JPH0310286B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a packaging bag material (hereinafter simply referred to as packaging material) for forming a packaging bag for photosensitive materials, particularly for photographic materials, which has improved curling properties and physical strength. Conventionally, packaging materials for photographic materials have been made of aluminum foil laminated with two layers of thermoplastic resin on both sides. The reason why aluminum foil is used is to solve the disadvantage of thermoplastic resin, which is increased peeling and electrification, but as a result, curling properties, tear strength, etc. are actually worse than when using only thermoplastic resin. Particularly, the problem of breakage occurs when packaging heavy items. Aluminum foil is also disadvantageous in terms of production cost. The present invention is inexpensive and solves these problems.
It provides a packaging material with excellent curlability and physical strength, and its structure is a laminated film that uses a paper support such as kraft paper instead of conventional aluminum foil. By using this paper support, curling property,
Both tear strength is significantly improved. That is, the packaging material for photosensitive materials of the present invention is a laminated film including three layers in which uniaxially stretched thermoplastic resin films are laminated on both sides of a paper support so that the stretching axes intersect at an angle of 45 to 90 degrees. (a) The paper support has a thickness of 20 to 110 μm, an extension until cutting of 5% or more in both length and width, and a moisture content of 1.5% or more;
(b) one layer of the uniaxially stretched film has a stretching ratio of ² .
~10x, the thickness is 20-70 μm, and the other layer is
The thickness is within ±30% of the thickness of the stretched film, and (c) the laminated film including the three layers has a weight of 0.5 to 15 g/
It is characterized by containing m ² of a light-blocking substance. The elongation of the paper used in the laminated film of the present invention until cutting is required to be 5% or more, preferably 5 to 40%. Such paper can be obtained by calendering, and the paper does not need to be kraft paper (bleached kraft paper), semi-bleached kraft paper or unbleached kraft paper), waste paper, or other inexpensive paper can be used. Can be used. The elongation of paper before cutting is determined by its strength (Gelbo test strength, tear strength, etc.)
This is because if it is less than 5%, the strength of the laminated film will also decrease. However, although there are some with 50% or more, those that stretch too well are not suitable because the tensile strength will drop. The density of the paper is approximately 0.98 g/cm ³ or less to 0.60 g/cm ³ . However, if the density is too low, there is a risk of delamination. The preferred range for normal use is 0.75
~0.90g/ ^cm3 , most preferably ~0.78
It is 0.85g/ ^cm2 . The thickness of the paper is selected depending on the purpose, but it is usually 20 to 110 μm, especially 30 to 110 μm.
90 μm paper is advantageous. The moisture content of paper greatly affects the properties of packaging materials.
Must be 1.5% or more. If the water content is less than 1.5%, the peel chargeability tends to increase, and in this case, there is a risk that the photographic material will be deteriorated by static electricity. Therefore, the moisture content is often 1.5 to about 10%.
Preferably it is 2 to 7%, particularly preferably 3 to 6%. If the moisture content exceeds 10%, steam will be generated during lamination and peeling will occur easily. Curling properties also tend to be inferior when the moisture content is low. Note that this moisture content is expressed as a weight percent based on the bone dry weight of the paper.
Indicated by The paper is preferably made of kraft pulp, sulfite pulp, or a mixture of both, which has no photographic effect, but it goes without saying that semi-bleached or unbleached kraft paper, ordinary paper, or waste paper can also be used. Further, the paper support 1 may be uncolored, colored, or a combination of both, and may further contain carbon black, pigments, dyes, etc., if necessary. Semi-bleached kraft paper, unbleached kraft paper, general paper,
Conventionally, paper and waste paper could not be used for this type of purpose. This was due to yellowing due to formalin treatment, but in the case of the present invention, since uniaxially stretched films are laminated on both sides of the paper, it can be used without any problems. It is also useful to incorporate various materials into the paper. For example, the combination of carbon black is effective in preventing static electricity, and of course also improves light blocking properties. 1~
Addition of 15% by weight is desirable. In addition to carbon black, metal powders such as aluminum, iron, magnesium, tin, zinc, or their alloys or compounds, pigments such as barium sulfate, clay, kaolin, talc, calcium carbonate, titanium oxide, or coloring dyes are used. , the amount of these additions is 0.1 for the entire packaging material.
