Preparation of thermosetting resin composition and sensor coating containing the same

Abstract

The purpose of this invention is to provide a conductive thermosetting resin composition whose thermosetting coating is flexible, conductive, and has its resistance controlled within stress-induced stress, thus achieving the purpose of a sensor. The rheological properties of this resin composition are suitable for high-speed printing, such as pad printing, gravure printing, and screen printing. The thermosetting resin is selected from A1 resin and A2 resin obtained by reacting 2,2-dihydromethylbutyric acid or 2,2-dihydromethylpropionic acid with 3-isocyanate-methylene-3,5,5-trimethylcyclohexyl isocyanate, combined with an epoxy resin.

Description

[Technical Field]

[001] This invention provides a high-speed printable thermosetting resin composition and a sensor coating comprising the same. [Previous Technology]

[002] Conductive coatings for stress varistors are needed in the electronics industry. Some emerging applications are in sensors, and these applications, along with many electronics markets, are driven by assembly costs and speed. As a result, stress varistor conductive materials are required to achieve high throughput. High throughput is summarized as high-speed printing technologies such as pad printing, gravure printing, and screen printing methods. For example, roll-to-roll automatic screen printing at approximately 60 meters per minute requires the stress varistor conductive material to possess appropriate rheological properties to utilize this high speed.

[003] Therefore, the present invention provides a stress-strain resistance conductive coating material with rheological properties that can withstand the test of high-speed printing technology (e.g., roll-to-roll automatic screen printing). [Summary of the Invention]

[004] The technical problem to be solved by the present invention is to provide a thermosetting resin composition and a sensor coating comprising the same, in order to overcome the shortcomings of the prior art.

[005] The purpose of this invention is to provide a thermosetting resin composition, wherein the main resin is a combination of thermosetting A resins, including a composition of A1 resin and A2 resin. The A1 resin and A2 resin are in a certain proportion. This improves the heat resistance of the acrylic structure and also improves the flexibility of the epoxy structure, thus balancing the requirements for both flexibility and heat resistance.

[005]

[005]

[006] Another object of the present invention is to provide a conductive thermosetting resin composition that has conductivity and can control the resistance under stress to achieve the purpose of a sensor.

[007] Another object of the present invention is to provide a resin composition based on the above-mentioned thermosetting A resin. It comprises: (a) a thermosetting A resin, comprising 30 to 60 wt% of the solid content of the thermosetting resin composition, wherein the thermosetting A resin includes A1 resin and A2 resin, wherein the weight ratio of A2 resin to A1 resin is between 0 and 1.5; (b) a conductive powder, comprising 5 to 20 wt% of the solid content of the thermosetting resin composition; (c) a crosslinking agent, comprising 5 to 20 wt% of the solid content of the thermosetting resin composition; and (d) a composite crosslinking initiator, comprising 0.1 to 3 wt% of the solid content of the thermosetting resin composition.

[008] In addition to the improvements in the above-mentioned physical properties, the coating processability has also been improved, including pad printing, gravure printing and screen printing. The sensing layer formed by the thermosetting resin composition of the present invention after curing has better flexibility and has its advantages in electronic product applications.

[009] Another object of the present invention is to utilize the aforementioned resin composition in prepreg films, curing sheets, and sensors manufactured by laminating with copper foil substrates for printed circuit boards. During operation, the resin composition exhibits good filling and cutting properties. Because the composition contains the aforementioned linear thermosetting A resin, the cured properties achieve high flexibility, high temperature resistance, and low moisture absorption, and it also exhibits excellent compatibility with other resins, fully demonstrating the advantages of this thermosetting A resin composition and achieving better sensor specifications.

[010] One of the beneficial effects of the present invention is that the thermosetting resin composition and the sensor coating containing it provided by the present invention can, through the technical solution of "conductive powder with a specific component ratio", enable the thermosetting resin composition to have good physical properties, such as glass transition temperature (Tg), flexibility and flowability, while maintaining a certain strain resistance sensor. Accordingly, the thermosetting resin composition has excellent filling and cutting properties during the manufacturing process.

