Multilayer film for medical use and single use container for cell cultivation using the same

Abstract

To provide a multilayer film for medical use which is excellent in content visibility.SOLUTION: A multilayer film for medical use contains an inner layer, a core layer, an outer layer and adhesive layers, wherein the inner layer is a polyolefin layer, the core layer is an ethylene vinyl alcohol copolymer layer with a thickness of 1 to 7% with respect to the total film thickness, the adhesive layers are arranged on each of both surfaces of the core layer and the inner layer and the outer layer are bonded to each other, the outer layer is a polyamide layer with a thickness of 3 to 20% with respect to the total film thickness, the polyamide layer contains polyamide obtained by ring opening polymerization of lactam having 11 or more carbon atoms or condensation polymerization of an ω-amino acid having 11 or more carbon atoms, and a thickness ratio (outer layer / core layer) of the outer layer to the core layer is 0.8 to 7.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a medical multilayer film and a single-use container for cell culture using the same, and more particularly to a medical multilayer film having excellent visibility of contents and a single-use container for cell culture using the same. [Background technology]

[0002] Traditionally, lightweight soft bags made from polyethylene, polypropylene, etc. have been used as medical bags for cell culture, infusions, medicinal fluids, enteral nutrients, etc. The films that make up medical soft bags are required to have various properties due to their medical nature, such as visibility of contents, suitability for bag making (mold releasability), flexibility, gas barrier properties, hygiene of the film (suppression of elution, prevention of impurity contamination), and high strength (plate drop strength, puncture strength).

[0003] As an example of a medical film that can meet such various characteristics, Patent Document 1 discloses a medical multilayer cast film having a five-layer structure of an inner layer (polyolefin) with oxygen barrier properties / adhesive layer / ethylene-vinyl alcohol copolymer layer / adhesive layer / outer layer (polyamide, polyester, or polyolefin).

[0004] Furthermore, Patent Document 2 discloses a multilayer film exhibiting high mechanical resistance for use in a single-use pouch (also called a "single-use bag"), the film comprising a core layer containing an ethylene-vinyl alcohol copolymer, a connecting layer containing a carboxylic acid-modified polyolefin, and an outer layer containing a specific low-density polyolefin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2001-506200 [Patent Document 2] Special Publication No. 2016-513980 Summary of the Invention [Problem to be solved by the invention]

[0006] Among the various properties mentioned above, in the field of medical films, discoloration and abnormal conditions of the contents are strictly controlled, and the visibility of the film contents is considered to be an important physical property. In addition, single-use soft bags used for cell culture are often used in 3D bags with a large capacity of 50 to 3000 L compared to general medical packaging, and there is a demand for wider films to accommodate large-sized containers. There is a concern that the appearance of the bag may deteriorate due to wrinkles and orange peel-like appearance defects caused by the wider width, and there is also an increasing demand for higher quality films.

[0007] The multilayer film disclosed in the above Patent Document 1 uses a medical film having an ethylene-vinyl alcohol copolymer layer, and thus has the effect of suppressing low molecular weight elution and improving the gas barrier, but does not take into consideration the visibility of the contents of the film.

[0008] In addition, the multilayer film disclosed in Patent Document 2 is a multilayer film for single-use bags having an ethylene-vinyl alcohol copolymer layer, and is an excellent technology in terms of bag rupture resistance, but there is still room for improvement in terms of visibility of the contents.

[0009] Under such circumstances, an object of the present invention is to provide a medical multilayer film that has excellent visibility of contents. [Means for solving the problem]

[0010] However, in light of these circumstances, the inventors conducted extensive research and discovered that by specifying the composition and thickness of each layer of the multilayer structure, a medical multilayer film with excellent visibility of the film's contents can be produced, and thus completed the present invention.

[0011] That is, the present invention has the following aspects. [1] A medical multilayer film comprising an inner layer, a core layer, an outer layer and an adhesive layer, the inner layer is a polyolefin layer, the core layer is an ethylene-vinyl alcohol copolymer layer having a thickness of 1 to 7% of the total thickness of the film, and the adhesive layer is disposed on both sides of the core layer to bond the inner layer and the outer layer, the outer layer is a polyamide layer having a thickness of 3 to 20% of the total thickness of the film, the polyamide layer containing a polyamide obtained by ring-opening polymerization of a lactam having 11 or more carbon atoms or by condensation polymerization of an ω-amino acid having 11 or more carbon atoms; A medical multilayer film, in which the thickness ratio of the outer layer to the core layer (outer layer / core layer) is 0.8 to 7. [2] A medical multilayer film comprising an inner layer, a core layer, an outer layer and an adhesive layer, the inner layer is a polyolefin layer, the core layer is an ethylene-vinyl alcohol copolymer layer, and adhesive layers are provided on both sides of the core layer to bond the core layer to the inner layer and the outer layer; A medical multilayer film, in which the thickness ratio of the outer adhesive layer to the inner adhesive layer (outer adhesive layer / inner adhesive layer) is 2-5. [3] A roll-shaped medical multilayer film comprising an inner layer, a core layer, an outer layer and an adhesive layer, the inner layer is a polyolefin layer, the core layer is an ethylene-vinyl alcohol copolymer layer, and adhesive layers are provided on both sides of the core layer to bond the core layer to the inner layer and the outer layer; The multilayer film has a roll shape with a film width of 750 to 4000 mm, A medical multilayer film, in which the image clarity C(2.0)-sheet of a single sheet of the roll-like multilayer film is 87.5% or more when measured by a transmission method in accordance with JIS K7374 "Plastics - Determination of image clarity". [4] A tubular medical multilayer film comprising an inner layer, a core layer, an outer layer and an adhesive layer, the inner layer is a polyolefin layer, the core layer is an ethylene-vinyl alcohol copolymer layer, and adhesive layers are provided on both sides of the core layer to bond the core layer to the inner layer and the outer layer; The multilayer film has a tubular shape with a film width of 500 to 2000 mm, A medical multilayer film in which the image clarity C(2.0)-tube of the tubular multilayer film consisting of two overlapping films measured by a transmission method in accordance with JIS K7374 "Plastics - Determination of image clarity" is 75% or more at an optical comb width of 2.0 mm. [5] The medical multilayer film according to any one of [1] to [4], wherein the thickness from the inner layer surface of the multilayer film to the interface between the outer adhesive layer and the core layer is 60 to 85% of the total thickness of the multilayer film. [6] The medical multilayer film according to any one of [1] to [5], wherein the multilayer film has a thickness of 200 to 500 μm. [7] The medical multilayer film according to any one of [1] to [6], wherein the polyolefin in the inner layer is polyethylene. [8] The medical multilayer film according to any one of [1] to [7], wherein the adhesive resin of the adhesive layer is a carboxylic acid-modified polyolefin. [9] The medical multilayer film according to any one of [4] to [8], wherein the multilayer film has a tube folded diameter of 500 to 2000 mm.

[10] The medical multilayer film according to any one of [2] to [9], wherein the outer layer is a polyamide layer, a polyester layer, or a polyolefin layer.

[11] The medical multilayer film according to any one of [2] to [9], wherein the outer layer is a polyamide layer, and the polyamide layer contains a polyamide obtained by ring-opening polymerization of a lactam having 11 or more carbon atoms or by condensation polymerization of an ω-amino acid having 11 or more carbon atoms.

[12] The medical multilayer film according to any one of [3] to

[11] , wherein an absolute value ΔC of an image clarity difference between the roll-shaped multilayer film and the tubular multilayer film is 12.5% ​​or less.

[13] The medical multilayer film according to any one of [1] to

[12] , wherein the multilayer film is obtained by a water-cooled inflation method.

[14] A single-use container for cell culture, comprising the medical multilayer film according to any one of [1] to

[13] . Effect of the Invention

[0012] The medical multilayer film of the present invention has excellent visibility of contents. Even when the multilayer film is made wide, the visibility of contents is excellent, so that the multilayer film can be suitably used as a film for large-sized containers. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will be described below based on examples of the mode for carrying out the present invention. However, the present invention is not limited to the embodiment described below.

[0014] In the present invention, the term "film" also includes the term "sheet". In the present invention, the "main component" refers to the component that is most abundant in the target object, and is usually preferably 50 mass% or more of the target object, more preferably 60 mass% or more, even more preferably 70 mass% or more, particularly preferably 80 mass% or more, especially preferably 90 mass% or more, and most preferably 100 mass%.

[0015] In the present invention, when expressed as "X to Y" (X and Y are any numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less", as well as "preferably greater than X" or "preferably smaller than Y". Furthermore, when it is expressed as "X or more" (X is any number) or "Y or less" (Y is any number), it also includes the meaning that "it is preferably greater than X" or "it is preferably less than Y". Furthermore, "x and / or y (x and y are optional configurations)" means at least one of x and y, and means the following three cases: x only, y only, and x and y.

[0016] A medical multilayer film according to one embodiment of the present invention (hereinafter sometimes referred to as "the present multilayer film") contains an inner layer, a core layer, an outer layer, and an adhesive layer. The layer structure of a multilayer film is usually composed of, from the side in contact with the contents, an inner layer / (inner layer side) adhesive layer / core layer / (outer layer side) adhesive layer / outer layer, with the outer layer being the layer in contact with the outside air. The inner layer may be one or more layers, but from the viewpoint of achieving both flexibility and resistance to bag rupture of the film, it is preferably a multi-layered film, and more preferably a two-layered film. The outer layer may be a single layer or multiple layers, but is preferably a single layer in view of the high strength required for the outer layer.

[0017] An example of an embodiment of the present invention will be described in detail below. However, the present invention is not limited to the following embodiment.

