JP5456419B2 - Shrink film for cover tape and cover tape - Google Patents

Description

  The present invention relates to a shrink film that can be used as a film for a cover tape. Specifically, the present invention relates to a shrink film for a cover tape and a cover tape that can be heat sealed to an embossed carrier tape for packaging electronic components.

In general, an embossed carrier tape is used for conveying electronic parts. Embossed carrier tape is a sheet formed into a concave shape according to the shape of the electronic component. Each embossed carrier tape is embedded in a semiconductor, etc., taken to an assembly factory, and set in a component assembly machine (mounting machine) called a mounter. The sheet is designed so that it can be conveyed.
With the miniaturization of electronic devices such as mobile phones and portable game machines, the electronic components used are also miniaturized. In the device assembly process, assembly is automated and speeded up, embossed carrier tape, etc. The accuracy of packaging is also required.

  At present, as a cover tape for an embossed carrier tape, a cover tape produced by extruding and laminating polyethylene to a PET film as a base material or dry laminating a polyethylene film to a PET film is mainly used. However, the cover tape as described above tends to be loosened easily due to warpage of the cover tape itself or expansion during heat sealing. When such a cover tape is used, the electronic component cannot be sufficiently fixed, and the electronic component may be greatly shaken and damaged in the embossed carrier tape due to vibration during transportation or transportation. Furthermore, if the cover tape is loose, in the appearance inspection after taping the cover tape on the embossed carrier tape, light is reflected on the PET film as the base material, and the visibility of the contents by image processing or visual inspection Decreases. As a result, in the appearance inspection, there is a high possibility of overlooking defects such as chipping of electronic components.

  Patent Document 1 discloses a cover tape for packaging electronic parts using a biaxially stretched film such as polyester, polypropylene, or nylon as a base material layer.

JP 2005-178870 A

  However, the film disclosed in Patent Document 1 has a high shrinkage temperature of the polyethylene terephthalate film of the base material layer, and the cover tape may not be shrunk even by heat at the time of heat sealing, and may be loosened.

  The problem to be solved by the present invention is a shrink film for a cover tape, which is excellent in transparency and can be tightly taped without loosening by moderate shrinkage even after heat sealing to an embossed carrier tape, and a cover using the same To provide a tape.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have at least two layers that are laminated, and each layer contains a specific resin and can be used as a base layer of a cover tape. The present invention has been completed by finding that the above problems can be solved by a cover tape using the same.

That is, this invention provides the following shrink films for cover tapes.
[1] At least two layers of a first layer including a high density polyethylene having a density of 0.942 to 0.970 g / cm ³ and a second layer including a high pressure method low density polyethylene are stacked. Shrink film for cover tape.
[2] The shrink film for cover tapes according to [1], wherein the second layer further includes high-density polyethylene having a density of 0.942 to 0.970 g / cm ³ .
[3] The high-pressure low-density polyethylene has a density of 0.910 to 0.930 g / cm ³ and a melt flow rate of 0.01 to 2.0 g / 10 minutes, [1] or [2 ] The shrink film for cover tapes of description.
[4] The shrink film for a cover tape according to any one of [1] to [3], wherein the first layer contains 0.1 to 40% by mass of a polymer type antistatic agent.
[5] The shrink film for cover tapes according to any one of [1] to [4], which is a biaxially stretched film.
[6] The cover according to any one of [1] to [5], wherein at least one of the first layer and the second layer is crosslinked with a resin constituting the layer. Shrink film for tape.
[7] The cover tape according to any one of [1] to [6], wherein a layer including a polyethylene resin is further laminated on the laminate of the first layer and the second layer. For shrink film.
[8] The heat sealant and / or the shrink film for cover tape according to any one of [1] to [7], and / or the heat sealant disposed on at least one main surface of the shrink film for cover tape. A cover tape comprising a layer containing a conductive agent.
[9] The shrink film for cover tape according to [7], and a layer containing a heat seal agent and / or a conductive agent disposed on the main surface of the layer containing the polyethylene resin of the shrink film for cover tape. And a cover tape.

  By using the shrink film for a cover tape of the present invention, it is possible to provide a cover tape that is excellent in transparency and that can be tightly taped without slackness by appropriate shrinkage even after heat-sealing to an embossed carrier tape.

  Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as the present embodiment) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary. Further, in the present specification, the density and melt flow rate of a mixture obtained by mixing two or more resins can be calculated from the density and melt flow rate of each resin and the mixing ratio of those resins. It is obvious from the description of the book.

The shrink film for cover tape of the present embodiment (hereinafter sometimes simply referred to as “film”) is a first layer containing a high density polyethylene having a density of 0.942 to 0.970 g / cm ³ ( A) and a second layer containing a high-pressure process low-density polyethylene (y) are provided by laminating at least two layers, and the second layer has a density of 0.942 to 0.970 g / It is preferable to further include high density polyethylene of cm ³ .

[First layer (A)]
The film of the present embodiment has a first layer (A) containing high-density polyethylene having a density of 0.942 to 0.970 g / cm ³ (hereinafter sometimes simply referred to as (A)). . Here, in the present embodiment, “density” is measured by the method described in JIS K 6922. By using high-density polyethylene having a density of 0.942 to 0.970 g / cm ^3, a film having excellent tensile rigidity and bending rigidity can be obtained.

Polyethylene is classified by density based on JIS K 6922, and a polyethylene having a density of 0.942 g / cm ³ or more is defined as high density polyethylene. Such high-density polyethylene can be produced by a generally known method such as a Philips method, a standard method, or a Ziegler method.

  In the present embodiment, in addition to excellent transparency, good tensile rigidity, bending rigidity and the like are also preferably required for the film. Moreover, it is preferable that the film of this embodiment has an appropriate haze and can be easily stretched during production.

The density of the high-density polyethylene is in the range of 0.942 to 0.970 g / cm ³ , and thereby particularly excellent bending elasticity and excellent transparency can be imparted to the film. From the viewpoint of imparting better bending rigidity to the film, the density of the high-density polyethylene is preferably 0.944 g / cm ³ or more, more preferably 0.946 g / cm ³ or more, and further preferably 0.948 g / cm ^3. That's it. Further, from the viewpoint of imparting better transparency to the film, the density of the high-density polyethylene is preferably 0.968 g / cm ³ or less, more preferably 0.967 g / cm ³ or less, and still more preferably 0.966 g / cm 2. cm ³ or less.

