TW201945446A - Roll of biaxially oriented release polyester film - Google Patents

Abstract

A biaxially oriented release polyester film characterized by having a width of 400 mm or greater and a thickness deviation [sigma] ([sigma]MD) with respect to the average value, determined through a continuous measurement over 10,000 m in the machine direction of the film, of 0.15 [mu]m or less. The release polyester film can give a less rigid support for green sheet forming and can reduce strain amounts during electrode printing. The release polyester film is optimal for ceramic-slurry application in forming thin green sheets.

Description

   Biaxially oriented polyester film roll for demolding   

The present invention relates to a biaxially oriented polyester film roll for demolding, which is obtained by rolling a biaxially oriented polyester film for demolding, which is excellent in film thickness uniformity when film slurry is applied.

From the viewpoints of mechanical properties, thermal properties, stiffness, and cost, biaxially oriented polyester films are used for various applications as industrial material applications. Especially recently, it is used as engineering paper related to electronic components for release films for forming green sheet of laminated ceramic capacitors, or isolation films for liquid crystal polarizers, substrates for photoresist for dry films, and interlayer insulating resins. Release substrate and the like.

With the recent advancement of the functions of smart phones, or the popularization of smart watches and wearable equipment, the miniaturization and high capacity of multilayer ceramic capacitors are being further developed. Regarding the release film used in the manufacture of multilayer ceramic capacitors, with the thinning of the green sheet, the demand for polyester films with high smoothness, no defects on the surface and inside of the film, and excellent flatness of the film continues to grow. On the other hand, the demand for multilayer ceramic capacitors mounted on automobiles has grown rapidly due to the expansion of electric vehicle production, the development of automotive IoT (Internet of Things), and the introduction of autonomous driving functions to automobiles. For these automotive multilayer ceramic capacitors, more stringent reliability is required than in the past. In particular, when forming a green sheet of a dielectric component of a multilayer ceramic capacitor, it is necessary to strictly control the uneven thickness of the thin film or the planar characteristics of the thin film. When the thin film is used as a substrate, it is laminated on the Unevenness of slurry thickness thereon.

It is known that the thickness of the film is uneven, as shown in Patent Document 1, by measuring 15 m in the longitudinal direction, or by measuring every 5 mm for a length of 1 m, which are known methods. In addition, as shown in Patent Document 2, in the orthogonal Nicolson method for inspecting a polarizing plate, the intensity unevenness of light leaked from the polarizing plate becomes strong and becomes an obstacle to inspection. Therefore, it is necessary to set the thickness unevenness to a predetermined value. range. As shown in Patent Document 3, it is known that this is achieved by performing simultaneous biaxial extension and improving the surface alignment.

Prior art literature Patent literature

Patent Document 1 Japanese Patent Application Publication No. 2008-246685

Patent Document 2 Japanese Patent Laid-Open No. 2017-007175

Patent Document 3 Japanese Patent Laid-Open No. 2004-291240

In recent years, requirements for capacitors have tended to be highly reliable in addition to miniaturization and large capacity. Miniaturization can be achieved by reducing the size of the electrodes. Larger capacity can be achieved by thinning the green sheet. In addition, high reliability can be achieved by improving the dimensional accuracy with respect to the width, length, and thickness directions when electrodes or green sheets are provided. Among them, the uniformity of the coating thickness during slurry coating, because the area of each electrode will become smaller in the subsequent step of electrode printing, so it is a major factor that determines the dielectric constant deviation of the capacitor (that is, the capacitance deviation of the capacitor). One example is the minimization of skew and offset of the electrode pattern. As a result, the requirements for the thickness unevenness of the thin film become stricter. In particular, it has been found that the steps of continuously monitoring the thickness of the slurry during capacitor manufacturing, and applying thin film to the slurry while correcting the inclination of the mold, etc., are affected by the uneven thickness of the base film over the entire length of the roll. The probability is high. Therefore, an object of the present invention is to reduce the uneven thickness of the film over the entire length of the roll when it is used as a support, particularly when forming a green sheet.

In view of the above facts, the inventors have carefully studied the results and found that by optimizing the characteristics of the film, the biaxially oriented polyester for mold release having excellent dimensional stability of the slurry in the long, wide, and thickness directions The biaxially oriented polyester film roll for demolding formed by rolling the film into a roll, thereby completing the present invention. That is, the present invention is characterized by a biaxially oriented polyester film roll for demolding, which has a film width of 400 mm or more and a deviation σ value (σ _MD ) is 0.15 μm or less.

According to the present invention, it is possible to provide a biaxially oriented polyester film for demolding, which can reduce the thickness deviation during green sheet molding and optimize the coating performance of ceramic slurry during super film green sheet molding. A roll of biaxially oriented polyester film for demolding.

Implementation of the invention

The present invention is described in more detail below.

The biaxially oriented polyester film roll for release of the present invention is obtained by winding a biaxially oriented polyester film for release (hereinafter sometimes referred to as a biaxially oriented polyester film) to a core material such as a core. Here, biaxial alignment refers to a state in which an unstretched (unaligned) film is extended in a two-dimensional direction by a conventional method, and means a pattern in which biaxial alignment is expressed by wide-angle X-ray diffraction. For extension, either one of sequential biaxial extension or simultaneous biaxial extension can be used. Sequential biaxial extension can extend the steps in the longitudinal direction (longitudinal direction) and the wide direction (horizontal direction), one time each in the vertical direction, and two times each in the vertical direction, the horizontal direction, and the vertical direction.

