Core for photosensitive material and roll of photographic film

Abstract: A substrate of a photosensitive web material of which the base end portion is gradually thinned toward the base end a core for a rolled photographic film which comprises a core body and a crosslinked foamed sheet having an expansion ratio of 18 to 45 times and a thickness of 0.2 to 2.0 mm which contains more than 50 wt. % in the sum of one or more members selected from the group consisting of polyethylene resin having a density of less than 0.930 g/cm³, ethylene-vinyl acetate copolymer resin having a comonomer content of less than 25 wt. % and ethylene-ethyl acrylate copolymer resin having a comonomer content of less than 25 wt. % in disposed on the surface of the core body. These substate and core sharply reduce the occurrence of marking troubles and pressure mark troubles on the photosensitive web material near the core caused by the difference in level induced by the base end portion of the web.

Description: This invention relates to a core for a photosensitive web material which improve marking troubles of the photosensitive web material formed near the core. The substrate base end of a conventional photosensitive web material is formed almost rectangular both in the section and in the plane figure, as shown by dashed lines in Figure 1. As a result, when the conventional photosensitive web material is wound around a core, as shown in Figure 13, a difference in level is formed between the base end 4 of the web 1 and the core 11 due to the thickness t of the web 1. The conventional core for the photosensitive web is formed by winding in spiral a dense kraft paper, regenerated paper or the like. The core is rendered as hard as possible in order to prevent deformation of the core by the winding pressure of the photosensitive web, shocks got during physical distribution and the like, and therefore, its flattening compressive strength is high. Since the photosensitive web was wound tight, creases 16 (Fig. 13), patterns and pressure marks are formed in several folds of the web near the core by the difference in level at the base end portion of the web, the spiral groove on the surface of the core, etc. Moreover, in the case of fixing the base end of the photosensitive web using an adhesive, tape marks were also formed. These marks are formed during winding the photosensitive web and during preservation by the winding tension and its own weight. The occurrence of these marks can be reduced to a certain degree by winding loosely. However, the loosely wound photosensitive web tends to project in a form of cone by shaking during distribution, inclined state or the like. Moreover, wound form tends defective, and packaging defectives also tends to generate. As a result, workability is shaply decreased. An optimal roll density is determined by the thickness, length and friction coefficient of the photosensitive web, the flexibility and surface hardness of the substrate, temperature, humidity, distribution means, passed time and so on, and it is difficult to determine a suitable roll density. A means for resolving the problem to form marks by the difference in level by the base end of the web is disclosed in Japanese Utility Model KOKAI Nos. 57-60141 and 63-41072 which forms a step portion 17 on the core corresponding to the thickness of the web in the axial direction, as shown in Figure 12, and the web is begun to be wound from the step portion. This means has not been put to practical use, because it is not easy to adjust the base end of the web to the step portion under a dark safty light. The manufacture of the core is a special order, and the height of the step must be changed according to the thickness of the web. As a result, the manufacturing cost of the core is expensive. Another means for resolving the problem to form marks by the difference in level by the base end of the web is disclosed in Japanese Utility Model KOKAI No. 53-32021 wherein the base end of the web is cut obliquely in the plane figure. In this means, workability is improved, because the positioning of the base end of the web is easy. The occurrence of marking troubles is reduced to a certain degree, but the occurrence of pressure marks still remains due to the rectangular cutting in the thickness direction. A means for resolving the problem due to the hardness of the core surface is disclosed in Japanese Utility Model KOKOKU No. 2-24116 which covers the circumferential face of the core in the whole width with a sheet having cushioning characteristic and elasticity, such as low density papers of less than 0.5 g/cm 3 , synthetic papers and foamed resin sheet having an expansion ratio of 5 to 15 times. When the above core covered with the foamed resin sheet or the like is used as the core for a roll of photographic printing paper where a photograpic emulsion layer is coated on a paper substrate or a water-resistant substrate made of paper of which both side are