Polyester film roll

Abstract

To provide an environment friendly polyester film roll which is excellent in cutting property when it is cut together with a release film in a state of a green sheet being laminated.SOLUTION: A polyester film roll is formed by winding a polyester film, wherein the polyester film contains a copolymerized polyester and has a birefringence (Δn×103) of 21.0 or less at any position with respect to the roll whole width. In the polyester film roll, when a plurality of films is laminated such that total thickness at measurement is equivalent to 500 μm, a y value by a color tone reflection method is larger than 0.3160, and the polyester film roll is used as a support of a ceramic green sheet in a production process of a laminated ceramic capacitor.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a polyester film roll used as a support for a ceramic green sheet in the manufacturing process of multilayer ceramic capacitors. [Background technology]

[0002] Polyester film is used in a wide variety of industrial applications due to its excellent mechanical properties, heat resistance, and affordability. In particular, as a process paper for electronic components, it is used as a release film when manufacturing multi-layer ceramic capacitors (MLCCs).

[0003] Furthermore, in recent years, with the increasing electrification of automobiles and the advancement of smartphone functionality, MLCCs have been becoming smaller and their capacity has increased.

[0004] MLCCs are manufactured as follows: First, a ceramic slurry containing ceramic components and binder resin is applied to a release film and dried to produce a ceramic green sheet (dielectric sheet). Electrodes are then printed onto this sheet using screen printing or other methods to form the internal electrodes. After drying, the printed ceramic green sheet is peeled off the release film, and multiple such green sheets are stacked. The stacked green sheets are pressed together to form a single unit, and then cut into individual chips. Finally, the internal electrodes and dielectric layer are sintered in an incinerator to produce an MLCC.

[0005] As described above, the manufacturing process of MLCCs includes a step in which the green sheets are cut together with the release film while they are stacked (half-cut). One example of a polyester film that focuses on the above-mentioned half-cutting process is Patent Document 1. Patent Document 1 discloses a polyester film that can suppress tearing of the film during the half-cutting process when used as a release film for the manufacture of MLCCs.

[0006] Furthermore, in light of the growing environmental concerns in recent years, just as PET bottle recycling is becoming commonplace, there is a growing demand for reducing environmental impact through reuse and recycling in the polyester film sector. In particular, with the miniaturization and increased capacitance of multilayer ceramic capacitors, the thinning of ceramic green sheets has progressed, and the number of green sheets to be laminated has increased, leading to a significant increase in the amount of release film used, making the reduction of environmental impact an urgent issue. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2021-38383 [Overview of the project] [Problems that the invention aims to solve]

[0008] Although the polyester film disclosed in Patent Document 1 mentioned above can suppress tearing of the film during the half-cutting process, its cutability during cutting (hereinafter sometimes simply referred to as "cutability") was sometimes insufficient. When the cutability is insufficient, the cut edges may fray, making it difficult to align the green sheets based on the edges when laminating many sheets. In recent years, in particular, the thinning of ceramic green sheets has progressed, and the number of layers of green sheets has increased. As a result, there is a growing need for ease of determining the reference surface when laminating, and the importance of cutability during cutting has increased.

[0009] Furthermore, while Patent Document 1 mentions reducing the film thickness as a way to reduce environmental impact, it does not disclose anything about recycling, and no further investigation has been conducted, as recycling is deemed difficult.

[0010] Therefore, the present invention has been made in view of the above circumstances, and its objective is to provide an environmentally friendly polyester film roll that offers excellent cutability when cutting the green sheets together with the release film while they are laminated. [Means for solving the problem]

[0011] As a result of diligent research, the inventors have found that the above problems can be solved by having the following configuration. The present invention has the following aspects.

[0012] [1] A polyester film roll formed by winding a polyester film, wherein the polyester film contains copolymerized polyester and has birefringence (Δn × 10) at any position with respect to the entire width of the roll. 3 A polyester film roll whose y-value by color reflection method is greater than 0.3160 ​​when multiple films are stacked so that the total thickness at the time of measurement is equivalent to 500 μm, and which is used as a support for ceramic green sheets in the manufacturing process of multilayer ceramic capacitors. [2] The polyester film roll according to [1], wherein the copolymerized polyester contains isophthalic acid as a dicarboxylic acid component, and the content of isophthalic acid in the total dicarboxylic acid component of the total polyester of the polyester film is 0.05 to 0.75 mol%. [3] The polyester film roll according to [1] or [2] above, wherein recycled bottle material is used as the copolymerized polyester. [4] The polyester film roll according to [3] above, wherein the content of the recycled bottle material is 5 to 50% by mass relative to the total polyester of the polyester film. [5] The polyester film roll according to any one of [1] to [4] above, wherein the polyester film has a laminated structure consisting of at least three layers having a surface layer, an intermediate layer, and a surface layer in that order. [6] The polyester film roll according to [5], wherein the laminated structure has alternating layers of homopolyester and layers containing copolymerized polyester. [7] The polyester film roll according to [5] or [6] above, wherein both surface layers of the laminated structure are made of homopolyester. [8] The polyester film roll according to any one of [5] to [7] above, wherein the intermediate layer of the laminated structure is a layer containing copolymerized polyester. [9] A polyester film roll according to any one of [6] to [8] above, wherein the sum of the thicknesses of the homopolyester layers and the sum of the thicknesses of the copolymerized polyester layers is 0.06 to 0.67.

[10] A polyester film roll according to any one of [5] to [9] above, wherein at least one of the surface layers contains inorganic particles and organic particles as particles.

[11] A polyester film roll according to any one of [5] to

[10] above, wherein the thickness of at least one of the surface layers is 5 μm or less.

[12] A polyester film roll according to any one of [1] to

[11] above, wherein the total thickness of the polyester film is 12 to 50 μm.

