Polyolefin resin film

Abstract

A polyolefin resin film (1) comprises, on at least one outermost surface, a functional layer (3) containing polyethylene, polypropylene, and an antistatic agent, wherein the antistatic agent content relative to the entire functional layer (3) is 10-30 mass%, and the polypropylene content relative to the entire polyolefin resin film (1) is 16-41 mass%.

Description

Polyolefin resin film

[0001] This invention relates to a polyolefin-based resin film (hereinafter sometimes simply referred to as "resin film").

[0002] In electronic components such as semiconductor chips, electromagnetic interference (EMI) in the electronic components is suppressed by forming an electromagnetic shielding film on the outer surface of the electronic component using the sputtering method.

[0003] Here, a method has been proposed to protect external connection terminals in order to prevent the formation of an electromagnetic shielding film on the external connection terminals when forming an electromagnetic shielding film on an electronic component having external connection terminals.

[0004] More specifically, for example, in the process of forming an electromagnetic shielding film on an electronic component having external connection terminals using the sputtering method, a method has been proposed in which adhesive tape for back surface protection is attached to cover the external connection terminals formed on the back side of the electronic component to prevent the electromagnetic shielding film from wrapping around to the back side of the electronic component (see, for example, Non-Patent Document 1).

[0005] Toshiba Review, Vol. 71, No. 6, December 2016, pp. 16-19

[0006] However, in the method of covering with adhesive tape described in Non-Patent Document 1 above, it may be difficult to completely cover large external connection terminals with the adhesive tape. As a result, the adhesion between the adhesive tape and the back surface of the electronic component on which the external connection terminal is formed may decrease, creating a gap, which can lead to the undesirable situation where the electromagnetic shielding film wraps around to the back surface of the electronic component.

[0007] Therefore, it is conceivable to improve the embedding ability of external connection terminals into the adhesive tape and hold the external terminals with the adhesive tape by using a multilayer adhesive tape (carrier film for electronic components) having a multilayer structure comprising, for example, a base material made of a resin film and a functional layer provided on the base material. However, since the process of forming an electromagnetic wave shielding film on electronic components having external connection terminals by sputtering is carried out at high temperatures (100°C or higher), for example, if the heat resistance of the base material constituting the adhesive tape is poor, the adhesive tape deforms due to thermal shrinkage of the base material, which leads to a problem of reduced retention of the external connection terminals.

[0008] Furthermore, for example, if the substrate constituting the adhesive tape has poor antistatic properties, there was a problem in the process of forming an electromagnetic wave shielding film on an electronic component having an external connection terminal using the sputtering method, where dust and other particles would adhere to the substrate, or electrostatic damage would occur.

[0009] Therefore, the present invention has been made in view of the above problems, and aims to provide a polyolefin resin film with excellent antistatic properties and heat resistance.

[0010] To achieve the above objective, the polyolefin resin film of the present invention is a polyolefin resin film having a functional layer containing polyethylene, polypropylene, and an antistatic agent on at least one of its outermost surfaces, characterized in that the content of the antistatic agent relative to the total functional layer is 10% by mass or more and 30% by mass or less, and the content of polypropylene relative to the total polyolefin resin film is 16% by mass or more and 41% by mass or less.

[0011] According to the present invention, it is possible to provide a polyolefin-based resin film with excellent antistatic properties and heat resistance.

[0012] This is a cross-sectional view showing a polyolefin resin film according to an embodiment of the present invention. This is a plan view showing a polyolefin resin film according to an embodiment of the present invention. This is a cross-sectional view showing a modified example of the polyolefin resin film of the present invention.

[0013] The polyolefin resin film of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments, and can be modified and applied as appropriate without altering the essence of the invention.

[0014] The resin film of the present invention is used as a substrate in the above-mentioned carrier film for electronic components, and is a resin film having a functional layer on at least one of its outermost surfaces, and is a resin film having a multilayer structure composed of a laminate of a core layer (intermediate layer) and a functional layer provided on at least one side of the core layer.

[0015] An example of a resin film having this multilayer structure is a resin film 1 having a three-layer structure, which is composed of a laminate of a core layer 2 and functional layers 3 laminated on both sides of the core layer 2, and is laminated in the order of functional layer / core layer / functional layer, as shown in Figure 1.

