JPS63227671A - Electron beam-curing type conductive paste - Google Patents

Abstract

PURPOSE:To obtain the titled paste having excellent printing and coating suitability even not contg. volatile solvent and providing printed or coated surfaces having smoothness and conductivity which is not inferior even under high humidity, by comprising a polyallyl compd., an electron beam-reactive group-contg. compd. and a conductive fine powder. CONSTITUTION:The objective paste comprises (A) a polyallyl compd. (preferably diallyl isophthalate oligomer), (B), if necessary, a >=two electron beam-reactive groups-contg. compd. excluding the component A [e.g., tris(2-acryloyloxyethyl) isocyanurate], (C) an one electron beam-reactive group-contg. compd. (e.g., 2-hydroxyethyl acrylate) and (D) a conductive fine powder (preferably >=one kind of carbon black having a oil absorption value of >=300cc/100g by DBP, graphite having an average particle size of 2-10mum and a conductive metal fine powder having an average particle size of <=5mum).

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an electron beam curable conductive paste. More specifically, the present invention relates to a conductive paste that is cured by applying electron beams after coating or printing on base materials such as electronic device parts and printed wiring boards.

(Prior art) Conventionally, conductive pastes have been used to form conductor circuits in the manufacturing process of printed wiring circuits or hybrid thick film circuits, and these pastes with low conductivity have been used for the purpose of forming resistive parts. used in Furthermore, it is well known that this type of paste is used for various electronic components such as membrane switches and resistors, as well as for electromagnetic wave shielding, in addition to the purpose of forming circuits mentioned in "2" above. However, 1 these pastes use inorganic substances such as thermosetting resin and/or glass frit as binders, so when applying them, it is necessary to heat them to a high temperature to harden and bake them after coating or printing on the base material. there were. However, hardening and firing requires a large amount of energy, heating time, and floor space for installing a heating device, which is not only uneconomical but also has major restrictions as described below. That is, a conductive paste using an inorganic substance such as glass frit as a binder is usually
It cannot be applied to synthetic resin base materials because it requires firing at temperatures higher than o 'c, and conductive pastes using thermosetting resin binders cannot be applied to synthetic resin base materials. However, the heat used to harden the paste deforms the base material, which poses a major problem, such as hindering the mounting of components in subsequent processes on printed wiring circuit boards, for example.

Additionally, some conductive pastes contain volatile solvents in their compositions to adjust viscosity.

The solvent had to be removed before curing and firing, and consideration had to be given to recovering the solvent. Furthermore, in the case of a solvent-containing conductive paste, the influence of printing conditions on the variation in conductivity of the paste after hardening has been a major problem.

In order to improve these drawbacks, a method has been developed in which the conductive paste is cured at or near room temperature by irradiation with active energy rays such as ultraviolet rays and electron beams. However, conductive pastes cured by these methods generally have the disadvantage that their conductivity is significantly reduced in environments of high temperature or high humidity. Furthermore, when the conductive paste used in these methods does not substantially contain volatile solvents, the printability and paintability are poor, and the resulting printed or painted surface is extremely rough.
Further, when a volatile solvent is included to improve printability or coating suitability, the above-mentioned drawbacks due to the inclusion of a volatile solvent cannot be improved.

(Problems to be Solved by the Invention) The present invention improves the various drawbacks mentioned above, and has a viscosity that is sufficiently low to allow printing or painting without adding volatile solvents, and has good printability and paintability. Excellent for.

The resulting printed and painted surfaces are smooth, can be cured by electron beam irradiation at or near room temperature, and after curing there is no change in conductivity even under high temperature or high humidity environments, making it suitable for inorganic and The present invention provides an electron beam-curable conductive paste that can be applied to both synthetic resin base materials and has performance equivalent to conductive pastes that use glass frit as a binder, which has been conventionally used for inorganic base materials. be.

[Structure of the invention]

(Means for solving the problems) The present invention comprises (A) a polyallyl compound, optionally (
B) a compound having at least two or more electron beam-reactive groups other than the above (A), (C) a compound having one electron beam-reactive group, and (D) a conductive fine powder, consisting essentially of l) An electron beam curable conductive paste characterized by not containing volatile solvents.

In the present invention, (A) the polyallyl compound is:
Monomers or oligomers such as triallyl isocyanurate, triallyl cyanurate, triallyl trimate, triallyl citrate, diallyl isophthalate, diallyl orthophthalate, diallyl chlorendate,
Alternatively, a mixture of these can be used, but from the viewpoint of printability and dispersibility of the conductive fine powder, it is preferable to use one containing diallylisophthalate oligomer as the main component.

In the present invention, (B) compounds having at least two or more electron beam reactive groups other than the above (A) include monomers having at least two or more ethylenically unsaturated double bonds other than the above (A); Oligomers, such as unsaturated polyesters, polyester poly(meth)acrylates, epoxy poly(meth)acrylates,
Polyurethane poly(meth)acrylates, polyol poly(meth)acrylates, polyether poly
(Meth)acrylates.

