PRINTING MATERIAL SET FOR PREPARING BAR-CODE LABELS

Abstract: Printing material sets for preparing bar-de labels by pressure-sensitive printing comprise (a) a first, printing, tape (6) comprising a film (1) carrying on the inside surface thereof micro-capsules (2) containing a dispersion of minute particles of a pigment in a solution of an adhesive compo­ nent in an organic solvent and (b) a second tape (7) comprising a strippable tape (5) on the upper surface of which papers (3) for bar-code labels are removably attached by adhesive (4), said printing tape (a) being superposed on said second tape (b) (7).

Description: The present invention relates to a printing material set for preparing bar-code labels by pressure-sensitive printing, by which bar-code labels utilized in the statistical treatment of data such as the names, prices and weights of commodities are simply prepared and utilized. Bar-code labels have hitherto been prepared by transcription using sheets of ordinary paper and ink. In addition to this method, a method has been devised in which printing is effected using simplified printers fitted to carbon paper, heat-sensitive paper or magnetic tape. However, according to the above-mentioned printing system, for instance, in the method using ink, the hands of the printer operator are apt to become stained when changing the ink-roller, printed images are apt to be uneven and special means are necessary to stabilize the printed image against friction. When using heat-sensitive paper, because of the co-existence of the colour-developer and the colour-coupler on the upper surface of the label even after printing, stains are apt to be caused by coloring due to post-heating of the material. In the case of carbon paper, the transcribed pigment and wax are adhered onto the surface of the label. Accordingly, the distinctness of the image is deteriorated by heat and/or friction. The above-mentioned defects are causes of reduction of the accuracy with which the printed images are read. The reduction is particularly remarkable when printing the bar-codes and attaching the printed labels onto articles. DE-A-2407822 discloses a self-adhesive record carrier, such as an adhesive label, composed of a base paper, an adhesive layer on the back, a non-stick silicone layer or the like and a disposable backing sheet. Pressure sensitive microcapsules containing a colour-former are provided together with a colour-generating reagent layer. The base paper or the backing sheet of the adhesive label contains at least one of the two layers. The record carrier is described as for use in a factory. For example, an original carrier in front can be used as an order confirmation, the adhesive layer can be used as an information carrier for goods during the production sequence, storage and transport, and further duplicate carriers can be used for controlling production, storage and transport, as a consignment note or the like. There is no mention of bar-code labels. The present invention provides a printing material set for preparing labels by pressure-sensitive printing, comprising an adhesive label which comprises a base paper, an adhesive layer and a backing sheet and, on top, a carrier which comprises a base which carries a coating of micro-capsules on its back, characterised in that the set comprises (a) a first, printing, tape comprising a plastic film as the base of the carrier, the micro-capsules containing a dispersion of minute particles of a pigment in a solution of an adhesive component in an organic solvent and (b) a second tape as the backing sheet comprising a strippable tape on the upper surface of which, as the base paper, papers for bar-code labels are removably attached by the adhesive, said printing tape (a) being superimposed on said tape (b). The printing material set of the present invention overcomes the defects of bar-code labels prepared by conventional methods. The present inventors have found that by using microcapsules containing a dispersion of minute particles of a pigment in a solution of an adhesive component in an organic solvent, while without using a colour-developer, the reduction of the accuracy of reading the printed images of the bar-code label is improved. The invention will be described with reference to Figures 1 to 3, in which: Figure 1 and Figure 3 are partial cross-sections of a printing material set of the present invention, and Figure 2 is a plan view of a bar-code label produced by a printing material set of the present invention. The present invention also provides the use of a printing material set as defined above to prepare bar-code labels. In use the first, printing, tape and the papers for bar-code labels are pressed together such that those microcapsules which contact the papers for bar-code labels break. The printing material set for preparing bar-code labels according to the present invention includes (i) those in which the