The polyester in the biaxially oriented polyester film of the present invention is a polyester containing a dibasic acid and a diol as constituent components. As the aromatic dibasic acid, terephthalic acid, isophthalic acid, and phthalic acid can be used. Formic acid, naphthalenedicarboxylic acid, diphenylphosphonium dicarboxylic acid, diphenyl ether dicarboxylic acid, benzophenone dicarboxylic acid, phenylindane dicarboxylic acid, sodium isophthalate sulfonate, dibromoterephthalic acid Formic acid and so on. Examples of the alicyclic dibasic acid include oxalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, and a dimer acid. As for the diol, as the aliphatic diol, ethylene glycol, propylene glycol, tetramethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, diethylene glycol, and the like can be used. As the aromatic diol, naphthalene glycol, 2,2-bis (4-hydroxydiphenyl) propane, 2,2-bis (4-hydroxyethoxyphenyl) propane, and bis (4-hydroxybenzene) can be used. Group), hydrazone, hydroquinone, etc. As the alicyclic diol, cyclohexanedimethanol, cyclohexanediol, etc. can be used.

The above polyester can be produced by a known method, and its inherent viscosity is preferably a lower limit of 0.5 and an upper limit of 0.8. The lower limit is more preferably 0.55 and the upper limit is 0.70. In addition, the measurement of intrinsic viscosity is a value calculated by the following formula using the viscosity of a solution measured in o-chlorophenol at 25 ° C.

ηsp / C = [η] + K [η] ² ‧C

Here, ηsp = (solution viscosity / solvent viscosity) -1, C is the mass of the dissolved polymer per 100 ml of the solvent (g / 100 ml, usually 1.2), and K is the Herkins constant (defined as 0.343). In addition, solution viscosity and solvent viscosity were measured using an Oschva viscosity meter. The unit is expressed in [dl / g].

The biaxially oriented polyester film of the present invention may be a single-layer film or a laminated structure of two or more layers. Polyester A layer and polyester B layer are included in the two-layer lamination. In the case of three layers, there are three layers including polyester A layer, polyester B layer, and polyester C layer, or polyester A layer and polyester B layer. Laminated film of 3 layers of polyester A layer. At this time, by controlling the amount of particles contained in the layer (laminated portion) constituting the surface layer, the raw materials can be recovered at the edge portion generated in the film forming process in a range that does not adversely affect the surface properties of the film on the inner layer portion, It can be used in a timely manner by mixing and recycling the recycled raw materials in other film-forming steps, which can reduce the consumption of petroleum resources and also obtain the cost advantage. Therefore, it has the best structure with a layer structure of three or more layers.

Moreover, it is preferable that the biaxially-oriented polyester film of the present invention contains a recycled material and / or a recycled material in the C layer. Accordingly, the C layer is preferably the thickest layer among the layer configurations. The melting specific resistance of the raw material contained in layer A (a smoother layer) is preferably 1.0 × 10 ⁶ Ω · cm or more and 1.0 × 10 ⁸ Ω · cm or less, and more preferably 5.0 × 10 ⁸ Ω · cm or less. . The raw material having a specific resistance value as described above is also preferably a polyester resin. The A layer is preferably a layer constituting a surface where SRa (A) described later is 1 nm or more and less than 15 nm. Moreover, it is preferable to have both the raw material composition or thickness-related characteristics of layer C and the raw material-related characteristics or surface shape-related characteristics of layer A.

In the biaxially oriented polyester film of the present invention, among the two or more layers, the surface of the two layers (that is, the polyester A layer and the polyester B layer) constituting the surface layer has both surface smoothness and transportation or Controllability such as winding is preferably a structure having a different thickness. That is, it is preferable that the center line thickness SRa (A) of one film surface is 1 nm or more and less than 15 nm, and the center line thickness SRa (B) of the other film surface is 20 nm or more and 40 nm or less. If SRa (A) is less than 1 nm, it will become difficult to perform peeling in the peeling step after the surface layer release layer and the ceramic slurry is laminated thereon. Moreover, if SRa (A) is 15 nm or more, the surface state of a slurry will worsen and thickness unevenness will generate | occur | produce, As a result, it will become easy to generate | occur | produce the dispersion | variation in the characteristic of a capacitor. If SRa (B) is less than 20 nm, the coiling after coating the release layer or the ceramic slurry after coiling will easily cause blocking, and static electricity will be generated when it is wound out. The surface of the polyester A layer and the polyester B layer is more preferably the center line thickness SRa (A) of one film surface is 2 nm or more and less than 12 nm, and the center line thickness SRa (B) of the other film surface is 25nm to 35nm.

The thickness of the biaxially oriented polyester film of the present invention is preferably 12 μm or more, more preferably 20 μm or more, and even more preferably 25 μm or more. The thickness is preferably 188 μm or less, more preferably 50 μm or less, and even more preferably 40 μm or less. If the thickness becomes thinner than 12 μm, the stiffness used to maintain the ceramic slurry will disappear, it will become impossible to support the ceramic slurry during the coating of the ceramic slurry, and it may not be uniformly dried or hot-wrinkled in the subsequent steps. When the suppression of pleats becomes insufficient. When the thickness exceeds 188 μm, the durability against thermal wrinkles is particularly excellent, but as the roll length decreases, the unit price per unit area as a base material for forming the ceramic slurry tends to increase, and during longitudinal extension, It is difficult to increase the temperature or extend the temperature, and it is the main cause of worsening the thickness unevenness. The preferable range of the thickness is 12 μm or more and 188 μm or less, more preferably 20 μm or more and 50 μm or less, and even more preferably 25 μm or more and 40 μm or less.

The biaxially oriented polyester film of the present invention may contain particles. The volume average particle diameter of the particles contained at this time is preferably 1.3 μm or less. If the volume average particle diameter of the particles exceeds 1.3 μm, there is a high chance that voids (ie, pores) will be generated at the interface between the particles and the polymer during elongation. Therefore, the unevenness of the surface structure may also occur. When thickness deviation becomes large. In addition, the ultra-thin green sheet in the present invention refers to a thickness of less than 1 μm.