  The melt flow rate of the high-density polyethylene (hereinafter sometimes simply referred to as “MFR”) is preferably in the range of 0.1 to 10.0 g / 10 minutes. In order to reduce the load on the extruder when the film is formed, the MFR is more preferably 0.5 g / 10 min or more, further preferably 1.0 g / 10 min or more, particularly preferably. 2.0 g / 10 min or more. Further, from the viewpoint of imparting stretching stability during film production, the MFR is more preferably 8.0 g / 10 min or less, still more preferably 6.0 g / 10 min or less, and particularly preferably 5.0 g / 10 min. It is as follows. Here, in the present embodiment, “melt flow rate (MFR)” is measured by the method described in JIS K 6922 under conditions of a temperature of 190 ° C. and a load of 2.16 kgf.

  The melting peak temperature of the high density polyethylene is preferably 125 to 140 ° C, more preferably 128 to 139 ° C, and further preferably 130 to 138 ° C. When the melting peak temperature is 125 ° C. or higher, the film can be stiff and exhibit rigidity, and when the melting peak temperature is 140 ° C. or lower, it is preferable from the viewpoint of the transparency of the film. In the present embodiment, the “melting peak temperature” is the temperature at the peak of the endothermic reaction peak that appears in the melting curve obtained by differential scanning calorimetry (DSC). In addition, when there are a plurality of melting peaks or when a plurality of high-density polyethylenes are used, the melting peak temperature on the highest temperature side may be within the above numerical range.

  In order to control the density, MFR, and melting peak temperature of the high density polyethylene within the above numerical range, the manufacturing conditions may be adjusted so that each physical property is within the above numerical range when the high density polyethylene is produced. . Alternatively, two or more types of high-density polyethylene having different physical properties may be mixed to obtain the high-density polyethylene of the present embodiment. In this case, the obtained high-density polyethylene has a density and MFR within the above numerical range. You may adjust the mixing ratio of each high-density polyethylene so that it may have.

  In this Embodiment, a 1st layer (A) does not exceed 50 mass% of all the materials which comprise a high pressure process low density polyethylene and / or linear low medium density polyethylene which comprises a 1st layer (A). It may be included in the range. Thereby, the rigidity and transparency of (A) can be adjusted as desired.

The first layer (A) may be subjected to a surface treatment. As such a surface treatment, a surface treatment such that the surface specific resistance value of the first layer (A) is n × 10 ¹² Ω or less (n is 1 to 9) is preferable. When the film is used as a cover tape by applying a polymer type antistatic agent, surfactant, conductive fine powder such as tin oxide to the surface of the first layer (A) by surface treatment. It is possible to prevent dust and the like from adhering to the product. The first layer (A) preferably contains a polymer type antistatic agent in an amount of 0.1 to 40% by mass, and more preferably 0.5 to 0.5% from the viewpoint of better transparency and expression of antistatic performance. 20% by mass, more preferably 1.0 to 10% by mass.

  Examples of the polymer type antistatic agent include a polyether-polyolefin block polymer and a polythiophene polymer. Examples of the surfactant include glycerin fatty acid ester. Examples of the material constituting the conductive fine powder include indium oxide in addition to tin oxide. These are used singly or in combination of two or more.

  In addition, when the film is used as a cover tape and the film is laminated with a seal layer described later, the first layer (A) contains inorganic particles such as silica and alumina, and cyclic olefin in order to prevent blocking of the seal layer. Further, it may be included. Cyclic olefins are particularly preferred because they do not drop off during taping and can be prevented from adhering to the contents (electronic parts). Examples of the cyclic olefin include Apel (trade name) manufactured by Mitsui Chemicals, Inc. and TOPAS (trade name) manufactured by Topas Advanced Polymers. These are used alone or in combination of two or more.

  The thickness of the first layer (A) is preferably 5 to 40 μm, and more preferably 10 to 35 μm.

[Second layer (B)]
The film of the present embodiment is provided with a second layer (B) (hereinafter may be abbreviated as (B)) laminated adjacent to the first layer (A). The second layer (B) is a layer containing a high-pressure method low-density polyethylene (y), and imparts cushioning properties to the film to provide stretching stability during production or to enhance sealing properties during taping. It functions as a cushioning layer.

The high pressure method low density polyethylene (y) used for the second layer (B) is a polyethylene produced by a so-called high pressure method (bulk polymerization method), and its density is 0.910 to 0.930 g / cm ³ . It is preferable. From the viewpoint of imparting cushioning properties that enhance sealing properties during taping, the density is more preferably 0.917 to 0.929 g / cm ³ , and still more preferably 0.918 to 0.928 g / cm ³ .

  The melt flow rate of the high pressure method low density polyethylene (y) is preferably in the range of 0.01 to 2.0 g / 10 min. From the viewpoint of extrudability when forming a film, it is more preferably 0.05 to 1.0 g / 10 minutes, and still more preferably 0.1 to 0.5 g / 10 minutes.

  The melting peak temperature of the high-pressure method low density polyethylene (y) is preferably 110 to 130 ° C, more preferably 115 to 125 ° C. When the melting peak temperature is equal to or higher than the lower limit value, the rigidity of the film is improved, and when the melting peak temperature is equal to or lower than the upper limit value, the cushioning property of the film is improved. In addition, when there are a plurality of melting peaks or when a plurality of high-pressure low-density polyethylene (y) is used, the highest melting peak temperature may be within the above numerical range.

  In order to control the density, MFR and melting peak temperature of the high pressure method low density polyethylene (y) within the above numerical range, each physical property falls within the above numerical range when the high pressure method low density polyethylene (y) is produced. The manufacturing conditions may be adjusted as described above. Alternatively, two or more types of high pressure method low density polyethylene (y) having known physical properties may be mixed to obtain the high pressure method low density polyethylene (y) of the present embodiment. The mixing ratio of each high-pressure method low-density polyethylene (y) may be adjusted so that the density polyethylene (y) has a density and MFR within the above numerical range.

