JPH01209134A - Packing material for photosensitive substance - Google Patents

Abstract

PURPOSE:To obtain a thick packing material having high physical strength, reduced in curling, generating no melt fracture and having light blocking properties, by respectively positioning a specific straight chain low density polyethylene resin film layer and a polyethylene resin film layer on both front and rear sides and containing a light blocking substance in at least one of the film layers and providing a multilayer coextrusion film having a specific thickness or more. CONSTITUTION:A packing material for a photosensitive substance has a straight chain low density polyethylene resin film layer containing 50 wt.% or more of a straight chain low density polyethylene resin having density of 0.925g/cm<3> or less and melt flow (MFR) of 1.0-7.0 g/10min and a polyethylene resin film layer containing 5wt.% or more of a polyethylene resin having density of 0.90g/cm<3> or more and MFT of 0.59/10min or more both of which are positioned on both front and rear sides. At least one of the film layers contains a light blocking substance and a multilayer coextrusion film having a thickness of 120mum or more is mounted. By this method, the packing material for a photosensitive substance excellent in film moldability, flexibility and physical strength and reduced in curling and having good heat sealability can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the use of photosensitive materials, particularly various photographic materials such as X-ray photographic films, lithographic films, cut films, various photographic papers, 25 plates, and photosensitive resin films. This invention relates to a thick, light-shielding packaging material suitable for packaging.

[Conventional technology]

In general, packaging materials for advanced technology products, such as photosensitive materials, are required to not only completely block light, but also have gas barrier properties, moisture proof properties, and physical strength (breaking strength, tear strength, impact puncture strength, gelbo test strength).

friction strength, etc.), heat sealability (heat seal strength,
cut-sealing properties, hot tank properties, contaminant sealing properties, etc.)
, antistatic properties, lubricity, low dust generation, flatness, and other properties are required.

Several proposals have been made to satisfy these properties.

The present inventor conducted extensive research to improve packaging materials for photosensitive materials, and discovered a material with improved physical strength by combining two layers of uniaxially stretched films (Japanese Patent Laid-Open No. 57-675
Publication No. 4) has already been disclosed.

Further, the present invention discloses a laminated film in which a uniaxially molecularly oriented thermoplastic resin film is heat-melted and bonded to both sides of a sheet-shaped foam so that the molecular orientation axes intersect at an angle of 30 degrees or more, and the thickness of the laminated film is compressed. (Japanese Unexamined Patent Publication No. 59-201848).

However, in such packaging materials consisting of multiple layers, each film layer is laminated by an adhesive layer or coextrusion, so
Each layer is completely integrated and bonded, making it hard, resulting in low physical strength and large curling, and when laminated to form a multi-layered film, trimming loss is large and uneconomical. .

For this reason, a light-shielding thick packaging material formed by multilayer coextrusion blown film, which has high physical strength and low curl, has been considered.

[Problem to be solved by the invention]

However, a multilayer coextruded blown film using carbon black-added L-LDPE resin, which is inexpensive, has good heat-sealability, and has excellent tear strength and impact puncture strength, does not cause abnormalities in thin layers. However, when the thickness is 120p or more, melt fracture occurs and surface roughness failure occurs, resulting in a problem of degrading the quality of the film surface.

An object of the present invention is to solve the above problems and provide a light-shielding thick packaging material that has high physical strength, low curl, and is free from melt fracture.

[Means to solve the problem]

The present invention has been made to achieve the above object, and is an improvement by adding a medium density or high density polyethylene resin to the resin component of the film layer.

That is, the packaging material for photosensitive materials of the present invention has a density of 0.
A linear low-density polyethylene resin film layer containing 50% by weight or more of a linear low-density polyethylene resin with a melt flow rate (hereinafter referred to as MFR) of 925 g/cffl or less and 1.1 to 7.0 g/10 minutes. and the density is 0.930
g/c or more, melt flow rate is 0.5g/10
Polyethylene resin film layers containing 5% by weight or more of polyethylene resin are located on both the front and back surfaces, and at least one film layer contains a light-shielding substance and has a thickness of 1% by weight or more.
It is characterized by comprising a multilayer coextruded film of 2 on or more.

