JP2011258498A - Transparent conductive polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent conductive polyester film having excellent thermal whitening resistance.SOLUTION: In the transparent conductive polyester film, a biaxially oriented polyester film is used as a base material film, and a transparent conductive thin film is laminated on one face of the base material film. The transparent conductive polyester film satisfies the following constitutional requirements (1) and (2). (1) An amount of a hydroxyl (OH) terminal group is 70 eq/ton or less. (2) A content of a cyclic trimer is 0.45 mass% or less.

Description

  The present invention relates to a transparent conductive polyester film. In detail, it is related with the transparent conductive polyester film excellent in the heating whitening suppression by post-processing.

  A transparent conductive polyester film obtained by laminating a transparent thin film with low electrical resistance on a polyester film is used for applications utilizing the transparency and conductivity, for example, flat panel displays such as liquid crystal displays and electroluminescence displays, Widely used in electrical and electronic fields such as transparent electrodes for touch panels.

  In recent years, with the widespread use of portable information terminals and notebook computers with touch panels, touch panels with higher reliability than ever have been required.

  When a transparent conductive polyester film is processed into a touch panel, heating at about 150 ° C. to 180 ° C. is necessary to print a silver paste or the like. However, when a polyester film is used as the base film, there is a problem that cyclic oligomers are precipitated on the surface of the base film due to the high temperature treatment and whitening occurs.

  Then, in order to reduce the oligomer in a polyester film, it is proposed to propose the amount of cyclic oligomers of a polyester raw material by a solid phase polymerization method (Patent Documents 1 to 4).

JP-A-9-99530 JP 2000-141570 A JP 2003-191413 A Japanese Patent Laid-Open No. 2003-301057

  However, in the methods proposed in Patent Documents 1 to 4, although the amount of the cyclic oligomer in the polyester can be reduced by solid phase polymerization, the polycondensation reaction of the polyester proceeds at the same time, and the degree of polymerization of the obtained polyester is increased. Furthermore, even if the amount of the cyclic oligomer in the film raw material is reduced, it is inevitable that the cyclic oligomer is generated as a by-product due to the thermal history in film melting and film formation. For this reason, efforts have been made to reduce the amount of cyclic oligomers in the film raw material as much as possible, but there is a limit to such measures from the viewpoint of productivity. Therefore, a sufficient low oligomer film has not been realized by regenerating the cyclic oligomer in the melt extrusion process during film formation.

  The present invention solves the problems of the above-mentioned conventional methods, and provides a transparent conductive polyester film excellent in transparency after heat processing, having little precipitation of cyclic oligomers, and excellent in low oligomer properties. Objective.

  As a result of intensive studies to solve the above problems, the present inventor has found that the cyclic oligomer regenerated when the polyester is melted depends on the amount of hydroxyl (OH) ends of the molecular chain. The reason is as follows. The cyclic trimer, which is the main component of the cyclic oligomer, is generated by a decomposition reaction from the end of the polyester molecular chain, but a cyclic trimer is easily generated at the hydroxyl (OH) end by a nucleophilic reaction by a hydroxyl (OH) group. Thus, in the present invention, the hydroxyl (OH) terminal amount of the polyester resin is set to a predetermined amount or less, thereby suppressing the regeneration of the cyclic oligomer amount at the time of melting and suitably suppressing the heating whitening. Thereby, the transparent conductive polyester film with high transparency can be obtained without heating whitening even in the heat treatment at a high temperature in the post-processing.

That is, the first invention in the present invention that can solve the above-mentioned problems is a transparent conductive polyester in which a biaxially stretched polyester film is used as a base film, and a transparent conductive thin film is laminated on one side of the base film. It is a film, Comprising: This base film is a transparent conductive polyester film which satisfy | fills the following structural requirements (1) and (2).
(1) Hydroxyl (OH) terminal amount is 70 eq / ton or less (2) Cyclic trimer content is 0.45 mass% or less

  The second invention in the present invention is the transparent conductive polyester film as described above, wherein the transparent conductive thin film is formed from an indium-tin composite oxide.

  The “transparent” in the transparent conductive polyester film of the present invention means a case where the light transmittance measured according to JIS K 7105 is 80% or more regardless of whether it is colorless and transparent or colored and transparent. Further, the “conductivity” is not limited as long as it has conductivity suitable for the application, but is preferably 10 kΩ / □ or less, for example.