[13] The polyester film roll according to any one of [1] to

[12] above, wherein the arithmetic mean roughness (Ra) of at least one of the polyester film surfaces is 30 nm or less.

[14] The polyester film roll according to any one of [1] to

[13] above, wherein the maximum protrusion height (Rp) of at least one of the polyester film surfaces is 300 nm or less.

[15] A release film roll comprising a release layer on at least one of the surfaces of the polyester film, in the case of a polyester film roll according to any of [1] to

[14] above.

[16] A laminated sheet comprising a green sheet on the release layer of the release film roll described in

[15] above.

Effect of the Invention

[0013] According to the present invention, there is provided an environmentally friendly polyester film roll having excellent cutting properties when cutting together with the release film in a state where the green sheet is laminated.

Mode for Carrying Out the Invention

[0014] Next, an example of an embodiment of the present invention will be described. However, the present invention is not limited to the embodiments described below.

[0015] <<<Polyester Film Roll>>> The polyester film roll of the present invention (hereinafter also referred to as "this roll") is a polyester film roll formed by winding a polyester film (hereinafter also referred to as "this film"), and has birefringence (Δn × 10 3 ) at any position with respect to the entire roll width is 21.0 or less. Further, it is characterized in that the y value by the colorimetric reflection method when a plurality of films are stacked so that the total thickness at the time of measurement corresponds to 500 μm is greater than 0.3160. Furthermore, this roll is used as a support for a ceramic green sheet in the manufacturing process of a multilayer ceramic capacitor.

[0016] This roll, as described above, has birefringence (Δn × 10 3 ) at any position with respect to the entire roll width is 21.0 or less. Thus, the birefringence (Δn × 10 3If the cut surface is within a specific range, it becomes easier to cut the film in the cutting direction. In other words, it is thought that the cutting performance during cutting will improve. When the cutting performance of the film improves, it is possible to suppress the reduction in the speed at which the cutting blade penetrates into the film. In other words, it is thought that the film will follow the penetration of the cutting blade tip, improving the cutting performance. As a result, the fraying of the cut edges is reduced, and alignment based on the edge surface becomes easier, which is advantageous for lamination of green sheets. From this perspective, the birefringence (Δn × 10 3 The value of birefringence is preferably 20.9 or less, more preferably 20.8 or less, and even more preferably 20.7 or less. Furthermore, from the viewpoint of improving the strength of the film due to stretch orientation, the lower limit of birefringence is preferably 3 or more, and more preferably 5 or more.

[0017] Furthermore, as mentioned above, this roll has a y-value greater than 0.3160 ​​when multiple films are stacked so that the total thickness at the time of measurement is equivalent to 500 μm, according to the color reflection method. A y-value greater than 0.3160 ​​indicates that the film has a strong yellow tint, meaning that the polyester film roll uses recycled materials. In other words, films with a y-value greater than 0.3160 ​​according to the color reflection method can be considered environmentally friendly. In particular, given the current demand for reducing environmental impact, we believe that being able to distinguish between environmentally friendly and non-environmentally friendly products is important. From this viewpoint, the y-value is preferably 0.3161 or higher, more preferably 0.3162 or higher, even more preferably 0.3165 or higher, and particularly preferably 0.3170 or higher. Furthermore, from the viewpoint of clearly distinguishing it from discoloration due to deterioration, the upper limit of the y-value is preferably 0.3355 or lower, and more preferably 0.3345 or lower.

[0018] This roll is a polyester film roll wound around a core such as a paper tube, metal tube, or plastic tube, and is preferably 0.2 m or wider, more preferably 0.3 m or wider, even more preferably 1.0 m or wider, and particularly preferably 1.5 m or wider. The upper limit of the roll width is not particularly limited, but is preferably 2.3 m or less, and more preferably 2.0 m or less. Furthermore, the length of the film wound onto the roll is not particularly limited, but is preferably 1000m or more, more preferably 6000m or more, and even more preferably 12000m or more. There is also no particular upper limit, but is usually 20000m or less, preferably 18000m or less.

[0019] <<Polyester film>> The film contains copolymerized polyester and is not particularly limited as long as it satisfies the above-mentioned physical properties when rolled. The film may have a single-layer structure or a laminated (multilayer) structure. If the film has a laminated structure, it may have a two-layer structure, a three-layer structure, or a four-layer or more multilayer structure, as long as it does not deviate from the gist of the present invention. The number of layers to be laminated is not particularly limited, but it is preferably 10 layers or less. With 10 layers or less, the thickness of each layer is sufficient, resulting in sufficient lamination during film formation, making it less likely for flow marks to occur, and ensuring sufficient film quality. Furthermore, if the film has a laminated structure of two or more layers, a 2-type 3-layer or 3-type 3-layer structure is preferred, and a 2-type 3-layer structure is more preferred.

[0020] In particular, it is preferable that at least one side of the film has excellent smoothness. Examples of such design methods include designing the film as a single layer, a two-type three-layer, or a three-type three-layer structure, with both sides of the film having excellent smoothness, or designing the film as a three-type three-layer structure, with one side of the film having excellent smoothness and the other side having a different roughness.

[0021] Furthermore, this film may be an unoriented film (sheet) or an oriented film. In particular, an oriented film stretched in one or two axes is preferred. Among these, a biaxially oriented film is more preferred in terms of superior balance of mechanical properties and flatness.

[0022] <Polyester> The polyester used as the raw material for this film refers to a polymer compound having ester bonds continuously in its main chain. Specifically, polyester obtained by polycondensation reaction of a dicarboxylic acid component and a diol component is an example. Furthermore, it is preferable to use a polyester that contains more than 50 mol% of aromatic dicarboxylic acid or aliphatic dicarboxylic acid when the dicarboxylic acid component is 100 mol%.

