JP2002072486A - Polyester film for photoresist - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film for a photoresist excellent in resolution in the photoresist while ensuring photosensitivity necessary for the photoresist, capable of preventing troubles such as cleavage and the falling of particles in the peeling of the substrate film and having good windability of the substrate film itself. SOLUTION: The polyester film comprises a laminated polyester obtained by disposing a polyester A layer having 0.03-3 μm thickness on at least one face of a polyester B layer, the content of inert particles having an average particle diameter 0.1-10 times the thickness of the polyester A layer in the polyester A layer is <0.5 wt.% and the content of inert particles having 0.05-2 μm average particle diameter in the polyester B layer is <0.5 wt.%. The haze of the laminated polyester film is <=5.0%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for a photoresist, and more particularly, to a laminated polyester film for a photoresist which is provided for a photoresist by laminating a photosensitive resin composition on one surface.

[0002]

2. Description of the Related Art A photoresist, especially a dry film photoresist, is a laminate in which a photosensitive resin composition is laminated on one side of a light-transmitting base film, and a cover film made of polyethylene or the like is provided thereon. Use

In the process of manufacturing a photoresist, first, the cover film is removed, and the exposed surface of the photosensitive resin composition is adhered to an object such as a substrate for producing a printed wiring board. In this state, the negative film is brought into close contact with the substrate film, and the photosensitive resin composition is exposed to a predetermined pattern by irradiating an actinic ray such as ultraviolet light from the negative film side so as to transmit the substrate film. After the exposure, the negative film is removed and the base film is peeled off. The unexposed unexposed portion of the photosensitive resin composition thus remaining is removed with a solvent or the like, whereby a target pattern is formed on the substrate.

In such dry photoresists, in recent years, higher resolution has been demanded due to the miniaturization of circuits of printed wiring boards and the like. Further, in order to achieve the above-mentioned high resolution upon exposure, it is required that the light-transmitting substrate film be as thin as possible while having the necessary self-retaining property. However, when the film is made thin, there is a problem that the film is easily broken when the base film is peeled off.

[0005] In order to increase the strength of the film, usually,
Although it is effective to increase the degree of orientation of the stretched film, in this application, since a force acts in the thickness direction during the above-described peeling, the film is easily cleaved if the degree of orientation in the thickness direction is too low. Become. On the other hand, if the degree of orientation in the thickness direction is too high, the film itself tends to be stretched, which causes a disadvantage that the film cannot be peeled off cleanly when the film is peeled.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to focus on the above-mentioned problems relating to the photoresist base film and to improve the resolution in the photoresist while ensuring the necessary light transmittance of the photoresist. It is an object of the present invention to provide a polyester film for a photoresist which can prevent troubles such as cleavage and detachment of particles when the base film is peeled off and has good winding property of the base film itself.

[0007]

The present invention comprises a laminated polyester film in which a polyester A layer having a thickness of 0.03 to 3 μm is laminated on at least one surface of a polyester B layer. The same layer of inert particles having an average particle size of 1 to 10 times (polyester A
Layer), the content of inert particles having an average particle size of 0.05 to 2 μm in the polyester B layer is less than 0.5% by weight. A polyester film for a photoresist, wherein the haze of the laminated polyester film is 5.0% or less.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The laminated polyester film constituting the present invention has an A / B laminated structure in which a polyester A layer is laminated on one side of a polyester B layer, and a polyester A layer is disposed on both sides of a polyester B layer. A stacked
/ B / A is basically used. As long as the basic structure is included, a polyester A layer, a polyester B layer, or a polyester C layer can be further laminated within a range that does not impair the effects of the present invention. Can be mentioned.
Here, the chemical composition of the polyester resin constituting the polyester A layer, the polyester B layer, and the polyester C layer and various additives such as inert particles may be the same or different. However, when the chemical composition is the same, it must be recognized as a different layer due to a difference in surface state. Regardless of the laminated configuration, at least one surface is desirably formed of the polyester A layer.

