TWI635958B - Biaxial alignment polyester film and preparation method thereof - Google Patents

Abstract

The present invention provides a biaxially oriented polyester film which is excellent in light-shielding property, concealing property, flame retardancy, and continuous productivity, and a method for producing the same.

A biaxially oriented polyester film conforming to the following (1) to (4).

(1) Carbon black particles are contained in the polyester resin composition constituting the film.

(2) The polyester resin composition constituting the film does not substantially contain a flame retardant or a dispersant.

(3) The optical density of the film is 3.5 or more.

(4) The flame retardancy is any of VTM-0, VTM-1, or VTM-2.

Description

Biaxial alignment polyester film and preparation method thereof

The present invention relates to a biaxially oriented polyester film which is excellent in light-shielding property, concealing property, flame retardancy, and excellent in continuous productivity, and a process for producing the same.

Polyester (especially polyethylene terephthalate, or polyethylene-2,6-naphthalate) resin has excellent mechanical properties, thermal properties, chemical resistance, electrical properties, formability, and can be used. Various uses. The biaxially oriented polyester film in the polyester film obtained by thinning the polyester resin can be used as an optical device, a solar battery back sheet, or a monitor, from the viewpoints of mechanical properties and electrical characteristics. It is used in various industrial materials such as electrical insulating materials, building materials, thermal transfer applications, and engineering paper.

Among these applications, flame retardancy is required for electrical insulating materials. Further, in the use of optical devices, particularly mobile phones, cameras, and video cameras, in addition to the miniaturization and weight reduction of devices, the components constituting them are gradually required to be flame retardant.

At present, a light-shielding member of an optical device such as a shutter or a diaphragm is made of metal, but as the size and weight are reduced, a synthetic resin film is gradually used. As a method of imparting light-shielding property to a synthetic resin film, carbon black is generally added to a polyester film. For example, it has been studied to add carbon black particles to a polyester resin having an ultimate viscosity [η] of 0.5 to 0.85 dl/g. A polyester film composed of a polyester resin composition (Patent Document 1).

Further, among the electrical insulating materials, in recent years, in the use of the solar battery back sheet, not only flame retardancy is desired, but also from the viewpoint of design, it is desirable that wiring to the power generating element or the like cannot be seen from the outside. For this reason, the solar cell backsheet not only needs to be flame retardant but also requires high concealment. In general, it is effective to blacken a polyester film in order to improve the concealability of a film, and a polyester film which has been added as a black pigment as a black pigment has been studied for solar cell back sheets (Patent Documents 2, 3). ).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2008-56871

[Patent Document 2] International Publication No. 2012/121076

[Patent Document 3] Japanese Laid-Open Patent Publication No. 2011-119651

However, the polyester film described in Patent Documents 1 to 3 is excellent in light-shielding property and concealing property, but the flame retardancy of the polyester film is not sufficient.

In order to improve the flame retardancy of the polyester film described in Patent Documents 1 to 3, the present inventors have studied the problem of adding a conventionally known flame retardant to the polyester resin composition constituting the film. . As a result, it is understood that the polyester film described in Patent Documents 1 to 3 is added/containing a flame retardant to obtain a certain effect of improving the flame retardancy. However, in order to obtain sufficient flame retardancy, it is necessary to add a large amount of difficulty. Burning agent In addition, when a large amount of a flame retardant is added, there is a problem that the formability of the film is deteriorated and the continuous productivity is deteriorated.

Further, in the case where a large amount of a flame retardant or carbon black particles are added to the polyester resin composition constituting the film, it is necessary to add a conventionally known dispersant in order to prevent aggregation of the flame retardant or the carbon black particles. When a dispersing agent is added, there is a problem that the flame retardancy is deteriorated.

Therefore, an object of the present invention is to provide a biaxially oriented polyester film which is excellent in light-shielding property, concealability, flame retardancy, and continuous productivity, and a process for producing the same.

In order to solve the above problems, the present invention adopts the following configuration. which is,

[I] A biaxially oriented polyester film which conforms to the following (1) to (4).

(1) Carbon black particles are contained in the polyester resin composition constituting the film.

(2) The polyester resin composition constituting the film does not substantially contain a flame retardant or a dispersant.

(3) The optical density of the film is 3.5 or more.

(4) The flame retardancy determined according to the following method is any one of VTM-0, VTM-1, and VTM-2.

<Evaluation method of flame retardancy>

(i) Sample preparation

The measurement sample (biaxially oriented polyester film) was cut into 20 cm × 5 cm.

A sample placed at 23 ° C and 50% RH for 48 hours was designated as sample A, and after being left at a temperature of 70 ° C for 168 hours, a sample cooled at a temperature of 23 ° C and 20% RH for 4 hours was designated as sample B. Prepare 5 samples each For 1 group.

(ii) Method of measurement

A line was drawn in a direction parallel to the short side at a position of 125 mm from the short side of each sample, and wound around a rod having a diameter of 12.7 mm so that the short side became the vertical direction. The 75 mm portion of the upper portion was fixed with a pressure-sensitive adhesive tape from the 125 mm mark, and the rod was taken out. The upper end of the sample was closed in a manner that did not have a chimney effect during the test. Next, each sample was erected vertically, and a skim cotton was placed under 300 mm. The Bunsen burner with a diameter of 9.5 mm and a flame length of 20 mm was used as a heating source so that the tube of the burner was located 10 mm from the lower end of the sample, and the center of the lower end of the sample was exposed to the blue flame for 3 seconds. Burning time after the flame (t1). Next, immediately after the flame was extinguished, the flame was immediately exchanged for 3 seconds, and the burning time (t2) and the ignition time (t3) after the second flame separation were measured. In addition, in the case of the first and second flames, it is observed whether there is burning of the 125 mm mark, and whether there is a burning falling object such as a defoaming fire. For the sample A and the sample B, one set (5 pieces) of each was subjected to the above measurement.

(iii) Evaluation of flame retardancy

The flame retardancy was evaluated as follows according to the following criteria.

VTM-0: Compliance with any of the criteria (a), (b), (c), (d), and (e).

VTM-1: Compliance with any of the criterions (a'), (b'), (c'), (d), and (e).

VTM-2: Compliance with any of the criterions (a'), (b'), (c'), and (d).

No VTM: Does not comply with any of VTM-0, VTM-1, VTM-2.

Judgment criterion (a): Burning time after the first flame separation in all samples The longer of (t1) or the second combustion time after the flame separation (t2) is 10 seconds or less.

Judgment criterion (a'): The longer of the combustion time (t1) after the first flame separation or the combustion time (t2) after the second flame separation in all the samples was 30 seconds or less.

Judgment criterion (b): The total of the combustion time after the flame separation for each group (the total of the combustion time (t1 + t2) after the flame separation of the five samples), and both the sample A and the sample B were 50 seconds or shorter.

Judgment criterion (b'): the total of the combustion time after the flame separation per group (the total of the combustion time (t1 + t2) after the flame separation of the five samples), and both the sample A and the sample B were 250 seconds or shorter.

Judgment criterion (c): The total of the burning time (t2) and the seeding time (t3) after the second off-flame in all the samples was 30 seconds or less.

Judgment criterion (c'): The total of the burning time (t2) and the seeding time (t3) after the second off-flame in all the samples was 60 seconds or less.

Judgment criterion (d): In all samples, the burning or fire did not reach the 125 mm mark.

Judgment criterion (e): In all of the samples, there was no case where the burned sample fell and the cotton was deflated.

[II] The biaxially oriented polyester film according to [I], wherein the film has a thickness of 50 μm or more and 300 μm or less.

[III] The biaxially oriented polyester film according to [I] or [II], wherein the content of the carbon black particles in the polyester resin composition constituting the film is in the range of 1 to 5% by weight.

[IV] The biaxially oriented polyester film according to any one of [I] to [III] which is used for a light shielding member of an optical device or a solar battery back sheet.

[V] The method for producing a biaxially oriented polyester film according to any one of [I] to [IV], which comprises the steps of (5) to (6) below.

(5) A carbon black-containing polyester resin composition obtained by mixing a polyester resin composition (a) having a kneading ultimate viscosity [η] of 0.7 dl/g or more and a carbon black particle in a polyester raw material for producing a film. Mother (b).