The linear low-density polyethylene (hereinafter referred to as L-LDPE resin) resin film layer is L-LDPE with a density of 0.925 g/c4 or less and an MFR of 0.1 to 7.0 g/10 minutes.
Contains 50% by weight or more of resin.

This L-LDPE resin is called the third polyethylene resin, and is a low-cost, high-strength resin that meets the demands of the times for energy and resource conservation, combining the advantages of both medium-low pressure and high-pressure polyethylene resins. . This resin is a copolymer obtained by copolymerizing ethylene with an α-olefin having 3 to 13 carbon atoms, preferably 4 to 8 carbon atoms, using a low-pressure method or a modified high-pressure method, and has an ethylene content of 85 to 99.5 mol%. It is a low to medium density polyethylene resin with a straight chain structure with short branches.

α-olefins include butene-1, octene-1, hexene-1,4-methylpentene-1, heptene-1,
etc., and the amount thereof is about 0.5 to 15 mol% of the polymer. The density is generally considered to be about that of low-medium pressure polyethylene, but commercially available products have a density of 0.87 to 0.95g10f.
Many of them are within the range of f.

Specific examples of L-LDPE resins are G-Resin (UCC), Dowlex (Dow Chemical), Sflare (DuPont Canada), Marlex (Philips), Neozex and Ultzex (Mitsui). Petrochemicals), Nippon Petrochemicals (Nippon Petrochemicals), and Stamilex (DSM).

The density of this L-LDPE resin is 0.925 g/c+a or less. When the density exceeds 0.925 g/cffl, molecular orientation tends to occur in the longitudinal direction, heat sealability, film formability, physical strength, etc. decrease, and flexibility and cold resistance deteriorate.

In addition, the MFR of L-LDPE resin is 0.1 to 7.0 g/
It's 10 minutes.

If the MFR is less than 1.1 g/10 minutes, the fluidity of the resin is insufficient and melt fracture is likely to occur;7.
If it exceeds 0 g/10 minutes, physical strength tends to decrease.

The L-LDPE resin as described above is contained in an amount of 50% by weight or more. If the L-LDPE resin content is less than 50% by weight, physical strength and heat sealability will decrease.

The polyethylene (hereinafter referred to as PE) resin film layer is
Density is O', 930g/c+f1 or more, MFR is 0.5
Contains 5% by weight or more of PE resin with a yield of 100 g/10 min or more.

This PE resin lowers the melt viscosity to prevent melt fracture, and also increases the crystallization rate to prevent drawdown during coextrusion. It also improves the lubricity of the coextruded film and prevents blocking.

If the density of the PE resin is less than 0.930 g/c+a, the crystallization rate will decrease.

Furthermore, if the MFR of the PE resin is less than 0.5 g/10 minutes, the melt viscosity is high and the prevention of melt fracture is not sufficient. Therefore, the film surface becomes rough. In addition, since the molecules are oriented in the longitudinal direction, the tear strength decreases and the rigidity increases, resulting in block failures and fisheye failures.

If the amount of the above PE resin is less than 5% by weight, the effect of improving film formability is insufficient.

The L-LDPE resin film layer and the PE resin film layer can contain various resins in addition to the resins mentioned above. In particular, the resin contained in the PE resin film layer is L-LDPE resin film layer and PE resin film layer.
LDPE resin is preferred.

A PE resin film layer containing medium density or high density PE resin; 1. - The LDPE resin film layer forms a two-layer coextruded blown film, with either one of the outer layer serving as the front surface of the film and the inner layer serving as the back surface of the film. Moreover, various film layers can be coextruded as intermediate layers between the two layers (7) by a multilayer coextrusion blown film forming method.

In the case of a two-layer coextruded blown film, the inner layer is a PE resin-based film layer containing a medium-density or high-density PE resin, and the outer layer is an L-LDPE resin-based film layer.
The resulting two-layer coextruded blown film does not exhibit blocking.

If the resin compositions of the inner layer and the outer layer are exchanged here, blocking occurs, so that pseudo adhesion of the blown film can be performed.

Further, the thickness of the multilayer coextruded film is required to be 120 mm or more in order to maintain light-shielding properties and provide strength.

