JP2018065250A - Biaxially oriented polyester film for dry film resist support and production method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially oriented polyester film for a dry film resist support, capable of responding to demands for higher quality and higher productivity, in which entrained dust is reduced by imparting antistatic performance to one surface of the sheet, offset of an antistatic component to the other surface is prevented by imparting antistatic performance by kneading the antistatic, thereby, high resolution of a resist can be achieved, and slipping property can be significantly improved by using two types of particles having different particle diameters together.SOLUTION: The biaxially oriented polyester film for a dry film resist support is a polyester film having a multilayer structure of at least three layers, in which a difference in the surface free energy between a surface (referred as surface (A)) of one outermost layer (referred as A layer) and a surface (referred as surface (B)) of the other outermost layer (referred as B layer) is 5.0 mN/m or more, the surface specific resistance value of the surface (A) is 1.0×10Ω/unit square or more, and the surface specific resistance value of the surface (B) is 1.0×10Ω/unit square or less.SELECTED DRAWING: None

Description

  The present invention relates to a polyester film for a dry film resist support.

Dry film resists (hereinafter sometimes referred to as DFR) are used to form circuits such as printed wiring boards, semiconductor packages, and flexible boards. The DFR has a structure in which a photosensitive layer (photoresist layer) is laminated on a polyester film as a support and then sandwiched between protective films (cover films) made of a polyethylene film, a polypropylene film, a polyester film, or the like. . To create a conductor circuit using this DFR, the following steps are generally performed.
1) Step of laminating the protective film from the DFR and laminating it with the substrate / conductive substrate layer so that the exposed surface of the resist layer and the surface of the conductive substrate layer such as copper foil on the substrate are in close contact with each other .
2) Next, a step of placing a photomask on which a conductor circuit pattern is baked on a support made of a polyester film and exposing the resist layer mainly composed of a photosensitive resin by irradiating with ultraviolet rays.
3) Then, after peeling the photomask and the polyester film, a step of dissolving and removing unreacted components in the resist layer with a solvent.
4) Next, a step of etching with acid or the like to dissolve and remove the exposed portion in the conductive base material layer.

  After the step 4), the photoreactive portion in the resist layer and the conductive base material layer portion corresponding to the photoreactive portion remain as they are, and then the step of removing the remaining resist layer, the conductor on the substrate A circuit will be formed. For this reason, it is requested | required that the polyester film which is a support body can permeate | transmit an ultraviolet-ray efficiently. Thereby, the conductor circuit pattern is accurately reflected on the resist layer. Particularly in recent years, with the miniaturization and weight reduction of IT equipment and the like, there is a demand for a polyester film for a dry film resist support that has excellent transparency, low haze, and high resolution. In addition, it is important that the polyester film as a support has an appropriate sliding property in order to improve the handleability when a resist film is produced by forming a resist layer on the support. However, when particles as an easy-to-slip material are included to give appropriate slipperiness, light scattering by the particles is caused in both transmission and reflection during ultraviolet irradiation during the exposure process, and the resolution of the resist is lowered. There was a problem that it would end up.

  Therefore, a polyester film for a dry film resist support has been proposed in which the surface of the film is highly smoothed and the haze value is lowered, and the transmittance at a wavelength of 365 nm is within a certain range ( Patent Document 1). Technology to improve handling of polyester film for resist by blending antistatic agent, prevention of dust and foreign matter adhesion, handling of resist film itself using the film, and prevention of dust and foreign matter adhesion Are disclosed (Patent Documents 2 and 3).

JP-A-2006-87854 JP 2001-117237 A JP 2006-327158 A

  However, even in these proposals, it is difficult to satisfy the demand for higher resolution, and the defects such as distortion and omission in resist patterning after development, and the state of the resist pattern wall surface cannot be sufficiently solved, and still remain. Therefore, there is a demand for quality improvement for higher resolution. Furthermore, as a result of supporting high resolution, the amount of particles added to the base film as a lubricant or applied on the base film is reduced, resulting in a decrease in yield in the film manufacturing process and the above DFR manufacturing process, especially in winding. Since related problems are conspicuously occurring, there is a demand for improvement in productivity (film winding property). In addition, in the case of imparting antistatic performance by the coating method, the resist is deactivated due to scraping with a roll or the like in the coating layer process, or the antistatic agent component is transferred to the back surface (resist surface). There is a possibility that defects (distortion, chipping, omission) may occur in patterning. In view of these circumstances, the present invention reduces the entrainment dust by providing antistatic performance on one surface, and prevents the settling to the other surface by imparting antistatic performance by kneading, thereby improving the high resolution of the resist. A biaxially oriented polyester film for a dry film resist support that can remarkably improve slipperiness by using two types of particles having different particle diameters, and can improve quality and productivity. The issue is to provide.

The present invention has the following features.
[I] A polyester film having a laminated structure of three or more layers,
The surface of one outermost layer (this layer is A layer) (the surface is the surface (A)) and the other outermost layer (this layer is the B layer) (the surface is the surface (B )) Is a surface free energy difference of 5.0 mN / m or more, the surface resistivity of the surface (A) is 1.0 × 10 ¹⁴ Ω / □ or more, and the surface resistivity of the surface (B). A biaxially oriented polyester film for a dry film resist support having a value of 1.0 × 10 ¹³ Ω / □ or less.
[II] The biaxially oriented polyester film for a dry film resist support according to [I], wherein the surface free energy of the surface (B) is larger than the surface free energy of the surface (A).
[III] The layer B contains two or more types of particles, one type of particles has a maximum particle size DA of less than 0.3 μm (the particles are referred to as particles A), and one type of particles is the maximum The biaxially oriented polyester film for dry film resist support according to [I] or [II], wherein the particle size DB is 0.3 μm or more and less than 1.0 μm (the particles are referred to as particles B).
[IV] The biaxially oriented polyester film for dry film resist support according to any one of [I] to [III], wherein the film haze is less than 1.0%.
[V] The biaxially oriented polyester film for dry film resist support according to any one of [I] to [IV] containing an antistatic agent.
[VI] Surface roughness SRa (A) of surface (A) and surface roughness SRa (B) of surface (B) are both 7 nm or less, surface roughness SRz (A) and surface of surface (A) The biaxially oriented polyester film for a dry film resist support according to any one of [I] to [V], wherein the surface roughness SRz (B) of (B) is 400 nm or less.
[VII] The surface roughness SRz (A) of the surface (A) is 100 nm or less, and the surface roughness SRz (B) of the surface (B) is 100 nm or more and 400 nm or less, and any one of [I] to [VI] 2. A biaxially oriented polyester film for a dry film resist support according to 1.
[VIII] The biaxially oriented polyester film for dry film resist support according to any one of [I] to [VII], which is used by laminating a resist layer on the surface (A).
[IX] The method for producing a biaxially oriented polyester film for a dry film resist support according to any one of [I] to [VIII], which is obtained by melt film formation by a coextrusion method.

