Porous resin sheet and carrier belt

Abstract

The objective of this invention is to provide a porous resin sheet that can be shaped without special steps such as heating or depressurization while suppressing paper dust content, and a carrier belt using the same. This invention relates to a porous resin sheet comprising a porous resin layer containing a thermoplastic resin, wherein the thickness of the porous resin layer is 40–350 μm, the porosity of the porous resin layer is 35–80%, the porous resin layer comprises a substrate layer and a first surface layer, both the substrate layer and the first surface layer containing thermoplastic resin and particles, the content of the aforementioned particles in the substrate layer being 20–45% by mass, and the content of the aforementioned particles in the first surface layer being 45–80% by mass.

Description

Technical Field

[0001] The present invention relates to a porous resin sheet and a carrier tape. Prior Art

[0002] To facilitate the handling of increasingly miniaturized electronic components, carrier tape is used. Because the carrier tape holds the electronic components one by one within its pockets, it is easier to prevent the electronic components from being lost or damaged.

[0003] Carrier tapes are typically made of pulp paper or resins such as polyvinyl chloride, polystyrene, amorphous polyethylene terephthalate, polycarbonate, and polypropylene. While pulp paper carrier tapes (e.g., Patent Document 1) are inexpensive, they are difficult to form into small pouches. Furthermore, when drilling vias, they easily produce burrs (paper dust) on the processed cross-section. Meanwhile, resin carrier tapes, while less prone to paper dust and capable of forming pouches of wider dimensions, are relatively lightweight and require heating or decompression (vacuuming) steps to form the pouches, making them less costly. [Prior Art Literature] [Patent Document]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-43975 Summary of the Invention

[0005] [Problems to be solved by the invention]

[0006] The object of the present invention is to provide a porous resin sheet and a carrier tape using the same, which can be shaped without requiring special steps such as heating or decompression while suppressing the amount of paper dust. [Means for solving the problem]

[0007] As a result of active research to address the above-mentioned issues, the present inventors have discovered a porous resin sheet comprising a porous resin layer containing a thermoplastic resin, wherein the thickness and porosity of the porous resin layer fall within specific ranges, the porous resin layer comprising a base layer and a first surface layer, both of which contain a thermoplastic resin and particles, and the particle content in the base layer and the first surface layer falls within specific ranges. This porous resin sheet can be used to obtain a porous resin sheet that can be shaped without requiring special steps such as heating or decompression while suppressing the amount of paper powder, and a carrier tape using the porous resin sheet, thereby completing the present invention.

[0008] That is, the present invention is as described below. <1> A porous resin sheet comprising a porous resin layer containing a thermoplastic resin, wherein: The thickness of the porous resin layer is 40~350μm. The porosity of the porous resin layer is 35-80%. The porous resin layer comprises a base material layer and a first surface layer. The aforementioned base material layer and the first surface layer both contain thermoplastic resin and particles. The content of the aforementioned particles in the aforementioned substrate layer is 20-45% by mass, and The content of the aforementioned particles in the aforementioned first surface layer is 45-80% by mass. <2> like <1> The porous resin sheet described above, wherein the first surface layer is a porous uniaxially stretched resin layer, and The substrate layer is a porous biaxially stretched resin layer. <3> like <1> or <2> The porous resin sheet described above, wherein the first surface layer has a thickness of 5 μm or more. <4> like <1> ~ <3> The porous resin sheet according to any one of the above, wherein the first surface layer has a thickness of 10 μm or more. <5> like <1> ~ <4> The porous resin sheet according to any one of the above, wherein the porous resin layer further includes a second surface layer on the surface of the substrate layer opposite to the first surface layer. <6> like <1> ~ <5> The porous resin sheet according to any one of the above, wherein the ratio of the porosity of the first surface layer to the porosity of the base layer is 0.80 to 1.20.

[0009] <7> like <1> ~ <6> The porous resin sheet according to any one of the above, wherein the breaking strength in the width direction is 0.1 to 10 kgf / mm2. <8> like <1> ~ <7> The porous resin sheet described in any one of the above items is used for a carrier tape. <9> A carrier belt having the following <1> ~ <8> The porous resin sheet as described in any one of the following, and A pocket is formed in the aforementioned porous resin sheet. [Effects of the Invention]

[0010] According to the present invention, a porous resin sheet and a carrier tape using the same can be provided, which can suppress the amount of paper powder and can be shaped without special steps such as heating or decompression. Simple diagram description

[0011] FIG1 is a diagram showing one embodiment of a cross section of a porous resin sheet according to the present invention in the lamination direction. FIG2 is a diagram showing a cross section in the lamination direction of another embodiment of the porous resin sheet of the present invention. FIG3 is a diagram showing a cross section in the lamination direction of a porous resin sheet of a comparative example. FIG4 is a diagram showing a carrier tape of a porous resin sheet according to another embodiment of the present invention, and is a diagram showing a cross section taken along the stacking direction of a bag. Implementation Method

[0012] The following is a detailed description of the porous resin sheet of the present invention. The following is an example (representative example) of the present invention, and the present invention is not limited thereto. In addition, in this specification, the numerical range "A to B" means "above A and below B".

[0013] The present invention relates to a porous resin sheet comprising a porous resin layer containing a thermoplastic resin, wherein the porous resin layer has a thickness of 40 to 350 μm and a porosity of 35 to 80%. The porous resin layer comprises a base layer and a first surface layer, both the base layer and the first surface layer containing a thermoplastic resin and particles, the base layer containing the particles in an amount of 20 to 45% by mass, and the first surface layer containing the particles in an amount of 45 to 80% by mass. By setting the thickness and porosity of a porous resin layer within a specific range in a porous resin sheet having a porous resin layer containing a thermoplastic resin, and the porous resin layer including a base layer and a first surface layer, and both the base layer and the first surface layer containing thermoplastic resin and particles, and setting the particle content in the base layer and the first surface layer within a specific range, a carrier tape can be obtained that can be shaped without undergoing special steps such as heating or decompression while suppressing the amount of paper powder.

[0014] <Porous Resin Layer> The porous resin sheet of the present invention comprises a porous resin layer containing a thermoplastic resin. The porous resin layer has a thickness of 40 to 350 μm and a porosity of 35 to 80%. The porous resin layer comprises a base layer and a first surface layer, both containing a thermoplastic resin and particles. The base layer contains 20 to 45% by mass of the particles, while the first surface layer contains 45 to 80% by mass of the particles. The inclusion of such a porous resin layer facilitates weight reduction of the carrier tape. Furthermore, the increased porosity provides a space for compressed components such as the resin and particles to escape during shaping, thereby improving shaping properties.

