Porous resin sheets and carrier tapes

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

[Technical Field]

[0001] This invention relates to porous resin sheets and carrier tapes. [Background technology]

[0002] Carrier tapes are used to facilitate the handling of increasingly miniaturized electronic components, such as during transport. Each electronic component is housed in its own pocket within the carrier tape, making it easier to protect them 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. However, while carrier tapes made of pulp paper (for example, Patent Document 1) are inexpensive, they have the problem of being difficult to form relatively small pockets and producing burrs (paper dust) on the processed cross-section when the feed holes are punched out. On the other hand, carrier tapes made of resin produce less paper dust and can form pockets of a wide range of sizes, but they are relatively lightweight and require heating and vacuum processes when forming pockets, making them disadvantageous in terms of manufacturing costs. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2000-43975 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The present invention aims to provide a porous resin sheet that can be shaped without undergoing special processes such as heating or reduced pressure, while suppressing the amount of paper dust, and a carrier tape using the same. [Means for solving the problem]

[0006] As a result of diligent research conducted by the inventors to solve the above problems, they have found that a porous resin sheet can be formed without special processes such as heating or reduced pressure while suppressing the amount of paper dust, and a carrier tape using the same can be obtained by providing a porous resin sheet comprising a porous resin layer containing a thermoplastic resin, 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 surface layer, both the base layer and the first surface layer contain thermoplastic resin and particles, and the particle content in the base layer and the first surface layer is within a specific range.

[0007] In other words, the present invention is as follows. <1> It comprises a porous resin layer containing a thermoplastic resin, The thickness of the porous resin layer is 40 to 350 μm. The porosity of the porous resin layer is 35-80%. The porous resin layer includes a base layer and a first surface layer, Both the base layer and the first surface layer contain thermoplastic resin and particles. The content of the particles in the substrate layer is 20 to 45% by mass. A porous resin sheet having a particle content of 45 to 80% by mass in the first surface layer. <2> The first surface layer is a porous uniaxially oriented resin layer, The aforementioned base layer is a porous biaxially oriented resin layer. <1> The porous resin sheet described above. <3> The first surface layer has a thickness of 5 μm or more. <1> or <2> The porous resin sheet described above. <4> The first surface layer has a thickness of 10 μm or more. <1> ~ <3> A porous resin sheet as described in any one of the following. <5> The porous resin layer further includes a second surface layer on the surface of the substrate layer opposite to the first surface layer. <1> ~ <4> A porous resin sheet as described in any one of the following. <6> The porous resin sheet according to any one of <1> to <5>, wherein the ratio of the porosity of the first surface layer to the porosity of the base material layer is 0.80 to 1.20.

[0008] <7> The porous resin sheet according to any one of <1> to <6>, having a breaking strength in the width direction of 0.1 to 10 kgf / mm 2 in. <8> The porous resin sheet according to any one of <1> to <7>, which is for a carrier tape. <9> A porous resin sheet according to any one of <1> to <8>, pockets formed in the porous resin sheet, and a carrier tape comprising the same.

Advantages of the Invention

[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.

Brief Description of the Drawings

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

Modes for Carrying Out the Invention

[0011] The porous resin sheet of the present invention will be described in detail below. The following is an example (representative 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 greater and B or less".

[0012] The present invention relates to a porous resin sheet comprising a porous resin layer containing a thermoplastic resin, wherein the porous resin layer has a thickness of 40 to 350 μm, the porosity of the porous resin layer is 35 to 80%, the porous resin layer comprises a base layer and a first surface layer, both of which contain thermoplastic resin and particles, the particle content in the base layer is 20 to 45% by mass, and the particle content in the first surface layer is 45 to 80% by mass. In a porous resin sheet comprising a porous resin layer containing a thermoplastic resin, a carrier tape can be obtained in which the thickness and porosity of the porous resin layer are within a specific range, the porous resin layer includes a base layer and a first surface layer, both the base layer and the first surface layer contain thermoplastic resin and particles, and the particle content in the base layer and the first surface layer is within a specific range, thereby suppressing the amount of paper dust and achieving the desired shape without undergoing special processes such as heating or reduced pressure.

[0013] <Porous resin layer> The porous resin sheet of the present invention comprises a porous resin layer containing a thermoplastic resin, the thickness of the porous resin layer being 40 to 350 μm, the porosity of the porous resin layer being 35 to 80%, the porous resin layer comprising a base layer and a first surface layer, both of which contain thermoplastic resin and particles, the particle content in the base layer being 20 to 45% by mass, and the particle content in the first surface layer being 45 to 80% by mass. By providing such a porous resin layer, it becomes easier to reduce the weight of the carrier tape. Furthermore, by increasing the porosity, it is possible to create escape routes for components such as resin and particles that are compressed during shaping, thereby improving shaping properties.

[0014] [Thermoplastic resin contained in the porous resin layer] The porous resin layer, by containing a thermoplastic resin, can suppress the generation of paper dust compared to pulp paper, and also increase water resistance and suppress dimensional changes due to humidity. There are no particular restrictions on the thermoplastic resin contained in the porous resin layer; for example, polyolefin resins such as polyethylene resin and polypropylene resin, polyvinyl chloride resin, polyethylene terephthalate resin, polycarbonate resin, polymethylpentene-1, and cyclic olefins can be used. Another example of a thermoplastic resin contained in the porous resin layer is a mixture containing two or more of the above-mentioned thermoplastic resins. Of these, from the viewpoint described later, polyolefin resins such as polyethylene resin and polypropylene resin are preferred, and polyethylene resin and polypropylene resin are more preferred. The thermoplastic resin is preferably composed solely of polyolefin resin, and more preferably composed solely of polyethylene resin and polypropylene resin.

