Resin sheet

Abstract

To provide a resin sheet that has excellent mechanical properties such as tensile elastic modulus and folding endurance, with a small difference in heat shrinkage rate between MD and TD directions.SOLUTION: A resin sheet has ΔHa of 0.5 J / g or more as calculated based on differential scanning calorimetry by the following formula (1). ΔHa(J / g)=|(ΔHm1+ΔHm2)-ΔHp|...(1). (In formula (1), ΔHm1 represents the heat quantity (J / g) at melting point Tm1, ΔHm2 represents the heat quantity (J / g) at melting point Tm2, and ΔHp represents the recrystallization heat quantity (J / g)).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a resin sheet. [Background technology]

[0002] 2. Description of the Related Art Trays, carrier tapes and the like obtained by molding resin sheets are mainly used as packaging materials for intermediate parts of various industrial products such as electronic devices and automobiles. In the carrier tape, recesses (embossments) for accommodating parts are formed by, for example, thermoforming such as press molding. In press molding, a resin sheet is placed between a main die having a protrusion and a second die having an insertion hole into which the main die is inserted, and the protrusion is inserted into the insertion hole to stretch the resin sheet. In this way, embosses are formed in the carrier tape. Patent Document 1 proposes a laminated sheet suitable for carrier tapes, trays, etc.

[0003] Meanwhile, resin sheets used for electronic component packaging materials such as carrier tapes and trays are required to have excellent mechanical properties such as tensile modulus and folding strength, and from the viewpoint of formability, to have a small difference in heat shrinkage rate between the MD and TD. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 146630 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide a resin sheet that is excellent in mechanical properties such as tensile modulus and folding strength, and has a small difference in heat shrinkage rate between the MD and TD directions. [Means for solving the problem]

[0006] As a result of extensive investigations, the inventors of the present application have found that the above-mentioned problems can be solved by a resin sheet having a ΔHa of 0.5 J / g or more as calculated by the following formula (1) based on differential scanning calorimetry. ΔHa(J / g)=|(ΔHm1+ΔHm2)-ΔHp| ···(1) (In formula (1), ΔHm1 represents the amount of heat (J / g) at the melting point Tm1, ΔHm2 represents the amount of heat (J / g) at the melting point Tm2, ​​and ΔHp represents the amount of heat of recrystallization (J / g).) Effect of the Invention

[0007] According to the present disclosure, it is possible to provide a resin sheet that has excellent mechanical properties such as tensile modulus and folding strength, and has a small difference in heat shrinkage rate between the MD and TD directions. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view showing one embodiment of a resin sheet according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present disclosure will be described in detail, but the scope of the present disclosure is not limited to the embodiment described here, and various modifications can be made within the scope of the present disclosure. Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. In addition, when multiple upper and lower limit values ​​are described for a specific parameter, any upper and lower limit values ​​among these upper and lower limit values ​​can be combined to form a suitable numerical range. In addition, the lower and / or upper limit values ​​of the numerical range described in this disclosure are numerical values ​​within the numerical range and may be replaced with numerical values ​​shown in the examples. The expression "X to Y" indicating a numerical range means "X or more and Y or less". When a specific description described for one embodiment is also applicable to other embodiments, the description may be omitted in other embodiments.

[0010] The configurations and combinations thereof in each embodiment are merely examples, and addition, omission, substitution, and other modifications of the configurations are possible as appropriate without departing from the spirit of the present disclosure. The present disclosure is not limited to the embodiments.

[0011] Each feature disclosed herein may be combined with any other feature disclosed herein.

[0012] [Resin sheet] The resin sheet according to this embodiment has a ΔHa of 0.5 J / g or more, calculated from the following formula (1) based on differential scanning calorimetry. ΔHa(J / g)=|(ΔHm1+ΔHm2)-ΔHp| ···(1) (In formula (1), ΔHm1 represents the amount of heat (J / g) at the melting point Tm1, ΔHm2 represents the amount of heat (J / g) at the melting point Tm2, ​​and ΔHp represents the amount of heat of recrystallization (J / g).)

[0013] <Differential scanning calorimetry> When the resin sheet according to this embodiment is heated from 30°C to 300°C at a heating rate of 10°C / min (1st RUN) using a differential scanning calorimeter (DSC) (e.g., Perkin Elmer, product name "Power compensation type DSC8500"), at least the melting point Tm1, the melting point Tm2, ​​and the recrystallization temperature Tc are observed.

[0014] The resin sheet according to the present embodiment is characterized in that the absolute value (ΔHa) of the value obtained by subtracting the "recrystallization heat (J / g): ΔHp" from the "total value (J / g): (ΔHm1+ΔHm2) of the heat of fusion at the melting points Tm1 and Tm2" is 0.5 J / g or more. The present inventors have found that a resin sheet containing a certain amount of crystalline components and having a ΔHa of 0.5 J / g or more has good mechanical properties such as tensile modulus and folding strength, and is likely to have small stress relaxation in the MD direction. As a result, it has been found that the heat shrinkage rate in the MD direction is likely to be smaller than that of a conventional resin sheet. Furthermore, the present inventors have also found that the moldability of the resin sheet is likely to be good due to the small difference in the heat shrinkage rate between the MD direction and the TD direction. In the present disclosure, the term "MD direction" refers to the longitudinal direction (flow direction) of a resin sheet when it is molded, while the term "TD direction" refers to the direction perpendicular to the MD direction and the width direction (transverse direction) of a resin sheet when it is molded.

