JP2021050297A - Polyester film roll - Google Patents

Abstract

To provide a polyester film roll that is small in variations of a peel-off characteristic and preferable in lamination accuracy when used in a molding base material for a laminate ceramic capacitor.SOLUTION: A polyester film roll consists of winding up a polyester film for use in mold-release applications. The film of the polyester film roll has a film width of 400 mm or greater and a film length of 1000 m or greater, in which hardness H is controlled at seven points dividing a linear line connecting one end in a width direction of the film roll and the other end together at the shortest into eight equal parts.SELECTED DRAWING: None

Description

The present invention relates to a polyester film roll obtained by winding a polyester film used for mold release.

Polyester films are used in various applications as industrial materials from the viewpoints of mechanical properties, thermal properties, stiffness and cost, and recently, they are widely used in various mold release applications. For example, as a release film for a process related to an electronic member, a green sheet of a multilayer ceramic capacitor is used as a base material for molding, a separator for a liquid crystal polarizing plate, a base material for a dry film resist, and the like.

With the recent sophistication of smartphone functions and the spread of smart watches and wearable devices, the size and capacity of multilayer ceramic capacitors are becoming smaller and higher. Regarding the release film used for manufacturing multilayer ceramic capacitors, the demand for polyester film with high smoothness, no defects on the film surface and inside, and excellent flatness of the film continues to grow as the green sheet becomes thinner. There is. On the other hand, the demand for multilayer ceramic capacitors installed in automobiles is rapidly expanding due to the introduction of IoT (Internet Of Things) in automobiles and the installation of automatic driving functions. These monolithic ceramic capacitors for automobiles are required to be more rigorous and reliable than conventional requirements. In particular, in the molding of a green sheet, which is a dielectric component of a multilayer ceramic capacitor, there are more stringent requirements for slurry defects caused by the film and non-uniformity of thickness.

As shown in Patent Document 1, the film thickness unevenness is determined by performing a measurement of 15 m in the longitudinal direction and determining by measuring a length of 1 m every 5 mm, which is known as a known method. There is. Further, as shown in Patent Document 2, in the cross-nicol method for inspecting a polarizing plate, the unevenness of the intensity of light leaking from the polarizing plate becomes strong, which hinders the inspection. Therefore, it is necessary to set the thickness unevenness within a predetermined range. .. As shown in Patent Document 3, it is known to achieve this by carrying out simultaneous biaxial stretching and increasing the plane orientation.

Japanese Unexamined Patent Publication No. 2008-2466885 JP-A-2017-007175 Japanese Unexamined Patent Publication No. 2004-291240

In recent years, the demand for capacitors has tended to be high in reliability in addition to miniaturization and large capacity. Miniaturization is achieved by reducing the size of the electrodes. The increase in capacity is achieved by thinning the green sheet, and the increase in reliability is achieved by improving the dimensional accuracy in the width, length, and thickness directions when the electrodes and the green sheet are provided. Among these, the uniformity of the coating thickness at the time of slurry coating is to minimize the distortion and deviation of the electrode pattern because each electrode area is fine in the step of performing electrode printing later. However, it is cited as one of the major factors that determine the variation in the dielectric constant of the capacitor, that is, the variation in the capacitance of the capacitor. For this reason, the demand for the film regarding the minimization of the thickness unevenness is becoming stricter. In particular, in the process of constantly monitoring the thickness of the slurry at the time of manufacturing the capacitor and applying the thin film of the slurry while correcting the inclination of the die, it is highly possible that the uneven thickness of the base film in the entire length of the roll contributes. It is known.

As a result of diligent studies by the present inventors, even if the thickness unevenness of the polyester film is suppressed at the stage of manufacturing the polyester film, the release layer is found from the roll-shaped pattern when the polyester film is wound into a roll. It was found that transfer defects such as those seen in film transfer fluttering and meandering during coating occur. Further, if the release layer is applied in a state where the transfer failure occurs, the application accuracy of the release layer deteriorates.

The present invention aims to solve such a problem, and is a polyester film roll obtained by winding a polyester film having a film width of 400 mm or more and a film length of 1000 m or more. It is an object of the present invention to provide a polyester film roll capable of improving the coating accuracy of the release layer when the release layer is applied to the polyester film unwound from the polyester film roll.

The film of the present invention has the following configuration in order to solve the above problems. That is,
(I) A polyester film roll obtained by winding a polyester film used for mold release, wherein the polyester film has a film width of 400 mm or more and a film length of 1000 m or more in the width direction of the polyester film roll. The hardness H is measured at 7 points that divide the line connecting one end and the other end into eight equal parts, and the hardness is measured from one end side to H1, H2, H3, H4, H5. , H6, and H7, _{H high} most things a high hardness of the hardness H1 to H7, the most things low hardness _H low, when the average of H1~7 was _{H ave,} the following (1), (2 ) A polyester film roll that meets the formula.
(H1 + H2 + H6 + H7) / 4- (H3 + H4 + H5) / 3 <0 ... (1)
4.0 x 10 ^-2 > ( _High- H _low ) / H _ave > 2.0 x 10 ^-3 ... (2)
[II] The circumference of the roll is measured at seven points that divide the line segment connecting one end and the other end in the width direction of the polyester film roll into eight equal parts, and from one end side. The circumference is L1, L2, L3, L4, L5, L6, L7, the circumference length L1 to L7 with the longest circumference is L _high , and the circumference with the shortest circumference is L. _low, when the average of L1~7 was _{L ave,} polyester film roll according to (3) below satisfies equation (4) [I].
(L1 + L2 + L6 + L7) / 4- (L3 + L4 + L5) / 3 <0 ... (3)
3.0 x 10 ^-3 > (L _high- L _low ) / _Love > 3.0 x 10 ^-5 ... (4)
[III] The center line roughness SRa (A) of one film surface of the polyester film is 1 nm or more and less than 15 nm, and the center line roughness SRa (B) of the other film surface is 20 nm or more and 40 nm or less. The polyester film roll according to [I] or [II].
[IV] The polyester film roll according to any one of [I] to [III], wherein the polyester film has a layer structure of three or more layers.
[V] The polyester film roll according to any one of [I] to [IV], wherein the thickness of the polyester film exceeds 10 μm and is 500 μm or less.
[VI] The polyester film roll according to any one of [I] to [V], which is used as a base material for molding a multilayer ceramic capacitor.
[VII] The polyester film roll according to any one of [I] to [V], which is used as a base material for molding a multilayer ceramic capacitor for automobiles.

