JPH0559931B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an active energy ray-curable conductive resin composition. More specifically, it relates to an active energy ray curable conductive resin composition containing an energy ray curable cation polymerizable organic substance, a conductive powder, an energy ray sensitive cation polymerization catalyst, and a heat sensitive cation polymerization catalyst as essential components. It is something. Generally, conductive resin compositions are used by blending metal powders such as silver and copper and carbon powders as conductivity imparting agents with thermosetting resins such as epoxy resins, alkyd resins, and phenolic resins. Curing of a curable resin requires heating at high temperatures for a long time, for example, it usually takes 30 minutes to several hours at 120 to 200°C. These heating and drying conditions not only cause deterioration and thermal deformation of insulating substrates made of phenol, epoxy, polyester, etc., which are inconvenient, but also have the disadvantage of extremely poor thermal energy efficiency and workability. Under these circumstances, attempts have recently been made to obtain a fast-curing conductive resin composition by using an ultraviolet curable resin as a binder for the conductive resin composition. However, since these ultraviolet curable conductive resin compositions contain conductivity imparting agents such as carbon powder and silver powder, their ultraviolet ray transmittance is significantly reduced and curing does not proceed sufficiently, especially in the case of certain thick coatings. A disadvantage arises in that only the surface layer is cured, while the interior of the coating film and the portions close to the substrate remain uncured. In addition, when used in applications that require a high degree of conductivity, it is necessary to use conductive metal fine powder in an amount of about 70 to 90 wt% of the entire composition, and the ultraviolet absorption due to the negative effect of the metal fine powder The polymerization reaction is significantly inhibited, and sufficient curing and drying cannot be carried out. The present invention was completed as a result of intensive studies to eliminate the various drawbacks of such conventional energy ray curable conductive resin compositions. The object of the present invention is to contain a large amount of conductive powder,
To provide an energy ray-curable conductive resin composition that can be sufficiently cured by practical energy ray irradiation and/or heating at a relatively low temperature for a short time even in the case of a relatively thick coating film. It is in. The conductive resin composition of the present invention has as essential components:
(a) an alicyclic epoxy resin, (b) a conductive powder, (c) an energy ray-sensitive cationic polymerization catalyst consisting of an aromatic onium salt that can release a Lewis acid upon receiving energy rays, and (d) a thermally It contains a heat-sensitive cationic polymerization catalyst consisting of an organic sulfonium salt capable of releasing a Lewis acid.
That is, the conductive resin composition of the present invention uses an energy ray-sensitive cationic polymerization catalyst and a heat-sensitive cationic polymerization catalyst as polymerization initiators in combination, so that the cationic polymerization reaction initiated by active energy rays and the radiant heat from the active energy rays can be combined. A cationic polymerization reaction initiated by radiation or heating at a relatively low temperature for a short time is carried out in parallel, so that the interior of the coating film, which is insufficiently transparent to active energy rays such as ultraviolet rays, can be sufficiently cured in a short time. This is what I did. The energy ray-curable cationically polymerizable organic substance (a) that is a component of the composition of the present invention is a cationically polymerizable compound that undergoes polymerization or crosslinking reaction by energy ray irradiation in the presence of an energy ray-sensitive cationic polymerization catalyst. Specifically, alicyclic epoxy resin is preferred. Preferred alicyclic epoxy resins include polyglycidyl ethers of polyhydric alcohols having at least one alicyclic ring, or compounds containing cyclohexene or cyclopentene rings, which are treated with a suitable oxidizing agent such as hydrogen peroxide or peracid. Examples thereof include cyclohexane oxide or cyclopentene oxide-containing compounds obtained by epoxidation. Typical examples of alicyclic epoxy resins include hydrogenated bisphenol A diglycidyl ether, 3,4-epoxycyclohexylmethyl-
3,4-epoxycyclohexanecarboxylate, 2-(3,4-epoxycyclohexyl-5,
5-spiro-3,4-epoxy)cyclohexane-meta-dioxane, bis(3,4-epoxycyclohexylmethyl)adipate, vinylcyclohexene dioxide, 4-vinylepoxycyclohexane, bis(3,4-epoxy-6-methyl) cyclohexylmethyl)adipate, 3,4-
