METHOD FOR FORMING METAL PATTERN

Abstract

The present invention relates to a method for forming a metal pattern on a pattern formation section set on a base material. In the present invention, a substrate provided with a fluorine-containing resin layer on a surface of the base material including the pattern formation section is used. The present inventive method for forming a metal pattern includes steps of: forming a functional group on the pattern formation section; and applying a metal ink including an amine compound and a fatty acid as protective agents to the base material surface to fix the metal particles on the pattern formation section. In the present invention, a fluorine-containing resin having a surface free energy measured by the Owens-Wendt method of 13 mN/m or more and 20 mN/m or less is applied as the fluorine-containing resin layer. Further, a metal ink including ethyl cellulose as an additive is applied as the metal ink.

Claims

1. A method for forming a metal pattern on a pattern formation section set in a part or the whole of a region on a base material, the base material comprising a fluorine-containing resin layer on a surface including at least the pattern formation section, the method comprising: a step of forming a functional group on the pattern formation section on the surface of the fluorine-containing resin layer; and a step of applying a metal ink in which metal particles protected by an amine compound serving as a first protective agent and a fatty acid serving as a second protective agent are dispersed in a solvent to the surface of the base material to fix the metal particles on the pattern formation section, wherein the fluorine-containing resin layer comprises a fluorine-containing resin having a surface free energy measured by the Owens-Wendt method of 13 mN/m or more and 20 mN/m or less, and the metal ink comprises ethyl cellulose as an additive.

2. The method for forming a metal pattern according to claim 1, wherein ethyl cellulose serving as the additive of the metal ink is a low-molecular weight ethyl cellulose having a number average molecular weight of 4,000 to 30,000.

3. The method for forming a metal pattern according to claim 1, wherein in the step of forming a functional group on the surface of the fluorine-containing resin layer, an energy of 1 mJ/cm.sup.2 or more and 4,000 mJ/cm.sup.2 or less is applied to the pattern formation section of the surface of the fluorine-containing resin layer.

4. The method for forming a metal pattern according to claim 1, wherein at least one of a carboxy group, a hydroxy group, and a carbonyl group is formed as the functional group.

5. The method for forming a metal pattern according to claim 1, wherein the amine compound serving as the first protective agent comprises at least one amine compound having 4 or more and 12 or less carbon atoms.

6. The method for forming a metal pattern according to claim 5, wherein the amine compound is at least one of butylamine, 1,4-diaminobutane, 3-methoxypropylamine, pentylamine, 2,2-dimethylpropylamine, 3-ethoxypropylamine, N,N-dimethyl-1,3-diaminopropane, hexylamine, heptylamine, benzylamine, N,N-diethyl-1,3-diaminopropane, octylamine, 2-ethylhexylamine, nonylamine, decylamine, diaminodecane, undecylamine, dodecylamine, and diaminododecane.

7. The method for forming a metal pattern according to claim 1, wherein the fatty acid serving as the second protective agent comprises at least one fatty acid having 4 or more and 26 or less carbon atoms.

8. The method for forming a metal pattern according to claim 7, wherein the fatty acid is at least one of oleic acid, stearic acid, linoleic acid, lauric acid, butanoic acid, and erucic acid.

9. The method for forming a metal pattern according to claim 1, wherein the solvent of the metal ink is an alcohol solvent having 3 or more and 8 or less carbon atoms, a hydrocarbon solvent having 6 or more and 10 or less carbon atoms, or a mixed solvent of these solvents.

10. The method for forming a metal pattern according to claim 1, comprising a step of heating the base material at a temperature of 40° C. or more and 250° C. or less after fixing the metal particles on the pattern formation section.

11. The method for forming a metal pattern according to claim 1, wherein the metal particles comprise at least one of silver, gold, platinum, palladium, copper, and an alloy of these metals.

12. The method for forming a metal pattern according to claim 2, wherein in the step of forming a functional group on the surface of the fluorine-containing resin layer, an energy of 1 mJ/cm.sup.2 or more and 4,000 mJ/cm.sup.2 or less is applied to the pattern formation section of the surface of the fluorine-containing resin layer.

