JPH02113075A - Ultraviolet ray curable composition exhibiting electrically conductive properties by curing - Google Patents

Abstract

PURPOSE:To obtain the title composition containing an acryloyl group-containing a photopolymerization compound, radical reaction type light initiator, azo compound based radical polymerization initiator and metal fine powder, readily curable by ultraviolet rays and exhibiting large conductivity. CONSTITUTION:The aimed composition containing an electrically conductive material consisting of (A) (i) a photo-polymerizable low-molecular weight compound having one or more acryloyl group and/or (ii) photo-polymerizable low- molecular weight low polymer having one or more acryloyl group, (B) a radical reaction type light initiator having main absorption in ultraviolet ray area of 300-450nm wavelength, (C) an azo compound based radical polymerization initiator having 40-70 deg.C temperature in one hour half-life period and (B) an ultrafine powder of metal and capable of curing and then exhibiting conductivity by irradiating a coating film having <=5mm thickness with ultraviolet rays.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention provides a conductive composition that is easily cured by ultraviolet rays, has high conductivity, and has excellent adhesion and strength to a substrate, as well as excellent other practical physical properties. The present invention relates to an ultraviolet curable resin composition that can be used to form objects.

Technical Background and Problems Conventionally, in order to obtain an ultraviolet curable conductive 1# resin composition, research has been conducted on a method using a composition in which a conductive powder such as silver powder is mixed with an ultraviolet curable resin 1@. However, even if the same composition is applied as a coating to a substrate and irradiated with ultraviolet rays, although the extremely thin resin layer on the surface of the coating hardens, the inside of the coating hardly hardens. If the amount is reduced or the coating film thickness is made extremely thin, sufficient conductivity will not be obtained even though it is cured.

The reason why the inside of the coating film is difficult to cure is presumed to be that the silver powder blocks the transmission of ultraviolet rays, so that no or almost no ultraviolet rays reach the interior of the coating film.

For this reason, conventionally proposed ultraviolet curable conductive compositions are made by forming an incompletely cured composition by irradiating ultraviolet rays onto a composition containing an ultraviolet curable resin and a conductive material. .

After that, other curing methods 1, such as a method of combining a heat curing method or a warm air curing reaction method to obtain a completely cured composition, or a method of using a substance with high ultraviolet transmittance as a conductive material 5, such as a metal oxide such as tin oxide. a method of using or a substance that improves ultraviolet transmittance when mixing the composition;
For example, by mixing small pieces of glass with silver powder, ultraviolet rays are transmitted not only to the surface of the ultraviolet curable conductive composition but also to the inside, thereby imparting curability. .

However, in the method of obtaining a completely cured composition by combining curing methods other than ultraviolet irradiation, one work step becomes complicated. In addition, it is impossible to form a highly conductive composition with the method of using an ultraviolet-transmitting conductive material or the method of incorporating a substance that increases ultraviolet transmittance. Due to the defect that it cannot be used in applications that require electrical conductivity, it does not have a wide range of applications.

Purpose of the Invention The present inventor has conducted extensive research in view of the fact that if it were possible to create a mixed composition of an ultraviolet curable composition and a highly conductive material that could be cured only by ultraviolet irradiation, it would have extremely excellent practical value. As a result, they discovered that a composition containing a special photopolymerization initiator and a specific radical polymerization initiator can be sufficiently cured with only short-term ultraviolet irradiation and has high conductivity, and the present invention has been completed. .

Summary of the Invention The present invention provides a photopolymerizable low molecular weight compound having one or more acryloyl groups and/or a photopolymerizable low polymer having one or more acryloyl groups as an ultraviolet curable composition. A radical-reactive photopolymerization initiator having a main absorption range in the ultraviolet region of 300nno to 450nm,
Ultraviolet rays are irradiated on a coating film with a thickness of 5 mm, which is made of an aso compound-based dical mold initiator with a 1-hour shelf life temperature of 40°C to 70°C, and a fine metal powder as a conductive material. It is characterized by hardened scales. The present invention provides an ultraviolet-curable f1 composition that exhibits conductivity upon curing.

