JP5488231B2 - Molded polyethylene terephthalate film for mold release - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a release laminated polyethylene terephthalate film, and more particularly to a release laminated polyethylene terephthalate film that can produce a release film for forming a ceramic green sheet with less pinholes.

  Conventionally, release films based on polyethylene terephthalate films have been used for ceramic molding of laminated ceramic capacitors, ceramic substrates and the like. In recent years, with the progress of miniaturization and increase in capacity of multilayer ceramic capacitors, the thickness of ceramic green sheets has been steadily becoming thinner. Along with the further thinning of the green sheet, especially when trying to mold a thin film green sheet with a thickness of 1 μm or less, if there are coarse protrusions on the release surface side of the release film, ceramic slurry will be formed on the release film. When applying, problems such as slurry repelling, pinholes, and green sheet breakage may occur when the green sheet is peeled off. As a result, a defect rate as a multilayer ceramic capacitor may be deteriorated.

  In order to solve this problem, it has been reported that the generation of pinholes can be suitably reduced by a film that substantially does not contain a lubricant on the surface to which the release agent is applied (Patent Document 1).

  On the other hand, conventionally known polyethylene terephthalate contains several percent of cyclic oligomers such as cyclic trimers. Such a cyclic oligomer such as a cyclic trimer has a problem that when a polyethylene terephthalate film is heat-treated, the oligomer is deposited on the film surface and the film is whitened. Therefore, in order to reduce the oligomer in the polyethylene terephthalate film, it has been proposed to propose the amount of cyclic oligomer of the polyethylene terephthalate raw material by a solid phase polymerization method (Patent Documents 2 to 5).

JP 2007-62179 A JP-A-9-99530 JP 2000-141570 A JP 2003-191413 A Japanese Patent Laid-Open No. 2003-301057

  When used as a release film, a release layer containing, for example, heat-added silicone as a main component is provided on one side of the base film in the subsequent step. In recent years, heat treatment at a higher temperature / longer time than in the past has been carried out in providing a release layer in order to improve productivity. Therefore, the problem of oligomer precipitation on the film surface due to heat treatment is becoming apparent. In addition, as the smoothness of the base film is improved, there has been a problem that surface irregularities caused by precipitation of oligomers on the film surface cause pinholes. Since oligomers such as a cyclic trimer form a hard crystal structure on the film surface, pinholes are generated when a thin film green sheet is prepared, and the defect rate is improved.

  Therefore, it is suitable to use polyethylene terephthalate with reduced oligomer as the base film, but in the methods proposed in Patent Documents 2 to 5, although the amount of cyclic oligomer in polyethylene terephthalate can be reduced by solid phase polymerization, There was a problem that the cyclic oligomer was regenerated during melting. That is, it is necessary to melt the raw material polyester in the film formation, and even if the amount of the cyclic oligomer in the film raw material is reduced by a conventionally known method, the cyclic oligomer is formed as a by-product due to the thermal history in the film melting film formation. It was inevitable to generate. Therefore, a sufficient low oligomer film has not been realized by regenerating the cyclic oligomer in the melt extrusion process during film formation.

  The object of the present invention is to solve the above-mentioned problems of the conventional methods and to provide a laminated polyethylene terephthalate film for mold release with little generation of pinholes even after heat processing.

  As a result of intensive studies to solve the above problems, the present inventor has found that the cyclic oligomer regenerated when the polyester is melted depends on the amount of hydroxyl (OH) ends of the molecular chain. The reason is as follows. The cyclic trimer, which is the main component of the cyclic oligomer, is generated by a decomposition reaction from the end of the polyester molecular chain, but a cyclic trimer is easily generated at the hydroxyl (OH) end by a nucleophilic reaction by a hydroxyl (OH) group. Therefore, in the present invention, by reducing the hydroxyl (OH) terminal amount of the polyethylene terephthalate on the release layer side to a predetermined amount or less, regeneration of the cyclic oligomer amount at the time of melting is suppressed, and pinholes are suitably used even after heat treatment. As a result, a film having excellent smoothness that suppresses the occurrence of the above has been obtained.

  That is, the first invention in the present invention, which can solve the above-mentioned problems, is a biaxially oriented laminated polyethylene terephthalate film composed of at least two layers, and forms a surface opposite to a surface on which a release agent is applied. The three-dimensional center plane average surface roughness (SRa) of the layer (surface layer B) is 10 to 50 nm, and the layer forming the surface on which the release agent is applied (surface layer A) contains substantially no particles. In other words, the polyethylene terephthalate constituting the surface layer A has a hydroxyl (OH) terminal content of 70 eq / ton or less and a cyclic trimer content of 0.45% by mass or less, and is a laminated polyethylene terephthalate film for mold release.

  According to the laminated polyethylene terephthalate film for mold release of the present invention, the surface oligomer is hardly deposited even after the heat treatment, so that the smoothness of the surface of the mold release layer is maintained at a high level and the generation of pinholes is suppressed.

