WO2011096222A1 - Electrically conductive ink, and laminate having electrically conductive pattern attached thereto and process for production thereof - Google Patents

Abstract

Disclosed are: a low-temperature-processing-type electrically conductive ink which enables the formation of an extremely fine electrically conductive pattern by screen printing, does not require any specialized process for production thereof, and has excellent resistance value stability; a laminate having an electrically conductive pattern attached thereto, which is produced using the electrically conductive ink; and a process for producing the laminate. The electrically conductive ink comprises electrically conductive particles each having a tap density of 1.0 to 10.0 (g/cm³), a D₅₀ particle diameter of 0.3 to 5 μm and a BET specific surface area of 0.3 to 5.0 m²/g, an epoxy resin having a number average molecular weight (Mn) of 10,000 to 300,000 and a hydroxy value of 2 to 300 (mgKOH/g), and a metal chelate capable of achieving an alcohol interchange reaction with a hydroxy group in the epoxy resin and contained in an amount of 0.2 to 20 parts by weight relative to 100 parts by weight of the epoxy resin, and has a storage modulus (G') of 5,000 to 50,000 (Pa).

Description

Conductive ink, laminate with conductive pattern and method for producing the same

The present invention relates to a conductive ink, a laminate with a conductive pattern obtained using the conductive ink, and a method for producing the same.

Etching methods and printing methods are generally known as electronic parts, thin film forming means for electromagnetic wave shielding, or conductive circuit forming means. The etching method means a processing technique in a broad sense including a surface treatment of a metal by dissolving or removing the surface or shape of the metal chemically or electrochemically. Etching is a kind of chemical processing, and is mainly performed to obtain a desired pattern shape on a metal film. However, the process is generally complicated and waste liquid treatment is required in the subsequent process, so the cost is also high. There are many problems. In addition, since the conductive circuit formed by the etching method is formed of a metal material such as aluminum or copper, there is a problem that the conductive circuit is weak against physical impact such as bending.

Therefore, in order to solve these problems and form a conductive circuit at a lower cost, conductive ink is attracting attention. A conductive circuit can be easily formed by printing conductive ink. Furthermore, since electronic components can be expected to be smaller and lighter, improve productivity, and reduce costs, research and development on conductive ink has been energetically performed, and many proposals have been made (for example, Patent Documents 1 to 4). 9).

Patent Document 1 describes a method for manufacturing a thermocompression bonding member in which a solvent absorption layer is formed and a conductive paste is screen-printed thereon.
In Patent Document 2, a high-definition conductive circuit is printed by using a conductive ink containing spherical or granular metal particles having a specific average particle size and a maximum particle size on a substrate having a roughened surface. Techniques for forming the are disclosed.
Patent Document 3 discloses a screen printing ink that controls a TI value (thixo index, thixo index) in order to form a high-definition color filter or the like.

Patent Document 4 discloses that 60 to 90% by weight of conductive powder having a tap density in the range of 2.5 to 6 g / cm ³ and an average particle size in the range of 0.02 to 1 μm. And a conductive ink for use in lithographic offset printing containing 10 to 40% by weight of an organic component.
In Patent Document 5, a copper powder having an average particle size of 20 μm or less or a silver-plated copper powder, a thermoplastic resin, an additive, and a silane coupling agent as an adhesion improver are added to the solid content of the conductive paint. A conductive paint dispersed in an organic solvent containing 001 to 5.0% by weight is disclosed.

Furthermore, in Patent Document 6, in order to provide a conductive paste having high adhesion to a polyimide substrate and having good bending resistance and solvent resistance, one or more of an aluminum compound and a silane coupling agent are used. A conductive paste using a binder resin containing two or more types is disclosed.

In Patent Document 7, when the electric resistance, migration resistance, and resistance change rate of the conductor after applying an electric field for a long time under high temperature and high humidity are exhibited, and silver or silver white is exhibited, and the substrate is a PET film. In order to provide a conductive paste that does not cause shrinkage / deformation of the substrate, a conductive paste containing a thermoplastic resin containing OH groups, scaly composite conductive powder, scaly silver powder, and a solvent is disclosed.

Patent Document 8 discloses a conductive paste containing a flat conductive powder, an irregularly shaped conductive powder, a thermoplastic synthetic resin, and a solvent in order to provide a conductive paste capable of imparting good conductivity. As examples of thermoplastic synthetic resins, it is disclosed that epoxy resins, acrylic resins, phenoxy resins, ethyl cellulose, polyvinyl butyral, and the like can be used.
Further, Patent Document 9 discloses a conductive paste in which an epoxy resin having an epoxy equivalent of more than 500 and a molecular weight of more than 10,000 is dissolved in a solvent having a boiling point of 200 to 250 ° C., and a conductive filler is dispersed. Yes.

Japanese Patent Application Laid-Open No. 06-68924 International Publication No. 2003/103352 Japanese Patent Laid-Open No. 2003-238876 JP 2001-234106 A JP 2005-29639 A JP 2006-310022 A JP 2003-68139 A JP 2003-331648 A Japanese Patent Laid-Open No. 2005-183301

However, the characteristics and performance required for conductive ink are severe, and a better conductive ink is required.

The conductive ink can be classified into a high-temperature firing type as in Patent Document 4 and a low-temperature treatment type. The high-temperature firing type applies a high temperature to the base material and the electronic component when forming the conductive pattern, so that problems such as damage to the electronic component and heat shrinkage are likely to occur. For this reason, in recent years, the demand for a low-temperature treatment type is rapidly increasing.
Moreover, simplification of a manufacturing process is calculated | required from a viewpoint of the product yield improvement and manufacturing cost reduction. For this reason, there is a need for a conductive ink that can be printed without the process of providing a solvent absorption layer as in Patent Document 1 or the process of roughening a substrate as in Patent Document 2.

In recent years, high-definition printing of conductive ink is also required. For example, a pattern performance capable of forming a line / space with a width of 100 μm or less (100 μm or less / 100 μm or less) (hereinafter abbreviated as “L / S”) is required in order to cope with higher definition of conductive circuit patterns. It has been. In addition, due to the downsizing of mobile terminals such as mobile phones and game machines, the introduction of touch screen panels, etc., the definition of conductive circuit patterns has been further increased, and a finer L / S (60 μm or less) with a width of 60 μm or less. / 60 μm or less) is also required.

As a printing method of conductive ink, a lithographic offset printing method as disclosed in Patent Document 4, a screen printing method, and the like are known. Among these, according to the screen printing method, it is possible to ensure a printing pattern having a thickness of several μm or more. On the other hand, according to other methods such as the lithographic offset printing method, it is the limit to form a printing pattern having a thickness of about 1 to 2 μm. For this reason, the screen printing method is suitable for realizing a reduction in resistance of a conductive pattern such as a conductive circuit.

However, the screen printing method has a problem that it is not suitable for applications and fields where high-definition printing accuracy is required, as described in Patent Document 4. This is because the screen printing method is a method in which the printing ink is printed on the screen printing plate through the mesh of the opening of the screen printing plate while being filled with the screen printing ink and pressed with a squeegee or the like. That is, the screen printing method is a method of bending and printing the screen printing plate by pressing with a squeegee or the like. For this reason, even if an L / S wiring pattern of, for example, 100 μm or less is formed by the screen printing method, the actual situation is that the line width of the printed material becomes larger than the target line width. As a result, problems such as adjacent wirings approaching or contacting each other and problems such as blurring of edge portions of wirings resulting in unclear borders are caused.

The reason why such a problem occurs is that the specific gravity of the conductive particles contained in the conductive ink is larger than that of a general printing ink and is contained in a large amount. The conductive ink passes through the opening of the screen plate, and after it is transferred to the base material, it is easy to flow and spread out from the printing area due to the weight of the conductive particles itself, etc., until it is dried and solidified. . Such a problem is particularly noticeable in a high-definition pattern in which the L / S wiring pattern corresponds to 100 μm or less.

Also, in order to print a high-definition conductive pattern (circuit pattern), it is necessary to use a fine screen mesh. In order to use a fine screen mesh, it is preferable to use conductive particles having a particle size as small as possible. However, the conductive particles having a small particle size are more likely to flow on the movement of the solvent or binder resin contained in the conductive ink being dried and solidified after printing, as compared with those having a large particle size. For this reason, the “thickening” phenomenon of the line width that protrudes outside the printing region is more likely to occur.

In addition, not only the above-mentioned high definition but also the items required for conductive circuit patterns used in touch screen panels that are often used in mobile terminals such as mobile phones and game machines in recent years, personal computers, etc. Resistance value stability is also mentioned. There are various types of touch screen panels, and examples include an optical method, an ultrasonic method, a resistive film method, a capacitance method, and a piezoelectric method. Of these, the resistive film method is most often used because of the simplicity of the structure. In a resistive film type touch panel, two transparent conductive substrates on which a transparent conductive film is formed are opposed to each other with an interval of approximately 10 to 150 μm. In the part touched with a finger, a pen or the like, both transparent electrode substrates come into contact with each other and operate as a switch to select a menu on the display screen, input a handwritten character, and the like.

The structure of the resistive film type touch screen panel will be described in more detail.
For example, a transparent conductive film is provided on a transparent plastic film so that the plastic film is partially exposed by indium oxide doped with tin (hereinafter referred to as ITO), and the conductive film is provided on the plastic film and the transparent conductive film. A conductive circuit (also referred to as a conductive pattern) is formed using ink. And an insulating layer is formed on a conductive circuit, and becomes a transparent conductive substrate. Next, two transparent conductive substrates are bonded together with a double-sided pressure-sensitive adhesive in a state where the transparent conductive films are not directly in contact with each other and are opposed to each other.

However, when the touch panel is exposed to a high-temperature and high-humidity environment, a problem that the resistance value between terminals, that is, the resistance value between two transparent conductive substrates, often increases thereafter. There was a big problem in the stability of the resistance value of the conductive ink. For example, in-vehicle touch panels used for car navigation systems and the like are sometimes exposed to high-temperature and high-humidity environments, and improvement of the durability of touch panels against such environmental loads is required.

The present invention has been made in view of the above-mentioned background, and its object is not a so-called high-temperature baking type, but a low-temperature treatment type conductive ink and high-definition conductivity by screen printing. Provided is a conductive ink that can form a pattern, does not require a special manufacturing process, and has excellent resistance value stability, a laminate with a conductive pattern using the same, and a method for manufacturing the same It is to be.

