WO2021060149A1 - Transparent polyurethane, production method therefor, transparent polyurethane-containing thermosetting composition, and transparent conductive film - Google Patents

Abstract

[Problem] To provide a transparent polyurethane having a low degree of coloration (yellowness), a production method therefor, a thermosetting composition containing the transparent polyurethane, and a transparent conductive film using a cured film obtained from the thermosetting composition as a protective film. [Solution] The invention involves using as a synthesis solvent a solvent having an SP value of less than 9.80 by the Fedors estimation method to synthesize (A) a carboxy group-containing transparent polyurethane having a b* value of 0.25 or lower when formed into a 50 μm-thick film. Next, a transparent base material and a transparent conductive layer on at least one surface of the transparent base material are provided, and a cured film obtained from a thermosetting composition containing (A) the carboxy group-containing transparent polyurethane, (B) an epoxy compound, and (C) a solvent is formed on the surface of the transparent conductive layer facing away from the transparent base material, thereby forming a transparent conductive film.

Description

Transparent polyurethane and its manufacturing method, thermosetting composition containing transparent polyurethane and transparent conductive film

The present invention relates to a transparent polyurethane, a method for producing the same, a thermosetting composition containing the transparent polyurethane, and a transparent conductive film using the cured film as a protective film. More specifically, the present invention relates to a transparent polyurethane having a small degree of coloring (yellowness), a method for producing the same, a thermosetting composition containing the transparent polyurethane, and a transparent conductive film using the cured film as a protective film.

Transparent conductive films include liquid crystal displays (LCDs), plasma display panels (PDPs), organic electroluminescent displays, transparent electrodes for solar cells (PV) and touch panels (TP), antistatic (ESD) films and electromagnetic shielding (EMI). It is used in various fields such as films. Conventionally, those using ITO (indium tin oxide) have been used as these transparent conductive films, but the supply stability of indium is low, the manufacturing cost is high, the flexibility is lacking, and the temperature is high at the time of film formation. There was a problem that was necessary. Therefore, the search for a transparent conductive film to replace ITO is being actively pursued. Among them, the transparent conductive film containing metal nanowires has excellent conductivity, optical properties, and flexibility, can be formed by a wet process, has a low manufacturing cost, and requires a high temperature during film formation. Therefore, it is suitable as an ITO alternative transparent conductive film. For example, a transparent conductive film containing silver nanowires and having high conductivity, optical properties, and flexibility is known (see Patent Document 1).

However, the transparent conductive film containing silver nanowires has a problem that it lacks environmental resistance because it has a large surface area per silver mass and easily reacts with various compounds. Due to the influence and the influence of oxygen and moisture in the air exposed by long-term storage, the nanostructures are easily corroded and the conductivity is easily lowered. Further, especially in applications such as electronic materials, a physical cleaning process using a brush or the like is often used in order to prevent the adhesion or mixing of fine particle impurities, dust, dust, etc. on the surface of the substrate. The problem is that the surface is also damaged by the process.

In order to solve this, various protective films are being studied. The protective film also needs to be transparent so as to have a function as a transparent conductive film. On the other hand, it is generally known that the resin used for the protective film causes so-called yellowing. When it turns yellow, the performance of the transparent conductive film is deteriorated (the image quality of the display and the photoelectric conversion efficiency of the solar cell are deteriorated).

Patent Document 2 discloses a polyurethane elastomer suitable for an optical sheet, which is synthesized by using a material having a specific skeleton (polyisocyanate containing 1,4-bis (isocyanatomethyl) cyclohexane), and is transparent. , It is described that it is also excellent in yellowing resistance. Further, Patent Document 3 describes a method for producing a transparent polyurethane resin, which has low hardness, has flexibility and elasticity, and is suitable for optical-related applications in which a plasticizer and / or a solvent does not bleed. Discloses a transparent coating coating made of flexible polyurethane having an antifogging effect. All of these have obtained transparent polyurethane by blending and synthesizing raw materials having a specific chemical structure in a specific ratio, but they can be used for independent sheets, films, molded products, or other transparent glass or other transparent glass. It is used as a coating material to improve the mechanical properties and wettability (anti-fog property) of plastic substrates, and functions as a protective film that imparts environmental resistance (temperature, humidity, natural light) to transparent conductive films. Is not mentioned.

Special Table 2010-507199 Japanese Unexamined Patent Publication No. 2011-236329 Japanese Unexamined Patent Publication No. 2005-272676 Japanese Unexamined Patent Publication No. 2-20580

An object of the present invention is to provide a transparent polyurethane having a small degree of coloring (yellowness), a method for producing the same, a thermosetting composition containing the transparent polyurethane, and a transparent conductive film using the cured film as a protective film.

Even if the monomers used for synthesizing polyurethane are the same, the present inventors can obtain polyurethane with less coloration and better transparency by synthesizing under specific synthetic conditions, and a transparent conductive film. It was found that it is suitable for the transparent conductive layer protective film of.

That is, the present invention has the following embodiments.

[1] A transparent polyurethane containing a carboxy group (A), characterized in that the b * value when a film is formed to a thickness of 50 μm is 0.25 or less.

[2] The transparent polyurethane (A) containing a carboxy group is synthesized by using (a1) a polyisocyanate compound, (a2) a polyol compound, and (a3) a dihydroxy compound containing a carboxy group as a monomer. The transparent polyurethane containing the (A) carboxy group according to [1].

[3] The transparent polyurethane containing the (A) carboxy group according to [2], wherein the (a2) polyol compound is a polycarbonate polyol.

[4] The transparent polyurethane containing the (A) carboxy group according to [2] or [3], wherein the (a1) polyisocyanate compound is an aliphatic polyisocyanate or an alicyclic polyisocyanate.

[5] Thermosetting containing (A) a transparent polyurethane containing a carboxy group having a b * value of 0.25 or less when a film is formed to a thickness of 50 μm, (B) an epoxy compound, and (C) a solvent. Sex composition.

[6] The thermosetting composition according to [5], which further contains (D) a curing accelerator.

[7] The thermosetting composition according to [5] or [6], wherein the (B) epoxy compound is a polyfunctional epoxy compound having three or more epoxy groups in one molecule.

[8] It has a transparent base material, a transparent conductive layer provided on at least one surface of the transparent base material, and a protective film provided on a surface of the transparent conductive layer opposite to the transparent base material. A transparent polyurethane which is a transparent conductive film and has a b * value of 0.25 or less when the protective film is formed to a thickness of 50 μm, (A) a transparent polyurethane containing a carboxy group, (B) an epoxy compound, and (C). A transparent conductive film, which is a cured film of a thermosetting composition containing a solvent.

[9] The transparent conductive film according to [8], wherein the transparent conductive layer contains metal nanowires.

[10] The transparent conductive film according to [9], wherein the metal nanowire is a silver nanowire.

[11] The transparent polyurethane containing the carboxy group (A) according to any one of [1] to [4], wherein a solvent having an SP value of less than 9.80 according to the Fedors estimation method is used as the synthetic solvent. Manufacturing method.

[12] The solvent is diethylene glycol monobutyl ether acetate, 1,4-butanediol diacetate, tripropylene glycol dimethyl ether, propylene glycol dimethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol dimethyl ether, n acetate. -Any one selected from the group consisting of propyl, n-butyl acetate, 1,4-dioxane, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, isophorone, tetrahydrofuran, 4-methyltetrahydropyran, cyclopentyl methyl ether [11]. The method for producing transparent polyurethane according to.

[13] The method for producing a transparent polyurethane according to [11], wherein the solvent is 4-methyltetrahydropyran or triethylene glycol dimethyl ether.

[14] The method for producing a transparent polyurethane according to [11], wherein the solvent is methyl tetrahydropyran.

According to the present invention, it is possible to provide a transparent polyurethane having a small degree of coloring (yellowness), a method for producing the same, a thermosetting composition containing the transparent polyurethane, and a transparent conductive film using the cured film as a protective film.

Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as embodiments) will be described.

<Transparent polyurethane and thermosetting composition containing it>
The transparent polyurethane (A) containing a carboxy group according to the first aspect of the present invention is characterized in that the b * value when a film is formed to a thickness of 50 μm is 0.25 or less.

As the resin that forms the protective film of the transparent conductive film, any resin that has high insulation performance and environmental resistance (temperature, humidity, natural light, etc.) can be used without any particular problem, but considering application to flexible devices, Polyurethane having a moderately flexible skeleton is suitable. Further, in order to prevent the transparent conductive layer constituting the transparent conductive film from being damaged, it is preferable that the curable resin has a cross-linking reactive group that can be cured after being applied onto the transparent conductive layer. After forming a protective film on the transparent conductive layer, curing with a cross-linking reactive group is preferable because scratch resistance and solvent resistance are improved. As the cross-linking reactive group, a thermosetting cross-linking reactive group is preferable in consideration of resistance to natural light.