[0018] <<First Aspect>> The medical multilayer film according to one embodiment of the present invention (first aspect) contains an inner layer, a core layer, an outer layer and an adhesive layer as described above, and is a film that has excellent visibility of the contents. In addition, the film has excellent flexibility and the resistance to tearing of a soft bag filled with the contents is also excellent.

[0019] Specifically, the inner layer is a polyolefin layer, the core layer is an ethylene-vinyl alcohol copolymer layer having a thickness of 1 to 7% of the total thickness of the film, and the adhesive layer is disposed on both sides of the core layer to bond the inner layer and the outer layer, the outer layer is a polyamide layer having a thickness of 3 to 20% of the total thickness of the film, the polyamide layer containing a polyamide obtained by ring-opening polymerization of a lactam having 11 or more carbon atoms or by condensation polymerization of an ω-amino acid having 11 or more carbon atoms; The thickness ratio of the outer layer to the core layer (outer layer / core layer) is 0.8-7.

[0020] This is achieved by using a polyamide with a specific structure for the outer layer, which has the effect of comprehensively improving film flexibility, bag rupture resistance, and visibility of the contents, and by making the core layer thinner and setting the outer layer thicker than the core layer, the film flexibility and visibility of the contents are further improved. The inner layer, the core layer, the outer layer and the adhesive layer will be described in this order below.

[0021] <Inner layer> The inner layer is a polyolefin layer and contains polyolefin as a main component. Such polyolefins include, for example, homopolymers and copolymers of α-olefins containing from 2 to 20 carbon atoms, more preferably from 2 to about 10 carbon atoms, which can be used alone or in combination of two or more kinds.

[0022] Suitable polyolefins include, for example, polymers and copolymers of α-olefins such as propylene, ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene, and may be copolymerized with lower alkyl and lower alkene acrylates and acetates, as well as their ionomers, if necessary. For the inner layer of the medical film, polypropylene and polyethylene, which are excellent in strength and melt moldability, are preferred, and polyethylene is more preferred in terms of flexibility and resistance to rupture. In addition, polyethylene is also excellent in hygiene and sealability at low temperatures.

[0023] By "lower alkyl" is meant alkyl groups having from 1 to 5 carbon atoms, such as ethyl, methyl, butyl, and pentyl. By "ionomer" is meant metal salts of acrylic acid copolymers having pendent carboxylate groups which are bonded to mono- or divalent cations such as zinc or sodium.

[0024] Examples of polyethylene include very low density polyethylene (VLDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), and high density polyethylene (HDPE). These may be used alone or in combination of two or more.

[0025] High density polyethylene is 0.940g / cm 3 Medium density polyethylene is polyethylene with a density greater than 0.925 g / cm 3 Larger than 0.940g / cm 3 Polyethylene with the following densities: Low density polyethylene (LDPE), linear low density polyethylene (LLDPE) has a density of 0.911 g / cm 3 Larger than 0.925g / cm 3 Very low density polyethylene (VLDPE) is 0.911 g / cm 3 It is a polyethylene having the following density:

[0026] The density of the polyethylene in the inner layer is set to 0.890 to 0.940 g / cm3 based on sealing properties at low temperatures and flexibility. 3 and more preferably 0.900 to 0.940 g / cm 3 If the density is too low, the strength is insufficient and the bag tends to break easily, whereas if the density is too high, the flexibility and low-temperature sealability tend to decrease.

[0027] The melt flow rate (MFR) of the polyethylene is not particularly limited, but in general, the MFR (190°C, load 2160 g) is preferably 0.1 to 15 g / 10 min, more preferably 0.5 to 10 g / 10 min, and even more preferably 1.0 to 5 g / 10 min. If the MFR is too low, the melt viscosity will be too high, which will tend to make extrusion difficult, whereas if the MFR is too high, the melt tension will be too low, which will tend to reduce the dimensional stability of the film extruded from the die. MFR can be measured in accordance with JIS K7210-1 Method A (2014).

[0028] The inner layer may be one or more layers, but preferably contains at least an innermost layer and a soft layer adjacent thereto. From the viewpoint of the characteristics required for a medical bag, it is preferable to use polyethylene for the innermost layer, which has superior strength and sealing properties to the flexible layer, and has a low elution rate and excellent hygiene so as to enable direct contact with the contents. Also, it is preferable that the density of the innermost layer is higher than that of the flexible layer. For example, if the flexible layer is VLDPE, the innermost layer is preferably LDPE, LLDPE, MDPE, or the like, which has a higher density.

[0029] The thickness of the innermost layer is preferably 10 to 50 μm, more preferably 20 to 40 μm, from the viewpoints of hygiene and sealing properties. If the thickness of the innermost layer is too small, sufficient hygiene and sealing properties tend not to be exhibited. If the thickness of the innermost layer is too large, flexibility tends to decrease.

[0030] The thickness of the flexible layer is preferably 200 to 250 μm, more preferably 210 to 240 μm, and even more preferably 215 to 235 μm, from the viewpoints of flexibility, bag-breaking resistance, and water vapor permeation resistance. If the thickness of the flexible layer is too small, sufficient flexibility, bag-breaking resistance, and water vapor permeation resistance tend not to be exhibited. If the thickness of the flexible layer is too large, the strength and puncture resistance tend to decrease.

[0031] Since medical multilayer films require high level hygiene control, it is preferable to use for the inner layer a polyolefin designed for medical use that does not contain antioxidants, antistatic agents, lubricants, antiblocking agents, UV absorbers, slip agents, etc. In particular, in the case of single-use cell culture containers, there is a concern that cell culture may be inhibited due to the elution of antioxidants, so it is more preferable to use polyolefins that do not contain added antioxidants.

[0032] <Core layer> The core layer is an ethylene-vinyl alcohol copolymer layer that acts as a barrier to the passage of gases (for example, oxygen and carbon dioxide), and contains ethylene-vinyl alcohol copolymer (hereinafter sometimes referred to as "EVOH") as a main component.

[0033] EVOH is a polymer obtained by saponifying an ethylene-vinyl ester copolymer. The ethylene content in EVOH is preferably 20 to 50 mol%, more preferably 21 to 40 mol%, and most preferably 22 to 30 mol%, from the viewpoint of gas barrier properties. The lower the ethylene content of EVOH, the higher the gas barrier effect of the layer, but at the same time, the harder the core layer becomes. If the core layer is too hard, the core layer may crack when the film is folded, or the resistance to bag breakage of the container tends to decrease. If the ethylene content of EVOH is too high, the flexibility of the core layer increases and the layer becomes soft, but the gas barrier effect of the layer tends to decrease.

[0034] The melting point of EVOH is preferably 160 to 200° C., more preferably 180 to 195° C. If the melting point of EVOH is too high, the extrusion temperature becomes high, which tends to easily cause thermal degradation products such as gel. If the melting point of EVOH is too low, the gas barrier effect of the layer tends to decrease.

[0035] The density of EVOH is 1.10~1.30g / cm 3 is preferable, and more preferably 1.15 to 1.25 g / cm 3 It is.

[0036] The MFR (210° C., load 2160 g) of the EVOH is not particularly limited, but from the viewpoint of film formability, it is 0.1 to 30 g / 10 min, preferably 0.5 to 15 g / 10 min, and more preferably 1.0 to 5 g / 10 min. If the MFR is too low, the melt viscosity will be too high, which will tend to make extrusion difficult, whereas if the MFR is too high, the melt tension will be too low, which will tend to reduce the dimensional stability of the film extruded from the die. MFR can be measured in accordance with JIS K7210-1 Method A (2014).

[0037] The thickness of the core layer is 1 to 7% of the total film thickness, preferably 2 to 6.5%, from the viewpoints of gas barrier property, bag rupture resistance, and flexibility. Specifically, the thickness of the core layer is preferably 0.1 to 30 μm, more preferably 5 to 20 μm (approximately 10 μm). If the ratio or thickness of the core layer is too small, sufficient gas barrier properties tend not to be exhibited, whereas if the ratio or thickness of the core layer is too large, bag rupture resistance and flexibility tend to decrease.

[0038] <Adhesive layer> The adhesive layer refers to a layer that is arranged on both sides of the core layer and adheres to the inner layer and outer layer. The adhesive layer allows the inner layer, core layer, and outer layer to adhere to each other during co-extrusion molding, and prevents these layers from separating during use as a medical soft bag. For convenience, the adhesive layer on the inner layer side is referred to as the "inner adhesive layer" and the adhesive layer on the outer layer side is referred to as the "outer adhesive layer". The compositions of these layers may be the same or different, but are preferably the same.

[0039] The adhesive resin of the adhesive layer is preferably composed mainly of a carboxylic acid-modified polyolefin in order to prevent delamination due to insufficient adhesion. A carboxylic acid-modified polyolefin grafted with a carboxylic acid or a carboxylic acid anhydride can be used alone or in combination with a polyolefin copolymer.

[0040] Examples of the polyolefin of the carboxylic acid-modified polyolefin include polypropylene and polyethylene, with polyethylene being preferred from the viewpoints of flexibility and resistance to bag rupture, and more preferably a copolymer of ethylene and one or more olefins having 3 or more carbon atoms, and even more preferably 4 to 8 carbon atoms (e.g., butene, hexene, or octene). The carboxylic acid of the carboxylic acid-modified polyolefin may be a carboxylic acid or a carboxylic acid anhydride, more preferably a carboxylic acid anhydride, and further preferably maleic anhydride.

[0041] The density range of adhesive resin is 0.870 to 0.940 g / cm for polyethylene adhesive resin. 3 and more preferably 0.880 to 0.910 g / cm 3 If the density is too low, the strength is insufficient and the bag tends to break easily. If the density is too high, the flexibility tends to decrease.