A light-shielding substance is added to at least one film layer to ensure light-shielding properties.

The light-shielding substance is one that can be kneaded or dispersed in each layer and does not allow visible light, ultraviolet rays, etc. to pass through.

Examples of light-shielding substances that can be used in the present invention include various carbon blacks, graphite, iron oxide, zinc white, titanium oxide, clay, aluminum powder, aluminum paste,
Examples include organic pigments and inorganic pigments such as aluminum short fibers, calcium carbonate, mica, barium sulfate, talc, cadmium pigments, Bengara, cobalt blue, copper phthalocyanine pigments, monoazo or polyazo pigments, and aniline black. .

Preferably, this light-shielding substance is contained in an amount of 0.1 to 15.0% by weight.

If it is less than 0.1% by weight, the effect of adding the light-shielding substance (ensuring light-shielding properties, preventing static electricity, etc.) cannot be expected, and the cost increases by the cost of crosstalk.

If it exceeds 15.0% by weight, the physical strength of the polyethylene resin film, especially the tear strength and impact puncturing strength, will decrease, and the heat sealability will deteriorate, making it difficult to put it into practical use.

Furthermore, there are frequent failures in which the photosensitive material is contaminated by the light blocking material on the film surface or the light blocking material is detached from the film surface and adheres to the photosensitive material, making it difficult to put it into practical use.

It is also preferable to mix two or more types of light blocking substances according to the required characteristics. Even in this case, the average particle diameter is 200 mμ
The following light-shielding substances are added per unit area (e) of the packaging material:
5 g/m'' to 50 g/m2 is preferable as a packaging material for photosensitive materials. Among these carbon blacks, carbon blacks with a pI of 5 to 9 and an average particle size of 10 to 120 mμ are preferable, particularly p) 16 to 9, Average particle size is 50
Furnace carbon black having a particle diameter of mμ or less is preferred. By using particles with such pH and particle size, there is less fogging, less increase and decrease in photosensitivity, greater light shielding ability, and no pinholes caused by carbon black lumps, fish eyes, etc. It is possible to obtain a packaging material that has a number of advantages such as improved physical strength and improved heat-sealing properties that are less likely to occur.

As mentioned above, there are various forms in which light-blocking substances are blended, but
The masterbatch method is preferable in terms of cost reduction and prevention of workplace contamination.

Next to carbon black, metal powder which is preferable as a light-shielding substance will be explained. This metal powder is a light-reflecting, light-shielding substance that gives it an appearance with high commercial value, and has excellent moisture-proofing, light-shielding, antistatic, heat-proofing properties under sunlight, gas barrier properties, etc. .

As the metal powder, it is particularly preferable to use aluminum powder or a substance obtained by removing lower volatile substances from aluminum paste and kneading it into a thermoplastic resin.

Aluminum paste here refers to the presence of mineral spirits and a small amount of higher fatty acids or fatty acid compounds such as stearic acid or oleic acid when making aluminum powder by a known method such as a ball mill method, a stamp mill method, or an atomization method. It is made into a paste based on In the present invention, this aluminum paste and polyolefin thermoplastic resins (various polypropylene resins, various polyethylene resins, ionomer resins, EVE resins, EEA resins, EAA resins, etc.) are heated and kneaded, and low volatile substances (mainly mineral spirits with a strong odor) are added. The material removed by heat or a vacuum pump is used as aluminum paste compound resin and aluminum paste masterbatch resin.

In particular, it is preferable to use it as an aluminum paste masterbatch resin in order to eliminate adverse effects on photographic materials and odor. For example, even if the mineral spirit content in a masterbatch resin with an aluminum paste content of 40% by weight is 1.0% by weight, if you try to make the aluminum paste concentration in the film layer 2% by weight, the aluminum paste 19 parts by weight of natural resin is mixed with 1 part by weight of the masterbatch, and some mineral spirit is removed as gas during film forming in the film layer, so the mineral spirit content is 0.05 parts by weight. % or less. As a result, there is no adverse effect on photographic materials (in addition, bad odors are reduced).

