JP2015211062A - Membrane structure of conductive pattern and method of manufacturing conductive pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a thin film pattern where metal nanoparticle film is never peeled off from a plastic base material even after optical burning, without inserting a new layer, such as a resin layer, between the plastic base material and metal nanoparticle film, and to provide its membrane structure.SOLUTION: In the membrane structure of a conductive pattern formed by optical burning after patterning metal nanoparticle diffusion ink on a base material, sintering progresses more for the metal nanoparticles at a part separated from the base material of the membrane structure, and the cavity in the membrane structure is reduced.

Description

  The present invention relates to a method for forming a thin film pattern and a film structure of the thin film pattern.

  In recent years, “printed electronics (PE)”, which is an electronic device formation process using printing technology, has been actively printing patterning of metallic functional materials having conductivity.

  For example, with respect to metal wiring formation, the printing process technology is competing among companies, and various printing methods have been developed focusing on high-resolution patterning technology.

  On the other hand, the high position accuracy patterning technology has a lower priority than the high resolution patterning technology. However, if high-resolution patterning technology advances, patterning technology with high positional accuracy will inevitably be required.

  In printed electronics, inexpensive plastic substrates such as PET film and PEN film are often used as printing substrates, and in order to achieve high positional accuracy patterning, patterning is accurately performed on the target plastic substrate. Of course, management and control of the plastic substrate after printing is also necessary.

  In particular, in the process of firing the material, high-temperature heat is often applied to the plastic substrate, and there is a problem in that a large amount of distortion occurs with respect to the plastic substrate with poor heat resistance.

  Thus, as a firing method for reducing the thermal load on the base material, a light firing method using a xenon flash light source or the like has attracted attention. When this method is used, only a patterned metallic functional material is loaded with high-temperature heat in a very short time, and the load on the plastic substrate that is the substrate can be reduced.

  Currently, metal nanoparticle-dispersed ink in which nano-sized fine particles of silver or copper are dispersed is often used as the functional material made of metal. For example, when this metal nanoparticle-dispersed ink is light baked with a xenon flash light source, the organic protective film around the metal nanoparticles is inactivated and the metal nanoparticles are sintered between each other within a few milliseconds. And high conductivity can be obtained.

  However, since photo-firing rapidly induces the sintering of metal nanoparticles to form a film, shrinkage stress due to sintering of metal nanoparticles or expansion / contraction of the substrate due to heat transfer from the metal nanoparticle film (substrate temperature) There is a problem that shearing stress is generated between the base material and the metal nanoparticle film due to the expansion and contraction of the base material due to the rise and fall of the base material, and the formed metal nanoparticle film is peeled off from the base material. The tendency is more conspicuous as the cheaper plastic substrate has poor heat resistance.

  As described above, light baking is one of effective means as a baking method that is a post-patterning process for patterning metal nanoparticle-dispersed ink on a plastic substrate with high positional accuracy and then obtaining functionality. However, due to the shrinkage stress caused by the sintering of metal nanoparticles and the expansion and contraction of the base material due to heat transfer from the metal nanoparticle film, a shear stress was generated between the base material and the metal nanoparticle film, which was formed from the base material. There is a problem that the metal nanoparticle film is peeled off.

  As a means for solving this problem, Patent Document 1 discloses a technique for inserting a resin layer between a plastic substrate and a metal nanoparticle film, but the cost increases by newly inserting a resin layer. Cannot be avoided.

JP 2014-11199 A

  In order to solve the above problems, the object of the present invention is to provide a metal nanoparticle from a plastic substrate even after light firing without inserting a new layer such as a resin layer between the plastic substrate and the metal nanoparticle film. It is an object of the present invention to provide a method for forming a thin film pattern in which a film does not peel and a film structure thereof.

  As a result of intensive studies to solve the above problems, the present invention has found a means for solving the problems. Specifically, by controlling the progress of particle sintering in the film thickness direction, further, in the thickness direction of the metal nanoparticle film, the surface vicinity emphasizes high conductivity and promotes particle growth, In the vicinity of the base material, it is possible to suppress the shearing stress between the plastic base material and the metal nanoparticle film at the same time as acquiring high conductivity by suppressing the progress of sintering of the particles with an emphasis on adhesion. As a result, the present invention has been completed.

  Therefore, as a means for solving the above-mentioned problem, claim 1 of the present invention is a film structure of a conductive pattern formed by patterning a metal nanoparticle-dispersed ink on a plastic substrate, followed by light baking, and The metal structure is a film structure of a conductive pattern characterized in that sintering progresses as the metal nanoparticles in a part of the film structure away from the substrate, and voids in the film structure decrease.