The polyester resin of the polyester A layer constituting the present invention (hereinafter referred to as polyester A) includes ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate, ethylene It is desirable that at least one structural unit selected from 2,6-naphthalate units be the main component. It is highly desirable that the polyester constituting the present invention be crystalline or have optical anisotropy when melted. The term "crystallinity" as used herein means that it is not amorphous, and quantitatively, the cold crystallization temperature Tcc in the crystallization parameters is detected, and the crystallization parameter ΔTcg is 150 ° C. or less. . further,
Those having a crystallinity of 7.5 cal / g or more in heat of fusion (change in enthalpy of fusion) measured by a differential scanning calorimeter are highly desirable. Note that two or more kinds of thermoplastic resins may be mixed or a copolymer may be used as long as the effects of the present invention are not impaired.

The inert particles in the polyester A of the present invention have a particle diameter ratio (long diameter / short diameter) of 1.
It is desirable that the particles have a particle size of 0 to 1.3, particularly spherical particles. It is particularly desirable that the inert particles in the polyester A of the present invention have a single particle index in the film of 0.7 or more, preferably 0.9 or more. The inert particles in the polyester A of the present invention preferably have a relative standard deviation in the film of 0.6 or less, more preferably 0.5 or less.

The kind of the inert particles in the polyester A of the present invention is not particularly limited. However, in order to satisfy the above-mentioned preferable particle characteristics, silica in which primary particles are agglomerated, internally protruding particles and the like are not preferable. Preferable are substantially spherical silica particles resulting from colloidal silica, alumina silicate, particles made of a crosslinked polymer (for example, crosslinked polystyrene), and the like. In particular, crosslinked polymer particles having a high degree of crosslinking until the temperature at the time of weight loss of 10% by weight (heating rate of 20 ° C / min as measured using a thermogravimetric analyzer Shimadzu TG-30M in nitrogen) becomes 380 ° C or more. Is particularly desirable. In the case of spherical silica originating from colloidal silica, it is particularly desirable to use substantially spherical silica produced by the alkoxide method and having a low sodium content. However, other particles, such as particles of calcium carbonate, titanium dioxide, alumina, etc., can be sufficiently used by appropriately controlling the film thickness and the average particle size. The crystallization promotion coefficient of the inert particles in the polyester A of the present invention is not particularly limited, but may be from -15 to 15 ° C, particularly from -5 ° C to 10 ° C.
C is desirable. As for the size of the inert particles, the average particle size in the film needs to be 0.1 to 10 times the film thickness, preferably 0.5 to 5 times, more preferably 1.1 to 10 times. The range is three times as large. Average particle size /
It is not preferable that the film thickness ratio is smaller or larger than the above range. The average particle size (diameter) of the inert particles in the film of the polyester A in the film is desirably 0.05 to 3 μm, and particularly desirably 0.05 to 1.5 μm.

It is necessary that the content of the inert particles in the polyester A of the present invention is less than 0.5% by weight in view of the haze of the laminated film and the resolution. It is particularly desirable not to contain such inert particles.

The polyester A layer of the present invention comprises, as a main component, a composition comprising the above-mentioned polyester A and inert particles, but may be blended with other polymers as long as the object of the present invention is not impaired. Further, organic additives such as antioxidants, heat stabilizers, lubricants, and ultraviolet absorbers may be added to the extent that they are usually added.

The polyester A layer is preferably a biaxially oriented film, and a uniaxial or non-oriented film is not preferred because the mechanical strength of the film is weakened.
When the mechanical strength of the film is weak, the film is deformed when the resist film is peeled off after the exposure, and the film is hardly peeled off.
Moreover, it will be torn and the peelability will deteriorate.
Although the degree of this orientation is not particularly limited, it is better when the Young's modulus, which is a measure of the degree of molecular orientation of the polymer, is 350 kg / mm ² or more in both the longitudinal direction and the width direction. The upper limit of the Young's modulus, which is a measure of the degree of molecular orientation, is not particularly limited, but usually about 5000 kg / mm ² is the manufacturing limit. Further, in the film of the present invention, even when the Young's modulus is within the above range, the orientation of the polymer molecules in a part in the thickness direction of the film, for example, near the surface layer is not oriented or uniaxially oriented. That is, it is desirable that the molecular orientation of all parts in the thickness direction be biaxial because the strength at the time of peeling is further improved.

The thickness of the polyester A layer containing polyester A of the present invention as a main component is 0.03 to 3 μm, preferably 0.05 to 2 μm, and more preferably 0.03 to 1.0 μm.
μm. It is not preferable that the film thickness is smaller or larger than the above range, since the light transmittance becomes poor.

