Porous resin sheet and carrier tape

Abstract

The present invention addresses the problem of providing: a porous resin sheet that suppresses the generation of paper dust and that can be shaped without being subjected to special steps such as heating and vacuuming; and a carrier tape using the porous resin sheet. The present invention pertains to a porous resin sheet comprising a porous resin layer that contains a thermoplastic resin. 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 substrate layer and a first surface layer; the substrate layer and the first surface layer each contain a thermoplastic resin and particles; the content of the particles in the substrate layer is 20-45 mass%; and the content of the particles in the first surface layer is 45-80 mass%.

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 increasingly miniaturized electronic components, such as by transporting them. Carrier tapes house each electronic component in its pocket, making it easier to protect the electronic components from loss or damage.

[0003] Carrier tapes are generally made of pulp paper or resins such as polyvinyl chloride, polystyrene, amorphous polyethylene terephthalate, polycarbonate, and polypropylene, but while pulp paper carrier tapes (e.g., Patent Document 1) are inexpensive, they have problems in 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 Publication No. 2000-43975

[0005] An object of the present invention is to provide a porous resin sheet that can be shaped without special processes such as heating or decompression while suppressing the amount of paper dust, 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, it was found that a porous resin sheet having a porous resin layer containing a thermoplastic resin, the thickness and porosity of the porous resin layer being within a specific range, the porous resin layer including a base layer and a first surface layer, both of which contain a thermoplastic resin and particles, and the particle contents in the base layer and the first surface layer being within specific ranges, can be used to obtain a porous resin sheet that can be shaped without undergoing special processes such as heating or decompression while suppressing the amount of paper powder, and a carrier tape using the same, and the present invention was completed.

[0007] That is, the present invention is as follows. <1> 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 includes a substrate layer and a first surface layer, and both the substrate layer and the first surface layer contain a thermoplastic resin and particles, and the content of the particles in the substrate layer is 20 to 45 mass %, and the content of the particles in the first surface layer is 45 to 80 mass %. <2> The porous resin sheet according to <1>, wherein the first surface layer is a porous uniaxially stretched resin layer, and the substrate layer is a porous biaxially stretched resin layer. <3> The porous resin sheet according to <1> or <2>, wherein the first surface layer has a thickness of 5 μm or more. <4> The porous resin sheet according to any one of <1> to <3>, wherein the first surface layer has a thickness of 10 μm or more. <5> The porous resin sheet according to any one of <1> to <4>, wherein the porous resin layer further includes a second surface layer on a surface of the base layer opposite to the first surface layer. <6> The porous resin sheet according to any one of <1> to <5>, wherein a ratio of the porosity of the first surface layer to the porosity of the base layer is 0.80 to 1.20.

[0008] <7> Breaking strength in the width direction is 0.1 to 10 kgf / mm ２ <8> The porous resin sheet according to any one of <1> to <7>, which is for use in a carrier tape. <9> A carrier tape comprising: the porous resin sheet according to any one of <1> to <8>; 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 undergoing special processes such as heating or decompression while suppressing the amount of paper dust, 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 containing a thermoplastic resin, the porous resin layer having a thickness of 40 to 350 μm and a porosity of 35 to 80%, the porous resin layer including a base layer and a first surface layer, both of which contain a thermoplastic resin and particles, the base layer having a particle content of 20 to 45% by mass, and the first surface layer having a particle content of 45 to 80% by mass. In the porous resin sheet comprising a porous resin layer containing a thermoplastic resin, the thickness and porosity of the porous resin layer are set within specific ranges, and the porous resin layer includes a base layer and a first surface layer, both of which contain a thermoplastic resin and particles, and the particle contents in the base layer and the first surface layer are set within specific ranges, thereby making it possible to obtain a carrier tape that is shaped without undergoing special processes such as heating or decompression while reducing the amount of paper powder.

[0013] <Porous Resin Layer> The porous resin sheet of the present invention includes a porous resin layer containing a thermoplastic resin, the porous resin layer having 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 surface layer, both of which contain a thermoplastic resin and particles, with the base layer containing 20 to 45% by mass of the particles and the first surface layer containing 45 to 80% by mass of the particles. The inclusion of such a porous resin layer facilitates weight reduction of the carrier tape. Furthermore, increasing the porosity provides an escape route for components such as resin and particles compressed during shaping, thereby improving shaping properties.

[0014] [Thermoplastic Resin Contained in the Porous Resin Layer] By including a thermoplastic resin 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. There are no particular restrictions on the thermoplastic resin contained in the porous resin layer, and examples 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 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 perspective 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, which makes it easier to transport the housed electronic components and the like without damaging them, and is therefore 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 polypropylene resin and 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.

