Porous resin sheet and carrier tape

Abstract

The present invention provides a porous resin sheet suitable for use as a carrier tape, the porous resin sheet being capable of serving as a carrier tape having an accommodation portion that is parallel to the surface of the carrier tape and has a flat bottom.　The present invention relates to a porous resin sheet having a thickness of 150-350 μm and including a base layer and a bottom-side surface layer, wherein both the base layer and the bottom-side surface layer contain a thermoplastic resin, the base layer has a porosity of 35-80%, and, on the surface of the porous resin sheet on the base layer side, the indentation recovery ratio, determined from the difference between the indentation depth when a load is increased from 5 mN to 130 mN and the indentation depth when the load is decreased from 130 mN to 20 mN, is 10.0% or less.

Description

Porous resin sheets and carrier tapes

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

[0002] Carrier tapes made of paper or the like are known to be used for transporting and storing electronic components such as microchips (Patent Document 1). In addition, in order to prevent the generation of paper dust by paper carrier tapes, resin sheets made of porous resin materials have been proposed as a base material for carrier tapes that can be replaced with paper. For example, Patent Document 2 proposes a porous resin sheet, which is a carrier tape material that can be shaped without undergoing special processes such as heating or reduced pressure, similar to paper base materials.

[0003] Regarding carrier tape materials, in order to house finer electronic components and ensure stable transport and reliable pickup during the assembly process of these components, it is necessary to have a housing section with a flat bottom parallel to the surface of the carrier tape. In particular, when manufacturing carrier tape materials continuously for long periods of time, a high defect rate due to bottom deformation reduces the yield, so there is an increasing demand for ensuring that the bottom of the housing section is reliably flattened.

[0004] Japanese Patent Publication No. 2000-43975, International Publication No. 2023 / 249024, Pamphlet

[0005] The present invention provides a porous resin sheet suitable as a carrier tape, which can be used to create a carrier tape having a storage portion that is parallel to the surface of the carrier tape and has a flat bottom.

[0006] As a result of diligent research to solve the above problems, the inventors have come up with the following invention.

[0007] In other words, the present invention is as follows: [1] A porous resin sheet having a thickness of 150 to 350 μm, comprising a base layer and a bottom surface layer, wherein both the base layer and the bottom surface layer contain a thermoplastic resin, the porosity of the base layer is 35 to 80%, and the indentation return rate determined from the difference between the indentation depth when pressurized from 5 mN to 130 mN and the indentation depth when depressurized from 130 mN to 20 mN on the surface of the porous resin sheet on the base layer side is 10.0% or less. [2] A porous resin sheet having a thickness of 150 to 350 μm, comprising a base layer and a bottom surface layer, wherein both the base layer and the bottom surface layer contain a thermoplastic resin, the porosity of the base layer is 35 to 80%, and the bottom surface layer has a porosity of less than 35% and a thickness of 20 to 60 μm. [3] A porous resin sheet comprising a base layer and a bottom surface layer, having a thickness of 150 to 350 μm, wherein both the base layer and the bottom surface layer contain a thermoplastic resin, the porosity of the base layer is 35 to 80%, and the bottom surface layer contains a plate-like filler and has a thickness of 1 μm or more and less than 20 μm. [4] A porous resin sheet according to any one of [1] to [3], wherein the base layer has a receiving surface layer on the opposite side of the bottom surface layer, either directly or via another layer, the receiving surface layer is a porous layer containing a thermoplastic resin, and the ratio (H1 / H0) of the porosity of the receiving surface layer to the porosity of the base layer (H0) is 0.80 to 1.20. [5] The porous resin sheet according to [4], wherein the thickness of the receiving surface layer is 5 μm or more. [6] A porous resin sheet according to any one of [1] to [5], having a functional layer directly or via another layer on the side of the base layer opposite to the bottom surface layer, wherein the functional layer contains a water-soluble or water-dispersible polymer and an antistatic agent. [7] A carrier tape that is a molded body of the porous resin sheet according to any one of [1] to [6] and has a housing portion. [8] An electronic component packaging body comprising the carrier tape according to [7] and a cover tape attached to the carrier tape.

[0008] According to the present invention, a porous resin sheet suitable as a carrier tape can be provided that includes a storage portion having a flat bottom parallel to the surface of the carrier tape.

[0009] This is a schematic cross-sectional view showing an example of a porous resin sheet in this embodiment. This is a schematic cross-sectional view showing another example of a porous resin sheet in this embodiment. This is an image diagram showing an example of a carrier tape. This is a schematic cross-sectional view showing an example of a carrier tape.

[0010] The present invention will be described in detail below with reference to the following embodiments. This embodiment is an example of the present invention, and the present invention is not limited to this embodiment. In this specification, the numerical range "〇 to △" indicates "〇 or more and △ or less".

[0011] [Porous resin sheet]

[0012] A detailed explanation of porous resin sheets and carrier tapes using porous resin sheets will be provided with reference to Figures 1 to 4.

[0013] Figure 1 is a schematic cross-sectional view showing an example of a porous resin sheet 10. The porous resin sheet 10 includes a base layer 120 and a bottom surface layer 140. The porous resin sheet 10 may include any other layers besides these. For example, as shown in Figure 2, it is also preferable for the porous resin sheet 10 to have a harbor-side surface layer 130 on the opposite side of the base layer 120 from the bottom surface layer 140. In addition, there may be a further functional layer (not shown) that becomes the outermost layer on the opposite side of the harbor-side surface layer 130 from the base layer 120 (the side with the harbor section P when used as a carrier tape). Furthermore, there may be any layer between the base layer 120 and the harbor-side surface layer 130, or between the base layer 120 and the bottom surface layer 140.

[0014] When the porous resin sheet 10 is used as a carrier tape 1, for example as shown in Figure 3, it is preferable that the bottom surface layer 140 is located at the bottom (opposite the side where the housing section P is provided). Figure 4 is a schematic cross-sectional view showing an example in which the porous resin sheet 10 is used as a carrier tape 1. The carrier tape 1 has a housing section P on the side where the housing-side surface layer 130 is located, which is capable of housing electronic components. The bottom surface layer 140 is located at the bottom opposite to the side where the housing section P is provided.

[0015] The inventors diligently studied how to make the bottom portion B of the containment portion P, formed by pressurization alone without heating or depressurization, smaller and flatter when the porous resin sheet 10 described above is used as a carrier tape 1. As a result, they found that if the indentation return rate determined on the surface of the base material layer 120 side (or the containment surface layer 130 side if there is a containment surface layer 130) of the porous resin sheet 10 is below a predetermined level, it is easier to realize the carrier tape 1 described above.

[0016] The porous resin sheet 10 of this embodiment comprises a base layer 120 and a bottom surface layer 140, and is a porous resin sheet 10 with a thickness of 150 to 350 μm, wherein both the base layer 120 and the bottom surface layer 140 contain a thermoplastic resin, the porosity of the base layer 120 is 35 to 80%, and the indentation return rate determined on the surface of the porous resin sheet 10 on the base layer 120 side is 10.0% or less.

[0017] When the porous resin sheet 10 described above is used as a carrier tape 1, it is preferable that the bottom surface layer 140 is positioned on the bottom side. This makes it easier for the carrier tape 1 to have a receiving section P with a flat bottom B parallel to the surface S when used as a carrier tape 1. Furthermore, when forming the receiving section P for use as a carrier tape 1, the porous resin sheet 10 can be formed without undergoing special processes such as heating or depressurization.

[0018] <Indentation Return Rate> In one embodiment of the porous resin sheet, the indentation return rate determined on the surface of the base material layer is 10.0% or less. As mentioned above, the porous resin sheet may have a hoisting surface layer on the opposite side of the bottom surface layer from the base material layer. In this case, the indentation return rate can be determined on the surface of the layer that is on the surface side of the base material layer, that is, on the surface of the hoisting surface layer. If there is an outermost layer or the like on an even more surface side than the hoisting surface layer, similarly, the indentation return rate can be determined on the surface of the outermost layer.

[0019] When such porous resin sheets are used as carrier tapes, the deformation when forming a containment area is small, and the bottom of the containment area tends to be very flat. The indentation return rate mentioned above refers to the percentage calculated from the amount of return of the indentation depth, measured by a test similar to the pressurization process during shaping and the subsequent depressurization process when using a porous resin sheet as a carrier tape. Specifically, the indentation return rate can be determined by measuring the indentation depth d1 when a probe is pressed into the sample surface with a load from 5 mN to 130 mN, and then measuring the indentation depth d2 when the load is depressurized to 20 mN, with the sample thickness being L, and calculating it using the following formula: Indentation return rate (%) = (d1 - d2) / L × 100

[0020] The specific configuration of the porous resin sheet of the present invention will be described below, with reference to the first and second embodiments as examples.

[0021] [First Embodiment] The first embodiment relates to a porous resin sheet having a thickness of 150 to 350 μm, comprising a base layer and a bottom surface layer, wherein both the base layer and the bottom surface layer contain a thermoplastic resin, the porosity of the base layer is 35 to 80%, and the bottom surface layer has a porosity of less than 35% and a thickness of 20 to 60 μm. The following describes in detail each layer included in the porous resin sheet of the first embodiment.