The average height of protrusions on the surface of the polyester A layer containing polyester A as a main component of the present invention is 5 to 500 n.
m, preferably 10 to 300 nm, more preferably 1
It is particularly preferable that the thickness be in the range of 5 to 200 nm, since the light transmittance is further improved.

It is particularly desirable that the average spacing between the protrusions of the polyester A layer containing polyester A as a main component of the present invention is 6 μm or less, preferably 4 μm or less, since the winding property is further improved.

It is particularly desirable that the polyester A has a refractive index in the thickness direction of 1.5 or less, since the releasability is further improved.

The polyester resin constituting the polyester B layer (hereinafter, referred to as polyester B) includes ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate,
When at least one structural unit selected from ethylene 2,6-naphthalate units is used as a main component, light transmission is particularly improved, which is preferable. However, within a range that does not impair the present invention, within a range that does not impair the desired crystallinity,
Preferably, other components may be copolymerized within 5 mol%.

The polyester B of the present invention may be blended with other polymers as long as the object of the present invention is not impaired, or may be an organic compound such as an antioxidant, a heat stabilizer, a lubricant or an ultraviolet absorber. It may be added to the extent that additives are usually added.

The average particle size of the polyester B layer containing polyester B as a main component is 0.05 to 2 μm, particularly 0.05 to 2 μm.
The content of inert particles of 1.5 μm should be less than 0.5% by weight, preferably 0.2% by weight or less, more preferably 0.15% by weight or less, even more preferably 0.1% by weight.
12% by weight or less. As the kind of the inert particles to be contained, it is desirable to use those desirably used for the polyester A. The types and sizes of the particles contained in the polyesters A and B may be the same or different.

In the present invention, the relationship between the refractive index (n) of the laminated polyester film, the refractive index (nA) of the inert particles in the polyester A, and the refractive index (nB) of the inert particles in the polyester B is as follows: n−nA | ≦ 0.17, |
n−nB | ≦ 0.17, and | n
−nA | ≦ 0.15, | n−nB | ≦ 0.15, more preferably | n−nA | ≦ 0.10, |
It is particularly desirable that n−nB | ≦ 0.10.

The haze of the laminated polyester film in the present invention needs to be 5.0% or less, preferably 3% or less, more preferably 1.8% or less. This is because, in recent years, with the miniaturization of the circuit of the printed wiring board, higher resolution is required more and more, and the above resolution at the time of exposure is achieved.

Next, a method for producing the film of the present invention will be described. First, as a method of causing the polyester A to contain inert particles, a method of dispersing in the form of a slurry of ethylene glycol, which is a diol component, and polymerizing the ethylene glycol with a predetermined dicarboxylic acid component does not cause stretching breakage. It is effective to obtain a film having a relationship between the thickness and the average particle size, the content, and the orientation state in a desirable range. Further, the method of adjusting the melt viscosity of the polyester containing inert particles, the copolymerization component, and the like to keep the crystallization parameter ΔTcg in the range of 40 to 65 ° C. does not cause stretching breakage, and has a thickness within the range of the present invention. It is effective to obtain a film having a relation of the average particle size and the content.

The method of heat-treating a slurry of ethylene glycol of inert particles at a temperature of 140 to 200 ° C., particularly 180 to 200 ° C., for 30 minutes to 5 hours, especially 1 to 3 hours, does not cause stretching breakage, and the present invention is not limited thereto. It is effective to obtain a film having a relationship between the thickness and the average particle size, the content, the orientation state in a desirable range, and the surface layer particle concentration ratio.

As a method of incorporating inert particles into the polyester, the particles are mixed with
~ 200 ° C, especially at a temperature of 180 ~ 200 ° C for 30 minutes ~ 5
After the heat treatment for 1 to 3 hours, the solvent is mixed with the polyester in the form of a slurry in which the solvent is replaced with water, and the mixture is kneaded with a vented twin-screw extruder and kneaded into the polyester. And the average particle size, the content, and the orientation of the film in a desirable range are extremely effective.

As a method of adjusting the content of particles, a high-concentration master is prepared by the above-described method, and the master is diluted with a polyester substantially free of inert particles at the time of film formation to adjust the content of particles. Is effective.

Next, the following method is effective as a method of laminating a film mainly composed of polyester A on at least one side of a film mainly composed of polyester B.