13. The method for forming a metal pattern according to claim 2, wherein at least one of a carboxy group, a hydroxy group, and a carbonyl group is formed as the functional group.

14. The method for forming a metal pattern according to claim 3, wherein at least one of a carboxy group, a hydroxy group, and a carbonyl group is formed as the functional group.

15. The method for forming a metal pattern according to claim 2, wherein the amine compound serving as the first protective agent comprises at least one amine compound having 4 or more and 12 or less carbon atoms.

16. The method for forming a metal pattern according to claim 3, wherein the amine compound serving as the first protective agent comprises at least one amine compound having 4 or more and 12 or less carbon atoms.

17. The method for forming a metal pattern according to claim 4, wherein the amine compound serving as the first protective agent comprises at least one amine compound having 4 or more and 12 or less carbon atoms.

18. The method for forming a metal pattern according to claim 2, wherein the fatty acid serving as the second protective agent comprises at least one fatty acid having 4 or more and 26 or less carbon atoms.

19. The method for forming a metal pattern according to claim 3, wherein the fatty acid serving as the second protective agent comprises at least one fatty acid having 4 or more and 26 or less carbon atoms.

20. The method for forming a metal pattern according to claim 4, wherein the fatty acid serving as the second protective agent comprises at least one fatty acid having 4 or more and 26 or less carbon atoms.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0076] FIG. 1 is an enlarged photograph of a silver wiring in which the fluorine-containing resin No. 2 is applied in the formation of a metal pattern of Second Embodiment; and

[0077] FIG. 2 is an enlarged photograph of a silver wiring in which the fluorine-containing resin No. 3 is applied in the formation of a metal pattern of Second Embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0078] First Embodiment (preliminary test): Hereinafter, a preferred embodiment of the present invention will be described. The present embodiment is a preliminary test for determining a preferred fluorine-containing resin and metal ink in the formation of a metal pattern. In this preliminary test, a resin film was used as the base material, and a plurality of fluorine-containing resins was applied to the base material to form fluorine-containing resin layers. Then, the surface free energy of the plurality of fluorine-containing resin layers was measured by the Owens-Wendt method. Then, two inks, that is, an ethyl cellulose-containing ink applicable to the present invention and the metal ink used in the conventional process (Patent Document 1) were applied to the plurality of fluorine-containing resins formed and the availability of printing (presence or absence of ink repellency) was evaluated.

[0079] [Formation of Fluorine-Containing Resin Layer]

[0080] A resin base material (size: 400 mm×200 mm) including polyethylene terephthalate (PET) was prepared as the base material. The following commercially available fluorine-containing resins were applied to this base material to form fluorine-containing resin layers.

TABLE-US-00001 TABLE 1 Product name (model number) Manufacturer No. 1 PC-3B + FG-5083F130-0.1 FluoroTechnology Co., LTD. No. 2 FS-1010C-4.0 FluoroTechnology Co., LTD. No. 3 Novec1720 3M Japan Limited No. 4 3% SA-PFA/HFX110 Chemours-Mitsui Fluoroproducts Co., Ltd. No. 5 SFE-DP02H AGC SEIMI CHEMICAL CO., LTD. No. 6 CYTOP M + CYTOP A AGC Inc.
For No. 1, PC-3B was applied and then FG-5083F130-0.1 was applied on PC-3B.
For No. 6, CYTOP M and CYTOP A were mixed and then applied.

[0081] In the formation of fluorine-containing resin layers with the fluorine-containing resins No. 2 to No. 6, 2004 of each of fluorine-containing resin was applied to the base material by a roll coating method, and the base material was heated and dried at 110° C. for 7 minutes. For the fluorine-containing resin No. 1, 2004 of PC-3B was applied to the base material by a roll coating method, and the base material was dried at 60° C. for 7 minutes, and further, 2004 of FG-5083F130-0.1 was applied to the base material by a roll coating method, and the base material was heated and dried at 110° C. for 7 minutes.