  The transparent conductive polyester film of the present invention is excellent in transparency after heat processing and has little oligomer precipitation. Therefore, it can be post-processed at a high temperature and is suitable as a touch panel member that requires high visibility.

(Base film)
The base film of the present invention is preferably a biaxially stretched polyester film from the viewpoints of mechanical strength, chemical resistance, heat resistance and the like.

  The stretching method of the polyester film is not particularly limited, and a sequential biaxial stretching method or a simultaneous biaxial stretching method is appropriately used.

  The base film may be a single layer or may have a multilayer structure of two or more layers made of the same or different polyester resins.

  The film haze change ΔHz (ΔHz = haze after heating−haze before heating) when the film of the present invention is heated at 170 ° C. for 20 minutes is preferably less than 0.5. In the case where ΔHz is 0.5 or more, cyclic oligomers may be deposited in the film post-processing step, and visibility may be lowered due to heating whitening. In the invention, the preferable upper limit of ΔHz is 0.3, more preferably 0.1. ΔHz is preferably small, and the lower limit of ΔHz is zero.

  It is important that the hydroxyl (OH) end amount of the film of the present invention is 70 eq / ton or less. Since the hydroxyl (OH) terminal amount is reduced to the above range, the film of the present invention can suitably reduce the formation of a cyclic trimer. Therefore, regeneration of the cyclic trimer in the melting step at the time of film formation can be suppressed, and the low oligomer amount of the film raw material can be suitably maintained. The hydroxyl (OH) terminal amount is more preferably 68 eq / ton or less, and still more preferably 65 eq / ton or less. The hydroxyl (OH) terminal amount is preferably small, but if it is too small, hydrolysis of the polyester resin tends to occur. Therefore, from the viewpoint of the durability of the film, the lower limit of the hydroxyl (OH) terminal amount is preferably 40 eq / ton or more, and more preferably 50 eq / ton or more. It is important for the present invention to find out the influence of hydroxyl (OH) terminal cyclic oligomer regeneration in the polyester resin, and there is no particular method for controlling the amount of hydroxyl (OH) terminal of the polyester film. By performing heat treatment in a water atmosphere, the amount of hydroxyl (OH) end can be suitably controlled.

  The cyclic trimer content of the base film of the present invention is desirably 0.45% by mass or less. When the cyclic trimer content is 0.45% by mass or more, oligomers may precipitate in the film-forming process, and heat whitening may occur easily, or the film-forming process and subsequent processes may be contaminated. . In order to make the amount of the cyclic trimer of the polyester film within the above range, it is preferable to heat-treat the polyester raw material. However, in the present invention, by reducing the amount of terminal hydroxyl (OH), the cyclic trimer in the film is reduced. The body weight can be suitably reduced within the above range. The upper limit of the preferable cyclic trimer content in the present invention is 0.40% by mass. Although the amount of cyclic trimer is preferably small, in view of productivity, the lower limit of the amount of cyclic trimer is preferably 0.05% by mass, more preferably 0.10% by mass, and 0.20% by mass. % Is more preferable.

  The intrinsic viscosity of the polyester film of the present invention is preferably in the range of 0.40 dl / g to 0.68 dl / g. When the intrinsic viscosity is lower than 0.40 dl / g, the film is easily torn, and when it is higher than 0.70 dl / g, the increase in filtration pressure is increased and high-precision filtration becomes difficult. The upper limit of the intrinsic viscosity of PET is preferably 0.65 dl / g, more preferably 0.63 dl / g. Furthermore, the lower limit is preferably 0.50 dl / g, more preferably 0.55 dl / g.

(Polyester resin)
The film of the present invention comprises a polyester resin obtained by a polycondensation reaction between a dicarboxylic acid component and a glycol component. Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and examples of the glycol component include ethylene glycol, diethylene glycol, 1,4-butanediol, and neopentyl glycol. In the present invention, polyethylene terephthalate and polyethylene naphthalate are preferable from the viewpoint of strength and transparency, and polyethylene terephthalate is particularly preferable.

  Polymerization of polyethylene terephthalate (hereinafter simply referred to as PET) includes direct polymerization of terephthalic acid and ethylene glycol and, if necessary, other dicarboxylic acid components and diol components directly, and dimethyl ester of terephthalic acid (required) Depending on the method, any production method such as a transesterification method in which a transesterification reaction of ethylene glycol (including other diol components as necessary) and ethylene glycol (including other dicarboxylic acid methyl esters) can be used.