[0016] (Functional layer) Functional layer 3 may include one containing polyethylene, polypropylene, and an antistatic agent.

[0017] <Polyethylene> Functional layer 3 contains polyethylene, a type of polyolefin resin, and has a density of 0.930 g / cm³. ３ It is preferable that the material contains low-density polyethylene (LDPE) with a density of 0.930 g / cm³. ３ In the following cases, excessive increases in crystallinity are suppressed, improving flexibility and thus enhancing the isotropy of the resin film.

[0018] Furthermore, from the perspective of improving processing stability, the density of low-density polyethylene is 0.860 g / cm³. ３ Preferably, it is 0.880 g / cm³ or more. ３ It is more preferable that the above conditions are met.

[0019] In other words, the density is 0.860 g / cm³. ３ 0.930g / cm or more ３The following low-density polyethylene has low surface adhesiveness. When used in a functional layer, it can suppress adhesion to the transport rolls during resin film conveyance, suppress blocking during resin film winding, and improve the processing stability of the resin film.

[0020] Also, among low-density polyethylenes, linear low-density polyethylene has side-chain branches in the linear structure of high-density polyethylene. And since these side-chain branches are short-chain and the number of short-chain branches is small, there is little steric hindrance. Compared with low-density polyethylene, it has a higher density, higher crystallinity, and higher melting point, so it has excellent heat resistance. Also, because it has the above-mentioned side-chain branches, compared with high-density polyethylene, its crystallinity does not become too high, and it also has excellent flexibility.

[0021] Also, the density of linear low-density polyethylene is preferably 0.910 to 0.925 g / cm ３ . In the case of 0.910 g / cm ３ or more, the crystallinity becomes high, so the heat resistance can be improved. In the case of 0.925 g / cm ３ or less, an excessive increase in crystallinity can be suppressed, and the isotropy (uniform expandability) of the resin film can be improved.

[0022] Also, the melt mass flow rate (MFR) of linear low-density polyethylene is preferably 0.5 to 7.5 g / 10 min, more preferably 1.0 to 6.0 g / 10 min, and even more preferably 2.0 to 5.0 g / 10 min. This is because when it is 0.5 g / 10 min or more, the molecular weight is not too large, and flexibility and processability can be improved. When it is 7.5 g / 10 min or less, the molecular weight is not too small, and heat resistance can be improved.

[0023] Note that the above melt mass flow rate can be obtained by measuring in accordance with the provisions of JIS K7210:1999.

[0024] Furthermore, from the viewpoint of suppressing surface tackiness, it is preferable that the polyethylene content of the functional layer 3 (i.e., each of the functional layers 3 laminated on both sides of the core layer 2) relative to the total (i.e., 100% by mass of each functional layer) be 32.5% by mass or more and 65% by mass or less.

[0025] Based on the above, in the resin film 1 of the present invention, by using linear low-density polyethylene as the resin for forming the functional layer 3, it is possible to improve the heat resistance at high temperatures of 100°C or higher in the process of forming an electromagnetic wave shielding film on an electronic component having an external connection terminal by sputtering, and to provide a resin film 1 with excellent flexibility and isotropy.

[0026] <Antistatic agent> In the resin film 1 of the present invention, the functional layer 3 contains an antistatic agent from the viewpoint of imparting antistatic properties to the resin film 1.

[0027] Examples of these antistatic agents include block copolymers of propylene resins and polyhydric alcohols, low molecular weight surfactants, and fillers such as carbon black. These antistatic agents may be used individually or in combination of two or more.

[0028] Furthermore, from the viewpoint of providing semi-permanent antistatic properties, it is preferable to use a block copolymer of a polymer-type antistatic agent, which is a propylene resin, and a polyhydric alcohol, as the antistatic agent.

[0029] A block copolymer of a propylene resin and a polyhydric alcohol is a block copolymer having a segment of propylene polymer containing structural units derived from propylene and a segment of polyhydric alcohol polymer containing structural units derived from the polyhydric alcohol.

[0030] This block copolymer of propylene resin and polyhydric alcohol has a structure in which the continuous phase (soft segment phase) of the polyether of the polyhydric alcohol contributes to the development of antistatic properties, while the hard segment phase of the propylene resin contributes to improved dispersibility in the resin forming the functional layer 3 and to the development of strength in that resin.