[0023] As described above, this film contains copolymerized polyester. The copolymerized polyester is preferably a polycondensation polymer of a dicarboxylic acid component and an aliphatic diol. The dicarboxylic acid component is preferably one or more of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acids (e.g., p-oxybenzoic acid). The aliphatic diol is preferably one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, and neopentyl glycol. The copolymerized polyester preferably contains isophthalic acid as a dicarboxylic acid, and more preferably contains isophthalic acid and terephthalic acid as dicarboxylic acid components, and contains ethylene glycol as an aliphatic diol.

[0024] In the case of the copolymerized polyester described above, it is preferable that the copolymer contains 30 mol% or less of a third component. The third component is a component other than the compound that is the main component (i.e., the component with the highest content) of the dicarboxylic acid component constituting the polyester, and the compound that is the main component (i.e., the component with the highest content) of the diol component. For example, in copolymerized polyethylene terephthalate, it is a component other than terephthalic acid and ethylene glycol. In the present invention, it is preferable that the copolymerized polyethylene terephthalate containing isophthalic acid is included as the third component.

[0025] It is preferable to use recycled bottle material as the copolymerized polyester. Recycled bottle material refers to recycled polyester made from PET bottles. The polyester used in PET bottles undergoes crystallinity control to improve the bottle's appearance, and as a result, polyester containing less than 10 mol% isophthalic acid is sometimes used. Therefore, in order to utilize recycled bottle materials, polyester containing isophthalic acid will be used.

[0026] The isophthalic acid content in the total dicarboxylic acid component of the total polyester of this film is preferably 0.05 to 0.75 mol%, more preferably 0.06 to 0.65 mol%, even more preferably 0.06 to 0.55 mol%, and particularly preferably 0.07 to 0.45 mol%. If the isophthalic acid content is 0.05 mol% or more, the birefringence of this roll (Δn × 10) 3 This makes it easier to adjust the properties to the desired range. On the other hand, if the isophthalic acid content is 0.75 mol% or less, the reduction in the mechanical properties of the film can be suppressed.

[0027] In the present invention, the content of the recycled bottle material is preferably 5 to 50% by mass, more preferably 5 to 40% by mass, and even more preferably 5 to 30% by mass, relative to the total polyester of the film. If the content of the recycled bottle material is 5% by mass or more, it can contribute to reducing the environmental burden. On the other hand, if the content of the recycled bottle material is 50 mol% or less, the impact of foreign matter derived from the recycled bottle material can be reduced. Furthermore, the reduction in the mechanical properties of the film due to the impact of isophthalic acid contained in the recycled bottle material can be suppressed.

[0028] This film only needs to contain copolymerized polyester, may contain multiple copolymerized polyesters, or may contain both copolymerized polyester and homopolyester. Homopolyesters are preferably obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic diol. Preferred aromatic dicarboxylic acids include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and preferred aliphatic diols include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Representative homopolyesters include polyethylene terephthalate (PET) and polyethylene-2,6-naphthalenedicarboxylate (PEN), with polyethylene terephthalate being preferred.

[0029] In addition to satisfying the above-mentioned isophthalic acid content, the film preferably contains 50 mol% or more of terephthalic acid in the total dicarboxylic acid components, more preferably 70 mol% or more, and even more preferably 90 mol% or more. Furthermore, the ethylene glycol content in the total diol components of the total polyester of this film is preferably 50 mol% or more, more preferably 70 mol% or more, and even more preferably 90 mol% or more. The content of ester units derived from terephthalic acid and isophthalic acid contained in the polyester raw material and the polyester constituting this film is determined by preparing a sample solution by dissolving the sample in a mixed solution of deuterated chloroform and trifluoroacetic acid (volume ratio 9 / 1), measuring the NMR of protons, calculating the peak intensity of a predetermined proton, and then calculating the content (mol%) of ester units derived from terephthalic acid and isophthalic acid in 100 mol% of ester units.

[0030] Normally, when polyester is produced (polycondensed) using ethylene glycol as one of the raw materials, diethylene glycol is produced as a by-product from ethylene glycol. In this specification, this diethylene glycol is referred to as by-product diethylene glycol. The amount of diethylene glycol produced as a by-product from ethylene glycol varies depending on the type of polycondensation, but it is approximately 5 mol% or less of the ethylene glycol. In the present invention, 5 mol% or less of diethylene glycol is considered as by-product diethylene glycol, and this by-product diethylene glycol is also included in ethylene glycol and distinguished from copolymer components. On the other hand, depending on the diethylene glycol content, more specifically if diethylene glycol is present in amounts exceeding 5 mol%, the diethylene glycol is treated as a copolymer component rather than as a by-product diethylene glycol.

[0031] (Preferred form) A preferred form of this film is a laminated structure consisting of at least three layers, having a surface layer, an intermediate layer, and another surface layer in that order. The thickness of at least one of the surface layers is preferably 5 μm or less, more preferably 4 μm or less, and even more preferably 3 μm or less. On the other hand, the lower limit of the thickness is preferably 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.3 μm or more. If the thickness is 5 μm or less, the uniformity of the protrusions formed based on the particles contained in the surface layer is improved. On the other hand, if the thickness is 0.1 μm or more, the shedding of particles contained in the surface layer can be suppressed.

[0032] In particular, the laminated structure of this film preferably has alternating layers of homopolyester and copolymerized polyester. With such a laminated structure, the film follows the cutting edge of the cutting blade well, improving the cutting performance during cutting. On the other hand, it can suppress the propagation of breakage when half-cut, thus preventing unintended tearing or ripping of the film. In other words, it is possible to achieve both good cutting performance and suppression of tearing and ripping of the film. Although this film may have layers other than the homopolyester layer and the copolymerized polyester layer, it is preferable that it is composed of a homopolyester layer and a copolymerized polyester layer from the viewpoint of film-forming properties and interlayer adhesion.

