TW201635311A - Bake-hardening type electroconductive paste - Google Patents

Abstract

The present invention provides a bake-hardening type electroconductive paste to form an electrode having excellent adherence or durability with flexible substrate, and excellent electrical conductivity. According to the present invention, a bake-hardening type electroconductive paste is provided. The bake-hardening type electroconductive paste comprises: (A) electroconductive powder; (B) thermosetting resin; and (C) hardening agent. The aforementioned (B) thermosetting resin comprises: (B1) multi-functional epoxy resin having more than two epoxide groups; (B2) flexible epoxy resin having a continuous structure of more than three secondary carbons; and (B3) monofunctional epoxy resin having one epoxide group.

Description

Heat-curing conductive paste

The present invention relates to a heat-curing conductive paste.

When forming an electrode of an electronic device part or the like, a conductive paste is widely used. Patent Document 1 to Patent Document 5 disclose a conductive paste which can be used for this purpose. For example, a conductive paste containing a binder resin containing a thermoplastic resin, a metal powder, and an organic solvent, and a touch panel including an electrode wiring provided with the conductive paste are disclosed in Patent Application No. 1 and the like. (touch panel). [Prior Art Document] [Patent Literature]

[Patent Document 1] International Patent Publication No. 2014-013899 [Patent Document 2] Japanese Patent Application Publication No. 2014-225709 [Patent Document 3] Japanese Patent Application Publication No. 2014-2992 (Patent Document 4) Japanese Patent Application Publication No. 2014 Japanese Patent Application Publication No. 2012-246433

As described in Patent Document 1, etc., in a flexible electronic component such as a touch panel, a thermoplastic resin is usually used as a bonding component. The object of the invention is to improve the adhesion between a flexible substrate and an electrode by using a resin having high flexibility. However, the electrode using a thermoplastic resin tends to have lower heat resistance, chemical resistance, and mechanical strength due to the "softness" of the resin, and may lack durability. In recent years, the use of flexible electronic components such as touch panels has expanded, and the exposure to harsh environments has increased. Therefore, the electrode is required to further improve heat resistance, durability, and reliability. Therefore, the inventors of the present invention attempted to form an electrode on a flexible substrate using a thermosetting resin having a mechanical strength or durability relatively higher than that of a thermoplastic resin. However, the thermosetting resin has a property of being hard and brittle (low flexibility) due to its rigid chemical structure. Therefore, the electrode using the thermosetting resin has an inherently high hardness. As a result, it is difficult for the electrode to follow the flexible operation of the flexible substrate, and it is easy to peel off from the substrate.

In addition, various types of electric and electronic equipment, such as miniaturization, high density, and high speed of operation, are progressing. Along with this, it is required for the electronic component for an electronic device to further reduce the resistance (improvement in conductivity).

In view of the above, an object of the present invention is to provide a heat-curable conductive paste which can form an electrode excellent in adhesion to a flexible substrate, durability, and conductivity.

In order to realize an electrode having the opposite properties of "toughness" and "softness" and good electrical conductivity, the inventors of the present invention have tried to optimize the configuration of a thermosetting resin as a component. Further, further research has been conducted to complete the present invention. According to the invention, a heat-curable conductive paste is provided. The heat-curable conductive paste contains (A) a conductive powder, (B) a thermosetting resin, and (C) a curing agent. The (B) thermosetting resin includes (B1) a polyfunctional epoxy resin having two or more epoxy groups, and (B2) a flexible epoxy resin having a structure in which three or more secondary carbons are continuous, And (B3) a monofunctional epoxy resin having an epoxy group.

According to this configuration, although the thermosetting resin is used, flexibility or flexibility is imparted to the electrode, and the deformation of the flexible substrate can be followed. Thereby, the adhesion and adhesion of the electrode to the substrate are improved. Further, according to the above configuration, the original properties of the epoxy resin can be exhibited, and an electrode excellent in heat resistance and durability can be obtained. Further, according to the above configuration, for example, a low-resistance electrode having a volume resistivity (heat-hardening condition: 130 ° C, 30 minutes) of 100 μΩ·cm or less can be obtained.

In a preferred aspect disclosed herein, the (B) thermosetting resin further comprises (B4) an epoxy group-containing acrylic resin having one or more epoxy groups. Thereby, at least one of the effects of improving the adhesion to the substrate, improving the durability, and improving the smoothness of the electrode surface can be exhibited. Therefore, the effects of the invention of the present application are exerted at a higher level.

In a preferred aspect disclosed herein, the (B) thermosetting resin contains the following components in a mass ratio: 5% by mass to 25% by mass of (B1) having more than two epoxy groups Functional epoxy resin; 1% by mass to 45% by mass of (B2) flexible epoxy resin having three or more secondary carbon continuous structures; 50% by mass to 70% by mass of (B3) having one epoxy a monofunctional epoxy resin; and 0% by mass to 20% by mass of (B4) an epoxy group-containing acrylic resin having one or more epoxy groups. Thereby, the effects of the invention of the present application are stably and more satisfactorily exhibited. In addition, the handling property of the paste or the workability at the time of printing paste can be improved.

In a preferred aspect disclosed herein, the number average molecular weight of the (B1) to (B3) is 10,000 or less. Thereby, the release property (release property) of the self-made plate becomes good at the time of printing paste, and the printing precision can be further improved. As a result, at least one of the effects of precisely forming the thin wire electrode and improving the smoothness of the electrode surface is exhibited.

In a preferred aspect disclosed herein, the (A) conductive powder does not contain scaly conductive particles. In another preferred aspect disclosed herein, the average particle diameter of the (A) conductive powder by laser diffraction/light scattering is 0.5 μm to 3 μm. The laser processing property is remarkably improved by satisfying at least one of the properties by the conductive powder. Therefore, the paste can be preferably used as a heat-curable conductive paste for laser etching.

Hereinafter, preferred embodiments of the present invention will be described. In addition to the matters specifically mentioned in the present specification (for example, the composition of the heat-curable conductive paste) and the matters necessary for carrying out the invention (for example, a method of preparing a heat-curable conductive paste or an electrode (conductive film)) The method of forming, etc., can be grasped as a design matter of those skilled in the art based on the prior art in the field. The present invention can be implemented in accordance with the contents disclosed in the present specification and the technical common knowledge in the field. In addition, in the present specification, "A to B (where A and B are arbitrary values)" are considered to include the values (upper limit value and lower limit value) of A and B unless otherwise specified.

