JP5569733B2 - Conductive silver paste, conductive pattern forming method, and printed conductive pattern - Google Patents

Description

  The present invention relates to a conductive silver paste for forming a conductive film, a conductive pattern printing method, and a printed conductive pattern.

Printing methods or etching methods are known as methods for forming conductive patterns such as conductive circuits and electrodes used in touch panels, electronic paper, and various electronic components.
When forming a conductive pattern by an etching method, after forming a resist film patterned by photolithography on a substrate on which various metal films are vapor-deposited, an unnecessary vapor-deposited metal film is dissolved and removed chemically or electrochemically, Finally, it is necessary to remove the resist film, and the process is very complicated and poor in mass productivity.
On the other hand, in the printing method, a desired pattern can be mass-produced at low cost, and conductivity can be easily imparted by drying or curing the printed coating film.
As these printing methods, flexographic printing, screen printing, gravure printing, gravure offset printing, ink jet printing, and the like have been proposed in accordance with the line width, thickness, and production speed of the pattern to be formed.

As a printed pattern, formation of a high-definition conductive pattern having a line width of 50 μm or less is required from the viewpoint of miniaturization of an electronic device and improvement in design.
In addition, in order to respond to the increasing demand for thinner, lighter, more flexible electronic devices, and high-productivity roll-to-roll printing, high conductivity is achieved by printing on plastic films and firing at low temperature and short time. There is a need for conductive inks that can provide good properties, substrate adhesion, film hardness, and the like. Furthermore, among plastic films, there is a need for a conductive ink that can provide the above-mentioned physical properties when printed on an inexpensive and highly transparent PET film or a transparent conductive film in which an ITO film is formed on the PET film. Yes.

In Patent Documents 1 and 2, when the baking temperature is 150 ° C. and the printing substrate is a PET film, there is a problem that the substrate is deformed.
In Patent Document 3, although the firing temperature is 120 ° C. and a relatively low temperature, the firing time is as long as 30 minutes and the productivity is poor. Moreover, the adhesiveness of the transparent conductive film to the ITO film has not been studied.
In patent document 4, although high electroconductivity is obtained by baking at low temperature for a short time, since the organic solvent with high drying property is used, it is inferior to on-machine stability. Also, the printed line width is as thick as 3 mm, and high-definition patterning has not been studied.

JP 2009-62523 A JP 2005-56778 A JP 2006-302825 A WO2006 / 095611 JP 2007-119682 A

  As described above, in the prior art, a conductive silver paste that can obtain a higher-definition conductive pattern in a short time of 10 minutes or less even at a low temperature of less than 150 ° C. has not yet been obtained. It was.

  Therefore, in order to solve the above problems, the present inventors have intensively studied, and as a result, by using a specific organic cyclic ether compound in combination at a specific ratio with respect to silver particles, the above-described drawbacks can be solved. As a result, the present invention has been completed.

That is, the present invention contains silver particles (A), a resin (B) that is solid at 25 ° C., and an organic cyclic ether compound (C) having a flash point of 50 to 200 ° C. as essential components, and in terms of mass. The conductive silver paste is 15 to 30 parts of the organic cyclic ether compound (C) per 100 parts of the silver particles (A).
Moreover, this invention provides the formation method of the electroconductive pattern printed on the base material with the above-mentioned electroconductive silver paste.
Furthermore, this invention provides the conductive pattern printed matter formed by the formation method of the above-mentioned conductive pattern.

In the conductive silver paste of the present invention, a specific organic cyclic ether compound is used in combination at a specific ratio with respect to silver particles, so that a highly fine conductive pattern can be obtained in a short time at a low temperature. There is an effect. In the present invention, high definition means an image line (thin line) that is thinner than the conventional line of less than 30 μm, especially 15 to 25 μm in terms of line width, although it depends on the shape of the conductive pattern to be obtained.
The conductive pattern forming method of the present invention uses a conductive silver paste in which a specific organic cyclic ether compound is used in combination at a specific ratio with respect to silver particles, so a high-definition conductive pattern and printed matter thereof Can be obtained in a short time at a low temperature.