The present invention
Conductive particles having a tap density of 1.0 to 10.0 (g / cm ³ ), a D50 particle size (50% particle size) of 0.3 to 5 μm, and a BET specific surface area of 0.3 to 5.0 m ² / g An epoxy resin having a number average molecular weight (Mn) of 10,000 to 300,000, a hydroxyl value of 2 to 300 (mgKOH / g), and an alcohol exchange reaction with a hydroxyl group in the epoxy resin, The present invention relates to a conductive ink having a storage elastic modulus (G ′) of 5,000 to 50,000 (Pa) containing 0.2 to 20 parts by weight of a metal chelate with respect to 100 parts by weight of an epoxy resin.
In the above invention, the conductive particles are preferably silver,
The epoxy resin is preferably a bisphenol type epoxy resin.

In any one of the above inventions, the epoxy resin preferably has a number average molecular weight (Mn) of 15,000 to 100,000. A more preferable range is that the epoxy resin has a number average molecular weight (Mn) of 20,000 to 100,000 and a hydroxyl value of 50 to 250 (mgKOH / g).

In any one of the inventions described above, the tap density of the conductive particles is more preferably 2.0 to 10.0 (g / cm ³ ).

In any one of the above inventions, the storage elastic modulus (G ′) is more preferably 5,000 to 20,000 (Pa).

In any one of the above inventions, the metal chelate is preferably an aluminum chelate,
The aluminum chelate preferably has a group selected from the group consisting of an acetylacetonate group, a methylacetoacetonate group, and an ethylacetoacetonate group.

The conductive ink described in any one of the inventions can be suitably used for screen printing.

In any one of the above inventions, it is preferable that the epoxy resin further contains a curing agent having a functional group capable of reacting with at least one of a hydroxyl group and an epoxy group of the epoxy resin,
The curing agent is preferably at least one selected from the group consisting of isocyanate compounds, amine compounds, acid anhydride compounds, mercapto compounds, imidazole compounds, dicyandiamide compounds, organic acid hydrazide compounds,
The curing agent is preferably contained in an amount of 0.5 to 50 parts by weight with respect to 100 parts by weight of the epoxy resin.

Furthermore, this invention comprises a base material and a conductive pattern formed on the base material, and the conductive pattern is provided with a conductive pattern formed of the conductive ink according to any one of the inventions described above. It relates to a laminate.
The laminate with a conductive pattern may further include an insulating layer stacked to cover the conductive pattern.

In addition, in any one of the laminates with a conductive pattern, another conductive film having a predetermined pattern electrically connected to the conductive pattern is further formed on the base material on a lower layer side of the conductive pattern. can do.
The other conductive film is preferably a transparent conductive film mainly composed of indium oxide doped with tin.
Any of the above laminates with a conductive pattern is suitably used for touch screen panel applications.

Furthermore, the present invention comprises a step of forming a conductive pattern having a desired pattern shape on a substrate by screen printing,
The said conductive pattern is related with the manufacturing method of the laminated body with a conductive pattern using the conductive ink in any one of the said aspect.

Furthermore, the present invention provides a step of forming a transparent conductive film having a predetermined pattern so as to be partially exposed on the base material, and the conductive material according to any one of the above aspects on the base material and the transparent conductive film. A step of forming a conductive pattern of a desired shape by screen printing using a conductive ink, and a step of forming an insulating layer on the substrate, the transparent conductive film and the conductive pattern,
The present invention relates to a method for producing a laminate with a conductive pattern, wherein the transparent conductive film is a film mainly composed of indium oxide doped with tin.
The substrate is preferably a polyester film.

The conductive ink according to the present invention is not a so-called high-temperature firing type, but a low-temperature treatment type conductive ink, and can form a high-definition conductive pattern by screen printing. An object of the present invention is to provide a conductive ink which does not require a special manufacturing process and is excellent in resistance value stability. Moreover, the outstanding effect that the laminated body with a conductive pattern formed using the said conductive ink and its manufacturing method can be provided is produced.

FIG. 3 is a schematic cross-sectional configuration diagram of a main part of an example of a resistive film type touch screen panel in which the conductive ink of the present invention is applied to a wiring structure, and corresponds to a II cut line in FIG. 2. It is a perspective view which shows the lamination | stacking state of a suitable resistive film type touch screen panel by applying the conductive ink of this invention to a wiring structure.

Embodiments of the present invention will be described below. In the present specification, the description “any number A to any number B” means a range larger than the numbers A and A but smaller than the numbers B and B.
The conductive ink of the present invention has a tap density of 1.0 to 10.0 (g / cm ³ ), a D50 particle size of 0.3 to 5 μm, and a BET specific surface area of 0.3 to 5.0 m ² / g. Active particles, an epoxy resin having a number average molecular weight (Mn) of 10,000 to 30,000, a hydroxyl value of 2 to 300 (mgKOH / g), and an alcohol exchange reaction with a hydroxyl group in the epoxy resin, It contains 0.2 to 20 parts by weight of metal chelate with respect to 100 parts by weight of the epoxy resin.

Examples of the conductive particles used in the conductive ink of the present invention include gold, silver, copper, silver-plated copper powder, silver-copper composite powder, silver-copper alloy, amorphous copper, nickel, chromium, palladium, rhodium, ruthenium, Metal powder such as indium, silicon, aluminum, tungsten, morphbutene, platinum, inorganic powder coated with these metals, powder of metal oxide such as silver oxide, indium oxide, tin oxide, zinc oxide, ruthenium oxide, these Inorganic powders coated with metal oxides, carbon black, graphite and the like can be used. These conductive particles may be used alone or in combination of two or more. Among these conductive particles, silver is preferable because of its cost, high conductivity, and little increase in resistivity due to oxidation. In addition, when using specific electroconductive particles, such as silver, the trace amount of other electroconductive particles may be contained in the range which does not affect printability and a characteristic. Or it is the electroconductive particle which has silver as a main component, Comprising: The composite particle which contains a trace amount of other electroconductive components in the range which does not affect printability and a characteristic may be sufficient.

The shape of the conductive particles is not particularly limited as long as the above properties are satisfied, and an indeterminate shape, an aggregated shape, a scale shape, a microcrystalline shape, a spherical shape, a flake shape, and the like can be appropriately used. From the viewpoint of the printability of the high-definition pattern and the adhesiveness of the conductor pattern to the substrate, a spherical or small aggregate having a small particle size is preferable as a relatively small aggregate.
The conductive particles used in the conductive ink according to the present invention have a tap density of 1.0 to 10.0 (g / cm ³ ), preferably 2.0 to 10.0 (g / cm ³ ). More preferably, it is in the range of 2.0 to 6.0 (g / cm ³ ).
The D50 particle size of the conductive particles is 0.3 to 5 μm, preferably in the range of 0.3 to 1.2 μm, and more preferably in the range of 0.3 to 1 μm.
Further, the BET specific surface area is 0.3 to 5.0 m ² / g, preferably 0.8 to 2.3 m ² / g, and 0.8 to 2.0 m ² / g. More preferably it is.

When the tap density of the conductive particles is less than 1.0 (g / cm ³ ), the conductive particles become bulky, and voids between the conductive particles become large, so that the contact point between the conductive particles becomes small. The volume resistivity of the printed material increases. Moreover, the dispersibility when using conductive ink is poor, and the printability of a high-definition pattern is poor.
On the other hand, when the tap density exceeds 10.0 (g / cm ³ ), the cost of the conductive particles increases and the manufacturing cost of the high-definition conductive circuit increases. In addition, when the conductive ink is used, the conductive particles are easily precipitated over time.

The tap density in the present invention refers to the weight per volume after a certain amount of powder is placed in a certain container while being vibrated up and down. The larger the value, the larger the packing density, and the larger the contact point between the particles when conductive particles are obtained, so that good conductivity can be obtained. In the present invention, the tap density is 10.0 (g / It is appropriate to use conductive particles of cm ³ ) or less.
The tap density was measured based on the JIS Z 2512: 2006 method. Specifically, conductive particles (powder amount 100 g) were collected in a graduated glass container (capacity 100 ml) and tapped with a predetermined touching device under a tap stroke of 3 mm and a tap count of 100 times / minute. .

If the D50 particle diameter of the conductive particles is less than 0.3 μm, the dispersibility of the conductive particles deteriorates when the conductive ink is used, resulting in poor contact between the conductive particles, resulting in a large printed resistance value. There is a possibility. In addition, the cost of the conductive particles increases.
On the other hand, if the D50 particle diameter exceeds 5 μm, the printability of the high-definition pattern may be inferior.
The cumulative particle size (D50) of the volume particle size distribution was measured using a laser diffraction particle size distribution measuring device “SALAD-3000” manufactured by Shimadzu Corporation.

When the BET specific surface area of the conductive particles is less than 0.3 m ² / g, the contact point between the conductive particles decreases, and the contact resistance increases.
In addition, when the BET specific surface area exceeds 5.0 m ² / g, a large amount of resin is required to coat the surface of the conductive particles. This is not preferable because the fluidity in the case becomes poor and the leveling property of the surface of the printed coating film is lowered. Moreover, since many resin is required to coat | cover the surface of electroconductive particle, the adhesiveness of the electroconductive pattern with respect to a base material also falls.
BET specific surface area is a method of adsorbing molecules whose adsorption occupation area is known to the powder particle surface at the temperature of liquid nitrogen, and obtaining the specific surface area of the sample from the amount, using low-temperature low-humidity physical adsorption of inert gas This is the BET method. The BET specific surface area is defined as a value calculated by using the following formula (1) as a surface area measured using a flow type specific surface area measuring device “Flowsorb II” manufactured by Shimadzu Corporation.
Formula (1) Specific surface area (m ² / g) = surface area (m ² ) / powder mass (g)

The conductive ink of the present invention preferably contains 60 to 95% by weight of conductive particles, more preferably 70 to 95% by weight, in a total of 100% by weight of the conductive particles and the epoxy resin described later. More preferably, the content is 85 to 95% by weight. If the conductive particles are less than 60% by weight, the conductivity is not sufficient, and if it exceeds 95% by weight, the epoxy resin is reduced, and the adhesion of the conductive ink to the substrate and the mechanical strength of the coating film may be reduced. There is no.

Next, the metal chelate will be described. In the present invention, the metal chelate is necessary for reacting with a hydroxyl group in an epoxy resin (described later) used in the conductive ink and imparting rheological properties necessary for printability of a high-definition pattern in the screen printing method. Such metal chelates are chelate compounds obtained by reacting metal alkoxide with a chelating agent such as β-diketone or ketoester (such as ethyl acetoacetate), and examples thereof include aluminum chelates, zirconium chelates, and titanium chelates. Aluminum chelate is preferably used because of cost, availability and the like.

