JP2022158018A - Biaxially oriented polyester film for dry film resist - Google Patents

Abstract

To provide a biaxially oriented polyester film which is provided with slipperiness by keeping, within a prescribed range, the number of aggregates of particles or the number of protrusions each nucleated around a dust being contaminated in a film, which has excellent handleability, in which impediment to light exposure is suppressed, and which can achieve formation of a resist having less defects.SOLUTION: A biaxially oriented polyester film for dry film resist contains one or more chemical elements selected from calcium, aluminum, antimony and silicon, and has 1 to 100/100 cm2 of foreign matters with outer diameters of 1.0 μm or more and 10.0 μm or less.SELECTED DRAWING: None

Description

The present invention relates to biaxially oriented polyester films for dry film resists.

Dry film resist (hereinafter sometimes referred to as DFR) is used to form circuits such as printed wiring boards, semiconductor packages, and flexible boards. 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 polyethylene film, polypropylene film, polyester film, or the like. . In order to create a conductor circuit using this DFR, the following steps are generally performed.
1) The step of peeling off the protective film from the DFR and laminating the substrate/conductive substrate layer so that the surface of the exposed resist layer and the surface of the conductive substrate layer such as copper foil on the substrate are in close contact. .
2) Next, a step of placing the photomask with the conductive circuit pattern printed on it on a support made of a polyester film, and irradiating the resist layer mainly composed of a photosensitive resin thereon with ultraviolet rays to expose it.
3) Then, after removing the photomask and the polyester film, a step of dissolving and removing the unreacted portion in the resist layer with a solvent.
4) Next, a step of etching with an acid or the like to dissolve and remove the exposed portion of the conductive substrate layer.

After step 4), the photoreacted portions in the resist layer and the conductive substrate layer portions corresponding to the photoreacted portions remain as they are. A circuit will be formed. Therefore, the polyester film used as the support is required to efficiently transmit ultraviolet rays. Thereby, the conductive circuit pattern is accurately reflected on the resist layer. In particular, in recent years, along with the miniaturization and weight reduction of IT equipment, etc., the miniaturization and high density of printed wiring boards have progressed. There is a need for polyester films for dry film resist supports that can achieve resolution. In addition, it is important for the polyester film used as the support to have moderate slipperiness in order to improve handling properties when a resist layer is formed on the support to produce a resist film. When particles are contained as an easy-to-slip material in order to impart slipperiness, the contained particles agglomerate, causing both transmission and reflection of light scattering by the particles when irradiated with ultraviolet light during the exposure process. A problem arises that the resolution of the resist is lowered.

Therefore, a polyester film for a dry film resist support has been proposed, which is characterized by making the surface of the film highly smooth, reducing the haze value, and keeping the transmittance at a wavelength of 365 nm within a certain range ( Patent document 1). In addition, a technique for improving the handleability and the adhesion prevention of dust and foreign matter when manufacturing a resist polyester film by incorporating an antistatic agent, and the handling property of the resist film itself using the film and the adhesion prevention of dust and foreign matter. is disclosed (Patent Documents 2, 3, 4). Further, a technique for improving dispersibility and preventing aggregation of particles by adding particles to be contained at an arbitrary production stage is disclosed (Patent Document 5). Furthermore, by reducing the number of coarse particles on the exposed surface, it is possible to suppress the loss of the resist pattern due to reflection and scattering in the vicinity of the film surface. Also disclosed is a technique capable of achieving more uniform exposure irradiation by appropriately scattering the light irradiated in the exposure process near the surface (Patent Document 6).

JP 2016-87854 A JP-A-2001-117237 JP 2006-327158 A JP 2007-254640 A JP 2014-98136 A JP 2018-100391 A

However, even with these proposals, it is difficult to satisfy the demand for higher resolution, and defects such as distortion and voids in the patterning of the resist after development and poor condition of the resist pattern walls cannot be sufficiently resolved. In particular, in recent years, there has been a demand for fine patterns with narrow wiring widths and narrow wiring intervals, and the presence of coarse particles leads to defects in the resist. In order to reduce coarse particles, the amount of particles added to the base film was reduced to prevent agglomeration, and the size of the particles to be included was reduced. Problems related to this are occurring conspicuously, so the demand for improved productivity (film windability) must also be met.
In view of these circumstances, the present invention provides smoothness by setting the number of projections whose cores are aggregates of particles added to the film or foreign matter mixed in the film within a predetermined range. An object of the present invention is to provide a biaxially oriented polyester film which is excellent in handleability, suppresses exposure inhibition, and achieves resist formation with few defects.