After a pellet containing a predetermined amount of inert particles is dried as required, a predetermined polyester A composition and a polyester B (A and B may be the same or different) may be used in a known melt laminating extruder. And extruded into a sheet from a slit die at a temperature higher than the melting point of the polyester and lower than the decomposition point, and then cooled and solidified on a casting roll to produce an unstretched film. That is, using two or three extruders, two or three layers of a manifold or a merging block, polyesters A and B are laminated, a two or three layers sheet is extruded from a die, cooled by a casting roll, and unstretched. Make a film. In this case, a method of installing a static mixer and a gear pump in the polymer flow path of the polyester A does not cause stretching breakage, and the relationship between the thickness and the average particle diameter in the range of the present invention, the content, the orientation state in the desired range, and the average projection height. , Rt / Rp ratio, Rt / Ra ratio, and surface layer particle concentration ratio. Further, it is possible to raise the melting temperature of the extruder on the polyester A side by 10 to 40 ° C. higher than that on the polyester B side without stretching and breaking. Orientation state, average protrusion height, Rt / Rp ratio, Rt / R
It is effective for obtaining a film having an a ratio and a surface layer particle concentration ratio.

The unstretched film is biaxially stretched and biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However, using a sequential biaxial stretching method in which stretching in the longitudinal direction and then in the width direction is performed first, the stretching in the longitudinal direction is divided into three or more stages, and the total longitudinal stretching ratio is 3.5 to 6.5 times. The method has no stretching breakage and is effective for obtaining a film having the relationship between the thickness and the average particle size within the range of the present invention, the content, the orientation state within the desired range, and the surface layer particle concentration ratio. In the longitudinal stretching temperature, the first stage is usually 50 to 130 ° C., and the second stage and the subsequent stages are preferably higher than that in the relationship between the thickness and the average particle size in the range of the present invention, the content,
This is effective for obtaining a film in a desired range of orientation. The longitudinal stretching speed is preferably in the range of 5,000 to 50,000% / min. As a stretching method in the width direction, a method using a stenter is generally used. The stretching ratio is 3.0 to
A range of 5.0 times is appropriate. The stretching speed in the width direction is 1
2,000 to 20,000% / min, and the temperature is preferably in the range of 80 to 160 ° C. Next, this stretched film is heat-treated.
The heat treatment temperature in this case is 170 to 250 ° C., particularly 180
To 240 ° C., and the time is preferably in the range of 0.5 to 60 seconds.

However, the stretching temperature was set to polyester B
Must be set as a reference. Further, in the heat treatment step of the two-layer laminated film, the hot air temperature blown to the polyester A layer is set to be 3 to 20 ° C. lower than that of the polyester B layer. Orientation state, average protrusion height, Rt / Rp ratio,
This is effective for obtaining a film having an Rt / Ra ratio and a surface particle concentration ratio.

[Method for Measuring Physical Properties and Method for Evaluating Effect] The method for measuring characteristic values and the method for evaluating effect according to the present invention are as follows.

(1) Average particle size of particles The polyester is removed from the film by a plasma low-temperature incineration method (for example, PR-503, manufactured by Yamato Scientific Co., Ltd.) to expose the particles. The processing conditions are selected such that the polyester is ashed but the particles are not damaged. This is SE
Observed with a scanning electron microscope (M), the image of the particles (shading of light generated by the particles) was linked to an image analyzer (for example, QTM900 manufactured by Cambridge Instrument), and the observation value was changed and the following numerical values were obtained when the number of particles was 5,000 or more. The processing is performed, and the number average diameter D obtained thereby is defined as the average particle diameter. D = ΣDi / N where Di is the equivalent circle diameter of the particles, and N is the number.

(2) Content of Particles A solvent in which the polyester is dissolved but the particles are not dissolved is selected, the particles are centrifuged from the polyester, and the ratio (% by weight) to the total weight of the particles is defined as the particle content.
In some cases, the combined use of infrared spectroscopy is also effective.

