JPS5833907B2 - Fast curing conductive coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fast-curing conductive coating composition whose curability is promoted by utilizing photocurability or the like.

Conventionally, for example, conductors used in printed circuit boards for electric circuits were made into a paint by blending silver powder with a curable resin composition, and this paint was screen printed on a laminated board made of phenol, epoxy, polyester, etc. to match the desired circuit. The coating is printed, crosslinked and cured, thereby fixing the coating film to the substrate and exhibiting predetermined physical properties.

To cure this resin, there are many so-called thermosetting resins that are polymerized and crosslinked via a polymerization initiator that activates prepolymers and monomers that have radically polymerizable double bonds in the resin composition by heat action. .

This heating usually takes 30 minutes to 2 hours at 120 to 200°C, which results in extremely poor workability and also causes problems such as thermal deformation of the substrate.

On the other hand, transparent photocurable resin compositions are known as fast-curing resin compositions, but when these photosensitive resin compositions contain opaque materials such as silver powder, their light transmittance deteriorates significantly, and for example, when a substrate In the case of a coating film applied to the substrate, there is a problem in that the portion close to the substrate remains uncured.

The present invention has been made in view of the above points, and includes 2.2.
-Providing a resin composition containing dimethoxy-2-phenylacetophenone, even when silver powder is included, it is 1/1
It is designed to be able to harden within a short period of time.

The composition of the present invention blends silver powder into a resin composition of a radically crosslinkable prepolymer and a vinyl monomer, and further contains 2,
This is a coating composition containing 2-dimethoxy-2-phenylacetophenone.

All conventionally known radically crosslinkable prepolymers and vinyl monomers can be used, but for example, as prepolymers that have radically polymerizable unsaturated double bonds, epoxy compounds and (meth)acrylic acid can be used. Epoxy (meth) obtained by addition reaction of
Acrylates, polyhydric alcohols and diisocyanates (
Urethane poly(meth)acrylate obtained by addition reaction with hydroxyalkyl meth)acrylate, polyester poly(meth)acrylate obtained by reacting the carboxyl group of polyester with hydroxyalkyl (meth)acrylate or glycidyl methacrylate. , polyester poly(meth)acrylate obtained by reacting polyester hydroxyl groups with (meth)acrylic acid, polyether polyol poly(meth)acrylate obtained by reacting polyether glycol with (meth)acrylic acid, fatty acid and ( Examples include polyester poly(meth)acrylate obtained by reacting hydroxyalkyl methacrylate or glycidyl methacrylate.

In addition, as vinyl monomers, styrene, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-
Hydroxypropyl (meth)acrylate, diethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethanetetra(meth)acrylate ) acrylate, dipentaerythritol hexa(meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxytetraethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, 2-hydroxydodecyl (meth)acrylate, etc. The polymer and the vinyl monomer can be used singly or in combination of two or more of each, if desired.

There are two types of silver powder: spherical powder made by a chemical reduction method and flattened powder made by flattening this spherical powder by mechanical processing, and these powders can be used alone or in combination.

As a polymerization initiator, 2,2-dimethoxy-2-phenylacetophenone (also referred to as benzyl methyl ketal) having the following structure and having thermal polymerizability is used.

In addition to the above, this composition also contains various substances used in general paints, such as colorants, waxes, polymerization inhibitors, organic peroxides, curing accelerators, thickeners, leveling agents, and antifoaming agents. Additives can also be used.

The composition ratio of the coating composition of the present invention is 10 to 50% of the resin composition containing a radically crosslinkable prepolymer and a vinyl monomer.
Weight percent, preferably 15-40 weight percent, silver powder 40-85 weight percent, preferably 50-80 weight percent
The weight percent of 2,2-dimethoxy-2-phenylacetophenone as a polymerization initiator is 0.1 to 10 weight percent, preferably 0.5 to 8 weight percent.

In order to produce the coating composition of the present invention, the prepolymer and silver powder are properly mixed while stirring well so that the silver powder is well coated with the prepolymer.

Then, the vinyl monomers are mixed and stirred until the mixture is homogeneous.Finally, 2,2-dimethoxy-2-phenylacetophenone is mixed and diluted with a solvent such as vinyl monomer as needed to make the product. .

In addition, in order to use the coating composition of the present invention, if it is printed on a circuit board, for example, by an appropriate means such as silk screen printing, and irradiated with ultraviolet rays, the surface layer of the coating film mainly undergoes polymerization, which is excited by the light. The initiator 2,2-dimethoxy-2-phenylacetophenone acts on the prepolymer and the vinyl monomer and adds to the double bonds they have, and the prepolymer is crosslinked with each other or through the vinyl monomer, forming a three-dimensional network. It gradually becomes tack-free and hardens.

Then, this surface layer portion is also thermally cured by heat rays emitted from, for example, an ultraviolet irradiation device, the coating film is solidified, and the silver powder is firmly fixed to the substrate.

On the other hand, only heat curing occurs in the deep layers of the coating where ultraviolet rays do not reach.

In this thermal curing, 2,2-dimethoxy-2phenylacetophenone is excited by heat, and this radical induces a reaction between the prepolymer and the vinyl monomer, resulting in crosslinking.
Dimensional reticulation and hardening.

When solidified in this way, the silver powder is fixed and can function as a circuit conductor.

Next, examples of the present invention will be described in comparison with reference examples.

Table 1 shows the formulations, curing conditions, and sheet resistance values when thermosetting resins are used, and Table 2 shows the formulations, curing conditions, and sheet resistance values when using the coating compositions of the present invention.

As shown in Tables 1 and 2, heat curing requires a curing time of 30 to 120 minutes, resulting in a rounded head, while the paint using this paint is equivalent to UV irradiation for 1 to 2 minutes. The sheet resistance value was obtained.

Note that the binder refers to a mixture of a prepolymer and a vinyl monomer, which becomes the main component of the coating film when cured.

In addition, in the test, the paint was applied to the substrate, the paint was irradiated with light, and the resistance value of the paint film was measured.

The formulation is shown in parts by weight, and if the total does not add up to 100 parts by weight, the weight is written in parentheses.

According to the present invention, since silver powder is blended into a composition containing 2,2-dimethoxy-2-phenylacetophenone in a radically crosslinkable prepolymer and a vinyl monomer, it has the characteristic of fast curing by light curing, and also has the characteristic of fast curing by light curing. The deep part of the coating film that does not penetrate can be compensated for by heat curing, and a coating film that cures quickly and has a high degree of hardening can be obtained as a whole.
The curing time is shortened to 15 to 1/25 times, significantly improving workability and maintaining performance as a conductor.

Claims (1)

[Claims] 1. For a resin composition containing a radically crosslinkable prepolymer and a vinyl monomer, 40 to 85 weight percent of silver powder and 0 to 0 of 2,2-dimethoxy-2-phenylacetophenone as a polymerization initiator are added to a resin composition containing a radically crosslinkable prepolymer and a vinyl monomer.
．． 1 to 10 weight percent of a fast-curing conductive coating composition.