Marking method using energy rays and marked molding

Abstract: The making method of forming a mark on a molding of the invention includes the steps of (a) feeding a film having a first surface and a second surface positioned at the back side of the first surface, (b) preparing a paint-containing film having a paint layer of lower heat resisting temperature than the film on one side, by disposing a paint containing a paint component on the first surface of the film, (c) positioning the paint containing film on the surface of a molding so that the surface of the paint layer may contact with the surface of the molding, and (d) forming a mark by emitting an energy ray from the second surface side of the paint-containing film, and transferring and disposing the paint component contained in the paint layer positioned on the first surface of the illuminated portion on the surface of the molding, thereby forming a mark. The molding is a resin molding formed of a material containing resin. In this constitution, a mark with a desired color can be formed on a molding. The mark is formed easily and inexpensively. A mark having an excellent wear resistance is formed. A mark having an excellent precision is easily formed on the surface of a molding having a complicated shape.

Description: FIELD OF THE INVENTION The present invention relates to a marking method of displaying characters and patterns on moldings by laser beam, electron beam, heat ray or other energy ray, and to marked moldings BACKGROUND OF THE INVENTION The following methods have been known conventionally as the marking method on resin molding by using energy ray such as laser beam. As disclosed in Japanese Patent Publication No. 61-11771 and Japanese Patent Publication No. 62-59663, a resin is mixed with a filler which is deformed by the actin of laser beam or energy ray, and the mixture is injection-molded to obtain a resin molding, and this resin molding is exposed to energy ray such as laser beam to be partly discolored, so that a desired character or pattern is formed. As disclosed in Japanese Laid-open Patent No. 60-4094 and Japanese Laid-open Patent No. 1-267092, a plurality of coat films are formed on the surface of a resin molding by applying paints of different colors preliminarily, and only the surface layer or a plurality of coat films are removed partly by emitting laser beam, so that a desired is left over. EP 0 605 803 discloses a process for marking plastics, in which a base material which is provided with a sublimable dyestuff is pressed against the plastic to be marked and in which the plastic surface is provided with colored characters or symbols by means of a laser emitting in the visible wavelength range. EP 0 201 627 discloses a process in which, with the aid of a directable laser beam, a material capable of being sublimed is diffused in a gaseous phase into the surface area region as a graphic character of any colour. WO95/13195 discloses a transfer printing medium that includes a carrier to which is applied a curable laser-transferable ink having one or more layers. The transfer medium is capable of converting laser energy to heat. The ink includes at least one colorant, at least one polymerization initiator and at least one curable prepolymer. The ink transfers to a surface of interest and cure in one step upon application of laser energy. Specific conventional methods are described below while referring to Fig 9 and Fig 10. Fig 9 is a front view for explaining a method of discolouring the filler in the resin molding, and Fig 10 is an essential sectional front view for explaining a method of removing the coat film of the paint on the resin molding. In Fig 9, the surface layer containing a paint powder 4 which is discoloured by the action of laser beam is formed on the surface of a resin molding 3. A laser beam 1 controlled by a deflection device 2 is emitted to the surface layer, and the portion exposed to the laser beam is changed in colour, and a mark 5 is formed. As the laser beam 1 is emitted by deflection control according to the desired character or pattern, the mark 5 is formed on the surface layer of the resin molding 3. In Fig 10, three colour paints are applied sequentially on the surface of a resin molding 6, and three layers of coat films 7, 8, 9 are formed. A laser beam 1 controlled by a deflection device 2 is controlled in reflection according to the emitting position corresponding to a desired character or pattern, and is also controlled in the amount of energy, and is emitted to the surface coat film 7 side of the resin molding 6. Depending on the amount of energy, the coat film, 7 coat film 8 or coat film 9 having a different color is cut off, and characters and patterns having different colors are formed as required. However, in the conventional marking method by making use of discoloration of the filler of the resin molding by laser beam, characters or patterns of different colors cannot be formed on one resin molding. On the other hand, in the conventional marking method by removing the coat film partly by irradiation with laser beam by preliminarily formed coat films on the surface of the resin molding, by forming coat film layers in multiple layers by different colors, combination of various color marks is possible, but it requires more steps in coating and drying. It is hence an object of the invention to present a method of marking desired characters or patterns, and making the molding with different colors, not limited in mark color, at low cost. SUMMARY OF THE INVENTION The present invention provides a method of forming a mark on a molding, comprising the steps of: (a) providing a film having a first surface and a second surface (b) disposing a paint on said first surface of said film, said paint having lower melting point than said film, said paint including an adhesive having a peelable tacky adhesiveness (c) positioning said film on a surface of the molding and pressing a deformable elastic