JP2016148013A - Polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film excellent in heat resistance and visibility in oil.SOLUTION: The polyester film satisfies the following (1) and (2). (1) The surface roughness Ra of at least one surface is not less than 50 nm and not greater than 400 nm, and the Rz is not less than 500 nm and not greater than 5,000 nm. (2) The light intensity reflecting in a direction making an angle of 10° to a direction vertical to the film when irradiating the film with an angle vertical to the film is not less than 10.SELECTED DRAWING: None

Description

The present invention relates to a polyester film excellent in oil resistance and visibility.

  Polyester resins, especially polyethylene terephthalate (hereinafter sometimes abbreviated as PET) and polyethylene 2,6-naphthalene dicarboxylate (hereinafter sometimes abbreviated as PEN) are mechanical properties, thermal properties, chemical resistance, electrical properties, It has excellent moldability and is used for various purposes. Polyester films made from polyester, especially biaxially oriented polyester films, are used for car air conditioners used in solar battery back sheets, water heater motors, hybrid vehicles, etc. due to their excellent mechanical and electrical properties. It is used as various industrial materials such as electric insulation materials for motors and drive motors, magnetic recording materials, capacitor materials, packaging materials, building materials, photographic applications, graphic applications, and thermal transfer applications.

  Among these uses, when used for electrical insulating materials (for example, compressor motors for air conditioners), PEN having high heat resistance is used because it is used in an environment where the temperature becomes high as the refrigerant is compressed and expanded. It has been studied (Patent Document 1). In addition, it has been proposed to use PET whose heat resistance is improved by adjusting the amount of metal species contained in PET, which is lower in cost than PEN but inferior in heat resistance (Patent Document 2). Furthermore, it has also been proposed to add opacity to the film so as not to overlook loading mistakes in visual inspection after loading a film as a slot liner or wedge in a motor slot (Patent Document 3).

Japanese Patent Laid-Open No. 9-300452 Japanese Patent Publication No. 3-26484 JP 2002-47368 A

  Patent Document 1 and Patent Document 2 described above focus on the heat resistance of the resin used. Although the film described in Patent Documents 1 and 2 has improved heat resistance in the presence of air, when the film is used as an electrical insulating material for a motor, it is used in an environment where it is in contact with high-temperature oil. The heat resistance in an environment where the oil is in contact with oil at a high temperature was not sufficient. In addition, a film imparted with opacity (higher haze) as in Patent Document 3 can achieve a certain visibility improvement effect, but has a structure in which the motor slot portion is shaded, or a light source and a film. When it is difficult for light to reach the direction of the observer depending on the angle, the visibility was insufficient in the visual inspection.

  In view of the background of the prior art, the object of the present invention is high in durability (oil resistance) in an environment in contact with high-temperature oil, and easy to confirm in visual inspection after loading in a motor slot (visibility) It is to provide a polyester film.

In order to solve the above problems, the present invention has the following configuration. That is,
[I] A polyester film satisfying the following (1) and (2).
(1) At least one surface roughness Ra is 50 nm or more and 400 nm or less, and Rz is 500 nm or more and 5000 nm or less.
(2) The light intensity reflected in the direction forming 10 ° with respect to the direction perpendicular to the film when irradiated with light perpendicular to the film, determined by the following measurement method, is 10 or more.
<Measurement method of light intensity>
Using a variable angle photometer (Model GP-200) manufactured by Murakami Color Research Co., Ltd., the light intensity is received and received under the following conditions, and the light intensity received by the light receiver at the light receiving angle of 10 ° is The light intensity is reflected in a direction forming 10 ° with respect to the direction perpendicular to the film when light is irradiated perpendicularly to the film.
・ Light source: Halogen lamp 12V50W
・ Receiver: Side-on photomultiplier tube R6355
・ Measurement mode: Reflection ・ Filter: None ・ Flux diaphragm: 3.0
・ Light receiving aperture: 1.0
-Incident angle: 0 °
・ Sample tilt angle: 0 °
・ Reception start angle: 0 °
・ Reception angle: 90 °
・ Sensitivity: 950
・ HIGH VOLT: 498V
・ Data interval: 0.1 °
[II] The polyester according to [I], wherein the polyester resin composition constituting the film contains particles, and the content thereof is 0.1 wt% or more and 10 wt% or less with respect to the entire polyester resin composition. the film.
[III] The polyester film according to [II], wherein the particles are crosslinked silicone resin particles.
[IV] The polyester film according to [III], wherein the crosslinked silicone resin particles contain 95 mol% or more of dimethylpolysiloxane.
[V] The polyester film according to any one of [I] to [IV], which has two or more layers.
[VI] The polyester film according to [V], wherein the polyester resin constituting the layer (A layer) having a surface satisfying (1) has a melting point of 255 ° C. or higher.
[VII] The polyester film according to [VI], wherein the polyester resin constituting the layer (B layer) in contact with the A layer has a melting point of 260 ° C. or lower.
[VIII] The polyester according to any one of [I] to [VII], wherein the time required for the strength retention to be 50% or less is 200 hours or more when placed under the condition of 200 ° C. and 0% RH the film.
[IX] The polyester film according to any one of [I] to [VIII], which is used as an insulating member of a motor.
[X] The polyester film according to any one of [I] to [VIII], which is used for applications in contact with R32.