[0015] In one embodiment, ΔHa calculated by formula (1) is preferably 1.0 J / g or more, more preferably 1.5 J / g or more, even more preferably 2.0 J / g or more, and particularly preferably 2.5 J / g or more, from the viewpoint that the heat shrinkage rate in the MD direction is likely to be smaller and the difference in the heat shrinkage rate in the MD direction and the TD direction is likely to be smaller. The upper limit of ΔHa is not particularly limited as long as the effect of the present disclosure is obtained. In one embodiment, ΔHa may be 1.0 to 6.0 J / g, or may be 2.0 to 5.0 J / g. A resin sheet having a ΔHa of 0.5 J / g or more calculated from the formula (1) is easily achieved when the resin sheet contains a polystyrene resin and a crystalline biomass-derived resin, and is more easily achieved when the proportion of the crystalline biomass-derived resin in the resin sheet is 10% by mass or more relative to the total mass of the resin sheet. Also, when the crystalline biomass-derived resin contains polylactic acid, the ΔHa calculated from the formula (1) is likely to be 0.5 J / g or more.

[0016] Heat at melting point Tm1 (ΔHm1): The melting point Tm1 refers to the peak top temperature of the first melting peak observed when the resin sheet is heated from 30°C to 300°C at a heating rate of 10°C / min (1st RUN) by DSC. The heat amount ΔHm1 (J / g) at the melting point Tm1 is a value calculated by DSC. Specifically, DSC measurement is performed under the above conditions in accordance with standard 9.4.3 of ISO 11357-3:2018 to determine the heat amount ΔHm1 at the melting point Tm1. The same applies to ΔHm2 and ΔHp. In one embodiment, the melting point Tm1 is preferably more than 100°C and not more than 140°C, and more preferably 120°C to 140°C.

[0017] In one embodiment, the heat quantity ΔHm1 at the melting point Tm1 is preferably 0.7 to 3.0 J / g, more preferably more than 0.7 and less than 3.0 J / g, and further preferably 0.8 to 2.8 J / g. When ΔHm1 is within the above range, the resin sheet is likely to satisfy the above formula (1).

[0018] Heat at melting point Tm2 (ΔHm2): The melting point Tm2 refers to the peak top temperature of the melting peak observed in a temperature range higher than the melting point Tm1 when the resin sheet is heated from 30°C to 300°C at a heating rate of 10°C / min (1st RUN) by DSC. The calorific value ΔHm2 at the melting point Tm2 is a value calculated by DSC. In one embodiment, the melting point Tm2 is preferably more than 140°C and not more than 180°C, and more preferably 160°C to 180°C.

[0019] In one embodiment, the heat quantity ΔHm2 at the melting point Tm2 is preferably 1.0 to 3.0 J / g, more preferably 2.5 to 6.0 J / g, further preferably 3.0 to 6.0 J / g, and particularly preferably 3.6 to 5.5 J / g. When ΔHm2 is within the above range, a resin sheet that satisfies the above formula (1) is easily obtained.

[0020] In one embodiment, the total heat of fusion (ΔHm1+ΔHm2) of the resin sheet measured under the above conditions in DSC is preferably 2.0 J / g or more. In a preferred embodiment, (ΔHm1+ΔHm2) may be 2.0 to 9.0 J / g, 3.0 to 9.0 J / g, or 4.0 to 9.0 J / g.

[0021] ·Recrystallization heat amount (ΔHp): The heat of recrystallization ΔHp refers to the heat at the recrystallization temperature Tc. The recrystallization temperature Tc is observed as an exothermic peak when the resin sheet is heated from 30°C to 300°C at a heating rate of 10°C / min (1st RUN) by DSC. ΔHp is calculated by determining the area surrounded by the exothermic peak at the recrystallization temperature Tc and the baseline. In one embodiment, ΔHp is preferably 1.0 to 5.5 J / g, more preferably 1.5 to 5.0 J / g, and more preferably 1.5 to 4.0 J / g. The value calculated by DSC is also used for ΔHp. In the DSC curve, the exothermic peak at the recrystallization temperature Tc and the baseline shift due to the glass transition temperature Tg may overlap. In that case, ΔHp is measured by measuring the heat in the range of 80 to 110°C.

[0022] In one embodiment, the recrystallization temperature Tc of the resin sheet may be 80 to 100°C, or may be 90 to 100°C.

[0023] The resin sheet of this embodiment has an absolute difference between the heat of recrystallization: ΔHp and the heat of fusion (ΔHm1+ΔHm2) of 0.5 J / g or more, and preferably has heat of fusion (ΔHm1+ΔHm2)>heat of recrystallization (ΔHp) and ΔHa of 0.5 J / g or more, thereby resulting in a resin sheet with excellent mechanical properties, a small heat shrinkage rate in the MD direction, and a smaller difference in heat shrinkage rate between the MD direction and the TD direction.