g/m ² to 7 g/m ² (more preferably 1 g/m ² to
5 g/m ² ). Furthermore, the paper does not necessarily have to be smooth; it is also permissible to create an uneven pattern on the surface, if necessary. It may be noted that the slip properties in particular vary considerably due to this. Note that it is also possible to use a certain type of nonwoven fabric in the laminate of the present invention as something similar to paper. As the uniaxially stretched thermoplastic resin film to be laminated on both sides of the paper support, films made of any thermoplastic resin that can be uniaxially stretched are applicable, but from the viewpoint of availability, versatility, manufacturing suitability, and cost. Films made of polyethylene, polypropylene, polystyrene, polyvinylidene chloride, polyvinyl chloride compounds, polycarbonate, polyethylene terephthalate, polyamide, nylon, etc. with various densities are preferred, and among these, uniaxial films with a density of 0.94 g/cm ³ or more are preferred. Stretched high density polyethylene film is preferred. The resin film used is uniaxially stretched,
The two layers are laminated on both sides of the paper so that their stretching axes intersect at an angle of 30 to 90 degrees, preferably 45 to 90 degrees. This is to improve tear strength, etc., and the effect will not be exhibited if the intersection angle is smaller than 30°. The tear strength and tensile strength tend to be better as the stretching ratio is larger, but the impact strength decreases, so the stretching ratio is preferably 2 to 10 times, preferably 2 to 7 times.
The direction of the stretching axis for the long film may be vertical, horizontal, or oblique, and the intersection of the stretching axes may be a combination of vertical stretching and horizontal stretching, or a combination of two oblique stretchings. The thickness of the stretched film is 20mm for normal packaging.
~70μm Preferably 30~60μm, but the two films may be exactly the same, depending on the material,
The thickness, stretching ratio, additives, etc. may be different. Regarding the thickness, if the thickness of the two stretched films is extremely different, the effect of cross-laminating the two films will not be fully demonstrated, and the properties of the thicker film will be stronger and will affect the properties of the entire laminate. I don't like it because it dominates me. Therefore, the relative ratio of the thickness of the two stretched films is ±30% of the thickness of one layer, preferably ±30% of the thickness of the other layer.
It is best to keep it within 15%. When a light-shielding substance such as carbon black is added to the stretched film, it is desirable that the amount be 0.5 to 7% by weight in order to avoid a decrease in strength. The uniaxially stretched film layer is usually laminated onto the paper support via a molten thermoplastic resin adhesive layer (hereinafter simply referred to as adhesive layer). The molten thermoplastic resin is a thermoplastic resin that can be bonded at a temperature that does not affect the properties of the uniaxially stretched film (if the uniaxially stretched film is HDPE, it can be bonded at approximately 250 to 350°C, such as high-pressure low density polyethylene (LDPE). ), ethylene vinyl acetate copolymer (EVA), ionomer resin, linear low-density polyethylene (L-LDPE), etc. can be used. The thickness of the adhesive layer is usually 10 to 40 μm, but cost, adhesion speed, It is determined based on the total thickness of the laminated film, but is not particularly limited to this value.The packaging material of the present invention can be used for packaging various products, but is particularly used as a packaging material for photographic materials.For this reason, Contains a predetermined amount of light blocking substance.
This light-shielding substance can be included by printing on a paper support, adding another light-shielding layer such as aluminum foil, etc., but the method of adding a light-shielding substance to any layer of the laminate has better performance. This method is advantageous in both simplicity and simplicity. The light-blocking substance may be added to paper, uniaxially stretched film, adhesive layer, or any other layer. As the light-shielding substance, those known as light-shielding substances for packaging materials for photosensitive materials can be used, and the most typical one is carbon black. In the case of carbon black, it can be contained in the entire laminate in an amount of 0.5 to 15 g/m ² without impairing other properties.