As the particles used in the present invention, inorganic particles such as spherical silica, agglomerated silica, calcium carbonate, alumina, barium titanate, titanium oxide, crosslinked polystyrene resin particles, and crosslinked silicone resin particles can be used. , Organic particles such as cross-linked acrylic resin particles, cross-linked styrene-acrylic resin particles, cross-linked polyester particles, polyimide particles, and melamine resin particles. These particles have the effect of forming protrusions on the surface of the film, and can also be used as a core material for forming pores. Therefore, it is preferable to select the particle size and the type at the same time. It is preferable to use organic particles having high elasticity. Organic particles, particularly preferably among the aforementioned organic particles, selected from the group consisting of crosslinked polystyrene resin particles, crosslinked silicone resin particles, crosslinked acrylic resin particles, crosslinked styrene-acrylic resin particles, and crosslinked polyester particles Among the organic particles. In terms of inorganic particles, spherical silica and alumina are particularly preferred.

The shape and particle size distribution of the particles are preferably uniform, and particularly preferably, the shape of the particles is approximately spherical. The volume shape factor is preferably f = 0.3 ~ π / 6, and more preferably f = 0.4 ~ π / 6. The volume shape factor f is expressed by the following formula.

f = V / Dm ³

Here, V is the particle volume (μm ³ ), and Dm is the maximum diameter (μm) on the projection plane of the particles.

In addition, the volume shape coefficient f takes the largest π / 6 (= 0.52) when the particle is a sphere. Moreover, it is preferable to remove agglomerated particles, coarse particles, and the like by filtering or the like as necessary. Among them, cross-linked polystyrene resin particles, cross-linked silicone resin particles, and cross-linked acrylic resin particles synthesized by an emulsion polymerization method or the like can be suitably used, and have a volume shape coefficient close to a true sphere, and the particle size distribution is extremely uniform and uniformly formed. From the viewpoint of film surface protrusions, particularly preferred are crosslinked polystyrene particles, crosslinked silicone, and even spherical silica.

The biaxially oriented polyester film of the present invention has a film width of 400 mm or more, and a deviation σ value (σ _MD ) from an average value of a thickness obtained by continuously measuring a film length direction of 10,000 m is 0.15 μm or less.

The following description will be made in order.

The biaxially oriented polyester film of the present invention has a film width of 400 mm or more, and a deviation σ value (σ _MD ) from an average value of a thickness obtained by continuously measuring a film length direction of 10,000 m is 0.15 μm or less. The thickness obtained by continuously measuring 10,000 m in the longitudinal direction of the film is the thickness when the film is continuously subjected to non-contact measurement. The width of the film and the length in the long-side direction indicate the size of the support. This support system is required when manufacturing multilayer ceramic capacitors in a certain batch. That is, it was found that the moldability of the green sheet can be improved by suppressing the variation in thickness within this size. In the following description, the σ _MD value may be regarded as a film thickness unevenness in the longitudinal direction.

Conventionally, the thickness of biaxially oriented polyester film is measured by scanning the film with a non-contact thickness meter in a wide direction during film formation, or with a contact thickness meter to measure the thickness of the film from the roll to the long side by about 20 m. The obtained sample was measured continuously at 10,000 m in the long side direction as described above, and a thickness unevenness that could not be confirmed in the past was found. Regarding this uneven thickness phenomenon, by reducing the deviation, the present invention can exert the following effects: it can reduce the uneven thickness of the slurry when the thin-film ceramic slurry is applied, reduce the deviation of the electrostatic capacitance, and can reduce the probability of short circuit. In addition, if σ _MD exceeds 0.15 μm, in the application of the thin-film ceramic slurry, the thickness unevenness of the slurry will increase, and the above-mentioned effects will be reduced.

In the biaxially oriented polyester film of the present invention, it is preferable that the center line thickness SRa (A) of one film surface is 1 nm or more and less than 15 nm, and the center line thickness SRa (B) of the other film surface is 20 nm or more. Below 40nm. In the biaxially oriented polyester film of the present invention, in consideration of the balance between the coating thickness of the slurry and the handleability, a mold release treatment can be performed on any surface, and a flattening treatment can also be performed before the mold release treatment to reduce the mold release layer. The roughness of the surface.

The manufacturing method of the biaxially oriented polyester film of the present invention is described below, but the present invention should not be construed as being limited to these examples.

As a method for making the polyester contain inactive particles, for example, the inactive particles are dispersed in the form of a slurry in ethylene glycol having a diol component at a predetermined ratio, and the ethylene glycol slurry is used before the polyester polymerization is completed. Add at any stage. At this time, when adding particles, for example, if the hydrosol or alcohol sol obtained during the synthesis of the particles is not dried and added first, the dispersibility of the particles is good, and the generation of coarse protrusions is preferably suppressed. Further, a method of directly mixing the aqueous slurry of particles with a predetermined polyester pellet and supplying it to a biaxial kneading extruder in a vented form to knead it with polyester is also effective for the production of the present invention.

The mother granules containing particles and pellets substantially free of particles and the like prepared as described above are mixed at a predetermined ratio, dried, and then supplied to a well-known extruder for melt-lamination. The extruder used in the production of the biaxially oriented polyester film of the present invention may be a uniaxial or biaxial extruder. In addition, in order to omit the drying step of the pellets, an exhaust-type extruder having a vacuum line in the extruder may be used. For the C layer with the largest extrusion amount, a so-called tandem extruder can be used, which shares the function of the molten pellets and the function of maintaining the molten pellets at a constant temperature with separate extrusion machines. The tandem extruder stabilizes the polymer temperature during high discharge. As a result, the viscosity deviation of the polymer can be reduced, so it is suitable as a process for reducing uneven thickness.