(3) Thickness of Polyester A Layer in Laminated Film Using a secondary ion mass spectrometer (SIMS), the thickness of the element resulting from the highest concentration of the particles in the film and the carbon element of the polyester are determined. The concentration ratio (M + / C +) is defined as the particle concentration, and the analysis is performed in the depth (thickness) direction from the surface of the polyester A layer. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. In the case of the film of the present invention, the particle concentration which has reached the maximum value once at the depth [I] starts to decrease again. Based on this concentration distribution curve, the depth [I
I] (where II> I) was taken as the lamination thickness. In addition, when the particles most contained in the film are organic polymer particles, it is difficult to measure by SIMS. Therefore, while etching from the surface, XPS (X-ray photoelectron spectroscopy), IR (infrared spectroscopy) or confocal microscopy is used. For example, the depth profile of the particle concentration may be measured, and the layer thickness may be obtained by the same method as described above. Further, instead of using the depth profile of the particle concentration described above, the polyester A
May be determined.

(4) Haze The haze of the film was measured according to JIS-K-7105.

(5) Refractive index (1) Film The refractive index in the thickness direction of the film was measured according to JIS-K-7105. (2) Particles A solvent having a known refractive index (for example, α-bromonaphthalene, kerosene) is adjusted using an Abbe refractometer in advance. Then, according to Larsen's oil immersion method, several mg of the sample powder was taken on a slide glass, a drop of a solvent having a known refractive index was added, a cover glass was applied, and the solvent was sufficiently immersed.
Observe the movement of the Becke line with an optical microscope and determine.

(6) Rollability The film was slit to a width of 1,000 mm and a length of 4000 m, wound on a paper core having a length of 1200 mm, an inner diameter of 6 inches and a thickness of 12 mm, and the state of winding was observed. . Rolls without defects such as wrinkles: ○ Those with defects such as wrinkles: ×.

(7) Peelability After laminating a film coated with a known photosensitive resin to a thickness of 45 μm on a copper-clad laminate, the film was exposed and the film was cleaved when the film was peeled off. The judgment was made based on the standard. No cleavage and no dropping of particles: ○ Cleavage and dropping of particles: ×.

(8) Resolution After laminating a film coated with a known photosensitive resin to a thickness of 45 μm on a copper-clad laminate, a negative film for evaluating the resolution (STOUFFER GRAPHIC ARTS)
EQUIPMENT, 21 STEP, SENSITI
VITY GUIDE, # T2115) and exposed to remove the film. Then, using a 1.0% by weight aqueous sodium carbonate solution at 30 ° C., a spray pressure of 1.0 kg / cm.
2 was sprayed for 60 seconds to remove the unexposed portions, and the number of steps of the step tablet of the photocured film on the copper-clad laminate was measured and judged according to the following criteria. The higher the number of steps, the better the resolution. Steps 8.0 or more: resolution ○ Steps less than 8.0: resolution ×

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on embodiments.

An ethylene glycol slurry containing crosslinked polystyrene particles having the particle diameters shown in Table 1, silica particles derived from colloidal silica, and calcium carbonate was prepared.
After a heat treatment for 5 hours, transesterification with dimethyl terephthalate was carried out and polycondensation was carried out to produce pellets of polyethylene terephthalate (hereinafter abbreviated as PET) containing the particles in an amount of 0.005 to 55% by weight. At this time, the intrinsic viscosity was adjusted to 0.70 by adjusting the polycondensation time (polyester A).
In addition, a PET substantially free of inert particles having an intrinsic viscosity of 0.62 was produced by a conventional method, and was referred to as polyester B. Each of these polymers was dried under reduced pressure (3 Torr) at 180 ° C. for 3 hours.

Comparative Examples 1 and 2 Polyester A was supplied to extruder 1 and melted at 310 ° C.
The film was wound around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method, cooled and solidified to form an unstretched film. At this time, an unstretched film was prepared with the ratio of die slit gap / unstretched film thickness being set to 10. Further, the discharge amount of the extruder was adjusted to adjust the thickness of the polyester film. This unstretched film was stretched 3.8 times in the longitudinal direction at a temperature of 80 ° C. This stretching was performed in four stages with a difference in peripheral speed between two sets of rolls. This uniaxially stretched film is stretched using a stenter at a stretching speed of 2000% / min.
The film was stretched 3.7 times in the width direction at 0 ° C. and heat-treated at 200 ° C. for 5 seconds under a constant length to obtain a biaxially oriented laminated film having a film thickness of 20 μm.

