JP2015009534A - Biaxially oriented multilayer black polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially oriented multilayer black polyester film with excellent fire retardancy, having antistatic properties and high partial discharge voltage.SOLUTION: A biaxially oriented multilayer black polyester film is a multilayer polyester film having, at least on one outermost layer, a layer made of a polyester resin composition including an antistatic agent. The biaxially oriented multilayer black polyester film includes a black pigment in the film, a quotient (ΔPD/T) of partial discharge voltage variation value ΔPD and an outermost layer film thickness T(μm) is 0.5 or more defined by the following equation: ΔPD=PDexp-(3.06×T+345). (In the equation, PDexp denotes a partial discharge voltage measurement value (V) of the polyester film, and T denotes thickness (μm) of the polyester film.)

Description

  The present invention relates to a biaxially oriented laminated black polyester film having good flame retardancy, antistatic properties and high partial discharge voltage.

  Photovoltaic power generation that converts light energy into electrical energy using the photoelectric conversion effect is widely performed as a means for obtaining clean energy. And with the improvement of the photoelectric conversion efficiency of a photovoltaic cell, the photovoltaic power generation system has come to be provided also in many private houses. In order to use such a solar power generation system as an actual energy source, a solar cell module having a configuration in which a plurality of solar cells are electrically connected in series is used.

  Solar cell modules are generally used for a long time on the roof of a house. And the back surface protective material for solar cells is used for a solar cell module. Patent Document 1 discloses an invention relating to a solar cell back surface protective material using a polyester film. Of course, since a house where people live is required to have flame retardancy and insulation, the solar cell module on the roof of the house is also required to have flame retardancy and insulation. That is, flame retardancy and insulation are also required for the polyester film for the back surface protective material for solar cells.

  Organic substances such as polyester are easy to burn if there is an ignition source. There are various causes of ignition, but if the film is charged, sparks are likely to occur. Therefore, as in Patent Document 2 and Patent Document 3, it is considered that a film in which an antistatic layer is provided on polyester by a coating method can be suitably used.

  However, even if the polyester film itself does not generate sparks derived from charging, when there are other sources of fire, it is difficult to prevent the flame from spreading unless the polyester film itself has a self-extinguishing property. The polyester film provided on the polyester film by coating the antistatic layer is composed of a low molecular weight material, so that when the flame comes into contact with the polyester film, the flammable low molecular components are likely to volatilize and the flame Is not preferred for use because it is difficult to self-extinguish.

  Further, since the partial discharge voltage increases in correlation with the thickness of the polyester film, increasing the thickness is an effective method for obtaining a polyester film having a high partial discharge voltage. However, achieving a high partial discharge voltage by increasing the thickness of the polyester film is not preferable from the viewpoint of space saving and weight reduction of the solar cell module.

  The partial discharge voltage can be increased by applying the antistatic layer to the surface of the polyester film. When a high voltage is applied in the thickness direction of the polyester film, a part of the electric field received by the film can be appropriately conducted and diffused in the film surface direction. Thereby, the amount of electricity received per unit volume in the thickness direction of the film can be reduced. As a result, even when a high voltage is applied, it is possible to suppress the concentration of the electric field on the portion with poor insulation performance, and the occurrence of the partial discharge phenomenon can be suppressed. Therefore, it is considered that a film in which an antistatic layer is provided on polyester by a coating method can be suitably used. However, since the antistatic ability was provided by coating, the low-molecular component derived from coating is highly flammable, which is not preferable from the viewpoint of flame retardancy.

  In order to enhance the designability of the solar cell module, there is a demand for coloring the back surface protective material of the solar cell. As a result, blackening is also demanded for the polyester film for the back surface protective material for solar cells.

Japanese Patent Laid-Open No. 2002-100788 JP 2006-076212 A JP 2003-048284 A

  This invention is made | formed in view of the said actual condition, The solution subject is good flame retardance, has antistatic property, and provides the biaxially-oriented laminated black polyester film which has a high partial discharge voltage. There is.

