Porous resin sheet and carrier tape

Abstract

The purpose of the present invention is to provide: a porous resin sheet which can be shaped without a special process such as heating or pressure reduction while suppressing the amount of paper powder, and which has good adhesiveness to a cover tape; and a carrier tape which uses the porous resin sheet. The present invention relates to a porous resin sheet which comprises a porous resin layer and a surface layer, 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 includes a base material layer and a first outer layer; the base material layer and the first outer layer both contain a thermoplastic resin (A) and a particle; the content of the particles in the base material layer is 20-45 mass%; the content of the particles in the first outer layer is 45-80 mass%; and the surface layer contains a thermoplastic resin (B) that has a melting point which is lower than that of the thermoplastic resin (A) by 15-35°C.

Description

Porous resin sheet and carrier tape

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

[0002] Carrier tapes are used to facilitate the handling of miniaturized electronic components, such as by transporting them. Carrier tapes house each electronic component in a pocket formed by a sheet with recesses and a cover tape covering the recesses, making it easier to protect the electronic components from loss or damage. Such carrier tapes are required to have formability when forming pockets and adhesive properties to the cover tape.

[0003] Carrier tapes are generally made of pulp paper or resins such as polyvinyl chloride, polystyrene, amorphous polyethylene terephthalate, polycarbonate, and polypropylene, but pulp paper carrier tapes (e.g., Patent Document 1) are inexpensive, but have the problem that it is difficult to form relatively small pockets and that burrs (paper dust) tend to appear on the processed cross section when punching holes. On the other hand, resin carrier tapes are less likely to produce paper dust and can form pockets of a wide range of sizes, but they are relatively lacking in lightness and require heating and decompression (vacuum) processes when forming the pockets, making them disadvantageous in terms of manufacturing costs.

[0004] Japanese Patent Application Publication No. 2000-43975

[0005] The present invention aims to provide a porous resin sheet that can be shaped without special processes such as heating or decompression while reducing the amount of paper powder, and that has good adhesion to a cover tape, and a carrier tape using the same.

[0006] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems, they have found that a porous resin sheet comprising a porous resin layer and a surface layer, wherein the thickness and porosity of the porous resin layer are within a specific range, the porous resin layer comprises a base layer and a first outer layer, both of which contain a thermoplastic resin (A) and particles, and the particle contents in the base layer and the first outer layer are within a specific range, can be used to obtain a porous resin sheet and a carrier tape using the same, which can be shaped without special processes such as heating or decompression while suppressing the amount of paper powder. Furthermore, the present inventors have found that by providing a surface layer on the porous resin layer containing a thermoplastic resin (B) having a melting point 15 to 35°C lower than that of the thermoplastic resin (A), the porous resin sheet can have good adhesion to a cover tape, and have completed the present invention.

[0007] That is, the present invention is as follows. <1> A porous resin sheet comprising a porous resin layer and a surface layer, wherein the porous resin layer has a thickness of 40 to 350 μm, and a porosity of 35 to 80%, the porous resin layer includes a base layer and a first outer layer, and both the base layer and the first outer layer contain a thermoplastic resin (A) and particles, the base layer having a particle content of 20 to 45 mass%, and the first outer layer having a particle content of 45 to 80 mass%, and the surface layer containing a thermoplastic resin (B) having a melting point 15 to 35°C lower than that of the thermoplastic resin (A). <2> The porous resin sheet according to <1>, wherein the surface layer contains a polar group-containing thermoplastic resin (C). <3> The porous resin sheet according to <1> or <2>, wherein the surface layer has a thickness of 10 μm or less. <4> The porous resin sheet according to any one of <1> to <3>, wherein the first outer layer is a porous uniaxially stretched resin layer, and the base layer is a porous biaxially stretched resin layer. <5> The porous resin sheet according to any one of <1> to <4>, wherein the first outer layer has a thickness of 5 μm or more. <6> The porous resin sheet according to any one of <1> to <5>, wherein the content of the thermoplastic resin (B) relative to the total thermoplastic resin in the surface layer is 25% by mass or more. <7> The porous resin sheet according to <2>, wherein the content of the polar group-containing thermoplastic resin (C) relative to the total thermoplastic resin in the surface layer is 10% by mass or more.

[0008] <8> Breaking strength in the width direction is 0.1 to 10 kgf / mm ２ <9> The porous resin sheet according to any one of <1> to <8>, which is for use in a carrier tape. <10> A carrier tape comprising: the porous resin sheet according to any one of <1> to <9>; and pockets formed in the porous resin sheet.

[0009] According to the present invention, it is possible to provide a porous resin sheet that can be shaped without special processes such as heating or decompression while reducing the amount of paper powder, and that has good adhesion to a cover tape, and a carrier tape using the same.

[0010] Fig. 1 is a diagram showing one embodiment of a cross section in the lamination direction of a porous resin sheet according to the present invention. Fig. 2 is a diagram showing a cross section in the lamination direction of another embodiment of a porous resin sheet according to the present invention. Fig. 3 is a diagram showing a cross section in the lamination direction of a porous resin sheet of a comparative example. Fig. 4 is a diagram showing a carrier tape using a porous resin sheet according to another embodiment of the present invention, showing a cross section in the lamination direction passing through a pocket.

[0011] The porous resin sheet of the present invention will be described in detail below. The following is an example (typical example) of the present invention, and the present invention is not limited thereto. In this specification, the numerical range "A to B" indicates "A or more and B or less."

[0012] The present invention relates to a porous resin sheet comprising a porous resin layer and a surface layer, the porous resin layer having a thickness of 40 to 350 μm and a porosity of 35 to 80%, the porous resin layer comprising a base layer and a first outer layer, both of which contain a thermoplastic resin (A) and particles, the base layer containing 20 to 45% by mass of the particles and the first outer layer containing 45 to 80% by mass of the particles, and the surface layer containing a thermoplastic resin (B) having a melting point 15 to 35° C. lower than that of the thermoplastic resin (A). In the porous resin sheet comprising a porous resin layer and a surface layer, the thickness and porosity of the porous resin layer are set within specific ranges, and the porous resin layer comprises the base layer and the first outer layer, both of which contain the thermoplastic resin (A) and particles, and the particle contents in the base layer and the first outer layer are set within specific ranges, thereby enabling a carrier tape to be obtained that is shaped without undergoing special processes such as heating or decompression while reducing the amount of paper powder. Furthermore, the porous resin sheet has a surface layer on the porous resin layer, the surface layer containing a thermoplastic resin (B) having a melting point 15 to 35°C lower than that of the thermoplastic resin (A), thereby improving adhesion to the cover tape.

[0013] <Porous Resin Layer> The porous resin sheet of the present invention comprises a porous resin layer and a surface layer, the porous resin layer having a thickness of 40 to 350 μm and a porosity of 35 to 80%, the porous resin layer comprising a base layer and a first outer layer, the base layer and the first outer layer both containing a thermoplastic resin (A) and particles, the base layer containing 20 to 45% by mass of the particles, and the first outer layer containing 45 to 80% by mass of the particles. By providing such a porous resin layer, the carrier tape can be made lighter. Furthermore, by increasing the porosity, escape routes for components such as resin and particles compressed during shaping can be created, improving shaping properties.

[0014] [Thermoplastic Resin Contained in the Porous Resin Layer] By including a thermoplastic resin (A) in the porous resin layer, compared to pulp paper, the generation of paper dust can be suppressed, water resistance is increased, and dimensional fluctuations due to humidity can be suppressed. The thermoplastic resin (A) contained in the porous resin layer is not particularly limited, and examples thereof include polyolefin-based resins such as polyethylene resin and polypropylene resin, polyvinyl chloride resin, polyethylene terephthalate resin, polycarbonate resin, polymethylpentene-1, cyclic olefin, etc. Another example of the thermoplastic resin (A) contained in the porous resin layer is a mixture containing two or more of the above thermoplastic resins. Of these, polyolefin-based resins such as polyethylene resin and polypropylene resin are preferred, and polyethylene resin and polypropylene resin are more preferred, from the viewpoint described below. The thermoplastic resin is preferably composed solely of a polyolefin-based resin, and more preferably composed solely of a polyethylene resin and a polypropylene resin.

[0015] The content of the thermoplastic resin in the porous resin layer is preferably 35% by mass or more, more preferably 40% by mass or more, and even more preferably 45% 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. A thermoplastic resin content of 35% by mass or more facilitates reduction in paper dust generation and improvement in water resistance.