<Heat-curing conductive paste> The heat-curable conductive paste (hereinafter sometimes simply referred to as "paste") disclosed herein contains (A) a conductive powder, (B) a thermosetting resin, and (C) a curing agent. Essential ingredients. In addition, it is typically free of thermoplastic resins. Further, it is characterized in that the (B) contains at least three predetermined components. Therefore, it is not particularly limited, and can be arbitrarily determined in accordance with various standards. For example, the composition ratio may be changed, or components other than the above (A) to (C) may be blended. Hereinafter, the constituent components of the paste and the like will be described.

<(A) Conductive Powder> The conductive powder is a component for imparting conductivity to the electrode. The conductive powder is not particularly limited, and various metals, alloys, and the like having desired conductivity or other physical properties can be suitably used depending on the application and the like. A preferred example is gold (Au), silver (Ag), copper (Cu), platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), iridium (Ir), osmium (Os). a metal such as nickel (Ni) or aluminum (Al) and a coating mixture or alloy of the metals. Among them, a simple substance of a noble metal such as silver (Ag), platinum (Pt) or palladium (Pd) and a mixture of the noble metals (silver-coated copper, silver-coated nickel) or an alloy (silver-palladium (Ag-Pd), Silver-platinum (Ag-Pt), silver-copper (Ag-Cu), etc.). In particular, in terms of relatively low cost and excellent electrical conductivity, silver and silver coated products, and silver alloys are preferred.

The shape of the conductive powder is not particularly limited, and various shapes such as a spherical shape, a scaly shape (flaky shape), and a needle shape can be considered. Among them, conductive particles having a spherical shape or a substantially spherical shape are preferable. Thereby, the viscosity of the paste can be lowered, and the workability of the paste or the workability at the time of printing the paste can be improved. In addition, the stability of the paste can also be improved. Further, a conductive film excellent in laser workability can be stably formed.

In the case where a spherical or substantially spherical conductive particle is used, the contact area between the particles is smaller than in the case of using conductive particles having a larger aspect ratio such as a scaly shape. Therefore, there is a concern that the volume resistance is increased, and there is a tendency to avoid use when forming an electrode requiring high conductivity. However, according to the technique disclosed herein, the effect of optimizing the (B) thermosetting resin described later can be achieved at a level comparable to that of the conventional paste using conductive particles having a large aspect ratio. Volume resistivity.

In addition, the term "substantially spherical" in the present specification is a term that also includes a spherical shape, a rugby ball shape, a polygonal shape, and the like, and means, for example, that the average aspect ratio (long diameter/short diameter ratio) is 1 to 2. Typically, it is a shape of from 1 to 1.5, for example from 1.1 to 1.4. In addition, the "average aspect ratio" in this specification means the average value of the long diameter / minor diameter ratio of several electroconductive particle. For example, at least 30 (for example, 30 to 100) conductive particles are observed using an electron microscope. Then, the minimum rectangle circumscribing each particle image is drawn, and the ratio (A/B) of the length A of the long side of the rectangle to the length (for example, thickness) B of the short side is calculated as the aspect ratio. The average aspect ratio can be obtained by arithmetically averaging the obtained aspect ratios.

In a preferred aspect, the conductive powder does not contain scaly conductive particles. That is, it is preferable that the conductive powder does not contain conductive particles having an aspect ratio of more than 10 (typically more than 5, preferably more than 3, for example, more than 2). In other words, the conductive powder may include spherical particles or substantially spherical (for example, an aspect ratio of 1.0 to 2.0) of conductive particles. Thereby, the detachability of the self-made plate (the detachment from the mesh) becomes good at the time of printing the paste, and the smoothness of the electrode surface or the printing precision can be improved. Further, the laser workability is further improved, and a thin line-shaped electrode can be formed with a stable processing line width. That is, in general, one particle of the conductive particles having a large aspect ratio has a large plan view area. Therefore, one conductive particle may exist in a state in which a portion remaining as an electrode and a portion (laser irradiation portion) removed by laser processing are present. According to the study by the inventors of the present invention, when the laser beam is irradiated in this state, the heat is transmitted to the conductive particles remaining as the electrode, and the conductive film may be scraped to the extent necessary or more. As a result, there is a case where the electrode is thinner or broken than the predetermined width, or the electrode surface is rough. Since the conductive powder does not contain scaly conductive particles, the proportion of such defective portions can be remarkably reduced.

The average particle diameter of the conductive powder is not particularly limited, but may be usually 0.1 μm or more, preferably 0.5 μm or more, and may be substantially 5 μm or less, preferably 3 μm or less, for example, 2.2 μm or less. When the average particle diameter is equal to or greater than a predetermined value, the contact points between the particles in the electrode are reduced, and the internal resistance is lowered. Therefore, high conductivity can be achieved. Further, it is possible to suppress the occurrence of aggregation in the paste and to improve homogeneity or dispersibility. Further, it is preferable to suppress the viscosity of the paste to be low, and to improve the workability of the paste or the workability at the time of printing the paste, for example. In addition, when the average particle diameter is equal to or less than a predetermined value, a film-shaped or thin-line electrode can be formed more stably. Further, for example, it is possible to effectively reduce the amount of conductive particles that are in a state of being spread across a portion remaining as an electrode and a portion undergoing thermal decomposition during laser processing. Therefore, the laser workability is improved, and a thin wire electrode can be stably formed.

In addition, the "average particle diameter" in the present specification means a particle diameter D _{50 which is} 50% cumulative from particles having a small particle diameter in a particle size distribution based on a volume standard based on a laser diffraction/light scattering method. Value (median diameter).

In a preferred embodiment, the conductive particles constituting the conductive powder are provided with a film containing a fatty acid on the surface thereof. According to this configuration, the hydroxyl group on the surface of the conductive particles is increased, and the hydrophilicity can be improved. Since the thermosetting resin is typically hydrophobic, the wettability of the conductive particles and the thermosetting resin is lowered. As a result, the thermosetting resin is less likely to be attached to the conductive particles, and the conductive particles are likely to form a contact with each other. Therefore, an electrode having more excellent conductivity can be formed. Further, examples of the fatty acid include a saturated higher fatty acid or an unsaturated fatty acid having 10 or more carbon atoms. From the viewpoint of exhibiting the above effects at a high level, a polyunsaturated fatty acid such as an alkyl succinic acid or an alkenyl succinic acid is preferred.

(A) The ratio of the conductive powder to the total mass of the essential constituent components of the paste (that is, (A) + (B) + (C)) is not particularly limited, and is usually 50% by mass or more, typically It is 60% by mass to 95% by mass, for example, 70% by mass to 90% by mass. By satisfying the above range, formation of an electrode having high conductivity and excellent workability and workability can be achieved at a high level.