The present invention has the following features.
[I] Biaxial for dry film resist having 1 to 100 foreign matters/100 cm ² containing at least one element selected from calcium, aluminum, antimony, and silicon and having an outer diameter of 1.0 μm or more and 10.0 μm or less Oriented polyester film.
[II] It is composed of at least two layers, a layer A forming one surface and a layer B forming the other surface. 01 pieces/100 cm ² or more and 1.0 pieces/100 cm ² or less, and the number of projections having a height of 0.3 μm or more and less than 0.5 μm is 5.0 pieces/100 cm ² or more and 30.0 pieces/100 cm ² or less. 2. The biaxially oriented polyester film for dry film resist according to 1.
[III] The biaxially oriented polyester film for dry film resist according to [1] or [2], which has a thickness of 10 to 100 μm.
[IV] Both the arithmetic average surface roughness SRa (A) of the A side and the arithmetic average surface roughness SRa (B) of the B side are 7 nm or less, and the ten-point average surface roughness SRz (A ) and the surface (B) have a ten-point average surface roughness SRz(B) of 100 nm or more and 300 nm or less.
[V] The biaxially oriented polyester film for dry film resist according to any one of claims 1 to 4, which has a film haze of less than 1.0%.
[VI] The biaxially oriented polyester film for dry film resist according to any one of claims 1 to 5, which is used so that the surface A is provided with a resist.

According to the present invention, by setting the number of protrusions whose nuclei are aggregates of particles or foreign matter mixed in the film to a predetermined range, the film is provided with slipperiness and excellent handleability, and exposure inhibition is prevented. can be suppressed, and resist formation with few defects can be achieved.

The term "foreign matter" as used in the present invention refers to aggregates that are unnecessary for the polyester film. Such contaminants include aggregates of particles contained in the film, catalyst residues and dust mixed in the film.

The biaxially oriented polyester film of the present invention contains 1 to 100 particles/100 cm ² of foreign matter having an outer diameter of 1.0 μm or more and 10.0 μm or less and containing one or more elements selected from calcium, aluminum, antimony, and silicon. must have. By allowing a very small amount of foreign matter having an outer diameter of 1.0 μm or more to 10.0 μm or less, it is possible to suppress exposure inhibition while maintaining excellent handleability. The number of foreign particles having an outer diameter of 1.0 μm or more and 10.0 μm or less is more preferably 1 to 70/100 cm ² , and still more preferably 1 to 50/100 cm ² . Foreign matter containing one or more elements selected from calcium, aluminum, antimony, and silicon is a method of controlling the type and amount of a polymerization catalyst when polymerizing polyester used in a polyester film, a particle type to be contained in a polyester film, By controlling the particle diameter, it is possible to easily form a foreign matter containing one or more elements selected from calcium, aluminum, antimony, and silicon, and the formed foreign matter can be used as a foreign matter trap during melt film formation. The method of controlling the mesh of the collection filter makes it easy to control the size and number of foreign matter.

There is no particular limitation on the method of making the above-mentioned foreign substances exist in the biaxially oriented polyester film of the present invention. For example, by the method of controlling the type and amount of the polymerization catalyst when polymerizing the polyester used for the polyester film described above, and the method of controlling the particle type and particle size to be contained in the polyester film, calcium, aluminum, antimony, silicon After forming the foreign matter containing one or more selected elements, in addition to the method of controlling the mesh of the foreign matter collection filter used during melt film formation, the film is separately added to the film at any stage after melt extrusion. Examples include a method of incorporating particles and the like.

The biaxially oriented polyester film of the present invention is composed of at least two layers, an A layer forming one surface and a B layer forming the other surface. 0.01/100 cm ² or more and 1.0/100 cm ² or less, and the number of projections with a height of 0.3 μm or more and less than 0.5 μm is 5.0/100 cm ² or more and 30.0/100 cm It is preferably ² or less. The number of protrusions with a height of 0.5 μm or more is more preferably 0.01/100 cm ² or more and 0.1/100 cm ² or less. The number of projections with a height of 0.3 μm or more and less than 0.5 μm is more preferably 5.0/100 cm ² or more and 20.0/100 cm ² or less, and still more preferably 5.0/100 cm ² or more and 10.0. /100 cm ² or less.

