JP2009226767A - Laminated polyester film for transparent conductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated polyester film for a transparent conductive film that is suitable for application requiring transparency and conductivity, which is reduced in the amount of precipitation of oligomer on the polyester film surface caused by heating processing and which inhibits dust from adhering within the processes by imparting antistatic properties. <P>SOLUTION: The laminated polyester film for the transparent conductive film has, on one surface of a polyester film, a coating layer containing a titanium alkoxide compound and has, on the other surface, an SiO<SB>2</SB>layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laminated polyester film for a transparent conductive film, and particularly to a polyester film that can be suitably used for a touch panel.

  There are various types of touch panels, but the resistive film method is popular in order to achieve thinning and power saving. In this resistive film type touch panel, a transparent conductive laminate and a glass with a transparent conductive thin film are arranged to face each other via a spacer, and an electric current is passed through the transparent conductive laminate in the glass with a transparent conductive thin film. It has a structure that measures voltage. When the transparent conductive laminate is brought into contact with the glass with the transparent conductive thin film through a pressing operation with a finger, a pen or the like, the contact portion is energized, whereby the position of the contact portion is detected.

The transparent conductive laminate is a laminate having a transparent conductive thin film, and the transparent conductive thin film is formed on a film substrate. In order to improve the adhesion between the film substrate and the transparent conductive thin film, improve the scratch resistance and flex resistance of the transparent and conductive thin film, and improve the hitting characteristics for touch panels, an SiO ₂ layer There has been proposed a method of providing (Patent Document 1).

  By the way, when forming a transparent conductive laminated body, it is common to heat-process. For example, in order to form a transparent conductive thin film, an ITO film is formed by a sputtering method, and then heat treatment is performed at 150 ° C. for crystallization (Patent Document 2). In some cases, it is left at 150 ° C. for 1 hour for the shrinking treatment (Patent Document 3). In these heat processing, the oligomer contained in a polyester film may precipitate on the surface. In the case of heat processing conditions where the oligomer is deposited, if it is deposited on the surface of the polyester film that is not on the transparent conductive thin film side, defects may occur in the post-processing of the heat processing, or the process may be contaminated. In some cases, transparency and visibility may deteriorate.

In order to further reduce defects, more precise post-processing is required. Therefore, not only a clean environment with a small amount of dust is required in post-processing, but also a polyester film as a substrate that requires little dust adhesion is required. However, the polyester film, like a general plastic film, has a problem that static electricity is easily generated, and dust in the process adheres during post-processing, which may cause deterioration of transparency and visibility.
JP-A-6-222352 JP 2007-200823 A JP 2007-42473 A

  The present invention has been made in view of the above circumstances, and its solution is to reduce the amount of oligomer deposited on the film surface by heat processing and to prevent the adhesion of dust within the process by providing antistatic properties. It is providing the laminated polyester film for transparent conductive films suitable for the transparent conductive use which can be performed.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the above-described problems can be easily solved by using a polyester film having a specific coating layer, and have completed the present invention.

That is, the gist of the present invention is a laminated polyester for a transparent conductive film, characterized in that it has a coating layer containing a titanium alkoxide compound on one side of a polyester film and a SiO ₂ layer on the other side. Be on film.

Hereinafter, the present invention will be described in more detail.
The polyester film in the present invention may have a single layer structure or a multilayer structure, and may have a multilayer structure of four layers or more as long as the gist of the present invention is not exceeded other than the two-layer or three-layer structure. Well, not particularly limited.

  The polyester used in the present invention is preferably obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol, and may be a polyester comprising one kind of aromatic dicarboxylic acid and one kind of aliphatic glycol. It may be a copolyester obtained by copolymerizing one or more other components. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical polyester includes polyethylene terephthalate and the like. On the other hand, examples of the dicarboxylic acid used as a component of the copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, and sebacic acid, and glycol components include ethylene glycol, diethylene glycol, and propylene. Examples include glycol, butanediol, 1,4-cyclohexanedimethanol, and neopentyl glycol. Oxycarboxylic acids such as p-oxybenzoic acid can also be used.