Among the metal chelates, the aluminum chelate used in the present invention preferably has a molecular weight of 420 or less, and is preferably an aluminum acetylacetonate complex. An acetylacetonate complex includes an acetylacetonate group: —O—C (CH ₃ ) ═CH—CO (CH ₃ ) and a methyl acetoacetate group: —O—C (CH ₃ ) ═CH—CO—O—CH. ₃ , ethyl acetoacetate group: —O—C (CH ₃ ) ═CH—CO—O—C ₂ H _{5 and the} like. The aluminum chelate used in the present invention preferably has 1 to 3 of these groups in one molecule, and has 1 to 3 acetylacetonate groups or 1 to 3 ethylacetoacetate groups. Chelates are more preferred.
Aluminum chelates with a molecular weight greater than 420, aluminum chelates with 4 or more acetylacetonate groups in one molecule, aluminum chelates with 4 or more ethyl acetoacetate groups, and aluminum chelates with long chain alkyl groups There is a risk that wetting with the conductive particles is hindered and the resistivity is increased.
Typical aluminum chelates include ethyl acetoacetate aluminum diisopropionate, aluminum tris (ethyl acetoacetate), alkyl acetoacetate aluminum diisopropylate, aluminum tris (acetyl acetate), aluminum monoacetyl acetate bis (ethyl acetoacetate). Acetate), aluminum di-n-butoxide monomethyl acetoacetate, aluminum diisobutoxide monomethyl acetoacetate, aluminum disec-butoxide monomethyl acetoacetate and the like.

Of the metal chelates, the zirconium chelate used in the present invention preferably has a molecular weight of 350 or more and 1,000 or less. Further, the zirconium chelate is more preferably an acetylacetonate complex containing 1 to 4 acetylacetonate groups and 0 to 2 ethylacetoacetate groups in one molecule. Zirconium chelates having a molecular weight of less than 350 may cause the dispersion state of the conductive ink to become unstable and increase the resistivity.
Typical zirconium chelates include zirconium tetraacetylacetonate, zirconium tributoxyacetylacetonate, zirconium monobutoxyacetylacetonate bis (ethylacetoacetate), zirconium dibutoxybis (ethylacetoacetate), zirconium tetraacetylacetate. And the like.

Of the metal chelates, titanium chelates used in the present invention preferably have a molecular weight of 250 to 1,500. Moreover, as a preferable example of a titanium chelate, alkoxy titanium which can be represented by (HOR ¹ O) ₂ Ti (OR ² ) ₂ or (H ₂ NR ¹ O) ₂ Ti (OR ² ) ₂ can be given. Here, R ¹ and R ² are hydrocarbon groups. For example, di-i-propoxybis (acetylacetonato) titanium, di-n-butoxybis (triethanolaminato) titanium, titanium-i-propoxyoctylene glycolate, titanium stearate, titanium acetylacetonate, titanium tetraacetyl Examples include acetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium ethyl acetoacetate, titanium lactate, and titanium triethanolamate. Zirconium chelates having a molecular weight of less than 250 may cause the dispersion state of the conductive ink to become unstable and increase the resistivity.

The content of the metal chelate used in the present invention is in the range of 0.2 to 20 parts by weight of metal chelate and more preferably in the range of 2 to 10 parts by weight with respect to 100 parts by weight of the epoxy resin described later. preferable. If the metal chelate is less than 0.2 parts by weight, the effect of imparting the elastic properties necessary for the printability of the high-definition pattern in the screen printing method is small, and if it exceeds 20 parts by weight, the imparting of the elastic properties of the conductive ink becomes large. As a result, screen printing cannot be performed, and the resistance value of the conductive ink may be increased.

Here, the viscosity of the conductive ink in screen printing will be described. In order to perform high-accuracy screen printing, various printing conditions such as screen mesh and emulsion thickness are set as appropriate, and the base material is selected as appropriate. Has been made. The amount of ink transferred to the substrate greatly depends on the amount of ink passing through the screen opening, and as the amount of passage increases, the thin line portion blurs and fattening easily occurs. When the ink viscosity is too low, when the ink passes through the opening of the screen plate, the ink passes through the back surface around the opening of the screen plate. Inconveniences such as this occur and printing with high accuracy cannot be performed.

Therefore, in order to suppress the amount of ink passing, a method of increasing the ink viscosity was taken. However, only by increasing the viscosity, it becomes difficult to sufficiently pass the ink from the opening of the screen plate, and high-precision printing cannot be performed. In particular, in continuous printing, fine lines are drawn or breakage is likely to occur. Therefore, in order to perform high-accuracy screen printing, it is necessary to have a so-called thixotropic property that lowers the viscosity when an external force is applied by a squeegee or the like and maintains a high viscosity when no external force is applied. It has been generally said that

説明 Explain the conventional way of thinking about the relationship between screen printing and thixotropy of screen printing ink. Considering the behavior during printing of screen printing ink, the printing ink moves on the screen printing plate while being rotated by a squeegee, called rolling, and is filled into the openings of a predetermined pattern on the screen. It is supplied onto the substrate through the part and transferred to the substrate. Screen printing ink that can form a high-definition print pattern has a lower viscosity at the time of filling and transfer, and when it is transferred to the base material, it rapidly increases in viscosity and is printed on the base material. Has been considered necessary to maintain. The viscosity at the time of ink filling / transition is regarded as corresponding to the viscosity at high speed rotation by a rotational viscometer. In addition, the ink becomes stationary when no external force is applied to the ink, and the viscosity in the stationary state is regarded as corresponding to the viscosity at low speed rotation by a rotational viscometer.

That is, using a rotational viscometer (divided into a double cylinder type, a cone-disk type, a parallel disk type, etc., depending on the shape of the measuring part), the viscosity is measured at different rotational speeds. When plotting the relationship in a logarithmic graph, the line connecting the plots becomes a straight line having a certain slope, or screen printing ink that exhibits a state close to it may form a high-definition print pattern. It has been considered a possible screen printing ink.
In the rotational viscometer, there is no absolute index as to which of the rotational speeds corresponds to the above-described high-speed and low-speed viscosities, but 10 of n rotations (low-speed rotations). In general, the rotation speed is about 100 to 100 times, and the ratio between the viscosity at high speed rotation and the viscosity at low speed rotation is obtained and evaluated as a TI value (thixo index, thixo index).

The same applies to the conductive ink. Viscosity = shear stress (Pa) when an arbitrary rotational speed = shear rate (/ sec) is measured (so-called static steady flow measurement), and further different rotational speeds = different shear rates. In many cases, viscosity = shear stress (Pa) is obtained, and thixotropy is evaluated from the relationship between the two viscosities.

In general, printable inks containing polymer materials such as synthetic resins have properties (viscoelasticity) that have elastic properties (elastic deformation) simultaneously with flow (viscous flow), but compared with elastic behavior. Since the ratio of viscous behavior is high, the viscous behavior is often grasped at a certain rotational speed, that is, a steady flow as described above.
However, the viscosity measured in a steady flow changes greatly with time, and reproducible data is often not obtained. From the data such as the TI value of a rotary viscometer, the actual fluidity (viscosity of ink) Flow) and printability is difficult to evaluate. In particular, when high-definition printing such as a line width of 50 μm is required, it is not sufficient to simply grasp and control viscous flow.

Previously, conductive inks controlled the amount of passage only by viscous flow (so-called viscosity), and a method of increasing the viscosity was used to suppress the amount of passage. However, if the viscosity is simply increased, fine lines are drawn or breakage is likely to occur in continuous printing. Moreover, in the steady flow measurement, even when using conductive ink imparted only with so-called thixotropy, the viscosity is high at a low shear rate and the viscosity is low at a high shear rate. It is difficult to print a pattern (for example, an L / S conductive pattern having a line width of 40 μm / a wiring width of 60 μm).

Therefore, the conductive ink according to the present invention imparts specific elastic properties by reacting an epoxy resin having a specific physical property range with a metal chelate, thereby controlling the amount of ink passing therethrough. Accordingly, a remarkable effect is exhibited in printing a high-definition conductive pattern (for example, a conductive pattern of L / S having a line width of 40 μm / a width of wiring of 60 μm).

That is, the conductive ink of the present invention has a storage elastic modulus G ′ of 5,000 to 50,000 (Pa) at 25 ° C., frequency 1 (Hz), vibration stress 50 (Pa), and elastic properties. The value obtained by dividing the loss elastic modulus G ″ by the storage elastic modulus G ′, that is, tan δ, is 1 or less, is necessary for imparting high-definition pattern printability. It is preferable that tan δ be 0.3 or more. When tan δ is less than 0.3, the storage elastic modulus G ′ often exceeds 50,000, and the fluidity as an ink is deteriorated, which may cause a problem in printability.
When the storage elastic modulus G ′ at 25 ° C., frequency 1 (Hz), and vibration stress 50 (Pa) is less than 5,000 Pa, the elasticity is weak, and the ink passes through the opening of the screen and is transferred to the substrate. It becomes difficult to maintain the shape of the pattern, and the printability of a high-definition pattern is poor.
On the other hand, when the storage elastic modulus G ′ of the conductive ink exceeds 50,000 Pa, the elasticity becomes too strong, the ink cannot be rolled on the screen printing plate, and it is difficult to fill a predetermined pattern provided on the screen. Therefore, screen printing is not possible.
The storage elastic modulus G ′ is preferably 5,000 to 30,000, and more preferably 5,000 to 20,000.
On the other hand, when tan δ of the conductive ink exceeds 1, the elastic properties tend to decrease and the printability of the high-definition pattern tends to be inferior.
There are various methods for evaluating the viscoelastic behavior of conductive ink, but the measurement method with fixed sine vibration frequency and changing vibration stress measures the dynamic viscoelasticity of dispersed systems such as conductive ink. Is preferred.