DETAILED DESCRIPTION OF THE INVENTION The reaction mechanism of the present invention when an ultraviolet curable composition is exposed to an acid is that first, a photopolymerization initiator activated by ultraviolet rays is used to react on the surface of a film-like or hemispherical ultraviolet curable composition. , the photopolymerizable low-molecular substance and/or photopolymerizable low-polymer starts a reaction and forms a very thin film of the cured product.1st, the photopolymerizable low-molecular substance and/or photopolymerizable low-polymer on the surface reacts. Due to the reaction heat generated along with the heat generated from the ultraviolet light emitting light source and the hardened thin film on one surface, the effect of blocking the addition that has a strong radical polymerization inhibiting effect,
Radicals that are activated at relatively low temperatures turn the intermediate initiator into radicals and cause a reaction of photopolymerizable low molecular weight substances and/or photopolymerizable low polymers.The heat of the polymerization reaction generated at this time is stored, and the radicals By causing a polymerization reaction, the ultraviolet curable composition undergoes a rapid curing reaction in a short period of time, not only in the form of a thin film but also in the case of thick film or hemispherical forms where ultraviolet rays do not reach the inside. Presumed.

Note that unless a photopolymerization initiator is used among the components used in the conductive composition of the present invention, not only the inside of the coating film but also the surface thereof will not be practically cured.

The photopolymerizable low molecular weight substance used in the present invention is a heptamer having an acryloyl group, and as a monofunctional monomer,
2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate,
As difunctional monomers such as isobornyl acrylate, dicyclopentagenyl acrylate, dimethylaminoethyl acrylate, 2-hydroxyethyl acryloyl phosphate, heptadecafluorodecyl acrylate, acryloyloxypropyltrimethoxysilane, etc.
．． 3-butanediol diacrylate, 1,4-butanediol diacrylate, l,6-hexanethiol di7acrylate, diethylene glycol diacrylate,
Neopentyl glycol diacrylate, tripropylene glycol diacrylate, bisphenol F diacrylate, trimethylolpropane diacrylate monoallyl ether, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, di These include pentaerythritol pentaacrylate, dipentaerythritol pentaacrylate monobutyl ether, dipentaerythritol hexaacrylate, and one or more of these may be used.

The photopolymerizable low polymer having one or more acryloyl groups as a functional group used in the present invention has a skeleton structure such as polyester, polyurethane,
These include structures derived from polyether, silicone, and other resins or epoxy resins, and all of them are low-polymerization polymers having a structure in which one or more acryloyl groups are added to the end.

More specifically, polyester acrylate is a polyhydric alcohol, ethylene glycol, 14-butanediol, 1,6-hexanediol, diethylene glycol, trimethylolpropane, dipropylene glycol, polyethylene glycol, pentaerythritol, etc., and a polybasic acid. There are polyesters with hydroxyl groups synthesized by reacting phthalic acid, adipic acid, maleic acid, itaconic acid, trimellitic acid, succinic acid, terephthalic acid, etc., and 7-acrylates of caprolactone-modified polyesters.

Epoxy acrylates are broadly classified into bisphenol-type, novolak-type, and alicyclic-type, and each of them is converted into bisphenol - shrimp chlorohydrin-type phenol novolac.
There are resins obtained by reacting shrimp chlorohydrin-type GS-type epoxy resins and other various epoxy resins with acrylic acid.

Polyurethane acrylate is a polymer synthesized by reacting an insinate group in a compound obtained using incyanate such as tolylene diisocyanate and diphenylmethane diisocyanate with an acrylate containing a hydroxyl group such as 2-hydroxyethyl acrylate. Polymerization synthesized by adding and reacting polyhydric alcohols such as 1,4-buta/diol, polypropylene glycol, and polyester polyol, and polyhydric amines such as 1,6-hexanediamine piperazine and dosaminoethyl ether. There are things.

Polyether acrylates include polymers synthesized by reacting polyether polyols such as polypropylene glycol and polytetramethylene glycol with acrylic acid.

In the present invention, preferably one or more types of photopolymerizable low polymers as described above are used.

Used in the present invention. Wavelength is 300nm to 4
Radical-reactive photoinitiators with a main absorption range in the ultraviolet region of 50 nm include 1, for example, as a carbonyl compound, 1
-Hydroxycyclohexyl phenyl ketone, benzyl dimethyl ketal bensoin ethyl ether, benzoin butyl ether, methyl orthobenzoyl benzony), 3,3-dimethyl-4-methoxybenzophenone, 2-hydroxy-2-methyl-1- 2-phenylproban-l-one, 1-(4-isopropylphenyl)-2
-Hydroxy-2-methylpropan-1-one, etc., as sulfur compounds 4-pensoyl-4'-methyldiphenyl sulfide 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-12,
Examples include 4-diethylthioxanthone, and one or more types are used.