  It is also possible to use low-oligomerized polyester for the outermost layer of a multilayer structure film in order to reduce the amount of oligomers contained in the film deposited on the surface of the film due to heat history during film processing, etc. It is. As a method for reducing the amount of oligomer in the polyester, a solid phase polymerization method or the like can be used.

  In the film of the present invention, it is preferable to blend particles for the main purpose of imparting slipperiness and preventing scratches in each step. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples of the particles include magnesium, kaolin, aluminum oxide, and titanium oxide. Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color, etc. Two or more kinds of these particles may be used in combination as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.01-3 micrometers normally, Preferably it is the range of 0.01-2 micrometers. When the average particle diameter is less than 0.01 μm, the particles are likely to aggregate and dispersibility may be insufficient. On the other hand, when the average particle diameter exceeds 3 μm, the surface roughness of the film becomes too rough and Problems may occur when various surface functional layers are applied in the process.

  Further, the content of particles in the polyester layer is usually in the range of 0.001 to 5% by weight, preferably 0.005 to 3% by weight. When the particle content is less than 0.001% by weight, the slipperiness of the film may be insufficient, while when it exceeds 5% by weight, the transparency of the film may be insufficient.

  The method for adding particles to the polyester is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage of producing the polyester constituting each layer, but it is preferably added after completion of esterification or transesterification.

  Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  In addition to the above-mentioned particles, conventionally known UV absorbers, antioxidants, antistatic agents, thermal stabilizers, lubricants, dyes, pigments, etc. may be added to the polyester film in the present invention as necessary. Can do.

  Although the thickness of the polyester film in this invention will not be specifically limited if it is a range which can be formed into a film as a film, Usually, 10-300 micrometers, Preferably it is the range of 15-100 micrometers.

  Next, although the manufacture example of the polyester film in this invention is demonstrated concretely, it is not limited to the following manufacture examples at all. That is, a method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, the film is stretched in the direction perpendicular to the first stretching direction. In that case, the stretching temperature is usually 70 to 170 ° C., and the stretching ratio is usually 3.0 to 7 times, preferably 3.5 to 6 times. is there. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  In the present invention, the simultaneous biaxial stretching method can also be adopted for the production of the polyester film. The simultaneous biaxial stretching method is a method in which the above-mentioned unstretched sheet is usually stretched and oriented in the machine direction and the width direction at a temperature controlled normally at 70 to 120 ° C., preferably 80 to 110 ° C. Is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area magnification. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, conventionally known stretching methods such as a screw method, a pantograph method, and a linear drive method can be employed.

  Next, the formation of the coating layer constituting the laminated polyester film in the present invention is provided by coating the film with a coating solution, and even if it is provided by in-line coating performed in the film manufacturing process, An off-line coating that is applied outside the system may be employed.

  Specifically, the in-line coating is a method in which the coating is performed at any stage from melt extrusion of the polyester to stretching, heat setting, and winding. Normally, it is coated on a substantially amorphous unstretched sheet obtained by melting and quenching, followed by a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction), or a biaxially stretched film before heat setting. To do. Among these, a method is generally used in which a uniaxially stretched film is coated, dried and stretched in the transverse direction, and further heat treated together with the base film.

  Although the film of this invention has a specific coating layer, the said coating layer needs to contain a titanium alkoxide type compound.

The titanium alkoxide compound used in the present invention is a compound in which one or more alkoxide compounds are bonded to at least one titanium atom in one molecule. Specific examples include oligomers such as titanium tetrabutoxide, titanium tetraisopropoxide, titanium tetra-2-ethylhexoxide, and dimers thereof. Moreover, you may have a crosslinked structure and you may hydrolyze. These compounds may be used alone or in combination of two or more. In addition, it is essential that the coating layer is formed on the polyester film side opposite to the SiO ₂ layer formed on the polyester film, but it is also laminated on the SiO ₂ layer side to prevent oligomer precipitation by heat processing. May be.

  In the laminated polyester film of the present invention, a binder polymer such as a polyester resin, an acrylic resin, a polyurethane resin, or polyvinyl may be used in combination in order to improve the surface condition of the coating layer, the oligomer precipitation preventing property, and the like.