[0024] When the resin sheet according to the present embodiment contains, for example, a polystyrene resin and a crystalline biomass-derived resin as shown in the examples described later, an exothermic peak at the recrystallization temperature Tc is observed in the temperature range of 80 to 100 ° C., an endothermic peak at the melting point Tm1 is observed in the temperature range of 120 ° C. to 140 ° C., and an endothermic peak at the melting point Tm2 is observed in the temperature range of 160 to 180 ° C. Based on the heat amounts of the melting points Tm1 and Tm2 and the recrystallization temperature Tc, ΔHa calculated from formula (1) is 0.5 J / g or more, and the heat of fusion > the heat of recrystallization. Such a resin sheet has excellent mechanical properties and a smaller difference in the heat shrinkage rate between the MD direction and the TD direction.

[0025] <Heat shrinkage rate> In one embodiment, the heat shrinkage ratio in the MD direction to the heat shrinkage ratio in the TD direction of the resin sheet (MD heat shrinkage ratio (%) / TD heat shrinkage ratio (%)) is preferably 2.5 or less when the resin sheet is heated at 130° C. for 30 minutes. If the MD heat shrinkage ratio / TD heat shrinkage ratio is 2.5 or less, the resin sheet tends to have better moldability. When a conventional resin sheet is heated at 130°C for 30 minutes, the heat shrinkage rate in the MD direction tends to be larger than that in the TD direction, as shown in Comparative Example 1. When such a resin sheet is molded into a carrier tape, the thickness of the embossed portion may become uneven, or holes may be formed in the embossed portion. The resin sheet according to the present embodiment has a small difference in the heat shrinkage rates between the MD direction and the TD direction (preferably, MD heat shrinkage rate (%) / TD heat shrinkage rate (%) is 2.5 or less), and therefore tends to have good moldability. In a preferred embodiment, the MD heat shrinkage rate (%) / TD heat shrinkage rate (%) after the resin sheet is heated at 130° C. for 30 minutes may be 2.0 or less, or may be 1.5 or less. The resin sheet according to this embodiment also includes an embodiment in which no shrinkage occurs in the MD direction and the TD direction when the resin sheet is heated under the above-mentioned conditions (i.e., an embodiment in which the MD heat shrinkage rate (%) and the TD heat shrinkage rate (%) are 0%). Therefore, the lower limit of the MD heat shrinkage rate (%) / TD heat shrinkage rate (%) may be 0.

[0026] In addition, when the resin sheet is heated at 130°C for 30 minutes, the heat shrinkage rate in the TD direction and the heat shrinkage rate in the MD direction of the resin sheet are both preferably 5.0% or less. Such a resin sheet is likely to have a MD heat shrinkage rate (%) / TD heat shrinkage rate (%) of 2.5 or less, and is likely to have better moldability. In a preferred embodiment, the heat shrinkage rate in the TD direction and the heat shrinkage rate in the MD direction of the resin sheet after heating at 130°C for 30 minutes may both be 4.0% or less, or may be 3.0% or less. The details of the method for measuring the heat shrinkage rate of the resin sheet will be described later.

[0027] <Layer configuration> The resin sheet according to the present embodiment may be composed of only a base layer (single layer structure), or may include a base layer and a surface layer provided on at least one surface of the base layer (multilayer structure). The surface layer may be provided on both surfaces of the base layer. When the resin sheet according to the present embodiment is used for a carrier tape or tray for the electronic component package described above, it is preferable that the resin sheet includes a base layer and surface layers provided on both surfaces of the base layer. 1 is a cross-sectional view showing an example of a resin sheet according to the present embodiment. The resin sheet 100 in FIG.

[0028] (base material layer) In the resin sheet according to the present embodiment, the base layer preferably contains a polystyrene-based resin and a crystalline biomass-derived resin. The base layer preferably contains a polystyrene-based resin as a main component. By providing such a base layer, the resin sheet is likely to satisfy the above formula (1). In this disclosure, "containing a polystyrene-based resin as a main component" means that the proportion of the polystyrene-based resin to the total mass of the resin composition constituting the base layer (hereinafter referred to as "resin composition for base layer") is more than 50 mass%.

[0029] Polystyrene resin Examples of polystyrene resins include general-purpose polystyrene resin (GPPS), high-impact polystyrene resin (rubber-modified styrene resin, HIPS), and resins containing a mixture of these as the main component. As described above, the term "main component" refers to a proportion of GPPS and / or HIPS exceeding 50% by mass relative to the total mass of the polystyrene resin.

[0030] Examples of aromatic vinyl monomers constituting polystyrene resin (GPPS) include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, 1,1-diphenylethylene, etc. Among these aromatic vinyl monomers, styrene, vinyltoluene, and o-methylstyrene are preferred, and styrene is more preferred. High impact polystyrene resin (HIPS) is a polystyrene resin in which a styrene monomer is graft-polymerized onto a rubber-like elastomer mainly composed of a conjugated diene. Examples of conjugated dienes include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. Of these, it is preferable to include 1,3-butadiene.

[0031] In one embodiment, from the viewpoint of easily obtaining a resin sheet having more excellent mechanical properties, it is preferable that the HIPS is contained. The content of the conjugated diene in the HIPS is preferably 3 to 10 mass%, more preferably 4 to 9 mass%, and further preferably 5 to 9 mass%.

[0032] The conjugated diene content in the polystyrene resin can be conveniently adjusted by blending GPPS and HIPS, but it may also be adjusted during the production stage of HIPS. The melt flow index (measured according to JIS-K-7210) of the GPPS and / or HIPS contained in the base layer is not particularly limited, but from the viewpoint of formability, it is preferable that the melt flow index is 1 to 15 g / 10 min under conditions of 200°C and a load of 5 kg.

