TRANSFER PAPER FOR IMPARTING SOLID PATTERN AND PROCESS FOR ITS PRODUCTION

Abstract: A transfer paper comprising a base sheet having prov­ ided thereon a release layer on which a predetermined pat­ tern is transferred from a printing sheet, and a process for producing the transfer paper which comprises extruding a thermoplastic resin having a releasability between a base sheet and a printing sheet having printed thereon a pre­ determined pattern to thereby transfer the pattern to the sur­ face of the thermoplastic resin, cooling the assembly, and releasing the printing sheet apart from the surface of the thermoplastic resin. Thus a transfer paper which can provide a solid or perspective pattern by combination of lusters and tones of various degrees can be produced inexpensively with ease.

Description: The invention relates to a method for transferring a three-dimensional pattern provided on a printing sheet to a transfer sheet and to a transfer sheet for transferring a three-dimensional pattern and further particularly pertains to transfer sheets capable of imparting at low price and with ease three-dimensional and perspective patterns having combinations of lusters and tones of various grades produced by way of printing. As a method of imparting three-dimensional patterns on floor materials formed of papers or plastic sheets, synthetic leathers, etc., the embossing process has been widely practiced from old days. The general way of embossing process is to preheat a sheet-shaped material, to impress a concavo-convex pattern from an embossing roll in which the specified pattern is carved, followed by cooling, and then, to take up the product. In GB-A-897313 a method of embossing laminated material consisting of a thin thermoplastic film and a base sheet of thermoplastic material is described, wherein the film and the backing sheet (base sheet) are embossed simultaneously by an embossing element. In the embossing step the backing sheet with the coating is heated, then passed through between the embossing roll and the backing roll together with the printed thermoplastic film. The printed thermoplastic film is forced into engagement with the coating on the backing sheet and both are embossed simultaneously. The embossed and printed film is separated from the coating and the backing sheet. However, the conventional embossing process involves problems such as: 1 ○ embossing rolls on which the specified patterns are carved, equal in number to said patterns, need to be prepared, inevitably resulting in high installation cost; 2 ○ since the luster of the embossed surface is normally uniform, it is not easy to create subtle modelings and external appearances of perspective and three-dimensional patterns due to grades of luster by differentiating the luster part by part; 3 ○ under roll forming technical restrictions, the freedom of the picture pattern is naturally limited; and 4 ○ the embossing roll needs to be replaced every time the pattern is changed, with inevitable disadvantage in work efficiency, which is fatel particularly in the case of multi-item small amount production. Hence the technical problem underlying the invention is to provide a method for easily transferring subtle three-dimensional patterns, which needs low installation costs, without restriction of the pattern dimensions and forms, wherein many different patterns can be transferred in small amounts with good working efficiency. This technical problem is solved by the features of claims 1 to 6. Fig. 1 is a schematic diagram illustrating the equipment used in Example 1. According to this invention, on the printing sheet of synthetic resin on which the pattern is printed, no limitation is particularly placed, except that it shall have high enough heat resistance to bear the temperature at which the pattern printed on said sheet is transferred to the transfer sheet; for example, it includes sheets (or films) of polyesters like PBT and PET, polyamides, plycarbonates and polypropylene. The base materials used for the transfer sheet of this invention are not particularly limited, except that they shall have high enough heat resistance to bear the temperature at which the pattern transferred to said transfer sheet is copied on the sheet like plastic sheet, etc., to which the stereographic pattern is to be imparted (hereinafter referred to as object sheet); as such materials, papers, cloths, synthetic resin sheets (films) such as of polyesters like PBT and PET, polyamides, polycarbonates, polyacetals, polypropylene, metal foils and laminates of metal foils and synthetic resin sheets (films) may be mentioned. It should be noted that when, for example, paper is used as the base material, normally the amount used ranges from 110 ∼ 150 g/m² in the conventional embossing process, but in the method of this invention, adequate amount is on the order of 40 ∼ 60 g/m². The release able thermoplastic resin layer used according to this invention is not limited, except