000.

And (3) spraying the sample into a surface to be tested or a die by using an ink-jet device according to the planned thickness, shape and size, and covering a transparent release film to isolate oxygen and prevent surface polymerization inhibition.

1.2 preparation of solid samples

The liquid sample prepared in 1.1 is placed in a UV light curing apparatus and irradiated at a set power and power density to initiate polymerization, and in the examples 100mW/cm 2, 5000mJ is used for curing (365 nmLED light source, shanghai Rui Tao electronic technologies Co., ltd., LED model UVS 200300). After the irradiation of the set capacity density is completed, the sample is taken out and cooled to room temperature for measurement.

2. Characterization of the properties of the samples

2.1 list of test equipment and remarks, see table 2.

TABLE 2

The detection method comprises the following steps:

1. mechanical properties

The test was carried out with reference to the method of GB/T1040.3-2006, with a controlled thickness of 0.5mm.

2. Initial tack Property

The test was carried out according to the method of GB/T4852-2002.

3. Optical Properties

Transmittance, haze: the test was performed according to the method of GB/T2410-2008.

Refractive index: the test was carried out according to the method of GB/T39691-2020.

4. Tg of (Tg)

The test was carried out according to the method of GB/T19466.2-2004.

5. Viscosity of the mixture

The test was carried out according to the method of GB/T2792-2014.

6. Surface tension

And (3) testing by using a Surfgauge DG-1, cleaning and wetting a test capillary, dripping a sample to be tested into a tetrafluoroethylene sample vessel, immersing a test end of the capillary below the liquid level of the sample, lifting the capillary after the liquid level rises, keeping a vertical state, waiting for the liquid level to rise continuously, reading after stopping, correcting the reading according to the density, and recording.

2.2 sample and reference sample test results are shown in Table 3.

TABLE 3 Table 3

The performance of the sample is evaluated mainly by the following points: 1) Whether the liquid state meets the requirement of ink-jet printing; 2) Whether the cured adhesive film meets the characteristics and the performances of an OCA adhesive film or not; 3) Whether or not the cured product meets the flexible scene application. In addition, the material is difficult to evaluate by a film transfer system such as a peeling force due to the specificity (liquid application) of the sample preparation, and therefore, physical parameters such as modulus and elongation are adopted.

From table 3 we can conclude that:

1) S1-S4, wherein the room temperature viscosity range in the liquid state meets the requirements of the ink-jet printing resin;

2) S1-S4, the surface energy of the liquid room temperature accords with the inkjet, and the surface suitability of the material;

3) S1-S4, after solidification, the mechanical property and the optical property meet the common OCA standard, tg after polymerization is below zero, and the surface provides adhesion and initial adhesion;

4) S3-S4, by adding the molecular structure regulator, the breaking elongation (more than 500%) is obviously improved, and meanwhile, the tensile strength is not increased, so that the stress generated by the same deformation during bending is less, and the risk of cover plate stripping during bending is reduced;

5) S5, the initial viscosity is relatively high compared with S1-S4 due to the fact that the addition amount of the acrylic acid oligomer is large, the effect is not as good as that of S1-S4 in the ink-jet equipment, and therefore, the addition amount of the acrylic acid oligomer cannot exceed 40 parts;

6) S6, the viscosity in the liquid state is low, after curing, the addition amount of the acrylic acid ester oligomer is low, and the stripping force performance is not as good as that of S1-S4, so that the addition amount of the acrylic acid oligomer cannot be lower than 5 parts, the tackifying and toughening effects are difficult to achieve, and the polyurethane acrylic acid ester is too little, and cannot have the most effective synergistic effect with the molecular structure regulator, so that the elongation at break is low. Meanwhile, the stripping force is greatly influenced;

7) S1 and S2 are comparison without adding molecular structure regulator, and the elongation at break is obviously lower under the premise of unchanged tensile strength, larger stress can be generated under the fixed deformation in a bending scene, the stress brought by deformation of different parts is difficult to absorb, and in actual observation, the optical module is quickly peeled off from a substrate in bending and aging tests, so that the requirements of application scenes are not met.

The above embodiments are provided to illustrate the technical concept and features of the present invention and are intended to enable those skilled in the art to understand the content of the present invention and implement the same, and are not intended to limit the scope of the present invention. All equivalent changes or modifications made in accordance with the spirit of the present invention should be construed to be included in the scope of the present invention.

Claims (10)

1. The OCA adhesive for ink-jet printing is characterized by comprising, by weight, 5-40 parts of an acrylic ester oligomer, 10-90 parts of a reactive diluent, 0.1-5 parts of a photoinitiator, 0.1-5 parts of a molecular structure regulator and 0-5 parts of an auxiliary agent, wherein the acrylic ester oligomer has a weight average molecular weight range of 500-100000Da and a functionality of 0.5-4, and the reactive diluent takes an acrylic ester monomer as a main component.

2. An OCA adhesive for inkjet printing according to claim 1 wherein the acrylate oligomer is selected from one or more of acrylates, acrylate urethanes, acrylate polyol polymers, polyesters miscible with acrylates.

3. The OCA adhesive for inkjet printing according to claim 1, wherein the acrylate monomer is selected from one or more of hydroxyethyl acrylate, hydroxybutyl acrylate, isodecyl acrylate, lauryl acrylate, isobornyl acrylate, and 3, 5-trimethylcyclohexyl acrylate.

4. An OCA adhesive for inkjet printing according to claim 1 wherein the photoinitiator is selected from one or more of 1-hydroxycyclohexylphenyl ketone, methyl benzoate, 2,4, 6-trimethylbenzoylbenzene-diphenyl phosphine oxide.

5. The OCA adhesive for inkjet printing according to claim 1, wherein the molecular structure modifier is one or more selected from isooctyl thioglycolate, n-dodecyl mercaptan, t-dodecyl mercaptan, 1, 4-bis (3-mercaptobutyryloxy) butane, 2, 4-diphenyl-4-methyl-1-pentene, pentaerythritol tetrakis (3-mercaptobutyrate), 1, 4-bis (3-mercaptobutyryloxy) butane, 1,3, 5-tris (3-mercaptobutyryloxyethyl) -1,3, 5-triazine-2, 4,6 (1 h,3h,5 h) -trione, trimethylolpropane tris (3-mercaptobutyl).

6. An OCA adhesive for inkjet printing according to claim 2 wherein the acrylate oligomer is selected from one or more of the group consisting of sandy CN8888 NS, sandy CN9021 NS, sandy CN8893 NS, sandy CN8894 NS, sandy CN8899 NS, sandy SR 495 NS, beauty source M100, and beauty source M200.

7. An OCA adhesive for inkjet printing according to claim 1 wherein the auxiliary agent comprises one or more of a light stabilizer, an antioxidant, an antifoaming levelling agent.

8. An OCA adhesive for inkjet printing according to claim 7 wherein the auxiliary agent comprises a light stabilizer added in an amount of 0 to 3 parts.

9. An OCA adhesive for inkjet printing according to claim 7 wherein the auxiliary agent comprises an antioxidant selected from one or more of Chemnox-1010, chemnox-1076, chemnox-1026, chemnox-DLTP,2, 6-di-tert-butyl-4-methylphenol, the antioxidant being added in an amount of 0 to 3 parts.

10. The OCA adhesive for inkjet printing according to claim 7, wherein the auxiliary agent comprises an accelerator, the accelerator employs a silane coupling agent, and the accelerator is added in an amount of 0 to 5 parts.