Aluminum powder is made by pulverizing molten aluminum into powder by atomizing, granulating, rotating disk dropping, evaporating, etc., or by crushing aluminum foil into flakes by ball milling, stamp milling, etc. Contains short aluminum fibers. Since aluminum powder alone is unstable, various known treatments are applied to make the surface of the aluminum powder inert. For example, surface treatment with a coupling agent, surface coating with a fatty acid metal salt, etc.

Further, in order to prevent deterioration of the film during high temperatures during production and during storage, it is preferable to add an antioxidant.

Typical antioxidants include those shown below.

Phenolic n-octadecy/L/-3(3',5'-di-t-butyl 4'hydroxyphenyl)propinate, 2.6 di-t-butyl 4-methylphenol, 2.6 di-t-butyl- p-cresol, 2.2゛-methylenebis(4-methyl-5-t-butylphenol), 4.4゛-thiobis(3-methyl6-t-butylphenol), 4.4゛-butylidenebis(3-methyl- 6-t-butylphenol), stearyl-β(3,5-di-4-butyl 4-hydroxyphenyl)propionate, Ll, 3-)lis(2-methyl-4-hydroxy-
5-t-butylphenyl)butane, L3.5-)listyl-2,4,6-)lis(3,5--di-t-butyl-4-hydroxybenzyl)benzene, octadecyl-3-(3 , 5-di-t-butyl-4-hydroxyphenyl)propionate, tetrakis[methylene-3(3',5"-di-t-butyl-4'-hydroxyphenyl)propionate comethane, etc. Sulfur-based dilauryl-3 , 3゛-thiodipropionate, similystyl-3,3''-thiodipropionate, laurylstearylthiodipropionate, distearyl-3゛-
Thiodipropionate, ditridecyl-3,3'-thiodipropionate, etc. Phosphorous trinonylphenyl phosphite, triphenyl phosphite, etc. Especially 2,6-di-t-butyl-p-cresol (BIT)
) and low-volatility high molecular weight phenolic antioxidants (product name 1reganox 1010+ lreganox
1076+1onox 330+ TopanolCA
etc.), dilaurylthiodipropionate, distearylthiodipropionate, sialkisphosphate, etc. It is effective to use one or more, especially two or more of them in combination.

The total amount added is preferably 0.001 to 2.0% by weight, whether used alone or in combination of two or more.

If the amount added is less than 0.001% by weight, there is almost no effect of the addition. On the other hand, if the amount added exceeds 2.0% by weight, it may have an adverse effect on photographic films that utilize oxidation and reduction effects, and abnormalities may occur in photographic performance. For this reason, it is preferable to add the antioxidant in the minimum amount that will not cause color failure or spots. Particularly preferred are phenolic antioxidants, and commercially available products include Irganox from Ciba Geigy and Sumilizer BHT+ from Sumitomo Chemical.
Sumilizer BP-76+Sumilize
r WX-R, Sumilizer BP-101, etc.

Furthermore, when used in combination with carbon black etc., the antioxidant effect is synergistically exerted.

Furthermore, it is preferable to add a lubricant to each layer in order to improve the fluidity of the resin and to improve product insertion, handling, and processing suitability, and addition of a fatty acid amide type lubricant is particularly preferable.

This lubricant is preferably contained in an amount of 0.01 to 5.0% by weight.

If the amount is less than 0.01% by weight, there will be little effect of improving the above properties and the kneading cost will only increase.

If it exceeds 5.0% by weight, slippage with the extruder screw will increase, making it difficult to form a film of uniform thickness.

Furthermore, they tend to bleed out, and when used in photographic materials, they adhere to the photosensitive layer and cause problems such as development inhibition.

Typical lubricants and their manufacturer's salts are listed below.
The present invention is not limited to these.