The number of protrusions with a height of 0.5 μm or more is 1.0/100 cm ² or less, and the number of protrusions with a height of 0.3 μm or more and less than 0.5 μm is 30.0/100 cm ² or less. This makes it possible to suppress the loss of the resist pattern due to the influence of reflection and scattering of light due to non-uniform incident angles of light in the exposure process. On the other hand, the number of protrusions with a height of 0.5 μm or more is 0.01/100 cm ² or more, and the number of protrusions with a height of 0.3 μm or more and less than 0.5 μm is 5.0/100 cm ² or more. It was found that it is possible to suppress the occurrence of omission. This is because the number of protrusions with a height of 0.5 μm or more is 0.01/100 cm ² or more, and the number of protrusions with a height of 0.3 μm or more and less than 0.5 μm is 5.0/100 cm ² or more. As a result of the excessively flattened slipperiness, the handleability in the film manufacturing process and the DFR manufacturing process deteriorates, resulting in a decrease in yield, especially problems related to winding, and scratches on the film surface. It is presumed that this is because the occurrence of exposure inhibition can be suppressed. Although the method for adjusting the number of protrusions to the above range is not particularly limited, examples thereof include a method of controlling the type and content of particles, which will be described later.

The biaxially oriented polyester film of the present invention must be biaxially oriented. In the present invention, biaxial orientation refers to a state in which an unstretched (unoriented) film is stretched in a two-dimensional direction by a conventional method (a film showing a biaxially oriented pattern in wide-angle X-ray diffraction). The stretching may be sequential biaxial stretching or simultaneous biaxial stretching. In sequential biaxial stretching, the process of stretching in the longitudinal direction (longitudinal) and in the width direction (horizontal) can be performed once in the longitudinal direction - in the lateral direction, or twice in the longitudinal direction - lateral direction - longitudinal direction - lateral direction. You can also

In the biaxially oriented polyester film of the present invention, having a polyester resin as a main component means that at least 70 mol% or more is a monomer or a low weight polymer having a dicarboxylic acid, a diol, and their ester-forming derivatives as main constituents. It is a polyester obtained by polymerization from coalescence. 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, 2,6-naphthalenedicarboxylic acid, and the like, with terephthalic acid being particularly preferred. These acid components may be used singly or in combination of two or more. Other aromatic dicarboxylic acids such as isophthalic acid or fatty acids may be partially copolymerized.

Examples of diol components include ethylene glycol, 1,2-propanediol, 1,3-propanediol, and neopentyl glycol. Among them, 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 of the present invention is preferably polyethylene terephthalate, polyethylene naphthalate and copolymers thereof, polybutylene terephthalate and copolymers thereof, polybutylene naphthalate and copolymers thereof, and further Examples include polyhexamethylene terephthalate and copolymers thereof, polyhexamethylene naphthalate and copolymers thereof, and polyethylene terephthalate is particularly preferred.

The polyester used in the present invention can be produced by a conventionally known method. For example, after directly esterifying the acid component with the diol component, the product of this reaction is heated under reduced pressure to polycondense while removing the excess diol component. A method of using an ester, subjecting it to transesterification with a diol component, and then subjecting it to polycondensation in the same manner as described above can be employed. In this case, conventionally known alkali metals, alkaline earth metals, manganese, cobalt, zinc, antimony, germanium, titanium compounds and the like can be used as reaction catalysts, if necessary.

The intrinsic viscosity of the above polyester preferably has 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 of the present invention preferably has a total thickness of 10 μm or more and 100 μm or less. Particularly preferably, the thickness is 12 μm or more and 40 μm or less. By setting the total thickness of the film to 10 μm or more, it is possible to have strength to the extent that it is easy to handle in the processing step, and by setting it to 100 μm or less, the light transmittance and haze value are good, and it is economical. The properties are also improved.

In the biaxially oriented polyester film of the present invention, the arithmetic mean surface roughness SRa (A) of side A and the arithmetic mean surface roughness SRa (B) of side B are both 7 nm or less, and the ten-point average surface roughness SRz (A) and SRz (B) are preferably 50 nm or more and 300 nm or less. Furthermore, SRa(A) is more preferably 3 nm or more and less than 6.5 nm, and SRz(A) is more preferably 50 nm or more and less than 250 nm. By achieving a surface roughness within this range, it is possible to obtain an appropriate smoothness that suppresses the influence of reflection on the film surface during exposure, to form a high-definition resist pattern, and at the same time to handle it during processing. You get sex. By setting SRa(A) and SRa(B) to 7 nm or less and SRz(A) and SRz(B) to be 300 nm or less, the incident angle of light in the exposure process due to the unevenness transferred from the film to the resist surface is It is possible to suppress the occurrence of omission of the resist pattern due to the influence of reflection and scattering of light due to non-uniformity. In order to make the surface roughness of the A side and the B side within the above range, the polyester resin constituting the layer having the A side (A layer) and the layer having the B side (B layer) contains specific organic particles described later. Alternatively, it can be achieved by containing a specific amount of inorganic particles.

Further, the biaxially oriented polyester film of the present invention preferably has a film haze of less than 1.0%. When the film haze is less than 1.0%, the scattering of ultraviolet rays by the polyester film, which is the support for the resist layer, increases when the resist layer is laminated on the polyester film and then exposed to ultraviolet rays. In addition, the patterning of the resist after development may be distorted or removed, the condition of the walls of the resist pattern may deteriorate, or the transmittance of the polyester film may be hindered.

