Composition for forming protective film for electroconductive pattern, protective film for electroconductive pattern, method for producing protective film, and method for producing transparent electroconductive film

Abstract

A composition for a protective film for electroconductive patterns, including: (A) a polyurethane containing a carboxyl group; (B) an epoxy compound; (C) a curing accelerator; and (D) a solvent, wherein the percentage of the solvent (D) contained is from 95.0% to 99.9% by mass, and the solvent (D) contains (D1) a solvent containing a hydroxyl group and having a boiling point in excess of 100° C., and (D2) a solvent having a boiling point that does not exceed 100° C., wherein the content of the solvent (D2) having a boiling point that does not exceed 100° C. is 30% to less than 70% by mass of total solvent in total. The composition can be cured by heating at a temperature not exceeding 100° C. for a heating time not exceeding 10 minutes.

Claims

1. A composition for a protective film for a conductive pattern, comprising (A) a polyurethane containing a carboxyl group, (B) an epoxy compound, (C) a curing accelerator, and (D) solvent, wherein the content of the solvent (D) is 95.0% by mass or more and 99.9% by mass or less of the total composition, (D) comprises (D1) and (D2), (D1) being a solvent having a boiling point exceeding 100° C. and containing a hydroxyl group, (D2) being a solvent having a boiling point of 100° C. or lower, and the content of the solvent (D2) having the boiling point of 100° C. or lower is 30% by mass or more and less than 70% by mass of the solvent in total.

2. A composition for a protective film for a conductive pattern according to claim 1, wherein (D1) solvent having the boiling point exceeding 100° C. and containing a hydroxyl group is at least one selected from a group consisting of propylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, and ethyl lactate.

3. A composition for a protective film for a conductive pattern according to claim 1, wherein (D2) solvent having the boiling point of 100° C. or lower is at least one selected from a group consisting of propylene glycol dimethyl ether, isopropyl alcohol, t-butyl alcohol, and methyl ethyl ketone.

4. A composition for a protective film for a conductive pattern according to claim 2, wherein (D2) solvent having the boiling point of 100° C. or lower is at least one selected from a group consisting of propylene glycol dimethyl ether, isopropyl alcohol, t-butyl alcohol, and methyl ethyl ketone.

5. A composition for a protective film for a conductive pattern according to claim 2, wherein (D1) solvent having the boiling point exceeding 100° C. and containing a hydroxyl group is at least one of diethylene glycol monoethyl ether (EC) and propylene glycol monomethyl ether (PGME).

6. A composition for a protective film for a conductive pattern according to claim 3, wherein (D2) solvent having the boiling point of 100° C. or lower is isopropyl alcohol (IPA).

7. A protective film for a conductive pattern which is made of a cured product of the composition for the protective film for the conductive pattern according to claim 1, and which has a cure degree of 45 or more.

8. A method for producing a protective film, wherein the composition for the protective film for the conductive pattern according to claim 1 is cured at a temperature of 100° C. or lower and for a heating time of 10 minutes or less.

9. A method for producing a transparent conductive film comprising a step of forming the protective film on the transparent conductive film by the method according to claim 7.

10. A composition for a protective film for a conductive pattern according claim 1, wherein (A) polyurethane containing a carboxyl group is polyurethane synthesized by using (a1) a polyisocyanate compound, (a2) a polyol compound, and (a3) a dihydroxy compound containing a carboxyl group, as monomers, (a1) being an alicyclic compound having 6 to 30 carbon atoms other than the carbon atoms in the isocyanato group (—NCO group), (a2) being either polycarbonate polyol or polybutadiene polyol, and (a3) being either 2,2-dimethylolpropionic acid or 2,2-dimethylolbutanoic acid.

11. A composition for a protective film for a conductive pattern according claim 1, wherein (B) epoxy compound having two or more epoxy groups in one molecule is selected from a group consisting of: an amino group-containing epoxy resin, an aliphatic-type epoxy resin containing a glycidyl group, and an alicyclic epoxy resin containing a glycidyl group.