Next, the epoxy resin will be described.
The epoxy resin used in the present invention has an epoxy group and a hydroxyl group, and has a number average molecular weight (Mn) of 10,000 to 300,000, preferably 15,000 to 100,000, more preferably It is 18,000 to 100,000, more preferably 20,000 to 100,000, and particularly preferably 20,000 to 70,000. Considering the availability of commercially available products or the ease of production, those having a number average molecular weight of 15,000 to 100,000 are preferred, 15,000 to 70,000 are more preferred, and about 15,000 to 55,000. Are more preferred.
The hydroxyl value is 2 to 300 (mgKOH / g), the hydroxyl value is preferably 10 to 250 (mgKOH / g), more preferably 50 to 250 (mgKOH / g), and 80 to 200 (mgKOH / g). Is more preferable.
The epoxy equivalent of the epoxy resin is related to the number average molecular weight of the epoxy resin. Considering that the resistance value between terminals when the conductive ink according to the present invention is printed on a conductive film is taken into consideration, the epoxy equivalent is preferably 5,000 or more. Although an upper limit is not specifically limited, Usually, it is 100,000 or less from the preferable range of a number average molecular weight. A more preferable epoxy equivalent is in the range of 5,000 to 50,000, and the range of 6,800 to 18,000 is particularly preferable considering the availability of commercial products.
As the epoxy resin, for example, bisphenol type epoxy resins such as bisphenol A, bisphenol F, bisphenol S, and bisphenol AD are preferable, and a phenoxy resin that is a so-called bisphenol type polymer epoxy resin can be suitably used.
Here, the hydroxyl group undergoes an alcohol exchange reaction with the alkoxy group of the metal chelate, as will be described later, and further imparts rheological properties such as storage elastic modulus G ′ necessary for the printability of the high-definition pattern in the screen printing method. When an agent is used, it is necessary as a functional group that reacts as an excess hydroxyl group after use in the reaction with the alkoxide group of the metal chelate.

If the number average molecular weight (Mn) of the epoxy resin is less than 10,000, a sufficient storage elastic modulus G ′ cannot be obtained even if a metal chelate is used, and if it exceeds 300,000, the storage elastic modulus G ′ becomes too high. Problems with screen printability may occur.
Further, if the hydroxyl group is less than 2 (mgKOH / g), a sufficient storage elastic modulus G ′ cannot be obtained even if a metal chelate is used, and if the hydroxyl value exceeds 300 (mgKOH / g), the storage elastic modulus G ′ is high. This may cause a problem in the screen printability of a high-definition pattern.

There are two general methods for producing general bisphenol-type epoxy resins, the toffee method and the advanced method.
The toffee method is a method in which epichlorohydrin and bisphenols such as bisphenol A and bisphenol F are condensed to a predetermined molecular weight in the presence of an alkali catalyst as necessary.
In the advanced method, a bisphenol-type epoxy monomer having an epoxy group at both ends of a bisphenol, such as a bisphenol A-type epoxy monomer or a bisphenol F-type epoxy monomer, and a bisphenol are optionally added in the presence of an alkali catalyst. Condensate to molecular weight, or treat commercially available epoxy resin as an epoxy monomer, and condense commercially available epoxy resin and bisphenols to the specified molecular weight in the presence of an alkali catalyst as necessary It is a way to let them.
The bisphenol type polymer epoxy resin suitably used in the present invention is a conventional method, for example, JP-A-07-109331, JP-A-10-77329, JP-A-11-147930, JP-A-2006-36801. As described in the above, it can be obtained by appropriately adjusting the type and amount of the alkali catalyst, the type and amount of the organic solvent to be used, the reaction temperature and time, and the like.

The conductive ink which concerns on this invention can form a conductive pattern by printing on a base material, and can manufacture a laminated body with a conductive pattern. This laminated body with a conductive pattern can further include an insulating layer so as to cover the conductive pattern. In addition, another conductive film having a predetermined pattern electrically connected to the conductive pattern can be further formed on the base material on the lower layer side of the conductive pattern. Of course, another conductive film may be provided in the upper layer of the conductive pattern, and a plurality of patterns made of conductive ink may be laminated. Moreover, it is also possible to form a conductive pattern or apply it by a method other than printing.
The conductive pattern formed with the conductive ink according to the present invention is particularly effective when it is connected to a transparent conductive film such as an ITO layer, because the resistance value stability that has been conventionally required can be realized. . Therefore, the laminate with a conductive pattern formed with the conductive ink according to the present invention is particularly suitable for a touch screen panel.

When the touch screen panel is exposed to high temperature and high humidity compared to other resins such as polyester resin and polyurethane resin, the epoxy resin having the above specific physical property range used in the present invention has a resistance between terminals of the touch screen panel. It is effective in suppressing the rise in value.
In a laminate for a touch screen panel, a conductive pattern (hereinafter also referred to as “conductive ink pattern”) formed of a conductive ink and a transparent conductive film include an ITO layer / It becomes a laminated structure of conductive ink pattern / insulating layer / adhesive layer or ITO layer / conductive ink pattern / adhesive layer.

When the adhesion of the conductive ink pattern to the ITO layer is remarkably poor, the conductive ink pattern is peeled from the ITO layer in an adhesion test using a cellophane tape without being exposed to high temperature and high humidity. In some cases, it may not be necessary to use cellophane tape, and may peel off.
When the adhesion of the conductive ink pattern to the ITO layer is slightly improved, the conductive ink pattern is in close contact with the ITO layer in the initial state. Peel off.
If the adhesion of the conductive ink pattern to the ITO layer is further improved, the conductive ink pattern will not peel off from the ITO layer even after an adhesion test after exposure to high temperature and high humidity. However, even when the above characteristics are obtained, after the conductive ink pattern is exposed to a high temperature and high humidity while the insulating layer or adhesive is in contact with the conductive ink pattern, the adhesion test is performed from above the insulating layer. Then, the conductive ink pattern easily peels off from the interface with the ITO layer together with the insulating layer. For this reason, when it has the laminated structure of ITO layer / conductive ink pattern / insulating layer, the further improvement of adhesiveness is needed.

In the conductive ink for forming a laminate for touch screen panel having a laminated structure of ITO layer / conductive ink pattern / insulating layer, the conductive ink pattern is in contact with the insulating layer and the adhesive under high temperature and high humidity. The conductive ink pattern is required to be not peeled off from the ITO layer together with the insulating layer by an adhesion test from above on the insulating layer or the like even if exposed to.
As the use of touch screen panels expands and the required performance increases, it is more strongly demanded that the resistance value between terminals does not increase as much as possible even when exposed to high temperature and high humidity.

In conductive inks using other resins such as polyester resins and polyurethane resins, there is a problem that when exposed to high temperature and high humidity, the resistance value between terminals is greatly increased as compared to before exposure.
On the other hand, by using the conductive ink according to the present invention, the increase in the inter-terminal resistance value can be reduced. This is because the epoxy resin having the specific physical property range described above was used. That is, with the conductive ink according to the present invention, in the laminate with a conductive pattern having a laminated structure of ITO layer / conductive ink pattern / insulating layer, which has been particularly problematic in terms of resistance value stability, good resistance value stability is achieved. It was found that sex was obtained.

In the above description, the ITO film is used as the transparent conductive film. However, a transparent conductive film such as indium oxide / zinc oxide (IZO) or zinc oxide (ZnO) may be applied. .

By adding a curing agent to the conductive ink of the present invention, an increase in resistance value between terminals before and after exposure to high temperature and high humidity can be further suppressed.
As this hardening | curing agent, what can react with an epoxy group and a hydroxyl group is used, and what reacts with an epoxy group is preferable. Examples of the curing agent include isocyanate compounds, amine compounds, acid anhydride compounds, mercapto compounds, imidazole compounds, dicyandiamide compounds, organic acid hydrazide compounds, and the like.
For example, when making it react with the hydroxyl group of an epoxy resin, an isocyanate compound can be used as a hardening | curing agent.
When making it react with the epoxy group of an epoxy resin, an amine compound, an acid anhydride compound, a mercapto compound, an imidazole compound, a dicyandiamide compound, and an organic acid hydrazide compound can be used as a curing agent.

Examples of the isocyanate compound that can be used as the curing agent include non-blocked isocyanate and blocked isocyanate.
As the isocyanate compound, a polyisocyanate compound is preferable. As the polyisocyanate compound, conventionally known aromatic polyisocyanate, aliphatic polyisocyanate, alicyclic polyisocyanate, or blocked isocyanate which is a block body thereof can be used, and these are used alone or in combination of two or more. May be. Examples of the aromatic polyisocyanate include a trimethylolpropane adduct of tolylene diisocyanate, an isocyanurate of tolylene diisocyanate, an oligomer of 4,4'-diphenylmethane diisocyanate, and the like.
Examples of the aliphatic polyisocyanates include biurets of hexamethylene diisocyanate, isocyanurates of hexamethylene diisocyanate, uretdiones of hexamethylene diisocyanate, and isocyanurates of copolymers consisting of tolylene diisocyanate and hexamethylene diisocyanate. Examples of the alicyclic polyisocyanate include isocyanurates of isophorone diisocyanate. As the blocked isocyanate, a conventionally known one in which polyisocyanate is blocked with ε-caprolactam, butanone oxime, phenol, active methylene compound or the like can be used.

Among the curing agents used in the conductive ink of the present invention, examples of the amine compound include aliphatic amines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenediamine, and diethylaminopropylamine, N-aminoethylpiperazine, Examples include alicyclic amines such as mensendiamine, isophoronediamine, hydrogenated m-xylenediamine, and aromatic amines such as m-xylylenediamine, m-phenylenediamine, diaminodiphenylmethane, and diaminodiphenylsorbone. Further, amine adducts and ketimines modified with these amines, polyamide resins having a reactive primary amine and secondary amine in the molecule, produced by condensation of dimer acid and polyamine, and the like are also included.

Among the curing agents used in the conductive ink of the present invention, examples of the acid anhydride compound include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, ethylene glycol bistrimellitate, glycerol tris. Trimellitate, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, methylendomethylenetetrahydrophthalic anhydride, methylbutenyltetrahydrophthalic anhydride, dodecenyl succinic anhydride, hexahydrophthalic anhydride Acid, methylhexahydrophthalic anhydride, succinic anhydride, methylcyclohexene dicarboxylic acid anhydride, alkylstyrene-maleic anhydride copolymer, chlorendic acid anhydride, polyazeline acid anhydride, anhydrous Etc. Chirunajikku acid, and the like.

Among the curing agents used in the conductive ink of the present invention, examples of the mercapto compound include liquid polymercaptan and polysulfide resin.

Among the curing agents used in the conductive ink of the present invention, examples of the imidazole compound include 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 2,4-dimethylimidazole, 2- Examples include imidazole compounds such as phenyl imidazole, and latent curing agents with improved storage stability such as a type in which these imidazole compounds and epoxy resins are reacted to insolubilize them, or a type in which imidazole compounds are encapsulated in microcapsules.

Among the curing agents used in the conductive ink of the present invention, examples of the dicyandiamide compound include dicyandiamide (DICY).