  ADVANTAGE OF THE INVENTION According to this invention, the polyester film excellent in durability (oil resistance) and visibility in the environment which contacts oil at high temperature can be provided. The polyester film obtained according to the present invention is suppressed in physical properties in high-temperature oil, and it is easy to confirm a loading error even in a visual inspection after loading in a motor slot, so even when used as an electric insulating member of a motor, A polyester film that can withstand long-term use can be provided.

It is the schematic when measuring the light intensity reflected in the direction which makes 10 degrees with respect to the direction perpendicular | vertical to a film when light is irradiated with respect to a film perpendicularly | vertically.

Hereinafter, the present invention will be described in detail with specific examples.
The film of the present invention needs to be a polyester film.

  The polyester here has a dicarboxylic acid component and a diol component. In addition, in this specification, a structural component shows the minimum unit which can be obtained by hydrolyzing polyester.

  Examples of the dicarboxylic acid component constituting the polyester include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelic acid, azelaic acid, methylmalon. Aliphatic dicarboxylic acids such as acid, ethylmalonic acid and the like, adamantane dicarboxylic acid, norbornene dicarboxylic acid, cyclohexane dicarboxylic acid, decalin dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalene Dicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 5-sodiumsulfoisophthalate Acid, fe Toluene boys carboxylic acid, anthracene dicarboxylic acid, phenanthrene carboxylic acid, 9,9'-bis (4-carboxyphenyl) dicarboxylic acids such as fluorene acids and aromatic dicarboxylic acids, or there may be mentioned an ester derivative thereof is not limited thereto.

  Examples of the diol component constituting the polyester include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butanediol. Aliphatic diols such as cyclohexanedimethanol, spiroglycol, bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, 9,9′-bis (4-hydroxy Examples include, but are not limited to, diols such as phenyl) fluorene and aromatic diols, and a series of a plurality of the above-mentioned diols.

The polyester film of the present invention must satisfy the following (1).
(1) At least one surface roughness Ra is 50 nm or more and 400 nm or less, and Rz is 500 nm or more and 5000 nm or less.

  A general polyester film is composed of crystalline polyester, and there are crystalline and amorphous parts of the polyester in the film. When this polyester film comes into contact with high-temperature oil, the oil soaks into the amorphous part of the surface layer of the film, and the molecular chain is cut from there to cause deterioration. The polyester film of the present invention has at least one surface roughness Ra of 50 nm or more and 400 nm or less and Rz of 500 nm or more and 5000 nm or less, so that oil repellency of the film surface layer is improved and deterioration due to oil penetration is suppressed. it can. Ra is preferably 100 nm or more and 300 nm or less, and more preferably 150 nm or more and 250 nm or less, so that deterioration in oil is further suppressed. On the other hand, if Ra is less than 50 nm, the effect of suppressing deterioration cannot be imparted. On the other hand, when Ra is larger than 400 nm, the contact area with the oil becomes large, and the deterioration easily proceeds. Rz is preferably 1000 nm to 4500 nm, more preferably 1500 nm to 4000 nm, and most preferably 2000 nm to 3500 nm. If Rz is less than 500 nm, the effect of suppressing deterioration cannot be imparted. On the other hand, if Rz is larger than 5000 nm, it becomes a starting point of deterioration due to oil and durability is lowered.

  In order to satisfy the above (1), it is necessary to control the surface state of the polyester film. For example, (i) the polyester resin constituting the film contains particles, (ii) imprinting on the film surface Forming projections, (iii) forming voids in the resin constituting the film, and imparting a shape to the film surface by the voids, (iv) mixing a plurality of types of polyester resin compositions to form a film It can adjust by giving a shape to the film surface by this. However, the method for obtaining the polyester film of the present invention is not limited to these.

When used for an electrical insulating material (for example, a compressor motor for an air conditioner), it is used in an environment where the temperature becomes high as the refrigerant gas is compressed and expanded. In recent years, hydrofluorocarbon (HFC) has been widely used as a refrigerant gas for air conditioners instead of hydrochlorofluorocarbon (HCFC) from the environmental aspect. R32 (chemical formula: CH ₂ F ₂ ), which is a refrigerant gas typified by HFC, has a higher operating environment temperature of the compressor than before and a higher operating environment pressure than conventional due to its thermal characteristics. Therefore, oil resistance higher than before is required for use in a film used for an application in contact with R32, particularly for an electrical insulating material of a device in which R32 is used as a refrigerant. Since the polyester film of the present invention is excellent in durability (oil resistance) in an environment in contact with high-temperature oil, it can be suitably used as a film for use in contact with R32. In that case, it is preferable to use the polyester film of this invention as a structure which contact | connects the surface which satisfy | fills (1) to R32.

Moreover, the polyester film of this invention needs to satisfy | fill following (2).
(2) The light intensity reflected in a direction forming 10 ° with respect to the direction perpendicular to the film when irradiated with light perpendicular to the film is 10 or more.