(6) In the case of producing the carbon black-containing polyester resin composition precursor (b), the ultimate viscosity of the polyester resin of the polyester resin composition (a) before the kneading, and the obtained carbon black-containing The ultimate viscosity of the polyester resin of the polyester resin composition precursor (b) conforms to the following formula (6-1).

(6-1) 0.75 ≦ [η] b / [η] a ≦ 0.90

[η]a: ultimate viscosity (dl/g) of polyester resin of polyester resin composition (a) of 0.7 dl/g or more

[η]b: ultimate viscosity (dl/g) of polyester resin of carbon black-containing polyester resin composition precursor (b)

[VI] The method for producing a biaxially oriented polyester film according to [V], wherein the content of the carbon black particles in the precursor (b) of the carbon black-containing polyester resin composition is 5 wt% or more and 30 wt% or less.

[VII] The method for producing a biaxially oriented polyester film according to [V] or [VI], which conforms to the following (7) to (9).

(7) The polyester raw material for producing a film comprises the carbon black-containing polyester resin composition precursor (b) and the carbon black-free polyester resin composition (c).

(8) The ultimate viscosity of the polyester resin of the carbon black-containing polyester resin composition precursor (b) and the carbon black-free polyester resin composition (c) conforms to the following formula (8-1).

(8-1)0.75≦[η]b/[η]c≦1.10

[η]b: ultimate viscosity (dl/g) of polyester resin of carbon black-containing polyester resin composition precursor (b)

[η]c: ultimate viscosity (dl/g) of polyester resin of carbon black-free polyester resin composition (c)

(9) The content Wb (% by weight) of the carbon black-containing polyester resin composition precursor and the content of the carbon black-free polyester resin composition (c) Wc (weight) with respect to the entire polyester raw material for producing the film %) conforms to the following formula (9-1).

(9-1)0.03≦Wb/Wc≦0.5

Wb: content (% by weight) of the carbon black-containing polyester resin composition precursor (b) with respect to the entire polyester raw material for producing a film

Wc: content (% by weight) of the polyester resin composition (c) containing no carbon black relative to the entire polyester raw material for producing a film

According to the present invention, it is possible to provide a biaxially oriented polyester film which satisfies high light-shielding property, concealability, flame retardancy, and continuous productivity. Further, by using such a film, it is possible to provide a light-shielding member of an optical device having high light-shielding property, concealability, and flame retardancy, or a solar battery back sheet.

[Formation of the Invention]

The polyester resin composition constituting the biaxially oriented polyester film of the present invention is composed of carbon black particles in a polyester resin composition.

The content of the polyester resin in the polyester resin composition is 85% by weight or more, more preferably 90% by weight or more, and particularly preferably 95% by weight or more based on the total resin composition constituting the film. By setting the content of the polyester resin to the above range, the mechanical properties of the film can be improved.

The polyester constituting the polyester film of the present invention is a polymer having a main bond chain having an ester bond as a main chain obtained by reacting a dicarboxylic acid constituent component and a diol constituent component.

Examples of the dicarboxylic acid constituent component constituting the polyester include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, and dimer acid. , an aliphatic dicarboxylic acid such as eicosanedioic acid, pimelic acid, sebacic acid, methylmalonic acid or ethylmalonic acid; adamantane dicarboxylic acid, norbornene dicarboxylic acid, isosorbide, cyclohexyl An alicyclic dicarboxylic acid such as an alkanedicarboxylic acid or decahydronaphthalene dicarboxylic acid; terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2, 6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, sodium 5-sulfoisophthalate, phenylethane a dicarboxylic acid such as an aromatic dicarboxylic acid such as dicarboxylic acid, phthalic acid dicarboxylic acid, phenanthrene dicarboxylic acid or 9,9'-bis(4-carboxyphenyl)nonanoic acid, or an ester derivative thereof, but is not limited thereto Wait.

Further, examples of the diol constituent component constituting the polyester include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,2-butanediol. , an aliphatic diol such as 3-butanediol; an alicyclic diol such as cyclohexanedimethanol, spiro glycerol or isosorbide; bisphenol A, 1,3-benzenedimethanol, 1, a diol such as 4-benzenedimethanol, 9,9'-bis(4-hydroxyphenyl)fluorene or an aromatic diol; and a plurality of diols As an example, it is not limited to this.

Moreover, as the polyester used in the present invention, polyethylene terephthalate or polyethylene naphthalate is preferred from the viewpoint of mechanical properties, electrical properties, durability, and productivity.

The biaxially oriented polyester film of the present invention preferably contains 1% by weight or more and 5% by weight or less of carbon black particles based on the entire polyester resin composition constituting the film. When the content of the carbon black particles is less than 1% by weight, the light-shielding property may be insufficient. On the other hand, when the content of the carbon black particles is more than 5% by weight, the dispersibility of the carbon black particles is deteriorated, and aggregates are formed, the flame retardancy is deteriorated, and productivity is deteriorated. A more preferable lower limit is 1.5% by weight or more. Further, as a more preferable upper limit, it is 4% by weight or less, and more preferably 3% by weight or less.

Further, the biaxially oriented polyester film of the present invention must have any of the flame retardancy VTM-0, VTM-1, and VTM-2 obtained by the method described later. The biaxially oriented polyester film of the present invention has excellent flame retardancy and is characterized in that such flame retardancy is achieved without substantially containing a flame retardant. Further, in the present invention, "substantially free of" means that the content is less than 0.05% by weight. Further, in the present invention, the content of the carbon black particles, the flame retardant, and the dispersant in the polyester resin composition constituting the polyester film means the amount of addition to the polyester resin composition constituting the polyester film. In the present invention, the flame retardant is a compound or a resin having a function of improving the flame retardancy of the resin (increasing the limit oxygen index value (LOI value) of the resin) by adding it to the resin.

It is widely known to add a flame retardant to improve the flame retardancy of a resin typified by a polyester resin. As a currently known flame retardant There are various types of, for example, chlorine-based flame retardants, bromine-based flame retardants, inorganic flame retardants, nitrogen-based flame retardants, phosphorus-based flame retardants, polyfluorene-based compounds, and poly Ammonium phosphate flame retardant, metal oxide.

For example, examples of the chlorine-based flame retardant include chlorinated paraffin, chlorinated polyethylene, tetrachlorophthalic anhydride, and chlorobridge acid. Examples of the bromine-based flame retardant include bromine-containing polyol, decabromodiphenyl ether, ethylene glycol bis(pentabromophenyl), bispentabromophenolethane, tribromophenol, hexabromobenzene, and fourteen. Bromodiphenoxybenzene, tetrabromobisphenol A (TBBA), TBBA-epoxy oligomer, TBBA-carbonate oligomer, tribromophenyl allyl ether, hexabromocyclododecane, double four Bromobisthylidene ethane, brominated polystyrene, decabromophenyl ether. Examples of the inorganic flame retardant include magnesium hydroxide, aluminum hydroxide, and cerium oxide. Examples of the cerium oxide include antimony trioxide, antimony pentoxide, and the like. Examples of the nitrogen-based flame retardant include a melamine compound, a ruthenium compound, and three Compound. Examples of the phosphorus-based flame retardant include a phosphate compound and ammonium polyphosphate, and examples thereof include triphenyl phosphate, tricresyl phosphate, resorcinol bis (diphenyl phosphate), and bisphenol A bis (phosphoric acid). Phenyl ester), resorcinol N bis(di-2,6-xylitol) phosphate, decylamine phosphate, red phosphorus, polyphosphate, phosphazene compound, ethylenediamine phosphate compound, three Compound. Examples of the polyoxygenated compound include a high molecular weight polysulfonated oil and a polyoxyxene elastomer.

As the flame retardant described above, in order to improve the flame retardancy of the present invention, it is necessary to add about several weight% to the film. When the flame retardant is added/contained, the formability of the resin, the mechanical strength may be lowered, and the surface defects due to the bleed out of the additive may increase. In particular, biaxial alignment polymerization comprising a step of biaxially aligning a film composed of a polyester resin composition containing carbon black particles in a high concentration In the ester film, when a large amount of the flame retardant as described above is added, film breakage at the time of film formation tends to occur, and the mechanical strength is likely to be lowered. The biaxially oriented polyester film of the present invention does not substantially contain the above-mentioned flame retardant in the polyester resin composition constituting the film. Therefore, it is excellent in productivity and formability, and is excellent in continuous productivity. In addition, the compound which is exemplified as the above-mentioned flame retardant is added or contained in the polyester resin composition constituting the film for the purpose of improving the flame retardancy, and the continuous productivity of the film is lowered. The cause. Therefore, it is quite important that the polyester resin composition constituting the film does not substantially contain the flame retardant exemplified above, except for the purpose of improving the flame retardancy.