12. A composition for a protective film for a conductive pattern according claim 1, wherein the mixing ratio of (A) polyurethane containing a carboxyl group relative to (B) epoxy compound is 0.5 to 1.5, in terms of equivalent ratio of the carboxyl groups of polyurethane relative to the epoxy groups of (B) epoxy compound, and the used amount of (C) curing accelerator is 0.1 to 10% by mass relative to the total mass of (A) polyurethane containing a carboxyl group and (B) epoxy compound.

13. A composition for a protective film for a conductive pattern according claim 10, wherein (A) polyurethane containing a carboxyl group has an acid value of 10 to 140 mg-KOH/g.

Description

EXAMPLES

(1) Hereinbelow, specific examples of the present disclosure will be specifically explained. The examples are described below for the purpose of easy understanding of the present disclosure, and the present disclosure is not limited to these examples.

Synthesis Example of (A) Polyurethane Containing Carboxyl Group

Synthesis Example 1

(2) 16.7 g of C-1015N (polycarbonate diol, molar ratio of raw material diols: 1,9-nonanediol:2-methyl-1,8-octanediol=15:85, molecular weight: 964, manufactured by Kuraray Co., Ltd.) as a polyol compound, 10.8 g of 2,2-dimethylol butanoic acid (manufactured by Huzhou Changsheng Chemical Co., Ltd.) as a dihydroxyl compound containing a carboxyl group, and 62.6 g of propylene glycol monomethyl ether acetate (PGMEA) (manufactured by Showa Denko K. K.) as a solvent were provided in a 2 L three-neck flask having a stirrer, a thermometer, and a condenser, and the 2,2-dimethylol butanoic acid was dissolved at 90° C.

(3) The temperature of the reaction liquid was lowered to 70° C., and 23.5 g of Desmodur (registered trademark)-W (bis(4-isocyanate cyclohexyl)methane), manufactured by Sumika Covestro Urethane Co., Ltd.) as polyisocyanate was dropped thereto for 30 minutes by a dropping funnel. After the dropping was complete, the temperature was raised to 100° C., and the reaction was performed at 100° C. for 15 hours. After the confirmation by IR that almost all of the isocyanate disappeared, 0.5 g of isobutanol was added, which was further reacted at 100° C. for 6 hours. The obtained carboxyl group-containing polyurethane had a weight average molecular weight of 33500, and a resin solution thereof had an acid value of 39.4 mgKOH/g.

Synthesis Example 2

(4) 37.0 g of C-1015N (polycarbonate diol, molar ratio of raw material diols: 1,9-nonanediol:2-methyl-1,8-octanediol=15:85, molecular weight: 964, manufactured by Kuraray Co., Ltd.) as a polyol compound, 20.7 g of 2,2-dimethylolpropionic acid (manufactured by Perstorp Japan Co., Ltd.) as a dihydroxyl compound containing a carboxyl group, and 132.1 g of propylene glycol monomethyl ether acetate (manufactured by Showa Denko K. K.) as a solvent were provided in a 2 L three-neck flask having a stirrer, a thermometer, and a condenser, and 2,2-dimethylolpropionic acid was dispersed at 90° C.

(5) The temperature of the reaction liquid was lowered to 70° C., and 50.3 g of Desmodur (registered trademark)-W (bis(4-isocyanate cyclohexyl)methane), manufactured by Sumika Covestro Urethane Co., Ltd.) as polyisocyanate was dropped thereto for 30 minutes by a dropping funnel. After the dropping was complete, the temperature was raised to 100° C., and the reaction was performed at 100° C. for 15 hours. After the confirmation by IR that almost all of the isocyanate disappeared, 0.5 g of isobutanol was added, which was further reacted at 100° C. for 6 hours. The obtained carboxyl group-containing polyurethane had a weight average molecular weight of 35000, and a resin solution thereof had an acid value of 37.4 mgKOH/g.