The second layer (B) may be made of a high-pressure method low-density polyethylene (y), but if it further contains high-density polyethylene (x) having a density of 0.942 to 0.970 g / cm ^3. preferable. In the present embodiment, the density of the high-density polyethylene (x) used for the second layer (B) is in the range of 0.942 to 0.970 g / cm ³ , whereby particularly excellent bending elasticity and excellent Transparency can be imparted to the film. From the viewpoint of imparting better bending rigidity to the film, the density of the high-density polyethylene (x) is preferably 0.944 g / cm ³ or more, more preferably 0.946 g / cm ³ or more, and further preferably 0.948 g. / Cm ³ or more. From the viewpoint of imparting better transparency to the film, the density of the high-density polyethylene (x) is preferably 0.968 g / cm ³ or less, more preferably 0.967 g / cm ³ or less, and still more preferably 0. 966 g / cm ³ or less.

  The melt flow rate (hereinafter sometimes simply referred to as “MFR”) of the high-density polyethylene (x) used in (B) is preferably in the range of 0.01 to 2.0 g / 10 minutes. In order to reduce the load on the extruder when the film is formed, the MFR is more preferably 0.05 g / 10 min or more, and further preferably 0.1 g / 10 min or more. Further, from the viewpoint of imparting stretching stability during film production, the MFR is more preferably 2.0 g / 10 min or less, further preferably 1.5 g / 10 min or less, and particularly preferably 1.0 g / 10 min. It is as follows.

  The melting peak temperature of the high-density polyethylene (x) is preferably 125 to 140 ° C, more preferably 128 to 139 ° C, and further preferably 130 to 138 ° C. When the melting peak temperature is 125 ° C. or higher, the film can be stiff and exhibit rigidity, and when the melting peak temperature is 140 ° C. or lower, it is preferable from the viewpoint of the transparency of the film. In addition, when there are a plurality of melting peaks or when a plurality of high-density polyethylene (x) is used, the melting peak temperature on the highest temperature side may be within the above numerical range.

  In order to control the density, MFR and melting peak temperature of the high density polyethylene (x) within the above numerical range, the production conditions are set so that each physical property is within the above numerical range when the high density polyethylene (x) is produced. May be adjusted. Alternatively, two or more types of high-density polyethylene (x) having known physical properties may be mixed to obtain the high-density polyethylene of the present embodiment. In this case, the obtained high-density polyethylene has a density within the above numerical range. And the mixing ratio of each high-density polyethylene (x) may be adjusted so as to have MFR.

  The second layer (B) contains high-density polyethylene (x) as described above from the viewpoint of imparting stretching stability during film production, imparting rigidity to the film, and suppressing curling of the film. Also good. When the second layer (B) contains high-density polyethylene (x), the content ratio is preferably 1 to 60% by mass with respect to the total amount of the second layer (B) from the above viewpoint. Preferably it is 5-55 mass%, More preferably, it is 10-50 mass%.

  Depending on the purpose, the second layer (B) may contain a resin other than those described above, for example, linear low and medium density polyethylene. Thereby, the intensity | strength of a film increases and a film fracture | rupture etc. can be decreased. Linear low and medium density polyethylene is a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms, and can be produced by a conventional method. Examples of the α-olefin include 1-butene and 1-hexene.

  The melting peak temperature of the linear low and medium density polyethylene is preferably 100 to 140 ° C, more preferably 105 to 135 ° C, and still more preferably 110 to 130 ° C. When the melting peak temperature is 100 ° C. or higher, it is preferable because it can give rigidity to the film and exhibit rigidity, and when it is 140 ° C. or lower, it is preferable from the viewpoint of imparting better transparency and strength to the film. . In addition, when there are a plurality of melting peaks or when a plurality of linear low and medium density polyethylenes are used, it is only necessary that the one on the higher temperature side is within the above numerical range.

The density of the linear low or medium density polyethylene is preferably 0.910~0.941g / cm ³ from the viewpoint of improving the maintenance and the film strength of the film stiffness, more preferably at 0.912~0.939g / cm ³ More preferably, it is 0.914 to 0.937 g / cm ³ .

  The MFR of the linear low and medium density polyethylene is 0.1 to 10.0 g / 10 min from the viewpoint of reducing the load on the extruder when the film is formed and the stretching stability at the time of film production. It is preferable that it is in the range. The MFR is more preferably 0.5 to 5.0 g / 10 minutes, and still more preferably 0.8 to 3.0 g / 10 minutes.

  When it is desired to improve the rigidity of the film, the second layer (B) may contain a hard resin typified by cyclic olefin or polypropylene. Further, when the film is used as a cover tape and when it is desired to increase the interlayer adhesion strength with the adjacent seal layer, the second layer (B) is formed by acid-modified linear low density polyethylene, acid-modified polypropylene, EVA (ethylene-acetic acid). An adhesive resin such as a vinyl copolymer) may be included.

  The second layer (B) may contain these resins in a range not exceeding 50% by mass with respect to the total amount.

  The thickness of the second layer (B) is preferably 5 to 40 μm, and more preferably 10 to 35 μm. When the thickness is equal to or more than the lower limit, the cushioning property of the film is improved and the sealing property is stabilized, and when the thickness is equal to or less than the upper limit, the rigidity of the film is improved.

  Further, at least one of the first layer (A) and the second layer (B) may contain a crystal nucleating agent for polyethylene. By using a crystal nucleating agent, it becomes easy to give orientation to the layer containing it, and as a result, the stretching stability of the film is improved. Furthermore, the transparency and rigidity of the film tend to be improved. Examples of crystal nucleating agents include known ones such as alkyl fatty acid calcium salts, alkyl fatty acid sodium salts, and phospholipids. The preferable addition amount is 100 to 3000 ppm, more preferably 500 to 2000 ppm with respect to the total amount of the layer containing it.

