Laminated Polyester Film

Abstract

To provide a laminated polyester film that can suppress contamination due to oligomer components and can be used suitably as e.g. a release film for a semiconductor package molding process.SOLUTION: A laminated polyester film has a coating layer on the surface of a polyester film, the coating layer composed of a coating liquid containing wax. In the total content of the nonvolatile components in the coating liquid, the proportion of the wax is 1 mass% or more and 40 mass% or less, and the wax has a softening point of 90°C or higher.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminated polyester film having a coating layer on the surface of a polyester film. [Background technology]

[0002] Polyester films have excellent properties such as mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, and optical properties, and also have excellent cost performance, so they are used in a variety of applications.

[0003] In recent years, as the uses of polyester films have become more diverse, properties other than those mentioned above are now being required. For example, when polyester films are used in semiconductor molding processes, in addition to the above properties, there may be a need for improved releasability from the mold and suppression of transfer of oligomer components (ester cyclic trimer components) contained in the polyester film to the mold.

[0004] In response to the above demands, for example, Patent Document 1 discloses a polyester film having a low surface gloss obtained by using a polyester having a low content of particles and oligomer components.

[0005] Furthermore, Patent Document 2 discloses a laminated polyester film having a coating layer containing a crosslinking agent and a release agent on at least one side of the polyester film, which suppresses the precipitation of oligomer components on the film surface and has moderate water repellency.

[0006] However, the polyester film described in Patent Document 1 uses a polyester with a high intrinsic viscosity, which makes extrusion molding difficult and raises concerns about a decline in production efficiency. In addition, because the polyester film comes into direct contact with the mold during the semiconductor molding process, there are concerns about insufficient releasability and insufficient prevention of transfer of oligomer components to the mold. Furthermore, although the laminated polyester film described in Patent Document 2 can prevent the precipitation of oligomer components on the film surface, there is concern that it does not sufficiently prevent the oligomer components from transferring to a mold. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-179334 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-30378 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a laminated polyester film that is inhibited from being contaminated by oligomer components, for example, in relation to a laminated polyester film used in a semiconductor molding process. [Means for solving the problem]

[0009] In view of the above-mentioned circumstances, the present inventors have conducted extensive research and have found that the above-mentioned problems can be easily solved by using a laminated polyester film having a specific structure, thereby completing the present invention.

[0010] That is, the gist of the present invention resides in a laminated polyester film having a coating layer on at least one surface of a polyester film, the coating layer being formed from a coating liquid containing wax, the wax accounting for 1% by mass or more and 40% by mass or less of the total non-volatile components in the coating liquid, and the wax having a softening point of 90°C or higher. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a laminated polyester film that is suppressed from being contaminated by oligomer components when used as a release film for use in, for example, a semiconductor molding process. DETAILED DESCRIPTION OF THE INVENTION

[0012] An example of an embodiment of the present invention will be described in detail below. However, the present invention is not limited to the following embodiment, and can be modified and implemented as desired without departing from the gist of the present invention.

[0013] The polyester film constituting the laminated polyester film of the present invention may have a single layer structure or a multilayer structure. In the case of a multilayer structure, it may have a two-layer structure, a three-layer structure, or may have four or more layers without departing from the gist of the present invention, and the number of layers is not particularly limited. In addition, the polyester film is preferably a biaxially oriented polyester film.

[0014] The polyester used may be a homopolyester or a copolymer polyester. In the case of homopolyesters, those obtained by polycondensation of aromatic dicarboxylic acids and aliphatic glycols are preferred. Examples of aromatic dicarboxylic acids include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of aliphatic glycols include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. A typical example of a polyester is polyethylene terephthalate. On the other hand, examples of the dicarboxylic acid component of the copolymer polyester include one or more of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid, and examples of the glycol component include one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexanedimethanol, and neopentyl glycol. From the viewpoint of effectively increasing the surface roughness of the polyester film, it is preferred that the third component contained is isophthalic acid. The copolymer polyester preferably contains the third component in an amount of 30 mol% or less, more preferably 5 mol% to 30 mol%, even more preferably 25 mol% or less, and even more preferably 7 mol% to 22 mol%. This range allows the surface roughness of the polyester film to be effectively increased while maintaining film formation stability.

[0015] Representative examples of polyester include polyethylene terephthalate (PET) and polyethylene-2,6-naphthalenedicarboxylate (PEN).

[0016] The polyester polymerization catalyst is not particularly limited, and conventionally known compounds can be used, such as titanium compounds, germanium compounds, antimony compounds, manganese compounds, aluminum compounds, magnesium compounds, and calcium compounds. Among these, titanium compounds and germanium compounds have high catalytic activity and can be used to carry out polymerization in small amounts. Therefore, the amount of metal remaining in the film is small, which suppresses the absorption of light transmitted through the laminated polyester film and increases the brightness of the laminated polyester film. Furthermore, since germanium compounds are expensive, it is more preferable to use titanium compounds.

[0017] In the case of polyesters using a titanium compound, the titanium element content in the polyester film is preferably 50 ppm or less, more preferably 1 to 20 ppm, and even more preferably 2 to 10 ppm. When the polyester film is multilayered, the titanium element content in each layer should be within the above range. By keeping the titanium compound content below the above upper limit, deterioration of the polyester during the melt-extrusion process can be prevented, preventing the resulting film from becoming strongly yellowish. Furthermore, by keeping the content above the above lower limit, polymerization efficiency is improved, costs are reduced, and a film with sufficient strength can be more easily obtained.

[0018] When using a polyester containing a titanium compound, it is preferable to blend a phosphorus compound with the polyester to reduce the activity of the titanium compound in order to prevent deterioration during the melt extrusion process. As the phosphorus compound, orthophosphoric acid and alkyl acid phosphates such as ethyl acid phosphate are preferred, taking into consideration the productivity and thermal stability of the polyester. The phosphorus element content in the polyester film is preferably in the range of 1 to 300 ppm, more preferably 3 to 200 ppm, and even more preferably 5 to 100 ppm. By setting the content of the phosphorus compound to the above upper limit or less, the phosphorus compound can be prevented from causing gelation or foreign matter. Furthermore, by setting the content to the above lower limit or more, the activity of the titanium compound can be sufficiently reduced, preventing the film from becoming yellowish. When the polyester film is multi-layered, the phosphorus content in the layer containing titanium element should be within the above range.

[0019] In the present invention, in order to suppress the amount of precipitation of oligomer components, the film may be produced using a polyester having a low content of oligomer components as the raw material. As a method for producing a polyester having a low content of oligomer components, various known methods can be used, such as a method in which solid-state polymerization is carried out after the polyester is produced. The amount of oligomer component precipitation may be suppressed by using a polyester film having three or more layers and using a polyester raw material with a low content of oligomer components as the outermost layer of the polyester film. Alternatively, the polyester may be obtained by carrying out an esterification or transesterification reaction, followed by melt polycondensation at a higher reaction temperature under reduced pressure.