Production of Protective Film Ink

Example 1

(6) As shown in Table 1, 1.8 g of the resin solution obtained by Synthesis Example 1 as (A) polyurethane containing a carboxyl group (in Table 1, expressed as urethane), 0.15 g of jER (registered trademark)-604 (N,N,N′,N′-tetraglycidyl diaminodiphenyl methane type epoxy compound, manufactured by Mitsubishi Chemical Corporation) as (B) epoxy compound, 0.048 g of SA102 (DBU octyl acid salt) (manufactured by San-Apro Ltd.) as (C) curing accelerator, and 31.78 g of isopropyl alcohol (IPA) and diethylene glycol monoethyl ether (EC) (IPA:EC=60:37 (mass ratio)) as (D) solvent, were added, which was stirred to become uniform by using Awatori Rentaro (registered trademark) ARV-310, i.e., a planetary centrifugal vacuum mixer manufactured by Thinky Corporation. Thereby, the protective film ink according to Example 1 was obtained. According to the calculation using masses before and after the solvent drying, the protective film ink had a solid content (total of (A) polyurethane containing a carboxyl group, (B) epoxy compound, and (C) curing accelerator) of 3% by mass.

Examples 2 to 10, Comparative Examples 1 to 9

(7) (A) polyurethane containing a carboxyl group, (B) epoxy compound, (C) curing accelerator, (D) solvent shown in Table 1 were used, and same operations as Example 1 were performed, and thereby, respective protective film inks were obtained. The amounts of the solvents were adjusted for the inks other than the inks having the solid content of 3% by mass, so that the objected concentrations can be obtained, respectively.

(8) Note that in Table, (B) epoxy compound, 2021P refers to Celloxide (registered trademark) 2021P, a bifunctional alicyclic epoxy compound (3′,4′-epoxy cyclohexyl methyl 3,4-epoxy cyclohexane carboxylate) manufactured by Daicel Corporation, EHPE (registered trademark) 3150 refers to 1,2-epoxy-4-(2-oxiranyl) cyclohexane adduct of 2,2-bis(hydroxy methyl)-1-butanol, manufactured by Daicel Corporation, BADG refers to bisphenol A diglycidyl ether (manufactured by Showa Denko K. K.), and Epolite 4000 refers to hydrogenated bisphenol A diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd.). Also, as (D) solvent, PGME refers to propylene glycol monomethyl ether (manufactured by Showa Denko K. K.).

(9) Table 1 shows the solubility of the obtained ink. Here, the solubility is a result of visual observation as to whether (A) polyurethane containing a carboxyl group, (B) epoxy compound, and (C) curing accelerator became a uniform clear solution having a predetermined concentration. When the ink is transparent by visual observation, “good” is inserted, and when to become clouded or precipitation of resin was observed, “poor” is inserted. With reference to Comparative Example 3 and Comparative Example 5, even if a solvent containing a hydroxyl group, such as isopropyl alcohol (IPA), is used, if a solution, the solubility of the resin to which is low, is contained in the solvent at a content of 70% by mass or more, uniform solution cannot be obtained.

(10) <Production of Silver Nanowire>

(11) Polyvinylpyrrolidone K-90 (manufactured by Nippon Shokubai Co., Ltd.) (0.98 g), AgNO.sub.3 (1.04 g), and FeCl.sub.3 (0.8 m g) were dissolved in ethylene glycol (250 ml), and heated and reacted at 150° C. for 1 hour. The obtained silver nanowire coarse dispersion liquid is dispersed in 2000 ml of methanol, and poured in a desktop small tester (using a ceramic membrane filter Cefilt, membrane area: 0.24 m.sup.2, pore size: 2.0 μm, sizeΦ: 30 mm*250 mm, differential pressure of filter: 0.01 MPa, manufactured by NGK Insulators, Ltd.), and impurities were removed by cross-flow filtration at a circulation flow rate of 12 L/min, and a dispersion liquid temperature of 25° C. Thereafter, the obtained dispersion liquid was condensed, and appropriate amount of methanol was added so that the calculated silver concentration became approximately 0.2% by mass. A part (10 g) of the methanol dispersion liquid was weighed in a PFA container, and dried by heating at 100° C. for 6 hours. The solid after the drying was heated by a thermogravimetric analyzer (differential thermal analyzer: TG-DTA2000SE, manufactured by NETZSCH) at a heating rate of 10° C./min to 500° C. The residue at 500° C. was treated as a mass of silver, and the component amount in the dispersion liquid was simply measured. As a result, the obtained silver nanowire methanol dispersion liquid had a silver concentration of 0.2% by mass, with silver nanowires having an average diameter of 36 nm, and an average length 20 μm. The average diameter and the average length of the silver nanowires were arithmetic average values obtained by observing 500 silver nanowires by SEM. Further, the above-mentioned methanol, ethylene glycol, AgNO.sub.3, and FeCl.sub.3 were the ones manufactured by Wako Pure Chemical Industries, Ltd.