Divinyl compounds, etc. or mixtures thereof can be used.

In the present invention, (C) a compound having one electron beam-reactive group includes styrenes such as α-alkylstyrene and styrene, (meth)acrylic acid, (meth)acrylic acid amide, and (meth)acrylonitrile.

(Meth)acrylic acid alkyl esters, (meth)acrylic acid hydroxyalkyl esters, glycidyl (meth)acrylate, vinyl acetate, allyl phthalate, oligoester mono (meth)acrylate.

Examples include phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, and mixtures thereof.

In the present invention, the conductive fine powder (C) is not particularly limited, and includes carbon blank and graphite.

Conductive metal fine powder, conductive metal oxide fine powder, or a mixture thereof can be used.

There are no particular restrictions on carbon blanks, including acetylene black, furnace blank, thermal black,
Channel black, those obtained by graft polymerization of vinyl monomers or those subjected to oxidation treatment, or mixtures thereof can be used. The graphite is not particularly limited, and purified natural graphite such as flake graphite and bead graphite, artificial graphite, or a mixture thereof may be used. The conductive metal fine powder is not particularly limited, and includes metal fine powder made of gold, silver, platinum, copper, nickel, chromium, palladium, aluminum, tungsten, molybdenum, etc., or alloys of these metals, or coated with these metals or alloys. fine inorganic powder, etc., or a mixture thereof can be used. Also, as metal oxide fine powder.

There are no particular restrictions; fine powder of oxides such as tin, titanium, iron, etc.
Alternatively, mixtures of these can be used.

However, among these conductive fine powders, carbon black, especially the oil absorption amount expressed by DBP value, is 3.
Carbon black below 00cc/100g.

Graphite, especially graphite with an average particle size of 2 to 10 μm, and electrically conductive metal fine powder, especially with an average particle size of 5 μm
It is preferable to use one whose main component is one or more selected from conductive metal fine powders having a particle diameter of m or less.

The oil absorption amount expressed by the DBP value of carbon black is 30
If it exceeds 0 cc/100 g, the resulting conductive paste tends to have low fluidity.

The content of carbon black cannot be increased from the viewpoint of printing suitability and coating suitability, and therefore it tends to be difficult to obtain a paste having high conductivity.

The oil absorption amount of graphite Hk powder is extremely small, and any oil absorption amount of graphite may be used in terms of the viscosity of the resulting conductive paste. The average particle size of graphite is 2
If it is less than μm or more than 10 μm,
The resulting conductive paste has a lower conductivity after curing, and a higher loading of graphite is required to obtain the desired conductivity, resulting in a higher viscosity of the resulting conductive paste, which is more difficult to print or paint. There is a tendency to If the average particle size of the conductive metal fine powder exceeds 5 μm, the conductivity of the resulting conductive paste after curing will be low, and in order to obtain the desired conductivity, it is necessary to increase the amount of conductive metal fine powder packed. .

The viscosity of the resulting conductive paste tends to be high, making printing and painting more difficult.

In the present invention, (C) conductive fine powder is (A).

It is preferably used in an amount of 5 to 90% by weight based on the total of (B) and (C). If it is less than 5% by weight, it tends to be difficult to form a conductive path due to contact between the conductive fine powders in the conductive paste after curing, and if it exceeds 90% by weight, the adhesive effect of the binder on the conductive fine powders will decrease. tends to be inhibited.

In the present invention, when (C) consists only of carbon blank, the resulting conductive paste acts as a so-called resistance paste with relatively low conductivity after curing,
When (C) consists of only the conductive metal fine powder 2, for example, silver powder, the conductive paste becomes highly conductive after curing. As described above, in the present invention, a desired electrically conductive paste can be obtained by appropriately adjusting the composition and content of type 3 (C).

Since the conductive paste of the present invention does not substantially contain volatile solvents, there is no need for the process and equipment to remove the solvent and collect it before curing, and the conductive paste can be handled as a non-hazardous material. , there is no variation in conductivity after curing, and solvent resources can be saved.

In addition to the above (A), optionally (B), (C), and (D), the conductive paste of the present invention may also contain a thixotropic agent such as finely divided silica to the extent that it does not impair its performance. , silica, calcium carbonate, magnesium carbonate, clay, talc, mica.

Inorganic fillers such as barium sulfate, adhesion improvers such as titanate compounds, etc. can be added.

The conductive paste of the present invention includes the above (A) and optionally (
After mixing B), (C) and (D), it can be easily produced by a method 9 which is commonly used in the production of conductive pastes, such as a method using a three-roll device.

Although screen printing is the most suitable method for applying the conductive paste of the present invention to a substrate, other printing and coating methods such as roller coating can also be used.