[0015] [Thermoplastic resin contained in the porous resin layer] Because the porous resin layer contains a thermoplastic resin, it not only reduces the generation of paper dust compared to pulp paper, but also offers improved water resistance and reduced dimensional change due to humidity. The thermoplastic resin contained in the porous resin layer is not particularly limited; examples include polyolefin resins such as polyethylene resin and polypropylene resin, polyvinyl chloride resin, polyethylene terephthalate resin, polycarbonate resin, polymethylpentene-1, and cyclic olefins. Further examples of the thermoplastic resin contained in the porous resin layer include mixtures of two or more of the aforementioned thermoplastic resins. Among these, polyolefin resins such as polyethylene resin and polypropylene resin are preferred, and polyethylene resin and polypropylene resin are more preferred, from the perspective described below. The thermoplastic resin is preferably composed solely of polyolefin resins, and more preferably composed solely of polyethylene resin and polypropylene resin.

[0016] The content of the thermoplastic resin in the porous resin layer is preferably 35% by mass or greater, more preferably 40% by mass or greater, and even more preferably 45% by mass or greater. Furthermore, this content is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. A thermoplastic resin content of 35% by mass or greater can reduce paper dust generation and improve water resistance.

[0017] (Polypropylene resin) Since polypropylene resin is used in the porous resin layer, it is preferable because it gives the porous resin layer flexibility and makes it easy to transport the porous resin layer without damaging the electronic components contained therein.

[0018] Specific examples of polypropylene resins include propylene homopolymers such as isotactic homopolypropylene resins and syndiotactic homopolypropylene resins, which are obtained by polymerizing propylene alone; propylene-ethylene copolymers, which are primarily propylene copolymerized with ethylene; propylene-α-olefin copolymers, which are primarily propylene copolymerized with an α-olefin having a carbon number of 4 or greater, such as 1-butene, 1-hexene, 1-heptene, 1-octene, and 4-methyl-1-pentene; and propylene-ethylene-α-olefin copolymers, which are primarily propylene. Propylene copolymers may be binary or ternary or higher-membered, and may be random, block, or reactor-mixed copolymers. More specifically, examples include propylene homopolymers, propylene-ethylene copolymers, propylene-1-butene copolymers, propylene-ethylene-1-butene copolymers, propylene-4-methyl-1-pentene copolymers, propylene-3-methyl-1-pentene copolymers, and propylene-ethylene-3-methyl-1-pentene copolymers. Among these, from the perspective of improving the stretchability and moldability of the porous resin layer, crystalline homopolypropylene resins obtained by polymerizing propylene alone are preferred, and homopolymeric homopolypropylene resins are more preferred.

[0019] Specific examples of polypropylene resins include, depending on their production methods, polypropylene produced using Ziegler-Natta polymerization catalysts, polypropylene produced using metallocene polymerization catalysts (single-site polymerization catalysts), olefin-based thermoplastic elastomers also known as reactor-TPO, and high melt tension polypropylene.

[0020] The melt flow rate (MFR) of the polypropylene resin in accordance with JIS K7210:2014 (temperature 230°C, 2.16 kg load) is preferably 0.2 g / 10 min or higher, more preferably 1 g / 10 min or higher, and even more preferably 2 g / 10 min or higher, from the perspective of improving the mechanical strength of the porous resin layer. Furthermore, it is preferably 20 g / 10 min or lower, more preferably 15 g / 10 min or lower, even more preferably 10 g / 10 min or lower, and particularly preferably 6 g / 10 min or lower.

[0021] When the porous resin layer contains a polypropylene resin, the content is preferably 15% by mass or more, more preferably 25% by mass or more, and even more preferably 35% by mass or more. Furthermore, the content is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less.

[0022] (Polyethylene resin) By using a polyethylene resin in the porous resin layer, stretchability can be imparted to the porous resin layer. Furthermore, polyethylene resin can be used in combination with other thermoplastic resins. This is preferred because it imparts stretchability to the polyethylene resin in addition to the properties of the other thermoplastic resins. For example, a polyethylene resin and a polypropylene resin can be used in combination as the resin components constituting the porous resin layer. Examples of the polyethylene resin that can be used include high-density polyethylene resin, medium-density polyethylene resin, linear low-density polyethylene resin, and copolymers mainly composed of ethylene.

[0023] When the porous resin layer contains polyethylene resin, it preferably contains 1 mass % or more, more preferably 3 mass % or more, and even more preferably 5 mass % or more. It is also preferably 20 mass % or less, more preferably 15 mass % or less, and even more preferably 10 mass % or less.

[0024] When the porous resin layer contains both polypropylene resin and polyethylene resin, the mass ratio (polypropylene resin: polyethylene resin) is preferably 1:99 to 99:1, more preferably 10:90 to 97:3, and even more preferably 65:35 to 95:5 from the perspective of pore formation.

[0025] [Particles contained in the porous resin layer] As will be described later, since both the base layer and the first surface layer contained in the porous resin layer contain particles, the porous resin layer contains particles. By stretching the particle-containing resin composition, a porous resin layer with numerous pores formed within the layer can be easily obtained. The porous resin layer is preferably a porous stretched resin layer containing particles and being stretched. The particle types that can be used are not particularly limited, and examples include organic particles and inorganic particles. Among these, inorganic particles are preferred from the perspective of preventing shape recovery after compression during stamping. Surface-treated particles can also be used.

[0026] Examples of inorganic particles that can be used in the porous resin layer include calcium carbonate, titanium oxide, calcined clay, talc, barium sulfate, aluminum sulfate, silicon dioxide, zinc oxide, magnesium oxide, and diatomaceous earth. By incorporating inorganic particles, a porous resin layer with internal pores can be easily formed. Finely powdered calcium carbonate, clay, or diatomaceous earth are preferred because they can easily form pores and are inexpensive. Finely powdered calcium carbonate is particularly preferred because of its wide variety, making it easy to adjust the porosity and color tone of the porous resin layer.

[0027] The average particle size is preferably 0.05 μm or larger, more preferably 0.1 μm or larger, and even more preferably 0.5 μm or larger. Furthermore, it is preferably 6 μm or smaller, more preferably 4 μm or smaller, and even more preferably 2 μm or smaller. When the average particle size falls within this range, it is easier to control the porosity within the desired range. The average particle size of the particles is a volume average particle size (D50) measured by a particle size distribution analyzer using laser diffraction.

[0028] The content of the particles in the porous resin layer is preferably 25% by mass or more, more preferably 30% by mass or more, and even more preferably 35% by mass or more. Furthermore, it is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. By setting the particle content in the porous resin layer to 25% by mass or greater, it is easier to achieve a high porosity due to pores formed starting from the particles during stretching, and it is easier to achieve a high forming depth corresponding to the size of the electronic components to be accommodated. Furthermore, by setting the particle content to 80% by mass or less, it is easier to maintain flexibility suitable for manufacturing and handling.

[0029] [Other additives that may be contained in the porous resin layer] The porous resin layer may contain additives such as a heat stabilizer (antioxidant), a light stabilizer, a conductive filler, a dispersant, and a lubricant as needed.

[0030] When the porous resin layer contains a thermal stabilizer, it generally contains 0.001 to 1% by mass of the thermal stabilizer. Examples of the thermal stabilizer include sterically hindered phenol-based, phosphorus-based, or amine-based thermal stabilizers. When the porous resin layer contains a light stabilizer, it generally contains 0.001 to 1% by mass of the light stabilizer. Examples of the light stabilizer include sterically hindered amine-based, benzotriazole-based, and benzophenone-based light stabilizers.