The polymer melted and extruded with an extruder was filtered through a filter. Even if very small foreign matter enters the film, it will become a coarse protrusion defect. Therefore, for a filter, it is effective to use a foreign matter of 3 μm or more to capture 95% or more high-precision capture efficiency. On the other hand, if the capture efficiency of the filter is too high, the pressure will increase. Therefore, the use of a filter with a capture efficiency of more than 95% with a higher accuracy of catching foreign objects smaller than 3 μm, sometimes in thickness The aspect of suppressing unevenness is a poor embodiment. Next, it is extruded into a sheet shape from a slit-shaped slit die, and is cooled and solidified on a casting roll to produce an unstretched film. For example, in the case of a three-layer laminate, three extruders, a three-layer manifold, or a manifold (such as a manifold with a rectangular manifold) are laminated into three layers, and the sheet is extruded from the die. In this case, it is preferable that the gap of the die can be automatically adjusted by a heater. The sheet extruded from the die was cooled by a mold roll to produce an unstretched film. At this time, from the viewpoints of stabilization of back pressure and suppression of thickness variation, a method of installing a static mixer and a gear pump in a polymer flow path is a means for suppressing thickness unevenness in the longitudinal direction in the present invention. effective. The gear pump has the function of blocking the pressure fluctuation in the extrusion step, so it is necessary to uniformly control the thickness in the long side direction. By setting the speed of the gear built in the gear pump to be constant, the long side can be set. The thickness unevenness in the direction is suppressed to be small. In the present invention, it is also effective to control the rotation speed of the gear pump by feeding back the thickness converted from the weight of the rolled intermediate product. This is because the discharge is reduced as the pressure of the filter increases, so the thickness of the film becomes gradually thinner with respect to the longitudinal direction.

Regarding the rotation accuracy of the mold roll, the speed fluctuation of the surface of the mold roll or the unevenness of the surface due to the eccentricity of the mold roll may affect the thickness unevenness in the longitudinal direction. In the past, the speed variation of the surface of the mold roll greatly affected the thickness unevenness in the longitudinal direction. Therefore, in order to reduce the foregoing, attaching a balance weight to any place on the circumference of the mold roll end surface to control the unevenness of the eccentricity is a preferred embodiment. In addition, the motor for rotating the casting drum is set to two, and the functions are divided according to driving and braking, etc. It is also preferable under the premise that the thickness in the longitudinal direction is not uniform. Implementation form. In the present invention, in order to control the σ _MD value, it is necessary to further improve the accuracy. Therefore, when evaluating the rotation accuracy of the mold roll, the distance from the sensor to the surface of the mold is measured over the entire circumference of the mold. The difference between the maximum value and the minimum value is defined as a deflection. The distance from the sensor to the mold surface is measured by a sensor provided on the floor where the mold drum is provided. This value is preferably within 50 μm, and more preferably within 30 μm, because the thickness unevenness (σ _MD ) in the longitudinal direction in the present invention can be improved. The displacement of the unevenness on the circumference of the mold at this time is specifically a laser displacement meter installed on the floor where the mold device is installed to measure the distance between the mold roller and the measurement portion of the laser displacement meter.

The unstretched film that falls on the mold roll uses a pinning device to make it adhere to the mold with electrostatic force. The pinning device is the entire width of the unstretched film. The charge is imparted to the mold roller by the electrostatic application wire, and the film and the mold roller are brought into close contact by the static electricity at the interface between the mold roller and the film. At this time, in order to set the strength of the electric charge constant in the width direction, it is preferable that the distance from the static electricity application lead to the film is equal over the entire width of the unstretched film. In addition, in order to maintain the adhesion between the mold roll and the film to an appropriate strength, it is preferable to adjust the strength of the current applied by static electricity.

Also, although the end portion of the unstretched film is adjusted so that the thickness of the end portion becomes thicker than that of the center in order to increase the gripping force of the clip when extending by the horizontal stretcher, the adhesion of the end portion is poor. The cooling efficiency of the mold roll becomes worse. As a result, the end portion crystallizes and becomes a cause of cracking. Therefore, in addition to the entire wide pinning device, an additional pinning device is only added to the end portion. The so-called edge pinning device makes the end of the unstretched film close to the mold and suppresses uneven cooling of the edge. It can suppress the vibration at the falling point of the mold and make the thickness in the long side direction. The unevenness becomes better. Furthermore, when an edge pinning device is applied to an unstretched film, effective pinning can be performed as long as it is carried out from a place at a distance of 5 mm or more from the edge portion of the unstretched film. The reason is that when static electricity is applied by the edge pinning device, the leakage current can be prevented from abnormally discharging the mold roll. In addition, the processing width of the edge pinning is adjusted according to the edge thickness profile of the unstretched film, and when the range is set to 20 mm or more and less than 100 mm, effective edge portion molding can be performed.

The film which is in close contact with the mold roller and cooled is a peeling film from the mold roller using a take-off roller, and the subsequent stretching step is introduced. Water can be passed to the extraction roller at this time to cool the film, or the extraction roller can be driven.

The extension method can be simultaneous biaxial extension or sequential biaxial extension. In the simultaneous biaxial extension, when the longitudinal and lateral extensions are performed at the same time, the uneven wind speed or the air flow (with the air flow) flowing along the film will affect the wide extension as an external disturbance, and also affect the long side direction. It also affects, so the successive biaxial extension system is a more suitable form.

When the polyester film of the present invention is produced by successive stretching, the initial stretching in the longitudinal direction is important on the premise of suppressing the generation of scratches and the thickness of the longitudinal direction is not all the same. The stretching temperature The temperature is from 90 ° C to 130 ° C, preferably from 100 ° C to 120 ° C. When the extension temperature becomes lower than 90 ° C, the film is easily broken, and when the extension temperature becomes higher than 130 ° C, the surface of the film becomes vulnerable to thermal damage. From the viewpoint of preventing uneven stretching and damage, stretching is preferably performed in two or more stages. The total magnification is 2.8 times to 5.0 times in the length direction, and preferably 3.3 times to 4.0 times. 3.5 times to 5 times in the width direction, preferably 4.0 times to 4.5 times. When the longitudinal stretching magnification is set to the aforementioned value, it is preferable to set a plurality of stretching intervals so as to prevent slipping of the stretching roller and the film, since it can suppress the change in stretching tension caused by the slipping. At this time, it is preferable to set the stretching magnification in one stretching section to 3.0 times or less, because it can secure an appropriate stretching tension. If the temperature and the magnification range are exceeded, problems such as uneven stretching and film breakage are caused, and it is difficult to obtain a film that is a feature of the present invention.