[0016] (Polypropylene Resin) By using a polypropylene resin for the porous resin layer, flexibility is imparted to the porous resin layer, and it becomes easy to transport the housed electronic components and the like without damaging them, which is preferable.

[0017] Specific examples of polypropylene resins include propylene homopolymers such as isotactic homopolypropylene resin and syndiotactic homopolypropylene resin obtained by homopolymerizing propylene; propylene-ethylene copolymers in which propylene is primarily copolymerized with ethylene; propylene-α-olefin copolymers in which propylene is primarily copolymerized with α-olefins having 4 or more carbon atoms such as 1-butene, 1-hexene, 1-heptene, 1-octene, and 4-methyl-1-pentene; and propylene-ethylene-α-olefin copolymers primarily composed of propylene. The propylene copolymer may be a binary system or a ternary or higher multi-component system, and may be a random copolymer, a block copolymer, or a reactor blend copolymer. More specific examples include propylene homopolymer, propylene-ethylene copolymer, propylene-1-butene copolymer, propylene-ethylene-1-butene copolymer, propylene-4-methyl-1-pentene copolymer, propylene-3-methyl-1-pentene copolymer, propylene-ethylene-3-methyl-1-pentene copolymer, etc. Among these, from the viewpoint of improving the stretch moldability of the porous resin layer, a crystalline homopolypropylene resin obtained by homopolymerizing propylene is preferred, and an isotactic homopolypropylene resin is more preferred.

[0018] Specific examples of polypropylene resins, depending on the production method, include polypropylene produced by a Ziegler-Natta polymerization catalyst, polypropylene produced by a metallocene polymerization catalyst (single-site polymerization catalyst), olefin-based thermoplastic elastomer also known as reactor TPO, and high melt tension polypropylene.

[0019] The melt flow rate (MFR) of the polypropylene resin according to JIS K7210:2014 (temperature 230°C, 2.16 kg load) is preferably 0.2 g / 10 min or more, more preferably 1 g / 10 min or more, and even more preferably 2 g / 10 min or more, from the viewpoint of improving the mechanical strength of the porous resin layer. Also, it is preferably 20 g / 10 min or less, more preferably 15 g / 10 min or less, even more preferably 10 g / 10 min or less, and particularly preferably 6 g / 10 min or less.

[0020] When the porous resin layer contains a polypropylene resin, it preferably contains 15% by mass or more, more preferably 25% by mass or more, and even more preferably 35% by mass or more, and preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less.

[0021] (Polyethylene Resin) By using a polyethylene resin in the porous resin layer, it is possible to impart stretch-moldability to the porous resin layer. Furthermore, a polyethylene resin can be used in combination with another thermoplastic resin. This is preferable because the stretch-moldability of the polyethylene resin can be imparted to the other thermoplastic resin in addition to the properties of the other thermoplastic resin. For example, a polyethylene resin can be used in combination with a polypropylene resin as a resin component constituting the porous resin layer. Examples of polyethylene resins that can be used include high-density polyethylene resin, medium-density polyethylene resin, linear low-density polyethylene resin, and copolymers mainly composed of ethylene.

[0022] When the porous resin layer contains a polyethylene resin, the content is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, and is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0023] When the porous resin layer contains both a polypropylene resin and a polyethylene resin, the mass ratio thereof (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 viewpoint of pore formability. The melting point of the thermoplastic resin (A) contained as a main component in the porous resin layer is, for example, 100 to 200°C, 120 to 190°C, 140 to 180°C, or 150 to 170°C.

[0024] [Particles contained in the porous resin layer] As described below, since both the substrate layer and the first outer layer contained in the porous resin layer contain particles, the porous resin layer contains particles. A porous resin layer having many pores formed therein can be easily obtained by stretching a resin composition containing particles. The porous resin layer is preferably a porous stretched resin layer containing particles and stretched. There are no particular restrictions on the particles that can be used, and examples include organic particles, inorganic particles, etc. Among these, it is preferable to use inorganic particles from the viewpoint of preventing shape recovery after press-molding compression. Furthermore, surface-treated particles can also be used as the particles.

[0025] 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, silica, zinc oxide, magnesium oxide, and diatomaceous earth. The incorporation of inorganic particles facilitates the formation of a porous resin layer having pores therein. Among these, fine powder of calcium carbonate, clay, or diatomaceous earth is preferred because it has good pore-forming properties and is inexpensive. Fine powder of calcium carbonate is particularly preferred because it is available in a wide variety of types, making it easy to adjust the porosity and the color of the porous resin layer.

[0026] The average particle size of the particles is preferably 0.05 μm or more, more preferably 0.1 μm or more, and even more preferably 0.5 μm or more. Also, it is preferably 6 μm or less, more preferably 4 μm or less, and even more preferably 2 μm or less. When the average particle size is within the above range, it is easy to control the porosity within a desired range. The average particle size of the particles is the volume average particle size (D50) measured with a particle size distribution analyzer using laser diffraction.

[0027] The particle content 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. It is also 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 more, it becomes easier to obtain a high porosity due to pores formed from the particles when stretched, and it becomes easier to obtain a high molding depth according to the size of the electronic components to be housed. Furthermore, by setting the content to 80% by mass or less, it becomes easier to maintain flexibility suitable for manufacturing and transportation.

[0028] [Other Additives That May Be Included 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 necessary.

[0029] When the porous resin layer contains a heat stabilizer, it usually contains 0.001 to 1 mass % of the heat stabilizer. Examples of the heat stabilizer include sterically hindered phenol-based, phosphorus-based, and amine-based heat stabilizers. When the porous resin layer contains a light stabilizer, it usually contains 0.001 to 1 mass % of the light stabilizer. Examples of the light stabilizer include sterically hindered amine-based, benzotriazole-based, and benzophenone-based light stabilizers.

[0030] The dispersant or lubricant can be used, for example, for the purpose of dispersing particles. The amount of dispersant or lubricant used in the porous resin layer is usually within the range of 0.01 to 4 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 salts thereof.

[0031] Among these, it is preferable to use a dispersant or a lubricant, because they can suppress the aggregation of particles contained in the porous resin layer, increase the surface area, and improve the pore formation efficiency, and even when a large amount of particles is contained, it is easy to obtain a porosity corresponding to the content. Furthermore, when a porous resin sheet having a porous resin layer is used as a carrier tape for electronic components, a conductive filler can also be used because it can suppress the adhesion of dust due to static electricity.

[0032] [Properties of the porous resin layer] (Thickness) The thickness of the porous resin layer is 40 to 350 μm. The thickness is preferably 80 μm or more, more preferably 100 μm or more, even more preferably 120 μm or more, even more preferably 160 μm or more, and particularly preferably 180 μm or more. 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 depending on the size of the article to be contained in the formed pocket or the like.

[0033] If the thickness of the porous resin layer is less than 40 μm, it becomes difficult to ensure a sufficient depth for shaping according to the size of the contained component, while if the thickness of the porous resin layer exceeds 350 μm, it becomes difficult to maintain flexibility suitable for manufacturing and transportation.

[0034] The "thickness" of a layer in this specification refers to a value measured in accordance with JIS K7130:1999. When the porous resin layer has a multilayer laminate structure, the value measured for all layers is taken as the thickness of the multilayer laminate structure. The thickness of each layer in the multilayer laminate structure is calculated by observing the cross section of the multilayer laminate structure using an electron microscope, determining the interface between the layers from their appearance, and determining the thickness ratio of each layer, and then calculating the thickness of the multilayer laminate structure measured above and the thickness ratio of each layer.

[0035] (Porosity) The porosity of the porous resin layer is 35 to 80%. The porosity is preferably 40% or more, and more preferably 45% or more. The porosity is preferably 70% or less, and more preferably 60% or less. In this specification, the "porosity" of a layer refers to the ratio (volume ratio) of the volume occupied by pores in the layer to the volume of the layer.

[0036] If the porosity is less than 35%, the porous resin layer may not be able to conform sufficiently to a shaped form without undergoing special processes such as heating or decompression. In such a case, for example, when attempting to form a shape such as a pocket having sides perpendicular to the surface of a porous resin sheet provided with a porous resin layer and a bottom parallel to the surface, molding defects such as tapered sides of the pocket or undulations at the bottom are likely to occur. A porosity of 35% or more makes it easier to form a deep shape without undergoing special processes such as heating or decompression. On the other hand, if the porosity exceeds 80%, sufficient mechanical strength cannot be obtained. In this specification, "conformability" refers to the property of the resin deformed by shaping not rebounding and trying to return to its pre-shaping state, but rather maintaining the shaped form stably.