[0020] When the laminated polyester film of the present invention is used as a release film for use in a semiconductor molding process, the polyester film preferably has a particle-containing layer A to improve releasability from the mold. When the polyester film of the present invention has a particle-containing layer A, the polyester film may be configured to consist of only the particle-containing layer A, or may have the particle-containing layer A on one or both sides of the base layer. Specific examples of the latter include a film having the particle-containing layer A on both sides of the base layer, a film having the particle-containing layer A on one side of the base layer and a particle-containing layer B different from the particle-containing layer A on the other side of the base layer, a film having the particle-containing layer A on one side of the base layer and no layer on the other side of the base layer, or a film having the particle-containing layer A on one side of the base layer and a layer not containing particles on the other side of the base layer. Among these, a polyester film having a particle-containing layer A on one side of a base layer and a particle-containing layer B different from the particle-containing layer A formed on the other side of the base layer, i.e., a configuration having the particle-containing layer A, base layer, and particle-containing layer B in this order, is preferred because curling of the film is suppressed and handling is good.

[0021] The particle-containing layer A, particle-containing layer B, base layer, and layer not containing particles are preferably layers containing polyester as a main component resin. Here, the term "main component resin" refers to the resin that is contained in the largest proportion among the resin components that make up each layer. The polyester used in each layer may be the polyester described above.

[0022] The particle-containing layer A is a layer containing particles therein.

[0023] The average particle size of the particles contained in the particle-containing layer A is preferably 2.0 μm or more. By containing particles with an average particle size of 2.0 μm or more in the particle-containing layer A, the surface of the polyester film on the particle-containing layer A side can be roughened and given a matte finish. However, if the average particle size of the particles is too large, the filter pressure increase during the polyester extrusion process during film production may be significant, resulting in reduced productivity. Therefore, the average particle size is preferably 2.0 μm or more, and more preferably 10.0 μm or less, more preferably 3.0 μm to 9.0 μm, and even more preferably 4.0 μm to 8.0 μm.

[0024] When the particles are powder, the average particle size can be determined by measuring the powder using a centrifugal sedimentation particle size distribution analyzer (e.g., Shimadzu Corporation, Model SA-CP3) and determining the particle size at an integrated volume fraction of 50% (d50) in the equivalent spherical distribution. The average particle size of particles in a film or layer can be determined by measuring the diameters of 10 or more particles using a scanning electron microscope (SEM) and averaging the measured diameters. In this case, for non-spherical particles, the average of the longest and shortest diameters can be measured as the diameter of each particle. The same applies to the particles described below.

[0025] The particles contained in the particle-containing layer A may have any shape, such as spherical, blocky, rod-like, flat, etc. However, from the viewpoint of obtaining a uniform matte surface, spherical shape is preferred. There are no particular limitations on the hardness, specific gravity, color, etc. of the particles, and two or more different types may be used in combination.

[0026] The particles contained in the particle-containing layer A are not particularly limited as long as they are capable of roughening the surface of the polyester film on the side of the particle-containing layer A. For example, they may be inorganic particles, organic particles, or crosslinked polymer particles. Inorganic particles are preferred because they may form voids in the film when stretched, making it easier to roughen the surface, while organic particles are preferred because they are less likely to form voids and therefore do not reduce the strength of the film.

[0027] Examples of inorganic particles include silica, calcium carbonate, kaolin, talc, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, lithium fluoride, calcium fluoride, lithium fluoride, zeolite, and molybdenum sulfide. Note that the silica particles may contain, in addition to silicon dioxide (SiO), for example, hydrous silicon dioxide.

[0028] Examples of organic particles include acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin, and benzoguanamine resin. Among these, particles made of a resin containing methyl methacrylate, styrene, or both as copolymerization components are preferred because they are particularly compatible with polyester films.

[0029] Examples of crosslinked polymer particles include homopolymers or copolymers of vinyl monomers such as divinylbenzene, styrene, acrylic acid, methacrylic acid, and acrylic acid or methacrylic acid. Other organic particles such as polytetrafluoroethylene, benzoguanamine resin, thermosetting epoxy resin, unsaturated polyester resin, thermosetting urea resin, and thermosetting phenolic resin may also be used.

[0030] The particle content in the particle-containing layer A is preferably 0.1 to 20% by mass, more preferably 1 to 18% by mass, even more preferably 2 to 15% by mass, and even more preferably 3 to 10% by mass, from the viewpoints of being able to suitably roughen the surface of the polyester film on the particle-containing layer A side and preventing breakage or the like during film stretching.

[0031] The thickness of the particle-containing layer A is preferably 1.0 to 20 μm, more preferably 2.0 μm to 20 μm, even more preferably 3.0 μm to 20 μm, and even more preferably 4.0 μm to 15 μm. By making the thickness of the particle-containing layer A 1.0 μm or more, the surface can be effectively roughened, and by making the thickness of the particle-containing layer A 20 μm or less, the surface roughening effect can be ensured.

[0032] The relationship between the thickness of the particle-containing layer A and the average particle size of the particles contained in the particle-containing layer A is, from the viewpoint of roughening the surface of the polyester film on the particle-containing layer A side and suppressing particle shedding, preferably such that (average particle size of particles) / (thickness of the particle-containing layer A) is 0.1 or more and 5.0 or less, more preferably 0.3 or more and 4.0 or less, and particularly preferably 0.5 or more and 3.0 or less.

[0033] The substrate layer is a layer having a particle-containing layer A on one side thereof. The base layer is the thickest layer among the layers constituting the polyester film, and its composition is arbitrary as long as it contains the above polyester as the main component resin.

[0034] The base layer may be a layer containing particles or a layer not containing particles, however, from the viewpoint of cost, it is preferable that the base layer is a layer not containing particles such as organic particles or inorganic particles described below.

[0035] From the viewpoint of preventing curling of the laminated polyester film, the thickness of the base layer is preferably 60 to 99% of the thickness of the polyester film, more preferably 65% ​​to 99%, and even more preferably 70% to 99%. By being in this range, the base layer itself has stiffness, making the laminated polyester film less likely to curl.

[0036] The particle-containing layer B is a layer laminated on the other side of the base layer having the particle-containing layer A on one side. The particle-containing layer B preferably contains particles with an average particle size of 2.0 μm or more, and an average surface roughness (Ra) of 0.02 μm or more, from the viewpoint of ease of handling and prevention of curling of the entire polyester film.

[0037] The particles used in the particle-containing layer B may have the same shape and type as those used in the particle-containing layer A, for example.

[0038] The particle content in the particle-containing layer B is preferably 0.05 to 10% by mass, more preferably 0.1 to 18% by mass, from the viewpoint of ease of handling and prevention of curling of the entire polyester film.

[0039] The content of particles used in particle-containing layer B is preferably 0.1 to 100% by mass of the content of particles contained in particle-containing layer A, and more preferably 1% to 95% by mass.