After the conductive paste of the present invention is printed and painted on the base material.

It is cured by electron beam irradiation in air or an inert gas atmosphere. The conditions for electron beam irradiation are an acceleration voltage of 150 to 300 KV, and an absorbed dose of 3 to 3 Q Mrad.
It is desirable that it be within the range of .

The conductive paste of the present invention can be put to practical use as it is after being cured by electron beam irradiation, but it can also be subjected to heat aging treatment or coated with a protective paint, etc., if necessary.

(Examples) The present invention will be explained in more detail below using Examples. In the examples, 1 part means part by weight.

Example 1 Diallylisophthalate oligomer 11 parts Tris(2-acryloyloxyethyl)isocyanurate 22 parts Acrylic #
2-Hydroxyethyl 33 parts Acetylene black "Denka Black" (manufactured by Denki Kagaku Kogyo ■, trade name, DBP value 250cc/100g) 3 parts Furnace black r U K -V U L CA
N P J (manufactured by CABOT, product name, DBP value 11
6cc/100g)
17 parts graphite rPOG-10J (manufactured by Sumitomo Aluminum Co., Ltd., trade name, average particle size 6 μm)
14 parts of electron beam curable conductive paste having the above composition, 165 parts
Using mesh stainless steel screen plate.

Printing was performed on a single-sided copper-clad paper phenol laminate on which a copper foil electrode portion had been previously formed by etching and polishing. The size between the copper foil electrodes of the printed conductive paste was 1 x 1 x 10 x 1 x 1 x x 1 x x 1 x x 1 x x 1 x x 1 x x 1 x x 1 x x 1 x x 1 x x 1 x x 1 x x 1 x x 1 x x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 x 1 , 1 x 1 , 2 , 3 , 3 and 4 , respectively . Next, the electron beam irradiation device (
The conductive paste was cured by irradiating an electron beam from the printed side of the laminate under conditions of an accelerating voltage of 160 KV and an absorbed dose of 10 Mrad in a nitrogen gas atmosphere. . Furthermore, an ultraviolet curing solder resist (USR-2B manufactured by Tamura Kaken) was printed on the cured conductive paste using a 200 mesh nylon screen plate, and an ultraviolet ray irradiation device (ozone-less high pressure mercury lamp, 2 KW, 80 W
/cm, distance between lamp samples 10cm, conveyor speed 1
．． The solder resist was cured using 0 m/min). In addition to evaluating the surface condition of the laminate sample thus obtained, the following three types of tests were conducted, the resistance before and after the test was measured, and the rate of change in sheet resistance due to the test was calculated.

Solder immersion test: Molten solder bath (Tin 60/
Immerse in lead 40) for 10 seconds.

Humidity resistance test: Leave for 500 hours in a constant temperature at a temperature of 40° C. and a relative humidity of 90 to 95%.

Temperature cycle test: Constant temperature incubator P made by Tabai Esbesoku ■
Using L-2GP type, -40°C 30 minutes, room temperature 15 minutes,
A cycle of 30 minutes at 85°C and 15 minutes at room temperature was repeated 5 times.

The sheet resistance value is determined by measuring the resistance value between the copper foil electrodes using a wide range digital ohmmeter DR-1 manufactured by Sansho Keiki Seisakusho.
000 CU and expressed in the unit Ω/mouth as a measure of conductivity. In addition, the resistance change rate in each test was calculated using the following formula.

] Resistance value before test The results obtained are shown in Table 1.

121 Example 2 Diallylisophthalate oligomer 10 parts Trimethylolpropane triacrylate 22 parts Tris(
2-Acryloyloxyethyl) isocyanurate
22 parts acrylic acid 2-
Hydroxyethyl 12 parts “Denka Black”
Part 3 rUK-VtJLcA
N Pj 17 part rPOG-10J
14 parts The electron beam curable conductive paste having the above composition was printed and cured by the same method as in Example 1, and the surface condition was evaluated, and the resistance value and the rate of change in resistance value were measured. Table 1 shows the results. .

Example 3 Diallylisophthalate oligomer 11 parts Methyl methacrylate 22 parts Oligoester monoacrylate [Alonisox M-IIIJ (
Manufactured by Toagosei Chemical Industry ■, product name) 33 parts "Denka Black" 3 parts r
UK-VULCAN PJ 17th part rP
OG-10J 14 parts The electron beam curable conductive paste having the above composition was printed and cured in the same manner as in Example 1, and the surface condition was evaluated, and the results of measuring the resistance value and the rate of change in resistance value are shown below. Shown in 1.