[0015] The content of 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 above 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 the reduction of paper dust generation and the improvement of water resistance.

[0016] (Polypropylene resin) Using polypropylene resin in the porous resin layer is preferable because it imparts flexibility to the porous resin layer, making it easier to transport electronic components and other items without damaging them.

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

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

[0019] The melt flow rate (MFR) of polypropylene resin, in accordance with 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. Furthermore, 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] If the porous resin layer contains polypropylene resin, it is preferable that it contains 15% by mass or more, more preferably 25% by mass or more, and even more preferably 35% by mass or more. Furthermore, it is preferable that it contains 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 polyethylene resin in the porous resin layer, stretch moldability can be imparted to the porous resin layer. Furthermore, polyethylene resin can be used in combination with other thermoplastic resins. In this case, it is preferable because, in addition to the properties of the other thermoplastic resin, the stretch moldability of polyethylene resin can be imparted. For example, polyethylene resin can be used in combination with 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] If the porous resin layer contains polyethylene resin, it is preferable that it contains 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more. Furthermore, it is preferable that it contains 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 (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 formation.

[0024] [Particles contained in the porous resin layer] As described later, since both the base layer and the first surface layer contained in the porous resin layer contain particles, the porous resin layer contains particles. By stretching a resin composition containing particles, a porous resin layer with many voids formed within the layer can be easily obtained. The porous resin layer is preferably a porous stretched resin layer containing particles. There are no particular restrictions on the types of particles that can be used; for example, organic particles, inorganic particles, etc., can be used. Of these, inorganic particles are preferable from the viewpoint of preventing shape recovery after press shaping and compression. Surface-treated particles can also be used.

[0025] Examples of inorganic particles that can be used in the porous resin layer include calcium carbonate, titanium dioxide, calcined clay, talc, barium sulfate, aluminum sulfate, silica, zinc oxide, magnesium oxide, or diatomaceous earth. The incorporation of inorganic particles facilitates the formation of a porous resin layer with internal voids. Among these, fine powdered calcium carbonate, clay, or diatomaceous earth are preferred because they have good void-forming properties and are inexpensive. Fine powdered calcium carbonate is particularly preferred because it is easy to adjust the porosity due to the wide variety of types available, and it is also easy to adjust the color of the porous resin layer.

[0026] The average particle diameter is preferably 0.05 μm or larger, more preferably 0.1 μm or larger, and even more preferably 0.5 μm or larger. Furthermore, it is preferably 6 μm or smaller, more preferably 4 μm or smaller, and even more preferably 2 μm or smaller. Having the average particle diameter within the above range makes it easier to control the porosity within the desired range. The average particle size of the above particles is the volume-average particle size (D50) measured using a laser diffraction particle size analyzer.

[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. Furthermore, it is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. By setting the particle content in the porous resin layer to 25% by mass or more, a high porosity can be easily obtained due to the voids formed starting from these particles when stretched, making it easier to obtain a high shaping depth corresponding to the size of the electronic component 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 can be included in the porous resin layer] The porous resin layer may contain additives such as heat stabilizers (antioxidants), light stabilizers, conductive fillers, dispersants, and lubricants, as needed.

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

[0030] Dispersants or lubricants can be used, for example, to disperse particles. The amount of dispersant or lubricant used in a porous resin layer is usually in the range of 0.01 to 4% by mass. Examples of dispersants or lubricants include silane coupling agents, higher fatty acids such as oleic acid and stearic acid, metal soaps, polyacrylic acid, polymethacrylic acid, and salts thereof.

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

[0032] [Properties of the porous resin layer] (thickness) The thickness of the porous resin layer is 40 to 350 μm. A thickness of 80 μm or more is preferred, more preferably 100 μm or more, and even more preferably 120 μm or more. Furthermore, a thickness of 300 μm or less is preferred, 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 secure sufficient depth for shaping according to the size of the contained parts. On the other hand, if the thickness of the porous resin layer exceeds 350 μm, it becomes difficult to maintain flexibility suitable for manufacturing and transport.

[0034] In this specification, the "thickness" of a layer refers to the value measured in accordance with JIS K7130:1999. If the porous resin layer has a multilayer laminated structure, the value measured for the entire multilayer laminated structure shall be taken as the thickness of the multilayer laminated structure. The thickness of each layer in a multilayer laminated structure is calculated by observing the cross-section of the multilayer laminated structure using an electron microscope, determining the interface between layers from the appearance to find the thickness ratio of each layer, and then combining the thickness of the multilayer laminated structure measured above with the thickness ratio of each layer.

[0035] (porosity) The porosity of the porous resin layer is 35-80%. A porosity of 40% or more is preferred, and 45% or more is more preferred. Furthermore, a porosity of 70% or less is preferred, and 60% or less is more preferred. In this specification, "porosity" of a layer refers to the ratio (volume ratio) of the volume occupied by voids 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 adequately conform to the shape formed without special processes such as heating or reduced pressure. In such cases, for example, when attempting to form a shape such as a pocket with sides perpendicular to the surface and a bottom parallel to the surface of a porous resin sheet with a porous resin layer, molding defects such as tapered sides or undulations at the bottom are likely to occur. A porosity of 35% or more makes it easier to form deep shapes without special processes such as heating or reduced pressure. On the other hand, if the porosity exceeds 80%, sufficient mechanical strength cannot be obtained. In this specification, "conformability" refers to the property of a resin that, after being deformed by shaping, does not attempt to return to its pre-shaping state by rebounding, but rather maintains its shape stably after shaping.