[0042] The MFR (190° C., load 2160 g) of the adhesive resin is not particularly limited, but from the viewpoint of film formability, it is usually 0.01 to 15 g / 10 min, preferably 0.05 to 10 g / 10 min, and more preferably 0.1 to 5 g / 10 min. If the MFR is too low, the melt viscosity will be too high, which will tend to make extrusion difficult, whereas if the MFR is too high, the melt tension will be too low, which will tend to reduce the dimensional stability of the film extruded from the die. MFR can be measured in accordance with JIS K7210-1 Method A (2014).

[0043] The thickness of each of the inner adhesive layer and the outer adhesive layer is preferably 1 to 50 μm, more preferably 3 to 40 μm, and further preferably 5 to 35 μm. If the thickness of the adhesive layer is too small, delamination between layers tends to occur due to insufficient adhesion, whereas if the thickness of the innermost layer is too large, the strength and puncture resistance tend to decrease.

[0044] The outer adhesive layer and the inner adhesive layer may have the same thickness, but in order to further improve visibility of the contents, it is preferable that the inner adhesive layer is thinner than the outer adhesive layer. For example, the thickness ratio of the outer adhesive layer to the inner adhesive layer (outer adhesive layer / inner adhesive layer) is usually 0.5-20, preferably 1-10, and more preferably 2-5. If the thickness ratio (outer adhesive layer / inner adhesive layer) is too small, the visibility of the contents of the film tends to decrease. If the thickness ratio (outer adhesive layer / inner adhesive layer) is too large, the gas barrier properties of the core layer tend to decrease due to the influence of humidity on the inner layer side.

[0045] <Outer layer> The outer layer is a polyamide layer, and contains as a main component a polyamide obtained by ring-opening polymerization of lactam having 11 or more carbon atoms or by condensation polymerization of ω-amino acid having 11 or more carbon atoms.

[0046] The lactam to be subjected to ring-opening polymerization has 11 or more carbon atoms, with the upper limit of the carbon number being 12. If the lactam monomer used to polymerize polyamide has too few carbon atoms, the lactam is likely to undergo a depolymerization reaction when used at high temperatures, which not only violates the elution test standards established for medical containers, but also increases hygroscopicity, which is undesirable as it causes whitening during steam sterilization under high pressure.

[0047] Examples of lactams include undecane lactam and lauryllactam. The ring-opening polymerization method is known as a method for producing polyamides, and is commercially available. Nylon 11 is obtained by ring-opening polymerization of undecane lactam, and nylon 12 is obtained by ring-opening polymerization of lauryllactam.

[0048] The ω-amino acid to be condensed and polymerized also has 11 or more carbon atoms, or the upper limit of the carbon number is 12. If the carbon number is less than 11, there are problems similar to those of lactams. Examples of ω-amino acids include 11-aminoundecanoic acid and 12-aminododecanoic acid. The condensation polymerization method is also known as a method for producing polyamides, and there are also commercially available products.

[0049] When considering the environmental impact, it is preferable to use, as the polyamide, nylon 11, which is 100% plant-derived and obtained by condensing 11-aminoundecanoic acid refined from castor oil, a plant-derived raw material, and it is even more preferable to use a grade designed for medical use that has a low elution rate.

[0050] The melting peak temperature of the polyamide is preferably 170° C. or higher, more preferably 175 to 200° C., and further preferably 175 to 195° C. This melting peak can be measured using a differential scanning calorimeter (DSC) in accordance with JIS-K7121.

[0051] The density of polyamide is 0.9 to 1.1 g / cm 3 and more preferably 0.95 to 1.05 g / cm 3 It is.

[0052] The melt volume rate (MVR) of polyamide (235℃, 10kg) is 0.5 to 50cm 3 / 10 minutes is preferable, and 1 to 25 cm is more preferable. 3 / 10 minutes. If the MVR is too low, the melt viscosity will be too high, which will tend to make extrusion difficult, whereas if the MVR is too high, the melt tension will be too low, which will tend to reduce the dimensional stability of the film extruded from the die. MVR can be measured in accordance with JIS K7210-1 Method B (2014).

[0053] The thickness of the outer layer is from 3 to 20% of the total film thickness, preferably from 3.5 to 16%, more preferably from 4 to 15%, and further preferably from 4.5 to 14%. If the outer layer is too thin, sufficient heat resistance cannot be obtained, and the film tends to adhere to the mold during sealing, resulting in poor bag-making properties.If the outer layer is too thick, the rigidity of the multilayer film tends to increase, and the flexibility required for medical containers tends to be impaired.

[0054] In addition, the specific thickness of the outer layer is preferably 1 to 60 μm, more preferably 5 to 50 μm, and further preferably 10 to 40 μm, from the viewpoints of bag-making processability and haze. The thickness ratio of the outer layer to the core layer (outer layer / core layer) is 0.8-7, preferably 0.85-6, more preferably 0.9-5, and further preferably 1.0-4. If the thickness ratio (outer layer / core layer) is too small, the rigidity of the multilayer film increases and the resistance to rupture tends to decrease, whereas if the thickness ratio (outer layer / core layer) is too large, sufficient gas barrier properties tend not to be obtained.

[0055] (optional ingredient) Each of the layers may contain optional components within the range that does not impair the effects of the present invention. Examples of optional components include plasticizers, lubricants, stabilizers, antioxidants, lubricants, pigments, dyes, excipients, slip agents, etc., which may be used alone or in combination of two or more. The content of the optional components in each layer is preferably 1% by mass or less, more preferably 0.1% by mass or less, further preferably 0.01% by mass or less, and particularly preferably 0.001% by mass or less.

[0056] <Multilayer films (multilayer laminates) and medical bags> The multilayer film has a layer structure consisting of at least an inner layer / (inner layer side) adhesive layer / core layer / (outer layer side) adhesive layer / outer layer. The multilayer film can be processed by a well-known standard technique, such as coextrusion molding, extrusion coating, lamination processing with an adhesive, or a combination thereof. Among them, coextrusion molding is preferred, and it is preferred to form a multilayer film in one step by a coextrusion method of 5 or more layers.

[0057] The co-extrusion molding may be a roll-shaped extrusion molding film by a T-die casting method, or a tubular extrusion molding film by an inflation method. If necessary, the original roll of the multilayer film in the form of a roll or the tubular multilayer film obtained by coextrusion may be slit to adjust the film width or the number of film rolls to any desired value.

[0058] Representative methods for obtaining a roll of multilayer film by the above-mentioned co-extrusion molding include a method in which a roll of multilayer film is produced by extrusion molding using a T-die casting method and a method in which a tubular multilayer film is produced by extrusion molding using an inflation method and both ends are folded and slit to obtain two rolls. In addition, when used for large containers such as single-use bags for cell culture, a method can be applied in which only one part of a tubular multilayer film extruded by the inflation method is slit in the MD direction, and then both slit ends are expanded to obtain a wide roll of multilayer film.

[0059] On the other hand, since medical films require high-level sanitary control to prevent contamination by foreign matter, insoluble fine particles, microorganisms, and bacteria, it is preferable to form the film into a tube shape in which the inner surface of the film that contains the drug solution is not easily exposed to the outside when making the medical container. Furthermore, in order to achieve high transparency, a water-cooled inflation method that can perform rapid cooling and solidification from a molten state is preferably used. A representative method for obtaining a tubular multilayer film by the above co-extrusion molding is to obtain a roll of tubular multilayer film produced by extrusion molding using an inflation method without slitting.

[0060] The width of the product obtained by the inflation method when the tube is folded flat and wound up is called the "folded tube diameter." When used for small or medium-sized containers such as 2D bags, the folded tube diameter is preferably 150 to 1000 mm, more preferably 250 to 750 mm, and even more preferably 300 to 600 mm.

[0061] When used for large containers such as 3D bags, the tube folding diameter is preferably 500 to 2000 mm, more preferably 550 to 1800 mm, and even more preferably 600 to 1600 mm so that it can be used for wide films with a folding width of 500 mm or more.

[0062] Furthermore, when the tubular multilayer film is used for a large container such as a single-use bag for cell culture, the width of the roll-like multilayer film obtained by slitting only one portion of the tubular multilayer film in the MD direction is preferably 750 to 4000 mm, more preferably 1000 to 3000 mm, and even more preferably 1200 to 2000 mm. If the tube diameter or film width is too small, it tends to be difficult to use in large containers or single-use cell culture bags that require a wide width.If the tube diameter or film width is too large, the film forming equipment becomes large and expensive, which increases the economic burden, and in terms of performance, the visibility of the contents, such as image clarity, tends to be poor.

[0063] The thickness of the multilayer film is preferably 200 to 500 μm, more preferably 250 to 400 μm, from the viewpoint of film strength. If the thickness is too small, the strength of the multilayer film is insufficient and the bag tends to break easily depending on the amount of contents when used as a large container, whereas if the thickness is too large, the rigidity of the multilayer film tends to increase and the flexibility tends to decrease.

[0064] The stiffness strength (flexibility index) of the multilayer film is preferably 0.25 to 0.36 N, more preferably 0.27 to 0.35 N, and further preferably 0.30 to 0.34 N. Examples of a method for measuring the stiffness strength include the measuring method described in the Examples below.

[0065] The lower the haze value (degree of white turbidity) of the multilayer film, the better, and it is preferably 9% or less, more preferably 8% or less, and even more preferably 7% or less. The haze value can be measured by the method described in the Examples below. The lower limit is usually 0%.

[0066] The higher the underwater transmittance of the multilayer film, the better, and it is preferably 82% or more, more preferably 85% or more, and even more preferably 87% or more. The underwater transmittance can be measured by the method described in the Examples below. The upper limit is usually 100%.

[0067] The multilayer film bag has a bag rupture resistance (drop strength height) of preferably 55 cm or more, more preferably 70 cm or more, and even more preferably 90 cm or more. The bag rupture resistance (drop strength height) can be measured by the method described in the Examples below.

