JP5677911B2 - Conductive pattern, method for forming the same, printed wiring board, and method for manufacturing the same - Google Patents

Description

  The present invention uses an inkjet technique, uses a method for forming a conductive pattern that is excellent in manufacturing suitability, has high adhesion and conductivity, and does not change between drawn conductive patterns before drying. And a printed wiring board manufactured by the manufacturing method.

Metal materials such as gold, silver, copper, platinum, aluminum, palladium, nickel and the like have been used for a long time as materials for constituting the electric member. Among them, copper or silver material is a low-cost, versatile material with good electrical conductivity, so even today, external electrodes such as printed wiring board circuit forming members, various electrical contact members, capacitors, etc. It is widely used as a material for ensuring electrical continuity of members and the like.
On the other hand, in recent years, electronic devices such as flexible displays have become smaller and thinner.
There is a further demand for miniaturization and thinning of members applied to such devices. For example, conductive materials such as metals are patterned by printing, and wiring is directly formed on a flexible substrate (resin etc.). It is attracting attention. By doing so, continuous roll-to-roll production becomes possible, which realizes significant productivity improvement and cost reduction, and allows patterning on non-smooth surfaces and allows variable patterns to be printed arbitrarily. As a result, the degree of freedom in design is increased, and production from a very small amount is expected to be realized.

As means for achieving patterning by printing as described above, Patent Document 1 proposes a metal nanoparticle dispersion that can be formed at a low temperature and can be applied to various printing applications.
Further, Patent Document 2 proposes a surface-protected metal nanoparticle dispersion for the purpose of preventing the performance of a printed circuit board or the like formed from copper paste from being deteriorated due to aggregation of copper particles. Has been.
Further, Patent Document 3 discloses a method for forming a conductive pattern by preparing an ink-jet ink containing metal nanoparticles (mainly silver, copper), loading the ink-jet ink into a printer, and printing directly on a substrate surface. Has been proposed.

Japanese Patent No. 4414145 Japanese Patent No. 4242176 JP 2004-247667 A

  However, when a metal is patterned on a flexible base material (resin or the like) that is an organic material, it is difficult to provide sufficient adhesion, which is a large wall in practice. Furthermore, the ink is difficult to be absorbed by the base material, the drawing pattern changes until the ink solvent is dried, and jaggies (distorted such as the outline of the pattern becomes jagged) and bulges (liquid pools) occur. There are problems such as fusion and inability to draw lines.

  The present invention has been made in view of such circumstances, and is a method for forming a conductive pattern, which is excellent in manufacturing suitability, has high adhesion and conductivity, and does not change the drawn conductive pattern before drying. It aims at providing the manufacturing method of the printed wiring board which uses a method, and the printed wiring board manufactured by this manufacturing method.

  The object of the present invention has been achieved by the following means.

[1]
A method for forming a conductive pattern, comprising: a composition gradient film having a composition that continuously changes from metal to resin from a side farthest from the base in the thickness direction to a side closest to the base in the thickness direction. And
A method for forming a conductive pattern, wherein an ink composition containing a metal and an ink composition containing a polymer or an oligomer are ejected onto the substrate by an ink jet method to form the composition gradient film. .
[2]
As the at least two kinds of ink compositions, at least an ink composition containing a metal and an ink composition containing a polymer or an oligomer are used,
The inkjet method uses at least a first inkjet head and a second inkjet head,
Supplying a first ink containing an ink composition containing the metal to a first inkjet head;
Supplying a second ink containing an ink composition containing the polymer or oligomer to a second inkjet head;
A control step of determining a ratio between the amount of the first ink ejected from the first inkjet head and the amount of the second ink ejected from the second inkjet head;
Forming a layer by discharging the first ink or the second ink from at least one of the first inkjet head and the second inkjet head according to the determined ratio;
A lamination step of repeating the formation step to obtain the composition gradient film by laminating a plurality of the layers on the substrate;
With
In the control step, the ratio of the first ink is increased and the ratio of the second ink is decreased from a layer close to the base to a layer far from the base in the thickness direction of the plurality of layers. The method for forming a conductive pattern according to [1], wherein the ratio is determined.
[3]
The method for forming a conductive pattern according to [2], wherein the polymer or oligomer contains a urethane polymer or oligomer.
[4]
The method for forming a conductive pattern according to [3], wherein the urethane polymer or oligomer has a repeating unit represented by the following general formula (1).

(In the above general formula, R _{1 to} R ₃ each independently represents an alkylene group, an arylene group or a biarylene group, and R _{4 to} R ₆ each independently represent a hydrogen atom, an alkyl group, an aryl group or a heteroaryl. Represents a group.)

[5]
The method for forming a conductive pattern according to any one of [2] to [4], wherein the substrate is a synthetic resin substrate.
[6]
In the forming step, the conductive pattern is formed according to any one of [2] to [5], in which the amount of ink discharged from the first and second inkjet heads is 0.3 to 100 pL. Method.
[7]
The method for forming a conductive pattern according to any one of [2] to [6], wherein in the forming step, a droplet diameter of droplets discharged from the first and second inkjet heads is 1 to 300 μm. .
[8]
As the at least two kinds of ink compositions, at least an ink composition containing a metal and an ink composition containing a polymer or an oligomer are used,
The inkjet method uses a plurality of inkjet heads,
A mixed ink in which a first ink containing the metal-containing ink composition and a second ink containing the polymer or oligomer-containing ink composition are mixed, each of which is mixed at different ratios Supplying the mixed ink to each inkjet head of the plurality of inkjet heads;
A selection step of sequentially selecting one inkjet head from the plurality of inkjet heads, the selection step sequentially selecting from the inkjet head to which the mixed ink having a high ratio of the second ink is supplied;
Forming a layer by discharging mixed ink from the selected inkjet head; and
A lamination step of repeating the formation step to obtain the composition gradient film by laminating a plurality of the layers on the substrate;
The method for forming a conductive pattern according to [1], comprising:
[9]
The method for forming a conductive pattern according to [8], wherein the polymer or oligomer contains a urethane polymer or oligomer.
[10]
The method for forming a conductive pattern according to [9], wherein the urethane polymer or oligomer has a repeating unit represented by the following general formula (1).

(In the above general formula, R _{1 to} R ₃ each independently represents an alkylene group, an arylene group or a biarylene group, and R _{4 to} R ₆ each independently represent a hydrogen atom, an alkyl group, an aryl group or a heteroaryl. Represents a group.)

[11]
The method for forming a conductive pattern according to any one of [8] to [10], wherein the substrate is a synthetic resin substrate.
[12]
The formation of the conductive pattern according to any one of [8] to [11], wherein, in the formation step, the ink amount of droplets ejected from the first and second inkjet heads is 0.5 to 150 pL. Method.
[13]
The method for forming a conductive pattern according to any one of [8] to [12], wherein in the forming step, a droplet diameter of droplets discharged from the first and second inkjet heads is 2 to 450 μm. .
[14]
The method for forming a conductive pattern according to any one of [1] to [13], wherein the metal has an average particle diameter of 5 to 1000 nm.
[15]
The metal is a particle including at least one selected from the group consisting of gold, silver, copper, platinum, aluminum, palladium, and nickel, or an alloy including two or more metals selected from the group. The method for forming a conductive pattern according to any one of [1] to [14].
[16]
The method for forming a conductive pattern according to any one of [1] to [15], wherein the ink composition containing the polymer and the oligomer further contains a solvent having a boiling point of 60 ° C to 300 ° C.
[17]
The manufacturing method of a printed wiring board which uses the formation method of the conductive pattern as described in any one of [1]-[16].
[18]
A printed wiring board produced by the production method according to [17].

  ADVANTAGE OF THE INVENTION According to this invention, it is excellent in manufacturing aptitude, adhesiveness and electroconductivity are high, and the conductive pattern formation method by which the drawn conductive pattern does not change before drying, and a printed wiring board using this formation method And a printed wiring board manufactured by the manufacturing method can be provided.