[0037] One method for adjusting the porosity of a porous resin layer is to adjust the porosity of the entire porous resin layer by adjusting the porosity of the base layer, the first surface layer, and / or the second surface layer, as described later.

[0038] There are no particular restrictions on the method for measuring the porosity of a porous resin layer. For example, it can be obtained by observing a cross-section of the porous resin layer with an electron microscope and calculating the percentage of the area occupied by voids in the porous resin layer (area ratio) within the observed area of ​​the resulting cross-sectional photograph. If the porous resin layer has a multilayer structure, the porosity of each layer can be calculated, and the overall porosity of the porous resin layer can be obtained by taking the average value of the porosity of each layer weighted by its thickness.

[0039] [Layer structure of porous resin layer] The porous resin layer may consist only of a base layer and a first surface layer, or it may consist of three or more layers. When the porous resin layer consists of three or more layers, for example, it may include a second surface layer in addition to the base layer and first surface layer described later.

[0040] A cross-sectional view in the lamination direction of a porous resin layer in a first embodiment is shown in Figure 1. In Figure 1, the porous resin layer 10 is composed only of a base layer 1 and a first surface layer 2. A cross-sectional view 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. The drawings shown in this specification are intended to schematically illustrate the positional relationships of each layer and pocket, and are not intended to show precise dimensions of the thickness of each layer, the width of each layer, the size of the pockets, etc.

[0041] The porous resin layer is not limited to the above embodiments and may include, for example, a further layer between the substrate layer and the first surface layer and / or the second surface layer. If the porous resin layer includes a further layer, the further layer is not particularly limited as long as it has a porous structure. For example, the porosity of the further layer may be 10% or more.

[0042] <Base material layer> The porous resin layer of the porous resin sheet of the present invention includes a base layer. The base layer provides the porous resin sheet with the mechanical strength necessary for transport and other purposes, and also provides spaces such as pockets for housing electronic components when shaping the porous resin sheet. When shapes such as pockets are formed in a porous resin sheet, it is preferable that the pockets do not penetrate the base material layer. Furthermore, it is even more preferable that the position of the interface opposite to the interface that is pressed down to form the pockets, of the two interfaces of the base material layer, does not change before and after the pockets are formed.

[0043] [Materials that make up the base layer] The base layer contains thermoplastic resin and particles. Unless otherwise specified, the materials constituting the base layer may be the same as those described for the porous resin layer, and the preferred range is also the same.

[0044] (thermoplastic resin) The base layer contains a thermoplastic resin. Unless otherwise specified, the preferred range of the thermoplastic resin is the same as that described for the porous resin layer.

[0045] The content of 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. Furthermore, the above content is preferably 85% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, and particularly preferably 70% by mass or less.

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

[0047] The base layer contains particles in an amount of 20% by mass or more, preferably 25% by mass or more, and more preferably 30% by mass or more. It also contains 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 substrate layer is less than 20% by mass, the amount of voids formed by stretching will be small, making it difficult to obtain a high shaping depth appropriate to the size of the electronic component to be housed. Furthermore, if the content exceeds 45% by mass, it becomes difficult to maintain flexibility suitable for manufacturing and transport. In particular, a inorganic particle content of 45% by mass or less is preferable because it facilitates compression of the porous resin layer by shaping, making it easier to obtain a shaping depth.

[0048] [Properties of the base material 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. Furthermore, the thickness is preferably 300 μm or less, more preferably 250 μm or less, even more preferably 200 μm or less, and particularly preferably 190 μm or less. In addition, the thickness of the base layer is preferably greater than the thickness of either the first surface layer or the second surface layer, which will be described later.

[0049] A base layer thickness of 35 μm or more is preferable because it makes it easier to obtain sufficient depth for shaping according to the size of the contained parts. Furthermore, a thickness of 300 μm or less is preferable because it makes it easier to maintain flexibility suitable for manufacturing and transport.

[0050] The method for measuring the thickness of the substrate layer can be the same as the method 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. Furthermore, 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 in the base layer is preferable because it allows for sufficient conformability to the shape even when forming deep shapes, and the shapes of the formed bottom and sides are more easily stabilized. Furthermore, a porosity of 80% or less is preferable because it makes it easier to obtain the mechanical strength of the porous resin sheet.

[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, and the stretching conditions.

[0054] The method for measuring the porosity of the substrate layer can be the same as the method 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 created in the base layer by stretching. When the stretching is biaxial stretching, a high porosity can be obtained while suppressing the particle content, which is preferable because it makes it easier to stabilize the shape even when forming deep shapes. Furthermore, since rigidity is imparted by biaxial stretching, it is preferable because process problems such as transportation are less likely to occur even if the porous structure is present.

[0056] <First surface layer> The porous resin layer of 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 pockets, etc., of the carrier tape is formed. By having a first surface layer with a high particle content in the porous resin sheet, it becomes easier to suppress the tapering of the side shape of the pockets, etc., during shaping.