Further, claim 2 is a method for producing a conductive pattern using metal nanoparticle-dispersed ink,
A pattern forming process for forming a metal nanoparticle-dispersed ink pattern on a plastic substrate;
A photo-firing step of sintering by irradiating light onto the pattern containing the metal nanoparticles formed in the above-mentioned steps, in this order,
The light baking step uses a light source in a wavelength region in which the substrate is transparent, and the irradiation time is 1 millisecond or less, and the integrated amount of light to be irradiated is 0.5 mJ / cm ² or more. It is the manufacturing method of the conductive pattern characterized.

  Further, according to claim 3, the particle diameter of the metal nanoparticles of the metal nanoparticle-dispersed ink is 100 nm or less in terms of a volume average diameter measured using a dynamic light scattering method. It is a manufacturing method of the conductive pattern of this conductive pattern.

  A fourth aspect of the present invention is the conductive pattern manufacturing method according to the second or third aspect, wherein the light source is a xenon flash light source or a pulse laser light source.

  Further, in claim 5, the pattern forming step uses relief printing, intaglio printing, stencil printing, planographic printing, or ink jet printing, and manufacturing the conductive pattern according to any one of claims 2 to 4. Is the method.

  Since the present invention has the above features, the following effects are obtained.

  That is, according to the first aspect of the invention, by controlling the progress of particle sintering in the film thickness direction, the surface of the thin film pattern on which electrons move increases the conductivity by encouraging particle sintering. In the vicinity of the base material, by suppressing the sintering of the particles, the volume of the film structure is reduced little, the generation of shrinkage stress is suppressed, and the adhesion with the base material is not impaired. As a measure of the progress of the sintering of the particles, the amount of voids in the film structure, grain size, crystallite size and the like are used. Further, regarding the vicinity of the base material, a large amount of the binder component remains in the voids in the film structure, whereby the adhesion can be improved.

  Further, according to the inventions according to the second and third aspects, since the fine particles are metal particles, a conductive function can be obtained after the particles are sintered, and the particle size is 100 nm or less. Compared to larger particles, the surface area per unit mass is much larger, and the sintering of particles, a phenomenon at the surface, is easier to sinter with smaller particles. In addition, problems such as sedimentation can be prevented.

  In addition, according to the invention according to the fourth aspect, by using a xenon flash lamp light source as an energy source, it is possible to obtain energy of intensity by light irradiation in a short time, and compatibility with firing of metal nanoparticle dispersed ink. Very good. In addition, there are operational advantages such as low running cost, fast tact, and simplicity of the device. Further, by using a pulse laser light source as an energy source, there is an advantage that energy of intensity can be obtained in an extremely short time as compared with other means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic explanatory diagram illustrating an example of the configuration of a reverse printing apparatus used in an embodiment of the present invention. The microscope picture of the sample before the light baking which patterned the copper metal nanoparticle dispersion | distribution ink on the PET film in the Example of this invention. The microscope picture of the sample photobaked by the conditions 1 and 2 about the sample which patterned the metal nanoparticle dispersion | distribution ink of copper on the PET film in the Example of this invention. It is a model inferred about the cross section of the metal nanoparticle film in the condition 1, and the surface side of the metal nanoparticle film is sintered and the voids are reduced, whereas the substrate side is sintered. The schematic diagram showing the situation where there is little progress and the space | gap is not reducing.

Embodiments of the present invention will be described below.
(Metal nanoparticle dispersed ink)
As a material for producing the metal nanoparticle film, a metal nanoparticle-dispersed ink in which metal nanoparticles having an organic protective film for stably dispersing the metal nanoparticles in a solvent is dispersed in the solvent is used. be able to. Gold, silver, copper, nickel, platinum, palladium, rhodium etc. are mentioned as a kind of metal nanoparticle.

  The particle size of the metal nanoparticles is preferably about 10 to 100 nm. Here, the particle diameter refers to a volume average diameter calculated from measurement data using a dynamic light scattering method. The smaller the particle size, the lower the fusion temperature between the metal nanoparticles due to the size effect, and the metal film can be formed with smaller thermal energy. However, the dispersion stability as the metal nanoparticle-dispersed ink is deteriorated, and the possibility of occurrence of aggregation is increased.