Schematic diagram of conductive pattern with composition gradient film Schematic diagram of conductive pattern with composition gradient film Overall configuration diagram of composition gradient film forming device Schematic of drawing part of composition gradient film making device Diagram for explaining composition gradient film creation by drawing mixing method The figure for demonstrating other embodiment of the drawing mixing method Overall configuration diagram of a composition gradient film forming apparatus according to an embodiment of an ink mixing method Diagram for explaining composition gradient film creation by ink mixing method The figure for demonstrating the landing position of each ink in a drawing mixing method

The present invention has a composition gradient film pattern in which the composition continuously changes from metal to resin from the side farthest from the base in the thickness direction toward the side closest to the base in the thickness direction. A pattern forming method comprising:
A method for forming a conductive pattern, wherein an ink composition containing a metal and an ink composition containing a polymer or an oligomer are ejected onto the substrate by an ink jet method to form the composition gradient film. About.

[Composition gradient film]
FIG. 1 schematically shows a cross section of a composition gradient film having a conductive pattern formed by the method according to the present invention.
The conductive pattern 1 according to the present invention has a pattern composed of a composition gradient film 3 on a substrate 2. The composition gradient film 3 is continuously formed from the metal to the resin in the thickness direction from the side A furthest to the base 2 toward the side B closest to the base 2 (that is, in the direction of the arrow in FIG. 1). The composition has changed.
Here, the “thickness direction” means the “film thickness direction” of the composition gradient film 3. “The composition changes continuously from metal to resin in the thickness direction” means that the composition gradient film is divided into regions of a certain thickness (for example, 0.1 to 5 μm) in the thickness direction, and the resin and metal in each region The difference in the resin content between adjacent regions is 50% or less, preferably 30% or less when the ratio of the resin mass to the total mass of the resin (hereinafter referred to as “resin content”) is observed. Means. If the difference in resin content between adjacent regions is greater than 50%, the change in the resin content becomes stepwise, and high adhesion and conductivity cannot be obtained. The difference in resin content between two adjacent regions may be 0%.
From the viewpoint of obtaining high conductivity, the content of the resin on the side A farthest from the base material of the composition gradient film 3 (for example, the content of the resin in the region from A to a thickness of 0.1 to 5 μm) is 0 to 50. %, More preferably 0 to 30%, and still more preferably 0% (0 to 0.2%). In addition, the content of the resin on the side B closest to the base material (for example, the content of the resin in the region from B to a thickness of 0.1 to 5 μm) is 50 to 100% from the viewpoint of obtaining high adhesion. It is preferably 70 to 100%, more preferably 100% (99 to 100%).
The resin content in each region can be obtained by, for example, an XPS depth profile.

The composition of the composition gradient film 3 is not particularly limited as long as there is a continuous change in the resin content as described above, but a structure in which a plurality of layers having different resin contents as shown in FIG. Take as an example.
The conductive film 1a shown in FIG. 2 has a composition gradient film 3 on a base material 2, and the composition gradient film 3 includes a plurality of layers 3-1, 3-2, 3-3 having different resin contents. 3-4, 3-5. The layers 3-1, 3-2, 3-3, 3-4, 3-5 are changed from the A-side layer 3-5 farthest to the base material 2 to the B-side layer 3-1 nearest to the base material 2. Towards (that is, in the direction of the arrow in FIG. 2), the resin content continuously increases within a range of 0% to 100%.
In obtaining good adhesion and conductivity, among the layers 3-1, 3-2, 3-3, 3-4, 3-5, the difference in the resin content of two adjacent layers is 50% or less. Preferably, it is 30% or less. Further, the resin content of the A-side layer 3-5 farthest from the substrate 2 is preferably 0% to 20%, more preferably 0% to 15%. The resin content of the layer 3-1 on the B side closest to the substrate 2 is preferably 80% to 100%, and more preferably 85% to 100%.
In FIG. 2, the composition gradient film 3 is formed by laminating five layers 3-1, 3-2, 3-3, 3-4, and 3-5, but the number of layers to be laminated is particularly limited. Not. Preferably it is 3-10 layers, More preferably, it is 3-7 layers. The thickness of each layer is preferably 0.1 μm to 5 μm, and more preferably 0.3 μm to 3 μm. It is preferable that the thickness of each layer is substantially equal (thickness error is in a range of ± 0.5 μm).
In addition, when the interface between layers is not clear, a region separated by a thickness of 0.1 μm to 5 μm in the thickness direction of the composition gradient film 3 may be regarded as a “layer”.
The resin content in each region can be obtained by, for example, an XPS depth profile.

(Film thickness)
The thickness of the composition gradient film in the present invention is preferably 1 μm or more, more preferably 1 μm to 20 μm, and still more preferably 3 μm to 10 μm. Within this range, a conductive pattern with good conductivity can be obtained. Moreover, this range is a preferable range also from a viewpoint of not impairing performance and commercial value of a device using the conductive pattern.

In the present invention, at least two types of ink compositions, that is, an ink composition containing a metal and an ink composition containing a polymer or oligomer, are ejected onto a substrate by an ink jet method to form a composition gradient film.
Hereinafter, the ink used in the present invention will be described.

(Ink composition)
The ink composition used in the present invention is roughly classified into an ink composition containing a metal and an ink composition containing a polymer or an oligomer. The ink composition may contain a solvent, a binder component, and other additives in addition to the metal, polymer, or oligomer.
The ink composition may be used alone as an ink, or two or more ink compositions may be mixed and used as an ink.

(ink)
As the ink used in the present invention, an ink containing an ink composition containing a metal and an ink containing an ink composition containing a polymer or oligomer may be used as two or more independent inks. The ink containing the metal-containing ink composition and the ink containing the polymer or oligomer-containing ink composition may be used as a mixed ink.
The ink may contain a solvent, a binder component, and other additives in addition to the metal, polymer, or oligomer.

(metal)
The metal contained in the ink composition used in the present invention is not particularly limited as long as it has conductivity. For example, gold, silver, copper, platinum, aluminum, palladium, nickel, ruthenium, Rhodium, osmium, iridium, and mixtures or alloys thereof can be used. Gold, silver, copper, platinum, aluminum, palladium, nickel and mixtures or alloys thereof are preferably used. From the viewpoint of low price, high versatility and good electrical conductivity, it is more preferable to use copper or silver, and it is most preferable to use copper.
The metal content in the ink is not particularly limited as long as the ink can be used in the ink jet method, but is preferably 5 to 70% by mass from the viewpoint of ink jet suitability. More preferably, it is 50 mass%, and it is especially preferable that it is 20-40 mass%.
From the viewpoint of inkjet compatibility and stability, the metal is preferably contained in the ink as particles of the metal or an alloy containing the metal. For example, gold, silver, copper, platinum, aluminum, palladium, nickel, and these The particle | grains which consist of a mixture or an alloy are mentioned. The average particle diameter of the particles is not particularly limited as long as the ink containing the particles can be used in the inkjet method, but is 5 nm to 1000 nm from the viewpoint of the suitability for producing a conductive pattern and the suitability for inkjet. It is preferably 5 nm to 500 nm, more preferably 5 nm to 200 nm.

(Polymer or oligomer)
The polymer or oligomer contained in the ink composition used in the present invention is not particularly limited as long as the ink can be used in the ink jet method. For example, urethane, alkyl methacrylate, alkyl acrylate, etc. Polymers or oligomers or mixtures thereof can be used.

  As the polymer or oligomer, a urethane polymer (hereinafter also referred to as “urethane polymer” or “polyurethane”) or a urethane oligomer (hereinafter also referred to as “urethane oligomer”) is preferably used, and a urethane oligomer is used. It is more preferable.

  The oligomer represented by the urethane oligomer in the present invention is not limited, but refers to, for example, a polymer having a molecular weight of 1,000 to 5,000. The polymer represented by the urethane polymer refers to, for example, a polymer having a molecular weight of 5,000 or more, and preferably refers to a compound having a molecular weight of 5,000 to 10,000.