[0033] Crystalline biomass-based resin The base layer preferably further contains a crystalline biomass-derived resin. The resin sheet according to the present embodiment is more likely to satisfy the above formula (1) by combining a polystyrene resin with a crystalline biomass-derived resin. Furthermore, by containing a biomass-derived resin, the resin sheet according to the present embodiment can be an "environmentally friendly resin sheet."

[0034] The term "biomass-derived resin" refers to a resin containing a renewable organic resource-derived substance as a raw material and obtained by chemical or biological synthesis, and having a number average molecular weight (Mn) of 1,000 or more. Examples of organic resources include waste organic resources such as food waste, livestock excrement, construction waste, and waste paper; unused organic resources such as inedible parts of agricultural crops and forest residues; resource grain organic resources (plants cultivated for the purpose of energy sources or raw materials for products); and new crop organic resources (marine plants and genetically modified plants suitable for organic resource production). Among these, from the viewpoint of producing a resin sheet with less environmental impact, it is preferable to include a biomass-derived resin made from waste organic resources and / or unused organic resources.

[0035] Examples of crystalline biomass-derived resins include polylactic acid (PLA), biopolyethylene, biopolyamide, polyhydroxyalkanoate (PHA), poly-3-hydroxybutyrate-3-hydroxyhexanoate (PHBH), polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT), polyethylene furanoate (PEF), etc. Among these, polylactic acid and biopolyethylene are preferred, and polylactic acid is more preferred, from the viewpoints of ease of availability and ease of satisfying formula (1).

[0036] In one embodiment, from the viewpoint of easily obtaining a resin sheet that satisfies the above formula (1) and is environmentally friendly, the proportion of the crystalline biomass-derived resin relative to the total mass of the resin composition for the base layer is preferably 10% by mass or more. From the viewpoint of easily achieving both mechanical properties and moldability of the resin sheet, the upper limit of the proportion of the crystalline biomass-derived resin is more preferably 10 to 50% by mass, even more preferably 10 to 40% by mass, and particularly preferably 12 to 30% by mass.

[0037] In a preferred embodiment, the resin sheet may contain a polystyrene resin and polylactic acid, and the proportion of polylactic acid to the total mass of the resin sheet may be 10% by mass or more. In a more preferred embodiment, the base layer of the resin sheet may contain a polystyrene resin and polylactic acid, and the proportion of polylactic acid to the total mass of the resin composition for the base layer may be 10% by mass or more, 11% by mass or more, or 13% by mass or more.

[0038] In a preferred embodiment, the base layer may contain only a polystyrene resin and a crystalline biomass-derived resin, or may contain only HIPS and polylactic acid. In this case, it is preferable to control the ratio of the polystyrene resin and the crystalline biomass-derived resin so that the amount of conjugated diene in the base layer is 3.0 to 7.0 mass% and the ratio of the crystalline biomass-derived resin is 10 mass% or more.

[0039] Other resins 1 The base layer may contain a resin (other resin 1) other than the above-mentioned polystyrene-based resin and crystalline biomass-derived resin. Examples of the other resin include a polycarbonate-based resin, a polyether-based resin, a polyester-based resin, polyvinyl chloride, and a polyolefin-based resin, and may be contained in a small amount within the range satisfying the above formula (1).

[0040] (Surface layer) When the resin sheet according to the present embodiment is used for a carrier tape for the above-mentioned electronic component packaging body or the like, it is preferable to provide a surface layer 20 on both surfaces of the base layer 10 as shown in Fig. 1. In addition, it is preferable that the surface layer 20 is composed of a conductive resin composition.

[0041] In one embodiment, the conductive resin composition preferably contains a polystyrene resin and a conductive material. The polystyrene resin may be the same as that described in the above-mentioned base layer. In a preferred embodiment, the surface layer preferably contains HIPS.

[0042] In one embodiment, the proportion of the polystyrene resin in the surface layer is preferably 46 to 85 mass %, more preferably 54 to 81 mass %, based on the total mass of the conductive resin composition, from the viewpoint of mechanical properties such as tensile elastic modulus.

[0043] Conductive materials The surface layer may contain a conductive material. The conductive material preferably contains carbon black such as furnace black, channel black, acetylene black, and ketjen black. Among these, it is preferable to contain acetylene black, which has a large specific surface area and is easily able to achieve high conductivity with a small amount added. The proportion of the conductive material in the surface layer is preferably 13 to 23 mass %, more preferably 16 to 21 mass %, based on the total mass of the conductive resin composition. If the proportion of the conductive material is within the above range, good conductivity is maintained, flowability during molding is unlikely to decrease, and the mechanical properties of the resin sheet are also unlikely to decrease.

[0044] Other Ingredients The surface layer may contain other components in addition to the polystyrene resin and conductive material described above. Examples of other components include resins other than polystyrene resins (other resins 2); various additives such as lubricants, plasticizers, heat stabilizers, processing aids, inorganic fillers, and matting agents. These may be used alone or in combination of two or more.

