JP2008251920A - Polyester film for liquid resist photomask protective tape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film for liquid resist photomask protective tape, such that production of internal foreign matter and oligomer of a protection tape base material is very small. <P>SOLUTION: A biaxially-oriented polyester film for liquid resist photomask protective tape which has a surface resistivity of 1.0×10<SP>13</SP>Ω/square, the biaxially aligned polyester film containing a titanium compound and a phosphorus compound by amounts, such that expressions (1) 0<W<SB>TI</SB>≤20 and (2) 1≤W<SB>P</SB>≤300 (where W<SB>TI</SB>is the content (ppm) of titanium elements in the polyester film, and W<SB>P</SB>is the content (ppm) of phosphorus elements in the polyester film) are satisfied, at the same time, and the content of an antimony element is 10 ppm or lower. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a substrate polyester film for a liquid resist photomask protective adhesive tape that is used in close contact with a photomask having adhesive properties such as a liquid resist in a circuit formation step or the like.

Conventionally, an adhesive photoresist such as a liquid resist is often used when producing a printed wiring board. The resist is cured by irradiating ultraviolet rays of around 365 nm through a negative film called a photomask. A polyester film having a thickness of 3 to 25 μm is used as a base material for the purpose of protecting the surface of the exposure photomask used in close contact with the photoresist from damage and damage, and an adhesive layer is provided on one side of the base material. A photomask protective tape having a release layer on its surface is well known (Patent Document 1).
Conventionally, as a photomask protective tape, conditions such as high light transmittance, no deterioration of adhesive properties due to ultraviolet rays, removal without leaving an adhesive on the photomask, and high durability of the release treatment layer are required. In addition, improvements such as a pressure-sensitive adhesive layer and a release layer of the photomask protective tape have been made (Patent Documents 2 and 3).

  In recent years, when the printed wiring board has been further refined and the width of the printed wiring has been increased to about several tens of μm, the internal foreign matter contained in the base film of the photomask protective tape has been irradiated with ultraviolet rays. At this time, there is a new problem that the light transmittance of the portion becomes insufficient, the resolution is lowered, and a precise circuit pattern cannot be obtained.

  In particular, antimony trioxide has been widely used as a polymerization catalyst at the time of polycondensation of polyester, which is a raw material for a base polyester film, because it is inexpensive and has excellent catalytic activity. When used in such an amount that a practical polymerization rate is exhibited, antimony trioxide is reduced during polycondensation to produce metal antimony particles of 10 μm or less. And metal antimony particle | grains aggregate by the melt-extrusion process at the time of film manufacture, and come to exist in a film as a 20-50 micrometers black foreign material.

  That is, when these metal antimony particle aggregates form a high-definition circuit pattern, the problem remains that the transmission of ultraviolet rays is shielded and the circuit pattern is defective.

  Even if a filter is used at the time of melt extrusion to remove these metal antimony particle aggregates, it has been difficult to completely remove the metal antimony particle aggregates through the filter while being deformed.

  Moreover, germanium compounds are known as polymerization catalysts for the polycondensation of polyester, which is a raw material for the base polyester film, but germanium compounds are very expensive and difficult to use for general purposes.

  Furthermore, it has also been proposed to use a titanium compound such as titanium tetrabutoxide as a polymerization catalyst other than the antimony compound, but the use of such a titanium compound solves the problem of black foreign matter, but the obtained polyester itself. Is colored yellow, and the thermal stability of the melt is also unstable, and there is a problem that the film is torn and the productivity is deteriorated. In order to solve the above-mentioned coloring problem, it is generally performed to add a cobalt compound to polyester to suppress yellowness, but the heat stability of melting is lowered, which also deteriorates productivity.

  In order to solve the above-mentioned problem, a proposal has been made to reduce the internal foreign matter of the film by specifying the contents of titanium element and phosphorus element (Patent Document 4), but an oligomer generated in the process of melt polymerization of polyester. It is not designed to take into account.

  Further, when the photomask protective tape is repeatedly peeled from the resist layer, there remains a problem that the surface of the protective tape is charged due to peeling charging and dust and dust are attached.