<(B) Thermosetting Resin (Mixture)> The thermosetting resin is a component for imparting adhesion or durability to the electrode. When the thermosetting resin is heated and added with a curing agent, a network-formed crosslinked structure is formed between the molecules to be cured. Once hardened, it is difficult to dissolve in the solvent, and it does not exhibit plasticity (no deformation) even when heated. Therefore, an electrode excellent in heat resistance, chemical resistance, mechanical strength, and durability can be realized as compared with the conventional product using a thermoplastic resin. The thermosetting resin of the paste disclosed herein is a mixture comprising at least three components: (B1) a polyfunctional epoxy resin; (B2) a flexible epoxy resin; and (B3) a monofunctional epoxy resin. Further, the (B) thermosetting resin may be composed of the components (B1) to (B3), and may contain other thermosetting resins previously known, such as phenol, in addition to the above (B1) to (B3). Resin, urea resin, melamine resin, alkyd resin, enamel resin, urethane resin, and the like. In a preferred embodiment, when the total amount of the (B) thermosetting resin is 100% by mass, the total amount of the above (B1) to (B3) is approximately 90% by mass or more, for example, 95% by mass or more.

<(B1) Polyfunctional Epoxy Resin> The polyfunctional epoxy resin has a rigid skeleton structure. The rigid skeleton structure means a cyclic hydrocarbon skeleton, and is, for example, a benzene ring skeleton or a cyclopentadiene skeleton. Thereby, the polyfunctional epoxy resin has a function of imparting excellent heat resistance, chemical resistance, and toughness to the electrode. Therefore, the mechanical strength or shape stability of the electrode can be improved, and an electrode having more excellent durability can be realized.

The polyfunctional epoxy resin may be an uncured (pre-cured) compound having two or more epoxy groups, and a conventionally known polyfunctional epoxy resin may be suitably used. A preferred example of the polyfunctional epoxy resin is bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, naphthalene type epoxy resin Resin, dicyclopentadiene type epoxy resin, trisphenol methane type epoxy resin, phenol aralkyl type epoxy resin, polyfunctional phenol type epoxy resin, biphenyl type epoxy resin, glycidyl ester type epoxy Resin, glycidylamine type epoxy resin, fluorene type epoxy resin, hydroquinone type epoxy resin, and modified type of these resins. These resins may be used alone or in combination of two or more. Among them, a novolac type epoxy resin, a dicyclopentadiene type epoxy resin, or a bisphenol type epoxy resin is preferable from the viewpoint of availability. In particular, a novolac type epoxy resin is preferred from the viewpoint of lowering the volume resistance at a higher level.

The epoxy equivalent of the polyfunctional epoxy resin is not particularly limited and may be approximately 100 g/eq to 3000 g/eq, typically 100 g/eq to 1000 g/eq, for example, 150 g/eq to 500 g/ Around eq. When the epoxy equivalent is at least a predetermined value, the function as an epoxy resin (that is, adhesion or adhesion) is more satisfactorily exhibited. In addition, when the epoxy equivalent is not more than a predetermined value, an electrode having more excellent durability or reliability can be obtained. In addition, the "epoxy equivalent" in this specification means the value measured by Japanese Industrial Standards (JIS) K7236 (2009).

The number average molecular weight Mc of the polyfunctional epoxy resin is not particularly limited, and may be approximately 10,000 or less, preferably 5,000 or less, typically 100 to 5,000, more preferably 2,000 or less, or, for example, about 300 to 1,500. When the number average molecular weight Mc is equal to or less than a predetermined value, the release property (release property) of the self-made plate becomes good when the paste is printed, and the printing accuracy is improved. In addition, the thermal decomposition property is improved and the laser processability can be improved. Further, when the number average molecular weight Mc is equal to or greater than a predetermined value, the adhesion to the substrate or the shape of the electrode can be improved. In addition, the "number average molecular weight" in this specification means the measurement by gel chromatography (Gel Permeation Chromatography (GPC)), and converted using the standard polystyrene calibration curve. The average molecular weight of the number basis.

(B1) The proportion of the polyfunctional epoxy resin in the entire thermosetting resin is not particularly limited, and is typically 5% by mass or more, preferably 7% by mass or more, for example, 10% by mass or more, and substantially It may be 25% by mass or less, preferably 23% by mass or less, for example, 22% by mass or less. Thereby, an electrode excellent in heat resistance, chemical resistance, and mechanical strength can be obtained more stably.

<(B2) Flexible Epoxy Resin> The flexible epoxy resin has a continuous (soft) structure of three or more secondary carbons. Therefore, the flexible epoxy resin has "flexibility" as described later, and has the function of alleviating the hardness by the component (B1) and imparting appropriate flexibility or elasticity to the electrode. Softness. Thereby, the adhesion (integralness) between the electrode and the flexible substrate is improved. Further, even when the flexible substrate is shrunk, warped, deformed, or the like at the time of manufacture (assembly) or use of the electronic device, the electrode can flexibly follow the operation. Therefore, peeling of the conductive film can be more satisfactorily suppressed, and excellent durability or reliability can be achieved.

The flexible epoxy resin may be an uncured (pre-hardened) compound having three or more secondary carbon continuous structural portions (segments), and the previously known flexibility may be suitably used. Epoxy resin. The flexible epoxy resin described herein typically has a repeating unit of at least three CH ₂ continuous structural moieties (ie, a structural moiety represented by —(CH ₂ ) _n — wherein n is n≧ 3 real numbers). The continuous structural portion of the repeating unit is typically included in the main chain skeleton in which the carbon number is the largest, but may, for example, also span the main chain skeleton and side chains extending from the main chain skeleton in a branch shape (side) Bit) exists. In a preferred aspect, the number of consecutive repeating units (the n) is n≧4, particularly n≧5. Thereby, the flexibility of the electrode is more improved, and the adhesion to the flexible substrate can be further improved. The upper limit of the number of consecutive units (the above-mentioned n) is not particularly limited, and may be approximately n≧10 from the viewpoint of maintaining the characteristics of (B1) and exhibiting the characteristics of (B2) more satisfactorily. . Further, in the case where the number of consecutive secondary carbons in a compound is randomly present, the smallest continuous number is regarded as the "continuous number".

The proportion of the repeating unit in the flexible epoxy resin is not particularly limited, and may be, for example, about 5% by mass to 90% by mass.