Among such thermosetting resins, the transparent polyurethane (A) containing a carboxy group has flexibility, and by blending with a compound having an epoxy group or an isocyanato group, the cross-linking reactive group (epoxy group or isocyanato) thereof. The group) can be crosslinked with the carboxy group of the transparent polyurethane (A) containing the carboxy group, which is more preferable.

(A) The transparent polyurethane containing a carboxy group can be synthesized from a polyol compound, a polyisocyanate compound, and a dihydroxy compound containing a carboxy group.

The protective film of the transparent conductive film is preferably formed by forming (A) a thermosetting composition containing a transparent polyurethane containing a carboxy group on the transparent conductive layer by printing, coating, or the like, and then curing the film. The thermosetting composition preferably contains (A) a transparent polyurethane containing a carboxy group, (B) an epoxy compound, and (C) a solvent, and if necessary, (D) a curing accelerator. It may be included.

The transparent polyurethane containing the carboxy group (A) preferably has a weight average molecular weight of 1,000 to 100,000, more preferably 2,000 to 70,000, and more preferably 3,000 to 50. It is more preferably 000. Here, the molecular weight is a polystyrene-equivalent value measured by gel permeation chromatography (hereinafter referred to as GPC). If the weight average molecular weight is less than 1,000, the elongation, flexibility, and strength of the coating film after printing may be impaired, and if it exceeds 100,000, the solubility of polyurethane in a solvent becomes low, and the solubility of polyurethane in a solvent becomes low. Even if it is dissolved, the viscosity becomes too high, which may increase restrictions on use.

In the present specification, unless otherwise specified, the measurement conditions of GPC are as follows.
Device name: HPLC unit HSS-2000 manufactured by JASCO Corporation
Column: Shodex column LF-804
Mobile phase: Tetrahydrofuran Flow velocity: 1.0 mL / min
Detector: RI-2031Plus manufactured by JASCO Corporation
Temperature: 40.0 ° C
Sample amount: Sample loop 100 μliter Sample concentration: Prepared to about 0.1% by mass

The acid value of the transparent polyurethane (A) containing a carboxy group is preferably 10 to 140 mg-KOH / g, more preferably 15 to 130 mg-KOH / g. If the acid value is less than 10 mg-KOH / g, the curability is lowered and the solvent resistance is also lowered. If it exceeds 140 mg-KOH / g, the solubility of the urethane resin in the solvent is low, and even if it is dissolved, the viscosity becomes too high and handling is difficult. In addition, since the cured product becomes too hard, problems such as warpage are likely to occur depending on the base film.

Further, in the present specification, the acid value of the resin is a value measured by the following method.
Approximately 0.2 g of the sample is precisely weighed in a 100 ml Erlenmeyer flask with a precision balance, and 10 ml of a mixed solvent of ethanol / toluene = 1/2 (mass ratio) is added thereto to dissolve the sample. Further, 1 to 3 drops of a phenolphthalein ethanol solution is added to this container as an indicator, and the sample is sufficiently stirred until it becomes uniform. This is titrated with a 0.1N potassium hydroxide-ethanol solution, and the end point of neutralization is when the indicator has a slight crimson color for 30 seconds. The value obtained from the result using the following formula is used as the acid value of the resin.
Acid value (mg-KOH / g) = [B × f × 5.611] / S
B: Amount of 0.1N potassium hydroxide-ethanol solution used (ml)
f: Factor S of 0.1N potassium hydroxide-ethanol solution: Sample collection amount (g)

(A) The transparent polyurethane containing a carboxy group is more specifically synthesized by using (a1) a polyisocyanate compound, (a2) a polyol compound, and (a3) a dihydroxy compound containing a carboxy group as a monomer. It is polyurethane. From the viewpoint of light resistance, it is desirable that (a1), (a2), and (a3) do not contain a functional group having conjugate properties such as an aromatic compound. Hereinafter, each monomer will be described in more detail.

(A1) Polyisocyanate compound (a1) As the polyisocyanate compound, diisocyanate having two isocyanato groups per molecule is preferable. Examples of the polyisocyanate compound include aliphatic polyisocyanates and alicyclic polyisocyanates, and one of these compounds can be used alone or in combination of two or more. As long as the transparent polyurethane (A) containing a carboxy group does not gel, a small amount of polyisocyanate having 3 or more isocyanato groups can also be used.

Examples of the aliphatic polyisocyanis include 1,3-trimethylen diisocyanis, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,9-nonamethylene diisocyanate, and 1,10-decamethylene diisocyanis, and 2, , 2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,2'-diethyleter diisocyanate, dimerate diisocyanate and the like.

Examples of the alicyclic polyisocyanate include 1,4-cyclohexanediisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, and 3-isocyanatomethyl-3,5. , 5-trimethylcyclohexylisocyanate (IPDI, isophorone diisocyanate), bis- (4-isocyanatocyclohexyl) methane (hydrogenated MDI), hydrogenated (1,3- or 1,4-) xylylene diisocyanate, norbornandiisocyanate (NBDI) ) Etc. can be mentioned.

Here, as the (a1) polyisocyanate compound, the polyurethane resin according to the embodiment is used by using an alicyclic compound having 6 to 30 carbon atoms other than carbon atoms in the isocyanato group (-NCO group). The protective film formed from is highly reliable especially at high temperature and high humidity, and is suitable for members of electronic device parts.

An aromatic or aromatic polyisocyanate compound having an aromatic ring can be used as the (a1) polyisocyanate compound, but from the viewpoint of weather resistance and light resistance, the (a1) polyisocyanate compound does not have an aromatic ring. It is preferable to use a compound. When an aromatic polyisocyanate or an aromatic aliphatic polyisocyanate is used, it is 50 mol% or less, preferably 30 mol% or less, based on the total amount (100 mol%) of the (a1) polyisocyanate compound in the (a1) polyisocyanate compound. , More preferably, it is preferably contained in an amount of 10 mol% or less.

The number average molecular weight (catalog value) of the (a2) polyol compound (a2) polyol compound (however, the (a2) polyol compound does not include the (a3) carboxy group-containing dihydroxy compound described later) is usually 250. It is 50,000 to 50,000, preferably 400 to 10,000, and more preferably 500 to 5,000.

The polyol compound (a2) is preferably a diol compound having hydroxy groups at both ends. For example, polycarbonate polyols, polyether polyols, polyester polyols, polylactone polyols. Among these, polycarbonate polyol is preferable in consideration of the balance between water resistance as a protective film, insulation reliability, and adhesion to a base material.

The polycarbonate polyol can be obtained by reacting a diol having 3 to 18 carbon atoms with a carbonic acid ester or phosgene, and is represented by, for example, the following structural formula (1).

In the formula (1), R ³ is a residue obtained by removing the hydroxyl group from the corresponding diol (HO-R ^3- _{OH), and n 3} is a positive integer, preferably 2 to 50.

Specifically, the polycarbonate polyol represented by the formula (1) is 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, or 3-methyl-1. , 5-Pentanediol, 1,8-octanediol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,10 -It can be produced by using decamethylene glycol, 1,2-tetradecanediol or the like as a raw material.

The above-mentioned polycarbonate polyol may be a polycarbonate polyol (copolymerized polycarbonate polyol) having a plurality of types of alkylene groups in its skeleton. The use of a copolymerized polycarbonate polyol is often advantageous from the viewpoint of preventing crystallization of the transparent polyurethane (A) containing a carboxy group. Further, considering the solubility in a solvent, it is preferable to use a polycarbonate polyol having a branched skeleton and a hydroxyl group at the end of the branched chain in combination.

The polyether polyol is obtained by dehydration condensation of a diol having 2 to 12 carbon atoms, or ring-opening polymerization of an oxylan compound, an oxetane compound, or a tetrahydrofuran compound having 2 to 12 carbon atoms, for example. It is represented by the following structural formula (2).

In the formula (2), R ⁴ is a residue obtained by removing the hydroxyl group from the corresponding diol (HO-R ^4- _{OH), and n 4} is a positive integer, preferably 4 to 50. The above-mentioned diols having 2 to 12 carbon atoms may be used alone to form a homopolymer, or may be used in combination of two or more to form a copolymer.

Specific examples of the polyether polyol represented by the above formula (2) include polyethylene glycol, polypropylene glycol, poly-1,2-butylene glycol, polytetramethylene glycol (poly1,4-butanediol), and the like. Examples thereof include polyalkylene glycols such as poly-3-methyltetramethylene glycol and polyneopentyl glycol. Further, for the purpose of improving the hydrophobicity of the polyether polyol, these copolymers, for example, a copolymer of 1,4-butanediol and neopentyl glycol, or the like can also be used.