[0022] <Base Layer> The base layer contains a thermoplastic resin (A). Preferably, the base layer further contains a filler. For example, by stretching a resin composition containing thermoplastic resin (A) and a filler, a layer can be formed in which many pores are formed with the filler as the core. Such a porous resin sheet is easily made lighter by having a layer in which many pores are formed, and is suitable as a carrier tape. Furthermore, by increasing the porosity of each layer of the porous resin sheet, the pores can be utilized as escape routes when the solid components of the sheet, namely the resin and filler, are compressed during shaping for use as a carrier tape, thereby improving shapeability. For this reason, it is easy to achieve the desired shape without requiring special processing such as heating or reduced pressure.

[0023] (Thermoplastic resin (A)) The type of thermoplastic resin (A) contained in the base layer is not particularly limited. Examples include polyethylene resins, polyolefin resins such as polypropylene resins, polyvinyl chloride resins, polystyrene resins, polyethylene terephthalate resins, polycarbonate resins, polymethylpentene-1, cyclic olefins, or mixtures containing two or more of these resins. As the thermoplastic resin (A), polyolefin resins such as polyethylene resins and polypropylene resins are preferred, polyethylene resins or polypropylene resins are more preferred, and polypropylene resins are even more preferred. The reasons why each resin is preferred will be explained below.

[0024] The content of thermoplastic resin (A) in the base layer is preferably 55% by mass or more, more preferably 60% by mass or more, and even more preferably 65% ​​by mass or more. Furthermore, the content of thermoplastic resin is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less. When the content of thermoplastic resin (A) is above the above lower limit, water resistance is improved, and if the base layer contains a filler, the generation of paper dust (shedding of the filler) tends to be reduced.

[0025] [Polypropylene resin]: When the base layer contains polypropylene resin, it is particularly easy to lighten the porous resin sheet, and flexibility can be given to the base layer, making it easier to prevent damage to the electronic components it contains.

[0026] 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, crystalline homopolypropylene resins obtained by homopolymerizing propylene are preferred, and isotactic homopolypropylene resins are more preferred, from the viewpoint of easily improving the stretchability of the substrate layer.

[0027] Furthermore, as polypropylene resins, polypropylene polymerized using a Ziegler-Natta polymerization catalyst, polypropylene polymerized using a metallocene polymerization catalyst (single-site polymerization catalyst), olefin-based thermoplastic elastomers also known as reactor TPO, and high melt-tension polypropylene can be used.

[0028] The melt flow rate (MFR) of polypropylene resins, 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 base layer. Furthermore, it is preferably 20 g / 10 min or less, more preferably 10 g / 10 min or less, and even more preferably 6 g / 10 min or less.

[0029] The polypropylene resin is preferably the main component of the thermoplastic resin (A) contained in the base layer. Specifically, it is preferably 50% by mass or more of the thermoplastic resin (A) contained in the base layer, more preferably 65% ​​by mass or more, and even more preferably 75% by mass or more. It is also possible for 100% by mass, i.e., the entire amount, of the thermoplastic resin (A) contained in the base layer to be polypropylene resin.

[0030] [Polyethylene Resin]: When the base layer contains polyethylene resin, the stretchability of the base layer is easily improved. Examples of polyethylene resins include high-density polyethylene resin, medium-density polyethylene resin, linear low-density polyethylene resin, and copolymers mainly composed of ethylene.

[0031] Furthermore, polyethylene resins can be used in combination with other thermoplastic resins. For example, the base layer may be a combination of polypropylene resin and polyethylene resin. This improves the stretchability of the base layer, while making it easier to obtain a layer with less stretching unevenness, a good appearance, and a uniform thickness. As a result, it becomes easier to form a housing with a uniform size when shaped.

[0032] When the base 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, even more preferably 50:50 to 95:5, and particularly preferably 65:35 to 95:5.

[0033] (Filler) There are no particular limitations on the type of filler that the base material layer may contain. Examples of the filler include organic fillers, inorganic fillers, and the like. From the viewpoint that shape recovery force is less likely to occur after press shaping compression, the filler is preferably an inorganic filler. The filler may be surface-treated.

[0034] Examples of the inorganic filler include calcium carbonate, titanium oxide, calcined clay, talc, barium sulfate, aluminum sulfate, silica, zinc oxide, magnesium oxide, diatomaceous earth, and the like. The blending of the inorganic filler facilitates formation of a base material layer having pores therein. Fine powder of calcium carbonate, clay or diatomaceous earth is more preferred because of good pore moldability and low cost. Fine powder of calcium carbonate is particularly preferred because it is easy to adjust the porosity due to abundant product types, and it is also easy to adjust the color tone of the base material layer.

[0035] The average particle diameter of the filler is preferably 0.05 µm or more, more preferably 0.1 µm or more, and still more preferably 0.5 µm or more. Further, the average particle diameter of the filler is preferably 6 µm or less, more preferably 4 µm or less, and still more preferably 2 µm or less. When the average particle diameter is within the above range, it becomes easy to control the porosity to a desired range. The average particle diameter of the filler is the volume average particle diameter (D50) measured by a particle size distribution meter based on laser diffraction.

[0036] The content of the filler in the base material layer is preferably 25% by mass or more, and more preferably 30% by mass or more. Further, the filler content is preferably 80% by mass or less, more preferably 70% by mass or less, and still more preferably 60% by mass or less. By setting the filler content in the base material layer to 25% by mass or more, it becomes easy to obtain high porosity from pores formed starting from the filler when stretched, resulting in good shapeability, and it becomes easy to obtain an accommodating portion having a molding depth corresponding to the size of the electronic component to be accommodated. Further, by setting the filler content in the base material layer to 80% by mass or less, the porous resin sheet tends to have flexibility suitable for production and transportation.

[0037] (Other Additives) The base material layer may contain components other than the aforementioned thermoplastic resin (A) and filler. For example, the base material layer may optionally contain additives such as heat stabilizers (antioxidants), light stabilizers, conductive fillers, dispersants, and lubricants.

[0038] When the base material layer contains a heat stabilizer, it is usually preferable to contain 0.001 to 1% by mass of the heat stabilizer. Examples of the heat stabilizer include sterically hindered phenol-based, phosphorus-based, and amine-based heat stabilizers. When the base material layer contains a light stabilizer, it is usually preferable to contain 0.001 to 1% by mass of the light stabilizer. Examples of the light stabilizer include sterically hindered amine-based, benzotriazole-based, and benzophenone-based light stabilizers.

[0039] The dispersant or lubricant can be used, for example, for the purpose of dispersing the filler. The content of the dispersant or lubricant in the base material layer is usually preferably 0.01 to 4% by mass. Examples of the dispersant or lubricant include silane coupling agents, higher fatty acids such as oleic acid and stearic acid, metal soaps, polyacrylic acid, polymethacrylic acid, and salts thereof.

[0040] It is preferable that the base material layer contains a dispersant or a lubricant as an additive, because this suppresses agglomeration of fillers, increases the surface area to easily improve the pore formation efficiency, and makes it easy to obtain a porosity corresponding to the filler content even when the filler content is high. Further, when the porous resin sheet is used as a carrier tape, it is also preferable that the base material layer contains a conductive filler as an additive, because this easily suppresses adhesion of dust due to static electricity.

[0041] (Thickness) The thickness of the base material layer is preferably 100 to 300 µm. The thickness of the base material layer is preferably 120 µm or more, more preferably 130 µm or more, and still more preferably 150 µm or more. Further, the thickness of the base material layer is preferably 280 µm or less, more preferably 250 µm or less, and still more preferably 210 µm or less. The thickness of the base material layer can be appropriately selected within the above range according to the size of the article accommodated in the accommodating portion (pocket).

[0042] If the thickness of the base material layer is less than the above range, it may be difficult to ensure sufficient depth of the housing when used as a carrier tape. Furthermore, if the base material layer exceeds the above range, it may be difficult to maintain flexibility suitable for manufacturing and transport.

[0043] In this specification, layer thickness refers to the value measured in accordance with JIS K7130:1999. The thickness of a layer composed of multiple layers refers to the total thickness of the layer (the total thickness of the layer including multiple layers). In a layer composed of multiple layers, the thickness of each layer can be calculated by observing its cross-section using an electron microscope, determining the thickness ratio of each layer from the observed interface between the layers, and then calculating the total layer thickness measured above and the thickness ratio of each layer.

[0044] (Porosity) The porosity of the base layer is 35 to 80%. Preferably, the porosity of the base layer is 40% or more, and more preferably 45% or more. Furthermore, preferably, the porosity of the base layer is 70% or less, and more preferably 60% or less.

[0045] If the porosity of the base layer is below the above range, it may be difficult to achieve sufficient shape conformability in the porous resin sheet after molding if the porous resin sheet is shaped without processes such as heating or reduced pressure. For example, when attempting to shape a porous resin sheet to form a housing with sides perpendicular to the surface and a bottom parallel to the surface, molding defects such as tapered sides of the housing or waviness at the bottom may occur. On the other hand, if the porosity of the base layer exceeds the above range, it may be difficult to obtain sufficient mechanical strength. The porosity of the base layer can be adjusted by the filler content in the base layer, the average particle size of the filler, the composition of the thermoplastic resin, and the stretching conditions of the base layer. Furthermore, the porosity of the entire porous resin sheet can be adjusted, for example, by adjusting the porosity of the base layer, the bottom surface layer, and the housing surface layer, respectively. In this specification, "shape conformability" refers to the property that a porous resin sheet deforms along the mold, and the deformed resin does not rebound and try to return to its pre-shaping state, and the shape after shaping is stably maintained.