In other words, in photoresists that require high-definition circuit patterns, protective tape is indispensable to prevent contamination and damage of the photomask surface. The problem that the adhered foreign matter prevents the light transmission during ultraviolet irradiation, the resolution is lowered, and a precise circuit pattern cannot be obtained remains.
JP-A-4-355759 Japanese Patent Laid-Open No. 9-230580 JP 2005-181564 A JP-A-6-170911

  The present invention is intended to solve the above-mentioned conventional problems, and the problem to be solved is to provide a polyester film for a photomask protective adhesive tape that prevents internal foreign matter and surface oligomers and has antistatic ability. That is.

  As a result of intensive studies in view of the above problems, the present inventor has found that the above problems can be easily solved by a film having a specific configuration, and has completed the present invention.

That is, the gist of the present invention is a biaxially oriented polyester film containing a titanium compound and a phosphorus compound in amounts satisfying the following formulas (1) and (2) at the same time and having an antimony element content of 10 ppm or less. It exists in the biaxially-oriented polyester film for liquid resist photomask protective tapes whose resistance is 1.0 * 10 < ¹³ > ohm / square or less.
0 <W _TI ≦ 20 (1)
1 ≦ W _P ≦ 300 (2)
(In the _{formula, W TI} titanium element content in the polyester film (ppm), _{W P} denotes phosphorus element content in the polyester film (ppm))

Hereinafter, the present invention will be described in detail.
In the present invention, the polyester film is a film that is melt-extruded from an extrusion die, and is stretched as necessary after cooling a molten polyester sheet extruded by a so-called extrusion method.

  The polyester constituting the film of the present invention refers to a polymer containing an ester group obtained by polycondensation from a dicarboxylic acid and a diol or from a hydroxycarboxylic acid. Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and the diol includes ethylene glycol and 1,4-butane. Examples include diol, diethylene glycol, triethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, polyethylene glycol and the like, and examples of hydroxycarboxylic acid include p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. be able to. As the production method, for example, a transesterification reaction is carried out between a lower alkyl ester of an aromatic dicarboxylic acid and a glycol, or an aromatic dicarboxylic acid and a glycol are directly esterified to form a substantially aromatic compound. A method is employed in which a bisglycol ester of a dicarboxylic acid or a low polymer thereof is formed and then polycondensed by heating under reduced pressure.

  Typical examples of such a polymer include polyethylene terephthalate and polyethylene-2,6-naphthalate. These polymers may be homopolymers or may be a copolymer of the third component.

  The catalyst used for the condensation polymerization reaction is preferably a titanium compound. In addition to titanium compounds, germanium compounds and antimony compounds can be used as polymerization catalysts. However, germanium compounds are very expensive and cannot be used for general purposes. It must be present, preferably no antimony element.

  If the amount of antimony compound is more than 10 ppm, the metal antimony particles are likely to aggregate, and when forming a high-definition circuit pattern with ultraviolet rays, the transmission of the ultraviolet rays is blocked, resulting in defects in the circuit pattern.

  The polyester film of the present invention needs to contain both a titanium compound and a phosphorus compound. The titanium element content of the film of the present invention needs to be 20 ppm or less, preferably 1 to 10 ppm, more preferably 1 to 2 ppm. If the content of the titanium compound is too large, oligomers are by-produced in the process of melt-extrusion of the polyester, and it is not possible to obtain a low-oligomer and highly transparent film. When a mold layer or an adhesive layer is applied, a surface oligomer is formed, which causes a harmful effect as a photomask protective tape. Further, when no titanium element is contained, the productivity at the time of production of the polyester raw material is inferior, and the polyester raw material reaching the target degree of polymerization cannot be obtained. On the other hand, the amount of phosphorus element needs to be 1 to 300 ppm, preferably 5 to 200 ppm, and more preferably 5 to 100 ppm. By containing a specific amount of the above-described titanium compound and containing a phosphorus compound, it is possible to exert a remarkable effect on the reduction of the contained oligomer. When there is too much content of a phosphorus compound, gelatinization will occur and it may become a foreign material and cause the quality of a film to fall. In this invention, when a titanium compound and a phosphorus compound are contained in the above-mentioned range, the by-product of an oligomer can also be prevented.