The polyester polyol is obtained by dehydration condensation of a dicarboxylic acid and a diol or a transesterification reaction of a lower alcohol esterified product of the dicarboxylic acid with a diol, and is represented by, for example, the following structural formula (3).

In formula (3), R ⁵ is the residue obtained by removing the hydroxyl group from the corresponding diol (HO-R ^{5- OH), and R 6} is the two carboxy groups from the corresponding dicarboxylic acid (HOCO-R ^6-COOH). Is a residue excluding, and n ₅ is a positive integer, preferably 2 to 50.

Specific examples of the diol (HO-R ^5- OH) include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, and 1 , 4-Butandiol, 1,5-Pentanediol, 1,6-Hexanediol, 3-Methyl-1,5-Pentanediol, 1,8-Octanediol, 1,3-Cyclohexanedimethanol, 1,4- Cyclohexanedimethanol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,10-decamethylene glycol or 1,2-tetradecanediol, 2,4-diethyl-1,5-pentanediol, Examples thereof include butyl ethyl propanediol, 1,3-cyclohexanedimethanol, diethylene glycol, triethylene glycol and dipropylene glycol.

Specific examples of the dicarboxylic acid (HOCO-R ^6- COOH) include succinic acid, glutalic acid, adipic acid, azelaic acid, sebacic acid, decandicarboxylic acid, brassic acid, and 1,4-cyclohexanedicarboxylic acid. , Hexahydrophthalic acid, methyltetrahydrophthalic acid, endomethylenetetrahydrophthalic acid, methylendomethylenetetrahydrophthalic acid, chlorendic acid, fumaric acid, maleic acid, itaconic acid, citraconic acid.

The polylactone polyol is obtained by a condensation reaction of a ring-opening polymer of lactone and a diol, or a condensation reaction of a diol and a hydroxyalkanoic acid, and is represented by, for example, the following structural formula (4).

In formula (4), R ⁷ is the residue obtained by removing the hydroxyl group and carboxy group from the corresponding hydroxyalkanoic acid (HO-R ^{7- COOH), and R 8} is the residue from the corresponding diol (HO-R ^8- OH). It is a residue excluding the hydroxyl group, and n ₆ is a positive integer, preferably 2 to 50. Examples of the diol (HO-R ^8- OH) include those equivalent to the above-mentioned diol (HO-R ^5-OH).

Specific examples of the hydroxyalkanoic acid (HO-R ^7- COOH) include 3-hydroxybutanoic acid, 4-hydroxypentanoic acid, 5-hydroxyhexanoic acid and the like. Examples of the lactone include ε-caprolactone.

(A3) Dihydroxy compound containing a carboxy group (a3) The dihydroxy compound containing a carboxy group has a molecular weight of 200, which has two of a hydroxy group and a hydroxyalkyl group having 1 or 2 carbon atoms. The following carboxylic acid or aminocarboxylic acid is preferable because the cross-linking point can be controlled. Specific examples thereof include 2,2-dimethylolpropionic acid (DMPA), 2,2-dimethyrolbutanoic acid (DMBA), N, N-bishydroxyethylglycine, N, N-bishydroxyethylalanine and the like. Of these, 2,2-dimethylolpropionic acid and 2,2-dimethyrolbutanoic acid are particularly preferable from the viewpoint of solubility in a solvent. These (a3) carboxy group-containing dihydroxy compounds can be used alone or in combination of two or more.

The transparent polyurethane containing the (A) carboxy group described above can be synthesized only from the above three components ((a1), (a2) and (a3)). Further, it can be further reacted with (a4) monohydroxy compound and / or (a5) monoisocyanate compound to synthesize. From the viewpoint of light resistance, it is preferable to use a compound that does not contain an aromatic ring or a carbon-carbon double bond in the molecule.

(A4) Monohydroxy Compound (a4) Examples of the monohydroxy compound include compounds having a carboxylic acid such as glycolic acid and hydroxypivalic acid.

(A4) The monohydroxy compound can be used alone or in combination of two or more.

Other examples of the (a4) monohydroxy compound include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, amyl alcohol, hexyl alcohol, and octyl alcohol.

(A5) Monoisocyanate compound (a5) Examples of the monoisocyanate compound include hexyl isocyanate and dodecyl isocyanate.

The transparent polyurethane containing the carboxy group (A) is the polyisocyanate compound (a1) described above, in the presence or absence of a known urethanization catalyst such as dibutyltin dilaurylate, using an appropriate organic solvent. It can be synthesized by reacting (a2) a polyol compound and (a3) a dihydroxy compound containing a carboxy group, but it is preferable to react without a catalyst because it is not necessary to consider the final contamination of tin and the like. is there.

The organic solvent used when synthesizing the transparent polyurethane containing the carboxy group (A) has low reactivity with the isocyanate compound and the solubility of the produced polyurethane is not low, and is a basic functional group such as amine. A solvent having a boiling point of 50 ° C. or higher, preferably 80 ° C. or higher, more preferably 100 ° C. or higher is preferable, and a solvent having an SP value of less than 9.80 according to the Fedors estimation method may be used. preferable. The SP (Solubility Parameter) value is a value that serves as a guideline for the solubility of a two-component solution, and substances having a similar SP value tend to be easily mixed.

The SP value (δ) was proposed by Hildebrand and Scott, and the cohesive force between the solute and the solvent is only the London dispersion force (Van der Waals force in the narrow sense), electrostatic interaction, and association (hydrogen). It is a value defined by the square root of the cohesive energy density as shown in the following equation according to the theory of (solution) that has no action such as bond) and dipole interaction.
δ = (ΔE / V) ^1/2 = [(ΔH-RT) / V)] ^1/2
Here, V is the molecular content of the solvent, ΔE is the aggregation energy (evaporation energy), ΔH is the evaporation enthalpy, R is the gas constant, and T is the absolute temperature. The SI unit of the SP value is (J / cm ³ ) ^1/2 and (MPa) ^1/2 , but in the present specification, (cal / cm ³ ) ^1/2 which is conventionally used conventionally is used. SP value is calculated from the latent heat of vaporization required for the liquid 1 cm ³ evaporates.

From the above definition, the SP value is limited to a known liquid whose boiling point can be measured, but it is inconsistent from the method of measuring the solubility of a polymer in a solvent having a known SP value for the purpose of applying it to polymers and various compounds. It was derived so that there would be no. There is a Fedors estimation method as one of the estimation methods of the SP value.

Fedors considers that both the aggregation energy density and the molar molecular weight depend on the type and number of substituents, and proposes the following formula and a predetermined constant for each substituent.
δ = [(Σe _i ) / Σv _i )] ^1/2
Here, Sigma] e _i is the cohesive energy, [sigma] v _i denote mole molecular volume. The unit of aggregation energy is often J / mol, but in this specification, cal / mol conventionally used is used.

As an example, a calculation example using 1-octanol is shown. _{-CH 3 (e i = 1125cal /} mol, v i = 33.5cm 3 / mol) is one _{unit, -CH 2 - (e i =} 1180cal / mol, v i = 16.1cm 3 / mol) is seven _{units, -OH (e i = 7120cal /} mol, v i = 10.0cm 3 / mol) is because it is composed of one _{unit, Σe i = 1125 × 1 +} 1180 × 7 + 7120 × 1 = 16505cal / _{mol, Σv i = 33.5 × 1} + 16.1 × 7 + 10.0 × 1 = 156.2cm 3 / mol ^{next, δ = (16505 / 156.2)} 1/2 = 10.28 (cal / cm 3) 1 ^{/ 2} , and so on.

Estimation method and a predetermined constant for each substituent of Fedors _{(e i, v} i) is, R. F. Fedors: Polym. Eng. Sci. , 14 [2], 147-154 (1974).

As a result of synthesizing (A) a transparent polyurethane containing a carboxy group using various solvents, the present inventor has found that the color tone of the (A) carboxy group-containing transparent polyurethane obtained differs depending on the solvent used. I found it. That is, it has been found that a transparent polyurethane containing an (A) carboxy group having a small yellowness (b * value) can be obtained by using a solvent having an SP value of less than 9.80 according to the above Fedors estimation method.