[0068] <<Second aspect>> Next, a medical multilayer film according to another embodiment (second aspect) of the present invention will be described. Like the first embodiment, the present multilayer film also contains an inner layer, a core layer, an outer layer and an adhesive layer, and is a film that provides excellent visibility of the contents. Specifically, the inner layer is a polyolefin layer, the core layer is an EVOH layer, and an adhesive layer is disposed on each side of the core layer to adhere to the inner layer and the outer layer; The thickness ratio of the outer adhesive layer to the inner adhesive layer (outer adhesive layer / inner adhesive layer) is characterized by being 2-5.

[0069] The multilayer film of the present invention provides excellent visibility of the contents, particularly excellent image clarity. This is because by making the outer adhesive layer adjacent to the EVOH layer thicker than the inner adhesive layer, the resin fluidity at the junction of the EVOH layer and adhesive layer during processing such as extrusion molding is stabilized, eliminating interlayer disorder, which is one of the causes of poor appearance, and resulting in a multilayer film with excellent visibility of the contents.

[0070] In the field of medical films, the visibility of the film contents is considered an important physical property, and is generally evaluated by haze and light transmittance, but in recent years, there has been an increasing demand for even higher levels of transparency improvement, such as image clarity. The present multilayer film can meet such demands.

[0071] Hereinafter, each layer constituting the multilayer film of the second embodiment will be described, but the inner layer, core layer, and adhesive layer are the same as those described in detail in the first embodiment. Here, differences from the first embodiment will be described in detail.

[0072] <Outer layer> The outer layer may be a polyamide layer, a polyester layer, or a polyolefin layer, and is preferably a polyamide layer. That is, the outer layer preferably contains at least one selected from the group consisting of polyamide, polyester, and polyolefin as a main component, more preferably contains polyamide as a main component, and further preferably contains polyamide obtained by ring-opening polymerization of lactam having 11 or more carbon atoms or condensation polymerization of ω-amino acid having 11 or more carbon atoms as a main component.

[0073] The lactam to be subjected to ring-opening polymerization usually has 4 to 12 carbon atoms, preferably 11 or more carbon atoms, with the upper limit of the carbon number being up to 12. If the lactam monomer used to polymerize polyamide has too few carbon atoms, the lactam is likely to undergo depolymerization reaction when used at high temperatures, not only failing to meet the elution test standards established for medical containers, but also increasing hygroscopicity, which tends to cause whitening during steam sterilization under high pressure, which is undesirable.

[0074] Preferred examples of lactams include undecane lactam and lauryllactam. The ring-opening polymerization method is known as a method for producing polyamides, and is commercially available. Nylon 11 can be obtained by ring-opening polymerization of undecane lactam, and nylon 12 can be obtained by ring-opening polymerization of lauryllactam.

[0075] The ω-amino acid to be polycondensed also has 11 or more carbon atoms, but the upper limit of the carbon number is 12. If the carbon number is less than 11, there is the same undesirable tendency as with lactams. Preferred examples of ω-amino acids include ω-aminoundecanoic acid and ω-aminododecanoic acid. Polycondensation methods are also known as methods for producing polyamides, and are commercially available.

[0076] Polyamides also include aliphatic polyamides resulting from the condensation reaction of diamines having carbon numbers ranging from 2 to 13, aliphatic polyamides resulting from the condensation reaction of diacids having carbon numbers ranging from 2 to 13, polyamides resulting from the condensation reaction of dimer fatty acids, and amide-containing copolymers. Thus, suitable aliphatic polyamides include, for example, nylon 66, nylon 6,10 and dimer fatty acid polyamides.

[0077] When considering the environmental impact, it is preferable to use, as the polyamide, nylon 11, which is 100% plant-derived and obtained by condensing 11-aminoundecanoic acid refined from castor oil, a plant-derived raw material, and it is even more preferable to use a grade designed for medical use that has a low elution rate.

[0078] Examples of the polyester include polycondensation products of di- or polycarboxylic acids and di- or polyhydroxy alcohols, or alkylene oxides. Among these, condensation products of ethylene glycol and saturated carboxylic acids (e.g., ortho- or isophthalic acid and adipic acid) are preferred.

[0079] More preferably, the polyester comprises: Polyethylene terephthalate produced by condensation of ethylene glycol and terephthalic acid; polybutylene terephthalate produced by condensation of 1,4-butanediol and terephthalic acid; and polyethylene terephthalate copolymers and polybutylene terephthalate copolymers having a third component which is an acid component such as phthalic acid, isophthalic acid, sebacic acid, adipic acid, azelaic acid, glutaric acid, succinic acid, oxalic acid, etc.; as well as diol components such as 1,4-cyclohexanedimethanol, diethylene glycol, propylene glycol, etc., and blended mixtures thereof. When heat resistance, melt moldability, etc. are taken into consideration, it is more preferable to use a homopolymer or copolymer of polybutylene terephthalate.

[0080] The polyolefin may be the same as the polyolefin described in detail for the inner layer of the first embodiment, and is preferably polypropylene or polyethylene. In terms of flexibility and resistance to bag breakage, polyethylene is more preferable. However, in terms of preventing the film from adhering to the sealing mold during bag production, high density polyethylene (HDPE) or medium density polyethylene (MDPE), which have a high melting point, are most preferable when used for the outer layer.

[0081] The melting peak temperature of the resin constituting the outer layer is preferably 110° C. or higher, more preferably 120 to 245° C., and further preferably 175 to 230° C. This melting peak can be measured using a differential scanning calorimeter (DSC) in accordance with JIS-K7121.

[0082] The thickness of the outer layer is preferably 3 to 20% of the total film thickness, more preferably 3.5 to 16%, further preferably 4 to 15%, and particularly preferably 4.5 to 14%. If the outer layer is too thin, the effect of cushioning damage caused by heat transfer during sealing tends to be insufficient, while if the outer layer is too thick, the rigidity of the multilayer film increases significantly, tending to impair flexibility as a medical container.

[0083] In addition, the specific thickness of the outer layer is preferably 1 to 60 μm, more preferably 5 to 50 μm, and further preferably 10 to 40 μm, from the viewpoints of bag-making processability and haze. The thickness ratio of the outer layer to the core layer (outer layer / core layer) is 0.8-7, preferably 0.85-6, more preferably 0.9-5, and further preferably 1.0-4. If the thickness ratio (outer layer / core layer) is too small, the rigidity of the multilayer film increases and the resistance to rupture tends to decrease, whereas if the thickness ratio (outer layer / core layer) is too large, sufficient gas barrier properties tend not to be obtained.

[0084] <Relationship between adhesive layer and outer layer> The thickness ratio of the outer adhesive layer to the inner adhesive layer (outer adhesive layer / inner adhesive layer) is usually 0.5-20, preferably 1-10, and more preferably 1.5-6. Furthermore, from the viewpoint of image clarity, the thickness ratio of the adhesive layer on the outer layer side to the adhesive layer on the inner layer side (outer adhesive layer / inner adhesive layer) is 2 to 5, more preferably 2.2 to 4, and even more preferably 2.3 to 3.5. By being in such a range, the film becomes more excellent in content visibility, especially image clarity.

[0085] <Multilayer films (multilayer laminates) and medical bags> The multilayer film and the medical bag using the same are generally similar to those described in detail in the first embodiment, but differences and / or additions from the first embodiment will be described in detail here.

[0086] The thickness of the present multilayer film from the "inner layer surface of the multilayer film (the film surface on the side in contact with the contents)" to the "interface between the outer adhesive layer and the core layer" is usually 90% or less of the total thickness of the multilayer film, and is preferably 60 to 87%, more preferably 70 to 85%, and even more preferably 75 to 83%. If this value is too high, i.e., if the core layer is located too close to the outer layer surface of the multilayer film, layer disturbance at the interface tends to occur easily and transparency tends to decrease, and if this value is too low, gas barrier properties tend to decrease when packaging a drug solution.

[0087] In the second aspect, when producing a wide film with a fold width of 500 mm or more, the interface position of the outer adhesive layer / core layer is set closer to the inner layer, which tends to stabilize the resin fluidity at the core layer / adhesive layer junction during extrusion molding, thereby eliminating interlayer disorder, which is one of the causes of poor appearance.

[0088] The image clarity of the multilayer film is preferably 0.8 to 2.0 points, more preferably 1.0 or more, and even more preferably 1.5 or more, in the evaluation of a tubular multilayer film. The image clarity can be measured by the method described in the Examples below.

[0089] <<Third Aspect>> Next, a medical multilayer film according to another embodiment (third aspect) of the present invention will be described. Like the second embodiment, the present multilayer film is a roll-like multilayer film that contains an inner layer, a core layer, an outer layer and an adhesive layer and has excellent visibility of the contents. Specifically, the inner layer is a polyolefin layer, the core layer is an EVOH layer, and an adhesive layer is disposed on each side of the core layer to adhere to the inner layer and the outer layer; The film has a roll shape with a film width of 750 to 4000 mm, The film is characterized by an image clarity C(2.0)-sheet of 87.5% or more for a single roll of multilayer film measured by a transmission method in accordance with JIS K7374 "Plastics - Determination of image clarity" at an optical comb width of 2.0 mm.

[0090] The image clarity C(W) of an optical comb width Wmm measured by the transmission method in accordance with JIS K7374 "Plastics - Determination of image clarity" can be obtained by measuring the amount of light transmitted through a film test piece using a moving optical comb. Specifically, an optical comb with a width W mm is moved perpendicular to the light axis of the light transmitted through the film test piece, and the maximum light amount M is measured when the transmitting part of the comb is on the light axis, and the minimum light amount m is measured when the light-shielding part of the comb is on the light axis, and the numerical value is calculated using the following formula. C(W)=(Mm) / (M+m)×100 (%) W: Width of optical comb (mm) M: Maximum light intensity when the transparent part of the comb is on the light axis m: The minimum amount of light when the light-shielding part of the comb is on the light axis

[0091] C(W) is a number ranging from 0 to 100%, with a higher C(W) value indicating better image clarity of the film and a lower C(W) value indicating poorer image clarity of the film. C(W) can be evaluated using an image clarity measuring device conforming to JIS K7374.