[0033] When the laminated structure has a surface layer, an intermediate layer, and another surface layer in that order, it is preferable that both surface layers are made of homopolyester. Furthermore, it is preferable that the intermediate layer is a layer containing copolymerized polyester. With such a laminated structure, for example, the influence of foreign matter derived from recycled bottle raw materials used as copolymerized polyester can be reduced. More specifically, when used as a support for a ceramic green sheet in the manufacturing process of a multilayer ceramic capacitor, it is preferable that at least one side of the film is a surface with excellent smoothness, and therefore it is preferable to minimize the influence of foreign matter on the surface layer and maintain smoothness.

[0034] As described above, the most preferable laminated structure of this film consists of three layers: a layer made of homopolyester, a layer containing copolymerized polyester, and a layer made of homopolyester. In this invention, a layer made of homopolyester means a layer in which homopolyester accounts for more than 95% by mass of the total resin constituting the layer, and a layer containing copolymerized polyester means a layer in which copolymerized polyester accounts for 5% by mass or more of the total resin constituting the layer.

[0035] Furthermore, when the laminated structure of this film has a layer made of homopolyester and a layer containing copolymerized polyester, the ratio of the sum of the thicknesses of the homopolyester layers to the sum of the thicknesses of the copolymerized polyester layers (sum of the thicknesses of the homopolyester layers / sum of the thicknesses of the copolymerized polyester layers) is preferably 0.06 to 0.67. If the ratio is 0.06 or higher, the film's ability to follow the cutting edge of the cutting blade is improved, enhancing the cutting performance during cutting. Furthermore, it becomes easier to increase the content of recycled bottle materials, thereby increasing the environmental impact reduction effect. On the other hand, if the ratio is 0.67 or lower, the propagation of breakage when the film is half-cut can be suppressed, preventing unintended tearing or ripping of the film. Additionally, the influence of foreign matter derived from recycled bottle materials is reduced, maintaining the smoothness of the film surface. From this viewpoint, the ratio is more preferably 0.07 to 0.63, even more preferably 0.08 to 0.60, particularly preferably 0.08 to 0.50, especially preferably 0.08 to 0.30, and most preferably 0.08 to 0.20. The layer structure and thickness of each layer of this film are determined by observing the cross-section, obtained by cryogenic fracture using an ultramicrotome, at a magnification of 3,000 to 200,000 times using a transmission electron microscope, and taking cross-sectional photographs.

[0036] <Polycondensation catalyst> There are no particular restrictions on the polycondensation catalyst used when polycondensing the above polyesters; conventionally known compounds can be used, such as titanium compounds, germanium compounds, antimony compounds, manganese compounds, aluminum compounds, magnesium compounds, and calcium compounds.

[0037] <Intrinsic viscosity> The intrinsic viscosity (IV) of this film is preferably 0.50 dL / g or higher, more preferably 0.52 dL / g or higher, and even more preferably 0.54 dL / g or higher. Within this range, there are advantages such as increased particle dispersion due to increased shear stress during kneading. Alternatively, the intrinsic viscosity (IV) may be, for example, 1.00 dL / g or lower.

[0038] <particle> This film can also contain particles. By containing particles, the polyester film is given slipperiness and prevents scratches during each process, resulting in improved handling. The types of particles to be included in this film are not particularly limited as long as they can impart slipperiness. Specific examples include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide, as well as crosslinked polymers such as crosslinked silicone resin particles, crosslinked acrylic resin particles, crosslinked styrene-acrylic resin particles, and crosslinked polyester particles, and organic particles such as calcium oxalate and ion exchange resins. Among these, it is preferable to use inorganic and organic particles in combination, and from the viewpoint of easily obtaining the desired surface roughness, the combination of calcium carbonate and organic particles is preferable. Furthermore, during the polyester manufacturing process, precipitated particles obtained by precipitating and finely dispersing a portion of metal compounds such as catalysts can also be used.

[0039] There are no particular restrictions on the shape of the particles used; spherical, lumpy, rod-shaped, flattened, or any other shape may be used. Furthermore, there are no particular restrictions on their hardness, specific gravity, color, etc. Two or more types of these particles may be used in combination as needed.

[0040] Furthermore, the average particle size of the particles used is usually 5 μm or less, preferably 0.01 to 3 μm, more preferably 0.02 to 1.5 μm, and even more preferably 0.03 to 1 μm. Within this range of average particle size, both the handling properties and surface smoothness of the film can be achieved. Furthermore, if the particles are in powder form, the average particle size can be determined by using a centrifugal sedimentation particle size distribution analyzer (e.g., Shimadzu Corporation's "SA-CP3" model) to measure the particle size distribution at 50% of the cumulative volume fraction (d50). For particles in films, layers, or resins, the average particle size can be determined by observing 10 or more particles with a scanning electron microscope (SEM), measuring the diameter of each particle, and taking the average value. In the case of non-spherical particles, the average of the longest and shortest diameters can be used as the diameter of each particle.

[0041] When incorporating particles into this film, it is preferable to provide a surface layer and an intermediate layer, with the particles being incorporated into the surface layer. Furthermore, in the case of a three-layer structure with different designs on the front and back, it is also possible to incorporate particles into at least one of the surface layers. Therefore, it is preferable to incorporate particles into at least one of the surface layers, and as described above, it is more preferable to use a combination of inorganic and organic particles. The particle content, although it also depends on the average particle size, is preferably 10,000 ppm or less by mass in the particle-containing layer, more preferably 8,000 ppm or less, even more preferably 7,000 ppm or less, and even more preferably 6,000 ppm or less. Within this range, the surface smoothness of the film can be made good. If there are no particles or if the particle content is low, the slipperiness may be insufficient, so the content is preferably 50 ppm or more, and more preferably 100 ppm or more.