  The reason why it is preferable to use a urethane polymer or oligomer is that the urethane polymer or oligomer has good adhesion to the base material, and has a cohesive force in the gradient film due to coordination interaction between the urethane bond and the metal particles. By improving, it is guessed that the firm film | membrane is formed.

  The content of the urethane polymer or oligomer in the ink is preferably 10% by mass or more based on the total mass of the ink. The more preferable content of the urethane polymer or oligomer in the ink is 30% by mass or more and 80% by mass or less, more preferably 30% by mass or more and 70% by mass or less, and particularly preferably 40% by mass. % Or more and 60% by mass or less.

  The urethane polymer or oligomer of the present invention is more preferably a polymer or oligomer having a repeating unit represented by the following general formula (1).

In the repeating unit represented by the above general formula, R _{1 to} R ₃ each independently represents an alkylene group, an arylene group, or a biarylene group, and R _{4 to} R ₆ each independently represent a hydrogen atom, an alkyl group, An aryl group or a heteroaryl group is represented.

As said alkylene group, a C1-C10 alkylene group is preferable.
As said arylene group, a phenylene group or a naphthylene group is preferable.
The biarylene group is preferably a biphenylene group or a binaphthylene group.
As said alkyl group, a C1-C10 alkyl group is preferable.
The aryl group is preferably a phenyl group or a naphthyl group.
As the heteroaryl group, a pyridyl group is preferable.

  As the urethane polymer or oligomer represented by the general formula (1), UN-1225 (manufactured by Negami Kogyo), CN962, CN965 (manufactured by Sartomer) and the like can be preferably used.

(solvent)
The ink composition according to the present invention is prepared by mixing a metal, polymer, or oligomer and a solvent.
As a solvent, it can select and use suitably from water and an organic solvent, It is preferable that it is a liquid whose boiling point is 50 degreeC or more, and it is more preferable that it is an organic solvent whose boiling point is the range of 60 to 300 degreeC.
It is preferable to use the solvent in such a ratio that the solid content concentration in the ink composition is 1 to 70% by mass. Furthermore, 5-60 mass% is preferable. Within this range, the resulting ink has a viscosity range with good workability.

Examples of the solvent include alcohols, ketones, esters, nitriles, amides, ethers, ether esters, hydrocarbons, halogenated hydrocarbons and the like. Specifically, alcohol (for example, methanol, ethanol, propanol, butanol, benzyl alcohol, ethylene glycol, propylene glycol, ethylene glycol monoacetate, cresol, etc.), ketone (for example, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, Methylcyclohexanone), esters (eg, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl formate, propyl formate, butyl formate, ethyl lactate, etc.), aliphatic hydrocarbons (eg, hexane, cyclohexane), halogenated hydrocarbons ( For example, methylene chloride, methyl chloroform, etc.), aromatic hydrocarbons (eg, toluene, xylene, etc.), amides (eg, dimethylformamide, dimethylacetamide, n-methylpyrrole) Don, etc.), ethers (eg, dioxane, tetrahydrofuran, ethylene glycol dimethyl ether, propylene glycol dimethyl ether, etc.), ether alcohols (eg, 1-methoxy-2-propanol, ethyl cellosolve, methyl carbinol, etc.), fluoroalcohols (eg, JP, 8-143709, A paragraph number [0020], 11-60807 gazette Paragraph number [0037], etc.).
These solvents can be used alone or in admixture of two or more. Preferred solvents include toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, isopropanol, and butanol.

(Additive)
The ink composition according to the present invention includes other additives such as a complexing agent, a surface tension adjusting agent, an antifouling agent, a water resistance imparting agent, and a chemical resistance imparting agent in addition to the metal, polymer or oligomer. be able to.
It is preferable to use a complexing agent and a dispersant for the ink containing a metal. Examples of the complexing agent include carboxylic acids such as acetic acid and citric acid, diketones such as acetylacetone, and amines such as triethanolamine. Examples of the dispersant include amines such as stearylamine and laurylamine.

(Ink properties)
The viscosity of the ink according to the present invention is preferably 5 to 40 cP, more preferably 5 to 30 cP, and even more preferably 8 to 20 cP from the viewpoints of uniformity during film formation, stability during inkjet ejection, and storage stability of the ink. preferable.
The surface tension of the ink is preferably 10 to 40 mN / m, more preferably 15 to 35 mN / m, from the viewpoints of uniformity during film formation, stability during inkjet ejection, and storage stability of the ink. 30 mN / m is more preferable.

(Base material)
Next, the base material constituting the conductive pattern formed by the method of the present invention will be described.
The substrate in the present invention is not particularly limited, and any organic, inorganic or metal substrate can be used.
On the other hand, when the method of the present invention is used in a method for producing a printed wiring board, it is preferable to use a synthetic resin base material that is lightweight, flexible, and inexpensive. Specifically, it is preferable to use a base material such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl acetate, acrylic resin, polyamide, polyacetal, polycarbonate, modified polyphenylene ether, polybutylene phthalate, polyethylene terephthalate, etc. It is particularly preferable to use a base material made of polyethylene terephthalate because of its high versatility at a low price.
Although the thickness of a base material can use about 25 micrometers-about 1000 micrometers normally, Preferably it is 25 micrometers-250 micrometers, and it is more preferable that it is 30 micrometers-90 micrometers.
Any width of the substrate can be used, but from the viewpoint of handling, yield, and productivity, a width of 1000 mm or less is usually used, preferably 800 mm or less, and more preferably 600 mm or less. preferable. The transparent support can be handled in the form of a roll, and is usually within 200 m, preferably within 100 m.
The surface of the substrate is preferably smooth, and the average roughness Ra is preferably 1 μm or less, more preferably 0.8 μm or less, and even more preferably 0.7 μm or less.

(Creation of composition gradient film by inkjet method)
Hereinafter, preparation of a composition gradient film by the inkjet method of the present invention will be described.
In the present invention, an ink containing an ink composition containing a metal and an ink containing an ink composition containing a polymer or an oligomer are ejected onto a substrate by an inkjet method as two or more independent inks. Alternatively, a mixed ink obtained by mixing an ink containing an ink composition containing a metal and an ink containing an ink composition containing a polymer or an oligomer is ejected onto a substrate by an inkjet method.

As an ink jet method, there is no limitation on an ink jet recording method as long as an image is recorded by an ink jet printer, and a known method, for example, a charge control method for discharging an ink composition using electrostatic attraction, a piezoelectric method, or the like. Drop-on-demand method (pressure pulse method) that uses the vibration pressure of the element, acoustic ink jet method that discharges the ink composition using radiation pressure by irradiating the ink composition by converting the electrical signal into an acoustic beam, and ink composition It is used in a thermal ink jet (Bubble Jet (registered trademark)) system or the like that uses a pressure generated by heating an object to form bubbles.
The ink droplets are mainly controlled by the print head. For example, in the case of the thermal ink jet method, it is possible to control the droplet ejection amount by the structure of the print head. That is, droplets can be ejected in a desired size by changing the sizes of the ink chamber, the heating unit, and the nozzle. Even in the case of the thermal ink jet method, it is possible to realize droplet ejection of a plurality of sizes by providing a plurality of print heads having different heating parts and nozzle sizes. In the case of a drop-on-demand method using a piezo element, it is possible to change the droplet ejection amount due to the structure of the print head, as in the case of the thermal ink jet method, but also by controlling the waveform of the drive signal that drives the piezo element. A plurality of sizes of droplets can be ejected with a print head having the same structure.

  As an ink ejection method (drawing method) on a base material, an ink containing an ink composition containing a metal and an ink containing an ink composition containing a polymer or an oligomer are supplied to separate ink jet heads. There is a drawing and mixing method in which the ratio of the discharge amount is adjusted and discharged on the substrate at the same time. As another method, a plurality of mixed inks in which an ink containing an ink composition containing an ink in advance and an ink containing an ink composition containing a polymer or an oligomer are mixed and the ratios of the two are different may be used. The prepared ink is supplied to an inkjet head, and the heads are selected in order, and mixed inks in which the ratio of the ink containing the metal-containing ink composition and the ink containing the polymer or oligomer-containing ink is different. There is a mixed ink method in which the ink is sequentially ejected and drawn.