According to the present invention, the polyester film roll is formed by winding a polyester film having a film width of 400 mm or more and a film length of 1000 m or more, and is separated from the polyester film unwound from the polyester film roll. It is possible to provide a polyester film roll capable of improving the coating accuracy when coating the mold layer.

Hereinafter, the present invention will be described in more detail.

The present invention relates to a polyester film roll obtained by winding a polyester film used for mold release. The polyester film wound on the roll of the present invention is preferably biaxially oriented. Here, the biaxial orientation refers to a state in which an unstretched (unaligned) film is stretched in a two-dimensional direction by a conventional method, and means a film showing a biaxial orientation pattern by wide-angle X-ray diffraction. As the stretching, either a sequential biaxial stretching method or a simultaneous biaxial stretching method can be adopted. In the sequential biaxial stretching, the steps of stretching in the longitudinal direction (vertical) and the width direction (horizontal) can be carried out once in the vertical-horizontal direction, or twice in the vertical-horizontal-vertical-horizontal manner. You can also do it.

The polyester in the polyester film of the present invention is a polyester containing dibasic acid and glycol as constituent components, and examples of the aromatic dibasic acid include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, and diphenylsulfonedicarboxylic acid. Diphenyl ether dicarboxylic acid, diphenyl ketone dicarboxylic acid, phenylindane dicarboxylic acid, sodium sulfoisophthalic acid, dibromoterephthalic acid and the like can be used. As the alicyclic dibasic acid, oxalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dimer acid and the like can be used. As the glycol, ethylene glycol, propylene glycol, tetramethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, diethylene glycol and the like can be used as the aliphatic diol, and naphthalene diol can be used as the aromatic diol. 2,2 bis (4-hydroxydiphenyl) propane, 2,2-bis (4-hydroxyethoxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, hydroquinone and the like can be used, and as the alicyclic diol, Cyclohexanedimethanol, cyclohexanediol and the like can be used.

The polyester can be produced by a known method, and it is preferable to use one having an intrinsic viscosity of 0.5 at the lower limit and 0.8 at the upper limit. More preferably, the lower limit is 0.55 and the upper limit is 0.70. For the measurement of the intrinsic viscosity, the value calculated by the following formula from the solution viscosity measured at 25 ° C. in orthochlorophenol is used.

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 Huggins constant (0.343). is there. The solution viscosity and solvent viscosity are measured using an Ostwald viscometer. The unit is indicated by [dl / g].

The polyester film of the present invention may be a single-layer film or may have a laminated structure of two or more layers. When two layers are laminated, it is composed of a polyester A layer and a polyester B layer, and in the case of three layers, it is composed of three layers of polyester A layer, polyester B layer and polyester C layer, or polyester A layer, polyester B layer and polyester A layer. It becomes a laminated film. When the structure is three or more layers, the recovery raw material of the edge portion generated in the film forming process or the recycling of other film forming processes is performed as long as the layer (inner layer) having no surface layer does not adversely affect the characteristics of the film surface. It is preferable because raw materials and the like can be mixed and used in a timely manner, the consumption of petroleum resources can be reduced, and cost benefits can be obtained.

The polyester film of the present invention preferably has different roughness between one film surface and the other film surface in order to achieve both surface smoothness and handleability such as transport and winding. That is, it is preferable that the center line roughness SRa (A) of one film surface is 1 nm or more and less than 15 nm, and the center line roughness SRa (B) of the other film surface is 20 nm or more and 40 nm or less. If SRa (A) on the surface of one of the films is less than 1 nm, it may be difficult to peel off in the peeling step after laminating a release layer on the surface and laminating a ceramic slurry on the surface. Further, when SRa (A) is 15 nm or more, the surface condition of the slurry is deteriorated and the thickness is uneven, and as a result, the characteristics of the capacitor may be easily varied. Further, when SRa (B) on the surface of the other film is less than 20 nm, blocking is likely to occur in winding after coating the release layer or winding after coating the ceramic slurry, and charging occurs when the film is unwound. May occur. More preferably, the center line roughness SRa (A) of one film surface is 2 nm or more and less than 12 nm, and the center line roughness SRa (B) of the other film surface is 25 nm or more and 35 nm or less.

The thickness of the polyester film of the present invention is preferably more than 10 μm, more preferably 20 μm or more, still more preferably 25 μm or more. Further, it is preferably 500 μm or less, more preferably 188 μm or less, and further preferably 50 μm or less. If the thickness is too thin, there will be no waist to hold the ceramic slurry, the ceramic slurry cannot be supported when applied, it will not be possible to dry uniformly in the subsequent process, and heat wrinkles will not be suppressed sufficiently. May become. If the thickness is too thick, the durability against heat wrinkles is remarkably excellent, but the unit price per unit area as a base material for forming the ceramic slurry tends to increase as the winding length decreases.

The 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 size of the particles is too large, there is a high chance that voids, that is, voids will be generated at the interface between the particles and the polymer during stretching, so that the surface structure may have irregularities, and the thickness of the slurry may vary. It may be large. This is especially noticeable when forming an ultra-thin green sheet. The ultra-thin green sheet in the present invention refers to a green sheet having a thickness of less than 1 μm. The polyester film of the present invention can suppress variations in slurry thickness even when forming an ultra-thin green sheet.

The particles used in the present invention are inorganic particles such as spherical silica, aggregated silica, calcium carbonate, aluminum oxide, barium titanate, titanium oxide, crosslinked polystyrene resin particles, crosslinked silicone resin particles, crosslinked acrylic resin particles, and crosslinked styrene-acrylic resin. Organic particles such as particles, crosslinked polyester particles, polystyrene particles, and melamine resin particles can be used. In addition to the role of forming protrusions on the film surface, these particles can also serve as a core material for forming voids, so it is desirable to select the type as well as the particle size. It is preferable to use organic particles having high elasticity of the particles. As the organic particles, among the above-mentioned organic particles, organic particles selected from crosslinked polystyrene resin particles, crosslinked silicone resin particles, crosslinked acrylic resin particles, crosslinked styrene-acrylic resin particles, and crosslinked polyester particles are particularly preferable. Among the inorganic particles, spherical silica and aluminum oxide are particularly preferable.