Further, the biaxially oriented polyester film of the present invention is particularly important in that the polyester resin composition constituting the film does not substantially contain a dispersant from the viewpoint of improving flame retardancy.

The dispersing agent added for the purpose of improving the dispersibility of the carbon black particles or the flame retardant may, for example, be stearic acid, a metal such as zinc stearate, magnesium stearate, aluminum stearate or calcium stearate. Soap; ethylene bisamide, hydrocarbon waxes such as polyethylene wax, polypropylene wax, and derivatives thereof, and waxes composed of acid modified or hydroxyl modified materials. For example, a metallocene-based polyolefin wax polymerized using a catalyst of a metallocene compound can be generally used.

The metallocene compound is a generic term for a compound having a tetravalent transition metal such as titanium, zirconium, nickel, palladium, rhodium, iridium or platinum, and a ligand having at least one or more cyclopentadienyl skeleton. . The ligand having a cyclopentadienyl skeleton may, for example, be a cyclopentadienyl group; a methylcyclopentadienyl group, an ethylcyclopentadienyl group, a positive or an isopropylcyclopentadienyl group; a mono-substituted cyclopentadienyl group such as n-, cyclohexadienyl, hexylcyclopentadienyl or octylcyclopentadienyl; Dienyl, methylethylcyclopentadienyl, methylpropylcyclopentadienyl, methylbutylcyclopentadienyl, methylhexylcyclopentadienyl, ethylbutylcyclopentane An alkyl disubstituted cyclopentadienyl group such as an alkenyl group or an ethylhexylcyclopentadienyl group; a trimethylcyclopentadienyl group, a tetramethylcyclopentadienyl group, and a pentamethylcyclopentadienyl group; a cyclopentadienyl group substituted by an alkyl group; a cyclopentadienyl group substituted by a cycloalkyl group such as a methylcyclohexylcyclopentadienyl group; an anthracenyl group, a 4,5,6,7-tetrahydroindenyl group; , 茀基.

Examples of the ligand other than the ligand having a cyclopentadienyl skeleton include a monovalent anionic ligand such as chlorine or bromine, a divalent anionic chelating ligand, a hydrocarbon group, and an alcoholate. Indoleamine, aryl decylamine, aryl oxide, phosphide, aryl phosphide, decylalkyl, substituted decylalkyl and the like. Examples of the hydrocarbon group include those having a carbon number of from 1 to 12, and examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, a pentyl group, an isopentyl group, a hexyl group, a heptyl group, and an octyl group. An alkyl group such as a mercapto group, a fluorenyl group, a cetyl group or a 2-ethylhexyl group; a cycloalkyl group such as a cyclohexyl group or a cyclopentyl group; an aryl group such as a phenyl group or a tolyl group; a benzyl group, a t-butylphenyl group or the like; Aralkyl; nonylphenyl.

As the metallocene compound having a ligand having a cyclopentadienyl skeleton, specifically, a cyclopentadienyl titanium ginate (dimethyl decylamine) or a methylcyclopentadienyl group is exemplified. Titanium ginseng (dimethyl decylamine), bis(cyclopentadienyl) titanium dichloride, dimethyl decyl tetramethylcyclopentadienyl tert-butyl decylamine zirconium dichloride, dimethyl矽alkyltetramethylcyclopentadienyl p-n-butylphenyl decylamine zirconium dichloride, methyl phenyl decyl alkyl tetramethyl Cyclopentadienyl tert-butyl decylamine ruthenium dichloride, dimethyl decyl alkyl tetramethylcyclopentadienyl tert-butyl decyl ruthenium dichloride, ruthenium titanium ginseng (dimethyl decylamine) ), bismuth-based titanium ginseng (diethyl decylamine), fluorenyl titanium bis(di-n-butyl decylamine), fluorenyl titanium bis(di-n-propyl decylamine), and the like.

The dispersant as described above can improve the dispersibility of the carbon black particles or the flame retardant contained in the resin composition, but on the other hand, the flame retardancy of the resin is greatly lowered. The biaxially oriented polyester film of the present invention does not substantially contain the above dispersing agent in the polyester resin composition constituting the film. Therefore, the flame retardancy is particularly excellent. In addition, the compound exemplified as the dispersant is added or contained in the polyester resin composition constituting the film for the purpose of improving the dispersibility, and the flame retardancy of the film is lowered. Therefore, it is quite important that the polyester resin composition constituting the film does not substantially contain the above-exemplified dispersant, except for the purpose of improving the dispersibility.

The biaxially oriented polyester film of the present invention has an optical density of 3.5 or more from the viewpoint of obtaining excellent light blocking properties and concealing properties. It is preferably 4 or more, more preferably 5 or more. The optical density can be adjusted by the thickness of the film and the content of the carbon black particles in the polyester resin composition constituting the film. When the optical density is less than 3, the light-shielding property and the concealing property are insufficient, and the optical function cannot be exhibited. The upper limit of the optical density is not particularly limited. However, in order to obtain a film having an optical density of more than 6, it is necessary to increase the thickness of the film, increase the content of the carbon black particles, and deteriorate the film forming property. Therefore, the optical density is preferably 6 or less.

The thickness of the biaxially oriented polyester film of the present invention is preferably in the range of 50 μm or more and 300 μm or less. As a better lower limit, 50 μm or more . Further, the upper limit is preferably 150 μm or less. When the thickness of the polyester film is in the above range, it is preferable from the viewpoint of any of light shielding property, concealing property, flame retardancy, and continuous productivity.

The biaxially oriented polyester film of the present invention is determined according to the following method (according to the flame retardancy test (UL94VTM combustion test) of Underwriters Laboratories Inc. (known as UL)) The flame retardancy must be any of VTM-0, VTM-1, and VTM-2. By having the above-described flame retardancy, it can be suitably used for a light shielding member for an optical device or a concealing member for a solar battery back sheet.

<Evaluation method of flame retardancy>

(i) Sample preparation

The measurement sample (biaxially oriented polyester film) was cut into 20 cm × 5 cm.

A sample placed at 23 ° C and 50% RH for 48 hours was designated as sample A, and after being left at a temperature of 70 ° C for 168 hours, a sample cooled at a temperature of 23 ° C and 20% RH for 4 hours was designated as sample B. Five samples were prepared as one set each.

(ii) Method of measurement

A line was drawn in a direction parallel to the short side at a position of 125 mm from the short side of each sample, and wound around a rod having a diameter of 12.7 mm so that the short side became the vertical direction. The 75 mm portion of the upper portion was fixed with a pressure-sensitive adhesive tape from the 125 mm mark, and the rod was taken out. The upper end of the sample was closed in a manner that did not have a chimney effect during the test. Next, each sample was erected vertically, and a skim cotton was placed under 300 mm. The Bunsen burner with a diameter of 9.5 mm and a flame length of 20 mm was used as a heating source with the tube of the burning lamp located 10 mm from the lower end of the sample, so that the center of the lower end of the sample was in contact with the blue fire. The flame was measured for 3 seconds, and the burning time (t1) after the first flame separation was measured. Next, immediately after the flame was extinguished, the flame was immediately exchanged for 3 seconds, and the burning time (t2) and the ignition time (t3) after the second flame separation were measured. In addition, in the case of the first and second flames, it is observed whether there is burning of the 125 mm mark, and whether there is a burning falling object such as a defoaming fire. For the sample A and the sample B, one set (5 pieces) of each was subjected to the above measurement.

(iii) Evaluation of flame retardancy

The flame retardancy was evaluated as follows according to the following criteria.

VTM-0: Compliance with any of the criteria (a), (b), (c), (d), and (e).

VTM-1: Compliance with any of the criterions (a'), (b'), (c'), (d), and (e).

VTM-2: Compliance with any of the criterions (a'), (b'), (c'), and (d).

No VTM: Does not comply with any of VTM-0, VTM-1, VTM-2.