  The release-use laminated polyethylene terephthalate film of the present invention is a laminate film composed of at least two or more polyethylene terephthalate layers. The layer that forms the surface to which the release agent is applied is the A layer, and the layer that forms the opposite surface is formed. When the B layer and the core layer other than these are C layers, the layer structure in the thickness direction may be a laminated structure such as A / B or A / C / B.

  In this invention, the hydroxyl (OH) terminal amount of the polyethylene terephthalate which comprises the layer (A layer) which provides a mold release layer is 70 eq / ton or less, and cyclic trimer content is 0.45 mass% or less. Features. By reducing the amount of polyethylene terephthalate cyclic trimer constituting the A layer, it is possible to suppress the precipitation of oligomers by heat treatment and to prevent the generation of pinholes. In order to more suitably suppress oligomer precipitation, polyethylene terephthalate in layers other than the A layer may also have the above characteristics.

  When the film of the present invention is heated at 170 ° C. for 20 minutes, the change in film haze ΔHz (ΔHz = haze after heating−haze before heating) is preferably less than 0.5. When ΔHz is 0.5 or more, cyclic oligomers are precipitated in the post-processing step of the film, and surface oligomer crystals that cause pinholes are likely to occur. On the other hand, when ΔHz is less than 0.5, precipitation of surface oligomers is suppressed even in heat treatment in post-processing, and generation of pinholes can be preferably suppressed. In the invention, the preferable upper limit of ΔHz is 0.3, more preferably 0.1. ΔHz is preferably small, and the lower limit of ΔHz is zero.

  It is important that the hydroxyl (OH) terminal amount of the polyethylene terephthalate constituting the A layer of the present invention is 70 eq / ton or less. Since the polyethylene terephthalate constituting the A layer has a hydroxyl (OH) terminal amount reduced to the above range, generation of a cyclic trimer can be suitably reduced. Therefore, regeneration of the cyclic trimer in the melting step at the time of film formation can be suppressed, and the low oligomer amount of the film raw material can be suitably maintained. The hydroxyl (OH) terminal amount is more preferably 68 eq / ton or less, and still more preferably 65 eq / ton or less. The hydroxyl (OH) terminal amount is preferably small, but if it is too small, hydrolysis of the polyethylene terephthalate constituting the A layer tends to occur. Therefore, from the viewpoint of the durability of the film, the lower limit of the hydroxyl (OH) terminal amount is preferably 40 eq / ton or more, and more preferably 50 eq / ton or more. In the present invention, it is important to find out the influence of hydroxyl (OH) terminal in the polyester resin on the cyclic oligomer regeneration, and the method for controlling the hydryl (OH) terminal amount of polyethylene terephthalate is not particularly limited. By performing heat treatment in a water atmosphere, the amount of hydroxyl (OH) end can be suitably controlled.

  The cyclic trimer content of the polyethylene terephthalate constituting the A layer of the present invention needs to be 0.45% by mass or less. When the cyclic trimer content is 0.45% by mass or more, surface oligomers that cause pinholes may be easily precipitated by heat treatment. In order to make the amount of the cyclic trimer of polyethylene terephthalate within the above range, it is preferable to heat-treat the resin raw material, but in the present invention, by reducing the amount of hydroxyl (OH) terminal, the cyclic trimer in the film The body weight can be suitably reduced within the above range. The upper limit of the preferable cyclic trimer content in the present invention is 0.40% by mass. Although the amount of cyclic trimer is preferably small, in view of productivity, the lower limit of the amount of cyclic trimer is preferably 0.05% by mass, more preferably 0.10% by mass, and 0.20% by mass. % Is more preferable.

  The intrinsic viscosity of the film of the present invention is preferably in the range of 0.40 dl / g to 0.68 dl / g. When the intrinsic viscosity is lower than 0.40 dl / g, the film is easily torn, and when it is higher than 0.70 dl / g, the increase in filtration pressure is increased and high-precision filtration becomes difficult. The upper limit of the intrinsic viscosity of PET is preferably 0.65 dl / g, more preferably 0.63 dl / g. Furthermore, the lower limit is preferably 0.50 dl / g, more preferably 0.55 dl / g.

  Polymerization of polyethylene terephthalate (hereinafter simply referred to as PET) includes direct polymerization of terephthalic acid and ethylene glycol and, if necessary, other dicarboxylic acid components and diol components directly, and dimethyl ester of terephthalic acid (required) Depending on the method, any production method such as a transesterification method in which a transesterification reaction of ethylene glycol (including other diol components as necessary) and ethylene glycol (including other dicarboxylic acid methyl esters) can be used.

  The intrinsic viscosity of the polyethylene terephthalate is preferably in the range of 0.45 dl / g to 0.70 dl / g. When the intrinsic viscosity is lower than 0.45 dl / g, the film is easily torn, and when it is higher than 0.70 dl / g, the increase in filtration pressure is increased and high-precision filtration becomes difficult. The upper limit of the intrinsic viscosity of PET is preferably 0.68 dl / g, more preferably 0.65 dl / g. Further, the lower limit is preferably 0.48 dl / g, more preferably 0.50 dl / g.