[011] To further understand the features and technical content of the present invention, please refer to the following detailed description of the present invention; however, the description is not intended to limit the present invention.

Implementation Method

[012] (I) Thermosetting resin composition:

[013] The thermosetting resin composition of the present invention contains a thermosetting resin, a conductive filler, and a crosslinking agent.

[014] The sensor coating of the embodiment of the present invention is formed by using the thermosetting resin composition of the embodiment of the present invention. The thermosetting resin contained in the thermosetting resin composition of the embodiment of the present invention becomes a sensor coating by curing.

[015] The thermosetting resin composition of the embodiments of the present invention is typically used in a liquid form in which its constituent components are dissolved or dispersed by an organic solvent or the like. Examples of such solvents include: methyl isobutyl ketone, propylene carbonate, butoxyethanol, ethyl butoxyacetate, toluene, xylene, butyl carbitol acetate, cyclohexanone, propylene glycol monomethyl ether, dipropylene glycol diethyl ether, and methyl carbitol acetate. The solvent may be only one type or two or more. Preferred examples are propylene carbonate and methyl carbitol acetate, and the amount of solvent used can be adjusted appropriately according to the purpose.

[016] (II) Thermosetting resins:

[017] Synthesis Example 1: Prepolymer (oligomer)-A1

[018] 1000g of 2,2-dialkylmethylbutyric acid was added to 800g of methyl carbitol acetate solvent, heated to 80℃, and stirred to dissolve. Then, 1000g of 3-isocyanate methylene-3,5,5-trimethylcyclohexyl isocyanate IPDI was added dropwise to the above solution for reaction. The dropwise reaction time was 100 minutes, and the dropwise temperature was 80℃. After the dropwise addition was completed, the temperature was maintained at 80℃ for aging reaction for 4 hours to obtain thermopolymerizable prepolymer A1. The OH valence was 0.11mgKOH / g, and the weight average molecular weight Mw was 1006.

[019] Synthesis Example 2: Prepolymer (oligomer)-A2

[020] Add 1000g of 2,2-dialkylmethylpropionic acid to 800g of methyl carbitol acetate solvent, heat to 80℃, stir to dissolve, and then add 1100g of 3-isocyanate methylene-3,5,5-trimethylcyclohexyl isocyanate IPDI dropwise to the above solution for reaction. The dropwise reaction time is 100 minutes, the dropwise temperature is 80℃, and after the dropwise addition is completed, maintain 80℃ for aging reaction for 4 hours to obtain thermopolymerizable prepolymer A2. The OH valence is 0.12mgKOH / g, and the weight average molecular weight Mw is 964.

[021] As a crosslinking agent, any suitable thermosetting resin may be used within the scope that does not impair the effects of the present invention. The thermosetting resin crosslinking agent may be only one type, or it may be two or more types. Prepolymer A is used in conjunction with the thermosetting resin crosslinking agent. Examples of thermosetting resin crosslinking agents include: bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic resin, cresolic resin, biphenyl phenol type epoxy resin, biphenyl aralkyl type epoxy resin, arylalkyl type epoxy resin, naphthalene type epoxy resin, anthracene type epoxy resin, dicyclopentadiene type epoxy resin, adamantane type epoxy resin, and other epoxy resins.

[022] In terms of further demonstrating the effects of the present invention, the thermosetting resin is preferably selected from at least one of the groups consisting of cyanate resins and epoxy resins. Examples of cyanate resins that can be used include: bisphenol-type cyanate resins such as phenolic varnish-type cyanate resins, bisphenol A-type cyanate resins, bisphenol E-type cyanate resins, and tetramethylbisphenol F-type cyanate resins; dicyclopentadiene-type cyanate resins; biphenylalkyl-type cyanate resins; and cyanate resins formed by reacting 2,2-dihydromethylbutyric acid or 2,2-dihydromethylpropionic acid with 3-isocyanate-methylene-3,5,5-trimethylcyclohexyl isocyanate. Among these cyanate resins, in terms of further demonstrating the effects of the present invention, cyanate resins formed by reacting 2,2-dihydromethylbutyric acid or 2,2-dihydromethylpropionic acid with 3-isocyanate-methylene-3,5,5-trimethylcyclohexyl isocyanate are preferred.