coated with various polyethylene resins, various physical marking troubles and pressure mark troubles can sharply be reduced. On the other hand, when the above core is used as the core for a roll of a photographic film of which the substrate is a plastic film having a less elasticity than the paper substrate, the marking troubles and pressure mark troubles occur in 5 to 6 folds of the film from the base end of the film. The Japanese Utility Model KOKOKU No. 2-24116 discloses a core provided nonwoven fabric. In this core, since the friction resistance is small between the photographic film and the nonwoven fabric, it is necessary to fix the photographic film to the nonwoven fabric using and adhesive tape. It is therefor the object of the invention to provide a means capable of decreasing sharply the physical marking troubles and pressure mark troubles of a photosensitive web material which is not necessary to form a step portion on the core and of which the workability is excellent and which is capable of decreasing sharply the physical marking troubles and pressure mark troubles of a rolled photographic film. This object has been solved by providing a core for a rolled photographic film which comprises a core body and a crosslinked foamed sheet disposed on the surface of the core body having an expansion ratio of 18 to 45 times and a thickness of 0.2 to 2.0 mm and containing more than 50 wt. % in the sum of one or more members selected from the group consisting of polyethylene resin having a density of less than 0.930 g/cm 3 , ethylene-vinyl acetate copolymer resin having a comonomer content of less than 25 wt. % and ethylene-ethyl acrylate copolymer resin having a comonomer content of less than 25 wt. % Furthermore the present invention provides a roll of a photographic film which comprises the above core and a rolled photographic film of which the substrate is made of plastic having a heat resistance (ASTM D-759) of more than 121°C (250°F) and a strength (ASTM D-882) of more than 48.265MPa (7,000 psi). Figure 1 is a perspective view illustrating the base end portion of the substrate of a photosensitive web material Figures 2 and 3 are sectional views illustrating various thinned forms of the base end portion Figure 4 indicates plan views of various forms of the base end portion of which the length of the base end is lengthened than the width of the web material. Figure 5 is a partial sectional view illustrating a wound state of a photosensitive web material of which the base end portion is gradually thinned around a core. Figure 6 is a perspective view illustrating a roll of a photographic film wound around a core comprising the core body and the crosslinked foamed sheet. Figure 7 is a side view with a partially enlarged section. Figure 8 is a front view with a partially enlarged section. Figure 9 is a perspective view illustrating a winding state of a photographic film of which the base end is obliquely cut in the width direction. Figures 10 and 11 are partially sectional views of crosslinked foamed sheets applicable to the invention. Figure 12 is a partial perspective view of a conventional core. Figure 13 is a partial sectional view illustrating a conventional wound state of a photosensitive web material. The rolled photographic film is composed of a silver halide photographic photosensitive material emulsion layer and a plastic film substrate coated therewith, and includes films for printing (lithfilm), films for roentgenogram, films for computerized type-setting syentem, microfilms, positive films (such as Fuji Crystal Paper), and the like. The plastic film substrate is formed of polyester, polycarbonate, cellulose triacetate, polystyrene, polypropylene or the like, and it may be nonstretched, uniaxially stretched or biaxially stretched, and clear or colored with white or color pigment. Moreover, it may be metallized by deposition, sputtering, etc. A plastic film suitable for the core covered with the crosslinked foamed sheet has a heat resistance (ASTM D-759) of more than 121°C (250°F) and a strength (ASTM D-882) of more than 48.265MPa (7,000 psi). Preferably the crosslinked foamed sheet contains more than 50 wt.% of the polyethylene resin. Preferably said resin is L-LDPE or a blend of homopolymethylene resin and L-LDPE. Preferably the density of this polyethylene resin is 0.910 to 0.925 g/cm 3 . Also preferred are crosslinked foamed sheets containing more than 50 wt.