[0082] Measurements of the surface free energy (γ.sub.s) by the Owens-Wendt method were performed on the produced various fluorine-containing resin layers. As mentioned above, the contact angles of two kinds of liquids whose γ.sub.L, γ.sub.L.sup.d, γ.sub.L.sup.h in Expression 1 are known were measured by the Owens-Wendt method. In the present embodiment, water and n-octane were used as specimens, and the contact angle of each liquid to each fluorine-containing resin layer was measured. Measurement conditions were such that 4±0.5 μL of a specimen was dropped on the surface of a fluorine-containing resin layer in an atmosphere of a temperature of 20 to 21° C. and a humidity of 25 to 35% and the contact angle after a lapse of 10 seconds was measured. The contact angle was measured by a drop method with a contact angle meter (DMs-401 manufactured by Kyowa Interface Science Co., Ltd.). In the drop method, a droplet is landed on the surface of a fluorine-containing resin layer, the states before and after landing were taken from a side with an optical camera attached to the meter, and the angle between the droplet after a lapse of 10 seconds and the surface of the specimen was measured as the contact angle θ. In the present embodiment, each fluorine-containing resin was measured at 5 points and the average value thereof was employed. Then, the contact angle between water and n-octane in each fluorine-containing resin was substituted in the above expression of Expression 3 and γ.sub.s.sup.d and γ.sub.s.sup.h were calculated, whereby the surface free energy (γ.sub.s) was determined. Into the values γ.sub.L, γ.sub.L.sup.d, and γ.sub.L.sup.h at liquid side which are required for calculation, γ.sub.L(w)=72.8 mN/m, γ.sub.L(w).sup.d=21.8 mN/m, and γ.sub.L(w).sup.h=51.0 mN/m were substituted as the values of water, and γ.sub.L(o)=21.6 mN/m, γ.sub.L(o).sup.d)=21.6 mN/m, and γ.sub.L(o).sup.h)=21.6 mN/m) were substituted as the values of n-octane. The surface free energy (γ.sub.s) of the fluorine-containing resins No. 1 to No. 6 was as follows.

TABLE-US-00002 TABLE 2 Product name (model number) γ.sub.s.sup.d (mN/m) γ.sub.s.sup.h (mN/m) γ.sub.s (mN/m) No. 1 PC-3B + FG-5083F130-0.1 20.56 2.57 23.13 No. 2 FS-1010C-4.0 13.92 0.02 13.94 No. 3 Novec1720 18.70 1.79 20.49 No. 4 3% SA-PFA/HFX110 15.54 2.31 17.85 No. 5 SFE-DP02H 13.58 1.20 14.78 No. 6 CYTOP M + CYTOP A 18.80 0.65 19.45

[0083] [Production of Metal Ink]

[0084] In the present embodiment, silver inks in which silver particles are dispersed were used as metal inks. The silver ink was produced by producing silver particles that use a thermally decomposable silver compound as the raw material by a thermal decomposition method and dispersing these silver particles in a solvent. In the present embodiment, two inks, that is, an ethyl cellulose-containing silver ink of the present invention (hereinafter referred to as KK ink) and the metal ink used in Patent Document 1 (hereinafter referred to as TG ink) were produced.

[0085] [Production of KK Ink]

[0086] For the silver compound serving as the raw material, silver carbonate was used. First, 25.56 g of silver carbonate (silver content: 20.56 g) and 9.32 g of water (33 wt % with respect to 100 parts by weight of silver carbonate) were mixed and stirred. Next, 3-methoxypropylamine as an amine compound serving as a protective agent was added to the silver compound at a 6-fold molar ratio with respect to the silver mass in the silver compound, whereby a silver-amine complex was produced.

[0087] Then, the produced silver-amine complex was heated from room temperature and decomposed to precipitate silver particles. Regarding the heating temperature at this time, the decomposition temperature of the complex was assumed to be 110 to 130° C., and this decomposition temperature was determined as the arrival temperature. The heating rate was set to 10° C./min. Thereafter, methanol was added to wash the silver particles, which were then centrifuged. The washing and centrifugation were repeated twice. The particle size of the silver particles was found to be 120 nm in mean particle size, from the results of SEM observations.