This SP value is more preferably 7.00 or more and less than 9.50, and further preferably 7.50 or more and less than 9.00. Solvents having an SP value of less than 9.80 according to Fedor's estimation method include propylene glycol monomethyl ether acetate (SP value 8.73), diethylene glycol monoethyl ether acetate (SP value 9.01), and diethylene glycol monobutyl ether acetate (SP value 9.01). SP value 8.94), 1,4-butanediol diacetate (SP value 9.64), tripropylene glycol dimethyl ether (SP value 8.06), propylene glycol dimethyl ether (SP value 7.52), diethylene glycol dimethyl ether (SP value 7.52). SP value 8.10), diethylene glycol dibutyl ether (SP value 8.29), triethylene glycol dimethyl ether (SP value 8.37), dipropylene glycol dimethyl ether (SP value 7.88), tripropylene glycol dimethyl ether (SP value 8) .06), n-propyl acetate (SP value 8.72), n-butyl acetate (SP value 8.70), 1,4-dioxane (SP value 8.64), methyl ethyl ketone (SP value 8.98), Methyl isobutyl ketone (SP value 8.68), diisobutyl ketone (SP value 8.50), isophorone (SP value 9.20), tetrahydrofuran (SP value 8.28), 4-methyltetrahydropyran (SP value 8.13) ), Cyclopentyl methyl ether (SP value 8.13) and the like. Among these, diethylene glycol monobutyl ether acetate, 1,4-butanediol diacetate, tripropylene glycol dimethyl ether, propylene glycol dimethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol dimethyl ether, n-propyl acetate, N-butyl acetate, 1,4-dioxane, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, isophorone, tetrahydrofuran, 4-methyltetrahydropyran and cyclopentyl methyl ether are preferable. As will be described later, when triethylene glycol dimethyl ether or 4-methyltetrahydropyran is used as the synthetic solvent, a transparent synthetic solution can be obtained, which is preferable in producing a transparent polyurethane film. A more preferred solvent is 4-methyltetrahydropyran.

The order in which the raw materials are charged when synthesizing the above-mentioned (A) carboxy group-containing transparent polyurethane is not particularly limited, but usually (a2) polyol compound and (a3) carboxy group-containing dihydroxy compound are first. After being dissolved or dispersed in the above solvent, the polyisocyanate compound (a1) was added dropwise at 20 to 150 ° C., more preferably 60 to 120 ° C., and then 30 to 160 ° C., more preferably 50 ° C. These are reacted at ~ 130 ° C.

The molar ratio of the raw material is adjusted according to the molecular weight and acid value of the target polyurethane, but when the (a4) monohydroxy compound is introduced into the polyurethane, the end of the polyurethane molecule becomes an isocyanate group. It is necessary to use (a1) a polyisocyanate compound in excess of (a2) a polyol compound and (a3) a dihydroxy compound containing a carboxy group (so that the isocyanato group is in excess of the total number of hydroxyl groups). When introducing a (a5) monoisocyanate compound into polyurethane, (a1) polyisocyanate is more than (a2) a polyol compound and (a3) a dihydroxy compound containing a carboxy group so that the end of the polyurethane molecule becomes a hydroxy group. It is necessary to use less compound (so that there are fewer isocyanato groups than the total number of hydroxyl groups).

Specifically, the molar ratio of these charges is as follows: (a1) isocyanato group of polyisocyanate compound: ((a2) hydroxyl group of polyol compound + hydroxyl group of dihydroxy compound containing (a3) carboxy group) is 0.5 to It is 1.5: 1, preferably 0.8 to 1.2: 1, more preferably 0.95 to 1.05: 1.

Further, the hydroxyl group of the (a2) polyol compound: the hydroxyl group of the dihydroxy compound containing the (a3) carboxy group is 1: 0.1 to 30, preferably 1: 0.3 to 10.

When the (a4) monohydroxy compound is used, the number of moles of the (a1) polyisocyanate compound is excessively larger than the number of moles of ((a2) polyol compound + (a3) dihydroxy compound containing a carboxy group), and (a4). ) It is preferable to use the monohydroxy compound in an amount of 0.5 to 1.5 times, preferably 0.8 to 1.2 times, the molar amount of the excess molar number of the isocyanate group.

When (a5) a monoisocyanate compound is used, the number of moles of ((a2) polyol compound + (a3) dihydroxy compound containing a carboxy group) is made larger than the number of moles of (a1) polyisocyanate compound, and the hydroxyl group is used. It is preferably used in an amount of 0.5 to 1.5 times, preferably 0.8 to 1.2 times, the excess molar amount.

In order to introduce the (a4) monohydroxy compound into the (A) carboxy group-containing transparent polyurethane, the reaction between the (a2) polyol compound and the (a3) carboxy group-containing dihydroxy compound and the (a1) polyisocyanate compound. (A4) monohydroxy in the reaction solution in order to react the isocyanato groups remaining at both ends of the transparent polyurethane containing the carboxy group with the (a4) monohydroxy compound. The compound is added dropwise at 20-150 ° C., more preferably 70-120 ° C. and then held at the same temperature to complete the reaction.

In order to introduce (a5) a monoisocyanate compound into (A) a transparent polyurethane containing a carboxy group, a reaction between (a2) a polyol compound and (a3) a dihydroxy compound containing a carboxy group and (a1) a polyisocyanate compound. (A5) Monoisocyanate compound in the reaction solution in order to react the hydroxyl groups remaining at both ends of the transparent polyurethane containing the carboxy group with the (a5) monoisocyanate compound. Is added dropwise at 20 to 150 ° C., more preferably 50 to 120 ° C., and then held at the same temperature to complete the reaction.

Examples of the (B) epoxy compound include bisphenol A type epoxy compound, hydrogenated bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, and N-glycidyl type. Epoxy resin, bisphenol A novolak type epoxy resin, chelate type epoxy resin, glioxal type epoxy resin, amino group containing epoxy resin, rubber modified epoxy resin, dicyclopentadiene phenolic type epoxy resin, silicone modified epoxy resin, ε-caprolactone modified epoxy Examples thereof include an epoxy compound having two or more epoxy groups in one molecule, such as a resin, an aliphatic epoxy resin containing a glycidyl group, and an alicyclic epoxy resin containing a glycidyl group.

In particular, a polyfunctional epoxy compound having three or more epoxy groups in one molecule can be used more preferably. Examples of such epoxy compounds include EHPE (registered trademark) 3150 (manufactured by Daicel Corporation), jER (registered trademark) 604 (manufactured by Mitsubishi Chemical Corporation), and EPICLON (registered trademark) EXA-4700 (manufactured by DIC Corporation). , EPICLON (registered trademark) HP-7200 (manufactured by DIC Corporation), pentaerythritol tetraglycidyl ether, pentaerythritol triglycidyl ether, TEPIC (registered trademark) -S (manufactured by Nissan Chemical Corporation) and the like.

The compounding ratio of the transparent polyurethane containing the (A) carboxy group to the (B) epoxy compound is 0.5 to 1.5 as the equivalent ratio of the carboxy group in the polyurethane to the epoxy group of the (B) epoxy compound. Is preferable, 0.7 to 1.3 is more preferable, and 0.9 to 1.1 is further preferable.

Examples of the (D) curing accelerator include phosphine compounds such as triphenylphosphine and tributylphosphine (manufactured by Hokuko Kagaku Kogyo Co., Ltd.) and Curesol (registered trademark) (imidazole-based epoxy resin curing agent: manufactured by Shikoku Kasei Kogyo Co., Ltd.). , 2-Phenyl-4-methyl-5-hydroxymethylimidazole, U-CAT (registered trademark) SA series (DBU salt: manufactured by San-Apro Co., Ltd.), U-CAT (registered trademark) 5003 (phosphine-based compound: San-Apro Co., Ltd.) Made) and the like. As for the amount of these used, if the amount used is too small, there is no effect of addition, and if the amount used is too large, the electrical insulation property deteriorates. Therefore, 0.1 to 0.1 to the total mass of (A) and (B). 10% by mass, more preferably 0.5 to 6% by mass, still more preferably 0.5 to 5% by mass, and particularly preferably 0.5 to 3% by mass.

Alternatively, a curing aid may be used in combination. Examples of the curing aid include polyfunctional thiol compounds and oxetane compounds. Examples of the polyfunctional thiol compound include pentaerythritol tetrakis (3-mercaptopropionate), tris-[(3-mercaptopropionyloxy) -ethyl] -isocyanurate, trimethylpropanthris (3-mercaptopropionate), and Karenz. (Registered trademark) MT series (manufactured by Showa Denko KK) and the like. Examples of the oxetane compound include Aron Oxetane (registered trademark) series (manufactured by Toagosei Co., Ltd.), ETERNCOLL (registered trademark) OXBP and OXMA (manufactured by Ube Industries, Ltd.). As for the amount of these used, if the amount used is too small, there is no effect of addition, and if the amount used is too large, the curing speed becomes too fast and the handleability deteriorates. Therefore, 0.1 with respect to the mass of (B). It is preferably from 10% by mass, more preferably 0.5 to 6% by mass.