  In order to improve workability in the film winding process, coating process, vapor deposition process, etc., it is desirable that the polyester film in the present invention contains fine particles. The fine particles include inorganic particles such as silica, calcium carbonate, magnesium carbonate, calcium sulfate, barium sulfate, lithium phosphate, magnesium phosphate, calcium phosphate, lithium fluoride, aluminum oxide, and kaolin, and organic particles such as acrylic resin and guanamine resin. In addition, there can be mentioned, but not limited to, precipitated particles in which the catalyst residual is made into particles. Among these particles, porous silica particles that are aggregate particles of temporary particles are particularly preferable. Since the porous silica particles are less likely to generate voids around the film when the film is stretched, the porous silica particles have the feature of improving the transparency of the film.

  The average particle diameter of primary particles constituting the porous silica particles is preferably in the range of 0.001 to 0.1 μm. If the average particle size of the primary particles is less than 0.001 μm, ultrafine particles are generated by crushing at the slurry stage, which may form an aggregate and cause a decrease in transparency. On the other hand, when the average particle size of the primary particles exceeds 0.1 μm, the porosity of the particles is lost, and as a result, there is a possibility that the feature with less generation of voids may be lost.

  Furthermore, the pore volume of the aggregated particles is usually in the range of 0.5 to 2.0 ml / g, preferably 0.6 to 1.8 ml / g. When the pore volume is less than 0.5 ml / g, the porosity of the particles is lost, and voids tend to be generated, and the transparency of the film may be lowered. On the other hand, if the pore volume is larger than 2.0 ml / g, crushing and aggregation are likely to occur, and it may be difficult to adjust the particle size.

  The average particle diameter of the porous silica particles is preferably in the range of 0.1 μm or more and less than 5.0 μm, and more preferably 0.5 μm or more and 4.0 μm or less. The addition amount is preferably in the range of 100 ppm or more and less than 2000 ppm, more preferably 200 ppm or more and 1500 ppm or less. When the average particle size is 0.1 μm or less, the addition amount must be increased in order to obtain the workability of the film, that is, the slipperiness, and the transparency may be impaired. When the average particle diameter exceeds 5.0 μm, the resolution may be lowered, and the edge of the conductor forming the circuit is not linear and is likely to be jagged. If the amount added is less than 100 ppm, the effect of imparting slipperiness tends to be poor, and if it exceeds 2000 ppm, the transparency may be impaired.

  The method for adding particles to the polyester in the present invention is not particularly limited, and a known method can be adopted. For example, it can be added at any stage for producing the polyester, but it is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or before the start of the polycondensation reaction after completion of the transesterification reaction. The condensation reaction may proceed. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  The intrinsic viscosity of the polyester used in the present invention is usually 0.40 to 0.90 dl / g, preferably 0.45 to 0.80 dl / g, and more preferably 0.50 to 0.75 dl / g. When the intrinsic viscosity is less than 0.40 dl / g, the mechanical strength of the film tends to be weakened. When the intrinsic viscosity exceeds 0.90, the melt viscosity becomes high and the extruder is loaded, and the manufacturing cost is increased. It takes.

  The polyester film in the present invention is melted by supplying the above-described polyester raw material to a known melt-extrusion apparatus represented by an extruder, and heating to a temperature equal to or higher than the melting point of the polymer. Next, while extruding the molten polymer from the slit-shaped die, it is rapidly cooled and solidified so that it is in the form of a rotary cooling drum or lower than the glass transition temperature to obtain a substantially amorphous unoriented sheet. This sheet is obtained by stretching in a biaxial direction to form a film and heat-setting. In this case, the stretching method may be sequential biaxial stretching or simultaneous biaxial stretching. Moreover, you may extend | stretch longitudinally and / or a horizontal direction again before or after performing heat setting as needed. In the present invention, in order to obtain sufficient dimensional stability, the draw ratio is preferably 8 times or more, more preferably 10 times or more, as the area ratio.

In the present invention, the antistatic property indicates, for example, that the surface specific resistance is 1.0 × 10 ¹³ Ω / □ or less, and preferably 1.0 × 10 ¹² Ω / □ or less. If it exceeds 1.0 × 10 ¹³ Ω / □, it is difficult to control the peeling charge. When the photomask protective tape is peeled from the resist layer, the surface of the protective tape is charged by the peeling charge, and dust and dust are generated. It adheres and adheres to the resist again, and when UV light is exposed to light, the UV light transmission is shielded, resulting in a defect in the circuit pattern.