[0088] The obtained silver particles were mixed with a mixed solvent of octane and 1-propanol (octane:1-propanol=7:3), and 3,500 ppm of hexylamine (0.115 mmol/g based on the metal mass) and 650 ppm of dodecylamine (0.0117 mmol/g based on the metal mass) which are amine compounds serving as protective agents, and further, 800 ppm of erucic acid (0.00787 mmol/g based on the metal mass) which is a fatty acid were added to the mixture. This solution was treated with a vibrator (CUTE MIXER CM 1000 manufactured by TOKYO RIKAKIKAI CO, LTD) at 1,800 Hz for 30 minutes, and then centrifuged, and the supernatant was removed. Thereafter, ethyl cellulose was added to obtain a metal ink. The addition of ethyl cellulose was performed by mixing a solution in which ethyl cellulose (NISSHIN-KASEI CO., LTD., trade name: ETHOCEL 7 (number average molecular weight: about 17,000) was dissolved with a mixed solvent of octane and 1-propanol. At this time, the amount of mixed solvent and ethyl cellulose was adjusted such that the content of ethyl cellulose is 1% by mass with respect to the metal ink and the content of silver is 35% by mass with respect to the metal ink. Finally, this solution was treated with a vibrator at 1,800 Hz for 10 minutes to obtain a milky silver ink (KK ink).

[0089] [Production of TG Ink]

[0090] In the production of the TG ink (Patent Document 1), silver oxalate was used as the silver compound serving as the raw material. To 1.519 g of silver oxalate serving as the raw material (silver: 1.079 g), 0.651 g of decane was added to wet silver oxalate. Then, an amine compound and a fatty acid serving as protective agents were added to this silver oxalate. Specifically, first, N,N-dimethyl-1,3-diaminopropane (0.778 g) was added and kneaded for some time, and then, hexylamine (1.156 g), dodecylamine (0.176 g), and oleic acid (0.042 g) were further added thereto and kneaded, and thereafter, the mixture was heated and stirred at 110° C. This heating and stirring operation was performed until no bubble was generated from the reaction system. After the end of the reaction, the reaction system was allowed to cool to room temperature, and methanol was added thereto and thoroughly stirred, which was subjected to centrifugation. An excessive amount of protective agent was thereby removed to purify silver particles. The addition of methanol and the purification of silver fine particles by centrifugation were repeated to obtain silver particles as precipitates. The particle size of these silver particles was 15 nm in mean particle size.

[0091] To the produced silver particles, a mixed solvent of octane and butanol (octane:butanol=4:1 (volume ratio)) was added to obtain a silver ink. The silver concentration of this silver ink was 40% by mass.

[0092] [Evaluation of Liquid-Repellency of Each Fluorine-Containing Resin]

[0093] Two kinds of silver inks produced as described above (KK ink and TG ink) were applied to the fluorine-containing resin layers No. 1 to No. 6, whereby the liquid-repellency was evaluated and the availability of printing by each silver ink was examined. In this evaluation method, the silver ink was applied to the base material (fluorine-containing resin layer) by a roll coating method and the total light transmittance (T.T) of the base material after application was measured. When the fluorine-containing resin layer exerts liquid-repellency to the silver ink, the silver ink is repelled, so that no silver ink remains on the surface of the fluorine-containing resin layer after passing of rolls and the base material is not colored. Thus, the difference between the transmittances before and after application (ΔT.T) becomes lower. In contrast, when the liquid-repellency of the fluorine-containing resin layer to the silver ink is poor, silver ink remains on the surface and the base material is colored.

