Method for forming a fine pattern

Abstract

To provide a method for forming a fine pattern with excellent linearity, in which a conductive coating film is irradiated with a laser to create a groove, the coating film being made of a carbon material excellent in corrosion resistance and costs.SOLUTION: A method for forming a conductive fine pattern on an insulating substrate is characterized in that a conductive coating film containing a carbon material and a binder is formed on the insulating substrate, and the conductive coating film is irradiated with a laser with a wavelength of 700 nm or less to create a groove.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for forming a fine pattern having conductivity by laser grooving.

Background Art

[0002] In recent years, mobile devices typified by smartphones have been evolving in terms of multifunctionality and high definition of displays while maintaining their size. In order to further improve these performances, it is necessary to mount electronic components at a higher density. For the high-density mounting of electronic components, miniaturization of the electronic components themselves and miniaturization of signal wirings are required, and the formation of conductive patterns is also required to be refined with improvements and new technologies. Also, performance improvement is required in biosensors, and the miniaturization of sensor circuits is progressing. For example, in a sensor chip for measuring the glucose concentration (blood sugar level) in blood, a sensor circuit on the order of one hundred micrometers is formed. However, if it can be miniaturized to the order of several tens of micrometers, the area of the electrode for detecting an electrochemical reaction can be increased, and an improvement in the accuracy of blood sugar level measurement can be expected.

[0003] Carbon materials have electrical conductivity, are superior in corrosion resistance compared to metals, and are also advantageous in terms of cost. Therefore, they are widely used as circuit materials such as wiring and electrodes for electronic devices. Circuits are often formed by screen printing using a carbon-containing paste. Conventionally, the limit of screen printing was about line / space = 100 μm / 100 μm, but recently, fine printing with line / space = 50 μm / 50 μm has become possible. However, the linearity is not yet sufficient. In addition to the screen printing method, in Patent Document 1, a fine circuit of a carbon material is formed by photolithography, but there is a problem that the manufacturing cost is high because a plurality of steps are required. Recently, a laser processing method for forming a circuit by irradiating a conductive film with a laser beam has been studied. In the laser processing method, a conductive paste is printed on an insulating substrate to form a conductive film, and a part of the conductive film is removed from the insulating substrate by a laser to form a circuit. This enables finer patterning than the screen printing method (for example, Patent Documents 2 to 4). However, the previous studies used a metal material as the conductive material, and the carbon material was only added in a trace amount as a laser sensitizer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] Although the laser processing method is a useful means for forming a fine pattern, there has been no previous study example on a conductive film formed from a paste mainly composed of a carbon material.

[0006] An object of the present invention is to provide a method for forming a fine pattern with excellent linearity by irradiating a conductive coating film made of a carbon material excellent in corrosion resistance and cost with a laser to perform grooving.

Means for Solving the Problems

[0007] As a result of intensive studies to solve the above problems, the present inventors have found that a fine pattern with excellent linearity can be formed by irradiating a conductive coating film containing a carbon material and a binder with laser light having a specific wavelength to perform grooving, and thus have reached the present invention. That is, the present invention relates to the following (1) to (3). (1) A method for forming a conductive fine pattern on an insulating substrate, comprising forming a conductive coating film containing a carbon material and a binder on the insulating substrate, and performing grooving by irradiating the conductive coating film with a laser having a wavelength of 700 nm or less. A method for forming a fine pattern, characterized in that.

[0008] (2) The method for forming a fine pattern according to claim 1, wherein the conductive coating film is a coating film formed from a paste composition containing a carbon material, a binder, and a solvent.

[0009] (3) The method for forming a fine pattern according to claim 1 or 2, wherein the fine pattern is an electrode pattern for a biosensor.

Effects of the Invention

[0010] According to the present invention, using a carbon material excellent in corrosion resistance and cost, a pattern with excellent linearity having a line and space on the order of several tens of micrometers can be formed by a simple process, and it can be applied to a biosensor electrode with improved measurement accuracy.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described. First, the conductive coating film applied to the fine pattern forming method of the present embodiment will be described. The conductive coating film applied to the present embodiment is characterized by containing a carbon material and a binder.

[0013] Examples of the carbon material include graphite, carbon black, carbon fiber, carbon nanotube, porous carbon, graphene nanoplatelet, nanoporous carbon, carbon nanofiber, carbon nanohorn, etc. These carbon materials can also be used alone or in combination of two or more. Among the above carbon materials, it is preferable to use graphite because an excellent conductive coating film can be obtained.