  The conductive silver paste of the present invention contains silver particles (A), a resin (B) that is solid at 25 ° C., and an organic cyclic ether compound (C) having a flash point of 50 to 200 ° C. as essential components. And it is the conductive silver paste which is the organic cyclic ether compound (C) 15-30 parts per 100 parts of the silver particles (A) in terms of mass.

As the silver particles (A) used in the conductive silver paste of the present invention, any known and conventional ones can be used. For example, a spherical particle whose median particle diameter (D50) is 100 nm to 15 μm as an average particle diameter. Silver powder can be used.
Examples of such silver particles (A) include SPQ03S (Mitsui Metal Mine Co., Ltd., average particle size D50: 0.5 μm), EHD (Mitsui Metal Mine Co., Ltd., average particle size D50: 0. 5 μm), AG2-1C (manufactured by DOWA Electronics Co., Ltd., average particle diameter D50: 0.8 μm), AG2-1 (manufactured by DOWA Electronics Co., Ltd., average particle diameter D50: 1.3 μm), Sylbest AgS-050 ( Examples include Tokuroku Chemical Laboratory Co., Ltd., average particle diameter D50: 1.4 μm), Sylbest C-34 (Tokuriki Chemical Laboratory Co., Ltd. average particle diameter D50: 0.6 μm), and the like.

  Among them, when a silver particle having a median diameter (D50) of 1.0 to 10.0 μm and a silver particle having a median diameter (D50) of 0.2 to 0.7 μm are used in combination, formation of a conductive pattern of a finer fine line, It is preferable because sufficient conductivity can be imparted by baking at less than 150 ° C., and in terms of mass, the median diameter (D50) is 0 per 100 parts of silver particles having a median diameter (D50) of 1.0 to 10.0 μm. The combined use of 50 to 200 parts of silver particles of 2 to 0.9 μm can further improve the fluidity of the conductive silver paste, and can be specified as flexographic printing, screen printing, gravure printing, or gravure offset printing. In the printing method, even when printing continuously on these printing presses, troubles do not easily occur and it becomes easy to obtain a good conductive pattern printed matter. Particularly preferred.

  In the conductive silver paste of the present invention, silver particles (A) are used as an essential component, but other single metal or alloy particles may be used together if necessary.

  Next, any resin (B) that is solid at 25 ° C. can be used as long as it can form a tack-free resin film by itself. For example, polyester resin, vinyl chloride resin, acrylic resin, polyester Examples thereof include resins and polyurethane resins. These may be used alone or in combination of two or more.

  In recent years, as a base material for forming a conductive pattern, use of a plastic film material having high flexibility (flexible) has been demanded so that electronic parts can be filled in a narrow casing with high density. Under such a demand, high adhesion is required so that the conductive pattern does not peel from the substrate even if it is held for a long time in a warped state. When the base material forming the conductive pattern of the conductive silver paste is, for example, polyethylene terephthalate (hereinafter referred to as PET), the resin (B) that is solid at 25 ° C. has good adhesion to PET. A vinyl chloride-vinyl acetate copolymer or a polyester resin is preferably used.

  Examples of the vinyl chloride-vinyl acetate copolymer described above include the Solvene series manufactured by Nissin Chemical Industry Co., Ltd., and examples of the polyester resin include the Byron series manufactured by Toyobo Co., Ltd.

  Since these resins (B) are solid at 25 ° C., it is usually necessary to apply or print a fine line pattern on the substrate after being dissolved in a liquid medium. Therefore, when selecting the resin (B), it is necessary to consider the solubility in the liquid medium.