The azo compound-based radical polymerization initiator used in the present invention has a 1-hour half-life temperature of 40°C to 70°C.
For example, 2,2'-azobis(4-medoxy2,4-
dimethylvaleronitrile), 2.2'-azobis(2-cyclopropylprobionitrile), and 2.2'-azobis(2,4-dimethylvaleronitrile), and one or more of these may be used.

In the present invention, the 1 hour half-life temperature is 40°C to 70°C.
The reason for using seven compound-based radical polymerization initiators is as follows.
Initiators at temperatures above 40°C will decompose during storage and the composition will gel in a short period of time, while initiators at temperatures above 70°C will not decompose quickly even when exposed to ultraviolet rays, resulting in a slow curing reaction. due to being too slow.

The shape of the conductive material used in the present invention is as follows:
There are no particular restrictions; for example, various shapes such as mackerel-shaped, granular, tan-shaped, and dendritic can be used alone or in combination.

Conductive W & fine metal powders include metals such as gold, platinum, iridium, palladium, silver, chromium, and nickel, as well as various types of two or more components such as a-copper alloy, copper alloy, bronze stainless steel, etc. Alloys can be used. Also, for example,
Metal powders with a multilayer structure such as copper in the center and silver on the surface can also be used, and powders in which the center is made of a non-metallic material such as glass, -/squid, high molecular weight material, etc. and the surface is coated with metal can also be used. The fine powder of the metal can also be used as the fine metal powder in the present invention.

The ultraviolet curable composition of the present invention may contain polymerizable vinyl compounds other than acrylate and low polymers such as glycerin trimethacrylate, epoxy trimethacrylate, didonylbenzene, N-t-butylmaleimide, etc. Peroxides 1 such as t-butyl-2-ethylhexanoate, paramenthane hydroperoxide and azo compounds such as azobisisobutyronitrile,
Stabilizers 9 such as dibutyl phthalate, dioctyl adipate, storage stabilizers, leveling agents, antifoaming agents, solvents and other various additives may be added.

Acryloyl in the present invention, m l (II or 2
The total amount of photopolymerizable low molecular weight substances having 11 or more and/or photopolymerizable low molecular weight substances having one or more acryloyl groups is usually 15B per 100 parts of fine powder of metal. The number of copies is between 100 and 100, preferably between 20 and 50.

The ultraviolet light source suitable for curing the conductive composition of the present invention has an emission wavelength of mainly 200 parts m to 460 parts m.
There are high-pressure mercury lamps, Canon short arc lamps, metal halide lamps, etc., and the lamp output is usually
80 W/(more than IRI, preferably 12
0 W/cm or more. Further, the irradiation time is usually 5 minutes or less.

Of course, it is also possible to apply heat in addition to ultraviolet rays when curing the ultraviolet curable +1 composition of the present invention.

Adhesive materials used to coat the conductive composition of the present invention include films of polymers such as polyester, polyimide, polysulfone, polyetherimide, polypropylene, ABSII resin, ethylene vinyl alcohol, glass fiber reinforced epoxy, paper, etc. Reinforced phenolic resin, polyetherketone, etc. resin boards, paper, non-woven fabrics,
There are various metals and various ceramics, and there are no special restrictions.

Effects of the Invention The ultraviolet curable composition of the present invention can be easily cured to the inside of the coating film only by ultraviolet irradiation, and
Because it has excellent conductivity, adhesion to the base material, and strength, conventionally proposed methods such as heat curing, anaerobic curing, etc., or curing methods that combine heat curing, anaerobic curing, etc., or materials with high ultraviolet transmittance or Compared to the method of mixing a substance that improves ultraviolet transmittance when mixing the composition, the curing process is extremely simple, and it can also be applied to adherent substrates that do not have sufficient heat resistance, such as plastics. It has the characteristic of curing in a short time not only in the form of a cloth but also in the form of a thick film, and even in the curing method of a film such as the Print 1 wiring board, it is difficult to take out lead wires and adhere them. , also applicable to hemispherical raised adhesive curing method.
Extremely versatile.

The ultraviolet curable composition of the present invention? There are various methods for forming the IIi film, such as spray painting, brush painting, electrostatic immersion + i coating, painting with a roll coater, print printing, printing using planography, letterpress, intaglio, etc., and discharging from a dispenser. Alternatively, after forming a coating film, the upper part may be covered with a transparent resin and irradiated with ultraviolet rays.