The conductive ink of the present invention may not contain a curing agent, but preferably contains 0.5 to 50 parts by weight of the curing agent with respect to 100 parts by weight of the epoxy resin. By setting the curing agent to 0.5 parts by weight or more, sufficient adhesion, heat resistance, and the like can be imparted to the printed matter. On the other hand, when the curing agent exceeds 50 parts by weight, the unreacted curing agent tends to remain in the conductive ink, and it is difficult to impart sufficient adhesion and heat resistance.

The conductive ink of the present invention can contain a curing accelerator that accelerates the thermal curing of the epoxy resin and the curing agent.

As such a curing accelerator, an organic tin compound, an amine compound, or the like can be used in the reaction between the hydroxyl group of the epoxy resin and the isocyanate compound. Examples of organotin compounds include stannous octaate (SO) and dibutyltin dilaurate (DBTDL). Examples of amine compounds include diazabicyclooctane (DABCO), N-ethylmorpholine (NEM), triethylamine (TEA), N, N, N ′, N ″, N ″ -pentamethyldiethyltriamine (PMDETA), and the like. It is done.

Further, as a curing accelerator in the reaction between the epoxy group of the epoxy resin and the curing agent described above, dialkyl such as dicyandiamide, tertiary amine compound, phosphine compound, imidazole compound, carboxylic acid hydrazide, aliphatic or aromatic dimethylurea Examples include ureas. Examples of the tertiary amine compound include triethylamine, benzyldimethylamine, 1,8-diazabicyclo (5.4.0) undecene-7, 1,5-diazabicyclo (4.3.0) nonene-5, and the like. Examples of the phosphine compound include triphenylphosphine and tributylphosphine. As an imidazole compound, the imidazole compound mentioned by the above-mentioned hardening | curing agent can be mentioned. For example, imidazole compounds such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 2,4-dimethylimidazole, 2-phenylimidazole, etc., and reacting these imidazole compounds with epoxy resins A latent curing accelerator with improved storage stability, such as a type insolubilized in a solvent or a type in which an imidazole compound is encapsulated in a microcapsule, can be mentioned. Examples of the carboxylic acid hydrazide include succinic acid hydrazide and adipic acid hydrazide.

The conductive ink of the present invention can be dissolved and diluted with various solvents, and the solid content is preferably 50 to 90% by weight.
The solvent for dilution can be selected according to the solubility of the resin used and the type of printing method.
For example, an ester solvent, a ketone solvent, a glycol ether solvent, an aliphatic solvent, an alicyclic solvent, an aromatic solvent, an alcohol solvent, water or the like may be used in combination. However, it is not limited to these.
Examples of the ester solvent include ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, and dimethyl carbonate.
Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone benzene, diisobutyl ketone, diacetone alcohol, isophorone, and cyclohexanenone.
Examples of glycol ether solvents include ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, etc., acetates of these monoethers, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene Examples include glycol monomethyl ether, propylene glycol monoethyl ether, and acetates of these monoethers.
Examples of the aliphatic solvent include n-heptane, n-hexane, cyclohexane, methylcyclohexane, and ethylcyclohexane.
Examples of the aromatic solvent include toluene, xylene, tetralin and the like.

The conductive ink of the present invention is obtained by blending conductive particles, epoxy resin, metal chelate, solvent, and the like at a predetermined ratio, mixing them with a disper, and mixing and dispersing them with three rolls if necessary. Can do.

In addition, the conductive ink of the present invention includes a dispersant, an antifriction agent, an infrared absorber, an ultraviolet absorber, a fragrance, an antioxidant, an organic pigment, an inorganic pigment, an antifoaming agent, and a silane coupling as necessary. An agent, a plasticizer, a flame retardant, a humectant, and the like can be added.

A high-definition conductive pattern can be formed by printing on a substrate by various printing methods using the conductive ink of the present invention. Examples of the conductive pattern include a conductive circuit pattern, various wiring patterns, and an electrode pattern, and are not particularly limited. The conductive circuit pattern can be suitably used for wiring of a circuit board of an electronic component.

The substrate film is not particularly limited, and examples thereof include a polyimide film, a polyparaphenylene terephthalamide film, a polyether nitrile film, a polyether sulfone film, a polyethylene terephthalate film, a polyethylene naphthalate film, and a polyvinyl chloride film. Can be mentioned.
In addition, as a base film, an ITO layer formed by sputtering, wet coating or the like on a polymer film such as polyethylene terephthalate, polyethylene naphthalate polyester film, polycarbonate, polyethersulfone, acrylic resin, etc., ITO layer ITO glass or the like formed on the glass may be used. In addition, ceramics, glass substrates and the like can be used. In particular, in a touch screen panel, an ITO film in which an ITO layer is formed on a polyester film and an ITO glass in which an ITO layer is formed on glass are often used.

In addition, if necessary, an anchor coat layer is provided on the substrate for the purpose of further improving the printability of the high-definition pattern wiring that is a conductive pattern formed from the conductive ink according to the present invention, and the anchor coat layer is formed on the anchor coat layer. A conductive ink can also be printed. The anchor coat layer is not particularly limited as long as it has good adhesion to the base material and further conductive ink, and organic fillers such as resin beads and inorganic fillers such as metal oxides are also necessary. Can be added. The method for providing the anchor coat layer is not particularly limited, and the anchor coat layer can be obtained by coating, drying and curing by a conventionally known coating method.

The conductive ink of the present invention can be suitably applied particularly to screen printing, but may be applied to various conventionally known printing methods. In the screen printing method, it is preferable to use a fine mesh screen, particularly preferably a fine mesh screen of about 400 to 650 mesh, in order to cope with high definition of the conductive circuit pattern. At this time, the open area of the screen is preferably about 20 to 50%. The screen wire diameter is preferably about 10 to 70 μm.
Examples of the screen plate include polyester screens, combination screens, metal screens, and nylon screens. Moreover, when printing the thing of a highly viscous paste state, a high tension | tensile_strength stainless steel screen can be used.
The screen printing squeegee may be round, rectangular or square, and an abrasive squeegee can be used to reduce the attack angle (angle between printing plate and squeegee). Other printing conditions and the like may be appropriately designed according to conventionally known conditions.

The conductive ink according to the present invention is printed on a substrate such as a substrate, and then heated to dry and solidify. Moreover, when the hardening | curing agent is added to electroconductive ink, this is hardened.
When the curing agent is not contained, the heating temperature is 80 to 230 for sufficient volatilization of the solvent, and when the curing agent is contained, for sufficient volatilization of the solvent and reaction between the curing agent and the epoxy resin. The heating time is preferably 10 to 120 minutes. Thereby, a laminated body with a conductive pattern can be obtained. The laminated body with a conductive pattern can be provided with an insulating layer so as to cover the conductive pattern, if necessary. The insulating layer is not particularly limited, and a known insulating layer can be applied. Moreover, the laminated body with a conductive pattern can be configured to be electrically connected to a conductive film formed in another layer. For example, a transparent conductive layer such as an ITO film and a conductive pattern formed from the conductive ink according to the present invention can be brought into contact with each other to be electrically connected.

The laminate with a conductive pattern according to the present invention can be suitably used particularly when a wiring structure is formed on a transparent electrode of a touch screen panel.
Here, an example in which the conductive ink of the present invention is applied to a resistive film type touch screen panel will be described with reference to FIGS. 1 and 2 are simple conceptual diagrams of the resistive touch screen panel, and the number of wirings, the wiring width, and the interval between the wirings are represented as conceptual diagrams. In FIG. 2, the laminated state of each substrate side is schematically shown with the viewpoint placed in the middle of the three layers, the position of the adhesive material 5, with the lower substrate 1 side looking down and the upper substrate 2 side looking up. .

The touch screen panel includes a lower substrate 1 and an upper substrate 2 made of a base material of glass or plastic film (polyethylene terephthalate film, polyethylene naphthalate film, acrylic resin film, polycarbonate film, or the like). Transparent electrodes 6 and 7 such as ITO are partially formed on the lower substrate 1 and the upper substrate 2, respectively. As a result, the lower substrate 1 and the upper substrate 2 and the transparent electrodes 6 and 7 are exposed.
Lower drive electrodes 13 and 14 made of the conductive ink pattern layer 3 are formed on both ends of the transparent electrode 6 on the lower substrate 1, respectively. The conductive ink layer 3 is covered with an insulating layer 4. As shown in FIG. 1, the conductive ink pattern layer 3 is in contact with the substrate 1, the transparent electrode 6 such as ITO, and the insulating layer 4.
Similarly, upper drive electrodes 9 and 10 made of the conductive ink layer 3 are formed on both ends of the transparent conductor 7 on the upper substrate 2.

Specifically, the conductive ink pattern layer 3 having a low resistance is formed on the end portion of the transparent electrode 7 on the upper substrate 2 side using the conductive ink of the present invention by screen printing, drying and curing. Next, an insulating resist (not shown) is printed on the conductive ink layer 3 and the upper substrate 2 in the vicinity of the conductive ink pattern layer 3 and the end of the transparent electrode 7 by screen printing or the like. Then, it dries and hardens | cures, forms an insulating layer, and forms the laminated body with an insulating resist of this invention. The same applies to the lower substrate 1 side.

In order to prevent the transparent electrodes 6 and 7 from coming into contact with the transparent electrodes 6 and 7 at an appropriate place on the transparent electrode 6 provided on the lower substrate 1 except when the input is the original purpose, as shown in FIG. Small dot spacers 8 are provided at regular intervals at appropriate positions above.
Then, a certain interval (for example, an interval of 10 to 150 μm) is opened (see FIG. 1) so that the transparent electrodes 6 and 7 do not come into contact with each other except when the input is the original purpose (see FIG. 1). The layer 4 and the upper substrate 2, the lower substrate 1 and the upper substrate 2, and the lower substrate 1 and the insulating layer 4 on the upper substrate 2 side are respectively bonded and laminated by the adhesive material 5. The adhesive material 5 can be arranged in a frame shape. In addition, as shown in FIG. 2, the drive electrodes 13 and 14 on the lower substrate 1 side and the upper drive electrodes 9 and 10 on the upper substrate 2 side may be formed to be orthogonal to each other in plan view.
Furthermore, connection electrodes 11 and 12 are connected to the drive electrodes 9 and 10 on the upper substrate 2 side by a conductive adhesive, respectively. Similarly, the drive electrodes 13 and 14 on the lower substrate 1 side are connected to the connection electrodes 15 and 16 with a conductive adhesive, respectively.