  As the catalyst for preparing crude polyethylene terephthalate, conventionally known Mn, Mg, Ca, Ti, Ge, Al, Sb, Co compound, phosphorus compound, antimony compound, and the like are used. A method of deactivating the catalyst has been proposed as a method of suppressing the regeneration of the cyclic oligomer when the polyester is melted. However, in the present invention, the regeneration of the cyclic oligomer can be suitably suppressed without going through the steps. Here, “crude polyethylene terephthalate” is expressed by classifying polyester before heat treatment described later.

  The composition containing the dicarboxylic acid component and the glycol component includes a stabilizer, a pigment, a dye, a nucleating agent, a filler, an ultraviolet absorber, an antioxidant, an antibacterial agent, and an antistatic agent, depending on the final use of the polyester. Additives such as lubricants and mold release agents can be contained.

  Next, the obtained crude polyethylene terephthalate is appropriately formed into a chip shape (for example, a cylindrical shape), a particle shape, or the like by a sheet cutting method, a strand cutting method, or the like. For example, in forming a chip, a melt of crude polyester is extruded from a die with a gear pump to form a strand, and this strand is cut with a cutter, and a major axis × minor axis × length is about 2.2 × 3.1 ×. A 3.4 mm elliptical columnar chip is formed. By molding into such a chip shape, the humidity control effect can be suitably exerted to the inside of the chip while suitably reducing the oligomer amount of the film raw material by heat treatment described later.

  Examples of the method for reducing the hydroxyl (OH) terminal amount of polyethylene terephthalate include a method of increasing the molecular weight to reduce the terminal amount per unit and a method of water-saturating the raw material chip. Among them, in the present invention, by subjecting crude polyethylene terephthalate as a film raw material to heat treatment in a water atmosphere, the cyclic oligomer content can be suitably reduced, and the hydroxyl (OH) terminal amount can be suitably reduced. preferable. The heat treatment is characterized by performing a high-temperature heat treatment at 190 to 260 ° C. under a flow rate of a moisture-containing inert gas containing water. By performing the heat treatment under an inert gas flow rate, it is possible to suitably reduce the cyclic oligomer without increasing the PET intrinsic viscosity more than necessary. This point is different from the conventional solid phase polymerization. Further, unlike the solid phase polymerization method conventionally performed by the batch method, the productivity is excellent in that the treatment can be continuously performed under a flow rate.

  Furthermore, the amount of hydroxyl (OH) ends in the polyethylene terephthalate resin can be suitably reduced by performing the heat treatment in a predetermined water atmosphere. The reason why the amount of hydroxyl (OH) ends is reduced in a water atmosphere is considered as follows. That is, the hydroxyl (OH) ends are bonded by a deethylene glycol reaction by heat treatment, and the hydroxyl (OH) ends are consumed. On the other hand, the reverse reaction of the ester reaction occurs in a water atmosphere, the polyester molecular weight is reduced, and a new molecular chain end is generated. Since these reactions occur as a mixture, it is believed that the resulting hydroxyl (OH) end will be reduced.

  The heat treatment conditions for the crude polyethylene terephthalate in the present invention are described in detail below.

In the heat treatment, the water content in the inert gas is preferably 3.5 to 30.0 g / Nm ³ , more preferably 4.0 to 20.0 g / Nm ³ . When the moisture content in the humidity control inert gas is less than 3.5 g / Nm ³ , the increase in intrinsic viscosity of the resulting polyethylene terephthalate is significant. When the moisture content in the humidity-conditioning inert gas is excessive, a hydrolysis reaction may occur and the intrinsic viscosity of the resulting polyethylene terephthalate may be reduced.

  As the inert gas, a gas inert to polyethylene terephthalate is used, and examples thereof include nitrogen gas, carbon dioxide gas, and helium gas. Nitrogen gas is particularly preferable because it is inexpensive.

  As the heat treatment apparatus, an apparatus capable of uniformly contacting the crude polyethylene terephthalate and the inert gas is desirable. Examples of such a heat treatment apparatus include a stationary dryer, a rotary dryer, a fluidized bed dryer, and a dryer having a stirring blade.

  In addition, it is more preferable to partially crystallize the polymer in order to remove the moisture of the polyethylene terephthalate appropriately before the heat treatment and to prevent fusion of the polymers during the heat treatment.

  In heat processing, heat processing temperature becomes like this. Preferably it is 190 to 260 degreeC, More preferably, it is 200 to 250 degreeC. When the heat treatment temperature is less than 190 ° C., the decrease rate of the cyclic oligomer in the crude polyethylene terephthalate may be small. When the heat treatment temperature exceeds the melting point of polyethylene terephthalate, the polyethylene terephthalate melts and adhesion is likely to occur. Therefore, it is difficult to take out the obtained polyethylene terephthalate from the heat treatment apparatus, and the molding operation may be difficult.