  The intrinsic viscosity of the polyester is preferably in the range of 0.45 dl / g to 0.70 dl / g. When the intrinsic viscosity is lower than 0.45 dl / g, the film is easily torn, and when it is higher than 0.70 dl / g, the increase in filtration pressure is increased and high-precision filtration becomes difficult. The upper limit of the intrinsic viscosity of PET is preferably 0.68 dl / g, more preferably 0.65 dl / g. Further, the lower limit is preferably 0.48 dl / g, more preferably 0.50 dl / g.

  Conventionally known Mn, Mg, Ca, Ti, Ge, Al, Sb, Co compound, phosphorus compound, antimony compound and the like are used as a catalyst for preparing the crude polyester. A method of deactivating the catalyst has been proposed as a method of suppressing the regeneration of the cyclic oligomer when the polyester is melted. However, in the present invention, the regeneration of the cyclic oligomer can be suitably suppressed without going through the steps. Here, “crude polyester” is expressed by classifying polyester before heat treatment described later.

  The composition containing the dicarboxylic acid component and the glycol component includes a stabilizer, a pigment, a dye, a nucleating agent, a filler, an ultraviolet absorber, an antioxidant, an antibacterial agent, and an antistatic agent, depending on the final use of the polyester. Additives such as lubricants and mold release agents can be contained.

  Next, the obtained crude polyester is appropriately formed into a chip shape (for example, a cylindrical shape), a particle shape, or the like by a sheet cutting method, a strand cutting method, or the like. For example, in forming a chip, a melt of crude polyester is extruded from a die with a gear pump to form a strand, and this strand is cut with a cutter, and a major axis × minor axis × length is about 2.2 × 3.1 ×. A 3.4 mm elliptical columnar chip is formed. By molding into such a chip shape, the humidity control effect can be suitably exerted to the inside of the chip while suitably reducing the oligomer amount of the film raw material by heat treatment described later.

  Examples of a method for reducing the hydroxyl (OH) terminal amount of polyester include a method of increasing the molecular weight of polyester to reduce the terminal amount per unit, and a method of water-saturating a raw material chip. Among them, in the present invention, the crude polyester as a film raw material is preferably heat-treated in a water atmosphere, so that the cyclic oligomer content can be suitably reduced and the hydroxyl (OH) terminal amount can be suitably reduced. . The heat treatment is characterized by performing a high-temperature heat treatment at 190 to 260 ° C. under a flow rate of a moisture-containing inert gas containing water. By performing the heat treatment under an inert gas flow rate, it is possible to suitably reduce the cyclic oligomer without increasing the PET intrinsic viscosity more than necessary. This point is different from the conventional solid phase polymerization. Further, unlike the solid phase polymerization method conventionally performed by the batch method, the productivity is excellent in that the treatment can be continuously performed under a flow rate.

  Furthermore, the amount of hydroxyl (OH) ends in the polyester resin can be suitably reduced by performing the heat treatment in a predetermined water atmosphere. The reason why the amount of hydroxyl (OH) ends is reduced in a water atmosphere is considered as follows. That is, the hydroxyl (OH) ends are bonded by a deethylene glycol reaction by heat treatment, and the hydroxyl (OH) ends are consumed. On the other hand, the reverse reaction of the ester reaction occurs in a water atmosphere, the polyester molecular weight is reduced, and a new molecular chain end is generated. Since these reactions occur as a mixture, it is believed that the resulting hydroxyl (OH) end will be reduced.

The heat treatment conditions for the crude polyester in the present invention are described in detail below.
In the heat treatment, the water content in the inert gas is preferably 3.5 to 30.0 g / Nm ³ , more preferably 4.0 to 20.0 g / Nm ³ . When the moisture content in the humidity control inert gas is less than 3.5 g / Nm ³ , the increase in intrinsic viscosity of the resulting polyester is remarkable. When the moisture content in the humidity control inert gas is excessive, a hydrolysis reaction may occur, and the intrinsic viscosity of the resulting polyester may be reduced.

  As the inert gas, a gas inert to polyester is used, and examples thereof include nitrogen gas, carbon dioxide gas, and helium gas. Nitrogen gas is particularly preferable because it is inexpensive.