Judgment criterion (a): The longer of the combustion time (t1) after the first flame separation or the combustion time (t2) after the second flame separation is 10 seconds or less in all the samples.

Judgment criterion (a'): The longer of the combustion time (t1) after the first flame separation or the combustion time (t2) after the second flame separation in all the samples was 30 seconds or less.

Judgment criterion (b): The total of the combustion time after the flame separation for each group (the total of the combustion time (t1 + t2) after the flame separation of the five samples), and both the sample A and the sample B were 50 seconds or shorter.

Judgment criterion (b'): the total of the combustion time after the flame separation per group (the total of the combustion time (t1 + t2) after the flame separation of the five samples), and both the sample A and the sample B were 250 seconds or shorter.

Judgment criterion (c): Burning time after the second off-flame in all samples The total of (t2) and the ignition time (t3) is 30 seconds or less.

Judgment criterion (c'): The total of the burning time (t2) and the seeding time (t3) after the second off-flame in all the samples was 60 seconds or less.

Judgment criterion (d): In all samples, the burning or fire did not reach the 125 mm mark.

Judgment criterion (e): In all of the samples, there was no case where the burned sample fell and the cotton was deflated.

The biaxially oriented polyester film of the present invention is characterized in that the above-mentioned flame retardancy is achieved without substantially containing a flame retardant in the polyester resin composition constituting the film. The polyester resin composition constituting the film substantially does not contain a flame retardant to achieve the above-described flame retardancy, and the polyester resin composition constituting the film does not substantially contain a dispersant, and includes The film was produced in accordance with the following steps (5) and (6).

The biaxially oriented polyester film of the present invention is obtained by a process comprising the steps (5) and (6), whereby the composition is formed even if the polyester resin composition constituting the film contains substantially no dispersant. In the polyester resin composition of the film, the dispersibility of carbon black is good, and it is excellent in flame retardancy and continuous productivity, which is preferable.

(5) A carbon black-containing polyester resin composition obtained by mixing a polyester resin composition (a) having a kneading ultimate viscosity [η] of 0.7 dl/g or more and a carbon black particle in a polyester raw material for producing a film. Mother (b).

(6) In the case of producing the carbon black-containing polyester resin composition precursor (b), the ultimate viscosity of the polyester resin of the polyester resin composition (a) before the kneading, and the obtained carbon black-containing The ultimate viscosity of the polyester resin of the polyester resin composition precursor (b) conforms to the following formula (6-1).

(6-1) 0.75 ≦ [η] b / [η] a ≦ 0.90

[η]a: ultimate viscosity (dl/g) of polyester resin of polyester resin composition (a) of 0.7 dl/g or more

[η]b: ultimate viscosity (dl/g) of polyester resin of carbon black-containing polyester resin composition precursor (b)

The carbon black-containing polyester resin composition precursor (b) of the present invention is a polyester resin composition having a final viscosity [η] of a kneaded polyester resin of 0.7 g/dl or more, more preferably 0.72 g/dl or more ( A), and carbon black particles are preferred. Here, the ultimate viscosity [η]a of the polyester resin of the polyester resin composition (a) and the ultimate viscosity [η]b of the polyester resin of the carbon black-containing polyester resin composition precursor (b) are preferred. In order to comply with the following formula (5-1).

(6-1) 0.75 ≦ [η] b / [η] a ≦ 0.90

A more preferable lower limit of [η]b/[η]a is 0.76 or more, and still more preferably 0.78 or more. Further, the upper limit is preferably 0.88 or less, and more preferably 0.85 or less. When [η]b/[η]a is less than 0.75, there is a case where the decrease in the ultimate viscosity of the matrix material is large, the mechanical properties of the film are deteriorated, and the film formation is often broken. When it exceeds 0.90, the shearing in the melt kneading becomes insufficient, and the dispersibility of the carbon black particles is deteriorated, and the light-shielding property and the concealability are deteriorated, or the filtration pressure at the time of film formation is increased, and the continuous productivity is deteriorated.

In the present invention, it has been found that it is important to use no dispersant from the viewpoint of exhibiting flame retardancy, and it has been found that [η]b/[η]a is in a range conforming to the range of the formula (6-1). By melt-kneading the polyester resin composition (a) and the carbon black particles, the dispersibility of the carbon black particles can be improved without containing a dispersant, and the flame retardancy, the light-shielding property, the concealability, and the continuous productivity are excellent. Polyester film.

[η]b/[η]a conforms to the method of the formula (6-1), and can appropriately adjust the temperature of the melt kneading section, the time of melt kneading (the residence time of the polymer), and the shear applied during the melt kneading. To achieve. The apparatus for melt-kneading may be a single-axis extruder or a two-axis or more extruder, but a high-shear mixer having a high shear stress such as a twin-screw extruder can be preferably used. method. Further, from the viewpoint of reducing the dispersion failure, it is preferable to equip three twin-axis type or two double-axis type screws. In the case of using a twin screw extruder, the melt kneading section preferably has a temperature range of 200 ° C to 280 ° C. A better temperature range is 210 ° C to 280 ° C, and a better temperature range is 220 ° C to 280 ° C. The residence time of the polymer at this time is preferably in the range of 1 to 5 minutes. Further, it is preferable to set the range of the number of rotations of the twin-shaft screw to 100 to 500 rpm, more preferably 200 to 300 rpm. By setting the number of rotations of the screw to a preferable range, it is easy to add a high shear stress, and the dispersibility of the carbon black particles can be improved, and the decomposition reaction of the polyester due to excessive application of the shear stress can be suppressed. Further, the ratio (L/D) of the twin screw extruder (screw shaft length/screw shaft diameter) is preferably in the range of 20 to 60, and more preferably in the range of 30 to 50.

Further, in the screw configuration of the twin screw extruder, it is preferable to provide a kneading portion composed of a kneading paddle (kneading disk) or the like in order to increase the kneading force, and it is preferable to provide the kneading portion (preferably two). More than the position, more preferably three or more parts of the screw. In this case, the order of mixing the polyester resin composition (a) and the carbon black particles is not particularly limited, and any of the following methods may be used: after the polyester resin composition (a) has been granulated and carbon black particles have been formulated a method of melt-kneading by the above method; melting the polyester resin composition (a) using a uniaxial or biaxial extruder In the process of melt extrusion, a method of mixing carbon black particles by a side feeder is used.

The content of the carbon black particles in the carbon black-containing polyester resin composition precursor (b) is preferably 5% by weight or more and 30% by weight or less. A more preferable lower limit is 10% by weight or more. Further, a more preferable upper limit is 25% by weight or less. When the content of the carbon black is more than 30% by weight, it may become difficult to control the heat generated by the shearing, and the dispersibility may be deteriorated. When the content of carbon black is less than 5% by weight, there is a case where the shearing heat is insufficient and the dispersibility is deteriorated.

In the biaxially oriented polyester film of the present invention, it is preferred that at least one of the surface center plane average roughness (SRa) is 40 nm or less. More preferably, it is 35 nm or less. If the center plane average roughness exceeds 40 nm, film formation cracking often occurs. In addition, carbon black is contained in the case where the dispersibility is poor, and the flame retardancy is deteriorated or the unevenness of the optical density is increased.

Here, the center plane average roughness (SRa) refers to a stylus type three-dimensional roughness meter having a stylus curvature radius of 2 μm, and the cutoff value is set to 0.25 mm to measure the length of 0.5 mm, which is orthogonal to a certain direction. The center line average roughness when measured 40 times at intervals of 5 μm in the direction.

The center-surface average roughness (SRa) of the biaxially oriented polyester film is in the above range, and for example, a method in which carbon black dispersibility is satisfactorily contained in the film is preferably used. The carbon black dispersibility is preferably contained in the film, and a biaxial extruder is used as a device for melt kneading, and the temperature of the melt kneading portion, the time of melt kneading (the residence time of the polymer), and the time of melt kneading are applied. The shearing force, the ratio of the screw shaft length (screw shaft length / screw shaft diameter) of the twin-screw extruder is set to the above preferred range, or the film is produced by a method comprising the steps corresponding to the above (5), (6). method.