  According to the present invention, the high resolution of the resist is achieved by reducing entrained dust by imparting antistatic performance to one surface and preventing settling to the other surface by imparting antistatic performance by kneading. In addition, by using two types of particles having different particle diameters together, it is possible to remarkably improve slipperiness, and to provide a biaxially oriented polyester film for a dry film resist support capable of improving quality and improving productivity. Can do.

  The polyester film for resist support according to the present invention has a laminated structure of three or more layers containing a polyester resin as a main component. Then, the arithmetic average surface roughness SRa (A) of the surface of the outermost layer (the layer is A layer) (the surface is the surface (A)) and the other outermost layer (the layer is B) The arithmetic average surface roughness SRa (B) of the surface of the layer (referred to as the surface (B)) is 7 nm or less, and the ten-point average surface roughness SRz (A) of the surface (A) and The ten-point average surface roughness SRz (B) of the surface (B) is preferably 400 nm or less. Preferably, SRz (A) is 100 nm or less, SRz (B) is 100 nm or more and 400 nm or less, and there is a difference between the surface (A) and the surface (B) in terms of achieving both performance and handling.

  On the surface (A), SRa (A) is preferably 7 nm or less and SRz (A) is preferably 400 nm or less. Furthermore, SRa (A) is more preferably 3 nm or more and less than 6 nm, and SRz (A) is more preferably 50 nm or more and less than 100 nm. The biaxially oriented polyester film for dry film resist support of the present invention is preferably used by laminating a resist layer on the surface (A) side when used for a resist support. By achieving the surface roughness within this range, it is possible to obtain appropriate smoothness that suppresses the influence of reflection on the film surface during exposure, and to form a high-definition resist pattern, and at the same time handling during processing You can get sex. When SRa (A) is larger than 7 nm or SRz (A) is larger than 400 nm, light reflection due to unevenness transferred from the film to the resist surface and unevenness of the incident angle of light in the exposure process due to the unevenness. The resist pattern may be lost due to the influence of scattering and scattering, which is not preferable.

  On the other hand, on the surface (B), SRa (B) is preferably 7 nm or less and SRz (B) is preferably 400 nm or less. Furthermore, SRa (B) is more preferably 3 nm or more and less than 6 nm, and SRz (B) is more preferably 100 nm or more and less than 400 nm. When the resist layer is laminated on the surface (A) side of the biaxially oriented polyester film for dry film resist support of the present invention, and the cover film is bonded and wound on the surface, the surface (B) side is covered. It will be the surface in contact with the film. When SRa (B) is less than 3 nm or SRz (B) is less than 100 nm, handling properties deteriorate in the resist coating process, coating becomes unstable, coating spots occur, and when winding after coating, This is not preferable because the entrained air may be difficult to escape and may cause winding deviation. Further, when SRa (B) is larger than 7 nm or SRz (B) is larger than 400 nm, light reflection or scattering due to unevenness of the incident angle of light in the exposure process due to the unevenness formed on the surface. This is not preferable because it causes noise when forming a resist pattern.

  In order to make the surface roughness of the A layer and the B layer within the above-mentioned range, specific organic particles described later are added to the polyester resin constituting the layer having the A surface (A layer) and the layer having the B surface (B layer). Alternatively, it can be achieved by containing a specific amount of inorganic particles.

  In order to impart high transparency to the polyester film, for example, an intermediate layer (C layer) existing between the A layer and the B layer is substantially contained while controlling the amount of particles in the A layer and the B layer. It is preferable to have no configuration.

  In addition, the biaxially oriented polyester film for dry film resist support of the present invention needs to be biaxially oriented. In the present invention, the biaxial orientation refers to a state in which an unstretched (unoriented) film is stretched in a two-dimensional direction by a conventional method (showing a biaxially oriented pattern by wide-angle X-ray diffraction). Stretching can take sequential biaxial stretching and simultaneous biaxial stretching. In sequential biaxial stretching, the process of stretching in the longitudinal direction (longitudinal) and the width direction (transverse) can be performed once in the length-width direction, or twice in the length-width-length-width direction. You can also

  In the present invention, a polyester resin as a main component means that at least 70 mol% or more is obtained by polymerization from a monomer or a low polymer mainly composed of a dicarboxylic acid, a diol, and an ester-forming derivative thereof. Polyester. In the present invention, it is preferable to use an aromatic dicarboxylic acid as the dicarboxylic acid.

  Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and terephthalic acid is particularly preferable. These acid components may be used alone or in combination of two or more, and may be partially copolymerized with other aromatic dicarboxylic acids such as isophthalic acid or fatty acids.

  Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, and the like. Of these, ethylene glycol is preferably used. These diol components may be used alone or in combination of two or more.

  The polyester used in the biaxially oriented polyester film for dry film resist support of the present invention is preferably polyethylene terephthalate, polyethylene naphthalate, and a copolymer thereof, polybutylene terephthalate and a copolymer thereof, polybutylene naphthalate, and Examples of the copolymer include polyhexamethylene terephthalate and a copolymer thereof, polyhexamethylene naphthalate and a copolymer thereof, and polyethylene terephthalate is particularly preferable.

  The polyester used in the present invention can be produced by a conventionally known method. For example, a method in which an acid component is directly esterified with a diol component, and then the product of this reaction is heated under reduced pressure to perform polycondensation while removing excess diol component, or a dialkyl as an acid component A method of producing an ester by transesterifying it with a diol component and then performing polycondensation in the same manner as described above can be employed. At this time, conventionally known alkali metals, alkaline earth metals, manganese, cobalt, zinc, antimony, germanium, titanium compounds, and the like can be used as a reaction catalyst, if necessary.