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

That is, the gist of the present invention is a laminated polyester film having a layer made of a polyester resin composition containing an antistatic agent in at least one outermost layer, a partial discharge voltage change value ΔPD defined by the following formula, and an outermost layer The quotient (ΔPD / T _A ) of the film thickness T _A (μm) is 0.5 or more, and the film is a biaxially oriented laminated polyester film characterized by containing a black pigment in the film.
ΔPD = PDexp− (3.06 × T + 345)
(In the above formula, PDexp is the measured partial discharge voltage (V) of the polyester film, and T is the thickness (μm) of the polyester film)

  ADVANTAGE OF THE INVENTION According to this invention, the polyester film used as a base material does not generate | occur | produce the spark derived from charging, has a self-extinguishing property of a flame, and can provide the biaxially oriented laminated polyester film which has a high partial discharge voltage. For example, the biaxially oriented laminated polyester film can be applied to a polyester film for a solar cell back surface protective material, and its industrial value is high.

Combustion test equipment

  In the present invention, the polyester used for the polyester film may be a homopolyester or a copolyester. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. 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. Representative polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN), and the like.

  On the other hand, in the case of a copolyester, a copolymer containing 30 mol% or less of the third component is preferable. Examples of the dicarboxylic acid component of the copolyester include one or two of isophthalic acid, terephthalic acid phthalate, 2,6-naphthalenedicarboxylic acid, adipic acid sebacic acid, and oxycarboxylic acid (for example, P-oxybenzoic acid). Examples of the glycol component include one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like.

  In any case, the polyester referred to in the present invention is usually 80 mol% or more, preferably 90 mol% or more of polyethylene terephthalate in which ethylene terephthalate units are formed, or polyethylene-2,6- in which ethylene-2,6-naphthalate units are formed. Refers to polyester such as naphthalate.

  The polyester resin layer that is the surface layer of the sheet of the present invention is obtained by adding an antistatic agent to a polyester resin. As the polyester resin for the surface layer, various polyester resins as described above can be used.

  Examples of the polymer type antistatic agent include polyetheramide-based conductive polymers and polythiophene-based conductive polymers. A high partial discharge voltage can be obtained by containing a polymer type antistatic agent, but in order to obtain the effect, it is usually necessary to add 15% by weight or more of an antistatic agent. The mechanical properties that are characteristic of the film may be impaired.

  Antistatic agents include anionic ionic antistatic agents such as dodecylbenzenesulfonic acid and its salts. Although this sulfonate type antistatic agent has a high antistatic effect, it has poor compatibility with the polyester resin, and lowers transparency, moldability and mechanical properties.

  It is preferable to use a nonionic antistatic agent for the antistatic agent of the said use. Examples of nonionic antistatic agents include glycerin fatty acid ester, polyoxyethylene-containing ether, polyoxyethylene alkylphenyl ether, N, N-bis (2-hydroxyethyl) alkylamine, and N-2 hydroxyethyl-N-2. -Hydroxyalkylamines, polyoxyethylene alkylamines, polyoxyethylene alkylamine fatty acid esters, alkyl diethanolamides and the like. Among them, it is desirable to use glycerin fatty acid ester from the viewpoints of compatibility, transparency, moldability, and mechanical properties.

  The ester of glycerin fatty acid ester in the present invention is preferably composed mainly of monoester or diester, but both may be used. Each will be described.

  Examples of fatty acids constituting the glycerin fatty acid monoester include lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, erucic acid, and 12-hydroxyoleic acid. The main component is one or a mixture of two or more selected from 12 to 22 aliphatic fatty acids.

  These glycerin fatty acid monoesters are esterification reactions of the above fatty acids with glycerin or beef tallow, lard, chicken tallow, fish oil, soybean oil, corn oil, rapeseed oil, palm oil, sunflower oil, safflower oil, castor oil or those The reaction product obtained by transesterification of a mixture of one or more hydrogenated oils with glycerol and glycerin is fractionated by methods such as molecular distillation, solvent fractionation, recrystallization, column chromatography, and supercritical gas extraction. In general, so-called distilled monoglycerides obtained by molecular distillation are suitable from the viewpoints of production simplicity, quality and price.