[0040] The polyester film of the present invention may contain an ultraviolet absorber in order to improve the weather resistance of the film and prevent deterioration of liquid crystal, etc. The ultraviolet absorber is not particularly limited as long as it is a compound that absorbs ultraviolet light and can withstand the heat applied in the production process of the polyester film.

[0041] The ultraviolet absorber includes organic ultraviolet absorbers and inorganic ultraviolet absorbers, and organic ultraviolet absorbers are preferred from the viewpoint of transparency.The organic ultraviolet absorbers are not particularly limited, but examples thereof include cyclic imino esters, benzotriazoles, and benzophenones.From the viewpoint of durability, cyclic imino esters and benzotriazoles are more preferred.In addition, two or more types of ultraviolet absorbers can be used in combination.

[0042] The method for adding particles to the polyester layer is not particularly limited, and any conventionally known method can be used. For example, the particles can be added at any stage in the production of the polyester constituting each layer, but it is preferable to add the particles after the completion of the esterification or transesterification reaction.

[0043] The thickness of the polyester film in the present invention is not particularly limited as long as it is within a range that allows film formation, but is usually in the range of 10 to 350 μm, preferably 25 to 250 μm.

[0044] Next, specific examples of polyester film production according to the present invention will be described, but the present invention is not limited to these examples. Specifically, a preferred method involves extruding dried pellets of the polyester raw material described above through a die in an extruder to form a molten sheet, followed by cooling and solidifying the pellets with a cooling roll to obtain an unstretched sheet. In this case, it is preferable to increase the adhesion between the sheet and a rotating cooling drum to improve the sheet's flatness, and an electrostatic adhesion method and / or a liquid application adhesion method are preferably employed. The unstretched sheet is then biaxially stretched. First, the unstretched sheet is stretched in one direction using a roll or tenter-type stretching machine. The stretching temperature is typically 70 to 120°C, preferably 80 to 110°C, and the stretch ratio is typically 2.5 to 7 times, preferably 3.0 to 6 times. Next, the sheet is stretched in a direction perpendicular to the first-stage stretching direction. In this case, the stretching temperature is typically 70 to 170°C, and the stretch ratio is typically 3.0 to 7 times, preferably 3.5 to 6 times. The film is then subsequently heat-treated at a temperature of 180 to 270°C under tension or relaxation of 30% or less to obtain a biaxially oriented film. The stretching may be performed in one direction in two or more stages. In this case, it is preferable to perform the stretching so that the final stretch ratios in both directions are within the above ranges.

[0045] A simultaneous biaxial stretching method can also be used to produce polyester films. In this method, the unstretched sheet is simultaneously stretched and oriented in both the machine direction and the width direction under temperature control, typically at 70 to 120°C, and preferably 80 to 110°C, with an areal stretching ratio of 4 to 50, preferably 7 to 35, and more preferably 10 to 25. The sheet is then subsequently heat-treated at 170 to 250°C under tension or relaxation of 30% or less to obtain a stretched and oriented film. Regarding the simultaneous biaxial stretching apparatus used in the above-described stretching method, any conventionally known stretching method, such as a screw method, a pantograph method, or a linear drive method, can be used.

[0046] Next, the formation of the coating layer constituting the laminated polyester film of the present invention will be described. The method for forming the coating layer is not particularly limited, but it is preferably formed by in-line coating, which treats the film surface during the film-forming process of the polyester film.

[0047] Inline coating is a method of coating within the polyester film production process. Specifically, it can be performed at any stage between melt extrusion of polyester, stretching, heat setting, and winding up. Typically, coating is performed on any of the following: an unstretched sheet obtained by melting and quenching; a stretched uniaxially stretched film; a biaxially stretched film before heat setting; or a film after heat setting and before winding up. While not limited to the following, for example, in sequential biaxial stretching, a method in which a uniaxially stretched film stretched in the longitudinal direction (machine direction) is coated and then stretched in the transverse direction is particularly advantageous. This method offers advantages in terms of production cost, as film formation and coating layer formation can be performed simultaneously. Since stretching is performed after coating, the thickness of the coating layer can be changed by adjusting the stretch ratio, making thin-film coating easier than with offline coating. Furthermore, by providing a coating layer on the film before stretching, the coating layer can be stretched together with the polyester film, thereby firmly adhering the coating layer to the polyester film. Furthermore, in the production of biaxially stretched polyester films, by stretching the film while gripping its edges with clips or the like, the film can be constrained in both the longitudinal and transverse directions, and in the heat setting step, high temperatures can be applied while maintaining flatness and without wrinkles, etc. Therefore, the heat treatment performed after coating can be performed at a high temperature that cannot be achieved by other methods, improving the film-forming properties of the coating layer and enabling stronger adhesion between the coating layer and the polyester film.Furthermore, a stronger coating layer can be formed, which improves performance such as adhesion to various functional layers that may be formed on the coating layer and moist heat resistance.

[0048] Next, the coating layer in the present invention will be described. In the present invention, a coating layer is provided on at least one surface of a polyester film, and the coating layer is formed from a coating solution containing wax, and essential requirements are that the wax accounts for 1% by mass or more and 40% by mass or less of the total nonvolatile components in the coating solution, and that the softening point of the wax is 90°C or higher.

[0049] The coating layer provided on the surface of the polyester film of the present invention can suppress contamination by oligomer components precipitated from the polyester film by heating, and can also be called a contamination-suppressing layer by oligomer components. The laminated polyester film of the present invention can be suitably used, for example, as a protective film for processing.

[0050] When the polyester film of the present invention comprises a particle-containing layer A, it is preferable that a coating layer be provided on the surface of the particle-containing layer A. When the polyester film consists of only the particle-containing layer A or comprises particle-containing layers A on both sides of the base layer, it is preferable that a coating layer be provided on at least one of the surfaces of the particle-containing layer A. A more preferred configuration is a polyester film having a particle-containing layer A, a substrate layer, and a particle-containing layer B in this order, with a coating layer provided on the surface of the particle-containing layer A side. When the laminated polyester film having the above-described configuration is used as a release film for a semiconductor molding process, it is possible to improve the releasability from the mold, prevent the transfer of oligomer components to the mold, and suppress process contamination.

[0051] The oligomer component in the present invention is a low molecular weight component of polyester that precipitates on the surface of the polyester film by heating, and refers to an ester cyclic trimer component.

[0052] The wax is selected from natural waxes, synthetic waxes, and waxes blended therewith.

[0053] The natural waxes mentioned above include vegetable waxes, animal waxes, mineral waxes, and petroleum waxes. Examples of vegetable waxes include candelilla wax, carnauba wax, rice wax, Japan wax, and jojoba oil. Examples of animal waxes include beeswax, lanolin, and spermaceti. Examples of mineral waxes include montan wax, ozokerite, and ceresin. Examples of petroleum waxes include paraffin wax, microcrystalline wax, and petrolatum.