[0014] Examples of graphite include artificial graphite and natural graphite. Artificial graphite is obtained by artificially orienting the orientation of minute graphite crystals with an irregular arrangement by heat-treating amorphous carbon, and is generally manufactured using petroleum coke or coal-based pitch coke as the main raw material. As natural graphite, flaky graphite, spherical graphite, scaly graphite, massive graphite, earthy graphite, etc. can be used. Also, expanded graphite (also referred to as expandable graphite) obtained by chemically treating scaly graphite, etc., and expanded graphite obtained by heat-treating expanded graphite to expand it and then making it finer or by pressing can also be used. Among these graphites, when used for a conductive coating film, natural graphite is preferable from the viewpoint of conductivity.

[0015] Also, two or more types of graphite can be used in combination, and it can also be used in combination with the other carbon materials described above. In these cases, a combination that makes the gaps between carbon particles small is preferable because the conductivity is enhanced.

[0016] Moreover, the conductive coating film applied to this embodiment preferably has an average particle diameter of 0.5 to 50 μm, and more preferably 2 to 10 μm. When the average particle diameter of the graphite used is larger than 50 μm, the line edge portion after laser grooving is likely to have a wavy shape, and the linearity of the pattern may deteriorate. When the average particle diameter is smaller than 0.5 μm, the contact resistance between the graphite may increase and the conductivity may deteriorate.

[0017] The average particle diameter referred to in the present invention is the particle diameter (D50) at which the volume ratio of the particles becomes 50% when the volume ratio of the particles is integrated from the finer particle diameters in the volume particle size distribution, and is measured by a general particle size distribution meter, for example, a particle size distribution meter of the dynamic light scattering method (Microtrac UPA manufactured by Nikkiso Co., Ltd.).

[0018] Examples of commercially available graphite include, for example, flake graphite such as CMX, UP-5N, UP-10N, UP-20N, UP-35N, CSSP, CSPE, CSP, CP, CPB, UCP, J-CPB, CB-150, CB-100, ACP, ACP-1000, ACB-50, ACB-100, ACB-150, SP-10, SP-20, SP-5030, J-SP, SP-270, HOP, GR-60, LEP, F#1, F#2, F#3 manufactured by Nippon Graphite Industries, Ltd.; CX-3000, FBF, BF, CBR, SSC-3000, SSC-600, SSC-3, SSC, CX-600, CPF-8, CPF-3, CPB-6S, CPB, 96E, 96L, 96L-3, 90L-3, CPC, S-87, K-3, CF-80, CF-48, CF-32, CP-150, CP-100, CP, HF-80, HF-48, HF-32, SC-120, SC-80, SC-60, SC-32 manufactured by Chugoku Graphite Co., Ltd.; CNP15, CNP7, Z-5F, EC1500, EC1000, EC500, EC300, EC100, EC50 manufactured by Ito Graphite Industries, Ltd.; 10099M, PB-99, etc. manufactured by Nishimura Graphite Co., Ltd. Examples of spherical natural graphite include CGC-20, CGC-50, CGB-20, CGB-50 manufactured by Nippon Graphite Industries, Ltd. Examples of amorphous graphite include Blue P, AP, AOP, P#1 manufactured by Nippon Graphite Industries, Ltd.; APR, S-3, AP-6, 300F manufactured by Chugoku Graphite Co., Ltd. Examples of artificial graphite include PAG-60, PAG-80, PAG-120, PAG-5, HAG-10W, HAG-150 manufactured by Nippon Graphite Industries, Ltd.; RA-3000, RA-15, RA-44, GX-600, G-6S, G-3, G-150, G-100, G-48, G-30, G-50 manufactured by Chugoku Graphite Co., Ltd.; SGP-100, SGP-50, SGP-25, SGP-15, SGP-5, SGP-1, SGO-100, SGO-50, SGO-25, SGO-15, SGO-5, SGO-1, SGX-100, SGX-50, SGX-25, SGX-15, SGX-5, SGX-1 manufactured by SEC Carbon Co., Ltd.