The particle shape and particle size distribution are preferably uniform, and the particle shape is particularly preferably spherical. The volume shape coefficient is preferably f = 0.3 to π / 6, and more preferably f = 0.4 to π / 6. The volume shape coefficient f is expressed by the following equation.

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

The volume shape coefficient f takes the maximum value of π / 6 (= 0.52) when the particle is a sphere. In addition, it is preferable to remove aggregated particles, coarse particles, and the like by performing filtration or the like as necessary. Among them, crosslinked polystyrene resin particles, crosslinked silicone resin particles, and crosslinked acrylic resin particles synthesized by an emulsion polymerization method or the like can be preferably used, but in particular, crosslinked polystyrene particles, crosslinked silicone, spherical silica, etc. have a volume shape coefficient. It is preferable from the viewpoint that it is close to a true sphere, the particle size distribution is extremely uniform, and the film surface protrusions are uniformly formed.

The polyester film roll of the present invention is formed by winding a polyester film having a film width of 400 mm or more and a film length of 1000 m or more. With respect to the polyester film unwound from the polyester film roll, the variation (σ _MD ) with respect to the average value of the thickness measured continuously in the longitudinal direction of the film is preferably 0.25 or less, and more preferably 0.20 or less. It is preferably 0.15 or less, and more preferably 0.15 or less. The thickness continuously measured at 1000 m in the longitudinal direction of the film here is the thickness when the film is continuously measured in a non-contact manner. Further, in the following, σ _MD may be referred to as film thickness unevenness in the longitudinal direction. By reducing σ _MD , it is possible to reduce the uneven thickness of the slurry when the thin film ceramic slurry is applied, reduce the variation in capacitance, and suppress the probability of short circuit. If the σ _MD is large, the thickness unevenness of the slurry may be large in the coating of the thin film ceramic slurry, and the above-mentioned effect may be reduced.

Further, as a result of diligent studies by the present inventors, even if the film thickness unevenness in the longitudinal direction is suppressed in the polyester film after the polyester film is melt-formed and before being wound on the film roll, the polyester film is wound into a roll shape. From the roll-shaped pattern at the time, it was found that transfer defects such as film transfer fluttering and meandering when the release layer was applied occurred, and the coating accuracy of the release layer deteriorated.

In order to solve such a problem, the polyester film roll of the present invention has a hardness H at seven points that divide the line segment connecting one end and the other end in the width direction of the polyester film roll into eight equal parts. Measured and set the hardness from one end side to H1, H2, H3, H4, H5, H6, H7, and the hardest of the hardnesses H1 to H7 is _High , and the hardness is the lowest. when H _low, an average of H1~7 was _{H ave,} the following (1), it is necessary to satisfy the expression (2).
(H1 + H2 + H6 + H7) / 4- (H3 + H4 + H5) / 3 <0 ... (1)
4.0 x 10 ^-2 > ( _High- H _low ) / H _ave > 2.0 x 10 ^-3 ... (2)
By winding the polyester film so that the hardness of the polyester film roll satisfies the equations (1) and (2), it is possible to suppress the occurrence of transfer defects such as film transfer fluttering and meandering when the release layer is applied to the polyester film. Therefore, the coating accuracy of the release layer can be improved. More preferably, (1)'and (2)' are satisfied.
-0.1> (H1 + H2 + H6 + H7) / 4- (H3 + H4 + H5) / 3> -4.0 ... (1)'
3.0 x 10 ^-2 > ( _High- H _low ) / H _ave > 3.0 x 10 ^-3 ... (2)'
Further, in the polyester film roll of the present invention, the circumference of the roll is measured at seven points that divide the line segment connecting one end and the other end in the width direction of the polyester film roll into eight equal parts. From one end side, the circumference is L1, L2, L3, L4, L5, L6, L7, and the circumference length L1 to L7 with the longest circumference is L _high , which is the most circle. things _L low circumferential length is short, when the average of L1~7 was _{L ave,} following (3) preferably satisfies the expression (4).
(L1 + L2 + L6 + L7) / 4- (L3 + L4 + L5) / 3 <0 ... (3)
3.0 × 10 ^-3 ＞ (L _high- L _low ) / _Love ＞ 3.0 × 10 ^-5・ ・ ・ (4)
By winding the polyester film so that the circumference length of the polyester film roll satisfies the equations (3) and (4), it is possible to suppress the unwinding of the polyester film, and the surface roughness of the polyester film can be varied. It can be suppressed. More preferably, (3)'and (4)' are satisfied.
-5.0 <(L1 + L2 + L6 + L7) / 4- (L3 + L4 + L5) / 3 <0 ... (3)'
1.0 x 10 ^-3 > (L _high- L _low ) / _Love > 7.0 x 10 ^-5 ... (4)'
Further, the polyester film roll of the present invention is formed by winding a polyester film having a film width of 400 mm or more and a film length of 1000 m or more. In a polyester film roll obtained by winding a polyester film having a film width of less than 400 mm or a film length of less than 1000 m, problems due to differences in roll hardness and circumference in the film width direction are less likely to occur. On the other hand, if the film width is widened or the film length is lengthened, it can be used for mold release of large molded members, and there is a cost advantage, but the roll hardness in the film width direction And problems due to the difference in circumference length are likely to occur. In the present invention, the film width is preferably 500 mm or more and 2500 mm or less, and more preferably 700 mm or more and 2200 mm or less. The film length is preferably 1000 m or more and 30,000 m or less.

Next, the method for producing the polyester film roll of the present invention will be described, but the present invention is not construed as being limited to such an example.