(12) <Printing Silver Nanowire Ink Coating Film>

(13) 174 g of the silver nanowire methanol dispersion liquid produced as above (silver concentration: 0.2% by mass, dispersion medium: methanol, average diameter of wire: 36 nm, average length of wire: 20 μm) was weighed in a 1000 ml eggplant flask. 3.1 g of 10% by mass aqueous solution of PVP K-90 (poly(N-vinylpyrrolidone), manufactured by Nippon Shokubai Co., Ltd.), 40.9 g of propylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.), and 112.3 g of PGME (manufactured by Tokyo Chemical Industry Co., Ltd.) were added to the flask, and dispersed well. Then, methanol was distilled away from the mixture using an evaporator. Thereafter, 63.2 g of pure water, 300 g of ethanol (manufactured by Kanto Chemical Co., Inc.), and 49.3 g of methanol (manufactured by Wako Pure Chemical Industries, Ltd.) were added. The resultant was stirred by the planetary centrifugal vacuum mixer, Awatori Rentaro (registered trademark) ARV-310, manufactured by Thinky Corporation, to thereby obtain a silver nanowire ink.

(14) The obtained silver nanowire ink has a silver concentration of 0.23% by mass (measured by AA280Z, Zeeman atomic absorption spectrophotometer, manufactured by Varian), and the concentration of the remaining methanol was 9.3% by mass. The measurement of concentration was performed by gas chromatography using Gas Chromatograph 7890A manufactured by Agilent Technologies Inc.

(15) Using the above silver nanowire ink, a 20-cm-square solid printed film (silver nanowire layer) was printed on a COP film (ZEONOR (registered trademark) ZF14, 50 μm thick, manufactured by Zeon Corporation) having a plasma treated surface, by a slit coater (FLOLIA (registered trademark), manufactured by Chugai Ro Co., Ltd.). The plasma treatment was performed under the air atmosphere, at the power output of 405 V for 3 seconds, using AP-T03 AtomosPheric High-density Plasma Cleaning System, manufactured by Sekisui Chemical Co., Ltd. After performing the solvent drying at 100° C., for 10 minutes, the obtained transparent conductive pattern had a surface resistance of 60Ω/□. The surface resistance was measured using a non-contact type resistance measurement instrument (EC-80P, manufactured by Napson Corporation) and a contact type resistance measurement instrument (Loresta GP MCP-T610, manufactured by Mitsubishi Chemical Analytech Co., Ltd.).

(16) <Printing Protective Film Ink>

(17) Each of the protective film inks according to Examples 1 to 10 and Comparative Examples 1 to 9 was printed to cover the produced 20-cm-square solid printed film, by the above-mentioned slit coater, and was subjected to thermal curing at 100° C., for 10 minutes, to form a protective film. In Comparative Example 2, the thermal curing was performed at 100° C., for 60 minutes. In Table 1, the productivity evaluation, “good” is inserted for the cases that the thermal curing was performed at 100° C., for 10 minutes, and “poor” is inserted for the cases that the thermal curing was performed at a higher temperature or for a longer time (100° C., 60 minutes).