  The intrinsic viscosity of the polyester is preferably a lower limit of 0.5 dl / g and an upper limit of 0.8 dl / g. More preferably, the lower limit is 0.55 dl / g and the upper limit is 0.70 dl / g.

  The biaxially oriented polyester film for a dry film resist support of the present invention preferably has a total film thickness of 10 to 350 μm, more preferably 10 to 50 μm. Particularly preferably, it is 12 μm to 40 μm. If the total thickness is less than 10 μm, the strength may be insufficient and handling in the processing step may be difficult, and if it exceeds 350 μm, it may be difficult to make the light transmittance and haze value within the range of the present invention.

  In the polyester film in the present invention, it is preferable that the dimensional change rate is in the following range, because generation of distortion and wrinkles due to thermal shrinkage in the DFR processing step can be suppressed. The dimensional change rate can be achieved by appropriately adjusting the conditions such as relaxation and heat treatment in the film forming conditions by a known method. The dimensional change rate at 150 ° C. is preferably 3.0% or less in the longitudinal direction and 2.5% or less in the width direction, 0.5% or more and 2.0% or less in the longitudinal direction, and 1.0% or more and 2 in the width direction. 0.0% or less is more preferable. The dimensional change rate at 100 ° C. is preferably 1.0% or less in both the longitudinal direction and the width direction, and more preferably in the range of 0.2% to 0.8%. If the dimensional change rate is below the lower limit of the above range, flatness defects due to tarmi occur when applying the resist layer, and if it exceeds the upper limit, shrinkage spots are generated in a tin shape due to shrinkage when applying the resist layer. However, the flatness becomes poor, and in any case, the coating thickness of the resist layer may be uneven.

  Moreover, it is preferable that the strength (hereinafter, this value is referred to as F-5 value) when the film in the longitudinal direction is stretched by 5% is 70 MPa or more and less than 150 MPa. If the F-5 value in the longitudinal direction is less than 70 MPa, the processing characteristics may be deteriorated due to scratches due to insufficient strength. On the other hand, when the F-5 value in the longitudinal direction is 150 MPa or more, it may be difficult to achieve compatibility with the F-5 value in the width direction. The F-5 value in the longitudinal direction is preferably 80 MPa or more and less than 140 MPa, more preferably 90 MPa or more and less than 130 MPa.

  Furthermore, the F-5 value in the width direction is preferably 80 MPa or more and less than 160 MPa. If the F-5 value in the width direction is less than 80 MPa, the processing characteristics due to the occurrence of scratches due to insufficient strength may be deteriorated, and if it is 160 MPa or more, it may be difficult to achieve compatibility with the F-5 value in the longitudinal direction. Preferably it is 90 MPa or more and less than 150 MPa, More preferably, it is 100 MPa or more and less than 140 MPa.

  The breaking strength in the longitudinal direction is preferably 200 MPa or more and less than 360 MPa, and more preferably 220 MPa or more and less than 340 MPa. The breaking strength in the width direction is preferably 260 MPa or more and less than 420 MPa, and particularly preferably 280 MPa or more and less than 400 MPa.

  The F-5 value and the breaking strength can be achieved by appropriately adjusting the stretching temperature and the stretching ratio in the longitudinal direction and the transverse direction.

  Furthermore, in the biaxially oriented polyester film for dry film resist support of the present invention, the film haze is preferably less than 1.0%. When the ratio is 1.0% or more, the resist film after development is increased because the polyester film, which is a support for the resist layer, is exposed by irradiating ultraviolet rays after laminating a resist layer on the polyester film. The patterning is distorted, missing, and the state of the resist pattern wall surface deteriorates. Moreover, the transmittance | permeability of a polyester film may be inhibited.

  As particles contained in the polyester layer (A layer, B layer) constituting the surface of the biaxially oriented polyester film for dry film resist support of the present invention, organic and inorganic particles can be used. Is, for example, polyimide resin, olefin or modified olefin resin, cross-linked polystyrene resin, silicone resin, etc., as inorganic, for example, silicon oxide, calcium carbonate, agglomerated alumina, aluminum silicate, mica, clay, talc, Examples thereof include barium sulfate. In adopting these particles, in order to suppress the increase in light transmittance and haze value, a method of improving the affinity with polyester by modifying the particle surface with a surfactant or the like is a void around the added particles. It can preferably be employed in terms of suppressing the occurrence. Further, the particle shape is almost spherical and the difference in refractive index from the polyester is preferably smaller because it can suppress scattered light when ultraviolet rays pass through the film layer, and colloidal silica and organic particles are particularly preferable. Furthermore, silicone particles and crosslinked polystyrene particles are suitable. Among these, crosslinked polystyrene particles made of a styrene-divinylbenzene copolymer prepared by emulsion polymerization are preferable because the particle shape is close to a true sphere, the particle size distribution is uniform, and uniform protrusions can be formed.

  It is also a desirable form to use the aggregated alumina together with the above-described particles in both the A layer and the B layer which are polyester layers. Here, the agglomerated alumina represents an aggregate of several to several hundred particles having an average primary particle diameter of 5 nm or more and less than 30 nm. The average primary particle diameter of the aggregated alumina is more preferably an average primary particle diameter of 8 nm or more and less than 15 nm. As the agglomerated alumina, one produced by a flame hydrolysis method using anhydrous aluminum chloride as a raw material or hydrolysis of alkoxide alumina can be employed. Agglomerated alumina is known in crystal form such as δ type, θ type, and γ type, and in particular, δ type alumina can be preferably used. These agglomerated alumina can be used by adding at the time of polyester polymerization.For example, as a slurry of ethylene glycol, which is part of the raw material at the time of polyester polymerization, pulverization and dispersion of a sand grinder, etc. By carrying out, an aggregated alumina having an average secondary particle diameter of 0.01 μm or more and less than 0.2 μm can be obtained. When the agglomerated alumina thus obtained is added to the film, it is arranged in the plane direction by biaxial stretching, so it does not form substantial protrusions, has little effect on the surface roughness, and is transparent. Since the property is good, deterioration of light transmittance and haze value can be suppressed. By including the aggregated alumina, the effect of reinforcing the background of the film surface is greatly obtained, the wear resistance is improved, and the effect of suppressing the dent defect generated when contacting with the roll during stretching is obtained. Aggregated alumina is preferably contained in the polyester resin composition constituting the surface layer (A layer, B layer), and the content is preferably 0.1 wt% or more and less than 5 wt% with respect to the entire polyester resin composition.

