JP2008144082A - Sheet for laser marking use and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet for laser marking use having high contrast of a printed part with a base color, giving good markings such as clear characters, marks, pictures and the like and able to develop color in addition to no color development. <P>SOLUTION: The sheet 1 for laser marking use has a light-transmissive sheet 2 comprising a thermoplastic resin and an adhesive layer 3 formed on the back face side of the light-transmissive sheet 2. The adhesive layer 3 is formed of an acrylic resin-based adhesive 4 in which an energy-absorbing agent 5 developing a color by absorbing laser beams is dispersed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser marking sheet and a method for producing the same. More specifically, by receiving laser light, the contrast between the printed part and the fabric color is high, markings such as clear letters, symbols, and photographs can be obtained well, and chromatic colors as well as achromatic colors can be developed. The present invention relates to a sheet for laser marking and a method for manufacturing the same.

  For printing on the surface of a plastic molded product, conventionally, a printing method using ink such as tampo printing, silk printing, ink jet printing, thermal transfer printing or the like is used. In this method, there is an environmental hygiene problem because ink containing an organic solvent is used, ink bleeding occurs during printing, the abrasion resistance of the printed part is inferior, and the weather resistance of the ink used outdoors. There are various problems such as that there is a problem in performance, and that a molded article having a complicated shape cannot be printed.

  Conventionally, plastic sheets have been used for substrates such as credit cards, cash cards, ID cards, tag cards, display boards, and authentication plates. Personal names, symbols, characters, and photographs are used on these cards and plates. Silk printing and sublimation printing are performed, but there is a problem that the production process is complicated and the productivity is inferior.

  On the other hand, as a printing method that does not use ink, there has been proposed a laser marking method (for example, see Patent Document 1 or 2) in which a laser beam is applied to print on a plastic molded product. Furthermore, in recent years, as a resin composition for color marking capable of color marking, for example, a resin composition in which a leuco compound (leuco dye) is contained as a coloring component in a thermosetting resin has been proposed (for example, a patent) References 3 and 4).

Japanese Examined Patent Publication No. 61-11771 Japanese Examined Patent Publication No. 2-47314 JP-A-9-302236 JP 2003-321615 A

  However, since the conventional marking resin composition as described above is a resin composition containing a coloring component in a resin such as a thermosetting resin or a thermoplastic resin, the marking resin composition has a predetermined shape. For example, when forming into a sheet or the like, a forming step with heating is required. Since the coloring component contained in the marking resin compositions of Patent Documents 3 and 4 is colored by heating, the coloring component in the resin composition is colored in the molding step described above, which is caused by laser marking. There is a problem in that the contrast between the printing portion and the fabric color is lowered, and clear markings such as characters, symbols, and photographs cannot be obtained.

  In addition, the marking resin composition used in the laser marking method described in Patent Document 1 or 2 described above contains carbon in the composition. Such a marking resin composition is a laser. There is a problem that the colors that can be developed by the marking are limited, and the usage is limited. For example, in such a laser marking method, it is extremely difficult to develop white color on a transparent molded product.

  The present invention has been made to solve the above-described problems of the prior art, and by receiving irradiation with a laser beam, the contrast between the printed portion and the fabric color is high, and clear characters, symbols, photographs, etc. Provided is a laser marking sheet capable of producing a marking and capable of developing not only an achromatic color but also a chromatic color, and a method for producing the same.

  As a result of diligent studies to solve the problems of the prior art as described above, the present inventor has obtained an acrylic resin in which an energy absorber that absorbs a laser beam and generates color is dispersed on the back side of the light transmissive sheet. It was conceived that the above-mentioned problems could be solved by forming an adhesive layer using a resin-based adhesive, and the present invention was completed. Specifically, the present invention provides the following sheet for laser marking and a method for producing the same.

[1] A light transmissive sheet made of a thermoplastic resin and an adhesive layer formed on the back side of the light transmissive sheet, wherein the adhesive layer absorbs a laser beam to cause color development. A sheet for laser marking, which is formed from an acrylic resin adhesive in which an agent is dispersed.

[2] The laser marking sheet according to [1], wherein the adhesive layer is formed from the adhesive having a viscosity of 2000 to 500,000 mPa · s at 25 ° C.

[3] The laser marking sheet according to [1] or [2], wherein the adhesive layer is formed of an acrylic resin adhesive in which carbon black is dispersed as the energy absorber.

[4] The adhesive layer according to [1] or [2], wherein the adhesive layer is formed from an acrylic resin adhesive in which a leuco dye and a developer are dispersed as the energy absorber. Laser marking sheet.

[5] The laser marking sheet according to any one of [1] to [4], wherein the adhesive layer has a thickness of 5 to 500 μm.

[6] The laser marking sheet according to any one of [1] to [5], wherein the adhesive layer is colored in advance.

[7] The laser marking sheet according to any one of [1] to [6], wherein the light transmissive sheet has a light transmittance of 40% or more.