  The heat treatment time is usually preferably 1 to 70 hours, more preferably 2 to 60 hours, and further preferably 4 to 50 hours. If it is less than 1 hour, the cyclic oligomer in the crude polyethylene terephthalate is not sufficiently reduced, and if it exceeds 70 hours, the rate of reduction of the cyclic oligomer in the crude polyester is small, and conversely there is a problem such as thermal deterioration. It may occur and the color tone is impaired.

  The flow rate of the inert gas is closely related to the intrinsic viscosity of polyethylene terephthalate. Moreover, the water content contained in the humidity control inert gas also affects the change in intrinsic viscosity of polyethylene terephthalate. Therefore, the flow rate of the inert gas should be appropriately selected according to the water content, the desired intrinsic viscosity of polyethylene terephthalate, the heat treatment temperature, and the like.

  For example, when the moisture content of the humidity control inert gas is high, the flow rate is preferably increased in order to avoid adverse effects such as hydrolysis by water. Moreover, when making heat processing temperature high, in order to suppress the raise of the intrinsic viscosity of a polyethylene terephthalate, it is preferable to reduce the flow volume of an inert gas.

  The flow rate of the inert gas is preferably at least 1 liter per hour per kg of polyethylene terephthalate, more preferably at least 5 liters. When the flow rate of the inert gas is less than 1 liter per hour per 1 kg of polyester, there is a risk of adverse effects such as yellowing of the resulting resin due to oxygen contamination. The upper limit of the flow rate of the inert gas is determined by the water content contained in the inert gas and the heat treatment temperature, but is 10,000 liters or less per kg of polyethylene terephthalate, preferably 5,000 liters or less, more preferably 2,000 liters or less. Even if the flow rate of the inert gas is set to 10,000 liters or more, it does not deviate from the object of the present invention, but it is not necessary to unnecessarily increase the flow rate in consideration of the economical aspect.

  The heat treatment of the present invention is carried out by heat treatment while circulating an inert gas under normal pressure to slightly pressurized pressure.

In this case, since the purpose of pressurization is to prevent moisture and oxygen in the atmosphere from being mixed into the reactor during the heat treatment, the pressurization condition of 5.0 kg / cm ² or less is sufficient. Even when the pressurization condition exceeds 5.0 kg / cm ² , the object of the present invention is not deviated, but since the equipment is costly, it is meaningless to increase the pressure more than necessary.

  Furthermore, the oxygen concentration in the inert gas circulated from the viewpoint of color tone is required to be 50 ppm or less, preferably 25 ppm or less. When the oxygen concentration is 50 ppm or more, the color tone deteriorates due to the deterioration of the polyester of the present invention, specifically, yellowing is severe, resulting in a problem in product quality.

The polyethylene terephthalate thus obtained preferably satisfies the following formula.
−0.05 dl / g ≦ Intrinsic viscosity before heat treatment −Intrinsic viscosity after heat treatment ≦ 0.05 dl / g

  In the conventional solid-state polymerization method, the intrinsic viscosity of polyethylene terephthalate increases, the load during extrusion molding increases, and the temperature of the polyester rises due to shear heat generation, causing thermal decomposition. On the other hand, in the above method, an increase in intrinsic viscosity can be suppressed and film formation can be suitably performed.

  By these treatments, the intrinsic viscosity (B) of the polyester composition after the heat treatment is preferably 0.50 dl / g or more and 0.70 dl / g or less, and further the intrinsic viscosity of the polyester composition (crude polyester) before the heat treatment. Between (A) and -0.05 dl / g≤ {(A)-(B)} ≤0.05 dl / g, and preferably -0.02 dl / g≤ {(A) -(B)} ≦ 0.02 dl / g is preferably satisfied. By setting the intrinsic viscosity (B) after the heat treatment to 0.50 dl / g or more, the occurrence of film breakage during film formation is reduced, which is advantageous. Moreover, by setting it as 0.70 dl / g or less, it can reduce that a temperature rises by the shear heat_generation | fever at the time of melt molding, and it is advantageous in suppressing the amount of cyclic oligomers in a product.

  Further, by satisfying −0.05 dl / g ≦ {(A) − (B)} ≦ 0.05 dl / g, there is no unnecessary temperature rise during film formation, and the amount of polyester cyclic oligomer is small and the color tone In addition to providing a good film, it is not necessary to newly provide a low-viscosity or high-viscosity brand for a polyester composition (crude polyester) before heat treatment, and an existing polymer that can be used as another product is used. It is possible to reduce the amount of cyclic oligomers used, which is economically advantageous.

  Further, the content of the cyclic trimer of the polyester composition after the heat treatment needs to be 0.4% by mass or less. More preferably, it is 0.35 mass%. When the content exceeds 0.4% by mass, the cyclic oligomer is regenerated at the time of film forming, and the cyclic oligomer is deposited on the film surface during film production or film processing process, causing the process to become a film product defect. There is.

