TW202031496A - Substrate for transparent conductive film and transparent conductive film capable of realizing a transparent conductive film having a small in-plane phase difference while suppressing warpage, whitening, and cracks - Google Patents

Abstract

The subject of the present invention is to provide a substrate for a transparent conductive film that is capable of realizing a transparent conductive film having a small in-plane phase difference while suppressing warpage, whitening, and cracks. The solution of the present invention is to use a film containing a predetermined polycarbonate resin and having a small dimensional shrinkage in a first direction and a second direction orthogonal to the first direction. Specifically, the substrate for transparent conductive film at 145 DEG C has a dimensional shrinkage in a 1 direction and a 2 direction orthogonal to the 1 direction less than 2%, while suppressing whitening and cracks in a sebum resistance test, and has an in-plane phase difference Re (550) less than 5 nm.

Description

Base material for transparent conductive film and transparent conductive film

The present invention relates to a substrate for a transparent conductive film and a transparent conductive film.

Conventionally, various resin films have been used as a base material for transparent conductive films used in touch panels and the like. Examples of materials constituting such resin films include polyethylene terephthalate (PET) and cycloolefin resins (COP). However, in conventional transparent conductive films, curling, whitening, and/or cracking may occur.

Prior art literature Patent literature Patent Document 1: Japanese Patent Application Publication No. 2017-190406

Problems to be solved by the invention

The present invention was made in order to solve the above-mentioned conventional problems, and its object is to provide a substrate for a transparent conductive film that can realize a transparent conductive film with a small in-plane phase difference while suppressing curling, whitening, and cracking. Means to solve the problem

(通式(I)中，Q表示可包含不同種原子之碳數3以上烴基，R₁ ~R₄ 分別獨立表示選自於由氫原子、碳數1~30脂肪族烴基及碳數6~20芳香族烴基所構成群組中之基團，n及m分別獨立表示0~10的整數；惟，Q不含與末端羥基鍵結的脂肪族烴基時，n及m分別獨立表示1~10的整數；且，R₁ 及R₂ 中之至少一者、與R₃ 及R₄ 中之至少一者分別選自於由氫原子及脂肪族烴基所構成之群組)； [化學式2]

(通式(II)中，R₁ 及R₂ 分別獨立表示鹵素原子、碳數1~20烷基、碳數1~20烷氧基、碳數6~20環烷基、碳數6~20芳基、碳數6~20環烷氧基或碳數6~20芳基氧基，p及q表示0~4的整數，X表示單鍵或選自下述通式(II’)所示二價有機基群中之基團)； [化學式3]

(通式(II’)中，R₃ 及R₄ 分別獨立表示氫原子、碳數1~10烷基或碳數6~10芳基，R₃ 與R₄ 亦可鍵結而形成脂肪族環)； (a)  具有以下通式(III)所示結構： [化學式4]

(通式(III)中，k表示4以上的整數，i表示1以上的整數，l表示1以上的整數，k’表示0或1的整數；R表示直鏈或支鏈烴基、可包含氟的苯基或氫原子；惟，上述樹脂總量中，70重量%以上為i=1)； (b)上述通式(I)所示結構單元與通式(II)所示結構單元的比率為1~30：99~70(莫耳比)%。 (c)重量平均分子量(Mw)為30,000~100,000； (d)相對於構成上述聚碳酸酯樹脂的結構單元總量，下述通式(1)及(2)所示的結構單元以雙酚酸換算值計分別含有2000ppm以下， 通式(1)： [化學式5]

通式(2)： [化學式6]

(上述通式(1)及(2)中的X與通式(II)中的相同)。 於一實施形態中，上述透明導電性薄膜用基材的玻璃轉移溫度(Tg)為145℃以上。 發明效果The transparent conductive film substrate in the embodiment of the present invention includes a polycarbonate resin, and the dimensional shrinkage rate at 145°C of the transparent conductive film substrate is in the first direction and the second direction orthogonal to the first direction. Each direction is 0.2% or less, whitening and cracking are suppressed in the sebum resistance test, and the in-plane phase difference Re(550) is 5 nm or less. In one embodiment, the thickness of the substrate is 10 μm to 80 μm. In one embodiment, the polycarbonate resin is substantially formed of the structural unit represented by the following general formula (I) and the structural unit represented by the following general formula (II), and satisfies the following conditions (a) to (d) , The structural unit represented by the following general formula (I) is derived from an aliphatic diol compound having an aliphatic hydrocarbon group bonded to a terminal hydroxyl group, [Chemical formula 1]

(In the general formula (I), Q represents a hydrocarbon group with 3 or more carbon atoms that may contain different kinds of atoms, and R ₁ to R ₄ are independently selected from hydrogen atoms, aliphatic hydrocarbon groups with 1 to 30 carbon atoms, and 6 to carbon atoms. In the group consisting of 20 aromatic hydrocarbon groups, n and m each independently represent an integer from 0 to 10; however, when Q does not contain an aliphatic hydrocarbon group bonded to the terminal hydroxyl group, n and m independently represent 1 to 10 And at least one of R ₁ and R ₂ and at least one of R ₃ and R ₄ are selected from the group consisting of a hydrogen atom and an aliphatic hydrocarbon group); [Chemical formula 2]

(In the general formula (II), R ₁ and R ₂ each independently represent a halogen atom, a C 1-20 alkyl group, a C 1-20 alkoxy group, a C 6-20 cycloalkyl group, a C 6-20 Aryl, C6-20 cycloalkoxy or C6-20 aryloxy, p and q represent an integer from 0 to 4, X represents a single bond or selected from the following general formula (II') The group in the divalent organic group); [Chemical formula 3]

