JP7000676B2 - Polyester film - Google Patents

Description

The present invention relates to a polyester film having excellent transparency and light transmittance.

Polyester resins, especially polyethylene terephthalate (hereinafter sometimes abbreviated as PET) and polyethylene 2,6-naphthalenedicarboxylate (hereinafter sometimes abbreviated as PEN) have mechanical properties, thermal properties, chemical resistance, and electrical properties. It has excellent formability and is used for various purposes. The polyester film made from the polyester, especially the biaxially oriented polyester film, is used for solar cell backsheets, electrical insulation materials for water heater motors, hybrid vehicles, etc. due to its excellent mechanical and electrical characteristics. Electrical insulation materials for car air conditioners and drive motors, process papers such as base materials and release films that are laminated with other materials and used during the process, magnetic recording materials, materials for capacitors, packaging It is used as an optical material such as a transparent electrode substrate for flexible displays and organic EL, taking advantage of various industrial materials such as materials and building materials, and excellent transparency.

In recent years, dry film resists (DFRs) using a polyester film as a base material are often used in the manufacture of printed wiring boards, semiconductor packages, flexible substrates and the like. Generally, the DFR has a sandwich structure in which a photosensitive layer (photoresist layer) is sandwiched between a base film made of a polyester film and a protective film (cover film) made of an LDPE film or the like. In order to manufacture a conductor circuit using this DFR, the following operations are generally performed.

That is, the protective film is peeled off from the DFR and laminated with the substrate / conductive substrate layer so that the surface of the exposed resist layer and the surface of the conductive substrate layer such as copper foil on the substrate are in close contact with each other. .. Next, the reticle on which the conductor circuit pattern is baked is placed on a base material made of a polyester film, and the resist layer mainly composed of a photosensitive resin is irradiated with light rays to expose the resist layer. Then, after peeling off the rectyl and the polyester film, the unreacted component in the resist layer is dissolved and removed with a solvent. Then, etching is performed with an acid or the like to dissolve and remove the exposed portion in the conductive base material layer. As a result, the photoreactive portion in the resist layer and the conductive base material layer portion corresponding to this photoreactive portion remain as they are. After that, if the remaining resist layer is removed, a conductor circuit on the substrate will be formed.

Since the conductor circuit is formed by such a method, the polyester film as a support is required to have high light transmittance that can transmit light rays without hindrance.

In particular, in recent years, with the miniaturization and weight reduction of OA equipment and IT equipment, there is a demand for a polyester filler for a dry film resist support which has excellent transparency, low haze, and high resolution.

Patent Document 1 discloses a film whose mechanical properties are controlled in order to suppress distortion in the process of the film which is a DFR support. Patent Document 2 discloses a film that does not use particles.

Japanese Unexamined Patent Publication No. 2008-239743 Japanese Unexamined Patent Publication No. 2016-16543

However, in order to make the conductor circuit finer, it is necessary to suppress light scattering on the film surface, which is a support, in addition to high transparency in order to achieve high resolution. Neither Patent Documents 1 and 2 have been able to solve this problem.

An object of the present invention is to provide a polyester film having excellent transparency and light transmission in view of the background of the prior art. Another object of the present invention is to provide a polyester film having a smooth surface and excellent handleability as a process paper. In particular, defect detection of mold release films and polarizing plates when manufacturing dry film resist (DFR) substrate films that require smoothness on the surface of the film, for example, MultiLayered Ceramics Condensers (MLCCs). It is preferably used as a release film used in the above.

The present invention for solving the above problems is characterized by the following configurations.
(1) A polyester film having a two-layer or three-layer structure, in which the protrusion height of at least one side (A side) of the polyester film is 10 nm or more and the protrusion height is 60 nm or more ( “ M60 / M10”). ] ) Is 0.1 or more and 3.0 or less, and the protrusion height (M60) on both sides of the polyester film is 60 nm or more and the protrusion density (M60) is 300 pieces / mm ² or less .
The layer constituting the layer forming the A surface contains particles, and the content of the particles contained in the layer forming the A surface is 0.05% by weight or more and 0.6% by weight with respect to the A layer. Is below
The particle size of the particles contained in the layer constituting the layer forming the A surface is 300 nm or less, and the particle size is 300 nm or less.
When the thickness of the layer constituting the layer forming the A surface is t (μm) and the largest particle size of the particles contained in the layer forming the A surface is d (μm), t / d is 1 or more. A polyester film of 10 or less .
[How to determine the ratio of protrusion height to protrusions with protrusion height of 10 nm or more to 60 nm or more ( " M60 / M10 " )]
M60; protrusion density with protrusion height of 60 nm or more (pieces / mm ² )
M10; Protrusion density with protrusion height of 10 nm or more (pieces / mm ² )
" M60 / M10 " = M60 / M10 × 100
[II] The polyester film according to [I], which satisfies the following requirements.
(1) When the ratio of the protrusion height of one surface (A side) of the polyester film to the protrusions having a protrusion height of 10 nm or more is 60 nm or more ( “ M60 / M10 ” ) is 0.1 or more and 3.0 or less. There is.
(2) The ratio ( “ M60 / M10 ” ) of the protrusion height of the surface (B side) opposite to the A side of the polyester film to the protrusions having a protrusion height of 10 nm or more is 0 or more and 0. Must be 5 or less .
[III] The polyester film according to [I] or [II], wherein the protrusion density (M10) having a protrusion height of 10 nm or more is 1000 pieces / mm ² or more and less than 8000 pieces / mm ² on both sides of the polyester film.
[IV] The polyester film according to any one of [I] to [III], wherein the amount of particles contained in the polyester film is 0.1% by weight or less with respect to the polyester film.
[V] The polyester film according to any one of [I] to [IV] having a film haze of 1.0% or less.
[VI] The polyester film according to any one of [I] to [V], wherein the polyester film has a COOH terminal group amount of 15 equivalents / t or more and 40 equivalents / t or less.
[VII] The polyester film according to any one of [I] to [VI], wherein the surface resistivity of at least one side of the polyester film is 1.0 × 10 ¹³ Ω / cm ² or less.
[VIII] The polyester film according to any one of [I] to [VII], wherein the arithmetic mean roughness (Ra) of the film surface of the polyester film is 4 nm or less on both sides.
[IX] The polyester film according to any one of [I] to [VIII], wherein the film has a thickness of 15 μm or more and 250 μm or less.
[X] The presence of particles obtained when the layer forming the A plane contains particles, and the volume-based particle size distribution of the particles is measured and plotted with the horizontal axis as the particle size and the vertical axis as the particle abundance ratio. When the particle size of the peak top with the largest particle size in the maximum of the ratio chart is d (μm) and the thickness of the layer forming the A surface is t (μm), t / d is 1 or more and 10 or less. The polyester film according to any one of [II] to [IX].
[XI] The polyester film according to any one of [I] to [X] used as a film for a dry film resist (DFR) substrate.
[XII] The polyester film according to any one of [I] to [X] used as a release film in a laminated ceramic capacitor (MLCC) manufacturing process.
[XIII] The polyester film according to any one of [I] to [X] used as a release film in the defect detection step of the polarizing plate.

According to the present invention, it is possible to provide a film which realizes high transparency and light transmission, has good resistability, and has excellent surface smoothness and handleability.