As the solvent, ester solvents, alcohol solvents, ether solvents, hydrocarbon solvents and the like are used. As ester solvents, propylene glycol monomethyl ether acetate, ethoxyethyl propionate, as alcohol solvents, 1-butanol, 3methoxy-3methyl-1butanol, 1-hexanol, 1,3 butanediol, 1-pentanol, 2-methyl 1-butanol, 4-methyl-2-pentanol, ether solvents such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol tertiary butyl ether, dipropylene glycol monomethyl ether, ethylene glycol butyl ether, ethylene glycol Ethyl ether, ethylene glycol methyl ether, diethylene glycol butyl ether, diethylene glycol ethyl ether, hydrocarbon As the solvent, Solvesso (produced by Exxon Chemical Co.) 100, (manufactured by Exxon Chemical Co.) Solvesso 150 and the like.

  In addition, from the viewpoint of coating properties and dispersion stability of the image-receiving layer composition, water, ethyl alcohol, isopropyl alcohol, toluene, xylene, ethyl cellosolve, ethyl cellosolve acetate, diclime, cyclohexanone are appropriately selected and used. Etc.

  As the binder resin, a cellulose-based resin, an epoxy-based resin, an acrylic-based resin, a urethane-based resin, or a composite resin thereof can be used in order to improve the adhesion with the plastic substrate. Moreover, what decomposes | disassembles at low temperature is desirable.

  Moreover, surfactant, antioxidant, a viscosity modifier, a leveling agent, etc. may be added to these inks as needed. The ink of the present invention is not limited to these.

(Light baking)
The xenon flash light source used for light baking is not particularly limited, but it is desirable to cut a specific wavelength region in accordance with the light transmittance of the plastic substrate. This is because the plastic substrate itself may generate heat by absorbing energy of a specific wavelength that cannot be transmitted by the plastic substrate.

  Moreover, regarding the frequency | count of irradiation, either single-shot irradiation or multiple irradiation can be selected with the metal nanoparticle of a metal nanoparticle dispersion ink, or a plastic base material. In the multiple irradiation, for example, the irradiation frequency can be selected from 0.1 Hz to 500 Hz, and the conditions can be set once to control the progress of the sintering of the particles after the light baking in the film thickness direction. Things are desirable.

Irradiation energy when a xenon flash light source is used as a light source can be set once for controlling the progress of particle sintering in the film thickness direction even if irradiation is performed a plurality of times. Here, in order to promote the sintering of the metal nanoparticles, the integrated amount of irradiation energy is desirably 0.5 J / cm ² or more. However, if the irradiation energy is too high, crater-like irregularities may be generated on the surface and the functionality may be impaired, so there is an upper limit depending on the type of metal nanoparticles.

  Moreover, not only single irradiation and multiple irradiations, one irradiation time is a short time within a range in which the sintering of the particles on the pattern surface can be promoted in order to promote the sintering of the particles on the pattern surface only. It is desirable. The time is preferably 1 millisecond or less. Here, the sintering of the particles means that the atoms constituting the metal nanoparticles move due to thermal diffusion and change in a direction in which the metal nanoparticles are fused and integrated. As a result, the conductivity of the pattern surface made of the metal nanoparticle film changes in a direction approaching the conductivity of the bulk of the metal. This is because the structure changes in a direction in which there are no voids between the metal nanoparticles. At the same time, since the volume is reduced, a stress (shrinkage stress) in the shrinking direction is generated in the metal nanoparticle film.

  On the other hand, the closer the film surface is to the film thickness direction, that is, the closer to the plastic substrate, the smaller the degree to which the metal nanoparticles are sintered and integrated. From the viewpoint of the stress in the film structure, this means that the closer to the plastic substrate, the closer to the original film structure, and the smaller the shrinkage stress, the harder it is to peel off from the plastic substrate. Further, the closer to the plastic substrate, the more voids in the film structure remain, and the binder resin in the metal nanoparticle-dispersed ink is present in the voids, so that the adhesion with the plastic substrate is improved.

  Further, in general thermal firing in the atmosphere, single-shot irradiation is desirable instead of multiple irradiations for materials that react with oxygen and affect functionality, such as copper particles.

(Metal nanoparticle film pattern formation)
The pattern formation method is preferably pattern formation by printing, and includes letterpress printing, intaglio printing, planographic printing, stencil printing, ink jet printing, and the like. In particular, flexographic printing, which is a type of letterpress printing, and reverse printing using a blanket, are capable of thin film and high-definition patterning.

  Further, when a uniform ink liquid film is required instead of pattern formation, for example, dipping, roll coating, gravure coating, reverse coating, air knife coating, die coating, spray coating, or the like can be used. Among them, the die coat, cap coat, roll coat, and applicator can form a uniform ink liquid film for ink having a wide range of viscosity.

(Plastic substrate)
Examples of the plastic substrate used include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether sulfone, cycloolefin polymer, polyimide, nylon, aramid, polycarbonate, polymethyl methacrylate, polyvinyl chloride, and triacetyl. A film or sheet of cellulose or the like can also be used.