[0057] [Materials constituting the first surface layer] The first surface layer contains thermoplastic resin and particles. Unless otherwise specified, the materials constituting the first surface layer may be the same as those described for the porous resin layer, and the preferred range is also the same.

[0058] (thermoplastic resin) The first surface layer contains a thermoplastic resin. Unless otherwise specified, the preferred range of the thermoplastic resin is the same as that described for the porous resin layer.

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

[0060] It is preferable to have a thermoplastic resin content of 10% by mass or more in the first surface layer, as this makes it easier to suppress fracture during molding. It is also preferable to have a thermoplastic resin content of 50% by mass or less, as this suppresses the repulsion of the resin during shaping. This is preferable because, for example, when attempting to shape a pocket or other shape having sides perpendicular to the surface of the porous resin sheet and a bottom parallel to it, it becomes easier to initiate deformation of the porous resin sheet due to fracture, suppressing the tapering of the side shape of the pocket or other shape during shaping, and making it easier to stabilize the shape of the bottom.

[0061] (particle) The first surface layer contains particles. Unless otherwise specified, the preferred range of particles is the same as that described for the porous resin layer.

[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. It also contains 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 when forming shapes such as pockets. On the other hand, if the particle content in the first surface layer is 45% by mass or more, for example, when attempting to form a pocket or the like with sides perpendicular to the surface of a porous resin sheet and a bottom parallel to it, the tapered shape of the sides during forming is suppressed, and the shape of the bottom becomes more stable. This is because at the boundary between the part where the forming die is pressed and the part where it is not pressed, the interface between particles or between particles and thermoplastic resin is more prone to fracture than between thermoplastic resins. When the particles are inorganic particles, this tendency is more pronounced with respect to the shape of the sides and bottom during forming, which is preferable. Furthermore, if the particle content exceeds 80% by mass, breakage during sheet molding becomes more likely.

[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. Furthermore, the thickness is preferably 50 μm or less, more preferably 40 μm or less, even more preferably 35 μm or less, particularly preferably 30 μm or less, and most preferably 25 μm or less.

[0065] A thickness of 5 μm or more in the first surface layer is preferable because it allows for the averaging of the strain in the portion including the first surface layer and a part of the base layer, which is compressed by the mold during the shaping of pockets and other shapes, thereby stabilizing the shape of the compressed porous resin layer at the bottom of pockets and other shapes, and making it easier to stabilize the shape during shaping. A thickness of 50 μm or less is preferable because it makes it easier to shape deeper shapes.

[0066] The method for measuring the thickness of the first surface layer can be the same as the method 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. Furthermore, the thickness ratio is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0.2 or less.

[0068] A ratio of the thickness of the first surface layer to the thickness of the base layer of 0.03 or more is preferable because it reduces repulsion from the resin during shaping, making it easier to stabilize the shape. Furthermore, a thickness ratio of 0.5 or less is preferable because it makes it easier to shape deeper forms.

[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. Furthermore, the porosity 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 it allows for sufficient conformability to the shape even when forming deep shapes, and the shapes of the formed bottom and sides are more easily stabilized. Furthermore, a porosity of 80% or less is preferable because it makes it easier to obtain mechanical strength in the sheet.

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

[0072] The method for measuring the porosity of the first surface layer can be the same as the method 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 higher, more preferably 0.85 or higher, and even more preferably 0.90 or higher. Furthermore, the porosity ratio is preferably 1.20 or lower, more preferably 1.15 or lower, and even more preferably 1.10 or lower.

[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 is suppressed. This is preferable because it prevents the shape of the sides of pockets, etc., from becoming tapered when attempting to form shapes such as pockets, which have sides perpendicular to the surface of the porous resin sheet and a bottom parallel to it, by shaping.

[0075] (Stretching) The first surface layer is preferably stretched, and more preferably uniaxially stretched. This is preferable because the orientation of the resin chains in the stretching direction facilitates fracture along the stretching direction during shaping, and also stabilizes the shape formed by shaping along the stretching direction. Furthermore, because the first surface layer contains particles, the uniaxial stretching of the first surface layer creates long voids in the stretching direction, which makes it easier to break along the stretching direction during shaping and also stabilizes the shape formed by shaping along the stretching direction, making it preferable. In particular, when shaping shapes such as pockets that have a longitudinal direction parallel to the stretching direction, the voids extending in the stretching direction are advantageous as they easily accommodate the shaping.

[0076] In this specification, "longitudinal direction of pocket, etc." means the direction of the long axis in a pocket, etc. of any shape with an aspect ratio other than 1:1. Also, "short direction of pocket, etc." means the direction of the short axis in a pocket, etc. of any shape with an aspect ratio other than 1:1.

[0077] Since both the first surface layer and the base layer contain particles, it is preferable that the first surface layer is uniaxially stretched and the base layer is biaxially stretched. This makes it possible to create 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.

[0078] This layered structure is preferable because, when attempting to form shapes such as pockets with sides perpendicular to the surface of the porous resin sheet and bottoms parallel to the surface, it suppresses molding defects such as tapered sides or undulations at the bottom.