[0019] Regarding other carbon materials, examples of commercially available carbon blacks include Tokablack #4400, #4500, #5500 manufactured by Tokai Carbon Co., Ltd., Printex L manufactured by Degussa AG, #2350, #2400B, #2600B, #3050B, #3230B, #3350B, #3400B, #5400B manufactured by Mitsubishi Chemical Corporation, Vulcan XC-72R, Black Pearls 2000 manufactured by Cabot Corporation, Ensaco 250G manufactured by TIMCAL, etc. of furnace black, EC-200L, EC-300J, EC-600JD, etc. of Ketjen black manufactured by Lion Specialty Chemicals Co., Ltd., Denka black manufactured by Denka Co., Ltd., acetylene black such as Denka black FX-35, etc.

[0020] Examples of commercially available carbon fibers and carbon nanotubes include vapor-grown carbon fibers such as VGCF manufactured by Showa Denko K.K., single-walled carbon nanotubes such as EC1.0, EC1.5, EC2.0, EC1.5-P manufactured by Meijo NanoCarbon Co., Ltd., FloTube9000, FloTube9100, FloTube9110, FloTube9200 manufactured by CNano, NC7000 manufactured by Nanocyl, 100T manufactured by Knano, etc.

[0021] Examples of commercially available porous carbons include porous carbons manufactured by Toyo Tanso Co., Ltd. such as Knobel MH grade, Knobel P(2)010 grade, Knobel P(3)010 grade, Knobel P(4)050 grade, Knobel MJ(4)030 grade, Knobel MJ(4)010 grade, Knobel MJ(4)150, etc.

[0022] Examples of commercially available graphene nanoplatelets include graphene nanoplatelets manufactured by XG Sciences, Inc. such as xGnP-C-750, xGnP-M-5, etc.

[0023] Examples of commercially available nanoporous carbons include nanoporous carbon manufactured by Easy-N Co., Ltd.

[0024] On the one hand, the binder is not particularly limited as long as it can impart the dispersibility of the carbon material, the adhesion to the insulating substrate, and the stability of the paste composition, and examples thereof include resins. For example, acrylic resin, polyurethane resin, polyester resin, phenol resin, epoxy resin, phenoxy resin, urea resin, melamine resin, alkyd resin, formaldehyde resin, silicone resin, fluororesin, synthetic rubbers such as styrene-butadiene rubber and fluororubber, conductive resins such as polyaniline and polyacetylene, and polymer compounds containing fluorine atoms such as polyvinylidene fluoride, polyvinyl fluoride, perfluorocarbon, and tetrafluoroethylene. Further, modified products, mixtures, or copolymers of these resins may also be used. These binders can be used alone or in combination of two or more.

[0025] In addition, a curable resin that undergoes a curing (crosslinking) reaction after the binder resin forms a coating film can also be used.

[0026] In addition, when using a mixed solvent of water and a solvent compatible with water as the solvent used in the paste composition described later, a binder generally called an aqueous emulsion can also be used. An aqueous emulsion is one in which the binder resin is dispersed in a particulate state without dissolving in water.

[0027] The emulsion to be used is not particularly limited, and examples thereof include (meth)acrylic emulsions, nitrile emulsions, urethane emulsions, diene emulsions (such as SBR (styrene-butadiene rubber)), and fluorine emulsions (such as PVDF (polyvinylidene fluoride) and PTFE (polytetrafluoroethylene)).

[0028] Next, the paste composition used to form the above conductive coating film will be described. The paste composition applied to this embodiment is characterized by containing a carbon material, a binder, and a solvent.

[0029] For the carbon material and the binder, those described above are used. Regarding the solvent, although it is not particularly limited, examples include alcohols, glycols, cellosolves, amino alcohols, amines, ketones, carboxylic acid amides, phosphoric acid amides, sulfoxides, carboxylic acid esters, phosphoric acid esters, ethers, nitriles, water, etc. These solvents can also be used alone or in combination of two or more kinds.

[0030] The paste composition containing a carbon material, a binder, and a solvent can be obtained by dispersing the carbon material and the binder in a solvent. When dispersing, dispersers, mixers, etc. commonly used for pigment dispersion can be used.

[0031] For example, mixers such as disper, homomixer, or planetary mixer; homogenizers such as "Claremix" manufactured by M Technique Co., Ltd. or "Filmix" manufactured by PRIMIX Corporation; media type dispersers such as paint shaker (manufactured by Red Devil), ball mill, sand mill (such as "Dynomill" manufactured by Shinmaru Enterprises Co., Ltd.), attritor, pearl mill (such as "DCP mill" manufactured by Eriez), or coball mill; media - less dispersers such as wet jet mill (such as "Genius PY" manufactured by Genesys, "Starburst" manufactured by Sugino Machine, "Nanomizer" manufactured by Nanomizer Co., Ltd.), "Clare SS - 5" manufactured by M Technique Co., Ltd., or "MICROS" manufactured by Nara Machinery Co., Ltd.; or other roll mills, etc., but not limited thereto. Also, as the disperser, it is preferable to use one that has been subjected to a treatment to prevent metal mixing from the disperser.