The biaxially oriented polyester film of the present invention preferably contains particles in at least one surface layer. As the particles, organic and inorganic particles can be used. Examples of organic particles include polyimide resins, olefin or modified olefin resins, crosslinked polystyrene resins, and silicone resins. , silicon oxide, calcium carbonate, agglomerated alumina, aluminum silicate, mica, clay, talc, barium sulfate, and the like. When using these particles, in order to suppress the increase in light transmittance and haze value, the surface of the particles is modified with a surfactant or the like to improve the affinity with polyester. It can be preferably employed in terms of suppressing generation. In addition, it is preferable that the particle shape is close to spherical and that the difference in refractive index from that of the polyester is small 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 them, crosslinked polystyrene particles composed of a styrene-divinylbenzene copolymer prepared by emulsion polymerization are preferable because they have a particle shape close to a true sphere, have a uniform particle size distribution, and can form uniform protrusions. Crosslinked polystyrene particles made of a styrene-divinylbenzene copolymer are preferably contained in the polyester resin composition constituting the surface layer (A layer), and the content thereof is 0.00% relative to the entire polyester resin composition constituting the surface layer. 01% by weight or more and less than 0.1% by weight is preferable. If the content is less than 0.01% by weight, the handling property deteriorates in the resist coating process, the coating becomes unstable, coating spots occur, and trapped air escapes during winding after coating. It may become difficult to roll, which may cause winding misalignment. If the content is 0.1% by weight or more, the crosslinked polystyrene particles tend to agglomerate with each other, and the reflection and scattering of light caused by the non-uniform incidence angle of light in the exposure process can affect the resist pattern. Dropouts may occur.

It is also one of desirable forms to use agglomerated alumina together with the above-described particles for the surface layer. Here, aggregated alumina refers to aggregated particles having an average primary particle size of 5 nm or more and less than 30 nm, from several to several hundreds. More preferably, the average primary particle size of the aggregated alumina is 8 nm or more and less than 15 nm. The agglomerated alumina can be produced by flame hydrolysis using anhydrous aluminum chloride as a raw material, or hydrolysis of alkoxide alumina. Agglomerated alumina is known as a crystal type such as δ-type, θ-type, and γ-type, and δ-type alumina is particularly suitable for use. These aggregated aluminas can be used by adding them during polyester polymerization. For example, as a slurry of ethylene glycol, which is part of the raw material for polyester polymerization, pulverization and dispersion are performed using a sand grinder or the like, followed by microfiltration. By doing so, aggregated alumina having an average secondary particle size of 0.01 μm or more and less than 0.2 μm can be obtained. When the agglomerated alumina obtained in this way is added to a film, it is arranged in the plane direction by biaxial stretching, so that it does not form substantial protrusions, has little effect on the surface roughness, and has a low permeability. Since it has good properties, deterioration of light transmittance and haze value can be suppressed. By containing agglomerated alumina, the effect of reinforcing the surface texture of the film is greatly obtained, the abrasion resistance is improved, and the effect of suppressing the dent defect that occurs when the film comes into contact with rolls during stretching is obtained. Agglomerated alumina is preferably contained in the polyester resin composition forming the surface layer, and the content thereof is preferably 0.1% by weight or more and less than 5.0% by weight with respect to the entire polyester resin composition. If the content is less than 0.1% by weight, the handling property deteriorates in the resist coating process, the coating becomes unstable, coating spots occur, and trapped air escapes during winding after coating. It may become difficult to roll, which may cause winding misalignment. If the content is 5.0% by weight or more, the agglomerated alumina tends to agglomerate more easily, and due to the influence of reflection and scattering of light due to non-uniform incident angles of light in the exposure process, the resist pattern is affected. Dropouts may occur.

Next, the method for producing the biaxially oriented polyester film of the present invention will be described. The polyester used in the present invention can be produced by a conventionally known method as described above. For example, after directly esterifying the acid component with the diol component, the product of this reaction is heated under reduced pressure to polycondense while removing the excess diol component. A method of using an ester, subjecting it to transesterification with a diol component, and then subjecting it to polycondensation in the same manner as described above can be employed. In this case, conventionally known alkali metals, alkaline earth metals, manganese, cobalt, zinc, antimony, germanium, titanium compounds and the like can be used as reaction catalysts, if necessary. At this time, it is possible to control the amount of foreign matters resulting from the catalyst residue by changing the addition amount and addition rate of the reaction catalyst to the transesterification reaction tank, the heating temperature and the residence time. For example, the larger the amount of reaction catalyst added to the transesterification reaction tank, the faster the addition rate, the higher the heating temperature, and the longer the residence time, the more the amount of foreign matter tends to increase.