[0046] The porosity of the substrate layer is determined by observing the cross-section of the substrate layer with an electron microscope and calculating the percentage of the area occupied by voids in the substrate layer (area ratio) within the observed area. In this specification, if the object to be measured is a multilayer structure, the porosity of each layer may be calculated, and the average value obtained by weighting the porosity of each layer by the thickness of each layer may be used as the porosity of the entire layer.

[0047] The base layer is preferably a stretched layer. More preferably, the base layer is biaxially stretched. If the base layer contains a filler, a porosity-containing base layer can be easily obtained by stretching the resin composition containing the filler. A biaxially stretched base layer can easily have a high porosity while keeping the filler content low, so when a porous resin sheet having this is used as a carrier tape, it is less likely to cause shape defects even when forming deep containment areas, and it is easier to mold stably.

[0048] <Bottom Surface Layer> The porous resin sheet includes a bottom surface layer. (Hereinafter, the bottom surface layer may be referred to as the "second surface layer.") When the porous resin sheet is used as a carrier tape, it is preferable that the second surface layer (bottom surface layer) be located on the side that becomes the bottom of the carrier tape (opposite the side where the containment portion is formed).

[0049] The second surface layer contains a thermoplastic resin (A). The type of thermoplastic resin (A) included in the second surface layer is not particularly limited. The thermoplastic resin (A) of the second surface layer can be the same as that shown for the base layer. The thermoplastic resin (A) included in the second surface layer may be the same as or different from the thermoplastic resin (A) included in the base layer.

[0050] The second surface layer may further contain a filler. For example, by stretching a resin composition containing a thermoplastic resin (A) and a filler, a layer can be formed in which numerous pores are formed with the filler as a nucleus. The type of filler included in the second surface layer is not particularly limited. The same type of filler as that shown for the base layer can be used for the second surface layer. The filler included in the second surface layer may be the same as or different from the filler included in the base layer.

[0051] From the viewpoint of reducing porosity and ensuring flatness of the bottom of the containment section, if the second surface layer contains a filler, the filler content is preferably 50% by mass or less, more preferably 35% by mass or less, even more preferably 20% by mass or less, and particularly preferably no filler is contained. However, since having some porosity is also effective in stably ensuring the depth of the containment section, the filler content is preferably 15% by mass or more.

[0052] (Thermoplastic resin (A)) The type of thermoplastic resin (A) included in the second surface layer is not particularly limited. The thermoplastic resin (A) of the second surface layer can be the same as that shown for the base layer.

[0053] From the viewpoint of suppressing the fracture of the second surface layer during porous resin sheet molding and from the viewpoint of reducing porosity, the content of thermoplastic resin (A) in the second surface layer is preferably 50% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 85% by mass or more. The content of thermoplastic resin (A) in the second surface layer may be approximately 100% by mass.

[0054] In the first embodiment, the second surface layer has a porosity of less than 35% and a thickness of 20 to 60 μm. When such a porous resin sheet is used as a carrier tape, the indentation return rate tends to be 10.0% or less.

[0055] (Indentation return rate) In the first embodiment, from the viewpoint of maintaining the shape of the housing after shaping, the indentation return rate is preferably 10.0% or less, and more preferably 7.0% or less. The indentation return rate may be 0%, but from the viewpoint of preventing damage to electronic components that come into contact with the bottom of the housing, it is preferably 0.5% or more.

[0056] The porosity and thickness of the second surface layer (bottom side surface layer) are described below. (Porosity) In the first embodiment, the porosity of the second surface layer is less than 35%. From the viewpoint of ensuring the flatness of the bottom of the housing, the porosity of the second surface layer is preferably 30% or less, more preferably 20% or less, even more preferably 10% or less, and particularly preferably substantially 0%. Furthermore, the lower limit of the porosity of the second surface layer is not particularly limited and may be 0%, but it is preferable that it be 10% or more, as having some porosity is also effective in stably ensuring the depth of the housing.

[0057] When the porosity of the second surface layer is less than 35%, it is easier to achieve the above-mentioned indentation return rate when used as a carrier tape. The porosity of the second surface layer can be adjusted by the filler content in the second surface layer, the average particle size of the filler, the composition of the thermoplastic resin, and the stretching conditions of the second surface layer. The porosity of the second surface layer can be measured in the same way as the porosity of the base layer.

[0058] (Thickness) In the first embodiment, the thickness of the second surface layer is 20 to 60 μm. From the viewpoint of stabilizing the shape of the bottom of the housing, the thickness of the second surface layer is preferably 25 μm or more. Furthermore, in order to stably ensure the depth of the housing, the thickness of the second surface layer is preferably 50 μm or less, and more preferably 40 μm or less. When the thickness of the second surface layer (bottom side surface layer) is within the above range, it is easier for it to function as a receiving layer for the housing side surface layer and base material layer that are compressed when shaped. The thickness of the second surface layer can be measured in the same way as the thickness of the base material layer.

[0059] The second surface layer is preferably stretched, and more preferably uniaxially stretched. When the second surface layer is uniaxially stretched, the mechanical strength in the uniaxial direction is improved, and shape stability is easily obtained.

[0060] <Accommodation-side surface layer> In the porous resin sheet of this embodiment, an accommodation-side surface layer may be present on the opposite side of the bottom-side surface layer, either directly or via another layer. (Hereinafter, the accommodation-side surface layer may be referred to as the "first surface layer.") The first surface layer (accommodation-side surface layer) may or may not be present. When the porous resin sheet is used as a carrier tape, it is preferable that the first surface layer be located on the side having an accommodation portion for accommodating electronic components (the side where the electronic components are accommodated, the side where the cover tape is attached).

[0061] The first surface layer preferably contains a thermoplastic resin (A). The type of thermoplastic resin (A) included in the first surface layer is not particularly limited. The thermoplastic resin (A) of the first surface layer can be one of those shown in the description of the base layer. The thermoplastic resin (A) included in the first surface layer may be the same as or different from the thermoplastic resin (A) included in the base layer or the thermoplastic resin (A) included in the second surface layer.

[0062] The first surface layer preferably further contains a filler. For example, by stretching a resin composition containing a thermoplastic resin (A) and a filler, a layer can be formed in which numerous pores with filler as nuclei are formed. The type of filler included in the first surface layer is not particularly limited. The fillers shown in the above description for the base layer can be used as the filler for the first surface layer. The filler included in the first surface layer may be the same as or different from the filler included in the base layer or the filler included in the second surface layer.

[0063] The first surface layer preferably contains 50 to 75% by mass of filler. More preferably, the filler content in the first surface layer is 55% by mass or more. More preferably, the filler content in the first surface layer is 70% by mass or less, and even more preferably 65% ​​by mass or less. If the filler content in the first surface layer is below the above lower limit, when a porous resin sheet is used as a carrier tape, the repulsion of the resin during shaping increases, making shaping difficult. On the other hand, if the filler content in the first surface layer is above the above lower limit, for example, when attempting to mold a housing having sides perpendicular to the surface of the porous resin sheet and a bottom parallel to it, it is easier to suppress the tapering of the side shape during shaping, and the shape of the bottom also becomes more stable. This is because, at the boundary between the parts pressed by the shaping mold and the parts not pressed, the interface between fillers or between fillers and thermoplastic resin (A) is more prone to fracture than between thermoplastic resin (A) itself. When the filler is an inorganic filler, the above-mentioned tendency becomes more pronounced in the shape of the sides and bottom of the containment section during shaping, which is preferable. Furthermore, if the filler content exceeds the above upper limit, the first surface layer may be more prone to rupture during porous resin sheet molding.

[0064] The content of thermoplastic resin (A) in the first surface layer is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, and particularly preferably 35% by mass or more. Furthermore, the content of thermoplastic resin (A) is preferably 55% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less. It is preferable that the content of thermoplastic resin (A) is above the lower limit above because it makes it easier to suppress the fracture of the first surface layer during porous resin sheet molding. Furthermore, it is preferable that the content of thermoplastic resin (A) is below the upper limit above because it makes it easier to suppress the repulsion of the resin during shaping. As a result, for example, when attempting to mold a housing portion having sides perpendicular to the surface of the porous resin sheet and a bottom parallel to it, it is easier to suppress the tapering of the shape of the sides of the housing portion and the shape of the bottom portion becomes more stable.

[0065] The first surface layer may contain components other than the thermoplastic resin (A) and filler described above. Other additives that can be used include those shown in the description of the base layer.

[0066] (Thickness) The thickness of the first surface layer is preferably 5 μm or more. When forming the housing portion when used as a carrier tape, the strain of the portion including the first surface layer and a part of the base material layer can be averaged at the bottom of the housing portion formed by compression with a mold, making it easier to stabilize the shape of the compressed layer at the bottom of the housing portion. The thickness of the first surface layer is more preferably 7 μm or more, and even more preferably 10 μm or more. Furthermore, the thickness of the first surface layer is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less. The thickness of the first surface layer can be measured in the same way as the thickness of the base material layer.

[0067] (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 of the first surface layer is preferably 80% or less, more preferably 70% or less, and even more preferably 60% or less. When the porosity of the first surface layer is 35% or more, it is easier to obtain sufficient shape conformability even when forming a deep-shaped containment, and the shape of the bottom and sides of the formed containment is easier to stabilize. When the porosity of the first surface layer is 80% or less, it is easier to obtain mechanical strength for the porous resin sheet. The porosity of the first surface layer can be adjusted by the filler content in the first surface layer, the average particle size of the filler, the composition of the thermoplastic resin, and the stretching conditions of the first surface layer. The porosity of the first surface layer can be measured in the same way as the porosity of the base layer.