  The film of the present embodiment may include a single layer or a plurality of layers each of the first layer (A) and the second layer (B), and in the case of including a plurality of layers, the first layer (A) and the second layer (B) Two layers (B) may be alternately stacked. In addition to the first layer (A) and the second layer (B), the film of the present embodiment may include a third layer (C) other than those. The third layer (C) is provided by being laminated on a laminate of the first layer (A) and the second layer (B). When the film is used for a cover tape, the third layer (C) functions as a cushion layer disposed between the laminate and a layer containing a heat sealant or a conductive agent described later. preferable. By functioning as a cushion layer, the sealing property of the cover tape is improved. From such a viewpoint, the third layer (C) is preferably a layer containing a polyethylene resin typified by ultra-low density polyethylene and high-pressure method low density polyethylene.

  As each of the materials in the film of the present embodiment, commercially available materials may be used as long as the physical property conditions are satisfied.

[Shrink film for cover tape]
In this Embodiment, the shrink film for cover tapes comprises the said 1st layer (A) and 2nd layer (B) laminated | stacked in those thickness directions. This film is biaxially stretched at a temperature equal to or higher than the melting point of the resin constituting the first layer (A) and the second layer (B) from the viewpoint of suppressing the shrinkage force of the film during heat sealing. A biaxially stretched film is preferred. The stretching ratio is preferably 1.5 times or more in the machine direction (MD) and 3 times or more in the transverse direction (TD), more preferably 1.8 times or more in the machine direction in order to suppress unevenness of the film thickness. It is 4 times or more in the direction, more preferably 2 times or more in the vertical direction, and 5 times or more in the horizontal direction.

  In the shrink film for a cover tape of the present embodiment, the resin constituting at least one of the first layer (A) and the second layer (B) is preferably cross-linked, and among them, the first The resin constituting the layer (A) is preferably crosslinked. For crosslinking, generally known methods can be used, for example, a method of irradiating ionizing radiation such as an electron beam. When the resins constituting these layers are cross-linked, the heat resistance of the film is improved, and it is also possible to prevent the film from sticking to the sealing iron during heat sealing by a taping machine. In addition, MFR in case resin is bridge | crosslinked is a thing before bridge | crosslinking.

  About the shrink film for cover tapes of this Embodiment, it is preferable that the heat shrinkage rate in 100 degreeC is 0 to 10%. Moreover, it is preferable that the heat shrinkage rate in 120 degreeC is 1 to 40%. In particular, when the shrinkage rate at 120 ° C. is 1% or more, the film shrinks appropriately during taping, and the cover tape is unlikely to loosen. When the shrinkage rate is 40% or less, it becomes easy to suppress the end of the cover tape with a sealing iron, and the sealing performance is stabilized. The heat shrinkage rate in this Embodiment is measured based on the method as described in the following Example.

  The heat shrinkage force at 120 ° C. of the film is preferably in the range of 0.1 to 1 N / 9.5 mm width. When the heat shrinkage force is 0.1 N / 9.5 mm or more, taping shrinkage becomes more sufficient and a tight finish can be obtained. When the heat shrinkage force is 1 N / 9.5 mm width or less, there is no fear that the seal portion is peeled off by the heat shrinkage force generated during heat sealing. The heat shrinkage force is more preferably 0.2 to 0.8 N / 9.5 mm width. The heat shrinkage force in the present embodiment is measured according to the method described in the following examples.

  In the present embodiment, the total light transmittance of the film is preferably 80% or more. A film having a total light transmittance of 80% or more can be taped without deteriorating the visibility of the contents (electronic parts), so it is also effective for visual inspection after taping and inspection by image processing. is there. The total light transmittance is more preferably 82% or more, and still more preferably 84% or more. The total light transmittance in this Embodiment is measured based on the method as described in the following Example.

The tensile strength at break of the film of the present embodiment is preferably 10 N / 9.5 mm width or more, and preferably 20 N / 9.5 mm width or more from the viewpoint of preventing breakage during taping and peeling. More preferred. The tensile modulus of the film is preferably 400 N / mm ² or more, more preferably 500 N / mm ² or more, from the viewpoint of the handleability of the film. The tensile breaking strength and tensile elastic modulus in the present embodiment are measured according to the methods described in the following examples.

  The film of this Embodiment can be made into a tight packaging body by shrinking moderately at the time of heat sealing as a shrink film for cover tapes. In order to obtain a tight package, the shrinkage temperature of the film can be adjusted as appropriate.

  The gel fraction of the film of the present embodiment is preferably 10% or more, more preferably, since it can be stretched at a higher magnification, and a thinner and more highly shrinkable film can be easily obtained. Is 20% or more, more preferably 30% or more. The gel fraction in this Embodiment is measured based on the method as described in the following Example.

  The thickness of the shrink film for cover tape in this Embodiment becomes like this. Preferably it is 10-100 micrometers, More preferably, it is 15-90 micrometers, More preferably, it is 20-80 micrometers. If the thickness of the film is in the range of 10 to 100 μm, the film does not easily loosen even after being taped to the embossed carrier tape, and it is effective to prevent the film from being cut even when the cover tape is peeled off in the subsequent steps.

[Method for producing shrink film for cover tape]
The shrink film for the cover tape of the present embodiment is obtained by melt-extruding the first layer (A), the second layer (B) and, if necessary, the resin constituting the other layer from a single extruder. Lamination in a multilayer die, melt coextrusion and quenching to obtain an unstretched original fabric, and heating the unstretched original fabric to the melting peak temperature of each resin or more, 1.5 times or more in the longitudinal direction And a step of biaxially stretching three times or more in the transverse direction.

  In the manufacturing method of the present embodiment, first, melt coextrusion is performed so that the film is composed of at least two layers having a first layer (A) and a second layer (B).

  The coextrusion is not particularly limited, and a method using a multilayer T die or a multilayer circular die can be used, but a method using a multilayer circular die is preferable. The use of a multi-layer circular die is advantageous in terms of the required space for equipment and the amount of investment, and is suitable for high-mix, low-volume production, making it easier to obtain heat shrinkability.

  Next, the coextruded resin is quenched. In the film manufacturing method of the present embodiment, water of 60 ° C. or lower is usually preferably used as the refrigerant used for rapid cooling, and is directly contacted with the molten resin or indirectly used as an internal refrigerant of the metal roll. The When used as an internal refrigerant, oil or other known materials can be used in addition to water, and in some cases, it can be used in combination with blowing cold air.

