TW202039621A - Substrate for transparent conductive film and transparent conductive film realizing a transparent conductive film in which curling, whitening, and cracking are suppressed and a small in-plane retardation is achieved - Google Patents

Abstract

The purpose of this invention is to provide a substrate for a transparent conductive film capable of realizing a transparent conductive film in which curling, whitening, and cracking are suppressed and a small in-plane retardation is achieved. The solution means is a film containing a predetermined polyester-based resin and having a small dimensional shrinkage in both the first direction and the second direction orthogonal to the first direction.

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.

In the past, various resin films have been used as substrates of 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, curling, whitening and/or cracking may occur in conventional transparent conductive films.

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 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

The transparent conductive film substrate in the embodiment of the present invention contains a polyester resin, and the dimensional shrinkage rate of the transparent conductive film substrate at 145°C 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 polyester resin includes a polymer of (A) an acid component and (B) an alcohol component, and the (A) component includes (A1) a monocyclic aromatic polycarboxylic acid component, and (A2) A cyclic aromatic polycarboxylic acid component and (A3) a fluorene-based polycarboxylic acid component, and the (B) component includes (B1) an aliphatic polyol component and (B2) a fluorene-based polyol component; relative to the (A) component The content of the (A1) component is 5 mol% or more and less than 30 mol%, the content of the (A3) component is 5 mol% or more and 50 mol% or less; the (B2) component does not contain the actual amount of 9, 9-bis(aryl-hydroxy(poly)alkoxyaryl)fluorene component. In one embodiment, the component (B2) includes the first fluorene component in which two substituents having a hydroxyl group are introduced at the 9 position. In one embodiment, the component (B1) contains a 1,2-propanediol component, and the component (B2) contains a 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene component. In one embodiment, the aforementioned component (A3) includes a second fluorene component in which two substituents having a carboxyl group and/or an ester group are introduced at the 9 position. In one embodiment, the component (A1) contains a terephthalic acid component, the component (A2) contains a 2,6-naphthalenedicarboxylic acid component, and the component (A3) contains 9,9-bis(carboxyethyl) Fluorene ingredients. 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 polyester resin and having 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. 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 polyester resin. The polyester resin represents a polymer containing (A) an acid component and (B) an alcohol component. The (A) component contains (A1) a monocyclic aromatic polyvalent carboxylic acid component, (A2) a polycyclic aromatic polyvalent carboxylic acid component, and (A3) a fluorene-based polyvalent carboxylic acid component. The (B) component contains (B1) an aliphatic polyol component and (B2) a fluorene-based polyol component. Typically, with respect to the total amount of the (A) component, the content of the (A1) component is 5 mol% or more and less than 30 mol%, and the content of the (A3) component is 5 mol% or more and 50 mol% or less. The component (B2) represents the 9,9-bis(aryl-hydroxy(poly)alkoxyaryl)fluorene component without substantial amount.

The monocyclic aromatic polyvalent carboxylic acid component (A1) may contain a component having a plurality of substituents having a carboxyl group introduced into the benzene ring. As (A1) component, a terephthalic acid component and an isophthalic acid component are mentioned, for example. In the component (A1), terephthalic acid is preferably 50 mol% or more, and preferably 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more, and more preferably 100 mol%. By using terephthalic acid as the main component, heat resistance can be improved.

The polycyclic aromatic polyvalent carboxylic acid component (A2) may contain a component having a plurality of substituents having a carboxyl group introduced into the naphthalene ring. In this specification, the component (A3) is not included in the component (A2). As the component (A2), for example, 2,6-naphthalenedicarboxylic acid component, 1,5-naphthalenedicarboxylic acid component, 1,6-naphthalenedicarboxylic acid component, 1,7-naphthalenedicarboxylic acid component, 1,8-Naphthalenedicarboxylic acid component. In the component (A2), the 2,6-naphthalenedicarboxylic acid component is preferably 50 mol% or more, and preferably 70 mol% or more, more preferably 80 mol% or more, more preferably 90 mol% or more, and more preferably 100 mol%. By using 2,6-naphthalenedicarboxylic acid as the main component, heat resistance can be improved.