The light intensity reflected in a direction forming 10 ° with respect to the direction perpendicular to the film is obtained by a method described later. In general, when light is irradiated perpendicularly to a film, the reflected light intensity decreases as the angle formed with respect to the direction perpendicular to the form increases. Visual inspection after loading a film as a slot liner or wedge in a motor slot is generally performed at an angle of 10 ° or less with respect to the direction perpendicular to the film when light is irradiated perpendicularly to the film. Is called.
Therefore, when the visual inspection is performed, the light intensity that is reflected most decreases, and the higher the light intensity that reflects in the direction perpendicular to the film at 10 °, the more the film is loaded into the motor slot as a slot liner or wedge. In the visual inspection after this, it is possible to reduce oversight of loading mistakes. The light intensity is preferably 20 or more, and more preferably 30 or more. On the other hand, when the light intensity exceeds 100, the glare of the film becomes high, and the visibility of the film in the back may be lowered by the reflected light of the front film.

  In order to satisfy the above (2), it is necessary to control the surface state of the polyester film. For example, (I) the surface shape of the film is set to a specific shape, (II) particles deposited on the surface of the film The amount and the particle size can be adjusted within a specific range. Regarding (I), the greater the irregularities on the surface of the film and the greater the number of irregularities, the more light is scattered, so the intensity of light reflected in a direction that forms 10 ° with respect to the direction perpendicular to the film increases. As for (II), the more the amount of particles deposited on the surface of the film and the larger the particle size of the particles deposited on the surface of the film, the more the light scatters. The intensity of the reflected light in the direction of forming increases. As a method of controlling (I), for example, the polyester resin constituting the surface layer contains particles, the protrusions are formed on the surface layer of the film by imprinting, and voids are formed in the resin constituting the film. It can be adjusted by imparting a shape to the film surface by the gap, or imparting a shape to the film surface by mixing a plurality of types of polyester resin compositions and forming a film. As a method of controlling (II), it can be adjusted by adjusting the amount and particle size of particles contained in the polyester resin constituting the film. However, the method for obtaining the polyester film of the present invention is not limited to these.

  In the polyester film of the present invention, the polyester resin composition constituting the film contains particles, and the content thereof is preferably 0.1% by weight or more and 10% by weight or less based on the entire polyester resin composition. . If the particle content is less than 0.1% by weight, the formation of surface protrusions may be insufficient. If the particle content is greater than 10% by weight, the surface area may increase and durability may decrease. A more preferable range is 2 wt% or more and 5 wt% or less.

  Examples of the type of particles include inorganic particles and organic particles. Examples of the inorganic particles include clay, mica, titanium oxide, calcium carbonate, carion, talc, wet silica, dry silica, colloidal silica, calcium phosphate, barium sulfate, alumina and zirconia, and aluminosilicate particles. Examples of the organic particles include particles containing acrylic acid, styrene resin, thermosetting resin, crosslinked silicone resin particles, imide compound, and the like as constituent components. Particles (so-called internal particles) that are precipitated by a catalyst or the like added during the polyester polymerization reaction are also preferably used. Among them, the crosslinked silicone resin particles are preferable because they have high oil repellency, and when they are deposited on the surface of the polyester film, the effect of suppressing deterioration by the oil is great. In addition, by dispersing the crosslinked silicone resin particles in the polyester resin composition constituting the film, the surface of the particles is acid-modified in a high-temperature test in the air and reacts with the polyester to cause fusion at the interface, resulting in deterioration of strength. In order to suppress, it is preferable also from a viewpoint of heat resistance improvement. The term “crosslinked silicone resin particles” as used herein refers to those in which the proportion of dimethylpolysiloxane obtained by the method described later exceeds 90 mol% among the components constituting the organic particles. The crosslinked silicone resin particles preferably contain 95 mol% or more of dimethylpolysiloxane in order to improve the oil repellent property, and more preferably contain 98 mol% or more.

  In addition, the above-mentioned particles preferably have a particle size of 0.5 μm or more and 10 μm or less determined by a method described later in order to control the surface shape, and more preferably 0.8 μm or more and 8 μm or less. . In addition, when the polyester film of this invention is a laminated polyester film of 3 layers or more, it is preferable that said particle | grains contained in the polyester resin composition which comprises a surface layer are 0.5 micrometer or more and 10 micrometers or less.

  Moreover, when the polyester film of this invention is a laminated polyester film of 3 or more layers, content of the said particle | grains of the polyester resin composition which comprises a surface layer is 0.00 with respect to the whole polyester resin composition which comprises a surface layer. 2% by weight or more and 9% by weight or less, and the content of the particles of the polyester resin composition constituting the layer not having the surface layer is 0 with respect to the entire polyester resin composition constituting the layer not having the surface layer. It is preferably 2% by weight or more and 5% by weight or less. By making the quantity of the particle | grains contained in each layer into the said range, film forming property can be made favorable, making oil resistance favorable.

  The polyester film of the present invention preferably has two or more layers.