The touch screen panel in which the conductive ink pattern layer 3 is formed using the conductive ink of the present invention on each of the lower substrate 1 side and the upper substrate 2 side has good resistance value stability and can be used for various electronic devices over a long period of time. It can be used stably as a component for switching the functions of the above, and has excellent electrical characteristics.
The conductive ink according to the present invention uses an epoxy resin having a number average molecular weight (Mn) of 10,000 to 300,000 and a hydroxyl value of 2 to 300 (mgKOH / g), and the epoxy resin. By containing 0.2 to 20 parts by weight of a metal chelate with respect to 100 parts by weight and further having a storage elastic modulus (G ′) in the range of 5,000 to 50,000 (Pa), high definition Pattern printing can be performed. By using the storage elastic modulus (G ′) in the above range, it is possible to suppress the spread of ink after passing through the screen printing plate and transferring to the substrate while using small conductive particles. Because. As a result of intensive studies by the present inventors, it is possible to easily adjust the storage elastic modulus (G ′) in the above specific range by using the above specific epoxy resin and using the metal chelate having the above mixing ratio. I understood.

Hereinafter, the present invention will be specifically described with reference to examples. In the examples, “parts” and “%” mean “parts by weight” and “% by weight”, respectively, and the hydroxyl value means KOH mg / g.

(Binder 1)
Japan Epoxy Resin Co., Ltd., JER1256 (weight average molecular weight 57,400, number average molecular weight 25,000, epoxy equivalent 7,500, hydroxyl value 190) 40 parts dissolved in 60 parts isophorone, 40% non-volatile content A binder (1) solution was obtained.

(Binder 2)
Japan Epoxy Resin Co., Ltd., JER4250 (weight average molecular weight 57,600, number average molecular weight 24,000, epoxy equivalent 8,500, hydroxyl value 180) 40 parts are dissolved in 60 parts isophorone and 40% non-volatile content A binder (2) solution was obtained.

(Binder 3)
Made by Japan Epoxy Resin Co., Ltd., JER1009 (weight average molecular weight 27,700, number average molecular weight 5,200, epoxy equivalent 2,500, hydroxyl value 220) 40 parts dissolved in 60 parts isophorone, 40% non-volatile content A binder (3) solution was obtained.

(Binder 4) Synthesis of Epoxy Resin In a reactor equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas introduction tube, 100 parts of bisphenol A liquid epoxy resin having a number average molecular weight of 380 and an epoxy equivalent of 190, and bisphenol A of 59 having a hydroxyl equivalent of 114. 1 part (epoxy group / hydroxyl molar ratio 1.015) and 106 parts of diethylene glycol monoethyl ether acetate were added. After dissolving and homogenizing by heating to 100 ° C under a nitrogen stream, 0.9 parts of a 50 wt% tetramethylammonium chloride aqueous solution is added as a catalyst, the temperature is raised to 160 ° C, and the polymerization reaction is carried out at 160 ° C for 7 hours. went. Further, 132 parts of isophorone was added to obtain a binder (4) solution having a nonvolatile content of 40%.
The obtained epoxy resin had a weight average molecular weight of 145,000, a number average molecular weight of 54,000, an epoxy equivalent of 16,500, and a hydroxyl value of 194 per solid content.

(Binder 5) Synthesis of Epoxy Resin In a reactor equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas introduction tube, 100 parts of a bisphenol A liquid epoxy resin having a number average molecular weight of 380 and an epoxy equivalent of 190, and a bisphenol A 57. 6 parts (epoxy group / hydroxyl molar ratio 1.041) and 105 parts of diethylene glycol monoethyl ether acetate were added. After dissolving and homogenizing by heating to 100 ° C under a nitrogen stream, 0.7 parts of 50 wt% tetramethylammonium chloride aqueous solution is added as a catalyst, the temperature is raised to 160 ° C, and the polymerization reaction is carried out at 160 ° C for 7 hours. went. Further, 131 parts of isophorone was added to obtain a binder (5) solution having a nonvolatile content of 40%.
The obtained epoxy resin had a weight average molecular weight of 51,600, a number average molecular weight of 17,000, an epoxy equivalent of 6,900, and a hydroxyl value of 185 per solid content.

(Binder 6) Synthesis of Epoxy Resin In a reactor equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas introduction tube, 100 parts of a bisphenol A liquid epoxy resin having a number average molecular weight of 380 and an epoxy equivalent of 190, and bisphenol A 57 of a hydroxyl group equivalent of 114. 4 parts (epoxy group / hydroxyl molar ratio 1.045) and 128 parts of diethylene glycol monoethyl ether acetate were added. After dissolving and homogenizing by heating to 100 ° C. in a nitrogen stream, 0.4 part of tripropylamine was added as a catalyst, and a polymerization reaction was carried out at 160 ° C. for 7 hours. Furthermore, after lowering the temperature in the reaction system to 70 ° C., 35 parts of phenyl isocyanate and 0.04 part of dibutyltin dilaurate were charged, and the temperature was raised between 100 ° C. and reacted for 6 hours. Furthermore, 161 parts of isophorone was added to obtain a binder (6) solution having a nonvolatile content of 40%.
The obtained epoxy resin had a weight average molecular weight of 60,500, a number average molecular weight of 27,000, an epoxy equivalent of 8,800, and a hydroxyl value of 92 per solid content.

(Binder 7) Synthesis of polyester resin A reactor equipped with a stirrer, a thermometer, a rectifying tube, a nitrogen gas introduction tube, and a decompression device, 20.3 parts of dimethyl terephthalate, 20.3 parts of dimethyl isophthalate, ethylene glycol 9 parts, 18.2 parts of neopentyl glycol, and 0.03 part of tetrabutyl titanate were charged, gradually heated to 180 ° C. while stirring under a nitrogen stream, and subjected to a transesterification reaction at 180 ° C. for 3 hours. Subsequently, 28.3 parts of sebacic acid was added and gradually heated to 180 to 240 ° C. to carry out the esterification reaction. Reaction was performed at 240 ° C. for 2 hours, and the acid value was measured. When the acid value became 15 or less, the reaction vessel was gradually depressurized to 1 to 2 Torr, and when the predetermined viscosity was reached, the reaction was stopped and taken out. A polyester resin having 52,900, a number average molecular weight of 23,000, a hydroxyl value of 5, and an acid value of 1 was obtained. 40 parts of the polyester resin was dissolved in 60 parts of isophorone to obtain a binder (7) solution having a nonvolatile content of 40%.

(Binder 8) Synthesis of polyurethane resin Polyester polyol obtained from isophthalic acid and 3-methyl-1,5-pentanediol in a reactor equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube (Corporation) Kuraray "Kuraray polyol P-2030", Mn = 2033) 127.4 parts, dimethylolbutanoic acid 4.2 parts, isophorone diisocyanate 19.2 parts, and diethylene glycol monoethyl ether acetate 32.5 parts, nitrogen stream The reaction is carried out at 90 ° C. for 3 hours, and then 115 parts of diethylene glycol monoethyl ether acetate is added. A polyurethane having a weight average molecular weight of 48,600, a number average molecular weight of 18,000, a hydroxyl value of 4, and an acid value of 10 A resin solution was obtained. 26 parts of isophorone was added to 100 parts of a polyurethane resin solution to obtain a binder (8) solution having a nonvolatile content of 40%.

The weight average molecular weight, number average molecular weight, epoxy equivalent, acid value and hydroxyl value of binders (1) to (8) were determined according to the following methods.

<Measurement of weight average molecular weight and number average molecular weight>
Apparatus: GPC (gel permeation chromatography)
Model: Shodex GPC-101 manufactured by Showa Denko KK
Column: GPC KF-G + KF805L + KF803L + KF8002 manufactured by Showa Denko KK
Detector: Differential refractive index detector Shodex RI-71 manufactured by Showa Denko K.K.
Eluent: THF
Flow rate: Sample side: 1 mL / min Reference side: 0.5 mL / min Temperature: 40 ° C
Sample: 0.2% THF solution (100 μL injection)
Calibration curve: A calibration curve was prepared using 12 standard polystyrenes with the following molecular weights manufactured by Tosoh Corporation.
F128 (1.09 X10 ⁶ ), F80 (7.06 X10 ⁵ ), F40 (4.27 X10 ⁵ ), F20 (1.90 X10 ⁵ ), F10 (9.64 X10 ⁴ ), F4 (3.79 X10 ⁴ ), F2 ( 1.81 × 10 ⁴ ), F1 (1.02 × 10 ⁴ ), A5000 (5.97 × 10 ³ ), A2500 (2.63 × 10 ³ ), A1000 (1.05 × 10 ³ ), A500 (5.0 × 10 ² ).
Baseline: Except for binder (3), the starting point of the first peak of the GPC curve was the starting point, and no peak was detected at a retention time of 25 minutes (molecular weight 3,150). The molecular weight was calculated using the line connecting both points as the baseline.
In the binder (3), the main peak was still detected at the retention time of 25 minutes. Therefore, the base line was set in the same manner as in the case of other binders, with a retention time of 30 minutes (molecular weight 250), where a plurality of continuous small peaks were almost not detected on the low molecular weight side of the main peak. Asked.

<Measurement of epoxy equivalent>
It measured based on JISK7236.
<Measurement of hydroxyl value and acid value>
Measurement was performed in accordance with JIS K 0070.

[Silver powder A]
A spherical silver powder (tap density 5.5 g / cm ³ , D50 particle diameter 0.9 μm, specific surface area 0.93 m ² / g) manufactured by DOWA Electronics Co., Ltd. was used as silver powder A.

[Silver powder B]
A spherical silver powder (tap density of 4.0 g / cm ³ , D50 particle diameter of 0.5 μm, specific surface area of 1.77 m ² / g) manufactured by DOWA Electronics Co., Ltd. was used as silver powder B.

[Silver powder C]
METALOR spherical silver powder (tap density 2.2 g / cm ³ , D50 particle diameter 0.8 μm, specific surface area 1.40 m ² / g) was defined as silver powder C.

[Silver powder D]
Spherical silver powder (tap density 4.5 g / cm ³ , D50 particle size 0.25 μm, specific surface area 1.70 m ² / g) manufactured by Mitsui Kinzoku Co., Ltd. was defined as silver powder D.

[Silver powder E]
Flake silver metal flake silver powder (tap density 4.8 g / cm ³ , D50 particle diameter 7.9 μm, specific surface area 0.95 m ² / g) was used as silver powder E.

[Silver powder F]
Spherical silver powder (tap density 0.9 g / cm ³ , D50 particle diameter 5.1 μm, specific surface area 1.91 m ² / g) manufactured by Mitsui Kinzoku Co., Ltd. was used as silver powder F.