  Furthermore, the hydroxyl (OH) terminal amount of the polyester composition after heat treatment needs to be 65 eq / ton or less. The lower the hydroxyl (OH) terminal amount, the more the oligomer regeneration during the melt extrusion in the film forming process of the polyester raw material can be suppressed. 60 eq / ton or less is more preferable.

  The generation of pinholes is caused by surface irregularities on the surface of the release layer. Therefore, the release layer side surface (surface layer A) is preferably smooth, and the surface layer A of the present invention desirably has a three-dimensional center plane average surface roughness (SRa) of 2 to 10 nm. When the three-dimensional center plane average surface roughness (SRa) of the surface on the release layer side exceeds 10 nm, it is not preferable because it leads to a decrease in quality in the formation of a thin film ceramic green sheet. In addition, the smaller the three-dimensional center plane average surface roughness (SRa) due to the minute unevenness is, the more preferable, but 2 nm is the lower limit in consideration of unevenness of the film thickness, waviness of the film during measurement, and the like.

  On the other hand, the three-dimensional center plane average surface roughness (SRa) of the releasable mold surface (surface layer B) is preferably 10 to 50 nm. When the three-dimensional center plane average surface roughness (SRa) of the surface layer B exceeds 40 nm, the concavo-convex structure is transferred to the surface layer A when wound up in a roll shape, and the above-mentioned fine skin-like unevenness is formed. This is not preferable because it easily leads to a decrease in quality in thin film ceramic green sheet molding. On the other hand, when the three-dimensional center plane average surface roughness (SRa) of the surface layer B is less than 10 nm, blocking is likely to occur during roll unwinding, which is not preferable. In order to prevent this, it is desirable that the protrusion height and protrusion density design on the reverse mold release surface and that there is no foreign matter.

  From the viewpoint of reducing pinholes, it is preferable that the layer forming the surface to which the release agent is applied (A layer) does not contain particles such as a lubricant and does not use a regenerated raw material.

  In the release-use laminated polyethylene terephthalate film of the present invention, the layer (surface layer A) that forms the surface on which the release agent is applied contains substantially no particles. This “substantially free of particles” means, for example, in the case of inorganic particles, a content that is 50 ppm or less, preferably 10 ppm or less, most preferably the detection limit or less when inorganic elements are quantified by fluorescent X-ray analysis. Means.

  The height and density of protrusions on the surface opposite to the surface to which the release agent is applied (surface of the surface layer B) are controlled by the content and / or average particle diameter and / or particle size distribution of the lubricant particles in the film. It is preferable to control by improving dispersion of inert fine particles such as silica and calcium carbonate, which are added as a lubricant, in the polyester.

  In the layer (B layer) forming the surface opposite to the surface to which the release agent is applied, particles such as silica or calcium carbonate particles are added in a total of 1000 to 1000 from the viewpoint of the slipperiness of the film and the ease of air removal. It is preferable to contain 15000 ppm. When the particle concentration is less than 1000 ppm, it is difficult to allow air to escape uniformly when the film is rolled up, and when the particle concentration exceeds 15000 ppm, agglomerates of the lubricant tend to occur, and the coarse protrusions cause wrinkles. Skin-like fine irregularities are generated, which leads to deterioration in quality in thin film ceramic green sheet molding, which is not preferable.

  In order to satisfy the relationship between the amount of lubricant added and the three-dimensional center plane average surface roughness (SRa), silica or calcium carbonate having an average particle size of 0.1 to 2.0 μm is preferably used. . Furthermore, the silica is preferably porous colloidal silica, and the calcium carbonate is more preferably light calcium carbonate surface-treated with a polyacrylic acid polymer compound from the viewpoint of preventing the lubricant from falling off.

  The biaxially oriented film constituting the laminated polyethylene terephthalate film for release of the present invention preferably has a thickness of 20 to 50 μm, more preferably 25 to 38 μm. When the thickness of the film is less than 20 μm, it is not preferable because it is easily deformed by heat at the time of film production, processing steps, and molding. On the other hand, if the thickness of the film is greater than 50 μm, the amount of the film discarded after use increases and the environmental load increases, which is not preferable.

  Moreover, it is preferable that the thickness ratio of the layer (A layer) on the side where the release layer is provided is 20% or more and 50% or less of the total layer thickness. If it is less than 20%, the influence of particles contained in the layer on the opposite side of the layer on which the release layer is provided is easily received from the inside of the film, and the three-dimensional center plane average surface roughness (SRa) satisfies the above conditions. It is difficult to satisfy, which is not preferable. If it is thicker than 50% of the total layer thickness, the use ratio of the regenerated raw material becomes low and it is not economical, which is not preferable.

  The film-forming method of the laminated polyethylene terephthalate film for mold release according to the present invention can be produced, for example, by the following method. That is, after melting PET and extruding it into a sheet, it is stretched 3 to 5 times in the machine direction and then stretched 3 to 4 times in the transverse direction, the so-called MD / TD method, and stretched 3 to 4.5 times in the transverse direction. Then, a TD / MD method of stretching 3.5 to 5.5 times in the longitudinal direction, a method of stretching again biaxially and then longitudinally or laterally, a simultaneous biaxial stretching method, and the like are also possible.