The thermosetting composition (sometimes referred to as protective film ink) preferably contains the solvent (C) in an amount of 95.0% by mass or more and 99.9% by mass or less, and preferably 96% by mass or more and 99.7% by mass or less. It is more preferable to contain 97% by mass or more and 99.5% by mass or less. As the solvent (C), it is preferable to use the solvent used for the synthesis of the transparent polyurethane (A) containing a carboxy group as it is, but another solvent is used in order to adjust the solubility and printability of the polyurethane resin. You can also do it. The other solvent that can be used may be a solvent outside the SP value range of the solvent that is preferably used for the synthesis of the transparent polyurethane (A) containing a carboxy group. Considering the stability of the thermosetting composition for the protective film, the boiling point of the solvent is preferably 60 ° C to 300 ° C, more preferably 70 ° C to 250 ° C. When the boiling point is less than 60 ° C., it is easy to dry at the time of printing and unevenness is likely to occur. If the boiling point is higher than 300 ° C., it is not suitable for industrial production because it requires a long time heat treatment at a high temperature during drying and curing.

Examples of such a solvent include propylene glycol monomethyl ether acetate (boiling point of 146 ° C.), γ-butyrolactone (boiling point of 204 ° C.), diethylene glycol monoethyl ether acetate (boiling point of 218 ° C.), tripropylene glycol dimethyl ether (boiling point of 243 ° C.) and the like. Solvents used for polyurethane synthesis, ether solvents such as propylene glycol dimethyl ether (boiling point 97 ° C.), diethylene glycol dimethyl ether (boiling point 162 ° C.), isopropyl alcohol (boiling point 82 ° C.), t-butyl alcohol (boiling point 82 ° C.), propylene Glycol monomethyl ether (boiling point 120 ° C), 1-hexanol (boiling point 151 ° C), diethylene glycol monomethyl ether (boiling point 194 ° C), diethylene glycol monoethyl ether (boiling point 196 ° C), diethylene glycol monobutyl ether (boiling point 230 ° C), triethylene glycol (boiling temperature 230 ° C) Solvents containing hydroxyl groups such as ethyl lactate (boiling point 276 ° C) and ethyl lactate (boiling point 154 ° C), methyl ethyl ketone (boiling point 80 ° C.), ethyl acetate (boiling point 77 ° C.) and n-propyl acetate (boiling point 102 ° C.) can be used. These solvents may be used alone or in combination of two or more. When two or more types are mixed, in addition to the solvent used for the synthesis of (A) carboxy group-containing transparent polyurethane, aggregation and precipitation may occur in consideration of the solubility of the polyurethane resin and epoxy resin used. It is preferable to use a solvent having a hydroxy group and a boiling point of more than 100 ° C., which does not occur, or a solvent having a boiling point of 100 ° C. or lower from the viewpoint of drying property of the protective film ink.

The protective film ink contains the transparent polyurethane containing the carboxy group (A), the epoxy compound (B), and the solvent (C), and the content of the solvent (C) is 95.0% by mass or more and 99.9. Mix so as to be less than% by mass. Further, if necessary, (D) a curing accelerator can be added. (D) When the curing accelerator is blended, it can be used by stirring so that it becomes uniform after blending.

The solid content concentration in such a protective film ink varies depending on the desired film thickness and printing method, but is preferably 0.1 to 10% by mass, preferably 0.5% by mass to 5% by mass. More preferred. When the solid content concentration is in the range of 0.1 to 10% by mass, there is no problem that electrical contact cannot be made due to the film thickness becoming too thick when applied on a transparent conductive film, and it is sufficient. A protective film having weather resistance and light resistance can be obtained.

Further, if the protective film ink contains halogen, when the protective film of the transparent conductive film is used, the halogen remains in the protective film and adversely affects the conductive portion. Therefore, the lower the halogen content, the better. preferable. The amount of halogen contained in the protective film ink is preferably 200 mass ppm or less, more preferably 100 mass ppm or less, still more preferably 50 mass ppm or less, and particularly preferably 10 mass ppm or less. (B) The epoxy compound is a halogen-free epoxy compound produced by a production method that does not use epichlorohydrin as a synthetic raw material, for example, oxidation of a compound containing a carbon-carbon double bond with a peroxide such as hydrogen peroxide. It is preferable to use it.

Using the protective film ink described above, a printing pattern is formed on the base material on which the transparent conductive layer is formed by a printing method such as a bar coat printing method, a gravure printing method, an inkjet method, or a slit coating method. After the solvent of the print pattern is dried and removed, it is cured by heat treatment as necessary to obtain a protective film. By forming the protective film on a transparent conductive layer formed on a transparent base material, a transparent conductive film having a transparent conductive layer having a protective film with little change in sheet resistance and haze after light irradiation can be obtained. Obtainable. As used herein, "transparent" means that the total light transmittance is 75% or more.

When the protective film ink is cured by heating, it is heated under the conditions of a temperature of 100 ° C. or less and a heating time of 10 minutes or less.

The transparent conductive layer can be produced by printing a conductive ink on a transparent base material. When a transparent conductive layer is produced using silver nanowire ink as the conductive ink, the surface area per unit mass of the silver nanowire is large, and fine wiring and the like have low insulation reliability at high temperature and high humidity. Protection with the protective film ink according to the embodiment is effective.

Next, a transparent conductive film to which the above protective film can be provided will be described. The transparent conductive film is provided with a transparent base material and a transparent conductive layer on at least one main surface of the transparent base material, and is provided with the protective film on the surface of the transparent conductive layer opposite to the transparent base material. One side or both sides of the transparent conductive film may be covered with a peeling (separate) film having a protective function.

<Transparent base material>
The transparent substrate preferably has a total light transmittance of 80% or more. For example, a resin film such as polyester (polyethylene terephthalate [PET], polyethylene naphthalate [PEN], etc.), polycarbonate, acrylic resin (polymethylmethacrylate [PMMA], etc.), cycloolefin polymer and the like can be preferably used. In addition, these transparent substrates may be provided with a single layer having functions such as easy adhesion, optical adjustment (anti-glare, anti-reflection, etc.), hard coat, etc., as long as the optical properties, electrical properties, and bending resistance are not impaired. A plurality of them may be provided, and one side or both sides may be provided. Among these resin films, polyethylene terephthalate and cycloolefin polymers are preferably used from the viewpoints of excellent light transmission (transparency), flexibility, mechanical properties and the like. Examples of cycloolefin polymers include norbornene hydride ring-opening metathesis polymerized cycloolefin polymers (ZEONOR (registered trademark, manufactured by Nippon Zeon Co., Ltd.), ZEONEX (registered trademark, manufactured by Nippon Zeon Co., Ltd.), ARTON (registered trademark, JSR stock). (Company), etc.), norbornene / ethylene-added copolymerized cycloolefin polymer (APEL (registered trademark, manufactured by Mitsui Kagaku Co., Ltd.), TOPAS (registered trademark, manufactured by Polyplastics Co., Ltd.)) can be used. Among these, those having a glass transition temperature (Tg) of 90 to 170 ° C. are preferable because they can withstand heating in a subsequent process such as a lead-out wiring and a connector portion, and those having a glass transition temperature (Tg) of 125 to 145 ° C. are more preferable. The thickness is preferably 1 to 200 μm, more preferably 5 to 150 μm, and even more preferably 8 to 100 μm.

<Transparent conductive layer>
Examples of the conductive fibers constituting the transparent conductive layer include metal nanowires and carbon fibers, and metal nanowires can be preferably used. The metal nanowire is a metal having a diameter on the order of nanometers, and is a conductive material having a wire-like shape. In this embodiment, metal nanotubes, which are conductive materials having a porous or non-porous tubular shape, may be used together with (mixed with) the metal nanowires or instead of the metal nanowires. In the present specification, both "wire-like" and "tube-like" are linear, but the former is intended to have a hollow center and the latter to be hollow in the center. The properties may be flexible or rigid. The former is referred to as "metal nanowires in a narrow sense" and the latter is referred to as "metal nanotubes in a narrow sense". Hereinafter, in the present specification, "metal nanowires" are used in the meaning of including metal nanowires in a narrow sense and metal nanotubes in a narrow sense. Metal nanowires in a narrow sense and metal nanotubes in a narrow sense may be used alone or in combination.

As a method for producing metal nanowires, a known production method can be used. For example, silver nanowires can be synthesized by reducing silver nitrate in the presence of polyvinylpyrrolidone using the Poly-ol method (see Chem. Matter., 2002, 14, 4736). Gold nanowires can also be similarly synthesized by reducing chloroauric acid hydrate in the presence of polyvinylpyrrolidone (see J. Am. Chem. Soc., 2007, 129, 1733). The techniques for large-scale synthesis and purification of silver nanowires and gold nanowires are described in detail in International Publication No. 2008/073143 and International Publication No. 2008/046058. Gold nanotubes having a porous structure can be synthesized by reducing a gold chloride solution using silver nanowires as a template. Here, the silver nanowires used in the template dissolve in the solution by a redox reaction with chloroauric acid, resulting in gold nanotubes having a porous structure (JAm. Chem. Soc., 2004, 126, 3892). See -3901).