[0031] Dispersants or lubricants can be used, for example, to disperse particles. The amount of dispersant or lubricant used in the porous resin layer is generally in the range of 0.01 to 4% by mass. Examples of dispersants or lubricants include silane coupling agents, higher fatty acids such as oleic acid and stearic acid, metal soaps, polyacrylic acid, polymethacrylic acid, and their salts.

[0032] Among these, a dispersant or a lubricant is preferably used because it can suppress the aggregation between particles contained in the porous resin layer, increase the surface area to improve the pore formation efficiency, and easily obtain a porosity corresponding to the content even when a large amount of particles are contained. Furthermore, when a porous resin sheet having a porous resin layer is used as a carrier tape for electronic components, a conductive filler can be used to suppress the adhesion of dust caused by static electricity.

[0033] [Properties of the porous resin layer] (thickness) The thickness of the porous resin layer is 40 to 350 μm. Preferably, the thickness is 80 μm or greater, more preferably 100 μm or greater, and even more preferably 120 μm or greater. Furthermore, the thickness is preferably 300 μm or less, more preferably 250 μm or less, and even more preferably 225 μm or less. The thickness of the porous resin layer can be appropriately changed within the above range according to the size of the items contained in the shaped pouch, etc.

[0034] If the thickness of the porous resin layer is less than 40 μm, it becomes difficult to ensure sufficient depth to be shaped to the size of the accommodated parts. On the other hand, if the thickness of the porous resin layer exceeds 350 μm, it becomes difficult to maintain the flexibility suitable for manufacturing and handling.

[0035] The term "thickness" of a layer in this specification refers to the value measured in accordance with JIS K7130:1999. If the porous resin layer has a multilayer laminate structure, the thickness of the multilayer structure is determined by measuring the thickness of all the layers. The thickness of each layer in the multilayer laminate structure is determined by observing a cross-section of the multilayer laminate structure using an electron microscope, identifying the interfaces between the layers based on their appearance, and calculating the thickness ratio of each layer. This is then calculated from the measured thickness of the multilayer laminate structure and the thickness ratio of each layer.

[0036] (Porosity) The porosity of the porous resin layer is 35-80%. The porosity is preferably 40% or greater, more preferably 45% or greater. Furthermore, the porosity is preferably 70% or less, more preferably 60% or less. In addition, the "porosity" of a layer in this specification refers to the ratio of the volume occupied by pores in the layer to the volume of the layer (volume fraction).

[0037] If the porosity is less than 35%, the porous resin layer may not be able to adequately conform to the shape formed without special steps such as heating or decompression. For example, when attempting to form a shape such as a pouch with sides perpendicular to the surface of the porous resin sheet and a bottom parallel to the surface of the porous resin layer, this can easily lead to forming defects such as tapered sides or undulations at the bottom. A porosity of 35% or higher facilitates deeper shaping without special steps such as heating or decompression. On the other hand, a porosity exceeding 80% may not provide sufficient mechanical strength. In addition, the so-called "conformability" described in this specification refers to the property that a resin deformed by shaping does not try to restore its state before shaping by rebounding, but stably maintains its shape after shaping.

[0038] As a method for adjusting the porosity of the porous resin layer, for example, there can be cited a method of adjusting the porosity of the entire porous resin layer by adjusting the porosity of each of the base layer, the first surface layer, and / or the second surface layer described below.

[0039] The porosity of the porous resin layer can be determined by any method, but for example, by observing a cross-section of the porous resin layer with an electron microscope and calculating the ratio of the area occupied by pores in the porous resin layer (area ratio) within the observed region of the resulting cross-sectional photograph. If the porous resin layer has a multilayer structure, the porosity of the entire porous resin layer can be determined by calculating the porosity of each layer and averaging the porosities weighted by their thickness.

[0040] [Layer structure of porous resin layer] The porous resin layer may consist solely of a base layer and a first surface layer, or may consist of three or more layers. When the porous resin layer consists of three or more layers, for example, the porous resin layer may include a second surface layer in addition to the base layer and first surface layer described below.

[0041] As a cross section in the lamination direction of the first embodiment of the porous resin layer, the embodiment shown in FIG1 can be cited. In FIG1 , the porous resin layer 10 is composed only of a base material layer 1 and a first surface layer 2 . As an example of a cross-section in the lamination direction of a second embodiment of a porous resin layer, the embodiment shown in FIG2 can be cited. In FIG2 , the porous resin layer 10 is composed of a base layer 1, a first surface layer 2, and a second surface layer 3. Here, the second surface layer 3 is provided on the surface of the base layer 1 opposite to the first surface layer 2. In addition, the drawings shown in this specification are intended to schematically illustrate the positional relationships of the layers, bags, etc., and are not intended to indicate the exact dimensions such as the thickness or width of the layers, the size of the bags, etc.

[0042] The porous resin layer is not limited to the above-described aspects. For example, an additional layer may be included between the substrate layer and the first and / or second surface layers. When the porous resin layer includes an additional layer, the additional layer is not particularly limited as long as it has a porous structure. For example, the porosity of the additional layer may be 10% or greater.

[0043] <Base Material Layer> The porous resin layer of the porous resin sheet of the present invention includes a substrate layer. The substrate layer not only provides the porous resin sheet with the mechanical strength necessary for transportation, but also provides space for forming a pouch, etc., when the porous resin sheet is shaped into a pouch for housing electronic components. When forming a pouch, etc., on a porous resin sheet, it is preferred that the pouch, etc., does not penetrate the base layer. Furthermore, it is preferred that, of the two interfaces of the base layer, the position of the interface opposite to the interface pressed down to form the pouch, etc., does not change before and after the pouch, etc., is formed.

[0044] [Materials constituting the base material layer] The substrate layer comprises a thermoplastic resin and particles. Unless otherwise specified, the materials constituting the substrate layer can be the same as those described for the porous resin layer, and the preferred ranges are also the same.

[0045] (Thermoplastic resin) The substrate layer comprises a thermoplastic resin. Unless otherwise specified, the preferred range of the thermoplastic resin is the same as that described for the porous resin layer.

[0046] The content of the thermoplastic resin in the substrate layer is preferably 35% by mass or greater, more preferably 40% by mass or greater, even more preferably 45% by mass or greater, particularly preferably 50% by mass or greater, and most preferably 55% by mass or greater. Furthermore, the content is preferably 85% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, and particularly preferably 70% by mass or less.

[0047] (particle) The substrate layer includes particles. The preferred range of the particles is the same as that described for the porous resin layer unless otherwise specified.