  Furthermore, a crosslinking agent may be used in the coating layer as long as the gist of the present invention is not impaired, and various known resins can be used, and examples thereof include melamine compounds, epoxy compounds, oxazoline compounds, and isocyanate compounds.

  Further, for the purpose of improving the adhesion and slipperiness of the coating layer, inert particles may be included in the coating layer, and specific examples include silica, alumina, kaolin, calcium carbonate, titanium oxide, organic particles, and the like. It is done.

  Furthermore, the coating layer contains an antifoaming agent, a surfactant, a thickener, an organic lubricant, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, etc. May be.

  In the present invention, as a method for providing the coating layer, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, spray coating or the like can be used. Regarding the coating method, there is a description example in “Coating method” published by Yasuharu Harasaki in 1979.

  In the present invention, the drying and curing conditions for forming the coating layer on the polyester film are not particularly limited. For example, when the coating layer is provided by off-line coating, usually in the range of 70 to 150 ° C., The heat treatment is preferably performed in the range of 80 to 110 ° C. for 3 to 200 seconds as a guide.

  Further, irrespective of off-line coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as required. The polyester film constituting the laminated polyester film in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

The amount of oligomer (cyclic trimer) extracted from the surface of the coating layer obtained by applying a titanium alkoxide compound and drying it after heat-treating the laminated polyester film in the present invention (180 ° C., 10 minutes). Is usually 1.5 mg / m ² or less, preferably 1.0 mg / m ² or less, more preferably 0.5 mg / m ² or less. When the amount of oligomer exceeds 1.5 mg / m ² , the amount of oligomer precipitation due to heat treatment increases in post-processing, and the transparency / visibility of the film decreases, or the oligomer deposits and adheres to the process equipment. As a result of accumulation and desorption, there is a possibility that a defect such as a foreign matter defect due to scattering on the film may occur.

The specific resistance of the coating layer surface containing the titanium alkoxide compound of the laminated polyester film of the present invention is usually 1 × 10 ¹³ Ω or less, preferably 1 × 10 ¹² Ω or less. If the surface resistivity is higher than 1 × 10 ¹³ Ω, transparency and visibility may be deteriorated due to a decrease in the ability to prevent foreign matter adhering to dust and the like. In some cases, the processing cannot be performed sufficiently.

Further, the present invention is a coating layer of the polyester film is required to have a SiO ₂ layer on the opposite surface.

As a method for forming the SiO ₂ layer, for example, it can be formed by a vacuum deposition method, a sputtering method, an ion plating method, a coating method, or the like.

The thickness of the SiO ₂ layer is usually in the range of 1 to 300 nm, preferably in the range of 10 to 50 nm. If the thickness is less than 10 nm, it is difficult to form a continuous film, and the scratch resistance may not be sufficiently improved. On the other hand, if the thickness exceeds 300 nm, the improvement of transparency may be insufficient, or cracks may occur.

Moreover, it is also possible to provide an underlay layer on the SiO ₂ layer in order to improve various performances. As the underlay layer, for example, the rate of change of the surface electrical resistance of the conductive thin film is suppressed, the purpose of forming a transparent conductive laminate having excellent stability, and the coloring of transmitted light when it is made a transparent conductive laminate For the purpose of suppressing the above, an SiO _x layer, a layer made of a metal oxide, or a layer made of an organic substance such as a melamine resin can be used. In order to further improve the prevention of oligomer precipitation, a coating layer obtained by coating with a coating solution containing a titanium alkoxide compound and drying can be provided as an underlay layer.

Furthermore, surface treatment such as corona treatment and plasma treatment can be performed in advance on the surface of the polyester film on the SiO ₂ layer lamination side in order to improve performance such as adhesion, and a coating layer is provided. Is also possible.

  The material of the transparent conductive thin film is not particularly limited, and a material capable of forming a transparent conductive film can be used. Examples thereof include indium oxide containing tin oxide and tin oxide containing antimony.