[0054] Examples of the synthetic wax include synthetic hydrocarbons, modified waxes, hydrogenated waxes, fatty acids, acid amides, amines, imides, ester waxes, and ketones.

[0055] Well-known synthetic hydrocarbons include Fischer-Tropsch wax (also known as Sazowar wax) and polyethylene wax, but they also include the following low-molecular-weight polymers (specifically, polymers with viscosity number average molecular weights of 500 to 20,000): polypropylene, ethylene-acrylic acid copolymer, polyethylene glycol, polypropylene glycol, and block or graft conjugates of polyethylene glycol and polypropylene glycol.

[0056] Specific examples of modified waxes include montan wax derivatives, paraffin wax derivatives, and microcrystalline wax derivatives, where the derivatives are compounds obtained by any one of purification, oxidation, esterification, and saponification, or a combination thereof.

[0057] Specific examples of hydrogenated waxes include hydrogenated castor oil and hydrogenated castor oil derivatives.

[0058] Among these waxes, synthetic hydrocarbon waxes are preferred because they provide stable performance and are easily available. Polyethylene wax, polypropylene wax, oxidized polyethylene wax, and oxidized polypropylene wax are more preferred because they can effectively suppress contamination by oligomer components, with polyethylene wax and oxidized polyethylene wax being particularly preferred.

[0059] The softening point of the wax in the present invention is preferably from 90° C. to 170° C., more preferably from 100° C. to 160° C., and even more preferably from 120° C. to 150° C. By using a wax with a softening point within this range, for example, when used as a protective film for processing, it is possible to improve the releasability and suppress processing contamination due to oligomer components contained in the polyester film. From the viewpoint of suppressing precipitation of oligomer components and suppressing process contamination due to oligomer components, polyethylene wax and oxidized polyethylene wax having a softening point of 90° C. or higher are particularly preferred. The softening point of the wax can be measured and calculated in accordance with JIS-K2207.

[0060] The mechanism by which the use of wax prevents contamination by oligomer components contained in polyester film is thought to be as follows: When polyester film is heated above its glass transition point, oligomer components precipitate on its surface. As the film passes through a coating layer containing wax as it precipitates on the surface, the wax has a high affinity with the oligomer components, causing the surface of the oligomer components to be coated with wax. This prevents the oligomer components from crystallizing, preventing their precipitation. In addition, the wax on the surface is thought to reduce adhesion to processing equipment such as molds, thereby preventing process contamination.

[0061] In the present invention, a crosslinking agent is preferably used in combination with the coating layer to improve adhesion to the polyester film and to strengthen the coating film. Examples of crosslinking agents include melamine compounds, oxazoline compounds, epoxy compounds, carbodiimide compounds, and isocyanate compounds. Among these, melamine compounds, oxazoline compounds, and epoxy compounds are preferred, and melamine compounds and oxazoline compounds are more preferred, as they can further suppress contamination by oligomer components contained in the polyester film.

[0062] The melamine compound refers to a compound having a melamine skeleton within the compound. Examples of such compounds include alkylolated melamine derivatives, compounds obtained by reacting alkylolated melamine derivatives with alcohols to partially or completely etherify them, and mixtures thereof. Suitable alcohols for etherification include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, and isobutanol. The melamine compound may be a monomer or a dimer or higher polymer, or a mixture thereof. Furthermore, melamine may be partially co-condensed with urea or the like, and a catalyst may be used to increase the reactivity of the melamine compound.

[0063] An oxazoline compound is a compound having an oxazoline group in the molecule. A polymer containing an oxazoline group is particularly preferred. The compound can be prepared by polymerizing an addition-polymerizable oxazoline group-containing monomer alone or with other monomers. Examples of the addition-polymerizable oxazoline group-containing monomer include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. These monomers can be used alone or in combination. Among these, 2-isopropenyl-2-oxazoline is preferred because it is readily available industrially. The other monomer is not limited as long as it is copolymerizable with the addition-polymerizable oxazoline group-containing monomer, and examples thereof include (meth)acrylic acid esters such as alkyl(meth)acrylate (the alkyl group can be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, and cyclohexyl); unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid, and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; (meth)acrylamide, N-alkyl(meth)acrylate, N-methyl-N ... Examples of suitable monomers include unsaturated amides such as t)acrylamide and N,N-dialkyl(meth)acrylamide (the alkyl group can be a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, a cyclohexyl group, and the like); vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α,β-unsaturated monomers such as vinyl chloride and vinylidene chloride; and α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene, and one or more of these monomers can be used.From the viewpoint of improving adhesion, the amount of oxazoline groups in the oxazoline compound is preferably in the range of 0.5 to 10 mmol / g, more preferably 1 to 9 mmol / g, still more preferably 3 to 8 mmol / g, and particularly preferably 4 to 6 mmol / g.

[0064] Epoxy compounds are compounds having an epoxy group in the molecule, and examples thereof include condensates of epichlorohydrin, ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A, etc. with a hydroxyl group or an amino group, polyepoxy compounds, diepoxy compounds, monoepoxy compounds, and glycidylamine compounds. Examples of polyepoxy compounds include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris(2-hydroxyethyl)isocyanate, glycerol polyglycidyl ether, and trimethylolpropane polyglycidyl ether. Examples of diepoxy compounds include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcinol diglycidyl ether, ethylene glycol ... Examples of the epoxy compounds include ethanol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and polytetramethylene glycol diglycidyl ether. Examples of the monoepoxy compounds include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl ether. Examples of the glycidylamine compounds include N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N-diglycidylamino)cyclohexane. From the viewpoint of improving adhesion, polyether-based epoxy compounds are preferred. Furthermore, in terms of the number of epoxy groups, polyepoxy compounds having a functionality of 3 or more are preferred over those having a functionality of 2.

[0065] A carbodiimide compound is a compound having a carbodiimide structure, and is a compound having one or more carbodiimide structures in the molecule. For better adhesion, etc., a polycarbodiimide compound having two or more carbodiimide structures in the molecule is more preferred.

[0066] Carbodiimide compounds can be synthesized by conventionally known techniques, and generally involve the condensation reaction of a diisocyanate compound. The diisocyanate compound is not particularly limited, and either an aromatic or aliphatic diisocyanate can be used. Specific examples include tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, and dicyclohexylmethane diisocyanate.

[0067] The content of carbodiimide groups contained in the carbodiimide compound, in terms of carbodiimide equivalent (weight [g] of the carbodiimide compound required to provide 1 mol of carbodiimide groups), is usually in the range of 100 to 1000, preferably 250 to 800, and more preferably 300 to 700. Use in the above range improves the durability of the coating film.

[0068] Furthermore, to improve the water solubility or water dispersibility of the polycarbodiimide compound, a surfactant may be added, or a hydrophilic monomer such as a polyalkylene oxide, a quaternary ammonium salt of a dialkylamino alcohol, or a hydroxyalkyl sulfonate may be added, within a range that does not impair the effects of the present invention.