In the successive stretching, the process of stretching in the longitudinal direction, because of the difference between the peripheral speed of the roller and the speed of the film when the film is in contact with the roller, is easy to cause scratches when the film slips, and it is also the main reason for the uneven thickness in the longitudinal direction. Therefore, it is preferable that the driving method of the roller peripheral speed can be set individually for each roller. In the process of stretching in the long side direction, the material of the conveying roller can be selected according to any of the following: heating the unstretched film above the glass transfer point before stretching; or keeping the temperature lower than the glass transfer point Conveyed to the extension zone, heated in one breath during extension. When the unstretched film is heated above the glass transition point before stretching, the adhesion caused by heating will induce uneven stretching. Therefore, under the premise of preventing the foregoing, it is preferably selected from non-adhesive silicone rollers, ceramics, and iron. Fluon (registered trademark). In addition, the temperature of the conveying roller in the heating process is preferably selected by a combination of material and conveying temperature. Until the unstretched film exceeds the glass transfer point, in order to suppress the adhesion caused by heating, it is preferable to set the conveying roller. It is a hard chromium-plated metal roller and the conveying temperature is set to less than 80 ° C. In this case, it is preferable to use an infrared heater in the extending step to supplement the heat.

In addition, the stretching roller exerts the most load on the film, and it is a step that is easy to occur due to the unevenness of the stretching caused by the flaws in the process and the thickness in the longitudinal direction. Therefore, the surface roughness Ra of the stretching roller is preferably 0.005 μm. It is 1.0 μm or less, more preferably 0.1 μm or more and 0.6 μm or less. If Ra is larger than 1.0 μm, the protrusions and depressions on the surface of the roller are easily transferred to the film surface during stretching. On the other hand, if it is smaller than 0.005 μm, the roller is adhered to the film surface, and the film is easily damaged by heat. In order to control the surface roughness, it is effective to appropriately adjust the particle size and the number of times of polishing.

In successive stretching, it is a better stretching condition to set the longitudinal stretching magnification to be lower than the lateral stretching magnification on the premise that the thickness in the long side direction is not uniform.

Next, the unstretched film is transported to the stretching zone while maintaining a temperature lower than the glass transition point, and the heating rollers in the preheating zone are preferably heated with hard chromium or tungsten carbide when stretched in one breath. A metal roller having a surface roughness Ra of 0.2 μm or more and 0.6 μm or less for surface treatment is used to suppress adhesion due to thermal wrinkles or uneven thickness in the longitudinal direction.

Next, the uniaxially stretched film extended in the long direction is heated to 90 ° C or higher and lower than 120 ° C by a transverse stretcher, and then stretched 3 or more times and 6 times or less in the wide direction as a biaxially stretched (biaxially oriented) )film. The horizontal stretching machine is self-circulating in each room of the oven, and blows warm air to the film, so that the film is heated, and the film is stretched and thermally fixed. At this time, in order to prevent oligomers precipitated from the thin film heat-treated in the oven from adhering to the cooled oven, air supply and exhaust may be performed in the oven to replace the air. At this time, when the air supplied to the oven and the circulating air flow converge, if the temperature of the air is close to the outdoor air, the temperature of the converged air will be uneven, and the thickness unevenness in the longitudinal direction and the width direction will be worsened. Therefore, it is preferable that the air supply flow is the same as the circulating air flow, or is heated at a temperature that matches the capacity of the heat exchanger that heats the circulating air flow.

In addition, on the premise of adjusting the air supply and exhaust volume in the oven, the direction of the air flowing up and down the conveyed film is preferably the same direction with respect to the moving direction of the film. In the chambers of the oven, the self-circulating air, the accompanying airflow flowing from the upstream to the same direction as the film conveying direction, and the supply or exhaust of air outside the oven will cause complicated changes in the air flow inside the STN. . At this time, the flow of air between the rooms, for example, the flow from upstream to downstream, will become the flow from downstream to upstream due to the pressure difference between the rooms. When the temperature of the air varies from room to room, the flow of air between the rooms is also related to the uneven stretching of the film. Therefore, as for the conditions of the intake air volume and exhaust air volume of the oven, the air volume can be induced to flow in the same direction by increasing the exhaust air volume over the air supply volume.

The biaxially-oriented polyester film of the present invention may be further re-stretched more than once in each direction, or may be simultaneously bi-axially re-stretched. As a method of suppressing the thickness unevenness in the long-side direction, a re-extension step in the long-side direction can be used to reduce the bowing caused by the previous horizontal extension step. At this time, the conveying rollers before the longitudinal extension in the longitudinal direction can be heated again at a temperature of 80 ° C to 100 ° C, or can be conveyed using unheated rollers. In addition, the longitudinal stretching step may be repeated without applying an stretching magnification. After the longitudinal stretching is performed again, the transverse stretching is further performed, and the film is subjected to a heat treatment after the stretching. The heat treatment may be performed in any conventionally known method and position such as in an oven or on a heated roll. The heat treatment temperature can be generally set to any temperature from 150 ° C. to 245 ° C., and the heat treatment time is usually preferably from 1 second to 60 seconds. The film may be subjected to heat treatment while relaxing the film in its longitudinal direction and / or width direction. In addition, after the heat treatment, the temperature can be relaxed from 0% to 10% in a wide direction at a temperature lower than the heat treatment temperature of 0 ° C to 150 ° C.