  As the fatty acid constituting the glycerin fatty acid diester, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, erucic acid, 12-hydroxyolein, as in the above monotype The main component is one or a mixture of two or more selected from aliphatic fatty acids having 12 to 22 carbon atoms such as acids.

  As the raw material, fatty acids and fats similar to those described above can be used. Diglycerin fatty acid esters are obtained by esterification reaction of these fatty acids with diglycerin or transesterification reaction of fats and oils with diglycerin, and as necessary, such as vacuum distillation, molecular distillation, solvent fractionation, column chromatography, etc. Unreacted diglycerin or by-product glycerin or glycerin fatty acid ester is removed and purified by the method.

  The content of the antistatic agent in the outermost layer is preferably 0.4% by weight or more, and more preferably 0.5% by weight or more. If the content of the antistatic agent in the outermost layer is less than 0.4% by weight, high partial discharge characteristics may not be obtained. About an upper limit, it is 1.3 weight% normally, Preferably it is 1.1 weight%, More preferably, it is 0.9 weight%. When the antistatic agent in the outermost layer is more than 1.3% by weight, flame retardancy may be deteriorated.

  In the polyester layer in the present invention, it is preferable to blend particles for the main purpose of imparting slipperiness. 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 magnesium phosphate. , Particles of kaolin, aluminum oxide, titanium oxide and the like. 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. These series of particles may be used in combination of two or more as required.

  The average particle size of the particles used preferably satisfies 0.1 to 5 [mu] m, more preferably 0.5 to 3 [mu] m. When the average particle size is less than 0.1 μm, the particles are likely to aggregate and dispersibility may be insufficient. On the other hand, when it exceeds 5 μm, the surface roughness of the film becomes too rough, Problems may occur in subsequent processes.

  Furthermore, the particle content in the polyester preferably satisfies 0.01 to 5% by weight, more preferably 0.01 to 3% by weight. When the particle content is less than 0.01% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 5% by weight, the smoothness of the film surface is poor. It may be enough.

  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 for producing the polyester, but the polycondensation reaction may proceed preferably after the esterification stage or after the transesterification reaction. 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 method of blending dried particles and a polyester raw material using a kneading extruder Etc.

  The black pigment in the polyester film may be one of black pigments such as carbon black (channel, furnace, acetylene, thermal, etc.), carbon nanotube (single-layer, multi-layer), aniline black, black iron oxide, etc. Two or more types can be used. Among them, it is preferable to use carbon black or black iron oxide, and it is more preferable to use carbon black.

  The black pigment content in the polyester film is preferably 0.2% by weight or more, more preferably 0.3% by weight or more, and particularly preferably 0.4% by weight or more. If the black pigment content is less than 0.2% by weight, the colorability and concealing property of the film may not be sufficient, and the design properties may not be satisfied. The upper limit is not particularly provided, but if it exceeds 3.0% by weight, the colorability and concealing properties are saturated, the effect of the black pigment content in the polyester film becomes difficult to see, and the cost also increases.

  Regarding the concealability of the polyester film of the present invention, the transmission density evaluated by a transmission densitometer described below for a single polyester film is preferably 1.0 or more, more preferably 1.5 or more, and 3.0 or more. Particularly preferred. If the transmission density is less than 1.0, the colorability and concealment of the polyester film may not be sufficient, and the design properties may not be satisfied.

  The method for adding the black pigment to the polyester is not particularly limited, and a conventionally known method can be adopted. For example, if polyester film and black pigment blended raw materials can be directly put into a kneading extruder feeder to form a film when a polyester film is produced, the polyester chip and black pigment raw material can be pre-mixed in the kneading extruder. There is also a method of forming a film by applying the master batch to a feeder of a kneading extruder together with a polyester raw material when forming a polyester film.

  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 using an extruder to cool and solidify with a cooling roll using a molten sheet extruded from a die is preferable.