The method for imparting antistatic properties in the present invention is not particularly limited, and examples thereof include a method of adding an antistatic agent to the film and a method of providing a coating layer containing the antistatic agent.
A typical example of the antistatic agent blended in the present invention is a sulfonic acid metal salt.

  Among these, metal alkyl sulfonates, alkyl benzene sulfonates, alkyl sulfoisophthalates, and alkyl naphthalene sulfonates can be exemplified. As the metal of the metal salt, lithium, potassium, and sodium are preferable. Here, as an alkyl group, a C8-C30 thing is good. When the number of carbon atoms is small, the compatibility with the polyester is poor, and when the number of carbon atoms is large, the effect of the antistatic ability is deteriorated.

  The blending amount of the antistatic agent is usually 0.05 to 10% by weight, preferably 0.1 to 5% by weight. When the blending amount is small, the antistatic effect is small, and when the blending amount is large, the film tends to slip and the film forming property tends to be poor. In actual use, a mixture of compounds having different carbon numbers is often used. Further, when blending, polyethylene glycol or styrene oligomer may be blended in order to improve dispersibility.

  Examples of the antistatic agent to be coated in the present invention include the sulfonates and alkyl sulfates described above and cationic compounds. Especially, it is preferable to coat the antistatic layer which improves adhesiveness.

  The alkyl group of the sulfonate or alkyl sulfate ester salt used in the present invention preferably has 8 to 30 carbon atoms. When the number of carbon atoms is small, the compatibility with the applied resin is poor, and when the number of carbon atoms is large, the effect of antistatic ability tends to be poor.

  Examples of the cationic antistatic agent used in the present invention include compounds having a quaternary ammonium base. This refers to a compound having a component containing a quaternary ammonium base in the main chain or side chain in the molecule. Examples of such constituents include pyrrolidinium ring, quaternized alkylamine, copolymerized with acrylic acid or methacrylic acid, quaternized N-alkylaminoacrylamide, vinylbenzyltrimethylammonium salt, 2 -Hydroxy 3-methacryloxypropyltrimethylammonium salt etc. can be mentioned. Further, these may be combined or copolymerized with other resins. In addition, examples of anions that serve as counter ions for these quaternary ammonium salts include ions such as halogen, alkyl sulfate, alkyl sulfonate, and nitric acid.

  In the present invention, the compound having a quaternary ammonium base is preferably a polymer compound. The number average molecular weight is usually 1000 or more, further 2000 or more, particularly 5000 or more and 500000 or less. If the molecular weight is too low, the antistatic agent may bleed out and cause troubles that transfer to the contacting surface. If the molecular weight is too high, the viscosity of the coating solution becomes too high, which may cause a problem that the coating property is deteriorated.

  The thickness of the antistatic layer is a dry thickness, and is usually 0.003 to 1.5 μm, preferably 0.005 to 0.5 μm. When the thickness of the antistatic layer is less than 0.003 μm, sufficient performance may not be obtained, and when it exceeds 1.5 μm, blocking between the films tends to occur.

  As a method of providing an antistatic layer on a polyester film, a biaxially stretched film may be coated by a conventional technique, or may be coated by a conventional technique in the process of producing a polyester film. For example, in the sequential biaxial stretching method, the film after longitudinal uniaxial stretching is coated with an aqueous dispersion containing an antistatic agent, then stretched laterally, and then thermally treated, or coated after the biaxially stretched film. Then there is a way to dry. Although the method is not limited, the method of coating a uniaxially stretched film, then laterally stretching, and heat-treating is preferable because it has a feature that the coat layer can be uniformly thinned.

  As a method of coating the polyester film with an antistatic agent, for example, a coating technique as shown in “Coating system” published by Yuji Harasaki, Tsuji Shoten, published in 1979 can be used. Specifically, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, impregnation coater, reverse roll coater, transfer roll coater, gravure coater, kiss roll coater, cast coater, spray coater, curtain coater, calendar coater And techniques such as an extrusion coater and a bar coater.

  The thickness of the film of the present invention is 3 to 25 μm, preferably 4 to 16 μm, and more preferably 4 to 12 μm. If the thickness exceeds 25 μm, light is scattered during exposure to lower the resolution, and if the thickness is less than 3 μm, handling at the time of preparing the protective tape becomes difficult and workability may be deteriorated or the film may be broken at the time of peeling. .