[8] A method for producing a laser marking sheet comprising a light-transmitting sheet made of a thermoplastic resin and an adhesive layer formed on the back surface side of the light-transmitting sheet, the acrylic resin-based bonding An energy absorbing agent that absorbs a laser beam to cause color development is dispersed in the agent to obtain an energy absorbing agent-containing adhesive, and the obtained energy absorbing agent-containing adhesive is disposed on the back side of the light-transmitting sheet. The manufacturing method of the sheet | seat for laser marking which coats and forms the said adhesive bond layer.

[9] The laser according to [8], wherein the energy absorbent-containing adhesive is prepared so that the viscosity at 25 ° C. is 2000 to 500000 mPa · s, and is applied to the back side of the light transmissive sheet. Manufacturing method of marking sheet.

  The sheet for laser marking according to the present invention includes an energy absorber because it includes an adhesive layer formed of an acrylic resin adhesive in which an energy absorber that absorbs a laser beam to cause color development is dispersed. When the layer is formed, a resin molding step involving heating such as compression molding or injection molding is not required. For this reason, color development of the energy absorber before laser marking is effectively prevented, and the contrast between the printed part and the fabric color is high by receiving the laser beam, and marking of clear characters, symbols, photographs, etc. is good Is obtained. In particular, the laser marking sheet of the present invention is effective not only for achromatic color development but also for chromatic color development. Moreover, the manufacturing method of the sheet | seat for laser markings of this invention can manufacture such a sheet | seat for laser markings simply and at low cost.

  BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as “embodiment”) will be specifically described. However, the present invention is not limited to the following embodiment and departs from the gist of the present invention. It should be understood that design changes, improvements, and the like can be made as appropriate based on ordinary knowledge of those skilled in the art.

[1] Laser marking sheet:
FIG. 1 is a schematic diagram illustrating the configuration of an embodiment of the laser marking sheet of the present invention, and is a view showing a cross section perpendicular to the surface of the laser marking sheet. The laser marking sheet 1 of the present invention includes a light transmissive sheet 2 made of a thermoplastic resin and an adhesive layer 3 formed on the back side of the light transmissive sheet 2, and the adhesive layer 3 is a laser beam. It is formed from an acrylic resin adhesive 4 in which an energy absorbing agent 5 that absorbs light and produces color is dispersed.

  In the laser marking sheet 1 of the present embodiment, since the energy absorbent 5 is included in the adhesive layer 3 described above, when the layer containing the energy absorbent 5 is formed, compression molding, injection molding, or the like is performed. A resin molding step with heating is not required. Specifically, by adhering the adhesive layer 3 of the laser marking sheet 1 to the surface of another sheet or molded product, the adhesive layer 3 is cured over time without heating, and energy absorption is performed. A cured layer 3 a (hereinafter sometimes referred to as “adhesive cured layer”) of the adhesive layer 3 formed from the adhesive 4 including the agent 5 can be formed. For this reason, the coloring by the energy absorber 5 before laser marking is effectively prevented, and by receiving the laser beam, the printed portion and the fabric color have high contrast, and marking of clear characters, symbols, photographs, etc. Obtained well. In particular, the laser marking sheet of the present embodiment is effective not only for achromatic color development but also for chromatic color development that tends to cause color development due to heat.

  As shown in FIG. 2, the laser marking sheet 1 of the present embodiment is irradiated with the laser beam 6 on the surface side of the light transmissive sheet 2 so that the laser beam 6 is transmitted through the light transmissive sheet 2 and bonded. The adhesive layer 3 or the adhesive cured layer 3a is cured, and the energy absorber 5 in the adhesive layer 3 absorbs the laser beam to cause color development. In this way, the marking 7 is formed in the portion that has been irradiated with the laser beam 6. Here, FIG. 2 is a schematic diagram showing a step of marking by irradiating the laser marking sheet shown in FIG. 1 with a laser beam.

  In addition, the sheet | seat for laser markings of this embodiment may adhere | attach another member on the adhesive bond layer beforehand. For example, as shown in FIG. 3, the sheet | seat 10 for laser marking further provided with the back surface sheet 11 affixed on the adhesive bond layer 3 formed in the back surface side of the transparent sheet 2 can be mentioned. Here, FIG. 3 is a schematic diagram illustrating the configuration of another embodiment of the laser marking sheet of the present invention, and is a view showing a cross section perpendicular to the surface of the laser marking sheet.

  As described above, in the laser marking sheet 10 in which another member such as the back sheet 11 is attached to the adhesive surface of the adhesive layer 3 in advance, the adhesive layer 3 is in a state before curing with fluidity. It may be a thing of the state already hardened, ie, above-mentioned adhesive hardening layer 3a.