As a method for incorporating inert particles into polyester in melt film formation by a coextrusion method, for example, inert particles are dispersed in the form of a slurry in a predetermined ratio in ethylene glycol, which is a diol component. After high-precision filtration capable of collecting 95% or more of coarse particles, this ethylene glycol slurry is added at any stage before the polyester polymerization is completed. Here, when adding the particles, for example, it is preferable to add the water sol or alcohol sol obtained during the synthesis of the particles without drying them once, because the dispersibility of the particles is good and the occurrence of coarse protrusions can be suppressed. A method in which an aqueous slurry of particles is directly mixed with predetermined polyester pellets, supplied to a vent-type twin-screw kneading extruder, and kneaded into polyester is also effective for the effects of the present invention.

In this way, the particle-containing master pellets and pellets substantially free of particles and the like prepared for each layer are mixed in a predetermined ratio, dried, and fed to a known melt lamination extruder. A single-screw or twin-screw extruder can be used as the extruder for producing the biaxially oriented polyester film of the present invention. In order to omit the pellet drying process, a vent type extruder provided with a vacuum drawing line can also be used. In addition, when an intermediate layer is provided, the extrusion rate is the highest, so it is recommended to use a so-called tandem extruder that shares the function of melting the pellets and the function of keeping the melted pellets at a constant temperature in each extruder. can be done. For extruding the layer constituting the surface of the biaxially oriented polyester film of the present invention, using a twin-screw vent type extruder can keep the dispersibility of the particles in good condition and suppress the agglomeration of the particles. preferable.

The polymer melted and extruded by the extruder is filtered through a filter. At this time, the size and number of foreign matter remaining on the polyester film can be controlled by the mesh diameter of the filter. For example, there is a method using two or more filters having different performances, and it is effective to use a filter that collects 95% or more of foreign matters of 2 μm or more and 5 μm or more. Subsequently, it is extruded into a sheet form through a slit-shaped slit die and cooled and solidified on a casting roll to form an unstretched film. That is, the sheets are laminated using a plurality of extruders, a multi-layered manifold or a confluence block (eg, a confluence block having a rectangular confluence), the sheet is extruded through a spinneret, and cooled on a casting roll to form an unstretched film. In this case, it is effective to install a static mixer or a gear pump in the polymer flow path from the viewpoint of stabilizing the back pressure and suppressing the thickness variation.

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 tends to break, and when the stretching temperature is 130°C or higher, the film surface tends to be thermally damaged, which is not preferable. From the viewpoint of preventing uneven stretching and scratches, the stretching is preferably performed in two or more stages, and the total magnification in the longitudinal direction is preferably 3 times or more and less than 4.5 times, more preferably 3.5 times. It is 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, the appropriate magnification can be selected. If the temperature and magnification are out of this range, problems such as uneven stretching or film breakage will occur, making it difficult to obtain the film characteristic of the present invention, which is not preferred. After longitudinal or transverse stretching, heat setting is preferably 200° C. or more and less than 230° C., more preferably 210° C. or more and less than 230° C., preferably 0.5 seconds or more and less than 20 seconds, more preferably 1 second or more and less than 15 seconds. I do. In particular, when the heat setting temperature is lower than 200° C., crystallization of the film does not proceed, and the structure is not stable, and the target properties such as heat shrinkage cannot be obtained, which is not preferable. After that, it is preferable to perform a relaxation treatment of 0.1% or more and less than 7.0% in the longitudinal direction and/or the width direction.

Furthermore, the surface roughness Ra of the stretching rolls 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. If Ra is 1.0 μm or more, the unevenness of the roll surface is transferred to the film surface during stretching, and if it is less than 0.005 μm, the roll and the film surface will adhere to each other, making the film susceptible to heat damage. . In order to control the surface roughness of the drawing rolls, it is effective to appropriately adjust the particle size of the abrasive for polishing the drawing rolls, the number of times the drawing rolls are polished, and the like. Especially for the stretching rolls, it is preferable to increase the number of polishing of the stretching rolls in order to avoid adhesion and accumulation of polyester decomposition products and oligomers, which are feared to cause pitting defects on the film surface.

Furthermore, it is particularly effective in producing the film that the total contact time between the rolls and the film in the stretching section is preferably less than 0.1 seconds, more preferably less than 0.08 seconds. If the contact time between the stretching rolls and the film is 0.1 second or longer, only the film surface is locally heated by the heat of the stretching rolls, which may lead to deterioration of the microflatness during heat loading. It may scratch the film. As a method for shortening the contact time, for example, a method of stretching the film in parallel between nip rolls without winding the film around stretching rolls is effective.