  As the heat treatment apparatus, an apparatus that can uniformly contact the crude polyester and the inert gas is desirable. Examples of such a heat treatment apparatus include a stationary dryer, a rotary dryer, a fluidized bed dryer, and a dryer having a stirring blade.

  Further, it is more preferable to partially crystallize the polymer in order to appropriately remove moisture from the polyester before the heat treatment and to prevent fusion of the polymers during the heat treatment.

  In heat processing, heat processing temperature becomes like this. Preferably it is 190 to 260 degreeC, More preferably, it is 200 to 250 degreeC. When the heat treatment temperature is less than 190 ° C., the decrease rate of the cyclic oligomer in the crude polyester may be small. When the heat treatment temperature exceeds the melting point of the polyester, the polyester melts and adhesion is likely to occur. Therefore, it is difficult to take out the obtained polyester from the heat treatment apparatus, and the molding operation may be difficult.

  The heat treatment time is usually preferably 1 to 70 hours, more preferably 2 to 60 hours, and further preferably 4 to 50 hours. If it is less than 1 hour, the cyclic oligomer in the crude polyester is not sufficiently reduced, and if it exceeds 70 hours, the rate of reduction of the cyclic oligomer in the crude polyester is small, and conversely problems such as thermal degradation occur. There is a fear, and the color tone is impaired.

  The flow rate of the inert gas is closely related to the intrinsic viscosity of the polyester. Further, the water content contained in the humidity control inert gas also affects the change in the intrinsic viscosity of the polyester. Therefore, the flow rate of the inert gas should be appropriately selected according to the water content, the desired intrinsic viscosity of the polyester, the heat treatment temperature, and the like.

  For example, when the moisture content of the humidity control inert gas is high, the flow rate is preferably increased in order to avoid adverse effects such as hydrolysis by water. Moreover, when making heat processing temperature high, in order to suppress the raise of the intrinsic viscosity of polyester, it is preferable to reduce the flow volume of an inert gas.

  The flow rate of the inert gas is preferably at least 1 liter per hour per kg of polyester, more preferably at least 5 liters. When the flow rate of the inert gas is less than 1 liter per hour per 1 kg of polyester, there is a risk of adverse effects such as yellowing of the resulting resin due to oxygen contamination. The upper limit of the flow rate of the inert gas is determined by the water content contained in the inert gas and the heat treatment temperature, but is 10,000 liters or less per kilogram of polyester, preferably 5,000 liters or less, more preferably 2 1,000 liters or less. Even if the flow rate of the inert gas is set to 10,000 liters or more, it does not deviate from the object of the present invention, but it is not necessary to unnecessarily increase the flow rate in consideration of the economical aspect.

  The heat treatment of the present invention is carried out by heat treatment while circulating an inert gas under normal pressure to slightly pressurized pressure.

In this case, since the purpose of pressurization is to prevent moisture and oxygen in the atmosphere from being mixed into the reactor during the heat treatment, the pressurization condition of 5.0 kg / cm ² or less is sufficient. Even when the pressurization condition exceeds 5.0 kg / cm ² , the object of the present invention is not deviated, but since the equipment is costly, it is meaningless to increase the pressure more than necessary.

  Furthermore, the oxygen concentration in the inert gas circulated from the viewpoint of color tone is required to be 50 ppm or less, preferably 25 ppm or less. When the oxygen concentration is 50 ppm or more, the color tone deteriorates due to the deterioration of the polyester of the present invention, specifically, yellowing is severe, resulting in a problem in product quality.

The polyester thus obtained preferably satisfies the following formula.
−0.05 dl / g ≦ Intrinsic viscosity before heat treatment −Intrinsic viscosity after heat treatment ≦ 0.05 dl / g

  By these treatments, the intrinsic viscosity (B) of the polyester composition after the heat treatment is preferably 0.50 dl / g or more and 0.70 dl / g or less, and further the intrinsic viscosity of the polyester composition (crude polyester) before the heat treatment. Between (A) and -0.05 dl / g≤ {(A)-(B)} ≤0.05 dl / g, and preferably -0.02 dl / g≤ {(A) -(B)} ≦ 0.02 dl / g is preferably satisfied. By setting the intrinsic viscosity (B) after the heat treatment to 0.50 dl / g or more, the occurrence of film breakage during film formation is reduced, which is advantageous. Moreover, by setting it as 0.70 dl / g or less, it can reduce that a temperature rises by the shear heat_generation | fever at the time of melt molding, and it is advantageous in suppressing the amount of cyclic oligomers in a product.