Epoxy-6-methylcyclohexyl-3,4-
Epoxy-6-methylcyclohexanecarboxylate, methylenebis(3,4-epoxycyclohexane), dicyclopentadiene diepoxide, di(3,4-epoxycyclohexylmethyl)ether of ethylene glycol, ethylenebis(3,4-epoxycyclohexanecarboxylate) ), dioctyl epoxyhexahydrophthalate, di-2-ethylhexyl epoxyhexahydrophthalate, and the like. The conductive powder (b) used in the present invention includes silver,
Conductive metal powders such as platinum, gold, copper, nickel, aluminum, palladium, iron, tin, lead, zinc, molybdenum, and their alloy powders, iron,
Cheap conductive metal powders such as copper, nickel, zinc, tin, lead, and aluminum coated with precious metals such as gold and silver, carbon fines such as carbon black, acetylene black, graphite, graphite, ferrite, and grafted carbon. Examples include powder. Other examples include fine carbon powder, glass powder, glass fiber, etc. whose surfaces are coated with highly conductive metals such as gold and silver. These conductive powders can be used alone or in combination depending on the required conductivity and purpose, and the type, shape, and size of the conductive fine powder can be selected as appropriate depending on the purpose of use of the composition. sell. The energy ray-sensitive cationic polymerization catalyst (c) used in the present invention is a compound capable of releasing a substance that initiates cationic polymerization upon irradiation with energy rays, and particularly preferred is a Lewis acid having the ability to initiate polymerization upon irradiation. It belongs to a group of double salts, which are onium salts that release . A typical example of such a compound is the general formula [R ¹ _a R ² _b R ³ _c R ⁴ _d Z] ^+m
[MX _o+n ] ^-m [In the formula, the cation is onium,
Z is S, Se, Te, P, As, Sb, Bi, O, halogen (for example, I, Br, Cl), N≡N, and R ¹ ,
R ² , R ³ and R ⁴ are organic groups which may be the same or different. a, b, c, and d are each integers of 0 to 3, and a+b+c+d is equal to the valence of Z. M is a metal or metalloid that is the central atom of the halide complex, and B, P, As,
Sb, Fe, Sn, Bi, Al, Ca, In, Ti, Zn, Sc,
V, Cr, Mn, Co, etc. X is a halogen, m is the net charge of the halide complex ion, and n is the number of halogen atoms in the halide complex ion. ]. Specific examples of the anion MX _o+n in the above general formula include tetrafluoroborate (BF ₄ ^- ), hexafluorophosphate (PF ₆ ^- ), hexafluoroantimonate (SbF ₆ ^- ), hexafluoroarsenate (AsF ₆ ^- ), hexachloroantimonate (SbCl ₆ ^- ), and the like. Furthermore, anions of the general formula MX _o (OH) ^- can also be used. In addition, other anions include perchlorate ion (ClO ₄ ^- ), trifluoromethylsulfite ion (CF ₃ SO ₃ ^- ), fluorosulfonate ion (FSO ₃ ^- ), toluenesulfonate anion,
Examples include trinitrobenzenesulfonic acid anion. Among these onium salts, it is particularly effective to use aromatic onium salts as cationic polymerization catalysts. Halonium salt, JP-A-50-151997, JP-A-52-30899,
A-group aromatic onium salts described in JP-A-56-55420, JP-A-55-125105, etc.;
A-group aromatic onium salts described in JP-A No. 158698, etc., oxosulfoxonium salts described in JP-A-56-8428, JP-A-56-149402, JP-A-57-192429, etc.; Aromatic diazonium salts described in US Pat. No. 49-17040 and the like, thiopyrylium salts described in US Pat. No. 4,139,655, and the like are preferred. Such cationic polymerization catalysts include benzophenone,
A photosensitizer such as benzoin isopropyl ether or thioxanthone can also be used in combination. The heat-sensitive cationic polymerization catalyst (d), which is another important component of the composition of the present invention, is (1) capable of causing cationic polymerization when activated in the presence of a cationically polymerizable organic substance at a temperature below 150°C; selected from onium salts that can be used. Other conditions, although not necessarily essential, are (2) substantially no large ultraviolet absorption in the wavelength range of 260 mμ to 400 mμ, and (3) thermosensitive decomposition. The activation energy of is 17~
It is preferably 20 Kcal/mole or more. Preferred heat-sensitive onium salts that satisfy the above conditions are those having a special organic group selected from alicyclic sulfonium salts, and can be represented by the following general formula (). Here, R ₁ and R ₂ are the same or different substituted or unsubstituted aliphatic or alicyclic groups, and R ₁ and R ₂ may form a ring, and there may be an unsaturated bond or an alkoxy group in the group. , nitro group, halogen group, hydroxyl group, carboxyl group, ester group, ether group, cyano group,
It can contain functional groups such as carbonyl groups, sulfone groups, and thioether groups. Y is an aliphatic group having an electron-withdrawing functional group at the α-position or β-position with respect to the sulfur atom, and is represented by the following general formula () or ()
Those shown are preferred.