The fluorene-based polycarboxylic acid component (A3) may include a component in which a plurality of substituents having a carboxyl group are introduced into fluorene. An example of the chemical formula of the fluorene-based polycarboxylic acid component is shown in the following chemical formula 1. (A3) The component may include, for example, a component in which two substituents having a carboxyl group and/or an ester group are introduced into the 9 position of fluorene. In Chemical Formula 1, R ¹ and R ² may adopt the same substituent. R ¹ and R ² can be, for example, carboxyalkyl (-(CH ₂ ) _n COOH). As the (A3) component, the 9,9-bis(carboxyethyl)fluorene component shown in the following chemical formula 2, etc. are mentioned, for example. Among the components (A3), the 9,9-bis(carboxyethyl) fluorene component is preferably 50 mol% or more, and preferably 70 mol% or more, more preferably 80 mol% or more, preferably 90 mol% or more, and more preferably 100 mol%. By using 9,9-bis(carboxyethyl)fluorene as the main component, birefringence can be reduced, and as a result, a transparent conductive film substrate having a desired in-plane retardation can be obtained.

[化學式2]

[Chemical formula 1]

[Chemical formula 2]

The content of the (A1) component relative to the total amount of the acid component is preferably 5 mol% or more, preferably 8 mol% or more, and more preferably 10 mol% or more. If the content of the component (A1) is less than 5 mol%, the birefringence may increase. The content of (A1) component relative to the total amount of acid components is preferably less than 30 mol%, preferably 29 mol% or less, and more preferably 28 mol% or less. If the content rate of (A1) component is 30 mol% or more, heat resistance may become insufficient.

(A2) The content of the component relative to the total amount of acid components is preferably 25 mol% or more, preferably 30 mol% or more, and more preferably 35 mol% or more. If the content of the component (A2) is less than 25 mol%, heat resistance may become insufficient. (A2) The content of the component relative to the total amount of acid components is preferably 70 mol% or less, preferably 60 mol% or less, and more preferably 55 mol% or less. If the content of the component (A2) exceeds 70 mol%, the birefringence may increase.

The content of the (A3) component relative to the total amount of acid components is preferably 5 mol% or more, preferably 10 mol% or more, and more preferably 15 mol% or more. If the content of the component (A3) is less than 5 mol%, the birefringence may increase. The content of (A3) component relative to the total amount of acid components is preferably 50 mol% or less, preferably 45 mol% or less, and more preferably 40 mol% or less. If the content rate of the component (A3) exceeds 50 mol%, the heat resistance may become insufficient.

The molar ratio (A1)/(A2) of the component (A1) to the component (A2) is preferably 0.1 to 0.9, preferably 0.2 to 0.8, and more preferably 0.3 to 0.75. The molar ratio (A1)/(A3) of the component (A1) to the component (A3) is preferably 0.4 to 3, preferably 0.5 to 2.7, and more preferably 0.6 to 2.5. The molar ratio (A2)/(A3) of (A2) component to (A3) component is preferably 0.8~3, preferably 1~2.7, and more preferably 1.2~2.5.

The aliphatic polyol component (B1) may contain an alkanediol component with 2 to 4 carbon atoms. As the (B1) component, for example, ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4- Butylene glycol. (B1) Among the components, the 1,2-propanediol component is preferably 50 mol% or more, and preferably 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more, and more preferably 100 mol%. By using 1,2-propanediol as the main component, it can increase the glass transition temperature compared to other aliphatic polyols.

The fluorene-based polyol component may include a component in which a plurality of substituents having hydroxyl groups are introduced into fluorene. An example of the chemical formula of the fluorene-based polyol component is shown in the following chemical formula 3. (B2) The component may include, for example, a component in which two substituents having a hydroxyl group are introduced at the 9 position of fluorene. In Chemical Formula 3, R ³ and R ⁴ may adopt the same substituent. R ³ and R ⁴ can be, for example, a hydroxyalkoxyaryl group. As the (B2) component, for example, 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene component, 9,9-bis[4-(2-hydroxyethoxy)-3 -Methylphenyl]fluorene component, 9,9-bis[4-(2-hydroxyethoxy)-3,5-dimethylphenyl]fluorene component, 9,9-bis[4-(2- Hydroxyethoxy)-3,5-diethylphenyl]fluorene component, etc. Among them, the component (B2) is particularly preferably a 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene component as shown in the following chemical formula 4. (B2) Among the components, the 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene component is preferably 50mol% or more, preferably 70mol% or more, more preferably 80mol% or more, and 90mol% The above is preferable, and 100 mol% is more preferable. By using 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene as the main component, the heat resistance of the obtained transparent conductive film substrate can be improved, and the birefringence can be reduced ( As a result, it is the in-plane phase difference). Especially in the component (B2), the 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene component is more preferably 70 mol% or more, and more preferably 80 mol% or more, and more preferably 90 mol% Above, 100 mol% is more preferable.