In the case where the biaxially oriented polyester film of the present invention is heat-treated at 190 ° C for 30 minutes, the heat shrinkage ratio is preferably 3.0% or less in both the longitudinal direction and the width direction. More preferably, it is 2.5% or less. When the heat shrinkage rate in the case of the heat treatment at 190 ° C for 30 minutes exceeds 3.0%, the unevenness in the combustion time is increased and the flame retardancy is deteriorated in the evaluation of the flame retardancy. Further, the heat shrinkage ratio in the present invention is obtained in accordance with the measurement method described later. Further, in the present invention, the longitudinal direction of the film (MD direction) means that if it is a biaxially oriented polyester film on a roll, the winding direction of the roll is set to the film length direction, and the roll is reeled. The width direction corresponds to the film width direction (TD direction). On the other hand, in the case of the cut sheet shape, the longitudinal direction of the film was calculated as the film longitudinal direction. When the shape of the film is a slight square, any one of the directions parallel to each side is regarded as the longitudinal direction and the width direction.

In order to set the heat shrinkage ratio of the biaxially oriented polyester film to the above range, for example, it may be applied in a length and/or a width direction by a method of applying heat treatment after biaxial stretching or simultaneously with heat treatment in a heat treatment step. The method of the relaxation treatment or the method of applying the annealing treatment after the heat treatment is obtained, but is not limited thereto.

The biaxially oriented polyester film of the present invention is preferably a raw material obtained by mixing the carbon black-containing polyester resin composition precursor (b) and the carbon black particle-free polyester resin composition (c). In particular, it is preferable to obtain a method including the following steps (7) to (9), from the viewpoint of exhibiting the effects of light blocking property, concealing property, flame retardancy, and continuous productivity. of.

(7) In the polyester raw material for producing a film, the aforementioned carbon-containing material is contained Black polyester resin composition precursor (b), and carbon black-free polyester resin composition (c).

(8) The ultimate viscosity of the polyester resin of the carbon black-containing polyester resin composition precursor (b) and the carbon black-free polyester resin composition (c) conforms to the following formula (8-1).

(8-1)0.75≦[η]b/[η]c≦1.10

[η]b: ultimate viscosity (dl/g) of polyester resin of carbon black-containing polyester resin composition precursor (b)

[η]c: ultimate viscosity (dl/g) of polyester resin of carbon black-free polyester resin composition (c)

(9) The content Wb (% by weight) of the carbon black-containing polyester resin composition precursor and the content of the carbon black-free polyester resin composition (c) Wc (weight) with respect to the entire polyester raw material for producing the film %) conforms to the following formula (9-1).

(9-1)0.03≦Wb/Wc≦0.5

Wb: content (% by weight) of the carbon black-containing polyester resin composition precursor (b) with respect to the entire polyester raw material for producing a film

Wc: content (% by weight) of the polyester resin composition (c) containing no carbon black relative to the entire polyester raw material for producing a film

When [η]b/[η]c and Wb/Wc are outside the above preferred range, the light-shielding property and the flame retardancy are deteriorated, and the continuous productivity is deteriorated (the filtration pressure at the time of film formation increases). . The details of the reason are still unclear, but if [η]b/[η]c, and Wb/Wc are outside the above preferred range, even in the carbon black-containing polyester resin composition precursor (b), When the carbon black particles are uniformly dispersed, aggregation of the particles occurs at the time of melt film formation, and it is estimated that the aggregates cause deterioration in flame retardancy and continuous productivity. From flame retardance, From the viewpoint of continuous productivity, a more preferable lower limit of [?]b/[?]c is 0.85 or more, and still more preferably 0.90 or more. Further, the upper limit is preferably 1.05 or less, more preferably 0.95 or less. Further, a lower limit of Wb/Wc is preferably 0.03 or more. A more preferable upper limit is 0.3 or less, and even more preferably 0.15 or less.

The biaxially oriented polyester film of the present invention is melt-extruded into a sheet shape from an extrusion port of a film forming machine, and is formed into a film, for example, under the following conditions. After being melt-extruded into a sheet shape from the extrusion port of the film forming machine, it is cooled and solidified by electrostatic sealing on a drum cooled to a surface temperature of 10 ° C to 60 ° C to prepare an unstretched sheet. The unstretched sheet obtained in this manner is biaxially stretched in the longitudinal direction and the transverse direction to form a sheet having an optimum thickness. The stretching can be performed by a sequential biaxial stretching method or a simultaneous biaxial stretching method. For example, in the case of sequential biaxial stretching, the unstretched sheet is guided to a roll group heated to 70 to 120 ° C, and stretched 2 to 5 times in the longitudinal direction (longitudinal direction, that is, the traveling direction of the film). The roller group of 20~30 °C is cooled. Then, while holding both ends of the stretched film with a jig in the longitudinal direction, one side is guided to a tenter, and stretched in a direction perpendicular to the longitudinal direction (lateral direction) in a gas atmosphere heated to 90 to 150 ° C. ~5 times. The biaxially stretched film obtained in this manner is subjected to a heat treatment step of 1 to 30 seconds in a tenter at 150 to 240 ° C in order to end the crystal alignment to impart planarity or thermal dimensional stability. After cooling, cool to room temperature and coil. Further, in the heat treatment step, a relaxation treatment of 3 to 12% may be applied in the longitudinal direction and/or the width direction as needed.

The biaxially oriented polyester film of the present invention has high light-shielding property, concealability, flame retardancy and excellent continuous productivity, and can be used in its active form. In particular, it is used as an electrical insulating material such as an optical device such as a mobile phone, a camera, or a camera, a solar battery back panel, or a monitor, or various industrial materials such as building materials, thermal transfer applications, and engineering paper. It is suitable for use as an optical device that requires flame retardancy, light blocking, and concealability, and a back sheet for solar cells.

[Method of evaluation of characteristics]

(1) melting point

According to JIS K7121-1987, DSC (RDC220) manufactured by SEIKO INSTRUMENT Co., Ltd., DISKSTATION (SSC/5200) manufactured by the company as a data analysis device, and a heating rate of 20 ° C / min on an aluminum tray were used. 5 mg of the sample was heated from room temperature to 300 ° C, kept molten at 300 ° C for 5 minutes, and rapidly cooled and held for 5 minutes, and then heated from room temperature at a temperature increase rate of 20 ° C / minute. The peak temperature of the endothermic peak of the melting observed at this time was taken as the melting point.

(2) Ultimate viscosity

The measurement sample was dissolved in 100 ml of o-chlorophenol (solution concentration C = 1.2 g/dl), and the viscosity of the solution at 25 ° C was measured using an Oswald viscometer. Further, the viscosity of the solvent was measured in the same manner. Using the obtained solution viscosity and solvent viscosity, [η] (dl/g) was calculated by the following formula (a), and the obtained value was defined as the ultimate viscosity.

(a) ηSp/C=[η]+K[η] ² ‧C (here, ηsp=(solution viscosity (dl/g)/solvent viscosity (dl/g))-1, K-system Huggins constant (set to 0.343)).

In addition, when there is an insoluble matter such as inorganic particles in the solution in which the measurement sample is dissolved, the measurement is carried out by the following method.

i) The measurement sample was dissolved in 100 mL of o-chlorophenol to prepare a solution having a solution concentration of 1.2 mg/mL. Here, the weight of the measurement sample to which the o-chlorophenol was supplied was taken as the weight of the measurement sample.

Ii) Next, the solution containing the insoluble matter is filtered, and the weight measurement of the insoluble matter and the volume measurement of the filtrate after filtration are performed.

Iii) adding o-chlorophenol to the filtrate after filtration (measured sample weight (g) - weight of insoluble matter (g)) / (volume of filtered filtrate (mL) + volume of added o-chlorophenol ( mL)) Adjusted to 1.2g/100mL. (For example, when the weight of the insoluble matter is 2.0 g/solution volume of 100 mL, the weight of the insoluble matter when the solution is filtered is 0.2 g, and when the volume of the filtrate after filtration is 99 mL, 51 mL of the adjacent side is added. Adjustment of chlorophenol ((2.0g-0.2g) / (99mL + 51mL) = 1.2g / mL))

Iv) using the solution obtained in iii), measuring the viscosity at 25 ° C using an Oswald viscometer, using the obtained solution viscosity, solvent viscosity, and calculating [η] using the above formula (C), The value is used as the ultimate viscosity.

(3) shading, concealment

The optical density was evaluated according to the old JIS K7605, and the light-shielding property and the concealing property were evaluated by the following criteria.