(18) According to the SEM observation of the cross-sectional surface, using JSM-7500FA, manufactured by JEOL Ltd., in Example, the total thickness of the silver nanowire layer and the cured protective film was approximately 100 nm; in Comparative Example 6, approximately 200 nm; in Comparative Example 7, approximately 500 nm; and in Comparative Example 8, approximately 1 μm.

(19) <Evaluation of Protective Film>

(20) The cure degree, contact resistance, reliability, and optical property of the obtained protective films were measured by the following methods. Table 1 shows the results.

(21) Cure Degree: Calculated by the above-mentioned ATR measurement. For the ATR measurement, Nicolet 6700, manufactured by Thermo Scientific K. K. was used.

(22) Contact Resistance: Measured by Loresta GP MCP-T610, manufactured by Mitsubishi Chemical Analytech Co., Ltd. The measurement was performed at arbitrarily selected 10 points on the protective film. When resistance could be measured at all measurement points, the film was evaluated as “good”; resistance could be measured at some of the points, the film was evaluated as “fair”; and resistance could not be measured at any of the points, the film was evaluated as “poor”.

(23) Reliability: In a thermo-hygrostat chamber maintained at 85° C., 85%, if the change in resistance after 500 hours passed was 10% or less, the reliability was evaluated as “good”, if the change exceeds 10% and 20% or less, evaluated as “fair”, and if the change exceeds 20%, evaluated as “poor”.

(24) Optical Property: In a thermo-hygrostat chamber maintained at 85° C., 85%, if the change in haze and total light transmittance of the film measured (by Haze meter NDH 2000 (manufactured by Nippon Denshoku Industries Co., Ltd.)) after 500 hours passed was both 10% or less, the optical property was evaluated as “good”, if either of them exceeds 10% and 20% or less, evaluated as “fair”, if both exceeds 20%, evaluated as “poor”.

(25) On the basis of the above results, the protective films were evaluated. Table 1 shows the results. If all of the contact resistance, reliability, and the optical property, as well as the above-mentioned productivity, were evaluated as “good the protective film was evaluated as “good”; at least one of them was “fair” and none of them was “poor”, evaluated as “fair”; and at least one of them was “poor”, evaluated as “poor.

(26) TABLE-US-00001 TABLE 1 (C) Curing (A) Urethane (B) Epoxy compound accelerator Solid (D) Solvent Cure Amount Amount Amount content Amount Mixing ratio (mass ratio) degree Contact Optical Type (mass %) Type (mass %) Type (mass %) (mass %) (mass %) IPA EC PGME PGMEA Solubility (%) resistance Reliability property Productivity Evaluation Ex. 1 Syn. 2.44 jER6C4 0.42 SA102 0.14 3 97 60 37 3 good 72 good good good good good Ex. 1 Ex. 2 Syn. 2.44 jER6C4 0.42 SA102 0.14 3 97 50 47 3 good 65 good good good good good Ex. 1 Ex. 3 Syn. 2.44 jER6C4 0.42 SA102 0.14 3 97 40 57 3 good 58 good good good good good Ex. 1 Ex. 4 Syn. 2.44 jER6C4 0.42 SA102 0.14 3 97 40 57 3 good 67 good good good good good Ex. 1 Ex. 5 Syn. 2.40 2021P 0.45 SA102 0.14 3 97 50 47 3 good 78 good good good good good Ex. 1 Ex. 6 Syn. 2.27 EHPE3150 0.59 SA102 0.14 3 97 50 47 3 good 65 good good good good good Ex. 1 Ex. 7 Syn. 2.31 BADG 0.54 SA102 0.14 3 97 60 37 3 good 51 good good good good good Ex. 1 Ex. 8 Syn. 2.14 Epolitc 0.72 SA102 0.14 3 97 50 47 3 good 69 good good good good good Ex. 1 400C Ex. 9 Syn. 2.43 jER6C4 0.43 SA102 0.14 3 97 50 47 3 good 71 good good good good good Ex. 2 Ex. Syn. 2.43 jER6C4 0.43 SA102 0.14 3 97 30 67 3 good 47 good good good good good 10 Ex. 2 Comp. Syn. 2.44 jER6C4 0.42 SA102 0.14 3 97 0 97 3 good 24 good poor fair good poor Ex. 1 Ex. 1 Comp. Syn. 2.44 jER6C4 0.42 SA102 0.14 3 97 0 97 3 good 69 good good good poor poor Ex. 2 Ex. 1 Comp. Syn. 2.44 jER6C4 0.42 SA102 0.14 3 97 70 27 3 poor — — — — — poor Ex. 3 Ex. 1 Comp. Syn. 2.44 jER6C4 0.42 SA102 0.14 3 97 20 77 3 good 34 good poor fair good poor Ex. 4 Ex. 1 Comp. Syn. 2.44 jER6C4 0.42 SA102 0.14 3 97 97 0 3 poor — — — — — poor Ex. 5 Ex. 1 Comp. Syn. 4.07 jER6C4 0.70 SA102 0.23 5 95 0 95 5 good 25 fair poor fair good poor Ex. 6 Ex. 1 Comp. Syn. 8.13 jER6C4 0.14 SA102 0.47 10 90 0 90 10 good 31 poor poor fair good poor Ex. 7 Ex. 1 Comp. Syn. 24.4 jER6C4 4.20 SA102 1.40 30 70 0 70 30 good 70 poor good good good poor Ex. 8 Ex. 1 Comp. Syn. 2.44 jER6C4 0.42 SA102 0.14 3 97 0 97 3 good 44 good fair good good fair Ex. 9 Ex. 1