(Preparation of ink)
Preparation of an ink containing an ink composition containing a metal and an ink composition containing a polymer or an oligomer, which is used in the drawing mixing method described later, will be described.
The ink can be prepared by mixing each material. When mixing each material, you may stir with a stirrer. Although stirring time is not specifically limited, Usually, it is 30 minutes-60 minutes, and 30 minutes-40 minutes are preferable. Moreover, the temperature at the time of mixing is 10 to 40 degreeC normally, and 20 to 35 degreeC is preferable.
In the ink mixing method described later, the inks prepared as described above can be mixed and used.

~ Drawing mixing method ~
As a method of the present invention, on the substrate, it has a composition gradient film whose composition continuously changes from metal to resin from the side farthest to the substrate in the thickness direction toward the side closest to the substrate. A method for forming a conductive pattern, comprising:
A method for forming a conductive pattern, wherein an ink composition containing a metal and an ink composition containing a polymer or an oligomer are ejected onto the substrate by an ink jet method to form the composition gradient film. In
As the at least two kinds of ink compositions, at least an ink composition containing a metal and an ink composition containing a polymer or an oligomer are used,
The inkjet method uses at least a first inkjet head and a second inkjet head,
Supplying a first ink containing an ink composition containing the metal to a first inkjet head;
Supplying a second ink containing an ink composition containing the polymer or oligomer to a second inkjet head;
A control step of determining a ratio between the amount of the first ink ejected from the first inkjet head and the amount of the second ink ejected from the second inkjet head;
Forming a layer by discharging the first ink or the second ink from at least one of the first inkjet head and the second inkjet head according to the determined ratio;
A lamination step of repeating the formation step to obtain the composition gradient film by laminating a plurality of the layers on the substrate;
With
In the control step, the ratio of the first ink is increased and the ratio of the second ink is decreased from a layer close to the base to a layer far from the base in the thickness direction of the plurality of layers. A method of determining the ratio is preferred.

  According to the drawing method, the ratio between the discharge amount of the first ink discharged from the first inkjet head and the discharge amount of the second ink discharged from the second inkjet head is determined and determined. By repeating the step of ejecting ink according to the ratio to form one layer, a plurality of layers are stacked on the base material, and the ratio of the first ink ejection amount increases as the plurality of layers move upward. The composition gradient film can be manufactured by using an ink jet technique by forming a layer having a small ratio of the ejection amount of the second ink.

-Embodiment by drawing mixed method-
FIG. 3 is an overall configuration diagram of the composition gradient film forming apparatus 100 according to the drawing mixing method, and FIG. 4 is a schematic diagram of the drawing unit 10 of the composition gradient film forming apparatus 100. As shown in these drawings, the composition gradient film forming apparatus 100 includes a drawing unit 10, and the drawing unit 10 uses a flatbed type ink jet drawing apparatus. Specifically, the drawing unit 10 includes a stage 30 on which a base material that is a base material is placed, a suction chamber 40 for sucking and holding the base material placed on the stage 30, and each ink toward the base material 20. Ink jet head 50A (hereinafter referred to as ink jet head 1) and ink jet head 50B (hereinafter referred to as ink jet head 2).

  The stage 30 has a width that is wider than the diameter of the substrate 20, and is configured to be freely movable in the horizontal direction by a moving mechanism (not shown). As the moving mechanism, for example, a rack and pinion mechanism, a ball screw mechanism, or the like can be used. The stage control unit 43 (not shown in FIG. 4) can move the stage 30 to a desired position by controlling the moving mechanism.

  A number of suction holes 31 are formed on the substrate holding surface of the stage 30. An adsorption chamber 40 is provided on the lower surface of the stage 30, and the adsorption chamber 40 is vacuum-sucked by a pump 41 (not shown in FIG. 4), whereby the substrate 20 on the stage 30 is adsorbed and held. Further, the stage 30 includes a heater 42 (not shown in FIG. 4), and the base material 20 that is attracted and held on the stage 30 by the heater 42 can be heated.

  The inkjet heads 1 and 2 eject ink supplied from an ink tank 60A (hereinafter referred to as ink tank 1) and an ink tank 60B (hereinafter referred to as ink tank 2) to a desired position of the transparent support 20. Here, a head having a piezoelectric actuator is used. The inkjet heads 1 and 2 are arranged and fixed as close as possible to each other by fixing means (not shown).

  The inks supplied to the inkjet heads 1 and 2 from the ink tanks 1 and 2 are referred to as ink 1 and ink 2, respectively. In the present invention, an ink containing an ink composition containing a metal (hereinafter also referred to as “metal ink”) is referred to as ink 1, and an ink containing an ink composition containing a polymer or oligomer (hereinafter referred to as “resin ink”). Also referred to as ink 2).

[Production of composition gradient film by drawing mixing method]
The production of a composition gradient film using the conductive pattern production apparatus 100 configured as described above will be described with reference to FIG.

  First, the base material 20 is placed on the stage 30 of the drawing unit 10 placed in a nitrogen atmosphere. The base material 20 is placed so that the back surface is in contact with the stage 30. Then, adsorption and heating of the substrate 20 to the stage 30 are performed by the adsorption chamber 40. Here, it is preferable to heat the base material 20 to 70 ° C.

  Next, one layer or several layers of ink (ink 2) supplied from the inkjet head 2 are laminated on the adsorbed / heated substrate 20 to form 24-1. 5A, the ink 2 is ejected by the inkjet head 2 while moving the stage 30 by the moving mechanism (moving leftward in the figure). Here, no ink is ejected from the inkjet head 1.

It is preferable to dry (semi-dry) the layer 24-1 of the ink 2 formed in this way to such an extent that the solvent component in the ink 2 is not completely evaporated. Specifically, drying is performed with less energy than that normally applied when drying (total drying).
In the present invention, as described above, it is preferable to have a step of semi-drying the layer ejected in the forming step. For semi-drying, for example, after the ink ejection is finished, the ambient temperature is set to 40 to 120 ° C. It is preferable to hold for a certain time, and it is preferable to hold for a certain time at an environmental temperature of 50 to 100 ° C. The holding time is preferably 10 to 120 seconds, and more preferably 20 to 90 seconds.

  Next, the mixed layer 24-2 of the ink 1 and the ink 2 is formed on the layer 24-1 of the ink 2 in a semi-dry state. As shown in FIG. 5B, the mixed layer 24-2 is formed by ejecting the ink 1 by the inkjet head 1 while moving the stage 30, and simultaneously ejecting the ink 2 by the inkjet head 2. At this time, the discharge amount of ink 1 and the discharge amount of ink 2 are adjusted to a desired ratio. Here, the discharge amount of each nozzle of the inkjet heads 1 and 2 is adjusted and discharged so that the discharge amount of ink 2 is 75% and the discharge amount of ink 1 is 25%. The “ejection amount” of ink in the present specification means the total amount of ink ejected to form each layer. On the other hand, the “droplet amount” of an ink droplet ejected from an inkjet head, which will be described later, is the amount of one ink droplet.

  The ratio of the ink discharge amount from the inkjet heads 1 and 2 may be adjusted by the dot pitch density of drawing. For example, by controlling the number of nozzles for ejecting ink so that the inkjet heads 1 and 2 are 75:25 while keeping the ejection amount of each nozzle of the inkjet heads 1 and 2 constant, the ratio of the ejection amount It is also possible to make adjustments.

After ink ejection, as shown in FIG. 5C, the mixed layer 24-2 is laminated by diffusing and mixing the ink 1 and the ink 2 ejected in the respective ejection amounts. Since the layer 24-1 of the ink 1 is in a semi-dry state, the ink solvent of the mixed layer 24-2 formed thereon is received by the layer 24-1 of the ink 1 and spreads extremely wet. There is no. That is, the heating temperature by the heater 42 needs to be adjusted according to the easiness of ink evaporation. Depending on the type of the solvent, drawing may be performed at a temperature lower than 70 ° C., for example, the substrate temperature is about 50 ° C.
That is, it is preferable that the forming step includes a step of diffusing and mixing the discharged first ink and the second ink. Examples of the diffusion mixing method include a method using convection by heating and a method using ultrasonic waves.