A preferred example of the flexible epoxy resin is a chain alicyclic epoxy resin such as a dimer acid type epoxy resin or a bisphenol modified epoxy resin, or a urethane modified ring. Modified epoxy resin such as oxygen resin or rubber modified epoxy resin. These resins may be used alone or in combination of two or more. Among them, a dimer acid type epoxy resin or a bisphenol modified type epoxy resin is preferable from the viewpoint of improving conductivity or hardenability.

The epoxy equivalent of the flexible epoxy resin is not particularly limited, and is typically larger than the above (B1), and is generally 200 g/eq to 3000 g/eq, in order to exhibit the effects of the present invention at a high level. It is about 300 g/eq to 2000 g/eq, for example, about 350 g/eq to 1000 g/eq.

The number average molecular weight Mc of the flexible epoxy resin is not particularly limited, and may be approximately 10,000 or less, preferably 5,000 or less, typically 100 to 5,000, more preferably 2,000 or less, or, for example, 500 to 1,000. When Mc is more than a predetermined value, the effect of improving flexibility can be sufficiently obtained. When Mc is less than or equal to a predetermined value, the workability of the paste or the workability at the time of printing can be improved.

Further, the "flexibility" of the epoxy resin can be evaluated by the following test. First, an epoxy resin (monomer) and a hardener are hardened, and a resin film is produced. The resin film was cut into a size of 10 mm in width, 40 mm in length, and 1 mm in thickness to prepare a test piece. Then, the test piece was bent in a cylindrical test piece along a radius of curvature of 25 mm (curvature 0.04/mm) (refer to Fig. 2). The case where the test piece is bent and the failure such as crack or breakage is not confirmed is regarded as "good". This test was carried out on 10 test pieces, and 10 pieces of all of the "good" epoxy resins were regarded as "having flexibility (Good)". On the other hand, if one of the ten sheets is confirmed to be in a bad condition, the epoxy resin is regarded as "non-flexible". A specific evaluation method will be shown in the examples described later.

In a preferred aspect, the flexibility of the epoxy resin is higher, for example, even if the test piece has a radius of curvature of 15 mm (curvature 0.06/mm) and a radius of curvature of 10 mm (curvature 0.1/mm). When the test piece of the cylindrical shape was bent, all of the ten test pieces were "good". These epoxy resins can be regarded as "good flexibility (Great)" and "very good flexibility (Excellent)". In a better aspect, the flexibility of the epoxy resin is remarkably high. For example, even when the test piece is bent by 180° so that the both ends of the test piece are in contact in the longitudinal direction, all of the 10 test pieces are "good". Such an epoxy resin can be regarded as "very good flexibility (Brilliant)".

The ratio of the (B2) flexible epoxy resin to the entire thermosetting resin is not particularly limited, and is typically 1% by mass or more, preferably 2% by mass or more, and for example, 4% by mass or more. Further, it may be approximately 45% by mass or less, preferably 40% by mass or less, for example, 35% by mass or less. Thereby, an electrode which has high flexibility and is excellent in adhesion to a flexible substrate can be obtained more stably.

<(B3) Monofunctional Epoxy Resin> The monofunctional epoxy resin is a component which reduces the viscosity of the paste by making the paste fluid. In addition, it is also a component that lowers the glass transition point of the paste. Thereby, the workability of the paste or the workability at the time of printing paste can be improved. This is also preferable from the viewpoint of obtaining a film-like (for example, a thickness of 10 μm or less) electrode suitable for laser processing. Further, the glass viscosity is lowered, whereby the flexibility of the epoxy resin is improved, and the epoxy resin easily flows during heat curing of the paste. As a result, an effect of repelling (excluding) the resin interposed between the conductive particles is obtained. Therefore, the contact area of the conductive particles increases, and the volume resistance can be suppressed to be lower.

The monofunctional epoxy resin may be an unhardened (pre-hardened) compound having one epoxy group in the molecule, and a conventionally known monofunctional epoxy resin may be suitably used. A preferred example of the monofunctional epoxy resin is an alkyl glycidyl ether having a carbon number of 6 to 36 (typically 6 to 26, for example, 6 to 18), an alkylphenyl glycidyl ether, or an alkenyl group. A glycidyl ether epoxy resin such as glycidyl ether, alkynyl glycidyl ether or phenyl glycidyl ether; alkyl glycidyl ester having a carbon number of 6 to 36 (typically 6 to 26, for example, 6 to 18) A glycidyl ester epoxy resin such as an alkenyl glycidyl ester or a phenyl glycidyl ester. These resins may be used alone or in combination of two or more. Among them, in order to exhibit the effects of the present invention at a high level, alkyl glycidyl ether, phenyl glycidyl ether, alkyl glycidyl ester, and phenyl glycidyl ester are preferred. Especially preferred is phenyl glycidyl ether.

The epoxy equivalent of the monofunctional epoxy resin is not particularly limited, and is typically substantially the same as the above (B1), and is generally 100 g/eq to 3000 g/eq, in order to exhibit the effects of the present invention at a high level. It is about 100 g/eq to 1000 g/eq, for example, about 100 g/eq to 500 g/eq.

The number average molecular weight Mc of the monofunctional epoxy resin is not particularly limited, and is typically smaller than the above (B1) and (B2), and in order to exhibit the effect of the present invention at a high level, it may be approximately 5,000 or less, typically It is 2000 or less, preferably 1,000 or less, for example, about 100 to 300.

(B3) The ratio of the monofunctional epoxy resin to the entire thermosetting resin is not particularly limited, and is typically 50% by mass or more, preferably 55% by mass or more, for example, 60% by mass or more, and substantially It may be 70% by mass or less, preferably 67% by mass or less, for example, 65% by mass or less. Further, in a preferred aspect, the mass ratio of the (B1) polyfunctional epoxy resin to the (B3) monofunctional epoxy resin is approximately 20:80 to 45:55. Thereby, an electrode excellent in conductivity and durability can be obtained more stably.

<(B4) Epoxy group-containing acrylic resin> In a preferred aspect, the (B) thermosetting resin further contains (B4) an epoxy group-containing acrylic resin having one or more epoxy groups. The epoxy group-containing acrylic resin functions to improve the adhesion between the electrode and the flexible substrate or to improve the smoothness of the electrode surface. In other words, since the epoxy group-containing acrylic resin contains an epoxy group, the affinity with the above (B1) to (B3) is good. Further, in the stage of heat curing of the coating film, the epoxy group of the epoxy group-containing acrylic resin (B4) is hardened, and a three-dimensional crosslinked structure is formed together with the above (B1) to (B3). Thereby, the adhesion between the electrode and the flexible substrate is further improved. Further, (B4) a part of the epoxy group-containing acrylic resin floats on the surface of the coating film before the resin component is completely cured, and functions to homogenize the surface tension of the coating film. In other words, the (B4) epoxy group-containing acrylic resin can also function as a so-called surface conditioner (leveling agent). Thereby, the smoothness of the electrode surface can be further improved.