When the polyester film of the present invention contains inert particles, examples of the method for incorporating the inert particles include a method for incorporating the inert particles at the stage of synthesizing the polyester raw material. Specifically, the inert particles are dispersed in ethylene glycol, which is a diol component, at a predetermined ratio in the form of a slurry, and this ethylene glycol slurry is added at an arbitrary stage before the completion of polyester polymerization. Here, when adding the particles, for example, if the water sol or alcohol sol obtained during the synthesis of the particles is added without being dried once, the dispersibility of the particles is good and the generation of coarse protrusions can be suppressed, which is preferable. Further, a method in which the aqueous slurry of particles is directly mixed with a predetermined polyester pellet and supplied to a vent type twin-screw kneading extruder and kneaded into the polyester is also effective for the production of the present invention.

In this way, the prepared particle-containing master pellet and the pellet containing substantially no particles or the like are mixed at a predetermined ratio, dried, and then supplied to a known fused deposition model extruder. As the extruder for producing the biaxially oriented polyester film of the present invention, a single-screw or twin-screw extruder can be used. Further, in order to omit the step of drying the pellets, a vent type extruder provided with a vacuum drawing line in the extruder can also be used.

The polymer melted and extruded by the extruder is filtered through a filter. If even a very small foreign matter enters the film, it becomes a coarse protrusion defect. Therefore, it is effective to use a filter having a high accuracy of collecting 95% or more of foreign matter of 3 μm or more, for example. Subsequently, it is extruded into a sheet from a slit-shaped slit die and cooled and solidified on a casting roll to form an unstretched film. For example, in the case of three-layer lamination, three extruders are used to laminate the three layers using a three-layer manifold or a merging block (for example, a merging block having a rectangular merging portion), and the sheet is extruded from the base. At this time, it is desirable that the gap between the caps can be automatically adjusted by the heater. Further, it is more desirable to be able to feed back the film thickness after stretching to the gap of the mouthpiece in order to suppress the thickness unevenness. Further, at this time, if the film thickness is made uniform in the polyester film width direction or the gap of the base is adjusted so that the central portion in the film width direction is slightly thickened, the hardness of the polyester film roll can be increased (1), (1). 2) It becomes easy to control so as to satisfy the equation. Further, the surface treatment of the base with tungsten carbide is preferable from the viewpoint of excellent scratch resistance and abrasion resistance during cleaning and maintenance of the base and suppressing streaks of the base. The base streaks have a fixed thickness at the generation position, and as a result, uneven thickness occurs. The sheet extruded from the base is cooled by a casting roll to form an unstretched film. In this case, the method of installing the static mixer and the gear pump in the polymer flow path from the viewpoint of stabilizing the back pressure and suppressing the thickness fluctuation is effective as a means for suppressing the thickness unevenness in the present invention. Since the gear pump has a function of blocking pressure fluctuations in the extrusion process, it is necessary to control the thickness uniformly, and it is possible to keep the thickness unevenness small by keeping the rotation speed of the gear built in the gear pump constant. it can. In the present invention, it is also effective to feed back and control the rotation speed of the gear pump by the weight-equivalent thickness of the wound intermediate product. This is because the discharge decreases as the filter pressure increases.

The film that has been cooled in close contact with the casting roll is peeled from the casting roll by using a pulling roll, and is led to the next stretching step. Water may be passed through the pulling roll at this time to cool the film, or the pulling roll may be driven.

The stretching method may be simultaneous biaxial stretching or sequential biaxial stretching. In the simultaneous biaxial stretching, when the vertical and horizontal stretching is performed at the same time, the wind speed unevenness and the airflow flowing along the film (accompanying airflow) are added to the stretching in the width direction and also affect the longitudinal direction as disturbance. It is a form in which stretching is preferably applied.

When the polyester film of the present invention is produced by using sequential stretching, it is preferable to stretch it in the longitudinal direction and then in the width direction. At this time, the first stretching in the longitudinal direction is important for suppressing the occurrence of scratches and the thickness unevenness in the longitudinal direction, and the stretching temperature is 90 ° C. or higher and 130 ° C. or lower, preferably 100 ° C. or higher and 120. It is below ° C. If the stretching temperature is lower than 90 ° C., the film may be easily broken, and if the stretching temperature is higher than 130 ° C., the film surface may be easily damaged by heat. From the viewpoint of preventing uneven stretching and scratches, stretching is preferably performed in two or more stages, and the total magnification is 2.8 times or more and 5.0 times or less, preferably 3.3 times in the length direction. It is 4.0 times or more, 3.5 times or more and 5 times or less in the width direction, preferably 4.0 times or more and 4.5 times or less. The area magnification (stretching ratio in the longitudinal direction × stretching ratio in the width direction) is preferably 10.0 times or more and 20.0 times or less, and more preferably 12.0 times or more and 18.0 times or less. When setting the longitudinal stretching ratio to the above-mentioned numerical value, it is desirable to set a plurality of stretching sections so that the stretching roll and the film are less likely to slip because the fluctuation of the stretching tension due to slipping can be suppressed. .. At this time, it is preferable that the stretching ratio in one stretching section is 3.0 times or less because an appropriate stretching tension can be ensured. If the temperature and magnification are out of the range, problems such as uneven stretching or film breakage occur, and it is difficult to obtain the film characterized by the present invention.

In the sequential stretching, in the stretching process in the longitudinal direction, the film and the roll come into contact with each other, and due to the difference between the peripheral speed of the roll and the speed of the film, scratches are likely to occur when the film slips, and a factor of thickness unevenness in the longitudinal direction is a factor. Therefore, a drive system in which the roll peripheral speed can be set individually for each roll is preferable. In the stretching process in the longitudinal direction, the material of the transport roll is such that the unstretched film is heated above the glass transition point before stretching or transported to the stretching zone while being kept at a temperature below the glass transition point, and all at once during stretching. It is selected by heating or either. When the unstretched film is heated to the glass transition point or higher before stretching, the adhesion due to heating induces stretching unevenness. To prevent this, select from non-adhesive silicone rolls, ceramics, and Teflon (registered trademark). It is preferable to do so.