  Further, the two inkjet heads are arranged as close as possible to prevent only one of the inks from being dried and insufficient mixing in the layers of both inks. When two inks are simultaneously ejected, the droplets of ink 1 ejected from the inkjet head 1 and the droplets of ink 2 ejected from the inkjet head 2 are collided in the air during flight and mixed. You may make it land from.

  Furthermore, although details will be described later, it is preferable that each of the two inkjet heads has a width larger than the width of the target substrate (the shorter one) and forms one layer in one scan. Thereby, the ink 1 and the ink 2 are easily mixed.

  Further, in order to promote mixing of ink, the stage 30 may be controlled to ultrasonically treat the substrate 20. At this time, it is preferable to sweep the frequency of the ultrasonic wave or change the position of the base material 20 so that the ultrasonic node is less likely to occur.

  When the mixed layer 24-2 formed in this manner is in a semi-dry state like the layer 24-1 of the ink 2, the mixed layer 24-2 has a ratio of the amount of 25:75, and the polymer contained in the ink 2 or The oligomer and the metal contained in the ink 1 are mixed and stacked.

  Next, the mixed layer 24-3 is formed on the mixed layer 24-2. Also in the formation of the mixed layer 24-3, as shown in FIG. 5D, ink is simultaneously ejected by the inkjet head 1 and the inkjet head 2 while moving the stage 30. Here, both ink 1 and ink 2 are ejected at a ratio of the ejection amount of 50%.

  Since the mixed layer 24-2 is also in a semi-dry state, the ink solvent of the mixed layer 24-3 formed thereon is received by the mixed layer 24-2. After ink ejection, as shown in FIG. 5E, the mixed layer 24-3 is laminated by diffusing and mixing the two inks.

  Further, the mixed layer 24-3 is also semi-dried in the same manner as the ink 24-layer 24-1. In the mixed layer 24-3, the ratio of the amount is 50:50, and the polymer or oligomer contained in the ink 2 and the metal contained in the ink 1 are mixed and stacked.

  In this way, each mixed layer is formed while changing the ratio of the ejection amount of ink 1 and ink 2 stepwise (so as to be inclined), and finally, a layer in which the ejection amount of ink 1 is 100% is formed.

  After the formation of all layers, the diffusion of each layer proceeds, and the layers formed in stages become continuous. As a result, as shown in FIG. 1, the composition gradient film 3 is formed in which the composition component ratio is 100% from the ink 2 to 100% from the B side to the A side in the film thickness direction.

  In this way, by forming the upper layer with the lower layer in a semi-dry state, diffusion is advanced to some extent in the upper and lower layers. At this time, it is preferable that the interface between the upper and lower layers is eliminated so that the upper and lower layers are not mixed and the upper and lower layers are not distinguished from each other.

  Note that after the formation of each layer is completed, a dummy pattern may be stacked in a region where the composition gradient film does not function, and the height of the dummy pattern may be measured by an optical displacement sensor using a laser or the like. In a state where the drying is not progressing and the solvent remains, the film thickness becomes high, so that the dry state can be detected by the height of the dummy pattern.

  As described above, a composition gradient film can be formed using an inkjet head. Further, according to the drawing mixing method of this embodiment, there is an advantage that the number of ink types and the number of ink jet heads can be reduced regardless of the number of layers to be formed. The mixed layers of the ink 1 and the ink 2 may be stacked in any number of layers as long as the mixing ratio of the respective inks is inclined stepwise.

In each layer forming step, the amount of ink droplets ejected from the first inkjet head and the second inkjet head is set to 0.3 to 100 pL from the viewpoint of film thickness control and fine line formability. Preferably, 0.5-80 pL is more preferable, and 0.7-70 pL is still more preferable.
In the formation process of each layer, the droplet diameter of the ink droplets ejected from the first inkjet head and the second inkjet head is preferably 1 to 300 μm, and preferably 5 to 250 μm from the viewpoints of film thickness control and fine line formability. Is more preferable, and 10-200 micrometers is still more preferable.
Further, in the step of forming each layer, for the ink having the smaller ejection amount ratio between the first ink and the second ink, at least one of the appropriate amount of the ink droplets ejected from the inkjet head and the droplet diameter is the ratio. Is preferably smaller than that of a large ink. For example, it is preferable that ink droplets of ink with a small ratio are 0.3 to 60 pL, and ink droplets of ink with a large ratio are 1 to 100 pL. Thereby, the time for diffusive mixing can be shortened, and the uniformity of mixing can be improved.
The “droplet diameter” of the ink droplet means the length of the droplet diameter, and can be measured from a flying state photograph at the time of ink jet discharge.

In this embodiment, the composition gradient film 3 in which the ink 2 is 100% to the ink 1 is 100% from the B side to the A side, but the ink 2 or the ink 1 is 100% on the B side or the A side. It is not always necessary to form a film, and the ratio of the ink 2 or the ink 1 on the B side or the A side can be arbitrarily changed as long as the composition gradient film 3 is obtained.
The ratio of the ink 2 or the ink 1 on the B side or the A side can be appropriately adjusted depending on the properties such as adhesion and conductivity of the composition gradient film to be obtained.

  In the present embodiment, the ink jet head 1 and the ink jet head 2 eject ink simultaneously to form each layer, but they may be ejected in order.

  For example, when forming the mixed layer 24-2, as shown in FIG. 6A, the ink 2 is first ejected onto the entire surface of the ink 2-layer 24-1 by the inkjet head 2. Next, as shown in FIG. 6B, the ink 1 is ejected over the entire surface by the inkjet head 1. Thereafter, as shown in FIG. 6C, the mixed layer 24-2 can be similarly formed by diffusing and mixing the respective inks.

  In this way, when each ink is ejected in order to form one layer, there is a difference between the ejection amounts of the two inks, that is, the ratio of the ejection amounts of the two inks is not 50% each. May be configured to eject the ink with the larger ejection amount first. In particular, when the ink discharged first is severely dried, the smaller the amount, the faster the drying. Therefore, it is preferable to discharge the larger amount of ink first. Thereby, mixing of two types of ink can be advanced smoothly.

  Further, in this case, the ink having a smaller ejection amount to be ejected later may be ejected by increasing the dot pitch density with small droplets (small liquid amount or small droplet diameter). Thereby, the time for diffusive mixing can be shortened.

  Further, the ink ejected later may be overlapped and landed at the position where the ink ejected earlier is landed. In particular, when the dots are separated from each other by performing intermittent operation, if the ink is landed before being dried at the same position, it becomes easy to mix the respective inks.

  For example, when forming the mixed layer 24-2, it is assumed that the ink 2 is ejected by intermittent printing by the inkjet head 2 in the first scanning. FIG. 9A shows ink 2 (24-2-B-1) landed on the ink 1 layer 24-1.

  Next, the ink 1 is ejected by the ink jet head 1 by intermittent scanning in the second scanning. At this time, as shown in FIG. 9B, the ink-jet head 1 uses the ejected ink 1 (24-2-A-1) to be landed in the first scan, the ink 2 (24-2-2). B-1) is discharged so as to land on the same position.

  Further, the ink 2 is intermittently hit by the inkjet head 2 in the third scanning. FIG. 9C shows ink 2 (24-2-B-2) landed between inks 2 (24-2-B-1).

  Thereafter, in the fourth scanning, the ink 1 is ejected by the inkjet head 1 so as to be landed on the same landing position as the ink 2 (24-2-B-2). As shown in FIG. 9D, the ejected ink 1 (24-2-A-2) is in the same position as the ink 2 (24-2-B-2) landed in the second scan. Discharge to land repeatedly.