(In the general formula (II'), R ₃ and R ₄ each independently represent a hydrogen atom, an alkyl group with 1 to 10 carbons, or an aryl group with 6 to 10 carbons. R ₃ and R ₄ can also be bonded to form an aliphatic ring ); (a) Having the structure shown in the following general formula (III): [Chemical formula 4]

(In the general formula (III), k represents an integer of 4 or more, i represents an integer of 1 or more, l represents an integer of 1 or more, k'represents an integer of 0 or 1; R represents a linear or branched hydrocarbon group, which may contain fluorine The phenyl group or hydrogen atom; However, in the total amount of the above resin, 70% by weight or more is i=1); (b) The ratio of the structural unit represented by the above general formula (I) to the structural unit represented by the general formula (II) 1~30: 99~70 (mole ratio)%. (c) The weight average molecular weight (Mw) is 30,000 to 100,000; (d) Relative to the total amount of the structural units constituting the polycarbonate resin, the structural units represented by the following general formulas (1) and (2) are bisphenol The acid conversion value contains 2000ppm or less, and the general formula (1): [Chemical formula 5]

General formula (2): [Chemical formula 6]

(X in the above general formulas (1) and (2) is the same as in the general formula (II)). In one embodiment, the glass transition temperature (Tg) of the said base material for transparent conductive films is 145 degreeC or more. Invention effect

According to the embodiment of the present invention, by using a film containing a predetermined polycarbonate resin with a small dimensional shrinkage in the first direction and the second direction orthogonal to the first direction, it is possible to achieve curling, whitening and cracking. A substrate for a transparent conductive film of a transparent conductive film that is suppressed and has a small in-plane phase difference.

Hereinafter, preferred embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

A. Overall structure of base material for transparent conductive film The transparent conductive film substrate of the embodiment of the present invention is composed of a film containing a polycarbonate resin. The polycarbonate resin used in the present invention is representatively substantially formed by the structural unit represented by the above general formula (I) and the structural unit represented by the general formula (II).

In the embodiment of the present invention, the dimensional shrinkage rate of the transparent conductive film substrate at 145°C is 0.2% or less in the first direction and the second direction orthogonal to the first direction, and preferably 0.15% or less. The first direction corresponds to, for example, the MD direction in the manufacturing method described later, and the second direction corresponds to, for example, the TD direction. As long as the dimensional shrinkage rate at 145°C is in the above-mentioned range, a substrate for a transparent conductive film can be obtained in which the occurrence of whitening and/or cracks and curling are suppressed.

In the embodiment of the present invention, the in-plane retardation Re (550) of the transparent conductive film is 5 nm or less, preferably 4.5 nm or less. The smaller the in-plane retardation Re(550), the better, and the lower limit is ideally 0 nm, and for example, it may be 1 nm. As long as the in-plane retardation is within the above-mentioned range, a substrate for a transparent conductive film with suppressed occurrence of whitening and/or cracks and curling can be obtained. In addition, in this specification, "Re(λ)" is the in-plane retardation measured with light of wavelength λnm at 23°C. Re(λ) is calculated by the formula: Re=(nx-ny)×d when the thickness of the layer (thin film) is d (nm). Therefore, "Re(550)" is the in-plane retardation measured at 23°C with light with a wavelength of 550 nm. Here, "nx" is the refractive index in the direction in which the in-plane refractive index becomes the largest (that is, the slow axis direction), and "ny" is the in-plane direction orthogonal to the slow axis (that is, the fast axis direction) Refractive index.

The substrate for transparent conductive film can display the reverse dispersion wavelength characteristic that the in-plane retardation increases according to the wavelength of the measurement light, and it can display the positive wavelength dispersion characteristic that the in-plane retardation decreases according to the wavelength of the measurement light. Flat wavelength dispersion characteristics in which the in-plane phase difference hardly changes with the wavelength of the measurement light.

In the embodiment of the present invention, the whitening and/or cracking of the substrate for a transparent conductive film is suppressed in the sebum resistance test. By suppressing whitening and/or cracks of the base material for transparent conductive films, a transparent conductive film advantageous for image display can be obtained.

The thickness of the substrate for the transparent conductive film is preferably 10 μm to 80 μm, preferably 10 μm to 60 μm, and more preferably 10 μm to 40 μm. As long as the thickness of the substrate for a transparent conductive film is in the above-mentioned range, a substrate for a transparent conductive film with suppressed occurrence of whitening and/or cracks and curling can be obtained.

The glass transition temperature of the substrate for the transparent conductive film is preferably 145°C or higher, more preferably 150°C or higher. As long as the glass transition temperature is within the above range, the transparent conductive film substrate can be used at high temperatures, and residual strain can be reduced during molding, so the birefringence of the obtained transparent conductive film substrate can be reduced ( As a result, it is the in-plane phase difference).

The elastic modulus of the transparent conductive film substrate is preferably 50 MPa to 350 MPa at a stretching speed of 100 mm/min. As long as the modulus of elasticity is in the above-mentioned range, a transparent conductive film excellent in transportability and handleability can be obtained. According to the embodiment of the present invention, it is possible to achieve both excellent elastic modulus (strength) and excellent flexibility or bending resistance (flexibility) as described above. In addition, the elastic modulus is measured in accordance with JIS K 7127: 1999.

The tensile elongation of the substrate for transparent conductive film is preferably 70% to 200%. As long as the tensile elongation is in the above range, there is an advantage that it is not easy to break during transportation. In addition, the tensile elongation is measured in accordance with JIS K 6781.