[023] The weight-average molecular weight of the cyanate ester resin can be any suitable weight-average molecular weight without impairing the effects of the present invention. For aspects that further enhance the effects of the present invention, a weight-average molecular weight of 500 to 3000 is preferred, and more preferably 600 to 2000. The weight-average molecular weight can be determined, for example, by GPC (gel permeation chromatography, standard material: polystyrene conversion).

[024] When the resin composition for sensor coating contains cyanate resin, the content of cyanate resin in the resin composition for sensor coating is preferably 5% to 90% by weight, more preferably 10% to 80% by weight, and even more preferably 20% to 50% by weight, relative to the total solid content of the resin composition.

[025] Examples of epoxy resins include: bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol E type epoxy resin, and other bisphenol-type epoxy resins; phenolic varnish type epoxy resins such as phenolic varnish type epoxy resin and cresol phenolic varnish type epoxy resin; arylalkyl type epoxy resins such as biphenyl type epoxy resin, diphenylene dimethyl type epoxy resin, and biphenyl arylalkyl type epoxy resin; and phenolic arylalkyl type epoxy resins such as phenolic arylalkyl type epoxy resin having a phenylene skeleton and phenolic arylalkyl type epoxy resin having a biphenylene skeleton. Emulsions; multifunctional epoxy resins such as triphenol methane type epoxy resin and alkyl-modified triphenol methane type epoxy resin; naphthol type epoxy resin, naphthyl diphenol type epoxy resin, difunctional to tetrafunctional naphthalene epoxy resin, naphthyl ether type epoxy resin, binaphthalene type epoxy resin, naphthyl aralkyl type epoxy resin, and other naphthalene type epoxy resins; anthracene type epoxy resin; phenoxy type epoxy resin; dicyclopentadiene type epoxy resin; norene type epoxy resin; adamantane type epoxy resin; fumonisin type epoxy resin; phenolic varnish type epoxy resin with condensed ring aromatic hydrocarbon structure.

[026] Regarding the epoxy resin, in terms of further demonstrating the effects of the present invention, it is preferable to select at least one from the group consisting of phenolic varnish-type epoxy resins having a condensed ring aromatic hydrocarbon structure and naphthalene-type epoxy resins, more preferably naphthalene-type epoxy resins. Examples of naphthalene-type epoxy resins include: naphthol-type epoxy resins, naphthiodiol-type epoxy resins, difunctional to tetrafunctional naphthalene-type epoxy resins, naphthyl ether-type epoxy resins, binaphthalene-type epoxy resins, naphthalene-arylalkyl-type epoxy resins, naphthalene-modified cresol phenolic varnish-type epoxy resins, etc.

[027] The weight-average molecular weight of the epoxy resin can be any suitable weight-average molecular weight without impairing the effects of the present invention. In terms of further demonstrating the effects of the present invention, a weight-average molecular weight of 500 to 20,000 is preferred, and more preferably 800 to 15,000. The weight-average molecular weight can be determined, for example, by GPC (gel permeation chromatography, standard material: polystyrene conversion).

[028] When the resin composition for sensor coating contains epoxy resin, the content of epoxy resin in the resin composition that can further demonstrate the effect of the present invention is preferably 1% to 55% by weight, and more preferably 2% to 40% by weight, relative to the total solid content of the resin composition.

[029] When the resin composition for sensor coating contains at least one of the group consisting of cyanate ester resin and epoxy resin, it may further contain phenolic resin. If these are used together, the crosslinking density can be controlled, and the reactivity can be easily controlled, exhibiting excellent dimensional stability.