  The polyester film of the present invention has an ultraviolet transmittance at a wavelength of 365 nm of 70% or more, preferably 75% or more. If the ultraviolet transmittance is less than 70%, the resist layer exposure and curing steps may not be completed smoothly.

  The polyester film of the present invention preferably has a longitudinal heat shrinkage of 1.0 to 5.0% when measured at 150 ° C. If the thermal contraction rate in the vertical direction is suppressed to less than 1.0%, the flatness of the film may be deteriorated and the transparency may be deteriorated. The polyester film of the present invention is used for a photomask protective tape. In this case, problems may occur in the manufacturing process, and the exposure and curing processes of the resist layer may not be completed smoothly. On the other hand, if the thermal shrinkage rate in the vertical direction exceeds 5.0%, shrinkage deformation may easily occur due to heat and solvent in each step.

  The surface roughness of the polyester film of the present invention is preferably 5 to 100 nm, more preferably 10 to 80 nm. If the surface roughness exceeds 100 nm, bubbles may enter when the photomask protective tape is brought into close contact with the resist layer, and light may be scattered during exposure to lower the resolution. If the surface roughness is less than 5 nm, it may be difficult to handle the protective tape when it is produced.

  The tensile breaking strength in the longitudinal direction of the polyester film of the present invention is preferably 150 MPa or more, more preferably 200 MPa or more. If the tensile strength at break in the longitudinal direction is less than 150 MPa, the protective tape may break when used.

  The polyester film for the liquid resist photomask protective adhesive tape of the present invention prevents the generation of adhering foreign matters due to internal foreign matter, oligomers, and electrification, and can be used for forming a high-definition circuit pattern as a liquid resist photomask protective tape. The industrial value of the present invention is high.

  EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention. In addition, the evaluation method and the processing method of a sample in an Example and a comparative example are as follows. Further, “parts” in Examples and Comparative Examples represents “parts by weight”.

(1) Measuring method of intrinsic viscosity of polyester 1 g of polyester from which other polymer components and pigments incompatible with polyester have been removed are precisely weighed, and 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) is added. And dissolved at 30 ° C.

(2) Average particle diameter (d50)
The particle size was measured by a sedimentation method based on the resistance value of the stock using a centrifugal sedimentation type particle size distribution analyzer SA-CP3 manufactured by Shimadzu Corporation.

(3) Oligomer (cyclic trimer) content in polyester film layer A predetermined amount of polyester layer is mixed with chloroform / 1,1,1,3,3,3-hexafluoro-2-propanol (mixing ratio: 3/2). ) After dissolving in the mixed solution, reprecipitated with chloroform / methanol (mixing ratio: 2/1) and filtered to remove linear polyethylene terephthalate. Then, the solvent in the obtained filtrate was removed using an evaporator. After evaporation, the resulting precipitate was dissolved in a predetermined amount of DMF. The obtained DMF was supplied to liquid chromatography (Shimadzu LC-7A) to determine the amount of oligomer (cyclic trimer) contained in the polyester, and this value was divided by the amount of polyester used for measurement to obtain a polyester film. The amount of oligomer (cyclic trimer) contained therein. The amount of oligomer (cyclic trimer) determined by liquid chromatography was determined from the peak area ratio between the standard sample peak area and the measured sample peak area (absolute calibration curve method).
The standard sample was prepared by weighing a preliminarily collected oligomer (cyclic trimer) and dissolving it in a weighed DMF (dimethylformamide). The conditions for the liquid chromatograph were as follows.

Mobile phase A: Acetonitrile Mobile phase B: 2% acetic acid aqueous solution Column: MCI GEL ODS 1HU manufactured by Mitsubishi Chemical Corporation
Column temperature: 40 ° C
Flow rate: 1 ml / min Detection wavelength: 254 nm

(4) Amount of oligomer on film surface after solvent treatment After applying methyl ethyl ketone to the polyester film surface and drying in a hot air circulation oven at 120 ° C for 1 minute in a nitrogen atmosphere, this film was circulated in a hot air at 180 ° C in a nitrogen atmosphere. The polyester film was treated for 10 minutes in an oven. The surface of the polyester film after heat treatment was brought into contact with DMF for 3 minutes to dissolve the oligomer deposited on the surface. For this operation, for example, the method described in the elution apparatus used for the single-side elution method in the elution test can be adopted in the voluntary standard for food containers and packaging made of synthetic resin such as polyolefin. Next, the concentration of the obtained DMF was adjusted by a method such as dilution as necessary, and the resulting DMF was supplied to liquid chromatography (Shimadzu LC-7A) to determine the amount of oligomer in DMF, and this value was contacted with DMF. Divided by the film area, the amount of oligomer on the film surface (mg / m ² ) was obtained. The amount of oligomer in DMF was determined from the peak area ratio between the standard sample peak area and the measured sample peak area (absolute calibration curve method).