The epoxy group-containing acrylic resin may be an uncured (pre-cured) compound having one or more epoxy groups at the terminal and/or side chain (lateral position) of the main chain skeleton of the acrylic resin. A previously known epoxy group-containing acrylic resin can be suitably used. A preferred example of the epoxy group-containing polymerizable monomer, a copolymer of the epoxy group-containing polymerizable monomer and another polymerizable monomer, and the like are mentioned. Examples of the epoxy group-containing polymerizable monomer include glycidyl (meth)acrylate, glycidyl methacrylate (GMA), methacrylic acid-α-methylglycidyl ester, and methacrylic acid. -3,4-epoxycyclohexylmethyl ester, vinyl glycidyl ether, allyl glycidyl ether, and the like. Among them, it is preferred to contain glycidyl methacrylate.

Examples of the other polymerizable monomer include (meth)acrylic acid; methyl (meth)acrylate; ethyl (meth)acrylate; n-propyl (meth)acrylate; n-butyl (meth)acrylate; Isobutyl (meth)acrylate, t-butyl (meth)acrylate (TBA), amyl (meth)acrylate, n-hexyl (meth)acrylate, (methyl) 2-ethylhexyl acrylate, n-octyl (meth)acrylate, butoxyethyl (meth)acrylate, phenyl (meth)acrylate, cyclopentyl (meth)acrylate, (meth)acrylic acid Cyclohexyl ester, methylcyclohexyl (meth)acrylate, trimethylhexyl (meth)acrylate, benzyl (meth)acrylate, naphthyl (meth)acrylate; methacrylic acid; Methyl methacrylate (MMA), ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, methacrylate Ester, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, butoxyethyl methacrylate, methyl propyl Benzyl acrylate, cyclopentyl methacrylate, cyclohexyl methacrylate, methylcyclohexyl methacrylate, trimethylcyclohexyl methacrylate, isobornyl methacrylate, naphthyl methacrylate, etc. Methacrylate; acrylonitrile; vinyl acetate; styrene; butadiene. Among them, it is preferred to contain at least one of acrylic acid, acrylate, methacrylic acid, and methacrylic acid ester.

The mixing ratio of the epoxy group-containing polymerizable monomer to the other polymerizable monomer is not particularly limited, and as a general standard, in a preferred embodiment, it may be about 3:1 to 1:3, for example, 2:1 to 1 : 2 or so. Thereby, the effect of the present invention can be exerted at a higher level.

The epoxy equivalent of the epoxy group-containing acrylic resin is not particularly limited, and is typically more than the above (B1) to (B3), and in order to exhibit the effect of the present invention at a high level, it is approximately 200 g/eq. 3000 g/eq, typically 300 g/eq to 2000 g/eq, for example 400 g/eq to 1000 g/eq.

The number average molecular weight Mc of the epoxy group-containing acrylic resin is not particularly limited, and is typically larger than the above (B1) to (B3), and is preferably 10,000 or less in order to exhibit the effect of the present invention at a high level. It is 5,000 or less, preferably 2,000 or less, for example, about 100 to 1,000.

The thermosetting resin may contain (B4) an epoxy group-containing acrylic resin, and may not contain (B4) an epoxy group-containing acrylic resin. When the thermosetting resin contains (B4) an epoxy group-containing acrylic resin, the ratio of the (B4) epoxy group-containing acrylic resin to the entire thermosetting resin is not particularly limited. The high level exerts an additive effect, and is typically 0.5% by mass or more, preferably 1% by mass or more, for example, 5% by mass or more, and substantially 20% by mass or less, preferably 17% by mass or less, for example, 15% by mass. %the following.

In a preferred aspect, the (B) thermosetting resin comprises the following components in a mass ratio: 5% by mass to 25% by mass of (B1) a polyfunctional epoxy resin having two or more epoxy groups; (B2) a flexible epoxy resin having a structure in which three or more secondary carbons are continuous; 50% by mass to 70% by mass of (B3) a monofunctional epoxy having one epoxy group Resin; and 0% by mass to 20% by mass of (B4) an epoxy group-containing acrylic resin having one or more epoxy groups. By forming the thermosetting resin in the above-described composition ratio, it is possible to realize an electrode having the opposite properties of "toughness" and "softness" at an extremely high level.

(B) The content of the thermosetting resin is not particularly limited, and when the conductive powder is 100 parts by mass, it is typically 3 parts by mass or more, preferably 5 parts by mass or more, and for example, 8 parts by mass or more. Further, it may be approximately 30 parts by mass or less, preferably 25 parts by mass or less, for example, 20 parts by mass or less. Thereby, an electrode excellent in adhesion to the substrate, durability, and conductivity can be obtained. (B) The ratio of the thermosetting resin (mixture) to the total mass of the essential constituent components of the paste (that is, (A) + (B) + (C)) is not particularly limited, and is typically 3 The mass% or more, preferably 5% by mass or more, for example, 7% by mass or more, and substantially 25% by mass or less, preferably 20% by mass or less, for example, 18% by mass or less. By satisfying the above range, the effects of the present invention can be exerted at a higher level.

<(C) Hardener> The curing agent is a component for forming a crosslinked structure between the molecules (B1) to (B3) or (B1) to (B4) and hardening the molecules. The curing agent is not particularly limited, and a compound which can react with an epoxy group of an epoxy resin to form a crosslinked structure can be suitably used. Preferable examples thereof include an imidazole curing agent, a phenol curing agent, an amine curing agent, a guanamine curing agent, an organic phosphine, and derivatives of these compounds. These compounds may be used alone or in combination of two or more.

The content of the curing agent is not particularly limited, and when the conductive powder is 100 parts by mass, it is typically 0.1 part by mass or more, preferably 0.5 part by mass or more, for example, 1 part by mass or more, and substantially 10 parts by mass or less, preferably 7 parts by mass or less, for example, 5 parts by mass or less. Thereby, it is possible to prevent the occurrence of hardening failure and to smoothly carry out the curing reaction. Further, it is possible to suppress the unreacted hardener from remaining in the electrode and suppress the volume resistance to be lower. The ratio of the hardener to the total mass of the essential constituent components of the paste (that is, (A) + (B) + (C)) is not particularly limited, and is typically 0.1% by mass or more, preferably 0.5. The mass% or more, for example, 1 mass% or more, and may be approximately 10% by mass or less, preferably 5% by mass or less, for example, 4% by mass or less. By satisfying the above range, an electrode whose volume resistance is lowered can be stably formed.