In the optical density meter, XRite 361T (manufactured by Nippon Heavy Industries, Ltd.) was used, and a vertical transmission beam was applied to the sample, and the ratio of the log (logarithm) to the state without the sample was defined as the optical density. The beam width is set to a circle having a diameter of 1 mm or is wider than it.

S: optical density is 5 or more

A: The optical density is 4 or more and less than 5

B: The optical density is 3.5 or more and less than 4

C: optical density is less than 3.5

S~B is good, and S is optimal.

(4) 190 ° C heat shrinkage rate

On the surface of the measurement sample, two lines were drawn so as to have a width of 10 mm and a measurement length of about 100 mm, and the distance between the two lines was measured at 23 ° C, and this was set to L0. The measurement sample was placed in an ESPEC hot air oven "HIGH-TEMP-OVEN PHH-200" set to 190 ° C (air flow meter "7") for 30 minutes, and again at 23 ° C under a load of 3 g. The distance between the two lines was measured, and this was set to L1, and the heat shrinkage rate was obtained by the following formula. Each of the five samples was measured in the longitudinal direction and the width direction, and each was evaluated by an average value.

Heat shrinkage rate (%) = (L0-L1) / L0 × 100

(5) Surface roughness (SRa)

Using the Surfcorder ET30HK manufactured by Otaru Laboratory, the average center line roughness (SRa) of both surfaces of the film was measured according to the following conditions, and the average value was obtained.

Contact lens radius of curvature: 2μm

Deadline: 0.25mm

Measuring length: 0.5mm

Measurement interval: 5μm

Number of measurements: 40 times.

(6) Flame retardancy

According to the UL-94 VTM method, it was evaluated by the following method.

(i) Sample preparation

The measurement sample (biaxially oriented polyester film) was cut into 20 cm × 5 cm.

A sample placed at 23 ° C and 50% RH for 48 hours was designated as sample A, and after being left at a temperature of 70 ° C for 168 hours, a sample cooled at a temperature of 23 ° C and 20% RH for 4 hours was designated as sample B. Five samples were prepared as one set each.

(ii) Method of measurement

A line was drawn at a position 125 mm from the bottom side of each long side of each sample, and wound around a rod having a diameter of 12.7 mm. The 75 mm portion of the upper portion was fixed with a pressure-sensitive adhesive tape from the 125 mm mark, and the rod was taken out. The upper end of the sample was closed in a manner that did not have a chimney effect during the test. Next, each sample was erected vertically, and a skim cotton was placed under 300 mm. The Bunsen burner with a diameter of 9.5 mm and a flame length of 20 mm was used as a heating source in such a manner that the cylinder of the burning lamp was located 10 mm from the lower end of the sample, and the center of the lower end of the sample was exposed to the blue flame for 3 seconds, and the first flame was measured. Burning time (t1). Next, immediately after the flame was extinguished, the flame was immediately exchanged for 3 seconds, and the burning time (t2) and the ignition time (t3) after the second flame separation were measured. In addition, in the case of the first and second flames, it is observed whether there is burning of the 125 mm mark, and whether there is a burning falling object such as a defoaming fire. For the sample A and the sample B, one set (5 pieces) of each was subjected to the above measurement.

(iii) Evaluation of flame retardancy

The flame retardancy was evaluated as follows according to the following criteria.

VTM-0: Compliance with any of the criteria (a), (b), (c), (d), and (e).

VTM-1: Compliance with any of the criterions (a'), (b'), (c'), (d), and (e).

VTM-2: Compliance with any of the criterions (a'), (b'), (c'), and (d).

No VTM: Does not comply with any of VTM-0, VTM-1, VTM-2.

Judgment criterion (a): In all of the samples, the longer of the first post-flame combustion time (t1) or the second post-flame burn time (t2) of each sample was 10 seconds or less.

Judgment criterion (a'): In all of the samples, the longer of the first post-flame burn time (t1) or the second post-flame burn time (t2) of each sample was 30 seconds or less.

Judgment criterion (b): The total of the combustion time after the flame separation for each group (the total of the combustion time (t1 + t2) after the flame separation of the five samples), and both the sample A and the sample B were 50 seconds or shorter.

Judgment criterion (b'): the total of the combustion time after the flame separation per group (the total of the combustion time (t1 + t2) after the flame separation of the five samples), and both the sample A and the sample B were 250 seconds or shorter.

Judgment criterion (c): The total of the burning time (t2) and the seeding time (t3) after the second off-flame in all the samples was 30 seconds or less.

Judgment criterion (c'): The total of the burning time (t2) and the seeding time (t3) after the second off-flame in all the samples was 60 seconds or less.

Judgment criterion (d): In all samples, the burning or fire did not reach the 125 mm mark.

Judgment criterion (e): In all of the samples, there was no case where the burned sample fell and the cotton was deflated.

(7) Continuous productivity

In the continuous production system, the number of times of film breakage at the time of film formation performed under the conditions of the examples and the comparative examples for 48 hours was converted into a calculated value per 24 hours, and the film materials used in the examples and the comparative examples were as follows. article The filtration pressure rise value at the time of the filter test was determined according to the following criteria.

S: the rupture is less than 1 every 24 hours and the filtration pressure rise value is less than 80 kg/cm ²

A: The rupture is less than 1 every 24 hours and the filtration pressure rise value is 80 kg/cm ² or more and less than 100 kg/cm ²

B: the rupture is less than 1 every 24 hours and the filtration pressure rise value is 100 kg/cm ² or more and less than 120 kg/cm ²

C: The rupture per 24 hours is 1 or more or the filtration pressure rise is 120 kg/cm ² or more.

S~B is good, and S is optimal.

<Conditions of filterability test>

The materials used in the examples and the comparative examples were dried at 140 ° C under a reduced pressure of 133 Pa or less for 8 hours. Using a dried granule, a uniaxial extruder, using this pellet, a X4 type 20 μm DYNALLOY filter (filter area: 4.5 cm ² ) manufactured by Watanabe Co., Ltd., at a polymer temperature of 280 ° C and a throughput of 10 g / min. filter. The filtration pressure (R0) at a throughput of 1200 g and the filtration pressure (R1) at 8400 g from the start of filtration were measured, and R1-R0 (kg/cm ² ) was set as a filtration pressure rise value.

(8) Film thickness

The film thickness was measured in accordance with JIS C 2151 (2006) "Micrometer method". The measuring instrument was measured in the width direction of the product at almost equal intervals using a micrometer, and an average value of 30 points in the width direction was taken.

[Examples]

Hereinafter, the present invention will be described by way of examples, but the present invention is not necessarily limited by these examples.

(Reference Example 1) Production of Polyethylene Terephthalate Resin A

In a mixture of dimethyl terephthalate and ethylene glycol, 0.09 wt% of calcium acetate and 0.03 wt% of antimony trioxide were added with respect to dimethyl terephthalate, and the transesterification was carried out by heating at a normal heating temperature. reaction. Next, in the obtained transesterification reaction product, 0.15 wt% of lithium acetate and 0.21 wt% of trimethyl phosphate were added to the raw material of the dimethyl terephthalate, and then transferred to a polymerization reaction tank. Next, the reaction system was gradually decompressed while heating and heating, and polymerization was carried out by a normal method at a reduced pressure of 1 mmHg at 290 ° C to obtain polyethylene terephthalate having an ultimate viscosity of 0.54 dl/g (PET). ). The obtained PET polymer was heat-treated at a temperature of 225 ° C for 35 hours under a reduced pressure of 1 mmHg or less using a rotary vacuum polymerization apparatus to obtain a poly(terephthalic acid) having a melting point of 255 ° C and an ultimate viscosity of 0.73 dl / g. Ethylene glycol resin A (PET pellet A).

(Reference Example 2) Production of Polyethylene Terephthalate Resin B

A polyethylene melting point of 255 ° C and an ultimate viscosity of 0.63 dl / g were obtained in the same manner as in Reference Example 1 except that polyethylene terephthalate (PET) having an ultimate viscosity of 0.54 dl / g was heat-treated for 20 hours in Reference Example 1. Polyethylene terephthalate resin B (PET pellet B).