The present invention will be described in detail below with reference to specific examples.
The polyester referred to in the present invention has a dicarboxylic acid component and a diol component. In addition, in this specification, a constituent component means the minimum unit which can be obtained by hydrolyzing polyester. Examples of the dicarboxylic acid constituents constituting the polyester include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 1,8-naphthalene. Examples thereof include aromatic dicarboxylic acids such as dicarboxylic acid, 4,4'-diphenyldicarboxylic acid, and 4,4'-diphenylether dicarboxylic acid, or ester derivatives thereof.

The diol constituents constituting the polyester include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butanediol. Examples thereof include aliphatic diols such as, cyclohexanedimethanol, alicyclic diols such as spiroglycol, and a series of the above-mentioned diols. Above all, from the viewpoint of mechanical properties and transparency, polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN), and isophthalic acid and naphthalenedicarboxylic acid are copolymerized with a part of the dicarboxylic acid component of PET. As a result, polyester obtained by copolymerizing cyclohexanedimethanol, spiroglycol, or diethylene glycol with a part of the diol component of PET is preferably used.

In the polyester film of the present invention, the ratio (M60 / M10) of the protrusion height of at least one side (A side) of the polyester film to the protrusions having a protrusion height of 10 nm or more is 0.1 or more and 3.0 or less. It is necessary that the height of protrusions on both sides of the polyester film is 60 nm or more and the protrusion density (M60) is 300 pieces / mm ² or less. Here, the method for determining the ratio (M60 / M10) of the protrusion height to the protrusion having a protrusion height of 10 nm or more and the protrusion height of 60 nm or more is as follows.
M60; protrusion density with protrusion height of 60 nm or more (pieces / mm ² )
M10; Protrusion density with protrusion height of 10 nm or more (pieces / mm ² )
(M60 / M10) = M60 / M10 × 100
Generally, the surface of the polyester film has fine irregularities. This unevenness can be imparted by various means, and it is possible to control the transportability of the film and the light scattering property on the film surface by the unevenness on the film surface.

The M60 in the present invention is a protrusion density (pieces / mm ² ) having a protrusion height of 60 nm or more, and represents the number density of large protrusions. When this M60 exceeds 300 pieces / mm ² on both sides of the film, light scattering on the film surface becomes large, and when used as a base material for DFR, it is not possible to expose a fixed shape, resulting in resistability. It is inferior and causes chipping of wiring. M60 is more preferably 200 pieces / mm ² or less. On the other hand, M10 represents the number density of fine protrusions with a protrusion density (pieces / mm ² ) having a protrusion height of 10 nm or more, and M60 / M10 represents the ratio of large protrusions to the fine protrusions on the film surface. be. M60 / M10 is below 0.1 when M10 is high or M60 is low, and M60 / M10 is above 3 when M10 is low or M60 is high. When a wiring pattern is formed using DFR, the base film of DFR is in contact with various surfaces such as a transport roll and the opposite surface of the film. When the M60 / M10 of the film of the present invention is less than 0.1, the contact area on the surface becomes large, so that the film is charged by friction and entrains dust, which affects the wiring formation or the positions where the films stick to each other. Misalignment occurs and wiring misalignment occurs. On the other hand, when M60 / M10 exceeds 3, the film is caught by the large protrusions on the film surface, the position of the film is displaced, and it becomes difficult to form accurate wiring. By setting M60 / M10 in the above range, it is possible to obtain a film having good resistability and excellent handleability by suppressing light scattering on the surface. M60 / M10 is preferably 0.5 or more and 2.5 or less, and more preferably 1.0 or more and 2.3 or less. The value of M10 is preferably 1000 pieces / mm ² or more and less than 8000 pieces / mm ² . When M10 is 1000 pieces / mm ² or less, the film surfaces stick to each other, the coefficient of friction between the film surfaces becomes high, and the position shift is likely to occur. When M10 is 8000 pieces / mm ² or more, light may be scattered on the surface and the light transmittance of the film may be inferior.

In order to control the unevenness of the film surface and keep it within the above range, (a) a method of containing particles in the polyester film, (b) a method of controlling the crystallinity of the polyester film, and (c) stretching of the polyester film. A method of controlling the pressure applied to the film by a stretching roll or a nip roll at the time, and a combination of these methods are preferably used. When the method (a) is used, the particle size of the particles contained in the polyester film, the content of the particles, and the thickness of the layer containing the particles to form a surface are important. In particular, in order for M60 to be 300 pieces / mm ² or less and M60 / M10 to be 0.1 or more and 3 or less, it is important that the particle size of the particles to be added / contained is 300 nm or less. The particle size of the particles referred to here is the maximum value of the chart of the abundance ratio of the particles obtained when the volume-based particle size distribution of the particles is measured and plotted with the horizontal axis as the particle size and the vertical axis as the abundance ratio of the particles. It means the particle size that becomes.

As the particles of the present invention, either inorganic particles or organic particles can be used. Organic particles have a high affinity with polyester, which is an organic compound, and are preferable because voids are less likely to be formed around the particles when added. Inorganic particles have higher hardness than polyester, such as metal rolls during film transport. This is preferable because it can prevent scratches on the film surface. Further, when considering the light transmittance, the refractive index is preferably 1.20 or more and 1.70 or less, and particularly preferably 1.45 or more and 1.59 or less. Generally, the biaxially stretched polyester film has a refractive index in the thickness direction of 1.35 to 1.55. Therefore, when the refractive index of the particles is in this range, the light incident on the film is less likely to be refracted. When the refractive index of the particles is low and less than 1.20, the refractive index of the polyester is high, so that light may be totally reflected at the interface between the polyester and the particles, and the light transmittance is lowered. Specific examples thereof include acrylic acids and styrene-based resins, but in order to control the protrusion diameter and protrusion density of the present invention, single dispersed spherical particles are particularly preferable.

Further, it is preferable that the polyester film of the present invention contains particles having different particle sizes, and by having this configuration, it is possible to simultaneously control M60, which is a large protrusion, and M10, which is a fine protrusion. Therefore, it is very preferable.

When the polyester film of the present invention is obtained by using the method (a), the amount of particles contained in the polyester film is preferably 0.1% by weight or less with respect to the polyester film. When the amount of particles exceeds 0.1% by weight, the light transmitted through the polyester film is scattered by the particles in the film, so that the transparency may decrease.

In order to reduce the amount of particles contained in the polyester film of the present invention to 0.1% by weight or less, it is also a preferred embodiment to use the polyester film of the present invention as a laminated film. That is, a two-layer structure in which the layer forming the A side is laminated on either one side of the polyester film, or a three-layer structure in which the layer forming the A side is arranged on both sides of the polyester film, or the A side is formed. A structure is preferably used in which the layer to be formed is arranged on one side of the polyester film, and a different side (B side) is laminated on the other side.

When the polyester film of the present invention has a laminated structure, the thickness t (μm) of the layer constituting the layer forming the A surface is set, and the particles contained in the layer forming the A surface are most determined by the method described later. When a large particle size is d (μm), t / d is preferably 1 or more and 10 or less. If t / d is less than 1, the particles may fall off the film and the surface may not be formed. When t / d exceeds 10, the particles are buried in the film and the fine protrusions M10 are reduced, so that the M60 / M10 tends to be too large.

When the B surface is provided on the opposite surface of the A surface of the polyester film of the present invention, the M60 / M10 of the B surface is preferably 0 or more and 0.5 or less. By providing a surface having less protrusions larger than the A surface, it is possible to suppress light scattering on the surface of the polyester film. Further, when the film of the present invention is used as a DFR base material, it is preferable to provide a resist layer on the B surface side in order to prevent light from being scattered on the film surface on the side close to the resist layer.