[0031] The segments of the propylene polymer can include segments of homopolypropylene obtained by polymerizing propylene alone, and segments of copolymers of propylene and α-olefins.

[0032] Examples of the polyhydric alcohol that constitutes the polymer segment of the polyhydric alcohol include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol (trimethylene glycol), propylene glycol, and the like.

[0033] Further, from the viewpoint of improving antistatic properties, it is preferable to use a block copolymer of a propylene-based resin and a polyhydric alcohol, such as a block copolymer of polypropylene and polyethylene glycol. <​​​​​​As described above, in the resin film 1 of the present invention, since the content of the antistatic agent with respect to the entire functional layer 3 is 10% by mass or more and 30% by mass or less, in the step of forming an electromagnetic wave shielding film by sputtering on an electronic component having an external connection terminal, the antistatic property of the resin film 1 can be improved, and adhesion of dust or the like and occurrence of electrostatic trouble due to the resin film 1 can be prevented. Therefore, it becomes possible to improve the productivity of the electronic component on which the electromagnetic wave shielding film is formed.

[0037] In the functional layer 3 containing polyethylene, polypropylene, and an antistatic agent, when the content of the antistatic agent with respect to the entire functional layer 3 is greater than 30% by mass, the heat resistance may decrease as in Comparative Example 2 described later.

[0038] <Polypropylene> Generally, as polypropylene, there are homopolypropylene obtained by polymerizing propylene alone, random polypropylene obtained by copolymerizing ethylene and propylene, and block polypropylene (block polypropylene copolymerized with ethylene) obtained by copolymerizing ethylene and propylene in the presence of homopolypropylene after polymerizing homopolypropylene.

[0039] Among these, from the viewpoint of further improving the heat resistance, it is preferable to use homopolypropylene. This is because homopolypropylene has high stereoregularity and a large crystallinity contributing to the melting point, and thus has excellent heat resistance. Further, since the crystallinity is large, the rigidity is large, but by mixing with the above-mentioned linear low-density polyethylene, the flexibility of the resin film 1 can be improved.

[0040] Block polypropylene copolymerized with ethylene is a block polypropylene composed of propylene and ethylene, and has a sea-island structure in which polyethylene (island component) is dispersed in homopolypropylene (sea component), and has an EPR phase (rubber phase) around the polyethylene. Therefore, while retaining the heat resistance of homopolypropylene, an EPR phase is formed at the boundary line of the sea and islands, so it has excellent flexibility.

[0041] Furthermore, from the viewpoint of further improving heat resistance, it is preferable that the polypropylene content of the functional layer 3 (i.e., each of the functional layers 3 laminated on both sides of the core layer 2) is 20% by mass or more and 50% by mass or less in relation to the total amount of each functional layer (i.e., 100% by mass of each functional layer).

[0042] Based on the above, in the resin film 1 of the present invention, by using polypropylene as the resin that forms the functional layer, it is possible to improve the heat resistance at high temperatures of 100°C or higher in the process of forming an electromagnetic wave shielding film on an electronic component having an external connection terminal by sputtering.

[0043] (Core layer) Core layer 2 may include one containing the polyethylene and polypropylene mentioned above.

[0044] Here, from the viewpoint of processability, it is preferable that the polyethylene content relative to the entire core layer 2 (i.e., 100% by mass of the core layer) be 62.5% by mass or more and 90% by mass or less.

[0045] Furthermore, from the viewpoint of further improving heat resistance, it is preferable that the polypropylene content relative to the entire core layer 2 (i.e., 100% by mass of the core layer) be 10% by mass or more and 37.5% by mass or less.

[0046] <Resin Film> In the resin film 1 of the present invention, the polypropylene content relative to the entire resin film 1 (i.e., 100% by mass of the resin film) is 16% by mass or more and 41% by mass or less. If it is less than 16% by mass, the heat resistance of the resin film 1 will decrease, and if it is more than 41% by mass, the processability of the resin film 1 will decrease.