[0042] The method for adding particles to this film is not particularly limited, and conventionally known methods can be employed. For example, in the case of a laminated polyester film, the particles can be added at any stage in the production of the polyester constituting each layer, but it is preferable to add them after the esterification or transesterification reaction is completed.

[0043] <Other> To suppress the precipitation of oligomer components, the film may be manufactured using polyester with a low oligomer content as the raw material. Various known methods can be used to manufacture polyester with a low oligomer content, such as a method of solid-phase polymerization after polyester production. Furthermore, the film may be constructed with three or more layers, and the surface layer of the film may be made of a polyester raw material with a low oligomer content to suppress the amount of oligomer component precipitated. Alternatively, polyester may be obtained by esterification or transesterification, followed by further increasing the reaction temperature and melt polycondensation under reduced pressure.

[0044] In addition to the particles mentioned above, conventionally known ultraviolet absorbers, antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, etc., may be added to this film as needed.

[0045] The total thickness of this film is not particularly limited as long as it is within the range that can be formed as a film, but from the viewpoint of mechanical strength, handling and productivity, it is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, particularly preferably 12 μm or more, and preferably 200 μm or less, more preferably 125 μm or less, even more preferably 80 μm or less, particularly preferably 50 μm or less.

[0046] <Method for manufacturing polyester film> Next, we will specifically describe examples of the production of this film in this roll, but we are not limited to the following examples. For example, when manufacturing a biaxially oriented film, it is preferable to extrude the dried pellets of the polyester raw material mentioned above as a molten sheet from a die using a melt extrusion device such as an extruder, and then cool and solidify them with a cooling roll such as a rotating cooling drum to obtain an unstretched sheet. Here, cooling is carried out to a temperature below the glass transition point of the polymer, for example, to obtain a substantially amorphous, unoriented sheet (unstretched sheet). Furthermore, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the cooling roll, and electrostatic application adhesion and / or liquid coating adhesion methods are preferably employed.

[0047] Next, the obtained unstretched sheet is stretched in two axial directions. In this case, first, the unstretched sheet is stretched in one direction using a roll or tenter type stretcher. The stretching temperature is usually 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is usually 2.5 to 7.0 times, preferably 3.0 to 6.0 times.

[0048] Next, the material is stretched in a direction perpendicular to the stretching direction of the first stage. In this case, the stretching temperature is usually 70 to 170°C, and the stretching ratio is usually 3.0 to 7.0 times, preferably 3.5 to 6.0 times.

[0049] Next, a heat treatment is performed at a temperature of typically 180-270°C, under tension or with a relaxation of up to 30%, to obtain a biaxially oriented film. This heat treatment is also called the heat setting process. The heat treatment may be carried out in two or more stages at different temperatures. Furthermore, cooling may be performed in a cooling zone after the heat treatment. The cooling temperature is preferably higher than the glass transition temperature (Tg) of the polyester constituting the film, and more specifically, it is preferably in the range of 100 to 160°C. This cooling may be carried out in two or more stages at different temperatures. In the stretching described above, a method of stretching in one direction in two or more stages can also be employed. In that case, it is preferable to ensure that the final stretching ratios in both directions fall within the above ranges.

[0050] Furthermore, simultaneous biaxial stretching can also be used in the manufacture of this film. Simultaneous biaxial stretching is a method of simultaneously stretching and oriented the aforementioned unstretched sheet in the machine direction (longitudinal direction) and width direction (transverse direction) while the temperature is controlled, usually at 70 to 120°C, preferably 80 to 110°C. The stretching ratio is preferably 4 to 50 times, more preferably 7 to 35 times, and even more preferably 10 to 25 times in terms of area. Then, heat treatment is carried out at a temperature of typically 170-250°C under tension or under relaxation of 30% or less to obtain a stretched and oriented film. For the simultaneous biaxial stretching apparatus employing the above stretching method, conventional known stretching methods such as screw type, pantograph type, and linear drive type can be used.

[0051] The longitudinal direction (MD) of the film refers to the direction in which the film progresses during the film manufacturing process, i.e., the winding direction of the film roll, and is also called the machine direction or vertical direction. The width direction (TD) of the film refers to the direction parallel to the film surface and perpendicular to the longitudinal direction; in other words, when the film is in a roll, it refers to the direction parallel to the central axis of the roll, and is also called the transverse direction.

[0052] When recycled bottle material is used as part of the polyester raw material, the recycled bottle material is obtained by sorting collected used PET bottles to prevent mixing with other materials or waste, removing labels and other items, and then crushing them to produce flakes and / or chips from the flakes. Conventional methods can be used to obtain flakes, including crushing them with a crusher. Conventional methods can also be used to chip the flakes, for example, by melt-extruding the flakes and then cutting the strand-shaped melt-extruded material to obtain chipped raw material. Furthermore, the flakes may have foreign matter attached to or mixed in them, or consumers may fill the PET bottles with chemical substances such as medicines or drugs. In such cases, conventional washing may not be sufficient to remove the chemical substances adsorbed on the surface of the PET bottle, so conventionally known alkaline washing may be used, and rinsing and drying may be added after the alkaline washing. Additionally, during the process of chipping the flakes, a filter may be used to remove fine foreign matter.