The average diameter of the metal nanowires is preferably 1 to 500 nm, more preferably 5 to 200 nm, further preferably 5 to 100 nm, and particularly preferably 10 to 50 nm. The average length of the major axis of the metal nanowire is preferably 1 to 100 μm, more preferably 1 to 80 μm, further preferably 2 to 70 μm, and particularly preferably 5 to 50 μm. In the metal nanowire, the average diameter and the average length of the major axis satisfy the above range, and the average aspect ratio is preferably larger than 5, more preferably 10 or more, and more than 100. It is more preferable, and it is particularly preferable that it is 200 or more. Here, the aspect ratio is a value obtained by a / b when the average diameter of the diameter of the metal nanowire is approximated to b and the average length of the major axis is approximated to a. a and b can be measured using a scanning electron microscope (SEM) and an optical microscope. Specifically, for b (average diameter), a field emission scanning electron microscope JSM-7000F (manufactured by JEOL Ltd.) was used to measure the dimensions (diameter) of 100 arbitrarily selected silver nanowires, and the arithmetic average thereof was measured. The value can be calculated. In addition, the shape measurement laser microscope VK-X200 (manufactured by Keyence Co., Ltd.) was used to calculate a (average length), and the dimensions (length) of 100 arbitrarily selected silver nanowires were measured, and the arithmetic was performed. The average value can be calculated.

As the material of such a metal nanowire, at least one selected from the group consisting of gold, silver, platinum, copper, nickel, iron, cobalt, zinc, ruthenium, rhodium, palladium, cadmium, osmium, and iridium, and metals thereof. Examples thereof include alloys in which the above are combined. In order to obtain a coating film having low surface resistance and high total light transmittance, it is preferable to contain at least one of gold, silver and copper. Since these metals have high conductivity, the density of the metal occupying the surface can be reduced when a constant surface resistance is obtained, so that a high total light transmittance can be realized. Among these metals, it is more preferable to contain at least one of gold or silver. Optimal embodiments include silver nanowires.

The transparent conductive layer contains conductive fibers and a binder resin. The binder resin can be applied without limitation as long as it has bending resistance and transparency, which is the subject of the present invention, but when a metal nanowire using the polyol method is used as the conductive fiber, it is used for manufacturing the binder resin. From the viewpoint of compatibility with the solvent (polyol), it is preferable to use a binder resin that is soluble in alcohol, water, or a mixed solvent of alcohol and water. Specifically, water-soluble cellulosic resins such as poly-N-vinylpyrrolidone, methylcellulose, hydroxyethylcellulose, and carboxymethylcellulose, butyral resin, and poly-N-vinylacetamide (PNVA (registered trademark)) can be used. Poly-N-vinylacetamide is a homopolymer of N-vinylacetamide (NVA), but a copolymer containing 70 mol% or more of N-vinylacetamide (NVA) can also be used. Examples of the monomer copolymerizable with NVA include N-vinylformamide, N-vinylpyrrolidone, acrylic acid, methacrylic acid, sodium acrylate, sodium methacrylate, acrylamide, acrylonitrile and the like. As the content of the copolymerization component increases, the sheet resistance of the obtained transparent conductive film increases, the adhesion between the silver nanowires and the substrate tends to decrease, and the heat resistance (thermal decomposition start temperature) also decreases. Since there is a tendency, the monomer unit derived from N-vinylacetamide is preferably contained in the polymer in an amount of 70 mol% or more, more preferably 80 mol% or more, and further preferably 90 mol% or more. The weight average molecular weight of such a polymer based on the absolute molecular weight is preferably 30,000 to 4,000,000, more preferably 100,000 to 3,000,000, and even more preferably 300,000 to 1,500,000. The absolute molecular weight is measured by the following method.

<Absolute molecular weight measurement>
The binder resin was dissolved in the following eluate and allowed to stand for 20 hours. The concentration of the binder resin in this solution is 0.05% by mass.
This was filtered through a 0.45 μm membrane filter, and the filtrate was measured by GPC-MALS.
GPC: Showa Denko Corporation Shodex (registered trademark) SYSTEM21
Column: TSKgel (registered trademark) G6000PW manufactured by Tosoh Corporation
Column temperature: 40 ° C
Eluent: 0.1 mol / L NaH ₂ PO ₄ aqueous solution + 0.1 mol / L Na ₂ HPO ₄ aqueous solution Flow rate: 0.64 mL / min
Sample injection volume: 100 μL
MALS Detector: Wyatt Technology Corporation, DAWN® DSP
Laser wavelength: 633 nm
Multi-angle fit method: Berry method

The above resins may be used alone or in combination of two or more. When two or more kinds are combined, a simple mixture may be used, or a copolymer may be used.

The transparent conductive layer is formed by printing a conductive ink containing the conductive fibers, a binder resin and a solvent on at least one main surface of a transparent base material and drying and removing the solvent.

The solvent is not particularly limited as long as the conductive fibers show good dispersibility and the binder resin dissolves in the solvent. However, when the conductive fibers are metal nanowires synthesized by the polyol method, they are used for their production. From the viewpoint of compatibility with the solvent (polyol), alcohol, water or a mixed solvent of alcohol and water is preferable. As described above, it is preferable to use a binder resin that is soluble in alcohol, water, or a mixed solvent of alcohol and water. It is more preferable to use a mixed solvent of alcohol and water in that the drying rate of the binder resin can be easily controlled. The alcohol is a saturated monohydric alcohol (methanol, ethanol, normal propanol and isopropanol) having 1 to 3 carbon atoms represented by _{C n} H _{2n + 1 OH (n is an integer of 1 to 3) [hereinafter, simply "carbon".} Notated as "saturated monohydric alcohol with 1 to 3 atomic numbers"]. It is preferable that the saturated monohydric alcohol having 1 to 3 carbon atoms is contained in an amount of 40% by mass or more based on the total alcohol. Using a saturated monohydric alcohol having 1 to 3 carbon atoms facilitates drying, which is convenient in terms of the process. As the alcohol, an alcohol other than the saturated monohydric alcohol having 1 to 3 carbon atoms can be used in combination. Examples of alcohols other than saturated monohydric alcohols having 1 to 3 carbon atoms that can be used in combination include ethylene glycol, propylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether. Be done. The drying rate can be adjusted by using in combination with the saturated monohydric alcohol having 1 to 3 carbon atoms. The total alcohol content in the mixed solvent is preferably 5 to 90% by mass. If the alcohol content in the mixed solvent is less than 5% by mass or more than 90% by mass, a striped pattern (coating spot) is generated when coating, which is unsuitable.

The conductive ink can be produced by stirring and mixing the binder resin, conductive fibers and a solvent with a rotating revolution stirrer or the like. The content of the binder resin contained in the conductive ink is preferably in the range of 0.01 to 1.0% by mass. The content of conductive fibers contained in the conductive ink is preferably in the range of 0.01 to 1.0% by mass. As the compounding ratio (mass ratio) of the conductive fiber and the binder resin, the binder resin is preferably 0.1 to 10 with respect to the conductive fiber. The content of the solvent contained in the conductive ink is preferably in the range of 98.0 to 99.98% by mass.

Further, if halogen is contained in the conductive ink as in the case of the protective film ink described above, when the conductive layer of the transparent conductive film is formed, the halogen remains in the conductive film and adversely affects the conductive portion. The lower the content, the better.

The conductive ink can be printed by a printing method such as a bar coating method, a spin coating method, a spray coating method, a gravure method, or a slit coating method. The shape of the printed film or pattern formed at this time is not particularly limited, but the wiring formed on the base material, the shape of the electrode as a pattern, or the film covering the entire surface or a part of the base material. The shape as (solid pattern) and the like can be mentioned. The formed pattern can be made conductive by heating and drying the solvent. The preferable thickness of the transparent conductive layer or the transparent conductive pattern obtained after solvent drying varies depending on the diameter of the conductive fibers used and the desired surface resistance value, but is 10 to 300 nm, more preferably 30 to 200 nm. If it is thicker than 10 nm, the number of intersections of conductive fibers increases, so that good conductivity is exhibited. Further, when it is thinner than 300 nm, light is easily transmitted and reflection by conductive fibers is suppressed, so that good optical characteristics are exhibited. The formed transparent conductive layer or transparent conductive pattern can be made conductive by heating and drying the solvent, but if necessary, the transparent conductive layer or the transparent conductive pattern may be appropriately irradiated with light.