papers for bar-code labels have been attached continuously at spaced intervals on the strippable tape and (ii) those in which paper for bar-code labels having perforations at regular intervals is attached continuously to the strippable tape, for both printing at any time and attaching the bar-code labels at any time to commodities. The present invention will be explained in more detail while referring to the drawings which show a printing material set according to the present invention. Figs. 1 and 3 show an enlarged vertical section of a printing material set according to the present invention, wherein a printing tape (6) comprises a plastic film (1) and micro-capsules (2 )containing the dispersion of minute particles of a pigment in a solution of an adhesive component in an organic solvent carried on the inside surface of the film (1), the bar-code label tape (7) comprises papers (3) for bar-code labels and a strippable tape (5), the papers (3) have the adhesive (4) on the undersurface thereof, the strippable tape (5) carries the papers (3) and is removably attached at predetermined intervals or with perforations to the adhesive (4), and the printing tape (6) is superposed on the bar-code label tape (7). In pressure-sensitive printing wherein the printing material set is used for forming bar-codes clearly on the papers for bar-code labels, it is necessary that the percussion pressure of the printer is large enough to uniformly break the microcapsules on the percussed part. For that purpose, the film carrying the microcapsules has a uniform thickness of, for instance, less than 30 µm, preferably from 6 to 20 µm. It is preferred that the printing tape itself is not broken by the percussion pressure of the printer. The microcapsules carried on the film can be produced by the method for producing microcapsules for use in conventional pressure-sensitive recording papers (EP-A-0046415). The size of the minute particles of pigment contained within the microcapsules is preferably less than 50 nm, particularly less than 30 nm. When the size is over 50 nm, the transfer of the minute particles of pigment from the microcapsules is not effected favorably, resulting in insufficient density of the coloured image. In addition, the content of the minute particles of pigment in the core material is preferably less than 25 % by weight, more preferably 5 to 20 % by weight, of the dispersion. Sufficient transfer of the minute particles of pigment from the microcapsules is not effected when the content is over 25 % by weight. Minute particles of a pigment having a deep colour are preferably used; minute particles of carbon are most preferred. The adhesive component which is contained within the microcapsules may be anything so long as it is soluble in an organic solvent and is able to adhere the minute particles of pigment transferred from the microcapsules after breaking thereof on the surface of the label. As the adhesive component, polystyrene, polyacrylates, polymethacrylates, low-molecular polyethylene, ethylcellulose, natural rubber and chloroprene rubber may be exemplified. The weight ratio of the adhesive component to the minute particles of pigment is generally from 8 : 2 to 2 : 8. The adhesive component is generally contained in the range of from 1.5 to 30 % by weight of the dispersion. A coloured dyestuff may be further contained in the microcapsules if necessary. As such a dyestuff, monoazo dyes, bisazo dyes, monoazo metal complex dyes, anthraquinone dyes, phthalocyanine dyes and triarylmethane dyes may be exemplified. The coloured dyestuff is generally contained in the range of from 0.15 to 10 % by weight of the dispersion. As the organic solvent for dissolving the adhesive component and dyestuff, alkylbenzenes such as toluene and xylene, diarylmethanes, diarylethanes, alkylbiphenyls and alkylnaphthalenes may be, for example, mentioned. To carry the microcapsules on the inside surface of the film, for instance, a suspension of microcapsules in a latex is preferably coated on the inside surface of the film and dried. Any tape may be used as the strippable tape so far as the papers for bar-code labels are attached removably to an adhesive. Although the "papers for bar-code labels" include all papers for recording, coating paper, art paper and synthetic paper are preferably used. In addition, the "strippable tape" may be any base material so long as it is easily detachable from the adhesive carried on the undersurface of the papers for bar-code labels. Accordingly, it does not necessarily mean a sheet of paper but also a sheet of plastic material. The adhesive is selected according to the material of the papers for bar-code labels, and the strippable tape material may be selected according to the kind of adhesive. In order to print bar-codes on the papers (3) using the superposed printing tape (6), the printing is carried out by impressing a predetermined figure of