[0045] Other resins 2 In one embodiment, from the viewpoint of easily suppressing detachment of the conductive material (particularly carbon black) from the polystyrene resin, it is preferable to include an olefin resin as the other resin 2. Furthermore, when an olefin resin is included, it is more preferable to include a hydrogenated resin of an aromatic vinyl-conjugated diene block copolymer from the viewpoint of further improving the compatibility between the polystyrene resin and the olefin resin. That is, it is particularly preferable that the other resin 2 contains both an olefin resin and a hydrogenated resin of an aromatic vinyl-conjugated diene block copolymer.

[0046] Olefin resin Examples of olefin resins include polyethylene resins such as high-density polyethylene, very low-density polyethylene, and linear low-density polyethylene; ethylene-α-olefin copolymers copolymerized with polypropylene and C3 or higher α-olefin hydrocarbons (e.g., propylene, 1-butene, 1-hexene, etc.); and copolymers of olefins and monomers having a polar group copolymerizable with olefins, such as ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, ethylene-ethyl acrylate copolymers, ethylene-methacrylic acid ester copolymers, ethylene-vinyl acetate-vinyl chloride copolymers, and ternary copolymers of ethylene, vinyl chloride, and acid anhydrides.

[0047] Hydrogenated resin of aromatic vinyl-conjugated diene block copolymer Representative examples of the hydrogenated resin of an aromatic vinyl-conjugated diene block copolymer include hydrogenated resin of a styrene-butadiene block copolymer, hydrogenated resin of a styrene-isoprene block copolymer, etc. Among these, hydrogenated resin of a styrene-butadiene block copolymer, i.e., SEBS (styrene-ethylene-butylene-styrene block copolymer) and SBBS (styrene-butadiene-butylene-styrene block copolymer), are preferred.

[0048] When the surface layer contains an olefin resin, the content is preferably 1 to 20 mass% based on the total mass of the conductive resin composition. When the surface layer contains a hydrogenated resin of an aromatic vinyl-conjugated diene block copolymer, the content is preferably 1 to 11 mass%, more preferably 1 to 7 mass%, based on the total mass of the conductive resin composition.

[0049] The total thickness of the resin sheet according to the present embodiment can be adjusted to any value within the range of 0.1 to 3.0 mm. If the total thickness of the resin sheet is 0.1 mm or more, the strength of the resin sheet is unlikely to be insufficient when the resin sheet is molded into a packaging container. If the total thickness of the resin sheet is 3.0 mm or less, the resin sheet is easily molded by pressure molding, vacuum molding, hot plate molding, etc.

[0050] When the resin sheet has the above-mentioned base layer and surface layer, the thickness ratio of the base layer to the surface layer (thickness of base layer / thickness of surface layer) is preferably 98 / 2 to 20 / 80, more preferably 95 / 5 to 50 / 60, and even more preferably 95 / 5 to 80 / 20. Here, the "thickness of the surface layer" refers to the "total thickness of the surface layers." That is, in the case of a three-layer structure in which surface layers are provided on both sides of the base layer, the thickness ratio refers to the thickness of the base layer / the total thickness of both surface layers.

[0051] In one embodiment, when the resin sheet contains a polystyrene-based resin and a crystalline biomass-derived resin, more preferably when the base layer contains a polystyrene-based resin and a crystalline biomass-derived resin, it is preferable that the ΔHb of the resin sheet calculated from the following formulas (2) to (3) based on differential scanning calorimetry is 1.5 J / g or more. ΔHb(J / g)=(ΔHm1+ΔHm2)-(ΔHp-ΔHg) ···(2) (In formula (2), ΔHm1 represents the amount of heat (J / g) at the melting point Tm1, ΔHm2 represents the amount of heat (J / g) at the melting point Tm2, ​​ΔHp represents the amount of heat of recrystallization (J / g), and ΔHg represents the amount of heat (J / g) calculated by the following formula (3).) ΔHg (J / g) = (proportion of polystyrene resin in resin sheet (mass%) / 96.6 mass%) × 1.84 (J / g) (3)

[0052] As with the above formula (1), ΔHb can be calculated by heating from 30° C. to 300° C. at a heating rate of 10° C. / min (1st RUN) using a DSC (e.g., Perkin Elmer, product name "power compensation type DSC8500"). ΔHb refers to the value obtained by subtracting "the difference between the recrystallization heat amount ΔHp and ΔHg" from "the total value (J / g) of the heat of fusion at the melting points Tm1 and Tm2: (ΔHm1+ΔHm2)".

[0053] ΔHg is a value calculated using the above formula (3). In formula (3), "1.84 J / g" is the amount of heat derived from the glass transition temperature (Tg) of polystyrene when a resin sheet (hereinafter referred to as "reference resin sheet"), in which a surface layer containing polystyrene resin (HIPS) and a conductive material (carbon black) in a mass ratio of "polystyrene resin / conductive material = 96.6 / 3.4" is laminated on both sides of a base material layer containing only polystyrene resin (HIPS), is heated from 30 ° C. to 300 ° C. at a heating rate of 10 ° C. / min (1st RUN) by DSC. ΔHg means the amount of heat (J / g) calculated by multiplying the heat amount (1.84 J / g) of the reference resin sheet by the ratio of the reference resin sheet to the polystyrene resin in the resin sheet according to this embodiment.