[0079] A porous resin layer in which the first surface layer is a porous uniaxially oriented resin layer and the base layer is a porous biaxially oriented resin layer can be manufactured, for example, through the following process. Step 1: A porous uniaxially oriented resin layer is obtained by uniaxially stretching a resin sheet for forming the base layer. Step 2: A resin sheet for forming the first surface layer is laminated onto 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 of 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 of the porous resin sheet of the present invention may further include a second surface layer on the surface of the base material layer opposite to the first surface layer. The second surface layer is the outermost layer of the porous resin layer and is located on the opposite side of the surface to which a shape such as a pocket is formed when such a shape is formed in the porous resin sheet of the present invention. The inclusion of a porous resin layer as a second surface layer is preferable because it stabilizes the bottom of the formed shape.

[0081] [Materials constituting the second surface layer] Unless otherwise specified, the material constituting the second surface layer may be the same as that described for the porous resin layer, and the preferred range is also the same.

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

[0083] If the second surface layer contains particles, it is preferable that it contains 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, and particularly preferable 55% by mass or more. Furthermore, it is 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 preferable 65% by mass or less. It is preferable to have a particle content of 40% by mass or more in the second surface layer, as this makes it easier for pores to form upon stretching. It is also preferable to have a particle content of 80% by mass or less, as this maintains the film's tensile strength.

[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. Furthermore, the thickness is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less.

[0085] A thickness of 5 μm or more for the second surface layer is preferable because it acts as a receiving layer for the compressed first surface layer and base layer of the press-formed section.

[0086] The method for measuring the thickness of the second surface layer can be the same as the method 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. Furthermore, the porosity is preferably 80% or less, more preferably 70% or less, and even more preferably 60% or less.

[0088] A porosity of 35% or more in the second surface layer is preferable because it allows for sufficient conformability to the shape even when forming deep shapes, and the shapes of the formed bottom and sides are more easily stabilized. Furthermore, a porosity of 80% or less is preferable because it makes it easier to obtain the mechanical strength of the porous resin sheet.

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

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

[0091] (Stretching) The second surface layer is preferably stretched, and more preferably uniaxially stretched. The uniaxial stretching of the second surface layer improves mechanical strength in the uniaxial direction, which is preferable because it facilitates shape stability after forming shapes such as pockets.

[0092] A porous resin layer in which the first and second surface layers are porous uniaxially oriented resin layers and the base layer is a porous biaxially oriented resin layer can be manufactured, for example, through the following process. Step 1: A porous uniaxially oriented resin layer is obtained by uniaxially stretching a resin sheet for forming the base layer. Step 2: A resin sheet for forming the first surface layer is laminated onto the porous uniaxially oriented resin layer obtained in Step 1, and a resin sheet for forming the second surface layer is laminated onto the surface of the porous uniaxially oriented resin layer opposite to 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 of Step 1 to obtain a porous resin layer in which the first surface layer and the second surface layer are porous uniaxially stretched resin layers and the base layer is a porous biaxially stretched resin layer.

[0093] (Method for manufacturing the porous resin layer, substrate layer, first surface layer, and second surface layer) The manufacturing method for the porous resin layer, as well as the base layer, first surface layer, and second surface layer, is not particularly limited and can be manufactured by conventional methods. For example, casting, calendering, rolling, or inflation molding can be used to extrude molten resin into a sheet using a T-die, I-die, etc., connected to a screw-type extruder. When manufacturing a porous resin layer with a multilayer laminated structure, the base layer, first surface layer, and / or second surface layer can be manufactured separately and then laminated using a lamination method or the like. Alternatively, film forming 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 multi-manifold, or an extrusion lamination method using multiple dies.

[0094] A porous resin sheet can be manufactured by laminating a porous resin layer with other layers as needed. If the porous resin layer, base layer, first surface layer and / or second surface layer are stretched, the base layer can be stretched before laminating the first surface layer and / or second surface layer, or it 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 oriented resin layer and the base layer is a porous biaxially oriented resin layer can be manufactured, for example, by the process described above.

[0095] Examples of stretching methods include longitudinal stretching using the difference in peripheral speed of a group of rolls, transverse stretching using a tenter oven, sequential biaxial stretching combining these methods, rolling, simultaneous biaxial stretching using a combination of a tenter oven and a pantograph, and simultaneous biaxial stretching using a combination of a tenter oven and a linear motor. In addition, simultaneous biaxial stretching (inflation molding), in which molten resin is extruded into a tube shape using a circular die connected to a screw-type extruder and then air is blown into it, can also be used.

[0096] Among these, the porous resin layer, substrate layer, first surface layer, and second surface layer are preferably manufactured by extruding a resin composition into a sheet from a T-die connected to an extruder, and then stretching the sheet, as this facilitates the realization of multilayering and adjustment of film thickness. Examples of stretching methods include longitudinal stretching, transverse stretching, and sequential biaxial stretching or simultaneous biaxial stretching, which combine these methods.

[0097] When performing stretching, the stretching temperature is preferably in a range above the glass transition temperature of the thermoplastic resin if the thermoplastic resin used is amorphous. If the thermoplastic resin is crystalline, the stretching temperature is preferably in a range above the glass transition temperature of the amorphous portion of the thermoplastic resin and below the melting point of the crystalline portion, and preferably 2 to 60°C lower than the melting point of the thermoplastic resin. Specifically, for propylene homopolymer (melting point 155 to 167°C), a stretching temperature of 100 to 164°C is preferred, and for 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, if the thermoplastic resin is crystalline, the stretching temperature is preferably 20°C or more lower than the melting point of the thermoplastic resin, and more preferably 25°C or more lower. The stretching temperature may be set based on the glass transition temperature or melting point of the thermoplastic resin 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 from the viewpoint of stable stretch molding, it is preferably in the range of 20 to 350 m / min.