  The standard sample was prepared by weighing a pre-sorted oligomer (cyclic trimer) and dissolving it in a weighed DMF (dimethylformamide). The concentration of the standard sample is preferably in the range of 0.001 to 0.01 mg / ml. The conditions of the liquid chromatograph were as follows.

Mobile phase A: Acetonitrile Mobile phase B: 2% acetic acid aqueous solution Column: MCI GEL ODS 1HU manufactured by Mitsubishi Chemical Corporation
Column temperature: 40 ° C
Flow rate: 1 ml / min Detection wavelength: 254 nm

(5) Quantification of amount of metal element and phosphorus element in film Using a fluorescent X-ray analyzer (model “XRF-1500” manufactured by Shimadzu Corporation), the film was subjected to FP method under the conditions shown in Table 1 below. The amount of elements in the film was determined by single-sheet measurement, and the detection limit in this method is usually about 1 ppm.

(6) Measuring method of foreign matter inside the film;
In a Class 1000 clean room, an A4 size film was measured for internal foreign matters of 10 μm or more with an FPT-80 type foreign matter detector manufactured by Yachiyo Corporation.

(7) Method for measuring film thickness;
Ten films were stacked and the thickness was measured by a micrometer method and divided by 10 to obtain an average value to obtain the film thickness.

(8) Method for measuring ultraviolet transmittance of film;
The ultraviolet transmittance at a wavelength of 365 nm was measured using a visible ultraviolet spectrophotometer UVIDEC-670 manufactured by JASCO.

(9) Measurement method of heat shrinkage rate;
A film was cut into a strip of 35 mm width × 1000 mm length in the length direction and width direction, and the sample was cut out in an oven set at 150 ° C. in a non-tensioned state (Tabaie specs Co., Ltd .: hot air circulating furnace) for 15 minutes. The length before and after the heat treatment was measured with a straight scale, and the thermal shrinkage rate was obtained by the following formula.
Thermal contraction rate (%) = [(ab) / a] × 100
(In the above formula, a represents the length (mm) of the sample before heat treatment, and b represents the length (mm) of the sample after heat treatment)

(10) Measuring method of surface roughness It measured according to the method of JIS-B-0601-1994 using the surface roughness measuring machine SE3500 by Kosaka Laboratory. The cut-off value was measured as 80 μm.

(11) Measuring method of tensile breaking strength;
Using an Intesco tensile tester model 2001, a sample sample having a length (between chucks) of 50 mm and a width of 15 mm was pulled at a strain rate of 200 mm / min in a room adjusted to a temperature of 23 ° C. and a humidity of 50% RH. The load at the time of film breakage was measured, and the tensile breakage rate was determined by the following formula.
Tensile strength at break (MPa) = Load during cutting (N) / Cross-sectional area of sample film (mm ² )

(12) Measuring method of surface specific resistance A 16008A, which is a concentric electrode having an inner electrode 50 mm diameter and an outer electrode 70 mm diameter, manufactured by Yokogawa Hewlett-Packard Co., Ltd. was placed on a sample in an atmosphere of 23 ° C. and 50% RH. A voltage was applied, and the volume resistivity of the sample was measured with a 4329A high resistance meter manufactured by the same company.