[0053] <Physical properties of polyester film> The arithmetic mean roughness (Ra) of at least one of the film surfaces is preferably smooth, for example, when used as a release film in the manufacture of MLCCs, from the viewpoint of enabling thinning of the ceramic layer and suppressing pinholes. More specifically, the arithmetic mean roughness (Ra) is preferably 30 nm or less, more preferably 28 nm or less, even more preferably 26 nm or less, and particularly preferably 24 nm or less. On the other hand, the arithmetic mean roughness (Ra) is not particularly limited, but is preferably 3 nm or more from the viewpoint of improving the windability of the film.

[0054] Furthermore, the maximum protrusion height (Rp) of at least one of the film surfaces is preferably smooth, similar to the arithmetic mean roughness (Ra) described, from the viewpoint of accommodating thin ceramic layers and suppressing pinholes. More specifically, the maximum protrusion height (Rp) is preferably 300 nm or less, more preferably 250 nm or less, and even more preferably 200 nm or less. On the other hand, although the maximum protrusion height (Rp) is not particularly limited, it is preferably 30 nm or more from the viewpoint of improving the winding properties of the film.

[0055] The tensile breaking strength of this film is preferably 150 MPa or more, more preferably 180 MPa or more, preferably 350 MPa or less, and more preferably 320 MPa or less. Furthermore, the tensile elongation at break of this film is preferably 50% or more, more preferably 70% or more, preferably 200% or less, and more preferably 180% or less. If the tensile strength and tensile elongation at break of this film are within the specified range, it can be said that the film has sufficient strength to be used as a support for ceramic green sheets in the manufacturing process of multilayer ceramic capacitors.

[0056] <<Release layer>> In the present invention, the release film roll is preferably a polyester film roll formed by winding a release film having a release layer on at least one side of its surface. The release layer is preferably laminated on the side of the polyester film constituting the roll that has excellent smoothness. The release layer is laminated onto the film either directly or via another layer.

[0057] The aforementioned release layer is formed from a release agent composition containing a release agent, but from the viewpoint of obtaining good release performance, it is particularly preferable that the release agent composition contains a silicone resin. Specifically, it is preferable that the composition contains a type mainly composed of a curable silicone resin, a modified silicone type obtained by graft polymerization with organic resins such as polyurethane resin, epoxy resin, or alkyd resin, or a fluorosilicone resin.

[0058] As the curable silicone resin, any existing curing reaction type can be used, such as addition-type, condensation-type, or other thermosetting types, or ultraviolet-curing types or other electron beam curing types. Multiple types of curable silicone resins may also be used in combination. Furthermore, there are no particular restrictions on the coating form of the curable silicone resin used to form the release layer; it may be in the form of a solution in an organic solvent, an aqueous emulsion, or a solvent-free form.

[0059] In addition to this, the release agent composition for forming the release layer may also contain, as necessary, a binder, an antifoaming agent, a coating property improver, a thickener, inorganic particles, organic particles, an organic lubricant, an antistatic agent, a conductive agent, an ultraviolet absorber, an antioxidant, a foaming agent, dyes, pigments, and the like.

[0060] The release layer is provided by coating the release agent composition on the film, and either in-line coating performed within the film forming process or so-called off-line coating applied outside the system on the once-manufactured film may be adopted.

[0061] Examples of the method for providing the release layer on the film include conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, and the like.

[0062] Regarding the curing conditions when forming the release layer, there is no particular limitation. When the release layer is provided by off-line coating, usually, heat treatment is preferably carried out with a temperature of 80°C or higher for 10 seconds or more, preferably 100 - 200°C for 3 - 40 seconds, more preferably 120 - 180°C for 3 - 40 seconds as a guide.

[0063] Also, if necessary, heat treatment and irradiation with active energy rays such as ultraviolet irradiation may be used in combination. Note that as an energy source for curing by irradiation with active energy rays, known devices and energy sources can be used.

[0064] The coating amount (after drying) of the release layer is usually 0.005 - 5 g / m 2 , preferably 0.005 - 1 g / m 2 , more preferably 0.005 - 0.1 g / m 2 within the range. When the coating amount (after drying) is 0.005 g / m 2 or more, the coating property is stabilized, and it becomes easier to obtain a uniform coating film. On the other hand, when it is 5 g / m 2 or less, it is not thickly coated, and it is possible to prevent the decrease in the coating film adhesion, curability, etc. of the release layer itself. The coating amount is calculated based on the liquid mass per unit of time applied (before drying), the non-volatile content concentration of the coating liquid, the application width, the stretching ratio, the line speed, etc.

[0065] <<<Application>>> This roll offers excellent cutting performance when cutting the green sheet together with the release film in a laminated state, making it suitable for use as a support for ceramic green sheets, particularly in the manufacturing process of multilayer ceramic capacitors (MLCCs). The ceramic green sheet is formed by applying, for example, a ceramic slurry to this film, which serves as the support. The present invention also includes laminated sheets having a green sheet on the release layer of a release film roll, which are manufactured in this manner.

[0066] In the future, as MLCCs for automobiles become increasingly electrified, it is predicted that miniaturization and increased capacity of MLCCs will progress, and the thinning of the ceramic green sheets used will accelerate. This roll offers excellent cutting performance when cutting green sheets together with the release film, making it advantageous for laminating green sheets. Furthermore, because this roll is environmentally friendly, it can address the urgent issue of reducing environmental impact caused by the increased use of release film. Therefore, this roll can be suitably used as a support for ceramic green sheets, particularly in the manufacturing process of multilayer ceramic capacitors for automobiles.