The light-shielding substance can also be contained in the uniaxially stretched film, and its content is 0 to 7% by weight, preferably 0.5 to 7% by weight. However, in order to improve the light-shielding properties as much as possible by adding the same amount, it is desirable to incorporate the light-shielding substance inside the paper support (on the side that contacts the product when packaged). Several other layers may be laminated on the laminate of the present invention. For example, in order to facilitate heat sealing, it is useful to form a layer on one surface layer (inner layer) that is easier to heat seal and has a lower melting point (preferably 10°C or more lower) than the uniaxially stretched film. For example, the thickness of the heat seal layer
High pressure low density polyethylene of about 10 to 100 μm, ethylene vinyl acetate copolymer, ionomer, linear low density polyethylene ethylene ethyl acrylate copolymer, etc. can be used. It is also permissible to additionally laminate other flexible sheet layers for the purpose of changing the aesthetic appearance, printability, moisture permeability, sliding properties, etc. of the packaging material. When encapsulating photographic light-sensitive materials, it is desirable that the layer in contact with the product has a sliding angle of 25 degrees or less (preferably 8 to 25 degrees), but such characteristics can be improved by adding a lubricant or by making the surface matte. Alternatively, the above slip characteristics can be satisfied by selecting the material of the film forming the heat-sealing surface (the surface of the film that contacts the product). Preferred embodiments of the present invention are, for example, as follows. That is, a suitable packaging material for photosensitive materials has a stretching ratio of 2.0 to 7.0 times and a carbon black content of 0.5 to 7% by weight.
A uniaxially stretched HDPE film, preferably a uniaxially obliquely stretched film (including a film obtained by slitting a vertically uniaxially stretched film into a spiral shape) with a thickness of 30 μm to 60 μm and a density of 0.94 g/cm ³ or more, is processed into a polyolefin-based film (LDPE, EEA, etc.). The adhesive layer (including polyethylene copolymers such as L-LDPE, PP, EVA, and ionomers) has a thickness of 30 μm to 90 μm, an elongation of 5 to 40% both vertically and horizontally, and a density of 0.5 to 1.2 g/cm ³ Paste on a paper support of
A uniaxially stretched film, preferably a uniaxially obliquely stretched film (including a film obtained by slitting a vertically uniaxially stretched film into a spiral shape), is bonded with a polyolefin adhesive layer, and one or more of the layers is coated with 0.5 to 15 g/m ² of carbon black. It is composed of a laminated film comprising: This packaging material is particularly suitable for use in photographic materials, and has significantly improved physical strength and curling properties. FIGS. 1 and 2 show the basic structure of a laminated film, which is the packaging material of the present invention. Uniaxially stretched films 2, 2' (FIG. 1), or 2a and 2'a (see FIG. 2, containing a light-shielding substance) are laminated. FIG. 3 shows a layer 6 of another uniaxially stretched film or flexible sheet on the surface of the basic structure (FIG. 1) with an adhesive layer 3 interposed therebetween.
4 and 5 show the heat seal layers 4a and 5 laminated on the surface of the uniaxially stretched film without (or through) an adhesive layer. The adhesive layer 3 or 3a is a hot-melt adhesive layer or other adhesive layer. Preferred embodiments of the present invention and their effects will be described below with reference to Examples. Two types of products of the present invention corresponding to FIG. 2 were prepared and compared with a conventional product using aluminum foil and a product simply cross-laminated with uniaxially stretched films. Products 1 and 2 of the present invention have a basis weight of 35 g/
^m2 , thickness 55μm density 0.64g/ ^cm3 , cutting length 12
Kraft paper with a width of 10% and a moisture content of 7% was used.
As a uniaxially stretched film, the density is 0.96g and the thickness
A 45 μm obliquely uniaxially oriented high-density polyethylene film (hereinafter referred to as "BKM45") was used. The stretching ratio is 3.5 times and the carbon black
It contains 4.5% by weight, and the stretching axes of the two layers are perpendicular to each other at 90 degrees. Lamination with paper support is 13μm thick in 1.
For LDPE, 2, this was done through an adhesive layer of ethylene ethyl acrylate with a thickness of 13 μm. As a comparative example, the same BKM45 is made of 10μm LDPE.