[0092] The optical comb width W specified in JIS K7374 can be selected from five types: 0.125 mm, 0.25 mm, 0.5 mm, 1.0 mm, and 2.0 mm. For the evaluation of this multilayer film, the image clarity with an optical comb width of 2.0 mm and the image clarity with an optical comb width of 1.0 mm shown below can be used. (a) Image clarity of a roll of multilayer film (one sheet of film) obtained by cutting the end of a tube C(2.0)-sheet: Image clarity (%) for optical comb width 2.0 mm C(1.0)-sheet: Image clarity (%) for optical comb width 1.0 mm (b) Image clarity in a tubular multilayer film with two overlapping films C(2.0)-tube: Image clarity (%) with optical comb width of 2.0 mm C(1.0)-tube: Image clarity (%) with optical comb width of 1.0 mm

[0093] Furthermore, as indices for evaluating the quality and resolution of the present multilayer film with respect to image clarity, the following numerical indices can be calculated from the image clarity obtained above. Ratio of image clarity with an optical comb width of 1.0 mm to that with an optical comb width of 2.0 mm for a roll of multi-layer film: CR-sheet CR-sheet = C(1.0)-sheet / C(2.0)-sheet -Ratio of image clarity with an optical comb width of 1.0 mm to that with an optical comb width of 2.0 mm in a tubular multilayer film: CR-tube CR-tube = C(1.0)-tube / C(2.0)-tube Absolute value of image clarity difference between roll of multi-layer film and tube of multi-layer film: ΔC ΔC = |C(2.0)-sheet - C(2.0)-tube|

[0094] A first feature of the third aspect is a roll-like multilayer film containing an inner layer, a core layer, an outer layer and an adhesive layer, in which the inner layer is a polyolefin layer, the core layer is an EVOH layer, and adhesive layers are arranged on both sides of the core layer to bond the inner layer and the outer layer, and the multilayer film is in the form of a roll with a film width of 750 to 4000 mm.

[0095] In the third embodiment, the width of the roll-like multilayer film is 750 to 4000 mm, more preferably 1000 to 3000 mm, and particularly preferably 1200 to 2000 mm. The width of a roll of multi-layer film is an important value when it is used for large containers such as 3D bags, and if the film width is too small, it tends to be difficult to use for single-use cell culture bags, which require a wide width. If the film width is too large, the film forming equipment becomes huge and expensive, which increases the economic burden, and in terms of performance, the visibility of the contents, such as image clarity, tends to be poor.

[0096] The second feature of the third aspect is that the image clarity C(2.0)-sheet of a roll of multilayer film measured by a transmission method in accordance with JIS K7374 "Plastics - Determination of image clarity" is 87.5% or more, more preferably 90% or more, and particularly preferably 95% or more. The C(2.0)-sheet of a roll of multilayer film is an important value in terms of the visibility of the contents of the medical multilayer film. If the C(2.0)-sheet is too small, the image clarity of the film will be insufficient, and the visibility of the contents will tend to decrease when used as a medical multilayer film.

[0097] Furthermore, for a film having high-quality visibility, the ratio of image clarity at an optical comb width of 1.0 mm to image clarity at an optical comb width of 2.0 mm in a roll-like multilayer film (CR-sheet) is preferably 0.60 to 1.00, more preferably 0.70 to 1.00, particularly preferably 0.80 to 1.00, and most preferably 0.90 to 1.00. CR-sheet is a number ranging from 0 to 1, and is an index of the resolution of image clarity. If CR-sheet is too small, image clarity for fine characters and contents tends to deteriorate, and the resolution of visual recognition of contents tends to decrease.

[0098] <<Fourth Aspect>> Next, a medical multilayer film according to another embodiment (fourth aspect) of the present invention will be described. Like the first embodiment, this multilayer film is a tubular multilayer film that contains an inner layer, a core layer, an outer layer and an adhesive layer and has excellent visibility of the contents. Specifically, the inner layer is a polyolefin layer, the core layer is an EVOH layer, and an adhesive layer is disposed on each side of the core layer to adhere to the inner layer and the outer layer; The film has a tubular shape with a film width of 500 to 2000 mm, The film is characterized by having an image clarity C(2.0)-tube of 75% or more at an optical comb width of 2.0 mm for a tubular multilayer film consisting of two overlapping films, measured by a transmission method in accordance with JIS K7374 "Plastics - Determination of image clarity."

[0099] A first feature of the fourth aspect is a tubular multilayer film containing an inner layer, a core layer, an outer layer and an adhesive layer, the inner layer being a polyolefin layer, the core layer being an EVOH layer, adhesive layers being disposed on both sides of the core layer to bond the inner layer and the outer layer, and the film having a tubular shape with a film width of 500 to 2000 mm.

[0100] In the fourth embodiment, the film width of the tubular multilayer film is 500 to 2000 mm, more preferably 550 to 1800 mm, and particularly preferably 600 to 1600 mm. The film width of tubular multilayer film is an important value when it is used for large containers such as 3D bags, and if the film width is too small, it tends to be difficult to use for single-use cell culture bags that require a wide width. If the film width is too large, the film forming equipment becomes huge and expensive, which is a heavy economic burden, and in terms of performance, the visibility of the contents, such as image clarity, tends to be poor.

[0101] A second feature of the fourth aspect is that the image clarity C(2.0)-tube of a tubular multilayer film consisting of two overlapping films at an optical comb width of 2.0 mm, measured by a transmission method in accordance with JIS K7374 "Plastics - Determination of image clarity", is 75% or more, more preferably 80% or more, and particularly preferably 90% or more. The C(2.0)-tube of a tubular multilayer film is an important value in terms of the visibility of the contents of the medical multilayer film. If the C(2.0)-tube is too small, the image clarity of the film will be insufficient, and the visibility of the contents will tend to decrease when used as a medical multilayer film.

[0102] Furthermore, for a film having high quality visibility, the ratio CR-tube of image clarity at an optical comb width of 1.0 mm to image clarity at an optical comb width of 2.0 mm in a tubular multilayer film is preferably 0.40 to 1.00, more preferably 0.50 to 1.00, particularly preferably 0.60 to 1.00, and most preferably 0.80 to 1.00. CR-tube is a value ranging from 0 to 1, and is an index of the degree of image clarity. If CR-tube is too small, image clarity for fine characters and contents tends to deteriorate, and the resolution of content visibility tends to decrease.

[0103] Furthermore, for a film with little quality unevenness in visibility of contents, the absolute value ΔC of the image clarity difference between a roll of multilayer film and a tubular multilayer film is preferably 12.5% ​​or less, more preferably 10% or less, particularly preferably 5% or less, and most preferably 1% or less. ΔC is a value expressed in the range of 0 to 100%, and is an index of the quality stability of the tubular film. If ΔC is too large, the difference in visibility between the front and back sides of the tubular film is large, and the quality of the tubular film tends to deteriorate.

[0104] Hereinafter, each layer constituting the multilayer film of the third and fourth embodiments will be described, but the inner layer, core layer, and adhesive layer are the same as those described in detail in the second embodiment. Here, differences from the second embodiment will be described in detail.

[0105] Although there are no particular limitations, the image clarity of such a roll-shaped multilayer film can be made to fall within a specified range (third embodiment), or the image clarity of such a tubular multilayer film can be made to fall within a specified range (fourth embodiment) by appropriately combining the following methods. (1) The tube folding width of the multi-layer film obtained by the inflation method is adjusted. (2) Adjust the thickness ratio of the adhesive layer on the outer layer side to the adhesive layer on the inner layer side of the multilayer film (outer adhesive layer / inner adhesive layer). (3) Adjust the position from the inner layer surface of the multilayer film to the interface between the outer adhesive layer and the EVOH layer, or from the inner layer surface to the interface between the inner adhesive layer and the EVOH layer. (4) Select an EVOH resin for the core layer of the multilayer film that can reduce the occurrence of interfacial disturbance with the adhesive layer. (5) Select an adhesive resin that can reduce the occurrence of interfacial disturbance with the EVOH layer for the adhesive layer of the multilayer film.

[0106] (1) The method for adjusting the tube fold width of the multilayer film obtained by the inflation method to satisfy the specified range of image clarity is the same as that described in detail in the first embodiment (Multilayer film (multilayer laminate) and medical bag). An effective method for increasing the image clarity of a multi-layer film is to narrow the tube folding width and increase the film forming speed, thereby shortening the resin residence time during co-extrusion. However, when used for large containers such as single-use bags for cell culture, the tube folding width must be made as wide as 400 mm or more, but the film forming speed must be slower than that for narrow-width films, which tends to reduce the image clarity of the multilayer film. In such cases, it is possible to satisfy the image clarity within a specified range by appropriately combining methods (2) to (5).

[0107] (2) The method of adjusting the thickness ratio of the adhesive layer on the outer layer side to the adhesive layer on the inner layer side of the multilayer film (outer adhesive layer / inner adhesive layer) to satisfy the image clarity within a specified range is the same as that described in detail in the second embodiment (relationship between adhesive layer and outer layer).

[0108] (3) The method of adjusting the position from the inner layer surface of the multilayer film to the interface of the outer adhesive layer / EVOH layer, or from the inner layer surface to the interface of the inner adhesive layer / EVOH layer to satisfy the image clarity within the specified range is the same as that described in detail in the second embodiment, <Multilayer film (multilayer laminate) and medical bag>.