  It does not specifically limit as a formation method of a transparent conductive thin film, A conventionally well-known method is employable. For example, a vacuum deposition method, a sputtering method, an ion plating method, and the like can be given.

  The film thickness of the transparent conductive thin film can be determined according to the purpose of use, and is usually 10 to 300 nm, preferably 15 to 50 nm. If the film thickness is less than 10 nm, it may be difficult to form a continuous film having good electrical resistance on the surface, and if it exceeds 300 nm, transparency may not be sufficiently obtained.

  According to the laminated polyester film for transparent conductive film of the present invention, the transparent conductive use that can prevent adhesion of dust in the process by reducing the amount of oligomer deposited on the film surface by heat processing and providing antistatic properties. A laminated polyester film suitable for the above can be provided, and its industrial value is high.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measurement method and evaluation method used in the present invention are as follows.

(1) Measuring method of intrinsic viscosity of polyester 1 g of polyester was precisely weighed, 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) was added and dissolved, and the measurement was performed at 30 ° C.

(2) Measuring method of average particle size (d ₅₀ : μm) Integration (weight basis) 50 in equivalent spherical distribution measured using centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type, manufactured by Shimadzu Corporation) % Was defined as the average particle size.

(3) Method for measuring the amount of oligomer (cyclic trimer) extracted from one surface of the laminated polyester film (the surface of the coating layer when there is a coating layer containing a titanium alkoxide compound) The polyester film is heated in air at 180 ° C. for 10 minutes. Thereafter, the heat-treated film is brought into close contact with the inner surface of a box having a top and width of 10 cm and a height of 3 cm with the top open to obtain a box shape. When the coating layer is provided, the coating layer surface is set to the inside. Next, 4 ml of DMF (dimethylformamide) is placed in the box prepared by the above method and left for 3 minutes, and then DMF is recovered. The recovered DMF was supplied to liquid chromatography (manufactured by Shimadzu Corporation: LC-7A) to determine the amount of oligomer in DMF, and this value was divided by the film area in contact with DMF to obtain the amount of film surface oligomer (mg / M ² ). The amount of oligomer in DMF was determined from the peak area ratio between the standard sample peak area and the measured sample peak area (absolute calibration curve method).

  The standard sample was prepared by accurately weighing an oligomer (cyclic trimer) collected in advance and dissolving it in accurately measured DMF. The concentration of the standard sample is preferably in the range of 0.001 to 0.01 mg / ml.

The conditions for the liquid chromatograph were as follows.
Mobile phase A: Acetonitrile Mobile phase B: 2% acetic acid aqueous solution Column: “MCI GEL ODS 1HU” manufactured by Mitsubishi Chemical Corporation
Column temperature: 40 ° C
Flow rate: 1 ml / min Detection wavelength: 254 nm

(4) Measuring method of surface resistivity of laminated polyester film Using a high resistance measuring instrument: HP4339B and measuring electrode: HP16008B manufactured by Japan Hewlett-Packard Company, the sample was conditioned for 30 minutes in a measurement atmosphere of 23 ° C. and 50% RH. Then, the surface specific resistance value of the film surface after 1 minute at an applied voltage of 100 V (when there is a coating layer obtained by applying a titanium alkoxide compound and drying) is measured. It can be said that the lower the surface resistivity, the better the antistatic property.

(5) Visibility evaluation method after laminating transparent conductive thin film Indium oxide 95 under an atmosphere of 0.4 Pa composed of argon gas 95% and oxygen gas 5% on the SiO ₂ layer provided on the laminated polyester film. An ITO film (transparent conductive thin film) having a thickness of 25 nm was formed by a reactive sputtering method using a sintered body material of 5% by weight and 5% by weight of tin oxide. The ITO film was crystallized by heat treatment at 150 ° C. for 1 hour. In this state, the film is observed, a coating solution containing a titanium alkoxide compound is applied, and the amount of oligomer precipitation is small on the surface of the coating layer obtained by drying, and no deterioration in transparency and visibility is observed. The case was evaluated as ◯, and the case where the amount of oligomer precipitation was large and the transparency and visibility were deteriorated was evaluated as x.