[0032] For example, when using a media type disperser, it is preferable to use a disperser in which the agitator and the vessel are made of ceramic or resin. When the agitator and the vessel are made of metal, it is preferable to use a disperser in which their surfaces are treated such as tungsten carbide spraying or resin coating. As the media, it is preferable to use glass beads or ceramic beads such as zirconia beads or alumina beads. Also, when using a roll mill, it is preferable to use a ceramic roll. Only one type of disperser may be used, or a combination of multiple types of dispersers may be used.

[0033] In addition, a general dispersant can be added together to the paste composition in order to improve the wettability and dispersibility of the carbon material in the solvent. As the dispersant, it is preferable to use an aqueous dispersant or an organic solvent-based dispersant suitable for the solvent contained in the paste composition, and two or more types may be used in combination.

[0034] Commercially available aqueous dispersants are not particularly limited. For example, as dispersants manufactured by BYK Chemie, DISPERBYK-180, 184, 187, 190, 191, 192, 193, 194, 199, 2010, 2012, 2015, 2096, etc. can be mentioned; as dispersants manufactured by Lubrizol Japan, SOLSPERSE12000, 20000, 27000, 41000, 41090, 43000, 44000, or 45000, etc. can be mentioned; as dispersants manufactured by BASF Japan, JONCRYL67, 678, 586, 611, 680, 682, 683, 690, 60, 61, 62, 63, HPD-96, Luvitec K17, K30, K60, K80, K85, K90, VA64, etc. can be mentioned; as dispersants manufactured by Kawaken Fine Chemicals, Hinolact A-110, 300, 303, or 501, etc. can be mentioned; as dispersants manufactured by Nitto Boseki Medical, PAA series, PAS series, amphoteric series PAS-410C, 410SA, 84, 2451, or 2351, etc. can be mentioned; as dispersants manufactured by ISP Japan, polyvinylpyrrolidone PVP K-15, K-30, K-60, K-90, or K-120, etc. can be mentioned; as dispersants manufactured by Maruzen Petrochemical, polyvinylimidazole PVI, etc. can be mentioned.

[0035] Examples of commercially available solvent-based dispersants are not particularly limited. For example, as dispersants manufactured by BYK-Chemie, Anti-Terra-U, U100, 204, DISPERBYK-101, 102, 103, 106, 107, 108, 109, 110, 111, 140, 161, 163, 168, 170, 171, etc. can be mentioned. As dispersants manufactured by Lubrizol Japan, SOLSPERSE3000, 5000, 9000, 13240, 13650, 13940, 17000, 18000, 19000, 21000, 22000, 24000SC, 24000GR, 26000, 28000, 31845, 32000, 32500, 32600, 33500, 34750, 35100, 35200, 36600, 37500, 38500, or 53095 can be mentioned. As dispersants manufactured by Ajinomoto Fine-Techno, Ajisper PB821, PB822, PN411, or PA111 can be mentioned. As dispersants manufactured by Kawaken Fine Chemicals, Hinacto KF-1000, 1300M, 1500, T-6000, 8000, 8000E, or 9100, etc. can be mentioned. As dispersants manufactured by BASF Japan, Luvicap, etc. can be mentioned.

[0036] In addition, the dispersant may contain a resin-type dispersant as a resin component other than the binder resin. For example, polymer compounds containing polysaccharide resins such as acrylic resin, polyurethane resin, polyester resin, polyamide resin, polyimide resin, polyallylamine resin, phenol resin, epoxy resin, phenoxy resin, urea resin, melamine resin, alkyd resin, formaldehyde resin, silicone resin, fluororesin, carboxymethylcellulose, etc. can be mentioned. These dispersants can also be used alone or in combination of two or more.

[0037] Next, a method for producing a conductive coating film from a paste composition containing a carbon material, a binder, and a solvent will be described. The conductive coating film applied to this embodiment can be formed by printing or coating a paste composition containing a carbon material, a binder, and a solvent on an insulating substrate, and further performing a pressing treatment or the like as necessary.