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

It is preferable for the biaxially oriented polyester film of the present invention to suppress the generation of shavings when the edges are cut. Edge cutting is performed using a round blade, a shear blade, or a straight blade. When using a straight blade, it is preferable to keep the blade from contacting the film in the same position, as this will reduce wear on the blade. is. Therefore, 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 the film cutting portion to suck the generated cutting powder and the scraped powder generated by scraping the ends of the film after cutting.

The intermediate product is slit to an appropriate width and length by a slitting process and wound up to obtain a roll of the biaxially oriented polyester film of the present invention. When cutting the film in the slitting process, the same cutting method as that for edge cutting can be selected.

The intermediate product is slit to a desired width to obtain the biaxially oriented polyester film of the present invention. The biaxially oriented polyester film of the present invention thus obtained has good permeability and slipperiness, and therefore can be suitably used as a dry film resist support.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention should not be construed as being limited thereto.

(Measuring method)
(1) Film surface roughness (SRa, SRz values)
Surface (A) and surface (B) are measured using a three-dimensional fine surface profiler (ET-350K manufactured by Kosaka Seisakusho), and from the obtained surface profile curve, the arithmetic average surface roughness is calculated according to JIS B0601. The surface roughness SRa value and the ten-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/sec.
Feed pitch in Y direction: 5 μm, number of lines in Y direction: 40 lines.
Cutoff: 0.25mm.
Stylus pressure: 0.02 mN.
Height (Z direction) Magnification: 50,000 times.

(2) Haze of film According to JIS K7105-1981, a sample cut out from the center of the film in the width direction to a size of 4.0 x 3.5 cm in width is used. 2DP (for C light source)).

(3) Total Thickness of Film Using a transmission electron microscope (TEM; Model H-600 manufactured by Hitachi Ltd.), the cross section of the film is observed as an ultra-thin section (RuO ₄ stained) at an accelerating voltage of 100 kV. Find the total thickness from the entire cross section. The magnification may be appropriately set, but generally 1000 times is suitable.

(4) Number of Foreign Matters and Number of Projections A 5 cm×5 cm piece of the biaxially oriented polyester film is cut out and observed with a shape analysis laser microscope (VK-X250 manufactured by KEYENCE). Observation conditions are automatic observation of 150 fields of view with a measurement area of 220 μm×290 μm using a 50× objective lens. This is repeated 10 times to observe a total of 1500 fields of view (=95.7 mm ² ). The center line of each field of view is calculated with 1024×768 pixels as the total number of measurement pixels per one field of view. When measuring the number of foreign matter, the captured image was subjected to binarization processing, and the number of foreign matter having a major axis of 1.0 μm or more was counted using a particle analysis module (VKH1XG manufactured by Keyence). Also, when measuring the number of protrusions, a multi-file analysis application (VK-Xseries manufactured by KEYENCE) counts protrusions with a threshold (protrusion height) of 0.3 μm or more and 0.5 μm or more for each field of view, and 1500 The number of protrusions was calculated from the total field of view, and a value per 100 cm ² was obtained.

(5) Elemental analysis of foreign matter After removing the polyester on the film surface by plasma low temperature ashing treatment, the foreign matter is exposed on the surface, observed at a magnification of about 1,000 times with a scanning electron microscope (SEM), and elemental analysis is performed. rice field.

(6) Visual Inspection of Resist Resolution Visual evaluation of resist resolution in the biaxially oriented polyester film of the present invention was performed according to the following procedure.
(i) A 6-inch Si wafer mirror-polished on one side was coated with a negative resist "PMER N-HC600" manufactured by Tokyo Ohka Co., Ltd., and spun with a large spinner to form a resist layer with a thickness of 7 μm. Then, preheat treatment was performed for about 20 minutes at a temperature of 70° C. using a ventilated oven with nitrogen circulation.
(ii) The A-layer side surface of the polyester film is placed in 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 formed thereon. was placed, and exposure was performed from above the photomask using an I-line stepper.
(iii) After peeling off the polyester film from the resist layer, the resist layer was placed in a container containing developer N-A5 and developed for about 1 minute. After that, it was taken out 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 formed after development was observed with a scanning electron microscope SEM at a magnification of 1000. Evaluation of resist resolution was based on the following criteria.
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.
×: L/S=15/15 μm cannot be clearly confirmed. (not applicable to production).