[0094] Specific evaluation conditions of this test were determined in accordance with JIS K7316-1 (Plastics-Determination of the total luminous transmittance of transparent materials). The amount of silver ink applied was 40 μL, and each sample was measured at three points (measurement point area ϕ50 mm). The total light transmittance (T.T) of the base material was measured with SH7000 manufactured by NIPPON DENSHOKU INDUSTRIES Co., Ltd. With respect to the measured difference between the transmittances before and after application (ΔT.T), one having a value of −4.5≤ΔT.T≤0 was judged as “no coloration” and considered good (◯), one having a value of −10.0≤ΔT.T<−4.5 was determined as “slightly colored” (Δ). When the value was ΔT.T<−10.0, the layer was judged as “entirely colored” and determined as failed (x). Table 3 shows the evaluation results of the liquid-repellency (printability) of the above.

TABLE-US-00003 TABLE 3 Liquid-repellency evaluation result Product name γ.sub.s Silver Judge- (model number) (mN/m) ink Δ T.T ment No. 1 PC-3B + FG-5083F130-0.1 23.13 KK INK  −5.55 Δ TG INK −65.99 x No. 2 FS-1010C-4.0 13.94 KK INK  −3.70 ○ TG INK −45.22 x No. 3 Novec1720 20.49 KK INK   23.01 x TG INK −65.15 x No. 4 3% SA-PFA/HFX110 17.85 KK INK  −2.75 ○ TG INK −67.05 x No. 5 SFE-DP02H 14.78 KK INK  −2.73 ○ TG INK −73.57 x No. 6 CYTOP M + CYTOP A 19.45 KK INK    2.36 ○ TG INK    2.40 ○

[0095] Table 3 shows that the fluorine-containing resins evaluated this time were, except for CYTOP (registered trademark) of No. 6, poor in liquid-repellency to the conventional silver ink (TG ink), and the ink remained on the surface of the base material and colored the base material. Consequently, it was confirmed that the conventional process has a problem as described above.

[0096] The fluorine-containing resin layers No. 1 to No. 5 will be examined. These fluorine-containing resin layers were found to exert preferred liquid-repellency in association with the fluorine-containing resin layers No. 2, 4, and 5, when the silver ink including ethyl cellulose (KK ink) to be applied in the present invention was applied. The fluorine-containing resin layers No. 2, 4, and 5 have a surface free energy (γ.sub.s) of 20 or less. It is found from the results that the preferred liquid-repellency is generated by the cooperation between the fluorine-containing resin having moderate liquid-repellency (surface free energy) and the silver ink which became less wettable due to ethyl cellulose, so that the printability is improved.

[0097] On the other hand, the fluorine-containing resin layers No. 1 and 3 have a surface free energy (γ.sub.s) of more than 20 mN/m, and it is deemed that they are resins having low liquid-repellency among the fluorine-containing resins examined this time. It is deemed that these fluorine-containing resin layers are poor in liquid-repellency and printability even by applying the silver ink containing ethyl cellulose (KK ink) as well as the silver ink containing no ethyl cellulose (TG ink).

[0098] The fluorine-containing resin layer (CYTOP (registered trademark)) No. 6 exhibits liquid-repellency to both silver inks. This fluorine-containing resin is also deemed to be applicable to the present invention. As can be seen from the values of the surface free energy (γ.sub.s) of the fluorine-containing resins examined this time, the fluorine-containing resin layers No. 2, 4, and 5 have lower free energy (γ.sub.s) values than CYTOP (registered trademark) of No. 6. Accordingly, it is deemed that the fluorine-containing resin layers No. 2, 4, and 5 have higher liquid-repellency based on water and n-octane than CYTOP (registered trademark). However, the liquid-repellency of the fluorine-containing resin layers No. 2, 4, and 5 is insufficient for the conventional silver ink (TG ink). When the silver ink containing ethyl cellulose (KK ink) of the present invention is applied, the liquid-repellency of the fluorine-containing resin layers No. 2, 4, and 5 improves. However, even the silver ink (KK ink) of the present invention cannot be applied to the fluorine-containing resins (No. 1 and 3) having free energy (γ.sub.s) values of more than 20 mN/m. Thus, it is deemed that, in the metal pattern formation process of the present invention, the effect was produced through optimization of the basic liquid-repellency of the fluorine-containing resin and the characteristics of the metal ink.