piece from said second surface side of said film so that the first surface of said film on which said paint is disposed conforms to the shape of the surface of said molding and said paint adheres to the surface of said molding then releasing said elastic piece from said second surface whereby said film is maintained in a position conforming to said shape of the surface of the molding, (d) forming the mark by irradiating an energy ray onto a predetermined portion of said second surface of said film, wherein said paint positioned on a portion of the first surface of the film adjacent to said predetermined portion is transferred and disposed onto the surface of the said molding. Preferably, the molding is a resin molding formed of a material containing resin. Preferably, the molding has at least one surface selected from the group consisting of (i) curved surface, (ii) concave surface, (iii) convex surface, (iv) convexo-concave surface, and (v) flat surface. Preferably, the molding has a coarser surface roughness than the first surface of the film. Preferably, the energy ray is controlled in emitting position by a deflection device. Preferably, the energy ray is emitted to the paint layer by passing through the film without causing effects on the film. Preferably, the energy ray is a laser beam. Preferably, the paint component has a specific color, and the mark has the specific color. Preferably, the paint component contains at least one of dye and pigment. Preferably, the paint component can be melted by irradiation with the energy ray, and when the paint containing film is irradiated with the energy ray, the paint component is melted and tranferred to the surface of the molding. Preferably, the paint component can be sublimated when irradiated with the energy ray, and when the paint-containing film is irradiated with the energy ray, the paint component is sublimated and transferred to the surface of the molding. In this constitution, a mark with a desired color can be formed on a molding. The mark is formed easily and inexpensively. A mark having an excellent wear resistance is formed. A mark having an excellent precision is easily formed on the surface of a molding having a complicated shape. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a front view for explaining a marking method on a molding in a first embodiment of the invention. Fig. 2 is a perspective view showing a marking execution state in the first embodiment. Fig. 3 is a perspective view showing a marking finished state in the first embodiment. Fig. 4 is a sectional view showing a marking finished state in the first embodiment. Fig. 5 is a perspective vie showing deflection of a film on a wide molding surface. Fig. 6 is a sectional view showing a film adhering method on a molding having a concave surface in the first embodiment. Fig. 7 is an essential sectional view for explaining a marking method in a second embodiment of the invention. Fig. 8 is a perspective view of a keyboard as an input device used in an electronic information appliance manufactured by a marking method of the invention. Fig. 9 is a front view for explaining a marking method on a resin molding in a prior art. Fig. 10 is an essential sectional front view for explaining a marking method on a resin molding in other prior art. REFERENCE NUMERALS 11, 21, 51, 61: Molding 12, 22, 52, 62: Film 13, 53: Paint 14 Laser beam 15 Deflection device 16 Laser beam device 17: Support stand 18, 72: Mark 54 Elastic piece 63 Dye 64 YAG laser beam 71 Key top DETAILED DESCRIPTION OF THE INVENTION A marking method in an embodiment of the invention comprises a step of feeding a film made of a heat resistant resin having a paint placed on a first surface at one side, a step of contacting the paint side to the surface of a molding as the object of transfer, a step of emitting an energy ray controllable in emitting position by a deflection device on a second surface at the back side of the film free from paint, and a step of transferring and fixing the paint only in the illuminated portion to the surface of the molding from the film surface. In this method, regardless of the molding as the object of transfer, the color of the mark can be changed by replacing the film made of heat resistant resin preliminarily coated with paint. As a result, moldings marked with desired colors may be obtained easily and at low cost. In this constitution, by using a sublimating dye as the paint, it is preferred to vaporize the dye by irradiation with energy ray, and mark by permeating the dye vaporized from the surface of the molding. In this method, the mark permeating to the surface layer of the molding is obtained. As a result, a mark having an excellent wear resistance is formed. In this constitution, using a transparent or translucent film made of heat resistant resin, it is preferred to mark by emitting YAG laser beam having a short wavelength. The YAG laser beam is a beam generated from an apparatus using yttrium-aluminum-garnet material. Since the YAG laser beam is short in wavelength, the beam penetrates through the film completely and the energy is concentrated on the surface layer of the molding, and therefore the texture of the surface layer is activated, and fixing of fused paint or permeation of vaporized paint is easier. As a result, a clearer mark excellent in wear resistance can be formed. In this constitution, the thickness of the film is preferred to be about 10 micron meter to about 200 micron meter. In this method, since the film has an adequate strength, the film can be handled easily in machine, and the transmissivity of energy ray is superior. Hence, melting or transfer of the paint disposed on the film, or vaporization of paint is easy. In this constitution, the film has a specified thickness and a specified folding and bending hardness. While holding both sides of the film so as to have a U-form deflection with the paint applied first surface at outside, the first surface having