[Silver powder G]
Metal powder G flake silver powder (tap density 6.1 g / cm ³ , D50 particle size 15.3 μm, specific surface area 0.09 m ² / g) was used as silver powder G.

[Silver powder H]
Flake silver powder (tap density 2.9 g / cm ³ , D50 particle size 5.2 μm, specific surface area 5.60 m ² / g) manufactured by SINO-PLATINUM was used as silver powder H.

<Measurement of tap density, D50 particle diameter and BET specific surface area of silver powder>
1) D50 particle size The cumulative particle size (D50) of the volume particle size distribution was measured using a laser diffraction particle size distribution analyzer “SALAD-3000” manufactured by Shimadzu Corporation.
2) Tap density It measured based on JIS Z 2512: 2006 method.
3) BET specific surface area A value calculated by the following calculation formula from the surface area measured using a flow type specific surface area measuring device “Flowsorb II” manufactured by Shimadzu Corporation was defined and described as a specific surface area.
Specific surface area (m ² / g) = surface area (m ² ) / powder mass (g)

[Metal chelate A]
As the aluminum chelate, ALCH (general formula (1), solid content 90%) manufactured by Kawaken Fine Chemical Co., Ltd. was used as the metal chelate A.

General formula (1)

[Metal chelate B]
As a titanium chelate, ORGATICS TC-100 (titanium acetylacetonate, solid content 75%) manufactured by Matsumoto Fine Chemical Co., Ltd. was used as metal chelate B.

[Metal chelate C]
As a zirconium chelate, ORGATIXX ZC-540 (zirconium tributoxy monoacetylacetonate, solid content 45%) manufactured by Matsumoto Fine Chemical Co., Ltd. was used as the metal chelate C.

[Curing agent 1]
A block type hexamethylene diisocyanate curing agent, Duranate MF-K60X (Asahi Kasei Chemicals, solid content 60%) was used as the curing agent (1).
[Curing agent 2]
An imidazole curing agent, Cureduct P-0505 (manufactured by Shikoku Kasei Co., Ltd., solid content: 100%) was used as the curing agent (2).

Example 1 <Preparation of conductive ink>
Binder (1) solution containing 40 parts by weight of epoxy resin: 100 parts by weight, metal chelate A containing 0.81 part by weight of aluminum ethyl acetoacetate diisopropionate: 0.9 parts by weight, silver powder A: 330 parts by weight Parts, diethylene glycol monoethyl ether acetate: 40 parts by weight were mixed with a disper and dispersed with three rolls to prepare a conductive ink.
The obtained conductive ink has a solid content of about 79% by weight. Of the total 370 parts by weight of the epoxy resin and the silver powder, the silver powder is about 89% by weight and the epoxy resin is 11% by weight.
Then, using a rheometer “AR-G2” manufactured by TA Instruments Inc., it is fixed at a frequency of 1 Hz at a temperature of 25 ° C., and a storage elasticity in the range of vibration stress of 1.0 to 10,000,000 Pa. When the dynamic viscoelastic properties such as the modulus G ′ were measured, the storage elastic modulus G ′ of the conductive ink of Example 1 was 7,200, and tan δ was 0.89.

Examples 2 to 9, Comparative Examples 1 to 9 <Preparation of conductive ink>
Silver powder, a binder resin solution, a metal chelate, a curing agent, and a solvent were mixed with a disper at the blending ratios shown in Tables 1 and 2, and dispersed with three rolls to prepare a conductive ink in the same manner as in Example 1. . The characteristic of the obtained conductive ink was measured by the following method.

[Create test piece]
A conductive ink of Examples 1 to 12 and Comparative Examples 1 to 9 was screen-printed in a 15 mm × 30 mm pattern shape on a 75 μm thick corona-treated polyethylene terephthalate film (hereinafter referred to as PET), and then in a 150 ° C. oven. The film was dried for 30 minutes to obtain a conductive printed material having a film thickness of 8 to 10 μm.

<Measurement of film thickness>
The film thickness of the printed matter was measured using an MH-15M type measuring instrument manufactured by Sendai Nikon.

<Measurement of manifest resistance>
The surface resistance value of the printed matter was measured using a Loresta APMCP-T400 measuring instrument manufactured by Mitsubishi Chemical Corporation in an environment of 25 ° C. and 50% humidity.

<Calculation of volume resistivity>
The volume resistivity was calculated from the surface resistance value measured by the above method and the film thickness. The target value of volume resistivity is 5.0 × 10 ⁻⁵ Ω · cm or less. Note that if it exceeds 5.0 × 10 ⁻⁵ Ω and 8.0 × 10 ⁻⁵ Ω · cm or less, it is practically useful, but if it exceeds 8.0 × 10 ^−5, it is usually not practical.
Volume resistivity (Ω · cm) = (Surface resistivity: Ω / □) x (Film thickness: cm)

<Adhesion to ITO laminated film>
A part of an ITO laminated film (Nitto Denko Corporation, V270L-TEMP, 75 μm thick) was etched with hydrochloric acid to remove the ITO layer to expose the substrate (polyethylene terephthalate film). Then, the conductive inks of Examples 1 to 9 and Comparative Examples 1 to 9 were applied to the ITO laminated portion and the portion where the base material was exposed by etching at 15 mm × so that the film thickness after drying was 8 to 10 μm. A 30 mm pattern was screen-printed and dried in a 150 ° C. oven for 30 minutes, and the adhesion of the printed material was evaluated. Evaluation methods and evaluation criteria are as follows.

<Tape adhesion test>: A tape adhesion test was performed in accordance with JIS K5600.
Put a total of 100 squares of 10 squares x 10 squares at 1 m width intervals into the conductive ink layer on each of the remaining ITO and ITO etched parts, and paste Nichiban cellophane tape (25 mm wide) on the printed surface. The evaluation was performed in the state of the cells that were peeled off rapidly and remained.
○: No peeling (good adhesion level)
Δ: Slightly chipped edges of the mass (adhesion is slightly poor, but practically usable level)
X: Peeling over 1 square is observed (adhesion failure level)

<Adhesion to polyimide film>
Each conductive ink of Examples 1 to 9 and Comparative Examples 1 to 9 on a polyimide film (Toray DuPont, Kapton 100H, 25 μm thickness) is 15 mm so that the film thickness after drying is 8 to 10 μm. A pattern of × 30 mm was screen printed. Then, it dried in 180 degreeC oven for 30 minutes, and evaluated the adhesiveness of this printed matter. Evaluation methods and evaluation criteria are as follows.
Nichiban cellophane tape (25 mm width) was applied to the surface of the printed material and peeled off rapidly to evaluate the adhesion of the printed material.
○: Good adhesion without peeling.
Δ: Slightly peeled off, adhesion slightly poor.
X: There is peeling across the entire surface and poor adhesion.

[Evaluation of fine line printability]
Using a high-precision screen printing device (SERIA manufactured by Tokai Seiki Co., Ltd.), each of the conductive inks of Examples 1 to 9 and Comparative Examples 1 to 9 was placed in a 200 mm × 200 mm area with a line width of 40 μm and a line spacing of 20 sheets of corona-treated PET having a thickness of 75 μm were continuously printed on a screen plate having many fine wiring patterns of 60 μm (L / S = 40 μm / 60 μm). Then, it was dried at 150 ° C. for 30 minutes. The printing conditions are as follows.

(Screen printing conditions)
・ Screen: Stainless steel plate 650 mesh ・ Emulsion thickness: 10 μm
・ Screen frame: 650x550mm
・ Squeegee angle: 70 °
・ Ski Dia Attack Angle: 50 °
・ Squeegee hardness: 80 °
・ Squeegee speed: 20mm / sec ・ Squeegee printing pressure: 10kg
・ Clearance: 3.5mm

(Evaluation of line width variation)
The fine wiring portion of the screen printed wiring pattern was photographed at a magnification of 500 times using a digital microscope (VHX-900 manufactured by Keyence Corporation). The fine line width after printing was read using the small-sized general-purpose image analyzer “LUZEX AP” manufactured by Nireco.
Specifically, for the printed matter on the 5th sheet and the 20th sheet, select 8 arbitrary thin lines respectively, measure the line widths at 460 points per line, a total of 3680 places, the minimum and maximum values The average value, the standard deviation, and the degree of thin line thickness “(average value−40 μm) / 40 μm (%)” were obtained.
Tables 1 and 2 show the average value, the standard deviation, and the thickness of the thin line.
The standard deviation indicates the linearity of the thin line (thickness of the thin line).

Further, the evaluation criteria for the degree of thickening of the thin line “(average value−40 μm) / 40 μm (%)” are as follows.
Less than 25%: almost no thickening of line width is observed, and fine line printability is good. 25-40%: slightly thickening of line width is recognized, but fine line printability exceeds practical level of 40% Wide width is recognized and thin line printability is poor.

Furthermore, the shape of the fine wiring part of the printed wiring pattern was evaluated according to the following criteria. The results are shown in Tables 1 and 2.
○: The fine wiring portion was free from variation in thickness due to meandering, bleeding, and wrinkling, and the boundary line of the fine wiring portion was clear and good.
Δ: Some variation in thickness due to meandering was observed in the fine wiring part, but it did not bleed or wrinkle, and was practically satisfactory.
X: The fine wiring portion was found to have a variation in thickness due to meandering, bleed and wrinkle, and the boundary line was unclear.

[Resistance stability evaluation]
A movable electrode substrate made of a transparent conductive film and a fixed electrode substrate made of a glass electrode substrate were bonded together with a double-sided adhesive layer made of double-sided tape to produce a resistive touch panel having the configuration shown in FIGS. .
The drive electrode, handling circuit, and connection electrode of FIG. 2 were screen printed on the substrate from which the ITO transparent electrode film portion and ITO were removed by etching using the conductive inks of Examples 1 to 12 and Comparative Examples 1 to 9. Then, printing was performed and drying was performed at 135 ° C. for 30 minutes.
Next, a polyurethane resin insulating resist (Rioresist NSP-11, manufactured by Toyo Ink Manufacturing Co., Ltd.) was printed on the drive electrode and the handling circuit by screen printing, and dried at 120 ° C. for 30 minutes. The completed upper and lower electrode substrates were bonded with a double-sided tape to produce a resistive touch screen panel. Note that an insulating resist layer was not provided in order for the terminal portion of the extraction circuit to be terminals A and B (not shown).