  Moreover, you may provide an anchor layer in these plastic base materials. As a material for forming the anchor layer, a coating composition containing a polymer and a solvent as main components and optionally added with fine particles and the like can be used. The material constituting the anchor layer of the present invention is required to have performance such as transparency, heat resistance, and good adhesion to metal particles.

  High molecular weight polymers include polyacrylate, polymethacrylate, polyethylacrylate, styrene-butadiene copolymer, butadiene copolymer, acrylonitrile-butadiene copolymer, chloroprene copolymer, and crosslinked acrylic resin. Cross-linked styrene resin, fluorine resin, vinylidene fluoride, benzoguanamine resin, phenol resin, polyolefin resin, cellulose, styrene-acrylate copolymer, styrene-methacrylate copolymer, polystyrene, styrene-acrylamide copolymer , N-isobutyl acrylate, acrylonitrile, vinyl acetate, acrylamide, silicone resin, polyvinyl acetal, polyamide, polyimide, rosin resin, polyethylene, polycarbonate, chloride Examples include, but are not limited to, nylidene resin, polyvinyl alcohol, cellulose resin, epoxy resin, vinyl acetate resin, ethylene-vinyl acetate copolymer, vinyl acetate-acrylic copolymer, vinyl chloride resin, polyurethane, and the like. is not. These polymers can be used as a curable polymer by adding a reactive site such as an acryl group, a carboxyl group, an isocyanate group or the like, and further adding a crosslinking agent, a photoinitiator or the like as necessary.

  Hereinafter, an example in which copper metal nanoparticle dispersed ink is patterned on a PET film will be described in more detail.

  As a printing method, a reverse printing method using an ink peelable film was selected. In this printing method, an ink liquid is applied to an ink peelable film, and a pre-dried ink is formed by pressing and separating a relief plate having a non-image pattern on a pre-dried ink film obtained by pre-drying the ink liquid. Transfer unnecessary parts of the film to the convex part of the relief plate, and transfer the image pattern remaining on the ink-releasable film to the substrate to be printed. It is said.

  As shown in FIG. 1, an apparatus that performs reverse printing includes an ink peelable film 106, a substrate to be printed 109, and an ink peelable film unwinding unit 107 that controls the conveyance of the ink peelable film 106 and the ink peelable. The film forming unit 108 includes a transport system, an ink coating unit 101, an ink drying unit 102, a pattern removing unit 103, an alignment unit 104, and a substrate bonding unit 105.

  The copper metal nanoparticle-dispersed ink used is an aromatic hydrocarbon type having an average particle size of 30 to 50 nm and a copper content of 20 to 50 wt%, and a leveling agent (addition amount of 0.5 wt%, BIC Chemie Japan Co., Ltd., product name: BYK333), binder (addition amount 5 wt%, Sekisui Chemical Co., Ltd., product name: ESREC BK), transferability imparting agent are mixed.

  As the ink peelable film 106, a film having a thickness of 10 μm was used by applying a peelable silicone rubber on a PET film having a substrate thickness of 100 μm and drying it. Further, in order to improve the coating properties of the metal nanoparticle-dispersed ink, a surface treatment that improves wettability with respect to the film surface (manufactured by USHIO, product name: SHV07, surface treatment method: spray coating, after drying, (Irradiation with ultraviolet light of 172 nm).

  First, in the ink coating unit 101, the ink releasable film 106 is fixed to the adsorption surface using the porous material provided on the movable stage, and the metal nanoparticle-dispersed ink is uniformly distributed to 200 nm using a die head. Solid film coating was performed by adjusting the thickness.

  Thereafter, the ink peelable film 106 on which the solid film of the metal nanoparticle-dispersed ink is formed is transported to the ink drying unit 102 that is a vacuum dryer, semi-dried, and transported to the pattern removing unit 103.

  The pattern removing unit 103 has a resin-made (or glass-made) relief plate attached to the movable stage by suction, and after the ink coating surface on the ink peelable film 106 is brought close to the relief plate, The roller provided is pressed from above the ink peelable film 106, applied with printing pressure while being rotated, and the ink peelable film 106 is peeled off from the relief printing plate to remove the coating film in contact with the relief of the relief printing plate. To obtain a pattern on the ink peelable film 106.

  Next, in the alignment unit 104 composed of a movable stage and a plurality of microscope cameras, a part of the pattern obtained on the ink peelable film 106 is obtained using the fact that the ink peelable film 106 is transparent. The alignment mark pattern (first alignment pattern) and the alignment pattern (second alignment pattern) provided in advance on the PET are recognized by the transmission image, and alignment is performed.