% EVA or EEA copolymer resin. The core for a rolled photographic film comprises a crosslinked foamed sheet and a core body. The crosslinked foamed sheet prevents the occurrence of various markings and pressure marks on the photographic film wound around the core by its elasticity, and contains at least one of polyethylene resin having a density of less than 0.930 g/cm 3 , ethylene-vinyl acetate (EVA) copolymer resin having a comonomer content of less than 25 wt. % and ethylene-ethyl acrylate (EEA) copolymer resin having a comonomer content of less than 25 wt. % in an amount of more than 50 wt. % in the sum of the above resins. When the amount is less than 50 wt. %, it is difficult to manufacture a foamed sheet having an expansion ratio of 18 times or more. The foamed sheet is insufficient in the cushionability and great in slipping characteristics. As a result, the winding of a photographic film is difficult, unless the base end is fixed to the core by an adhesive tape or an adhesive agent, and various marking troubles and pressure mark troubles tend to occur on the rolled photographic film. The polyethylene resin may be selected from various high pressure branched low density homopolyethylene (LDPE) resins, linear low density polyethylene (L-LDPE) resins which are ethylened-α-olefin copolymer resins and blends of them. The L-LDPE resin is called the third polyethylene resin, and it is a low cost high strength resin having the advantages of both medium, low density polyethylene resin and high density polyethylene resin and meeting the requirements of the times of saving energy and resources. The L-LDPE resin is a copolymer produced by copolymerizing ethylene with an α-olefin having a number of carbon atoms of 3 to 13, preferably 4 to 10, through the low presure process or the modified high pressure process, and has a linear structure with short branches. Preferred α-olefins in view of physical strength and cost are butene-1, heptene-1, hexene-1, 4-methylpentene-1, octene-1 and the like. As the polymerization process of L-LDPE, there are the vapor phase process and the liquid phase process using a medium, low pressure apparatus and the ionic polymerization process using an apparatus for the modified high pressure process. The density of polyethylene resin is less than 0.930 g/cm 3 , preferably 0.90 to 0.92 g/cm 3 , more preferably 0.910 to 0.925 g/cm 3 . When the density exceeds 0.930 g/cm 3 , it is difficult to manufacture a foamed sheet having an expansion ratio of 18 times or more. The foamed sheet is insufficient in the cushionability and great in slipping characteristics. As a result, the winding of a photographic film is difficult, unless the base end is fixed to the core by an adhesive tape or an adhesive agent, and various marking troubles and pressure mark troubles tend to occur on the rolled photographic film. The EVA resin having a comonomer content of less than 25 wt. % does not affect adversely photographic films, such as fogging or sensitivity deviation, and acetic acid odor is little. The EEA resin having a comonomer content of less than 25 wt. % does not affect adversely photographic films, such as fogging or sensitivity deviation, and acrylic acid odor, apple-like odor, is weak and does not give discomfort to uses. When the comonomer content exceeds 25 wt. %, the EVA resin and the EEA resin adversely affects photographic films, such as fogging or sensitivity deviation. Acetic acid odor or acrylic acid odor becomes strong and give discomfort to users. The melt index (MI) of the above polyethylene resin, EVA resin and EEA resin is preferably less than 20 g/10 minutes, preferably 0.1 to 15 g/10 minutes, more preferably 0.5 to 10 g/10 minutes. When the MI exceeds 20 g/10 minutes, moldability is occasionally inferior. Blowing agents applicable to manufacturing the crosslinked foamed sheet are sodium hydrogen carbonate, azido compounds such as CaN 6 and BaN 6 , light metals reacting with water to generate hydrogen gas such as Mg, Zn and Al, azo compounds such as azodicarbonamide and azobisisobutyronitrile, sulfonyl hydrazide compounds such as p-toluenesulfonyl hydrazide, volatile organic blowing agents of halogenated hydrocarbons and mixture thereof such as various mixtures of dichlorotetrafluoroethane with another halogenated hydrocarbon, e.g. trichlormonofluoromethane, methylene chloride, trichlorotrifluoroethane, dichloromonofluoromethane or dichlorofluoromethane, and so on. Undesirable blowing agents are heat-decomposable blowing agents of which a principal component is an ammonium compound, a formalin compound or a sulfur compound, because they adversely affect photographic films, such as fogging or sensitivity deviation. Preferred blowing agents are those generating harmless gas to photographic films, such as N 2 or carbon dioxide gas, which include azodicarbonamide and N,N'-dinitrosopentamethylenetetramine and 4,4'-hydroxybenzenesulfonyl hydrazide, mixtures of halogenated hydrocarbons which are volatile organic blowing agent, and the like. The crosslinking method may be chemical crosslinking or radiation crosslinking, the expansion ratio of the crosslinked foamed sheet is 18 to 45 times, preferably 20 to 40 times, more preferably 25 to 35 times. When the expansion ratio is less than 18 times, marking troubles are less than 18 times, marking troubles are liable to occur due to insufficient cushionability. When the expansion ration exceeds 45 times, it is difficult to ensure wear resistance, surface