[0038] As a method of printing or coating a paste composition on an insulating substrate, there is no particular limitation. For example, general methods such as screen printing, inkjet printing, flexographic printing, offset printing, gravure printing, gravure offset printing, knife coater, bar coater, blade coater, spray, dip coater, spin coater, roll coater, comma coater, die coater, curtain coater, etc. can be applied. After printing or coating, it is preferable to perform a drying process. Examples of the drying device include known drying devices such as a hot air oven, an infrared oven, a microwave oven, and a combined oven combining these ovens.

[0039] Also, after drying, a rolling process may be performed using a lithographic press or a calendar roll, etc. In order to soften the conductive coating film and make it easier to press, it may be performed while heating.

[0040] The insulating substrate is not particularly limited, and examples include a polyimide film, a polyparaphenylene terephthalamide film, a polyether nitrile film, a polyether sulfone film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polybutylene terephthalate film, a polycarbonate film, a polyvinyl chloride film, and a polyacrylic film.

[0041] The thickness of the substrate is not particularly limited, but is about 30 to 350 μm, and more preferably 50 to 250 μm. With the thickness in the above range, the mechanical properties, shape stability, dimensional stability, and handling surface, etc. of the substrate are likely to be appropriate.

[0042] The thickness of the conductive coating film is usually preferably 1 to 50 μm. If the thickness is less than 1 μm, the conductivity will be insufficient, and if the thickness is greater than 50 μm, the amount of energy required for laser grooving will increase, and peeling or heat sagging, etc. will occur in the non-laser irradiated part.

[0043] Next, a method for forming a fine pattern by performing laser grooving on a conductive coating film containing a carbon material and a binder formed on an insulating substrate will be described.

[0044] The laser light used in the present invention has a wavelength of 700 nm or less. For example, excimer lasers (wavelength of fundamental wave: 193 to 308 nm), second harmonics (532 nm) and third harmonics (355 nm) of YVO4 lasers (wavelength of fundamental wave: 1064 nm), second harmonics (532 nm) and third harmonics (355 nm) of YAG lasers (wavelength of fundamental wave: 1064 nm), and semiconductor lasers, etc. can be mentioned. When the laser wavelength becomes larger than 700 nm, when performing grooving with a groove width on the order of several tens of micrometers, resin components such as binders may cause thermal sag, and the upper end surface of the groove may become a smooth shape, which is not preferable. Further, when the laser wavelength is 700 nm or less, in the UV region such as the third harmonic, the insulating substrate may be damaged. Therefore, a wavelength region (500 to 570 nm) called a green laser such as the second harmonic is more preferable.

[0045] The processing conditions such as the average output, output intensity, spot diameter, presence or absence of defocus, repetition frequency, and scan speed when using the laser light may be any conditions as long as the conductive coating film can be removed, and are not limited, but can be defined by the energy density represented by the following formula. Energy density = (average output × output intensity) / repetition frequency / spot area The energy density shown in the above formula represents the amount of energy per unit area at the laser spot. The energy density is preferably 1 to 20 J / cm 2 When it is lower than 1 J / cm 2 grooving may be insufficient, and when it is higher than 20 J / cm 2 damage to the substrate and unirradiated portions may increase. More preferably, it is 2 to 10 J / cm 2 ​When using a laser marker with a defocus function, the spot diameter can be adjusted, and the spot area can be controlled. Also, by adjusting the scanning speed, the amount of energy irradiated can be controlled. In addition, the scanning (printing) of the laser beam can be repeated multiple times. It is preferable to print a smaller amount of energy in multiple times rather than applying the amount of energy required for the target pattern formation in a single print, because a fine pattern with excellent grooving properties can be obtained.

[0046] The fine conductive pattern on the insulating substrate obtained by the formation method of the present invention is useful for high definition of signal wiring of electronic devices, and can also be used as an electrode for high-performance biosensors.

[0047] The biosensor is not particularly limited as long as it utilizes the molecular recognition ability of biological materials such as microorganisms, enzymes, and antibodies, and uses the biological material as a molecular recognition element to form an electrochemical measurement device. Examples include enzyme sensors, microorganism sensors, and immunosensors.

Examples

[0048] Hereinafter, the present invention will be described more specifically by way of examples. However, the following examples do not limit the scope of the present invention in any way. In the examples and comparative examples, "parts" represents "parts by mass" and "%" represents "% by mass".