<(D) Other Components> The paste disclosed herein may contain various additional components as needed in addition to the components (A) to (C). Examples of such an additive component include a reaction accelerator (activating catalyst), a laser light absorber, an inorganic filler, a surfactant, a dispersant, a tackifier, an antifoaming agent, a plasticizer, a stabilizer, and an antioxidant. , pigments, diluted solvents, etc. As the additional components, those known to be usable in a usual conductive paste can be suitably used.

Examples of the reaction accelerator (cocatalyst) include an alkoxide, a chelate (compound), and a telluride containing a metal element such as zirconium (Zr), titanium (Ti), aluminum (Al), or tin (Sn). . These compounds may be used alone or in combination of two or more. Among them, it is preferred to contain an organic zirconium compound. In addition, examples of the diluent solvent include organic solvents such as a glycol solvent, a glycol ether solvent, an ester solvent, an alcohol solvent, and a hydrocarbon solvent.

The content of the component to be added is not particularly limited, and may be, for example, 10 parts by mass or less, preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, based on 100 parts by mass of the conductive powder.

<Preparation of Paste> Such a paste can be prepared by weighing the above-mentioned materials in such a manner as to have a predetermined content ratio (mass ratio), and uniformly mixing them by stirring. The agitation and mixing of the materials can be carried out using various agitation mixing devices previously known, such as a roll mill, a magnetic stirrer, a planetary mixer, a disperser or the like.

<Method of Using Paste> In one use example of the paste, the substrate is first prepared. For the substrate, for example, a plastic substrate, an amorphous germanium substrate, a glass substrate, or the like can be considered. Particularly in the case of using a substrate comprising a material having low heat resistance, the present invention can be preferably employed. Then, the paste is applied (coated) to the substrate so as to have a desired thickness (for example, 1 μm to 50 μm, preferably 10 μm or less, for example, 1 μm to 10 μm, more preferably 7 μm or less). The paste can be applied, for example, by screen printing, a bar coater, a slit coater, a gravure coater, a dip coater, a spray coater or the like. Then, the paste applied to the substrate is dried by heating. The heating temperature can be, for example, a temperature equal to or higher than the glass transition point of the (B) thermosetting resin. Further, from the viewpoint of suppressing damage of the substrate or improving productivity, the heating and drying temperature can be sufficiently lower than the heat resistant temperature of the flexible substrate, and typically 200 ° C or less, preferably 180 ° C or less. More preferably, it is 100 ° C - 150 ° C, especially 100 ° C - 130 ° C. Further, the heat drying time can be typically from 1 minute to 60 minutes, for example from 10 minutes to 30 minutes. Thereby, the thermosetting resin in the paste is cured, and a film-shaped conductive film (electrode) is formed on the substrate.

In a preferred aspect, the conductive film is covered so as to have a desired shape (for example, a thin line shape), and the other portions are irradiated with laser light. The type of the laser is not particularly limited, and a laser known to be usable for such use can be suitably used. A preferred example is an infrared (IR) laser, a fiber laser, a CO ₂ laser, a quasi-molecular laser, a Yttrium Aluminum Garnet (YAG) laser, a semiconductor laser, or the like. For example, a laser that produces a near-infrared laser light having a wavelength range of 750 nm to 1500 nm and further a wavelength range of 900 nm to 1100 nm can be used. In a preferred embodiment, the laser type is selected such that the absorption wavelength range of the substrate does not coincide with the fundamental wavelength of the laser light. Thereby, damage to the substrate can be suppressed to a minimum. In another preferred embodiment, the laser species is selected in such a manner that the wavelength of the laser light coincides with the absorption wavelength range of the components constituting the conductive film. Thereby, the conductive film has an absorption band for the wavelength of the laser light, and the workability or productivity at the time of laser processing can be improved. For example, the absorption wavelength of the cured film constituting the conductive film (specifically, the cured product obtained by curing the (B) thermosetting resin by the (C) curing agent) ranges from approximately 9000 cm ^-1 to 10000 cm ^{-1 .} , for example, the case of the range of ^-1 ~ ^{9900cm -1} 9300 cm, can be preferably used the fundamental wavelength 1064 nm IR laser.

The irradiation conditions of the laser light are not particularly limited. For example, the laser output is also approximately 0.5 W to 100 W from the viewpoint of avoiding damage to the substrate and appropriately removing unnecessary portions of the conductive film depending on the thickness of the conductive film. For example, when a conductive film having a thickness of about 1 μm to 10 μm is processed by using an IR laser, the laser output can be set to about 1 W to 10 W. In addition, regarding the scanning speed of the laser, the productivity can be maintained high and the unnecessary portion of the conductive film can be appropriately removed, and can be approximately 1000 mm/s to 10000 mm/s, for example, 1500 mm/ s ~ 5000 mm / s.

The laser's light energy is converted into thermal energy and reaches the conductive film. Thereby, the conductive film is thermally decomposed, melted, and removed in the irradiated portion of the laser light. Further, the electrode is formed only by the portion that is not irradiated with the laser light. As described above, a structure (wiring substrate) in which an electrode (wiring) having a predetermined pattern is provided on a substrate can be obtained.

<Use of Paste> The paste disclosed herein can form an electrode having high flexibility or flexibility. Therefore, for example, it can be preferably used for forming an electrode on a flexible substrate having a high degree of freedom of deformation. In the present specification, the term "flexible substrate" means that when the substrate is bent so as to have a cylindrical test member along a radius of curvature of 25 mm (curvature of 0.04/mm), no crack is confirmed in the substrate. Or break, etc. Further, the paste disclosed herein can form a low-resistance electrode by thermal hardening at a low temperature for a short period of time. Therefore, it can be preferably used to form an electrode on a substrate which is reduced in performance if exposed to a high temperature. Further, in a preferred aspect, the laser processability is also excellent, and in particular, it can be preferably used to form a thin line having an L/S = 80 μm / 80 μm or less, for example, L/S = 50 μm / 50 μm or less. Electrode. A typical use of the electrodes includes the formation of electrodes of various electronic components, or the formation of a conductor circuit of a flexible member such as a touch panel or a liquid crystal display or an electronic paper. For example, the flexible substrate may include polypropylene (polypropylene), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polycarbonate (polycarbonate, PC), a film-shaped plastic substrate of a resin such as polyamide or a glass substrate. Further, a state in which a conductive film containing an oxide such as an indium tin oxide (ITO) film is formed on a flexible substrate may be used.