Further, since the stretched roll is a process in which the film is most loaded and the stretched unevenness that causes scratches and thickness unevenness in the longitudinal direction is likely to occur in the process, the surface roughness Ra of the stretched roll is 0.005 μm or more. It is preferably 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 unevenness of the roll surface during stretching is likely to be transferred to the film surface, while if it is less than 0.005 μm, the roll and the film surface adhere to each other, and the film is susceptible to heat damage. In order to control the surface roughness, it is effective to appropriately adjust the particle size of the abrasive, the number of times of polishing, and the like.

In the sequential stretching, setting the longitudinal stretching ratio lower than the transverse stretching ratio is a preferable stretching condition in order to reduce the thickness unevenness in the longitudinal direction.

Next, the unstretched film was transported to the stretching zone while being kept at a temperature below the glass transition point, but when the unstretched film was heated all at once during stretching, the transport roll in the preheating zone was surface-treated with hard chrome or tungsten carbide. It is preferable to use a metal roll having a surface roughness Ra of 0.2 μm or more and 0.6 μm or less in order to suppress adhesion that causes heat wrinkles and thickness unevenness. Further, it is also preferable to adopt the nip roll method in the stretching step, and it is desirable that the variation in the roll diameter of the nip roll is within ± 0.05% in the width direction from the viewpoint of suppressing thickness unevenness in the width direction. It is also effective to check the surface pressure distribution of the nip roll and adjust the pressure balance in the width direction.

Next, the uniaxially stretched film stretched in the longitudinal direction is heated to 90 ° C. or higher and lower than 120 ° C. by a transverse stretching machine, then stretched in the width direction at 3 times or more and less than 6 times, and biaxially stretched (biaxially stretched). Orientation) Film. This transverse stretching machine performs self-circulation in each oven room and blows warm air onto the film to raise the temperature of the film and perform stretching and heat fixing. At that time, in order to prevent the oligomers precipitated from the film heat-treated in the oven from being cooled and adhering to the oven, it is preferable to perform air supply and exhaust in the oven to replace the air. At this time, when the air supplied into the oven merges with the circulating air, if the temperature of the air remains close to the outside air, temperature unevenness occurs in the merged air, and the thickness unevenness in the longitudinal direction and the width direction occurs. It is preferable to heat the supply air at the same temperature as the circulating air or at a temperature commensurate with the capacity of the heat exchanger that heats the circulating air.

Further, in adjusting the amount of air supply / exhaust in the oven, it is preferable that the directions of the air flowing above and below the film to be conveyed are the same. In each chamber of the oven, in addition to the self-circulating air, the accompanying airflow that flows from the upstream in the same direction as the film transport direction, and the air supply or exhaust outside the oven change the air flow inside the STN in a complicated manner. .. At this time, due to the pressure difference between the chambers, the air flow between the chambers, for example, the flow from the upstream to the downstream may change to the flow from the downstream to the upstream. The flow of air between chambers can also lead to uneven expansion and contraction of the film when the temperature of the air varies between chambers. Therefore, regarding the intake / exhaust conditions of the oven, it is possible to induce the flow of air in the same direction by increasing the exhaust amount more than the supply air amount. Since the film obtained by adopting such an air supply / exhaust method has uniform stretching behavior and relaxing behavior in the width direction, the thickness distribution in the width direction can be stabilized.

The polyester film of the present invention may be further re-stretched once or more in each direction, or may be re-stretched on two axes at the same time. As a method of suppressing the thickness unevenness in the longitudinal direction, it is possible to alleviate the Boeing generated in the previous transverse stretching step in the re-stretching step in the longitudinal direction. At this time, the transport roll before re-longitudinal stretching in the longitudinal direction may be heated at a temperature of 80 ° C. to 100 ° C., or the unheated roll may be used for transport. Further, the re-longitudinal stretching step may be passed without applying the stretching ratio. After the re-longitudinal stretching, the transverse stretching is further carried out, and the heat treatment of the film is carried out after the stretching. This heat treatment can be carried out by any conventionally known method such as in an oven or on a heated roll. The heat treatment temperature can usually be any temperature of 150 ° C. or higher and lower than 245 ° C., and the heat treatment time is usually preferably 1 second or longer and 60 seconds or shorter. The heat treatment may be performed while relaxing the film in the longitudinal direction and / or the width direction thereof. Further, after the heat treatment, it is preferable to relax at a temperature lower than the heat treatment temperature of 0 ° C. or higher and 150 ° C. or lower and 0% or higher and 10% or lower in the width direction.

The film after the heat treatment can be provided with, for example, an intermediate cooling zone and a decooling zone, and the dimensional change rate and flatness can be adjusted. In particular, in order to impart specific heat shrinkage, it may be relaxed in the vertical direction and / or in the horizontal direction in the intermediate cooling zone or the cooling zone during or after the heat treatment. In this case, it is desirable to control the temperature difference in the width direction inside the oven within 5 ° C. in order to improve the thickness unevenness in the width direction.

The film after biaxial stretching is cooled in a transport process, cut at the edges, slit to an appropriate width and length by a slit process, and wound around a core to obtain a roll of biaxially oriented polyester film. ..

There are two methods for winding around the core: center wind method (winding by rotating shaft drive arranged at the center of winding) and surface wind method (winding by surface drive or in combination with surface drive). Either method may be selected in order to obtain the roll of the present invention.

The polyester film roll of the present invention is a polyester film having a thickness unevenness in the width direction suppressed by the above manufacturing conditions, having a winding tension of 4 to 20 kg / m, a winding contact pressure of 5 to 45 kg / m, and a winding speed of 150 to. It is preferable to wind the film under winding conditions of 450 m / min. By winding the polyester film roll under such winding conditions, it is possible to suppress the occurrence of local winding tightness and winding when the film length is wound to 1000 m or more. Therefore, the hardness of the polyester film roll is set to (1), (1). It becomes easy to control so as to satisfy the equations 2), and it becomes easy to control the circumference length of the polyester film roll so as to satisfy the equations (3) and (4). More preferably, the take-up tension is 6 to 15 kg / m, the take-up contact pressure is 10 to 35 kg / m, and the take-up speed is 200 to 350 m / min.