  Next, the obtained unstretched original fabric is heated to the melting peak temperature or more of each resin, and stretched 1.5 times or more in the longitudinal direction and 3 times or more in the transverse direction. The draw ratio is appropriately selected depending on the purpose, and if necessary, the film may be subjected to heat treatment after stretching to adjust the heat shrinkage rate and heat shrinkage force of the film.

  Examples of the stretching method include a direct inflation method in which air or nitrogen is blown into a tube immediately after melt extrusion to perform stretching. A film that shrinks by this method may also be obtained. However, in order to express high shrinkage like the film of the present embodiment, a method of stretching biaxially is preferable, and more preferably, the unstretched raw material obtained by the aforementioned circular die is heated biaxially stretched. It is a tubular method (also called a double bubble method).

  The film of the present embodiment is preferably a biaxially stretched multilayer film produced by a tubular method that is biaxially stretched.

  The method for producing a film in the present embodiment may include a step of performing a resin crosslinking treatment before or after stretching. When performing the crosslinking treatment, it is more preferable to carry out the crosslinking treatment by irradiation with energy rays before heating and stretching the resin. Thereby, the melt tension of the film in the stretching process is increased, and the stretching can be further stabilized.

  Moreover, you may irradiate an energy beam to the film after extending | stretching and perform the crosslinking process of resin. Examples of energy rays to be used include ionizing radiation such as ultraviolet rays, electron beams, X-rays, and γ rays, preferably electron beams, and preferably used in an irradiation dose range of 10 to 300 KGy. From the viewpoint of imparting stretching stability to the film and imparting heat resistance during sealing, the irradiation amount is more preferably 50 kGy or more, and even more preferably 80 kGy or more. Further, from the viewpoint of imparting low temperature sealing properties, the irradiation amount is preferably 280 kGy or less, more preferably 250 kGy or less.

  The layer that crosslinks the resin by irradiation can be arbitrarily selected according to the purpose. In addition, for example, in the case where it is mainly desired to crosslink the vicinity of the surface of each layer, a method of adjusting the dose distribution in the thickness direction by adjusting the acceleration voltage according to the thickness of the stretched raw fabric, and a shielding plate such as aluminum A mask irradiation method that similarly adjusts the dose distribution according to use, a method of irradiating an electron beam from an oblique direction with respect to the stretched original surface, and the like can be used.

  When the crosslinking treatment is performed, an arbitrary crosslinking inhibitor or crosslinking assistant (crosslinking accelerator) may be added to each layer including the resin to be crosslinked. Examples of the crosslinking aid include triallyl isocyanurate, trimethallyl isocyanurate, trimethylpropane triacrylate, triallyl cyanurate, and trimethallyl cyanurate.

  The film obtained by the method for producing a film in the present embodiment has an appropriate heat shrinkage property and is suitable as a shrink film for a cover tape, and is embossed without generating wrinkles, loosening, loosening, etc. on the film after taping. The fixing and holding can be continued by being in close contact with the carrier tape. In addition, if the film is peeled off from the embossed carrier tape due to the large shrinkage stress generated during taping, or if the embossed carrier tape is warped, a thermal relaxation treatment is added after stretching. It can be freely adjusted within the range of the heat shrink characteristics specified by the form.

[Cover tape]
The cover tape of this Embodiment is provided with the said shrink film for cover tapes, and the layer containing the heat seal agent and / or electrically conductive agent arrange | positioned on the at least one main surface of the film. Here, the “heat sealing agent and / or conductive agent” is a concept including a heat sealing agent and a conductive agent as well as a mixture thereof (hereinafter also referred to as “conductive heat sealing agent”). The layer containing a heat sealant and / or a conductive agent is formed by coating or extrusion laminating one main surface of the film with a heat sealant, a conductive agent, or a conductive heat sealant, and the laminate is embossed. It can be used as a cover tape for carrier tape.

  When the film is a two-layer film composed of the first layer (A) / second layer (B), a layer containing a heat sealant and / or a conductive agent on the surface of the second layer (B) Is preferably formed. When the film has a symmetrical three-layer configuration of first layer (A) / second layer (B) / first layer (A), heat is applied on the surface of one of the first layers (A). It is preferable that a layer containing a sealing agent and / or a conductive agent is formed. When the film is a three-layer film composed of the first layer (A) / second layer (B) / third layer (C), heat is applied on the surface of the third layer (C). It is preferable that a layer containing a sealing agent and / or a conductive agent is formed.

  The layer containing the heat sealant and / or the conductive agent (hereinafter also referred to as “seal layer”) may be a single layer or may be composed of a plurality of layers. For example, the sealing layer may be a plurality of layers in which a layer containing a heat sealing agent and a layer containing a conductive agent are laminated. In this case, the order of lamination of the layers includes the heat sealing agent from the film side. The order may be the order of the layer and the layer containing the conductive agent, or the order of the layer containing the conductive agent and the layer containing the heat sealant. Furthermore, only the layer containing the conductive heat sealing agent in which the heat sealing agent and the conductive agent are mixed may be disposed as the sealing layer.

  The thickness of the sealing layer is preferably 0.1 to 25 μm, more preferably 0.2 to 20 μm, and still more preferably 0.3 to 15 μm. The thickness of the seal layer can be appropriately selected depending on the required seal strength.

  When forming the seal layer, it is preferable to activate the surface by performing corona treatment or plasma treatment on the surface to form the seal layer before coating or extrusion laminating.

  The heat sealant is for facilitating heat sealing of the cover tape. As the heat sealant, for example, at least one selected from the group consisting of acrylic resins such as polymethyl methacrylate, styrene resins such as styrene-butadiene block polymers, polyester resins, and polyurethane resins is preferable. However, depending on the purpose, a heat seal agent made of an adhesive resin such as an ethylene-glycidyl methacrylate copolymer or an ethylene copolymer such as ethylene-methyl methacrylate may be used.

  The conductive agent is for preventing the generation of static electricity particularly when the cover tape is peeled off. Examples of the conductive agent include tin oxide, polyether-polyolefin block polymer, and polythiophene polymer. These are used singly or in combination of two or more.