the paint is pressed to contact tightly with the surface of the molding, and energy ray is emitted from the back side of the film in this state. In this method, using a simple marking device, the film is tightly formed on the molding, and a desired mark is provided. In this constitution, when the surface of the molding to be marked has a convex part, while the first surface having the paint is held in a state of covering the convex part of the molding, the film is pulled from both sides, so that the film is contacted to the surface of the convex part to be marked, and energy ray is emitted in this state. In this method, the film can be contacted tightly to the molding having a convex appearance, so that the desired mark can be formed at an appropriate position. In this constitution, when the surface of the molding to be marked has a convex part, while the first surface having the paint is held in a state of covering the convex part, the surrounding of the molding is evacuated, so that the film is contacted to the surface of the convex part to be marked, and laser beam or energy ray is emitted in this state. The film can be contacted tightly to the molding having a convex appearance, so that the desired mark can be formed. In this constitution, the paint is a paint mixed with a peelable adhesive having a tacky adhesiveness. Using an elastic piece having a shape corresponding to the surface shape of the molding to be marked, by pressing the coated with a paint at one side, energy ray is emitted to the sate of tightly contacting the film to the surface of the molding. In this method, the film of the side having the film of tacky adhesiveness is contacted and held on the surface of the molding to be marked. Accordingly, on the surface of the molding having various shapes such as flat, convex, concave or other surface, the film can be appropriately adhered tightly, and therefore a desired mark can be formed, and then the film can be easily peeled off. In this marking method, marked moldings having various marks can be manufactured. Having various colors, desired characters and patterns, moldings having excellent wear resistant marks can be obtained. As the molding, a thermoplastic resin is preferred. In this case, the degree of freedom of selection of materials for molding is large. Hence, it is possible to cope flexibly with various colors, shapes, colors, and patterns. The molding main body is used in the key top of a keyboard used as an input device of an electronic information appliance. In this constitution, key tops of different marks in a same shape, or one key top having colors in plural colors will provide marks of high quality and excellent wear resistance. Usable materials for the molding include thermoplastic resin, thermosetting resin, compound resin containing filler, ceramic materials, metal materials, and others. In particular, the resin is preferable for the molding, and the above effects will be further enhanced in this case. In this constitution, as the energy ray, laser beam, electron beam, electron ray, heat ray, and other energy ray having high energy may be used. Preferred embodiments of marking method and marked molding of the invention are described below while referring to the drawings. Exemplary embodiment 1 Fig. 1 is a front view for explaining a marking method on a resin molding in a first embodiment of the invention, Fig. 2 is a perspective view showing a marking execution state, Fig. 3 is a perspective view showing a marking finished state, and Fig. 4 is a sectional view showing a marking finished and paint transferred state. In Fig. 1, Fig. 2, Fig. 3, and Fig. 4, a marking apparatus comprises a laser beam generator 16, a deflector 15 for controlling deflection of laser beam, a laser beam 14 controlled by the deflector 15, a support stand 17 for positioning and supporting a resin molding 11, and a paint 13 disposed to one side of a film 12 made of polyethylene terephthalate (PET). The upper surface of the resin molding 11 in this embodiment has a flat shape. The PET film 12 is made of a thermoplastic heat resistant resin. The PET film 12 is colorless and transparent. The thickness of the film 12 is preferred to be in a range of about 10 micron meter to about 200 micron meter, and the PET film having this thickness has an adequate strength, and when marking by using the marking apparatus, it is easy to handle, and the PET film of this thickness has an excellent transmissivity to laser beam. If the thickness of the film 12 is less than 10 micron meter, the film may be torn. If the thickness of the film 12 exceeds 200 micron meter, the contact of the film 12 and the molding may be inferior. Further, the PET film has a fine or smooth surface of smaller surface roughness than the surface of the resin molding 11. That is, the resin molding 11 has a surface roughness so as to may dispose the molten or sublimated paint. The deflector 15 controls the deflection of the laser beam by the numerical control (NC) data. The marking procedure by such marking apparatus is explained below. At a specified position beneath the deflector 15, the resin molding 11 is placed and positioned. Next, a film coated with the paint 13 at one side is prepared. The surface of the paint 13 of the film 12 held parallel to the upper surface of the resin molding 11 is pressed and contact to the upper surface of the resin molding 11 from above the resin molding 11. Later, the laser beam 14 emitted from the laser beam source 16 is emitted with a specified intensity to the second surface opposite to the coating side of the paint 13 of the film 12 through the deflector 15. The laser beam 14 generates heat locally by acting on the film 12 and the paint 13 at its lower side and the resin molding 11 beneath it. By this heat, the paint 13 is melted, and is transferred and disposed to the surface of the resin molding 11 having a coarser surface than the film 12. Herein, the emitting position of the laser beam 14 