Further, among the plurality of slitter transport rolls used for transporting the plurality of slitters used for transporting the slit step, it is preferable that more than half of the rolls are rubber rolls. More preferably, all the transport rolls in the slit process are rubber rolls. Here, the rubber roll means a roll in which at least the surface of the roll is covered with rubber (of course, a roll in which the entire roll is rubber is also included). By using such a rubber roll, it is effective to suppress meandering of the film in the slit. The type of rubber used for the rubber roll is at least one rubber selected from ditrile rubber (copolymer of acrylonitrile and butadiene), croprene rubber (polychloroprene), ethylene propylene diene rubber, and chlorosulfonated polyethylene rubber. It is preferable to have. More preferably, chloroprene rubber is used. Chloroprene rubber is preferable because it can obtain an appropriate grip force, can control the charging characteristics of the film, and can effectively perform slip treatment. Further, on the surface of the rubber roll, a groove is dug diagonally in order to eliminate air that has entered between the film and the roll during transportation (this processing is hereinafter referred to as "mesh processing", and "mesh processing". It is preferable to use a rubber roll (referred to as a "diamond cut roll"). It is preferable that the meshed groove has a width of 1 to 2 mm and a depth of 1 to 1.5 mm, and is provided in an X shape at an angle of 20 to 45 ° with respect to the roll width direction. Further, it is preferable that the rubber roll is subjected to a slip treatment by a treatment for deteriorating the rubber surface by UV (ultraviolet light) irradiation or the like. However, if the slip treatment is performed too much, the grip force of the roll is lowered, and the peripheral speed difference between the roll and the film is likely to occur, which leads to deterioration of the transport state and the film roll appearance. Therefore, the static friction coefficient of the roll surface is deteriorated. The μs is preferably 0.5 or more and 1.0 or less. Further, it is desirable to use a contact roll as a method for removing air when winding the core. The contact roll is effective for controlling the shape pattern in the width direction, and it is preferable to use a contact roll having a width of 1.05 times to 1.25 times the film width.
In order to suppress bending when surface pressure is applied, it is also preferable to increase the wall thickness of the central portion of the inner cylinder or to use a structure in which the core metal and the inner cylinder portion are held by bearings. Further, it is preferable that the diameter of the contact roll is φ40 mm to φ200 mm from the viewpoint of air exclusion.
The rigidity of the contact roll ^{is preferably 20} tf / mm 2 or more.
Further, the core used for winding the polyester film includes a cylindrical winding core made of plastic. It is preferable to use a core that has less expansion and contraction due to humidity and less deformation due to winding pressure because it can suppress the occurrence of local winding tightening and unwinding when the film length is wound to 1000 m or more. The elastic modulus in the axial direction and the circumferential direction of the take-up core is preferably 9.8 GPa or more, more preferably 14.0 GPa or more. If a take-up core that is less than this range is used, the take-up core may be deformed due to the tension and contact pressure applied when the film is taken up. Further, it is desirable to use a core width of 1.05 to 1.25 times the film width from the viewpoint of suppressing deflection. Further, it is desirable that the diameter of the core is 6 inches or more from the viewpoint of preventing air from being mixed due to the deflection at the beginning of winding. The method for adjusting the strength of the take-up core to such a range is not particularly limited, but there is a method of reinforcing the plastic with glass fiber or carbon fiber. The film cutting step in the slitting step is a step of removing unnecessary portions of the intermediate product to obtain a polyester film roll having a desired product width. In this cutting step, 3 to 10 points are cut at the same time in the width direction of the intermediate product. The method used for this cutting can be selected from a method of cutting by shearing the lower blade and the upper blade and a method of cutting in the air between the pass lines. As the blade used for the slit, a shear blade, a round blade, a leather blade or the like is used, but from the viewpoint of controlling the edge height of the end face, it is preferable to use a round blade or a leather blade.

The film width is the width of the film after slitting by the slitting step, and by adjusting the cutting place in the cutting step described above in the width direction, a polyester film roll having a desired product width can be obtained. .. Further, the length in the longitudinal direction of the film in the present invention is measured by a length measuring device installed on an arbitrary roll in the slit process. In the present invention, an intermediate product obtained by cutting an intermediate product in the width direction and winding it around a core at an arbitrary length is referred to as a polyester film roll.

Since the polyester film roll obtained by the above method suppresses variations in the thickness of the polyester film unwound from the polyester film roll in the longitudinal direction, it can be used for mold removal, especially as a member for molding a multilayer ceramic capacitor. Further, it can be more preferably used as a molding member for a monolithic ceramic capacitor for automobiles. The release application in the present invention means that the film unwound from the polyester film roll of the present invention is used as a base material for molding, a member is molded on the polyester film, and the polyestel film base material is formed after the member is molded. Refers to the use of peeling from a member. The members referred to here include green sheets in multilayer ceramic capacitors, interlayer insulating resins (electrically insulating resins) in multilayer circuit boards, and polycarbonates in optical-related members (used in solution film formation in this case). Can be mentioned.

Hereinafter, the present invention will be described in detail with reference to Examples.

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

(1) Film thickness unevenness in the longitudinal direction (σ _MD )
Using SI-80P manufactured by KEYENCE CORPORATION installed in the rewinding inspection machine, the thickness in the longitudinal direction of the central portion in the product roll width direction was measured by 10,000 m. The rewinding speed was 50 m / min, the sampling period was 20 msec, and the deviation σ with respect to the average value was obtained based on this thickness data, and this was defined as the film thickness unevenness in the longitudinal direction.

(2) Film surface roughness Surface center line roughness (SRa value)
Measured using a three-dimensional fine surface shape measuring instrument (ET-350K manufactured by Kosaka Seisakusho), and from the obtained surface profile curve, according to JIS B0601 (1994), arithmetic mean roughness (center line roughness) SRa Find the value. The measurement conditions are as follows.
X-direction measurement length: 0.5 mm
X-direction feed rate: 0.1 mm / sec Y-direction feed pitch: 5 μm
Number of lines in the Y direction: 40 Cutoff: 0.25 mm
Needle pressure: 0.02 mN
Height (Z direction) Magnification: 50,000 times.
The X direction is the width direction of the sample, and the Y direction is the longitudinal direction of the sample.