In the following, several embodiments related to the present invention are described, but it is not intended to limit the invention to the contents shown in the embodiments.

I. Evaluation of Flexibility of Epoxy Resin First, the following four kinds of epoxy resins were prepared. ·Flexible epoxy resin 1: Dimer acid type epoxy resin (continuous number of secondary carbon ≧5) ·Flexible epoxy resin 2: bisphenol modified epoxy resin (continuous number of secondary carbon ≧4) ·Flexible epoxy resin 3: Hydrogenated bisphenol epoxy resin (continuous number of secondary carbon <3) ·Multifunctional epoxy resin: bisphenol epoxy resin (continuous number of secondary carbon< 3)

Then, the epoxy resin is cured by a curing agent (herein, an imidazole-based curing agent is used) to prepare a resin film. The resin film was cut into a size of 10 mm in width, 40 mm in length, and 1 mm in thickness, and 10 test pieces were prepared. In addition, a test member having a cylindrical shape having the following curvature was prepared. A cylindrical member having a radius of curvature of 25 mm, 15 mm, 10 mm (curvature of 0.04/mm, 0.06/mm, 0.1/mm), and then the test piece is bent along the circular arc shape of the cylindrical member (refer to Fig. 2). Then, it was confirmed whether or not there was a problem such as crack or breakage in the bent test piece. For the test piece which can be bent with a curvature radius of 10 mm, the 180° bending is further performed. The results are shown in Table 1. In Table 1, "○" indicates that none of the 10 test pieces has been confirmed to be defective (10 pieces are "good"), and "△" indicates that one to two pieces of the 10 pieces have been confirmed to be in a bad condition, and "X" indicates that 10 pieces are in a bad condition. Three or more of them were confirmed to be in a bad condition.

[Table 1] Table 1 (large) ←←←←Flexibility

As shown in Table 1, the flexible epoxy resin 1 having a continuous number of secondary carbons of 3 or more and the flexible epoxy resin 2 can be deformed along a shape having a radius of curvature of 15 mm (curvature of 0.06/mm). Excellent flexibility. The flexibility of the epoxy resin 1 is "Brilliant," and the flexible epoxy resin 2 is "flexible" (Great). )".

Further, as a reference, a bending elastic modulus was measured for the three kinds of epoxy resins using a viscoelastic spectrometer (Dynamic Mechanical Spectrometer (DMS)). The results are shown in Table 2. [Table 2] Table 2

As shown in Table 2, the evaluation result of "flexibility" in the present specification is different from the tendency of the measurement result of the normal bending elastic coefficient based on DMS. In other words, the evaluation result of "flexibility" disclosed herein cannot be estimated only by the measurement of the usual "elastic coefficient".

II. Evaluation of Conductive Paste First, the following materials which are constituent components of the heat-curable conductive paste are prepared. <<(A) Conductive powder>> Conductive powder 1: Spherical silver powder ("Ag-2-8" manufactured by DOWA ELECTRONICS Co., Ltd., D ₅₀ = 1.0 μm, average aspect ratio is 1.1) Conductive powder 2: Spherical silver powder ("Ag-2-1C" manufactured by DOWA ELECTRONICS Co., Ltd., D ₅₀ = 0.5 μm, average aspect ratio is 1.0) · Conductive powder 3: Spherical silver powder ("Ag-5-8" manufactured by DOWA ELECTRONICS Co., Ltd., D ₅₀ = 3.0 μm, average aspect ratio is 1.1) · Conductive powder 4: spherical silver-coated copper powder (same "AO-DCL-1" manufactured by DOWA ELECTRONICS Co., Ltd., D ₅₀ = 2.2 μm, average aspect ratio is 1.1) · Conductive powder 5: spherical silver-coated copper powder (DOWA ELECTRONICS) "AO-DCL-2" manufactured by the company, D ₅₀ = 2.2 μm, average aspect ratio is 1.1) · Conductive powder 6: scaly silver powder (FA-D manufactured by DOWA ELECTRONICS Co., Ltd. -4 ", D ₅₀ = 15 μm, aspect ratio 16.7) Electrically conductive powder 7: scaly silver powder (with and electron (DOWA ELECTRONICS) Manufacturing Co., "FA-S-11", D ₅₀ = 2.8 μm, average aspect ratio 2.2) << (B) thermosetting resin >> (B1 Polyfunctional epoxy resin·Multifunctional epoxy resin 1: Novolac type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent: 193 g/eq, number average molecular weight Mc: 1100) · Multifunctional epoxy Resin 2: Dicyclopentadiene type epoxy resin (manufactured by Di Ai Sheng (DIC) Co., Ltd., epoxy equivalent: 258 g/eq, number average molecular weight Mc: 550) · Multifunctional epoxy resin 3: bisphenol type Epoxy resin (made by ADEKA Co., Ltd., epoxy equivalent of 170 g/eq, number average molecular weight Mc is 340) (B2) Flexible epoxy resin · Flexible epoxy resin 1: two Polyacid type epoxy resin (manufactured by Mitsubishi Chemical Corporation, with an epoxy equivalent of 390 g/eq, a number average molecular weight Mc of 560, a continuous number of secondary carbons of ≧5, and a particularly good flexibility (Brilliant)) Flexible Epoxy Resin 2: Bisphenol Modified Epoxy Resin (DIC) Co., Ltd. manufactured with an epoxy equivalent of 403 g/eq, a number average molecular weight Mc of 900, a continuous number of secondary carbons of ≧4, and good flexibility. · Flexible epoxy resin 3: Hydrogenated bisphenol type epoxy resin (manufactured by Mitsubishi Chemical Corporation, epoxy equivalent of 210 g/eq, number average molecular weight Mc of 400, continuous number of secondary carbon <3, with flexibility) (B3 Monofunctional epoxy resin phenyl glycidyl ether type epoxy resin (manufactured by ADEKA Co., Ltd., epoxy equivalent: 206 g/eq, number average molecular weight Mc: 210) (B4) epoxy Base acrylic resin/epoxy group-containing acrylic resin 1: Acrylic resin produced by radical polymerization of 50 parts of MMA and 50 parts of GMA (epoxy equivalent weight: 497 g/eq, number average molecular weight Mc is 2500) - Epoxy group-containing acrylic resin 2: Acrylic resin produced by radical polymerization of 50 parts of TBA and 50 parts of GMA (epoxy equivalent weight: 486 g/eq, number average molecular weight Mc: 2,400) <<(C)hardener>> Hardener 1: Imidazole hardener (flavor Manufactured by Ajinomoto Fine-techno Co., Ltd.) · Hardener 2: A tertiary amine hardener (Ajinomoto Fine-techno Co., Ltd.) <<(D) Additive>> Zirconium Chelate (Matsumoto Fine Chemical Co., Ltd.)