[0037] As a method for adjusting the porosity of the porous resin layer, for example, a method can be mentioned in which the porosity of the entire porous resin layer is adjusted by adjusting the porosity of each of the substrate layer, the first outer layer, and / or the second outer layer, which will be described later.

[0038] There is no particular limitation on the method for measuring the porosity of the porous resin layer, but for example, the porosity can be obtained by observing a cut surface 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) in the observation region of the obtained cross-sectional photograph. When the porous resin layer has a multilayer laminate structure, the porosity of each layer is calculated, and the porosity of each layer is weighted by the thickness to obtain the average value, thereby obtaining the porosity of the entire porous resin layer.

[0039] [Layer structure of porous resin layer] The porous resin layer may be composed of only a substrate layer and a first outer layer, or may be composed of three or more layers. When the porous resin layer is composed of three or more layers, it may be a porous resin layer including a second outer layer in addition to the substrate layer and the first outer layer described below.

[0040] An example of a cross section in the lamination direction of a first embodiment of a porous resin layer is shown in FIG. 1. In FIG. 1, a porous resin layer 10 is composed only of a base layer 1 and a first outer layer 2. A porous resin sheet 20 is composed of a surface layer 5 and a porous resin layer 10. An example of a cross section in the lamination direction of a second embodiment of a porous resin layer is shown in FIG. 2. In FIG. 2, the porous resin layer 10 is composed of a base layer 1, a first outer layer 2, and a second outer layer 3. Here, the second outer layer 3 is provided on the surface of the base layer 1 opposite to the first outer layer 2. The porous resin sheet 20 is composed of a surface layer 5 and a porous resin layer 10. The drawings shown in this specification are intended to schematically show the positional relationships of each layer, pocket, etc., and are not intended to show the exact dimensions of the thickness of each layer, the width of each layer, the size of the pocket, etc.

[0041] The porous resin layer is not limited to the above embodiment, and may include, for example, an additional layer between the substrate layer and the first outer layer and / or the second outer layer. 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 more.

[0042] <Substrate Layer> The porous resin layer provided in the porous resin sheet of the present invention includes a substrate layer. The substrate layer imparts mechanical strength necessary for transportation, etc. to the porous resin sheet, and also provides space for pockets, etc. when a shape such as a pocket for accommodating electronic components is formed in the porous resin sheet. When a shape such as a pocket is formed in the porous resin sheet, it is preferable that the pocket does not penetrate the substrate layer. Furthermore, it is more preferable that, of the two interfaces of the substrate layer, the position of the interface opposite the interface that is pressed down to form the shape of the pocket, etc., does not change before and after forming the shape of the pocket, etc.

[0043] [Materials for Constituting the Base Layer] The base layer contains a thermoplastic resin and particles. Unless otherwise specified, the materials for constituting the base layer can be the same as those described for the porous resin layer, and the preferred ranges are also the same.

[0044] (Thermoplastic Resin) The substrate layer contains a thermoplastic resin. The preferred range of the thermoplastic resin is the same as that described for the porous resin layer unless otherwise specified.

[0045] The content of the thermoplastic resin in the base layer is preferably 35% by mass or more, more preferably 40% by mass or more, even more preferably 45% by mass or more, particularly preferably 50% by mass or more, and most preferably 55% by mass or more, and 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.

[0046] (Particles) The substrate layer contains particles. The preferred range of the particles is the same as that described for the porous resin layer unless otherwise specified.

[0047] The base layer contains particles at 20% by mass or more, preferably 25% by mass or more, and more preferably 30% by mass or more. Also, the base layer contains particles at 45% by mass or less, preferably less than 45% by mass, more preferably 40% by mass or less, and even more preferably 35% by mass or less. If the particle content in the base layer is less than 20% by mass, the amount of voids formed by stretching is reduced, making it difficult to obtain a high molding depth corresponding to the size of the electronic components to be housed. Furthermore, if the content exceeds 45% by mass, it becomes difficult to maintain flexibility suitable for manufacturing and transportation. In particular, a content of inorganic particles of 45% by mass or less is preferred because it makes it easier for the porous resin layer to be compressed by molding, making it easier to obtain a molding depth.

[0048] [Properties of the base layer] (Thickness) The thickness of the base layer is preferably 35 μm or more, more preferably 70 μm or more, even more preferably 90 μm or more, and particularly preferably 110 μm or more. 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. The thickness of the base layer is preferably greater than the thickness of either the first outer layer or the second outer layer described below.

[0049] The thickness of the base layer is preferably 35 μm or more, since it is easy to obtain a sufficient depth for shaping according to the size of the contained component, and it is preferably 300 μm or less, since it is easy to maintain flexibility suitable for manufacturing and transportation.

[0050] The thickness of the substrate layer can be measured by the same method as that for measuring the thickness of the porous resin layer.

[0051] (Porosity) The porosity of the substrate layer is preferably 35% or more, more preferably 40% or more, and even more preferably 45% or more. The porosity is preferably 80% or less, more preferably 70% or less, and even more preferably 60% or less.

[0052] A porosity of 35% or more of the base material layer is preferable because sufficient conformability to the shape can be obtained even when a deep shape is formed, and the shape of the formed bottom and side portions can be easily stabilized. Also, a porosity of 80% or less is preferable because the mechanical strength of the porous resin sheet can be easily obtained.

[0053] The porosity of the substrate layer can be adjusted by the particle content in the substrate layer, the average particle size, the thermoplastic resin composition, the stretching conditions, and the like.

[0054] The porosity of the substrate layer can be measured by the same method as that for measuring the porosity of the porous resin layer.

[0055] (Stretching) The base layer is preferably stretched, and more preferably biaxially stretched. Since the base layer contains particles, pores can be easily formed in the base layer by stretching. When the stretching is biaxially stretched, a high porosity can be obtained while suppressing the particle content, which is preferable because the shape is easily stabilized even when forming a deep shape. In addition, since rigidity is imparted by biaxial stretching, even if the base layer has a porous structure, problems in processes such as transportation are less likely to occur, which is preferable.

[0056] <First outer layer> The porous resin layer provided in the porous resin sheet of the present invention includes a first outer layer. The first outer layer is the outermost layer of the porous resin layer and is located on the side where the shape of the pockets of the carrier tape or the like is formed. By providing the porous resin sheet with a first outer layer having a high particle content, it becomes easier to prevent the side shapes of the pockets or the like from becoming tapered during forming. The first outer layer is preferably located between the base layer and the surface layer.

[0057] [Materials Constituting the First Outer Layer] The first outer layer contains a thermoplastic resin and particles. Unless otherwise specified, the materials constituting the first outer layer can be the same as those described for the porous resin layer, and the preferred ranges are also the same.

[0058] (Thermoplastic Resin) The first outer layer contains a thermoplastic resin. The preferred range of the thermoplastic resin is the same as that described for the porous resin layer unless otherwise specified.

[0059] The content of the thermoplastic resin in the first outer layer is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, and is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less.

[0060] By setting the content of the thermoplastic resin in the first outer layer to 10% by mass or more, it is preferable to easily suppress breakage during molding. Furthermore, by setting the content of the thermoplastic resin to 50% by mass or less, it is preferable to suppress repulsion by the resin during shaping. This makes it easier to trigger deformation of the porous resin sheet due to breakage when attempting to shape, for example, a pocket having sides perpendicular to the surface of the porous resin sheet and a bottom parallel to the surface, and it is preferable because it prevents the side shapes of the pockets, etc. from becoming tapered during shaping and makes it easier to stabilize the shape of the bottom.

[0061] (Particles) The first outer layer contains particles. The preferred range of the particles is the same as that described for the porous resin layer unless otherwise specified.

[0062] The first outer layer contains particles in an amount of 45% by mass or more, preferably 50% by mass or more, and more preferably 55% by mass or more, and 80% by mass or less, preferably 75% by mass or less, more preferably 70% by mass or less, and even more preferably 65% ​​by mass or less.

[0063] If the particle content in the first outer layer is less than 45% by mass, it becomes difficult to control the shape of the sides and bottom during shaping of pockets, etc. In contrast, if the particle content in the first outer layer is 45% by mass or more, for example, when attempting to shaping a pocket having sides perpendicular to the surface of the porous resin sheet and a bottom parallel to the surface, tapering of the sides during shaping is suppressed, and the shape of the bottom is more likely to be stabilized. This is because the interface between particles or between particles and thermoplastic resin is more likely to break at the boundary between the pressed and unpressed portions of the shaping mold than between thermoplastic resins. If the particles are inorganic particles, this tendency is more pronounced in the shape of the sides and bottom during shaping, which is preferable. Furthermore, if the particle content exceeds 80% by mass, breakage during sheet formation is more likely to occur.