[0024] [Particles contained in the porous resin layer] As described below, since both the substrate layer and the first surface 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, and even more preferably 120 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 surface layer, and / or the second surface 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 surface 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, for example, a second surface layer in addition to the substrate layer and first surface 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 Figure 1. In Figure 1, a porous resin layer 10 is composed only of a base layer 1 and a first surface layer 2. An example of a cross section in the lamination direction of a second embodiment of a porous resin layer is shown in Figure 2. In Figure 2, 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. Note that 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 accurate dimensions such as the thickness or width of each layer or the size of the pocket.

[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 surface layer and / or the second surface 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 transport, 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. Also, 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. Also, the thickness of the base layer is preferably greater than the thickness of either the first surface layer or the second surface 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 surface layer> The porous resin layer provided in the porous resin sheet of the present invention includes 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 pocket or the like of the carrier tape is formed. By providing the porous resin sheet with a first surface layer having a high particle content, it is easier to prevent the shape of the side of the pocket or the like from becoming tapered during forming.

[0057] [Materials for Constituting the First Surface Layer] The first surface layer contains a thermoplastic resin and particles. Unless otherwise specified, the materials for 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.

[0058] (Thermoplastic Resin) The first surface 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 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, 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 surface layer to 10% by mass or more, it is preferable because breakage during molding can be easily suppressed. Furthermore, by setting the content of the thermoplastic resin to 50% by mass or less, it is preferable because repulsion by the resin during shaping can be suppressed. 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 pocket, etc. from becoming tapered during shaping and makes it easier to stabilize the shape of the bottom.

[0061] (Particles) The first surface 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 surface 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 surface layer is less than 45% by mass, it becomes difficult to control the shape of the sides and bottom during molding of a pocket or other shape. On the other hand, if the particle content in the first surface layer is 45% by mass or more, for example, when attempting to mold a pocket or the like having sides perpendicular to the surface of the porous resin sheet and a bottom parallel to the surface, tapering of the sides during molding 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 molding die than between thermoplastic resins. When the particles are inorganic particles, this tendency is more pronounced in the shape of the sides and bottom during molding, which is preferable. Furthermore, if the particle content exceeds 80% by mass, breakage during sheet molding is more likely to occur.

[0064] [Properties of the first surface layer] (Thickness) The thickness of the first surface 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 surface layer is 5 μm or more, distortion of the portion including the first surface 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 surface layer can be measured using the same method as that for measuring the thickness of the porous resin layer.

[0067] The ratio of the thickness 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, 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 surface 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 surface 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 in the first surface 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 sheet can be easily obtained.

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

[0072] The porosity of the first surface 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 surface layer to the porosity of the base 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 surface layer to the porosity of the base layer within this range, the difference between the shape of the surface 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 surface 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 surface layer contains particles, uniaxial stretching of the first surface 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 surface layer and the substrate layer contain particles, it is preferable that the first surface layer is uniaxially stretched and the substrate layer is biaxially stretched, thereby forming a porous resin layer in which the first surface 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] A 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 produced, for example, through the following steps. Step 1: A resin sheet for forming the base layer is uniaxially stretched to obtain a porous uniaxially stretched resin layer. Step 2: A 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: 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 first surface layer is a porous uniaxially stretched resin layer and the base layer is a porous biaxially stretched resin layer.

[0080] <Second Surface Layer> The porous resin layer provided in the porous resin sheet of the present invention can further include a second surface layer on the surface of the base layer opposite to the first surface layer. The second surface layer is the outermost layer of the porous resin layer and is located opposite to the surface on which a shape such as a pocket is formed when the shape is formed in the porous resin sheet of the present invention. The porous resin layer preferably includes the second surface layer because the bottom of the formed shape is stabilized.

[0081] [Materials for Constituting Second Surface Layer] Unless otherwise specified, the materials for constituting the second surface layer can be the same as those described for the porous resin layer, and the preferred ranges are also the same.

[0082] (Particles) The second surface layer may contain particles. The preferred range of the particles is the same as that described for the porous resin layer unless otherwise specified.

[0083] When the second surface 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 is also preferable that it 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 surface layer to 40% by mass or more, voids are more likely to appear upon stretching, which is preferred. Furthermore, by setting the particle content to 80% by mass or less, it is preferred that the breaking strength of the film is maintained.

[0084] [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. The thickness is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less.

[0085] The thickness of the second surface layer is preferably 5 μm or more, since it serves as a receiving layer for the compressed first surface layer of the press-shaped portion and the base material layer.

[0086] The thickness of the second surface layer can be measured using the same method as that for measuring the thickness of the porous resin layer.

[0087] (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, and is preferably 80% or less, more preferably 70% or less, and even more preferably 60% or less.