[0054] In formula (2), the amount of heat of recrystallization derived from the crystalline biomass-derived resin in the resin sheet, preferably polylactic acid, can be calculated by subtracting ΔHg from ΔHp. Furthermore, a resin sheet in which the value (ΔHb) obtained by subtracting the amount of heat of recrystallization of the crystalline biomass-derived resin from the total amount of heat of fusion is 1.5 J / g or more and ΔHa calculated by formula (1) is 0.5 J / g or more has better mechanical properties such as tensile modulus and folding strength, and has a smaller difference in heat shrinkage between the MD and TD directions.

[0055] In one embodiment, ΔHb is preferably 2.0 J / g or more, more preferably 3.0 J / g or more, and particularly preferably 4.0 J / g or more. The upper limit of ΔHb is not particularly limited as long as the effect of the present disclosure is achieved. In one embodiment, ΔHb may be 1.5 to 7.0 J / g, or 2.0 to 6.0 J / g.

[0056] [Manufacturing method of resin sheet] The method for producing the resin sheet according to the present embodiment is not particularly limited. For example, the resin composition for the base layer (or the resin composition for the base layer and the conductive resin composition) may be mixed uniformly by a high-speed mixer, kneaded and pelletized by a known method using an extruder or the like, and then the resin sheet according to the present embodiment may be obtained by a known method using an extruder or the like.

[0057] In one embodiment, when preparing a resin sheet having a base layer and a surface layer, the resin composition for the base layer and the conductive resin composition are each molded into a sheet or film by a separate extruder, and then laminated in stages by a thermal lamination method, a dry lamination method, an extrusion lamination method, or the like. Alternatively, it is also possible to laminate the conductive resin composition to be the surface layer on both sides of a preformed base layer sheet by a method such as extrusion coating. In order to manufacture more inexpensively, it is preferable to prepare a resin sheet by laminating them all at once by a multi-layer co-extrusion method using a multi-manifold die or a feed block. In addition, in this type of resin sheet manufacturing method, scrap resin generated in the manufacturing process of the sheet or molded container can be crushed and recycled into the base layer. In the manufacture of the resin sheet according to this embodiment, scrap resin may be mixed into the base layer as long as the resin sheet finally obtained satisfies the above-mentioned formula (1) and does not have a significant effect on strength reduction, burr generation, etc.

[0058] [Application] As described above, the resin sheet according to the present embodiment can be suitably used for electronic component packaging applications. When the resin sheet is used as an electronic component packaging, it can be molded into a shape according to the application by a known thermoforming method such as a vacuum molding method, a pressure molding method, a press molding method, etc. Specifically, it can be applied to vacuum-formed trays, magazines, embossed carrier tapes, cover tapes, etc. The resin sheet according to the present embodiment has a small difference in heat shrinkage rate between the MD direction and the TD direction and has good moldability, so it can be suitably used for embossed carrier tapes, trays, etc. EXAMPLES

[0059] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following description.

[0060] [Evaluation method] Each evaluation was performed by sampling the resin sheet in the extrusion direction (MD) and by the following methods. (1) Differential scanning calorimetry 9 to 10 mg of the sheet sample was heated from 30°C to 300°C at a heating rate of 10°C / min (1st RUN) using a differential scanning calorimeter (DSC) (manufactured by Perkin Elmer, product name "Input compensation type DSC8500"). The measurement was performed according to standard 9.4.3 of ISO 11357-3:2018, and the melting point Tm1, melting point Tm2, ​​recrystallization temperature Tc, ΔHm1, ΔHm2, and ΔHp were obtained from the obtained DSC curve. In addition, ΔHg was obtained from the proportion of polystyrene resin in the sheet sample. These were applied to the following formulas (1) to (3) to calculate ΔHa and ΔHb. ΔHa(J / g)=|(ΔHm1+ΔHm2)-ΔHp| ···(1) ΔHb(J / g)=(ΔHm1+ΔHm2)-(ΔHp-ΔHg) ···(2) ΔHg (J / g) = (proportion of polystyrene resin in resin sheet (mass%) / 96.6 mass%) × 1.84 (J / g) (3) (In formula (1), ΔHm1 represents the amount of heat (J / g) at the melting point Tm1, ΔHm2 represents the amount of heat (J / g) at the melting point Tm2, ​​and ΔHp represents the amount of heat of recrystallization (J / g).) (In formula (2), ΔHm1 represents the amount of heat (J / g) at the melting point Tm1, ΔHm2 represents the amount of heat (J / g) at the melting point Tm2, ​​ΔHp represents the amount of heat of recrystallization (J / g), and ΔHg represents the amount of heat (J / g) calculated by formula (3).)

[0061] (2) Tensile modulus The sheet samples were subjected to the tensile test in accordance with JIS-K-7127 (1999) using a product called "Strograph VE-1D" manufactured by Toyo Seiki Seisakusho Co., Ltd. The test environment was 23°C / 50% RH, the tensile speed was 5mm / min, the chuck distance was 25mm, and the test piece was a dumbbell-shaped specimen with a width of 6mm (N=3). The average value was taken as the tensile modulus (MPa).

[0062] (3) Folding strength For the sheet samples, test pieces with a length of 150 mm, width of 15 mm, and thickness of 0.2 mm were prepared in accordance with JIS-P-8115 (2001), and the MIT folding endurance strength was measured using an "MIT folding fatigue tester" manufactured by Toyo Seiki Seisakusho Co., Ltd. At this time, the test was performed at a folding angle of 135 degrees, a folding speed of 175 times / min, and a measuring load of 250 g (N=3), and the average value was taken as the folding endurance strength (number of times).