[0068] The ratio (H1 / H0) of the porosity of the first surface layer to the porosity (H0) of the base layer is preferably 0.80 to 1.20. The ratio (H1 / H0) is more preferably 0.85 or higher, and even more preferably 0.90 or higher. Furthermore, the ratio (H1 / H0) is more preferably 1.15 or lower, and even more preferably 1.10 or lower. When the ratio (H1 / H0) of the porosity of the first surface layer to the porosity (H0) of the base layer is within the above range, the difference between the shape of the first surface layer formed by shaping and the shape of the base layer is suppressed, making it easier to form a housing portion having sides perpendicular to the surface of the porous resin sheet and a bottom parallel to it, and making it easier to suppress the tapering of the sides of the housing portion.

[0069] The first surface layer is preferably stretched, and more preferably uniaxially stretched. The orientation of the resin chains in the stretching direction makes it easier to stabilize the shape formed by shaping along the stretching direction. In addition, the filler contained in the first surface layer forms voids that are long in the stretching direction by uniaxial stretching. For this reason, when shaping a housing portion having a longitudinal direction parallel to the stretching direction, the voids that extend in the stretching direction are advantageous as they easily correspond to the shaping. In this specification, "longitudinal direction of the housing portion" means the direction on the long axis side of a housing portion of any shape whose aspect ratio is not 1:1 in a plan view in the sheet surface direction. Also, "short direction of the housing portion" means the direction on the short axis side of a housing portion of any shape whose aspect ratio is not 1:1.

[0070] As described above, in both the first surface layer and the base layer containing filler, it is preferable that the first surface layer is uniaxially stretched and the base layer is biaxially stretched. That is, the first surface layer can be a porous uniaxially stretched resin layer, and the base layer can be a porous biaxially stretched resin layer. By using the above layer structure, when forming a housing portion having sides perpendicular to the surface of the porous resin sheet and a bottom parallel to it, it is easier to suppress molding defects such as tapered sides of the housing portion and waviness at the bottom.

[0071] When the first and second surface layers are porous uniaxially oriented resin layers and the base layer is a porous biaxially oriented resin layer, it can be manufactured, for example, by 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 laminated sheet 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.

[0072] <Other layers> The porous resin sheet may optionally include layers other than those described above.

[0073] (Functional layer) The porous resin sheet preferably has a functional layer on the side opposite to the second surface layer of the base layer (the side forming the containment portion), either directly or via another layer. The functional layer preferably contains a water-soluble or water-dispersible polymer (B) and an antistatic agent (C). By having such a functional layer, the porous resin sheet can be made to have appropriate adhesion to the cover tape while also possessing antistatic properties.

[0074] (Solid content per unit area) The solid content per unit area of ​​the functional layer is 5 g / m². ２ The following is preferable. Within the above range, when used as a carrier tape, less seal residue is generated when peeling off the cover tape. The solid content of the functional layer is preferably 0.03 g / m² from the viewpoint of adhesion to the cover tape and antistatic properties when used as a carrier tape. ２ More preferably 0.05 g / m ２ More preferably, 0.06 / m ２ That concludes the explanation. Furthermore, when used as a carrier tape, the amount of solid content in the functional layer is preferably 0.12 g / m², as this reduces the generation of sealant residue when peeling off the cover tape. ２ More preferably, 0.10 g / m ２More preferably, 0.08 g / m ２ The following applies:

[0075] (Water-soluble or water-dispersible polymer (B)) The functional layer contains a water-soluble or water-dispersible polymer (B), which improves adhesion to the cover tape when a porous resin sheet is used as a carrier tape. Here, a water-dispersible polymer is a polymer that forms an aqueous resin emulsion. A water-soluble polymer is particularly preferred as the water-soluble or water-dispersible polymer (B) (hereinafter sometimes simply referred to as "polymer (B)"). Polymer (B) may also be an ionic polymer to improve adhesion to the cover tape, and a cationic polymer is particularly preferred. The functional layer may also contain polymers other than polymer (B) as long as they do not hinder the above effects.

[0076] Examples of polymer (B) include (meth)acrylic polymers or ethyleneimine polymers having an amino group or ammonium salt structure, water-soluble polymers having a phosphonium salt structure, vinyl polymers that are cationized by modification of water-soluble polymers such as polyvinylpyrrolidone and polyvinyl alcohol, and one of these can be used alone or in combination of two or more. From the viewpoint of improving adhesion to the cover tape, (meth)acrylic polymers having an amino group or ammonium salt structure are preferred. In this invention, the expressions "having a ~ group" or "having a ~ structure" refer to polymers that have the said group or structure in their molecular skeleton, and polymers that have a compound containing the said structure as a counterion, for example, are not included in this definition.

[0077] When using a (meth)acrylic polymer or ethyleneimine polymer having an amino group or ammonium salt structure as polymer (B), it is preferable from the viewpoint of safety that it has primary to tertiary amino groups or primary to tertiary ammonium salt structures. Furthermore, from the viewpoint of improving adhesion to the cover tape, secondary to tertiary amino groups or secondary to tertiary ammonium salt structures are more preferable, and tertiary amino groups or tertiary ammonium salt structures are even more preferable. For these reasons, it is particularly preferable that the water-soluble polymer is a (meth)acrylic polymer having a tertiary amino group.

[0078] Commercially available polymers can also be used as polymer (B). For example, commercially available (meth)acrylic polymers include Polyment (manufactured by Nippon Shokubai Co., Ltd.), etc. Commercially available ethyleneimine polymers include Epomin (manufactured by Nippon Shokubai Co., Ltd.) and Polymin SK (manufactured by BASF).

[0079] The weight-average molecular weight of polymer (B) is preferably 10,000 or more, and more preferably 20,000 or more, from the viewpoint of improving adhesion to other layers and adhesion to the cover tape. On the other hand, the weight-average molecular weight of polymer (B) is preferably 1,000,000 or less, and more preferably 500,000 or less. The weight-average molecular weight of polymer (B) can be obtained by converting the value measured by the GPC (Gel Permeation Chromatography) method to polystyrene equivalent.

[0080] The polymer (B) content in the functional layer is preferably 5 to 65% by mass from the viewpoint of easily improving adhesion to the cover tape. The carrier tape and the cover tape are required to adhere sufficiently when storing and transporting electronic components in the housing described later, and to be easily peeled off with a desired force during the mounting process of electronic components to various devices. Therefore, the adhesive strength between the two must be in an appropriate range that is neither too strong nor too weak, and the polymer (B) content is more preferably 10% by mass or more, and even more preferably 20% by mass or more. It is also more preferably 60% by mass or less, and even more preferably 55% by mass or less. The polymer (B) content can be calculated from the basis weight (solid content) of the functional layer described above. The appropriate range of adhesive strength between the carrier tape and the cover tape, which is neither too strong nor too weak, is appropriately selected depending on the intended use of the carrier tape.

[0081] The water solubility or water dispersibility of polymer (B) described above is sufficient if it has enough solubility that the aqueous medium containing polymer (B) becomes a solution when preparing the coating solution for forming the functional layer.

[0082] (Antistatic agent (C)) The functional layer preferably contains an antistatic agent (C) from the viewpoint of providing the necessary antistatic effect when used as a carrier tape. A polymer-type antistatic agent is preferred as the antistatic agent (C) from the viewpoint of easily obtaining the antistatic effect. The type of polymer-type antistatic agent is not particularly limited, and cationic, anionic, amphoteric, or nonionic antistatic agents can be used. Each antistatic agent can be used alone or in combination of two or more types.

[0083] In particular, when a cationic polymer such as a (meth)acrylic polymer having an amino group or ammonium salt structure, an ethyleneimine polymer, or a water-soluble polymer having a phosphonium salt structure is used as the polymer (B), aggregation of polymer (B) can be suppressed, so a cationic antistatic agent is preferred as the polymer-type antistatic agent. Among these, a nitrogen-containing polymer-type antistatic agent is more preferred, an antistatic agent having an ammonium salt is even more preferred, an acrylic polymer having a tertiary or quaternary ammonium salt is particularly preferred, and an acrylic polymer having a quaternary ammonium salt is most preferred. As the polymer-type antistatic agent, commercially available products such as Saftomer ST-1000, ST-1100, and ST-3200 (trade names) manufactured by Mitsubishi Chemical Corporation can be used.

[0084] From the viewpoint of antistatic properties, the content of the antistatic agent (C) in the functional 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, since the content of the aforementioned polymer (B) becomes relatively insufficient, the amount of the antistatic agent (C) in the functional layer is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less.

[0085] The various physical properties and manufacturing methods of the porous resin sheet, including the layers described above, are explained below.

[0086] <Thickness of Porous Resin Sheet> The thickness of the porous resin sheet is 150 to 350 μm. Preferably, the thickness of the porous resin sheet is 160 μm or more, more preferably 180 μm or more, and even more preferably 190 μm or more. Also, preferably, the thickness of the porous resin sheet is 340 μm or less, and more preferably 320 μm or less. The thickness of the porous resin sheet can be appropriately selected within the above range depending on the size of the article to be stored in the storage section (pocket).

[0087] If the thickness of the porous resin sheet is less than 150 μm, it may be difficult to ensure sufficient depth in the receiving area when used as a carrier tape. Furthermore, if the porous resin sheet exceeds 350 μm, it may be difficult to maintain flexibility suitable for manufacturing and transport, and the handling of the wound product tends to decrease. The thickness of the porous resin sheet can be measured in the same way as the thickness of the base layer.