In the electroconductive silver paste of this invention, it is preferable to make the organic cyclic ether compound (C) of flash point 50-200 degreeC mentioned later function as the said liquid medium.
Therefore, as the vinyl chloride-vinyl acetate copolymer, a copolymer containing 3 to 9% by weight of a polymer unit of vinyl alcohol and / or hydroxyalkyl ester (meth) acrylate in the copolymer is a hydroxyl group. Compared to the case where the hydrophilic group is not present, the dispersibility of the silver particles (A) can be promoted, and the adhesiveness to PET can be enhanced.
Moreover, as a polyester resin, a linear polyester resin itself is easily dissolved by an organic cyclic ether compound (C) having a flash point of 50 to 200 ° C., and includes an aromatic ring such as a benzene ring in the molecular structure. The linear aromatic polyester resin can be expected to have higher adhesion due to structural similarity with PET.

A vinyl chloride-vinyl acetate copolymer containing vinyl alcohol polymer units in the copolymer can be easily obtained by partially saponifying the vinyl chloride-vinyl acetate copolymer. Vinyl chloride-vinyl acetate copolymer containing polymerized units of (meth) acrylic acid hydroxyalkyl ester, such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate in addition to vinyl chloride and vinyl acetate (meta ) It can be easily obtained by copolymerization using hydroxyalkyl acrylate as a comonomer.
The linear polyester resin is formed by, for example, dehydrating condensation of dicarboxylic acid such as terephthalic acid and / or isophthalic acid or an acid chloride thereof and organic diol such as ethylene glycol, propylene glycol, or butanediol. It can be easily obtained by dehydrochlorination.

Examples of the organic cyclic ether compound (C) having a flash point of 50 to 200 ° C. include a monofunctional oxetane compound having one oxetane ring which is a functional group capable of cationic polymerization, a bifunctional oxetane compound, and a trifunctional or higher oxetane compound. . Among them, Oxetane series manufactured by Toagosei Co., Ltd., which is liquid at 25 ° C. and has no polymerizable functional group other than the oxetane ring, OXT-101, OXT-212, OXT-121 and OXT-221 etc. are mentioned. These may be used alone or in combination of two or more.
However, in order to increase the film toughness of the conductive silver paste on the substrate, it is preferable to use a bifunctional oxetane compound as an essential component as the organic cyclic ether compound (C) having a flash point of 50 to 200 ° C.

  The ratio of the resin (B) that is solid at 25 ° C. and the organic cyclic ether compound (C) having a flash point of 50 to 200 ° C. is not particularly limited, but the former resin (B) in terms of mass. The non-volatile content of the latter compound (C) is preferably 1 to 10 parts, and more preferably 1 to 7.5 parts.

  The conductive pattern can be obtained by either UV curing or heat drying. However, if the conductive pattern is obtained by heat drying without containing a polymerization initiator in the conductive silver paste, the UV irradiation is performed separately. It is preferable that an expensive apparatus such as an apparatus is not required to be prepared again, and a conductive pattern can be obtained at a lower cost by hot air drying, IR drying, or the like.

  As described above, in the present invention, since the organic cyclic ether compound (C) itself having a flash point of 50 to 200 ° C. acts as a liquid medium in the conductive silver paste, it has been conventionally used for the preparation of the conductive silver paste. It becomes unnecessary to use an organic solvent in combination. In addition, as described later, when forming a conductive pattern from a conductive silver paste with a printing apparatus, printing was performed for a long time in combination with a commonly used linear ether-based or ether ester-based organic solvent. It is also possible to delay or eliminate the deterioration of plates, blankets, rolls, etc., which has been strongly concerned in some cases.

  The conductive silver paste of the present invention is prepared by mixing silver particles (A), a resin (B) that is solid at 25 ° C., and an organic cyclic ether compound (C) having a flash point of 50 to 200 ° C. can do. The conductive silver paste can be produced by kneading and homogenizing the above raw materials as essential components.

  In the present invention, the resin (B), which is solid at 25 ° C., is not sufficient by making the organic cyclic ether compound (C) 15-30 parts per 100 parts of the silver particles (A) in terms of mass. It was sufficient to improve the plasticity of the conductive silver paste and improve the handleability as a fluid, and succeeded in obtaining a finer conductive pattern within a short time of less than 10 minutes even at a low temperature of less than 150 ° C. .