Thereafter, in the same manner, ink is ejected over the entire surface of the layer 1 of the ink 1 and then is diffused and mixed.
By discharging in this way, it is possible to shorten the time of diffusion mixing when forming the mixed layer 24-2.

  Further, when one of the inks is quickly dried, the ink may be ejected later.

  Further, in the present embodiment, each mixed layer is formed using two pure inks, ink 1 and ink 2, but an ink obtained by mixing these may be used in combination. For example, it is conceivable to form a mixed layer by simultaneously using three types of ink, that is, two pure inks and a mixed ink having a mixing ratio of ink 1 and ink 2 of 50:50. Although the number of inkjet heads increases by the amount of mixed ink, since two pure inks are sufficiently mixed in advance with the mixed ink, the time required for diffusion mixing after ink ejection can be shortened.

~ Ink mixing method ~
As a method of the present invention, on the substrate, it has a composition gradient film whose composition continuously changes from metal to resin from the side farthest to the substrate in the thickness direction toward the side closest to the substrate. A method for forming a conductive pattern, comprising:
A method for forming a conductive pattern, wherein an ink composition containing a metal and an ink composition containing a polymer or an oligomer are ejected onto the substrate by an ink jet method to form the composition gradient film. In
As the at least two kinds of ink compositions, at least an ink composition containing a metal and an ink composition containing a polymer or an oligomer are used,
The inkjet method uses a plurality of inkjet heads,
A mixed ink in which a first ink containing the metal-containing ink composition and a second ink containing the polymer or oligomer-containing ink composition are mixed, each of which is mixed at different ratios Supplying the mixed ink to each inkjet head of the plurality of inkjet heads;
A selection step of sequentially selecting one inkjet head from the plurality of inkjet heads, the selection step sequentially selecting from the inkjet head to which the mixed ink having a high ratio of the second ink is supplied;
Forming a layer by discharging mixed ink from the selected inkjet head; and
A method including a lamination step of repeating the formation step to obtain the composition gradient film by laminating a plurality of layers on the base material is preferable.

  According to the above method, the first ink and the second ink are mixed inks, and a plurality of mixed inks mixed at different ratios are supplied to the respective inkjet heads, and the first ink is supplied. Since each layer is formed by sequentially ejecting mixed ink from an inkjet head to which a mixed ink having a low ratio is supplied, and a plurality of layers are laminated on the substrate, a composition gradient film is formed using an inkjet technique. Can be manufactured.

-Embodiment by ink mixing method-

  FIG. 7 is an overall configuration diagram of a composition gradient film forming apparatus 101 according to the second embodiment. As shown in the figure, the composition gradient film forming apparatus 101 according to the present embodiment includes a drawing unit 11, and the drawing unit 11 includes ink tanks 60-1 to 60-5 that store five types of ink, and each ink. Inkjet heads 50-1 to 50-5 to which ink is supplied from a tank are provided. Each inkjet head 50-1 to 50-5 discharges the ink supplied from each ink tank 60-1 to 60-5 to the substrate 20.

  The ink supplied from the ink tanks 60-1 to 60-5 to the inkjet heads 50-1 to 50-5 has a mixing ratio of ink 1 and ink 2 of 0: 100, 25:75, and 50:50, respectively. 75:25 and 100: 0. That is, the pure ink of ink 2 from the ink tank 60-1, the pure ink of ink 1 from the ink tank 60-5, and the ink 1 and ink 2 from 60-2 to 60-4 at a predetermined ratio. Mixed mixed ink is supplied.

[Production of composition gradient film by ink mixing method]
Similarly to the embodiment using the drawing mixing method, the base material 20 is placed on the stage 30 and suction and heating are performed.

  Next, one layer or several layers of the ink 2 are laminated on the adsorbed / superheated substrate to form the ink 28 layer 28-1. As shown in FIG. 8A, the ink 2 is stacked while the stage 30 is moved by the moving mechanism (moved leftward in the figure), and the ink tank 60- is applied to the substrate by the inkjet head 50-1. 1 is discharged (ink having a mixing ratio of ink 1 and ink 2 of 0: 100). At this time, ink is not discharged from the other inkjet heads 50-2 to 50-5.

Therefore, the layer 28-1 of the ink 2 formed in this way is the same layer as the layer 24-1 of the ink 2 shown in FIG. Here, when the solvent in the ink 2 is dried (semi-dried) to the extent that the solvent evaporates, the metal contained in the ink 1 is stacked.
Also in the ink mixing method, it is preferable to have a step of semi-drying the layer ejected in the forming step. For semi-drying, for example, after the ink ejection is completed, the ambient temperature is maintained at 40 to 120 ° C. for a certain time It is preferable to hold it at an environmental temperature of 50 to 100 ° C. for a certain time. The holding time is preferably 10 to 120 seconds, and more preferably 20 to 90 seconds.

  Next, mixed ink (mixed ink in which the mixing ratio of ink 1 and ink 2 is 25:75) supplied from the ink tank 60-2 by the inkjet head 50-2 is applied on the layer 2-1 of ink 2. The mixed layer 28-2 is formed by discharging.

  As shown in FIG. 8B, the mixed layer 28-2 is formed by discharging the mixed ink by the inkjet head 50-2 while moving the stage 30. As in the embodiment using the drawing mixing method, since the ink 2 layer 28-1 is in a semi-dry state, the ink solvent of the mixed layer 28-2 formed thereon is received by the ink 2 layer 28-1. It has never been extremely wet and spread. Therefore, the heating temperature needs to be adjusted according to the ease of ink evaporation.

  The mixed layer 28-2 is also semi-dried, so that the mixed layer 28-2 is in a state where the metal contained in the ink 1 and the polymer or oligomer contained in the ink 2 are stacked.

  Further, mixed ink (mixing ratio of ink 1 and ink 2 is 50:50) supplied from the ink tank 60-3 by the ink jet head 50-3 (not shown in FIG. 8) on the mixed layer 28-2. The mixed ink 28) is discharged to form the mixed layer 28-3.

  Since the mixed layer 28-2 is in a semi-dry state, the ink solvent of the mixed layer 28-3 formed thereon is received by the mixed layer 28-2. Further, the mixed layer 28-3 is also semi-dried.

  As described above, the mixed inks are ejected in the order of increasing the mixing ratio of ink 2 (in the order of decreasing the mixing ratio of ink 1) to stack the mixed layers (28-2 to 28-4), and finally the inkjet head. Ink 1 supplied from the ink tank 60-5 by 50-5 (ink having a mixing ratio of ink 1 and ink 2 of 100: 0) is discharged, and the layer 28-5 (ink 1) in which ink 1 is 100% is discharged. (FIG. 8C).

  After the formation of all layers, a composition gradient film 3 having a composition component ratio of 100% for ink 2 to 100% for ink 1 is formed as shown in FIG.

In the formation process of each layer, the amount of ink droplets ejected from the inkjet head is preferably 0.5 to 150 pL, more preferably 0.7 to 130 pL, and more preferably 1 to 100 pL from the viewpoint of stable ejection. Is more preferable.
In the step of forming each layer, the droplet diameter of the ink droplets ejected from the inkjet head is preferably 2 to 450 μm, more preferably 5 to 350 μm, and still more preferably 10 to 250 μm, from the viewpoint of good film formation.

  As described above, a composition gradient film can be formed using a mixed ink. According to the ink mixing method of the present embodiment, since the ink is sufficiently mixed at the ink stage, a composition gradient film with high accuracy of change in the conductive gradient can be created. Further, as compared with the embodiment using the drawing mixing method, the time for diffusing and mixing the two types of functional inks is not required, and there is an advantage that the process time can be shortened.

  In this embodiment, three mixed layers of ink 1 and ink 2 are formed. However, the number of layers is not limited to this, and any number of layers can be used as long as the mixing ratio of each ink can be inclined. But you can. It is necessary to prepare ink tanks and inkjet heads as many as the number of layers to be formed.