(7) Handleability of resist film (slipperiness 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 layer A side by coating to prepare a resist film. Evaluation of slipperiness as handleability at the time of resist film production was performed according to the following criteria.
⊚: Appropriate slidability, almost no problems related to winding or scratches on the film surface, and good handleability.
◯: Problems related to winding and scratches on the film surface occur sporadically, but the handleability is within the range of practical use.
Δ: Poor smoothness, problems related to winding and scratches on the film surface, and poor handleability.
x: Due to the lack of proper slipperiness, problems related to winding and scratches on the film surface frequently occur, and the handling property is so poor that it is difficult to apply it to production.

(material)
(Preparation of polyester A)
86.5 parts by weight of terephthalic acid and 37.1 parts by weight of ethylene glycol are subjected to an esterification reaction at 255° C. while distilling off water. After completion of the esterification reaction, 0.02 parts by weight of trimethylphosphoric acid, 0.06 parts by weight of magnesium acetate, 0.01 parts by weight of lithium acetate, and 0.0085 parts by weight of antimony trioxide were added, followed by stirring at 290 parts by weight under vacuum. The mixture was heated to 0° C. to carry out a polycondensation reaction to obtain polyester pellets having an intrinsic viscosity of 0.63 dl/g. (Polyester A).

(Creation of polyester B)
In producing polyester in the same manner as above, after transesterification, spherical silica having a volume average particle diameter of 0.06 μm, a volume shape factor of f = 0.51, and a Mohs hardness of 7 is added, and a polycondensation reaction is performed to obtain particles. A silica-containing master pellet containing 0.5% by weight of polyester was obtained (polyester B). The spherical silica used was obtained by adding a mixed solution of ethanol, pure water, and ammonia water as a basic catalyst to a mixed solution of ethanol and ethyl silicate while stirring the mixed solution. was stirred to carry out the hydrolysis reaction of ethyl silicate and the polycondensation reaction of the hydrolyzed product, followed by post-reaction stirring to obtain monodisperse silica particles.

(Preparation of Polyester C)
In producing polyester in the same manner as described above, after transesterification, spherical silica having a volume average particle diameter of 0.2 μm, a volume shape factor of f = 0.51, and a Mohs hardness of 7 is added, and a polycondensation reaction is performed to obtain particles. A silica-containing master pellet containing 2% by weight of polyester was obtained (Polyester C). The spherical silica used was obtained by adding a mixed solution of ethanol, pure water, and ammonia water as a basic catalyst to a mixed solution of ethanol and ethyl silicate while stirring the mixed solution. was stirred to carry out the hydrolysis reaction of ethyl silicate and the polycondensation reaction of the hydrolyzed product, followed by post-reaction stirring to obtain monodisperse silica particles.

(Preparation of Polyester D, E, F, G)
Separately, an aqueous slurry of divinylbenzene/styrene copolymer crosslinked particles having a volume average particle diameter of 0.15 μm and a volume shape factor f of 0.51 obtained by a method of adsorbing a monomer was prepared substantially free of particles. Homopolyester pellets are incorporated using a vented twin-screw kneader to obtain master pellets containing 1% by weight of divinylbenzene/styrene copolymer crosslinked particles with a volume average particle size of 0.15 μm based on the polyester (Polyester D). . In addition, master pellets containing divinylbenzene/styrene copolymer crosslinked particles having volume average particle sizes of 0.3 μm, 0.45 μm, and 0.80 μm are the same as master pellets containing 0.2% by weight and 1% by weight of polyester. (Polyester E, F, G).

(Preparation of polyester H)
Further, calcium carbonate having an average particle size of 1.0 μm was prepared and made into a 10% ethylene glycol slurry. This slurry was subjected to dispersion treatment for one hour with a jet agitator, and then subjected to high-precision filtration with a filter of 5 μm or more and a collection efficiency of 95%. 1.9 mol of ethylene glycol, 0.05% of magnesium acetate tetrahydrate and 0.015% of phosphoric acid were added to dimethyl terephthalate to carry out heat transesterification, and the above slurry containing calcium carbonate was added after transesterification. Subsequently, 0.025% of antimony trioxide is added, the temperature is raised, and the polycondensation reaction is performed under vacuum to obtain 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. containing master pellets were obtained. (Polyester H).

(Preparation of Polyester I and J)
Furthermore, as agglomerated alumina, a 10% ethylene glycol slurry of delta-alumina is used, pulverized and dispersed using a sand grinder, and filtered using a 3 μm filter with a collection efficiency of 95%. , then antimony trioxide is added to perform a polycondensation reaction, and a master with an intrinsic viscosity of 0.62 dl / g containing 1.5% by weight and 6.0% by weight of agglomerated alumina A pellet was obtained. (Polyester I, J).