[0067] <<<Explanation of terms>>> In this invention, the term "film" includes "sheets," and the term "sheet" includes "film." In this invention, when "X~Y" (where X and Y are any numbers) is written, unless otherwise specified, it means "X or greater and Y or less," and also includes the meaning of "preferably greater than X" or "preferably less than Y." Furthermore, when "X or greater" (where X is any number) is written, unless otherwise specified, it includes the meaning of "preferably greater than X," and when "Y or less" (where Y is any number) is written, unless otherwise specified, it also includes the meaning of "preferably less than Y." [Examples]

[0068] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following embodiments, unless it exceeds the gist of the invention.

[0069] <Evaluation Method> (1) Intrinsic viscosity of polyester (IV) One g of polyester, from which incompatible components had been removed, was accurately weighed, and 100 mL of a phenol / tetrachloroethane mixed solvent (50 / 50 by mass ratio) was added to dissolve it. The viscosity was then measured at 30°C using a viscosity measuring device "VMS-022UPC·F10" (manufactured by Rigosha Co., Ltd.).

[0070] (2) Average particle size For the average particle size of the particles contained in the polyester, the particle size at which the cumulative volume fraction of 50% of the equivalent spherical distribution was measured using a centrifugal sedimentation particle size distribution analyzer (SA-CP3 type) manufactured by Shimadzu Corporation was defined as the average particle size d50.

[0071] (3) Birefringence (Δn × 10 3 ) A sample piece measuring 50 mm in the longitudinal direction (MD) and 20 mm in the width direction (TD) was taken from a designated location on the polyester film, and the principal axis direction was determined using an Olympus Corporation BX50 polarizing microscope. A marking line was drawn along the principal axis direction of the sample piece, and a 20 mm x 10 mm sample for refractive index measurement was cut from the designated location so that the marking line and the long side of the sample were parallel. In the example, the central position relative to the entire width of the roll was measured as the predetermined location (the same applies to other measurements).

[0072] Using an Abbe-type refractometer (NAR-1T) manufactured by Atago Co., Ltd., the refractive index nγ in the direction of the principal axis of orientation and the refractive index nβ in the direction of the minor axis of orientation were determined, and the birefringence (Δn), which is the absolute value of (nγ-nβ), was calculated. The refractive index was measured using a sodium D line at 23°C.

[0073] (4) Color (y value) The color (y-value) of the polyester film was determined using a Konica Minolta Japan CM-3700d spectrophotometer as follows. Samples were obtained by punching out a sample from a designated location using a round holder blade with a diameter of approximately 60 mm. The number of test sheets was determined to be the number of sheets that resulted in a stack thickness (total thickness at the time of measurement) closest to 500 μm. For example, for a 25 μm film, 20 films would be used, and for a 38 μm film, 13 films would be used. The measurement conditions were reflective conditions. The color measurements were taken in an environment of 23°C.

[0074] (5) Arithmetic mean roughness (Ra) and maximum protrusion height (Rp) The arithmetic mean surface roughness (Ra) of the polyester film was determined using a surface roughness meter (SE-3500) manufactured by Kosaka Research Institute Co., Ltd., as follows. Specifically, when a portion of a standard length L (2.5 mm) is extracted from the film cross-sectional curve obtained by measurement in the direction of its centerline, and the centerline of this extracted portion is taken as the x-axis and the direction of the vertical magnification as the y-axis, the roughness curve y = f(x) is represented, the surface arithmetic mean roughness is the value given by the following formula, expressed in [nm]. The arithmetic mean roughness was obtained by taking 10 roughness curves from the surface of the sample film and expressing it as the average value of the arithmetic mean roughness of the extracted portion obtained from these roughness curves. The tip radius of the stylus was set to 2 μm, the load to 30 mg, and the cutoff value to 0.08 mm.

[0075]

number

[0076] Furthermore, the maximum surface protrusion height (Rp) of the polyester film represents the maximum height from the average plane of the film cross-sectional curve obtained by the above method.

[0077] The arithmetic mean roughness (Ra) and maximum protrusion height (Rp) were measured on both sides of the polyester film.

[0078] (6) Tensile breaking strength and tensile breaking elongation Sample pieces measuring 15 mm in width and 150 mm in length were taken from designated locations on the polyester film, and the tensile breaking strength and tensile elongation were measured using an Autograph AGX-V manufactured by Shimadzu Corporation. Gauge marks were marked at 50 mm intervals in the center of each test piece, and a tensile test was performed using a tensile testing machine with a gripping distance of 50 mm and a tensile speed of 200 mm / min. The load and elongation at the time of breakage were measured, and the tensile breaking strength and tensile elongation were determined.

[0079] <Materials used> Raw material A: Homopolyethylene terephthalate (intrinsic viscosity = 0.64 dL / g) Raw material B: A masterbatch made by blending 0.5% by mass of organic particles with an average particle size of 0.4 μm into homopolyethylene terephthalate (intrinsic viscosity = 0.62 dL / g). Raw material C: A masterbatch containing 2.0% by mass of calcium carbonate particles with an average particle size of 0.7 μm, made from homopolyethylene terephthalate (intrinsic viscosity = 0.61 dL / g). Raw material D: Copolymerized polyethylene terephthalate obtained by copolymerizing 1.4 mol% isophthalic acid with the total dicarboxylic acid component (intrinsic viscosity = 0.71 dL / g) Raw material E: Copolymerized polyethylene terephthalate obtained by copolymerizing 1.5 mol% isophthalic acid with the total dicarboxylic acid component (intrinsic viscosity = 0.69 dL / g)

[0080] Furthermore, raw materials D and E are recycled polyester (bottle recycled material) made from PET bottles.