(1) Silicone lubricants: various grades of dimethylpolysiloxane (Shin-Etsu Silicone, Toshi Silicone), etc. (2) Oleic acid amide lubricants Near-Moslip CP (Lion Akzo), Neutron (Nippon Sakka), Neutron E-18 (Nippon Rukka)
, Amide 0 (Nitto Kagaku), Decylflow E-10 (Nippon Oil & Fats), Diamond O-200 (Nippon Kasei), Diamond G-200 (Nippon Kasei), etc. (3) Ericic acid amide lubricant: Alflow P-10 (Japan) fats and oils), Neutron S (
(4) Stearic acid amide lubricant: Alflo S 10 (Nippon Oil & Fats), Neutron 2
(Nippon Kasei), Diamit 200 (Nippon Kasei), etc. (5) Bis-fatty acid amide lubricants: Bisamide (Nippon Kasei), Diamit 200 Bis (Nippon Kasei), Armowax EBS (Lion Akzo), etc. (6) Alkylamine-based Lubricant: Electro Stripper TS-2 (Kao Soap), etc. Each film layer contains an antioxidant and a lubricant, as well as
Various additives can be added.

Representative examples of additives are described below, but the present invention is not limited thereto, and any known additives can be selected.

(Additive type) (Representative example) (1) Plasticizer
; Phthalate ester, glycol ester, fatty acid ester, phosphate ester, etc. (2) Stabilizer; Lead-based, cadmium-based, zinc-based, alkaline earth metal-based, organotin-based, fatty acid metal salt, etc. (3) Antistatic agent ; Cationic surfactants, anionic surfactants, nonionic surfactants, bifacial active agents, various carbon blacks, metal powders, graphite, etc. (4) Flame retardants ; Phosphate esters, halogenated phosphate esters, Halides, inorganic substances, phosphorous-containing polyols, etc. (5) Fillers: alumina, kaolin, clay, calcium carbonate, mica, talc, titanium oxide, silica, etc. (6) Reinforcers: glass roving, metal fiber, glass fiber, glass milled Fiber, carbon fiber, etc. (7) Colorant; Inorganic pigment (AI, Feze3.
Ti0z.

(ZnO, CdS, etc.), organic pigments (carbon black, dyes, etc.) (8) Blowing agents; Inorganic blowing agents, (ammonia carbonate, sodium bicarbonate) organic blowing agents, troso-based, azo-based), etc. (9) Vulcanizing agents; Sulfur accelerators, accelerators, etc. (10) Deterioration inhibitors; ultraviolet absorbers, antioxidants, metal deactivators, peroxide decomposition agents, etc. (11) Coupling agents; silane-based, titanate-based, chromium-based (12) Various thermoplastic resins, rubbers, etc. The packaging material of the present invention can be used for packaging various products, especially for packaging photosensitive materials such as photographic materials, foodstuffs, pharmaceuticals, and chemicals. suitable for

In particular, silver halide photographic materials, diazo photographic materials, direct positive color photographic materials, photosensitive resins, self-developing photographic materials, diffusion transfer photographic materials, whose quality is destroyed by slight gases, light, and humidity; Suitable for photographic light-sensitive materials such as photosensitive heat-sensitive materials.

When the packaging material of the present invention is applied to, for example, the above-mentioned photographic materials, - double flat bags, double flat bags, self-standing bags, - heavy gusset bags, double gusset bags, laminated films, inner lining of moisture-proof boxes, bright room loading. It can be used for all known forms such as inner lining of light-shielding magazines and leader paper. In particular, it is effective to use the cylinder in its cylindrical form for bulk rolls of photographic materials, collective packages, etc., and the work process can be made more efficient.

The bag making method is based on conventionally known plastic film sealing methods such as heat sealing, fusing sealing, impulse sealing, ultrasonic sealing, hot air sealing, and high frequency sealing, depending on the properties of the laminated film used. Note that it is also possible to make bags using an appropriate adhesive, adhesive, or the like.

[Effect]

The packaging material for photosensitive materials of the present invention mainly uses L-LDP.
Because the PE resin film layer containing E resin is added with medium density or high density PE resin with high MFH,
The combined thickness with the L-LDPE resin film layer is 120 mm.
Melt fracture and blocking do not occur even when forming thick multilayer coextruded blown films of gm or more.

In addition, L with a resin component density of 0.925 g/cffl or less
- Since the LDPE resin is the main component, the multilayer coextruded blown film has high physical strength, flexibility, and excellent film formability.

〔Example〕

Examples of packaging materials according to the present invention are shown in FIGS. 1 to 9 below.
This will be explained based on the diagram.

1 to 9 are partial cross-sectional views showing the layer structure of the packaging material for photosensitive materials.