  The laser marking sheet of the present embodiment can be suitably used for various cards, specifically, credit cards, cash cards, ID cards, tag cards, display boards, authentication plates, ETC cards, and the like. Moreover, it can be used suitably also for a signboard, a window, a container, a flooring, a scaled window, a level window, a stationery, a filing case, an underlay, a calendar, a ruler, etc.

[1-1] Light transmissive sheet:
As shown in FIG. 1, the light-transmitting sheet 2 of the laser marking sheet 1 of the present embodiment is used as a surface layer of the laser marking sheet 1 and can transmit a laser beam for performing laser marking. Furthermore, when coloring is caused by the energy absorber 5 in the adhesive layer 3, a sheet made of a thermoplastic resin in which coloring (marking) can be visually recognized from the surface side of the light transmissive sheet 2. is there. The light transmissive sheet 2 serves as a base material for the adhesive layer 3 containing the energy absorber 5, and the light transmissive sheet 2 allows the adhesive layer 3 or the adhesive layer 3 to be cured. The agent curing layer 3a can also be protected. Thereby, there is no damage of an external appearance and the laser marking excellent in surface smoothness is attained.

  The light transmissive sheet 2 used for the laser marking sheet 1 of the present embodiment preferably has a total light transmittance of 40% or more, more preferably 70% or more, and more preferably 80% or more. Particularly preferred. The total light transmittance is a value measured in accordance with JIS-K7105 (light transmittance and total light reflectance). For example, the total light transmittance can be measured using a haze meter (trade name: “NDH 2000”) manufactured by Nippon Denshoku Industries Co., Ltd.

  Examples of the material constituting the light-transmitting sheet made of the thermoplastic resin include polycarbonate (PC), polyethylene terephthalate (PET, A-PET, PETG), polycyclohexane 1,4-dimethylphthalate (PCT), polystyrene ( PS), polymethyl methacrylate (PMMA), transparent ABS (MABS), polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), and the like can be used. In the laser marking sheet of the present invention, polycarbonate (PC), polymethyl methacrylate (PMMA) and the like excellent in transparency, heat resistance, impact resistance, toughness and the like are particularly preferable.

  The thickness of the light transmissive sheet is preferably 0.5 to 2000 μm, more preferably 1 to 1500 μm, and particularly preferably 5 to 1000 μm.

  In addition, this light-transmitting sheet can be provided with, for example, a colorant, a stabilizer, a release agent, an antioxidant, an ultraviolet absorber, an infrared absorber, a reinforcing agent, etc., as long as the desired light transmittance is obtained. It may be included.

  Such a light-transmitting sheet can be obtained by a method of forming a sheet made of a conventionally known thermoplastic resin. For example, a method of forming the above-described thermoplastic resin into a sheet using a melt extruder can be exemplified.

[1-2] Adhesive layer:
The adhesive layer 3 of the laser marking sheet of the present invention is formed from an acrylic resin adhesive 4 in which an energy absorber 5 that absorbs a laser beam and produces color is dispersed. The adhesive layer 3 is formed on the back side of the light transmissive sheet 2 described above. Such an adhesive layer 3 is obtained by coating (converting) the adhesive 4 having the above-described configuration (hereinafter, also referred to as “energy absorber-containing adhesive”) on the back surface side of the light-transmitting sheet 2. Can be formed.

  In the laser marking sheet 1 of the present invention, the adhesive layer 3 is bonded to another sheet or a molded product, and then the adhesive layer 3 is cured to cure the adhesive layer 3 including the energy absorber 5. The hardened layer 3a can be formed. For this reason, the color development by the energy absorber 5 before laser irradiation is effectively prevented.

  As described above, as the adhesive 4 for forming the adhesive layer 3 of the laser marking sheet 1 of the present invention, an acrylic resin-based adhesive mainly composed of an acrylic resin is used. By using such an adhesive 4, as shown in FIG. 2, when the laser beam 6 is irradiated, the printed portion and the fabric color have high contrast, and the markings 7 such as clear characters, symbols, and photographs are excellent. Obtainable.

  The quality of the contrast by laser marking also depends on the viscosity of the adhesive 4 that forms the adhesive layer 3. Specifically, the viscosity at 25 ° C. of the adhesive 4 is preferably 2000 to 500000 mPa · s, more preferably 5000 to 300000 mPa · s, and particularly preferably 10000 to 200000 mPa · s. By forming the adhesive layer 3 using the adhesive 4 having such a viscosity, a marking excellent in contrast can be obtained satisfactorily. The viscosity of the adhesive can be measured using a known rotary viscometer.

  There is no restriction | limiting in particular as an energy absorber, A conventionally well-known energy absorber for laser marking can be used. Specifically, for example, when an achromatic color (for example, white or black) is generated by irradiation with a laser beam, carbon black, metal oxide, metal sulfide, carbonate, The adhesive layer may be formed using an acrylic resin adhesive in which metal silicate or the like is dispersed. For example, this carbon black can generate white color by lowering the power of the laser beam, and can generate black color by increasing the power of the laser beam.