  Further, by satisfying −0.05 dl / g ≦ {(A) − (B)} ≦ 0.05 dl / g, there is no unnecessary temperature rise during film formation, and the amount of polyester cyclic oligomer is small and the color tone In addition to providing a good film, it is not necessary to newly provide a low-viscosity or high-viscosity brand for a polyester composition (crude polyester) before heat treatment, and an existing polymer that can be used as another product is used. It is possible to reduce the amount of cyclic oligomers used, which is economically advantageous.

  Further, the content of the cyclic trimer of the polyester composition after the heat treatment needs to be 0.4% by mass or less. More preferably, it is 0.35 mass%. When the content exceeds 0.4% by mass, the cyclic oligomer is regenerated at the time of film forming, and the cyclic oligomer is deposited on the film surface during film production or film processing process, causing the process to become a film product defect. There is.

  Furthermore, the hydroxyl (OH) terminal amount of the polyester composition after heat treatment needs to be 65 eq / ton or less. The lower the hydroxyl (OH) terminal amount, the more the oligomer regeneration during the melt extrusion in the film forming process of the polyester raw material can be suppressed. 60 eq / ton or less is more preferable.

(Transparent conductive thin film)
The transparent conductive thin film that can be used in the film of the present invention is not particularly limited as long as the transparency and conductivity required for the film of the present invention can be ensured. For example, indium oxide, tin oxide, zinc oxide, indium-tin composite oxide, tin-antimony composite oxide, zinc-aluminum composite oxide, indium-zinc composite oxide, silver and silver alloy, copper and copper alloy, gold The thing of the single layer structure of these, or the laminated structure of two or more layers is mentioned. Of these, indium-tin composite oxide or tin-antimony composite oxide is preferable from the viewpoint of environmental stability and circuit processability.

  The thickness of the transparent conductive thin film is preferably 4 to 800 nm, particularly preferably 5 to 500 nm. When the thickness of the transparent conductive thin film is less than 4 nm, it is difficult to form a continuous thin film, and it is difficult to show good conductivity. On the other hand, when it is thicker than 800 nm, the transparency tends to decrease.

  In forming the transparent conductive thin film, using the metal oxides and metals exemplified above, for example, from known film formation methods such as vacuum deposition, sputtering, CVD, ion plating, spraying, etc. A suitable method according to the required film thickness can be selected as appropriate.

  For example, in the case of the sputtering method, a normal sputtering method using a metal oxide target or a reactive sputtering method using a metal target is used. At this time, oxygen, nitrogen, or the like may be introduced as a reactive gas, or means such as ozone addition, plasma irradiation, or ion assist may be used in combination. In addition, a bias such as direct current, alternating current, and high frequency may be applied to the substrate as long as the object of the present invention is not impaired.

  For example, when a transparent conductive thin film is formed by sputtering, the pressure in the vacuum chamber is evacuated to a vacuum level of 0.001 Pa or less before performing sputtering, and then an inert gas such as Ar reacts with oxygen or the like. It is preferable to perform sputtering by introducing a property gas into the vacuum chamber, generating discharge in a pressure range of 0.01 to 10 Pa. The same applies to other methods such as vacuum deposition and CVD.

  In addition, a hard coat layer may be provided on the opposite surface of the transparent conductive thin film in order to improve scratch resistance during pen input. The thickness of the hard coat layer is preferably 0.5 to 10 μm. If the thickness is less than 0.5 μm, the scratch resistance tends to be insufficient, and if it exceeds 10 μm, it is not preferable from the viewpoint of productivity.

A known curable resin is used as a material for the hard coat layer. A resin having an acrylate-based functional group is preferable. Specific examples of such curable resins include, for example, relatively low molecular weight polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins, and many others. Examples thereof include oligomers or prepolymers of polyfunctional compounds such as monohydric alcohols and (meth) acrylates. In the case of laminating a hard coat layer, it is desirable from the viewpoint of improving adhesiveness to subject the surface of the base film to corona treatment or to perform easy adhesion treatment such as forming an easy adhesion layer.

  Next, the effect of this invention is demonstrated using an Example and a comparative example. First, the evaluation method of the characteristic values used in the present invention is shown below.