By making the polyester film into two or more layers, different properties can be imparted to each layer. Preferably, there are three or more layers.
When the polyester film of the present invention is a laminated polyester film composed of two or more layers, the melting point of the polyester resin constituting the layer (A layer) having a surface satisfying the above (1) is preferably 255 ° C. or higher. . The melting point of the polyester resin constituting the A layer is set to 255 ° C. or more to prevent thermal deterioration of the resin of the A layer in a high temperature oil environment, and in addition, the resin constituting the layer (B layer) in contact with the A layer Since deterioration can also be suppressed, it is preferable. A more preferable range is 260 ° C. or higher.

  Moreover, when the polyester film of this invention is a laminated polyester film which consists of two or more layers, it is preferable that melting | fusing point of the polyester resin which comprises the layer (B layer) which contact | connects the said A layer is 260 degrees C or less. By setting the melting point of the polyester resin constituting the B layer to 260 ° C. or less, the rigidity of the film is reduced, the film-forming property is improved, and it is difficult to break during processing of the film, which is preferable. A more preferable range is 255 ° C. or less.

  When the polyester film of the present invention is placed at 200 ° C. and 0% RH, the time required for the strength retention to be 50% or less is preferably 200 hours or more. When the polyester film is placed at 200 ° C. and 0% RH, the time required for the strength retention to be 50% or less is 200 hours or more, thereby suppressing deterioration due to oxygen in the air. This is preferable because durability when used in an environment (for example, an insulating member of a motor) in an environment in which oil and oxygen in the air coexist is improved. More preferably, it is 300 hours or more, and the most preferable range is 450 hours or more.

  Next, although an example is given and demonstrated about the manufacturing method of the polyester film of this invention, this invention is limited to only the thing obtained by this example, and is not interpreted.

  As a method for obtaining the polyester used in the present invention, a conventional polymerization method can be employed. For example, after a dicarboxylic acid component such as terephthalic acid or an ester-forming derivative thereof and a diol component such as ethylene glycol or an ester-forming derivative thereof are transesterified or esterified by a known method, a melt polymerization reaction is performed. Can be obtained by doing. If necessary, the polyester obtained by the melt polymerization reaction may be subjected to a solid phase polymerization reaction at a temperature lower than the melting point of the polyester.

  As a method for incorporating particles into the polyester resin composition constituting the polyester film of the present invention, a conventionally known method can be used at any stage of producing the polyester film. For example, a slurry of particles dispersed in ethylene glycol or water and a polyester raw material may be mixed to perform an esterification reaction or transesterification reaction. After the esterification or transesterification reaction is completed, the slurry is dispersed in ethylene glycol or water. You may add the slurry of the made particle. Moreover, you may melt-knead the polyester raw material and particle | grains which comprise a polyester film using a melt-kneader. Among these, a means for melting and kneading the polyester raw material and particles constituting the polyester film is preferable. A master batch method is also preferably used in which a master batch is prepared by previously melting and kneading particles at a high concentration in the same polyester as the polyester constituting the polyester film, and diluted as necessary.

  In general, the organic particles are aggregated with each other, making it difficult to uniformly disperse them in the film. Therefore, when using organic particles as particles, a master batch in which organic particles are previously melt-kneaded is prepared, and further, the master batch is used to melt and knead the polyester with the polyester to form the organic particles. This is preferable because it can be dispersed more uniformly. Further, it is preferable that the organic particles are more uniformly dispersed in the film, so that not only the film forming property is improved but also the film performance such as heat resistance, moist heat resistance and workability is improved.

  The polyester film of the present invention can be obtained by a conventionally known production method, but is preferable because Ra and Rz can be easily within the above ranges by producing the stretching and heat treatment steps under the following conditions.

  The polyester film of this invention can use the method (melt cast method) which heat-melts the raw material dried as needed in an extruder, and extrudes it on the cast drum cooled from the nozzle | cap | die, and processes it into a sheet form. As another method, the raw material is dissolved in a solvent, and the solution is extruded from a die onto a support such as a cast drum or an endless belt to form a film, and then the solvent is dried and removed from the film layer to form a sheet. A method (solution casting method) or the like can also be used.

  When two or more layers of the laminated polyester film are produced by the melt casting method, the raw material of each layer is melted by using an extruder for each layer constituting the laminated polyester film, and these are merged between the extrusion device and the die. A method of laminating in a molten state with an apparatus, guiding to a die, and extruding the die onto a cast drum to process it into a sheet is preferably used. The laminated sheet is adhered and cooled and solidified by static electricity on a drum cooled to a surface temperature of 10 ° C. or higher and 40 ° C. or lower to produce an unstretched sheet, or the unstretched sheet is further biaxially stretched. A polyester film can be obtained.

  When performing melt extrusion in an extruder, it is better that the time from melting in a nitrogen atmosphere to supplying chips to the extruder and extruding with a die is as short as possible. As a guideline, it is 30 minutes or less, more preferably 15 minutes. Hereinafter, more preferably 5 minutes or less, from the viewpoint of suppressing the increase in the amount of terminal carboxyl groups, and when using a plurality of types of polyester raw material, the polyester is copolymerized by a transesterification reaction in the extruder. It is preferable from the viewpoint of suppression. The amount of the terminal carboxyl group of the resin constituting the polyester film of the present invention is 15 eq. / T (equivalent / t) or less is preferable. The temperature of the extruder at the time of melt extrusion with an extruder is from the viewpoint of suppressing an increase in the amount of terminal carboxyl groups, and when multiple types of polyester raw materials are used, the polyester is copolymerized by a transesterification reaction in the extruder. From the viewpoint of suppressing this, it is preferably less than 300 ° C, more preferably less than 290 ° C.