  In addition, easy adhesion coat to improve the adhesion with the release agent to be applied and easy slip and heat resistance to the opposite surface (reverse release surface) of the release film to which the release agent is applied You may apply | coat to the sheet | seat or film before extending | stretching in the film forming process, or after uniaxial stretching.

  The stretched film needs to be heat-set at 190 to 240 ° C. Moreover, it is necessary to adjust the heat shrinkage rate so that the film flatness after applying and drying the mold release agent does not deteriorate. In order to adjust the heat shrinkage rate, the longitudinal and / or lateral relaxation treatment may be performed together with the heat setting treatment. Then, after cutting both ends and winding up as a full width roll (mill roll), it is common to slit to a required width and wind up as a slit roll.

  As the release layer applied to the release film of the present invention, a release layer containing a silicone resin as a main component is suitable. The silicone resin is not particularly limited, and a curable silicone resin such as an addition reaction system, a condensation reaction system, an ultraviolet curable silicone resin, or an electron beam curable silicone resin can be used.

  Examples of the addition reaction type silicone resin include those obtained by reacting polydimethylsiloxane having a vinyl group introduced at the terminal thereof with hydrodienesiloxane using a platinum catalyst to form a three-dimensional crosslinked structure.

  Examples of the condensation reaction type silicone resin include those obtained by reacting polydimethylsiloxane having —OH group at the terminal with hydrodienesiloxane using a platinum catalyst to form a three-dimensional crosslinked structure.

  Examples of UV-curable silicone resins include those that use the same radical reaction as ordinary silicone rubber crosslinks as the most basic types, those that introduce photopolymerization by introducing unsaturated groups, and thiol addition to vinyl siloxane. Examples include those that crosslink by reaction, and those that decompose an onium salt with ultraviolet rays to generate a strong acid, thereby cleaving an epoxy group to crosslink.

  The method for forming the release layer is not particularly limited. For example, a coating solution in which a curable silicone resin is dissolved or dispersed in a solvent is applied to the surface of the polyester film, and after removing the solvent by drying, heating and ultraviolet irradiation are performed. A method of curing the resin is suitable. The conditions for heat curing the resin and removing the solvent by drying may be selected in a timely manner so as to react quickly according to the type of resin used, the thickness of the release layer, and the size of the release film for producing the ceramic sheet. . If the laminated polyethylene terephthalate fill for mold release of the present invention is used, precipitation of the oligomer is suppressed even by a high temperature heat load, which can contribute to improvement of productivity at the time of post-processing.

  Examples of the application method of the coating liquid mainly composed of a curable silicone resin in the mold release process include a roll coating method such as a gravure coating method and a reverse coating method, a bar coating method such as a Mayer bar, a spray coating method, and an air knife. A known coating method such as a coating method can be used.

  Next, the present invention will be specifically described with reference to examples and comparative examples. The characteristic values used in the present invention were evaluated using the following methods. In Examples, “%” means mass% unless otherwise specified.

(1) Particle average particle diameter (μm)
The particle powder is sufficiently dispersed in the ethylene glycol slurry by high-speed agitation, and the particle size distribution in the obtained slurry is converted into a light transmission type centrifugal sedimentation type particle size distribution measuring machine (manufactured by Shimadzu Corporation, trade name “SRA-CP3 type”). )), And the value of the integrated 50% in this distribution was read to obtain the average particle diameter.

(2) Surface layer A, hydroxyl (OH) terminal amount of polyester resin The resin was finely pulverized, and 15 mg was weighed. After completely dissolving in 0.1 ml of hexafluoroisopropanol (HFIP) -d2, it was diluted with 0.6 ml of deuterated chloroform. Furthermore, in order to shift the OH group peak of HFIP, 30 μl of pyridine-d5 was added, and measurement was performed by H-NMR (BBO-5 mm probe).
In addition, the sample of the surface layer A produced the film sample extruded only by A layer, and used it as the sample.

(3) Amount of cyclic trimer The resin was finely pulverized, and 0.1 g was dissolved in 3 ml of a mixed solvent of hexafluoroisopropanol (HFIP) / chloroform (2/3 (volume ratio)). To the resulting solution, 20 ml of chloroform was added and mixed uniformly. 10 ml of methanol was added to the resulting mixture to reprecipitate the linear polyester. Next, this mixed solution was filtered, and the precipitate was washed with 30 ml of a mixed solvent of chloroform / methanol (2/1 (volume ratio)) and further filtered. The obtained filtrate was concentrated to dryness on a rotary evaporator. 10 ml of dimethylformamide was added to the concentrated dried product to prepare a cyclic trimer measurement solution. This measurement solution was quantified using LC100 type high performance liquid chromatography manufactured by Yokogawa Electric Corporation.
In addition, the sample of the surface layer A produced the film sample extruded only by A layer, and used it as the sample.