  In the biaxially oriented polyester film for dry film resist support of the present invention, the polyester layer (B layer) having the surface (B) has a particle A having a maximum particle size DA of less than 0.3 μm and a maximum particle size DB of 0. It is preferable to include two or more kinds of particles including particles B of 3 μm or more and less than 1.0 μm. The surface (A) preferably contains particles A having a maximum particle diameter DA of less than 0.3 μm. The maximum particle diameter referred to in the present invention represents an intermediate value of the upper 2% from the larger data of equivalent-circle diameters of particles determined by the method described later. When a resist layer is laminated on the surface (A), the particles contained in the A layer are affected by the reflection and scattering of light irradiated in the exposure step, thereby affecting the formation of the resist layer. When the maximum particle diameter DA contained in the A layer is 0.3 μm or more, the influence of the particles becomes noise when forming the resist pattern, and the resist pattern may be chipped. Also, the surface (B) constitutes the opposite surface of the resist layer, but if the particles contained in the B layer are affected by the reflection or scattering of light irradiated in the exposure process, the formation of the resist layer is affected. give. When the maximum particle size DB included in the layer B is 1.0 μm or more, the influence of the particles becomes noise when forming the resist pattern, and the resist pattern may be chipped. Also, if the average particle diameter DB is less than 0.3 μm, the handling property is deteriorated in the resist coating process, the coating becomes unstable, the coating spots are generated, and the air taken in at the time of winding after coating is Winding misalignment may occur due to difficulty in removal. More specifically, in the B layer, by containing agglomerated alumina as the particle A and a crosslinked polystyrene particle as the particle B, the slippage deteriorated due to the addition of the antistatic agent described later can be remarkably improved. It becomes possible.

  The B layer of the biaxially oriented polyester film for dry film resist support of the present invention preferably contains an antistatic agent. By including an antistatic agent in the B layer, handling properties when producing a resist polyester film, prevention of adhesion of dust and foreign materials, handling property of the resist film itself using the film, prevention of adhesion of dust and foreign materials Can be improved.

  The antistatic agent is a compound used for the purpose of imparting antistatic properties, and is an unsaturated monomer having a sulfonate group (for example, sodium vinylsulfonate, sodium methacrylate, sodium styrenesulfonate). Polymer type antistatic agent composed of one or more polymers, alkyl sulfonate (eg, sodium pentane sulfonate, sodium octane sulfonate), aryl sulfonate (eg, sodium benzyl sulfonate, toluyl sulfonic acid) Sodium), a low molecular weight antistatic agent of an aromatic sulfonate having an alkyl group (for example, sodium dodecylbenzenesulfonate), and the like.

  The antistatic agent may be kneaded into the polyester layer in an extruder or may be laminated by coating with a binder resin, but when the antistatic agent is laminated by a coating method, Extruders may cause loss of antistatic performance due to scraping on rolls, etc., and failure of resist patterning (distortion, chipping, omission) due to antistatic agent component transfer to the back surface (resist surface). Among them, it is preferable to be kneaded into the polyester layer. Furthermore, when an antistatic agent is laminated | stacked by the apply | coating system, it is unpreferable also at the point which causes the process contamination by the accumulation of a shaving thing, whitening of a conveyance roll, etc.

  The content of the antistatic agent contained in the B layer is preferably 0.5% by weight or more and less than 2.0% by weight, more preferably 0.7% by weight or more and 1%, based on the polyester of the B layer. Less than 5% by weight. When the content of the antistatic agent is 2.0% by weight or more, the haze in the biaxially oriented polyester film for dry film resist support of the present invention is increased, the slipping property is remarkably deteriorated due to blocking, and the handling property May decrease. On the other hand, when the content of the antistatic agent is less than 0.5% by weight, the antistatic property becomes insufficient.

  In the biaxially oriented polyester film for dry film resist support of the present invention, the difference in surface free energy between the surface (A) and the surface (B) needs to be 5.0 mN / m or more. Preferably, it is 7.0 mN / m or more. Moreover, it is preferable that the surface free energy of the surface (B) is larger than the surface free energy of the surface (A). The difference in surface free energy between the surface (A) and the surface (B) is less than 5.0 mN / m because the antistatic agent component on the surface (B) is transferred to the surface (A) which is a resist surface. As a result, there is a possibility that a defect (distortion, chipping, omission) in resist patterning may occur.

Although the details of the calculation method of the surface free energy here will be described later, the contact angles of four kinds of solutions of pure, ethylene glycol, formamide, and diiodomethane were measured on the film surface, The energy (γ) is separated into three components of a dispersion force component (γ _s ^d ), a polar force component (γ _s ^p ), and a hydrogen bond force component (γ _s ^h ), and an expression that expands the Fowks expression (expanded Fowks expression) ) "Is a value obtained as the sum of dispersion force, polarity force, and hydrogen bonding force.

  The difference in the surface free energy between the surface (A) and the surface (B) can be controlled within the above range by kneading the antistatic agent only in the B layer of the polyester layer in an extruder.

In the biaxially oriented polyester film for dry film resist support of the present invention, the surface specific resistance value of the surface (A) is 1.0 × 10 ¹⁴ Ω / □ or more and the surface specific resistance value of the surface (B) is 1. It must be 0 × 10 ¹³ Ω / □ or less. Furthermore, the surface specific resistance value of the surface (B) is preferably 1.0 × 10 ¹² Ω / □ or less, and more preferably 1.0 × 10 ¹¹ Ω / □ or less. When the surface specific resistance value of the surface (B) exceeds 1.0 × 10 ¹³ Ω / □, the charge on the film surface increases, and the handling property deteriorates when a polyester film for resist is produced, and dust and foreign matter adhere. May increase, the handling property of the resist film itself using the film may deteriorate, and the adhesion of dust and foreign matter may increase. On the other hand, when the surface specific resistance value of the surface (A) is less than 1.0 × 10 ¹⁴ Ω / □, the antistatic agent component on the surface (B) is transferred to the surface (A) which is the resist surface. As a result, there is a possibility that a defect (distortion, chipping, omission) in resist patterning may occur.

  In order to make the surface specific resistance value of the surface (A) and the surface (B) into the above-mentioned range, it can be achieved by kneading an antistatic agent only in the B layer of the polyester layer in an extruder.