The heat-treated film may be provided with, for example, an intermediate cooling zone and a cooling zone, and the dimensional change rate or planarity may be adjusted. Moreover, especially in order to provide specific heat shrinkability, relaxation may be performed in the longitudinal direction and / or the lateral direction in the intermediate cooling zone and the decooling zone during or after the heat treatment. At this time, on the premise that the thickness unevenness in the width direction is made good, the temperature difference in the width direction inside the oven is preferably controlled within 5 ° C.

After the biaxially stretched film is cooled in the conveying step, the edge is cut and then wound up to obtain an intermediate product. In this conveying step, the thickness of the film in the wide direction can be measured, and this data can be used for feedback to adjust the thickness of the mold, etc., thereby adjusting the thickness of the film, and the defect detector can be used for foreign object detection. The thickness can be measured by β-ray, X-ray, or light interference. The measurement may be: a method in which one measuring device travels laterally in a wide direction and the entire thickness is measured; or a method in which a plurality of measuring devices travel laterally in an interval divided in the wide direction to measure the entire wide thickness; When the measurement range is wide, a plurality of measurement devices are fixed in a wide direction, and the entire thickness is measured. The timing of the measurement may be measured in the above-mentioned conveying step or performed offline using a biaxially oriented polyester film roll obtained by slitting an intermediate product.

The intermediate product is cut into a suitable width and length through a slitting step, and wound up to the core to obtain a biaxially oriented polyester film roll. The core is a cylindrical roll core made of plastic or paper. For uneven thickness, it is also preferable to use a core with less expansion and contraction due to temperature and humidity and less deformation due to coiling pressure, so it is preferable to use a plastic one. It is more preferable to use a glass fiber or carbon fiber reinforced plastic core. When paper is used as the core, the surface can be impregnated with a resin to increase the strength. The cutting step of the film in the slitting step is a step for removing unnecessary portions of the intermediate product to obtain a polyester film roll having a desired product width. In this cutting step, for the wide direction of the intermediate product, 3 to 10 positions are cut simultaneously. The method used for this cutting can be selected from the following methods: cutting method by cutting the following blades and upper blades, or cutting method by cutting in the air between passing routes.

The film width refers to the width of the film cut by the slitting step. By adjusting the cutting position in the foregoing cutting step in the wide direction, a polyester film roll having a desired product width can be obtained. The length in the longitudinal direction of the film in the present invention is measured by a length measuring device provided on an optional roll in the slitting step. As described above, the intermediate product is cut in a wide direction and wound up to a core at an arbitrary length, and is referred to as a polyester film roll in the present invention.

The biaxially oriented polyester film roll obtained by the above method is obtained by rolling up a film having a small thickness variation in the longitudinal direction. Therefore, the film can be suitably used as a mold release application, especially as a laminated ceramic. Capacitor molding members are even used as automotive multilayer ceramic capacitor molding members. In addition, the mold release application in the present invention refers to using a film obtained from the biaxially oriented polyester film roll of the present invention as a molding member and using it as a base material, molding the member, and peeling the member after molding. Of its purpose. The components mentioned here include green sheets in multilayer ceramic capacitors, interlayer insulating resins (electrical insulating resins) in multilayer circuit boards, and polycarbonates in optical-related components (in this case, used in solution filming) )Wait.

    [Example]    

Hereinafter, the present invention will be described in detail using examples.

The measurement method and evaluation method of the present invention are as follows.

(1) Uneven film thickness in the longitudinal direction (σ _MD )

Using a SI-T80 manufactured by Keynes Corporation installed in a rewind inspection machine, the thickness in the longitudinal direction of 10,000 m was measured at the center in the width direction of the product. The rewinding speed was 50 m / minute and the sampling period was 20 milliseconds. Based on the thickness data, the deviation σ from the average value was determined, and this was taken as the film thickness unevenness in the longitudinal direction.

(2) Roughness of film surface centerline roughness (SRa value)

The measurement was performed using a three-dimensional fine surface shape measuring device (ET-350K manufactured by Kosaka Manufacturing Co., Ltd.), and an arithmetic average roughness (centerline thickness) SRa value was obtained from the obtained surface profile curve in accordance with JIS · B0601 (1994). The measurement conditions are as follows.

Measuring length in X direction: 0.5mm

X direction feed rate: 0.1mm / s

Y-direction feed pitch: 5μm

Number of Y-direction lines: 40

Cutoff: 0.25mm

Stylus pressure: 0.02mN

Height (Z direction) magnification: 50,000 times

The X direction is measured in the width direction of the sample, and the Y direction is measured in the length direction of the sample.

(3) Melt specific resistance of polyester resin

150 g of the polyester resin was put into a 50φ test tube replaced with pure water, and dried under reduced pressure at 180 ° C for 3 hours. Thereafter, melting was performed at 290 ° C. under a nitrogen gas flow of 50 minutes, and an electrode was inserted into the molten polymer. From the amount of current when a voltage of 5,000 V was applied across the electrodes, the resistance value was calculated, thereby obtaining the specific melting resistance. In addition, a Teflon (registered trademark) spacer was sandwiched between two copper plates ( ²² cm ² ) so that the copper plates became 9 mm between each other and electrodes were formed.

(Example 1)

(1) Preparation of polyester pellets

(Production of polyester A)

86.5 parts by mass of terephthalic acid and 37.1 parts by mass of ethylene glycol were subjected to an esterification reaction while distilling off water at 255 ° C. After the completion of the esterification reaction, 0.02 parts by mass of trimethylphosphoric acid, 0.06 parts by mass of magnesium acetate, 0.01 parts by mass of lithium acetate, and 0.0085 parts by mass of antimony trioxide were added, and then heated to 290 ° C under reduced pressure, and The polycondensation reaction was performed to obtain a polyester pellet A having an intrinsic viscosity of 0.63 dl / g. As a result of measuring the melting specific resistance of the tablet, it was 7.0 × 10 ⁷ Ω · cm.