  In this case, in order to improve the flatness of the sheet, it is necessary 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 are 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. Subsequently, the extending | stretching temperature orthogonal to the extending | stretching direction of the 1st step is 130-170 degreeC normally, and a draw ratio is 3.0-7 times normally, Preferably it is 3.5-6 times. 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. It is also possible to perform simultaneous biaxial stretching. As the simultaneous biaxial stretching method, the unstretched sheet is stretched simultaneously in the machine direction (or machine direction) and transverse direction (or width direction) at a temperature of usually 70 to 120 ° C., preferably 80 to 110 ° C. The stretching ratio 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.

  As for the simultaneous biaxial stretching apparatus using the above-described stretching method, a conventionally known stretching method such as a screw method, a pantograph method, a linear drive method, or the like can be adopted. The “screw method” is a method in which a clip is placed in the groove of the screw to increase the clip interval. The “pantograph method” is a method of expanding the clip interval using a pantograph. The “linear motor system” has an advantage that the clip interval can be arbitrarily adjusted by applying the linear motor principle and controlling the clips individually.

  Further, simultaneous biaxial stretching may be performed in two or more stages. In that case, stretching may be performed in one tenter or a plurality of tenters may be used in combination. The simultaneous biaxial stretching method is a method in which the unstretched sheet is usually stretched and oriented in the machine direction and the width direction at 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is as follows. 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.

  The polyester film of the present invention preferably has no coating layer from the viewpoint of self-extinguishing properties. That is, it is preferable not to apply a so-called coating stretching method (in-line coating) in which the film surface is treated during the above-described polyester film stretching step.

  In the present invention, two or three or more polyester melt extruders can be used to form a laminated film of two layers or three or more layers by a so-called coextrusion method. As the layer structure, an A / B structure using a raw material A containing a glycerin fatty acid ester and a polyester raw material B, or an A / B / A structure, and an A / B / C structure using a C raw material or higher It can be set as the film of the structure which increased the number of layers. About the raw material A containing glycerol fatty acid ester, it is desirable to exist in the one side of a polyester film at least.

  When the A / B / A configuration or the A / B / C configuration is adopted, the polyester raw material B may also contain a glycerin fatty acid ester, but the high partial discharge performance is saturated.

  Although the thickness of the polyester film of this invention is not specifically limited, Usually, 20-350 micrometers, Preferably the range of 30-300 micrometers is good.

  In general, the thickness of the layer containing the polyester raw material A is preferably 1 to 50 μm on one side from the viewpoint of functionality such as high partial discharge voltage and transparency. Usually, the object can be achieved when the surface layer thickness is 2 to 20%, preferably 5 to 15% of the total thickness of the sheet.

In the film of the present invention, the quotient (ΔPD / T _A : hereinafter abbreviated as Q) of the partial discharge voltage change value ΔPD defined by the following formula (1) and the outermost layer film thickness T _A (μm) is 0.5. It is necessary to be above.
ΔPD = PDexp− (3.06 × T + 345)
(In the above formula, PDexp is the measured partial discharge voltage (V) of the polyester film, and T is the thickness (μm) of the polyester film)

  The upper limit of Q is not particularly limited, but is usually 60 and is preferably in the range of 50 to 0.8. If Q is less than 0.5, high partial discharge characteristics cannot be obtained, and antistatic properties are difficult to obtain. When Q exceeds 60, flame retardancy may deteriorate.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to the following examples, unless the meaning is exceeded. In addition, the measurement and evaluation method of various physical properties of a film are shown below.

(1) Flame retardance I Test piece preparation As a film test piece, it is cut into 200 mm x 50 mm, and a marked line is made across the width of the sample at 125 mm from one end (lower part) of the sample. The sample longitudinal axis is tightly wound around the mandrel with a diameter of 12.7 mm so that a 125 mm line is exposed to the outside and becomes a rolled cylinder with a length of 200 mm. The edge that protrudes outside the sample is fixed with an adhesive tape between 75 mm above the 125 mm mark (upper part of the cylinder). Then pull out the mandrel.