(4) Intrinsic viscosity 0.2 g of polyester was dissolved in 50 ml of a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (60/40 (weight ratio)), and an Ostwald viscometer was used at 30 ° C. It was measured. In addition, the sample of the surface layer A produced the film sample extruded only by A layer, and used it as the sample.

(5) Three-dimensional center plane average surface roughness (SRa) of the surface on which the release agent is applied and the opposite surface
A film having an area of 50 mm × 50 mm is cut out, and a three-dimensional surface shape measuring device (manufactured by Ryoka System Co., Ltd., Micromap 550N (measurement conditions: wave mode, measurement wavelength 560 nm, objective lens 10 times)) is used on the film surface. On the other hand, measurement was performed from the vertical direction, a 400 μm × 400 μm CCD camera image capturing area was designated, and SRa given by the following equation was obtained. On both sides of the film, the number of measurements was 16 and the average value was obtained. The fractions after the decimal point are rounded off to the nearest whole number.

Here, S _M = L _X × M _Y , L _X and M _Y are ranges in the x and y directions, and f (x, y) is the height from the average plane of the measurement point (x, y). .

(6) Ceramic green sheet moldability (preparation of mold release agent)
A thermosetting silicone resin (manufactured by Toshiba Silicone Co., Ltd., TPR6712) is mixed and dispersed in a solvent (toluene / MEK = 50/50; mass ratio) so that the solid content concentration is 1.0% by mass. A release agent for coating by adding 1 part by mass of a platinum catalyst as a curing catalyst to 100 parts by mass of the silicone resin was used.

(Preparation of ceramic slurry)
A composition comprising the following materials was stirred and mixed to form a paste, and then dispersed for 2 days in a ball mill to obtain a ceramic slurry.
・ Toluene 15% by mass
・ Ethanol 15% by mass
・ Barium titanate (Fuji Titanium) 50% by mass
・ Polyvinyl butyral (Sekisui Chemical Co., Ltd.) 10% by mass

(Production of release film)
Using a gravure coater, after applying a release agent to the layer A side of the polyethylene terephthalate film obtained in the examples and comparative examples of the present invention, drying is performed at 170 ° C. for 5 minutes under a high temperature condition for a long time, A release layer having a thickness of 0.5 μm was provided.

(Ceramic green sheet molding test)
The ceramic slurry was coated on the surface of the release layer of the release film by a doctor blade method so that the dry thickness was 1 μm, and dried at 100 ° C. for 5 minutes to obtain a ceramic sheet.

(Ceramic sheet pinhole evaluation)
The film laminate in which the ceramic sheet layer is laminated on the release layer surface of the release film is irradiated with light from the opposite surface of the ceramic sheet layer in a range of 100 cm ² to observe the occurrence of pinholes, and visually judged according to the following criteria ,evaluated.
○: No pinhole.
Δ: Almost no pinholes.
X: There are many pinholes.

(Production of PET (A) I and PET (A) V)
1,000 parts of dimethyl terephthalate, 700 parts of ethylene glycol, and 0.3 part of zinc acetate dihydrate were charged into a transesterification reaction can and subjected to a transesterification reaction at 120 to 210 ° C., and the produced methanol was distilled off. When the transesterification reaction was completed, 0.13 phosphoric acid and 0.3 part antimony trioxide were added, and the pressure in the system was gradually reduced to 1 mmHg or less in 75 minutes. At the same time, the temperature was gradually raised to 280 ° C. A polycondensation reaction was carried out for 70 minutes under the same conditions, and the molten polymer was extruded into water from a discharge nozzle and formed into a cylindrical chip having a diameter of about 3 mm and a length of about 5 mm by a cutter. The obtained crude polyester had an intrinsic viscosity of 0.610 dl / g, a hydroxyl (OH) terminal amount of 70 eq / ton, and a cyclic trimer content of 1.05% by mass. In addition, all “parts” in the examples represent parts by mass. Let the obtained crude polyester be a polyester resin (PET (A) V).

The polyester resin (PET (A) V) is dried at 160 ° C. under reduced pressure, and then nitrogen gas conditioned to a moisture content of 6.4 g / Nm ³ is circulated at a rate of 70 liters per kg of crude polyester. Then, heat treatment was performed at 207 ° C. for 48 hours. The obtained polyester had an intrinsic viscosity of 0.631 dl / g, a hydroxyl (OH) end amount of 59 eq / ton, and a cyclic trimer content of 0.27% by mass.

(Preparation of PET (A) II)
The polyester resin (PET (A) V) was dried at 160 ° C. under reduced pressure, and then nitrogen gas conditioned to a moisture content of 15.3 g / Nm ³ was circulated at 300 liters per kg of crude polyester. Heat treatment was performed at 230 ° C. for 12 hours. The obtained polyester had an intrinsic viscosity of 0.617 dl / g, a hydroxyl (OH) terminal amount of 63 eq / ton, and a cyclic trimer content of 0.28% by mass.