The component (B2) should preferably not contain substantial amounts of 9,9-bis(aryl-hydroxy(poly)alkoxyaryl)fluorene component. The 9,9-bis(aryl-hydroxy(poly)alkoxyaryl) fluorene component can be, for example, as shown in the following chemical formula 5, 9,9-bis[4-(2-hydroxyethoxy)-3- Phenylphenyl] fluorene component. If the 9,9-bis(aryl-hydroxy(poly)alkoxyaryl) fluorene component is included, the mechanical properties and/or moldability may become insufficient. Here, the "substantial amount" refers to the amount that can produce the effect of the 9,9-bis(aryl-hydroxy(poly)alkoxyaryl) fluorene component.

[化學式4]

[化學式5]

[Chemical formula 3]

[Chemical formula 4]

[Chemical formula 5]

The content of the component (B1) relative to the total amount of alcohol components is preferably 3 mol% or more, and preferably 5 mol% or more, and more preferably 8 mol% or more. If the content of the (B1) component is less than 3 mol%, the mechanical properties and/or moldability may become insufficient. (B1) The content of the component relative to the total amount of alcohol components is preferably 30 mol% or less, and is preferably 20 mol% or less, and more preferably 15 mol% or less. If the content of the component (B1) exceeds 30 mol%, the heat resistance may become insufficient.

(B2) The content of the component relative to the total amount of alcohol components is preferably 70 mol% or more, preferably 80 mol% or more, and more preferably 85 mol% or more. If the content of (B2) component is less than 70 mol%, heat resistance may become insufficient. (B2) The content of the component relative to the total amount of alcohol components is preferably 97 mol% or less, preferably 95 mol% or less, and more preferably 92 mol% or less. If the content of the component (B2) exceeds 97 mol%, mechanical properties and/or moldability may become insufficient.

The molar ratio (B2)/(B1) of (B1) component to (B2) component is preferably 4-30, 6-20, and 7-10 more preferably.

The details of the polyester resin are described in, for example, Japanese Patent Application Laid-Open No. 2018-168210. In this specification, the description of the publication is cited as a reference.

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, in the sebum resistance test, the whitening and/or cracking of the substrate for a transparent conductive film is suppressed. 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. On the other hand, the glass transition temperature is preferably 170°C or less, more preferably 160°C or less. 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. 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: forming a film-forming material (resin composition) containing the polyester resin described in item A above into a film; and, the formed The film is stretched.

The film forming material may contain other resins as described above in addition to the above-mentioned polyester-based resin, 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 above-mentioned temperature, a transparent conductive film substrate having suitable characteristics can be obtained in the embodiment of the present invention.

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, more 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 polyester-based resin as 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.

C. 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 according to the embodiment of the present invention includes the transparent conductive film substrate and the conductive layer described in the above items 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-blocking 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 , 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 of the transparent conductive film substrate opposite to the HC layer. 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, the "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 alkali glass The test piece was obtained on one side of the surface. 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. Polymerization of polyester resin As the raw material of the monocyclic aromatic polycarboxylic acid component (A1), dimethyl terephthalate is used; as the raw material of the polycyclic aromatic polycarboxylic acid component (A2), dimethyl 2,6-naphthalene dicarboxylic acid is used Esters; 9,9-bis(methoxycarbonylethyl) fluorene is used as the raw material of the fluorene polycarboxylic acid component (A3); 1,2-propanediol is used as the raw material of the aliphatic polyol component (B1); fluorene The raw material of the polyol component (B2) used 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene. Put (A1) raw material 15 mol%, (A2) raw material 50 mol%, (A3) raw material 55 mol%, (B1) raw material 10 mol% and (B2) raw material 90 mol% into a 30-liter stainless steel reaction vessel, and react After nitrogen replacement in the container, the raw materials were dissolved at 150°C. Next, manganese acetate tetrahydrate and calcium acetate monohydrate were introduced as transesterification catalysts, the temperature was gradually increased to 240°C over 4 hours, and the reaction was continued for 1 hour while maintaining the temperature at 240°C. It was confirmed that by-products were no longer distilled out and predetermined by-products were distilled out. Next, an aqueous solution of trimethyl phosphate and germanium dioxide is prepared and added. Then, the temperature increase and the pressure decrease were gradually started, and after 90 minutes, the temperature became 270° C. and 0.13 kPa. In this state, the polycondensation reaction proceeded, and the reaction continued until the predetermined torque was reached. After reaching a predetermined torque, the inside of the reaction vessel was pressurized with nitrogen, the resin was extruded into a bundle in cooling water, and cut to obtain pellets of polyester resin. The glass transition temperature of the obtained polyester resin was 155°C.