[0048] The substrate layer contains 20% by mass or more of particles, preferably 25% by mass or more, and more preferably 30% by mass or more. Furthermore, it preferably contains 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less. If the particle content in the substrate layer is less than 20% by mass, the amount of pores formed by stretching is reduced, making it difficult to achieve a high forming depth corresponding to the size of the electronic components to be accommodated. Furthermore, if the particle content exceeds 45% by mass, it becomes difficult to maintain flexibility suitable for manufacturing and handling. In particular, it is preferred that the content of the inorganic particles is 45% by mass or less because compression of the porous resin layer due to shaping is easily generated and shaping depth is easily obtained.

[0049] [Properties of the substrate layer] (thickness) The thickness of the substrate layer is preferably 35 μm or greater, more preferably 70 μm or greater, even more preferably 90 μm or greater, and particularly preferably 110 μm or greater. Furthermore, the thickness is preferably 300 μm or less, more preferably 250 μm or less, even more preferably 200 μm or less, and particularly preferably 190 μm or less. Furthermore, the thickness of the substrate layer is preferably greater than the thickness of both the first surface layer and the second surface layer described below.

[0050] A base material layer thickness of 35 μm or greater is preferred because it easily achieves sufficient depth for shaping the size of the received component. A thickness of 300 μm or less is preferred because it easily maintains flexibility suitable for manufacturing and handling.

[0051] The thickness of the base material layer can be measured by the same method as that for measuring the thickness of the porous resin layer.

[0052] (Porosity) The porosity of the substrate layer is preferably 35% or more, more preferably 40% or more, and even more preferably 45% or more. Furthermore, the porosity is preferably 80% or less, more preferably 70% or less, and even more preferably 60% or less.

[0053] A base material layer porosity of 35% or greater is preferred, as it allows for sufficient conformability to the shape even when forming a deep shape, and facilitates stabilization of the bottom and side shapes. Furthermore, a porosity of 80% or less is preferred, as it facilitates mechanical strength of the porous resin sheet.

[0054] The porosity of the substrate layer can be adjusted by adjusting the content of particles in the substrate layer, the average particle size, the composition of the thermoplastic resin, and the stretching conditions.

[0055] The porosity of the base material layer can be measured by the same method as that of the porous resin layer.

[0056] (extend) The substrate layer is preferably stretched, more preferably biaxially stretched. Because the substrate layer contains particles, pores can be easily created in the substrate layer through stretching. Biaxial stretching is preferred because it allows for a high porosity while minimizing the particle content. This facilitates shape stabilization even when creating deep shapes. Furthermore, because biaxial stretching imparts rigidity, even with a porous structure, problems associated with handling and other processes are less likely to occur, making this a preferred method.

[0057] <First Surface Layer> The porous resin sheet of the present invention comprises a porous resin layer comprising a first surface layer. The first surface layer is the outermost layer of the porous resin layer and is located on the side where the shape of the pouch, etc., of the carrier tape is formed. By having a first surface layer containing a high particle content in the porous resin sheet, the side of the pouch, etc., can be prevented from tapering during forming.

[0058] [Material constituting the first surface layer] The first surface layer contains a thermoplastic resin and particles. Unless otherwise specified, the materials constituting the first surface layer can be the same as those described for the porous resin layer, and the preferred ranges are also the same.

[0059] (Thermoplastic resin) The first surface layer comprises a thermoplastic resin. Unless otherwise specified, the preferred range of the thermoplastic resin is the same as that described for the porous resin layer.

[0060] The content of the thermoplastic resin in the first surface layer is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. Furthermore, it is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less.

[0061] Setting the thermoplastic resin content in the first surface layer to 10% by mass or more is preferred because it easily suppresses breakage during molding. Setting the thermoplastic resin content to 50% by mass or less is also preferred because it suppresses springback during molding caused by the resin. This facilitates the creation of opportunities for deformation of the porous resin sheet due to breakage, prevents the sides of the porous resin sheet from becoming tapered during molding, and stabilizes the bottom shape, making it preferred.

[0062] (particle) The first surface layer includes particles. The preferred range of the particles is the same as that described for the porous resin layer unless otherwise specified.

[0063] The first surface layer contains 45% by mass or more of particles, preferably 50% by mass or more, and more preferably 55% by mass or more. Furthermore, it preferably contains 80% by mass or less, 75% by mass or less, more preferably 70% by mass or less, and even more preferably 65% ​​by mass or less.

[0064] If the particle content in the first surface layer is less than 45% by mass, it becomes difficult to control the shape of the sides and bottom when forming into a shape such as a pouch. In contrast, if the particle content in the first surface layer is 45% by mass or greater, for example, when forming a pouch having sides perpendicular to the surface of the porous resin sheet and a bottom parallel to the surface, the tapered shape of the sides is suppressed during forming, while the shape of the bottom is more likely to be stabilized. This is because the interface between particles or between particles and the thermoplastic resin at the boundary between the portion pressed by the forming mold and the portion not pressed is more likely to fracture than between thermoplastic resins. Inorganic particles are preferred because this tendency becomes more pronounced in the shape of the sides and bottom during forming, making this more desirable. Furthermore, if the particle content exceeds 80% by mass, the sheet is likely to break during forming.

[0065] [Properties of the first surface layer] (thickness) The thickness of the first surface layer is preferably 5 μm or greater, more preferably 10 μm or greater, even more preferably 13 μm or greater, particularly preferably 15 μm or greater, and most preferably 18 μm or greater. Furthermore, the thickness is preferably 50 μm or less, more preferably 40 μm or less, even more preferably 35 μm or less, particularly preferably 30 μm or less, and most preferably 25 μm or less.

[0066] A first surface layer thickness of 5 μm or greater is preferred because deformation of the bottom portion of the bag, etc., formed by compression by the mold during shaping, including the first surface layer and a portion of the base layer, is averaged. This stabilizes the shape of the bottom portion of the bag, etc., and the shape is easily stabilized during shaping. Furthermore, a thickness of 50 μm or less is preferred because it facilitates shaping of deeper shapes.

[0067] The thickness of the first surface layer can be measured using the same method as that used to measure the thickness of the porous resin layer.

[0068] The thickness ratio of the first surface layer to the thickness of the base layer is preferably 0.03 or more, more preferably 0.05 or more, and even more preferably 0.07 or more. Furthermore, the thickness ratio is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0.2 or less.

[0069] A thickness ratio of the first surface layer to the base layer of 0.03 or greater is preferred because it reduces the risk of springback caused by the resin during shaping and stabilizes the shape. Furthermore, a thickness ratio of 0.5 or less is preferred because it facilitates deep shaping.

[0070] (Porosity) The porosity of the first surface layer is preferably 35% or more, more preferably 40% or more, and even more preferably 45% or more. Furthermore, the porosity is preferably 80% or less, more preferably 70% or less, and even more preferably 60% or less.

[0071] A porosity of 35% or greater in the first surface layer is preferred, as it allows for sufficient conformability to the shape even when forming a deep shape, and facilitates stabilization of the bottom and side shapes. Furthermore, a porosity of 80% or less is preferred, as it facilitates mechanical strength of the sheet.

[0072] The porosity of the first surface layer can be adjusted by adjusting the content of particles in the first surface layer, the average particle size, the composition of the thermoplastic resin, and the stretching conditions.