that it can bear the temperature at which the transfer is done on such an object sheet as plastic sheet, etc.; for example, releasable thermoplastic resins such as poly-4-methyl-pentene-1 (TPX), polypropylene and ethylene-propylene copolymer, silicone resin, and mixtures of these with additives for giving the releasable property should preferably be utilized. Any releaseable thermoplastic resin layer thickness will do, but the usual thicknesses in the embossing process of more than 25 µm are not necessary, about 5 ∼ 20 µm being satisfactory. The forming of the release able thermoplastic resin layer on the base material is done by extrusion, which provides high productivity and work efficiency. The print in sheet used in this invention is formed by appropriately combining in varied quantities and colors powders or granules usable for the printing, such as metal powders, ceramic powders and metal oxides, besides inks and pigments, or by varying the particle diameters, configurations, and degrees of dispersion, to have combinations of various grades of lusters and tones. The pattern may be either design, picture, character, letter or code, but is not particularly limited thereto. As the method for transferring the aforementioned printing sheet pattern to the transfer sheet, by the method of extrusion, the two processes _ laminating the base material and the release able thermoplastic resin layer, that is, manufacturing the transfer sheet, and transferring the printed pattern to said releasable thermoplastic resin layer _ is performed simultaneously. This is quite advantageous. For the extrusion process, the most preferable is the so-called sandwich laminating process in which the base material is fed in from one side, while the printing sheet is brought in from the other side, and between them, a releasable thermoplastic resin is extruded. It is, of course, possible to preferably adopt the method of first extruding a releasable thermoplastic resin on a base material, thereby forming a molten resin layer, and then, laminating the printing sheet with them, thereby transferring the pattern to said molten resin layer. In whichever case, by peeling off and separating the printing sheet from the release able thermoplastic resin layer after cooling, a transfer sheet with the printing sheet's pattern transferred to its surface may be obtained. For imparting the three-dimensional patterns using the transger sheets obtained in this way, various methods may be employed. For example, after heating the object sheet by use of a preheating roll or an infrared heater, it is fed to under a press or between pressuring rollers, together with the transfer sheet of this invention, to transfer under pressure the pattern on the transfer sheet to the surface of said object sheet, followed by cooling, and then, the transfer sheet is peeled off and separated therefrom, yielding a sheet to which the pattern has been imparted. In the case of resin, a method of laminating said resin layer on the transfer sheet by coating or extrusion process, followed by cooling, and then, peeling it off is applicable; and in the case of ink (containing resin) or metal vapor deposited layer, the method of heating and pressuring from back, followed by cooling, and then, peeling off the transfer sheet, and the like methods may be applied. When the transfer sheet of this invention is applied on metal vapor deposited layers, frosted lusters and tones will be obtained; accordingly, the pattern will be gradated and give weighty maganificent appearances, to be suitable for use on members of "byobu" (folding screen), "fusuma" (sliding partitions), wall papers, ceilings, picture frames, tea utensils, Buddhist altar fittings, marking tapes, etc. On the other hand, by direct metal vapor deposition on the transfer sheet of this invention, more lustrous and clear patterns, as compared with the aforementioned products, may be produced. This method is suitable for producing light reflecting labels, etc., besides the similar uses as above-mentioned. The object sheet to which the stereographic pattern is to be imparted is not particularly limited. Resin (including expanded matters) sheets (films) and metal vapor-deposited layers, etc. may be mentioned as examples. The three-dimensional pattern imparting method by use of the transfer sheet of this invention may be jointly used with the embossing process. In that way, unique modelings having both the microscopic and delicate three-dimensional and perspective feelings due to the luster grades of this invention and the macroscopic and dynamic three-dimensional and perspective feelings due to the concavo-convex surfaces of embossing becomes practical, whereby patterns more copious in varieties can be offered. In the following, the present invention will be explained in connection with its preferred embodiment, but it will not be restricted thereby. Example 1. Using the equipment shown in Fig. 1 and with use of