【formula】

[Formula] Here, R ₃ to _{R 3} are groups selected from hydrogen atoms, substituted or unsubstituted aliphatic groups, and R ₃ and R ₄ or R ₅ and R ₆
may be the same or different. Y′ is an electron-withdrawing functional group. Here, the term "electron-withdrawing functional group" refers to a group that exerts an attractive effect on electrons of adjacent carbon atoms, and such groups include nitro groups, cyano groups, alkenyl groups, alkynyl groups, carboxyl groups, and carbonyl groups. , hydroxyl group, ester group, sulfone group, halogen group, etc. Among these, particularly preferred is an allyl group or a tertiary aliphatic group in which Y is substituted with at least one aliphatic group. Further, the anion A is a halogen-containing complex ion selected from metal halides, such as BF ₄ ^- ,
_PF6- ^{, SbF6-} , _Sbcl6- ^, _AsF6- ^, _SbF5 (OH) ^- , etc. are preferred. Furthermore, other anions include
Examples include ClO ₄ ^- , CF ₃ SO ₃ ^- , FSO ₃ ^- and the like. Such sulfonium salts are relatively easily synthesized, for example, by reacting the corresponding sulfide with a highly active alkyl halide to synthesize a sulfonium salt having a halogen anion, and then HMQ _n ,
NaMQ _n , KMQ _n , NH ₄ MQ _n (where M is B, P,
It can also be obtained by anion exchange using a reagent such as an atom selected from Sb, As, Fe, Al, Cu, Ti, Cd, Zn, and Sn, Q is a halogen atom, and m is an integer from 1 to 6. Alternatively, it can be synthesized in good yield by directly reacting the sulfide with a Mehrwein reagent such as triethyloxonium tetrafluoroborate. When a tertiary aliphatic group is reacted with a sulfide, a sulfonium salt can be obtained by carrying out the reaction under acidic conditions using the corresponding alcohol as a starting material. The composition ratio of the composition of the present invention can be varied widely depending on the required performance. For example, the conductive powder (b) is 3 to 600 parts by weight, preferably 5 to 400 parts by weight, and the energy ray sensitive cationic polymerization catalyst (c) is 0.01-10 parts by weight, preferably 0.05-10 parts by weight
5 parts by weight, heat sensitive cationic polymerization catalyst (d) 0.03~
It can be contained in an amount of 10 parts by weight, preferably 0.05 to 7 parts by weight. As long as the composition of the present invention does not impair the effects of the present invention,
Various modifying resins such as acrylic resins and polyester resins other than the cationically polymerizable organic substances mentioned above, colorants such as pigments and dyes, antifoaming agents, leveling agents, thickeners, flame retardants, and antioxidants. Appropriate amounts of various paint additives such as silica, fillers such as glass powder, and the like can be used. The composition of the present invention can be applied, impregnated, or injected onto various insulating substrates, molded containers, etc., and then cured by irradiation with energy rays and/or heating. Active energy rays used when crosslinking and curing the composition of the present invention include ultraviolet rays, electron beams, X-rays, radiation, and high frequency waves.