(3) Film roll hardness H
Pressing load using Asker rubber hardness tester C type (Polymer Meter Co., Ltd.) at 7 points that divide the line connecting one end and the other end in the width direction of the polyester film roll into eight equal parts. 1 kg, the hardness H is measured, and the hardness is set to H1, H2, H3, H4, H5, H6, H7 from one end side, and the highest hardness of the hardnesses H1 to H7 is _High. most things low hardness _H low, an average of H1~7 was _{H ave.} The hardness H was measured immediately after the slit.

(4) Film roll circumference L
At seven points that divide the line segment connecting one end and the other end in the width direction of the polyester film roll into eight equal parts, a band-shaped scale (JIS class 1) with an accuracy of 0.1 mm is used to measure the roll. The circumference was measured. From one end side, the hardness is L1, L2, L3, L4, L5, L6, L7, and the one with the longest circumference among the circumference lengths L1 to L7 is L _LigL , and the circumference length is the most. short the _L low, an average of L1~7 was _{L ave.}

(Example 1)
(1) Preparation of polyester pellets (preparation of polyester A)
The esterification reaction is carried out at 255 ° C. with 86.5 parts by mass of terephthalic acid and 37.1 parts by mass of ethylene glycol while distilling water. After completion of the esterification reaction, 0.02 parts by mass of trimethylphosphate, 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 subsequently, under reduced pressure, 290 parts. The mixture was heated to ° C. and heated to a high temperature to carry out a polycondensation reaction to obtain polyester pellet A having an intrinsic viscosity of 0.63 dl / g. Results The melt specific resistance was measured in this chip was 7.0 × 10 ⁷ Ω · cm.

(Creation of polyester B)
In producing polyester in the same manner as above, after transesterification, spherical silica having a volume average particle size of 0.2 μm, a volume shape coefficient f = 0.51, and a moth hardness of 7 is added and a polycondensation reaction is carried out to obtain particles of polyester. A silica-containing master pellet containing 1% by volume was obtained (polyester B).

The spherical silica used in Polyester B is obtained by adding a mixed solution of ethanol, pure water, and aqueous ammonia as a basic catalyst to the mixed solution while stirring the mixed solution of ethanol and ethyl silicate. These are monodisperse silica particles obtained by stirring the reaction solution to carry out a hydrolysis reaction of ethyl silicate and a polycondensation reaction of the hydrolysis product, and then stirring after the reaction.

(Creation of polyesters C and D)
Separately, the volume average particle size of 0.3 μm, the volume shape coefficient f = 0.51, obtained by the method of adsorbing a monomer composed of 80% by mass of divinylbenzene, 15% by mass of ethylvinylbenzene and 5% by mass of styrene by the seed method. A water slurry of divinylbenzene / styrene copolymer crosslinked particles (crosslinking degree 80%) having a moth hardness of 3 is contained in the above-mentioned homopolypoly pellets containing substantially no particles by using a bent twin-screw kneader, and the volume is increased. Master pellets containing 1% by mass of divinylbenzene / styrene copolymer crosslinked particles having an average particle size of 0.3 μm and 0.8 μm with respect to polyester were obtained (polyester C, polyester D), respectively.

(Creation of polyester E)
In producing polyester A, after transesterification, 10 parts by mass of calcium carbonate and 90 parts by mass of ethylene glycol prepared by the carbon dioxide gas method (volume average particle size, volume average particle size 1.1 μm, moth hardness 3) were wet-pulverized. , Calcium carbonate / ethylene glycol dispersion slurry was obtained. The volume average particle size of this calcium carbonate was 1.1 μm. On the other hand, 0.04 part by mass of manganese acetate and 0.03 part by mass of antimony trioxide were added as catalysts to 100 parts by mass of dimethyl terephthalate and 64 parts by mass of ethylene glycol to carry out a transesterification reaction, and then trimethyl as a phosphorus compound was added to the reaction product. 0.04 parts by mass of phosphate was added, and then 1 part by mass of the previously prepared slurry was added to carry out a transesterification reaction to obtain a master pellet (polyester E) containing 1% by mass of calcium carbonate with respect to polyester. ..

On the other hand, the film after producing the film having the following formulation was recovered, and the pelletized film was used as the recovery raw material A. The ratio described below is expressed as a mass ratio (mass%) with respect to the mass of the entire film.
Polyester A 93.4
Polyester D: 0.6
Polyester G: 6.0.

(2) Preparation of polyester pellets The polyester pellets supplied to the extruders of the A layer, the B layer, and the C layer were prepared in the following ratios. The ratio described below is a mass ratio (unit: mass%) with respect to the polyester pellets constituting each layer.

Layer A 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) Production of Biaxially Oriented Polyester Film After stirring the raw materials prepared for each layer in the blender, the raw materials for layers A and C are the raw materials after stirring, and the raw materials for the A and C layers are vented. The raw material of the B layer was dried under reduced pressure at 160 ° C. for 8 hours, and then supplied to the single-screw extruder for the B layer. It is melt-extruded at 275 ° C., filtered through a high-precision filter that collects 95% or more of foreign matter of 3 μm or more, and then merged and laminated with a rectangular merging block for three different layers, consisting of layers A, B, and C. Three layers were laminated. Then, the sheet is extruded from the base through the base kept at 285 ° C. At this time, the film thickness was adjusted to be uniform in the product width direction. An unstretched laminated film was obtained by winding it around a casting drum having a surface temperature of 25 ° C. and cooling and solidifying it by using an electrostatic application casting method in which electrostatic application was applied to the entire width of the unstretched film. At this time, the cast adjusted the alignment, and the runout was 25 μm.

The unstretched laminated film was sequentially stretched (longitudinal direction, width direction). First, the film was stretched in the longitudinal direction, transported at 105 ° C., and then stretched 3.8 times in the longitudinal direction at 120 ° C. to obtain a uniaxially stretched film.