[Evaluation methods]
(1) Haze Measured according to JIS K 7105 “Testing method for optical properties of plastic” haze (cloudiness value). NDH-300A type turbidimeter manufactured by Nippon Denshoku Industries Co., Ltd. was used for the measuring instrument.

(2) Evaluation of Haze Change (ΔHz) The film was cut into a 50 mm square, and the haze before heating was measured according to JIS K 7105 “Testing Method for Optical Properties of Plastics” haze (cloudiness value). NDH-300A type turbidimeter manufactured by Nippon Denshoku Industries Co., Ltd. was used for the measuring instrument. After the measurement, the film is set in an oven heated to 170 ° C., and the film is taken out after 20 minutes. After heating, the film is measured for haze by the same method as described above to obtain haze after heating. The haze difference before and after heating is set to ΔHz.
ΔHz = (Haze after heating) − (Haze before heating)

(3) Hydroxyl (OH) terminal amount of polyester film or polyester resin The polyester film or resin was finely pulverized, and 15 mg was weighed. After completely dissolving in 0.1 ml of hexafluoroisopropanol (HFIP) -d2, it was diluted with 0.6 ml of deuterated chloroform. Furthermore, in order to shift the OH group peak of HFIP, 30 μl of pyridine-d5 was added, and measurement was performed by H-NMR (BBO-5 mm probe).

(4) Amount of cyclic trimer The polyester film or polyester resin was finely pulverized, and 0.1 g was dissolved in 3 ml of a mixed solvent of hexafluoroisopropanol (HFIP) / chloroform (2/3 (volume ratio)). To the resulting solution, 20 ml of chloroform was added and mixed uniformly. 10 ml of methanol was added to the resulting mixture to reprecipitate the linear polyester. Next, this mixed solution was filtered, and the precipitate was washed with 30 ml of a mixed solvent of chloroform / methanol (2/1 (volume ratio)) and further filtered. The obtained filtrate was concentrated to dryness on a rotary evaporator. 10 ml of dimethylformamide was added to the concentrated dried product to prepare a cyclic trimer measurement solution. This measurement solution was quantified using LC100 type high performance liquid chromatography manufactured by Yokogawa Electric Corporation.

(5) Intrinsic viscosity 0.2 g of polyester was dissolved in 50 ml of a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (60/40 (weight ratio)), and an Ostwald viscometer was used at 30 ° C. It was measured. The unit is dl / g.

(6) Melting | fusing point measurement It measured with the differential thermal analyzer (DSC) by the Seiko Electronics Industry Co., Ltd., RDC-220. Using 10 mg of the sample, the temperature was raised at a rate of temperature rise of 20 ° C./min and held at 290 ° C. for 3 minutes. The peak temperature of the melting peak observed when the temperature was raised was defined as the melting point (Tm).

(7) Surface resistance Measured by a four-terminal method according to JIS K 7194 using “Lotest AMCP-T400” manufactured by Mitsubishi Yuka Co., Ltd. as a measuring device.

Example 1
1,000 parts of dimethyl terephthalate, 700 parts of ethylene glycol, and 0.3 part of zinc acetate dihydrate were charged into a transesterification reaction can and subjected to a transesterification reaction at 120 to 210 ° C., and the produced methanol was distilled off. When the transesterification reaction was completed, 0.13 phosphoric acid and 0.3 part antimony trioxide were added, and the pressure in the system was gradually reduced to 1 mmHg or less in 75 minutes. At the same time, the temperature was gradually raised to 280 ° C. A polycondensation reaction was carried out for 70 minutes under the same conditions, and the molten polymer was extruded into water from a discharge nozzle and formed into a cylindrical chip having a diameter of about 3 mm and a length of about 5 mm by a cutter. The obtained crude polyester had an intrinsic viscosity of 0.610 dl / g, a hydroxyl (OH) terminal amount of 70 eq / ton, a cyclic trimer content of 1.05% by mass, and a melting point of 252 ° C. It was. In the examples, “parts” are all parts by weight. Let the obtained crude polyester be a polyester resin (A).

PET resin (A) was dried at 160 ° C. under reduced pressure, and then nitrogen gas conditioned to a water content of 6.4 g / Nm ³ was circulated at a rate of 70 liters per kg of crude polyester at 207 ° C. For 48 hours. The obtained polyester had an intrinsic viscosity of 0.631 dl / g, a hydroxyl (OH) end amount of 59 eq / ton, and a cyclic trimer content of 0.27% by mass.