[0069] The isocyanate compound refers to a compound having an isocyanate or an isocyanate derivative structure, such as a blocked isocyanate. Examples of the isocyanate include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate, aliphatic isocyanates having an aromatic ring such as α,α,α',α'-tetramethylxylylene diisocyanate, aliphatic isocyanates such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate, and alicyclic isocyanates such as cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylenebis(4-cyclohexyl isocyanate), and isopropylidenedicyclohexyl diisocyanate. Further examples include polymers and derivatives of these isocyanates, such as biuretized products, isocyanurated products, urethodionated products, and carbodiimide-modified products. These may be used alone or in combination. Among the above isocyanates, aliphatic isocyanates or alicyclic isocyanates are more preferred than aromatic isocyanates in order to prevent yellowing due to ultraviolet rays.

[0070] When used in the form of a blocked isocyanate, examples of the blocking agent include bisulfites, phenolic compounds such as phenol, cresol, and ethylphenol, alcohol compounds such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, and ethanol, active methylene compounds such as methyl isobutanoylacetate, dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, and acetylacetone, mercaptan compounds such as butyl mercaptan and dodecyl mercaptan, lactam compounds such as ε-caprolactam and δ-valerolactam, amine compounds such as diphenylaniline, aniline, and ethyleneimine, acetanilide, acid amide compounds of acetic acid amide, and oxime compounds such as formaldehyde, acetaldoxime, acetone oxime, methyl ethyl ketone oxime, and cyclohexanone oxime, and these may be used alone or in combination of two or more.

[0071] The isocyanate compound of the present invention may be used alone or as a mixture or bond with various polymers. In order to improve the dispersibility and crosslinkability of the isocyanate compound, it is preferable to use a mixture or bond with a polyester resin or a urethane resin.

[0072] In forming the coating layer, various conventionally known polymers such as polyester resin, acrylic resin, urethane resin, etc. may be used in combination as a binder to improve the coating appearance and transparency, etc. Furthermore, particles may also be used in combination for the purpose of improving anti-blocking properties and slip properties, etc., within the scope of the present invention.

[0073] It can be assumed that the coating layer of the present invention contains unreacted compounds of various compounds in the coating solution, reacted compounds, or a mixture thereof.

[0074] In the present invention, the wax content of the coating solution is generally 1% by mass to 40% by mass, preferably 10% by mass to 35% by mass. If the wax content is less than 1% by mass, there is a concern that the mold releasability and contamination due to oligomer components contained in the polyester film may be impaired. If the wax content is more than 40% by mass, the high affinity between the wax and the oligomer components may increase the amount of oligomer components precipitation from the polyester film, which may worsen contamination or deteriorate the appearance of the coating layer and the coating strength.

[0075] In the present invention, the crosslinking agent is preferably present in an amount of 20% by mass to 70% by mass, more preferably 30% by mass to 60% by mass, and even more preferably 30% by mass to 50% by mass, relative to the total nonvolatile components in the coating solution. Within the above ranges, both coating film strength and adhesion to the polyester film can be achieved. In the present invention, from the viewpoints of suppressing precipitation of oligomer components, coating film strength, and adhesion to a polyester film, it is preferred that the crosslinking agent accounts for 20% by mass or more and 70% by mass or less of all non-volatile components in the coating solution, and that the crosslinking agent is a melamine compound or an oxazoline compound.

[0076] When forming a coating layer by inline coating, it is preferable to produce a laminated polyester film by coating a coating liquid onto a polyester film, the coating liquid being prepared by preparing an aqueous solution or aqueous dispersion of the above-mentioned series of compounds so that the solid content concentration is approximately 0.1 to 50 mass %.

[0077] The thickness of the coating layer is preferably 0.002 μm or more and 1.0 μm or less, more preferably 0.005 μm or more and 0.50 μm or less, even more preferably 0.01 μm or more and 0.20 μm or less, and particularly preferably 0.03 μm or more and 0.08 μm or less. If the film thickness is within the above range, it is possible to suppress the deposition of oligomer components and to suppress contamination due to transfer of oligomer components. When an uneven structure exists on the surface of the particle-containing layer A side, the thickness of the coating layer is measured at the flat part of the recesses.

[0078] The polyester film of the present invention may have, for example, a hard coat layer, an adhesive layer or an easy-adhesion layer on the surface on the non-coated layer side, or may have coating layers on both sides of the film. For example, when the laminated polyester film of the present invention is used as a release film for the molding process of a semiconductor package, it is preferable to provide an adhesive layer to fix a substrate such as a lead frame. Specifically, it is preferable to provide a coating layer on one side of the polyester film and an adhesive layer on the other side. In the above-mentioned configuration, it is also preferable to provide an easy-adhesion layer between the adhesive layer and the polyester film in order to increase the adhesion between the polyester film and the adhesive layer. Furthermore, as described above, the polyester film preferably has a configuration in which a particle-containing layer A is provided on one side of the base layer and a particle-containing layer B different from the particle-containing layer A is formed on the other side of the base layer, i.e., a configuration in which the particle-containing layer A, base layer, and particle-containing layer B are provided in this order.For example, when the laminated polyester film of the present invention is used as a release film for a molding process of a semiconductor package, preferred configurations include coating layer / particle-containing layer A / base layer / particle-containing layer B / adhesive layer and coating layer / particle-containing layer A / base layer / particle-containing layer B / easy-adhesion layer / adhesive layer.

[0079] The adhesive layer is provided to fix a substrate such as a lead frame in, for example, a molding process for a semiconductor package. After the purpose of the film is achieved, the adhesive layer is removed together with the process release film, so it is preferable that the adhesive layer be peelable from the substrate such as the lead frame and not leave adhesive residue or contaminate the surface after peeling.

[0080] The adhesive layer contains a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition can be any composition that can impart adhesiveness, and examples thereof include acrylic pressure-sensitive adhesives, urethane pressure-sensitive adhesives, rubber pressure-sensitive adhesives, and silicone pressure-sensitive adhesives. Among these, acrylic pressure-sensitive adhesives are preferred because they are easy to adjust the adhesive properties and have excellent transparency. In addition, examples of methods for forming the pressure-sensitive adhesive include heat-curing, active energy ray-curing, and hot-melt types.

[0081] Methods for forming the adhesive layer include, for example, dissolving or dispersing an adhesive substance or a composition thereof in a solvent consisting of a single or mixture of suitable solvents such as toluene or ethyl acetate to prepare an adhesive solution of approximately 10 to 40 wt %, coating this on a protective film, heating and drying to form an adhesive layer, and laminating a separator, or coating this on a separator, heating and drying to form an adhesive layer, and laminating a protective film.

[0082] The adhesive liquid can be applied by any known method, including the methods described above for applying the coating layer.

[0083] The thickness of the adhesive layer is preferably in the range of 1 to 500 μm, more preferably 5 to 200 μm, and even more preferably 10 to 100 μm. Within the above range, sufficient adhesive strength can be obtained and peeling can be facilitated.