is moved by the deflector 15 according to the NC data. The paint in the melted portion locally heated by the irradiation with the laser beam is cooled naturally, and is affixed to the surface of the resin molding 11. In other portion after moving of the laser 14, the paint is heated and changed similarly. By operating such action continuously, as shown in Fig. 3 and Fig. 4, the paint 13 is transferred from the film 12 to the surface of the resin molding 11. In this method, a mark 18 such as desired character or pattern is formed on the surface of the resin molding 11. Thus, according to the embodiment, the paint disposed on the film can be easily transferred to the surface of the resin molding. Moreover, plural films provided with paints of different colors at one side may be sequentially used as required. In this method, various color marks may be formed on the surface of individual resin moldings, and also a plurality of marks of different colors may be easily formed on the surface of one resin molding. In the foregoing embodiment, the film 12 is held parallel to the surface of the resin molding 11, but other methods as shown in Fig. 5 to Fig. 6 may be also possible. As shown in Fig. 5, in which the marking area of the resin molding 21 is relatively wide, if the above marking method of holding a film 22 parallel to the surface of a resin molding 21 is employed, deflection is caused on the surface of the resin moldiing 21, and the contact between the film 22 and resin molding 21 is spoiled. To prevent this, a marking method as shown in Fig. 6 is possible. In Fig. 6, the surface of a resin molding 51 has a concave shape. In this case, a paint 53 disposed to a film 52 contains an acrylic resin as an adhesive having a peelable tacky adhesiveness. On the concave surface of the resin molding 51, the surface of the paint 53 of the film 52 is confronting, and the second surface at the opposite side of the film 52 is pressed by using an elastic piece 54 in a shape corresponding to the concave shape, and the film 52 and the paint 53 are adhered and held in the concave shape of the resin molding 51. In this method, the surface of the paint 53 can be securely contacted to the surface of the resin molding 51, and after finishing the marking, the film 52 can be easily peeled off. According to the marking method in Fig. 6, if the surface of the resin molding has a complicated shape such as a spherical, convex or concave shape or has an extremely wide area, the surface of the paint installed at one side of the film may be securely contacted to the surface of the molding. The paint fused by irradiation with laser beam is transferred and marked to the surface of the resin molding at an excellent precision. In the embodiment, the laser beam is used, but not limited to this, any energy ray having a high energy such as electron beam, electron ray or heat ray capable of melting the paint can be used. Exemplary embodiment 2 Fig. 7 is an essential sectional view for explaining a marking method in a second embodiment of the invention. In Fig. 7, a sublimating paint 63 is disposed on one side of a PET colorless transparent film 61 which is a thermoplastic heat resistant resin. As the energy ray, a YAG layer beam 64 capable of obtaining a short wavelength is used. The YAG laser beam is a beam generated from an apparatus using yttrium-aluminium-garnet material. The other method is same as in embodiment 1. In Fig. 7, a YAG laser beam 64 controlled by a deflector 15 completely penetrates through a film 62, and is concentrated and emitted to the dye 63 and the surface layer of the resin molding 61 beneath it. At this time, the sublimating dye 63 is vaporized, and the texture of the surface layer of the resin molding 61 is activated, and the vaporized dye 63 easily permeates into the surface layer of the molding. Thus, the dye 63 is disposed to the molding 61, and a mark is formed on the surface of the molding 61. In this method, the mark can be formed by permeating the vaporized dye 63 on the activated surface layer of the resin molding 61, so that the mark having an excellent wear resistant may be formed. in the embodiment, the resin molding 61 is flat, but not limited to this shape, it may have complicated shapes as shown in Fig. 6, and the same contact is obtained as in embodiment 1, and the same effect as in embodiment 1 is obtained in this case. Exemplary embodiment 3 Fig. 8 shows an embodiment of a resin molding forming a mark by using a marking method of the invention, and it is a partial perspective view of a keyboard as an input device used in an electronic information appliance or the like. In Fig. 8 marks 72 are formed on the surface of key tops 71 which are a plurality of resin moldings of an operation unit. The key tops 71 is made of a thermoplastic resin excellent in processability, and marks 72 are formed on the operation surface. The marks 72 are formed by a method of emitting YAG laser beam by the same method as in embodiment 2, by using a plurality of films coated with sublimating dyes of different colors on one side. Paints of different colors are vaporized and permeate into the surface layer of the key tops 71, so that the plurality of marks 72 such as characters of patterns are clearly formed on the surface of the key tops 71 at high quality. The marks 72 have an excellent wear resistance. In the embodiment, a colorless transparent film is used, but not limited to this, a colored translucent film may be used depending on the kind of the laser beam or the color of the applied paint. Thus, according to the invention, by the deflection control by NC data, desired characters or patterns can be marked on the surface of the molding. Marks of various colors can be also formed. Moreover, the marks can be formed on the molding at lower cost. Marks having excellent wear resistance can be further formed. In addition, marks of excellent precision can be formed on the surface of the molding having complicated shape.