(Reference Example 3) Production of Polyethylene Terephthalate Resin C

A polyethylene melting point of 255 ° C and an ultimate viscosity of 0.80 dl / g were obtained in the same manner as in Reference Example 1 except that polyethylene terephthalate (PET) having an ultimate viscosity of 0.54 dl / g was heat-treated for 50 hours in Reference Example 1. Polyterephthalic acid Ethylene glycol resin C (PET pellet C).

(Reference Example 4) Production of a carbon black-containing polyester resin composition precursor A

80% by weight of PET pellet A produced in Reference Example 1 and 20% by weight of furnace black (#3030B) manufactured by Mitsubishi Chemical Corporation as carbon black particles were placed in a vacuum discharge hole provided with a kneading paddle kneading section. Rotating and kneading into a rotary biaxial kneading extruder (L/D=40) at a residence time of 90 seconds, a screw rotation number of 300 rpm, and a temperature of 290 ° C. The strand shape was used at a temperature of 25 ° C. Immediately after the water was cooled, the carbon black-containing polyester resin composition precursor A (parent granule A) having an ultimate viscosity of 0.58 dl/g was produced.

(Reference Example 5) Production of a carbon black-containing polyester resin composition precursor B

A carbonaceous material having an ultimate viscosity of 0.64 dl/g was produced in the same manner as in Reference Example 4 except that the number of screw rotations of the co-rotating biaxial kneading extruder with a discharge hole was set to 100 rpm in Reference Example 4. Black polyester resin composition precursor B (parent granule B).

(Reference Example 6) Production of a carbon black-containing polyester resin composition precursor C

A carbonaceous having an ultimate viscosity of 0.55 dl/g was produced in the same manner as in Reference Example 4 except that the number of screw rotations of the co-rotating biaxial kneading extruder with a discharge hole was set to 400 rpm in Reference Example 4. Black polyester resin composition precursor C (parent pellet C).

(Reference Example 7) Production of a carbon black-containing polyester resin composition precursor D

A carbonaceous material having an ultimate viscosity of 0.63 dl/g was produced in the same manner as in Reference Example 4 except that PET pellet A obtained in Reference Example 1 and 10% by weight of carbon black were used in Reference Example 4 in an amount of 90% by weight. Black polyester resin composition matrix D (parent pellet D).

(Reference Example 8) Production of a carbon black-containing polyester resin composition precursor E

A carbonaceous material having an ultimate viscosity of 0.65 dl/g was produced in the same manner as in Reference Example 4 except that the PET pellet A obtained in Reference Example 1 and the carbon black obtained in Reference Example 1 were 94% by weight in Reference Example 4. Black polyester resin composition precursor E (parent pellet E).

(Reference Example 9) Production of a carbon black-containing polyester resin composition precursor F

In addition to 78% by weight of the PET pellet A obtained in Reference Example 1, 20% by weight of carbon black, and 2% by weight of an olefin wax "Licowax PP230" (manufactured by CLARIENT Co., Ltd.) as a dispersing agent, The carbon black-containing polyester resin composition precursor F (parent pellet F) having an ultimate viscosity of 0.55 dl/g was produced in the same manner as in Reference Example 4.

(Reference Example 10) Production of a carbon black-containing polyester resin composition precursor G

A carbon black-containing polyester resin composition precursor G (precursor pelletized) having an ultimate viscosity of 0.46 dl/g was produced in the same manner as in Reference Example 4 except that the PET pellets B produced in Reference Example 2 were used in Reference Example 4. G).

(Reference Example 11) Production of carbon black-containing polyester resin composition precursor H

In addition to the addition of 78% by weight in Reference Example 4, the obtained in Reference Example 1 In the same manner as in Reference Example 4 except that PET pellet A, 20% by weight of carbon black, and 2% by weight of a condensed phosphate ester (PX200 manufactured by Daisaku Chemical Co., Ltd.) as a flame retardant were produced to produce an ultimate viscosity of 0.55 dl/ The carbon black-containing polyester resin composition of the parent material H (parent granule H).

(Reference Example 12) Production of a carbon black-containing polyester resin composition precursor I

A carbonaceous material having an ultimate viscosity of 0.49 dl/g was produced in the same manner as in Reference Example 4 except that the PET pellet A obtained in Reference Example 1 and the carbon black obtained in Reference Example 1 were set to Reference Example 4 at 65% by weight. Black polyester resin composition precursor I (parent pellet I).

(Example 1)

10% by weight of the precursor pellet A obtained in Reference Example 4 and 90% by weight of the polyethylene terephthalate resin B obtained in Reference Example 2 were vacuum dried at 180 ° C for 2 hours, respectively. Next, it was supplied to the extruder under a nitrogen atmosphere. The polymer which had been melted in the extruder was filtered with a filter set to a temperature of 290 ° C, and then melt-extruded from the extrusion port of the T die which had been set to a temperature of 280 ° C while applying static electricity to a surface temperature of 25 ° C. The cast drum is cooled and hardened on one side to produce an unstretched film.

The unstretched film was stretched at a magnification of 3.3 times in the longitudinal direction at a temperature of 90 ° C using a longitudinal stretching machine including a plurality of heated rolls. Thereafter, the both ends of the film were held by a jig, and guided to a tenter, and stretched in the width direction of the film at a stretching temperature of 95 ° C and a draw ratio of 3.5 times, and heat treatment was performed at 225 ° C for 8 seconds to obtain a thickness. 50 μm biaxially oriented polyester film.

The characteristics and the like of the obtained biaxially stretched polyester film are shown in the table.

(Example 2)

A biaxially stretched polyester film was obtained in the same manner as in Example 1 except that the film thickness of Example 1 was changed to 100 μm. The characteristics and the like of the obtained biaxially stretched polyester film are shown in the table.

(Example 3)

The biaxially stretched polyester was obtained in the same manner as in Example 1 except that the content of the precursor granule A and the polyethylene terephthalate resin B was changed as shown in the table, and the thickness of the film was changed to 200 μm. film. The characteristics and the like of the obtained biaxially stretched polyester film are shown in the table.

(Example 4)

A biaxially stretched polyester film was obtained in the same manner as in Example 1 except that the contents of the mother pellet A and the polyethylene terephthalate resin B were changed as shown in the Table. The characteristics and the like of the obtained biaxially stretched polyester film are shown in the table.

(Example 5)

A biaxially stretched polyester film was obtained in the same manner as in Example 1 except that 10% by weight of the parent pellet B obtained in Reference Example 5 was used instead of the mother pellet A. The characteristics and the like of the obtained biaxially stretched polyester film are shown in the table.

(Example 6)

A biaxially stretched polyester film was obtained in the same manner as in Example 1 except that 10% by weight of the mother pellet C obtained in Reference Example 6 was used instead of the mother pellet A. Characteristics of the obtained biaxially stretched polyester film Etc.

(Example 7)

Except that 20% by weight of the precursor pellet D obtained in Reference Example 7 was used, 80% by weight of the polyethylene terephthalate resin B obtained in Reference Example 2 was used as the polyester raw material for producing the film, in accordance with A biaxially stretched polyester film was obtained in the same manner as in Example 1. The characteristics and the like of the obtained biaxially stretched polyester film are shown in the table.

(Example 8)

Except that 33% by weight of the precursor pellet E obtained in Reference Example 8 and 67% by weight of the polyethylene terephthalate resin B obtained in Reference Example 2 were used as the polyester raw material for producing the film, The biaxially stretched polyester film was obtained in the same manner as in Example 1. The characteristics and the like of the obtained biaxially stretched polyester film are shown in the table.

(Example 9)

Except that in Reference Example 1, 10% by weight of the precursor pellet A obtained in Reference Example 4 and 90% by weight of the polyethylene terephthalate resin C obtained in Reference Example 3 were used, in accordance with Example 1 The same method gave a biaxially stretched polyester film. The characteristics and the like of the obtained biaxially stretched polyester film are shown in the table.

(Embodiment 10)

A biaxially stretched polyester film was obtained in the same manner as in Example 1 except that the heat treatment of Example 1 was changed to 235 °C. The characteristics and the like of the obtained biaxially stretched polyester film are shown in the table.

(Comparative Example 1)

In addition to using the parent pellet F obtained in Reference Example 9, replacing the parent cut A biaxially stretched polyester film was obtained in the same manner as in Example 1 except for the pellet A. The characteristics and the like of the obtained biaxially stretched polyester film are shown in the table.