  The biaxially oriented polyester film for dry film resist support of the present invention is required to be a polyester film having a laminated structure of three or more layers. Examples of the film having a three-layer laminated structure include those composed of A layer / C (intermediate layer) / B layer. Examples of the film having a laminated structure of four or more layers include those in which the intermediate layer has a laminated structure. The particle type, average particle diameter, and content contained in the A layer and B layer as the surface layer portion may be different. Particles may be added to the polyester layer constituting the surface layer in the coating step, but from the viewpoint of dispersibility of the particles, a polyester resin composition containing the particles is used to perform melt film formation by a coextrusion method. It is preferable to obtain.

  In the above configuration, the layer thickness (A layer, B layer) constituting the surface of the film is preferably 0.1 μm or more and less than 2 μm, and more preferably 0.4 μm or more and less than 1.8 μm. When the particle size is less than 0.1 μm, dropout of the particles added to the polyester layer becomes large. It becomes necessary, and it may be difficult to achieve compatibility with processing characteristics.

  Next, the manufacturing method of the biaxially-oriented polyester film for dry film resist supports of this invention is demonstrated. As a method of adding inert particles to polyester in melt film formation by co-extrusion method, for example, inert glycol is dispersed in a predetermined ratio in ethylene glycol, which is a diol component, for example, coarse particles of 3 μm or more. After high-precision filtration capable of collecting 95% or more, this ethylene glycol slurry is added at an arbitrary stage before completion of polyester polymerization. Here, when adding the particles, for example, it is preferable to add the water sol or alcohol sol obtained at the time of synthesis without drying once because the dispersibility of the particles is good and the generation of coarse protrusions can be suppressed. Also effective for the effect of the present invention is a method in which a water slurry of particles is directly mixed with predetermined polyester pellets, supplied to a vent type twin-screw kneading extruder and kneaded into polyester.

  In this way, the particle-containing master pellets prepared for each layer and the pellets substantially free of particles and the like are mixed at a predetermined ratio, dried, and then supplied to a known melt laminating extruder. As the extruder for producing the biaxially oriented polyester film for a dry film resist support of the present invention, a uniaxial or biaxial extruder can be used. Moreover, in order to omit the drying process of a pellet, the vent type extruder which provided the vacuum drawing line in the extruder can also be used. In addition, when providing an intermediate layer, since the amount of extrusion is the largest, use a so-called tandem extruder that shares the function of melting the pellets and the function of maintaining the molten pellets at a constant temperature. Can do. In order to extrude the layer constituting the surface of the biaxially oriented polyester film for dry film resist support of the present invention, it is preferable to use a biaxial vent type extruder because the dispersibility of the particles can be kept good.

  The polymer melted and extruded by the extruder is filtered through a filter. Since even a very small foreign substance enters a film and becomes a coarse protrusion defect, it is effective to use a high-accuracy filter that collects 95% or more of a foreign substance of 5 μm or more, for example. Subsequently, the sheet is extruded from a slit-shaped slit die and cooled and solidified on a casting roll to form an unstretched film. That is, it laminates using a plurality of extruders, a plurality of layers of manifolds or a merge block (for example, a merge block having a rectangular merge portion), extrudes a sheet from a die, and cools with a casting roll to produce an unstretched film. In this case, a method of installing a static mixer and a gear pump in the polymer flow channel is effective from the viewpoint of stabilizing the back pressure and suppressing thickness fluctuation.

  The stretching method may be simultaneous biaxial stretching or sequential biaxial stretching. In the case of sequential stretching, the first longitudinal stretching is important, and the stretching temperature is preferably 90 ° C. or higher and lower than 130 ° C., more preferably 100 ° C. or higher and lower than 125 ° C. When the stretching temperature is less than 90 ° C., the film is easily broken, and when the stretching temperature is 130 ° C. or more, the film surface is easily damaged by heat. Further, from the viewpoint of preventing stretching unevenness and scratches, stretching is preferably performed in two or more stages, and the total magnification is preferably 3 times or more and less than 4.5 times, more preferably 3.5 times in the length direction. 2 times or more and less than 4.3 times, and preferably 3.2 times or more and less than 5 times, more preferably 4.0 times or more and less than 4.6 times in the width direction. In order to achieve the target breaking strength of the film, a timely magnification can be selected. If the temperature and magnification range are out of this range, problems such as uneven stretching or film breakage are caused, and it is difficult to obtain a film characterized by the present invention. After re-longitudinal or transverse stretching, the heat setting is preferably 200 ° C. or higher and lower than 230 ° C., more preferably 210 ° C. or higher and lower than 230 ° C., preferably 0.5 second or longer and shorter than 20 seconds, more preferably 1 second or longer and shorter than 15 seconds. I do. In particular, when the heat setting temperature is less than 200 ° C., the crystallization of the film does not proceed, the structure is not stable, and the target characteristics such as heat shrinkage cannot be obtained. Thereafter, it is preferable to perform a relaxation treatment of 0.1% or more and less than 7.0% in the longitudinal and / or width direction.

  Furthermore, the surface roughness Ra of the drawing roll is preferably 0.005 μm or more and less than 1.0 μm, more preferably 0.1 μm or more and less than 0.6 μm. When Ra is 1.0 μm or more, unevenness on the roll surface during stretching is transferred to the film surface. On the other hand, when it is less than 0.005 μm, the roll and the film background adhere to each other, and the film is easily damaged by heat. . In order to control the surface roughness of the drawing roll, it is effective to appropriately adjust the particle size of the abrasive for polishing the drawing roll, the number of times of polishing the drawing roll, and the like. In particular, with respect to the stretching roll, it is preferable to increase the number of polishing of the stretching roll in order to avoid adhesion and accumulation of polyester degradation products and oligomers, which are a cause of dent defects on the film surface.

  Further, the total contact time between the roll and the film in the stretched portion is preferably less than 0.1 seconds, more preferably less than 0.08 seconds, which is particularly effective in producing the film. When the contact time between the stretching roll and the film is 0.1 seconds or more, only the film surface is locally heated by the heat of the stretching roll, which may cause a deterioration in micro-planarity at the time of heat load, or The film may be scratched. As a method for shortening the contact time, for example, a method in which a film is stretched in parallel between nip rolls without being wound around a stretch roll is effective.