The polyester film of the present invention preferably has a coefficient of static friction between the A side and the B side, which is obtained by the measurement method described later, of 0.35 or less. By setting the coefficient of static friction within the above range, the unwinding and transportability of the polyester film is improved, and the resist layer can be easily formed. The method for setting the coefficient of static friction between the A surface and the B surface within the above range is not particularly limited, but may include setting M60 / M10 within the above range.

The COOH terminal group amount of the polyester film of the present invention is preferably 15 equivalents / t or more and 40 equivalents / t or less. By setting the amount of COOH terminal groups in the above range, the adhesion between the polyester film and the resist layer is good, and the mechanical properties and processability can be improved. Therefore, it is used for dry film resist substrates. It can be particularly preferably used as a film. When the amount of COOH terminal groups is less than 15 equivalents / t, the adhesion between the polyester film and the resist layer may be poor. When the amount of COOH terminal groups exceeds 40 equivalents / t, the polyester may be deteriorated, and the mechanical properties and workability may be inferior.

The surface resistivity of at least one side of the polyester film of the present invention is preferably 1.0 × 10 ¹³ Ω / cm ² or less. By setting the surface resistivity of at least one side to 1.0 × 10 ¹³ Ω / cm ² or less, when the polyester film is wound or stacked on a roll, the polyester film is charged and the films stick to each other to form a pattern. This is preferable because it can prevent the time from shifting. More preferably, the surface resistivity is 1.0 × 10 ¹¹ Ω / cm ² or less. As a method for setting the surface specific resistance in a preferable range, a method of adding a surfactant such as a linear alkylbenzene sulfonate to polyester, a method of adding an ionic liquid consisting of ammonium and imide to polyester, and a method of using a polythiophene-based conductive material as polyester. Examples include a method of coating a film.

The arithmetic mean roughness (Ra) of the film surface of the polyester film of the present invention is preferably 4 nm or less on both sides. When Ra exceeds 4 nm, the transportability and processability are excellent, but the film permeability tends to be inferior due to the rough surface. It is more preferably 3 nm or less.

The thickness of the polyester film of the present invention is preferably 15 μm or more and 250 μm or less. When the thickness of the film exceeds 250 μm, the polyester itself constituting the film also absorbs light, which may deteriorate the exposure property. If the film thickness is less than 15 μm, the handleability and transportability of the film may deteriorate. When the thickness of the polyester film is within the above range, the exposure property, the handleability, and the transportability are good, and the polyester film can be suitably used as a film for a DFR base material.

The polyester film of the present invention preferably has a haze of 1.0% or less. By setting the haze in the above range, the light transmission can be kept high, and the film can be suitably used as a DFR base film.

Since the polyester film of the present invention controls fine irregularities on the film surface, it can be suitably used as a mold release film used in the MLCC manufacturing process. In particular, if M60 / M10 is within the above range in the step of manufacturing the ceramic green sheet on the release film, it is preferable because the unevenness of the film does not cause pinholes or dents due to transfer. If M60 / M10 is small, the transportability in the manufacturing process is poor, which may cause pinholes. If M60 / M10 is large, it may cause a dent.

Since the polyester film of the present invention controls minute abruptness of the film surface, it can be suitably used as a mold release film used in the defect detection step of the polarizing plate. In the defect detection step of the polarizing plate, the defects of the polarizing plate are observed as bright spots. Therefore, if the film used as the release film has irregularities (dents), the depressions are observed as bright spots, and the defects of the polarizing plate are observed. May not be observable. When M60 / M10 is within the above range, it is preferable that there are few coarse protrusions and few dents on the film surface. When M60 / M10 is large, there are many coarse protrusions, and when the film surfaces overlap each other in the film forming process or the like, it may cause a dent on the film surface. When M60 / M10 is small, the film surface may be scratched and observed as a dent in the film forming step or other steps.

Next, a method of forming a film will be described.

When the film of the present invention is melt-formed by the following method, the methods (b) and (c) can be preferably used. That is, by forming fine crystal nuclei in the process of cooling and solidifying from the molten state to obtain a sheet, it becomes possible to form fine protrusions starting from the crystal nuclei in the stretching step. Further, when the stretching step using a roll is adopted in the stretching step, it is also possible to apply pressure to the film surface by the pressure of the nip roll to form fine protrusions.

After the polyester constituting each layer is heated and melted in separate extruders, these are laminated in a molten state by a merging device provided between the extruder and the mouthpiece, then guided to the mouthpiece and extruded from the mouthpiece onto the cast drum. Get an unrolled sheet. When the surface unevenness is controlled by the method (b) described above, the cast drum temperature is preferably 50 ° C. or higher.

Next, the unstretched sheet is subjected to an area magnification of 10.0 times or more and 16.0 times in the longitudinal direction (MD) of the film and the width direction (TD) of the film at a temperature T1n (° C.) satisfying the following formula (i). Biaxial stretching is performed below.
(I) Tg (° C.) ≤ T1n (° C.) ≤ Tg + 40 (° C.)
Tg: Glass transition temperature (° C) of polyester film
As a method of stretching the film in the longitudinal direction, a method using a speed difference in roll feeling is preferably used. At this time, the film is fixed with a nip roll so that the film does not slip. However, when the surface unevenness is controlled by the method (c) described above, the pressure of the nip roll is preferably 0.5 MPa or more.

Next, the biaxially stretched film is heat-fixed at a temperature (Th0 (° C.)) satisfying the following formula (ii) for 1 second or more and 30 seconds or less, slowly cooled uniformly, and then cooled to room temperature. To obtain a polyester film.
(Ii) Tmf-35 (° C.) ≤ Th0 (° C.) ≤ Tmf (° C.)
Tmf: Melting point of film (° C)
By obtaining a biaxially stretched film under the conditions satisfying (ii), it is possible to impart an appropriate orientation to the film and obtain a film having good mechanical properties.

The film of the present invention obtained by the above method has excellent transparency and light transmittance, and also has good handleability and transportability, and can be suitably used for DFR substrate applications.

[Characteristic evaluation method]
A. Film melting point (Tmf) (° C)
The sample was prepared by a method based on JIS K 7121 (1999), using a differential scanning calorimetry device "Robot DSC-RDC220" manufactured by Seiko Electronics Inc., and a disk session "SSC / 5200" for data analysis. Perform the measurement as follows.
The sample is weighed in a sample pan in an amount of 5 mg each, and the sample is heated from 25 ° C. to 320 ° C. at a heating rate of 20 ° C./min (1stRUN). Obtain a 1st RUN differential scanning calorimetry chart (vertical axis is thermal energy, horizontal axis is temperature). The temperature of the peak top at the crystal melting peak, which is the endothermic peak, of the differential scanning calorimetry chart of the 1st Run is obtained, and this is defined as the melting point (° C.). When two or more crystal melting peaks are observed, the temperature of the peak top having the largest peak area is taken as the melting point.

B. Tg (° C) of the resin constituting the film
According to JIS K 7121 (1999), use the differential scanning calorimetry device "Robot DSC-RDC220" manufactured by Seiko Electronics Inc., and the disk session "SSC / 5200" for data analysis, as described below. , Carry out the measurement.