The packaging material for photosensitive materials shown in Figure 1 is P containing a light-shielding substance.
It is composed of a multilayer coextruded light-shielding film consisting of two layers: an E resin film layer 1a and an L-LDPE resin film layer 2.

The packaging material for photosensitive materials shown in FIG. 2 is composed of a multilayer coextruded light-shielding film consisting of two layers: a PE resin film layer 1 and an L-LDPE resin film layer 2a containing a light-shielding substance.

The packaging material for photosensitive materials shown in Figure 3 is P containing a light-shielding substance.
It is composed of a multilayer coextruded light-shielding film consisting of two layers: -E resin film layer 1a and L-LDPE resin film layer 2a.

The packaging material for photosensitive materials shown in Figure 4 is P containing a light-shielding substance.
It is composed of a three-layer coextruded light-shielding film in which an intermediate layer 3 is laminated between an E resin film layer 1a and an L-LDPE resin film layer 2.

The packaging material for photosensitive materials shown in FIG. 5 includes a PE resin film layer 1 and a LDPE resin film layer 2 containing a light-shielding substance.
It is composed of a multilayer coextruded light-shielding film consisting of three layers, with an intermediate layer 3 laminated between a.

The packaging material for photosensitive materials shown in Figure 6 is P containing a light-blocking substance.
It is composed of a three-layer coextruded light-shielding film in which an intermediate layer 3 is laminated between an E resin film layer 1a and an L-LDPE resin film layer 2a.

The packaging material for photosensitive materials shown in Figure 7 is P containing a light-shielding substance.
It is composed of a three-layer coextruded light-shielding film in which an intermediate layer 3a containing a light-shielding substance is laminated between an E resin film layer 1a and an L-LDPE resin film layer 2.

The packaging material for photosensitive materials shown in FIG. 8 has a multi-layer coextrusion light-shielding structure consisting of three layers in which an intermediate layer 3a is laminated between a PE resin film layer 1 and an L-LDPE resin film layer 2a containing a light-shielding substance. Consists of film.

The packaging material for photosensitive materials shown in Figure 9 is P containing a light-shielding substance.
It is composed of a three-layer coextruded light-shielding film consisting of an intermediate layer 3a laminated between an E resin film layer 1a and an L-LDPE resin film layer 2a.

FIG. 10 is a partial sectional view showing the layer structure of a comparative example, which is composed of a single layer consisting of only the PE resin film layer 1a.

FIG. 11 is a partial cross-sectional view showing the layer structure of a comparative example, and is
It is composed of a single layer consisting of only the DPE resin film layer 2a.

Next, experimental results will be explained using products 1 to ① of the present invention and comparative products I and H.

Invention product■ Product I of the present invention corresponds to the layer structure shown in FIG.

The light-shielding PE resin film layer has a density of 0.954 g/
HDPE resin 20 with crR1MFR of 1.1g/10min
Weight%, density 0.920g/c/, MFR 2.1g
/10 minutes L-LDPE resin (copolymer resin of ethylene and 4-methylpentene-1) 76.8% by weight, carbon blank 3% by weight, and antioxidant 0.2% by weight, with a thickness of 70 μm. It was formed into a mountain.

The light-shielding L-LDPE resin film layer has a density of 0.
L-LD with 920g/cn and MFR of 2.1g/10min
PE resin 95.949% by weight, carbon black 3.7
5% by weight of antioxidant, 0.25% by weight of antioxidant, and 0.051% by weight of oleic acid amide as a lubricant, with a thickness of 70%.
It was molded into n.

The blown film was formed using a ring die with a lip clearance of 1 mm and a blow ratio of 1.76.
With the PE resin film layer as the inner layer, L-LDP
The thickness of each layer is 1O with the E resin film layer as the outer layer.
A total of 140 pieces of two-layer coextrusion blown film were formed.

The obtained two-layer coextruded blown film does not cause blocking or melt fracture.
It was a thick light-shielding film with excellent smoothness and excellent dispersibility of carbon black.

Invention product■ The product (2) of the present invention corresponds to the layer structure shown in FIG.