II Conditioning The specimens obtained above are pretreated at 23 ° C. and 50% relative humidity for 48 hours.

III Combustion test procedure (i) Fixation of test piece As shown in Fig. 1, with the vertical axis of the sample vertical, fix it with a clamp with a strong spring at a position of 6 mm in length at the upper end, and close the upper end of the cylinder. Avoid the chimney effect during the test. The lower end of the sample is 300 mm above a single horizontal 0.05 g defatted 100% cotton (50 mm × 50 mm) with a maximum thickness of 6 mm. See FIG.

(Ii) Adjusting the burner Adjust so that a blue flame with a height of 20 mm comes out from the burner. In order to put out the flame, the gas supply and the air inlet of the burner are adjusted so that the yellow flame with a yellow tip of 20 mm comes out. Then increase the air supply until the yellow tip just disappears. Measure the flame height again and readjust as necessary. In addition, the methane gas supply to a burner adjusts a flow volume by the method according to ASTMD5207.

(Iii) First flame contact The flame is centered on the center point of the lower end of the sample and the tip of the burner is 10 mm below that point at the lower end of the sample. Continue for 3 seconds. However, the burner is moved in response to any change in the length or position of the sample. If a molten or fuming substance drips during flame contact, tilt the burner angle up to 45 degrees, just below the sample to prevent the substance from falling into the burner tube. Move from. However, the interval between the center of the tip of the burner and the remaining portion of the sample must be kept 10 mm ± 1 mm during that time. When the sample has an indirect flame for 3 seconds, the burner is immediately moved away from the sample at a rate of about 300 mm at a rate of at least 150 mm per second, and at the same time, the after flame time t ₁ is started to be measured in seconds by the timing device. And it records the _{t 1.}

(Iv) Second flame contact When the after flame of the sample is extinguished (even if the burner is not completely removed to a distance of 150 mm from the sample), immediately bring the burner under the sample, A burner is held at a location 10 mm ± 1 mm away from the rest of the sample. However, if necessary, move the burner so that the natural behavior of the fallen object can be confirmed without any obstructions. After this sample 3 seconds flame application, immediately away at least 150mm at a speed of about 300 mm, starts weighing the remaining flame time t ₂ seconds by a timing device at the same time.

(V) Flame Retardancy Evaluation Criteria The test is performed on the five test pieces according to the procedures I to III. The evaluation with the lowest standard among the five samples was taken as the evaluation value of the sample.

(2) Antistatic property The antistatic property is the surface resistivity of the sample film, using a resistivity measuring device (HP4339B) manufactured by Hewlett Packard, at a measurement temperature of 23 ° C. and a measurement humidity of 50% at an applied voltage of 100V. Measure the surface resistivity (Ω / □) after 1 minute.
◎: Less than 1 × 10 ¹² Ω / □ ○: 1 × 10 ¹² Ω / □ or more and less than 1 × 10 ¹³ Ω / □ △: 1 × 10 ¹³ Ω / □ or more and less than 1 × 10 ¹⁴ Ω / □ ×: 1 × 10 ¹⁴ Ω / □ or more

(3) Transmission density; OD
A single film was measured using a Macbeth densitometer TD-904 type. Reading was performed after the displayed value stabilized. The standard of transmission density is as follows.
A: OD ≧ 2.0
○: 2.0> OD ≧ 1.5
Δ: 1.5> OD ≧ 1.0
×: 1.0> OD

(4) Partial discharge voltage and partial discharge voltage change value ΔPD
Partial discharge voltage was measured according to IEC 61730-2, Section 11.1, using a partial discharge tester: DAC-PD-7 (manufactured by Soken Denki Co., Ltd.). Next, a partial discharge voltage change value ΔPD was obtained from the following equation.
ΔPD = PDexp− (3.06 × T + 345)
(In the above formula, PDexp is the measured partial discharge voltage (V) of the polyester film, and T is the thickness (μm) of the polyester film)

(5) Film thickness T
Obtained with a micrometer.