[0099] Furthermore, the stretching ratio can be appropriately determined considering the characteristics of the thermoplastic resin used. For example, when using a propylene homopolymer or propylene copolymer, the stretching ratio when stretching in one direction is usually 1.1 times or more at the lower limit, preferably 2 times or more, and 10 times or less at the upper limit, preferably 9 times or less. On the other hand, the stretching ratio when biaxially stretched is an area stretching ratio, and is usually 1.5 times or more at the lower limit, preferably 4 times or more, and 75 times or less at the upper limit, preferably 50 times or less. When stretching other thermoplastic resin films in one direction, the stretching ratio is usually 1.2 times or more at the lower limit, preferably 2 times or more, and 10 times or less at the upper limit, preferably 5 times or less. The stretching ratio when biaxially stretched is an area stretching ratio, and is usually 1.5 times or more at the lower limit, preferably 4 times or more, and 20 times or less at the upper limit, preferably 12 times or less. Within the above range of stretching ratios, the desired porosity and basis weight are easily obtained, and opacity is easily improved. Furthermore, the film is less prone to tearing, and the stretch molding process is more stable. When the pores in the porous resin layer are formed by stretching, starting from particles, it is preferable that the stretching ratio, stretching temperature, and particle content all meet the above 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 comprises the porous resin layer described above.

[0101] [Properties of porous resin sheets] (Breaking strength) The breaking strength in the width direction of the porous resin sheet is 0.1 kgf / mm². 2 Preferably, it is 1.0 kgf / mm² or higher. 2 It is more preferable that the value be greater than or equal to 2.0 kgf / mm². 2 It is even more preferable that the above conditions are met. Furthermore, the breaking strength in the width direction should be 10 kgf / mm². 2 The following is preferable: 8 kgf / mm2 More preferably, it is as follows, and 6 kgf / mm 2 Even more preferably, it is as follows. Here, the "breaking strength in the width direction of the porous resin sheet" is 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] When the breaking strength in the width direction of the porous resin sheet is 0.1 kgf / mm 2 or more, it is preferable from the viewpoint of maintaining the film shape during conveyance. Also, when the breaking strength in the width direction is 10 kgf / mm 2 or less, it is preferable from the viewpoint of shape maintenance when press-molded.

[0103] In order to increase the number of pockets or the like per unit length of the carrier tape, generally, the longitudinal direction of the pockets or the like may be formed parallel to the width direction of the carrier tape. For this reason, it is preferable that the porous resin sheet is designed to have the above-described breaking strength in the width direction. Also, when the longitudinal direction of the pockets or the like is formed parallel to the length direction of the carrier tape, it is also possible to design the porous resin sheet to have the above-described breaking strength in the length direction.

[0104] [Use] The porous resin sheet of the present invention has suitable properties for forming a carrier tape. Therefore, the porous resin sheet of the present invention is preferably used for a carrier tape.

[0105] For example, it can be a carrier tape including the above-described porous resin sheet and pockets formed in the porous resin sheet. The size of the pocket can be, for example, a vertical dimension × a horizontal dimension of 0.1 × 0.1 mm to 3 × 3 mm.

[0106] One example of a carrier tape utilizing one embodiment of the porous resin sheet according to the present invention is the configuration shown in Figure 4, which is a cross-section in the lamination direction passing through the pocket. As shown in Figure 4, it is preferable that the pocket 4 does not penetrate the base material layer 1. Furthermore, of the two interfaces 1a and 1b of the base material layer 1, it is more preferable that the position of the interface 1b opposite to the interface 1a that is pressed down for the shaping of the pocket 4 does not change before and after the shaping of the pocket 4. On the other hand, it is preferable that the interface 1a on the side in which the shape of the pocket of the carrier tape is formed is linear or substantially 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 components, 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. Examples of components include electronic components.

[0109] <Method for shaping porous resin sheets> There are no particular restrictions on the method for forming pockets or other shapes in a porous resin sheet, but examples include pressure molding, press molding, and vacuum rotary molding. Of these, from the viewpoint of cost and other factors, it is preferable to form the shape in the porous resin sheet by press molding at room temperature.

[0110] Furthermore, the shape formed on the porous resin sheet is selected according to the shape of the component to be contained within, and there are no particular restrictions, but examples of shapes include cylindrical shapes and prismatic shapes. [Examples]

[0111] The present invention will be described in more detail below with reference to 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 shown in Table 1.

[0113] [Table 1]

[0114] <Porous resin sheet> [Example 1] Resin composition A was kneaded in an extruder set to 230°C, then supplied to an extrusion die set to 250°C and extruded into a sheet. This sheet was then cooled using a cooling device to obtain an unstretched sheet. This unstretched sheet was heated to 130°C and stretched four times in the longitudinal direction (length direction) using a number of rolls with different peripheral speeds to obtain a four-fold stretched film. Next, resin composition C was kneaded in an extruder set to 250°C, then supplied to an extrusion die set to 250°C and extruded into a sheet. This was then laminated onto the surface of the four-fold stretched film prepared above to obtain a two-layer laminated film. Next, the laminated film was cooled to 60°C, reheated to approximately 140°C using a tenter oven, and stretched eight times in the transverse direction (width direction). After that, it was annealed in an oven adjusted to 160°C, cooled to 60°C, and the edges were slit to obtain a porous resin sheet with a two-layer structure (first surface layer / base layer; composition: resin composition C / resin composition A, porosity: 40.0% / 49.0%, thickness: 15 μm / 185 μm, stretching: uniaxial / biaxial), a thickness of 200 μm, and a porosity of 48.3%.