Weigh 5 mg of the sample in a sample pan, heat the sample from 25 ° C. to 300 ° C. at a heating rate of 20 ° C./min (1stRUN), hold it in that state for 5 minutes, and then quench it to 25 ° C. or lower. Immediately thereafter, the temperature is raised again from 25 ° C to 20 ° C / min to 300 ° C for measurement, and the 2ndRUN differential scanning calorimetry chart (vertical axis is thermal energy and horizontal axis is temperature). To get. In the differential scanning calorimetry chart of the 2nd RUN, in the stepped change part of the glass transition, the straight line at the same distance in the vertical axis direction from the extended straight line of each baseline and the curve of the stepped change part of the glass transition are Find from the point of intersection. When two or more glass transition stepped portions are observed, the glass transition temperature is obtained for each, and the average value of these temperatures is taken as the glass transition temperature (Tg) (° C.) of the sample.

C. Film thickness (μm)
The film thickness was measured at any 5 locations with 10 films stacked in accordance with the JIS K7130 (1992) A-2 method using a dial gauge. The average value was divided by 10 to obtain the film thickness.

H. Thickness of each layer of laminated film (μm)
When the film was a laminated film, the thickness of each layer was determined by the following method. A cross section of the film is cut out with a microtome in a direction parallel to the film width direction. The cross section is observed with a scanning electron microscope at a magnification of 5000 times, and the thickness ratio of each laminated layer is determined. The thickness of each layer is calculated from the obtained lamination ratio and the above-mentioned film thickness.

D. COOH terminal group amount (terminal carboxyl group amount)
The amount of COOH terminal groups was measured by the following method according to the method of Maurice. (Reference: MJ Maurice, F. Huizinga, Anal. Chim. Acta, 22 363 (1960))
2 g of the measurement sample (polyester resin (raw material) or the P1 layer of the laminate separated) was dissolved in 50 mL of o-cresol / chloroform (weight ratio 7/3) at a temperature of 80 ° C., and 0.05 N KOH / It was titrated with a methanol solution, the terminal carboxyl group concentration was measured, and the value was shown as equivalent / polyester 1t (eq./t). Phenol red was used as the indicator for titration, and the end point of the titration was the change from yellowish green to pink. If the solution in which the measurement sample is dissolved contains insoluble matter such as inorganic particles, the solution is filtered to measure the weight of the insoluble matter, and the value obtained by subtracting the weight of the insoluble matter from the measurement sample weight is the measurement sample weight. The correction was made.

E. Film-forming property The number of times the film is torn in one hour during film-forming is counted, and those with less than 5 times are evaluated as A, and those with 5 or more times are evaluated as B. A has the best film-forming property, and B has the worst.

F. Particle content in film or in each layer (wt%)
1 g of the sample scraped from the film or each layer is weighed, and the sample is put into 200 ml of a 1N-KOH methanol solution and heated to reflux to dissolve the polymer. 200 ml of water is added to the dissolved solution, and then the liquid is centrifuged to settle the particles and the supernatant liquid is removed. Water is further added to the particles, washing and centrifugation are repeated twice, the obtained particles are dried, and the mass thereof is measured to calculate the particle content (wt%).

G. Particle size (nm)
F. When the volume-based particle size distribution of the particles obtained by the above method is measured and plotted with the horizontal axis as the particle size and the vertical axis as the particle abundance ratio, the maximum value of the particle abundance ratio chart obtained is defined as the particle size. do. When multiple maximum values are observed, each maximum value is used as the particle size of the particles. Microtrack EX150 manufactured by Microtrack Bell Co., Ltd. is used for volume-based particle size distribution measurement.

H. Protrusion height density M10 of 10 nm or more, protrusion height density M60 of 60 nm or more (pieces / mm ² )
Three-dimensional surface roughness is measured under the following conditions using a surf-coder ET-4000A manufactured by Kosaka Laboratory, and then particle analysis (multiple levels) is performed using the built-in analysis software. The measurement conditions are as follows. The slice levels are set at equal intervals of 10 nm, the average diameter and density of each slice level are measured 5 times at different locations, and the average value is used as the value. The sample set is set on the sample table so that the X direction of the visual field measurement is the width direction of the biaxially oriented polyester film. M10 indicates a value obtained by rounding off the tens digit of the value obtained by the measurement.

M60: Protrusion density at slice level of 60 nm (pieces / mm ² )
Protrusion density at M10: 10 nm slice level (pieces / mm ² )
Equipment: "surf-corder ET-4000A" manufactured by Kosaka Research Institute
Analysis software: i-Face model TDA31
Radius of stylus tip: 0.5 μm
Measurement field of view: X direction: 380 μm Pitch: 1 μm
Y direction: 280 μm Pitch: 5 μm
Needle pressure: 50 μN
Measurement speed: 0.1 mm / s
Cutoff value: Low range-0.8mm, High range-None Leveling: Whole area filter: Gaussian filter (2D)
Magnification: 100,000 times Particle analysis (multiple levels) Condition Output content setting: Mountain particle Hysteresis width: 5 nm
Slice level equal spacing: 10 nm
I. Arithmetic Mean Roughness Ra (nm)
The above H. The three-dimensional roughness of the surface is measured 10 times at different locations under the measurement conditions described above, and the average value thereof is taken as the center line surface roughness Ra.

J. Haze (%)
In accordance with JIS-K 7136 (2000), using NDH-5000 manufactured by Nippon Denshoku Industries Co., Ltd., 5 locations are randomly selected from the film and used for measurement, and the average value is calculated and used as haze.

K. Surface resistivity (Ω / cm ² )
After leaving the sample at 25 ° C. and a relative humidity of 65% for 24 hours, the sample is measured at an applied voltage of 100 V using an Advantest digital ultra-high resistance / micro ammeter R8340A in that atmosphere. Five locations are randomly selected from the film and subjected to measurement, and the average value is calculated and used as the surface resistivity.

L. Resistability evaluation The following a. From c. Evaluation is performed by the method of.
a. A negative resist "PMERN-HC600" manufactured by Tokyo Ohka Co., Ltd. is applied on a single-sided mirror-polished 6-inch Si wafer and rotated with a large spinner to prepare a resist layer having a thickness of 7 μm. Next, a preheat treatment is performed for about 20 minutes under a temperature condition of 70 ° C. using a ventilation oven with a nitrogen cycle.
b. The polyester film is layered so as to be in contact with the resist layer, the polyester film is laminated on the resist layer using a rubber roller, and a reticle patterned with chrome metal is placed on the polyester film. Exposure is performed using a linear (ultraviolet ray having a peak at a wavelength of 365 nm) stepper.
c. After peeling the polyester film from the resist layer, the resist layer is placed in a container containing the developer N-A5 and developed for about 1 minute. After that, remove it from the developer and add about 1 with water.
Perform a minute of washing. 30 states of L / S (μm) (Line and Space) = 10/10 μm of the resist pattern created after development were observed using a scanning electron microscope SEM at a magnification of about 800 to 3000, and the pattern was chipped. Evaluate as follows with a certain number.

S; 0 to 3 missing lines A; 4 to 8 missing lines B; 9 to 13 missing lines C; 13 to 15 missing lines D; number of missing lines 16 or more, S has the best resistability, and D has the worst.