Claims: A method of forming a mark on a molding, comprising the steps of: (a) providing a film having a first surface and a second surface (b) disposing a paint on said first surface of said film, said paint having lower melting point than said film, said paint including an adhesive having a peelable tacky adhesiveness (c) positioning said film on a surface of the molding and pressing a deformable elastic piece from said second surface side of said film so that the first surface of said film on which said paint is disposed conforms to the shape of the surface of said molding and said paint adheres to the surface of said molding then releasing said elastic piece from said second surface whereby said film is maintained in a position conforming to said shape of the surface of the molding, (d) forming the mark by irradiating an energy ray onto a predetermined portion of said second surface of said film, wherein said paint positioned on a portion of the first surface of the film adjacent to said predetermined portion is transferred and disposed onto the surface of the said molding. The method of claim 1, wherein said molding is a resin molding formed of a material containing resin. The method of claim 1, wherein said molding is a resin molding formed of a material containing thermoplastic resin. The method of claim 1, wherein emission of said energy ray is controlled by a deflection device. The method of claim 1, wherein said molding has at least one surface selected from the group consisting of (i) curved surface, (ii) concave surface, (iii) convex surface, and (iv) convexo-concave surface, and at said step (c), said paint disposed on said film is in tight contact with said one selected surface of said molding. The method of claim 1, wherein said molding has a flat surface, and at said step (c), said painting disposed on said film is in tight contact with said flat surface of said molding. The method of claim 1, wherein said molding has a coarser surface roughness than said first surface of said film, and said paint transferred to said coarser surface of said molding. The method of claim 1 wherein, said energy ray irradiates said paint by passing through said film without causing any effects on said film. The method of claim 1, wherein said energy ray is a laser beam. The method of claim 1, wherein said paint has a specific color, and said mark has said specific color. The method of claim 1 wherein said paint contains at least one clement selected from the group consisting of dye and pigment. The method of claim 1, wherein said paint is melted by irradiation with said energy ray, and transferred to said surface of said molding. The method of claim 1, wherein said paint is melted by irradiation with said energy ray, said molding is a resin molding formed of a material containing resin, when said paint is irradiated with said energy ray, the surface of said resin molding forms an activated surface layer, and said paint is melted and the melted paint disposed over said surface of said molding to form said mark. The method of claim 1, wherein said paint is sublimated when irradiated with said energy ray, and transferred to said surface of said molding. The method of claim 1, wherein said paint is sublimated when irradiated with said energy ray, said molding is a resin molding formed of a material containing resin, when said paint is irradiated with said energy ray, the surface of said resin molding forms an activated surface layer, and said paint is sublimated and the sublimated paint is disposed over said surface of said molding to form said mark. The method of claim 1, wherein said energy ray is a laser beam, said laser beam created by a laser using yttrium-aluminum-garnet material. The method of claim 1, wherein said film has at least one of transparent and translucent properties with respect to said energy ray. The method of claim 1, wherein said film has a property of maintaining thermal characteristics as without melting, even during irradiation of said energy ray. The method of claim 1, wherein said film has a thickness in a range from about 10 microns to about 200 microns. The method of claim 1, wherein: at said step (a), a plurality of films are provided, at said step (b), a plurality of paints are provided, where each of said plurality of paints has mutually different color, one of said plurality of paints is disposed on the first surface of one of said plurality of films, another of said plurality of paints is disposed on the first surface of another of said plurality of films, and a mark having a plurality of colors is formed on the surface of said molding, by using each of said plurality of said paints disposed respectively on each of said plurality of said films.

Inventors: FUKUMURA TOYOSHI, KIKUDA HIROFUMI, WATANABE KAZUYUKI, FUKUMURA, TOYOSHI, KIKUDA, HIROFUMI, WATANABE, KAZUYUKI
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD
Application year: 1998
Main classification: B41M5
IPC codes: B05D1, B41M5, B41J2, B44C1