[0064] [Properties of the first outer layer] (Thickness) The thickness of the first outer layer is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 13 μm or more, particularly preferably 15 μm or more, and most preferably 18 μm or more. 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.

[0065] When the thickness of the first outer layer is 5 μm or more, distortion of the portion including the first outer layer and a part of the base material layer, which is compressed by a mold to form the bottom of the pocket etc. when forming the shape of the pocket etc., can be averaged, and the shape of the compressed porous resin layer at the bottom of the pocket etc. is stabilized, which makes it easier to stabilize the shape when forming. Also, when the thickness is 50 μm or less, it is easier to form a deep shape, which is preferable.

[0066] The thickness of the first outer layer can be measured by the same method as that for measuring the thickness of the porous resin layer.

[0067] The ratio of the thickness of the first outer layer to the thickness of the substrate layer is preferably 0.03 or more, more preferably 0.05 or more, and even more preferably 0.07 or more, and is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0.2 or less.

[0068] The ratio of the thickness of the first outer layer to the thickness of the base layer is preferably 0.03 or more, since the resin is less likely to repel the resin during shaping, and the shape is more likely to be stabilized. Also, the ratio of the thicknesses is preferably 0.5 or less, since a deep shape can be more easily shaped.

[0069] (Porosity) The porosity of the first outer layer is preferably 35% or more, more preferably 40% or more, and even more preferably 45% or more, and is preferably 80% or less, more preferably 70% or less, and even more preferably 60% or less.

[0070] A porosity of 35% or more of the first outer layer is preferable because it can provide sufficient conformability to the shape even when a deep shape is formed, and the shape of the formed bottom and side portions is easily stabilized. Also, a porosity of 80% or less is preferable because it can easily provide the mechanical strength of the sheet.

[0071] The porosity of the first outer layer can be adjusted by the particle content in the first outer layer, the average particle size, the thermoplastic resin composition, the stretching conditions, and the like.

[0072] The porosity of the first outer layer can be measured by the same method as that for measuring the porosity of the porous resin layer.

[0073] The ratio of the porosity of the first outer layer to the porosity of the substrate layer is preferably 0.80 or more, more preferably 0.85 or more, and even more preferably 0.90 or more, and is preferably 1.20 or less, more preferably 1.15 or less, and even more preferably 1.10 or less.

[0074] By setting the ratio of the porosity of the first outer layer to the porosity of the base layer within this range, the difference between the shape of the outer layer formed by shaping and the shape of the base layer can be reduced, and when attempting to form a shape such as a pocket having sides perpendicular to the surface of the porous resin sheet and a bottom parallel to it by shaping, the shape of the sides of the pocket can be prevented from becoming tapered, which is preferable.

[0075] (Stretching) The first outer layer is preferably stretched, and more preferably uniaxially stretched. By orienting the resin chains in the stretching direction, it becomes easier to break along the stretching direction during shaping, and it is also preferable because it can stabilize the shape formed by shaping along the stretching direction. Furthermore, since the first outer layer contains particles, uniaxially stretching the first outer layer forms long voids in the stretching direction, which makes it easier to break along the stretching direction during shaping, and it is also preferable because it can stabilize the shape formed by shaping along the stretching direction. In particular, when shaping a shape such as a pocket having a longitudinal direction parallel to the stretching direction, it is advantageous because the voids elongated in the stretching direction can easily accommodate shaping.

[0076] In this specification, the "longitudinal direction of a pocket or the like" refers to the direction of the long axis of a pocket or the like of any shape whose aspect ratio is not 1:1. The "short direction of a pocket or the like" refers to the direction of the short axis of a pocket or the like of any shape whose aspect ratio is not 1:1.

[0077] Since both the first outer layer and the substrate layer contain particles, it is preferable that the first outer layer is uniaxially stretched and the substrate layer is biaxially stretched. This allows for a porous resin layer in which the first outer layer is a porous uniaxially stretched resin layer and the substrate layer is a porous biaxially stretched resin layer. Furthermore, this allows for a porous resin sheet in which the first outer layer is a porous uniaxially stretched resin layer and the substrate layer is a porous biaxially stretched resin layer.

[0078] This type of layer structure is preferable because when attempting to form a shape such as a pocket having sides perpendicular to the surface of the porous resin sheet and a bottom parallel to the surface, molding defects such as tapered sides of the pocket or undulations at the bottom can be suppressed.

[0079] <Surface Layer> The porous resin sheet of the present invention comprises a surface layer on a porous resin layer, and the surface layer contains a thermoplastic resin (B) having a melting point 15 to 35°C lower than that of the thermoplastic resin (A) contained in the porous resin layer. When the melting point of the thermoplastic resin (B) contained in the surface layer is at least 15°C lower than that of the thermoplastic resin (A) contained in the porous resin layer, good adhesion to the cover tape can be obtained without destroying the shape of the porous resin sheet when adhering the porous resin sheet to the cover tape. Furthermore, by not lowering the melting point of the thermoplastic resin (B) contained in the surface layer by more than 35°C lower than the melting point of the thermoplastic resin (A) contained in the porous resin layer, excessive adhesive strength can be suppressed. In the process of housing electronic components in the pockets of the carrier tape, the adhesiveness between the carrier tape and the cover tape is primarily achieved by melting the cover tape due to heating during the process. However, the surface layer does not itself exhibit adhesiveness due to heating during the process, but rather can be said to assist the adhesiveness of the cover tape due to heating. This suppresses cohesive failure of the porous resin layer when the cover tape is peeled from the carrier tape, reduces the generation of paper dust, and makes it easier to prevent problems such as the detachment of electronic components due to vibration when the cover tape is peeled off. Note that in the case of "thermoplastic resin (B) having a melting point 15 to 35°C lower than that of thermoplastic resin (A)," when multiple thermoplastic resins (A) are contained in the porous resin layer, "thermoplastic resin (A)" refers to the thermoplastic resin (A) contained as the main component in the porous resin layer (i.e., the thermoplastic resin (A) contained in the porous resin layer at more than 50% by mass of the total thermoplastic resin).

[0080] The melting point of the thermoplastic resin (B) contained in the surface layer is preferably 20° C. or more, more preferably 25° C. or more lower than that of the thermoplastic resin (A) contained in the porous resin layer.

[0081] The thermoplastic resin (B) contained in the surface layer may be the same as that contained in the porous resin layer, and may be selected depending on the melting point of the thermoplastic resin (A) contained in the porous resin layer. For example, when the porous resin layer contains a propylene homopolymer (melting point: about 165°C), the surface layer may contain a propylene-ethylene random copolymer (melting point: about 135°C).

[0082] From the viewpoint of adhesion to the cover tape, the content of the thermoplastic resin (B) in the surface layer is preferably 25% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and particularly preferably 70% by mass or more, relative to the total thermoplastic resin contained in the surface layer. From the same viewpoint, the content of the thermoplastic resin (B) in the surface layer is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and particularly preferably 25% by mass or more, relative to the entire surface layer. From the same viewpoint, when the surface layer contains a thermoplastic resin (A), the content of the thermoplastic resin (A) per 100 parts by mass of the thermoplastic resin (B) in the surface layer is preferably 100 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 30 parts by mass or less. It is preferable that the surface layer does not contain a thermoplastic resin (A).

[0083] The surface layer preferably further contains a polar group-containing thermoplastic resin (C). The polar group-containing thermoplastic resin (C) preferably contains a polymerization component common to the thermoplastic resins contained in the surface layer and the porous resin layer. For example, when the thermoplastic resin contained in the surface layer and the porous resin layer is a polypropylene resin containing propylene as the main polymerization component, the polar group-containing thermoplastic resin (C) is preferably a polar group-containing polypropylene resin. Furthermore, when the thermoplastic resin contained in the surface layer and the porous resin layer is a polyethylene resin containing ethylene as the main polymerization component, the polar group-containing thermoplastic resin (C) is preferably a polar group-containing polyethylene resin. For these reasons, the polar group-containing thermoplastic resin is preferably a polar group-containing polyolefin resin.