[0063] (4) Heat shrinkage rate The sheet sample was cut into three rectangular pieces with a width (TD direction) of 120 mm x length (MD direction) of 120 mm. Then, a mark was made 100 mm from the end in each of the width and length directions of the sheet sample (marked line in the length (MD) direction: AB, marked line in the width (TD) direction: CD. The distance between AB and CD was 100 mm). Next, the sheet sample was sandwiched between papers and left in an oven at 130°C ± 2°C for 30 minutes. At this time, the sheet sample was kept horizontal. After 30 minutes, the sample was taken out of the oven and allowed to cool to room temperature, and the lengths AB and CD were measured with calipers, and the heat shrinkage rate in each of the MD and TD directions was calculated using the following formula (4). S = [(L2 - L1) / L2] × 100 (4) (In formula (4), S represents the heat shrinkage rate (%), L2 represents the gauge length (mm) between AB or CD before heating, and L1 represents the gauge length (mm) between AB or CD after heating.) The heat shrinkage rate of each of the three sheet samples was measured, and the average value was calculated.

[0064] The components used in the examples and comparative examples are as follows. <Resin composition for base layer> Polystyrene resin-1: Impact resistant polystyrene resin, conjugated diene content: 8.5 mass%. Crystalline biomass-derived resin: Polylactic acid (PLA) As the crystalline biomass-derived resin, a mixed resin of HIPS and PLA (product name "Toyo Enelights (registered trademark) BM-600" manufactured by Toyo Styrene Co., Ltd., HIPS / PLA=70 / 30) was used. <Conductive resin composition> Polystyrene resin-2: impact resistant polystyrene resin, conjugated diene content: 7.4 mass%. Conductive material: Masterbatch containing carbon black.

[0065] (Examples 1 to 3 and Comparative Examples 1 to 2) For the surface layer, pellets of the conductive resin composition shown in Table 1 were used, and for the base layer, pellets of the base layer resin composition shown in Table 1 were used. A φ65 mm extruder (L / D=28) for the base layer, a φ40 mm extruder (L / D=26) for the surface layer, and a 500 mm wide T-die were used for the feed block method to laminate the surface layers on both sides of the base layer to obtain the resin sheets of each example. The thickness ratio of the resin sheets of each example was surface layer / base layer / surface layer=0.5 / 9 / 0.5, and the total thickness of the resin sheets was 0.3 mm. The mechanical properties and heat shrinkage rate of the resin sheets obtained in each example were measured by the above-mentioned method. In addition, the moldability was evaluated according to the following evaluation criteria. The results are shown in Table 1. (Evaluation criteria for formability) Pass: The heat shrinkage rates in both the MD and TD directions were 5.0% or less, and the MD heat shrinkage rate (%) / TD heat shrinkage rate (%) was 2.5 or less. Failed: The heat shrinkage rate in the MD direction and / or the TD direction was more than 5.0%, or the MD heat shrinkage rate (%) / TD heat shrinkage rate (%) was more than 2.5.

[0066] [Table 1]

[0067] As shown in Table 1, the resin sheets of Examples 1 to 3 satisfying the configuration of this embodiment were excellent in mechanical properties and had small differences in heat shrinkage in the MD and TD directions. The resin sheets of Examples 1 to 3 had very small heat shrinkage in the MD direction, and as a result, the differences in heat shrinkage in the MD and TD directions were small. It is presumed that such resin sheets also have good moldability when molded into, for example, a carrier tape or a tray. On the other hand, the resin sheet of Comparative Example 2, in which ΔHa was less than 0.5, had good folding strength but had a tensile modulus inferior to the resin sheets of Examples 1 to 3. In addition, the heat shrinkage in the MD direction was large, and as a result, the differences in heat shrinkage in the MD and TD directions were also large. In addition, the resin sheet of Comparative Example 1 is a conventional resin sheet having a base layer containing only a polystyrene-based resin, but had lower folding strength and tensile modulus than the resin sheets of Examples 1 to 3. In addition, the heat shrinkage in the MD direction was very large, and the differences in heat shrinkage in the MD and TD directions were also large. From the above results, it was confirmed that the resin sheet according to this embodiment has excellent mechanical properties such as tensile elastic modulus and folding strength, and has a small difference in heat shrinkage rate between the MD and TD directions.