B. Polycarbonate resin (1) Structural unit shown in general formula (I) The structural unit represented by the general formula (I) is derived from an aliphatic diol compound. Here, the aliphatic diol compound in the present invention is a compound having an aliphatic hydrocarbon group bonded to a terminal hydroxyl group. The terminal hydroxyl group refers to a hydroxyl group that contributes to the formation of a carbonate bond with the aromatic polycarbonate prepolymer through a transesterification reaction.

Examples of the aliphatic hydrocarbon group include an alkylene group and a cycloalkylene group, and some of these may be substituted with an aromatic group, a heterocyclic group, and the like. [Chemical formula 7]

In the above general formula (I), Q represents a hydrocarbon group with 3 or more carbon atoms which may contain different kinds of atoms. The lower limit of the carbon number of the hydrocarbon group is preferably 3, more preferably 6, and more preferably 10, and the upper limit is preferably 40, more preferably 30, and more preferably 25.

Examples of the different kinds of atoms include oxygen atoms (O), sulfur atoms (S), nitrogen atoms (N), fluorine atoms (F), and silicon atoms (Si). Among these, oxygen atoms (O) and sulfur atoms (S) are particularly desirable. The hydrocarbon group may be linear, branched, or cyclic. In addition, Q may include a cyclic structure such as an aromatic ring and a heterocyclic ring.

In the above general formula (I), R ₁ , R ₂ , R ₃ and R ₄ are each independently selected from a hydrogen atom, preferably an aliphatic hydrocarbon group with a carbon number of 1 to 30, more preferably a carbon number of 1 to 10, and It is preferably a group in the group consisting of a carbon number of 6-20, and more preferably a carbon number of 6-10 aromatic hydrocarbon groups.

Specific examples of the aliphatic hydrocarbon group include linear or branched alkyl groups and cycloalkyl groups. Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tertiary butyl, n-pentyl, isopentyl, n-hexyl, isohexyl, and the like. As the cycloalkyl group, a cyclohexyl group can be mentioned. As an aromatic hydrocarbon group, a phenyl group, a naphthyl group, etc. are mentioned.

However, at least one of R ₁ and R ₂ and at least one of R ₃ and R ₄ are respectively selected from the group consisting of a hydrogen atom and an aliphatic hydrocarbon group. As R ₁ to R ₄ , it is particularly preferable to independently represent a group selected from the group consisting of a hydrogen atom and an aliphatic hydrocarbon group having a carbon number of 1 to 30, and more preferably a carbon number of 1 to 10. As a particularly desirable aliphatic hydrocarbon group, a linear or branched alkyl group can be mentioned. Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tertiary butyl, and isopentyl.

In addition, it is most desirable that R ₁ to R ₄ are all hydrogen atoms. That is, the aliphatic diol compound that can be derived from the above general formula (I) is preferably a primary diol compound, and more preferably a primary diol compound other than the linear aliphatic diol.

n and m each independently represent an integer of preferably 0-10, more preferably 0-4. However, when Q does not contain an aliphatic hydrocarbon group bonded to a terminal hydroxyl group, n and m each independently represent an integer of preferably 1 to 10, more preferably 1 to 4.

The aliphatic diol compound from which the structural unit (I) can be derived is a compound having a glycolic hydroxyl group represented by the following general formula (A). In the general formula (A), Q, R ₁ to R ₄ , n and m are the same as in the above general formula (I).

[Chemical formula 8]

As specific examples of the aforementioned terminal structures "HO-(CR ₁ R ₂ )n-" and "-(CR ₃ R ₄ )m-OH", the following structures can be cited.

[Chemical formula 9]

[Chemical formula 10]

(2) Structural unit shown in general formula (II) The aromatic polycarbonate forming unit of the polycarbonate resin of the present invention is a structural unit represented by the general formula (II).

[Chemical formula 11]

In the general formula (II), R ₁ and R ₂ each independently represent a halogen atom, a C 1-20 alkyl group, a C 1-20 alkoxy group, a C 6-20 cycloalkyl group, and a C 6-20 aromatic group. Group, C6-20 cycloalkoxy or C6-20 aryloxy. p and q represent an integer of 0-4. X represents a single bond or a group selected from the group of divalent organic groups represented by the following general formula (II').

[Chemical formula 12]

In the general formula (II'), R ₃ and R ₄ each independently represent a hydrogen atom, a C 1-10 alkyl group, or a C 6-10 aryl group, and R ₃ and R ₄ may be bonded to form an aliphatic ring.

As the aromatic dihydroxy compound that can derive the structural unit represented by the above general formula (II), a compound represented by the following general formula (II") can be mentioned.

[Chemical formula 13]

In the general formula (II"), R ₁ to R ₂ , p, q, and X are the same as in the general formula (II).

As the aromatic dihydroxy compound, specifically, bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxybenzene) Base) propane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, bis(4-hydroxyphenyl)phenylmethane, 1,1-bis (4-hydroxyphenyl)-1-phenylethane, bis(4-hydroxyphenyl)diphenylmethane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 1,1-bis (4-Hydroxy-3-tertiary butylphenyl)propane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3- Phenylphenyl) propane, 2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3-bromophenyl)propane, 2,2-bis( 3,5-Dibromo-4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclopentane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 2,2 -Bis(4-hydroxy-3-methoxyphenyl)propane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxy-3,3'-dimethylphenyl ether, 4 ,4'-dihydroxyphenyl sulfide, 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfide, 4,4'-dihydroxydiphenyl sulfide, 4,4'-di Hydroxy-3,3'-dimethyldiphenyl sulfene, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxy-3, 3'-Dimethyldiphenyl sulfide etc.