  Examples of the metal oxide include zinc oxide, magnesium oxide, alumina, iron oxide, iron black, titanium oxide, silicon oxide, and antimony trioxide. Furthermore, examples of the metal sulfide include zinc sulfide and cadmium sulfide. Further, as carbonates, calcium carbonate and the like, and as metal silicates, alumina silicate, iron-containing alumina silicate (mica), hydrous silicate silicate (kaolin), magnesium silicate (talc), silicate Calcium, magnesium silicate, etc. can be mentioned. These energy absorbers can be used alone or in combination of two or more.

  An energy absorber that produces such achromatic color, such as carbon black, is 100 parts by mass of an acrylic resin-based adhesive (which does not include an energy absorber) for forming an adhesive layer. 0.001 to 10 parts by mass is preferable, and 0.01 to 1.0 part by mass is more preferable. In addition, when the amount of the energy absorber is less than 0.001 part by mass, the color development becomes light and sufficient contrast may not be obtained. On the other hand, when the amount exceeds 10 parts by mass, the energy absorbing function becomes excessive and the contrast is lowered, and the adhesive layer or the adhesive cured layer may be damaged.

  In addition, when a chromatic color is generated by irradiation with a laser beam, an adhesive layer is formed using an acrylic resin adhesive in which a leuco dye and a developer are dispersed as an energy absorber. do it. The leuco dye is an electron-donating dye that develops color when oxidized, such as thiazine leuco dyes such as benzoyl leucomethylene blue, fluorane leuco dyes, spiropyran leuco dyes such as 3-methyldinaphthospiropyran, crystal violet, and the like. Examples thereof include triphenylmethane leuco dyes such as lactones and diphenylmethane leuco dyes such as leucooramines.

  For example, commercially available products of such leuco dyes are all trade names “RED-40”, “BLUE-63”, “GREEN-118”, and “ODB” (manufactured by Yamamoto Kasei Co., Ltd.), “ RED500 "," CVL ", and" ETAC "(manufactured by Yamada Chemical Co., Ltd.). In addition, by using a combination of a plurality of leuco dyes, it is possible to generate various colors such as yellow, blue, red, green, orange, and purple.

  Such a leuco dye is contained in an amount of 0.01 to 30 parts by mass with respect to 100 parts by mass of an acrylic resin-based adhesive (which does not include an energy absorber) for forming an adhesive layer. It is more preferable that 0.1-15 mass parts is contained. When the amount of the leuco dye is less than 0.01 parts by mass, the color development becomes light and sufficient contrast may not be obtained. On the other hand, if it exceeds 30 parts by mass, the energy absorbing function becomes excessive, the contrast is lowered, and the adhesive layer or the cured adhesive layer may be damaged.

  Moreover, as a color developer used with a leuco dye, the color developer used for a conventionally well-known thermal dye etc. can be used, for example, bishydroxyphenyl, such as bis (4-hydroxyphenyl) sulfone <bisphenol S>. Preferred examples include sulfones and 4-hydroxyphenylaryl sulfones such as 4-hydroxy-4′-isopropoxydiphenyl sulfone. For example, as a commercial product of such a developer, “BPS-MAE” (manufactured by Nikka Chemical Co., Ltd.) can be given as a trade name.

  Such a developer is contained in an amount of 0.01 to 60 parts by mass with respect to 100 parts by mass of an acrylic resin adhesive (which does not include an energy absorber) for forming the adhesive layer. The content is preferably 0.1 to 30 parts by mass. If the amount of the developer is less than 0.01 parts by mass, the color development becomes weak and sufficient contrast may not be obtained. On the other hand, if it exceeds 60 parts by mass, the energy absorption function becomes excessive, and the contrast may be lowered, or the adhesive layer or the cured adhesive layer may be damaged.

  When using the above-described leuco dye and developer as the energy absorber, either the leuco dye or the developer, or the leuco dye and the developer may be encapsulated separately. Examples of the encapsulation method include a method in which water is used as a dispersion medium and a leuco dye or a developer is wet-pulverized and then encapsulated by a coacervation method or an in-situ method. With such a configuration, it is possible to realize clearer color development and to effectively prevent the leuco dye and the developer from reacting and developing color before laser irradiation.

  The wall film material for encapsulating the energy absorber is not particularly limited as long as the wall film material can be destroyed during laser marking. For example, gelatin can be used in the above-described coacervation method. In the above-described in-situ method, a melamine-formaldehyde resin can be used.

  When the solid leuco dye is wet-pulverized and encapsulated, it is preferable to use, for example, an anionic polymer such as arabic rubber, sodium alginate, or carboxymethylcellulose as a dispersing agent at the time of pulverization. By comprising in this way, the capsule obtained by the coacervation of this anionic polymer and gelatin becomes easy to be destroyed at the time of laser marking, and clear color development can be realized.