Furthermore, in this embodiment, the composition gradient film 3 having a composition component ratio of 100% from ink 2 to 100% from ink 1 is created. However, a composition component ratio from 100% of ink 2 or 100% of ink 1 is adopted. The composition component ratio can be arbitrarily changed as long as the composition gradient film 3 can be obtained.
The composition component ratio can be appropriately adjusted depending on the properties such as adhesion and conductivity of the composition gradient film to be obtained.

[Conductive pattern and printed wiring board]
The line width of the conductive pattern according to the present invention is not particularly limited, but is preferably 1 μm or more and 200 μm or less, and more preferably 2 μm or more and 150 μm or less. When the line width is 1 μm or more and 200 μm or less, a low resistance conductive pattern can be formed relatively easily.
The volume resistivity of the conductive pattern is preferably 1 × ^{10 -2} Ω · m or less, more preferably 1 × ^{10 -3} Ω · m or less, is not more than 1 × ^{10 -4} Ω · m More preferably. Although the volume resistivity is preferably as low as possible, the practical lower limit is 1 × 10 ⁻⁴ Ω · m or more.
The method for forming a conductive pattern according to the present invention can be preferably applied to a method for producing a printed wiring board.
The printed wiring board manufactured by the manufacturing method is excellent in manufacturing suitability, high adhesion and conductivity, and has no fusion of conductive patterns. Can be applied to.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the scope of the present invention should not be construed as being limited thereto.

<Example 1>
(Create metal ink)
~ Metal ink A1 ~
Copper nanoparticle MD50 (average particle size 50 nm, manufactured by Ishihara Sangyo) 10 g
Laurylamine (Tokyo Kasei Co., Ltd.) 3g
Cyclohexanone (Wako Pure Chemical Industries, Ltd.) 27g

The above material and 60 g of zirconia beads are put in a 200 ml plastic container and sealed, dispersed with a paint shaker disperser (manufactured by Toyo Seiki Co., Ltd.) for 30 minutes, then filtered with a 2 μm filter, and metal ink A1 It was created.

(Create resin ink)
~ Resin ink B1 ~
Urethane oligomer UN-1225 (manufactured by Negami Kogyo Co., Ltd.) 50 g
450 g of cyclohexanone (manufactured by Wako Pure Chemical Industries, Ltd.)

  The material was put into a 2 L container, and the liquid temperature was kept at 40 ° C. or lower with a Silverson high speed stirrer, followed by stirring for 20 minutes. Then, it filtered with a 2 micrometer filter and created resin ink B1.

(Formation of conductive pattern)
On a transparent PET substrate (film thickness 150 μm, manufactured by Fuji Film), a conductive pattern (line width 100 μm) made of a composition gradient film having a thickness of 10 μm is formed by the following ink jet drawing method A. The adhesion, conductivity, and pattern formation were evaluated.

~ Inkjet drawing method A ~
Ink tank 1 and ink tank 2 as shown in FIG. 3 were filled with metal ink A1 and resin ink B1, respectively. The inks supplied to the inkjet head 1 and the inkjet head 2 are the metal ink A1 and the resin ink B1, respectively.
First, the appropriate amount of ink droplets ejected from the inkjet head 2 was controlled to be 10 pL and the droplet diameter was 30 μm, and the resin ink B1 was ejected from the inkjet head 2 in a nitrogen gas atmosphere. Here, the metallic ink A1 is not ejected from the inkjet head 1 (that is, the ratio (mass%) of the ejection amount of the ink ejected from the inkjet head 2 to the ejection amount of the ink ejected from the inkjet head 1 is 100: 0). Ink layer 1 was formed and dried at 80 ° C. for 30 seconds and semi-dried.
Subsequently, the ratio (% by mass) of the amount of ink discharged from the inkjet head 2 and the amount of ink discharged from the inkjet head 1 is 75:25 (ink layer 2), 50:50 (ink layer 3), 25:75 (ink layer 4) and 0: 100 (ink layer 5) were changed, and lamination and semi-drying were repeated. Finally, the film was completely dried (110 ° C. for 60 seconds) to form a conductive pattern composed of a composition gradient film. did.
Here, when the ink layer 2 is formed, the appropriate amount of ink droplets of the metal ink A1 discharged from the inkjet head 1 is 5 pL, the droplet diameter is 20 μm, and the appropriate amount of ink droplets of the resin ink B1 discharged from the inkjet head 2 is 10 pL and the droplet diameter were 30 μm. When the ink layer 3 was formed, the appropriate amount of ink droplets of the metal ink A1 was 10 pL, the droplet diameter was 30 μm, the appropriate amount of ink droplets of the resin ink B1 was 10 pL, and the droplet diameter was 30 μm. When the ink layer 4 was formed, the appropriate amount of ink droplet of the metal ink A1 was 10 pL, the droplet diameter was 30 μm, the appropriate amount of ink droplet of the resin ink B1 was 5 pL, and the droplet diameter was 20 μm. When the ink layer 5 was formed, the appropriate amount of ink droplets of the metal ink A1 was 10 pL and the droplet diameter was 30 μm. In addition, the film thicknesses of the ink layers 1 to 5 after being completely dried were each set to 2 μm.

(Evaluation of conductive pattern)
<Adhesion>
A cross hatch test (EN ISO 2409) was performed on the produced conductive film. About evaluation criteria, based on ISO2409, the result was shown by score evaluation of 0-5 points.

<Conductivity>
The created conductive film was measured for volume resistivity with Loresta MP MCP-T350 (manufactured by Mitsubishi Chemical Corporation), and the results were evaluated according to the following criteria.
4: Volume resistivity: 1 × 10 ⁻⁵ Ω · m or less 3: Volume resistivity: 1 × 10 ⁻⁵ Ω · m greater than 1 × 10 ⁻⁴ Ω · m 2: Volume resistivity: 1 × 10 ⁻ Greater than ⁴ Ω · m, 1 × 10 ⁻² Ω · m or less 1: volume resistivity: greater than 1 × 10 ⁻² Ω · m

<Pattern shape>
A conductive pattern made of a composition gradient film having a line width of 100 μm is drawn on a transparent PET base material (film thickness: 150 μm, manufactured by Fuji Film) by inkjet, and the linearity of the drawn straight line is visually evaluated. The evaluation was conducted using the limit sample.
4: Both line widths are straight lines and reproduce line widths within 100 μm ± 5 μm 3: Zigzag remains in both line widths, line widths reproduce line widths within 100 μm ± 10 μm 2: Both lines widths Zigzag is remarkable, and the line width reproduces the line width within 100μm ± 20μm 1: Zigzag is remarkable in both widths of the line, the line width is not uniform, and bulge is partially generated

  The evaluation results of the conductive pattern formed in Example 1 are shown in Table 1 below.

<Example 2>
Ink G1 (mixing ratio (mass%) A1: B1 = 25: 75), G2 (mixing ratio (mass%) A1: B1 = 50: 50 mixed with metal ink A1 and resin ink B1 used in Example 1. ), G3 (mixing ratio (mass%) A1: B1 = 75: 25) and using five print heads for each of the five inks including A1 and B1, a transparent PET substrate (film thickness) From a composition gradient film (line width: 100 μm) having a film thickness of 10 μm in the order of B1 (lowermost layer), G1, G2, G3, and A1 (uppermost layer) in the order of 150 μm (manufactured by FUJIFILM) A conductive pattern was formed. Using the transparent PET substrate on which this conductive pattern was formed, the adhesion, conductivity, and pattern shape between the composition gradient film and the substrate were evaluated. The results are shown in Table 1 below.