(6) the outermost layer film thickness _{T A}
Using a microtome, the film cross section was cut perpendicularly to the film surface direction without crushing in the thickness direction. Next, the cut section was observed with an electron microscope, and an image magnified 500 times was obtained. In addition, although an observation place shall be defined at random, the up-down direction of an image shall be parallel to the thickness direction of a film, and the left-right direction of an image was respectively parallel to the surface direction of a film. In addition, when the entire thickness direction did not fit in one image, observation was performed by shifting the observation position in the thickness direction, and by combining a plurality of images, an image in which the entire thickness could be confirmed was prepared. The measurement was carried out at 10 locations at different locations, and the average value was taken as the outermost layer film thickness T _A (μm).

(7) Haze Evaluation Criteria Haze evaluation criteria were as follows.
When film thickness is less than 150 μm ○: Less than 1.4
Δ: 1.4 or more, less than 5.0 ×: 5.0 or more When the film thickness is 150 μm or more ○: Less than 6.0
Δ: 6.0 or more, less than 9.0 ×: 9.0 or more

The example of the polyester raw material which comprises a polyester film is as follows.
<Method for producing polyester raw material (1)>
86 parts of terephthalic acid and 70 parts of ethylene glycol were placed in a reactor and subjected to a transesterification reaction at about 250 ° C. for 4 hours. Add 0.03 part of antimony trioxide, 0.01 part of phosphoric acid, 0.1 part of silicon dioxide particles with an average particle size of 1.5 μm, gradually raise the temperature from 250 ° C. to 285 ° C. and gradually reduce the pressure. 0.5 mmHg. After 4 hours, the polymerization reaction was stopped to obtain polyethylene terephthalate having an intrinsic viscosity of 0.65.

<Method for producing polyester raw material (2)>
A polyester raw material (2) was obtained in the same manner as the polyester raw material (1) except that silicon dioxide particles having an average particle diameter of 1.5 μm were not added during the production of the polyester raw material (1). Polyethylene terephthalate having an intrinsic viscosity of 0.65 was obtained.

<Method for producing polyester raw material (3)>
20% by weight of a mixture of 80% by weight of the polyester raw material (2) and glycerin palmitic acid ester and glycerin stearic acid ester = 50/50 was melt-kneaded at 290 ° C. in a vented twin-screw extruder to obtain chips. The polyester (3) was created as a glycerin fatty acid ester master batch.

<Method for producing polyester raw material (4)>
The polyester (2) is subjected to a twin screw extruder with a vent, and carbon black (oil furnace black average primary particle size 70 nm) is supplied so as to be 20% by weight to form a chip. Polyester (4): carbon Black master batch pellets were obtained.

Example 1:
The polyester obtained by mixing the polyester (1), polyester (2), polyester (3), and polyester (4) in a ratio of 5.0: 90.5: 2.0: 2.5 is the polyester layer (A). A polyester obtained by mixing the polyester (2) and the polyester (4) at a ratio of 97.5: 2.5 was used as a raw material for the polyester layer (B).
Both raw materials are melt-kneaded at 290 ° C. in a twin-screw extruder, and the resulting melt has a composition ratio of A / B / A = 2.5 / 45.0 / 2.5 in the multilayer T-die. And extrude into a slit shape. Using an electrostatic application adhesion method, the sheet was rapidly cooled and solidified on a casting drum set at a surface temperature of 40 ° C. to obtain an unstretched two-kind three-layered sheet.
After the obtained sheet was stretched 3.3 times in the machine direction at 83 ° C., the temperature [° C.] in each zone of preheating / transverse stretching / heat setting 1 / heat setting 2 / heat setting 3 / cooling was set to 95/110 / By guiding to a tenter set to 200/221/180/125 ° C., the film was stretched 3.8 times in the transverse direction to form a film. The average thickness of the obtained film was 50 μm. The evaluation results are shown in Table 2 below.