  The heat sealant and the conductive agent may be separately coated or extrusion laminated, or the conductive agent may be dispersed or mixed in the heat sealant and coated or extrusion laminated at once. Furthermore, when extruding and forming a film, a cover tape may be produced by co-extruding a seal layer.

  When extruding and laminating the third layer (C) that may function as a cushion layer and the sealing layer, a seal is made immediately after laminating the third layer (C) using a tandem extrusion laminating machine. Laminating the layers is preferable because both the third layer (C) and the sealing layer can be laminated in one step.

  The peel strength of the cover tape after taping is preferably 10 to 130 g. If the peel strength is 10 g or more, the cover tape becomes difficult to peel from the embossed carrier tape due to vibration during transportation or storage, and the risk of the contents (electronic parts) popping out is reduced. When the peel strength is 130 g or less, problems such as breakage of the cover tape at the time of peeling are reduced. The peel strength in the present embodiment is measured according to the method described in “(7) Peel strength test” in the following examples.

  Hereinafter, the present embodiment will be described more specifically with reference to examples and comparative examples. However, the present embodiment is not limited to only these examples. Note that the evaluation method and measurement method used in this embodiment are as follows.

(1) Gel fraction A sample was extracted from boiling paraxylene for 12 hours, and the ratio of insoluble matter expressed by the following formula was used as a gel fraction, which was used as a measure of the degree of crosslinking of the resin in the film.
Gel fraction (mass%) = (sample weight after extraction / sample weight before extraction) × 100

(2) Tensile strength at break Using an autograph manufactured by Shimadzu Corporation, a tensile test was performed on each film slit to a width of 9.5 mm under the conditions of a sample length of 50 mm and a tensile speed of 200 mm / min. The tensile strength at break was determined.

(3) Tensile elastic modulus Measurement of tensile elastic modulus based on JIS K 7113 for a sample cut into a size of 9.5 mm in width and 100 mm in length using an autograph manufactured by Shimadzu Corporation Went.

(4) Total light transmittance Total light transmittance was measured according to JIS K7361-1.

(5) Heat shrinkage force The film is sampled in a strip shape with a width of 9.5 mm in each direction of MD and TD, and set to a chuck with a strain gauge without loosening to 50 mm between the chucks, at a measurement temperature of 120 ° C. It was measured. The film was immersed in silicone oil heated to a predetermined temperature, the shrinkage force after 1 minute was measured at each temperature for MD, and the obtained value was defined as the heating shrinkage force, and the arithmetic average of five measurement results. Obtained as a value.

(6) Heat shrinkage rate After putting a 100 mm square film sample into an air oven type thermostat set at 100 ° C. or 120 ° C. and heat-treating for 10 minutes in a freely shrinkable state, between the center points of the facing sides Measure the distance to determine the amount of film shrinkage, and measure the MD and TD shrinkage ratios twice as a percentage of the original dimension (distance between the center points of each facing side before heat treatment). It calculated | required as an arithmetic mean value of a result.

(7) Peel strength test Using a semi-automatic taping machine PTS-180 manufactured by Palmec Co., Ltd., a 12 mm wide polystyrene embossed carrier under the conditions of seal time = 0.3 sec, feed pitch = 8 mm, seal pressure = 0.4 MPa Each film slit to 9.5 mm width was taped at 120 ° C. on a tape (Sumi Carrier (trade name, 12 mm width) manufactured by Sumitomo Bakelite Co., Ltd.), and three peel test samples were obtained. Next, using a peel strength tester PFT-50S manufactured by Palmec Co., Ltd., the film was peeled from a sample for peeling test under the conditions of peeling speed = 300 mm / min and peeling angle = 170 °, after 1 hour of taping, Was peeled off to measure the peel strength, which was performed for a total of 3 floors, and the peel strength was determined from the arithmetic mean value.

(8) Appearance inspection of taping sample The looseness of the cover tape of the peel test sample (packaging sample) obtained in (7) was visually evaluated.
○: There is no slack and it is tightly packaged.
X: The cover tape is loose.

(9) Surface resistance Using a superinsulator SM-8220 (manufactured by Hioki Electric Co., Ltd.), the surface resistance value of each film was measured according to the resistivity measurement method described in JIS K6911. The measurement temperature was 23 ° C. and the humidity was 45%.

Resins used in Examples and Comparative Examples are as follows.
[First layer (A)]
HD1: High density polyethylene (Suntech HD (registered trademark) J240 manufactured by Asahi Kasei Chemicals Corporation), MFR (190 ° C., 2.16 kgf) = 5.5 g / 10 min, density = 0.966 g / cm ³ , melting peak temperature = 134 ° C)
HD2: High density polyethylene (Suntech HD (registered trademark) B871 manufactured by Asahi Kasei Chemicals Corporation), MFR (190 ° C., 2.16 kgf) = 0.35 g / 10 min, density = 0.956 g / cm ³ , melting peak temperature = 130 ° C)
HD3: high density polyethylene (Suntech HD (registered trademark) S362 manufactured by Asahi Kasei Chemicals Corporation), MFR (190 ° C., 2.16 kgf) = 0.8 g / 10 min, density = 0.952 g / cm ³ , melting peak temperature = 129 ° C)