  After the biaxially stretched film is cooled in the conveying step, the edge is cut and wound to obtain an intermediate product. In this conveying step, the thickness of the film is measured, the data is fed back and used to adjust the film thickness by adjusting the die thickness and the like, and foreign matter detection is performed by a defect detector.

  In the biaxially oriented polyester film for dry film resist support of the present invention, it is preferable to suppress the generation of chips when cutting the edge. Edge cutting is performed using a round blade, a shear blade, and a straight blade, but when using a straight blade, it is preferable not to always make the location where the blade hits the film the same location, because it is possible to suppress wear of the blade. It is. For this reason, it is preferable to have a mechanism for oscillating the blade to the upper limit. Moreover, it is preferable to provide a suction device at a film cutting location to suck generated chips and scraped powder generated by cutting the film ends after cutting.

  The intermediate product is slit into an appropriate width and length by a slitting process and wound to obtain a biaxially oriented polyester film roll for dry film resist support of the present invention. When cutting the film in the slitting process, it can be selected from the same cutting method as the above-described edge cutting.

  The intermediate product is slit to a desired width to obtain the biaxially oriented polyester film for dry film resist of the present invention.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not construed as being limited thereto.

(Measuring method)
(1) Maximum particle diameter of particles The layer constituting the film surface is measured as follows. The polymer is removed from the film by plasma low temperature ashing to expose the particles. The processing conditions are selected such that the polymer is ashed but the particles are not damaged as much as possible. The treated sample was observed with a scanning electron microscope (SEM; model S-4000 manufactured by Hitachi, Ltd.), the particle image was taken into an image analyzer (LUZEX_AP manufactured by Nireco Corporation), and the equivalent circle equivalent diameter was measured. The volume average particle diameter of is determined. The magnification of SEM is appropriately selected from 5000 to 20000 times depending on the particle diameter. Measure the equivalent circle equivalent diameter of at least 5000 particles, arbitrarily changing the observation location, and determine the maximum particle diameter from the middle value of the equivalent circle equivalent diameter of the top 2% from the larger of the measured equivalent circle equivalent diameter data. Ask for.

  About the layer which does not comprise the film surface, a film cross section is observed by 3000 to 20000 times by a particle diameter using a transmission electron microscope (TEM; Hitachi, Ltd. H-600 type | mold). The TEM slice thickness is about 100 nm, the equivalent circle equivalent diameter of 1000 particles is measured at different locations, and the middle of the equivalent circle equivalent diameter of the top 2% of the particles from the larger equivalent circle equivalent diameter data measured. The maximum particle size is obtained from the value.

  In addition, when measuring the volume average particle diameter of the particles, when observed by SEM and TEM, even if 10 fields of view are confirmed at 5000 times, if no particles are found, the particles should be substantially not contained. to decide.

(2) Film surface roughness (SRa, SRz value)
Surface (A) and surface (B) were measured using a three-dimensional fine surface profile measuring instrument (ET-350K manufactured by Kosaka Manufacturing Co., Ltd.), and an arithmetic average surface roughness was obtained from the obtained surface profile curve according to JIS / B0601. SRa value and 10-point average surface roughness SRz value are obtained. The measurement conditions are as follows.
X direction measurement length: 0.5 mm, X direction feed rate: 0.1 mm / second.
Y direction feed pitch: 5 μm, number of Y direction lines: 40.
Cut-off: 0.25 mm.
Stylus pressure: 0.02 mN.
Height (Z direction) Magnification: 50,000 times.

(3) Haze of film In accordance with JIS K7105-1981, a sample cut into a dimension of length 4.0 × width 3.5 cm from the center in the film width direction was used as a sample, and the haze was measured using a haze meter (HGM-manufactured by Suga Test Instruments). 2DP (for C light source)).

(4) Surface free energy The surface energy (unit: mN / m) of the biaxially oriented polyester film is calculated by the following method. The biaxially oriented polyester film is allowed to stand for 24 hours in an atmosphere having a room temperature of 23 ° C. and a relative humidity of 65%. Thereafter, the contact angle of each of the four types of solutions of pure water, ethylene glycol, formamide, and diiodomethane with respect to the surface (A) and the surface (B) under the same atmosphere is a contact angle meter CA-D type (Kyowa). 5 points are measured respectively by Interface Science Co., Ltd. The average value of the three measured values excluding the maximum value and the minimum value of the five measured values is defined as the contact angle of each solution.

Next, using the contact angles of the four types of solutions obtained, “the surface free energy (γ) of the solid, which is proposed by Hata et al., Is expressed as a dispersion force component (γ _s ^d ) and a polar force component (γ _s ^p ). , and separated into three components of the hydrogen bond force component (gamma _s ^h), the geometric mean method based on equations that extends Fowkes equation (extended Fowkes equation) "dispersion force of the present invention, polar forces, and dispersion forces and The surface energy that is the sum of the polar forces is calculated.

A specific calculation method is shown. The meaning of each symbol is described below. When γ _SL is the tension at the interface between the solid and the liquid, Equation (1) is established.
γ _S ^L : surface free energy of film surface and known solution
γ _S : Surface free energy on the film surface
γ _L : Surface free energy of known solution
γ _S ^d : Dispersive force component of surface free energy on film surface
γ _S ^p : Polar force component of surface free energy on film surface
γ _S ^h : Hydrogen bond strength component of surface free energy on film surface
γ _L ^d : Dispersion force component of surface free energy of known solution
γ _L ^p : Polar force component of the surface free energy of a known solution
γ _L ^h : hydrogen bonding force component of surface free energy of known solution
^{_{γ S L = γ S + γ}} L -2 (γ S d · γ L d) 1 / 2-2 (γ S p · γ L p) 1 / 2-2 (γ S h · γ L h) 1/2 ... Formula (1).

The state when the smooth solid surface and the droplet are in contact with each other at the contact angle (θ) is expressed by the following equation (Young's equation).
γ _S = γ _S ^L + γ _L cos θ (2).

When these mathematical formulas (1) and (2) are combined, the following formula is obtained.
(Γ _s ^d · γ _L ^d ) ^1/2 + (γ _s ^p · γ _L ^p ) ^1/2 + (γ _s ^h · γ _L ^h ) ^1/2 = γ _L (1 + cos θ) / 2 Formula (3).