The obtained unstretched sheet is biaxially stretched under the condition (i).
(I) At a temperature T1n satisfying the following expression (a), the film is biaxially stretched in an area magnification of 6 times or more in the longitudinal direction (MD) and the width direction (TD) of the film.
(A) Tg ≦ T1n ≦ Tg + 30 ° C.
Tg: Glass transition temperature (° C.) of polyester resin as a main constituent
As a method of biaxial stretching, in addition to a sequential biaxial stretching method in which stretching in the longitudinal direction (MD) of the film and stretching in the width direction of the film (direction perpendicular to the longitudinal direction of the film, TD) is performed, the longitudinal direction Examples thereof include a simultaneous biaxial stretching method in which stretching in the direction and the width direction is simultaneously performed.

  When the stretching temperature (T1n) is Tg or less, stretching cannot be performed. Moreover, when T1n is in the above range, it becomes possible to impart orientation to the resin constituting the polyester film.

  Next, in order to complete the crystal orientation of the obtained biaxially stretched film and to impart flatness and dimensional stability, it is 30 seconds or more at a temperature of Tg or more and less than the melting point of the main constituent polyester resin. The polyester film of the present invention is obtained by performing a heat treatment for 2 seconds or less, uniformly cooling, and then cooling to room temperature.

  The film obtained by the present invention has excellent visibility, and even when immersed in high-temperature oil, since the deterioration of physical properties is suppressed, the operating environment temperature of the compressor using HFC (R32) or the like as a refrigerant is low. It can be suitably used for electric insulating members of motors that are hotter than before, particularly compressor motors for air conditioners.

[Characteristic evaluation method]
A. Surface roughness (Ra), maximum height roughness (Rz)
The surface morphology of the polyester film is measured under the following conditions in accordance with JIS-B0601 (1994) using a high-definition fine shape measuring instrument (three-dimensional surface roughness meter) of the stylus method.
・ Measuring device: 3D fine shape measuring instrument (model ET-4000A), manufactured by Kosaka Laboratory Ltd./Analyzing equipment: 3D surface roughness analysis system (model TDA-31)
-Stylus: Tip radius 0.5 μm R, diameter 2 μm, made of diamond • Needle pressure: 100 μN
・ Measurement direction: film longitudinal direction and film width direction average after each measurement ・ X measurement length: 1.0 mm
-X feed speed: 0.1 mm / s (measurement speed)
・ Y feed pitch: 5μm (measurement interval)
-Number of Y lines: 81 (measured number)
・ Z magnification: 2000 times (vertical magnification)
・ Low frequency cut-off: 0.20mm (swell cut-off value)
High frequency cut-off: R + Wmm (roughness cut-off value) R + W means not cut off.
-Filter method: Gaussian space type-Leveling: Available (tilt correction)
- reference area: ^1mm 2.

B. Light intensity The intensity of light received by the light receiver at a light receiving angle of 10 ° when measured under the following conditions using a variable angle photometer (Model GP-200) manufactured by Murakami Color Research Laboratory. On the other hand, when the light was irradiated vertically, the light intensity was reflected in a direction forming 10 ° with respect to the direction perpendicular to the film.
・ Light source: Halogen lamp 12V50W
・ Receiver: Side-on photomultiplier tube R6355
・ Measurement mode: Reflection ・ Filter: None ・ Flux diaphragm: 3.0
・ Light receiving aperture: 1.0
-Incident angle: 0 °
・ Sample tilt angle: 0 °
・ Reception start angle: 0 °
・ Reception angle: 90 °
・ Sensitivity: 950
・ HIGH VOLT: 498V
・ Data interval: 0.1 °
Moreover, visibility was evaluated from the obtained light intensity.
(Visibility)
When the light intensity is 30 or more: A
When the light intensity is 20 or more and less than 30: B
When the light intensity is 10 or more and less than 20: C
When the light intensity is less than 10: D
A to C are good, and A is the best among them.

C. Particle content 1 g of polymer pellets or film was put into 200 ml of 1N-KOH methanol solution and heated to reflux to dissolve the polymer. 200 ml of water was added to the solution after dissolution, and the liquid was then centrifuged to sediment the inert particles, and the supernatant was removed. Water was further added to the particles, and washing and centrifugation were repeated twice. The particles thus obtained were filtered and dried with a filter paper (filter) through which particles smaller than 2 μm passed, and the content of the particles was calculated by measuring the mass.

D. Particle size The surface of the film is etched using a 1N-KOH methanol solution to expose the particles, and a 100-field photograph is taken at a measurement magnification of 10,000 using a scanning electron microscope (SEM). The area of each particle on the photograph was measured by an image analyzer, and the diameter of a circle having an area equal to the area was calculated to obtain an equivalent circle diameter. For each particle, the equivalent circular diameter was calculated and used as the particle size of those particles.