bar-codes on the upper surface of the printing tape (6) (namely, the plastic film (1)) with a percussion pressure, for example obtained by using a bar-printer or dot-printer. The printing of the bar-codes on the surface of the paper for bar-code labels is accomplished simultaneously with the impressing. As a result of rapid evaporation of the solvent for the adhesive component and dye-stuff from the paper for bar-code labels, the printed bar-codes on the label are fixed in a stable state soon after the printing, are not stained even by friction and are maintained distinctly even after several months. The characteristic feature of the performance of the printing material set for preparing bar-code labels according to the present invention is that the minute particles of a pigment dispersed in the solution of the adhesive component are released from the microcapsules which have been broken by the percussion pressure of printing, and rapidly adhere to the papers for bar-code labels. After evaporation of the solvent, the minute particles of pigment adhere to the papers firmly and are maintained in a stable state. Accordingly, according to the present invention, the defects seen in conventional printing material sets for preparing bar-code labels by pressure-sensitive printing, such as staining, reduction of the distinctness of the printed bar-code and stains due to friction, are profitably improved. EXAMPLE 1 : 1-1: Preparation of two prepolymers After adjusting the pH of 162 g of an aqueous 37 % solution of formaldehyde (hereinafter referred to as formalin) by the addition of aqueous 2 % solution of sodium hydroxide to 9.0, it was mixed with 63 g of melamine, and the mixture was brought into reaction while stirring at 70°C. Just after confirming the complete dissolution of melamine in the reaction mixture, 225 g of water were added, and the mixture was stirred for 3 min to obtain an aqueous solution of a prepolymer of a melamine-formaldehyde resin (hereinafter referred to as M4F prepolymer, M4F meaning that the molar ratio of m elamine to f ormaldehyde is 1 : 4 in the prepolymer). Separately, after adjusting the pH of 146 g of formalin by the addition of triethanolamine to 8.5, it was mixed with 60 g of urea, and the mixture was brought into reaction for 1 hour at 70°C to prepare an aqueous solution of a prepolymer of urea-formaldehyde resin (hereinafter referred to as U 1.8 F prepolymer). 1-2: Preparation of an oily dispersion Into 670 g of diisopropylnaphthalene, 50 g of polystyrene (DICELASTYRENE®, made by DAINIPPON INK Chem. Co., Ltd.) were dissolved, and in the solution obtained 85 g of carbon black (made by MITSUBISHI KASEI Co., Ltd., #33, size of 28 nm) was dispersed. 1-3: Microcapsulation A mixture consisting of 100 g of M4F prepolymer (refer to 1-1), 50 g of U 1.8 F prepolymer (refer to 1-1), 10 g of an aqueous solution of a water-soluble cationic urea resin (Uramine® P-1500, made by URAMINE Ind. Co., Ltd.), 210 g of water and 1 g of triethanolamine was adjusted to pH 5.2 by the addition of an aqueous 10 % solution of citric acid. By mixing the mixture with 3 g of an aqueous 10 % solution of NEOPELEX® No. 6 (sodium dodecylbenzenesulfonate, made by KAO-ATLAS Co., Japan) a solution called "A-liquid" was obtained. Into the A-liquid, 100 ml of the oily dispersion were dispersed so that the mean diameter of the oily dispersed particles was about 3 to 15 micrometers. The thus obtained aqueous dispersion was brought into reaction for 25 hours while gently stirring and maintaining the aqueous dispersion at a temperature of 30°C, and after adding an aqueous 10 % solution of citric acid to the aqueous dispersion to adjust the pH of the dispersion to 3.0, the aqueous dispersion was continuously reacted under stirring to obtain a slurry of microcapsules encapsulating an oily dispersion of carbon black together with the adhesive. EXAMPLE 2 : 2-1: Preparation of two prepolymers After adjusting the pH of 162 g of formalin by the addition of an aqueous 2 % solution of sodium hydroxide to 9.0, it was mixed with 63 g of melamine, and the mixture was brought into reaction while stirring at 70°C. Just after confirming the complete dissolution of melamine in the reaction mixture, 225 g of water were added, and the mixture was stirred for 3 min to obtain an aqueous solution of a prepolymer of melamine-formaldehyde resin (M4F prepolymer). Separately, after adjusting the pH of 146 g of formalin by the addition of triethanolamine to 8.5, it was mixed with 60 g of urea, and the mixture was brought into reaction for 1 hour at 70°C to prepare an aqueous solution of a prepolymer of urea-formaldehyde resin (U 1.8 F prepolymer). 2-2: Preparation of an oily dispersion Into 670 g of diisopropylnaphthalene, 1 g of an oil-soluble dyestuff (OIL BLUE BOS, made by Orient Chem. Co., Ltd.) and 50 g of polystyrene (DICELASTYRENE®, made by DAINIPPON INK Chem. Co., Ltd.) were dissolved, and in the solution obtained 78 g of carbon black (made by MITSUBISHI KASEI Co., Ltd., #33, size of 28 nm) was dispersed. 