[0088] The porosity of the second surface 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 of the second surface layer is preferably 80% or less, since the mechanical strength of the porous resin sheet can be easily obtained.

[0089] The porosity of the second surface layer can be adjusted by the content of particles in the first surface layer, the average particle size, the thermoplastic resin composition, the stretching conditions, and the like.

[0090] The porosity of the second surface layer can be measured by the same method as that for measuring the porosity of the porous resin layer.

[0091] (Stretching) 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, which is preferable because shape stability after forming a pocket or the like is easily obtained.

[0092] A porous resin layer in which the first and second surface layers 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 resin sheet for forming the base layer is uniaxially stretched to obtain a porous uniaxially stretched resin layer. Step 2: A resin sheet for forming the first surface layer is laminated on the porous uniaxially stretched resin layer obtained in Step 1, and a resin sheet for forming the second surface layer is laminated on the surface of the porous uniaxially stretched resin layer opposite the resin sheet for forming the first surface layer 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 first and second surface layers are porous uniaxially stretched resin layers and the base layer is a porous biaxially stretched resin layer.

[0093] (Methods for manufacturing porous resin layer, substrate layer, first surface layer, and second surface layer) The methods for manufacturing the porous resin layer, and the substrate layer, first surface layer, and second surface layer are not particularly limited and can be manufactured by conventional methods. Examples include cast molding, calendar molding, roll molding, inflation molding, etc., in which a molten resin is extruded into a sheet using a T-die, I-die, or the like connected to a screw-type extruder. When manufacturing a porous resin layer with a multilayer laminate structure, the substrate layer, the first surface layer, and / or the second surface layer can be manufactured separately and then laminated by a lamination method or the like. Alternatively, film molding and lamination of each layer can be performed 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.

[0094] A porous resin sheet can be produced by laminating a porous resin layer with other layers as necessary. When the porous resin layer, substrate layer, first surface layer, and / or second surface layer are stretched, the substrate layer can be stretched before laminating the first surface layer and / or second surface layer, or can be stretched after lamination. In one embodiment, a porous resin layer in which 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 can be produced, for example, through the above-mentioned process.

[0095] 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.

[0096] Among these, the porous resin layer, the base material layer, the first surface layer, and the second surface 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.

[0097] 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).

[0098] 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.

[0099] 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.

[0100] <Porous Resin Sheet> The porous resin sheet of the present invention includes the porous resin layer described above.

[0101] [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.

[0102] 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.

[0103] 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.

[0104] [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.

[0105] For example, a carrier tape may be provided that includes the porous resin sheet described above and a pocket formed in the porous resin sheet, and the size of the pocket may be, for example, 0.1×0.1 mm to 3×3 mm in length×width.

[0106] 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.

[0107] The carrier tape using the porous resin sheet of the present invention may further include other necessary members such as a cover tape.

[0108] 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.

[0109] <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.

[0110] 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.

[0111] 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.

[0112] <Resin Composition> The materials and blending ratios of the resin compositions used in the examples and comparative examples are as shown in Table 1.

[0113]

[0114] <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, extruded into a sheet, and 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 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 4-times stretched film prepared above to obtain a two-layer laminated film. Next, this laminated film was cooled to 60°C, heated again to about 140°C using a tenter oven, and stretched 8 times in the transverse direction (width direction), after which it was annealed in an oven adjusted to 160°C, cooled to 60°C, and the edge portions were slit to obtain a porous resin sheet with a two-layer structure (first surface layer / substrate layer; composition: resin composition C / resin composition A, porosity: 40.0% / 49.0%, thickness: 15 μm / 185 μm, stretching: uniaxial / biaxial), thickness: 200 μm, and porosity: 48.3%.

[0115] 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".

[0116] (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 a temperature of −60° C. or lower with liquid nitrogen, and a sample placed on a glass plate was cut with a razor blade (product name: Proline Blade, manufactured by Schick Japan Co., Ltd.) at a right angle to prepare 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.

[0117] (Porosity Measurement) The porosity (%) of each layer in the multilayer laminate structure 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 and TD directions, 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 using 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 all layers.

[0118] [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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122]

[0123] [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.

[0124] [Comparative Example 3] Resin composition B was kneaded in an extruder set at 230 ° C, then fed into a feed block type multilayer die set at 250 ° C, extruded into a sheet, and 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 to obtain a 4-fold stretched 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 single-layer structure (substrate layer; composition: resin composition B, porosity: 50.0%, thickness: 200 μm, stretching: biaxial) shown in Figure 3, a total thickness of 200 μm, and a porosity of 50.0%.