[0049] <Preparation Example of Conductive Carbon Paste> [Preparation Example 1] 20 parts of natural flaky graphite UP-10N (manufactured by Nippon Graphite Co., Ltd., average particle diameter 10 μm), 3 parts of furnace black VULCAN (registered trademark) XC72 (manufactured by CABOT), 4 parts (solid content 50%) of an emulsion type acrylic resin dispersion solution (manufactured by Toyochem Co., Ltd.: W-168) as a binder, 50 parts of an aqueous carboxymethyl cellulose solution (solid content 2%) as a dispersant, and 50 parts of water as a solvent were put into a mixer and mixed, and then put into a sand mill for dispersion to obtain conductive carbon paste (1).

[0050] [Preparation Example 2] A conductive carbon paste (2) was obtained in the same manner as in Preparation Example 1, except that natural flaky graphite CB-150 (manufactured by Nippon Graphite Co., average particle diameter 40 μm) was used instead.

[0051] The manufacturing method of the conductive coating film and the evaluation method of the laser grooving property in the following Examples 1 to 8 and Comparative Examples 1 and 2 are shown. [Manufacture of Conductive Coating Film] A conductive carbon paste was applied to a 100-μm-thick polyethylene terephthalate film (Lumirror T60 manufactured by Toray Industries, Inc.) as a substrate using an applicator, and dried in an oven at 80°C for 60 minutes to obtain a conductive coating film with a thickness of about 20 μm. The film thickness at this time was calculated by measuring a sheet composed of the substrate and the conductive coating film using a contact-type film thickness measuring device (Nikon MS-5C) and subtracting the measured value of the substrate alone.

[0052] [Evaluation of Laser Grooving Property] For the obtained conductive coating film, laser grooving was performed using a laser marker for the purpose of forming a fine pattern (line / space = 50 μm / 50 μm, 10 spaces, length 200 mm) as shown in FIG. 2. The laser processing conditions were optimized according to the laser marker used. Arbitrary 100 locations were selected in 8 of the 10 spaces formed, excluding the two ends of the 10 spaces, and the groove shape was observed with a scanning confocal laser microscope (Olympus OLS3000). Then, the upper groove width (W1), the bottom groove width (W2), and the groove depth (D) as shown in FIG. 3 were measured, and the average value (A) and standard deviation of the upper groove width, the average value (B) and standard deviation of the bottom groove width, and the difference between the upper and bottom groove widths were calculated. The evaluation of the grooving property was determined according to the following criteria. 〇: Standard deviation is 0 to 2.0 μm, and the difference in groove width is 0 to 22 μm. Good. △: Standard deviation is 2.1 to 2.5 μm, or the difference in groove width is 23 to 30 μm. No problem in practical use. ×: Standard deviation is 2.6 or more, or the difference in groove width is 31 μm or more. Not practical.

[0053] [Examples 1 - 5] A conductive coating film was prepared from the conductive carbon paste (1), and using a green laser marker (Keyence Corporation's MD - S9910), the fine patterns shown in FIGS. 1 and 2 were formed under the laser processing conditions shown in Table 1.

[0054] [Example 6] A conductive coating film was prepared from the conductive carbon paste (2), and using a green laser marker (Keyence Corporation's MD - S9910), the fine patterns shown in FIGS. 1 and 2 were formed under the laser processing conditions shown in Table 1.

[0055] [Examples 7 - 8] A conductive coating film was prepared from the conductive carbon paste (1), and using a UV laser marker (Keyence Corporation's MD - U1000C), the fine patterns shown in FIGS. 1 and 2 were formed under the laser processing conditions shown in Table 1.

[0056] [Comparative Examples 1 - 2] A conductive coating film was prepared from the conductive carbon paste (1), and using a hybrid laser marker (Keyence Corporation's MD - X2500), the fine patterns shown in FIGS. 1 and 2 were formed under the laser processing conditions shown in Table 1.