[Second layer (B)]
HD1: High density polyethylene (Suntech HD (registered trademark) J240 manufactured by Asahi Kasei Chemicals Corporation), MFR (190 ° C., 2.16 kgf) = 5.5 g / 10 min, density = 0.966 g / cm ³ , melting peak temperature = 134 ° C)
HD2: High density polyethylene (Suntech HD (registered trademark) B871 manufactured by Asahi Kasei Chemicals Corporation), MFR (190 ° C., 2.16 kgf) = 0.35 g / 10 min, density = 0.956 g / cm ³ , melting peak temperature = 130 ° C)
HD3: high density polyethylene (Suntech HD (registered trademark) S362 manufactured by Asahi Kasei Chemicals Corporation), MFR (190 ° C., 2.16 kgf) = 0.8 g / 10 min, density = 0.952 g / cm ³ , melting peak temperature = 129 ° C)
LD1: High pressure method low density polyethylene (Suntech LD (registered trademark) M2102 manufactured by Asahi Kasei Chemicals Corporation), MFR (190 ° C., 2.16 kgf) = 0.2 g / 10 min, density = 0.922 g / cm ³ , melting peak Temperature = 121 ° C)
LD2: High-pressure method low-density polyethylene (Suntech LD (registered trademark) M1920 manufactured by Asahi Kasei Chemicals Corporation), MFR (190 ° C., 2.16 kgf) = 2.0 g / 10 min, density = 0.922 g / cm ³ , melting peak Temperature = 121 ° C)
LL1: linear medium density polyethylene (Prime Polymer Co., Ltd., Evolue (registered trademark) SP4020)), MFR (190 ° C., 2.16 kgf) = 1.8 g / 10 min, density = 0.937 g / cm ³ )
LL2: Modified polyethylene (Mitsui Chemicals Admer (registered trademark) NF308), MFR (190 ° C., 2.16 kgf) = 1.7 g / 10 min, density = 0.932 g / cm ³

[ Reference Example 1]
As the first layer (A), 75% by mass of HD1, 20% by mass of HD2, 5% by mass of polymer type antistatic agent Sanconol (registered trademark) TBX-25 (manufactured by Sanko Chemical Co., Ltd.), As a layer (B), HD2 is 50 mass%, LD1 is 50 mass%, the layer arrangement is the first layer / second layer, and the thickness ratio (%) of each layer is 30/70. After being extruded using a circular multilayer die, it was rapidly cooled and solidified with cold water to obtain a tube-shaped unstretched original fabric having a uniform thickness accuracy for each layer having a folding width of 130 mm and a thickness of about 650 μm. On the other hand, electron beam irradiation (acceleration voltage = 1 MV, irradiation dose = 120 kGy) is performed, and the obtained unstretched cross-linked raw fabric is passed between two pairs of differential nip rolls, and the heating temperature at the stretching start point is about 140. Inject air to form a bubble to form a bubble, stretch 3.0 times MD and 4.8 times TD (14.4 times the area stretch ratio), for cover tapes with a thickness of 45 μm A shrink film was obtained. The evaluation results of the obtained film are shown in Table 1.

[ Reference Examples 2 to 12]
A shrink film for a cover tape having a thickness of 45 μm was obtained in the same manner as in Reference Example 1 except that the layer configuration and the composition and thickness of each layer were changed as shown in Tables 1 to 3. The evaluation results of the obtained film are shown in Tables 1-3.

[ Reference Example 13]
Except that the layer configuration and the composition of each layer were changed as shown in Table 3, in the same manner as in Reference Example 1, a tube-shaped unstretched raw material having a uniform thickness accuracy was obtained for each layer having a thickness of about 180 μm. On the other hand, electron beam irradiation (acceleration voltage = 1 MV, irradiation dose = 120 kGy) is performed, and the obtained unstretched cross-linked raw fabric is passed between two pairs of differential nip rolls, and the heating temperature at the stretching start point is about 140. Bubbles are formed by injecting air to reach ℃, 4.0 times MD and 1.0 times TD (4.0 times area draw ratio), for cover tape with a thickness of 45μm A shrink film was obtained. The evaluation results of the obtained film are shown in Table 3.

[ Reference Examples 14 to 17]
A cover tape shrink film having a thickness of 45 μm was obtained in the same manner as in Reference Example 1 except that the layer configuration and the composition of each layer were changed as shown in Table 4. Table 4 shows the evaluation results of the obtained film.

[ Reference Example 18]
On the surface of the second layer (B) side of the shrink film for cover tape obtained in Reference Example 1, 1 μm of acrylic coating agent Dianal BR-87 (trade name, manufactured by Mitsubishi Rayon Co., Ltd.) is used as a heat sealant. A seal layer was formed by coating with a thickness to obtain a cover tape. Table 5 shows the evaluation results of the obtained cover tape.

[Example 19]
As the first layer (A), 75% by mass of HD1, 20% by mass of HD2, 5% by mass of polymer type antistatic agent Sanconol (registered trademark) TBX-25 (manufactured by Sanko Chemical Co., Ltd.), As a layer (B), HD2 is 50 mass%, LD1 is 50 mass%, the layer arrangement is the first layer / second layer, and the thickness ratio (%) of each layer is 30/70. After being extruded using an annular multilayer die, the tube was rapidly cooled and solidified with cold water to obtain a tube-shaped unstretched original fabric having a uniform thickness accuracy for each layer having a folding width of 130 mm and a thickness of about 500 μm. On the other hand, electron beam irradiation (acceleration voltage = 1 MV, irradiation dose = 120 kGy) is performed, and the obtained unstretched cross-linked raw fabric is passed between two pairs of differential nip rolls, and the heating temperature at the stretching start point is about 140. The air is injected to form a bubble to form a bubble, 3.0 times MD and 4.8 times TD (14.4 times area stretch ratio), and a shrink film having a thickness of 35 μm is formed. Obtained. On the surface on the second layer side of the obtained film, polyethylene (Suntech LD (registered trademark) L1850K manufactured by Asahi Kasei Chemicals Corporation), MFR (190 ° C., 2.16 kgf) = 6.8 g / 10 min, density = 0. 918 g / cm ³ ) was extrusion-laminated to obtain a shrink film for a cover tape further comprising a layer containing a polyethylene resin on the film. On the surface of the layer containing the polyethylene resin, an acrylic coating agent, Dianal BR-87 (product name, manufactured by Mitsubishi Rayon Co., Ltd.) is applied to a thickness of 1 μm as a heat sealant to form a seal layer, and the cover I got a tape. Table 5 shows the evaluation results of the obtained cover tape.

[ Reference Example 20]
On the surface of the seal layer of the cover tape obtained in Reference Example 18, antimony-doped tin oxide dispersion coating agent Colcoat SP-2001 (trade name, manufactured by Colcoat Co., Ltd.) was applied as a conductive agent to a thickness of 0.4 μm. A conductive cover tape was obtained. Table 5 shows the evaluation results of the obtained cover tape. In addition, the result of measuring the surface specific resistance value (temperature 20 ° C., humidity 30% RH) on the conductive agent side of the obtained cover tape was 1.3 × 10 ⁸ Ω, and sufficient antistatic performance could be confirmed. .