[0081] (Example 1) Mixed raw materials A, B, and C were prepared in proportions of 49% by mass, 31% by mass, and 20% by mass, respectively, to form the raw materials for both surface layers. Mixed raw materials A and D were prepared in proportions of 94% by mass and 6% by mass, respectively, to form the raw material for the intermediate layer. Each of the raw materials for both surface layers and the intermediate layer was supplied to two extruders, melted at 280°C, and then co-extruded and cooled on a cooling roll set at 25°C in a layer configuration of 2 types and 3 layers (discharge volumes of surface layer / intermediate layer / surface layer = 1.2 / 22.6 / 1.2) to obtain an unstretched sheet. Next, the obtained unstretched sheet was stretched 3.5 times in the longitudinal direction (MD) at 85°C using a roll stretcher. Furthermore, after preheating in a tenter at 100°C, it was stretched 4.5 times in the width direction (TD) at 110°C. Finally, it was heat-treated at 220°C to obtain a biaxially oriented polyester film with a thickness of 25 μm (each surface layer: 1.2 μm, intermediate layer: 22.6 μm). The evaluation results are shown in Table 2.

[0082] (Examples 2-3) The procedure was the same as in Example 1, except that the composition and film formation conditions were as described in Table 1 below. The evaluation results are shown in Table 2.

[0083] (Comparative Example 1) The procedure was the same as in Example 1, except that the composition and film formation conditions were as described in Table 1 below. The evaluation results are shown in Table 2.

[0084] [Table 1]

[0085] Note that in Table 1, "ratio of sum of layer thicknesses" means the sum of the layer thicknesses of the homopolyester layers / the sum of the layer thicknesses of the copolymerized polyester layers. The homopolyester layers are the surface layers, and the copolymerized polyester layers are the intermediate layers.

[0086] [Table 2]

[0087] As shown in the results in Table 2, the polyester film roll of the present invention exhibits birefringence (Δn × 10 3 The birefringence (Δn × 10) is 21.0 or less. 3 Within the range covered by the above, we believe that the cutting performance during cutting will improve, which will be advantageous for laminating the green sheets. Furthermore, the polyester film roll of the present invention has a color (y-value) greater than 0.3160. As long as the y-value falls within this range, it can be considered environmentally friendly, as described above.

[0088] As an example of an embodiment that satisfies the above physical properties, the polyester film of the present invention consists of a layer made of homopolyester, a layer containing copolymerized polyester, and a layer made of homopolyester. If recycled bottle material is used as the copolymerized polyester, the influence of foreign matter originating from the recycled material on the surface layer can be minimized, and it can be seen that the effect on surface smoothness such as arithmetic mean roughness (Ra) and maximum protrusion height (Rp) is actually small. Furthermore, by limiting the amount of recycled bottle material to 50% by mass or less, it is possible to keep the deterioration of mechanical properties caused by isophthalic acid contained in the recycled bottle material within a practical range. [Industrial applicability]

[0089] The polyester film roll of the present invention offers excellent cutability when cutting the green sheet together with the release film, and is environmentally friendly. Therefore, the embodiments of this disclosure can be suitably used as a support for a ceramic green sheet in the manufacturing process of a multilayer ceramic capacitor.

[0090] In the future, as automobiles become increasingly electrified, it is predicted that multilayer ceramic capacitors will become smaller and have higher capacitance, and that the thinning of the ceramic green sheets used will accelerate. As described above, the polyester film roll of the present invention is advantageous for thinning green sheets and can address the issue of reducing environmental impact. Therefore, it can be suitably used as a support for ceramic green sheets, particularly in the manufacturing process of multilayer ceramic capacitors for automobiles.

Claims

1. A polyester film roll made by winding up polyester film, The aforementioned polyester film contains copolymerized polyester, Birefringence at any position relative to the entire width of the roll (Δn × 10) ３ ) is 21.0 or less, When multiple films are stacked so that the total thickness at the time of measurement is equivalent to 500 μm, the y value by the color reflection method is greater than 0.3160. The polyester film has a laminated structure consisting of at least three layers, with a surface layer, an intermediate layer, and another surface layer in that order. Both surface layers of the aforementioned laminated structure are made of homopolyester. The intermediate layer of the aforementioned laminated structure is a layer containing copolymerized polyester, The sum of the thicknesses of the homopolyester layers and the sum of the thicknesses of the copolymerized polyester layers is 0.06 to 0.

67. A polyester film roll used as a support for ceramic green sheets in the manufacturing process of multilayer ceramic capacitors.

2. The polyester film roll according to claim 1, wherein the copolymerized polyester contains isophthalic acid as a dicarboxylic acid component, and the content of isophthalic acid in the total dicarboxylic acid component of the total polyester of the polyester film is 0.05 to 0.75 mol%.

3. The polyester film roll according to claim 1 or 2, wherein recycled bottle material is used as the copolymerized polyester.

4. The polyester film roll according to claim 3, wherein the content of the recycled bottle material is 5 to 50% by mass relative to the total polyester of the polyester film.

5. The polyester film roll according to claim 1 or 2, wherein the laminated structure alternately comprises layers made of homopolyester and layers containing copolymerized polyester.

6. The polyester film roll according to claim 1 or 2, wherein at least one of the surface layers contains inorganic particles and organic particles as particles.

7. The polyester film roll according to claim 1 or 2, wherein the thickness of at least one of the surface layers is 5 μm or less.

8. The polyester film roll according to claim 1 or 2, wherein the total thickness of the polyester film is 12 to 50 μm.

9. The polyester film roll according to claim 1 or 2, wherein the arithmetic mean roughness (Ra) of at least one of the polyester film surfaces is 30 nm or less.

10. The polyester film roll according to claim 1 or 2, wherein the maximum protrusion height (Rp) of at least one of the surfaces of the polyester film is 300 nm or less.

11. A release film roll according to claim 1 or 2, wherein at least one of the surfaces of the polyester film is provided with a release layer.

12. A laminated sheet comprising a green sheet on the release layer of the release film roll according to claim 11.

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