Actually, the contact angle (θ) and the components of the surface tension of the known solution (γ _L ^d , γ _L ^p , γ _L ^h ) are expressed in four types of solutions of water, ethylene glycol, formamide, and diiodomethane. Substituting into (3), the four simultaneous equations are solved. As a result, the solid surface energy (γ), that is, the surface energy of the surface (A) and the surface (B) of the biaxially oriented polyester film for dry film resist support is calculated.

(5) Surface specific resistance Measured at an applied voltage of 100 V using a digital ultrahigh resistance / microammeter (R8340A manufactured by Advantest) under the same conditions after adjusting the humidity by leaving it to stand for 24 hours at a temperature of 23 ° C. and a relative humidity of 65%. Went. The unit is Ω / □, and the smaller the value, the better the antistatic performance.

(6) Visual inspection of resist resolution The visual evaluation method of resist resolution in the biaxially oriented polyester film of the present invention was performed in the following procedure.
(I) A negative resist “PMER N-HC600” manufactured by Tokyo Ohka Co., Ltd. was applied on a 6-inch Si wafer that had been polished on one side, and a resist layer having a thickness of 7 μm was prepared by rotating with a large spinner. Next, a pre-heat treatment was performed for about 20 minutes under a temperature condition of 70 ° C. using a ventilation oven with nitrogen circulation.
(Ii) The polyester film is stacked so as to come into contact with the resist layer, the polyester film is laminated on the resist layer using a rubber roller, and a photomask patterned with chromium metal is disposed thereon, Exposure was performed using an I-line stepper on the photomask.
(Iii) After peeling the polyester film from the resist layer, the resist layer was placed in a container containing the developer N-A5 and developed for about 1 minute. Then, it removed from the developing solution and washed with water for about 1 minute.
(Iv) The state of L / S (μm) (Line and Space) of the resist pattern prepared after development was observed at 1000 magnifications using a scanning electron microscope SEM. The resolution of the resist was evaluated according to the following criteria. Note that an evaluation of ◯ or higher is a practical level.
A: L / S = 8/8 μm can be clearly confirmed.
○: L / S = 8/8 μm cannot be clearly confirmed, but L / S = 10/10 μm can be clearly confirmed.
Δ: L / S = 10/10 μm cannot be clearly confirmed, but L / S = 15/15 μm can be clearly confirmed.
X: L / S = 15/15 μm cannot be clearly confirmed. (Production not applicable).

(7) Handling of resist film (slipability evaluation)
Using the biaxially oriented polyester film of the present invention as a support, a resist layer made of a negative photosensitive resin was formed on the A layer side by coating to prepare a resist film. The evaluation of slipperiness as handleability during the production of a resist film was in accordance with the following criteria. Note that an evaluation of ◯ or higher is a practical level.
○: Appropriate slipperiness and good handleability.
(Triangle | delta): Sliding property is bad and it is inferior to handleability.
×: Since it does not have proper sliding properties, it cannot be handled (production not applicable).

(8) Resist film handling (chargeability evaluation)
The evaluation of chargeability as the handleability during the production of the resist film produced in the above evaluation (7) was in accordance with the following criteria. Note that an evaluation of ◯ or higher is a practical level.
○: No charge is generated and the handleability is good.
(Triangle | delta): Charge arises and it is inferior to handleability.
X: Charging occurs and cannot be handled (not applicable for production).

(material)
(Creation of polyester A)
Esterification reaction is carried out while distilling water at 255 ° C. with 86.5 parts by weight of terephthalic acid and 37.1 parts by weight of ethylene glycol. After completion of the esterification reaction, 0.02 part by weight of trimethyl phosphoric acid, 0.06 part by weight of magnesium acetate, 0.01 part by weight of lithium acetate, and 0.0085 part by weight of antimony trioxide were added. The polycondensation reaction was carried out by heating up to 0 ° C. to obtain polyester pellets having an intrinsic viscosity of 0.63 dl / g. (Polyester A).

(Creation of polyester B, C and polyester D)
In addition, a water slurry of divinylbenzene / styrene copolymer crosslinked particles having a volume average particle diameter of 0.3 μm and a volume shape factor f = 0.51 obtained by a method for adsorbing monomers is substantially free of the above particles. A homopolyester pellet is contained using a vent type biaxial kneader to obtain a master pellet containing 2% by weight of divinylbenzene / styrene copolymer crosslinked particles having a volume average particle diameter of 0.3 μm with respect to the polyester (polyester B). .

  Master pellets containing divinylbenzene / styrene copolymer crosslinked particles having a volume average particle size of 0.45 μm and 0.8 μm were obtained in the same manner as the master pellets containing 1% by weight with respect to the polyester (polyester C and polyester D, respectively). .

(Creation of polyester E)
In the production of polyester in the same manner as described above, after transesterification, the volume average particle size 0.2 μm, the volume shape factor f = 0.51, the volume average particle size 0.06 μm, the volume shape factor f = 0.51, the Mohs hardness No. 7 spherical silica was added and a polycondensation reaction was performed to obtain silica-containing master pellets containing 1% by weight of the particles with respect to the polyester (Polyester E). The spherical silica to be used was obtained by adding a mixed solution consisting of ethanol, pure water, and ammonia water as a basic catalyst to this mixed solution while stirring the mixed solution of ethanol and ethyl silicate, and the resulting reaction solution The mixture was stirred to carry out a hydrolysis reaction of ethyl silicate and a polycondensation reaction of this hydrolysis product, followed by stirring after the reaction to obtain monodispersed silica particles.

(Creation of polyester F)
Furthermore, calcium carbonate having an average particle diameter of 1.0 μm was prepared to prepare a 10% ethylene glycol slurry. This slurry was subjected to a dispersion treatment with a jet agitator for one hour, and was subjected to high-precision filtration with a filter having a collection efficiency of 95% of 5 μm or more.
Dimethyl terephthalate is added with 1.9 moles of ethylene glycol and magnesium acetate tetrahydrate and 0.055% phosphoric acid to perform transesterification, and the slurry containing calcium carbonate is added after the transesterification. Subsequently, 0.025% of antimony trioxide was added, the temperature was raised and the polycondensation reaction was performed by evacuation, and the calcium carbonate having an intrinsic viscosity of 0.63 dl / g containing 1% by weight of calcium carbonate having an average particle size of 1.0 μm. A contained master pellet was obtained. (Polyester F).