This uniaxially stretched film was stretched 4.0 times in the lateral direction at 115 ° C. in a stainless steel, and then heat-fixed at 230 ° C., at which time it was relaxed by 5% in the width direction and cooled in a conveying step, and then the edges were formed. After cutting and winding, the film was slit with a slitter to obtain a polyester film roll obtained by winding a biaxially oriented polyester film having a thickness of 31 μm, a film width of 1400 mm and a length in the longitudinal direction of 15,000 m. At this time, in the oven inside the stenter, the air supply and exhaust from outside the oven were adjusted so that the air flowed in a certain direction. The core for winding the film is a plastic core reinforced with glass fiber having an elastic modulus of 11.5 GPa in both the axial direction and the circumferential direction. The conditions for winding the film are a winding tension of 10 kg / m. The contact pressure was 15 kg / m and the winding speed was 250 m / min.
As a result of measuring the laminated thickness of this biaxially oriented polyester film, it was found that the A layer: 6.5 μm, the B layer: 23.5 μm, and the C layer: 1.0 μm. Data were collected from the obtained products, and the characteristics evaluation results are shown in Table 1.

(4) Application of release layer Next, a coating liquid prepared by adjusting a crosslinked primer layer (trade name BY24-846 manufactured by Toray Dow Corning Silicone Co., Ltd.) to a solid content of 1% by mass on this biaxially oriented polyester film roll. Was coated / dried, coated with a gravure coater so that the coating thickness after drying was 0.1 μm, and dried and cured at 100 ° C. for 20 seconds. Within 1 hour after that, 100 parts by mass of an addition reaction type silicone resin (trade name: LTC750A manufactured by Toray Dow Corning Silicone Co., Ltd.) and 2 parts by mass of a platinum catalyst (trade name: SRX212 manufactured by Toray Dow Corning Silicone Co., Ltd.) were applied. The coating liquid adjusted to a solid content of 5% by mass was applied with a gravure coat so that the coating thickness after drying was 0.1 μm, dried and cured at 120 ° C. for 30 seconds, and then wound to obtain a release film. At this time, if good transport is achieved without fluttering or meandering due to unwinding, ◎, if weak fluttering or meandering occurs at a level where there is no problem with application, ○, fluttering or meandering occurs, and coating spots The case where is visible is marked as x.

(Example 2)
The same procedure as in Example 1 was carried out except that the film forming conditions of the draw ratio were changed as shown in Table 1. The results obtained are shown in Table 1.

(Example 3)
The rotation speed control of the gear pump was lowered in response to the increase in the polymer filter pressure to correct the center value of the thickness. The same procedure as in Example 1 was carried out except that the stretching ratio and the film forming conditions of the thickness were changed. The results obtained are shown in Table 1.

(Examples 4 to 6)
Film formation was carried out under the same conditions as in Example 1 except that the film winding conditions were changed as shown in Table 1. The results obtained are shown in Table 1.

(Example 7)
Film formation was carried out under the same conditions as in Example 1 except that the gap between the caps was adjusted so that the central portion became thicker in the width direction of the polyester film roll after slitting. The results obtained are shown in Table 1.

(Comparative Examples 1 and 2)
The same procedure as in Example 1 was carried out except that the film forming conditions of the draw ratio were changed as shown in Table 2. In Comparative Example 1, a paper core having an elastic modulus of 1.3 GPa was used as the core in both the axial direction and the circumferential direction. The results obtained are shown in Table 2. The film roll hardness and the circumference length deviated from the target ranges, and the transport state at the time of coating the release layer deteriorated.

(Comparative Examples 3 to 5)
The same procedure as in Example 1 was carried out except that the film winding conditions were changed as shown in Table 2. The film roll hardness and the circumference length deviated from the target ranges, and the transport state at the time of coating the release layer deteriorated.

(Comparative Example 6)
In order to increase the ventilation frequency of air in the heat-fixing zone and remove oligomers in the oven, intake and exhaust were performed in each chamber of the heat-fixing zone, and other film forming conditions were the same as in Example 1. The film roll hardness and the circumference length deviated from the target ranges, and the transport state at the time of coating the release layer deteriorated.

(Comparative Example 7)
The same procedure as in Example 1 was carried out except that the gap between the bases was adjusted so that the central portion became thicker in the width direction of the polyester film roll after the slit. The results obtained are shown in Table 2. The film roll hardness and the circumference length deviated from the target ranges, and the transport state at the time of coating the release layer deteriorated.

Claims (7)

A polyester film roll made by winding a polyester film used for mold release.
The polyester film has a film width of 400 mm or more and a film length of 1000 m or more.
The hardness H is measured at 7 points that divide the line connecting one end and the other end in the width direction of the polyester film roll into eight equal parts, and the hardness is determined from the one end side. H2, H3, H4, H5, H6, and H7, _{H high} most things a high hardness of the hardness H1 to H7, the most things low hardness _H low, when the average of H1~7 was _{H ave,} A polyester film roll that satisfies the following formulas (1) and (2).
(H1 + H2 + H6 + H7) / 4- (H3 + H4 + H5) / 3 <0 ... (1)
4.0 x 10 ^-2 > ( _High- H _low ) / H _ave > 2.0 x 10 ^-3 ... (2) The circumference of the roll is measured at seven points that divide the line connecting one end and the other end in the width direction of the polyester film roll into eight equal parts, and the circumference is measured from one end side. The lengths are L1, L2, L3, L4, L5, L6, and L7, the one with the longest circumference among the circumferences L1 to L7 is L _high , and the one with the shortest circumference is L _low , L1. when the average to 7 was _{L ave,} following (3), a polyester film roll according to claim 1 which satisfies the equation (4).
(L1 + L2 + L6 + L7) / 4- (L3 + L4 + L5) / 3 <0 ... (3)
3.0 x 10 ^-3 > (L _high- L _low ) / _Love > 3.0 x 10 ^-5 ... (4) The center line roughness SRa (A) of one film surface of the polyester film is 1 nm or more and less than 15 nm, and the center line roughness SRa (B) of the other film surface is 20 nm or more and 40 nm or less. Or the polyester film roll according to 2. The polyester film roll according to any one of claims 1 to 3, wherein the polyester film has a layer structure of three or more layers. The polyester film roll according to any one of claims 1 to 4, wherein the thickness of the polyester film is more than 10 μm and not more than 500 μm. The polyester film roll according to any one of claims 1 to 5, which is used as a base material for molding a multilayer ceramic capacitor. The polyester film roll according to any one of claims 1 to 5, which is used as a base material for molding a multilayer ceramic capacitor for automobiles.