Ultraviolet light with a wavelength of 1800 to 6000 Å is economically preferable, and its light sources include high- and low-pressure mercury lamps,
Xenon lamps, sodium lamps, germicidal lamps, alkali metal lamps, fluorescent lamps, laser lights, etc. can be used. Furthermore, for molded products such as thick coatings and sheets, the object of the present invention can be advantageously achieved by a method using high-energy electron beam irradiation. When curing the composition of the present invention, for example, when irradiating with an air-cooled high-pressure mercury lamp, the radiant heat rays from the mercury lamp can be utilized, so additional heating is not necessarily necessary in many cases, but active energy irradiation equipment that does not generate much heat rays A complete curing reaction can be carried out more effectively by using heating before, simultaneously or after the active energy ray irradiation. In addition, the composition of the present invention may be cured without irradiation with activation energy rays, and in some cases it may be possible to cure the composition by heating alone.
It can be cured in a few seconds to several minutes at a temperature range of ~150°C. While conventional thermosetting conductive resin compositions require heating at high temperatures for long periods of time, the composition of the present invention takes advantage of the fast curing characteristic of energy ray curing while also reducing the penetration of energy rays. The deep layer of the coating film, which is difficult to cure, is made to undergo a thermal reaction at a relatively low temperature and in a short period of time, resulting in rapid curing as a whole, which significantly improves workability, and at the same time improves adhesion to the substrate, flexibility, Various physical properties such as electrical properties and thermal deformation and deterioration of the base material can be improved. Specific uses of the present invention include, for example, conductive paints, conductive inks, conductive adhesives, paints for electromagnetic wave sheets, conductive film sheets, magnetic shielding paints, conductive casting/molding materials, and impregnated materials. Examples include. In particular, epoxy resin has excellent electrical properties, so it can be applied to various electrical and electronic parts fields such as printed circuit boards for electrical circuits, chips, capacitors, resistors, conductive elements, switches, and motors. Hereinafter, typical examples of the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples. In the examples, "parts" means parts by weight. Example 1 3,4-epoxychlorohexylmethyl-3,4
- 75 parts of epoxychlorohexane carboxylate,
Trimethylolpropane triglycidyl ether
Mix well 25 parts and 0.5 parts of silicone surfactant to form a uniform resin. To 100 parts of this resin, 0.7 parts of triphenylsulfonium hexafluoroantimonate as an energy-beam-sensitive cationic polymerization catalyst and 0.7 parts of prenyltetramethylenesulfonium hexafluoroantimonate as a heat-sensitive cationic polymerization catalyst are thoroughly mixed to achieve uniform energy-beam curing. A mold resin composition was obtained. This composition
60 parts of flat silver powder was added to 40 parts and dispersed sufficiently to obtain a viscous paste-like conductive resin composition. This was printed on an insulating substrate to a thickness of 20 μm by screen printing, and was cured by irradiating it for 40 seconds at a distance of 13 cm using an 80 W/cm mercury lamp irradiation device. The resulting cured coating film was sufficiently cured in the deep layer, had a low sheet resistance of 100 mΩ, a pencil hardness of 3H, and a cross-cut tape peel test of 100/100. Example 2 3,4-epoxycyclohexylmethyl-3,
4-Epoxycyclohexanecarboxylate 30
1 part, 60 parts of bis(3,4-epoxycyclohexylmethyl) adipate, 10 parts of cresyl glycidyl ether, and 1 part of a silicone surfactant are thoroughly mixed to form a uniform resin. Bis-[4-(diphenylsulfonio)phenyl]sulfide bisdihexafluoroantimonate was added as an energy ray-sensitive cationic polymerization catalyst to 100 parts of this resin.