Among them, for reasons such as stability as a monomer and easy availability of a product with a small amount of impurities contained therein, a more desirable example includes 2,2-bis(4-hydroxyphenyl)propane.

As the aromatic polycarbonate forming unit in the present invention, for the purpose of controlling the glass transition temperature, improving fluidity, improving refractive index, reducing birefringence, etc., controlling optical properties, etc., the above-mentioned various monomers (aromatic A variety of structural units derived from dihydroxy compounds).

(3) Requirements (a) The polycarbonate resin of the present invention is characterized by having a structure represented by the following general formula (III). Here, in the general formula (III), (I) represents the structural unit represented by the general formula (I), and (II) represents the structural unit represented by the general formula (II).

[Chemical formula 14]

In the above general formula (III), R represents a linear or branched hydrocarbon group, a phenyl group which may contain fluorine, or a hydrogen atom. Specifically, methyl, propyl, isopropyl, ethyl, butyl, isobutyl, pentyl, isopentyl, hexyl, tetrafluoropropyl, tertiary butyl-phenyl, five Fluorophenyl and so on.

In the above general formula (III), k represents the average chain length of a chain (aromatic polycarbonate chain) composed of aromatic polycarbonate forming units. The aromatic polycarbonate forming unit is a structural unit that becomes the main body of the polycarbonate resin of the present invention, and the aromatic polycarbonate chain composed thereof can form the main polymer structure of the polycarbonate resin. k is preferably 4 or more, more preferably 4 to 100, and more preferably 5 to 70. If the chain length does not have a certain length or more, the structural part indicated by "-(I)i-" will increase relatively. As a result, the random copolymerizability of the polycarbonate resin of the present invention will increase, and the original polycarbonate resin will be lost. The characteristics of heat resistance and other trends.

The structural unit "-(II)k-" (aromatic polycarbonate chain) is a structural unit derived from an aromatic polycarbonate prepolymer, and its weight average molecular weight (Mw) is preferably 5,000~60,000, more preferably 10,000 ~50,000, preferably 10,000~40,000, particularly preferably 15,000~35,000.

If the molecular weight of the aromatic polycarbonate chain is too low, the polycarbonate resin of the present invention may be more affected by the physical properties of the copolymer component. Although physical properties can be improved by this, there are still cases where the effect of maintaining useful physical properties of aromatic polycarbonate is insufficient.

If the molecular weight of the aromatic polycarbonate chain is too high, the polycarbonate resin of the present invention may not be able to maintain the useful physical properties of the aromatic polycarbonate and has high fluidity.

i represents the average chain length of the site "-(I)i-" composed of structural units derived from an aliphatic diol compound. i is preferably 1 or more, more preferably 1 to 5, and more preferably 1 to 3, particularly preferably 1 to 2, and most preferably 1, the closer the average chain length is to 1, the better. If the average chain length of the aliphatic diol portion "-(I)i-" is too long, the heat resistance and mechanical strength will decrease, and the effects of the present invention cannot be obtained.

l represents the average chain length of the structural unit "-[-(II)k-(I)i-]l-" composed of an aromatic polycarbonate chain and an aliphatic diol moiety. l is more than 1, preferably 1~30, more preferably 1~20, particularly preferably 1~10. k'is preferably an integer of 0 or 1. That is, the aliphatic diol moiety "-(I)i-" has an aromatic polycarbonate chain on both sides, and an aromatic polycarbonate chain only on one side, but most of them are There are aromatic polycarbonate chains on both sides.

In the aforementioned polycarbonate resin, the ratio (molar ratio) of the aromatic polycarbonate chain "-(II)k-" to the aliphatic diol site "-(I)i-" is not particularly limited, and polycarbonate The average value of the entire resin is preferably "-(II)k-"/"-(I)i-"=0.1~3, more preferably 0.6~2.5, particularly preferably 2. In addition, k/l is not particularly limited, and is preferably 2 to 200, and more preferably 4 to 100.

However, for the aforementioned polycarbonate resin of the present invention, the total polymer molecules constituting it are preferably 70% by weight or more, more preferably 80% by weight or more, more preferably 90% by weight or more, particularly preferably 95% by weight In the above polymer molecule, i=1. That is, the resin is generally an aggregate of high molecular compounds (polymer molecules) having various structures and molecular weights, but the polycarbonate resin of the present invention is characterized in that it contains 70% by weight or more of long-chain aromatic polycarbonate chains ( -(II)k-) is an aggregate of polymer compounds with a structure bonded to one structural unit (-(I)-) derived from an aliphatic diol compound. When the polymer compound of i=1 is less than 70% by weight, the ratio of the copolymerization component is high, and therefore, it is easily affected by the physical properties of the copolymerization component, and the original physical properties of the aromatic polycarbonate cannot be maintained. The ratio of the polymer compound with i=1 in the polycarbonate resin of the present invention can be analyzed by 1H-NMR analysis of the polycarbonate resin.

(4) Requirements (b) In the polycarbonate resin of the present invention, the ratio of the structural unit represented by the aforementioned general formula (I) to the structural unit represented by the general formula (II) is preferably 1-30:99-70 (molar ratio)%, more preferably 1 ~25: 99~75 (molar ratio), and 1~20: 99~80 (molar ratio) is better.