2-3: Microcapsulation A mixture consisting of 100 g of M4F prepolymer (refer to 2-1), 50 g of U 1.8 F prepolymer (refer to 2-1), 10 g of an aqueous solution of a water-soluble cationic urea resin (Uramine® P-1500, made by URAMINE Ind. Co., Ltd.), 210 g of water and 1 g of triethanolamine was adjusted to pH 5.2 by the addition of an aqueous 10 % solution of citric acid. By mixing the mixture with 3 g of an aqueous 10 % solution of NEOPELEX® No. 6 (sodium dodecylbenzenesulfonate, made by KAO-ATLAS Co., Japan) a solution called "A-liquid" was obtained. Into the A-liquid, 100 ml of the oily dispersion (refer to 2-2) were dispersed so that the mean diameter of the oily dispersed particles was about 3 to 15 micrometers. The thus obtained aqueous dispersion was brought into reaction for 25 hours while gently stirring and maintaining the aqueous dispersion at a temperature of 30°C, and after adding an aqueous 10 % solution of citric acid to the dispersion to adjust the pH of the dispersion to 3.0, the aqueous dispersion was continuously reacted under stirring to obtain a slurry of microcapsules encapsulating an oily dispersion of carbon black together with the adhesive and the coloured dyestuff. EXAMPLE 3 : Preparation of printing material set : The microcapsules obtained in Examples 1 and 2 were suspended in a latex of polyvinylidenechloride, and then each suspension of the microcapsules was applied on the surface of a tape of a polyethylene film 15 µm thick. Each coated polyethylene tape was superposed on the bar-code label tape comprising coated paper for bar-code labels, a natural rubber adhesive and paper coated with silicone resin as a strippable tape. Preparation of bar-code label : Each printing material set as shown in Fig. 3 was printed by applying a percussion pressure and the printed images shown in Fig. 2 were fixed on the surface of the paper for bar-code labels. The printed images were not stained by friction and were maintained distinctly even after one year.

Claims: A printing material set for preparing labels by pressure-sensitive printing, comprising an adhesive label which comprises a base paper, an adhesive layer and a backing sheet and, on top, a carrier which comprises a base which carries a coating of micro-capsules on its back, characterised in that the set comprises (a) a first, printing, tape (6) comprising a plastic film (1) as the base of the carrier, the micro-capsules (2) containing a dispersion of minute particles of a pigment in a solution of an adhesive component in an organic solvent and (b) a second tape (7) as the backing sheet comprising a strippable tape (5) on the upper surface of which, as the base paper, papers (3) for bar-code labels are removably attached by the adhesive (4), said printing tape (a) (6) being superimposed on said tape (b) (7). A printing material set according to claim 1, wherein the size of said minute particles of pigment is less than 30 nm. A printing material set according to claim 1 or 2, wherein said minute particles of pigment are minute particles of carbon. A printing material set according to any one of the preceding claims, wherein the weight ratio of said adhesive component to said minute particles of a pigment in said dispersion is from 8 : 2 to 2 : 8. A printing material set according to any one of the preceding claims, wherein said adhesive component comprises from 1.5 to 30% by weight of said dispersion. A printing material set according to any one of the preceding claims, wherein said adhesive component is a polystyrene, polymethacrylate, polyacrylate, low-molecular weight polyethylene, ethylcellulose, natural rubber or chloroprene rubber. The printing material set according to any one of the preceding claims, wherein said dispersion further comprises a coloured dyestuff dissolved in the organic solvent. A printing material set according to claim 7, wherein said coloured dyestuff is selected from monoazo dyes, bisazo dyes, monoazo dyes of metal complex type, anthraquinone dyes, phthalocyanine dyes and triarylmethane dyes. A printing material set according to claim 7 or 8, wherein said coloured dyestuff comprises from 0.15 to 10 % by weight of said dispersion. A printing material set according to any one of the preceding claims, wherein said organic solvent is selected from alkylbenzenes, diarylmethanes, diarylethanes, alkylbiphenyls and alkylnaphthalenes. A printing material set according to any one of the preceding claims, wherein said film (1) has a thickness of from 6 to 20 µm. Use of a printing material set according to any one of the preceding claims to prepare bar-code labels.

Inventors: AHIKO, NOBUO, IGARASHI, YURIKO, OKADA, YOSHIO
Applicants: KUREHA KAGAKU KOGYO KABUSHIKI KAISHA
Application year: 1985
Main classification: G09F3
IPC codes: B41M5, G06K19, G09F3, B42D15, B41J3