[0084] The easy-adhesion layer is a layer that improves the adhesion between the polyester film surface and other layers.

[0085] The easy-adhesion layer can be provided by various conventionally known methods, such as coating, transfer, and lamination. Among these, providing by coating is preferred from the viewpoint of ease of production. The easy-adhesion layer may be provided by in-line coating or offline coating, but in-line coating is preferably used from the viewpoint of production costs and improving the strength of the easy-adhesion layer and adhesion to the film due to heat treatment during the film production process.

[0086] The resin contained in the easy-adhesion layer may be a conventionally known resin, such as a polyester resin, an acrylic resin, a urethane resin, or a polyvinyl resin (such as polyvinyl alcohol, vinyl chloride vinyl acetate copolymer, etc.). Among these, polyester resins, acrylic resins, and urethane resins are preferred from the viewpoint of adhesion to the polyester film, and acrylic resins are particularly preferred from the viewpoint of adhesion to the adhesive layer.

[0087] In order to increase the strength of the adhesive layer, it is preferable to use a crosslinking agent in combination. As the crosslinking agent, various known crosslinking agents can be used, such as oxazoline compounds, melamine compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, and silane coupling compounds. Among these, from the viewpoint of adhesion, oxazoline compounds, epoxy compounds, isocyanate compounds and carbodiimide compounds, especially oxazoline compounds and isocyanate compounds, are more preferred, and from the viewpoint of increasing the strength of the easy-adhesion layer, melamine compounds are preferred.

[0088] When forming an easy-adhesion layer by coating, the coating liquid may contain, in addition to the above-mentioned resin, for example, other binders, surfactants, particles, antifoaming agents, coatability improvers, thickeners, antioxidants, ultraviolet absorbers, foaming agents, dyes, pigments, and the like. Furthermore, before coating, the surface of the polyester film may be subjected to chemical treatment, corona discharge treatment, plasma treatment, or the like.

[0089] The thickness of the adhesive layer is preferably in the range of 0.001 to 1 μm, more preferably 0.01 to 0.5 μm, and even more preferably 0.02 to 0.2 μm. By using an adhesive layer with a thickness in the above range, good adhesion to other layers can be achieved.

[0090] The average surface roughness (Ra) of the coating layer side surface of the laminated polyester film of the present invention is preferably 0.2 μm or more, more preferably 0.3 μm or more. There is no particular upper limit, but it is usually 3.0 μm or less. By making the average surface roughness (Ra) of the coating layer side surface 0.2 μm or more, when the laminated polyester film of the present invention is used as a release film for the semiconductor molding process, the releasability from the mold can be improved. Methods for making the average surface roughness (Ra) of the coating layer side surface 0.2 μm or more include adding particles to the coating layer and using a polyester film provided with the particle-containing layer A described above.

[0091] The average surface roughness (Ra) of the non-coated layer side surface of the laminated polyester film of the present invention is preferably smaller than the average surface roughness (Ra) of the coated layer side surface from the viewpoint of facilitating lamination of a desired layer on the surface, and specifically, the average surface roughness (Ra) is preferably less than 0.20 μm. On the other hand, the lower limit is preferably 0.020 μm or more, more preferably 0.025 μm or more, from the viewpoints of film processability, easy slippage, and anti-blocking properties.

[0092] The laminated polyester film of the present invention preferably has a film haze change (ΔH) of 1.5% or less, more preferably 1.0% or less, and even more preferably 0.5% or less, before and after heat treatment (150°C, 90 minutes). It is known that the film haze of a polyester film increases due to the precipitation of oligomer components on the film surface by heat treatment, and ΔH is an index showing the precipitation of oligomer components on the film surface before and after heat treatment. When the film haze change (ΔH) is 1.5% or less, contamination due to precipitation of oligomer components may be suppressed.

[0093] The coating layer can be formed by a conventional coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, or the like.

[0094] The drying and curing conditions when forming a coating layer on a polyester film are not particularly limited. For example, when forming a coating layer by offline coating, it is usually recommended to carry out heat treatment at 80 to 200°C for 3 to 40 seconds, preferably at 100 to 180°C for 3 to 40 seconds.

[0095] On the other hand, when the coating layer is formed by in-line coating, it is usually recommended to carry out heat treatment at 70 to 280° C. for 3 to 200 seconds.

[0096] Regardless of whether off-line coating or in-line coating is used, heat treatment and irradiation with active energy rays such as ultraviolet rays may be used in combination, if necessary. The polyester film constituting the laminated polyester film of the present invention may be previously subjected to a surface treatment such as a corona treatment or a plasma treatment.

[0097] The various components in the coating layer can be analyzed by, for example, TOF-SIMS, ESCA, fluorescent X-ray analysis, or the like.

[0098] The laminated polyester film of the present invention can be used for protective films and release films in various processing steps, and is particularly suitable for use as a release film in the molding process of semiconductors. An example of a method for manufacturing a semiconductor package will be described. First, a plurality of semiconductor chips arranged on a lead frame are inserted into the spaces for molding semiconductor packages in one mold A, and then a release film and the other mold B are positioned in sequence. Next, mold A and mold B are clamped together at a predetermined pressure so that the release film is tightly attached to the surface of the lead frame. Then, molten molding resin is filled into each semiconductor package molding space and allowed to harden for a predetermined time, thereby forming one semiconductor package per semiconductor package molding space. Next, mold A and mold B are removed from the semiconductor package, forming the semiconductor package on the lead frame. After this, the lead frame is cut into individual semiconductor packages. The release film used is removed when mold A and mold B are detached from the semiconductor package, and is supplied with each molding cycle. The laminated polyester film of the present invention suppresses contamination caused by oligomer components precipitated from the polyester film. For example, when the laminated polyester film of the present invention is used as a release film for the molding step of a semiconductor package, more specifically, as a release film for the molding step of a semiconductor package that is disposed between a lead frame on which a semiconductor chip is mounted and a mold and is used in a semiconductor package manufacturing method in which a molding resin is filled into the mold, contamination of the mold by oligomer components can be prevented, and therefore the laminated polyester film can be suitably used for this application. However, the laminated polyester film of the present invention is not limited to the above-mentioned uses, and can also be suitably used, for example, as a transfer film capable of transferring a matte appearance, or as a film for molding in a mold such as insert molding or in-mold molding. [Example]

[0099] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples within the scope of the present invention. The measurement and evaluation methods used in the present invention are as follows.

[0100] (1) Intrinsic viscosity of polyester 1 g of polyester from which components incompatible with the polyester had been removed was precisely weighed, dissolved in 100 ml of a mixed solvent of phenol / tetrachloroethane = 50 / 50 (weight ratio), and measured at 30°C.