[0047] In other words, in the resin film 1 of the present invention, the polypropylene content relative to the total resin film 1 is 16% by mass or more and 41% by mass or less. Therefore, a decrease in processability can be prevented, and the heat resistance at high temperatures of 100°C or higher can be improved in the process of forming an electromagnetic wave shielding film on an electronic component having external connection terminals by sputtering. Consequently, a decrease in the retention of external connection terminals due to thermal shrinkage can be prevented.

[0048] Furthermore, in the resin film 1 of the present invention, it is preferable that the thermal shrinkage rate when heated at 120°C for 15 minutes in the mechanical axis (longitudinal direction) (hereinafter referred to as "MD") and the direction perpendicular thereto (hereinafter referred to as "TD") of the resin film 1, as shown in Figure 2, is 2% or less. If the thermal shrinkage rate is greater than 2%, the resin film 1 will shrink excessively, causing deformation of the resin film 1 due to thermal shrinkage, which may reduce the adhesion between the core layer 2 and the functional layer 3, and reduce the retention of the external connection terminals due to thermal shrinkage.

[0049] Furthermore, from the viewpoint of suppressing the aforementioned decrease in retention, the thermal shrinkage rate of the resin film 1 is preferably 1.8% or less, and more preferably 1.5% or less.

[0050] Furthermore, the aforementioned "thermal shrinkage rate" can be determined by the method described in the examples below.

[0051] Furthermore, in the resin film 1 of the present invention, the surface resistivity is 1.00 × 10 １３ It is preferable that the ratio is Ω / □ or less, and 1.00 × 10 １1 It is more preferable that the ratio is less than or equal to Ω / □, and is 1.00 × 10 １０ It is even more preferable that the surface resistivity is Ω / □ or less. １３ If the value is greater than Ω / □, when forming an electromagnetic shielding film on an electronic component with external connection terminals using the sputtering method, the static electricity generated by the resin film may damage the circuitry in the electronic component.

[0052] In other words, the surface resistivity is 1.00 × 10⁻⁶ １３ When the value is less than or equal to Ω / □, it exhibits excellent antistatic properties, thus preventing the inconvenience of damage to circuits in electronic components caused by static electricity.

[0053] The "surface resistivity" referred to here is obtained by measurement in accordance with the provisions of JIS K6911:2006, and can be determined by the method described in the examples below.

[0054] The thickness of the resin film 1 of the present invention is preferably 30 to 300 μm, and more preferably 50 to 150 μm. If the thickness of the resin film is 30 μm or more, handling properties can be improved, and if the thickness is 300 μm or less, processability can be improved.

[0055] Furthermore, in the case of a resin film having a three-layer structure in which a functional layer / core layer / functional layer is laminated in that order, the thickness of the functional layer is not particularly limited, but is preferably 2 to 60 μm, and more preferably 4 to 40 μm. Similarly, the thickness of the core layer is not particularly limited, but is preferably 40 to 120 μm, and more preferably 50 to 80 μm.

[0056] Furthermore, in the case of a resin film having a three-layer structure in which a functional layer / core layer / functional layer is laminated in that order, from the viewpoint of processability and low cost, the ratio of the core layer to the entire resin film is preferably 50 to 95%, and more preferably 55 to 90%.

[0057] <Manufacturing Method> For example, when manufacturing a resin film 1 having a three-layer structure in which a functional layer / core layer / functional layer is laminated in that order, as shown in Figure 1, first, a resin material for forming the functional layer and a resin material for forming the core layer are prepared.

[0058] Next, using a co-extruder equipped with a T-die for three types of three layers, the resin material for forming the functional layer and the resin material for forming the core layer are simultaneously extruded and molded at a predetermined temperature to produce a resin film 1 having the multilayer structure of the present invention, which is composed of a laminate of a core layer 2 and functional layers 3 laminated on both sides of the core layer 2. Alternatively, the resin film 1 of the present invention may be produced by known calendering or inflation methods.

[0059] <Other Embodiments> The resin film 1 of the present invention may contain various additives, to the extent that the effects of the present invention are not impaired. As additives, known additives commonly used in resin films 1 can be used, such as antiblocking agents, nucleating agents, processing aids, heat stabilizers, antioxidants, ultraviolet absorbers, lubricants, and colorants. These additives may be used individually or in combination of two or more.