  Moreover, there is no restriction | limiting in particular about the usage-amount of the wall film material in the case of encapsulation, However, It is preferable that it is 5-20 mass parts with respect to 100 mass parts of solid leuco dyes. In particular, when the wall film material is gelatin, if the amount of gelatin used is less than 5 parts by mass, the wall film material is likely to be destroyed too much, and the effect of encapsulation may be reduced. On the other hand, when the amount exceeds 20 parts by mass, the capsule becomes difficult to be destroyed, the power of the laser beam necessary for color development increases, and the contrast between the printed part and the fabric color may be lowered.

  Moreover, when using a leuco dye and a color developer as an energy absorber, it may further contain a sensitizer. As such a sensitizer, a sensitizer used for conventionally known thermal dyes and the like can be used. For example, m-terphenyl, 1-hydroxy-2-naphthoic acid phenyl ester, p-benzyloxybenzoate Acid benzyl, benzyl naphthyl ether, dibenzyl terephthalate, diphenyl carbonate, ditolyl carbonate, diphenyl sulfone, 1,2-bis (m-tolyloxy) ethane, p-benzylbiphenyl, 1,5-bis (p-methoxyphenoxy) -3 -Oxapentane, oxalic acid diesters, oxalic acid di (4-methylbenzyl), 1,4-bis (p-tolyloxy) benzene, 1,4-bis [2- (4-methylbenzyloxy) ethoxy] benzene, etc. Can be cited as a preferred example. For example, as a commercial item of such a sensitizer, “PMB-2” (manufactured by Nikka Chemical Co., Ltd.) can be given as a trade name.

  When such a sensitizer is used, the total amount of the developer and the sensitizer is an acrylic resin adhesive (including an energy absorber) for forming an adhesive layer. None) It is preferably 0.01 to 60 parts by mass, more preferably 0.1 to 30 parts by mass with respect to 100 parts by mass.

  Further, the adhesive layer before being irradiated with the laser beam may be transparent, or may be white or black achromatic or various chromatic colors. When coloring an adhesive layer, the method of making an acrylic resin-type adhesive contain a well-known colorant can be mentioned. Examples of the colorant include inorganic pigments, organic pigments, dyes, and the like. Among these, as inorganic pigments, white pigments such as titanium oxide, barium sulfate, zinc sulfide and zinc oxide, yellow pigments such as iron oxide and titanium yellow, red pigments such as iron oxide, blue pigments such as cobalt blue and ultramarine blue, etc. Can be mentioned. Examples of organic pigments include yellow pigments such as monoazo, condensed azo, anthraquinone, disazo, and heterocyclic rings, red pigments such as quinacridone, anthraquinone, perylene, and monoazo, blue pigments such as phthalocyanine, and green pigments such as phthalocyanine. Can be mentioned. Furthermore, examples of the dye include yellow dyes such as monoazo, anthraquinone, disazo and heterocyclic rings, red dyes such as anthraquinone, perinone, thioindigo and disazo, and blue dyes such as anthraquinone. In addition, it is preferable to select the color tone of the adhesive layer that has good color and contrast with the energy absorbing agent.

  The amount of the colorant used varies depending on the use of the laser marking sheet of the present embodiment, but is 0 with respect to an acrylic resin adhesive (which does not include an energy absorber) for forming an adhesive layer. 0.01 to 50 parts by mass, more preferably 0.05 to 30 parts by mass, and particularly preferably 0.1 to 10 parts by mass. When the colorant exceeds 50 parts by mass, laser color development may be deteriorated. On the other hand, when the colorant is less than 0.01 parts by mass, the coloring power may be weak. Moreover, such a coloring agent may be contained in the thermoplastic resin constituting the light transmissive sheet described above to color the light transmissive sheet.

  Moreover, there is no restriction | limiting in particular about the thickness of an adhesive bond layer, For example, it is preferable that it is 5-500 micrometers, It is more preferable that it is 10-400 micrometers, It is especially preferable that it is 15-300 micrometers. If the thickness of the adhesive layer is less than 5 μm, the adhesive layer is too thin, and the amount of energy absorber for causing color development is reduced, and sufficient color development may not be obtained. Even if the thickness exceeds 500 μm, the contrast between the printing portion and the fabric color does not change thereafter, and the cost may increase. Also, the adhesive layer may be too thick and difficult to handle.

  The energy absorber-containing adhesive for forming this adhesive layer includes other additives such as mold release agents, stabilizers, antioxidants, ultraviolet absorbers, infrared absorbers, and reinforcing agents. You may go out.

  The energy absorber-containing adhesive for forming the adhesive layer can be prepared, for example, by dispersing the above-described energy absorber in an acrylic resin adhesive.

  When a leuco dye and a developer are used as the energy absorber, either one of the leuco dye and the developer, or each of them is separately encapsulated by the above-described coacervation method or in-situ method. May be used.