E. Composition ratio of dimethylpolysiloxane (mol%)
The particles separated by the method described in C above are subjected to a ²⁹ Si-NMR spectrum and a ¹³ C-NMR spectrum by a DD method (dipole decoupling method) using a solid nuclear magnetic resonance measuring apparatus (model number CMX-300) manufactured by Chemagnetics. taking measurement. From the ²⁹ Si, ¹³ C peak area of dimethylpolysiloxane, the proportion of the dimethylpolysiloxane in the particles is calculated and used as the constituent proportion (mol%) of dimethylpolysiloxane.

F. Melting point (Tm)
In accordance with JIS K7122 (1999), a differential scanning calorimeter “Robot DSC-RDC220” manufactured by Seiko Denshi Kogyo Co., Ltd. was used, and a disk session “SSC / 5200” was used for data analysis. Perform the measurement.

  5 mg of a sample is weighed in a sample pan, and the sample is heated from 25 ° C. to 300 ° C. at a heating rate of 20 ° C./min (1stRUN), held in that state for 5 minutes, and then rapidly cooled to 25 ° C. or lower. Immediately thereafter, the temperature is raised again from 25 ° C. to 300 ° C. at a rate of temperature increase of 20 ° C./min to obtain a 2ndRUN differential scanning calorimetry chart (vertical axis is thermal energy and horizontal axis is temperature). In the differential scanning calorimetry chart of 2ndRun, the temperature of the peak top at the crystal melting peak, which is the endothermic peak, is obtained, and this is defined as Tm (° C.). When two or more crystal melting peaks are observed, the temperature of the peak top having the lowest temperature is defined as Tm (° C.).

G. Oil resistance Films were cut into 1cm x 20cm sizes with long sides parallel to the longitudinal and width directions of the film, respectively. Based on ASTM-D882 (1997), 5cm between chucks, pulling speed 300mm / Measure the breaking strength when pulled in minutes. The number of samples is n = 5, and after measuring in the longitudinal direction and the width direction of the film, the average value thereof is obtained, and this is set as the breaking strength E0 of the film.
Next, the film cut out in the same manner is immersed in a commercially available polyvinyl ether oil (“Dafney Hermetic Oil FV68S” manufactured by Idemitsu Kosan Co., Ltd.), and then suspended in a gear oven under the condition of 180 ° C. and 0% RH. And after 1 hour of heat treatment, it is immersed again in the polyvinyl ether oil. As described above, the film is immersed in oil once per hour in 180 ° C. and 0% RH treatment. Thereafter, the oil on the surface is removed and the breaking strength is measured. In addition, it is set as n = 5 and it measures about each of the longitudinal direction of a film, and the width direction, and let the average value be breaking strength E1. Using the obtained breaking strengths E0 and E1, the strength retention is calculated by the following equation. The treatment time was changed by 1 hour, and the time required for the strength retention to be 50% or less was determined.

Strength retention (%) = E1 / E0 × 100
From the time required for the obtained strength retention to be 50% or less, the oil resistance of the film was determined as follows.
When the time required for the strength retention to be 50% or less is 60 hours or more: A
When the time required for the strength retention to be 50% or less is 48 to 60 hours: B
When the time required for the strength retention to be 50% or less is 36 hours or more and less than 48 hours: C
When the time required for the strength retention to be 50% or less is less than 36 hours: D
A to C are good, and A is the best among them.

H. Heat resistance [Heat resistance strength half-life]
The film is cut into a size of 1 cm × 20 cm so that the long side is parallel to the longitudinal direction and the width direction of the film, respectively, and according to ASTM-D882 (1997), the chuck is 5 cm and the pulling speed is 300 mm / min. Measure the breaking strength when pulled. The number of samples is n = 5, and after measuring in the longitudinal direction and the width direction of the film, the average value thereof is obtained, and this is set as the breaking strength E0 of the film.
Next, the film cut in the same manner is subjected to a dry heat treatment in a gear oven manufactured by Tabai Espec Co., Ltd. under a high temperature condition of a temperature of 200 ° C. and a relative humidity of 0% RH, and then the breaking strength is measured. In addition, it is set as n = 5 and it measures about each of the longitudinal direction of a film, and the width direction, and let the average value be breaking strength E1. Using the obtained breaking strengths E0 and E1, the strength retention is calculated by the following equation. The treatment time was changed by 1 hour, and the time required for the strength retention to be 50% or less was determined.

Strength retention (%) = E1 / E0 × 100
From the time required for the obtained strength retention to be 50% or less, the heat resistance of the film was determined as follows.
When the time required for the strength retention to be 50% or less is 450 hours or more: A
When the time required for the strength retention to be 50% or less is 300 hours or more and less than 450 hours: B
When the time required for the strength retention to be 50% or less is 200 hours or more and less than 300 hours: C
When the time required for the strength retention to be 50% or less is less than 200 hours: D
A to C are good, and A is the best among them.