  The obtained polyester resin was dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours and then supplied to an extruder. The raw material supplied to the extruder was melt-extruded into a sheet form from the die at a resin temperature of 280 ° C. until the melting part, kneading part, polymer pipe, gear pump, and filter of the extruder, and 275 ° C. in the subsequent polymer pipe. . In addition, a stainless steel sintered filter medium (nominal filtration accuracy: 95 μm of 10 μm particles) was used for each of the filters. The temperature of the die was controlled so that the temperature of the extruded resin was 275 ° C.

  The extruded resin was cast on a cooling drum having a surface temperature of 30 ° C. and brought into close contact with the surface of the cooling drum using an electrostatic application method, and solidified by cooling to prepare an unstretched film having a thickness of 1360 μm.

  The obtained unstretched sheet was heated to 78 ° C. with a roll group heated to 78 ° C., then heated to 105 ° C. with an infrared heater, and 3 rolls in the longitudinal direction with a roll group having a peripheral speed difference. Stretched 4 times.

  Subsequently, the obtained uniaxially stretched film was gripped with a clip and subjected to transverse stretching. The transverse stretching temperature was 120 ° C. and the transverse stretching ratio was 4.0 times. Next, heat treatment was performed at 240 ° C. for 15 seconds, and 3% relaxation treatment was performed at 210 ° C. to obtain a 100 μm biaxially stretched polyethylene terephthalate film.

Next, a transparent conductive thin film made of indium-tin composite oxide was formed on one side of the obtained biaxially stretched polyethylene terephthalate film. At this time, the pressure before sputtering was set to 0.0007 Pa, and a DC power of ² W / cm ² was used for indium oxide containing 5% tin oxide as a target (Mitsui Metal Mining Co., Ltd., density 7.1 g / cm ³ ). Was applied. A transparent conductive thin film was formed by a DC magnetron sputtering method with Ar gas flowing at 130 sccm and oxygen gas flowing at a flow rate of 10 sccm and a pressure of 0.4 Pa. However, in order to prevent arc discharge instead of normal DC, a pulse with a width of 5 μs was applied at a 50 kHz period using “RPG-100” manufactured by Nippon NAI. The center roll temperature was 50 ° C. While constantly monitoring the oxygen partial pressure in the atmosphere using a sputter process monitor (“SPM200” manufactured by Hakuto Co., Ltd.), an oxygen gas flow meter is used so that the degree of oxidation in the indium-tin composite oxide thin film becomes constant. And back to DC power. A transparent conductive thin film made of an indium-tin composite oxide having a thickness of 22 nm was formed by the above operation and conditions to obtain a transparent conductive polyester film.

  Transparent conductive film No. 1 is used as one panel plate, and the other panel plate is a transparent conductive thin film made of indium-tin composite oxide (tin oxide content: 10%) having a thickness of 20 nm on a glass substrate by plasma CVD (Japan) Soda Co., Ltd. “S500”) was used. The two panel plates were arranged through epoxy beads having a diameter of 30 μm so that the transparent conductive thin film faced to prepare a touch panel. The obtained touch panel was good in both visibility and conductivity.

(Example 2)
The polyester resin (A) was dried at 160 ° C. under reduced pressure, and then nitrogen gas conditioned to a moisture content of 15.3 g / Nm ³ was circulated at 300 liters per kg of crude polyester at 12 hours at 230 ° C. Heat treatment was performed for a time. The obtained polyester had an intrinsic viscosity of 0.617 dl / g, a hydroxyl (OH) terminal amount of 71 eq / ton, and a cyclic trimer content of 0.28% by mass. A transparent conductive polyester film was obtained in the same manner as in Example 1 except that a newly obtained polyester resin was used.

(Example 3)
In the same manner as in Example 1, the intrinsic viscosity is 0.648 dl / g, the hydroxyl (OH) terminal amount is 64 eq / ton, the content of the cyclic trimer is 1.2% by mass, and the melting point is 245 ° C. A crude polyester was obtained. The obtained crude polyester was dried at 160 ° C. under reduced pressure, and then nitrogen gas conditioned to a water content of 15.3 g / Nm ³ was circulated at 300 liters per kg of the crude polyester at 220 ° C. Heat treatment was performed for 24 hours. The obtained polyester had an intrinsic viscosity of 0.623 dl / g, a hydroxyl (OH) terminal amount of 57 eq / ton, and a cyclic trimer content of 0.27% by mass. A transparent conductive polyester film was obtained in the same manner as in Example 1 except that a newly obtained polyester resin was used.