[0099] Second Embodiment: In the present embodiment, four kinds of fluorine-containing resins No. 2 to No. 5 of First Embodiment were used to perform study tests of the formation or non-formation of a metal pattern.

[0100] [Formation of Metal Pattern]

[0101] The same PET substrate as in First Embodiment was prepared, and after 200 μL of each fluorine-containing resin was applied to the base material by a roll coating method, the base material was heated and dried at 110° C. for 7 minutes to form a fluorine-containing resin layer, similarly to First Embodiment.

[0102] Next, a photomask having a linear wiring pattern (line width: 20 μm) was brought into contact with the surface of the substrate on which a fluorine-containing resin layer was formed (contact exposure with a mask-substrate distance of 0), and this was irradiated with an ultraviolet ray (VUV light). The VUV light was applied at 11 mW/cm.sup.−2 with a wavelength of 172 nm for 5 seconds.

[0103] As described above, the metal ink was applied to the substrate on which a functional group was formed by subjecting the surface of the fluorine-containing resin layer to exposure treatment. As the metal ink, the KK ink containing ethyl cellulose which was produced in First Embodiment was applied. Application of the metal ink was performed by applying 40 μL of the ink to the substrate by a roll coater method. Thereafter, the substrate was hot air-dried at 120° C. to form a silver wiring (L/S=20 μm/20 μm).

[0104] [Evaluation of Metal Pattern]

[0105] The silver wiring formed as described above was observed with an optical microscope to check the presence or absence of blur of the wiring. The silver wiring having no blur was judged as passed “◯” and the silver wiring having blur or an obviously non-uniform line width was judged as failed “x”. In addition, the line width of the passed silver wiring was measured. The average value of the values obtained by measuring the line width at arbitrary three points with an optical microscope was determined as the line width of the silver wiring. Table 4 shows the evaluation results.

TABLE-US-00004 TABLE 4 Pattern formation result Average Product name γ.sub.s line width (model number) (mN/m) Silver ink Pass/fail (μm) No. 2 FS-1010C-4.0 13.94 KK INK ○ 19.45 No. 3 Novec1720 20.49 x — No. 4 3VoSA-PFA/HFX110 17.85 ○ 19.11 No. 5 SFE-DPO2H 14.78 ○ 19.36

[0106] It was confirmed from Table 3 that silver wiring with a good pattern can be formed by applying fluorine-containing resins No. 2, No. 4, and No. 5 which had good liquid-repellency in First Embodiment. FIG. 1 is an optical micrograph (×200 and 2,000) of the silver wiring to which the fluorine-containing resin No. 2 was applied. It can be confirmed that a clear silver wiring was formed. It can also be confirmed that a silver wiring having a line width approximate to a target line width can be formed by applying these fluorine-containing resins.

[0107] On the other hand, when the fluorine-containing resin No. 3 which had insufficient liquid-repellency in First Embodiment was applied, an entirely thin silver wiring was formed and measurement of the line width was impossible. FIG. 2(a) is an optical micrograph (×2,000) of a portion where a silver wiring was formed, but the outer edge of the wiring is unobvious and it is far from a wiring. In addition, since this fluorine-containing resin No. 3 has poor liquid-repellency, silver particles were adsorbed to non-exposed regions (region where no functional group is formed) (FIG. 2(b)). In such a state where silver particles adsorbed to portions other than wiring pattern, it cannot be deemed that a good pattern was formed. In addition, such a state may cause a short circuit and the function as wiring cannot be exerted.

INDUSTRIAL APPLICABILITY

[0108] As described above, a fine metal pattern can be efficiently formed by the present invention. With such an effect, the range of choice of the fluorine-containing resin that is the essential configuration in the present invention is widened. The present invention can be effectively applied to not only the formation of electrodes and wiring for various kinds of semiconductor devices, but also the formation of wiring on a panel surface of a touch panel that is required to have light transmissivity. Since the present invention can be implemented at low cost, it can be applied to a base material having a large area and can also be applied to building materials and the like.