[0068] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of the present disclosure are set forth below. [1] A resin sheet having a ΔHa of 0.5 J / g or more as calculated from the following formula (1) based on differential scanning calorimetry: ΔHa(J / g)=|(ΔHm1+ΔHm2)-ΔHp| ···(1) (In formula (1), ΔHm1 represents the amount of heat (J / g) at the melting point Tm1, ΔHm2 represents the amount of heat (J / g) at the melting point Tm2, ​​and ΔHp represents the amount of heat of recrystallization (J / g).) [2] The resin sheet according to [1], wherein the melting point Tm1 is 120°C or higher and 140°C or lower, and the melting point Tm2 is 160°C or higher and 180°C or lower. [3] The resin sheet according to [1] or [2], wherein (ΔHm1+ΔHm2) in the formula (1) is 2.0 J / g or more. [4] The resin sheet according to any one of [1] to [3], wherein, when the resin sheet is heated at 130°C for 30 minutes, the heat shrinkage rate in the MD direction relative to the heat shrinkage rate in the TD direction of the resin sheet (MD heat shrinkage rate (%) / TD heat shrinkage rate (%)) is 2.5 or less. [5] The resin sheet according to any one of [1] to [4], wherein when the resin sheet is heated at 130°C for 30 minutes, the heat shrinkage rate in the TD direction and the heat shrinkage rate in the MD direction of the resin sheet are both 5.0% or less. [6] The resin sheet according to any one of [1] to [5], wherein the resin sheet contains a polystyrene-based resin and a crystalline biomass-derived resin. [7] The resin sheet according to any one of [1] to [6], wherein the resin sheet contains a polystyrene-based resin and polylactic acid. [8] The resin sheet contains a polystyrene-based resin and a polylactic acid, The resin sheet according to any one of [1] to [7], wherein the proportion of the polylactic acid to the total mass of the resin sheet is 10 mass % or more. [9] The resin sheet has a base layer and a surface layer provided on at least one surface of the base layer, the base layer contains a polystyrene resin and a polylactic acid, The resin sheet according to any one of [1] to [8], wherein the proportion of the polylactic acid to the total mass of the resin sheet is 10 mass% or more.

[10] The resin sheet according to any one of [6] to [9], having a ΔHb of 1.5 J / g or more as calculated from the following formulas (2) to (3) based on differential scanning calorimetry: ΔHb(J / g)=(ΔHm1+ΔHm2)-(ΔHp-ΔHg) ···(2) (In formula (2), ΔHm1 represents the amount of heat (J / g) at the melting point Tm1, ΔHm2 represents the amount of heat (J / g) at the melting point Tm2, ​​ΔHp represents the amount of heat of recrystallization (J / g), and ΔHg represents the amount of heat (J / g) calculated by the following formula (3).) ΔHg(J / g)=(proportion (mass%) of the polystyrene-based resin in the resin sheet / 96.6 mass%)×1.84(J / g) (3)

[11] The resin sheet according to any one of [1] to

[10] , which is for use in packaging for electronic components.

[12] The resin sheet according to any one of [1] to

[11] , which is a carrier tape or a tray. [Explanation of symbols]

[0069] 10: Base material layer 20: Surface layer 100: Resin sheet

Claims

1. A resin sheet having a ΔHa of 0.5 J / g or more calculated from the following formula (1) based on differential scanning calorimetry. ΔHa (J / g) = | (ΔHm1 + ΔHm2) - ΔHp | ... (1) (In formula (1), ΔHm1 represents the amount of heat (J / g) at the melting point Tm1, ΔHm2 represents the amount of heat (J / g) at the melting point Tm2, ​​and ΔHp represents the amount of heat of recrystallization (J / g).)

2. The resin sheet according to claim 1 , wherein the melting point Tm1 is 120° C. or more and 140° C. or less, and the melting point Tm2 is 160° C. or more and 180° C. or less.

3. The resin sheet according to claim 1 or 2, wherein (ΔHm1 + ΔHm2) in the formula (1) is 2.0 J / g or more.

4. 3. The resin sheet according to claim 1, wherein the heat shrinkage rate in the MD direction relative to the heat shrinkage rate in the TD direction of the resin sheet when the resin sheet is heated at 130 ° C. for 30 minutes (MD heat shrinkage rate (%) / TD heat shrinkage rate (%)) is 2.5 or less. The resin sheet according to claim 1 or 2.

5. The resin sheet according to claim 1 or 2, wherein when the resin sheet is heated at 130° C. for 30 minutes, the heat shrinkage rate in the TD direction and the heat shrinkage rate in the MD direction of the resin sheet are both 5.0% or less.

6. The resin sheet according to claim 1 or 2, wherein the resin sheet contains a polystyrene-based resin and a crystalline biomass-derived resin.

7. The resin sheet according to claim 1 or 2, comprising a polystyrene-based resin and a polylactic acid.

8. The resin sheet contains a polystyrene resin and a polylactic acid, The resin sheet according to claim 1 , wherein a ratio of the polylactic acid to a total mass of the resin sheet is 10 mass % or more.

9. The resin sheet has a base layer and a surface layer provided on at least one surface of the base layer, the base layer contains a polystyrene resin and a polylactic acid, The resin sheet according to claim 1 , wherein a ratio of the polylactic acid to a total mass of the resin sheet is 10 mass % or more.

10. The resin sheet according to claim 6, wherein ΔHb calculated from the following formulas (2) to (3) based on differential scanning calorimetry is 1.5 J / g or more. ΔHb (J / g) = (ΔHm1 + ΔHm2) - (ΔHp - ΔHg) ... (2) (In formula (2), ΔHm1 represents the amount of heat (J / g) at the melting point Tm1, ΔHm2 represents the amount of heat (J / g) at the melting point Tm2, ​​ΔHp represents the amount of heat of recrystallization (J / g), and ΔHg represents the amount of heat (J / g) calculated by the following formula (3).) ΔHg (J / g)=(proportion (mass%) of the polystyrene-based resin in the resin sheet / 96.6 mass%)×1.84 (J / g) (3)

11. The resin sheet according to claim 1 or 2, which is for use in a packaging body for electronic components.

12. The resin sheet according to claim 1 or 2, which is a carrier tape or a tray.

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