[0115] The properties of the obtained porous resin sheet were measured as follows. (Overall thickness) The overall thickness (μm) of the porous resin sheet was measured using a constant-pressure thickness gauge (device name: PG-01J, manufactured by Teclock Co., Ltd.) in accordance with JIS K7130:1999 "Plastics - Films and sheets - Method for measuring thickness".

[0116] (Thickness of each layer) The thickness (μm) of each layer in the multilayer structure was measured as follows. A porous resin sheet was cooled to a temperature of -60°C or lower using liquid nitrogen. A razor blade (product name: Proline Blade, manufactured by Schick Japan) was applied at a right angle to the sample placed on a glass plate to prepare a sample for cross-sectional measurement. The cross-section of the obtained sample was observed using a scanning electron microscope (instrument name: JSM-6490, manufactured by JEOL Ltd.). , outside The boundaries of each layer were identified from the observation, and the thickness ratio of each layer in the porous resin sheet was determined. The thickness of each layer was determined by multiplying the measured total thickness by the thickness ratio of each layer.

[0117] (Measurement of porosity) The porosity (%) of each layer in the multilayer laminated structure was measured as follows: A portion of a porous resin sheet was cut out, embedded in epoxy resin, and solidified. Then, using a microtome, it was cut perpendicular to the planar and TD directions of the porous resin sheet to be measured, and the cut surface was attached to an observation sample stage so that it would be the observation surface. Gold or gold-palladium was deposited on the observation surface, and the cut surface of the porous resin sheet was observed using a scanning electron microscope at a magnification of any suitable size (e.g., 500x to 3000x), and the observed area was captured as image data. The obtained image data was processed using an image analysis device to determine the area ratio (%) of voids in each layer of the porous resin sheet, and the average of the area ratios (%) obtained at 10 or more arbitrary locations was taken as the void ratio (%) of each layer. The porosity of all layers was obtained by taking the average of the porosity values ​​of each layer weighted by thickness.

[0118] [Example 2], [Comparative Example 1], [Comparative Example 4] Porous resin sheets for Example 2, Comparative Example 1, and Comparative Example 4 were obtained by the same method 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 using the same method as in Example 1, except that the stretching temperature in the lateral direction (tenter oven temperature) was changed to 145°C.

[0120] [Example 4] A porous resin sheet of Example 4 was obtained using the same method as in Example 1, except that the temperature for stretching in the longitudinal direction was changed to 140°C.

[0121] [Comparative Example 2] A porous resin sheet of Comparative Example 2 was obtained by the same method as in Example 2, except that the temperature for stretching in the longitudinal direction was changed to 145°C.

[0122] [Table 2]

[0123] [Example 5] The porous resin sheet of Example 5 was obtained by the same method as in Example 1, except that the resin composition was changed as shown in Table 3 and the stretching temperature in the lateral direction (tenter oven temperature) was changed to 135°C.

[0124] [Comparative Example 3] Resin composition B was kneaded in an extruder set to 230°C, then fed into a feed-block type multilayer die set to 250°C and extruded into a sheet. This sheet was then cooled using a cooling device to obtain an unstretched sheet. This unstretched sheet was heated to 135°C and stretched four times in the longitudinal direction to obtain a four-fold stretched film. Next, this four-fold stretched film was cooled to 60°C, heated again to approximately 135°C using a tenter oven, and stretched eight times in the transverse direction. After that, it was annealed in an oven adjusted to 160°C, cooled to 60°C, and the edges were slit to obtain a porous resin sheet with a single-layer structure (base layer; composition: resin composition B, porosity: 50.0%, thickness: 200 μm, stretching: biaxial) as shown in Figure 3, with a total thickness of 200 μm and a porosity of 50.0%.

[0125] [Example 6] Resin composition A was kneaded in an extruder set to 230°C, then supplied to an extrusion die set to 250°C and extruded into a sheet. This sheet was then cooled using a cooling device to obtain an unstretched sheet. This unstretched sheet was heated to 135°C and stretched four times in the longitudinal direction using a number of rolls with different peripheral speeds to obtain a four-fold stretched film. Next, resin composition C was kneaded in an extruder set to 250°C, then supplied to an extrusion die set to 250°C and extruded into a sheet. This was then laminated onto the front and back surfaces of the four-fold stretched film prepared above to obtain a three-layer laminated film. Next, the laminated film was cooled to 60°C, reheated to approximately 135°C using a tenter oven, stretched eight times in the transverse direction, then annealed in an oven adjusted to 160°C, cooled to 60°C, and the edges were slit to obtain a porous resin sheet with a three-layer structure (first surface layer / substrate layer / second surface layer; composition: resin composition C / resin composition A / resin composition C, porosity: 40.0% / 50.0% / 40.0%, thickness: 15μm / 170μm / 15μm, stretching: uniaxial / biaxial / uniaxial), a thickness of 200μm, and a porosity of 49.2%.