Comparative Examples 3 and Examples 1 to 4 A predetermined amount of inert particles having an average particle diameter shown in Table 1 was contained.
The pellets (polyester A) prepared as in Example 1 were supplied to the extruder 1, and a predetermined amount of inert particles having an average particle size shown in Table 1 was contained. B) was fed to the extruder 2 and 280
These polymers are melted at ℃, and these polymers are merged and laminated by a merging block (feed block), wound around a casting drum having a surface temperature of 30 ° C. by using an electrostatic application casting method, cooled and solidified, and formed into two layers of A / B. An unstretched film of the structure was made. At this time, an unstretched film was prepared with the ratio of die slit gap / unstretched film thickness being set to 10. Further, the discharge amount of each extruder was adjusted to adjust the total thickness and the thickness of the polyester A layer. This unstretched film was stretched 3.8 times in the longitudinal direction at a temperature of 80 ° C. This stretching was performed in four stages with a difference in peripheral speed between two sets of rolls. This uniaxially stretched film is stretched using a stenter at a stretching speed of 2000% / min.
Stretched 3.7 times in the width direction at 00 ° C, and 200 ° C under constant length
Heat treated for 5 seconds at a total thickness of 15 μm, polyester A
A biaxially oriented laminated film having a layer thickness of 0.003 to 15 μm was obtained. When the parameters of the present invention were within the ranges, the rollability, peelability, and resolution were as shown in Table 1, but otherwise, no satisfactory film was obtained.

Comparative Example 4, Examples 5 to 7 A predetermined amount of inert particles having an average particle diameter shown in Table 1 was contained.
The pellets (polyester A) prepared as in Example 1 were supplied to the extruder 1, and a predetermined amount of inert particles having an average particle size shown in Table 1 was contained. B) was supplied to the extruder 2 to prepare a biaxially oriented laminated film having a polyester A layer thickness as shown in the table as in Example 3. However, a three-layer structure of A / B / A was used, and the total thickness was 20 μm. The parameters of the present invention for these films are as shown in Table 1, and when the parameters of the present invention are within the ranges, the rollability, peelability and resolution were as shown in Table 1, but not so. In this case, a satisfactory film was not obtained.

[0046]

[Table 1]

[0047]

As described above, according to the present invention, a polyester film for a photoresist which is excellent in all of the high resolution, the cleaving property at the time of peeling the base film, and the winding property of the base film itself, which could not be achieved conventionally, was obtained.

Continued on front page F term (reference) 2H025 AA02 AA16 AB11 AB15 AC01 AD01 CC20 DA17 DA19 DA21 4F100 AA08A AA08B AA08C AA08H AA20A AA20B AA20C AA20H AK41A AK41B AK41C AK41B AK41C BA02 BA03 BA18 BA01 DE01 DE01 DE01 DE01 DE01 JN18C JN18H YY00 YY00A YY00B YY00C YY00H 4J002 BC032 CF001 CF061 CF081 CF121 DJ006 DJ016 FA082 FA086 FD012 FD016 GF00 GP03

Claims (5)

[Claims] 1. A polyester film comprising a polyester A layer having a thickness of 0.03 to 3 μm laminated on at least one surface of a polyester B layer, having an average particle size of 0.1 to 10 times the thickness of the polyester A layer. Inactive polyester particles having a content of inert particles in the same layer of less than 0.5% by weight and an average particle size of 0.05 to 2 μm
A polyester film for a photoresist, wherein the content in the layer is less than 0.5% by weight, and the haze of the laminated polyester film is 5.0% or less. 2. The inactive particles contained in the polyester A layer and the polyester B layer have a refractive index of nA and nB, respectively.
The polyester film for a photoresist according to claim 1, wherein the following formula is satisfied, where n is a refractive index of the laminated polyester film. | N−nA | ≦ 0.17 | n−nB | ≦ 0.17 where n = (nMD + nTD + nZD) / 3, where nMD is the refractive index in the longitudinal direction of the film, nTD is the refractive index in the width direction of the film, and nZD is Indicates the refractive index in the film thickness direction. 3. The polyester film for a photoresist according to claim 1, wherein the polyester B layer contains no inert particles. 4. The polyester film for a photoresist according to claim 1, wherein the laminated polyester film is obtained by laminating a polyester A layer on both sides of a polyester B layer. 5. The polyester film for a photoresist according to claim 1, wherein the haze of the laminated polyester film is 1.8% or less.