[0073] The porosity of the first surface layer can be measured using the same method as that used for the porous resin layer.

[0074] The porosity ratio of the first surface layer to the porosity of the base layer is preferably 0.80 or greater, more preferably 0.85 or greater, and even more preferably 0.90 or greater. Furthermore, the porosity ratio is preferably 1.20 or less, more preferably 1.15 or less, and even more preferably 1.10 or less.

[0075] By setting the ratio of the porosity of the first surface layer to the porosity of the substrate layer within this range, the difference between the shape of the surface layer formed by shaping and the shape of the substrate layer can be suppressed. Moreover, when shaping is intended to form a shape such as a bag having sides perpendicular to the surface of the porous resin sheet and a bottom parallel thereto, the shape of the side of the bag can be suppressed from becoming conical, which is better.

[0076] (extend) The first surface layer is preferably stretched, more preferably uniaxially stretched. Because the resin chains are aligned in the stretching direction, they are easily broken along the stretching direction during shaping. Furthermore, shaping along the stretching direction stabilizes the shape formed, making this preferred. Furthermore, since the first surface layer contains particles, uniaxial stretching of the first surface layer creates long pores in the stretching direction. This makes it easier to break along the stretching direction during shaping, and stabilizes the shape formed by shaping along the stretching direction, making this advantageous. This is particularly advantageous when shaping into a shape such as a pouch having a longitudinal direction parallel to the stretching direction, as pores extending in the stretching direction easily accommodate the shaping.

[0077] In this specification, the term "long side direction of a bag, etc." refers to the direction along the long axis of a bag, etc., of any shape with a non-1:1 aspect ratio. Furthermore, the term "short side direction of a bag, etc." refers to the direction along the short axis of a bag, etc., of any shape with a non-1:1 aspect ratio.

[0078] Since both the first surface layer and the substrate layer contain particles, it is preferred that the first surface layer be uniaxially stretched and the substrate layer be biaxially stretched. This allows the first surface layer to be a porous uniaxially stretched resin layer and the substrate layer to be a porous biaxially stretched resin layer.

[0079] By setting such a layer structure, when the shape of a bag having sides perpendicular to the surface of the porous resin sheet and a bottom parallel to the bag is to be formed, it is preferable to prevent the side of the bag from becoming conical or causing undulations at the bottom.

[0080] The porous resin layer in which the first surface layer is a porous uniaxially stretched resin layer and the base layer is a porous biaxially stretched resin layer can be manufactured, for example, through the following steps. Step 1: A porous uniaxially stretched resin layer is obtained by uniaxially stretching a resin sheet for forming a base layer. Step 2: The resin sheet for forming the first surface layer is laminated on the porous uniaxially stretched resin layer obtained in step 1 to obtain a laminated sheet. Step 3: By uniaxially stretching the laminated sheet obtained in step 2 in a direction perpendicular to the stretching direction of step 1, a porous resin layer is obtained in which the first surface layer is a porous uniaxially stretched resin layer and the base material layer is a porous biaxially stretched resin layer.

[0081] <Second Surface Layer> The porous resin layer of the porous resin sheet of the present invention may further include a second surface layer on the surface of the base material layer opposite the first surface layer. The second surface layer is the outermost layer of the porous resin layer. When a shape such as a pouch is formed on the porous resin sheet of the present invention, the second surface layer is located on the opposite side of the surface where the shape is formed. The porous resin layer preferably includes the second surface layer because the bottom of the shaped shape can be stabilized.

[0082] [Material constituting the second surface layer] Unless otherwise specified, the material constituting the second surface layer may be the same as that described for the porous resin layer, and the preferred range is also the same.

[0083] (particle) The second surface layer may contain particles. The preferred range of particles is the same as that described for the porous resin layer unless otherwise specified.

[0084] When the second surface layer contains particles, the content is preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, and particularly preferably 55% by mass or more. Furthermore, the content is preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 70% by mass or less, and particularly preferably 65% ​​by mass or less. Setting the particle content in the second surface layer to 40% by mass or more is preferred because it facilitates the development of pores by stretching. Setting the particle content to 80% by mass or less is also preferred because it maintains the film's breaking strength.

[0085] [Properties of the second surface layer] (thickness) The thickness of the second surface layer is preferably 5 μm or more, more preferably 7 μm or more, and even more preferably 10 μm or more. Furthermore, the thickness is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less.

[0086] The second surface layer having a thickness of 5 μm or more is preferably a receiving layer for the compressed first surface layer and the base material layer of the stamping shaping portion.

[0087] The thickness of the second surface layer can be measured by the same method as that for the porous resin layer.

[0088] (Porosity) The porosity of the second surface layer is preferably 35% or more, more preferably 40% or more, and even more preferably 45% or more. Furthermore, the porosity is preferably 80% or less, more preferably 70% or less, and even more preferably 60% or less.

[0089] A second surface layer with a porosity of 35% or greater is preferred, as it allows for sufficient conformability to the shape even when a deep shape is applied, and facilitates stabilization of the bottom and side shapes. Furthermore, a porosity of 80% or less is preferred, as it facilitates mechanical strength of the porous resin sheet.

[0090] The porosity of the second surface layer can be adjusted by adjusting the content, average particle size, thermoplastic resin composition, and stretching conditions of the particles in the first surface layer.

[0091] The porosity of the second surface layer can be measured using the same method as that used for the porous resin layer.

[0092] (extend) The second surface layer is preferably stretched, more preferably uniaxially stretched. By uniaxially stretching the second surface layer, the mechanical strength in the uniaxial direction is improved, thereby making it easier to obtain shape stability after forming a shape such as a pouch, which is preferred.

[0093] The porous resin layer in which the first surface layer and the second surface layer are porous uniaxially stretched resin layers and the base layer is a porous biaxially stretched resin layer can be manufactured, for example, through the following steps. Step 1: A porous uniaxially stretched resin layer is obtained by uniaxially stretching a resin sheet for forming a base layer. Step 2: The resin sheet for forming the first surface layer is laminated on the porous uniaxially stretched resin layer obtained in step 1, and then the resin sheet for forming the second surface layer is laminated on the surface of the porous uniaxially stretched resin layer on the opposite side of the resin sheet for forming the first surface layer to obtain a laminated sheet. Step 3: By uniaxially stretching the laminated sheet obtained in step 2 in a direction perpendicular to the stretching direction of step 1, a porous resin layer is obtained in which the first surface layer and the second surface layer are porous uniaxially stretched resin layers and the base material layer is a porous biaxially stretched resin layer.

[0094] (Method for Manufacturing Porous Resin Layer, Base Material Layer, First Surface Layer, and Second Surface Layer) The method for producing the porous resin layer, as well as the base layer, first surface layer, and second surface layer, is not particularly limited and can be produced by general methods. For example, casting, calendering, calendaring, or inflation molding, in which molten resin is extruded into a sheet using a T-die or I-die connected to a screw-type extruder, can be used. When producing a porous resin layer having a multi-layer laminated structure, the base layer, first surface layer, and / or second surface layer can be produced separately and then laminated using a lamination method. Alternatively, film formation and lamination of each layer can be performed simultaneously using general techniques such as a multi-layer die method using a feedblock or a multi-manifold, or an extrusion and lamination method using multiple dies.