M. Ceramic green sheet manufacturability The following d. From f. Evaluation is performed by the method of.
d. A coating solution prepared by adjusting a crosslinked primer layer (trade name BY24-846 manufactured by Dow Corning Silicone Co., Ltd.) to a solid content of 1% by weight is applied / dried on a polyester film, and the coating thickness after drying is 0.1 μm. It is applied with a gravure coater so as to be, and dried and cured at 100 ° C. for 20 seconds. Within 1 hour after that, 100 parts by weight of an addition reaction type silicone resin (trade name: LTC750A manufactured by Toray Dow Corning Silicone Co., Ltd.) and 2 parts by weight of a platinum catalyst (trade name: SRX212 manufactured by Toray Dow Corning Silicone Co., Ltd.) were applied. The coating liquid adjusted to have a solid content of 5% by weight is coated with a gravure coat so that the coating thickness after drying is 0.1 μm, dried and cured at 120 ° C. for 30 seconds, and then wound to obtain a release film.
e. Barium titanate (trade name HPBT-1 manufactured by Fuji Titanium Industry Co., Ltd.) 100 parts by weight, polyvinyl butyral (trade name BL-1 manufactured by Sekisui Chemical Co., Ltd.) 10 parts by weight, dibutyl phthalate 5 parts by weight and toluene-ethanol (Weight ratio 30:30) Glass beads having a number average particle size of 2 mm are added to 60 parts by weight, mixed and dispersed in a jet mill for 20 hours, and then filtered to prepare a paste-like ceramic slurry. The obtained ceramic slurry was subjected to d. On the release film obtained in 1 above, the film is applied with a die coater so that the thickness after drying is 2 μm, dried, and wound to obtain a green sheet.
f. The green sheet wound up above is unwound and visually observed in a state where it is not peeled off from the release film, and the presence or absence of pinholes and the coating state of the sheet surface and edges are confirmed. The area to be observed is 300 mm in width and 500 mm in length. While illuminating the green sheet molded on the release film with a backlight unit of 1000 lux from the back, observe pinholes due to coating omission or dents due to surface transfer on the back of the release film, as shown below. evaluate. A has the best manufacturability and C has the worst.
A: There are no pinholes or dents.
B: There are no pinholes and no more than 3 dents are recognized. C: There are pinholes, 4 or more dents, or both.

N. Number of dent defects (pieces / m ² )
A polyester film is used in a range of 10 m ² (for example, 1 m wide and 10 m long), a spotlight is used as a light source, and reflected light and transmitted light are used to visually inspect the surface of the film, paying attention to bright spots based on light scattering. , Mark the defect with a pen. Further, a method of detecting a deflection disturbance bright spot due to cross Nicol by using a polarized light source is also used. For the marked defects, measure the maximum diameter of the dent with a stereomicroscope, and for dents with a maximum diameter of 3 mm or more, use a stereomicroscope with a Millow-type two-luminous flux interference detector (SMZ-10 manufactured by Nikon) to determine the depth of the dent. The number is measured with a dent having a depth of 0.5 μm or more and a maximum diameter of 3 mm or more as a dent defect. The depth of the dent is obtained by reading the disturbance of the interference fringes obtained at the obtained λ / 2 pitch with a micrometer eyepiece and using the equation (iii). The depth is the maximum depth in the thickness direction from the film surface, and when a bulge is generated around the dent defect, the maximum depth from the top of the bulge to the bottom of the dent is obtained.
(Iii) Depth = λ / 2 × (h / g)
λ: 546 nm
g: Reading value of λ / 2 by the eyepiece
h: Disturbance amount of interference fringes A: Number of dent defects is 5 / m ² or less B: Number of dent defects is 6 / m ² or more and 10 pcs m ² or less C: Number of dent defects is 11 / m ² or more In the above measurement, when the longitudinal direction and the width direction of the film to be measured are not known, the direction having the maximum refractive index in the film is regarded as the longitudinal direction, and the direction orthogonal to the longitudinal direction is regarded as the width direction. Further, 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 a refractive index meter, and the slow axis direction may be determined by a phase difference measuring device (birefringence measuring device) or the like. It may be obtained by deciding.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not necessarily limited thereto.

[Production of PET-A] Polymerization was carried out from terephthalic acid and ethylene glycol by a conventional method using antimony trioxide as a catalyst to obtain melt-polymerized PET. The obtained melt-polymerized PET has a glass transition temperature of 81 ° C., a melting point of 255 ° C., an intrinsic viscosity of 0.62, and an amount of terminal carboxyl groups of 20 eq. It was / t.

[Production of PET-B] In the polymerization of PET-A, sodium dodecylbenzene sulfonate was added so as to be 1.0 wt% based on the total weight of PET to obtain PET-B. The glass transition temperature is 81 ° C, the melting point is 255 ° C, the intrinsic viscosity is 0.62, and the amount of terminal carboxyl groups is 20 eq. It was / t.

[Production of PET-C] In the polymerization of PET-A, PET-C was obtained by adding sodium dodecylbenzene sulfonate to 2.5 wt% based on the total weight of PET. The glass transition temperature is 81 ° C, the melting point is 255 ° C, the intrinsic viscosity is 0.62, and the amount of terminal carboxyl groups is 20 eq. It was / t.

[Preparation of MB-A] 20 parts by mass (crosslinked polystyrene particles) of 10% by weight water slurry of PET-A 80 parts by weight and crosslinked polystyrene particles (styrene / acrylate copolymer, refractive index 1.60) having a particle size of 0.10 μm. 2 parts by weight) was supplied, and the vent holes were maintained at a reduced pressure of 1 kPa or less to remove water, and MB containing 2% by weight of crosslinked polystyrene particles was obtained. The glass transition temperature is 81 ° C, the melting point is 255 ° C, the intrinsic viscosity is 0.60, and the amount of terminal carboxyl groups is 22eq. It was / t.

[Preparation of MB-B] 20 parts by weight (crosslinked polystyrene particles) of 10% by weight water slurry of PET-A 80 parts by weight and crosslinked polystyrene particles (styrene / acrylate copolymer, refractive index 1.60) having a particle size of 0.20 μm. 2 parts by weight) was supplied, the vent holes were maintained at a reduced pressure of 1 kPa or less to remove water, and MB containing 2% by weight of copolymer polystyrene particles was obtained. The glass transition temperature is 81 ° C, the melting point is 255 ° C, the intrinsic viscosity is 0.60, and the amount of terminal carboxyl groups is 22eq. It was / t.

[Preparation of MB-C] 20 parts by weight (crosslinked polystyrene particles) of 10% by weight water slurry of PET-A 80 parts by weight and crosslinked polystyrene particles (styrene / acrylate copolymer, refractive index 1.60) having a particle size of 0.30 μm. 2 parts by weight) was supplied, and the vent holes were maintained at a reduced pressure of 1 kPa or less to remove water, and MB containing 2% by weight of crosslinked polystyrene particles was obtained. The glass transition temperature is 81 ° C, the melting point is 255 ° C, the intrinsic viscosity is 0.60, and the amount of terminal carboxyl groups is 22eq. It was / t.

[Preparation of MB-D] 20 parts by weight (crosslinked polystyrene particles) of 10% by weight water slurry of PET-A 80 parts by weight and crosslinked polystyrene particles (styrene / acrylate copolymer, refractive index 1.60) having a particle size of 0.40 μm. 2 parts by weight) was supplied, and the vent holes were maintained at a reduced pressure of 1 kPa or less to remove water, and MB containing 2% by weight of crosslinked polystyrene particles was obtained. The glass transition temperature is 81 ° C, the melting point is 255 ° C, the intrinsic viscosity is 0.60, and the amount of terminal carboxyl groups is 22eq. It was / t.