[0088] [Second Embodiment] The second embodiment relates to a porous resin sheet having a thickness of 150 to 350 μm, comprising a base layer and a bottom surface layer, wherein both the base layer and the bottom surface layer contain a thermoplastic resin, the porosity of the base layer is 35 to 80%, the bottom surface layer contains a plate-like filler, and has a thickness of 1 μm or more and less than 20 μm.

[0089] <Base Layer> The base layer contains a thermoplastic resin (A). The constituent materials and their content of the base layer can be the same as those shown in the first embodiment. As in the first embodiment, the base layer may contain a filler. The materials constituting the base layer and their content are also the same as those shown in the first embodiment.

[0090] (Thickness) The thickness of the base layer is preferably 100 to 300 μm. The thickness of the base layer is preferably 120 μm or more, more preferably 130 μm or more, and even more preferably 140 μm or more. Furthermore, the thickness of the base layer is preferably 280 μm or less, more preferably 250 μm or less, and even more preferably 210 μm or less. The thickness of the base layer can be appropriately selected within the above range depending on the size of the article to be stored in the storage section (pocket).

[0091] If the thickness of the base material layer is less than the above range, it may be difficult to ensure sufficient depth in the storage area when used as a carrier tape. Furthermore, if the base material layer exceeds the above range, it may be difficult to maintain flexibility suitable for manufacturing and transport.

[0092] (Porosity) The porosity of the base layer is 35 to 80%. Preferably, the porosity of the base layer is 40% or more, and more preferably 45% or more. Furthermore, preferably, the porosity of the base layer is 70% or less, and more preferably 60% or less. If the porosity of the base layer is below the above range, when the porous resin sheet is shaped without processes such as heating or depressurization, it may be difficult to achieve sufficient shape conformability in the porous resin sheet after molding. For example, when attempting to shape the porous resin sheet to form a housing with sides perpendicular to the surface and a bottom parallel to the surface, molding defects such as tapered sides of the housing or waviness at the bottom may occur. On the other hand, if the porosity of the base layer exceeds the above range, it may be difficult to obtain sufficient mechanical strength. The porosity of the base layer can be adjusted by the filler content in the base layer, the average particle size of the filler, the composition of the thermoplastic resin, and the stretching conditions of the base layer. Furthermore, the porosity of the entire porous resin sheet can be adjusted, for example, by adjusting the porosity of the base layer, the housing side surface layer, and the bottom side surface layer, respectively. The porosity of the substrate layer can be measured and calculated by the same method as in the first embodiment described above.

[0093] <Bottom Surface Layer> The porous resin sheet includes a bottom surface layer. (Hereinafter, the bottom surface layer may be referred to as the "second surface layer.") When the porous resin sheet is used as a carrier tape, it is preferable that the second surface layer (bottom surface layer) be located on the side that will be the bottom of the carrier tape.

[0094] The second surface layer contains a thermoplastic resin (A). In the second embodiment, the second surface layer further contains a plate-shaped filler. When such a porous resin sheet is used as a carrier tape, the indentation return rate described above tends to be 10.0% or less.

[0095] (Indentation return rate) In the second embodiment, from the viewpoint of maintaining the shape of the housing after shaping, the indentation return rate is preferably 8.0% or less. The indentation return rate may be 0%, but from the viewpoint of preventing damage to electronic components that come into contact with the bottom of the housing, it is preferably 5.0% or more.

[0096] (Plate-shaped filler) The plate-shaped filler is preferably a filler composed of an inorganic material. The plate-shaped filler has a flaky or scaly shape, and the aspect ratio, that is, the ratio of the major axis to the thickness (major axis / thickness) is preferably 1.2 to 100, more preferably 2 to 50, still more preferably 5 to 35, and particularly preferably 15 to 35. By setting the aspect ratio to 1.2 or more, it is easy to secure the rigidity of the second surface layer, and by setting it to 100 or less, it is easy to secure the flexibility required for a porous resin sheet.

[0097] Further, the major axis of the plate-shaped filler is preferably about 0.5 to 45 µm, more preferably about 1 to 15 µm, and still more preferably about 1 to 7 µm. The thickness of the plate-shaped filler is preferably about 0.02 to 1.0 µm, and more preferably about 0.05 to 0.5 µm. Note that the aspect ratio, major axis, and thickness are average values obtained by measuring 18 fillers with a scanning electron microscope (SEM) and averaging the measured values.

[0098] The plate-shaped filler is preferably at least one selected from the group consisting of talc, mica, clay, diatomaceous earth, and glass flakes. Among these, talc is preferable as the plate-shaped filler because it easily maintains the shape of the filler when kneaded and dispersed in a resin and has good heat resistance.

[0099] The content of the plate-shaped filler in the second surface layer is preferably 20% by mass or more. From the viewpoint of easily improving the rigidity of the porous resin sheet, the content of the plate-shaped filler is preferably 25% by mass or more, and more preferably 35% by mass or more. From the viewpoint of easily maintaining appropriate flexibility, the content of the plate-shaped filler is preferably 80% by mass or less, more preferably 70% by mass or less, and particularly preferably 60% by mass or less.

[0100] Average particle diameter D of plate-shaped filler ５０ is preferably less than 7 µm. From the viewpoint that pores are less likely to be formed during stretching of the layer and the rigidity of the porous resin sheet is easily improved, the average particle diameter D of the plate-shaped filler ５０ is more preferably 6 µm or less, and still more preferably 5 µm or less. Average particle diameter D of plate-shaped filler５０ The lower limit is not particularly limited, but from the standpoint of availability and low cost, it is preferably 1 μm or larger, and more preferably 3 μm or larger.

[0101] Average particle diameter (D ５０ ) is the volume-average particle diameter (cumulative 50% particle size) that accounts for 50% of the cumulative particle size distribution measured by a particle measuring device, such as the laser diffraction particle measuring device "Microtrac" (manufactured by Nikkiso Co., Ltd., product name).

[0102] The apparent density of the plate-shaped filler is 0.05–0.35 g / cm³. ３ Preferably, it is 0.10 to 0.30 g / cm³. ３ It is more preferable that the concentration be 0.13 to 0.28 g / cm³. ３ It is even more preferable that the concentration be 0.05 to 0.35 g / cm³. ３ As a result, porous resin sheets produced using this material can easily achieve sufficient rigidity, and carrier tapes obtained using these porous resin sheets can easily suppress deformation of the bottom of the storage section.

[0103] The second surface layer may contain, in place of, a portion of the plate-shaped filler described above, or together with the plate-shaped filler, a filler other than the plate-shaped filler (hereinafter sometimes referred to as "other filler"). The other fillers may be those indicated for the base layer.

[0104] If the second surface layer contains other fillers, it is preferable that the content of other fillers be small, specifically 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 30% by mass or less. Including other fillers and forming voids by stretching the layer is effective in ensuring a stable depth of the containment section. On the other hand, from the viewpoint of ensuring the flatness of the bottom of the containment section, it is preferable that the porosity of the second surface layer be low, and that it not contain fillers other than plate-shaped fillers.

[0105] (Thermoplastic resin (A)) The type of thermoplastic resin (A) included in the second surface layer is not particularly limited. The thermoplastic resin (A) of the second surface layer can be one of those shown in the base layer above. The second surface layer containing the plate-shaped filler is more preferably a polyolefin resin as the thermoplastic resin (A).

[0106] As for the polyolefin resin, a polypropylene resin with a higher elastic modulus is preferred from the viewpoint of easily ensuring the rigidity of the second surface layer. Examples of polypropylene resins include isotactic homopolypropylene and syndiotactic homopolypropylene obtained by homopolymerizing propylene, as well as polypropylene copolymers with various stereoregularities obtained by copolymerizing propylene with α-olefins such as ethylene, 1-butene, and 1-pentene. The propylene copolymer may be a binary system or a multi-component system of ternary or more, and may be a random copolymer or a block copolymer. Among these, homopolypropylene (h-PP) is preferred because it increases the rigidity of the resin film. In particular, the homopolypropylene content in the polyolefin resin is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more. Note that if the homopolypropylene content is high, voids tend to be more easily formed in the layer when stretched. As the porosity of the layer increases, the rigidity of the porous resin sheet decreases. Therefore, the porosity of the second surface layer can be adjusted to the range described later by, for example, increasing the stretching temperature, adjusting the stretching ratio, or by using a small amount of a resin with a lower melting point than homopolypropylene in combination. Only one type of polyolefin resin may be used, or two or more types may be used in combination. From the viewpoint of moldability, the polyolefin resin is preferably contained in the resin composition forming the second surface layer at a concentration of 20 to 80% by mass, more preferably at 30 to 75% by mass, and even more preferably at 40 to 60% by mass.

[0107] The content of thermoplastic resin (A) in the second surface layer is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more. Furthermore, from the viewpoint of preventing a relative reduction in the content of plate-like filler, the content of thermoplastic resin (A) is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 65% ​​by mass or less. A content of thermoplastic resin (A) of 20% by mass or more is preferable because it makes it easier to suppress the fracture of the second surface layer during porous resin sheet molding.

[0108] (Porosity) In the second embodiment, the porosity of the second surface layer is not particularly limited, but is preferably 35% or less, more preferably 30% or less, and even more preferably 20% or less. Furthermore, the lower limit of the porosity of the second surface layer is not particularly limited and may be 0%, but it is preferable that it be 3% or more, as having some porosity is effective in stably ensuring the depth of the containment portion.