[0109] (4) Methods for selecting an EVOH resin that can reduce the occurrence of interfacial disturbance with the adhesive layer in the core layer of a multilayer film include blending one or more types of EVOH resins with different ethylene contents or MFRs.

[0110] (5) Methods for selecting an adhesive resin capable of reducing the occurrence of interfacial disturbance with the EVOH layer for the adhesive layer of a multilayer film include a method of using one or more adhesive resins with different carboxylic acid modification amounts or MFRs, and a method of blending an adhesive resin with a polyolefin resin that is not modified with carboxylic acid.

[0111] The method for obtaining the roll-like multilayer film exemplified in the third embodiment is the same as that described in detail in the first embodiment <Multilayer film (multilayer laminate) and medical bag>.

[0112] The method for obtaining the tubular multilayer film exemplified in the fourth embodiment is the same as that described in detail in the first embodiment <Multilayer film (multilayer laminate) and medical bag>.

[0113] <<Application>> The multilayer film of the present invention exemplified in the above first, second, third and fourth embodiments is a film used for medical soft bags. Since medical films require high level hygiene management, it is preferable to use a resin raw material designed for medical use that does not contain components such as plasticizers, lubricants, stabilizers, antioxidants, lubricants, pigments, dyes, excipients and slip agents.

[0114] The multilayer film is also suitable as a film for single-use bags for cell culture, specifically, as a soft bag for cell culture that is widely used for single use (single use). Although 2D bags with relatively small capacity and 3D bags with large capacity of 50 to 3000 L are known as single-use bags for cell culture, the multilayer film of the present invention has excellent visibility of the contents even when it is wide, and therefore can be particularly preferably used as a film for such 3D soft bags.

[0115] Since the present multilayer film has excellent content visibility, etc., as described above, a single-use container for cell culture obtained using the present multilayer film also has excellent content visibility, etc., in a medical bag obtained using the present multilayer film for cell culture, infusion, medicinal solution, enteral nutritional agent, etc. In particular, a single-use bag for cell culture obtained using the present multilayer film has excellent content visibility and is therefore suitable for cell culture. EXAMPLES

[0116] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples as long as it does not depart from the gist of the present invention.

[0117] <<First Aspect>> (1) Materials used The following resin materials were used in the following Examples and Comparative Examples. <Polyolefin resin> · Polyethylene resin A1 Medium density polyethylene (melting point: 125 °C, density: 0.937 g / cm 3 MFR [190 °C, 2160 g]: 2.3 g / 10 min (antioxidant-free grade) · Polyethylene resin A2 Linear low density polyethylene (melting point: 120 °C, density: 0.919 g / cm 3 MFR [190 °C, 2160 g]: 2.1 g / 10 min (antioxidant-free grade) · Polyethylene resin A3 Ultra-low density polyethylene (melting point: 110 °C, density: 0.904 g / cm 3 MFR [190 °C, 2160 g]: 1.3 g / 10 min (antioxidant-free grade)

[0118] <Adhesive resin> · Maleic anhydride-modified polyethylene resin B1 (Density: 0.903 g / cm 3 MFR [190 °C, 2160 g]: 0.7 g / 10 min)

[0119] <EVOH resin> · Ethylene-vinyl alcohol copolymer C1 (Melting point: 190 °C, ethylene content: 27 mol%, density: 1.21 g / cm 3 MFR [210 °C, 2160 g]: 4 g / 10 min)

[0120] <Polyamide resin> · Polyamide 11 D1 (Melting point: 186 °C, density: 1.03 g / cm 3 MVR [235 °C, 10 kg]: 6 cm 3 / 10 min (medical grade) · Polyamide 6 / 66 copolymer D2 (Melting point: 190 °C, density: 1.14 g / cm 3 Relative viscosity: 3.7)

[0121] (2) Manufacturing of multilayer films For each of the Examples and Comparative Examples, the resin materials shown in (1) above were subjected to water-cooled co-extrusion inflation molding based on the blending ratios (parts by mass) shown in Table 1-1 to produce multilayer films having the film thickness and tube folding diameter shown in Table 1-1.

[0122] (3) Manufacture of film bags Using the multilayer film obtained in (2) above, a film bag was produced under the following conditions. Bag dimensions Fillable volume 400mL Inner dimension (vertical): 170mm Inner dimension (width) 120mm Edge dimension (vertical) 210mm Edge dimension (horizontal) 130mm Side seal width 5mm Heat seal welding conditions Upper mold temperature 150℃ Lower mold temperature 100℃ Welding pressure: 0.25MPa Welding time: 5 seconds

[0123] (4) Evaluation test of multilayer film (4-1) Stiffness rating To evaluate the flexibility of the multilayer film, the stiffness strength was evaluated using a universal material testing machine. The multilayer film obtained in (2) above was cut into strips 40 mm wide and 180 mm long, and the test pieces were held in a loop shape by the chuck of a universal material testing machine (Instron Corporation, "INSTRON 5565"), and the loop was compressed 35 mm in the diameter direction of the loop with a 50 mm diameter indenter at a compression speed of 200 mm / min, and the compression load (N) was measured. The lower the compression load value, the better the flexibility of the film.

[0124] (4-2) Haze evaluation The transparency of the multi-layer film was evaluated by measuring the haze value using a haze meter. The multilayer film obtained in (2) above was measured for haze value (%) according to JIS K7105 using a haze meter ("NDH5000" manufactured by Nippon Denshoku Industries Co., Ltd.) The haze value is expressed as a percentage by dividing the diffuse light transmittance of the test piece by the total light transmittance, and a lower haze value indicates better film transparency (less cloudiness).

[0125] (4-3) Underwater transmittance evaluation To evaluate the visibility of contents in the multilayer film, the underwater transmittance was measured using an ultraviolet-visible spectrophotometer. The film obtained in (2) above was measured for light transmittance (%) of visible light with a wavelength of 450 nm using an ultraviolet-visible spectrophotometer (Shimadzu Corporation's "UV-1800") by inserting one sheet of film into a quartz glass cell filled with water. This is the visible light transmittance when the film is immersed in water, and the higher the light transmittance value, the better the visibility of the contents of the film.

[0126] (5) Film bag evaluation test (5-1) Fall strength evaluation To evaluate the resistance to tearing of the film bag, the plate drop strength was measured using a plate drop strength tester. The film bag obtained in (3) above was filled with 220 mL of water, heat sealed, and left to stand at 23°C for 24 hours. The film bag after the standing storage was set in a drop strength tester, and a 6.4 kg iron plate was dropped onto the film bag from a height of 10 cm to check whether the bag broke or there was leakage due to pinholes. If there was no breakage or leakage, the drop height of the iron plate was increased by 10 cm at a time, and the same test was repeated until breakage or leakage occurred. The maximum drop height at which no breakage or leakage occurred was taken as the measurement result. The higher the maximum drop height, the better the resistance of the film bag to breakage.

[0127] The results are shown in Table 1-1 below.

[0128] [Table 1-1]

[0129] [Example 1-1] A multilayer film with a tube folded diameter of 450 mm was obtained with a six-layer structure laminated in the following order: Layer 1 (inner layer) polyethylene resin (A1 / A2=50 / 50) with a thickness of 30 μm; Layer 2 polyethylene resin (A3) with a thickness of 225 μm; Layer 3 maleic anhydride modified polyethylene resin (B1) with a thickness of 10 μm; Layer 4 ethylene-vinyl alcohol copolymer (C1) with a thickness of 10 μm; Layer 5 maleic anhydride modified polyethylene resin (B1) with a thickness of 30 μm; and Layer 6 (outer layer) polyamide 11 (D1) with a thickness of 25 μm. This multilayer film has a polyamide 11 layer thickness ratio of 7.6% to the total thickness, an EVOH layer thickness ratio of 3.0% to the total thickness, and a polyamide 11 layer / EVOH layer thickness ratio of 2.5. This gives the film excellent flexibility and transparency, and also shows good results in terms of bag rupture resistance when used as a film bag.

[0130] [Example 1-2] A multilayer film was obtained in the same manner as in Example 1-1, except that the maleic anhydride modified polyethylene resin (B1) of layer 5 was changed to a thickness of 35 μm, and the polyamide 11 (D1) of layer 6 (outer layer) was changed to a thickness of 20 μm. This multilayer film has a polyamide 11 layer thickness ratio of 6.1% to the total thickness, an EVOH layer thickness ratio of 3.0% to the total thickness, and a polyamide 11 layer / EVOH layer thickness ratio of 2.0. This gives the film excellent flexibility and transparency, and also shows good results in terms of bag rupture resistance when used as a film bag.

[0131] [Examples 1-3] A multilayer film was obtained in the same manner as in Example 1-1, except that in Example 1-1, the polyethylene resin (A3) in Layer 2 was changed to a thickness of 210 μm, the maleic anhydride modified polyethylene resin (B1) in Layer 3 was changed to a thickness of 25 μm, the ethylene-vinyl alcohol copolymer (C1) in Layer 4 was changed to a thickness of 7.5 μm, the maleic anhydride modified polyethylene resin (B1) in Layer 5 was changed to a thickness of 25 μm, and the polyamide 11 (D1) in Layer 6 (outer layer) was changed to a thickness of 30 μm. This multilayer film is characterized by increasing the thickness of the maleic anhydride modified polyethylene resin (B1) in layer 3 and decreasing the thickness of the ethylene-vinyl alcohol copolymer (C1) in layer 4, thereby increasing the thickness ratio of polyamide 11 layer / EVOH layer to 4.0.Compared to Example 1-1, the flexibility and transparency of the film were equivalent, but there was a tendency for the bag rupture resistance to be slightly reduced.