[0084] Examples of polar group-containing polyolefin resins include acid-modified polyolefin resins. Examples of acid-modified polyolefin resins include acid anhydride group-containing polyolefins randomly or graft-copolymerized with maleic anhydride, carboxylic acid group-containing polyolefins randomly or graft-copolymerized with unsaturated carboxylic acids such as methacrylic acid and acrylic acid, and epoxy group-containing polyolefins randomly or graft-copolymerized with glycidyl methacrylate. Maleic anhydride-modified polyolefins are particularly preferred. Furthermore, from the viewpoint of interlaminar strength, the polar group-containing polyolefin resin is preferably the same type of resin as the thermoplastic resin contained in the porous resin layer. For example, when the thermoplastic resin contained in the porous resin layer contains polypropylene resin as the main component, the polar group-containing polyolefin resin is preferably a polar group-containing polypropylene resin. When the thermoplastic resin contained in the porous resin layer contains polyethylene resin as the main component, the polar group-containing polyolefin resin is preferably a polar group-containing polyethylene resin.

[0085] More specific examples of polar group-containing polyolefin resins include maleic anhydride-modified polypropylene, maleic anhydride-modified polyethylene, acrylic acid-modified polypropylene, ethylene-methacrylic acid random copolymer, ethylene-glycidyl methacrylate random copolymer, ethylene-glycidyl methacrylate graft copolymer, glycidyl methacrylate-modified polypropylene, etc. Among these, the polar group-containing polyolefin resin preferably contains maleic anhydride-modified polypropylene or maleic anhydride-modified polyethylene, and more preferably contains maleic anhydride-modified polypropylene.

[0086] From the viewpoint of adhesion to the cover tape, the content of the polar group-containing thermoplastic resin (C) in the 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, relative to the total thermoplastic resin contained in the surface layer. The content of the polar group-containing thermoplastic resin (C) in the surface layer is preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 55% by mass or less, relative to the total thermoplastic resin contained in the surface layer. By having the content of the polar group-containing thermoplastic resin (C) relative to the total thermoplastic resin in the surface layer be 70% by mass or less, excessive adhesive strength can be suppressed. This suppresses cohesive failure of the porous resin layer when the cover tape is peeled from the carrier tape, reduces the generation of paper dust, and makes it easier to prevent problems such as electronic components falling off due to vibration when the cover tape is peeled off.

[0087] The surface layer is preferably a porous layer from the viewpoint of formability. The surface layer is preferably a porous stretched resin layer containing particles and stretched. The preferred range of particles is the same as that described for the porous resin layer unless otherwise specified.

[0088] When the surface layer contains particles, the content of the particles 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, from the viewpoint of controlling the shape of the sides and bottom when forming a pocket, etc. Furthermore, the content of the particles is preferably 70% by mass or less, from the viewpoint of suppressing a decrease in adhesion to the cover tape.

[0089] [Properties of the surface layer] (Thickness) The thickness of the surface layer is preferably 0.5 μm or more, more preferably 1 μm or more, even more preferably 1.2 μm or more, and particularly preferably 1.5 μm or more. The thickness is preferably 10 μm or less, more preferably 8 μm or less, even more preferably 5 μm or less, and particularly preferably 3 μm or less.

[0090] When the thickness of the surface layer is 0.5 μm or more, adhesion to the cover tape is easily obtained, and when the thickness is 10 μm or less, it is easy to form a deep shape.

[0091] (Porosity) The porosity of the surface layer may be 0%, but is preferably 20% or more, more preferably 25% or more, and even more preferably 30% or more. The porosity is preferably 80% or less, more preferably 70% or less, and even more preferably 60% or less.

[0092] By setting the porosity of the surface layer to 20% or more, sufficient conformability to the shape can be obtained even when a deep shape is formed, and the shape of the formed bottom and side portions can be easily stabilized. Furthermore, by setting the porosity to 80% or less, the mechanical strength of the sheet can be easily obtained.

[0093] (Stretching) The surface layer is preferably stretched, more preferably uniaxially stretched. By orienting the resin chains in the stretching direction, it becomes easier to break along the stretching direction during shaping, and the shape formed by shaping along the stretching direction can be stabilized.

[0094] A porous resin layer in which the surface layer and first outer layer are porous uniaxially stretched resin layers and the base layer is a porous biaxially stretched resin layer can be manufactured, for example, by the following steps. Step 1: A resin sheet obtained by extrusion molding a resin composition for forming the base layer is uniaxially stretched to obtain a porous uniaxially stretched resin layer. Step 2: A co-extruded resin sheet obtained by co-extrusion molding a resin composition for forming the surface layer and a resin composition for forming the first outer layer is laminated on the porous uniaxially stretched resin layer obtained in step 1 so that the first outer layer and the base layer face each other to obtain a laminated sheet. Step 3: The laminated sheet obtained in step 2 is uniaxially stretched in a direction perpendicular to the stretching direction in step 1 to obtain a porous resin layer in which the surface layer and first outer layer are porous uniaxially stretched resin layers and the base layer is a porous biaxially stretched resin layer.

[0095] <Second outer layer> The porous resin layer provided in the porous resin sheet of the present invention can further include a second outer layer on the surface of the base layer opposite to the first outer layer. The second outer layer is the outermost layer of the porous resin layer and is a layer located opposite to the outside where a shape such as a pocket is formed in the porous resin sheet of the present invention. The porous resin layer preferably includes the second outer layer because the bottom of the formed shape is stabilized.

[0096] [Materials for Constituting Second Outer Layer] Unless otherwise specified, the materials for constituting the second outer layer can be the same as those described for the porous resin layer, and the preferred ranges are also the same.

[0097] (Particles) The second outer layer may contain particles. The preferred range of the particles is the same as that described for the porous resin layer unless otherwise specified.

[0098] When the second outer layer contains particles, it preferably contains 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. It also preferably contains 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. By setting the particle content in the second outer layer to 40% by mass or more, voids are more likely to appear upon stretching, which is preferable. Furthermore, by setting the particle content to 80% by mass or less, it is preferable to maintain the breaking strength of the film.

[0099] [Properties of the second outer layer] (Thickness) The thickness of the second outer layer is preferably 5 μm or more, more preferably 7 μm or more, and even more preferably 10 μm or more. The thickness is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less.

[0100] The second outer layer preferably has a thickness of 5 μm or more, since it serves as a receiving layer for the compressed first outer layer and base material layer of the press-shaped portion.

[0101] The thickness of the second outer layer can be measured by the same method as that for measuring the thickness of the porous resin layer.

[0102] (Porosity) The porosity of the second outer layer is preferably 35% or more, more preferably 40% or more, and even more preferably 45% or more, and is preferably 80% or less, more preferably 70% or less, and even more preferably 60% or less.

[0103] The porosity of the second outer layer is preferably 35% or more, since sufficient conformability to the shape can be obtained even when a deep shape is formed, and the shape of the formed bottom and side portions can be easily stabilized. Also, the porosity is preferably 80% or less, since the mechanical strength of the porous resin sheet can be easily obtained.

[0104] The porosity of the second outer layer can be adjusted by the particle content in the first outer layer, the average particle size, the thermoplastic resin composition, the stretching conditions, and the like.

[0105] The porosity of the second outer layer can be measured by the same method as that for measuring the porosity of the porous resin layer.

[0106] (Stretching) The second outer layer is preferably stretched, more preferably uniaxially stretched. By uniaxially stretching the second outer layer, the mechanical strength in the uniaxial direction is improved, which is preferable because shape stability after forming a pocket or the like is easily obtained.

[0107] A porous resin layer in which the surface layer, first outer layer, and second outer layer are porous uniaxially stretched resin layers and the base layer is a porous biaxially stretched resin layer can be produced, for example, by the following steps. Step 1: A resin sheet obtained by extrusion molding a resin composition for forming the base layer is uniaxially stretched to obtain a porous uniaxially stretched resin layer. Step 2: A co-extruded resin sheet obtained by co-extrusion molding a resin composition for forming the surface layer and a resin composition for forming the first outer layer is laminated on the porous uniaxially stretched resin layer obtained in Step 1 so that the first outer layer and the base layer face each other. Also, a resin sheet for forming the second outer layer is laminated on the surface of the porous uniaxially stretched resin layer opposite the co-extruded resin sheet to obtain a laminated sheet. Step 3: The laminated sheet obtained in Step 2 is uniaxially stretched in a direction perpendicular to the stretching direction in Step 1 to obtain a porous resin layer in which the surface layer, first outer layer, and second outer layer are porous uniaxially stretched resin layers and the base layer is a porous biaxially stretched resin layer.