[Preparation of MB-E] 20 parts by weight (2 parts by weight as alumina particles) of 10% by weight water slurry of PET-A 98 weight and 0.10 μm particle size alumina particles (refraction coefficient 1.76) was supplied and vented. MB containing 2% by weight of alumina particles was obtained while keeping the pores at a reduced pressure of 1 kPa or less. The glass transition temperature is 81 ° C, the melting point is 255 ° C, the intrinsic viscosity is 0.60, and the amount of terminal carboxyl groups is 22eq. It was / t.

[Preparation of MB-F] 20 parts by weight (2 parts by weight as colloidal silica particles) of 10% by weight water slurry of PET-A 80 parts by weight and colloidal silica particles (refractive index 1.44) having a particle size of 0.12 μm is supplied. Then, the vent holes were maintained at a reduced pressure of 1 kPa or less to remove water, and MB containing 2% by weight of colloidal silica particles was obtained. The glass transition temperature is 81 ° C, the melting point is 255 ° C, the intrinsic viscosity is 0.60, and the amount of terminal carboxyl groups is 22eq. It was / t.

[Preparation of MB-G] 20 parts by weight (2 parts by weight as colloidal silica particles) of 10% by weight water slurry of PET-A 80 parts by weight and colloidal silica particles (refractive index 1.44) having a particle size of 0.20 μm is supplied. Then, the vent holes were maintained at a reduced pressure of 1 kPa or less to remove water, and MB containing 2% by weight of colloidal silica particles was obtained. The glass transition temperature is 81 ° C, the melting point is 255 ° C, the intrinsic viscosity is 0.60, and the amount of terminal carboxyl groups is 22eq. It was / t.

[Preparation of MB-H] 20 parts by weight (2 parts by weight as colloidal silica particles) of 10% by weight water slurry of PET-A 80 parts by weight and colloidal silica particles (refractive index 1.44) having a particle size of 0.30 μm is supplied. Then, the vent holes were maintained at a reduced pressure of 1 kPa or less to remove water, and MB containing 2% by weight of colloidal silica particles was obtained. The glass transition temperature is 81 ° C, the melting point is 255 ° C, the intrinsic viscosity is 0.60, and the amount of terminal carboxyl groups is 22eq. It was / t.

[Preparation of MB-I] 20 parts by weight (2 parts by weight of acrylic particles) of 10% by weight water slurry of PET-A 80 parts by weight and acrylic particles (acrylate copolymer, refractive index 1.50) having a particle size of 0.10 μm. ) Was supplied, the vent hole was maintained at a reduced pressure of 1 kPa or less to remove water, and MB containing 2% by weight of acrylic particles was obtained. The glass transition temperature is 81 ° C, the melting point is 255 ° C, the intrinsic viscosity is 0.60, and the amount of terminal carboxyl groups is 22eq. It was / t.

[Preparation of MB-J] 20 parts by weight (2 parts by weight of acrylic particles) of 10% by weight water slurry of PET-A 80 parts by weight and acrylic particles (acrylate copolymer, refractive index 1.50) having a particle size of 0.30 μm. ) Was supplied, the vent hole was maintained at a reduced pressure of 1 kPa or less to remove water, and MB containing 2% by weight of acrylic particles was obtained. The glass transition temperature is 81 ° C, the melting point is 255 ° C, the intrinsic viscosity is 0.60, and the amount of terminal carboxyl groups is 22eq. It was / t.

[Preparation of MB-K] 20 parts by weight (2 parts by weight as colloidal silica particles) of 10% by weight water slurry of PET-A 80 parts by weight and colloidal silica particles (refractive index 1.44) having a particle size of 0.05 μm is supplied. Then, the vent holes were maintained at a reduced pressure of 1 kPa or less to remove water, and MB containing 2% by weight of colloidal silica particles was obtained. The glass transition temperature is 81 ° C, the melting point is 255 ° C, the intrinsic viscosity is 0.60, and the amount of terminal carboxyl groups is 22eq. It was / t.

[Preparation of MB-L] 20 parts by weight (2 parts by weight as alumina particles) of 10% by weight water slurry of PET-A98 weight and alumina particles (refraction coefficient 1.76) having a particle size of 0.08 μm was supplied and vented. MB containing 2% by weight of alumina particles was obtained while keeping the pores at a reduced pressure of 1 kPa or less. The glass transition temperature is 81 ° C, the melting point is 255 ° C, the intrinsic viscosity is 0.60, and the amount of terminal carboxyl groups is 22eq. It was / t.

(Example 1)
PET-A, MB-A, and MB-C are used as the resins constituting the A layer and the B layer, the raw materials are blended so that the particle content is as shown in the table, and the raw materials are vacuum dried at 160 ° C. for 2 hours and then extruded. It was put into the machine 1. Further, 100 parts by weight of PET-A as a resin constituting the inner layer (C layer) was vacuum-dried at 160 ° C. for 2 hours, and then charged into the extruder 2. Each raw material is melted at 280 ° C. in the extruder, and the resin charged into the extruder 1 is merged into the A layer and the B layer of the film by the merging device, and extruded onto a casting drum having a surface temperature of 25 ° C. 3 A laminated sheet having a layered structure was produced. Subsequently, the sheet was preheated with a heated roll group, then stretched 3.5 times in the longitudinal direction (MD direction) at a temperature of 90 ° C., and then cooled with a roll group at a temperature of 25 ° C. to form a uniaxially stretched film. Got While gripping both ends of the obtained uniaxially stretched film with clips, the film was stretched 4.0 times in the width direction (TD direction) perpendicular to the longitudinal direction in a heating zone having a temperature of 110 ° C. in the tenter. Further, subsequently, heat fixing was performed at a temperature of 230 ° C. for 10 seconds in the heat treatment zone in the tenter. Then, after slowly cooling uniformly in the cooling zone, the film was wound to obtain a film having a thickness of 16 μm. Each property of the film is shown in the table. Moreover, the resist property was evaluated by laminating the resist layer on the A layer. The ratio of coarse protrusions (M60 / M10) was small, and when used as a base material for DFR, it had good resistability and could be sufficiently used. In addition, the ceramic green sheet has good manufacturability, and the number of dented defects is small, so that it can be sufficiently used as a mold release film in the MLCC manufacturing process and a mold release film in the polarizing plate defect detection process.

(Example 2-8)
The film was formed in the same manner as in Example 1 except that the composition of the resin and the film forming conditions were changed as shown in the table. The characteristics of the film are shown in the table. The ratio of coarse protrusions (M60 / M10) was small, and when used as a base material for DFR, it had good resistability and could be sufficiently used. Further, it can be sufficiently used as a mold release film in the MLCC manufacturing process and a mold release film in the defect detection step of the polarizing plate.

(Example 9)
PET-A, MB-A, and MB-C are used as the resins constituting the layer A, the raw materials are blended so that the particle content is as shown in the table, and the raw materials are vacuum dried at 160 ° C. for 2 hours and then put into the extruder 1. I put it in. Further, 100 parts by weight of PET-A was vacuum dried at 160 ° C. for 2 hours and then charged into the extruder 2. Each raw material was melted at 280 ° C. in an extruder to prepare a laminated sheet having a two-layer structure. Subsequently, the sheet was preheated with a heated roll group, then stretched 3.5 times in the longitudinal direction (MD direction) at a temperature of 90 ° C., and then cooled with a roll group at a temperature of 25 ° C. to form a uniaxially stretched film. Got While gripping both ends of the obtained uniaxially stretched film with clips, the film was stretched 4.0 times in the width direction (TD direction) perpendicular to the longitudinal direction in a heating zone having a temperature of 110 ° C. in the tenter. Further, subsequently, heat fixing was performed at a temperature of 230 ° C. for 10 seconds in the heat treatment zone in the tenter. Then, after slowly cooling uniformly in the cooling zone, the film was wound to obtain a film having a thickness of 16 μm. Each property of the film is shown in the table. When a resist layer was laminated on the B layer and a resist evaluation was carried out, it was found that the resist had good resistability and could be sufficiently used. In addition, the green sheet manufacturability of the B layer is good, and both the A layer and the B layer have a small number of dented defects, which is sufficient as a mold release film in the MLCC manufacturing process and a mold release film in the polarizing plate defect detection process. It was usable.