Example 4
In the same manner as in Example 1, the intrinsic viscosity is 0.613 dl / g, the hydroxyl (OH) terminal amount is 70 eq / ton, the content of the cyclic trimer is 1.03% by mass, and the melting point is 255 ° C. A crude polyester was obtained. The polyester was dried at 160 ° C. under reduced pressure, and then nitrogen gas conditioned to a water content of 6.4 g / Nm ³ was circulated at a rate of 70 liters per kg of the crude polyester. The pressure was adjusted to ² kg / cm ^{2 and} the heat treatment was performed at 207 ° C. for 48 hours. The obtained polyester had an intrinsic viscosity of 0.629 dl / g, a hydroxyl (OH) terminal amount of 60 eq / ton, and a cyclic trimer content of 0.28 weight. A transparent conductive polyester film was obtained in the same manner as in Example 1 except that a newly obtained polyester resin was used.

(Comparative Example 1)
The crude polyester obtained in the same manner as in Example 1 was dried at 160 ° C. under reduced pressure, adjusted to a slight pressure of 0.1 kg / cm ² under a nitrogen atmosphere, and heat-treated at 215 ° C. for 24 hours. The obtained polyester had an intrinsic viscosity of 0.622 dl / g, a hydroxyl (OH) terminal amount of 73 eq / ton, and a cyclic trimer content of 0.30% by mass.

  A transparent conductive polyester film was obtained in the same manner as in Example 1 for the heat-treated polyester.

(Comparative Example 2)
In the same manner as in Example 1, the intrinsic viscosity is 0.592 dl / g, the hydroxyl (OH) terminal amount is 83 eq / ton, the content of the cyclic trimer is 1.2% by mass, and the melting point is 250 ° C. A crude polyester was obtained. The obtained crude polyester was dried at 160 ° C. under reduced pressure, and then nitrogen gas conditioned to a water content of 35.0 g / Nm ³ was circulated at 180 liters per kg of the crude polyester at 220 ° C. Heat treatment was performed for 24 hours. Intrinsic viscosity in the obtained polyester was 0.482 dl / g.

  Although the unstretched film was obtained for the polyester after the heat treatment in the same manner as in Example 1, a rupture occurred in the stretching process, and the film could not be obtained.

(Comparative Example 3)
The crude polyester obtained in the same manner as in Example 1 was dried at 160 ° C. under reduced pressure, and nitrogen gas conditioned to a moisture content of 18.1 g / Nm ³ was then added at 40 liters per kg of crude polyester. And heat-treated at 170 ° C. for 24 hours. The content of the cyclic trimer in the obtained polyester was 1.00% by mass and did not decrease at all.

  A transparent conductive polyester film was obtained using the polyester after the heat treatment in the same manner as in Example 1. However, when the obtained film was heated, an oligomer was precipitated, and a predetermined function could not be obtained.

(Comparative Example 4)
The crude polyester obtained in the same manner as in Example 1 was dried at 160 ° C. under reduced pressure, and nitrogen gas conditioned to a moisture content of 18.1 g / Nm ³ was then added at 40 liters per kg of crude polyester. And heat-treated at 263 ° C. for 12 hours. The obtained polyester was melted in the can and could not be obtained.

  The transparent conductive polyester film of this invention is comprised as mentioned above, and the transparency fall by the heating in a touchscreen preparation process is suppressed. Therefore, the touch panel using the transparent conductive polyester film of the present invention is suitable with few appearance defects generated in the manufacturing process.

Claims (2)

A biaxially stretched polyester film as a base film, a transparent conductive polyester film in which a transparent conductive thin film is laminated on one side of the base film,
A transparent conductive polyester film satisfying the following constitutional requirements (1) and (2).
(1) Hydroxyl (OH) terminal amount is 70 eq / ton or less (2) Cyclic trimer content is 0.45 mass% or less   The transparent conductive polyester film according to claim 1, wherein the transparent conductive thin film is formed from an indium-tin composite oxide.