[0095] A porous resin sheet can be manufactured by laminating a porous resin layer and other layers as needed. When the porous resin layer, substrate layer, first surface layer, and / or second surface layer are stretched, the substrate layer may be stretched before laminating the first surface layer and / or second surface layer, or after laminating the first surface layer and / or second surface layer. In one embodiment, the porous resin layer may be produced by the above-described steps, wherein the first surface layer and / or second surface layer is a porous uniaxially stretched resin layer, and the substrate layer is a porous biaxially stretched resin layer.

[0096] Examples of stretching methods include longitudinal stretching using a differential peripheral speed of a roll group, transverse stretching using a tenter oven, sequential biaxial stretching methods combining these methods, calendaring, simultaneous biaxial stretching using a combination of a tenter oven and a pantograph, and simultaneous biaxial stretching using a combination of a tenter oven and a linear motor. Furthermore, simultaneous biaxial stretching (inflation molding) methods can also be used, in which a molten resin is extruded into a tube using a circular die connected to a screw extruder and then air is blown into the tube.

[0097] Among these, it is preferred to produce the porous resin layer, base layer, first surface layer, and second surface layer by extruding the resin composition into a sheet through a T-die connected to an extruder and then stretching the sheet, as this facilitates multi-layering and adjusting the film thickness. Examples of stretching methods include longitudinal stretching, transverse stretching, sequential biaxial stretching combining these methods, and simultaneous biaxial stretching.

[0098] When the thermoplastic resin used is amorphous, the stretching temperature is preferably above the glass transition temperature of the thermoplastic resin. Furthermore, when the thermoplastic resin is crystalline, the stretching temperature is preferably above the glass transition temperature of the amorphous portion of the thermoplastic resin and below the melting point of the crystalline portion of the thermoplastic resin, preferably 2-60°C lower than the melting point of the thermoplastic resin. Specifically, for propylene homopolymer (melting point 155-167°C), a stretching temperature of 100-164°C is preferred, while for high-density polyethylene resin (melting point 121-134°C), a stretching temperature of 70-133°C is preferred. In particular, from the perspective of achieving higher porosity, when the thermoplastic resin is crystalline, the stretching temperature is preferably at least 20°C lower than the melting point of the thermoplastic resin, and more preferably at least 25°C lower. Furthermore, the stretching temperature can be set based on the glass transition temperature or melting point of the thermoplastic resin used mainly (for example, the thermoplastic resin used in an amount of 50% by mass or more in the entire thermoplastic resin).

[0099] The stretching speed is not particularly limited, but is preferably within the range of 20 to 350 m / min from the perspective of stable stretching and forming.

[0100] Furthermore, the stretching ratio can be appropriately determined by considering the properties of the thermoplastic resin used. For example, when using a propylene homopolymer or propylene copolymer, the stretching ratio when stretched in one direction is generally at least 1.1 times, preferably at least 2 times, and the upper limit is 10 times or less, preferably 9 times or less. On the other hand, the stretching ratio when biaxially stretched is generally at least 1.5 times, preferably at least 4 times, and the upper limit is 75 times or less, preferably 50 times or less, as measured by the area stretching ratio. When stretching other thermoplastic resin films in one direction, the stretching ratio is generally at least 1.2 times, preferably at least 2 times, and the upper limit is 10 times or less, preferably 5 times or less. The stretching ratio when biaxially stretched is generally at least 1.5 times, preferably at least 4 times, as measured by the area stretching ratio, and the upper limit is 20 times or less, preferably 12 times or less. Within the aforementioned stretching ratio range, the target porosity and basis weight are easily achieved, and opacity is easily enhanced. Furthermore, film breakage is less likely to occur, and stretching and forming are easily stabilized. If the pores in the porous resin layer are formed by stretching with particles as the starting point, in order to achieve a high porosity in the porous resin layer, the stretching ratio, stretching temperature, and particle content preferably all meet the aforementioned specific conditions.

[0101] <Porous resin sheet> The porous resin sheet of the present invention includes the above-mentioned porous resin layer.

[0102] [Properties of porous resin sheet] (Breaking Strength) The porous resin sheet preferably has a breaking strength in the width direction of 0.1 kgf / mm² or greater, more preferably 1.0 kgf / mm² or greater, and even more preferably 2.0 kgf / mm² or greater. Furthermore, the breaking strength in the width direction is preferably 10 kgf / mm² or less, more preferably 8 kgf / mm² or less, and even more preferably 6 kgf / mm² or less. Here, the "breaking strength of the porous resin sheet in the width direction" refers to the breaking strength measured by stretching the porous resin sheet in the width direction (TD direction). Breaking strength can be measured, for example, in accordance with JIS-K7127:1999.

[0103] A porous resin sheet with a breaking strength of 0.1 kgf / mm² or greater in the width direction is preferred for maintaining the film's shape during transport. Furthermore, a breaking strength of 10 kgf / mm² or less in the width direction is preferred for maintaining the film's shape during punching.

[0104] In order to increase the number of pouches per unit length of the carrier tape, the pouches are generally formed so that the longitudinal direction of the pouches is parallel to the width direction of the carrier tape. To this end, the porous resin sheet is preferably designed to have the above-mentioned breaking strength in the width direction. Furthermore, when the long side direction of the bag or the like is formed in parallel with the longitudinal direction of the carrier tape, the longitudinal direction of the porous resin sheet can also be designed to have the above-mentioned breaking strength.

[0105] [use] The porous resin sheet of the present invention has suitable properties for forming a carrier tape. Therefore, the porous resin sheet of the present invention is preferably used for a carrier tape.

[0106] For example, a carrier tape may be provided, which comprises the aforementioned porous resin sheet and a pouch formed on the porous resin sheet. The pouch may have a size, for example, of 0.1 mm x 0.1 mm to 3 mm x 3 mm in length x width.

[0107] Figure 4 illustrates a cross-section of a carrier tape using one embodiment of the porous resin sheet of the present invention, taken along the direction of pouch lamination. As shown in Figure 4 , the pouch 4 preferably does not penetrate the substrate layer 1. Furthermore, of the two interfaces 1a and 1b of the substrate layer 1, the position of the interface 1b opposite to the interface 1a pressed down to shape the pouch 4 preferably remains unchanged before and after the pouch 4 is formed. Furthermore, the interface 1a on the side of the carrier tape where the pouch, etc., is shaped preferably remains linear or substantially linear in a cross-section through the carrier tape.

[0108] The carrier tape using the porous resin sheet of the present invention may further include other necessary components, such as a cover tape.

[0109] The carrier tape formed of the porous resin sheet of the present invention can be suitably used as a carrier tape for storing components. Examples of the components include electronic components.