In addition to the one laminated with an adhesive layer, a conventional product was tested in which 7 μm aluminum foil was laminated instead of paper in Product 1 of the present invention. The results showed that the product of the present invention had excellent tear strength, impact puncture strength, curling strength, Gelbo test strength, and drop strength, as well as excellent tensile strength and folding strength. Furthermore, the charging performance is comparable to that of conventional products, and it is also advantageous in terms of cost. The results of tests in which the products 1 and 2 of the present invention were actually used for packaging roll film, sheet-like photographic paper, etc. also confirmed that accidents such as breakage were reduced. This tendency was more pronounced as the weight of the packaged object increased, and as the thickness and volume of the packaged object increased. That is, the laminate of the present invention is cut into a rectangular shape,
Those that are heat-sealed on three sides to form an envelope are roll products such as photographic paper, film for movies, photosensitive film for printing, X-ray film, etc., and are particularly heavy, weighing 5 kg or more. Even when the film edge was used to encapsulate sharp objects, there was little chance of breakage. Therefore, the product of the present invention is particularly advantageous when these articles are stored and transported in bag-shaped packaging (flat bags, gusset bags, etc.). Moreover, the rigidity was appropriate and it was easy to seal the open end with tape, and it was also easy to completely seal it by heat sealing. The light-shielding properties were particularly good for those containing carbon black in the inner layer.

【table】

[Table] Measuring method Note (1) Curl property Create a circular specimen with a diameter of 10 cm using the sheet to be tested, and place each sheet on a flat plate with no load for 24 hours in an atmosphere with a temperature of 20°C and a humidity of 65%. After leaving it for a while, find the length l of both end faces and measure it as 10-l (cm). (2) Drop strength: Put 1 kg of sand in a bag made of packaging material and drop it 1 m above the floor.
Measure the number of times the bag ruptures after being dropped from a height of

[Brief explanation of drawings]

FIGS. 1 and 2 are partial cross-sectional views showing the structure of the packaging material for photosensitive materials according to the present invention. Figure 3,
FIGS. 4 and 5 are partial sectional views showing an application example of the present invention. 1... Paper support, 2, 2a, 2', 2'a... Uniaxially stretched film, 3, 3a... Adhesive layer, 4a, 5
...Heat seal layer. (The subscript a indicates those containing light-blocking substances.)

Claims (1)

[Scope of Claims] 1 A laminated film comprising three layers of uniaxially stretched thermoplastic resin films laminated on both sides of a paper support so that the stretching axes intersect at an angle of 30 to 90 degrees, a) The paper support has a thickness of 20 to 110 μm, an extension of 5% or more in both length and width, and a moisture content of 1.5% or more,
(b) one layer of the uniaxially stretched film has a stretching ratio of ² .
~10x, the thickness is 20-70 μm, and the other layer is
The thickness is within the range of ±30% of the thickness of the stretched film, and (c) the laminated film including the three layers has a thickness of 0.5 to 15%.
A packaging bag material for photosensitive materials, characterized in that it contains a light-shielding substance of g/m ² . 2. The packaging bag material according to claim 1, wherein the uniaxially stretched film is adhered to the paper support via an adhesive layer. 3. The packaging bag material according to claim 1 or 2, wherein a heat seal layer having a melting point lower than that of the uniaxially stretched film is laminated on the surface of the uniaxially stretched film. 4. The uniaxially stretched film is made of a thermoplastic resin such as low-pressure high-density polyethylene, polypropylene, polystyrene, polyester, nylon, polyvinylidene chloride, polyvinyl chloride compound, polycarbonate, polyamide, etc.
The packaging bag material described in item 3 of item 3. 5 The adhesive layer is made of high pressure low density polyethylene,
The packaging bag material according to claim 2, which is a thermoplastic resin such as ethylene-vinyl acetate copolymer, ionomer, linear low-density polyethylene, or ethylene-ethyl acrylate copolymer. 6 The uniaxially stretched film contains 0 to 0 light-shielding substances.
The packaging bag material according to any one of claims 1 to 5, containing 7% by weight.