[0126] [Example 7] The porous resin sheet of Example 7 was obtained by the same method as in Example 1, except that resin composition A and resin composition C were extruded into sheets, respectively, 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 porous resin sheet of Example 8 was obtained by the same method as in Example 1, except that resin composition A and resin composition C were extruded into sheets, respectively, 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] The porous resin sheet of Example 9 was obtained by the same method as in Example 1, except that the resin composition was changed as shown in Table 3 and the stretching temperature in the lateral direction (tenter oven temperature) was changed to 150°C.

[0129] [Example 10] Except for changing the lateral stretching temperature (tenter oven temperature) to 130°C, the process was carried out in the same manner as in Example 1. Example 10 A porous resin sheet was obtained.

[0130] [Table 3]

[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 which the sheet fractured in the width direction was measured in accordance with JIS-K7127:1999 (Plastics - Test methods for tensile properties). Specimen size: 15mm x 150mm Tensile speed: 300 mm / min. The same sample was measured three times, and the average value was calculated.

[0133] [Formability] Using a debossing metal plate manufactured by Tsukaya Hamono Seisakusho Co., Ltd. (tip: 400 μm x 200 μm rectangle, blade angle: 90°), and a press machine (Mini Test Press manufactured by Toyo Seiki Co., Ltd.), a pseudo-pocket shape was formed from the first surface layer to the base layer of the porous resin sheet obtained in the above examples and comparative examples 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. 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) The evaluation was as follows: A: Excellent We were able to achieve depths of 30 μm or more, and shape the sheet to a depth of between 85% and 90% of its thickness. B: Good We were able to achieve depths of 30 μm or more, and shape the sheet to a depth of between 80% and 85% of its thickness. C: No problem level We were able to achieve depths of 30 μm or more, and shape the sheet to a depth of between 75% and 80% of its thickness. D: Bad We were able to achieve a depth of 30 μm or more, but we were unable to shape the sheet to a depth exceeding 75% of its thickness. E: Extremely bad We were unable to achieve a depth of 30 μm or more.

[0135] (Taper suppression) The evaluation was as follows: A: Excellent The angle between the base and the sides was 85° or more. B: Good The angle between the base and the sides was between 80° and 85°. C: No problem level The angle between the base and the sides was between 75° and 80°. D: Bad The angle between the base and the sides was between 60° and less than 75°. E: Extremely bad The angle between the base and the sides was less than 60°.

[0136] (bottom stability) The distance between the bottom of the formed pocket and the surface opposite the first surface layer of the porous resin sheet was measured from a cross-sectional image. For 10 pockets, the maximum and minimum values ​​of this distance were recorded, and the average difference was calculated. Bottom stability was evaluated from the average value as follows. A: Excellent (average value less than 1 μm) B: Good (average value greater than 1 μm and less than or equal to 3 μm) C: No problem level (average value greater than 3μm but less than or equal to 5μm) D: Poor (average size greater than 5 μm but less than or equal to 10 μm) E: Extremely poor (average size greater than 10 μm)

[0137] [Table 4]

[0138] [Table 5]

[0139] Examples 1 to 10 show that the porous resin sheet of the present invention exhibits good breaking strength and formability even when the thickness balance, porosity, stretching method, and layer structure are changed within a predetermined range. Furthermore, Examples 1, 7, and 8 show that bottom stability improves as the thickness of the first surface layer increases. In addition, Examples 9 and 10 show that increasing the particle content in the first surface layer and / or lowering the stretching temperature of the first surface layer increases the porosity of the first surface layer, thereby improving formability. In contrast, the porous resin sheet of Comparative Example 1 could not be shaped to a sufficient depth because its overall thickness was insufficient. The porous resin sheet of Comparative Example 2 had a low overall porosity, resulting in poor shapeability in terms of taper suppression and bottom stability. The porous resin sheet of Comparative Example 3 was composed only of a base layer, resulting in poor shapeability in terms of taper suppression. The porous resin sheet of Comparative Example 4 had insufficient particle content in the first surface layer, resulting in poor shapeability in terms of taper 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 these examples. It is clear to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of the present invention. Furthermore, the components of the above embodiments may be combined in any way without departing from the spirit of the invention.

[0141] This application is based on the Japanese Patent Application No. 2022-102194 filed on June 24, 2022, the contents of which are incorporated by reference within this application. [Industrial applicability]

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

[0143] 1 Base material layer 2 First surface layer 3 Second surface layer 4 pockets 10 Porous resin layer

Claims

1. It comprises a porous resin layer containing a thermoplastic resin, 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 includes a base layer and a first surface layer, Both the base layer and the first surface layer contain thermoplastic resin and particles. The content of the particles in the substrate layer is 20 to 45% by mass. The content of the particles in the first surface layer is 45 to 80% by mass. A porous resin sheet having a breaking strength in the width direction of 0.1 to 10 kgf / mm².

2. The first surface layer is a porous uniaxially oriented resin layer, The porous resin sheet according to claim 1, wherein the base layer is a porous biaxially oriented 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 the 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. A porous resin sheet according to claim 1 or 2, for use as a carrier tape.

8. A porous resin sheet according to claim 1 or 2, A pocket formed in the porous resin sheet, A carrier tape equipped with this feature.

9. comprising a porous resin layer containing a thermoplastic resin, 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 includes a base layer and a first surface layer, Both the base layer and the first surface layer contain thermoplastic resin and particles. The content of the particles in the substrate layer is 20 to 45% by mass. A porous resin sheet having a particle content of 45 to 80% by mass in the first surface layer, A pocket formed in the porous resin sheet, A carrier tape equipped with this feature.

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