(Production of polyester B)

When the polyester is produced in the same manner as described above, after transesterification, spherical silica having a volume average particle diameter of 0.2 μm, a volume shape coefficient f = 0.51, and a Mohs hardness of 7 is added to perform a polycondensation reaction to obtain a polycondensation reaction. The ester contains 1% by mass of silica-containing master batches (polyester B).

In addition, the spherical silica used in the polyester B is a monodispersed silica particle, which is added to the mixed solution including ethanol, pure water, and while stirring a mixed solution of ethanol and ethyl silicate, and As a mixed solution of an alkaline catalyst in ammonia water, the obtained reaction solution was stirred and subjected to a hydrolysis reaction of ethyl silicate and a polycondensation reaction of the hydrolysis product, followed by stirring after the reaction.

(Made of polyester C, D)

In addition, a monomer containing 80% by mass of divinylbenzene, 15% by mass of ethyl vinylbenzene, and 5% by mass of styrene was adsorbed by a seed method, so that the volume average particle diameter obtained by this method was 0.3 μm The volume shape factor f = 0.51, the aqueous slurry of divinylbenzene / styrene copolymerized crosslinked particles (crosslinking degree 80%) with Mohs hardness 3 is included in the above essence by using a vented biaxial kneader Homogeneous polyester pellets containing no particles on the surface, master batches (polyvinylbenzene / styrene copolymer crosslinked particles containing 1% by mass of polyester with a volume average particle diameter of 0.3 μm and 0.8 μm, respectively) Ester C, polyester D).

(Made of polyester E)

In the production of polyester A, after transesterification, 10 parts by mass of calcium carbonate and 90 parts by mass of ethylene glycol were prepared by the carbonic acid gas method (volume average particle diameter, volume average particle diameter 1.1 μm, Mohs hardness 3). It was pulverized by a method to obtain a calcium carbonate / ethylene glycol dispersion slurry. The volume average particle diameter of this calcium carbonate was 1.1 μm. On the other hand, to 100 parts by mass of dimethyl terephthalate and 64 parts by mass of ethylene glycol, 0.04 parts by mass of manganese acetate and 0.03 parts by mass of antimony trioxide were added as catalysts, and then a transesterification reaction was performed. For the reaction product, 0.04 parts by mass of trimethyl phosphate as a phosphorus compound was added, and then 1 part by mass of the previously prepared slurry was further added to perform a polycondensation reaction to obtain a polyester containing 1% by mass of calcium carbonate relative to the polyester. Masterbatch (polyester E).

On the other hand, a film obtained by preparing the film of the following prescription was recovered and pelletized as the recovery raw material A. In addition, the ratios described below represent mass ratios (% by mass) to the mass of the entire film.

Polyester A: 93.4

Polyester D: 0.6

Polyester G: 6.0

(2) Blending of polyester pellets

The polyester pellets supplied to the extruder of each of the A, B, and C layers were blended at the following ratios. In addition, the ratio described below is a mass ratio (unit: mass%) with respect to the polyester pellet which comprises each layer.

A layer

Polyester A: 87.5

Polyester B: 12.5

B layer

Polyester A: 60.0

Recovered raw material A: 40.0

C layer

Polyester A: 65.0

Polyester C: 30.0

Polyester D: 5.0

(3) Manufacturing of biaxially oriented polyester film

After mixing the aforementioned raw materials prepared for each layer in the blender, the raw materials of the A and C layers are supplied to the A and C layers of the twin shaft with exhaust ports. The extruder was dried under reduced pressure at 160 ° C. for 8 hours, and was supplied to a uniaxial extruder for the B layer. In addition, layer B is melt-extruded by a tandem extruder at 275 ° C, and is filtered by a filter that can capture more than 95% of high-precision filters using foreign matter of 3 μm or more. The device performs confluence layering to form three layered layers including layer A, layer B, and layer C. Thereafter, an electrostatically-applied casting method in which static electricity was applied to the entire width of the unstretched film through a slit die maintained at 285 ° C was wound and solidified by being wound around a casting drum having a surface temperature of 30 ° C to obtain an unstretched laminated film. At this time, the mold system was adjusted for alignment, and the displacement was 25 μm.

This unstretched laminated film was sequentially stretched (long-side direction, wide direction). First, the film was stretched in the longitudinal direction. After being conveyed at 105 ° C, it was stretched 3.8 times in the longitudinal direction at 120 ° C to become a uniaxially stretched film.

This uniaxially stretched film was stretched 4.0 times at 115 ° C in a transverse direction in a tenter, and then heat-fixed at 230 ° C. At this time, it was relaxed by 5% in a wide direction, cooled in a conveying step, and then cut After the edge was wound, an intermediate product of a biaxially stretched film having a thickness of 31 μm was obtained. The oven of the tenter is to adjust the air supply and exhaust from outside the oven to make the air flow in a certain direction. This intermediate product was slit with a slitter to obtain a roll of a biaxially stretched film having a thickness of 31 μm. As a result of measuring the laminated thickness of this biaxially stretched film, it was A layer: 6.5 μm, B layer: 23.5 μm, and C layer: 1.0 μm. Data were collected from the obtained products, and the results of the characteristic evaluation are shown in Table 1.

(4) Coating of release layer

Next, a crosslinked primer layer (Dow Corning Toray (trade name: BY24-846)) was applied to the roll of the biaxially stretched film to adjust the coating liquid with a solid content of 1% by mass and dried to apply the dried coating. Coating was performed with a gravure coater so that the thickness became 0.1 μm, and drying and curing were performed at 100 ° C. for 20 seconds. Thereafter, within 1 hour, 100 parts by mass of the addition reaction type silicone resin (trade name LTC750A manufactured by Dow Corning Toray Co., Ltd.) and 2 parts by mass of platinum catalyst (trade name SRX212 manufactured by Dow Corning Toray Co., Ltd.) The coating liquid was adjusted to a solid content of 5% by mass, and the coating was applied by gravure coating so that the coating thickness after drying became 0.1 μm. After drying and curing at 120 ° C. for 30 seconds, the coating was taken up to obtain a release film.