(Example 1)
After stirring the mixture of raw materials prepared according to the formulation shown in Table 1 for each layer in a blender, the raw materials for the A layer and B layer are mixed with the vented biaxial extrusion for the A layer and the B layer. The raw material for the C layer was dried under reduced pressure at 120 to 140° C. for 1 hour or more and fed to a single screw extruder for the C layer. Subsequently, it was melt extruded at 275° C., and the A layer was filtered with a high-precision filter that collects 95% or more of foreign substances of 2 μm or more, and the B layer was filtered with a high-precision filter that collects 95% or more of foreign substances of 5 μm or more. After that, they were merged and laminated in a rectangular three-layer confluence block to form a three-layer lamination consisting of an A layer, a B layer, and a C layer. After that, the film was wound on a casting drum having a surface temperature of 23° C. using an electrostatic casting method on a chill roll through a slit die kept at 285° C., and solidified by cooling to obtain an unstretched laminated film.

After preheating this unstretched film with a heating roll at 70 to 130 ° C., it is stretched 4 times in the longitudinal direction at 110 to 120 ° C. using a stretching roll with a surface roughness Ra of 0.2 μm. The temperature was lowered by 80 to 100° C. to cool the film after uniaxial stretching. Furthermore, subsequently, after stretching 4.5 times in the width direction under hot air of 110 to 115 ° C. with a stenter, heat treatment is performed at 220 ° C. for 4 seconds under constant tension, and then 0.1% in the longitudinal direction and 0.1% in the width direction. A 3.2% relaxation treatment was applied to obtain an intermediate product of a biaxially oriented polyester film having a thickness of 16 μm. This intermediate product was slit by a slitter to obtain a roll of biaxially oriented polyester film having a thickness of 16 μm. Table 2 shows the evaluation results of the obtained film. Thus, the biaxially oriented polyester film of the present invention was excellent in slipperiness and resist resolution.

(Examples 2-5)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the compositions of the layers A, B and C were changed as shown in Table 1. Table 2 shows the evaluation results of the obtained film. As described above, the biaxially oriented polyester film of the present invention was excellent in slipperiness and resist resolution as in Example 1.

(Comparative Examples 1 to 3)
A biaxially oriented polyester film was obtained in the same manner as in Example 1, except that the compositions of the A layer, B layer, and C layer were changed as shown in Table 1. Table 2 shows the evaluation results of the obtained film. However, the biaxially oriented polyester film of the present invention contained many foreign substances that inhibited exposure, and the resist resolution was inferior to those of Examples 1 to 5, which was insufficient for production application.

(Comparative Example 4)
The compositions of the A layer, B layer, and C layer were changed as shown in Table 1, and each layer was passed through two high-precision filters that capture 95% or more of foreign matter of 1 μm or more. A biaxially oriented polyester film was obtained in the same manner as in Example 1. Table 2 shows the evaluation results of the obtained film. The resist resolution of the biaxially oriented polyester film of the present invention was as good as that of Example 1, but the number of projections was small and the handleability was poor.

(Comparative Example 5)
Same as Example 1 except that the compositions of the A layer, B layer, and C layer were changed as shown in Table 1, and a high-precision filter that collects 95% or more of foreign matter of 5 μm or more was used in the A layer. to obtain a biaxially oriented polyester film. Table 2 shows the evaluation results of the obtained film. However, the biaxially oriented polyester film of the present invention had a large number of foreign substances that hindered exposure, and the resist resolution was inferior to that of Examples 1 to 5, which was insufficient for production application.

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

Claims (6)

A biaxially oriented polyester film for dry film resist containing 1 or more elements selected from calcium, aluminum, antimony, and silicon and having 1 to 100 particles/100 cm ² of foreign matter with an outer diameter of 1.0 μm or more and 10.0 μm or less. . It consists of at least two layers, an A layer forming one surface and a B layer forming the other surface, and the number of protrusions with a height of 0.5 μm or more on the B layer surface (B surface) is 0.01/ ^{2. The number of protrusions having a height of 0.3 μm or more and less than 0.5 μm is 5.0/100 cm 2 or more and 30.0/100 cm 2 or} less. biaxially oriented polyester film for dry film resist. 3. The biaxially oriented polyester film for dry film resist according to claim 1, which has a thickness of 10 to 100 μm. The arithmetic average surface roughness SRa (A) of surface A and the arithmetic average surface roughness SRa (B) of surface B are both 7 nm or less, and the ten-point average surface roughness SRz (A) of surface (A) and surface 4. The biaxially oriented polyester film for dry film resist according to claim 1, wherein (B) has a ten-point average surface roughness SRz(B) of 50 nm or more and 300 nm or less. The biaxially oriented polyester film for dry film resist according to any one of claims 1 to 4, which has a film haze of less than 1.0%. The biaxially oriented polyester film for dry film resist according to any one of claims 1 to 5, which is used so that the surface A is provided with a resist.