(27) As can be seen from the results shown in Table 1, comparison among Examples 1 to 4, Comparative Example 1, and Comparative Examples 3 to 5 reveals that if IPA, the solubility of (A) polyurethane containing a carboxyl group to which is low, is contained 70% by mass or more, the ink cannot be uniform. Further, the smaller the IPA ratio, the lower the cure degree, and when the cure degree becomes less than 45, the result of the reliability becomes worse.

(28) Comparative Example 2 is different from Comparative Example 1 in the point that the curing conditions were changed from 100° C. and 10 minutes to 100° C. and 60 minutes. The sufficient heating leads to the increase of the cure degree, and the improvement of the reliability. This reveals that the result of reliability depends on the cure degree. However, when heating is performed for a long time, the productivity is decreased.

(29) The solid content of the ink is different between Comparative Examples 6 to 8 and Comparative Example 1. As in Comparative Example 8, if the solid content is high, namely, if the amount of solvent is small, the vaporization heat when solvent evaporates is small. Thus, even under the curing conditions of 100° C. and 10 minutes, the cure degree becomes higher, and a reliable protective film can be obtained. However, the film thickness becomes large, and thus, the contact resistance cannot be obtained. Accordingly, when a dilute ink is used, the composition of the solvent becomes very important.

(30) In each of Example 4 and Comparative Example 9, the solvent of the ink includes PGME instead of EC, PGME having a lower boiling point than EC. In both cases, the cure degrees of the inks are higher than the corresponding inks. This suggests that the boiling point of the solvent is an important factor. In Comparative Example 9, the ink does not include (D2) solvent having the boiling point of 100° C. or lower, and thus, the added heat is used for the evaporation of the solvent, and thus, the cure degree becomes low, and the reliability becomes worse.

(31) In Examples 5 to 8, the epoxy resins in the ink are changed in various ways, on the basis of Example 2. In view of them, it can be found that, even if the epoxy resin is changed, the cure degree is important for the reliability.

(32) In Example 9 and Example 10, the polyurethane containing a carboxyl group is changed. Judging from the cure degrees of Example 2 and Example 9, it is assumed that the reactivity of the carboxyl group becomes higher, compared to the case where the polyurethane according to Synthesis Example 1 is used.

(33) In view of the above, it is suggested that, as a protective film composition used for a transparent conductive film, capability of obtaining a high cure degree at a low energy and for a short time is important, and that selecting an appropriate solvent (type, amount) is important in order to obtain the cure degree control, and a superior contact resistance and reliability.