[0060] Furthermore, although a resin film having a three-layer structure in which a functional layer / core layer / functional layer is laminated in that order was described as an example, the resin film having a multilayer structure of the present invention only needs to have at least one of the above-mentioned functional layers. For example, as shown in Figure 3, one of the functional layers 3 in Figure 1 is a surface layer 4, and the resin film 10 has a three-layer structure in which a surface layer / core layer / functional layer is laminated in that order. As the surface layer 4, for example, general-purpose resins such as polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMMA), acrylic resins, and ionomers can be used. Furthermore, by using these general-purpose resins, it is possible to reduce costs.

[0061] Furthermore, in the resin film of the present invention, from the viewpoint of further improving antistatic properties, the core layer 2 and the surface layer 4 may be configured to contain the above-mentioned antistatic agent.

[0062] Furthermore, the resin film 1 of the present invention is not limited to a three-layer structure, but may also be a resin film having a five-layer structure in which a functional layer / functional layer / core layer / functional layer / functional layer is laminated in that order.

[0063] The present invention will be described below based on examples. However, the present invention is not limited to these examples, and these examples can be modified and altered in accordance with the spirit of the invention; such modifications do not exclude them from the scope of the invention.

[0064] The materials used to produce the resin film are as follows: (1) LLDPE1: Linear low-density polyethylene, melting point: 121°C, density: 0.922 g / cm³ ３ (2) LLDPE2: Linear low-density polyethylene, melting point: 120°C, density: 0.913 g / cm³ ３ , MFR: 2.0 g / 10 min (3) HomoPP: Homopolypropylene obtained by polymerizing propylene alone, melting point: 163°C, density: 0.900 g / cm³ ３MFR: 0.5 g / 10 min (4) Antistatic agent 1: Block copolymer having polypropylene segments and polyethylene glycol segments, melting point: 150°C, density: 1.0 g / cm³ ３ , MFR: 8.0 g / 10 min (5) Antistatic agent 2: Block copolymer having polypropylene segments and polyethylene glycol segments, melting point: 135°C, density: 1.1 g / cm³ ３ MFR: 15.0g / 10 min

[0065] (Example 1) <Preparation of polyolefin resin film> First, the materials shown in Table 1 were blended to prepare a resin material for forming a functional layer and a resin material for forming a core layer having the compositions (parts by mass) shown in Table 1.

[0066] Next, using a co-extruder equipped with a T-die for three types of three layers, the resin material for forming the functional layer and the resin material for forming the core layer were simultaneously extruded and molded under conditions of a die temperature of 180 to 230°C and a chill roll temperature of 30°C to obtain a polyolefin resin film having the thickness shown in Table 1 and a three-layer structure in which the functional layer / core layer / functional layer is laminated in that order.

[0067] As shown in Table 1, in the polyolefin resin film of this embodiment, the polypropylene content of the functional layer is 37.5 [mass%], and the ratio of the functional layer to the total polyolefin resin film is 20 [μm] / 80 [μm] = 0.25. Therefore, the polypropylene content based on the functional layer in the polyolefin resin film is 37.5 × 0.25 = 9.375 [mass%]. In addition, the polypropylene content of the core layer is 37.5 [mass%], and the ratio of the core layer to the total polyolefin resin film is 60 [μm] / 80 [μm] = 0.75. Therefore, the polypropylene content based on the core layer in the polyolefin resin film is 37.5 × 0.75 = 28.125 [mass%]. Consequently, the polypropylene content [mass%] of the total polyolefin resin film (i.e., 100 mass%) was 9.375 + 28.125 = 37.5 [mass%].

[0068] <Calculation of Heat Shrinkage Rate> A sample of the specified size (10 cm x 10 cm) was cut from the prepared resin film. Orthogonal markings, each 8 cm long and parallel to the edge, were drawn 1 cm inward from each edge of the sample. The sample was placed in a 120°C oven and heated for 15 minutes. After removal, it was cooled to room temperature (approximately 25°C). The distance between the markings [cm] at the medium diameter (MD) and top diameter (TD) of the heat-treated sample was measured. The heat shrinkage rate [%] was calculated from the change in the distance between the markings at the MD and TD before and after heating using the following formula (1), and this was used as an indicator of heat resistance. The results are shown in Table 1.