[0125] [Example 6] Resin composition A was kneaded in an extruder set at 230 ° C, then fed into an extrusion 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 machine direction using a group of multiple rolls with different peripheral speed differences to obtain a 4-times stretched film. Next, resin composition C 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 each of the front and back surfaces of the 4-times stretched film prepared above to obtain a three-layer laminate film. Next, this laminated film was cooled to 60°C, heated again to about 135°C using a tenter oven, and stretched 8 times in the transverse direction, after which it was annealed in an oven adjusted to 160°C, cooled to 60°C, and the edge portions were slit to obtain a porous resin sheet with a three-layer structure (first surface layer / base layer / second surface layer; composition: resin composition C / resin composition A / resin composition C, porosity: 40.0% / 50.0% / 40.0%, thickness: 15 μm / 170 μm / 15 μm, stretching: uniaxial / biaxial / uniaxial), thickness: 200 μm, and porosity: 49.2%.

[0126] [Example 7] The resin composition A and the resin composition C were each extruded into a sheet shape so that the thickness of the base layer was 190 μm and the thickness of the first surface layer was 10 μm, respectively. A porous resin sheet of Example 7 was obtained in the same manner as in Example 1, except that the resin composition A and the resin composition C were each extruded into a sheet shape so that the thickness of the base layer was 190 μm and the thickness of the first surface layer was 10 μm.

[0127] [Example 8] The resin composition A and the resin composition C were each extruded into a sheet so that the thickness of the base layer was 195 μm and the thickness of the first surface layer was 5 μm, respectively. A porous resin sheet of Example 8 was obtained in the same manner as in Example 1, except that the resin composition A and the resin composition C were each extruded into a sheet so that the thickness of the base layer was 195 μm and the thickness of the first surface layer was 5 μm.

[0128] [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.

[0129] Example 10 The 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 130°C.

[0130]

[0131] <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 4 and 5.

[0132] [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.

[0133] [Shaping ability] Using a debossing metal plate manufactured by Tsukatani Cutlery Manufacturing Co., Ltd. (tip: 400 μm × 200 μm rectangle, blade angle: 90 °), a press machine (Toyo Seiki Co., Ltd. mini test press) was used to press the porous resin sheet obtained in each of the above examples and comparative examples from the first surface layer toward the base layer at 1 MPa / 10 sec. / room temperature under pressing conditions of 400 μm in length, 200 μm in width, and 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 (HRX-01 manufactured by Hirox Co., Ltd.) and evaluated as follows.

[0134] (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

[0135] (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°

[0136] (Bottom Stability) The distance between the bottom of the formed pocket and the surface of the porous resin sheet opposite the first surface layer was measured from the 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)

[0137]

[0138]

[0139] Examples 1 to 10 demonstrated that the porous resin sheets 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 surface layer increased. Furthermore, Examples 9 and 10 demonstrated that increasing the particle content in the first surface layer and / or lowering the stretching temperature of the first surface layer increased the porosity of the first surface layer, thereby improving formability. In contrast, the porous resin sheet of Comparative Example 1 was unable to form a shape to a sufficient depth due to an insufficient thickness of the entire sheet. The porous resin sheet of Comparative Example 2 had a low porosity throughout the sheet, resulting in poor formability in terms of tapering suppression and bottom stability. The porous resin sheet of Comparative Example 3 was 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 particle content in the first surface layer, resulting in poor formability in terms of tapering suppression and bottom stability.

[0140] 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.

[0141] This application is based on a Japanese patent application (Patent Application No. 2022-102194) filed on June 24, 2022, the contents of which are incorporated by reference into this application.

[0142] The porous resin sheet of the present invention can be suitably used, for example, as a porous resin sheet for a carrier tape.

[0143] REFERENCE SIGNS LIST 1 base layer 2 first surface layer 3 second surface layer 4 pocket 10 porous resin layer

Claims

1. A porous resin sheet comprising a porous resin layer containing a thermoplastic resin, wherein the thickness of the porous resin layer is 40 to 350 μm, the porosity of the porous resin layer is 35 to 80%, the porous resin layer comprises a substrate layer and a first surface layer, the substrate layer and the first surface layer both contain a thermoplastic resin and particles, the content of the particles in the substrate layer is 20 to 45 mass%, and the content of the particles in the first surface layer is 45 to 80 mass%.

2. The porous resin sheet according to claim 1, wherein the first surface layer is a porous uniaxially stretched resin layer, and the substrate layer is a porous biaxially stretched resin layer.

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

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

5. The porous resin sheet according to claim 1 or 2, wherein the porous resin layer further comprises a second surface layer on a surface of the substrate layer opposite to the first surface layer.

6. The porous resin sheet according to claim 1 or 2, wherein the ratio of the porosity of the first surface layer to the porosity of the base layer is 0.80 to 1.

20.

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

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