If the ratio of the structural unit represented by the general formula (I) is too small, it will not meet the conditions of high molecular weight and high fluidity characteristic of polycarbonate resin; if it is too large, aromatic polycarbonate such as mechanical strength and heat resistance The excellent physical properties inherent in the ester resin will be impaired.

The polycarbonate resin of the present invention may also contain structures derived from other copolymerization components within the scope of the spirit of the present invention. It is desirable that the polycarbonate resin of the present invention contains 1-30 moles relative to the total amount of structural units. %, more preferably 1-25 mol%, and more preferably 1-20 mol% of the structural unit represented by the general formula (I).

(5) Requirements (c) The weight average molecular weight (Mw) of the polycarbonate resin of the present invention is preferably 30,000 to 100,000, more preferably 30,000 to 80,000, and more preferably 35,000 to 75,000, which has a high molecular weight and high fluidity.

If the weight average molecular weight of the polycarbonate resin is too low, when it is used for blow molding, extrusion molding, etc., the melt tension becomes low, and it is easy to sag, and a satisfactory molded product cannot be obtained. In addition, when used for applications such as injection molding, satisfactory molded products cannot be obtained due to wire drawing. In addition, the mechanical properties, heat resistance, and other physical properties of the obtained molded product may be reduced. In addition, the oligomer area increases, and physical properties such as organic solvent resistance also decrease.

If the weight average molecular weight of the polycarbonate resin is too high, injection molding of precision parts and thin materials becomes difficult, and the molding cycle time becomes long, which adversely affects production costs. Therefore, measures such as increasing the molding temperature are needed, but there is a possibility of gelation, different structures, and increased N values at high temperatures.

(6) Requirements (d) In the polycarbonate resin of the present invention, the structural unit includes structural units represented by the following general formulas (1) and (2) (hereinafter referred to as "structural unit (1)" and "structural unit (2)") At least one of them is a different kind of structure. X in the following general formulas (1) and (2) is the same as X in the above general formula (II).

Structural unit (1): [Chemical formula 15]

Structural unit (2): [Chemical formula 16]

In addition, the two structural formulas (i) and (ii) in the above structural formula (2) are isomers of each other and cannot be distinguished analytically, so they are treated as the same structure in the present invention. Therefore, when referring to structural formula (2) in the present invention, it means either or both of the above structural formulas (i) and (ii). In addition, the content of the structural unit (2) in the present invention means the total amount of the above two structural formulas (i) and (ii).

In the present invention, the content ratio of at least one of the above-mentioned structural units (1) and (2) relative to the total amount of structural units constituting the aromatic polycarbonate resin is preferably 2000 ppm or less in terms of bisphenol acid conversion value. It is more preferably 1500 ppm or less, preferably 1000 ppm or less, particularly preferably 500 ppm or less, and most preferably 300 ppm or less. If the content of structural units (1) and (2) are both greater than 2000 ppm, the branching degree will increase and the thermal stability will tend to decrease. Moreover, since these structural units are naturally occurring branches, they have the following disadvantages: it is difficult to simply control the degree of branching by the amount of branching agent added, or the fluidity is reduced and the formability is deteriorated.

As described above, in the present invention, the content ratio of at least one of the above-mentioned structural units (1) and (2) needs to be 2000 ppm or less in terms of bisphenolic acid conversion value, which means that the structural units (1) and ( 2) Any one of them should be 2000ppm or less. As a preferred aspect, it is desirable to contain at least 2000ppm or less, more preferably 1500ppm or less, and more preferably 1000ppm or less, particularly 500ppm or less, and most preferably 300ppm or less structural units. (1). In particular, the structural unit (1) has a large influence on the retention stability and color tone. If the ratio of the structural unit (1) is small, the thermal stability and color tone will be significantly improved.

Next, it is desirable that both structural units (1) and (2) are respectively calculated as bisphenolic acid conversion value to be 2000ppm or less, more preferably 1000ppm or less, and preferably 1000ppm or less, especially 500ppm or less, and most preferably 300ppm the following.

In addition, it is desirable that the total ratio of the structural units represented by the above structural units (1) and (2) is 5000 ppm or less in terms of bisphenol acid conversion value, more preferably 3000 ppm or less, more preferably 2000 ppm or less, particularly preferably Below 1000 ppm, most preferably below 600 ppm.

The details of the structural units represented by the general formulas (I) and (II) used in the present invention are described in, for example, Japanese Patent Application Laid-Open No. 2014-101417. In this specification, the description of the publication is cited as a reference.

Commercially available polycarbonate resins can be used. As a commercially available product, for example, the product name "Iupizeta (registered trademark)" manufactured by Mitsubishi Gas Chemical Corporation can be cited.

C. Manufacturing method of substrate for transparent conductive film The method for producing a substrate for a transparent conductive film according to an embodiment of the present invention includes: molding a film-forming material (resin composition) containing the polycarbonate resin described in item A above into a film; and, the molded The film is stretched.

In addition to the above-mentioned polycarbonate resin, the film forming material may contain other resins as described above, may contain additives, or may contain a solvent. As the additive, any appropriate additive can be adopted according to the purpose. Specific examples of additives include reactive diluents, plasticizers, surfactants, fillers, antioxidants, anti-aging agents, ultraviolet absorbers, leveling agents, thixotropic agents, antistatic agents, and conductive materials. , Flame retardant. The number, type, combination, addition amount, etc. of additives can be appropriately set according to the purpose.