(Creation of polyester G)
Further, δ-alumina is made into 10% ethylene glycol slurry as agglomerated alumina, pulverized and dispersed using a sand grinder, and further filtered using a 3 μm filter with a collection efficiency of 95%. Was added to the transesterification reaction product prepared above, followed by polycondensation reaction by adding antimony trioxide to obtain a master pellet having an intrinsic viscosity of 0.62 dl / g and containing 2% by weight of aggregated alumina. (Polyester G).

(Creation of polyester H)
Furthermore, when manufacturing polyester similarly to the above, the silica containing master pellet which contains 6 weight% of antistatic agents (sodium dodecylbenzenesulfonate) was obtained (polyester H).

(Preparation of coating layer (D) forming coating solution)
The coating solution for forming the coating layer containing the antistatic agent was coated with Nicazole RX-7013ED (acrylic polyester resin emulsion) manufactured by Nippon Carbide Co., Ltd., and Versa YE-910 manufactured by Nippon NSC (lithium polyester sulfonate). Salt-based antistatic agent) in a solid content mass ratio of RX-7013ED / YE-910 = 90/10 was diluted with water, and the surfactant RY-2 manufactured by Kyosei Chemical Co. has a total liquid ratio of 0.00. It was prepared by adding 1% by weight.

Example 1
After stirring the mixture of the raw materials prepared in the blend shown in Table 1 for each layer in the blender, the raw materials for the A layer and the B layer are the stirred raw materials, and the biaxial extrusion with vents for the A layer and the B layer The raw material of the C layer was dried under reduced pressure at 160 ° C. for 8 hours and supplied to the single screw extruder for the C layer. It is melt-extruded at 275 ° C., filtered with a high-precision filter that collects 95% or more of foreign matters of 5 μm or more, and then merged and laminated with a rectangular three-layer confluence block, consisting of A layer, B layer, and C layer 3 Layer lamination was used. Thereafter, the film was wound around a casting drum having a surface temperature of 25 ° C. on a cooling roll through a slit die maintained at 285 ° C. by using an electrostatic application casting method, and solidified by cooling to obtain an unstretched laminated film.

  This unstretched film was stretched 4.2 times in the longitudinal direction at 110 ° C. using a stretching roll having a surface roughness Ra of 0.2 μm. Further, after stretching 4.5 times in the width direction with hot air at 115 ° C. with a stenter, heat treatment was performed at 215 ° C. for 4 seconds under constant tension, and then 0.1% in the longitudinal direction and 3.2% in the width direction. % Relaxation treatment was performed to obtain an intermediate product of a biaxially oriented polyester film having a thickness of 16 μm. This intermediate product was slit with a slitter to obtain a roll of biaxially oriented polyester film having a thickness of 16 μm. The evaluation results of the obtained film are shown in Table 2. Thus, the biaxially oriented polyester film of the present invention was excellent in slipperiness, antistatic properties and resist resolution.

(Examples 2 to 5)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the compositions of the A layer, the B layer, and the C layer were changed as shown in Table 1. The evaluation results of the obtained film are shown in Table 2. Thus, the biaxially oriented polyester film of the present invention was excellent in slipperiness, antistatic properties and resist resolution, as in Example 1. Particularly in Examples 2 to 4, the resist resolution was particularly excellent.

(Comparative Examples 1-7)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the compositions of the A layer, the B layer, and the C layer were changed as shown in Table 1. The evaluation results of the obtained film are shown in Table 2. However, the biaxially oriented polyester film of the present invention was inferior to the sliding property, antistatic property and resist resolution as compared with Example 1, and a film satisfying all of them could not be obtained.

(Comparative Example 8)
The composition of the A layer, the B layer, and the C layer was changed as shown in Table 1, and the coating layer (D) forming coating solution containing the antistatic agent after stretching in the longitudinal direction was changed to a bar using a metalling bar. A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that it was applied by a coating method and dried simultaneously with stretching in a tenter to form an antistatic layer. The evaluation results of the obtained film are shown in Table 2. However, the biaxially oriented polyester film of the present invention was inferior in all of the slip property, antistatic property, and resist resolution compared to Example 1 because the antistatic agent component was transferred to the back surface (resist surface). It was.

  Since the biaxially oriented polyester film of the present invention has good permeability, slipperiness and antistatic properties, it can be suitably used for a dry film resist support.

Claims (9)

A polyester film having a laminated structure of three or more layers,
The surface of one outermost layer (this layer is A layer) (the surface is the surface (A)) and the other outermost layer (this layer is the B layer) (the surface is the surface (B )) Is a surface free energy difference of 5.0 mN / m or more, the surface resistivity of the surface (A) is 1.0 × 10 ¹⁴ Ω / □ or more, and the surface resistivity of the surface (B). A biaxially oriented polyester film for a dry film resist support having a value of 1.0 × 10 ¹³ Ω / □ or less. The biaxially oriented polyester film for a dry film resist support according to claim 1, wherein the surface free energy of the surface (B) is larger than the surface free energy of the surface (A). The B layer includes particles having a maximum particle size DA of less than 0.3 μm (the particles are referred to as particles A) and particles having a maximum particle size DB of 0.3 μm or more and less than 1.0 μm (the particles are converted to particles B). The biaxially oriented polyester film for a dry film resist support according to claim 1 or 2. The biaxially oriented polyester film for a dry film resist support according to any one of claims 1 to 3, wherein the film haze is less than 1.0%. The biaxially oriented polyester film for a dry film resist support according to any one of claims 1 to 4, comprising an antistatic agent. The arithmetic average surface roughness SRa (A) of the surface (A) and the arithmetic average surface roughness SRa (B) of the surface (B) are both 7 nm or less,
The 10-point average surface roughness SRz (A) of the surface (A) and the 10-point average surface roughness SRz (B) of the surface (B) are both 400 nm or less. Biaxially oriented polyester film for film resist support. The dry film according to any one of claims 1 to 6, wherein the surface roughness SRz (A) of the surface (A) is 100 nm or less, and the surface roughness SRz (B) of the surface (B) is 100 nm or more and 400 nm or less. Biaxially oriented polyester film for resist supports. The biaxially oriented polyester film for a dry film resist support according to any one of claims 1 to 7, wherein a resist layer is laminated on the surface (A). The method for producing a biaxially oriented polyester film for a dry film resist support according to any one of claims 1 to 8, which is obtained by melt film formation by a coextrusion method.