[0109] When the porosity of the second surface layer is 35% or less, it is easier to achieve the above-mentioned indentation return rate when used as a carrier tape. The porosity of the second surface layer can be adjusted by the filler content in the second surface layer, the average particle size of the filler, the composition of the thermoplastic resin, and the stretching conditions of the second surface layer. The porosity of the second surface layer can be measured in the same manner as in the first embodiment of the base layer.

[0110] (Thickness) In the second embodiment, the thickness of the second surface layer is 1 μm or more and less than 20 μm. In the second embodiment, by including a plate-like filler in the second surface layer, it is easier to ensure the rigidity of the second surface layer, and therefore even if the thickness is within the above range, it is easier to achieve the above-mentioned indentation return rate.

[0111] The thickness of the second surface layer is preferably 10 μm or less, and more preferably 8 μm or less. Furthermore, the thickness of the second surface layer is preferably 3 μm or more. If the thickness of the second surface layer is below the upper limit, it is easier to form a receiving portion of the desired depth; if it is above the lower limit, it is easier to function as a receiving layer for the compressed first surface layer and base layer during shaping. The thickness of the second surface layer can be measured in the same way as the thickness of the base layer.

[0112] The thickness of the second surface layer relative to the total thickness of the porous resin sheet is preferably 10% or less. Having a second surface layer minimizes the shape change of the base layer that occurs when the porous resin sheet is formed. The second surface layer in the porous resin sheet of the second embodiment contains plate-like fillers, which effectively improves the hardness (rigidity, modulus of elasticity, etc.) of the layer. Therefore, even if the thickness of the second surface layer relative to the total thickness of the porous resin sheet is within the above range, it is easy to maintain the mechanical strength necessary to maintain the handling properties of the porous resin sheet for various applications.

[0113] From the viewpoint of improving the rigidity of the porous resin sheet, the thickness of the second surface layer relative to the total thickness of the porous resin sheet is preferably 0.5% or more, and more preferably 1% or more.

[0114] The second surface layer is preferably stretched, and more preferably uniaxially stretched. Furthermore, the stretching direction of the second surface layer and the manufacturing process examples for porous resin sheets where the base layer is a porous biaxially stretched resin layer can be the same as those shown in the first embodiment.

[0115] <Accommodating Surface Layer> In the porous resin sheet of this embodiment, an accommodating surface layer may be present on the side opposite to the bottom surface layer, either directly or via another layer. (Hereinafter, the accommodating surface layer may be referred to as the "first surface layer.") In the porous resin sheet of this embodiment, the first surface layer (accommodating surface layer) may or may not be present.

[0116] The first surface layer preferably contains a thermoplastic resin (A). The constituent materials and content of the first surface layer can be the same as those shown in the first embodiment. As in the first embodiment, the first surface layer may contain a filler. The types and content of fillers that can be used are also the same as those shown in the first embodiment. The thermoplastic resin (A) contained in the first surface layer may be the same as or different from the thermoplastic resin (A) contained in the base layer.

[0117] (Thickness) The thickness of the first surface layer is preferably 5 μm or more. When forming the housing portion when used as a carrier tape, the strain of the portion including the first surface layer and a part of the base material layer can be averaged at the bottom of the housing portion formed by compression with a mold, making it easier to stabilize the shape of the compressed layer at the bottom of the housing portion. The thickness of the first surface layer is more preferably 7 μm or more, and even more preferably 10 μm or more. Furthermore, the thickness of the first surface layer is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less. The thickness of the first surface layer can be measured in the same way as the thickness of the base material layer.

[0118] (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 of the first surface layer is preferably 80% or less, more preferably 70% or less, and even more preferably 60% or less. When the porosity of the first surface layer is 35% or more, it is easier to obtain sufficient shape conformability even when forming a deep-shaped containment, and the shape of the bottom and sides of the formed containment is easier to stabilize. When the porosity of the first surface layer is 80% or less, it is easier to obtain mechanical strength for the porous resin sheet. The porosity of the first surface layer can be adjusted by the filler content in the first surface layer, the average particle size of the filler, the composition of the thermoplastic resin, and the stretching conditions of the first surface layer. The porosity of the first surface layer can be measured in the same way as the porosity of the base layer.

[0119] The ratio (H1 / H0) of the porosity of the first surface layer to the porosity (H0) of the base layer is preferably 0.80 to 1.20. The ratio (H1 / H0) is more preferably 0.85 or higher, and even more preferably 0.90 or higher. Furthermore, the ratio (H1 / H0) is more preferably 1.15 or lower, and even more preferably 1.10 or lower. When the ratio (H1 / H0) of the porosity of the first surface layer to the porosity (H0) of the base layer is within the above range, the difference between the shape of the first surface layer formed by shaping and the shape of the base layer is suppressed, making it easier to form a housing portion having sides perpendicular to the surface of the porous resin sheet and a bottom parallel to it, and making it easier to suppress the tapering of the sides of the housing portion.

[0120] The first surface layer is preferably stretched, and more preferably a uniaxially stretched layer. Furthermore, the stretching direction of the first surface layer and the manufacturing process examples for porous resin sheets where the base layer is a porous biaxially stretched resin layer can be the same as those shown in the first embodiment.

[0121] <Other Layers> The porous resin sheet may optionally include layers other than those described above. Other layers similar to those shown in the first embodiment can be used.

[0122] <Thickness of Porous Resin Sheet> The thickness of the porous resin sheet is 150 to 350 μm. Preferably, the thickness of the porous resin sheet is 160 μm or more, more preferably 180 μm or more, and even more preferably 190 μm or more. Also, preferably, the thickness of the porous resin sheet is 340 μm or less, and more preferably 320 μm or less. The thickness of the porous resin sheet can be appropriately selected within the above range depending on the size of the article to be stored in the storage section (pocket).

[0123] If the thickness of the porous resin sheet is less than 150 μm, it may be difficult to ensure sufficient depth of the containment area when used as a carrier tape in a molded product. Furthermore, if the porous resin sheet exceeds 350 μm, it may be difficult to maintain flexibility suitable for manufacturing and transport, and the handling of the wound product tends to decrease. The thickness of the porous resin sheet can be measured using the same method as in the first embodiment.

[0124] [Method for Manufacturing Porous Resin Sheets] The method for manufacturing porous resin sheets is not particularly limited. The method for manufacturing porous resin sheets is not particularly limited to the typical manufacturing methods described above, and may be manufactured by other methods. Each layer can be manufactured, for example, by casting, calendering, rolling, or inflation molding, in which molten resin is extruded into a sheet shape using a T-die, I-die, etc., connected to a screw-type extruder. To manufacture each layer of the multilayer structure, the base layer and each surface layer can be manufactured and then laminated by an extrusion lamination method, etc. Alternatively, the molding and lamination of each layer may be carried out in parallel using a multilayer die method using a feed block, a multi-manifold, or an extrusion lamination method using multiple dies.

[0125] When each layer is stretched, the base layer may be stretched before laminating each surface layer, or it may be stretched after laminating the base layer and each surface layer. Examples of stretching methods include longitudinal stretching using the peripheral speed difference of a roll group, 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.

[0126] Among these methods, it is preferable to manufacture the resin by extruding the resin composition into a sheet from a T-die connected to an extruder, and then stretching this sheet. This method facilitates multilayering and allows for easy adjustment of the thickness of the porous resin sheet. Examples of stretching methods include longitudinal stretching, transverse stretching, and sequential biaxial stretching or simultaneous biaxial stretching, which combine these methods.

[0127] The stretching temperature is preferably in the range above the glass transition temperature of the thermoplastic resin (A) when the thermoplastic resin (A) used is amorphous. When the thermoplastic resin (A) is crystalline, the stretching temperature is preferably in the range above the glass transition temperature of the amorphous portion of the thermoplastic resin (A) and below the melting point of the crystalline portion, and preferably 2 to 60°C lower than the melting point of the thermoplastic resin (A). 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.

[0128] 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.

[0129] The stretching ratio can be appropriately determined considering the properties of the thermoplastic resin (A). For example, when using a propylene homopolymer or propylene copolymer as the thermoplastic resin (A), the stretching ratio when stretching in one direction is usually 1.1 times or more, preferably 2 times or more, and usually 10 times or less, preferably 9 times or less. On the other hand, when biaxially stretched, the stretching ratio is usually 1.5 times or more, preferably 4 times or more, and usually 75 times or less, preferably 50 times or less, in terms of area stretching ratio. When stretching other thermoplastic resins (A) in one direction, the stretching ratio is usually 1.2 times or more, preferably 2 times or more, and usually 10 times or less, preferably 5 times or less. When biaxially stretched, the stretching ratio is usually 1.5 times or more, preferably 4 times or more, and usually 20 times or less, preferably 12 times or less, in terms of area stretching ratio. Within the above range of stretching ratios, the desired porosity and thickness are easily obtained, and the desired opacity is easily ensured. Furthermore, breakage is less likely to occur, and the stretch molding process is easily stabilized.

[0130] [Carrier Tape] The porous resin sheet described above has properties suitable for forming a carrier tape equipped with a storage section. In other words, the carrier tape is a molded body of the porous resin sheet of the present invention, and the carrier tape equipped with a storage section is suitably used for storing and transporting electronic components. The size of the storage section for accommodating electronic components formed in the porous resin sheet can be, for example, about 0.1 × 0.1 mm to 3 × 3 mm.