(Example 10-12)
PET-A, MB-A, and MB-C are used as the resins constituting the layer A, the raw materials are blended so that the particle content is as shown in the table, and the raw materials are vacuum dried at 160 ° C. for 2 hours and then put into the extruder 1. I put it in. Further, PET-A and MB-E were used as the resins constituting the B layer, the raw materials were blended so that the particle content was as shown in the table, vacuum dried at 160 ° C. for 2 hours, and then put into the extruder 2. .. Further, 100 parts by weight of PET-A as a resin constituting the inner layer (C layer) was vacuum-dried at 160 ° C. for 2 hours, and then charged into the extruder 3. Casting with a surface temperature of 25 ° C. A laminated sheet having a three-layer structure was produced by extruding onto a drum, and a film having a thickness of 16 μm was obtained by the same method as in Example 1. Each property of the film is shown in the table.

In Examples 10-12, a resist layer was laminated on the B layer side, and resist evaluation was carried out. In Example 10, the inclusion of particles in the B layer increased the M10 on the B surface, decreased the frictional force between the A surface and the B surface, and showed good resistability. Further, in Examples 11 and 12, the t / d of the A layer was changed. In Example 12 in which t / d was 10, the resistability was slightly inferior, but it could be sufficiently used.

In Example 10, the green sheet manufacturability of the B layer is good, the number of coarse protrusions is small in both the A layer and the B layer, and the release film in the MLCC manufacturing process and the release film in the polarizing plate defect detection step. It was fully usable as a product. In Examples 11 and 12, since the t / d of the A layer was changed, the green sheet manufacturability was slightly inferior and the number of dent defects increased, but it was sufficiently usable.

(Example 13-14)
PET-A and MB-C were used as the resins constituting the A layer and the B layer, and they were put into an extruder so as to have the composition as shown in the table, and the cast temperature was set to 50 ° C. In the same manner, a film having a thickness of 16 μm was formed. Fine protrusions could be formed by crystallization of the film, and it could be used as a DFR substrate.

Further, as a result of evaluating the green sheet manufacturability and the number of dent defects, it was found to be usable as a release film for the MLCC manufacturing process and a release film for the defect detection process of the polarizing plate.

(Examples 15-16)
Example 1 except that PET-A and MB-C were used as the resins constituting the A layer and the B layer, and the resin was put into an extruder so as to have the composition as shown in the table, and the nip pressure was set to 0.5 MPa. A film having a thickness of 16 μm was formed in the same manner as in the above. By applying pressure during stretching, large protrusions could be crushed to form fine protrusions, which could be used as a DFR substrate.

Further, as a result of evaluating the green sheet manufacturability and the number of dent defects, it was found to be usable as a release film for the MLCC manufacturing process and a release film for the defect detection process of the polarizing plate.

(Examples 17-18)
A film having a thickness of 16 μm was obtained in the same manner as in Example 10 except that PET-A, MB-A, and MB-B were used as the resins constituting the A layer. Each property of the film is shown in the table. When the resist layer was laminated on the B layer side in the same manner as in Example 10 and the resist was evaluated, the resist property was good.
Further, when the green sheet manufacturability and the number of dented defects were evaluated, they could be sufficiently used as a mold release film for the MLCC manufacturing process and a mold release film for the defect detection step of the polarizing plate.

(Example 19-20)
A film having a thickness of 16 μm was obtained in the same manner as in Example 10 except that PET-A, MB-I, and MB-J were used as the resins constituting the A layer. Each property of the film is shown in the table. When the resist layer was laminated on the B layer side in the same manner as in Example 10 and the resist was evaluated, the resist property was very good because the acrylic particles having a refractive index of 1.50 were used.

Further, when the green sheet manufacturability and the number of dented defects were evaluated, they could be sufficiently used as a mold release film for the MLCC manufacturing process and a mold release film for the defect detection step of the polarizing plate.

(Example 21-23)
The same as in Example 10 except that the resin used for the layer A was PET-A, MB-F, MB-H in Example 21, and PET-A, MB-B, MB-E in Examples 22 and 23. A film having a thickness of 16 μm was formed on the surface of the film, and the film was evaluated as a DFR substrate in the same manner as in Example 10. It was found that all of them showed good resistability.

Further, when the green sheet manufacturability and the number of dented defects were evaluated, they could be sufficiently used as a mold release film for the MLCC manufacturing process and a mold release film for the defect detection step of the polarizing plate.

(Example 24-26)
A film was obtained in the same manner as in Example 10 except that the film thickness was changed as shown in the table. Evaluation as a DFR base material was carried out in the same manner as in Example 10. In Example 26, the thickness of the film was slightly thick, and the resistability was slightly inferior, but the film could be sufficiently used.

Further, when the green sheet manufacturability and the number of dented defects were evaluated, they could be sufficiently used as a mold release film for the MLCC manufacturing process and a mold release film for the defect detection step of the polarizing plate.

(Example 27-29)
The PET resin used for the A layer was changed to PET-B, and a film was formed using MB-A, MB-C, and MB-C so as to have the particle content shown in the table with reference to Example 10. The obtained film was evaluated as a DFR base material in the same manner as in Example 10. It was found that the surface resistivity was small and the resistability was very good.
Further, when the green sheet manufacturability and the number of dented defects were evaluated, they could be sufficiently used as a mold release film for the MLCC manufacturing process and a mold release film for the defect detection step of the polarizing plate.

(Example 30-31)
The PET resin used for the A layer was changed to PET-C, and a film was formed using MB-A, MB-C, and MB-C so as to have the particle content shown in the table with reference to Example 10. The obtained film was evaluated as a DFR base material in the same manner as in Example 10. It was found that the surface resistivity was smaller than that of Examples 27 and 29, and the resistability was very good.
Further, when the green sheet manufacturability and the number of dented defects were evaluated, they could be sufficiently used as a mold release film for the MLCC manufacturing process and a mold release film for the defect detection step of the polarizing plate.

(Example 32)
A film was formed in the same manner as in Example 10 except that MB-A was added to the resin used for the C layer. Since the amount of particles increased, the resistability was slightly inferior when used as a DFR base material, but it could withstand use.
Further, as a result of evaluating the green sheet manufacturability and the number of dent defects, it was found to be usable as a release film for the MLCC manufacturing process and a release film for the defect detection process of the polarizing plate.

(Comparative Examples 1-3, 5, 9-14)
As the resins used for the A layer and the B layer, PET-A, MB-A, MB-C in Comparative Examples 1, 2 and 5, PET-A and MB-A in Comparative Example 3, and PET- in Comparative Examples 9 and 10. Particles shown in the table using A, MB-A, MB-D, PET-A and MB-C in Comparative Examples 11 and 12, and PET-A, MB-B and MB-L in Comparative Examples 13 and 14. A film having a thickness of 16 μm was obtained in the same manner as in Example 1 so that the content and stretching conditions were met, and the resistability was evaluated as a DFR substrate.