About the obtained resistive film type touch screen panel, the resistance value between terminals A and B in FIG. 2 was measured in an environment of 25 ° C. and 50% humidity. Next, the resistance value between terminals after storage for 240 hours in an environment of 60 ° C. and 90% was measured in an environment of 25 ° C. and a humidity of 50%, and the increase rate of the resistance value between terminals after the environmental storage test was as follows. Evaluation based on the criteria. The results are shown in Tables 1 and 2. In addition, the resistance value between terminals was measured using the Sanwa Denki Keiki PC500 type | mold tester.
○: Increase rate of resistance between terminals after environmental preservation test is 0 to 10%
Δ: 10% to 20% increase in resistance between terminals after environmental preservation test
×: The increase rate of the resistance value between terminals after the environmental preservation test exceeds 20%. The increase rate of the resistance value between terminals after the environmental preservation test is 20% or less. It is.

As is apparent from Table 1, the conductive inks of Examples 1 to 12 show good (volume resistivity, fine line printability, adhesion to an ITO laminated film).
In Example 10 to which the curing agent (1) was added, the adhesion to the polyimide film was improved. Further, when used in a touch screen panel, even if exposed to a high temperature and high humidity environment, the increase in resistance between terminals is small and good.
On the other hand, Example 11 to which the curing agent (2) was added and Example 12 to which the curing agent (3) was added had the same adhesion to the polyimide film as in the case where the curing agent was not added. In addition to being excellent in terms of performance, when used in a touch screen panel, it is excellent in that the resistance between terminals is small even when exposed to a high temperature and high humidity environment.

On the other hand, as shown in Table 2, in Comparative Example 1, since the binder resin was a polyester resin, the resistance between terminals of the touch panel increased at 60 ° C., 90%, and 240 hours, and the resistance value stability was poor.
Moreover, since the binder resin was also a urethane resin in Comparative Example 2, the resistance value stability was poor.
In Comparative Example 3, the binder resin is an epoxy resin, but the resistance value stability is poor because the number average molecular weight is less than 10,000, and the thin line printability is also poor because the elastic component of the conductive ink is small.
In Comparative Example 3 using an epoxy resin having a hydroxyl value of 220 (mgKOH / g) and a number average molecular weight of 5,200, the storage elastic modulus (G ′) is 3,500 even when a metal chelate is used. A sufficient storage elastic modulus (G ′) was not obtained. In Comparative Example 9 in which no metal chelate was added, the storage elastic modulus (G ′) was remarkably low at 1,100. In Comparative Example 9, high-definition printing was not obtained.

In Comparative Example 4, the D50 particle size of the silver powder used was less than 0.3 μm, the volume resistivity of the ink coating film was high, and the level was unusable.
On the other hand, in Comparative Example 5, the silver powder used had a D50 particle size of more than 5 μm, and when 20 sheets were printed with fine line printability, the fine lines were severed, so the line width could not be measured. When the mesh portion of the screen printing plate after printing was observed, it was observed that the silver powder was clogged in the mesh at many locations. This is considered to be a problem due to the size increase of D50 particles of silver powder.

In Comparative Example 6, the tap density of the used silver powder was less than 1.0 g / cm ³ , and the volume resistivity of the ink coating film was high, so that it was unusable.

In Comparative Example 7, the specific surface area of the silver powder used was less than 0.3 m ² / g, and the volume resistivity of the ink coating film was high, so that it was unusable. Moreover, since the diameter of D50 particles of the silver powder used exceeded 5 μm and 20 sheets were printed with fine line printability as in Comparative Example 2, the line width was measured because the fine lines were wrinkled due to clogging of the mesh. could not.

In Comparative Example 8, the specific surface area of the silver powder used exceeded 5.0 m ² / g, and a large amount of binder resin was required to cover the surface of the conductive particles. The adhesion was poor.

In Comparative Example 9, no metal chelate was used, the elastic component of the conductive ink was small, it was difficult to maintain the shape after the ink transferred to the base material, and the line was “thick”.

For Example 3 and Comparative Example 9, the viscosity was measured and the thixotropy was further evaluated.
In addition, Example 3 and Comparative Example 9 differ only in the point of using a binder (1) solution and silver powder C, and containing a metal chelate.

(Viscosity measurement method)
Measuring machine: E type viscometer TVE-22H made by Toki Sangyo
Rotor: Cone type rotor # 7 (θ3 °, R7.7mm)
Measurement temperature: 25 ° C
Sample volume: 0.1 mL
Rotation speed: 2rpm, 5rpm, 20rpm
Measuring method: 0.1 mL of a silver paste sample is measured using a 1 mL syringe and set in a viscometer. After standing for 1 minute, the viscosity after stirring for 2 minutes at 2 rpm is measured. Thereafter, the viscosity after stirring for 2 minutes at 5 rpm and 20 rpm is measured.
The TI value is calculated by the following formula.
TI = (viscosity at 2 rpm) / (viscosity at 20 rpm)
In the case of Example 3 containing a metal chelate, 2 rpm: 150 Pas, 5 rpm: 95 Pas, 20 rpm: 56 Pas, and TI value: 2.68.
On the other hand, in the case of the comparative example 9 which does not contain a metal chelate, they were 2 rpm: 168 Pas, 5 rpm: 92 Pas, 20 rpm: 46 Pas, and TI value: 3.66.
That is, there is not much difference between the two in terms of mere viscosity and thixotropy. However, the storage elastic modulus G ′ of Example 3 is 6,100, and the storage elastic modulus G ′ of Comparative Example 9 is 1,100, showing completely different results in printability.

The conductive ink according to the present invention is particularly suitable for screen printing applications, but may be applied to other printing methods.
Moreover, you may apply the electroconductive ink which concerns on this invention not only to a printing use but to a conductive adhesive use, an electromagnetic wave shielding material, etc.
Furthermore, since the laminate with a conductive pattern formed using the conductive ink according to the present invention has little change in conductivity when the humidity is increased, it is suitably used for forming a conductive circuit for printed wiring boards, electronic devices, and the like. be able to.

This application was filed on February 5, 2010, Japanese Patent Application No. 2010-23964, filed on April 28, 2010, Japanese Application No. 2010-103992, and filed on May 6, 2010. Claims priority based on Japanese Patent Application No. 2010-106202 and Japanese Application No. 2010-276401 filed on Dec. 10, 2010, the entire disclosure of which is incorporated herein.

1: Lower substrate 2: Upper substrate 3: Conductive ink pattern layer 4: Insulating layer 5: Adhesive material (bonding)
6: Transparent electrode of the lower substrate 7: Transparent electrode of the upper substrate 8: Dot spacer 9, 10: Upper drive electrode 11, 12: Upper connection electrode 13, 14: Lower drive electrode 15, 16: Lower connection electrode 17: Handling circuit

Claims (21)

1. Conductive particles having a tap density of 1.0 to 10.0 (g / cm ³ ), a D50 particle size of 0.3 to 5 μm, and a BET specific surface area of 0.3 to 5.0 m ² / g;
   An epoxy resin having a number average molecular weight (Mn) of 10,000 to 300,000 and a hydroxyl value of 2 to 300 (mgKOH / g);
   Alcohol exchange reaction with a hydroxyl group in the epoxy resin is possible, and contains 0.2 to 20 parts by weight of a metal chelate with respect to 100 parts by weight of the epoxy resin.
   A conductive ink having a storage elastic modulus (G ′) of 5,000 to 50,000 (Pa).
2. The conductive ink according to claim 1, wherein the conductive particles are silver.
3. The conductive ink according to claim 1 or 2, wherein the epoxy resin is a bisphenol type epoxy resin.
4. The conductive ink according to any one of claims 1 to 3, wherein the epoxy resin has a number average molecular weight (Mn) of 15,000 to 100,000.
5. The conductivity according to any one of claims 1 to 4, wherein the epoxy resin has a number average molecular weight (Mn) of 20,000 to 100,000 and the hydroxyl value of 50 to 250 (mgKOH / g). ink.
6. The conductive ink according to any one of claims 1 to 5, wherein a tap density of the conductive particles is 2.0 to 10.0 (g / cm ³ ).
7. The conductive ink according to any one of claims 1 to 6, wherein the metal chelate is contained in an amount of 2 to 10 parts by weight with respect to 100 parts by weight of the epoxy resin.
8. The conductive ink according to any one of claims 1 to 7, which has a storage elastic modulus (G ') of 5,000 to 20,000 (Pa).
9. The conductive ink according to any one of claims 1 to 8, further comprising a curing agent having a functional group capable of reacting with at least one of a hydroxyl group and an epoxy group of the epoxy resin.
10. 10. The conductive ink according to claim 1, wherein the conductive ink is for screen printing.
11. The conductive ink according to any one of claims 1 to 10, wherein the metal chelate is an aluminum chelate.
12. The conductive ink according to claim 9, comprising 0.5 to 50 parts by weight of the curing agent with respect to 100 parts by weight of the epoxy resin.
13. The conductive ink according to claim 9 or 12, wherein the curing agent is at least one selected from the group consisting of an isocyanate compound, an amine compound, an acid anhydride compound, a mercapto compound, an imidazole compound, a dicyandiamide compound, and an organic acid hydrazide compound. .
14. The conductive ink according to claim 11, wherein the aluminum chelate has a group selected from the group consisting of an acetylacetonate group, a methylacetoacetonate group, and an ethylacetoacetonate group.
15. A substrate;
    A conductive pattern formed on the substrate,
    A laminate with a conductive pattern, wherein the conductive pattern is formed of the conductive ink according to any one of claims 1 to 14.
16. The laminate with a conductive pattern according to claim 15, further comprising an insulating layer laminated to cover the conductive pattern.
17. The conductive pattern according to claim 15 or 16, wherein another conductive film having a predetermined pattern electrically connected to the conductive pattern is further formed on the base material on a lower layer side of the conductive pattern. Laminated body.
18. The laminate with a conductive pattern according to any one of claims 15 to 17, wherein the other conductive film is a transparent conductive film mainly composed of indium oxide doped with tin.
19. The laminate with a conductive pattern according to any one of claims 15 to 18, which is used for touch screen panel applications.
20. Comprising a step of forming a conductive pattern having a desired pattern shape on a substrate by screen printing;
    The method for producing a laminate with a conductive pattern, wherein the conductive pattern uses the conductive ink according to any one of claims 1 to 14.
21. Forming a transparent conductive film of a predetermined pattern on the substrate so as to be partially exposed;
    Forming a conductive pattern of a desired shape by screen printing on the base material and the transparent conductive film using the conductive ink according to any one of claims 1 to 14;
    Forming an insulating layer on the base material, the transparent conductive film and the conductive pattern;
    The said transparent conductive film is a manufacturing method of the laminated body with a conductive pattern which is a film | membrane which has a tin-doped indium oxide as a main component.

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