[0101] (2) Average particle size The equivalent sphericity distribution of the powder particles was measured using a centrifugal sedimentation particle size distribution analyzer (SA-CP3 model) manufactured by Shimadzu Corporation, and the cumulative volume fraction of each particle size range was calculated. The particle size at a cumulative volume fraction of 50% in the equivalent sphericity distribution of the particles measured was taken as the average particle size.

[0102] (3) Average surface roughness (Ra) The surface roughness was measured using a surface roughness measuring instrument (SE-3500) manufactured by Kosaka Laboratory Co., Ltd., as follows: A section of reference length L (2.5 mm) was cut out from the film cross-sectional curve in the direction of the mean line. When the mean line of this cut section was taken as the x-axis and the direction of longitudinal magnification as the y-axis, and the roughness curve y = f(x), the value given by the following formula was expressed in nm. Ten roughness curves were obtained from the sample film surface, and the average surface roughness was expressed as the average value of the average surface roughness values ​​of the cut sections obtained from these roughness curves. The stylus tip radius was 2 μm, the load was 30 mg, and the cutoff value was 0.08 mm. Ra=(1 / L)∫L0|f(x)|dx

[0103] (4) Coating layer thickness The surface of the coating layer was stained with RuO4 and embedded in epoxy resin. Then, sections prepared by ultrathin sectioning were stained with RuO4, and the cross-sections of the coating layer were measured using a transmission electron microscope (TEM) (Hitachi High-Technologies Corporation, H-7650, accelerating voltage 100 kV).

[0104] (5) Softening point of wax The softening point of the wax was measured in accordance with JIS-K2207.

[0105] (6) Heat treatment of film The laminated polyester film obtained in each Example and Comparative Example was placed on Kent paper with the coating layer side surface exposed, and then heat-treated by leaving it at 150°C for 90 minutes in a nitrogen atmosphere. However, in Comparative Example 6, no coating layer was provided, so Kent paper was placed on top of the polyester film with the particle-containing layer A side surface exposed.

[0106] (7) Film haze The film haze of the sample film was measured in accordance with JIS-K-7136 using a haze meter (HM-150) manufactured by Murakami Color Research Laboratory Co., Ltd.

[0107] (8) Change in film haze due to heat treatment A mixed coating solution consisting of 80 parts by weight of dipentaerythritol hexaacrylate, 20 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, 5 parts by weight of a photopolymerization initiator (product name: Irgacure 184, manufactured by Ciba Specialty Chemicals Co., Ltd.), and 200 parts by weight of methyl ethyl ketone was applied to the surface opposite the coating layer of the laminated polyester film obtained in each Example and Comparative Example to a dry thickness of 3 μm, dried, and then cured by irradiation with ultraviolet light to form a hard coat layer. In Comparative Example 6, no coating layer was provided on the polyester film, and a hard coat layer was formed on the particle-containing layer B side of the polyester film. The film haze of the laminated polyester film having a hard coat layer was measured from the non-hard coat layer side using method (7). After heating using method (6), the film haze after heat treatment was measured using method (7). The difference between the haze after heat treatment and the haze before heat treatment was calculated and used as the film haze change. The lower the film haze change, the less the precipitation of oligomer components (ester cyclic trimer components) due to heat treatment, which is favorable.

[0108] (9) Transfer of oligomer components A laminated polyester film and a 0.5 mm thick stainless steel plate (product name: HS0543) were cut into a 10 cm x 5 cm piece, and the particle-containing layer A surface of the film was overlapped with the stainless steel plate, and the sample was created by pressing in a heat press at 180°C and a pressure of 20 MPa for 5 minutes. Immediately after preparing the sample, the laminate of the film and stainless steel plate was placed horizontally with the film facing up, and then the film was lifted vertically and peeled off. The film-side surface of the stainless steel plate was observed, and the area ratio of the staining (transferred oligomer components) to the area of ​​the film-side surface of the stainless steel plate was evaluated. A good sample with no visible staining was rated ◯ (very good), a sample with a stained area ratio of 5% or less of the stainless steel plate that was practically acceptable was rated △ (good), and a sample with noticeable staining exceeding 5% that was practically problematic was rated × (bad).

[0109] The following composition was used for the polyester film. Polyester (I): A polyester resin composition made of polyethylene terephthalate (intrinsic viscosity: 0.63 dl / g). Polyester (II): A polyethylene terephthalate composition (intrinsic viscosity: 0.61 dl / g) containing 10% by mass of alkyl methacrylate-styrene copolymer particles having an average particle size of 4.5 μm. Polyester (III): A polyethylene terephthalate composition (intrinsic viscosity: 0.61 dl / g) containing 0.7% by mass of silica particles having an average particle size of 2.7 μm. Polyester (IV) A polyethylene terephthalate composition (intrinsic viscosity: 0.62 dl / g) containing 0.3% by mass of silica particles having an average particle size of 2.0 μm.

[0110] The following coating liquid composition was used. Wax 1 (W1): Oxidized polyethylene wax with a softening point of 130°C. Wax 2 (W2): Polyethylene wax with a softening point of 138°C Wax 3 (W3): Polyethylene wax with a softening point of 110°C Wax 4 (W4): Polyethylene wax with a softening point of 60°C Wax 5 (W5): Paraffin wax with a softening point of 65°C Wax 6 (W6): Carnauba wax with a softening point of 85°C

[0111] Melamine compound (C1): Hexamethoxymethylolmelamine

[0112] Oxazoline compound (C2): Acrylic polymer with oxazoline group and polyalkylene oxide chain, product name "Epocross" (oxazoline group amount = 7.7 mmol / g, manufactured by Nippon Shokubai Co., Ltd.)

[0113] Epoxy compound (C3): Water-soluble polyglycerol polyglycidyl ether

[0114] Polyester resin (B1): Aqueous dispersion of 42 parts by mass of polyester resin formed from (acid component) isophthalic acid / / (diol component) diethylene glycol / neopentyl glycol = 100 / / 70 / 30 (mol%) and 58 parts by mass of polymethyl methacrylate.

[0115] [Example 1] A mixture of polyesters (I) and (II) in proportions of 50% by mass and 50% by mass was used as the raw material for particle-containing layer A, polyester (I) was used as the raw material for the base layer, and a mixed raw material of polyesters (I) and (III) in proportions of 70% by mass and 30% by mass was used as the raw material for particle-containing layer B. These materials were fed into three extruders, melted at 285°C, and then co-extruded onto a cooling roll set at 40°C in a layer structure of three types and three layers (particle-containing layer A / base layer / particle-containing layer B = 5:30:3 in discharge rate), followed by cooling and solidification to obtain an unstretched sheet. Next, the film was stretched 3.4 times in the longitudinal direction at a film temperature of 85°C using the difference in roll peripheral speed, and then coating solution 1 shown in Table 1 below was applied to the surface of particle-containing layer A of this longitudinally stretched film, which was then introduced into a tenter and stretched 4.0 times in the transverse direction at 110°C, heat-treated at 225°C, and then relaxed by 2% in the transverse direction to obtain a laminated polyester film having a thickness of 38 μm (particle-containing layer A / base layer / particle-containing layer B=5 μm / 30 μm / 3 μm) with a coating layer thickness (after drying) of 0.05 μm. The average surface roughness (Ra) of the particle-containing layer A surface of the obtained laminated polyester film was 0.33 μm, and the average surface roughness (Ra) of the particle-containing layer B surface was 0.025 μm. The increase in film haze (ΔH) due to heat treatment was 0.2%, and the area ratio of the contaminated area due to transfer of oligomer components was less than 5% of the stainless steel plate, which was a good result. The properties of this film are shown in Table 2 below.