As a method of forming a thin film from a thin film forming material, any appropriate forming method can be adopted. Specific examples include compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP molding, cast coating (for example, casting), and calendering. Forming method, hot pressing method, etc. It is preferably an extrusion molding method or a casting coating method. This is because the smoothness of the obtained film can be improved, and good optical uniformity can be obtained. The molding conditions can be appropriately set according to the composition or kind of the resin used, the characteristics desired for the transparent conductive film substrate, and the like.

The stretching method of the film is representatively biaxial stretching, more specifically, successive biaxial stretching or simultaneous biaxial stretching. This is because a transparent conductive film substrate with a small in-plane retardation Re (550) can be obtained. Sequential biaxial stretching or simultaneous biaxial stretching represents the use of a tenter stretching machine. Therefore, the extension direction of the film is representatively the length direction and the width direction of the film.

The stretching temperature may vary depending on the in-plane retardation and thickness desired for the transparent conductive film substrate, the type of resin used, the thickness of the film used, the stretching ratio, and the like. Specifically, the stretching temperature relative to the glass transition temperature (Tg) of the film is preferably Tg+5℃~Tg+50℃, and more preferably Tg+10℃~Tg+40℃. By stretching at the aforementioned temperature, the embodiment of the present invention can obtain a substrate for a transparent conductive film having suitable characteristics.

The stretching ratio can be changed according to the in-plane retardation and thickness desired for the transparent conductive film substrate, the type of resin used, the thickness of the film used, the stretching temperature, and the like. When biaxial stretching (such as sequential biaxial stretching or simultaneous biaxial stretching) is used, the difference between the stretching magnification in the first direction (such as the length direction) and the stretching magnification in the second direction (such as the width direction) should be as small as possible , More preferably substantially equal. With this configuration, a substrate for a transparent conductive film with a small in-plane retardation Re (550) can be obtained. When biaxial stretching (for example, sequential biaxial stretching or simultaneous biaxial stretching) is used, the stretching magnification may be 1.1 times to 3.0 times in the first direction (for example, the length direction) and the second direction (for example, the width direction), respectively.

In the embodiment of the present invention, the elongation speed is preferably 10%/sec or less, and preferably 7%/sec or less, more preferably 5%/sec or less, and particularly preferably 2.5%/sec or less. By stretching a film containing the specific polycarbonate resin described above at a low stretching speed as described above, a substrate for a transparent conductive film with a small in-plane retardation Re (550) can be obtained. The lower limit of the extension speed may be 1.2%/sec, for example. If the extension speed is too small, productivity may become impractical. In addition, when biaxial stretching (such as sequential biaxial stretching or simultaneous biaxial stretching) is used, the difference between the stretching speed in the first direction (such as the length direction) and the stretching speed in the second direction (such as the width direction) is as small as possible Preferably, it is more appropriate to be substantially equal. With this configuration, the in-plane retardation Re (550) of the substrate for transparent conductive film can be reduced.

D. Transparent conductive film The substrates for transparent conductive films described in the above items A and B are suitably used for transparent conductive films. Therefore, the embodiment of the present invention also includes a transparent conductive film. The transparent conductive film of the embodiment of the present invention includes the transparent conductive film substrate and the conductive layer described in the above A and B. The conductive layer is typically formed on the visible side surface of the transparent conductive film substrate. The transparent conductive film may have an index matching (IM) layer, a hard coat (HC) layer, and/or an anti-adhesion hard coat (ABHC) layer as required.

(Conductive layer) The conductive layer represents a transparent conductive layer. The total light transmittance of the conductive layer is preferably 80% or more, preferably 85% or more, and more preferably 90% or more.

The density of the conductive layer is preferably 1.0 g/cm ³ to 10.5 g/cm ³ , and more preferably 1.3 g/cm ³ to 8.0 g/cm ³ .

The surface resistance of the conductive layer should be 0.1Ω/□~1000Ω/□, and should be 0.5Ω/□~500Ω/□, more preferably 1Ω/□~250Ω/□.

As a representative example of the conductive layer, a conductive layer containing a metal oxide can be cited. Examples of metal oxides include indium oxide, tin oxide, zinc oxide, indium-tin composite oxide, tin-antimony composite oxide, zinc-aluminum composite oxide, and indium-zinc composite oxide. Among them, indium-tin composite oxide (ITO) is preferred.

The thickness of the conductive layer is preferably 0.01 μm to 0.06 μm, more preferably 0.01 μm to 0.045 μm. As long as it is in the above range, a conductive layer excellent in conductivity and light transmittance can be obtained.

The conductive layer can be formed by sputtering on the surface of the film substrate.

(Index matching (IM) layer) The IM layer may be formed on one side of the conductive layer. Regarding the IM layer, a well-known structure in the industry can be adopted, so detailed description is omitted.

(Hard coating (HC) layer) The HC layer can be formed between the above-mentioned IM layer and the substrate for a transparent conductive film. Regarding the HC layer, a structure well-known in the industry can be adopted, so detailed description is omitted.

(Anti-adhesive hard coating (ABHC) layer) The ABHC layer can be formed on the surface on the opposite side to the HC layer in the transparent conductive film substrate. The details of the ABHC layer are described in, for example, JP 2016-107503 A. In this specification, the description of the publication is cited as a reference. Example

Hereinafter, the present invention will be specifically described with examples, but the present invention is not limited by these examples. The measurement methods of each characteristic in the examples are as follows. In addition, unless otherwise specified, "parts" and "%" in the examples are based on weight.