I. Workability A test is performed based on JIS P-8115 (1994). The film is cut out to 5 mm × 100 mm so that the direction to be measured becomes the long side, using a folding test machine manufactured by Toyo Seiki Co., Ltd., tension 9.8 N / mm 2, clamp R 0.38 mm, folding angle 135 ° The test is performed at a rotational speed of 175 cpm. A test is performed at n5 in each of the width direction and the longitudinal direction of the laminated film, and the number of times until the film breaks is measured. The bending strength FE is calculated from the average value N by the following formula (c), and the workability is evaluated.
(C) FE = logN
FE <4.1: Workability x
4.1 ≦ FE ≦ 4.5: Workability ○
4.5 <FE: Workability x
J. et al. Haze Three points (three pieces) of a square film sample having a side of 5 cm are prepared. The sample is then allowed to stand for 40 hours in a normal state (23 ° C., relative humidity 50%). Each sample is carried out by using a turbidimeter “NDH5000” manufactured by Nippon Denshoku Industries Co., Ltd., in accordance with JIS “How to Determine Haze of Transparent Material” (K7136 2000 version). The haze value of each of the three points (three pieces) is averaged to obtain the haze value of the film.

  In the above evaluation, when the longitudinal direction and the width direction of the film are not known, the direction having the maximum refractive index in the film is regarded as the longitudinal direction, and the direction perpendicular to the longitudinal direction is regarded as the width direction. In addition, the direction of the maximum refractive index in the film may be obtained by measuring the refractive index in all directions of the film with an Abbe refractometer, for example, by using a phase difference measuring device (birefringence measuring device) or the like. You may obtain | require by determining an axial direction.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not necessarily limited to these.

[Production of PET]
Polymerization was carried out from terephthalic acid and ethylene glycol by a conventional method using antimony trioxide as a catalyst to obtain PET-α. The obtained PET-α was solid-phase polymerized by a conventional method to obtain PET.

[Manufacture of PEN]
A transesterification reaction was carried out from dimethyl 2,6-naphthalenedicarboxylate and ethylene glycol using manganese acetate as a catalyst. After the transesterification reaction, PEN was obtained by a conventional method using antimony trioxide as a catalyst.

[Production of polycyclohexylene dimethylene terephthalate (PCHT)]
A transesterification reaction was carried out from dimethyl terephthalate and 1,4-cyclohexanedimethanol using manganese acetate as a catalyst. After the transesterification reaction, PCHT was obtained by a conventional method using antimony trioxide as a catalyst.

[Production of polybutylene terephthalate (PBT)]
A transesterification reaction was carried out from dimethyl terephthalate and 1,4-butanediol using manganese acetate as a catalyst. After the transesterification reaction, PBT was obtained by a conventional method using antimony trioxide as a catalyst.

[Production of particle master batch of polyester resin composition]
80 parts by weight of the polyester resin and 20 parts by weight of the particles were put into an vented extruder and melt-kneaded in the extruder at 280 ° C. to prepare a polyester composition particle master batch.

(Examples 1-6)
As the resin constituting the A layer, the resin having the physical properties shown in the table and the master batch of particles having the physical properties shown in the table were blended so as to have the addition amount shown in the table, followed by vacuum drying at 180 ° C. for 2 hours. It put into the post-extruder. The raw material was melted in an extruder and extruded into a casting drum to produce a sheet. Subsequently, the sheet is preheated with a heated roll group, and then stretched at a stretching ratio shown in the table in the longitudinal direction (MD direction) at a temperature of 95 ° C., and then cooled with a roll group at a temperature of 25 ° C. to be uniaxial. A stretched film was obtained. The resulting uniaxially stretched film was stretched at a stretching ratio shown in the table in the width direction (TD direction) perpendicular to the longitudinal direction in a heating zone at a temperature of 110 ° C. in the tenter while holding both ends with clips. Subsequently, a heat treatment was performed for 10 seconds at a temperature of 220 ° C. in a heat treatment zone in the tenter, and a relaxation treatment was further performed in the 4% width direction at a temperature of 220 ° C. Next, the film was gradually cooled in the cooling zone and wound up to obtain a laminated polyester film having a lamination ratio and thickness shown in the table. Each characteristic of the obtained film is shown in the table. The film was found to be excellent in oil resistance and visibility.

(Examples 7 to 15)
As a resin constituting the A layer, PEN, PET, and PBT having physical properties shown in the table and a master batch of particles having physical properties shown in the table are blended so as to have an addition amount described in the table, and 2 at 180 ° C. After vacuum drying for a time, it was put into the extruder 1. Further, as a resin constituting the B layer, PET having the physical properties shown in the table and a master batch of particles having the physical properties shown in the table were blended, vacuum-dried at 180 ° C. for 2 hours, and then charged into the extruder 2. The respective raw materials were melted in an extruder, merged with a merging apparatus, extruded into a casting drum shape, and a laminated sheet having a two-layer structure was produced. A two-layer laminated film was obtained in the same manner as in Examples 1 to 6 except for the above steps. Each characteristic of the obtained film is shown in the table. The film was found to be excellent in oil resistance and visibility. In addition, Ra, Rz, and light intensity evaluated the A layer side.

