PRINTING SHEETS

Abstract: A printing sheet shaped from a resin containing 5 to 80 wt. % of a fibrous electrically conductive filler less than 100 Ω·cm in volume resistivity, having 3 to 50 µm in average fiber length, 0.01 to 5 µm in average fiber diameter and 3 to 100 in aspect ratio and having a surface coated with an electrically conductive layer containing at least a tin oxide and an antimony oxide, or a printing sheet comprising a film substrate and a covering layer formed on at least one surface of the substrate and comprising a resin containing the above conductive filler.

Description: TECHNICAL FIELD The present invention relates to currency bills, securities and admission tickets. BACKGROUND ART Attempts have been made in recent years to use bills made by printing a resin film as substitutes for conventional paper currency. (The term "bill" as used herein includes paper currency and currency made from a resin sheet.) As compared with the conventional paper currency, these bills have the advantage of being superior in durability, water resistance and prevention of counterfeiting. However, resins generally have the drawbacks of being readily chargeable and difficult to print because of low wettability with ink. Resin films are liable to electrostatically adhere to one another during circulation and therefore difficult to count up or identify by machines, and further have the problem that bills of such film are difficult to count up manually since they are devoid of suitable surface roughness required of bills. EP-A-586846 discloses an ink jet recording sheet comprising a support and an ink-receiving layer containing a cation-modified non-spherical colloidal silica. The cation-modifier used is preferably hydrous aluminum oxide, hydrous zirconium oxide or hydrous tin oxide. EP-A-267535 discloses acicular electroconductive titanium oxide having an electroconductive surface layer comprising tin oxide and antimony oxide. JP-A-61-136532 discloses a fibrous white electroconductive substance comprising potassium titanate fiber, an antimony component and tin oxide. The substance may be added to paper, plastic, rubber etc. to obtain electrostatic copying paper, antistatic plastic, antistatic paints, or the like. An object of the present invention is to provide a currency bill, security or admission ticket which are free of all the problems including charging and which feel like paper currency. The present invention provides a currency bill, security or admission ticket comprising a substrate and printing on at least one side of said substrate, the substrate being made by shaping a resin composition containing 5 to 80 wt.% of a fibrous electrically conductive filler having a volume resistivity of less than 100 Ω cm, an average fiber length of 3 to 50 µm, an average fiber diameter of 0.01 to 5 µm and an aspect ratio of 3 to 100, and having a surface coated with an electrically conductive layer containing at least a tin oxide and an antimony oxide. We have conducted intensive research in view of the foregoing problems and consequently found that a sheet feeling like paper currency and free of any of the problems such as charging can be realized by using a resin having a fibrous material of specific shape incorporated therein. The fibrous conductive filler for use in the invention comprises a core material, for which various inorganic or organic fibrous materials of specified shape are usable. Examples of such materials usable are potassium tetratitanate fiber, potassium hexatitanate fiber, potassium octatitanate fiber, titania fiber, monoclinic titania fiber, aluminum borate fiber, magnesium borate fiber, alumina fiber, wollastonite, xonotlite, silicon nitride fiber, boron fiber, boron fiber, glass fiber, siliceous fiber, carbon fiber, cellulose fiber, polyester fiber and polyamide fiber. Among these, monoclinic titania fiber and potassium hexatitanate fiber are especially suited for fulfilling the object of the invention since these fibers have the feature of being relatively small in hiding power, therefore permit watermarking, and are further useful for reinforcing the resulting sheet. The fibrous conductive filler for use in the present invention comprises such a fibrous core material and a conductive layer formed thereon and containing at least a tin oxide and an antimony oxide. The conductive layer containing these oxides is suited to the contemplated use since the layer has high conductivity and is white. Although the method of covering the core material with the conductive layer is not limited specifically, it is desirable, for example, to simultaneously add an alkali and a hydrochloric acid solution of tin oxide and antimony oxide dropwise to a slurry of the core material to effect coprecipitation. While the amount of coating is suitably determined so that the resulting filler has a volume resistivity of less than 100 Ω·cm, preferably 10 -2 to 10 Ω·cm, usually used for coating are 5 to 100 parts by weight of tin oxide and 0.01 to 10 parts by weight of antimony oxide per 100 parts by weight of the core material. In addition to these oxides, an indium oxide, a cobalt oxide, etc. are also usable suitably. In this case, each or one of the additional oxides is used in an amount of about 0.01 to about 10 parts by weight per 100 parts by weight of the core material. These methods are disclosed in detail in JP-B-26933/1986, JP-B-4328/1987, JP-B-23221/1995, JP-B-54644/1995, JP-A-170860/1990, etc. Such fillers are commercially available under the brand names of "Dentall® WK300," and "Dentall® WK500" (both products of OTSUKA KAGAKU KABUSHIKI KAISHA). When the fibrous conductive filler is to be incorporated into a resin sheet itself, a resin and the fibrous conductive filler are mixed together by dry blending or by melting and kneading, and the mixture is formed into a sheet as by extrusion in a molten state, biaxial orientation, calendering or casting. The resin to be used is not limited specifically, but various resins are usable which can be made into a film or sheet. Specific examples of resins to be used are polyethylene resin, polypropylene resin and like polyolefin resins, polyethylene terephthalate resin, aramid resin, polyamide resin, polyetheretherketone resin, polyetherimide resin and polyimide resin. The proportion of the fibrous conductive filler relative to the resin can be suitably determined that the resulting sheet will have surface resistance in the range of 10 to 10 10 Ω and retain flexibility without impairment. The filler is used usually in a proportion of about 5 to about 80 wt. %, preferably about 10 to about 40 wt. %, of the combined amount of the resin and the filler. In preparing the currency bill, security or admission ticket of the invention, various methods are usable for the prevention of counterfeiting which include, for example, sandwiching metal tape yarns between the components of the sheet, or incorporating a magnetic material into the resin. Various inks are usable for printing the resin sheet obtained. Examples of printing methods usable are flexographic printing, gravure printing, offset printing, screen printing and ink-jet printing. The present invention will be described below in greater detail with reference to the following examples and comparative examples, in which the term "parts" means "parts by weight." The conductive fillers described below were used. Conductive Filler A A conductive filler comprising monoclinic titania fiber (core material), and a tin oxide (25 parts per 100 parts of the core material) and an antimony oxide(1 part per 100 parts of the core material) coating the surface of the fiber. Average fiber length 7 µm, average fiber diameter 0.2 µm and volume resistivity 1 Ω·cm. Conductive Filler B A conductive filler comprising potassium hexatitanate fiber (core material), and a tin oxide (25 parts per 100 parts of the core material) and an antimony oxide (1 part per 100 parts of the core material) coating the surface of the fiber. Average fiber length 15 µm, average fiber diameter 0.4 µm and volume resistivity 1 Ω·cm. Conductive Filler C A conductive filler comprising titania fiber (core material), and a tin oxide (25 parts per 100 parts of the core material) and an antimony oxide (1 part per 100 parts of the core material) coating the surface of the fiber. Average fiber length 4 µm, average fiber diameter 0.1 µm and volume resistivity 1 Ω·cm. Conductive Filler D A conductive filler comprising titania powder (core material), and a tin oxide (25 parts per 100 parts of the core material) and an antimony oxide (1 part per 100 parts of the core material) coating the surface of the powder. Average particle size 5 µm and volume resistivity 1 Ω·cm. Example 1 Polypropylene resin pellets were melted and kneaded in a twin-screw kneader. Conductive Filler A was charged in through a side hopper, and the mixture was extruded into a 100-µm -thick sheet, whereby a printing resin sheet of the invention was obtained. The resin sheet contained 30 wt. % of Conductive Filler A. Example 2 A printing resin sheet was prepared in the same manner as in Example 1 except that the filler was replaced by Conductive Filler B. Example 3 A printing resin sheet was prepared in the same manner as in Example 1 except that the filler was replaced by Conductive Filler C. Comparative Example 1 A printing resin sheet was prepared in the same manner as in Example 1 except that the filler was replaced by Conductive Filler D. Comparative Example 2 A printing resin sheet was prepared in the same manner as in Example 1 except that no filler was used. Test Example 1 The sheets obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were checked for static breaking energy (kg· cm/cm 3 ). The results obtained were Example 2>Example 1>Example 3>>Comparative Example 1>Comparative Example 2. Example 2 180, Example 1 171, Example 3 168, Comp. Ex. 1 133, Comp. Ex. 2 120. Test Example 2 The sheets obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were checked for surface resistance value (ASTM D257) with the following results. Example 1: 3.0 × 10 8 Ω , Example 2: 5.0 × 10 7 Ω, Example 3: 3.0 × 10 8 Ω, Comparative Example 1: 3.0 × 10 10 Ω, Comparative Example 2: 4.0 × 10 15 Ω. Test Example 3 The sheets obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were checked for surface smoothness (Ra, average surface smoothness, µm). The results obtained were Comparative Example 2<<Example 2 Example 1 Example 3<Comparative Example 1. Comp. Ex. 2 0.10 µm, Example 2 0.30 µm, Example 1 0.28 µm, Example 3 0.32 µm, Comp. Ex. 1 0.62 µm. INDUSTRIAL APPLICABILITY The currency bill, security and admission ticket of the present invention are shaped from a conductive resin composition containing a fibrous material of specified shape, are therefore given a feel resembling that of paper currency, have improved tear strength, and are prevented from charging and extremely convenient for printing and handling. They further have the advantage of being less prone to cause troubles such as jams when mechanically handled as by vending machines or automated teller machines (ATMs).