[0132] [Examples 1-4] A multilayer film was obtained in the same manner as in Example 1-1, except that in Example 1-1, the polyethylene resin (A3) in Layer 2 was changed to a thickness of 200 μm, the maleic anhydride modified polyethylene resin (B1) in Layer 3 was changed to a thickness of 25 μm, the ethylene-vinyl alcohol copolymer (C1) in Layer 4 was changed to a thickness of 20 μm, the maleic anhydride modified polyethylene resin (B1) in Layer 5 was changed to a thickness of 25 μm, and the polyamide 11 (D1) in Layer 6 (outer layer) was changed to a thickness of 30 μm. This multilayer film is characterized by increasing the thickness of the maleic anhydride modified polyethylene resin (B1) in Layer 3 and decreasing the thickness ratio of polyamide 11 layer / EVOH layer to 1.5. However, compared to Example 1-1, the flexibility and transparency of the film were reduced, and there was also a tendency for the bag rupture resistance to decrease slightly.

[0133] [Comparative Example 1-1] A multilayer film was obtained in the same manner as in Example 1-4, except that in Example 1-4, the polyethylene resin (A3) in Layer 2 was changed to a thickness of 210 μm, the ethylene-vinyl alcohol copolymer (C1) in Layer 4 was changed to a thickness of 25 μm, and the polyamide 11 (D1) in Layer 6 (outer layer) was changed to a thickness of 15 μm. This multilayer film is characterized by a significant reduction in the thickness ratio of the polyamide 11 layer to the EVOH layer to the total thickness of 4.5% and 7.6%, respectively, with the polyamide 11 layer / EVOH layer thickness ratio being 0.6. Although the flexibility and transparency of the film were good, this resulted in a decrease in the rupture resistance of the film bag.

[0134] [Comparative Example 1-2] A multilayer film was obtained in the same manner as in Example 1-4, except that the resin of Layer 6 (outer layer) was changed to a polyethylene resin (A1). This multilayer film is characterized by the use of a polyethylene resin in the outer layer, but the transparency of the film tended to be lower than that of Example 1-4, which used polyamide 11 in the outer layer. In addition, when compared with Example 1-1, the film was inferior in all performances in terms of flexibility, transparency, and bag rupture resistance.

[0135] [Comparative Example 1-3] A multilayer film was obtained in the same manner as in Example 1-4, except that the resin of Layer 6 (outer layer) was changed to polyamide 6 / 66 copolymer (D2). This multilayer film is characterized by the use of a polyamide 6 / 66 copolymer in the outer layer, but the transparency of the film tended to be lower than that of Example 1-4, which used polyamide 11 in the outer layer. In addition, when compared to Example 1-1, the flexibility was the same, but the transparency and bag rupture resistance were inferior.

[0136] <<Second to fourth aspects>> (1) Materials used The following resin materials were used in the following examples and comparative examples. <Polyolefin resin> Polyethylene resin A1 Medium density polyethylene (melting point: 125°C density: 0.937g / cm 3 MFR[190℃ 2160g]: 2.3g / 10min (antioxidant-free grade) · Polyethylene resin A2 Linear low density polyethylene (Melting point: 120 °C, Density: 0.919 g / cm 3 MFR [190 °C, 2160 g]: 2.1 g / 10 min (Grade without antioxidant) · Polyethylene resin A3 Ultra low density polyethylene (Melting point: 110 °C, Density: 0.904 g / cm 3 MFR [190 °C, 2160 g]: 1.3 g / 10 min (Grade without antioxidant)

[0137] <Adhesive resin> · Maleic anhydride modified polyethylene resin B1 (Density: 0.903 g / cm 3 MFR [190 °C, 2160 g]: 0.7 g / 10 min

[0138] <EVOH resin> · Ethylene-vinyl alcohol copolymer C1 (Melting point: 190 °C, Ethylene content: 27 mol%, Density: 1.21 g / cm 3 MFR [210 °C, 2160 g]: 4 g / 10 min · Ethylene-vinyl alcohol copolymer C2 (Melting point: 188 °C, Ethylene content: 29 mol%, Density: 1.21 g / cm 3 MFR [210 °C, 2160 g]: 4 g / 10 min

[0139] <Polyamide resin> · Polyamide 11 D1 (Melting point: 186 °C, Density: 1.03 g / cm 3 MVR [235 °C, 10 kg]: 6 cm 3 / 10 min (Medical grade)

[0140] (2) Manufacture of multilayer film For each of the Examples and Comparative Examples, the resin materials shown in (1) above were subjected to water-cooled co-extrusion inflation molding based on the blending ratios (parts by mass) shown in Tables 2-1(A) and 2-2(A) to produce multilayer films having the thicknesses shown in Tables 2-1(A) and 2-2(A). For the tubular multilayer film obtained by water-cooled co-extrusion inflation molding, only one edge portion was slit in the MD direction and then both slit ends were spread out to obtain two types of multilayer film: (a) a roll-like multilayer film, and (b) a tubular multilayer film, which was obtained without slitting. For example, in the case of Example 2-1, the tube folded diameter is 570 mm, so that (a) the film width of the roll-like multilayer film is 1140 mm, and (b) the film width of the tubular multilayer film is 570 mm.

[0141] [Table 2-1(A)]

[0142] [Table 2-2(A)]

[0143] (3) Evaluation test of multilayer film (3-1) Image clarity evaluation The multilayer films obtained in (2) above were evaluated under the following conditions for image clarity: (a) a roll of multilayer film obtained by slitting the tube to make a single film, and (b) an image clarity of a tubular multilayer film consisting of two overlapping films.

[0144] (Image clarity evaluation conditions) Equipment: Image clarity measuring device ICM-1 (manufactured by Suga Test Instruments Co., Ltd.) Evaluation conditions: Compliant with JIS K7374, evaluated using the transmission method Sample arrangement: The optical comb direction and the MD direction of the multilayer film are aligned in the same direction. The outer surface of the multi-layer film is arranged facing the light projection surface. Evaluation items (a) Image clarity evaluation of a roll of multilayer film (one sheet of film) obtained by cutting the end of a tube C(2.0)-sheet: Image clarity (%) for optical comb width 2.0 mm C(1.0)-sheet: Image clarity (%) for optical comb width 1.0 mm (b) Image clarity evaluation of a tubular multilayer film with two overlapping films C(2.0)-tube: Image clarity (%) with optical comb width of 2.0 mm C(1.0)-tube: Image clarity (%) with optical comb width of 1.0 mm

[0145] Furthermore, the following index values ​​were calculated from the evaluation results of image clarity obtained above. Ratio of image clarity with an optical comb width of 1.0 mm to that with an optical comb width of 2.0 mm for a roll of multi-layer film: CR-sheet CR-sheet = C(1.0)-sheet / C(2.0)-sheet -Ratio of image clarity with an optical comb width of 1.0 mm to that with an optical comb width of 2.0 mm in a tubular multilayer film: CR-tube CR-tube = C(1.0)-tube / C(2.0)-tube Absolute value of image clarity difference between roll of multi-layer film and tube of multi-layer film: ΔC ΔC = |C(2.0)-sheet - C(2.0)-tube|

[0146] (3-2) Image clarity evaluation using visual acuity testing method The image clarity of the multi-layer film was evaluated by visual acuity testing. The multilayer film obtained in (2) above was evaluated for image clarity under the conditions shown below. A higher score in the visual acuity test indicates a more excellent image clarity of the film.

[0147] (Evaluation conditions according to visual acuity test method) - Visual acuity test chart: A test chart that is 25% reduced from the Landolt visual acuity test chart (international standard 5m). *Outer diameter of ring with score 1.0: 1.8mm *Gap diameter for score 1.0: 0.36mm Rating score 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.2 1.5 2.0 Number of rings for each evaluation score: 3 rings Distance between the inspection sheet and the multi-layer film: 10cm Distance between the inspection chart and the operator's line of sight: 20cm

[0148] (Evaluation method) A visual evaluation was conducted with the multilayer film placed between the eye chart and the examiner's line of sight, and the score at which all three parallel Randall rings were visible in the gap direction was recorded as the film's image clarity score.

[0149] The results when a polyamide resin was used for layer 6 (outer layer) are shown in Table 2-1(B) below.

[0150] [Table 2-1(B)]

[0151] [Example 2-1] A multilayer film with a tube folded diameter of 570 mm was obtained with a six-layer structure laminated in the following order: Layer 1 (inner layer) polyethylene resin (A1 / A2=50 / 50) with a thickness of 30 μm; Layer 2 polyethylene resin (A3) with a thickness of 225 μm; Layer 3 maleic anhydride modified polyethylene resin (B1) with a thickness of 10 μm; Layer 4 ethylene-vinyl alcohol copolymer (C1) with a thickness of 10 μm; Layer 5 maleic anhydride modified polyethylene resin (B1) with a thickness of 30 μm; and Layer 6 (outer layer) polyamide 11 (D1) with a thickness of 25 μm. This multilayer film was found to have good image clarity by having a thickness ratio of outer adhesive layer / inner adhesive layer of 3.0, a position from the inner layer surface of the multilayer film to the interface of the outer adhesive layer / EVOH layer that was 83% of the multilayer film thickness, and a position from the inner layer surface of the multilayer film to the interface of the inner adhesive layer / EVOH layer that was 80% of the multilayer film thickness.

[0152] [Example 2-2] A multilayer film was obtained in the same manner as in Example 2-1, except that the tube folded diameter was made as wide as 690 mm. This multilayer film was susceptible to interfacial disturbance between the adhesive layer and the EVOH layer due to the wide tube folding diameter, resulting in a slight decrease in image clarity compared to Example 2-1. However, by setting the thickness ratio of the outer adhesive layer / inner adhesive layer to 3.0, the position from the inner layer surface of the multilayer film to the interface between the outer adhesive layer / EVOH layer at 83% of the multilayer film thickness, and the position from the inner layer surface of the multilayer film to the interface between the inner adhesive layer / EVOH layer at 80% of the multilayer film thickness, good image clarity was observed even in the wide film.