  In preparing the conductive silver paste of the present invention, in terms of mass, the resin (B) that is solid at 25 ° C. per 100 parts of silver particles (A) is 1 to 10 parts as a non-volatile content, and the flash point is 50 to 200 ° C. It is preferable to use 20 to 35 parts of the organic cyclic ether compound (C) in that the performance of the finally obtained conductive pattern can be improved.

  The content of silver particles (A) in the conductive silver paste is preferably 60 to 95% by mass, and more preferably 70 to 90% by mass. Within this range, the density of the silver particles (A) in the film is sufficient, good electrical conductivity can be obtained, and it becomes easy to prepare a fluid paste.

  The content of the resin (B) that is solid at 25 ° C. in the conductive silver paste is preferably 1 to 10% by mass, and more preferably 2 to 7% by mass. Within this range, it is possible to ensure adhesion to the substrate on which the conductive pattern is provided.

  The content of the organic cyclic ether compound (C) having a flash point of 50 to 200 ° C. in the conductive silver paste is preferably 10 to 40% by mass, and more preferably 15 to 25% by mass. In this range, the paste viscosity becomes more appropriate, and in gravure printing or gravure offset printing, a higher-definition conductive pattern can be formed without causing pinhole defects at the corners of the image lines or at the intersections of the matrix. Can be formed.

  The conductive silver paste of the present invention is preferably prepared so as to have a viscosity applicable to various printing methods, but a viscosity of 3 to 30 Pa · S at 25 ° C. may be used for printing such as gravure printing or gravure offset printing. It is preferable to enable application to the method. With such a viscosity, it is possible to form a higher-definition conductive pattern without causing pinhole defects at the corners of the image line or at the intersections of the matrix, and inking on the intaglio. Further, the problem of transferability from the intaglio to the blanket is less likely to occur. The viscosity of the conductive silver paste in the present invention is a value measured with a rheometer.

  In the conductive silver paste of the present invention, various additives such as an organic solvent, a dispersant, an antifoaming agent, and a plasticizer can be appropriately blended as necessary in addition to the above-described components.

  The conductive silver paste of the present invention can form a conductive pattern by any method, for example, by applying or printing on a plastic film, ceramic film, glass or metal plate substrate. .

  The conductive silver paste of the present invention can form a conductive pattern on an arbitrary substrate by, for example, printing by flexographic printing, screen printing, gravure printing, or gravure offset printing.

  The method of forming a conductive pattern from the conductive silver paste of the present invention includes at least a step of supplying a conductive ink to an intaglio printing plate having a conductive pattern, pressing a silicone blanket, and placing the conductive ink on the blanket. A gravure offset printing method having a step of transferring to a substrate and a step of transferring the conductive ink on the blanket to a substrate can be suitably employed.

  As the intaglio printing plate at this time, an ordinary gravure plate, an intaglio plate formed by exposing, developing and washing a photosensitive resin on a glass plate, and an intaglio plate formed by chemical etching and laser etching can be used.

  The silicone blanket is a sheet having a layer structure such as a silicone rubber layer, a PET layer, or a sponge layer. Usually, it can be used in a state of being wound around a rigid cylinder called a blanket cylinder.

  In the method for forming a conductive pattern from the conductive silver paste of the present invention, when the gravure offset printing method is employed, the silicone blanket is required to have transferability from the intaglio and transferability to the substrate. In order to obtain sufficient transferability to the substrate, it is necessary to absorb the liquid component in the conductive silver paste at a certain rate on the blanket surface. If the absorption is insufficient, the conductive silver paste layer is likely to delaminate at the time of transfer to the substrate, and conversely if absorbed above a certain percentage, the conductive silver paste dries on the blanket surface, There was a problem that transfer defects were likely to occur.

  In the conductive silver paste of the present invention, the main component of the liquid component is composed of an organic cyclic ether compound (C) having a flash point of 50 to 200 ° C., and after itself is dried at a low temperature in a short time. , It is incorporated into the conductive pattern. Therefore, troublesome work of selecting an appropriate organic solvent to solve the above-mentioned problems, disadvantages as the handling of the paste that occurs when using only an organic solvent, and higher-definition conductive patterns There is a great advantage that a defect cannot be manifested in

  The conductive pattern formed from the conductive silver paste of the present invention may be a solid line having a solid line width, but the characteristics when the conductive silver paste of the present invention is used are as described above. This is particularly noticeable when a narrower line width than conventional ones is provided on a substrate.