[0131] The method for forming the housing portion in a porous resin sheet is not particularly limited and can include, for example, pressure molding, press molding, and vacuum rotary molding. From the viewpoint of cost, it is preferable to form the porous resin sheet by press molding at room temperature. Furthermore, the shape of the housing portion formed in the porous resin sheet can be appropriately selected according to the shape of the part to be housed. Examples of housing portion shapes include cylindrical shapes and prismatic shapes.

[0132] [Electronic Component Packaging] The carrier tape of the present invention is suitably used as electronic component packaging by providing a cover tape to cover the housing portion. Examples of electronic component packaging include those comprising a carrier tape and a cover tape attached to the carrier tape, as shown in Figure 3. With the carrier tape of the present invention, it is easy to maintain the adhesion between the carrier tape and the cover tape within an appropriate range.

[0133] 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. Unless otherwise specified, "parts," "%," etc., in the examples refer to mass-based measurements. "MD direction" refers to the flow direction of the porous resin sheet and coincides with the longitudinal uniaxial stretching direction of the base material layer described later.

[0134] In this embodiment, the porosity and thickness were measured as follows: (Porosity) The sample to be measured (porous resin sheet) was cooled to a temperature of -60°C or lower using liquid nitrogen. It was placed on a glass plate and cut with a razor blade (product name: Proline Blade, manufactured by Schick Japan) applied at a right angle to create a cut surface parallel to the plane formed by the thickness direction and MD direction of the sample. The resulting cross-section of the sample was observed at 3000x magnification using a scanning electron microscope (product name: JCM-6000, manufactured by JEOL Ltd.), and the pore portions of each layer were binarized using image processing software (Inkscape), and the area ratio (%) of pores occupying the measurement range was calculated and defined as the porosity (%) of each layer.

[0135] (Thickness) The total thickness of porous resin sheets, etc., was measured in accordance with JIS K7130:1999 using a constant-pressure thickness gauge (product name: PG-01J, manufactured by Teclock Co., Ltd.). The thickness of each layer was determined by observing the cross-section of a sample prepared in the same manner as when measuring porosity, using a scanning electron microscope (product name: JCM-6000, manufactured by JEOL Ltd.), identifying the boundary lines for each thermoplastic resin composition of each layer from the appearance, and multiplying the total sheet thickness by the thickness ratio of each observed layer.

[0136] Examples 1-5, Comparative Examples 1-2 Resin sheets for each example and comparative example were obtained according to the following procedure. Details of the materials used in each example and comparative example are summarized in Table 1. Furthermore, the types, blending ratios, and evaluations of the materials used in the production of the resin sheets for each example and comparative example are summarized in Table 2 below. The material symbols shown in Table 2 correspond to the material symbols shown in Table 1.

[0137]

[0138] [Example 1] A porous resin sheet including a first surface layer, a base layer, and a second surface layer was obtained by the following procedure. (Preparation of porous resin sheet) As a composition for forming the base layer, 70 parts by mass of polypropylene (manufactured by Nippon Polypropylene Co., Ltd., product name: Novatec PP FY4) and 30 parts by mass of heavy calcium carbonate (manufactured by Bihoku Powdering Industry Co., Ltd., product name: Softon #1800) were melt-kneaded in an extruder set to 230°C to prepare resin composition A. This was melt-kneaded in an extruder set to 230°C and supplied to an extrusion die set to 250°C to be extruded into a sheet, and cooled to 70°C in a cooling device to obtain a single-layer unstretched sheet. This unstretched sheet was reheated to 135°C and stretched four times in the longitudinal direction using the difference in peripheral speed between a number of rolls to obtain a longitudinally uniaxially oriented film.

[0139] As a composition for forming the first surface layer, 40 parts by mass of polypropylene (manufactured by Nippon Polypropylene Co., Ltd., product name: Novatec PP FY4) and 60 parts by mass of heavy calcium carbonate (manufactured by Bihoku Powdering Industry Co., Ltd., product name: Softon #1800) were melt-kneaded in an extruder set to 250°C to prepare resin composition B. This was melt-kneaded in an extruder set to 250°C, supplied to an extrusion die set to 250°C, and extruded into a sheet. This sheet was then laminated onto the surface of the 4x stretched film prepared above to obtain a two-layer laminated film.

[0140] As the second surface layer, 100 parts by mass of polypropylene (manufactured by Nippon Polypropylene Co., Ltd., product name: Novatec PP FY4) was melt-kneaded in an extruder set to 250°C to prepare resin composition N. This was supplied to an extrusion die set to 250°C and extruded into a sheet, which was then laminated to the back surface of the 4x stretched film prepared above to obtain a three-layer laminated film.

[0141] Next, the laminated film was cooled to 60°C, then 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 then the edges were slit to obtain a porous resin sheet with a three-layer structure (first surface layer / substrate layer / second surface layer, resin composition B / resin composition A / resin composition N, porosity 40% / 50% / 0%, thickness 15 μm / 155 μm / 30 μm, uniaxially oriented layer / biaxially oriented layer / uniaxially oriented layer).

[0142] The resulting porous resin layer sheet had a thickness of 200 μm, and the overall porosity of the sheet was 42%.

[0143] Samples were cut from the obtained porous resin sheet, and the indentation depth was measured using the following method to calculate the indentation return rate and evaluate the bottom surface stability. The results are shown in Table 2.

[0144] (Indentation Return Rate) A 1.0 mm diameter quartz needle-inserted probe was mounted inside a thermomechanical analyzer. A sample cut from the porous resin sheet obtained in Example 1 was placed directly below the probe needle in a quartz sample tube, with the first surface layer side facing the probe needle's indentation surface. The displacement when the probe was pressed into the sample surface with a load of 5 mN was set to 0. The indentation depth (μm) when a force was applied up to a load of 130 mN at a pressurization rate of 5 mN / min was defined as d1. Then, the indentation depth (μm) when the pressure was reduced to a load of 20 mN at a depressurization rate of 5 mN / min was defined as d2. The thickness of the sample (μm) was defined as L. The indentation return rate was calculated using the following formula (1). The thermomechanical analyzer used was a "TMA7100" manufactured by Hitachi High-Tech Science Co., Ltd. The measurement ambient temperature was adjusted to a constant 20°C. Indentation return rate (%) = (d1 - d2) / L × 100 (1)

[0145] (Bottom Shape Stability) Using a simple die-cutting machine (RDC-FB type) manufactured by Tsukaya Hamono Seisakusho Co., Ltd., and a micro-perforating blade (blade angle 180°, 1.2T, 0.4 mm width, 0.4 mm length) manufactured by Tsukaya Hamono Seisakusho Co., Ltd., a pseudo-pocket (container) shape was created on the first surface layer side surface of the porous resin sheet of each example and comparative example. The depth of the pseudo-pocket was adjusted to 150 μm. The shape of the pseudo-pocket was observed using a white light interference laser microscope (VK-X3100) manufactured by Keyence Corporation and evaluated as follows. <Observation Conditions> Objective lens: 20X Zoom: 1.0X Scan mode: Focus variation

[0146] Shape retention (bottom shape stability) was evaluated as follows. For images of pseudo-pockets whose shape was observed, 100 cross-sectional shape data points were acquired at 1 μm intervals from the center in the MD direction of the pseudo-pocket using the VK-X3000 multi-file analysis application, and the average value was used as the pocket's cross-sectional shape profile. At this time, tilt correction was performed so that the line connecting the two intersection points (ends) of the bottom surface and the side surface of the pseudo-pocket was horizontal. The bottom surface was defined as a 300 μm range centered on the midpoint of the line connecting both ends of the bottom surface, and the difference between the maximum height and maximum depth (i.e., the sum of the absolute values ​​of the maximum height and maximum depth) was recorded, and the average value of this difference was calculated for 10 pockets. Bottom shape stability was evaluated as follows from the average value: A: Average value is 2 μm or less B: Average value is greater than 2 μm and 4 μm or less C: Average value is greater than 4 μm and 5 μm or less D: Average value is greater than 5 μm

[0147] Furthermore, the adhesion (cover adhesion) and antistatic properties of the first surface layer to the cover tape were measured using the following method. The results are shown in Table 2.

[0148] (Cover Adhesion) A porous resin sheet and a cover tape for carrier tape (product name: Sumilight CSL-Z7302, manufactured by Sumitomo Bakelite Co., Ltd.) were each cut to a width of 8 mm and a length of 300 mm. The cover tape was placed on the first surface layer side of the porous resin sheet of Example 1, and a sample for measurement was obtained by heat sealing at a load of 2.5 MPa and 90°C for 0.1 seconds using a thermal gradient tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.), and then leaving it at 23°C for 15 minutes.

[0149] Next, a tensile testing machine (product name: Tensilon Universal Material Testing Machine RTG-1225, A&D Company, Ltd.) was used to peel the cover tape from the test sample at a speed of 300 mm / min at a 180-degree angle, and the load at the time of peeling was measured. Five measurements were taken, and the average value was taken as the adhesive strength (gf / mm). The adhesive strength of the cover tape is preferably moderate, neither too strong nor too weak. Specifically, an adhesive strength of more than 4.0 gf / mm and less than 6.0 gf / mm is considered good, and an adhesive strength of 6.0 gf / mm or more and 8.0 gf / mm or less is considered very good.