(Comparative Example 2)

The same procedure as in Example 1 was carried out except that 35% by weight of the precursor pellet A obtained in Reference Example 4 and 65% by weight of the polyester resin obtained in Reference Example 2 were used as the polyester raw material for producing the film. Biaxially stretched polyester film. The characteristics and the like of the obtained biaxially stretched polyester film are shown in the table.

(Comparative Example 3)

A biaxially stretched polyester film was obtained in the same manner as in Example 1 except that the parent pellet G obtained in Reference Example 10 was used instead of the precursor pellet A. The characteristics and the like of the obtained biaxially stretched polyester film are shown in the table.

(Comparative Example 4)

Except that 2.5% by weight of the precursor granule A obtained in Reference Example 4 and 97.5% by weight of the polyethylene terephthalate resin B obtained in Reference Example 2 were used as the polyester raw material for producing the film, The biaxially stretched polyester film was obtained in the same manner as in Example 1. The characteristics and the like of the obtained biaxially stretched polyester film are shown in the table.

(Comparative Example 5)

A biaxially stretched polyester film was obtained in the same manner as in Example 1 except that the precursor pellet H obtained in Reference Example 11 was used instead of the precursor pellet A. The characteristics and the like of the obtained biaxially stretched polyester film are shown in the table.

(Comparative Example 6)

A biaxially stretched polyester film was obtained in the same manner as in Example 1 except that the heat treatment of Example 1 was changed to 200 °C. The characteristics and the like of the obtained biaxially stretched polyester film are shown in the table.

(Comparative Example 7)

The same procedure as in Example 1 was carried out, except that 6 wt% of the precursor pellet I obtained in Reference Example 12 and 94 wt% of the polyethylene terephthalate resin B obtained in Reference Example 2 were used. Biaxially stretched polyester film. The characteristics and the like of the obtained biaxially stretched polyester film are shown in the table.

[Industrial availability]

According to the present invention, it is possible to provide a biaxially oriented polyester film which satisfies high light-shielding property, concealability, flame retardancy, and continuous productivity. Further, by using such a film, it is possible to provide a light shielding member of an optical device having both high light blocking properties and flame retardancy, or a solar battery back sheet.

Claims (8)

A biaxially oriented polyester film which conforms to the following (1) to (4): (1) contains carbon black particles in a polyester resin composition constituting the film; (2) a polyester resin composition constituting the film It does not substantially contain a flame retardant or a dispersant; (3) the optical density of the film is 3.5 or more; (4) the flame retardancy obtained by the following method is VTM-0, VTM-1, VTM-2 Either <Evaluation method of flame retardancy> (i) Sample preparation A sample (biaxially oriented polyester film) was cut into 20 cm × 5 cm, and a sample set at 23 ° C and 50% RH for 48 hours was set. For sample A, after 168 hours at a temperature of 70 ° C, a sample cooled at a temperature of 23 ° C and 20% RH for 4 hours was set as sample B, and five samples were prepared as one set; (ii) the measurement method was Each sample was drawn from a short side of 125 mm in a direction parallel to the short side, and wound on a rod having a diameter of 12.7 mm in such a manner that the short side was up and down; the 75 mm part of the inner pressure sensitive tape was used from the 125 mm mark. After the fixation, the rod is withdrawn; the upper end of the sample is closed in a manner that does not have a chimney effect in the test; next, each sample is vertically erected in it The cotton wool is placed under the 300mm; the burner is placed at a distance of 10mm from the lower end of the sample, and the Bunsen burner with a diameter of 9.5mm and a flame length of 20mm is used as a heating source, so that the center of the lower end of the sample contacts the blue flame. Seconds, after the first flame separation Burning time (t1); next, the flame is immediately extinguished for 3 seconds, and the burning time (t2) and the fire time (t3) after the second flame separation are measured; in addition, in the first and second times At the time of the flame, whether there is burning of the 125 mm mark, whether there is a burning falling object such as a defoaming fire, and one sample (5 pieces) of each of the sample A and the sample B are subjected to the above measurement; (iii) Evaluation of flame retardancy The flame retardancy was evaluated as follows according to the following criteria: VTM-0: meeting the criteria (a), (b), (c), (d), and (e) One; VTM-1: conforms to any of the criteria (a'), (b'), (c'), (d), (e); VTM-2: meets the criterion (a'), ( Any of b'), (c'), (d); no VTM: does not comply with any of VTM-0, VTM-1, VTM-2, criterion (a): in all samples, The longer one of the burning time after the flame is (t1) or the second burning time after the second flame (t2) is 10 seconds or less; the criterion (a'): in all the samples, after the first flame The longer of the burning time (t1) or the burning time after the second flame leaving (t2) is 30 seconds or less; (b): the total of the burning time after each flame in each group (the total of the burning time (t1 + t2) after leaving the flame of 5 samples), the sample A and the sample B are all 50 seconds or less; b'): total of burning time after each flame in the group (Total of the burning time (t1+t2) of the five samples after the flame separation), the sample A and the sample B are all 250 seconds or less; the criterion (c): the combustion after the second off-flame in all the samples The total of the time (t2) and the tinder time (t3) is 30 seconds or less; the criterion (c'): the total of the combustion time (t2) and the tinder time (t3) after the second off-flame in all the samples is 60 seconds or less; judgment criterion (d): in all the samples, the combustion or the fire did not reach the 125 mm mark; the criterion (e): in all the samples, there was no case where the burned sample fell and the cotton was deflated. The biaxially oriented polyester film of claim 1, wherein the film has a thickness of 50 μm or more and 300 μm or less. The biaxially oriented polyester film of claim 1 or 2, wherein the content of the carbon black particles in the polyester resin composition constituting the film ranges from 1 to 5% by weight. The biaxially oriented polyester film of claim 3, which is used for any one of a light shielding member of an optical device and a solar battery back sheet. A biaxially oriented polyester film according to claim 1 or 2, which is used for any one of a light shielding member of an optical device and a solar battery back sheet. A method for producing a biaxially oriented polyester film according to any one of claims 1 to 5, which comprises the steps of (5) to (6) below: (5) comprising a kneading in the polyester material for producing a film a polyester resin composition (a) having a viscosity [η] of 0.7 dl/g or more and a carbon black-containing polyester resin composition obtained by carbon black particles (b); (6) producing the carbon black Polyester resin composition precursor (b) The ultimate viscosity of the polyester resin of the polyester resin composition (a) before the kneading and the ultimate viscosity of the polyester resin of the obtained carbon black-containing polyester resin composition precursor (b) are in accordance with the following formula: (6-1): (6-1) 0.75 ≦ [η] b / [η] a ≦ 0.90 [η] a: ultimate viscosity of the polyester resin of the polyester resin composition (a) of 0.7 dl/g or more (dl/g), [η]b: ultimate viscosity (dl/g) of the polyester resin of the carbon black-containing polyester resin composition precursor (b). The method for producing a biaxially oriented polyester film according to claim 6, wherein the content of the carbon black particles in the matrix (b) of the carbon black-containing polyester resin composition is 5 wt% or more and 30 wt% or less. The method for preparing a biaxially oriented polyester film according to claim 6 or 7, which conforms to the following (7) to (9): (7) comprising a polyester resin comprising the carbon black in a polyester raw material for producing a film. a precursor (b), and a carbon black-free polyester resin composition (c); (8) a carbon black-containing polyester resin composition precursor (b), and a carbon black-free polyester resin composition ( The ultimate viscosity of the polyester resin of c) is in accordance with the following formula (8-1): (8-1) 0.75 ≦ [η] b / [η] c ≦ 1.10 [η] b: composition of the polyester resin containing carbon black The ultimate viscosity (dl/g) of the polyester resin of the precursor (b), [η]c: the ultimate viscosity (dl/g) of the polyester resin of the polyester resin composition (c) containing no carbon black; 9) Polycarbon black-containing aggregates relative to the entire polyester raw material from which the film is made The content Wb (% by weight) of the ester resin composition precursor and the content Wc (% by weight) of the polyester resin composition (c) not containing carbon black satisfy the following formula (9-1): (9-1) 0.03 ≦Wb/Wc≦0.5 Wb: content (% by weight) of the carbon black-containing polyester resin composition precursor (b) as a whole of the polyester raw material for producing the film, Wc: relative to the entire polyester raw material for producing the film, The content (% by weight) of the carbon black-free polyester resin composition (c).