(Examples 16 to 36)
As a resin constituting the A layer, PEN and PET having physical properties shown in the table and a master batch of particles having physical properties shown in the table are blended so as to have the addition amount shown in the table, and vacuumed at 180 ° C. for 2 hours. After drying, it was put into the extruder 1. Further, as a resin constituting the B layer, PET having the physical properties shown in the table and a master batch of particles having the physical properties shown in the table were blended, vacuum-dried at 180 ° C. for 2 hours, and then charged into the extruder 2. Each raw material was melted in an extruder, and the resin charged into the extruder 1 was merged by a merger so as to be both surface layers of the film, and extruded into a casting drum shape to produce a laminated sheet having a three-layer structure. A three-layer laminated film was obtained in the same manner as in Examples 1 to 6 except for the above steps. Each characteristic of the obtained film is shown in the table. The film was found to be excellent in oil resistance and visibility.

(Examples 37 to 39)
A three-layer laminated film was obtained by the same method as in Examples 16 to 36, and then molded by an imprint apparatus using a mold having a surface shape shown in the table. Each characteristic of the obtained film is shown in the table. The film was found to be excellent in oil resistance and visibility.

(Examples 40 and 41)
A three-layer laminated film was obtained in the same manner as in Examples 16 to 36 except that the resin constituting the A layer was PCHT instead of PET. Each characteristic of the obtained film is shown in the table. The film was found to be excellent in oil resistance and visibility.

(Example 42)
After obtaining a three-layer laminated film containing no particles in the same manner as in Examples 16 to 36, the film surface was coated with particles having the physical properties described in the table so as to have the particle concentrations described in the table, and the coating layer A film containing particles was obtained. Each characteristic of the obtained film is shown in the table. The film was found to be excellent in oil resistance and visibility.

(Comparative Examples 1 and 2)
A three-layer laminated film was obtained in the same manner as in Examples 16 to 36. The physical properties of the film are shown in the table. Since Ra is outside the range of 50 nm or more and 400 nm or less, the film was inferior in oil resistance.

(Comparative Examples 3 and 4)
A three-layer laminated film was obtained in the same manner as in Examples 16 to 36. The physical properties of the film are shown in the table. Since Rz was outside the range of 500 nm or more and 5000 nm or less, the film was inferior in oil resistance.

(Comparative Example 5)
A three-layer laminated film was obtained in the same manner as in Examples 16 to 36. The physical properties of the film are shown in the table. Since the particle size of the contained particles was small and the surface unevenness was insufficient, the light intensity was less than 10 and the film was inferior in visibility.

The polyester film of the present invention can be suitably used as an electric insulating member of a motor because deterioration of physical properties is suppressed in high-temperature oil and it is easy to confirm a loading error even in a visual inspection after loading in a motor slot.

a: Sample stage b: Polyester film measurement sample c: Light source d: Light beam incident direction e: Light receiver f: Direction that forms 10 ° with respect to the direction perpendicular to the film

Claims (10)

A polyester film satisfying (1) and (2) below.
(1) At least one surface roughness Ra is 50 nm or more and 400 nm or less, and Rz is 500 nm or more and 5000 nm or less.
(2) The light intensity reflected in the direction forming 10 ° with respect to the direction perpendicular to the film when irradiated with light perpendicular to the film, determined by the following measurement method, is 10 or more.
<Measurement method of light intensity>
Using a variable angle photometer (Model GP-200) manufactured by Murakami Color Research Co., Ltd. The light intensity is reflected in a direction forming 10 ° with respect to the direction perpendicular to the film when light is irradiated perpendicularly to the film.
・ Light source: Halogen lamp 12V50W
・ Receiver: Side-on photomultiplier tube R6355
・ Measurement mode: Reflection ・ Filter: None ・ Flux diaphragm: 3.0
・ Light receiving aperture: 1.0
-Incident angle: 0 °
・ Sample tilt angle: 0 °
・ Reception start angle: 0 °
・ Reception angle: 90 °
・ Sensitivity: 950
・ HIGH VOLT: 498V
・ Data interval: 0.1 ° The polyester film according to claim 1, wherein the polyester resin composition constituting the film contains particles, and the content thereof is 0.1 wt% or more and 10 wt% or less with respect to the entire polyester resin composition. The polyester film according to claim 2, wherein the particles are crosslinked silicone resin particles. The polyester film according to claim 3, wherein the crosslinked silicone resin particles contain 95 mol% or more of dimethylpolysiloxane. The polyester film according to claim 1, which has two or more layers. The polyester film according to claim 5, wherein the polyester resin constituting the layer (A layer) having a surface satisfying (1) has a melting point of 255 ° C. or higher. The polyester film according to claim 6, wherein the polyester resin constituting the layer (B layer) in contact with the A layer has a melting point of 260 ° C. or less. The polyester film according to any one of claims 1 to 7, wherein the time required for the strength retention to be 50% or less when placed under the condition of 200 ° C and 0% RH is 200 hours or more. The polyester film according to claim 1, which is used as an insulating member for a motor. The polyester film according to any one of claims 1 to 8, which is used for applications in contact with R32.

Images