[0110] <Shaping Method of Porous Resin Sheet> The method for shaping the porous resin sheet into a pouch or similar shape is not particularly limited, and examples thereof include compressed air forming, stamping, and vacuum spin forming. Among these, stamping at room temperature is preferred for shaping the porous resin sheet from the perspective of cost.

[0111] The shape of the porous resin sheet is selected according to the shape of the component to be accommodated, and is not particularly limited. For example, a cylindrical shape, a rectangular prism shape, and the like can be mentioned. [Example]

[0112] The present invention is described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0113] <Resin Composition> The materials and blending ratios of the resin compositions used in the Examples and Comparative Examples are shown in Table 1.

[0114] [Table 1]

[0115] <Porous resin sheet> [Example 1] Resin composition A was mixed and kneaded in an extruder set at 230°C, then supplied to an extrusion die set at 250°C and extruded into a sheet. This sheet was then cooled using a cooling device to produce an unstretched sheet. This unstretched sheet was heated to 130°C and stretched four times in the vertical direction (longitudinal direction) using a plurality of rolls with varying peripheral speeds to produce a four-fold stretched film. Next, resin composition C was mixed and kneaded in an extruder set at 250°C, then supplied to an extrusion die set at 250°C and extruded into a sheet. This sheet was then laminated onto the surface of the four-fold stretched film to produce a two-layer laminated film. Next, the laminated film was cooled to 60°C and heated again to approximately 140°C in a tenter oven. After being stretched eight times in the horizontal direction (width direction), it was bonded in an oven adjusted to 160°C. After cooling to 60°C, the ears were cut open to obtain a porous resin sheet with a two-layer structure (first surface layer / base material layer; composition: resin composition C / resin composition A, porosity: 40.0% / 49.0%, thickness: 15μm / 185μm, stretching: uniaxial / biaxial) with a total thickness of 200μm and a porosity of 48.3%.

[0116] Furthermore, the properties of the obtained porous resin sheet were measured in the following manner. (Total thickness) The overall thickness (μm) of the porous resin sheet was measured using a constant pressure thickness gauge (machine name: PG-01J, manufactured by Teclock) based on JIS K7130:1999 "Plastics - Film and Sheeting - Determination of Thickness".

[0117] (Thickness of each layer) The thickness (μm) of each layer in the multilayer laminate structure was measured as follows. A porous resin sheet was cooled to below -60°C with liquid nitrogen and cut with a razor blade (trade name: Proline Blade, manufactured by Shick Japan) at a perpendicular angle to the sample placed on a glass plate to prepare a sample for cross-sectional measurement. The resulting sample cross section was observed using a scanning electron microscope (JSM-6490, manufactured by JEOL Ltd.). The boundary lines between the layers were identified based on the composition and appearance, and the thickness ratio of each layer in the porous resin sheet was calculated. The thickness of each layer was calculated by multiplying the total thickness measured above by the thickness ratio of each layer.

[0118] (Determination of porosity) The porosity (%) of each layer in the multilayer laminate structure was measured as follows. A random portion of a porous resin sheet is cut out, embedded in epoxy resin, and cured. The sheet is then cut perpendicularly to the plane and the TD direction of the porous resin sheet using a microtome. The cut surface is then attached to an observation sample stage so that the observation surface is the observation surface. Gold or gold-palladium is vapor-deposited onto the observation surface. The cut surface of the porous resin sheet is observed using a scanning electron microscope at a convenient magnification (e.g., 500x to 3000x), and image data of the observed area is collected. The obtained image data is processed using an image analyzer to determine the area ratio (%) of the pores in each layer of the porous resin sheet. The average of the area ratios (%) determined at at least 10 random locations is used as the porosity (%) of each layer. The porosity of the entire layer is obtained by taking the average value of the porosity of each layer weighted by its thickness.

[0119] [Example 2], [Comparative Example 1], [Comparative Example 4] The porous resin sheets of Example 2, Comparative Example 1 and Comparative Example 4 were obtained by the same method as Example 1, except that the resin composition, thickness of each layer and porosity of each layer were changed as shown in Table 2 or Table 3.

[0120] [Example 3] The porous resin sheet of Example 3 was obtained by the same method as Example 1 except that the horizontal stretching temperature (temperature of the tenter oven) was changed to 145°C.

[0121] [Example 4] A porous resin sheet of Example 4 was obtained by the same method as Example 1 except that the temperature for stretching in the vertical direction was changed to 140°C.

[0122] [Comparative Example 2] A porous resin sheet of Comparative Example 2 was obtained by the same method as in Example 2 except that the temperature for stretching in the vertical direction was changed to 145°C.

[0123] [Table 2]

[0124] [Example 5] The porous resin sheet of Example 5 was obtained by the same method as in Example 1, except that the resin composition was changed as shown in Table 3 and the horizontal stretching temperature (temperature of the tenter oven) was changed to 135°C.

[0125] [Comparative Example 3] Resin composition B was mixed and kneaded in an extruder set at 230°C, then fed to a feedblock multilayer die set at 250°C and extruded into a sheet. This sheet was then cooled in a cooling device to produce an unstretched sheet. This unstretched sheet was then heated to 135°C and stretched 4x in the vertical direction to produce a 4x stretched film. This 4x stretched film was then cooled to 60°C and heated again to approximately 135°C in a tenter oven. It was stretched 8x in the horizontal direction and then bonded in an oven set at 160°C. After cooling to 60°C, the tabs were cut open to produce a porous resin sheet with a total thickness of 200 μm and a porosity of 50.0%, as shown in Figure 3 (substrate layer; composition: resin composition B, porosity: 50.0%, thickness: 200 μm, stretching: biaxial).

[0126] [Example 6] Resin composition A was mixed and kneaded in an extruder set at 230°C, then supplied to an extrusion die set at 250°C and extruded into a sheet. This sheet was then cooled using a cooling device to produce an unstretched sheet. This unstretched sheet was heated to 135°C and stretched four times in the vertical direction using a plurality of rolls with varying peripheral speeds to produce a four-fold stretched film. Next, resin composition C was mixed and kneaded in an extruder set at 250°C, then supplied to an extrusion die set at 250°C and extruded into a sheet. This sheet was then laminated onto the front and back surfaces of the four-fold stretched film, producing a three-layer laminated film. Next, the laminated film was cooled to 60°C and reheated to approximately 135°C in a tenter oven. After being stretched eight times in the horizontal direction, it was bonded in an oven adjusted to 160°C. After cooling to 60°C, the ears were cut open to obtain a porous resin sheet with a three-layer structure (first surface layer / base material layer / second surface layer; composition: resin composition C / resin composition A / resin composition C, porosity: 40.0% / 50.0% / 40.0%, thickness: 15μm / 170μm / 15μm, stretching: uniaxial / biaxial / uniaxial) with a total thickness of 200μm and a porosity of 49.2%.

[0127] [Example 7] The porous resin sheet of Example 7 was obtained by the same method as Example 1, except that the resin composition A and the resin composition C were extruded into sheets so that the thickness of the base layer became 190 μm and the thickness of the first surface layer became 10 μm.