In Comparative Example 1, since the particle content of the A layer is high and the M60 is large, the resistability is poor and it cannot withstand the use as a DFR base material. Further, it cannot be used as a release film for the MLCC manufacturing process and a release film for the defect detection process of the polarizing plate.

In Comparative Example 2, since the particle content is low and M60 / M10 is small, the resistability is poor and it cannot be used as a DFR base material. Further, in the process of evaluating the green sheet manufacturability, the film is easily damaged, pinholes and dents are observed, and it cannot be used as a release film for the MLCC manufacturing process. Further, since the M60 / M10 on both sides is small, the number of dented defects increases, and the film cannot be used as a mold release film in the defect detection step of the polarizing plate.

In Comparative Examples 3, 11 and 12, since M60 / M10 cannot be controlled because it contains only a single particle, it has poor resistability and cannot withstand use as a DFR substrate. Further, it cannot be used as a release film for the MLCC manufacturing process and a release film for the defect detection process of the polarizing plate.

In Comparative Example 5, since the t / d value is large and M60 / M10 is large, the resistability is poor and it cannot be used as a DFR base material. Further, it cannot be used as a release film for the MLCC manufacturing process and a release film for the defect detection process of the polarizing plate.

In Comparative Example 9, since the particles contained have a large particle size and a large M60, the resistability is poor and the particles cannot be used as a DFR. Further, it cannot be used as a release film for the MLCC manufacturing process and a release film for the defect detection process of the polarizing plate.

In Comparative Examples 13 and 14, since the particle content is small and the particle size is also small, M60 / M10 is small and the resistability is poor, so that it cannot be used as a DFR base material. Further, it cannot be used as a release film for the MLCC manufacturing process and a release film for the defect detection process of the polarizing plate.

(Comparative Example 4)
A film was formed in the same manner as in Example 10 except that the t / d of the A layer was changed as described in the table, and the film was evaluated as a DFR substrate. Since t / d is large and M60 / M10 is large, the resistability is poor and it cannot be used as a DFR base material. Further, it cannot be used as a release film for the MLCC manufacturing process and a release film for the defect detection process of the polarizing plate.

(Comparative Example 6-7)
In Comparative Example 6, PET-A and MB-G and MB-K were used as the resins constituting the A layer, PET-A and MB-F were used as the resins constituting the B layer, and in Comparative Example 7, the A layer was used. PET-A, MB-H, MB-K, and PET-A, MB-F are used as the constituent resins, and the same as in Example 10 so that the constituents are as described in the table. The film was formed. Since the t / d of the A layer is large and the M60 / M10 is large, the resistability is poor and it cannot be used as a DFR base material. Further, it cannot be used as a release film for the MLCC manufacturing process and a release film for the defect detection process of the polarizing plate.

(Comparative Example 8)
PET-A and MB-G and MB-K are used as the resins constituting the A layer, and PET-A and MB-F are used as the resins constituting the B layer so that the configurations are as shown in the table. In the same manner as in Example 9, a film having a two-layer structure and a thickness of 5 μm was formed. Since M60 / M10 becomes large, the resistability is poor and it cannot withstand the use as a DFR base material. Moreover, since the thickness is thin, the film forming property is also inferior. Further, it cannot be used as a release film for the MLCC manufacturing process and a release film for the defect detection process of the polarizing plate.

The polyester film of the present invention is excellent in transparency and light transmission. Further, while the film surface is smooth, it also has excellent handleability. Therefore, it can be suitably used as an optical film, a process paper for mold release, and particularly as a film for a dry film resist (DFR) substrate.

Claims (13)

A two-layer or three-layer polyester film having a protrusion height of at least one side (A side) of the polyester film of 10 nm or more and a protrusion height of 60 nm or more (“M60 / M10”). The protrusion density (M60) of the polyester film having a protrusion height of 60 nm or more and a protrusion density (M60) of 300 pieces / mm ² or less is 0.1 or more and 3.0 or less, and constitutes a layer forming the A surface. The layer contains particles, and the content of the particles contained in the layer forming the A surface is 0.05% by weight or more and 0.6% by weight or less with respect to the A layer, and the A surface is formed. The particle size of the particles contained in the layer constituting the layer is 100 nm or more and 300 nm or less, the thickness of the layer constituting the layer forming the A surface is t (μm), and the particles contained in the layer forming the A surface are formed. A polyester film having a t / d of 1 or more and 10 or less, where d (μm) is the largest particle size.
[How to determine the ratio of protrusion height to protrusions with protrusion height of 10 nm or more to 60 nm or more (“M60 / M10”)]
M60; protrusion density with protrusion height of 60 nm or more (pieces / mm ² )
M10; Protrusion density with protrusion height of 10 nm or more (pieces / mm ² )
"M60 / M10" = M60 / M10 × 100 The polyester film according to claim 1, which meets the following requirements.
(1) When the ratio of the protrusion height of one surface (A side) of the polyester film to the protrusions having a protrusion height of 10 nm or more is 60 nm or more (“M60 / M10”) is 0.1 or more and 3.0 or less. There is.
(2) The ratio (“M60 / M10”) of the protrusion height of the surface (B side) opposite to the A side of the polyester film to the protrusions having a protrusion height of 10 nm or more is 0 or more and 0. Must be 5 or less.
[How to determine the ratio of protrusion height to protrusions with protrusion height of 10 nm or more to 60 nm or more (“M60 / M10”)]
M60; protrusion density with protrusion height of 60 nm or more (pieces / mm ² )
M10; Protrusion density with protrusion height of 10 nm or more (pieces / mm ² )
"M60 / M10" = M60 / M10 × 100 The polyester film according to claim 1 or 2, wherein the protrusion density (M10) having a protrusion height of 10 nm or more is 1000 pieces / mm ² or more and less than 8000 pieces / mm ² on both sides of the polyester film. The polyester film according to any one of claims 1 to 3, wherein the amount of particles contained in the polyester film is 0.1% by weight or less with respect to the polyester film. The polyester film according to any one of claims 1 to 4, wherein the film haze is 1.0% or less. The polyester film according to any one of claims 1 to 5, wherein the polyester film has a COOH terminal group amount of 15 equivalents / t or more and 40 equivalents / t or less. The polyester film according to any one of claims 1 to 6, wherein the surface resistivity of at least one side of the polyester film is 1.0 × 10 ¹³ Ω / cm ² or less. The polyester film according to any one of claims 1 to 7, wherein the arithmetic mean roughness (Ra) of the film surface of the polyester film is 4 nm or less on both sides. The polyester film according to any one of claims 1 to 8, wherein the film has a thickness of 15 μm or more and 250 μm or less. A chart of the abundance ratio of particles obtained when the layer forming the A plane contains particles, and the volume-based particle size distribution of the particles is measured and plotted with the horizontal axis as the particle size and the vertical axis as the abundance ratio of the particles. The claim that t / d is 1 or more and 10 or less when the particle size of the peak top having the largest particle size is d (μm) and the thickness of the layer forming the A surface is t (μm). The polyester film according to any one of 2 to 9. The polyester film according to any one of claims 1 to 10, which is used as a film for a dry film resist (DFR) substrate. The polyester film according to any one of claims 1 to 10, which is used as a release film in a laminated ceramic capacitor (MLCC) manufacturing process. The polyester film according to any one of claims 1 to 10, which is used as a release film in a defect detection step of a polarizing plate.