[0057]

Table 1

[0058]

Table 2

[0059] The evaluation results of the laser grooving properties of the above - mentioned examples and comparative examples are shown in Table 2. In Examples 1 to 3 and 5, the standard deviation of each groove width at the top and bottom was less than 2.0 μm, and the difference between the groove widths at the top and bottom was also less than 22 μm, so good grooves were formed. Comparing the results of Examples 1 and 5, which have the same energy density but different scan speeds, it can be seen that the standard deviation and difference in groove width increase when the scan speed is increased. In addition, in Example 4, in which the energy density was increased to more than twice that of Example 1, the difference in groove width at the upper and lower portions was large, but this was determined to be at a level that would not cause any practical problems. In Example 6, in which a conductive coating made of conductive carbon paste (2) using natural graphite with an average particle size about four times larger than that of the natural graphite used in the conductive carbon paste (1) was laser processed, the standard deviations of the grooves at the top and bottom were large, but this was determined to be at a level that would not be a problem in practical use. The reason for the large standard deviation is thought to be that large graphite particles protrude unevenly like burrs from the end faces of the grooves.

[0060] In Examples 7 and 8, which were made using a UV laser marker, the standard deviation of the groove widths at the top and bottom was good, but the difference between the groove widths at the top and bottom was large. However, this was judged to be at a level that would not cause any problems in practical use.

[0061] On the other hand, in Comparative Examples 1 and 2, in which a laser marker with a wavelength of 1064 nm was used, the standard deviation of the groove widths at the top and bottom, and the difference between the groove widths at the top and bottom were both very large values, and were judged to be at a level that was not practical. In particular, since the top end surface of the groove has a gentle shape, the groove width at the top becomes very large, resulting in a significant reduction in the amount of coating film at the line portion. This is presumably due to the heat generated by the laser, which causes a state similar to resin dripping. This effect is also reflected in the size of the standard deviation of the groove widths at the top and bottom, so it is considered difficult to form a fine pattern of about 50 μm with a laser marker with a wavelength of 1064 nm.

[0062] [Example 9] <Preparation of electrodes for biosensors> A conductive carbon paste (1) was used to fabricate a conductive coating film in the same manner as in Example 1. For the obtained conductive coating film, an electrode pattern shown in FIG. 4 was formed using a green laser marker (Keyence MD-S9910) (the white part is the part to be grooved, S = 50 μm, L1 = L2 = 200 μm, L3 = 100 μm). The laser processing conditions were an energy density of 5.9 J / cm 2 2, and a scanning speed of 400 mm / s. Next, using a CO2 laser marker (average output 30 W, laser wavelength 10.6 μm: Keyence ML-Z9510), laser cutting was performed along the dotted line part shown in FIG. 4 to obtain an electrode chip. The laser processing conditions were an output intensity of 16%, a scanning speed of 100 mm / s, and the number of printing times of 3 times.

[0063] For the obtained electrode chip, as shown in FIG. 5, each part serving as the working electrode 6, reference electrode 7, and counter electrode 8 was defined by masking with an insulating tape. A silver / silver chloride paste (silver / silver chloride ink for reference electrode; manufactured by BAS) was applied to the part of the reference electrode 7 to form a reference electrode.

[0064] <Electrochemical Evaluation> The responsiveness of the electrode chip was evaluated by cyclic voltammetry measurement. The three-electrode (working electrode 6, reference electrode 7, counter electrode 8) side of the electrode chip was immersed in an electrolytic cell containing 0.1 M phosphate buffer (pH 7.0) in which 5 mM potassium ferricyanide was dissolved, and connected to a potentiostat via a connection terminal from the opposite side. When measured under the conditions of a scanning range of -0.7 V to +0.7 V and a scanning speed of 10 mV / s with the reference electrode as a reference, distinct oxidation-reduction peaks were confirmed. That is, an electrode chip having a fine pattern shape with a space between lines constituting the three electrodes of several tens of μm fabricated by the fine pattern forming method of the present invention is considered to function as an electrode for a biosensor.

Explanation of Reference Numerals

[0065] 1 Sheet composed of a substrate and a conductive coating film 2 Fine pattern 3 Line part 4 Space part 5 Insulating tape 6 Working electrode 7 Reference electrode 8 Counter electrode 9 Substrate

Claims

1. A method for forming a conductive fine pattern on an insulating substrate, comprising: forming a conductive coating film (excluding those containing metal powder) containing a carbon material and a binder on the insulating substrate, wherein the carbon material contains graphite, and subjecting the conductive coating film to grooving by irradiating it with a green laser having a wavelength of 500 to 570 nm. A method for forming a fine pattern, characterized by this.

2. The method for forming a fine pattern according to claim 1, wherein the conductive coating film is a coating film formed from a paste composition containing a carbon material, a binder, and a solvent, and the carbon material contains graphite.

3. The method for forming a fine pattern according to claim 1 or 2, wherein the fine pattern is an electrode pattern for a biosensor.

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