Examples 2-7:
In Example 1, a polyester film similar to Example 1 was obtained except that the formulation shown in Table 2 was used. The evaluation results are shown in Table 2 below.

Example 8:
The polyester obtained by mixing the polyester (1), polyester (2), polyester (3), and polyester (4) in a ratio of 5.0: 88.0: 2.0: 2.5 A polyester obtained by mixing the polyester (2) and the polyester (4) at a ratio of 97.5: 2.5 was used as a raw material for the polyester layer (B).
Both raw materials were melt-kneaded in a twin-screw extruder at 290 ° C., and the resulting melt was merged in a multilayer T die so as to have a composition ratio of A / B = 5.0 / 45.0 to form a slit. Extrude into Using an electrostatic application adhesion method, the sheet was rapidly cooled and solidified on a casting drum set to a surface temperature of 40 ° C. to obtain a laminated sheet composed of two types of unstretched two layers. After the obtained sheet was stretched 3.3 times in the machine direction at 83 ° C., the temperature [° C.] in each zone of preheating / transverse stretching / heat setting 1 / heat setting 2 / heat setting 3 / cooling was set to 95/110 / By guiding to a tenter set to 200/221/180/125 ° C., the film was stretched 3.8 times in the transverse direction to form a film. The average thickness of the obtained film was 50 μm. The evaluation results are shown in Table 3 below. The surface resistivity is a value evaluated for the A layer.

Example 9:
The polyester obtained by mixing the polyester (1), polyester (2), polyester (3), and polyester (4) in a ratio of 5.0: 90.5: 2.0: 2.5 is the polyester layer (A). As a raw material, the polyester (2) is used as a raw material for the polyester layer (B), and the polyester (1), the polyester (2), and the polyester (4) are mixed in a ratio of 5.0: 92.5: 2.5. The obtained polyester was used as a raw material for the polyester layer (C). Each raw material is melt-kneaded at 290 ° C. in a twin-screw extruder, and the resulting melt has a composition ratio of A / B / C = 2.5 / 45.0 / 2.5 in a multilayer T die. And extrude into a slit shape. Using an electrostatic application adhesion method, the sheet was rapidly cooled and solidified on a casting drum whose surface temperature was set to 40 ° C. to obtain a laminated sheet composed of unstretched three types and three layers. After the obtained sheet was stretched 3.3 times in the machine direction at 83 ° C., the temperature [° C.] in each zone of preheating / transverse stretching / heat setting 1 / heat setting 2 / heat setting 3 / cooling was set to 95/110 / By guiding to a tenter set to 200/221/180/125 ° C., the film was stretched 3.8 times in the transverse direction to form a film. The average thickness of the obtained film was 50 μm. The evaluation results are shown in Table 3 below. The surface resistivity is a value evaluated for the A layer.

Example 10:
The polyester obtained by mixing the polyester (1), polyester (2), polyester (3), and polyester (4) in a ratio of 5.0: 90.5: 2.0: 2.5 is the polyester layer (A). A polyester obtained by mixing the polyester (2) and the polyester (4) at a ratio of 97.5: 2.5 was used as a raw material for the polyester layer (B).
Both raw materials are melt-kneaded at 290 ° C. in a twin-screw extruder, and the resulting melt has a composition ratio of A / B / A = 2.5 / 245.0 / 2.5 in the multilayer T-die. And extrude into a slit shape. Using an electrostatic application adhesion method, the sheet was rapidly cooled and solidified on a casting drum set at a surface temperature of 40 ° C. to obtain an unstretched two-kind three-layered sheet. After the obtained sheet was stretched 3.3 times in the machine direction at 83 ° C., the temperature [° C.] in each zone of preheating / transverse stretching / heat setting 1 / heat setting 2 / heat setting 3 / cooling was set to 95/110 / By guiding to a tenter set to 200/221/180/125 ° C., the film was stretched 3.8 times in the transverse direction to form a film. The average thickness of the obtained film was 250 μm. The evaluation results are shown in Table 3 below.