[0153] [Example 2-3] A multilayer film was obtained in the same manner as in Example 2-2, except that the ethylene-vinyl alcohol copolymer (C1) in Layer 4 was changed to an ethylene-vinyl alcohol copolymer (C2) having a different ethylene content. In this multilayer film, unlike the layer structure of Example 2-2, an EVOH resin was selected for the core layer of the multilayer film, which can reduce the occurrence of interfacial disturbance with the adhesive layer, and therefore very good image clarity was observed even in a wide film.

[0154] [Comparative Example 2-1] A multilayer film was obtained in the same manner as in Example 2-1, except that in Example 2-1, the polyethylene resin (A3) in Layer 2 was changed to a thickness of 210 μm, the maleic anhydride-modified polyethylene resin (B1) in Layer 3 was changed to a thickness of 25 μm, the ethylene-vinyl alcohol copolymer (C1) in Layer 4 was changed to a thickness of 25 μm, the maleic anhydride-modified polyethylene resin (B1) in Layer 5 was changed to a thickness of 25 μm, and the polyamide 11 (D1) in Layer 6 (outer layer) was changed to a thickness of 15 μm. This multilayer film had a thickness ratio of outer adhesive layer / inner adhesive layer of 1.0, the position from the inner surface of the multilayer film to the interface of the outer adhesive layer / EVOH layer was 88% of the multilayer film thickness, and the position from the inner surface of the multilayer film to the interface of the inner adhesive layer / EVOH layer was 80% of the multilayer film thickness.However, the image clarity of the film was reduced due to the strong influence of interfacial disturbance between the adhesive layer / EVOH layer.

[0155] Next, the results when a polyethylene resin was used for layer 6 (outer layer) are shown in Table 2-2(B) below.

[0156] [Table 2-2(B)]

[0157] [Example 2-4] A multilayer film with a tube folded diameter of 450 mm was obtained with a six-layer structure laminated in the following order: Layer 1 (inner layer) polyethylene resin (A1 / A2=50 / 50) with a thickness of 30 μm; Layer 2 polyethylene resin (A3) with a thickness of 225 μm; Layer 3 maleic anhydride modified polyethylene resin (B1) with a thickness of 10 μm; Layer 4 ethylene-vinyl alcohol copolymer (C1) with a thickness of 10 μm; Layer 5 maleic anhydride modified polyethylene resin (B1) with a thickness of 25 μm; and Layer 6 (outer layer) polyethylene resin (A1) with a thickness of 30 μm. This multilayer film was found to have good image clarity by having a thickness ratio of outer adhesive layer / inner adhesive layer of 2.5, a position from the inner layer surface of the multilayer film to the interface of the outer adhesive layer / EVOH layer at 83% of the multilayer film thickness, and a position from the inner layer surface of the multilayer film to the interface of the inner adhesive layer / EVOH layer at 80% of the multilayer film thickness.

[0158] [Example 2-5] A multilayer film was obtained in the same manner as in Example 2-4, except that the polyethylene resin (A3) of Layer 2 had a thickness of 235 μm and the polyethylene resin (A1) of Layer 6 (outer layer) had a thickness of 20 μm. In this multilayer film, the thickness of the polyethylene resin (A1) in layer 6 (outer layer) was reduced so that the position from the inner layer surface of the multilayer film to the interface of the outer adhesive layer / EVOH layer was 86% of the multilayer film thickness, and the position from the inner layer surface of the multilayer film to the interface of the inner adhesive layer / EVOH layer was 83% of the multilayer film thickness. However, compared to Example 2-4, there was a tendency for the image clarity of the film to decrease.

[0159] [Example 2-6] A multilayer film was obtained in the same manner as in Example 2-4, except that the polyethylene resin (A3) of Layer 2 had a thickness of 245 μm and the polyethylene resin (A1) of Layer 6 (outer layer) had a thickness of 10 μm. In this multilayer film, the thickness of the polyethylene resin (A1) in layer 6 (outer layer) was further reduced so that the position from the inner layer surface of the multilayer film to the interface of the outer adhesive layer / EVOH layer was 89% of the multilayer film thickness, and the position from the inner layer surface of the multilayer film to the interface of the inner adhesive layer / EVOH layer was 83% of the multilayer film thickness. However, compared to Examples 2-4 and 2-5, there was a tendency for the image clarity of the film to decrease.

[0160] [Comparative Example 2-2] A multilayer film was obtained in the same manner as in Example 2-4, except that the polyethylene resin (A3) in Layer 2 had a thickness of 240 μm and the maleic anhydride modified polyethylene resin (B1) in Layer 5 had a thickness of 10 μm. In this multilayer film, the thickness of the maleic anhydride modified polyethylene resin (B1) in layer 5 was reduced so that the thickness ratio of outer adhesive layer / inner adhesive layer was 1.0, the position from the inner surface of the multilayer film to the interface of the outer adhesive layer / EVOH layer was 88% of the multilayer film thickness, and the position from the inner surface of the multilayer film to the interface of the inner adhesive layer / EVOH layer was 85% of the multilayer film thickness. However, the image clarity of the film was reduced due to the strong influence of interfacial disturbance between the adhesive layer / EVOH layer.

[0161] It can also be seen that the single-use cell culture container obtained by using the multilayer film of the above-obtained example has excellent visibility of the contents. [Industrial Applicability]

[0162] The medical multilayer film of the present invention has excellent visibility of the contents and can be widely used for bags for cell culture, infusions, medicinal liquids, enteral nutrients, etc.

Claims

1. A medical multilayer film comprising an inner layer, a core layer, an outer layer and an adhesive layer, the inner layer is a polyolefin layer, the core layer is an ethylene-vinyl alcohol copolymer layer having a thickness of 1 to 7% of the total thickness of the film, and the adhesive layer is disposed on both sides of the core layer to adhere to the inner layer and the outer layer, the outer layer is a polyamide layer having a thickness of 3 to 20% of the total thickness of the film, the polyamide layer containing a polyamide obtained by ring-opening polymerization of a lactam having 11 or more carbon atoms or by condensation polymerization of an ω-amino acid having 11 or more carbon atoms; A medical multilayer film, wherein the thickness ratio of the outer layer to the core layer (outer layer / core layer) is 0.8 to 7.

2. A medical multilayer film comprising an inner layer, a core layer, an outer layer and an adhesive layer, the inner layer is a polyolefin layer, the core layer is an ethylene-vinyl alcohol copolymer layer, and adhesive layers are provided on both sides of the core layer to bond the core layer to the inner layer and the outer layer; A medical multilayer film, in which the thickness ratio of the outer adhesive layer to the inner adhesive layer (outer adhesive layer / inner adhesive layer) is 2 to 5.

3. A roll-shaped medical multilayer film comprising an inner layer, a core layer, an outer layer and an adhesive layer, the inner layer is a polyolefin layer, the core layer is an ethylene-vinyl alcohol copolymer layer, and adhesive layers are provided on both sides of the core layer to bond the core layer to the inner layer and the outer layer; The multilayer film is in the form of a roll of cloth having a film width of 750 to 4000 mm, A medical multilayer film, in which the image clarity C(2.0)-sheet of one sheet of the roll-like multilayer film measured by a transmission method in accordance with JIS K7374 "Plastics - Determination of image clarity" is 87.5% or more at an optical comb width of 2.0 mm.

4. A tubular medical multilayer film comprising an inner layer, a core layer, an outer layer and an adhesive layer, the inner layer is a polyolefin layer, the core layer is an ethylene-vinyl alcohol copolymer layer, and adhesive layers are provided on both sides of the core layer to bond the core layer to the inner layer and the outer layer; The multilayer film has a tubular shape with a film width of 500 to 2000 mm, A medical multilayer film, in which the image clarity C(2.0)-tube of the tubular multilayer film in which two films are overlapped, measured by a transmission method in accordance with JIS K7374 "Plastics - Determination of image clarity", is 75% or more at an optical comb width of 2.0 mm.

5. The medical multilayer film according to any one of claims 1 to 4, wherein the thickness from the inner layer surface of the multilayer film to the interface between the outer adhesive layer and the core layer is 60 to 85% of the total thickness of the multilayer film.

6. The medical multilayer film according to any one of claims 1 to 4, wherein the multilayer film has a thickness of 200 to 500 µm.

7. The medical multilayer film according to any one of claims 1 to 4, wherein the polyolefin in the inner layer is polyethylene.

8. The medical multilayer film according to any one of claims 1 to 4, wherein the adhesive resin of the adhesive layer is a carboxylic acid-modified polyolefin.

9. 5. The medical multi-layer film according to claim 4, wherein the tube folded diameter of the multi-layer film is 500 to 2000 mm.

10. The medical multilayer film according to any one of claims 2 to 4, wherein the outer layer is a polyamide layer, a polyester layer, or a polyolefin layer.

11. The medical multilayer film according to any one of claims 2 to 4, wherein the outer layer is a polyamide layer, and the polyamide layer contains a polyamide obtained by ring-opening polymerization of a lactam having 11 or more carbon atoms or by condensation polymerization of an ω-amino acid having 11 or more carbon atoms.

12. 5. The medical multilayer film according to claim 3, wherein the absolute value ΔC of the image clarity difference between the roll-like multilayer film and the tubular multilayer film is 12.5% ​​or less.

13. The medical multilayer film according to any one of claims 1 to 4, wherein the multilayer film is obtained by a water-cooled inflation method.

14. A single-use container for cell culture, comprising the medical multilayer film according to any one of claims 1 to 4.

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