[0069] [Equation 1] Thermal shrinkage rate [%] in MD (or TD) = [(gauge between gauge marks before heating (8 cm) - gauge between gauge marks after heating) / gauge between gauge marks before heating (8 cm)] × 100 (1)

[0070] <Measurement of Surface Resistivity> The surface resistivity of the fabricated resin film was measured in accordance with the provisions of JIS K6911:2006. More specifically, first, a sample of A4 size (width 210 mm, length 297 mm) was obtained for measurement using the fabricated resin film. Next, the surface resistivity of the obtained sample was measured using a high resistivity meter (manufactured by Nitto Seikou Analytech Co., Ltd., product name: High Resista UX). The surface resistivity was measured when a voltage of 1000 V was applied and held for 10 seconds under conditions of a temperature of 23°C and humidity of 50% with the probe pressed against the sample. The results are shown in Table 1.

[0071] (Examples 2-10, Comparative Examples 1-4) Resin films having the thicknesses shown in Tables 1 and 2, and having a three-layer structure with the functional layer / core layer laminated in that order, were prepared in the same manner as in Example 1 above, except that the composition of the resin components in the functional layer and core layer was changed to the compositions (parts by mass) shown in Tables 1 and 2.

[0072] Then, the thermal shrinkage rate was calculated and the surface resistivity was measured in the same manner as in Example 1 described above. The results are shown in Tables 1 and 2.

[0073]

[0074]

[0075] As shown in Table 1, in the resin films of Examples 1 to 10 in which the functional layer contains an antistatic agent and the amount of the antistatic agent relative to the total functional layer is 10% by mass or more and 30% by mass or less, the surface resistivity is 1.00 × 10 １３ Since the ratio is less than or equal to Ω / □, it can be seen that it has excellent antistatic properties.

[0076] Furthermore, as shown in Table 1, in the resin films of Examples 1 to 10, in which the functional layer contains polypropylene and the polypropylene content relative to the total polyolefin resin film is 16% by mass or more and 41% by mass or less, the heat shrinkage rate in MD and TD is 2% or less, indicating excellent heat resistance.

[0077] On the other hand, as shown in Table 2, in the resin films of Comparative Examples 1, 3-4, since the functional layer does not contain an antistatic agent, the surface resistivity is 1.00 × 10⁻⁶. １３ The value is greater than Ω / □, indicating poor antistatic properties.

[0078] Furthermore, as shown in Table 2, in the resin film of Comparative Example 2, the content of the antistatic agent relative to the total functional layer is greater than 30% by mass (50% by mass), so the thermal shrinkage rate in MD is greater than 2%, indicating poor heat resistance.

[0079] Furthermore, as shown in Table 2, in the resin film of Comparative Example 3, since polypropylene is not included in the polyolefin resin film, the heat shrinkage rate in MD is greater than 2%, indicating poor heat resistance.

[0080] As described above, the present invention is suitable for polyolefin resin films.

[0081] 1. Resin film 2. Core layer 3. Functional layer 4. Surface layer

Claims

1. A polyolefin resin film having a functional layer on at least one of its outermost surfaces containing polyethylene, polypropylene, and an antistatic agent, wherein the content of the antistatic agent relative to the entire functional layer is 10% by mass or more and 30% by mass or less, and the content of the polypropylene relative to the entire polyolefin resin film is 16% by mass or more and 41% by mass or less.

2. The polyolefin resin film according to claim 1, characterized in that the antistatic agent is a block copolymer of a propylene resin and a polyhydric alcohol.

3. The polyolefin resin film according to claim 1 or 2, characterized in that the antistatic agent is a block copolymer of polypropylene and polyethylene glycol.

4. The polyolefin resin film according to claim 1, characterized in that the polypropylene content relative to the entire functional layer is 20% by mass or more and 50% by mass or less.

5. The polyolefin resin film according to claim 1 or 4, characterized in that the polypropylene is homopolypropylene obtained by polymerizing propylene alone.

6. The polyolefin resin film according to claim 1, characterized in that the polyethylene content relative to the entire functional layer is 32.5% by mass or more and 65% by mass or less.

7. The polyolefin resin film according to claim 1 or 6, characterized in that the polyethylene is linear low-density polyethylene.

8. A carrier film for electronic components using the polyolefin resin film described in claim 1 as a base material.

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