strength, physical strength and productivity. The thickness of the crosslinked foamed sheet is 0.2 to 2,0 mm, preferably 0.3 to 1.5 mm, more preferably 0.45 to 1.2 mm, in view of ensuring various properties and productivity. The crosslinked foamed sheet is attached to the core body in spiral (with spaces), the whole circumferential surface, stripes, or the like. The attached area is preferably more than 70 % of the whole circumferential area. Preferably the sheet is wound around the core body in a single fold. The core body may be a conventional core, such as a core produced by winding a dense kraft paper or regenerated paper in spiral, a core produced by winding a cardboard in spiral on a mandrel and then winding a surface layer sheet in spiral thereon, a core made of plastic, a core made of metal, and any other known cores. Moreover, cores for taking up a web disclosed in Japanese Utility Model KOKOKU No. 3-28053 can also be applicable to the invention which have a mouthpiece portion, i.e. a contact portion with chucking apparatus which takes up a substrate used for manufacturing a photographic film or a photographic film manufactured by coating a photosensitive layer of silver halide emulsion or the like onto the substrate. The foamed sheet having an expansion ratio of 18 to 45 times is preferably produced using a polyolefin resin which does not affect adversely photographic photosensitive materials. Such a polyolefin resin includes low, medium, high density homopolyethylne resins, very low density polyethylene resins, ethylene-α-olefin copolymer resins, homopolypropylene resins, propylene-α-olefin copolymer resins, ethylene-vinyl acetate copolymer resins, ethylene-ethyl acrylate copolymer resins, ethylene-acrylic acid copolymer resins, ionomer resins, adhesive polyolefin resins (acid-modified polyolefin resins), ethylene-propylene copolymer resins, ethylene-butadiene copolymer resins, ethylene-propylene elastomers, ethylene-methyl acrylate copolymer resins, ethylene-vinyl chloride copolymer resins. In the case that the expansion ratio is more than 18 times, in order to ensure the film strength at a high expansion state, suitable resin sheets are a forementioned ones produced by crosslinking a polyolefin resin containing at least one of polyethylene resin having a density of less than 0.930 g/cm 3 , EVA resin having a comonomer content of less than 25 wt. % and EEA resin having a comonomer content of less than 25 wt. % in an amount of more than 50 wt. % in the sum of the above resins. When the expansion ratio exceeds 45 times, wear resistance, surface strength, etc. are degraded. Moreover, compression deformation is too great, and therfore, the core cannot be put to practical use. In the core for a rolled photographic film of the invention, the crosslinked foamed sheet sinks elastically to prevent the occurrence of physical marking troubles, pressure mark troubles and sensitivity deviation troubles. EXAMPLES Example IX An example of the roll of a photographic film of the invention is illustrated in Figures 6 and 7. The photographic film 1 which is a photosensitive web material is wound around a core 11 consisting of a core body 12 and a crosslinked foamed sheet 13. The core body 12 was made of brown paper composed of 30 wt. % of unbreached kraft paper and 70 wt. % of waste corrugated board paper wound in spiral, and the thickness was 5.5 mm. The crosslinked foamed sheet was produced by foaming EVA resin having a density of 0.940 g/cm 3 at an expansion ratio of 20 times, and the thickness was 0.5 mm. Vinyl acetate comonomer content was 15 wt.%. The crosslinked foamed sheet 13 was wound around the core body 12 in a single fold in spiral. The photographic film 1 was a positive roll film 150 m in length of which the substrate 2 was a biaxially stretched polyester resin film about 170 µm in thickness rendered white opaque by blending BaSO 4 , coated with a photographic emulsion layer. The base end of the photographic film was conventional, i.e. cut in parallel to the width direction perpendicular to the longitudinal direction of the film. The base end portion was not thinned. The roll was left at 35°C for one week, and it was confirmed that no occurrence of physical marks around the base end portion. Pressure marks and sensitivity deviation did not occur, too. Flattening compressive strength was sufficient, and the roll form of the photographic film was excellent. Streaks were not formed. The core could readily be discriminated even under a safty light, and the photographic film was easily fixed to the core. Comparative Example I The core body was made of kraft paper having a density of 0.75 g/cm 3 wound in spiral, and the thickness was 6.0 mm. Nonwoven fabric having a density of 0.32 g/cm 3 and an areal weight of about 130 g/cm 3 was used instead of the foamed sheet, and wound thereon in spiral. The results of the same evaluation tests as Example IX are shown in Table 2. Comparative III This roll was the