[ Reference Example 21]
On the surface of the second layer (B) side of the shrink film for cover tape obtained in Reference Example 7, an olefin copolymer emulsion (manufactured by Chuo Rika Kogyo Co., Ltd.) with a thickness of 2.0 μm as a conductive sealant. Coating was performed to form a seal layer, and a conductive cover tape was obtained. Table 5 shows the evaluation results of the obtained cover tape. In addition, the result of measuring the surface specific resistance value (temperature 20 ° C., humidity 30% RH) on the conductive agent side of the obtained cover tape was 2.5 × 10 ⁸ Ω, and sufficient antistatic performance was confirmed. .

[ Reference Example 22]
On the surface on the second layer (B) side of the shrink film for cover tape obtained in Reference Example 10, an olefin copolymer emulsion (manufactured by Chuo Rika Kogyo Co., Ltd.) with a thickness of 2.0 μm as a conductive sealant. Coating was performed to form a seal layer, and a conductive cover tape was obtained. Table 5 shows the evaluation results of the obtained cover tape. The surface resistivity value (temperature 20 ° C., humidity 30% RH) on the conductive agent side of the obtained cover tape was measured to be 3.3 × 10 ⁸ Ω, and sufficient antistatic performance was confirmed. .

[Comparative Example 1]
As a 1st layer (A), LL1 is 95 mass%, polymeric antistatic agent Sanconol (trademark) TBX-25 (made by Sanko Chemical Co., Ltd.) is 5 mass%, and as a 2nd layer (B), Using LL1 50% by mass and LD1 50% by mass, the layer arrangement is the first layer / second layer, and the thickness ratio (%) of each layer is a two-layer structure with 30/70. After extruding using a die, it was rapidly cooled and solidified with cold water to obtain a tube-shaped unstretched original fabric having a uniform thickness accuracy for each layer having a folding width of 130 mm and a thickness of about 650 μm. On the other hand, electron beam irradiation (acceleration voltage = 1 MV, irradiation dose = 120 kGy) is performed, and the obtained unstretched cross-linked raw fabric is passed between two pairs of differential nip rolls, and the heating temperature at the stretching start point is about 140. Inject air to form a bubble to form a bubble, stretch 3.0 times MD and 4.8 times TD (14.4 times the area stretch ratio), for cover tapes with a thickness of 45 μm A shrink film was obtained. The evaluation results of the obtained film are shown in Table 3.

[Comparative Example 2]
An attempt was made to obtain a shrink film for a cover tape in the same manner as in Reference Example 1 except that the composition of the second layer was changed to HD1 100%. Film could not be produced and could not be evaluated.

[Comparative Example 3]
On the second layer side of the film obtained in Comparative Example 1, an acrylic coating agent, Dianal BR-87 (trade name, manufactured by Mitsubishi Rayon Co., Ltd.) was applied to a thickness of 1 μm to obtain a cover tape. Table 5 shows the evaluation results of the obtained cover tape.

[Comparative Example 4]
An isocyanate-based adhesive was applied to a commercially available PET film (Lumirror (registered trademark) # 12 manufactured by Toray Industries, Inc.) by the gravure coating method, and the first layer of the film obtained in Comparative Example 1 ( A) side was bonded together to obtain a film having a thickness of 57 μm. The acrylic coating agent Dianal BR-87 (trade name, manufactured by Mitsubishi Rayon Co., Ltd.) is applied to the second layer (B) side of the obtained film by gravure coating to a thickness of 1 μm, and a cover tape is applied. Obtained. Table 5 shows the evaluation results of the obtained cover tape.

From the results shown in Tables 1 to 4, the shrink films for cover tapes of Reference Examples 1 to 17 are excellent in transparency, have sufficient rigidity and appropriate shrinkage, and cover tapes using them ( Reference Example 18). From the results shown in Table 5 to 21 and Example 19 ), it was found that due to heat applied during heat sealing, shrinkage occurred moderately and tight taping without loosening was possible.

On the other hand, from the results shown in Table 1, since the film obtained in Comparative Example 1 does not use high-density polyethylene, the film has low rigidity and is easy to stretch for use as a base film of a cover tape. Sexuality became difficult.
Since the cover tape obtained in Comparative Example 3 does not use high-density polyethylene, when sealing to the embossed carrier tape, the film shrinks due to the heat of the iron, and the seal becomes unstable. No taping sample was obtained.
Further, in Comparative Example 4 laminated on a PET film, the rigidity is obtained from the PET film, but the shrinkability is hindered by the PET film, and the cover tape does not shrink appropriately and the cover tape is loosened. It became.

  The shrink film for a cover tape of the present invention can be suitably used as a base film for a cover tape that can be heat sealed to an embossed carrier tape for packaging electronic components.

Claims (6)

Shrink film for cover tape,
A layer containing a heat sealant and / or a conductive agent;
With
Shrink film for the cover tape, the laminate of the second layer density which comprises a first layer and a high-pressure method low density polyethylene containing high-density polyethylene 0.942~0.970g / cm ^3, further polyethylene Layered with a layer containing resin,
Said layer comprising a heat-sealing material and / or conductive agent, disposed on the main surface of the layer containing the polyethylene resin of the shrink film for the cover tape, Kabate flop. The second layer has a density further comprises a high density polyethylene 0.942~0.970g / cm ^3, Kabate flop of claim 1. The high-pressure low-density polyethylene, density of 0.910~0.930g / cm ^3, a is 0.01 to 2.0 g / 10 min melt flow rate, Kabate flop according to claim 1 or 2 . It said first layer containing 0.1 to 40 wt% of a polymeric antistatic agent, Kabate flop according to any one of claims 1 to 3. The cover tape for shrink film is biaxially a stretched film, Kabate flop according to any one of claims 1-4. Wherein at least one layer of the first layer and the second layer, the layer constituting the resin is crosslinked, Kabate flop according to any one of claims 1 to 5.