The polyester used in the examples and comparative examples was prepared as follows.
<Method for producing polyester (I)>
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is placed in the reactor, the reaction start temperature is set to 150 ° C., and the methanol is distilled off gradually. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.04 part of ethyl acid phosphate to this reaction mixture, 0.04 part of antimony trioxide was added, and a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester (I) was 0.63.

<Method for producing polyester (II)>
In the method for producing polyester (I), after adding 0.04 part of ethyl acid phosphate, 0.3 part of silica particles having an average particle diameter of 1.6 μm dispersed in ethylene glycol and 0.04 part of antimony trioxide are added. In addition, polyester (II) was obtained using the same method as the production method of polyester (I) except that the polycondensation reaction was stopped at the time corresponding to the intrinsic viscosity of 0.65. The obtained polyester (II) had an intrinsic viscosity of 0.65.

Examples of compounds constituting the coating layer are as follows.
(Compound example)
(A): Titanium tetranormal butoxide, manufactured by Matsumoto Fine Chemical Co., Ltd. “Orgatechs TA-25”
(B): Titanium tetra-2-ethylhexoxide, “Orgatics TA-30” manufactured by Matsumoto Fine Chemical Co., Ltd.
(C): Titanium oligomer, “Origatix PC-605” manufactured by Matsumoto Fine Chemical Co., Ltd.

<Method for Forming SiO ₂ Layer (X)>
A cured film having a thickness of 200 nm made of a thermosetting resin of melamine resin: alkyd resin: organosilane condensate = 2: 2: 1 (weight ratio) was formed on the surface opposite to the polyester film coating layer. . Next, on the cured film, silica sol (“Colcoat P” manufactured by Colcoat Co., Ltd.), which is diluted with ethanol so as to have a solid content concentration of 2%, is applied, dried at 150 ° C. for 2 minutes, and cured. A SiO ₂ layer having a thickness of 30 nm was formed.

<Method for Forming SiO ₂ Layer (Y)>
On the surface opposite to the polyester film coating layer, silica sol (“Colcoat P” manufactured by Colcoat Co., Ltd.) diluted with ethanol to a solid content concentration of 2% is applied and dried at 150 ° C. for 2 minutes. Thereafter, it was cured to form a SiO ₂ layer having a thickness of 30 nm.

Example 1:
A mixed raw material in which polyesters (I) and (II) are mixed at a ratio of 85% and 15%, respectively, is supplied to an extruder, melted at 285 ° C., then extruded onto a cooling roll set at 40 ° C., and cooled and solidified. An unstretched sheet was obtained. Next, the film was stretched 3.4 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, then led to a tenter, stretched 4.3 times at 120 ° C. in the transverse direction, and heat-treated at 225 ° C. Thereafter, the film was relaxed in the lateral direction to obtain a polyester film having a thickness of 25 μm. On the obtained polyester film, the coating liquid (A) diluted with MEK (methyl ethyl ketone) was applied so that the coating amount after drying was 0.1 g / m ² , dried at 80 ° C., and the coating layer A laminated polyester film having was obtained. A SiO ₂ layer (X) was provided on the surface opposite to the side having the coating layer. The finished polyester film showed a low amount of oligomer precipitation by heating and a low surface resistivity. The characteristics of this film are shown in Table 1 below.

Examples 2-7:
In Example 1, the coating layer, and the SiO ₂ layer was prepared in the same manner as in Example 1 except that changed as shown in Table 1, to obtain a laminated polyester film. The characteristics of the obtained polyester film are shown in Table 1 below.

Comparative Example 1:
In Example 1, it manufactured similarly to Example 1 except having not provided the application layer, and obtained the polyester film. The characteristics of the obtained polyester film are shown in Table 1 below.

  All the coating solutions were diluted with MEK.

  The film of this invention can be utilized suitably for the transparent conductive use used for touch panel etc., for example.

Claims (1)

A laminated polyester film for a transparent conductive film having a coating layer containing a titanium alkoxide compound on one surface of a polyester film and an SiO ₂ layer on the other surface.