same as Comparative I, except that chipboard paper having a density of 0.5 g/cm 3 and a thickness of 1.0 mm was wound around the core body in one fold as the cushioning material. The results of the same evaluation tests as Example VII are shown in Table 2. Comparative IV This roll was the same as Comparative I, except that kraft paper having a density of 0.75 g/cm 3 was wound around the core body in spiral. The results of the same evaluation tests as Example VII are shown in Table 2. Comparative V The rolled film employed was a rolled photographic negative film 50 m in length composed of a biaxially stretched polyester resin film substrate 100 µm in thickness and a photographic emulsion layer for lithfilm coated thereon, and the others are the same as Conventional Example 2. The results of the same evaluation tests as Example IX are shown in Table 2. Example IX Comparative I III IV V Core Surface Sheet Crosslinked Foamed EVA Sheet Kraft Paper Foamet LDPE Sheet Chipboard Paper Foamet LDPE Sheet Kind Material EVA Paper LDPE Paper LDPE Expansion Ratio 20 - 5.0 - 5.0 Density - 0.75 - 0.5 - Thickness 0.5 6.0 1.0 1.0 1.0 Substrate for Roll Biaxially Stretched Biaxially Streched Biaxially Stretched Blaxially Stretched Blaxially Stretched Film Kind Polyester Film Polyester Film Polyester Film Polyester Film Polyester Film Thickness 170 170 170 170 100 Form of Winging Base End FIG. 1 (dashed line) FIG. 1 (dashed line) FIG. 1 (dashed line) FIG. 1 (dashed line) FIG. 1 (dashed line) Photographic Emulsion Positive Positive Positive Positive Negative Marking by Core Surface B F D F E Marking by Winding End B F D F E Pressure Mark by Winding End A E C E D Tape-Form Marking B F E F E Streaks A D C D C

Claims: A core for a rolled photographic film which comprises a core body and a crosslinked foamed sheet disposed on the surface of the core body, said crosslinked foamed sheet having an expansion ratio of 18 to 45 times and a thickness of 0.2 to 2.0 mm and containing more than 50 wt.% in the sum of one or more members selected from the group consisting of polyethylene resins having a density of less than 0.930 g/cm 3 , ethylene-vinyl acetate copolymer resins having a comonomer content of less than 25 wt. % and ethylene-ethyl acrylate copolymer resins having a comonomer content of less than 25 wt.%. The core of claim 1, wherein said crosslinked foamed sheet contains more than 50 wt.% of the polyethylene resin. The core of claim 2, wherein said polyethylene resin is linear low density polyethylene resin or a blend of homopolyethylene resin and linear low density polyethylene resin. The core of claim 2, wherein the density of the polyethylene resin is 0.910 to 0.925 g/cm 3 . The core of claim 1, wherein said crosslinked foamed sheet contains more than 50 wt.% of ethylene-vinyl acetate copolymer resin. The core of claim 1, wherein said crosslinked foamed sheet contains more than 50 wt.% of ethylene-ethyl acrylate copolymer resin. The core of claim 1, wherein said crosslinked foamed sheet is foamed without using a heat-decomposable blowing agent of which a principal component is an ammonium compound, a formalin compound or a sulfur compound. The core of claim 1, wherein the expansion ratio is 20 to 40 times. The core of claim 1, wherein the expansion ratio is 25 to 35 times. The core of claim 1, wherein the crosslinked foamed sheet is wound around the core body in a single fold. A roll of photographic film which comprises the core of claim 1 and a rolled photographic film of which the substrate is made of plastic having a heat resistance (ASTM D-759) of more than 121° C (250° F) and a strength (ASTM D-882) of more than 48.265 MPa (7,000 psi). The roll of photographic film of claim 11, wherein the crosslinked foamed sheet contains more than 50 w.% of the polyethylene resin. The roll of photographic film of claim 11, wherein the polyethylene resin is linear low density polyethylene resin or a blend of a homopolyethylene resin and linear low density polyethylene resin. The roll of photographic film of claim 11, wherein the density of the polyethylene resin is 0.910 to 0.925 g/cm 3 . The roll of photographic film of claim 11, wherein the crosslinked foamed sheet contains more than 50 wt.% of ethylene-vinyl acetate copolymer resin. The roll of photographic film of claim 11, wherein the crosslinked foamed sheet contains more than 50 wt.% of ethylene-ethyl acrylate copolymer resin.

Inventors: AKAO MUTSUO, FUJII SHINICHI, ISHIZAKI KEIICHI, OSANAI HIROYUKI, TAKEUCHI TAKASHI, AKAO, MUTSUO, FUJII, SHINICHI, ISHIZAKI, KEIICHI, OSANAI, HIROYUKI, TAKEUCHI, TAKASHI, AKAO, MUTSUO, C/O FUJI PHOTO FILM CO., LTD., Fujii, Shinichi, c/o Fuji Photo Film Co., Ltd., Ishizaki, Keiichi, c/o Fuji Photo Film Co., Ltd., Osanai, Hiroyuki, c/o Fuji Photo Film Co., Ltd., Takeuchi, Takashi, c/o Fuji Photo Film Co., Ltd.
Applicants: FUJI PHOTO FILM CO LTD, FUJI PHOTO FILM CO., LTD.
Application year: 1992
Main classification: G03C1
IPC codes: G03C1, B65H75