[0128] [Example 8] The porous resin sheet of Example 8 was obtained by the same method as Example 1, except that the resin composition A and the resin composition C were extruded into sheets so that the thickness of the base layer became 195 μm and the thickness of the first surface layer became 5 μm.

[0129] [Example 9] The porous resin sheet of Example 9 was obtained by the same method as in Example 1, except that the resin composition was changed as shown in Table 3 and the horizontal stretching temperature (temperature of the tenter oven) was changed to 150°C.

[0130] [Example 10] The porous resin sheet of Example 3 was obtained by the same method as Example 1 except that the horizontal stretching temperature (temperature of the tenter oven) was changed to 130°C.

[0131] [Table 3]

[0132] <Evaluation of porous resin sheet> The porous resin sheets obtained in the above examples and comparative examples were evaluated in the following manner. The results are shown in Tables 4 and 5.

[0133] [Breaking strength] The stress at break in the width direction of the sheet was measured according to JIS-K7127:1999 (Plastics - Test methods for tensile properties). Test piece size: 15mm × 150mm Tensile speed: 300mm / min. The same sample was measured three times and the average value was calculated.

[0134] [Shapeability] Using a metal plate for pattern indentation (top: 400μm x 200μm rectangular, blade angle: 90°) manufactured by Tsukaya Hatmono Co., Ltd., and a press machine (Mini Test Press manufactured by Toyo Seiki Co., Ltd.), the porous resin sheets obtained in the above-described Examples and Comparative Examples were pressed at 1 MPa / 10 sec. / room temperature, with the first surface layer facing the substrate layer. This produced a pouch-like shape with a length of 400μm, a width of 200μm, and a depth of 90% of the sheet thickness. A cross-section of this pouch-like portion was cut with a razor blade, and the cross-sectional shape was observed using an electron microscope (HRX-01 manufactured by HIROX Co., Ltd.). Evaluation was then performed as follows.

[0135] (depth) Evaluation was performed in the following manner. A: Very good The depth can reach more than 30μm, and the depth can be more than 85% and less than 90% of the sheet thickness. B: Good The depth can reach more than 30μm, and the depth can be more than 80% and less than 85% of the sheet thickness. C: No problem The depth can reach more than 30μm, and the depth can be more than 75% and less than 80% of the sheet thickness. D: Bad It can reach a depth of more than 30μm, but cannot be shaped at a depth exceeding 75% of the sheet thickness. E: Extremely bad Unable to reach a depth of more than 30μm

[0136] (Suppression cone) Evaluation was performed in the following manner. A: Very good The angle between the bottom and the side is more than 85° B: Good The angle between the bottom and the side is more than 80° but less than 85° C: No problem The angle between the bottom and the side is greater than 75° and less than 80° D: Bad The angle between the bottom and the side is greater than 60° and less than 75° E: Extremely bad The angle between the bottom and the side is less than 60°

[0137] (Bottom stability) Measure the distance from the bottom of the shaped pouch to the surface opposite the first surface layer of the porous resin sheet from the cross-sectional image. Record the maximum and minimum values ​​of this distance for 10 pouches, and calculate the average of the differences. Based on the average value, evaluate the bottom stability as follows. A: Very good (average value is less than 1 μm) B: Good (average value is more than 1 μm and less than 3 μm) C: No problem (average value is more than 3μm and less than 5μm) D: Defective (average value exceeds 5μm and is less than 10μm) E: Extremely poor (average value exceeds 10μm)

[0138] [Table 4]

[0139] [Table 5]

[0140] Examples 1-10 demonstrate that the porous resin sheet of the present invention exhibits excellent breaking strength and formability even when the balance of thickness, porosity, stretching pattern, and layer structure are varied within specific ranges. Furthermore, Examples 1, 7, and 8 demonstrate that increasing the thickness of the first surface layer improves bottom stability. Furthermore, Examples 9 and 10 demonstrate that increasing the particle content in the first surface layer and / or lowering the stretching temperature of the first surface layer can increase the porosity of the first surface layer, thereby improving formability. In contrast, the porous resin sheet of Comparative Example 1 was insufficiently thick throughout the sheet, making it impossible to achieve sufficient depth. The porous resin sheet of Comparative Example 2 had low porosity throughout the sheet, resulting in poor shapeability from the perspective of suppressing the taper shape and maintaining bottom stability. The porous resin sheet of Comparative Example 3 consisted solely of a base material layer, resulting in poor shapeability from the perspective of suppressing the taper shape. The porous resin sheet of Comparative Example 4 had insufficient particle content in the first surface layer, resulting in poor shapeability from the perspective of suppressing the taper shape and maintaining bottom stability.

[0141] While various embodiments have been described above with reference to the accompanying drawings, the present invention is not limited to these examples. Those skilled in the art will readily appreciate that various modifications and variations are readily conceivable within the scope of the claims, and these variations and modifications are naturally within the technical scope of the present invention. Furthermore, the components of the above embodiments may be arbitrarily combined without departing from the spirit of the invention.

[0142] In addition, this application is based on the Japanese patent application (Japanese Patent Application No. 2022-102194) filed on June 24, 2022, the contents of which are incorporated herein by reference. [Industrial Applicability]

[0143] The porous resin sheet of the present invention can be suitably used as a porous resin sheet for a carrier tape, for example.

[0144] 1: Base material layer 2: First surface layer 3: Second surface layer 4: sac 10: Porous resin layer

Claims

1. A porous resin sheet comprising a porous resin layer containing a thermoplastic resin, the porous resin layer having a thickness of 40-350 μm and a porosity of 35-80%, the porous resin layer comprising a substrate layer and a first surface layer, both the substrate layer and the first surface layer containing a thermoplastic resin and particles, the substrate layer containing 20-45% by mass of the aforementioned particles, the first surface layer containing 45-80% by mass of the aforementioned particles, and the first surface layer having a porosity of 35% to 60%.

2. The porous resin sheet as claimed in claim 1, wherein, The first surface layer is a porous uniaxially extended resin layer, and the substrate layer is a porous biaxially extended resin layer.

3. The porous resin sheet as requested in item 1 or 2, wherein, The first surface layer has a thickness of more than 5 μm.

4. The porous resin sheet as requested in item 1 or 2, wherein, The first surface layer has a thickness of more than 10 μm.

5. The porous resin sheet as requested in item 1 or 2, wherein, The porous resin layer further includes a second surface layer on the surface of the substrate layer opposite to the first surface layer.

6. The porous resin sheet as requested in item 1 or 2, wherein, The ratio of the porosity of the first surface layer to the porosity of the substrate layer is 0.80 to 1.

20.

7. The porous resin sheet of claim 1 or 2 has a tensile strength in the width direction of 0.1 to 10 kgf / mm2.

8. The porous resin sheet as requested in item 1 or 2 is used for the carrier belt.

9. A carrier belt comprising a porous resin sheet as claimed in claim 1 or 2, and a pouch formed in the porous resin sheet.

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