It should be noted that the mixed composition of the present invention is relatively stable and at room temperature (
When stored at 18° C.), it is possible to easily prepare a mixed composition that does not gel for more than 31 days and can be used normally.

Furthermore, when it is necessary to store the ultraviolet curable composition of the present invention for a long period of time, place it in a refrigerator, freezer, etc.
Il below 0℃! It is advisable to store at 30°C.

Next, the present invention will be explained by examples.

Example 1 50 parts of trimethylolpropane triacrylate was used as a photopolymerizable low-molecular compound, and diacrylate of a polyether polyol (8 parts) containing about 4 moles of ethylene oxide in 1 mole of bisphenol was used as a photopolymerizable low-molecular compound. 50 parts of Kayarad R-551 (manufactured by Yakuza Co., Ltd.) and 250 parts of scaly fine silver powder were mixed, and 2.4-
Diethylthioxanthone and 2°2'-azobis(2,4-dimethylvaleronitrile) as a radical initiator were added in respective proportions to the resin and mixed in a three-roll mixer. The same mixed composition was applied in the form of a film with a thickness of 0.2 mm, and gF: External irradiation 11 device (manufactured by World Engineering Co., Ltd., metal halide lamp k 20 W)
/ crs, irradiation distance 15c+a), and irradiated with ultraviolet rays three times at a conveyor speed of 400 W/min.

Table 1 Note that all the mixed compositions did not gel for more than 3 days even when stored in room 1i1 (18° C.) in the dark.

*1 *2 Pencil scratch hardness test method: The adhesion and strength of the cured coating film can be determined by the zero-scratch test method based on the JIS K5401 method.

Specific resistance measurement method i Thickness 0.2+w on ABS resin plate
A method was used in which a film-like cured product with a cap length of 5 m and a length of 50 m was prepared, and the resistance was calculated from the measured resistance value.

Example 2 2% 2,4-diethylthioxanthone as photoinitiator
, 2.2゛azobis(2,4
-dimethylvaleronitrile) was mixed into the same composition as in Example 1, and the mixture 1i11& was irradiated with ultraviolet light each number of times in the same manner as in Example 1.

Table 2 Mix a specified amount of silver powder in each.

Example 1 same as It was irradiated with ultraviolet light three times using the same method.

Table 3 2.4-diethylthioxane 2% as photoinitiator,
2,2°-azobis(2,4
-dimethylvaleronitrile) was added to 50 parts of the same photopolymerizable low molecular weight polymer as in Example 1, and 2% of the photoinitiator was added to the same composition. , 3% of 22°-azobis(2,4-dimethylvaleronitrile) as a radical polymerization initiator was mixed into the same composition as in Example 1, and the mixed composition was applied to the lead wire. Ultraviolet rays were irradiated three times in the same manner as in 1.

Table 4 Wood 3 A; B: C; D: Tensile strength test method; O++-diameter PVC-covered tin-plated copper wires were bonded in parallel with this trial@cured composition to ensure sufficient tensile strength in the horizontal direction.

Benzoin ethyl ether benzyl dimethyl kecool 2-methyl-1-[4-(methylthionophenyl]-2
-morpholinopropanone-1 to 4-, fluoro-4'-methylphenyl sulfite 2,4-diethylthioxanthone implementation g15 2% 2,4-diethylthioxanthone as photoinitiator
, 3% of a radical polymerization initiator was mixed into the same composition as in Example 1, and the same mixed composition was glued to the lead wire outlet.
Ultraviolet rays were irradiated three times in the same manner as in Example 1.

Table 5 A: C; 2.2°-azobis(4-methoxy-24-dimethylvaleronitrile) 2.2′-azobis(2-cyclopropylpropionitrile) 2.2°-azobis(2,4-) methylvaleronitrile)

Claims (1)

[Claims] A photopolymerizable low-molecular compound having one or more acryloyl groups and/or a photopolymerizable low-molecular compound having one or more acryloyl groups as an ultraviolet curable composition, in the ultraviolet region with a wavelength of 300 nm to 450 nm. It consists of a radical reaction type photoinitiator with a main absorption range, an azo compound-based radical polymerization initiator with a 1-hour half-life temperature of 40°C to 70°C, and a fine metal powder as a conductive material.
An ultraviolet curable composition that exhibits electrical conductivity upon curing, characterized in that it can be cured by irradiating a coating film with a thickness of 5 mm or less with ultraviolet rays.