Example 4 Diallyl orthophthalate oligomer 22 parts Trimethylolpropane triacrylate 22 parts TetrahyF rofurfuryl methacrylate 22 parts "Denka Black" 3 parts rUK-VUL
CAN PJ 17 part rPOG-10J
14 parts The electron beam curable conductive paste having the above composition was printed and cured by the same method as in Example 1, and the surface condition was evaluated, and the resistance value and the rate of change in resistance value were measured. Table 1 shows the results. .

Example 4 Diallyl orthophthalate oligomer 22 parts Trimethylolpropane triacrylate 22 parts Tetrahydrofurfuryl methacrylate-I 22 parts "Denka Blank" 3 parts rUK-VU
LCAN PJ 17th part rPOG-10
J 14 parts The electron beam curable conductive paste having the above composition was printed and cured in the same manner as in Example 1, and the surface condition was evaluated. The resistance value and the rate of change in resistance value were measured. Table 1 shows the results. Shown below.

Example 5 Diallylisophthalate oligomer 8 parts trimethylolpropane triacrylate 11 parts phenoxyethyl acrylate 6 parts silver powder rD-
25j (manufactured by Deguza Japan, product name.

Average particle size: 1.1 μm) 75 parts The electron beam curable conductive paste having the above composition was printed and cured in the same manner as in Example I, and the surface condition was evaluated, and the resistance value and the rate of change in resistance value were measured. The results are shown in Table 1.

Comparative Example 1 Tris(2
-The surface condition after printing and curing of the electron beam curable conductive base was evaluated in the same manner as in Example 1 except that acryloyloxyethyl) isocyanurate was used, and the resistance value and the rate of change in resistance value were evaluated. The results of the measurements are shown in Table 1.

Comparative Example 2 Tetramethylolmethane triacrylate 22 parts Tris(2-acryloyloxyethyl) isocyanate 22 parts Polyester diacrylate 10E-A410J (manufactured by Nippon Shokubai Kagaku Kogyo 91, trade name) 22 parts "Denka Black" 3 parts rUK-VULCA
NPJ 17 part rPOG-10j
The electron beam curable conductive paste having the composition 1.4 parts was printed and cured in the same manner as in Example 1, and the surface condition was evaluated, and the resistance value and the rate of change in resistance value were measured. It is shown in Table 1.

(Margin below) = 16 = Table 1 Comparative Example 3 Trimethylolpropane triacrylate 24 parts Tris(2-acryloyl ethyl ester) isocyanurate 12 parts Tin oxide powder I
T-IJ (Mitsubishi Metals (Structure, product name, average particle size 0.
1 μm) 34 parts After printing and curing the electron beam curable conductive paste with the above composition in the same manner as in Example 1, the resistance 11'I was 5 MΩ/mouth or more, which was completely unacceptable for practical use. Ta.

Comparative Example 4 Trimethylolpropane triacrylate 12 parts Tris(2-acryloyl ethyl ester) isocyanurate 12 parts 2-hydroxyethyl acrylate 12 parts Scale-like tin oxide powder rSn-3-200J (manufactured by Fukuda Metal Foil and Powder Industry)
Product name, average particle size 6. θμm, thickness 0゜4μm or less)
34 parts After printing and curing the electron beam curable conductive paste having the above composition in the same manner as in Example 1, the resistance value was 5 MΩ/mouth or more, which was completely unsuitable for practical use.

〔Effect of the invention〕

According to the present invention: (1) Although free of volatile solvents.

It has a sufficiently low viscosity that it can be printed or painted. (2)
Since it does not contain volatile solvents, it is possible to omit the process of evaporating the volatile solvent and the process of treating the evaporated volatile solvent, such as recovering it, streamlining the process, preventing air pollution, and saving resources and energy. The conductive paste can be treated as a non-hazardous material, and the base material will not be damaged as in the case of conventional curing of thermosetting conductive paste. (2) The surface of the conductive paste after printing and curing is smooth. Because of its high hardness,
It can be used not only as a printed wiring board, but also as keyboard contacts, etc. (3) After curing, it is now possible to obtain an electron beam-curable conductive paste that does not lose its conductivity even when kept in a high-temperature or high-humidity environment for a long period of time, and whose quality is highly reliable over time. .

Claims (1)

[Claims] 1. (A) a polyallyl compound, optionally (B) a compound having at least two or more electron beam reactive groups other than the above (A), (C) an electron beam reactive group 1 and (D) a conductive fine powder, substantially consisting of (E)
An electron beam-curable conductive paste that does not contain volatile solvents. 2. (D) The conductive fine powder is carbon black with an oil absorption amount expressed by DBP value of 300 cc/100 g or less, graphite with an average particle size of 2 to 10 μm, and an average particle size of 5
The electron beam curable conductive paste according to claim 1, which contains as a main component one or more kinds selected from conductive metal fine powder of .mu.m or less. 3. The electron beam curable conductive paste according to claim 1 or 2, wherein the polyallyl compound (A) contains diallyl isophthalate oligomer as a main component.