  In addition, since the conductive pattern from the conductive silver paste of the present invention can be formed at a lower temperature and in a shorter time than conventional, the conductive silver paste of the present invention is characterized by heat resistance such as ceramic film, glass or metal plate. When the conductive pattern is formed on a general-purpose plastic film such as PET, which has a lower heat resistance and is more easily thermally deformed than a substrate having a high thickness, it is particularly prominent.

  Thus, using the conductive silver paste of the present invention, the base material provided with the conductive pattern by printing on various base materials by various printing methods can be used as a printed conductive pattern, with wiring or the like as necessary. By carrying out, it can be set as various electrical components and electronic components. Specifically, the conductive silver paste of the present invention is excellent in adhesion to a transparent conductive film such as a transparent ITO electrode.

  Examples of the final product include a touch panel extraction electrode, a display extraction electrode, electronic paper, a solar battery, and other wiring products.

  Hereinafter, the present invention will be specifically described with reference to examples. Here, “%” is “% by mass” unless otherwise specified.

Using silver particles, a resin that is solid at 25 ° C., an organic cyclic ether compound (C) having a flash point of 50 to 200 ° C. and the like so as to have the parts by mass shown in Table 1 below, these raw materials are sufficiently used. By mixing, each conductive silver paste of the present invention as an example and each conventional conductive silver paste as a comparative example were prepared. Each of the conductive silver pastes of Examples and Comparative Examples was in the range of a viscosity of 3 to 30 Pa · S at 25 ° C.
About each of these electroconductive silver paste, the characteristic of electroconductive silver paste itself, the characteristic of the electroconductive pattern obtained from it, and the productivity of the electroconductive pattern were evaluated in the following measurement items. The evaluation results are also summarized in Table 1 below.

  The technical effect of the present invention that “a higher-definition conductive pattern can be obtained in a short time of 10 minutes or less even at a low temperature of less than 150 ° C.” is the column “specific resistance” in Table 1 Judging from the fact that the results of “on-machine stability” and “thin line reproducibility” in the column of appropriate printing are excellent (combined).

(Specific resistance)
Specific resistance means volume resistivity. Using an applicator, the conductive silver paste was applied onto the transparent conductive film (ITO film surface) so that the film thickness after drying was 6 μm and dried at 140 ° C. for 2 minutes. Using the dried coating film, measurement was performed by a four-terminal method using a Loresta GP MCP-T610 (manufactured by Mitsubishi Chemical Corporation). The smaller this value, the better the conductivity.

(Base material adhesion)
A test was carried out in accordance with the procedure of ISO 2409 (Paints and varnishes-Cross-cut test) using a dry coating film prepared from the paste, which was produced in the same manner as the evaluation of the specific resistance, and was evaluated according to the following criteria.
Pass: Class 0 or Class 1 (coating peeling is within 5%)
Fail: Classification 2-5 (peeling film exceeds 5%)

(Onboard stability)
After measuring the viscosity of the conductive silver paste, it was allowed to stand for 10 hours in a state stretched to a thickness of about 10 μm, and then the viscosity of the paste was measured in the same manner. The thickening rate of the paste before and after standing was calculated and evaluated according to the following criteria.
Pass: Thickening rate is less than 10% Fail: Thickening rate is 10% or more

(Fine line reproducibility)
Using conductive silver paste, gravure offset printing was performed by the following method to create a conductive circuit.
The conductive paste of the present invention was inked onto a glass intaglio plate using a doctor blade, and then pressed and brought into contact with a cylinder around which the blanket was wound to transfer a desired pattern onto the blanket. Thereafter, the coating film on the blanket was pressed and transferred to a transparent conductive film as a base material to produce a conductive circuit having a line width of 20 μm to 100 μm. Among the conductive circuits described above, a line width of 20 μm was observed microscopically, and fine line reproducibility was evaluated according to the following criteria.
Pass: Excellent linearity of the wire, no disconnection point Fail: Inferior linearity of the wire, disconnection point