Claims: A currency bill, security or admission ticket comprising a substrate and printing on at least one side of said substrate, the substrate being made by shaping a resin composition containing 5 to 80 wt.% of a fibrous electrically conductive filler having a volume resistivity of less than 100 Ω cm, an average fiber length of 3 to 50 µm, an average fiber diameter of 0.01 to 5 µm and an aspect ratio of 3 to 100, and having a surface coated with an electrically conductive layer containing at least a tin oxide and an antimony oxide. A currency bill, security or admission ticket according to claim 1 wherein the volume resistivity is 10 -2 to 10 Ω cm. A currency bill, security or admission ticket according to claim 1 or 2 wherein the fibrous material comprises monoclinic titania fiber or potassium hexatitanate fiber.

Inventors: HAREYAMA YUKIYA, OGAWA HIDETOSHI, HAREYAMA, YUKIYA, OGAWA, HIDETOSHI, HAREYAMA, Yukiya, Otsuka Kagaku K. K., OGAWA, Hidetoshi, Otsuka Kagaku K. K.
Applicants: OTSUKA KAGAKU KK, OTSUKA KAGAKU KABUSHIKI KAISHA
Application year: 1997
Main classification: C08K9
IPC codes: C08J5, C08K7, B32B27, B32B7, B32B9, B41M5, C08K9