polypropylene (manufactured by Mitsui Petroleum Chemical Company "LA221") as a releasable thermoplastic resin, extrusion was made from a T die extrusion laminator (1) (diameter 115 mm, L/D25) under conditions of T die outlet resin temperature 290°C and screw resolution 130 rpm. A quality paper (52.3 g/m²) was used as the base material (4); the surface to be in contact with the aforementioned resin (molten film) (5) was subjected to corona discharge treatment (30 W/m²/min). On the other hand, a printing sheet (6) was so arranged as to bring the specified pattern printed on the surface thereof in contact with the aforementioned resin. These two parties were pressure-bonded (pressure 35 kg/cm²) by means of a press roll (2) with the resin pinched between them (generally called polysandwich), whereby a laminating process was run at a rate of 150 m/min and to a resin thickness of 20 µm and a formed width of 1600 mm. Then after cooling on a cooling roll (3), said laminate (printing sheet/resin/base material) (7) was integrally wound on a take-up reel (8). Then by peeling the printing sheet (6) from the resin surface of the laminate thus taken up, a transfer sheet to which the intended pattern was exactly transferred was obtained. As this transfer sheet was coated with urethane resin, followed by cooling, and then, released therefrom, a urethane resin sheet to which a delicate stereoscopic pattern was imparted was obtained. By making metal vapor deposition on the urethane resin sheet to which the stereoscopic pattern had been imparted, a sheet suitable for use as a marking tape or on "byobu", etc. was obtained. Possibility of Industrial Utilization As described above the undermentioned advantages will be derived from this invention: 1 ○ It is proper to prepare a printing sheet in place of the conventional stamping roll; therefore, the installation cost will be greatly cut down. 2 ○ The pattern drawing by printing is by far easier and highly diversified, as compared with carving of roll surface, thus contributing to conspicuous enhancement of pattern's freedom and improvement in cultural lives. 3 ○ Microscopic and delicate three-dimensional perspective feelings which can not be achieved by the conventional embossing process are realizable. 4 ○ Expression of the unique pattern possessing both the microscopic and delicate three-dimensional perspective feelings obtaines by this invention and the macroscopic and dynamic three-dimensional and perspective feelings obtained by the embossing process is made possible through its combination with the latter. 5 ○ Change of pattern may be made merely by replacing the printing sheet. Accordingly, this method is particularly suitable for multi-item small production. 6 ○ Since thin base materials and release able thermoplastic resin layers are usable, as compared with the conventional embossing process, the material costs are greatly cut down for the benefit of economy. 7 ○ Productivity of "byobu" and "fusuma", etc. is very low, requiring high degree of proficiency, because they are formed by a method of joining a plural number of metal foils. When the transfer sheet of this invention is utilized, exactly the same appearance as the conventional joined metal foils can be produced with ease and in large quantity with a sheet formed by metal vapor deposition, thus making it possible to offer low priced "byobu" and "fusuma" without requiring high degree of skill. And may other advantages will be derived.

Claims: 1. A method for transferring a three-dimensional pattern provided on a printing sheet to a transfer sheet, comprising the steps of: a) extruding a releasable thermoplastic resin between a base material (4) and the printing sheet (6) resulting in a laminate; b) cooling the laminate; and c) peeling off the printing sheet (6) resulting in a transfer sheet. 2. Method according to claim 1, wherein the base material is selected from papers, cloths, synthetic resins, metal foils, laminates of metal foils and synthetic resins. 3. Method according to claim 1 or 2, wherein the releasable thermoplastic resin is formed of at least one member selected from poly-4 -methyl pentene-1, polypropylene, ethylene-propylene, copolymer and silicone resins. 4. Method according to anyone of claims 1 to 3, wherein the printing sheet is made of a synthetic resin. 5. Method according to claim 4, wherein the synthetic resin of the printing sheet is at least one member selected from polyesters, polyamides, polycarbonates and polypropylene. 6. Transfer sheet for transferring a three-dimensional pattern producible with the method of anyone of claims 1 to 5 comprising a base material (4) and an extruded layer of releasable thermoplastic resin on the base material (4), wherein the pattern is formed on the exposed surface of the extruded layer.

Inventors: OHARA, SHUZO, TOKUNO, ISAO
Applicants: GOYO PAPER WORKING CO. LTD.
Application year: 1986
Main classification: B44C1
IPC codes: B32B33, B32B15, B44C1, B29C59