[0108] (Methods for Producing the Surface Layer, Porous Resin Layer, Base Layer, First Outer Layer, and Second Outer Layer) The methods for producing the surface layer, porous resin layer, base layer, first outer layer, and second outer layer are not particularly limited and can be produced by conventional methods. Examples include cast molding, calendar molding, roll molding, inflation molding, etc., in which molten resin is extruded into a sheet using a T-die, I-die, or the like connected to a screw-type extruder. When producing a porous resin layer with a multilayer laminate structure, the surface layer, base layer, first outer layer, and / or second outer layer can be produced separately and then laminated by a lamination method or the like. Alternatively, film formation and lamination of each layer can be carried out in parallel using conventional methods such as a multilayer die method using a feed block or a multi-manifold, or an extrusion lamination method using multiple dies.

[0109] A porous resin sheet can be produced by laminating a porous resin layer and a surface layer, and then laminating other layers as necessary. When the surface layer, porous resin layer, base layer, first outer layer, and / or second outer layer are stretched, the base layer can be stretched before laminating the surface layer, first outer layer, and / or second outer layer, or can be stretched after lamination. In one embodiment, a porous resin layer in which the surface layer, first outer layer, and / or second outer layer are porous uniaxially stretched resin layers and the base layer is a porous biaxially stretched resin layer can be produced, for example, through the above-mentioned process.

[0110] Examples of the stretching method include a longitudinal stretching method utilizing the difference in peripheral speed between a group of rolls, a transverse stretching method utilizing a tenter oven, a sequential biaxial stretching method combining these, a rolling method, a simultaneous biaxial stretching method using a combination of a tenter oven and a pantograph, a simultaneous biaxial stretching method using a combination of a tenter oven and a linear motor, etc. Also usable is a simultaneous biaxial stretching (inflation molding) method in which a molten resin is extruded into a tubular shape using a circular die connected to a screw extruder, and then air is blown into the extruded tubular shape.

[0111] Among these, the surface layer, porous resin layer, base layer, first outer layer, and / or second outer layer are preferably produced by extruding a resin composition into a sheet form from a T-die connected to an extruder and then stretching the sheet, since this facilitates realizing multilayering and adjusting the film thickness. Examples of the stretching method include a longitudinal stretching method, a transverse stretching method, and a sequential biaxial stretching method or a simultaneous biaxial stretching method that combines these.

[0112] When the thermoplastic resin used is an amorphous resin, the stretching temperature when stretching is preferably in the range of the glass transition temperature of the thermoplastic resin or higher. Furthermore, when the thermoplastic resin is a crystalline resin, the stretching temperature is preferably in the range of the glass transition temperature of the amorphous portion of the thermoplastic resin or higher and the melting point of the crystalline portion of the thermoplastic resin or lower, and is preferably 2 to 60°C lower than the melting point of the thermoplastic resin. Specifically, in the case of propylene homopolymer (melting point 155 to 167°C), a stretching temperature of 100 to 164°C is preferred, and in the case of high-density polyethylene resin (melting point 121 to 134°C), a stretching temperature of 70 to 133°C is preferred. In particular, from the viewpoint of obtaining a higher porosity, when the thermoplastic resin is a crystalline resin, the stretching temperature is preferably 20°C or higher, more preferably 25°C or higher, lower than the melting point of the thermoplastic resin. The stretching temperature can be set based on the glass transition temperature or melting point of the thermoplastic resin mainly used (for example, a thermoplastic resin used in an amount of 50% by mass or more of the total thermoplastic resin).

[0113] The stretching speed is not particularly limited, but is preferably within the range of 20 to 350 m / min from the viewpoint of stable stretching.

[0114] The stretching ratio can also be appropriately determined taking into consideration the characteristics of the thermoplastic resin used. For example, when a propylene homopolymer or a propylene copolymer is used, the stretching ratio in unidirectional stretching is usually 1.1 times or more, preferably 2 times or more, and the upper limit is 10 times or less, preferably 9 times or less. On the other hand, the stretching ratio in biaxial stretching is usually 1.5 times or more, preferably 4 times or more, and the upper limit is 75 times or less, preferably 50 times or less, in terms of areal stretching ratio. When other thermoplastic resin films are stretched in one direction, the stretching ratio is usually 1.2 times or more, preferably 2 times or more, and the upper limit is 10 times or less, preferably 5 times or less. When biaxially stretching is used, the stretching ratio is usually 1.5 times or more, preferably 4 times or more, and the upper limit is 20 times or less, preferably 12 times or less, in terms of areal stretching ratio. Within the above stretching ratio range, the desired porosity and basis weight are easily obtained, and opacity is easily improved. In addition, the film is less likely to break, and stretch molding is more likely to be stabilized. When the pores in the porous resin layer are formed from particles by stretching, it is preferable that the stretch ratio, stretching temperature, particle content, and the like all satisfy the above-mentioned specific conditions in order for the porous resin layer to have a high porosity.

[0115] <Porous Resin Sheet> The porous resin sheet of the present invention includes the porous resin layer described above.

[0116] [Properties of Porous Resin Sheet] (Breaking Strength) The breaking strength of the porous resin sheet in the width direction is 0.1 kgf / mm ２ It is preferable that the resistance is 1.0 kgf / mm or more. ２ More preferably, it is 2.0 kgf / mm or more. ２ It is more preferable that the breaking strength in the width direction is 10 kgf / mm or more. ２ It is preferable that the resistance is 8 kgf / mm or less. ２ More preferably, it is 6 kgf / mm or less. ２It is more preferable that the breaking strength of the porous resin sheet in the width direction is as follows: Here, the "breaking strength of the porous resin sheet in the width direction" refers to the breaking strength measured by pulling the porous resin sheet in the width direction (TD direction). The breaking strength can be measured, for example, in accordance with JIS-K7127:1999.

[0117] The breaking strength of the porous resin sheet in the width direction is 0.1 kgf / mm ２ The breaking strength in the width direction is preferably 10 kgf / mm or more from the viewpoint of maintaining the film shape during transport. ２ It is preferable that the thickness is not more than 100 μm from the viewpoint of maintaining the shape when press-molded.

[0118] In order to increase the number of pockets, etc. per unit length of the carrier tape, the longitudinal direction of the pockets, etc. is generally formed parallel to the width direction of the carrier tape. Therefore, it is preferable to design the porous resin sheet so that it has the above-mentioned breaking strength in the width direction. Furthermore, when the longitudinal direction of the pockets, etc. is formed parallel to the length direction of the carrier tape, it is also possible to design the porous resin sheet so that it has the above-mentioned breaking strength in the length direction.

[0119] [Uses] The porous resin sheet of the present invention has properties suitable for forming a carrier tape, and therefore, the porous resin sheet of the present invention is preferably used for a carrier tape.

[0120] For example, a carrier tape can be provided that includes the porous resin sheet described above and a pocket formed in the porous resin sheet. The size of the pocket can be, for example, a length x width of 0.1 x 0.1 mm to 3.0 x 3.0 mm. The length x width dimensions may be equal to or larger than 0.2 x 0.1 mm, or equal to or larger than 0.4 x 0.2 mm. Furthermore, the length x width dimensions may be equal to or smaller than 1.0 x 1.0 mm, or equal to or smaller than 0.6 x 0.3 mm.

[0121] An example of a cross section in the lamination direction passing through a pocket of a carrier tape using one embodiment of the porous resin sheet according to the present invention is shown in Figure 4. As shown in Figure 4, it is preferable that the pocket 4 does not penetrate the base layer 1. Furthermore, of the two interfaces 1a and 1b of the base layer 1, it is more preferable that the position of the interface 1b opposite the interface 1a that is pressed down to form the pocket 4 does not change before and after forming the pocket 4. On the other hand, it is preferable that the interface 1a on the side where the shape of the pocket or the like of the carrier tape is formed is linear or approximately linear in the cross section passing through the pocket of the carrier tape.

[0122] The carrier tape using the porous resin sheet of the present invention may further include other necessary members such as a cover tape.

[0123] The carrier tape formed from the porous resin sheet of the present invention can be suitably used as a carrier tape for housing components, such as electronic components.

[0124] <Method of Shaping Porous Resin Sheet> There are no particular limitations on the method of forming a shape such as a pocket in a porous resin sheet, and examples thereof include compressed air forming, press forming, vacuum rotary forming, etc. Among these, from the viewpoint of cost, etc., it is preferable to form a shape in a porous resin sheet by press forming at room temperature.

[0125] The shape of the porous resin sheet is selected according to the shape of the parts to be housed, and is not particularly limited, but examples thereof include a cylindrical shape, a prismatic shape, and the like.

[0126] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to the following examples.

[0127] <Resin Composition> The materials and blending ratios of the resin compositions used in the examples and comparative examples are as shown in Table 1.