Example 11:
In Example 10, a polyester film similar to Example 10 was obtained except that the composition shown in Table 3 was used. The evaluation results are shown in Table 3 below.

Example 12:
In Example 10, the formulation shown in Table 3 was used, and each raw material was melt-kneaded at 290 ° C. in a twin-screw extruder, and the resulting melt was A / B / A = 50. A polyester film similar to Example 10 was obtained except that the composition ratio was 0 / 150.0 / 50.0. The evaluation results are shown in Table 3 below.

Example 13:
In Example 1, a polyester film similar to Example 1 was obtained except that the composition shown in Table 3 was used. The evaluation results are shown in Table 3 below.

Example 14:
In Example 10, a polyester film similar to Example 10 was obtained except that the composition shown in Table 3 was used. The evaluation results are shown in Table 3 below.

Comparative Examples 1-2:
In Example 1, a polyester film similar to Example 1 was obtained except that the composition shown in Table 4 was used. The evaluation results are shown in Table 4 below.

Comparative Example 3:
In Example 10, a polyester film similar to Example 10 was obtained except that the formulation shown in Table 4 was used. The evaluation results are shown in Table 4 below.

Comparative Example 4:
In Example 1, a polyester film similar to Example 1 was obtained except that the composition shown in Table 4 was used. The evaluation results are shown in Table 4 below.

Comparative Example 5:
Polytrimethylaminoethyl methacrylate quaternized product / polyvinyl alcohol / methoxymethylol melamine having a saponification degree = 88 mol% and a polymerization degree = 500, becamine manufactured by Dainippon Ink and Chemical Co., Ltd./silica sol having an average particle size of 0.05 μm, An aqueous solution containing a converted weight composition ratio of 40/20/35/5 was prepared in advance. Using the polyester (1), polyester (2), and polyester (4) mixed in a ratio of 5.0: 92.5: 2.5 as a raw material for the polyester layer (A), the polyester (2), Polyester mixed with polyester (4) at a ratio of 97.5: 2.5 was used as a raw material for the polyester layer (B). Both raw materials are melt-kneaded at 290 ° C. in a twin-screw extruder, and the resulting melt has a composition ratio of A / B / A = 2.5 / 45.0 / 2.5 in the multilayer T-die. And extrude into a slit shape. Using an electrostatic application adhesion method, the sheet was rapidly cooled and solidified on a casting drum set at a surface temperature of 40 ° C. to obtain an unstretched two-kind three-layered sheet.
The obtained sheet was stretched 3.3 times in the longitudinal direction at 83 ° C., and then the above aqueous solution was applied to the upper surface of the longitudinally stretched film, led to a tenter, and preheated / laterally stretched / heat fixed 1 / heat fixed 2 / heated. The film was formed by stretching 3.8 times in the transverse direction by guiding it to a tenter in which the temperature [° C.] in each zone of fixed 3 / cooling was set to 95/110/200/221/180/125 ° C. . The average thickness of the obtained film was 50 μm. The evaluation results are shown in Table 4 below.

  According to the present invention, the film of the present invention can provide a biaxially oriented laminated polyester film in which the polyester film serving as a base material does not generate sparks derived from charging and has self-extinguishing properties. For example, it can be applied to a polyester film for a solar cell back surface protective material, and its industrial value is high.

1 Clamp 2 Adhesive Tape 3 125mm Mark 4 Burner 5 Cotton

Claims (2)

A laminated polyester film having a layer made of a polyester resin composition containing an antistatic agent in at least one outermost layer, and having a partial discharge voltage change value ΔPD defined by the following formula and an outermost layer film thickness T _A (μm) _A biaxially oriented laminated black polyester film having a quotient (ΔPD / TA) of 0.5 or more and containing a black pigment in the film.
ΔPD = PDexp− (3.06 × T + 345)
(In the above formula, PDexp is the measured partial discharge voltage (V) of the polyester film, and T is the thickness (μm) of the polyester film) The biaxially oriented laminated polyester film according to claim 1, comprising a nonionic antistatic agent.

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