[030] (III) Conductive filler material:

[030] One or more conductive fillers are used in the composition. Typical conductive fillers include, but are not limited to, silver, copper, gold, palladium, platinum, nickel, gold- or silver-plated nickel, carbon black, carbon fiber, graphite, aluminum, indium tin oxide, silver-plated copper, silver-plated aluminum, metal-coated glass spheres, metal-coated fillers, metal-coated polymers, silver-coated fibers, silver-coated spheres, antimony-doped tin oxide, conductive nanospheres, nano-silver, nano-aluminum, nano-copper, nano-nickel, carbon nanotubes, and mixtures thereof. In one specific embodiment, the conductive filler is conductive carbon black. One or more conductive fillers are contained in the composition in the range of about 5 to about 40 weight percentages and preferably in the range of about 5 to about 20 weight percentages.

[031] As a conductive filler, a mixture of conductive carbon black of different sizes is preferred in terms of improving the filling properties of the conductive filler.

[032] The conductive filler may be only one type or two or more types.

[033] Examples 1-2

[033] A prepolymer was substituted into the conductive ink formulation, the formulation of which is detailed in Table 1. After thorough grinding using a three-roll mill, an ink composition was obtained. The ink composition thus obtained was coated onto a 3cm x 3cm polyimide (PI) test plate by screen printing, and a thickness of 15 to 20 μm was obtained by this method. The coating was then baked at 130 to 180°C for 0.5 to 1 hour to obtain a fully cured coating.

[034] Comparative Example 1

[034] Comparative Example 1 is an ink formulation composition without the addition of conductive powder, and its formulation composition is detailed in Table 1.

[035] In Table 1, the information of each component is as follows: naphthalene-type epoxy resin model EBA-65, conductive carbon black model Carbon ECP-600JD, and imidazole-based 2-methylimidazolium.

[035]

[035]

[036] Test Board Fabrication and Testing

[036] The ink was screen-printed onto a 3cm x 3cm polyimide (PI) test plate using a 200-mesh screen printing machine. The wet film thickness was 15μm, and the plate was baked at 130℃ for 60 minutes to harden, resulting in a 12μm coating thickness after curing. A wire was pulled out from the hardened test plate, and the plate was then fixed using an electrical testing instrument clamp. Simultaneously, both ends of the polyimide (PI) test plate were fixed using a tensile testing machine. Forces were applied in opposite directions to stretch the plate by 0.2% and 0.5% respectively, and the resistance changes were recorded. The strain gauge factor was calculated using the formula.

[037] The resin composition for sensor coating, sensor film, and sensor circuit board of the present invention are useful in the field of electronic stress sensing devices. They are particularly useful in the field of developing next-generation electronic stress sensing devices.

Claims

1. A thermosetting resin composition comprising: (a) a thermosetting A resin comprising 30 wt% to 60 wt% of the solid content of the thermosetting resin composition, wherein the thermosetting A resin comprises A1 resin and A2 resin, wherein the weight ratio of A1 resin to A2 resin is 2; (b) a conductive filler comprising 5 wt% to 20 wt% of the solid content of the thermosetting resin composition; (c) a crosslinking agent being an epoxy resin comprising 5 wt% to 20 wt% of the solid content of the thermosetting resin composition; and (d) a curing accelerator being an imidazole derivative comprising 0.1 wt% to 3 wt% of the solid content of the thermosetting resin composition; wherein the A1 resin is of the structural formula shown in (a):

1. The structural formula (II) of the A2 resin system is shown below:

2. The thermosetting resin composition as described in claim 1, wherein, The OH valences of the A1 resin and A2 resin are 0.11 and 0.12 mg KOH / g, respectively.

3. The thermosetting resin composition as described in claim 1, wherein, The conductive filler is conductive carbon black.

4. A sensor coating preparation, said coating being made from a thermosetting resin composition as described in any one of claims 1 to 3.