-LDP used for the PE resin film layer of the invention product (■)
Using the same resin composition as Inventive Product I, except that E resin was replaced with a copolymer resin of ethylene and 4 methylpentene-1 having a density of 0.915 g/c+it and an MFR of 2°3 g/10 min. A two-layer coextrusion blown film was molded using a two-layer coextrusion blown film molding method.

The resulting two-layer coextruded blown film was a thick light-shielding film with excellent film formability, no blocking or melt fracture, excellent smoothness, and high physical strength, similar to Invention Product I.

Invention product■ −26= The product (2) of the present invention corresponds to the layer structure shown in FIG.

A two-layer coextrusion blown film was formed, with the outer layer having the same composition as the PE resin film layer of Product I of the present invention and the inner layer having the same composition as the L-LDPR resin film layer.

The resulting two-layer coextruded blown film was a thick light-shielding film with no melt fractures other than blocking, and excellent smoothness, physical strength, and carbon black dispersibility. This thick light-shielding film is bonded by blocking, so the thickness is 2
With a thickness of 80 μm, the film has properties that are substantially equivalent to or better than those of a four-layer laminated film, resulting in a significant cost reduction.

Comparison hole■ Comparison hole (3) corresponds to the layer structure shown in FIG.

The density used in the invention product is 0.920g/cd, M
96% by weight of L-LDPE resin with F R of 2.1g/10min, 3.75% by weight of carbon black, 0.0% antioxidant.
A single-layer inflation film having a composition of 25% by weight was formed using a ring die with a lip clearance of 1 scale and a blow ratio of 1.76 to a thickness of 140 Inl.

The obtained single-layer blown film is a thick light-shielding film that is prone to blocking and melt fractures, has poor smoothness, and often has lump-like failures, and is not suitable as a packaging material for photosensitive materials. It was a thick light-shielding film.

Comparison hole■ Comparison hole (3) corresponds to the layer structure shown in FIG.

Density is 0.923g/c11, MFR is 2.4g/10
20% by weight of LDPE resin, the density used in the invention product (■) is 0°920g/cm, and the MFR is 2.1g/10
A single layer having a composition of 76.8 parts by weight of L-LDPE resin, 3% by weight of carbon black, and 0.2% by weight of antioxidant was blown into a single layer with a thickness of 140 mm under the same conditions as comparative hole I. Film molding was performed.

The obtained single-layer light-shielding blown film exhibited blocking similar to the light-shielding blown film with comparative hole ①, and had many wrinkles, streaks, and drawdown, and had poor smoothness. It was a thick light-shielding film that was not suitable for

〔Effect of the invention〕

Although the present invention is a thick film, there is no melt fracture, the film surface is smooth, and carbon black, which is a light-shielding substance, has good dispersibility.

Therefore, it is possible to provide a packaging material for photosensitive materials that has excellent film formability, is flexible, has excellent physical strength such as tear strength and impact puncture strength, has little curl, has good heat sealability, and is inexpensive. .

[Brief explanation of the drawing]

1 to 9 are partial sectional views showing the layer structure of the packaging material for photosensitive materials of the present invention, and FIGS. 10 and 11 are partial sectional views showing the layer structure of comparative examples. 1... PE resin film layer 1a... PE resin film layer containing light-blocking substance 2...
・L-LDPE resin film layer 2a...PE resin film layer containing light-blocking substance 3...Intermediate layer 3a...Intermediate layer containing light-blocking substance Patent applicant Fuji Photo Film Co., Ltd. Agent Patent attorney Japan China Political Situation Name Procedural Amendment (Voluntary) March 31, 1989

Claims (1)

[Claims] A linear low density polyethylene resin film layer containing 50% by weight or more of a linear low density polyethylene resin with a density of 0.925 g/cm^3 or less and a melt flow rate of 0.1 to 7.0 g/10 minutes; , density is 0.930g/cm^3
In the above, polyethylene resin film layers containing 5% by weight or more of polyethylene resin with a melt flow rate of 0.5 g/10 minutes or more are located on both the front and back surfaces, and at least one film layer contains a light-shielding substance, and the film layer is thick. length 120μm
Packaging material for photosensitive materials characterized by comprising the above multilayer coextruded film