1 part, and 0.5 part of crotyltetramethylenesulfonium hexafluoroantimonate as a heat-sensitive cationic polymerization catalyst were thoroughly mixed to obtain a homogeneous composition. To 40 parts of this composition, 45 parts of flat silver powder and 15 parts of spherical silver powder were added and dispersed sufficiently uniformly to form a viscous paste-like conductive resin composition, which was then printed on a polyimide film substrate by screen printing. in thickness
Print on 20μ and under 80W/cm mercury lamp irradiation device.
It was cured by irradiation for 30 seconds. The resulting cured coating had a sheet resistance of 130 mΩ, a pencil hardness of 2H, and a cross-cut tape peel test of 100/100. Even in a 180° bending test with the coating surface facing either the outside or the inside, the coating showed no damage and was found to have sufficient flexibility and adhesion. Example 3 The cured coating film that was cured by heating at 130°C for 2 minutes after irradiating with a mercury lamp every hour for 5 seconds as the curing condition in Example 1 was almost the same as the cured coating film that was cured using a mercury lamp alone. The coating performance was shown to be as follows. Example 4 3,4-epoxycyclohexylmethyl-3,
4-Epoxycyclohexanecarboxylate 50
1 part, 50 parts of vinyl cyclohexene dioxide, and 1 part of a silicone surfactant are thoroughly mixed to form a uniform resin. 1 part of triphenylsulfonium hexafluoroantimonate as an energy ray-sensitive cationic polymerization catalyst per 100 parts of this resin;
0.5 parts of prenyltetramethylenesulfonium hexafluoroantemonate as a heat-sensitive cationic polymerization catalyst was thoroughly mixed to obtain a uniform energy ray-curable resin composition. 55 parts of graphite as a conductive powder was mixed into 45 parts of this composition using a roll mill so as to be sufficiently uniform to obtain a conductive resin composition.
This was screen printed on an insulating substrate to a thickness of 20 μm and irradiated with ultraviolet light for 60 seconds under a 120 W/cm high pressure mercury lamp, resulting in a cured coating film with a sheet resistance of 350 Ω. It also had excellent chemical resistance. Example 5 In Example 4, an electron beam irradiation device was used instead of ultraviolet irradiation using a high-pressure mercury lamp as the curing condition.
When irradiated with an electron beam at an accelerating voltage of 150 Kev at a dose of 15 Mrad, a conductive coating film almost the same as that obtained by curing by ultraviolet irradiation was obtained. Comparative Example 1 A conductive resin composition was prepared in the same manner as in Example 1 except that only the heat-sensitive cationic polymerization catalyst prenyltetramethylene sulfonium hexafluoroantimonate was removed. This energy ray-curable conductive resin composition was printed on an insulating substrate and irradiated with ultraviolet rays under the same curing conditions as in Example 1, but only the surface portion of the coating was cured, while the deeper portions of the coating were sufficiently cured. I didn't. Further UV irradiation for 60
Although this was carried out for several seconds, the inside of the coating did not harden. Comparative Example 2 A conductive resin composition was prepared in the same manner as in Example 4 except that only the heat-sensitive cationic polymerization catalyst prenyltetramethylene sulfonium hexafluoroantimonate was removed. This was printed on an insulating substrate in the same manner as in Example 4 and irradiated with ultraviolet rays, but the deep layer portion of the coating was not sufficiently cured. Comparative Example 3 A thermosetting conductive composition consisting of 10 parts of phenolic resin, 20 parts of epoxy resin, 15 parts of butanol, 15 parts of xylene, 20 parts of acetylene black and 20 parts of graphite was obtained. This composition was printed on an insulating substrate to a thickness of 20 μm by screen printing and thermally cured at 150° C. for 5 hours, resulting in a conductive coating film with a sheet resistance of 300Ω.

Claims (1)

[Claims] 1. As essential components, (a) alicyclic epoxy resin, (b)
conductive powder, (c) an energy ray-sensitive cationic polymerization catalyst consisting of an aromatic onium salt capable of releasing a Lewis acid upon receiving energy rays, and (d) an organic sulfonium salt capable of releasing a Lewis acid by heat. A conductive resin composition comprising a heat-sensitive cationic polymerization catalyst.