  Moreover, as a method of forming an adhesive layer using the thus obtained energy absorbent-containing adhesive, a conventionally known coating method, for example, a coating device manufactured by Matsuo Sangyo (trade name: “K A method of coating using a hand coater ") can be mentioned.

[1-3] Back sheet:
As shown in FIG. 3, as the back sheet 11 adhered to the adhesive layer 3 formed on the back side of the light transmissive sheet 2, any material can be used as long as the sheet can be adhered to the adhesive layer. For example, a sheet made of a thermoplastic resin can be used. Specifically, polycarbonate (PC), polyethylene terephthalate (PET, A-PET, PETG), polycyclohexane 1,4-dimethylphthalate (PCT), polystyrene (PS), polymethyl methacrylate (PMMA), ABS, poly Preferred examples include vinyl chloride (PVC), polypropylene (PP), polyethylene (PE) and the like. In the laser marking sheet of the present invention, among these resins, polycarbonate (PC), polymethyl methacrylate (PMMA) and the like excellent in heat resistance, impact resistance, toughness and the like are particularly preferable.

  Such a back sheet may not be a light-transmitting sheet, but is configured in the same manner as the light-transmitting sheet used as the surface layer of the laser marking sheet of the present invention described above. A suitable sheet can be used. For example, when the back sheet is a light transmissive sheet, laser marking can be performed on both the front and back surfaces.

  Although not particularly limited, when the laser marking sheet 10 according to the present embodiment is a laminated body of sheets including the light-transmitting sheet 2 and the back sheet 11 as surface layers as described above. Can also be used as a card application. In that case, the thickness of the laser marking sheet 10 is preferably 0.1 to 2 mm. Such a laminate can be suitably used for various cards, specifically, credit cards, cash cards, ID cards, tag cards, display boards, authentication plates, ETC cards, and the like.

  Moreover, in the laser marking sheet of the present embodiment, as shown in FIG. 1, the adhesive layer 3 may be directly formed on the back surface of the light transmissive sheet 2, but as shown in FIG. Alternatively, the base layer 12 may be formed on the back surface of the light transmissive sheet 2, and the adhesive layer 3 may be formed on the base layer 12. Here, FIG. 4 is a schematic diagram illustrating the configuration of another embodiment of the laser marking sheet of the present invention, and is a view showing a cross section perpendicular to the surface of the laser marking sheet of the present invention.

  The underlayer 12 may be transparent as long as the light transmissive sheet 2, but preferably has a high light transmittance so that the laser beam irradiated on the light transmissive sheet 2 can be transmitted satisfactorily. Can be used.

[2] Manufacturing method of laser marking sheet:
Next, an embodiment of a method for producing a laser marking sheet of the present invention will be described. As shown in FIG. 1, the laser marking sheet manufacturing method of the present embodiment includes a light-transmitting sheet 2 made of a thermoplastic resin and an adhesive layer 3 formed on the back side of the light-transmitting sheet 2. It is a method for producing a laser marking sheet 1 provided, and an energy absorbent containing an energy absorber is obtained by dispersing an energy absorbent that absorbs a laser beam to cause color development in an acrylic resin adhesive. This is a method for producing a sheet for laser marking, in which the energy absorbent-containing adhesive is applied to the back side of the light transmissive sheet to form the adhesive layer.

  By comprising in this way, the sheet | seat 1 for laser marking as shown in FIG. 1 can be manufactured simply and at low cost.

  For the light transmissive sheet, the energy absorber, and the acrylic resin-based adhesive used in the method for manufacturing the laser marking sheet of the present embodiment, those described in the above-described embodiment of the laser marking sheet are suitable. Can be used.

  For example, the light transmissive sheet may be polycarbonate (PC), polyethylene terephthalate (PET, A-PET, PETG), polycyclohexane 1,4-dimethylphthalate (PCT), polystyrene (PS), polymethyl methacrylate (PMMA), It can be obtained by molding a thermoplastic resin such as transparent ABS (MABS), polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE) or the like into a sheet using a melt extruder.

  The energy absorber-containing adhesive is prepared by dispersing the above-described energy absorber in an acrylic resin adhesive.

  Moreover, as a method for coating (converting) the thus obtained energy absorbent-containing adhesive on the back surface side of the light-transmitting sheet, a conventionally known coating method, for example, a coating made by Matsuo Sangyo Co., Ltd. The method of coating using an apparatus (brand name: "K hand coater") can be mentioned.

  In the method for manufacturing a laser marking sheet of the present embodiment, a base layer may be formed on the back surface of the light transmissive sheet before the energy absorbent-containing adhesive is applied to the back surface side of the light transmissive sheet. . Such an underlayer can be formed, for example, by melt coextrusion of the material of the underlayer.

  In addition, when a leuco dye and a developer are used as the energy absorber, either or both of the leuco dye and the developer are separately used, for example, water as a dispersion medium, and the leuco dye and the developer. After the colorant is wet pulverized, it may be encapsulated by a coacervation method or an in-situ method.