(Preparation of PET (A) III)
The intrinsic viscosity is 0.648 dl / g, the hydroxyl (OH) terminal amount is 64 eq / ton, and the cyclic trimer is the same as the polyester resin (PET (A) V) except that the polymerization time is adjusted. A crude polyester having a content of 1.2% by mass was obtained. The obtained crude polyester was dried at 160 ° C. under reduced pressure, and then nitrogen gas conditioned to a water content of 15.3 g / Nm ³ was circulated at 300 liters per kg of the crude polyester at 220 ° C. Heat treatment was performed for 24 hours. The obtained polyester had an intrinsic viscosity of 0.623 dl / g, a hydroxyl (OH) terminal amount of 57 eq / ton, and a cyclic trimer content of 0.27% by mass.

(Preparation of PET (A) IV)
The polyester resin (PET (A) V) was dried at 160 ° C. under reduced pressure, adjusted to a slight pressure of 0.1 kg / cm ² under a nitrogen atmosphere, and heat-treated at 215 ° C. for 24 hours. The obtained polyester had an intrinsic viscosity of 0.622 dl / g, a hydroxyl (OH) terminal amount of 73 eq / ton, and a cyclic trimer content of 0.30% by mass.

(Preparation of PET (B) I)
In the production of PET (A) V, 0.2% by mass of porous colloidal silica having an average particle size of 0.9 μm and 1% by mass of ammonium salt of polyacrylic acid per 1% of calcium carbonate during the transesterification reaction 0.4% by mass of synthetic calcium carbonate having a diameter of 0.6 μm was added as a 10% EG slurry. Thereafter, PET (B) I was produced in the same manner as PET (A) V except that the polymerization reaction time was adjusted. The obtained polyester had an intrinsic viscosity of 0.620 dl / g.

(Production of PET (B) II, III, IV)
PET (B) II, III, and IV were prepared in the same manner as PET (B) I except that the particle type and particle concentration were changed as shown in Table 2.

Example 1
After the PET (A) I and PET (B) II chips were dried, they were melted at 285 ° C., melted at 290 ° C. with a separate melt extruder extruder, joined in a feed block, and PET (B) II Layer B (reverse release surface side layer) and PET (A) I are laminated to form layer A (release surface side layer), extruded into a sheet shape, and placed on a casting drum at 30 ° C. by electrostatic adhesion. Was subjected to electrostatic adhesion and cooling to obtain an unstretched polyethylene terephthalate sheet. The layer ratio was adjusted so that A / B = 60% / 40% in the discharge amount calculation of each extruder.

  Next, this unstretched sheet was stretched 3.5 times in the machine direction at a roll temperature of 80 ° C. due to the speed difference between the rolls. Thereafter, the film was guided to a tenter and stretched 4.2 times in the transverse direction at 140 ° C. Subsequently, it heat-processed at 210 degreeC in the heat setting zone. Thereafter, a relaxation treatment of 2.3% was performed in the transverse direction at 170 ° C. to obtain a biaxially stretched polyethylene terephthalate film having a thickness of 31 μm.

(Examples 2 and 3, Comparative Examples 1 and 2)
A biaxially stretched polyethylene terephthalate film having a thickness of 31 μm was obtained in the same manner as in Example 1 except that the PET constituting the A layer (release surface side layer) in Example 1 was changed as shown in Table 3.

(Example 4)
Example 1 except that the PET constituting the B layer in Example 1 was changed as shown in Table 3, and the layer ratio was adjusted to A / B = 80% / 20% in the discharge amount calculation of each extruder. In the same manner as in Example 1, a biaxially stretched polyethylene terephthalate film having a thickness of 31 μm was obtained.

(Example 5, Comparative Example 3)
In Example 1, the PET constituting each layer was changed as shown in Table 3, and the film layer configuration was A / C / B. The layer ratio was adjusted to be A / C / B = 20% / 40% / 40% by calculating the discharge amount of each extruder, and the biaxially stretched polyethylene terephthalate film having a thickness of 31 μm was prepared in the same manner as in Example 1. Got.

  The laminated polyethylene terephthalate film for mold release of the present invention is excellent in smoothness, has less oligomer precipitation even after heat treatment at high temperature, and has less pinholes. It can be used and contributes to the industry.

Claims (1)

A biaxially oriented laminated polyethylene terephthalate film consisting of at least two layers,
The biaxially oriented laminated polyethylene terephthalate film has a surface layer A and a surface layer B,
The layer (surface layer B) that forms the surface opposite to the surface to which the release agent is applied has a three-dimensional central surface average surface roughness (SRa) of 10 to 50 nm,
The layer forming the surface on which the release agent is applied (surface layer A) does not substantially contain particles,
A laminated polyethylene terephthalate film for mold release having a hydroxyl (OH) terminal content of polyethylene terephthalate constituting at least surface layer A of 70 eq / ton or less and a cyclic trimer content of 0.45 mass% or less.