[0150] (Antistatic properties) The porous resin sheet obtained in Example 1 was stored in an atmosphere of 23°C and 10% RH relative humidity for more than 2 hours to adjust the condition of the porous resin sheet, and then the surface resistivity (logΩ) of the first surface layer was measured using an insulation meter (HIOKI E.E. CORPORATION, product name: DSM-8104). The antistatic properties of the first surface layer were good if the surface resistivity was less than 11.0 logΩ, and very good if it was less than 10.0 logΩ.

[0151] [Examples 2-3 and Comparative Examples 1-2] Porous resin sheets were prepared and evaluated in the same manner as in Example 1, except that the resin compositions listed in Table 2 were used instead of resin composition N. The results are shown in Table 2.

[0152] [Example 4] A porous resin sheet was prepared and evaluated in the same manner as in Example 1, except that the thickness of the second surface layer was 50 μm. The results are shown in Table 2.

[0153] [Example 5] A porous resin sheet was prepared in the same manner as in Example 1, except that a functional layer was provided on the surface of the first surface layer using a coating solution prepared by the following method. The cover adhesion and antistatic properties of the obtained porous resin sheet were evaluated in the same manner as in Example 1, except that they were measured on the surface of the functional layer. The results are shown in Table 2.

[0154] <Preparation of coating solution> 40 parts by mass of isopropanol (Tokuyama Corporation, trade name: Tokuso IPA) was charged into a reactor equipped with a reflux condenser, nitrogen inlet tube, stirrer, thermometer, dropping funnel, and heating jacket. While stirring, 12.6 parts by mass of N,N-dimethylaminoethyl methacrylate (Sanyo Chemical Industries, trade name: Methacrylate DMA), 12.6 parts by mass of butyl methacrylate (Mitsubishi Rayon, trade name: Acryester B), and 2.8 parts by mass of higher alcohol methacrylate (Mitsubishi Rayon, trade name: Acryester SL, a mixture of lauryl methacrylate and tridecyl methacrylate) were charged. After purging the system with nitrogen and raising the internal temperature to 80°C, 0.3 parts by mass of 2,2'-azobisisobutyronitrile (Wako Pure Chemical Industries, trade name: V-60 (AIBN)) was added as a polymerization initiator, and polymerization was started. Polymerization was carried out for 4 hours while maintaining the reaction temperature at 80°C, and the resulting copolymer was neutralized with 4.3 parts by mass of glacial acetic acid (manufactured by Wako Pure Chemical Industries, Ltd.). While distilling off isopropanol from the reactor, 48.3 parts by mass of ion-exchanged water was added to replace the system, and a viscous aqueous solution of a tertiary amino group-containing methacrylic polymer (weight-average molecular weight 40,000) (solid content concentration, i.e., concentration of tertiary amino group-containing methacrylic polymer, was 35% by mass) was obtained. The obtained aqueous solution was used as an aqueous solution of cationic water-soluble polymer (B1) as a coating liquid for forming a functional layer.

[0155] <Formation of Functional Layer> As a coating liquid for forming the functional layer, 50% by mass of the water-soluble polymer (B1) obtained above (based on solid content) and 50% by mass of an antistatic agent (acrylic resin having a quaternary ammonium salt structure, trade name: Saftomer ST3200, manufactured by Mitsubishi Chemical Corporation) were blended and stirred in a mixer to obtain a composition for forming the functional layer. A coating amount of 0.033 g / m² after drying was applied to the surface of the first surface layer of the three-layer laminate obtained in the same manner as the porous resin sheet of Example 1. ２ A coating liquid for forming a functional layer was applied in this manner. The coating film was dried in an oven at 70°C to form a functional layer, and the porous resin sheet of Example 5 was obtained.

[0156]

[0157] As shown in Table 2, the porous resin sheets in each example all had a bottom shape stability of C or higher (average value of 5 μm or less), which was at a level that posed no practical problems. Furthermore, Example 5, which had a functional layer, exhibited good cover adhesion and antistatic properties.

[0158] Examples 11-16, Comparative Examples 11-13: Porous resin sheets for each example and comparative example were obtained according to the following procedure. The types of materials used in the production of each porous resin sheet, their mixing ratios, and evaluations are summarized in Table 3 below. The material symbols shown in Table 3 correspond to the material symbols shown in Table 1.

[0159] [Example 11] A porous resin sheet including a first surface layer, a base layer, and a second surface layer was obtained by the following procedure. (Preparation of porous resin sheet) As the base layer, the above resin composition A was supplied to an extrusion die set to 250°C and extruded into a sheet, and cooled to 70°C in a cooling device to obtain a single-layer unstretched sheet. This unstretched sheet was reheated to 135°C and stretched four times in the longitudinal direction using the difference in peripheral speed between a number of rolls to obtain a longitudinally uniaxially oriented film.

[0160] As the first surface layer, the above resin composition B was supplied to an extrusion die set to 250°C and extruded into a sheet, which was then laminated onto the surface of the 4x stretched film prepared above to obtain a two-layer laminated film.

[0161] As a composition for forming the second surface layer, 80 parts by mass of polypropylene (manufactured by Nippon Polypropylene Co., Ltd., product name: Novatec PP FY4) and 20 parts by mass of fine talc powder (manufactured by Nippon Talc Co., Ltd., product name: Microace Series P-3) were melt-kneaded in an extruder set to 250°C to prepare resin composition D. This was supplied to an extrusion die set to 250°C and extruded into a sheet, which was then laminated onto the back surface of the 4x stretched film prepared above to obtain a three-layer laminated film.

[0162] Next, the laminated film was cooled to 60°C, then 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 then the edges were slit to obtain a porous resin sheet with a three-layer structure (first surface layer / substrate layer / second surface layer, resin composition B / resin composition A / resin composition D, porosity 40% / 50% / 5%, thickness 15 μm / 183 μm / 2 μm, uniaxially oriented layer / biaxially oriented layer / uniaxially oriented layer).

[0163] The resulting porous resin layer sheet had a thickness of 200 μm, and the overall porosity of the sheet was 49%.

[0164] Samples were cut from the obtained porous resin sheets, the indentation-rebound rate was determined using the method described above, and the bottom shape stability was evaluated.

[0165] [Examples 12-13, Comparative Examples 11-13] Porous resin sheets were prepared and evaluated in the same manner as in Example 11, except that the resin composition listed in Table 3 was used instead of resin composition D, and in Comparative Example 13, the porosity of the second surface layer was further set to 40%. The results are shown in Table 3.

[0166] [Example 14] A porous resin sheet was prepared and evaluated in the same manner as in Example 12, except that the porosity of the second surface layer was set to 15% and the thickness to 5 μm. The results are shown in Table 3.

[0167] [Example 15] A porous resin sheet was prepared and evaluated in the same manner as in Example 12, except that the thickness of the second surface layer was 15 μm. The results are shown in Table 3.

[0168] [Example 16] A porous resin sheet was prepared and evaluated in the same manner as in Example 12, except that talc 2 was used instead of talc 1 in resin composition E (i.e., resin composition H was used). The results are shown in Table 3.

[0169]

[0170] As shown in Table 3, the porous resin sheets of each example all had a bottom shape stability of C or higher (average value of 5 μm or less), which was at a level that posed no practical problems.

[0171] 1 Carrier tape 2 Cover tape P Storage section S Surface of carrier tape B Bottom of storage section 10 Porous resin sheet 120 Base material layer 130 Storage side surface layer 140 Bottom side surface layer

Claims

1. A porous resin sheet having a thickness of 150 to 350 μm, comprising a base layer and a bottom surface layer, wherein both the base layer and the bottom surface layer contain a thermoplastic resin, the porosity of the base layer is 35 to 80%, and the indentation return rate determined by the difference between the indentation depth when pressurized from 5 mN to 130 mN and the indentation depth when depressurized from 130 mN to 20 mN on the surface of the porous resin sheet on the base layer side is 10.0% or less.

2. A porous resin sheet having a thickness of 150 to 350 μm, comprising a base layer and a bottom surface layer, wherein both the base layer and the bottom surface layer contain a thermoplastic resin, the porosity of the base layer is 35 to 80%, and the bottom surface layer has a porosity of less than 35% and a thickness of 20 to 60 μm.

3. A porous resin sheet having a thickness of 150 to 350 μm, comprising a base layer and a bottom surface layer, wherein both the base layer and the bottom surface layer contain a thermoplastic resin, the porosity of the base layer is 35 to 80%, and the bottom surface layer contains a plate-like filler and has a thickness of 1 μm or more and less than 20 μm.

4. A porous resin sheet according to any one of claims 1 to 3, wherein the base layer has a receiving surface layer directly or via another layer on the side opposite to the bottom surface layer of the base layer, the receiving surface layer is a porous layer containing a thermoplastic resin, and the ratio (H1 / H0) of the porosity of the receiving surface layer to the porosity of the base layer (H0) is 0.80 to 1.

20.

5. The porous resin sheet according to claim 4, wherein the thickness of the containment side surface layer is 5 μm or more.

6. A porous resin sheet according to any one of claims 1 to 3, wherein the base layer has a functional layer on the side opposite to the bottom surface layer, either directly or via another layer, and the functional layer contains a water-soluble or water-dispersible polymer and an antistatic agent.

7. A carrier tape comprising a porous resin sheet molded body according to any one of claims 1 to 3, and having a storage portion.

8. An electronic component packaging comprising a carrier tape as described in claim 7 and a cover tape attached to the carrier tape.

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