[3] Laser marking method:
As a method for performing laser marking using the laser marking sheet of the present invention, for example, an Nd: YAG laser (trade name: “RSM30D”) manufactured by Roffin Basel is used for the laser marking sheet of the present invention. And a method of printing by irradiating a laser having a multimode beam diameter of 80 to 100 μm.

  The laser marking sheet of the present invention is excellent in laser markability by the above-described laser marking method, and can easily and beautifully draw lines and the like on the surface thereof. Therefore, the laser marking sheet of the present invention can be effectively used for printing on electric parts, electronic parts, automobile parts, building materials, cases of various recording media, various display boards, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these Examples. In the following examples and comparative examples, “parts” and “%” mean parts by mass and mass% unless otherwise specified. Various evaluations and measurements in the examples were performed by the following methods.

[Evaluation of Marking Property]: The marking property was evaluated by performing marking at a laser irradiation speed of 400 mm / sec, and confirming whether the color developed by the marking and the color of the fabric are good in contrast. For the laser marking, a laser marker of Nd: YAG laser (trade name: “RSM30D”, manufactured by Roffin Basel) was used. The contrast was visually evaluated according to the following criteria in four stages of ◎, ○, Δ, and ×.
◎: Very good visibility ○: Good visibility △: Visibility ×: No visibility

(Example 1)
A light transmissive sheet was formed by extrusion molding using a polycarbonate (PC) resin (trade name: “Taflon A2500 Natural”, manufactured by Idemitsu Kosan Co., Ltd.). The thickness of the light transmissive sheet was 200 μm. The light transmittance of this light transmissive sheet was 90%. The light transmittance of the light transmittance sheet is a value obtained by measuring the total light transmittance using a haze meter (trade name: “NDH2000”) manufactured by Nippon Denshoku Industries Co., Ltd.

  Next, 100 parts by mass of an acrylic resin adhesive (trade name: “Auto Clear Super”, manufactured by Nippon Paint Co., Ltd.) and carbon black (trade name: “Carbon Black # 10”, manufactured by Mitsubishi Chemical Corporation) as an energy absorber. ) 0.2 parts by mass was added to prepare an energy absorber-containing adhesive for forming an adhesive layer. The energy absorbent-containing adhesive has a viscosity at 25 ° C. of 80000 mPa · s.

  The obtained energy absorber-containing adhesive was applied to the back side of the light-transmitting sheet using a coating device (trade name: “K Hand Coater”) manufactured by Matsuo Sangyo Co., Ltd. An adhesive layer was formed to produce a sheet for laser marking (Example 1). The thickness of the adhesive layer was 100 μm. The above-described marking property was evaluated using the obtained laser marking sheet. Table 1 shows the results of evaluation of marking properties.

(Example 2)
Instead of the above-described carbon black, as an energy absorber, 5 parts by mass of a leuco dye (trade name: “RED-40”, manufactured by Yamamoto Kasei Co., Ltd.), a developer (trade name: “BPS-MAE”, Nikka Chemical) 10 parts by mass), and 10 parts by mass of a sensitizer (trade name: “PMB-2”, manufactured by Nikka Chemical Co., Ltd.) are used. An agent was prepared, and a laser marking sheet (Example 2) was produced using this energy absorbent-containing adhesive. The energy absorbent-containing adhesive has a viscosity at 25 ° C. of 80000 mPa · s.

(Example 3)
Instead of the above-described carbon black, as an energy absorber, 5 parts by mass of a leuco dye (trade name: “BLUE-63”, manufactured by Yamamoto Kasei Co., Ltd.), a developer (trade name: “BPS-MAE”, Nikka Chemical) 10 parts by mass) and 10 parts by mass of sensitizer (trade name: “PMB-2”, manufactured by Nikka Chemical Co., Ltd.) An agent was prepared, and a laser marking sheet (Example 3) was produced using the energy absorbent-containing adhesive. The energy absorbent-containing adhesive has a viscosity at 25 ° C. of 80000 mPa · s.

Example 4
Instead of the above carbon black, as an energy absorber, 5 parts by mass of a leuco dye (trade name: “GREEN-118”, manufactured by Yamamoto Kasei Co., Ltd.) and a developer (trade name: “BPS-MAE”, Nikka) Chemical absorber) 10 parts by mass and sensitizer (trade name: “PMB-2”, manufactured by Nikka Chemical Co., Ltd.) 10 parts by mass, except that energy absorbers are contained in the same manner as in Example 1. An adhesive was prepared, and a laser marking sheet (Example 4) was produced using this energy absorbent-containing adhesive. The energy absorbent-containing adhesive has a viscosity at 25 ° C. of 80000 mPa · s.