Hereinafter, examples of the present invention will be specifically described. The following examples are for facilitating the understanding of the present invention, and the present invention is not limited to these examples.

<Synthesis example of (A) transparent polyurethane containing a carboxy group>
Synthesis example 1.
In a 2L three-necked flask equipped with a stirrer, thermometer, and condenser, C-1015N (manufactured by Kuraray Co., Ltd., polycarbonate diol, 1,9-nonanediol and 2-methyl-1,8-octanediol) as the (a2) polyol compound (Catalog value) 23.23 g, (a3) 2,2-dimethylolbutanoic acid (DMBA) (manufactured by Koshu Chosei Kako Co., Ltd.) as a dihydroxy compound containing a carboxy group, and (a3) 15 g. 86.8 g of propylene glycol monomethyl ether acetate (PMA (SP value: 8.73)) was charged as a solvent, and the 2,2-dimethylolbutanoic acid was dissolved at 90 ° C.

After visually confirming that it was dissolved, a dropping funnel was used to obtain (a1) Death Module (registered trademark) -W (bis- (4-isocyanatocyclohexyl) methane) as a polyisocyanate compound, manufactured by Sumika Cobestrourethane Co., Ltd. ) 32.78 g was added dropwise over 30 minutes. After completion of the dropwise addition, the temperature was raised to 100 ° C., the reaction was carried out at 100 ° C. for 7 hours, and after confirming by IR that the isocyanato group had almost disappeared, 0.5 g of isobutanol was added, and the reaction was further carried out at 100 ° C. for 2 hours. Was done.

45.1 g of PMA as a solvent was added so that the solid content concentration became 35% by mass, and the mixture was stirred until it became uniform. The weight average molecular weight of the obtained transparent polyurethane (A) containing a carboxy group was 32,300.

Synthesis Examples 2 to 13.
A transparent polyurethane containing (A) carboxy group was synthesized in the same manner as in Synthesis Example 1 except that the raw materials shown in Table 1 were used. The main skeleton and molecular weight of the (a2) polyol compound other than C-1015N used in Synthesis Example 1 in the table are as follows.
UC-100: Polyalkylene carbonate diol, molecular weight 1000 (catalog value) (manufactured by Ube Industries, Ltd.)
PH-50: Polyalkylene carbonate diol, molecular weight 500 (catalog value) (manufactured by Ube Industries, Ltd.)
G3450J: Polyalkylene carbonate diol, molecular weight 800 (catalog value) (manufactured by Asahi Kasei Chemicals Co., Ltd.)
T5651: Polyalkylene carbonate diol, molecular weight 1000 (catalog value) (manufactured by Asahi Kasei Chemicals Co., Ltd.)

Synthesis Examples 14-23
The synthesis was carried out in the same manner except that the solvent in Synthesis Example 1 was changed as shown in Table 2. In the case of a solvent having a boiling point of 100 ° C. or lower, the reaction was carried out under the condition that the reaction temperature was lowered by 5 ° C. from the boiling point.

The abbreviations in the table are shown below. The NPAc used was manufactured by Showa Denko KK, but the other solvent used was purchased from Fujifilm Wako Pure Chemical Industries, Ltd.
PGDM: Propylene glycol dimethyl ether (SP value: 7.52)
DEGDM: Diethylene glycol dimethyl ether (SP value: 8.1)
CPME: Cyclopentyl methyl ether (SP value: 8.13)
MTHP: 4-Methyltetrahydropyran (SP value: 8.13)
TEGDM: Triethylene glycol dimethyl ether (SP value: 8.37)
NPAc: n-propyl acetate (SP value: 8.72)
BCA: Diethylene glycol monobutyl ether acetate (SP value: 8.94)
ECA: Diethylene glycol monoethyl ether acetate (SP value: 9.01)
BDDA: 1,4-butanediol diacetate (SP value: 9.64)
NMP: N-methylpyrrolidone (SP value: 11.52)

<Visual inspection>
Tables 1 and 2 show the visual appearance of each polyurethane resin solution obtained in Synthesis Examples 1 to 23.
It can be seen that in Synthesis Examples 1 to 8 in Table 1, the appearance of the obtained resin does not change only by changing the conditions such as polyol, polyisocyanate, dicarboxylic acid, and acid value. In Synthesis Examples 1, 2, 3, 5, and 8 and Synthesis Examples 9 to 13, only the solvent at the time of synthesis was changed, but it can be seen that they are colored.

Further, from Table 2, it can be seen that even if the obtained resin skeleton is the same, the appearance changes remarkably only by changing the solvent.

From these results, it can be seen that the solvent used during the synthesis has a great influence on the coloring and does not depend on the specific resin structure in the examined range. It should be noted that white turbidity and milky whiteness are caused by the compatibility between the resins, and there is no problem because they become transparent when they are formed into a film, which is the shape to be finally used. However, there is no problem because the turbidity is eliminated by adding a good solvent.

<Evaluation of optical characteristics>
Example 1
To 10 g of the polyurethane resin solution having a solid content concentration of 35% by mass obtained in Synthesis Example 14, 10 g of 1-hexanol (manufactured by Toyo Synthetic Chemical Industry Co., Ltd.) was added, and the mixture was stirred with an AS ONE mix rotor for 3 hours to have a solid content concentration of 17 It was set to 5.5% by mass. After that, using a film applicator with a micrometer (manufactured by Takumi Giken Co., Ltd.), a COP film (ZF14-100 manufactured by Nippon Zeon Corporation, thickness 100 μm) with no surface treatment was coated with a wet film thickness of 300 μm, and at 100 ° C. It was dried for 30 minutes. The transparent polyurethane film obtained on the COP film was peeled off from the COP, and the film thickness measured with a micrometer was 50 μm. Using this film, a test piece cut out to a size of 3 cm × 3 cm was cut out to a size of 3 cm × 3 cm, and a color difference meter COH7700 manufactured by Nippon Denshoku Kogyo was used to set the light source to D65 in accordance with the color measurement method of JIS Z8722, and the color difference (b *). Value) was measured.

Examples 2 to 10, Comparative Examples 1 and 2.
The measurement was carried out in the same manner as in Example 1 except that the polyurethane resin solution obtained in each synthetic example shown in Table 3 was used. The results are shown in Table 3.

From Table 3, it can be seen that in Examples 1 to 10, the optical characteristics, particularly the b * value, are 0.25 or less, and the film is suitable for use in obtaining a colorless and transparent film.

<Thermosetting composition for protective film>
Preparation Example 1
(A) 10 g of the 35 mass% polyurethane resin solution obtained in Synthesis Example 14 as a transparent polyurethane containing a carboxy group, and (B) 0.49 g of pentaerythritol tetraglycidyl ether (manufactured by Showa Denko Co., Ltd.) as an epoxy resin. D) 0.24 g of U-CAT (registered trademark) 5003 as a curing accelerator, 65.19 g of 1-hexanol as a solvent (C), and 65.19 g of ethyl acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to the mix rotor. The mixture was stirred for 2 hours so as to be uniform. The halogen content of the obtained protective film ink was 10 mass ppm or less. The halogen atom content is a value measured according to JIS K7243-3.

Preparation Examples 2 to 12
A composition was prepared in the same manner as in Preparation Example 1 except that the polyurethane resin solution was replaced with the one shown in Table 4.

Preparation Examples 13, 14
A composition was prepared in the same manner as in Preparation Example 1 except that the polyurethane resin solution was replaced with the one shown in Table 4 and the curing accelerator was replaced with U-CAT (registered trademark) SA102 (manufactured by Sun Appro Co., Ltd.).

Preparation Example 15
A composition was prepared in the same manner as in Preparation Example 1 except that the polyurethane resin solution was replaced with that shown in Table 4 and no curing accelerator was used.

<Transparent conductive film>
<Manufacturing of silver nanowires>
Polyvinylpyrrolidone K-90 (manufactured by Nippon Shokubai Co., Ltd.) (0.98 g), AgNO ₃ (1.04 g) and FeCl ₃ (0.8 mg) were dissolved in ethylene glycol (250 ml) and 1 at 150 ° C. Heat reaction for hours. The obtained crude silver nanowire dispersion was dispersed in 2000 ml of methanol, and a small desktop tester (manufactured by Nippon Gaishi Co., Ltd., using ceramic membrane filter Sepilt, membrane area 0.24 m ² , pore diameter 2.0 μm, size Φ30 mm × 250 mm, filtration It was poured into a differential pressure of 0.01 MPa), cross-flow filtration was performed at a circulation flow velocity of 12 L / min and a dispersion temperature of 25 ° C. to remove impurities, and then concentrated until the total amount reached 100 g, and silver nanowires (average diameter:: average diameter: A methanol dispersion (26 nm, average length: 20 μm) was obtained. To calculate the average diameter of the obtained silver nanowires, a field emission scanning electron microscope JSM-7000F (manufactured by JEOL Ltd.) was used to measure the dimensions of 100 arbitrarily selected silver nanowires, and the arithmetic mean value thereof was measured. Asked. Further, in order to calculate the average length of the obtained silver nanowires, a shape measurement laser microscope VK-X200 (manufactured by Keyence Co., Ltd.) was used to measure the dimensions of 100 arbitrarily selected silver nanowires, and the arithmetic average value thereof was measured. Asked. As the methanol, ethylene glycol, AgNO ₃ , and FeCl ₃ , reagents manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. were used.