1-2. Production of polyester resin film After vacuum-drying the obtained polyester resin at 80°C for 5 hours, a uniaxial extruder (manufactured by Isuzu Kakoki, screw diameter 25mm, cylinder setting temperature: 270°C), T-die (width 200mm, Set temperature: 270°C), cooling roll (set temperature: 120~130°C), and the film forming device of the coiler to produce a polyester resin film with a thickness of 120μm.

1-3. Production of base material for transparent conductive film The polyester-based resin film obtained above was simultaneously biaxially stretched twice in the longitudinal direction and the width direction. The extension temperature is [Tg+25°C] (ie 180°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 3.4 nm, and the dimensional change rate (MD/TD) was 0.08/0.1.

1-4. 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 a transparent conductive film was 2.6 nm, and the dimensional change rate (MD/TD) was 0.08/0.07. 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 3.7 nm, and the dimensional change rate (MD/TD) was 0.11/0.13. 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 thickness was 25 μm and the stretching temperature was [Tg+20°C] (that is, 175°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 4.1 nm, and the dimensional change rate (MD/TD) was 0.12/0.1. 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 0.21/0.26. 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> In place of the polyester resin film, an ultra-high retardation polyethylene terephthalate film (manufactured by Mitsubishi Chemical Corporation, trade name "Diafoil", Tg: 81°C) was used, and the operation was performed in the same manner as in Example 1, except that 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 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 polyester resin film, a polycycloolefin film (manufactured by Zeon Corporation, trade name "ZEONOR", Tg: 160°C) was used, and except for that, the same procedure as in Example 1 was carried out to obtain a base material for a transparent conductive film. 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 assumed that this can be achieved by stretching a film containing a specific polyester resin. Furthermore, when the examples are compared with the comparative examples, it is clear that by using a polyester-based resin and using a substrate for a transparent conductive film with a thickness in 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 (9)

A substrate for transparent conductive film, containing polyester 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 polyester-based resin includes a polymer of (A) an acid component and (B) an alcohol component, This (A) component contains (A1) a monocyclic aromatic polycarboxylic acid component, (A2) a polycyclic aromatic polycarboxylic acid component, and (A3) a fluorene-based polycarboxylic acid component, The (B) component includes (B1) an aliphatic polyol component and (B2) a fluorene-based polyol component; Relative to the total amount of the (A) component, the content of the (A1) component is 5 mol% or more and less than 30 mol%, and the content of the (A3) component is 5 mol% or more and 50 mol% or less; This (B2) component does not contain a substantial amount of 9,9-bis(aryl-hydroxy(poly)alkoxyaryl)fluorene component. The substrate for a transparent conductive film according to claim 3, wherein the component (B2) includes a first fluorene component in which two substituents having a hydroxyl group are introduced at the 9 position. The substrate for a transparent conductive film according to claim 3, wherein the aforementioned component (B1) contains a 1,2-propanediol component, and the aforementioned component (B2) contains 9,9-bis[4-(2-hydroxyethoxy)benzene Base] fluorene component. The substrate for a transparent conductive film according to claim 3, wherein the component (A3) includes a second fluorene component in which two substituents having a carboxyl group and/or an ester group are introduced at the 9 position. The transparent conductive film substrate of claim 3, wherein the aforementioned component (A1) contains a terephthalic acid component, the aforementioned component (A2) contains a 2,6-naphthalenedicarboxylic acid component, and the aforementioned component (A3) contains 9, 9-bis(carboxyethyl)fluorene component. 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 8 and a conductive layer.