(1) In-plane phase difference Re (550) The transparent conductive film substrates obtained in the examples and comparative examples were cut into a length of 4 cm and a width of 4 cm, which were used as measurement samples. The in-plane retardation and thickness direction retardation were measured using the product name "Axoscan" manufactured by Axometrics Corporation for this measurement sample. The measurement wavelength is 550 nm, and the measurement temperature is 23°C. (2) Size shrinkage rate The dimensional shrinkage rates in the MD and TD directions of the base material for transparent conductive films were measured as follows. Specifically, the transparent conductive film substrate was cut into a width of 100 mm and a length of 100 mm (test piece), and cross scratches were given to four corners, and the cross scratches were measured using a CNC three-dimensional measuring machine (LEGEX774 manufactured by Mitutoyo Corporation) The length before heating (mm) between the MD and TD directions at 4 points in the central part. Then, it was put into an oven and heat-treated (145°C, 60 minutes). After leaving to cool at room temperature for 1 hour, the length (mm) of the 4 corners and 4 points after heating in the MD and TD directions was measured again with a CNC three-dimensional measuring machine, and the measured value was substituted into the following equation to obtain Thermal shrinkage in MD and TD directions. Dimensional shrinkage (%)=[[Length before heating (mm)-Length after heating (mm)]/Length before heating (mm)]×100 (3) Sebum resistance test The transparent conductive films obtained in the examples and comparative examples were cut into 5cm×5cm, and the adhesive was applied to the surface where the ITO film was formed and the other surface with a hand roller, and the adhesive surface was applied to the soda glass A test piece was obtained on one side. The obtained test piece was immersed in an oleic acid solution under the conditions of 65° C. and 90% RH for 72 hours, and the transparent test piece after removal was marked as ○, and the whitened or cracked test piece was marked as x. (4) Curl The transparent conductive films obtained in the examples and comparative examples were cut into a size of 20 cm×20 cm. After heating at 145°C for 60 minutes with the ITO face up, it was left to cool at room temperature (23°C) for 1 hour. Then, the sample is placed on a horizontal surface with the ITO layer facing upward, and the height of the central part from the horizontal surface (curl value A) is measured. In addition, the heights of the four corners from the horizontal plane were measured, and the average value (curl value B) was calculated. The curl value A minus the curl value B (A-B) was calculated as the curl amount. When the curl value is in the range of 0-50 mm, it is recorded as ○, and the other is recorded as ×.

>Example 1> 1-1. Production of polycarbonate resin film As a polycarbonate resin, the product name "Iupizeta (registered trademark)" (Tg: 174°C) manufactured by Mitsubishi Gas Chemical Co., Ltd. was vacuum dried at 120°C for 5 hours, and then a uniaxial extruder (manufactured by Isuzu Kakoki) was used. , Screw diameter 25mm, barrel setting temperature: 295℃), T-die (width 200mm, setting temperature: 295℃), cooling roll (setting temperature: 140~150℃) and film forming device for coiler, manufacturing A polycarbonate resin film with a thickness of 100 μm was produced.

1-2. Production of base material for transparent conductive film The polycarbonate resin film obtained above was simultaneously biaxially stretched twice in the longitudinal direction and the width direction. The extension temperature is [Tg+25°C]. In the manner described above, a substrate for a transparent conductive film (thickness 25 μm) was obtained. The in-plane retardation Re (550) of the obtained substrate for a transparent conductive film was 2.8 nm, and the dimensional change rate (MD/TD) was 0.06/0.04.

1-3. Production of transparent conductive film An anti-blocking hard coat (ABHC) layer is formed on the surface of one side of the transparent conductive film substrate obtained above, and a hard coat (HC) layer is formed on the surface on the side opposite to the ABHC layer. A refractive index matching (IM) layer is formed on the surface of the HC layer on the opposite side of the transparent conductive film substrate. ITO was sputtered on the surface of the IM layer opposite to the HC layer to form a conductive layer, and a transparent conductive film was obtained. The obtained transparent conductive film was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

>Example 2> Except that the thickness was 15 μm, the same procedure as in Example 1 was carried out to obtain a substrate for a transparent conductive film. The in-plane retardation Re (550) of the obtained substrate for transparent conductive film was 2.1 nm, and the dimensional change rate (MD/TD) was 0.04/0.04. Furthermore, in the same manner as in Example 1, the obtained substrate for a transparent conductive film was used to obtain a transparent conductive film. The obtained transparent conductive film was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

>Example 3> Except that the thickness was 40 μm, the same procedure as in Example 1 was carried out to obtain a substrate for a transparent conductive film. The in-plane retardation Re (550) of the obtained substrate for a transparent conductive film was 2.8 nm, and the dimensional change rate (MD/TD) was 0.08/0.09. Furthermore, in the same manner as in Example 1, the obtained substrate for a transparent conductive film was used to obtain a transparent conductive film. The obtained transparent conductive film was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

>Example 4> Except that the stretching temperature was set to [Tg+20°C], the same procedure as in Example 1 was carried out to obtain a substrate for a transparent conductive film. The in-plane retardation Re (550) of the obtained substrate for a transparent conductive film was 3.4 nm, and the dimensional change rate (MD/TD) was 0.09/0.1. Furthermore, in the same manner as in Example 1, the obtained substrate for a transparent conductive film was used to obtain a transparent conductive film. The obtained transparent conductive film was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

>Comparative Example 1> Except having set the thickness to 90 μm, the same procedure as in Example 1 was carried out to obtain a substrate for a transparent conductive film. The in-plane retardation Re (550) of the obtained substrate for a transparent conductive film was 4.7 nm, and the dimensional change rate (MD/TD) was 0.22/0.22. Furthermore, in the same manner as in Example 1, the obtained substrate for a transparent conductive film was used to obtain a transparent conductive film. The obtained transparent conductive film was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