In Table 1, the details of each raw material used for the preparation of the conductive silver paste are as follows.
・ Silvesto AGS-050:
Silver particle dry powder with a median diameter (D50) of 1.4 μm (manufactured by Tokuri Chemical Laboratory Co., Ltd.)
・ Sylvest C-34:
Silver particle dry powder having a median diameter (D50) of 0.35 μm (manufactured by Tokuru Chemical Laboratory Co., Ltd.)
・ Solvine C:
Vinyl chloride-vinyl acetate copolymer having a vinyl chloride / vinyl acetate copolymer mass ratio of 87/13 (manufactured by Nissin Chemical Industry Co., Ltd.)
・ Solvine AL:
Vinyl chloride-vinyl acetate copolymer with a vinyl chloride / vinyl acetate / vinyl alcohol copolymer mass ratio of 93/2/5 (manufactured by Nissin Chemical Industry Co., Ltd.)
-OXT-221:
Bifunctional oxetane compound with a flash point of 144 ° C (Aron Oxetane, manufactured by Toa Gosei Co., Ltd.)
-OXT-101:
Monofunctional oxetane compound with a flash point of 112 ° C (Aron Oxetane, manufactured by Toa Gosei Co., Ltd.)
・ BDGAc: Diethylene glycol monobutyl ether acetate ・ PGMAc: Propylene glycol monomethyl ether acetate

As can be seen from the evaluation results in Table 1, the conductive silver pastes of Examples 1 to 3 are at a level where both the specific resistance and the printability can be satisfied, whereas the conductive silver pastes of Comparative Examples 1 and 2 are It is clear that one or both of these are at an unsatisfactory level.
Further, from the comparison between Example 1 and Example 3, as a vinyl chloride-vinyl acetate copolymer, 3 to 9 wt% of a polymer unit of vinyl alcohol and / or hydroxyalkyl (meth) acrylate is contained in the copolymer. It is clear that the content of% is superior to the adhesion to PET as compared with the case of not containing it.

  The conductive silver paste of the present invention can be used as a conductive silver paste for forming conductive patterns of various electric parts and electronic parts.

Claims (8)

It contains silver particles (A), a resin (B) that is solid at 25 ° C., and an organic cyclic ether compound (C) having a flash point of 50 to 200 ° C. as essential components, and in terms of mass, the silver particles ( A) 100 parts of natural Symbol organic cyclic ether compound (C) 15 to 30 parts of der is,
The conductive silver paste , wherein the resin (B) that is solid at 25 ° C is a vinyl chloride-vinyl acetate copolymer and / or a linear polyester resin .   The conductive silver paste according to claim 1, which has a viscosity of 3 to 30 Pa · S at 25 ° C.   The conductive silver paste according to claim 1 or 2, wherein the organic cyclic ether compound (C) having a flash point of 50 to 200 ° C is a bifunctional oxetane compound. The vinyl chloride-vinyl acetate copolymer is a vinyl chloride-vinyl acetate copolymer containing 3 to 9% by weight of polymer units of vinyl alcohol and / or hydroxyalkyl ester (meth) acrylate in the copolymer. The electroconductive silver paste as described in any one of Claims 1-3 . As silver particles (A), in terms of mass, 50 to 200 parts of silver particles having a median diameter (D50) of 0.2 to 0.9 μm per 100 parts of silver particles having a median diameter (D50) of 1.0 to 10.0 μm. The electroconductive silver paste as described in any one of Claims 1-4 used together. The electroconductive silver paste as described in any one of Claims 1-5 which does not contain a polymerization initiator. The formation method of the electroconductive pattern which carries out the gravure printing or the gravure offset printing on the base material with the electroconductive silver paste as described in any one of Claims 1-6 . The electroconductive pattern printed matter formed with the electroconductive silver paste as described in any one of Claims 1-6 .