~ Inkjet drawing method B ~
Ink tanks 60-1 to 60-5 shown in FIG. 7 were filled with inks B1, G1, G2, G3, and A1, respectively. The inks supplied to the inkjet heads 50-1 to 50-5 are inks B1, G1, G2, G3, and A1, respectively.
First, the ink B1 was ejected from the inkjet head 50-1 in a nitrogen gas atmosphere while controlling the amount of ink droplets ejected from the inkjet head to be 10 pL and the droplet diameter to be 30 μm.
The ink B1 layer thus formed was dried at 80 ° C. for 30 seconds and semi-dried.
Next, the ink G1 was similarly discharged from the inkjet head 50-2, and the ink G1 layer was laminated and semi-dried. This was repeated for the inks G2, G3, and A1, lamination and semi-drying were repeated, and finally the composition was completely dried (110 ° C. for 60 seconds) to form a composition gradient film.
In addition, the film thicknesses of the ink layers B1, G1, G2, G3, and A1 after complete drying were set to 2 μm, respectively.

<Examples 3 to 11>
The metal and polymer or oligomer contained in the metal ink and the resin ink are replaced with those described in Table 1 below, and the others are the same as in Example 1 and consist of a composition gradient film (line width 100 μm) with a film thickness of 10 μm. A conductive pattern was formed, and adhesion with the substrate, conductivity, and pattern shape were evaluated. The results are shown in Table 1 below.

<Comparative Example 1>
Using only the metal ink A1 used in Example 1, a conductive pattern (line width 100 μm) having a film thickness of 10 μm composed of only one layer is formed on a transparent PET substrate (film thickness 150 μm, manufactured by Fuji Film). It formed by inkjet drawing and evaluated the adhesiveness with a base material, electroconductivity, and pattern shape. The results are shown in Table 1 below.

<Comparative example 2>
The metal ink A1 and the resin ink B1 used in Example 1 were mixed in advance (mixing ratio (mass ratio) = 1: 1), and mixed PET E1 obtained by stirring well to obtain a transparent PET substrate (film) A conductive pattern (line width: 100 μm) consisting of only one layer is formed by inkjet drawing on a 150 μm thick (made by Fuji Film), and the adhesion to the substrate, conductivity, and pattern shape are evaluated. did. The results are shown in Table 1 below.

Examples 1 to 11 have good adhesion to the base material, electrical conductivity, and pattern shape, and conductive patterns having functionally gradient structures formed by various ink jet methods A (drawing mixing method) and B (ink mixing method). Is effective in practical use, and there is no difference in effect between the two ink-jet methods, and either method can form a conductive pattern having a sufficient function.
Also, when examining the difference in performance between inks containing different resins, the adhesion is better when using inks containing urethane resins than when using inks containing other resins. Showed good performance. In addition to good adhesion to the urethane resin base material, this phenomenon is that the cohesive force in the gradient film is improved by the coordination interaction between the urethane bond and the metal particles, and a strong film is formed. It is thought to be caused by.

On the other hand, when the conductive pattern is formed using only the ink containing the metal as in Comparative Example 1, the adhesion between the metal film and the resin base material does not appear, and the conductive pattern easily peels off.
Further, as in Comparative Example 2, when a metal ink and a resin ink are mixed to form a single-layer conductive pattern having no composition gradient, sufficient adhesion to the base material, high conductivity, and good pattern are not exhibited. It was. Since the conductive pattern is formed of a mixture of an organic substance and a metal, not only sufficient conduction is hindered due to the insulating property of the organic substance, but also the wetting and spreading property to the substrate as an ink is not controlled, It is thought that the occurrence of bulge and the like became prominent.

DESCRIPTION OF SYMBOLS 1 Conductive pattern 2 Base material 3 Composition gradient film 10 Drawing part 100 Composition gradient film preparation apparatus

Claims (18)

A method for forming a conductive pattern, comprising: a composition gradient film having a composition that continuously changes from metal to resin from a side farthest from the base in the thickness direction to a side closest to the base in the thickness direction. And
A method for forming a conductive pattern, wherein an ink composition containing a metal and an ink composition containing a polymer or an oligomer are ejected onto the substrate by an ink jet method to form the composition gradient film. . As the at least two kinds of ink compositions, at least an ink composition containing a metal and an ink composition containing a polymer or an oligomer are used,
The inkjet method uses at least a first inkjet head and a second inkjet head,
Supplying a first ink containing an ink composition containing the metal to a first inkjet head;
Supplying a second ink containing an ink composition containing the polymer or oligomer to a second inkjet head;
A control step of determining a ratio between the amount of the first ink ejected from the first inkjet head and the amount of the second ink ejected from the second inkjet head;
Forming a layer by discharging the first ink or the second ink from at least one of the first inkjet head and the second inkjet head according to the determined ratio;
A lamination step of repeating the formation step to obtain the composition gradient film by laminating a plurality of the layers on the substrate;
With
In the control step, the ratio of the first ink is increased and the ratio of the second ink is decreased from a layer close to the base to a layer far from the base in the thickness direction of the plurality of layers. The method for forming a conductive pattern according to claim 1, wherein the ratio is determined.   The method for forming a conductive pattern according to claim 2, comprising a urethane polymer or oligomer as the polymer or oligomer. The method for forming a conductive pattern according to claim 3, wherein the urethane polymer or oligomer has a repeating unit represented by the following general formula (1).

(In the above general formula, R _{1 to} R ₃ each independently represents an alkylene group, an arylene group or a biarylene group, and R _{4 to} R ₆ each independently represent a hydrogen atom, an alkyl group, an aryl group or a heteroaryl. Represents a group.)   The method for forming a conductive pattern according to claim 2, wherein the base material is a synthetic resin base material.   The method for forming a conductive pattern according to any one of claims 2 to 5, wherein, in the forming step, an ink amount of droplets ejected from the first and second inkjet heads is 0.3 to 100 pL.   The method for forming a conductive pattern according to claim 2, wherein in the forming step, a droplet diameter of droplets discharged from the first and second inkjet heads is 1 to 300 μm. As the at least two kinds of ink compositions, at least an ink composition containing a metal and an ink composition containing a polymer or an oligomer are used,
The inkjet method uses a plurality of inkjet heads,
A mixed ink in which a first ink containing the metal-containing ink composition and a second ink containing the polymer or oligomer-containing ink composition are mixed, each of which is mixed at different ratios Supplying the mixed ink to each inkjet head of the plurality of inkjet heads;
A selection step of sequentially selecting one inkjet head from the plurality of inkjet heads, the selection step sequentially selecting from the inkjet head to which the mixed ink having a high ratio of the second ink is supplied;
Forming a layer by discharging mixed ink from the selected inkjet head; and
A lamination step of repeating the formation step to obtain the composition gradient film by laminating a plurality of the layers on the substrate;
The method for forming a conductive pattern according to claim 1, comprising:   The method for forming a conductive pattern according to claim 8, wherein the polymer or oligomer contains a urethane polymer or oligomer. The method for forming a conductive pattern according to claim 9, wherein the urethane polymer or oligomer has a repeating unit represented by the following general formula (1).

(In the above general formula, R _{1 to} R ₃ each independently represents an alkylene group, an arylene group or a biarylene group, and R _{4 to} R ₆ each independently represent a hydrogen atom, an alkyl group, an aryl group or a heteroaryl. Represents a group.)   The method for forming a conductive pattern according to claim 8, wherein the base material is a synthetic resin base material.   12. The method for forming a conductive pattern according to claim 8, wherein, in the forming step, an ink amount of droplets ejected from the first and second inkjet heads is 0.5 to 150 pL.   13. The method for forming a conductive pattern according to claim 8, wherein in the forming step, a droplet diameter of droplets discharged from the first and second inkjet heads is 2 to 450 μm.   The method for forming a conductive pattern according to claim 1, wherein the metal has an average particle diameter of 5 to 1000 nm.   The metal is a particle including at least one selected from the group consisting of gold, silver, copper, platinum, aluminum, palladium, and nickel, or an alloy including two or more metals selected from the group. The formation method of the conductive pattern as described in any one of Claims 1-14 which exists.   The method for forming a conductive pattern according to any one of claims 1 to 15, wherein the ink composition containing the polymer and the oligomer further contains a solvent having a boiling point of 60C to 300C.   The manufacturing method of a printed wiring board formed using the formation method of the conductive pattern as described in any one of Claims 1-16.   A printed wiring board manufactured by the manufacturing method according to claim 17.