<Making conductive ink (silver nanowire ink)>
11 g of methanol dispersion of silver nanowires synthesized by the above polyol method (silver nanowire concentration 0.62% by mass), 3.5 g of water, 10.8 g of ethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), propylene glycol monomethyl ether (PGME) , Fujifilm Wako Pure Chemical Industries, Ltd.) 12.8 g, propylene glycol 1.2 g (PG, manufactured by Asahi Glass Co., Ltd.), PNVA (registered trademark) aqueous solution (manufactured by Showa Denko Co., Ltd., solid content concentration 10% by mass, weight average) 0.7 g (molecular weight 900,000) was mixed and stirred with a mix rotor VMR-5R (manufactured by AS ONE Co., Ltd.) for 1 hour at room temperature and in an air atmosphere (rotation speed 100 rpm) to prepare 40 g of silver nanowire ink.

<Formation of transparent conductive layer (silver nanowire layer)>
A4 as a transparent substrate subjected to plasma processing (gas used: nitrogen, transport speed: 50 mm / sec, processing time: 6 sec, set voltage: 400 V) using a plasma processing device (AP-T03 manufactured by Sekisui Chemical Industry Co., Ltd.) Using TQC automatic film applicator standard (manufactured by Cortec Co., Ltd.) and wireless bar coater OSP-CN-22L (manufactured by Cortec Co., Ltd.) on a cycloolefin polymer film ZF14-050 (thickness 50 μm manufactured by Nippon Zeon Co., Ltd.). , Silver nanowire ink was applied to the entire surface of the transparent substrate (ZF14-050) so that the wet film thickness was 22 μm (coating speed 500 mm / sec). Then, it was dried with hot air in an air atmosphere at 80 ° C. for 1 minute in an incubator HISPEC HS350 (manufactured by Kusumoto Kasei Co., Ltd.) to form a silver nanowire layer (film thickness after drying: 90 nm). The film thickness was measured using a film thickness measuring system F20-UV (manufactured by Filmometrics Co., Ltd.) based on the optical interferometry. The measurement points were changed, and the average value measured at three points was used as the film thickness. A spectrum from 450 nm to 800 nm was used for the analysis. According to this measurement system, the film thickness (Tc) of the silver nanowire ink coating film (transparent conductive layer) formed on the transparent base material (ZF14-050) can be directly measured.

<Formation of protective film (production of transparent conductive film)>
Example 11
On the silver nanowire layer formed on the transparent substrate, the thermosetting composition for the protective film of Preparation Example 1 shown in Table 4 was applied by TQC automatic film applicator standard (manufactured by Cortec Co., Ltd.) to the wireless bar coater OSP-. It was applied using CN-10M so that the wet film thickness was 5 μm. Then, it was dried with hot air (thermosetting) in an air atmosphere at 80 ° C. for 1 minute in an incubator HISPEC HS350 (manufactured by Kusumoto Kasei Co., Ltd.) to form a protective film (film thickness after drying: 90 nm). The film thickness of the protective film was measured using a film thickness measuring system F20-UV (manufactured by Filmometrics Co., Ltd.) based on the optical interferometry as well as the film thickness of the silver nanowire ink coating film described above. The measurement points were changed, and the average value measured at three points was used as the film thickness. A spectrum from 450 nm to 800 nm was used for the analysis. According to this measurement system, the total film thickness (Tc) of the silver nanowire ink coating film (transparent conductive layer) formed on the transparent substrate and the film thickness (Tp) of the protective film formed on the film thickness (Tp). Since (Tc + Tp) can be directly measured, the film thickness (Tp) of the protective film can be obtained by subtracting the film thickness (Tc) of the silver nanowire ink coating film (transparent conductive layer) measured earlier from this measured value.

Examples 12 to 23 and Comparative Examples 3 and 4 A transparent conductive film was produced in the same manner as in Example 11 except that the protective film compositions were replaced with those shown in Table 4.

<Surface resistance measurement>
A 3 cm x 3 cm test piece was cut out from the silver nanowire coating film coated on the entire surface of the above A4 size, and the terminal of the manual non-destructive resistance measuring instrument EC-80P (manufactured by Napson Co., Ltd.) was applied to the center of the test piece for measurement. .. Both films showed a sheet resistance value of about 40Ω / □.

<Total light transmittance, haze measurement, color measurement (b *)>
Using the above 3 cm x 3 cm test piece, a color difference meter based on the JIS Z8722 color measurement method, the JIS K7361-1 transparent material total light transmission measurement method, and the JIS K7136 transparent material haze determination method. Using COH7700 (manufactured by Nippon Denshoku Industries Co., Ltd.), the light source was set to D65, and the total light transmittance, haze, and color difference (b * value) were measured. The measurement results are summarized in Table 4.

From Table 4, the transparent conductive film with a protective film prepared from a resin synthesized using a solvent having an SP value of 9.80 or more has rainbow unevenness and cloudiness in appearance, and the b * value exceeds 1.00. .. In particular, when NMP having an SP value of more than 10 is used, the haze also has a value of more than 2.0, which shows that it is not suitable for a transparent conductive film. On the other hand, when the protective film resin is synthesized using a solvent having an SP value of less than 9.80 as in Examples 11 to 23, the haze is 2.0 or less and the b * value is 1.00. It is clear that it is less than that and suitable for a transparent conductive film.

Claims (14)

1. (A) A transparent polyurethane containing a carboxy group, characterized in that the b * value when a film is formed to a thickness of 50 μm is 0.25 or less.
2. Claim 1 in which the transparent polyurethane (A) containing a carboxy group is synthesized by using (a1) a polyisocyanate compound, (a2) a polyol compound, and (a3) a dihydroxy compound containing a carboxy group as a monomer. (A) A transparent polyurethane containing a carboxy group according to.
3. The transparent polyurethane containing the (A) carboxy group according to claim 2, wherein the (a2) polyol compound is a polycarbonate polyol.
4. The transparent polyurethane containing the (A) carboxy group according to claim 2 or 3, wherein the (a1) polyisocyanate compound is an aliphatic polyisocyanate or an alicyclic polyisocyanate.
5. A thermosetting composition containing (A) a transparent polyurethane containing a carboxy group having a b * value of 0.25 or less when a film is formed to a thickness of 50 μm, (B) an epoxy compound, and (C) a solvent. ..
6. The thermosetting composition according to claim 5, further comprising (D) a curing accelerator.
7. The thermosetting composition according to claim 5 or 6, wherein the (B) epoxy compound is a polyfunctional epoxy compound having three or more epoxy groups in one molecule.
8. A transparent conductive film having a transparent base material, a transparent conductive layer provided on at least one surface of the transparent base material, and a protective film provided on a surface of the transparent conductive layer opposite to the transparent base material. And
   The protective film contains (A) a transparent polyurethane containing a carboxy group having a b * value of 0.25 or less when the film is formed to a thickness of 50 μm, (B) an epoxy compound, and (C) a solvent. A transparent conductive film characterized by being a cured film of a thermosetting composition.
9. The transparent conductive film according to claim 8, wherein the transparent conductive layer contains metal nanowires.
10. The transparent conductive film according to claim 9, wherein the metal nanowire is a silver nanowire.
11. The method for producing a transparent polyurethane containing a carboxy group (A) according to any one of claims 1 to 4, wherein a solvent having an SP value of less than 9.80 according to the Fedors estimation method is used as the synthetic solvent.
12. The solvent is diethylene glycol monobutyl ether acetate, 1,4-butanediol diacetate, tripropylene glycol dimethyl ether, propylene glycol dimethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol dimethyl ether, n-propyl acetate, 10. The eleventh claim, which is any one selected from the group consisting of n-butyl acetate, 1,4-dioxane, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, isophorone, tetrahydrofuran, 4-methyltetrahydropyran, and cyclopentyl methyl ether. Method for producing transparent polyurethane.
13. The method for producing a transparent polyurethane according to claim 11, wherein the solvent is 4-methyltetrahydropyran or triethylene glycol dimethyl ether.
14. The method for producing a transparent polyurethane according to claim 11, wherein the solvent is methyl tetrahydropyran.