[0128]

[0129] <Porous Resin Sheet> [Example 1] Resin composition A was kneaded in an extruder set at 230 ° C., then fed into an extrusion die set at 250 ° C. and extruded into a sheet, which was then cooled using a cooling device to obtain an unstretched sheet. This unstretched sheet was heated to 130 ° C. and stretched 4 times in the machine direction (length direction) using a group of multiple rolls with different peripheral speed differences to obtain a 4-times stretched film. Next, resin composition C and resin composition E were kneaded in two extruders set at 250 ° C., respectively, and then fed into a co-extrusion die set at 250 ° C. The two types of resin composition C and resin composition E were laminated in the co-extrusion die and extruded into a sheet, which was then laminated on the surface of the 4-times stretched film obtained above to obtain a three-layer laminate film. Next, this laminated film was cooled to 60 ° C., heated again to about 140 ° C. using a tenter oven, stretched 8 times in the transverse direction (width direction), and then annealed in an oven adjusted to 160 ° C., cooled to 60 ° C., and the ears were slit to obtain a porous resin sheet having a thickness of 200 μm and a three-layer structure (surface layer / first outer layer / base layer; composition: resin composition E / resin composition C / resin composition A, porosity: 20.0% / 40.0% / 49.0%, thickness: 2 μm / 13 μm / 185 μm, stretching: uniaxial / uniaxial / biaxial). The porosity of the porous resin layer consisting of the first outer layer and the base layer was 48.4%.

[0130] The properties of the obtained porous resin sheet were measured as follows: (Total Thickness) The total thickness (μm) of the porous resin sheet was measured using a constant pressure thickness gauge (device name: PG-01J, manufactured by Teclock Corporation) based on JIS K7130:1999 "Plastics - Films and sheets - Thickness measurement method".

[0131] (Thickness of each layer) The thickness (μm) of each layer in the porous resin sheet was measured as follows. The porous resin sheet was cooled to a temperature of −60° C. or lower with liquid nitrogen, and a razor blade (product name: Proline Blade, manufactured by Schick Japan Co., Ltd.) was applied perpendicularly to the sample placed on a glass plate to cut it, preparing a sample for cross-section measurement. The cross-section of the obtained sample was observed with a scanning electron microscope (instrument name: JSM-6490, manufactured by JEOL Ltd.), and the boundary lines of each layer were determined from the composition appearance to determine the thickness ratio of each layer in the porous resin sheet. The thickness of each layer was determined by multiplying the measured total thickness by the thickness ratio of each layer.

[0132] (Porosity Measurement) The porosity (%) of each layer in the porous resin sheet was measured as follows. An arbitrary portion of the porous resin sheet was cut out, embedded in epoxy resin, and solidified. After that, a microtome was used to cut the porous resin sheet to be measured perpendicular to the plane direction and the TD direction, and the cut surface was attached to an observation sample stage so that it served as the observation surface. Gold, gold-palladium, or the like was vapor-deposited on the observation surface, and the cut surface of the porous resin sheet was observed with a scanning electron microscope at an arbitrary magnification (for example, a magnification of 500 to 3000 times) that made it easy to observe, and the observed area was captured as image data. The obtained image data was subjected to image processing using an image analyzer to determine the area ratio (%) of the pore portion in each layer of the porous resin sheet, and the average value of the area ratio (%) determined at any 10 or more locations was taken as the porosity (%) of each layer. The porosity of each layer was calculated by averaging the values ​​weighted by thickness to obtain the porosity of the entire layer.

[0133] [Example 2], [Comparative Example 1], and [Comparative Example 4] Porous resin sheets of Example 2, Comparative Example 1, and Comparative Example 4 were obtained in the same manner as in Example 1, except that the resin composition, the thickness of each layer, and the porosity of each layer were changed as shown in Table 2 or Table 3.

[0134] Example 3 A porous resin sheet of Example 3 was obtained in the same manner as in Example 1, except that the stretching temperature in the transverse direction (temperature of the tenter oven) was changed to 145°C.

[0135] Example 4 A porous resin sheet of Example 4 was obtained in the same manner as in Example 1, except that the temperature for stretching in the machine direction was changed to 140°C.

[0136] Comparative Example 2 A porous resin sheet of Comparative Example 2 was obtained in the same manner as in Example 2, except that the temperature for stretching in the machine direction was changed to 145°C.

[0137]

[0138] [Example 5] A porous resin sheet of Example 5 was obtained in the same manner as in Example 1, except that the resin composition was changed as shown in Table 3 and the stretching temperature in the transverse direction (temperature of the tenter oven) was changed to 135°C.

[0139] [Comparative Example 3] Resin composition B was kneaded in an extruder set at 230°C, then fed into a feedblock-type multilayer die set at 250°C, extruded into a sheet, and cooled in a cooling device to obtain an unstretched sheet. This unstretched sheet was heated to 135°C and stretched 4 times in the longitudinal direction to obtain a 4x stretched film. Next, resin composition E was kneaded in an extruder set at 250°C, then fed into an extrusion die set at 250°C, extruded into a sheet, and laminated on the surface of the 4x stretched film prepared above to obtain a two-layer laminated film. Next, this 4-fold stretched film was cooled to 60 ° C., heated again to about 135 ° C. using a tenter oven, stretched 8 times in the transverse direction, and then annealed in an oven adjusted to 160 ° C. After cooling to 60 ° C., the edge portions were slit to obtain a porous resin sheet with a two-layer structure (surface layer / base layer; composition: resin composition E / resin composition B, porosity: 20.0% / 50.0%, thickness: 15 μm / 185 μm, stretching: uniaxial / biaxial) and a total thickness of 200 μm, as shown in Figure 3. The porosity of the porous resin layer consisting of the base layer was 50.0%.

[0140] [Example 6] Resin composition A was kneaded in an extruder set at 230 ° C., then fed into an extrusion die set at 250 ° C. and extruded into a sheet, which was then cooled using a cooling device to obtain an unstretched sheet. This unstretched sheet was heated to 135 ° C. and stretched 4 times in the longitudinal direction using a group of multiple rolls with different peripheral speed differences to obtain a 4x stretched film. Next, resin compositions C and E were kneaded in two extruders set at 250 ° C., and then fed into a co-extrusion die set at 250 ° C. Meanwhile, resin composition C was kneaded in an extruder set at 250 ° C. and then fed into an extrusion die set at 250 ° C. The two resin compositions C and E were laminated in the co-extrusion die and extruded into a sheet, which was laminated on the surface of the 4x stretched film obtained above, and resin composition C was extruded from the extrusion die into a sheet and laminated on the back surface of the 4x stretched film obtained above to obtain a four-layer laminate film. Next, this laminated film was cooled to 60 ° C., heated again to about 135 ° C. using a tenter oven, stretched 8 times in the transverse direction, and then annealed in an oven adjusted to 160 ° C. After cooling to 60 ° C., the ears were slit to obtain a 4-layer structure (surface layer / first outer layer / base layer / second outer layer; composition: resin composition E / resin composition C / resin composition A / resin composition C, porosity: 20.0% / 40.0% / 50.0% / 40.0%, thickness: 2 μm / 13 μm / 170 μm / 15 μm, stretching: uniaxial / uniaxial / biaxial / uniaxial) and a thickness of 200 μm. The porosity of the porous resin layer consisting of the first outer layer, base layer and second outer layer was 48.6%.

[0141] [Example 7] The resin composition A, the resin composition C, and the resin composition E were laminated so that the thickness of the base layer was 190 μm and the thickness of the first outer layer was 8 μm, respectively, and extruded into a sheet shape, respectively. The porous resin sheet of Example 7 was obtained in the same manner as in Example 1, except that the resin composition A, the resin composition C, and the resin composition E were laminated so that the thickness of the base layer was 190 μm and the thickness of the first outer layer was 8 μm, respectively.

[0142] [Example 8] The resin composition A, the resin composition C, and the resin composition E were laminated so that the thickness of the base layer was 195 μm and the thickness of the first outer layer was 5 μm, respectively, and extruded into a sheet shape, respectively. The porous resin sheet of Example 8 was obtained in the same manner as in Example 1, except that the resin composition A, the resin composition C, and the resin composition E were laminated so that the thickness of the base layer was 195 μm and the thickness of the first outer layer was 5 μm, respectively.

[0143] [Example 9] A porous resin sheet of Example 9 was obtained in the same manner as in Example 1, except that the resin composition was changed as shown in Table 3 and the stretching temperature in the transverse direction (temperature of the tenter oven) was changed to 150°C.

[0144] Example 10 A porous resin sheet of Example 10 was obtained in the same manner as in Example 1, except that the stretching temperature in the transverse direction (temperature of the tenter oven) was changed to 130°C.