[0116] [Examples 2 to 10] A laminated polyester film was obtained in the same manner as in Example 1, except that the composition of the coating solution was changed to the composition shown in Table 1. As shown in Table 2, the obtained laminated polyester film had good results in terms of film haze increase (ΔH) due to heat treatment and transfer of oligomer components.

[0117] [Example 11] A mixture of polyesters (I) and (IV) in proportions of 94% by mass and 6% by mass, respectively, was used as the raw material for particle-containing layer A, and polyester (I) was used as the raw material for the base layer. These materials were fed into two extruders, melted at 285°C, and then co-extruded onto a cooling roll set at 40°C in a layer structure of two types and three layers (particle-containing layer A / base layer / particle-containing layer A = 4:30:4 in discharge rate), followed by cooling and solidification to obtain an unstretched sheet. Next, the film was stretched 3.4 times in the longitudinal direction at a film temperature of 85°C using the difference in roll peripheral speed, and then coating solution 3 shown in Table 1 below was applied to one side of this longitudinally stretched film, which was then introduced into a tenter and stretched 4.0 times in the transverse direction at 110°C. After heat treatment at 225°C, the film was relaxed by 2% in the transverse direction to obtain a laminated polyester film having a thickness of 38 μm (particle-containing layer A / base layer / particle-containing layer A=4 μm / 30 μm / 4 μm) with a coating layer thickness (after drying) of 0.05 μm. The average surface roughness (Ra) of the particle-containing layer A side surface of the obtained laminated polyester film was 0.010 μm, and as shown in Table 2, the obtained laminated polyester film had good results in terms of film haze increase (ΔH) due to heat treatment and transfer of oligomer components.

[0118] [Comparative Examples 1 to 5] A laminated polyester film was obtained in the same manner as in Example 1, except that the composition of the coating solution was changed to the composition shown in Table 1. As shown in Table 2, the obtained laminated polyester film showed that the area ratio of the contaminated areas due to transfer of the oligomer component exceeded 5% relative to the stainless steel plate.

[0119] Comparative Example 6 Except for not providing a coating layer, a polyester film was obtained in the same manner as in Example 1. As shown in Table 2, the increase in film haze (ΔH) of the obtained polyester film due to heat treatment was 1.8%, and the area ratio of the contaminated areas exceeded 5% relative to the stainless steel plate.

[0120] [Table 1]

[0121] [Table 2]

[0122] From the results of the above Examples and Comparative Examples and the results of tests conducted by the inventors, it has been found that a laminated polyester film having a coating layer formed from a coating solution in which wax having a softening point of 90°C or higher is used and the wax accounts for 1% by mass or more and 40% by mass or less of the total non-volatile components can suppress transfer of oligomer components. [Industrial Applicability]

[0123] The laminated polyester film of the present invention is excellent in preventing contamination during processing and can be suitably used, for example, as a film for process protection or a release film for use in the molding process of semiconductor packages.

Claims

1. A method for inhibiting transfer of oligomer components contained in a polyester film to a mold during mold molding (hereinafter referred to as the "method for inhibiting oligomer component transfer"), which comprises forming a coating layer having a thickness of 0.02 μm or more on the surface of a polyester film using a coating solution containing 5% by mass to 40% by mass of wax having a softening point of 90°C or higher, in terms of the proportion of the total non-volatile components in the coating solution.

2. The method for inhibiting transfer of oligomer components according to claim 1 , wherein the coating liquid contains a crosslinking agent and / or a binder.

3. A method for inhibiting transfer of oligomer components as described in claim 1 or 2, wherein the coating liquid contains a crosslinking agent.

4. The method for inhibiting transfer of oligomer components according to claim 3, wherein the content of the crosslinking agent contained in the coating liquid is 20% by mass or more and 70% by mass or less, as a proportion of all non-volatile components in the coating liquid.

5. The method for inhibiting transfer of oligomer components according to claim 3 or 4, wherein the crosslinking agent is at least one selected from the group consisting of melamine compounds, oxazoline compounds, and epoxy compounds.

6. The method for inhibiting transfer of oligomer components according to claim 3 or 4, wherein the crosslinking agent is at least one selected from the group consisting of a melamine compound and an oxazoline compound.

7. The method for inhibiting transfer of oligomer components according to any one of claims 1 to 6, wherein the coating layer has a thickness of 0.03 µm or more and 0.5 µm or less.

8. A mixed coating liquid consisting of 80 parts by mass of dipentaerythritol hexaacrylate, 20 parts by mass of 2-hydroxy-3-phenoxypropyl acrylate, 5 parts by mass of a photopolymerization initiator, and 200 parts by mass of methyl ethyl ketone was applied to the surface of the polyester film opposite to the surface on which the coating layer was formed, so as to have a thickness of 3 μm after drying, and then dried and cured by irradiation with ultraviolet light to form a hard coat layer, thereby obtaining a sample film. The method for inhibiting oligomer component transfer according to any one of claims 1 to 7, wherein the change in film haze on the coating layer side of the sample film before and after heat treatment at 150°C for 90 minutes in a nitrogen atmosphere is 1.5% or less.

9. The method for inhibiting transfer of oligomer components according to any one of claims 1 to 8, wherein the coating layer side film surface has an average surface roughness (Ra) of 0.2 µm or more.

10. The method for inhibiting oligomer component transfer according to any one of claims 1 to 9, wherein the polyester film comprises a particle-containing layer A, a base layer, and a particle-containing layer B in this order, and the coating layer is provided on the particle-containing layer A side surface of the polyester film.

11. The method for inhibiting transfer of oligomer components according to claim 10, wherein the ratio of the thickness of the substrate layer to the thickness of the polyester film ((thickness of the substrate layer) / (thickness of the polyester film)) is 0.60 or more and 0.99 or less.

12. The method for inhibiting transfer of an oligomer component according to any one of claims 1 to 11, wherein the polyester film contains an ester cyclic trimer component as an oligomer component.

13. The method for inhibiting transfer of oligomer components according to any one of claims 1 to 12, which is used in a semiconductor molding process, transfer molding, insert molding, or in-mold molding.

14. The method for inhibiting transfer of oligomer components according to any one of claims 1 to 12, which is used in a semiconductor molding process.

15. A method for manufacturing a semiconductor package, comprising the method for inhibiting oligomer component transfer according to any one of claims 1 to 14.

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