[Formation of Conductive Film] When the resin is in a solid state, it is suitably dissolved in an organic dispersion medium (here, diethylene glycol monobutyl ether acetate is used), and the prepared material is referred to as Table 3 and Table. The mass ratio shown in 4 was weighed and mixed to prepare a heat-curable conductive paste (Examples 1 to 20).

[Adhesive evaluation] The prepared paste was applied to the following three types of flexible substrates in a square shape of □ 2 cm × 2 cm by screen printing, and dried by heating at 130 ° C for 30 minutes. Then, adhesion evaluation (cross cutting method - 100 grid test) was carried out in accordance with JIS K5400 (1990). The results are shown in the columns of "Adhesiveness" in Tables 3 and 4. In addition, in Tables 3 and 4, "○" indicates that no peeling occurred, and "X" indicates that peeling occurred in one or more compartments. <<Flexible Substrate>> · ITO-PET film (manufactured by Oike Industrial Co., Ltd., a flexible substrate on which indium tin oxide is formed on polyethylene terephthalate) · PET film (Toray) Co., Ltd. manufactured, annealed) · Polycarbonate film (made by Asahi Glass Co., Ltd.)

[Measurement of Volume Resistivity] Using a resistivity meter (manufactured by Mitsubishi Chemical Analytech Co., Ltd., model: Lowres GP MCP-T610), the PET film was applied by a four-terminal method. The conductive film measures the volume resistivity. The results are shown in the column of "volume resistivity" in Tables 3 and 4.

[Evaluation of Laser Processing Property] The prepared paste screen was printed (overcoated) on the surface of an ITO-PET film by screen printing, and dried by heating at 130 ° C for 30 minutes. Thereby, the epoxy resin is hardened to form a conductive film on the ITO-PET film. The formed conductive film was irradiated with laser light under the following nine conditions, and attempts were made to form fine lines of L/S = 30 μm / 30 μm, respectively. <<Laser processing conditions (9 conditions)>> · Laser type: IR laser (basic wavelength: 1064 nm) · Laser output: 5 W, 7 W, 9 W · Scanning speed: 1000 mm/s, 2000 Mm/s, 3000 mm/s

The thin line formed by the laser processing was observed with a laser microscope to confirm whether or not an electrode having a desired line width was formed. When observing the microscope, three fields of view were confirmed at a magnification of 10 times. The results are shown in the column of "laser processing property" in Tables 3 and 4. In addition, in Tables 3 and 4, "○" indicates that the thin line can be formed under all conditions, "△" indicates that a thin line can be formed only under a part of the conditions, and "x" indicates that a thin line cannot be formed. Moreover, as an example, the observation image of Example 1 is shown in FIG.

[Table 3] Table 3

[Table 4] Table 4

As shown in Tables 3 and 4, in Examples 8, 19, and 20 which do not contain (B2) a flexible epoxy resin having a structure in which three or more secondary carbons are continuous, the adhesion to the flexible substrate is poor. . Further, in Examples 9 and 10 in which the (B1) polyfunctional epoxy resin was not contained, the volume resistivity was relatively high. With respect to these reference examples, the thermosetting resin contains (B1) a polyfunctional epoxy resin, (B2) a flexible epoxy resin having a structure in which three or more secondary carbons are continuous, and (B3) a monofunctional ring. In Examples 1 to 7 of the oxygen resin, the adhesion to the flexible substrate was improved. Further, the volume resistivity (heat curing condition: 130 ° C, 30 minutes) can be suppressed to be low, and is 100 μΩ·cm or less. Further, the laser processability is also good. Further, according to the comparison of Examples 11 to 18, since the conductive powder (A) does not contain scaly conductive particles, the laser processing suitability can be further improved.

[Measurement of Surface Roughness Ra] The surface roughness Ra of the conductive films of Examples 1 and 5 was measured in accordance with JIS B0601 (2001). As a result, in Example 1 in which the epoxy group-containing acrylic resin was not contained, Ra was 0.8 μm, and in Example 5 containing the epoxy group-containing acrylic resin, Ra was 0.7 μm. That is, by adding an epoxy group-containing acrylic resin, the flatness of the electrode surface can be improved. Although the reason is not clear, it is presumed that one of the epoxy group-containing acrylic resins floats on the surface of the coating film and functions as an acrylic leveling agent.

The present invention has been described in detail above, but the invention is not limited thereto, and various modifications may be made without departing from the spirit and scope of the invention.

no

1 is a laser microscope image of the electrode of Example 1. FIG. 2 is an explanatory diagram for explaining a method of evaluating "flexibility".

Claims (6)

A heat-curing conductive paste comprising (A) a conductive powder, (B) a thermosetting resin, and (C) a curing agent, wherein the (B) thermosetting resin comprises: (B1) having two or more An epoxy group-containing polyfunctional epoxy resin, (B2) a flexible epoxy resin having three or more secondary carbon continuous structures, and (B3) a monofunctional epoxy resin having one epoxy group. The heat-curable conductive paste according to the first aspect of the invention, wherein the (B) thermosetting resin further comprises (B4) an epoxy group-containing acrylic resin having one or more epoxy groups. The heat-curable conductive paste according to the first or second aspect of the invention, wherein the (B) thermosetting resin contains the following components in a mass ratio: 5% by mass to 25% by mass (B1) a polyfunctional epoxy resin having two or more epoxy groups; 1% by mass to 45% by mass of (B2) a flexible epoxy resin having a structure in which three or more secondary carbons are continuous; 50% by mass to 70% by mass (% by mass) of (B3) a monofunctional epoxy resin having one epoxy group; and 0% by mass to 20% by mass of (B4) an epoxy group-containing acrylic resin having one or more epoxy groups. The heat-curable conductive paste according to the first or second aspect of the invention, wherein the number average molecular weight of the (B1) to (B3) is 10,000 or less. The heat-curable conductive paste according to the first or second aspect of the invention, wherein the (A) conductive powder does not contain scaly conductive particles. The heat-curable conductive paste according to the first or second aspect of the invention, wherein the (A) conductive powder has an average particle diameter of 0.5 μm to 3 μm by laser diffraction/light scattering. .