Example 1:
<Manufacture of polyester (A1)>
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, adding tetrabutoxy titanate as a catalyst to the reactor, setting the reaction start temperature to 150 ° C., and gradually increasing the reaction temperature as methanol is distilled off. After 3 hours, the temperature was 230 ° C. After 4 hours, the transesterification reaction was substantially terminated. This reaction mixture was transferred to a polycondensation tank, and an ethylene glycol slurry of silica particles having an average particle size of 2.5 μm was added so that the content of the particles with respect to the polyester would be 0.15% by weight, and a polycondensation reaction was performed for 4 hours. went. After 4 hours, the transesterification reaction was substantially terminated. Ethyl acid phosphate was added to the reaction mixture, which was then transferred to a polycondensation tank and subjected to a polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.55 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester chip. The intrinsic viscosity was 0.55. The obtained polyester chip was subjected to solid phase polymerization at 220 ° C. to obtain polyester (A1) having an intrinsic viscosity of 0.65.

<Manufacture of polyester (B1)>
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, magnesium acetate / tetrahydrate is added as a catalyst to the reactor, the reaction start temperature is set to 150 ° C., and the reaction temperature is gradually increased as methanol is distilled off. Was raised to 230 ° C. after 3 hours.
After 4 hours, the transesterification reaction was substantially terminated. This reaction mixture was transferred to a polycondensation tank, and after adding normal phosphoric acid, a polycondensation reaction was performed for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester (B1) chip. The intrinsic viscosity of the polyester (B1) was 0.63.

<Manufacture of film>
A raw material in which the polyester (A1) chip and the polyester (B1) chip are blended at a ratio of 95 parts by weight and 5 parts by weight, respectively, is melt-extruded at 290 ° C. by a twin screw extruder with a vent, and an electrostatic application adhesion method is used. Then, it was cooled and solidified on a cooling roll whose surface temperature was set to 40 ° C. to obtain an unstretched sheet. Next, the film was stretched 3.8 times in the machine direction at 83 ° C. To this longitudinally uniaxially stretched film, after coating the coating liquid A described below on both sides of the film, the film was guided to a tenter, stretched 4.0 times in the transverse direction at 110 ° C, and further heat treated at 225 ° C, A polyester film having a thickness of 6 μm was obtained. The amount of oligomer in the obtained film was 0.60% by weight, and the contents of antimony, titanium, and phosphorus were 0 ppm (below the lower limit of detection), 5 ppm, and 50 ppm, respectively. Hereinafter, the oligomer amounts, antimony, titanium, phosphorus element contents and surface specific resistance values in the films obtained in each Example and Comparative Example are shown in Table 2 and Table 3 below.
Coating liquid A: A coating liquid containing water as a medium was prepared so that the solid content of the following compound was the following number of parts.

20 parts polydiallyldimethylammonium chloride (average molecular weight: about 30000) as an antistatic agent Nonionic water dispersion of methyl methacrylate / ethyl acrylate / methylol acrylamide copolymer (monomer ratio: 47.5 / 47.5 / 5 mol%) is 60 parts and 20 parts of methoxymethylolmelamine is used as a crosslinking agent.

Example 2:
A polyester film was obtained in the same manner as in Example 1 except that the coating liquid B described below was used instead of the coating liquid A.
Coating liquid B: A coating liquid containing water as a medium was prepared so that the solid content of the following compound was the following number of parts.
・ 60 parts of Hydran AP-40 (trade name), a polyurethane manufactured by Dainippon Ink & Chemicals, Inc. ・ 25 parts of Finetex ES-670 (trade name), a polyester manufactured by Dainippon Ink & Chemicals, Inc. ・ Alkyl sulfonate 5 parts of the brand name Latemul PS manufactured by Kao Corporation and 10 parts of methoxymethylol melamine as the cross-linking agent

Example 3:
A raw material obtained by blending polyester (A1) chip and polyester (B1) chip with 94 parts by weight, 5 parts by weight and 1 part by weight of sodium alkyl sulfonate consisting of 14, 15, and 16 carbon atoms, respectively, is provided with a vent. It melt-extruded at 290 degreeC with the axial extruder, and it solidified by cooling on the cooling roll which set the surface temperature to 40 degreeC using the electrostatic application adhesion method, and obtained the unstretched sheet. Subsequently, the film was stretched 3.8 times in the longitudinal direction at 83 ° C., led to a tenter, stretched 4.0 times in the transverse direction at 110 ° C., and further heat-treated at 225 ° C. to obtain a polyester film having a thickness of 6 μm. .

Example 4:
In the production of the polyester (B1), a polyester (B2) chip having an intrinsic viscosity of 0.62 was obtained in the same manner as in the general production method except that the addition amount of normal phosphoric acid was changed. In Example 1, a polyester film was obtained in the same manner as in Example 1 except that a polyester (B2) chip was used instead of the polyester (B1) chip used.