The laminating unit 105 is provided with a roller on a movable stage installed in the alignment unit 104. PE fixed to a movable stage installed in the bonding unit 105
T and the ink peelable film 106 installed with a slight gap are pressed against the roller installed in the bonding section 105, and the printing pressure is applied while rotating the roller as the movable stage moves. Then, the ink peelable film 106 was peeled off from the PET, whereby the pattern was transferred to the PET film as the substrate 109 to be printed.

  The result of patterning the copper metal nanoparticle dispersed ink on the PET film is shown in FIG. In the case of a stripe pattern, a good pattern of 10 μm or less was obtained.

  The obtained sample was light baked by a light baking apparatus equipped with a xenon light source flash light source. A sample (Condition 1) that has been light baked with high energy in a very short time (200 ns or less), and as a comparative example, the voltage applied to the light baked apparatus is reduced so that the accumulated energy is equivalent to Condition 1; A sample (condition 2) was produced under the condition (2000 ns) where the irradiation time was set longer than condition 1.

  When the adhesion after light baking was compared, in condition 1, the metal nanoparticle film was peeled off from the PET film, whereas in condition 2, the metal nanoparticle film peeled off from the PET. Occurred. (Figure 3)

  FIG. 4 shows a model estimated for the cross section of the metal nanoparticle film under the condition 1. This is because, since the irradiation time of the xenon flash light source at the time of light firing is short, the sintering of the particles is promoted only on the extreme surface of the metal nanoparticle film, and the progress of the sintering of the metal nanoparticles can be inclined. It is thought that it was made.

  In the metal nanoparticle film, there are voids between the metal nanoparticles and the metal nanoparticles. Further, as the photo-sintering progresses, the metal nanoparticles behave as if they are melted and integrated, and the apparent particle size increases. In addition, the gap is reduced and the conductivity is increased. The crystallite size that can be measured from X-ray diffraction also increases. In addition, contraction stress is generated in a direction in which the voids are crushed and the volume is reduced.

  On the other hand, although the metal nanoparticles near the surface of the substrate 109 to be printed, that is, the PET film, are given a thermal load by heat conduction, the temperature is lower than the surface of the metal nanoparticle film, and the sintering of the particles is suppressed. As a result, since the generation of shrinkage stress of the metal nanoparticle film was small, it can be estimated that the shrinkage difference from the PET film was small and the metal nanoparticle film was not peeled off. Under condition 2, since the irradiation time of the xenon flash light source was long, the sintering of the particles progressed to the metal nanoparticles near the surface of the PET film. As a result, the generation of shrinkage stress of the metal nanoparticle film increased. The shrinkage difference between the metal nanoparticle film and the metal nanoparticle film was peeled off.

  As described above, by controlling the degree of particle growth of the metal nanoparticles with respect to the thickness direction of the metal nanoparticle film and imparting an inclination, it is possible to form a high-definition pattern without any problem of adhesion.

DESCRIPTION OF SYMBOLS 101 ... Ink application part 102 ... Ink drying part 103 ... Pattern removal part 104 ... Alignment part 105 ... Bonding part 106 ... Ink peelable film 107 ... Ink peelability Film unwinding part 108 ... Ink peelable film winding part 109 ... Printed substrate

Claims (5)

  It is a film structure of a conductive pattern formed by patterning a metal nanoparticle-dispersed ink on a plastic substrate, followed by photo-baking, and the metal nanoparticles in a part of the film structure that is away from the substrate are sintered as much as possible. A film structure of a conductive pattern, characterized in that the voids in the film structure are reduced. A method for producing a conductive pattern using metal nanoparticle dispersed ink,
A pattern forming process for forming a metal nanoparticle-dispersed ink pattern on a plastic substrate;
A photo-firing step of sintering by irradiating light onto the pattern containing the metal nanoparticles formed in the above-mentioned steps, in this order,
The light baking step uses a light source in a wavelength region in which the substrate is transparent, and the irradiation time is 1 millisecond or less, and the integrated amount of light to be irradiated is 0.5 mJ / cm ² or more. A method for producing a conductive pattern.   3. The conductive pattern of the conductive pattern according to claim 2, wherein a particle diameter of the metal nanoparticles of the metal nanoparticle-dispersed ink is 100 nm or less in terms of a volume average diameter measured using a dynamic light scattering method. Production method.   4. The method for producing a conductive pattern according to claim 2, wherein the light source is a xenon flash light source or a pulse laser light source.   5. The method for producing a conductive pattern according to claim 2, wherein the pattern forming step uses letterpress printing, intaglio printing, stencil printing, planographic printing, or ink jet printing.