[0145]

[0146] [Example 11] to [Example 13] and [Comparative Example 5] Porous resin sheets of Examples 11 to 13 and Comparative Example 5 were obtained in the same manner as in Example 1, except that the resin composition and porosity were changed as shown in Table 4.

[0147] Comparative Example 6 A porous resin sheet of Comparative Example 6 was obtained in the same manner as in Example 1, except that no surface layer was provided and the thickness of the first outer layer was set to 15 μm.

[0148]

[0149] <Evaluation of Porous Resin Sheets> The porous resin sheets obtained in the above Examples and Comparative Examples were evaluated as follows. The results are shown in Tables 5 to 7.

[0150] [Breaking Strength] The stress at break in the width direction of the sheet was measured according to JIS-K7127:1999 (Plastics - Testing methods for tensile properties). Test piece size: 15 mm x 150 mm, Tensile speed: 300 mm / min. The same sample was measured three times, and the average value was calculated.

[0151] [Shaping ability] Using a debossing metal plate (tip: 400 μm × 200 μm rectangle, blade angle: 90 °) manufactured by Tsukatani Cutlery Manufacturing Co., Ltd. and a press (Mini Test Press manufactured by Toyo Seiki Co., Ltd.), the porous resin sheet obtained in each of the above examples and comparative examples was pressed from the surface layer (first outer layer in Comparative Example 6) toward the base layer under pressing conditions of 1 MPa / 10 sec. / room temperature, with a vertical dimension of 400 μm, a horizontal dimension of 200 μm, and a depth of 90% of the sheet thickness. A pseudo-pocket shape was formed. The cross section of the pseudo-pocket was cut with a razor blade, and the cross-sectional shape was observed using a digital microscope (device name: HRX-01, manufactured by Hirox Co., Ltd.) and evaluated as follows.

[0152] (Depth) Evaluation was made as follows: A: Very good A depth of 30 μm or more could be produced, and shaping was possible to a depth of more than 85% but not more than 90% of the sheet thickness B: Good A depth of 30 μm or more could be produced, and shaping was possible to a depth of more than 80% but not more than 85% of the sheet thickness C: No problem A depth of 30 μm or more could be produced, and shaping was possible to a depth of more than 75% but not more than 80% of the sheet thickness D: Poor A depth of 30 μm or more could be produced, but shaping was not possible to a depth of more than 75% of the sheet thickness E: Very poor A depth of 30 μm or more could not be produced

[0153] (Taper suppression) Evaluation was made as follows: A: Very good The angle between the bottom and side was 85° or more B: Good The angle between the bottom and side was 80° or more and less than 85° C: Acceptable The angle between the bottom and side was 75° or more and less than 80° D: Poor The angle between the bottom and side was 60° or more and less than 75° E: Very poor The angle between the bottom and side was less than 60°

[0154] (Bottom Stability) The distance between the bottom of the formed pocket and the surface of the porous resin sheet opposite the first outer layer was measured from a cross-sectional image. The maximum and minimum values ​​of the distance were recorded for 10 pockets, and the average value of the differences was calculated. The bottom stability was evaluated based on the average value as follows: A: Very good (average value of 1 μm or less) B: Good (average value of more than 1 μm and less than 3 μm) C: Acceptable level (average value of more than 3 μm and less than 5 μm) D: Poor (average value of more than 5 μm and less than 10 μm) E: Very poor (average value of more than 10 μm)

[0155] [Cover Tape Adhesion] A porous resin sheet and a carrier tape cover tape (product name: SUMILITE CSL-Z7302, manufactured by Sumitomo Bakelite Co., Ltd.) were each cut into a width of 8 mm and a length of 300 mm. The cover tape was placed on the surface of the surface layer of the porous resin sheet, and the sheet was heat-sealed at a load of 2.5 MPa and 140 ° C for 0.5 seconds using a thermal gradient tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.) and left at 23 ° C for 15 minutes to obtain a measurement sample. Next, using a tensile tester (product name: Autograph AGS-5kNJ, manufactured by Shimadzu Corporation), the cover tape was peeled 180 ° from the measurement sample at a rate of 300 mm / min, and the load at the time of peeling was measured. The average value of five measurements was taken as the adhesive strength (gf / mm). The adhesiveness of the cover tape was evaluated according to the following criteria. A: Excellent (adhesive strength of 10 gf / mm or more) B: Good (adhesive strength of 8 gf / mm or more and less than 10 gf / mm) C: Acceptable (adhesive strength of 7 gf / mm or more and less than 8 gf / mm) D: Poor (adhesive strength of 5 gf / mm or more and less than 7 gf / mm) E: Very poor (adhesive strength less than 5 gf / mm)

[0156]

[0157]

[0158]

[0159] Examples 1 to 10 demonstrated that the porous resin sheet of the present invention exhibited good breaking strength and formability even when the thickness balance, porosity, stretching mode, and layer structure were changed within a specified range. Furthermore, Examples 1, 7, and 8 demonstrated that the bottom stability improved as the thickness of the first outer layer increased. Furthermore, Examples 9 and 10 demonstrated that increasing the particle content in the first outer layer and / or lowering the stretching temperature of the first outer layer increased the porosity of the first outer layer, thereby improving formability. In contrast, the porous resin sheet of Comparative Example 1 was unable to form to a sufficient depth due to an insufficient thickness of the porous resin layer. The porous resin sheet of Comparative Example 2 had poor formability in terms of tapering suppression and bottom stability due to the low porosity of the porous resin layer. The porous resin sheet of Comparative Example 3 had a porous resin layer composed only of a substrate layer, resulting in poor formability in terms of tapering suppression. The porous resin sheet of Comparative Example 4 had an insufficient content of particles in the first outer layer, and therefore was inferior in formability in terms of tapering suppression and bottom stability.

[0160] In Examples 11 to 13 and Comparative Example 5, the composition of the surface layer was changed in various ways. In Example 13, the surface layer did not contain a polar group-containing thermoplastic resin, so although the adhesion to the cover tape was inferior compared to Example 1, etc., it was found to be to a level that was not problematic in practical use. In Comparative Example 5, the surface layer did not contain the thermoplastic resin (B), so it was found to be inferior in adhesion to the cover tape compared to Example 1, etc. In Comparative Example 6, no surface layer was provided, so it was found to be inferior in adhesion to the cover tape compared to Example 1, etc.

[0161] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0162] This application is based on a Japanese patent application (Patent Application No. 2023-216998) filed on December 22, 2023, the contents of which are incorporated herein by reference.

[0163] The porous resin sheet of the present invention can be suitably used, for example, as a porous resin sheet for a carrier tape.

[0164] REFERENCE SIGNS LIST 1 base material layer 2 first outer layer 3 second outer layer 4 pocket 5 surface layer 10 porous resin layer 20 porous resin sheet

Claims

1. A porous resin sheet comprising a porous resin layer and a surface layer, wherein the porous resin layer has a thickness of 40 to 350 μm, the porous resin layer has a porosity of 35 to 80%, the porous resin layer comprises a base layer and a first outer layer, the base layer and the first outer layer both contain a thermoplastic resin (A) and particles, the content of the particles in the base layer is 20 to 45 mass%, the content of the particles in the first outer layer is 45 to 80 mass%, and the surface layer comprises a thermoplastic resin (B) having a melting point 15 to 35° C. lower than that of the thermoplastic resin (A).

2. The porous resin sheet according to claim 1, wherein the surface layer comprises a polar group-containing thermoplastic resin (C).

3. The porous resin sheet according to claim 1 or 2, wherein the surface layer has a thickness of 10 μm or less.

4. The porous resin sheet according to claim 1 or 2, wherein the first outer layer is a porous uniaxially stretched resin layer, and the base layer is a porous biaxially stretched resin layer.

5. The porous resin sheet according to claim 1 or 2, wherein the first outer layer has a thickness of 5 μm or more.

6. A porous resin sheet according to claim 1 or 2, wherein the content of said thermoplastic resin (B) relative to the total thermoplastic resin in said surface layer is 25 mass% or more.

7. The porous resin sheet according to claim 2, wherein the content of the polar group-containing thermoplastic resin (C) relative to the total thermoplastic resin in the surface layer is 10 mass % or more.

8. Breaking strength in the width direction is 0.1 to 10 kgf / mm ２ The porous resin sheet according to claim 1 or 2, 9. The porous resin sheet according to claim 1 or 2, which is for use in a carrier tape.

10. A carrier tape comprising: the porous resin sheet according to claim 1 or 2; and a pocket formed in the porous resin sheet.

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