>Comparative Example 2> Instead of the polycarbonate resin film, an ultra-high retardation polyethylene terephthalate film (manufactured by Mitsubishi Chemical Corporation, trade name "Diafoil") was used, except that the same procedure as in Example 1 was carried out to obtain a transparent conductive film Use substrate. The in-plane retardation Re (550) of the obtained substrate for a transparent conductive film was 1500 nm, and the dimensional change rate (MD/TD) was 0.6/0.6. Furthermore, in the same manner as in Example 1, the obtained substrate for a transparent conductive film was used to obtain a transparent conductive film. The obtained transparent conductive film was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

>Comparative Example 3> In place of the polycarbonate resin film, a polycycloolefin film (manufactured by Zeon Corporation, trade name "ZEONOR", Tg: 160°C) was used, and except that it was carried out in the same manner as in Example 1, a substrate for a transparent conductive film was obtained. The in-plane retardation Re (550) of the obtained substrate for a transparent conductive film was 1.2 nm, and the dimensional change rate (MD/TD) was 0.07/0.08. Furthermore, in the same manner as in Example 1, the obtained substrate for a transparent conductive film was used to obtain a transparent conductive film. The obtained transparent conductive film was used for the evaluation of (3) and (4) above. The results are shown in Table 1.

[Table 1]

>Evaluation> It is clear from Table 1 that the substrates for transparent conductive films of the examples of the present invention have suppressed whitening and/or cracks in the sebum resistance test, and suppressed curling. It is speculated that this can be achieved by stretching a film containing a specific polycarbonate resin. Furthermore, when comparing the examples with the comparative examples, it is clear that by using a polycarbonate resin and using a substrate for a transparent conductive film with a thickness within a predetermined range, excellent characteristics (small in-plane retardation and small的dimensional shrinkage). Industrial availability

The substrate for a transparent conductive film of the present invention is suitably used for a transparent conductive film. By using the substrate for a transparent conductive film of the present invention, a transparent conductive film advantageous for image display can be obtained.

(no)

Claims (5)

A substrate for transparent conductive film, containing polycarbonate resin, The dimensional shrinkage rate of the transparent conductive film substrate at 145°C is 0.2% or less in the first direction and the second direction orthogonal to the first direction, respectively, In the sebum resistance test, whitening and cracking are suppressed, and The in-plane retardation Re (550) is 5 nm or less. The substrate for a transparent conductive film according to claim 1, wherein the thickness of the substrate is 10 μm to 80 μm. The substrate for a transparent conductive film according to claim 1, wherein the polycarbonate resin is substantially formed of a structural unit represented by the following general formula (I) and a structural unit represented by the following general formula (II), and satisfies the following Conditions (a) to (d), the structural unit represented by the following general formula (I) is derived from an aliphatic diol compound having an aliphatic hydrocarbon group bonded to a terminal hydroxyl group, [Chemical formula 1]

(In the general formula (I), Q represents a hydrocarbon group with 3 or more carbon atoms that may contain different kinds of atoms, and R ₁ to R ₄ are independently selected from hydrogen atoms, aliphatic hydrocarbon groups with 1 to 30 carbon atoms, and 6 to carbon atoms. In the group consisting of 20 aromatic hydrocarbon groups, n and m each independently represent an integer from 0 to 10; however, when Q does not contain an aliphatic hydrocarbon group bonded to the terminal hydroxyl group, n and m independently represent 1 to 10 And at least one of R ₁ and R ₂ and at least one of R ₃ and R ₄ are selected from the group consisting of a hydrogen atom and an aliphatic hydrocarbon group); [Chemical formula 2]

(In the general formula (II), R ₁ and R ₂ each independently represent a halogen atom, a C 1-20 alkyl group, a C 1-20 alkoxy group, a C 6-20 cycloalkyl group, a C 6-20 Aryl, C6-20 cycloalkoxy or C6-20 aryloxy, p and q represent an integer from 0 to 4, X represents a single bond or selected from the following general formula (II') The group in the divalent organic group); [Chemical formula 3]

(In the general formula (II'), R ₃ and R ₄ each independently represent a hydrogen atom, an alkyl group with 1 to 10 carbons, or an aryl group with 6 to 10 carbons. R ₃ and R ₄ can also be bonded to form an aliphatic ring ); (a) Having the structure shown in the following general formula (III): [Chemical formula 4]

(In general formula (III), k represents an integer of 4 or more, i represents an integer of 1 or more, l represents an integer of 1 or more, k'represents an integer of 0 or 1, and R represents a linear or branched hydrocarbon group, which may contain fluorine Phenyl or hydrogen atom; However, in the total amount of the aforementioned resin, 70% by weight or more is i=1); (b) The ratio of the structural unit represented by the aforementioned general formula (I) to the structural unit represented by the general formula (II) 1-30: 99-70 (mole ratio)%; (c) The weight average molecular weight (Mw) is 30,000-100,000; (d) Relative to the total amount of structural units constituting the aforementioned polycarbonate resin, the following general formula The structural units shown in (1) and (2) respectively contain 2000 ppm or less in terms of bisphenolic acid conversion value, and the general formula (1): [Chemical formula 5]

General formula (2): [Chemical formula 6]

(X in the above general formulas (1) and (2) is the same as X in the general formula (II)). The transparent conductive film substrate of claim 1 has a glass transition temperature (Tg) of 145°C or higher. A transparent conductive film comprising the substrate for a transparent conductive film according to any one of claims 1 to 4 and a conductive layer.