Example 5:
In Example 1, except that the polyester (A1) chip and the polyester (B1) chip were blended at a ratio of 95 parts by weight and 5 parts by weight, instead of the polyester (A1) chip alone, the example was used. A polyester film was obtained in the same manner as in 1.

Example 6:
In the production of polyester (A1), a polyester (A2) chip having an intrinsic viscosity of 0.64 was obtained in the same manner as in the general production method, except that the addition amount of ethyl acid phosphate was changed. In Example 3, a polyester film was obtained in the same manner as in Example 1 except that a polyester (A2) chip was used instead of the polyester (A1) chip used.

Comparative Example 1:
A raw material in which polyester (A1) chip and polyester (B1) chip are blended at a ratio of 95 parts by weight and 5 parts by weight, respectively, is melt-extruded at 290 ° C. by a twin screw extruder with a vent, and an electrostatic application adhesion method is used. Then, it was cooled and solidified on a cooling roll having a surface temperature set to 40 ° C. to obtain an unstretched sheet. Next, the film was stretched 3.8 times in the longitudinal direction at 83 ° C, the film was guided to a tenter, stretched 4.0 times in the lateral direction at 110 ° C, and further heat treated at 225 ° C to obtain a polyester film having a thickness of 6 µm. It was.

Comparative Example 2:
In the production of the polyester (B1), a polyester (B3) chip having an intrinsic viscosity of 0.62 was obtained in the same manner as in the general production method except that the addition amount of normal phosphoric acid was changed. In Example 1, a polyester film was obtained in the same manner as in Example 1 except that a polyester (B2) chip was used instead of the polyester polyester (B1) chip used. In the obtained film, the foreign material considered to be the cause of the gelled product was generated, and a large amount of surface oligomer was generated after the solvent treatment, which was not suitable for use as a photomask protective tape.

Comparative Example 3:
A polyester (A3) chip having an intrinsic viscosity of 0.66 was obtained in the same manner as in the general production method except that the amount of tetrabutoxy titanate was changed in the production of the polyester. In Example 1, a polyester film was obtained in the same manner as in Example 1 except that a polyester (A3) chip was used instead of the polyester (A1) chip used.

Comparative Example 4:
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, magnesium acetate tetrahydrate is added as a catalyst to the reactor, the reaction start temperature is 150 ° C., and the reaction temperature is gradually increased as methanol is distilled off. The temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding ethyl acid phosphate to the reaction mixture, the mixture was transferred to a polycondensation tank, and an ethylene glycol slurry of silica particles having an average particle diameter of 2.5 μm was added so that the content of the particles with respect to polyester was 0.14% by weight. Then, antimony trioxide was added and a polycondensation reaction was performed for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure to obtain a polyester chip. The intrinsic viscosity of this polyester was 0.63. The obtained polyester chip was subjected to solid phase polymerization at 220 ° C. under vacuum to obtain a polyester (C) having an intrinsic viscosity of 0.67. Polyester (C) was melt-extruded at 290 ° C with a vented twin-screw extruder, and cooled and solidified on a cooling roll having a surface temperature set to 40 ° C using an electrostatic application adhesion method to obtain an unstretched sheet. . Next, the film was stretched 3.8 times in the longitudinal direction at 83 ° C., then led to a tenter, stretched 4.0 times in the transverse direction at 110 ° C., and further heat-treated at 225 ° C. to obtain a polyester film having a thickness of 6 μm. .

  The film of the present invention can be suitably used, for example, as a film for a liquid resist photomask protective tape.

Claims (1)

A biaxially oriented polyester film containing a titanium compound and a phosphorus compound in amounts that simultaneously satisfy the following formulas (1) and (2) and having an antimony element content of 10 ppm or less, and having a surface resistivity of 1.0 × 10 ¹³ A biaxially oriented polyester film for a liquid resist photomask protective tape, characterized in that it is Ω / □ or less.
0 <W _TI ≦ 20 (1)
1 ≦ W _P ≦ 300 (2)
(In the _{formula, W TI} titanium element content in the polyester film (ppm), _{W P} denotes phosphorus element content in the polyester film (ppm))