(5) Form coating of green sheet

100 parts by mass of barium titanate (brand name HPBT-1 manufactured by Fuji Titanium Industry), 10 parts by mass of polyvinyl butyral (brand name BL-1 manufactured by Sekisui Chemical Co., Ltd.) 5 parts by mass of butyl ester and 60 parts by mass of toluene-ethanol (mass ratio 30:30), glass beads with a number average particle diameter of 2 mm were added, mixed and dispersed in a jet mill for 20 hours, and then filtered to prepare a paste-like ceramic Slurry. The obtained ceramic slurry was applied and dried on a release film with a die coater so that the thickness after drying was 0.5 μm, and the thickness of the dried slurry was continuously measured in a non-contact manner at the center of the coating. Then, it is wound up to obtain a green sheet. At this time, the value σ of the thickness unevenness of the slurry was evaluated as good, less than 0.13, good, 0.13 or more and less than 0.15 as acceptable, and more than 0.15 as bad. The thickness of the slurry in the embodiment of Example 1 was not all good, and the moldability of the green sheet was good. In this case, good is a grade that is practically free of problems.

(Examples 2 to 4)

Except that the film forming conditions for changing the stretching magnification and thickness were implemented in the same manner as in Example 1, the results obtained are shown in Table 1.

(Example 5)

In response to the increase in the pressure of the polymer filter, the speed control of the gear pump is reduced, and the central value of the thickness is corrected. Except that the film forming conditions for changing the stretching ratio and thickness were changed in the same manner as in Example 1, the results obtained are shown in Table 1.

(Example 6)

An edge pinning device is applied to a mold sheet. The pinning is performed by applying static electricity in a range of 5 mm inside to 50 mm inside of the unstretched sheet. Film formation conditions were performed under the same conditions as in Example 1. The obtained results are shown in the table.

(Comparative Examples 1, 2)

Except that the film forming conditions for changing the stretching ratio and thickness were changed in the same manner as in Example 1, the results obtained are shown in Table 2. The uneven thickness of the slurry was worse than that of Examples 1 to 4, and the evaluation was acceptable.

(Comparative example 3)

Except that the longitudinal stretching magnification and the lateral stretching magnification were changed to 4.5 times and 4.5 times, respectively, the same procedure was performed as in Example 1. Although the purpose is to flatten the unevenness that occurred before the step by setting it to a high magnification, the result is that σ _MD deteriorates. σ _MD , a frequency analysis of uneven thickness was performed, and as a result, it was confirmed that it appears to be a period of uneven extension due to longitudinal extension.

(Comparative Example 4)

The flow path of the cooling water deteriorates, and as a result, the displacement of the mold becomes 50 μm. Except that this casting mold was used to change the film formation conditions of the stretching ratio and thickness, it was carried out in the same manner as in Example 1, and the results obtained are shown in Table 2. The evaluation of the uneven thickness of the slurry was defective.

(Comparative example 5)

As a raw material contained in the layer A, a melt specific resistance of 5.0 × 10 ⁸ was used. Observation of the flakes after casting with the reflected light revealed that there was unevenness in the horizontal section. When measuring the film thickness unevenness σ _MD in the longitudinal direction, it is seen that the waveform of the original data has a periodic thickness unevenness. Since the thickness is significantly uneven, silicone coating and slurry coating were not performed.

(Comparative Example 6)

In the embodiment of Comparative Example 5, an edge pinning device was applied. However, the improvement effect against the mold failure seen in Comparative Example 5 was not obtained.

(Comparative Example 7)

The oligomers in the oven are removed by increasing the number of air exchanges in the heat-fixed zone, so the air is sucked and exhausted in each room of the heat-fixed zone, but other film-forming conditions are the same as in Example 1. As a result, the cycle was indefinite, but a state in which the uneven thickness of the film was deteriorated was observed. The thickness of the slurry is not acceptable.

Industrial availability

The biaxially oriented polyester film of the present invention is excellent in planar characteristics over the entire longitudinal direction, and therefore can be suitably used for mold release applications. In particular, it can counteract the tension during processing, and the in-plane expansion and contraction behavior is uniformized. Therefore, it can be particularly suitably used for demolding the use of a green sheet in a multilayer ceramic capacitor as a component.

Claims (6)

A biaxially oriented polyester film roll for demolding, characterized in that the film width is 400 mm or more, and the deviation σ value (σ _MD ) from the average value of the thickness obtained by continuously measuring the length 10,000 m of the film in the longitudinal direction is 0.15 μm. the following.     For example, the biaxially oriented polyester film roll for demolding in claim 1, wherein the center line thickness SRa (A) of one of the film surfaces of the biaxially oriented polyester film for demolding is 1 nm or more and less than 15 nm, and the other The center line thickness SRa (B) of the film surface is 20 nm or more and 40 nm or less.         For example, the biaxially oriented polyester film roll for demolding according to claim 1 or 2, wherein the biaxially oriented polyester film for demolding has a layer structure of three or more layers.     For example, the biaxially oriented polyester film roll for release of item 2 or 3, wherein the layer (layer A) constituting the film surface of the SRa (A) of 1 nm or more and less than 15 nm contains a melting specific resistance of 1.0 × 10 ⁶ Ω Polyester resin of ‧cm or more and 1.0 × 10 ⁸ Ω‧cm or less     The biaxially oriented polyester film roll for demolding according to any one of claims 1 to 4, wherein the biaxially oriented polyester film for demolding is used as a member for forming a laminated ceramic capacitor.         The biaxially oriented polyester film roll for demolding according to claim 5, wherein the biaxially oriented polyester film for demolding is used as a member for molding a laminated ceramic capacitor for an automobile.