(Examples 5-7)
Except not using a sensitizer, each energy absorber containing adhesive was adjusted by the same method as the energy absorber containing adhesive of Examples 2-4, and laser marking was carried out using this energy absorber containing adhesive. Sheets (Examples 5 to 7) were produced. The energy absorbent-containing adhesive has a viscosity at 25 ° C. of 80000 mPa · s.

(Examples 8 to 10)
Using the same material as in Example 1, an energy absorbent-containing adhesive was prepared so that the viscosity at 25 ° C. would be the value shown in Table 1, and using this energy absorbent-containing adhesive, a laser marking sheet ( Examples 8 to 10) were prepared.

(Examples 11 to 13)
Using the same material as in Example 2, an energy absorbent-containing adhesive was prepared so that the viscosity at 25 ° C. would be the value shown in Table 1, and a laser marking sheet ( Examples 11 to 13) were prepared.

(Examples 14 to 17)
Except having changed the usage-amount of carbon black as shown in Table 1, the energy absorber containing adhesive agent was prepared by the method similar to Example 1, and the sheet | seat for laser markings using this energy absorber containing adhesive agent (Examples 14 to 17) were produced. The energy absorbent-containing adhesive has a viscosity at 25 ° C. of 80000 mPa · s.

(Examples 18 to 21)
An energy absorber-containing adhesive was prepared by the same method as in Example 2 except that the amounts of the leuco dye, the developer, and the sensitizer were changed as shown in Table 1, and this energy absorber contained Laser marking sheets (Examples 18 to 21) were produced using an adhesive. In addition, the viscosity in 25 degreeC of this energy absorber containing adhesive agent is 80000 mPa * s.

(Comparative Example 1)
Acrylic resin adhesive (trade name: “Auto Clear Super”, manufactured by Nippon Paint Co., Ltd.) is absorbed on the back side of the light transmissive sheet configured in the same manner as the light transmissive sheet used in Example 1. Coating was performed without adding an agent to form an adhesive layer, and a laser marking sheet (Comparative Example 1) was produced. The viscosity of the adhesive at 25 ° C. is 80000 mPa · s.

(Comparative Example 2)
Carbon black (trade name: “Carbon Black # 10”, manufactured by Mitsubishi Chemical Corporation) is not used on the back side of the light transmissive sheet configured similarly to the light transmissive sheet used in Example 1. As a result, an energy absorber layer made of carbon black was formed to produce a laser marking sheet (Comparative Example 2). Carbon black was applied in an amount equivalent to that of carbon black contained in the adhesive layer (100 μm) in Example 1. The amount of carbon black in Table 1 is a value when the amount of the adhesive used in Example 1 is 100 parts by mass.

(Comparative Example 3)
A leuco dye (trade name: “RED-40”, manufactured by Yamamoto Kasei Co., Ltd.), a developer (trade name: product name) is provided on the back side of the light transmissive sheet configured in the same manner as the light transmissive sheet used in Example 1. “BPS-MAE” (manufactured by Nikka Chemical Co., Ltd.), and a sensitizer (trade name: “PMB-2”, manufactured by Nikka Chemical Co., Ltd.) are directly applied without using an adhesive, and a leuco dye, An energy absorber layer composed of a developer and a sensitizer was formed to produce a sheet for laser marking (Comparative Example 3). The leuco dye, developer, and sensitizer were applied in the same amounts as the leuco dye, developer, and sensitizer contained in the adhesive layer (100 μm) in Example 2. Further, the amounts of the leuco dye and the developer in Table 1 are values when the amount of the adhesive used in Example 1 is 100 parts by mass.

  The marking properties described above were evaluated using the obtained laser marking sheets of Examples 2 to 21 and Comparative Examples 1 to 3. Table 1 shows the results of evaluation of marking properties.

(Discussion)
As shown in Table 1, the laser marking sheets of Examples 1 to 21 were able to obtain markings having visibility of the printed portion and the fabric color contrast by being irradiated with a laser beam. This eliminates the need for a resin molding step that involves heating such as compression molding or injection molding when a layer containing an energy absorber is formed, and color development by the energy absorber before laser marking is effectively prevented. It seems that it was because it was. In particular, in the conventional laser marking, even in the chromatic marking in which the contrast is lowered, for example, a marking with very good or good visibility of the contrast between the printing portion and the fabric color as in Examples 2 to 7 is used. I was able to get it.

  On the other hand, in Comparative Example 1 in which the adhesive layer was formed using only the adhesive, color development did not occur even when laser marking was performed. Further, in Comparative Examples 2 and 3 in which an energy absorber layer was formed by applying only an energy absorber without using an adhesive (acrylic resin adhesive), color development occurred by performing laser marking. However, there was no contrast visibility. Thus, even when only the energy absorber was applied to the sheet and used, the visibility of the contrast of the laser marking could not be obtained.

  Moreover, it turns out that the visibility of contrast is dependent on the viscosity of an energy absorber containing adhesive agent from the comparison with Example 1 and 2 and Examples 8-13. In particular, when the viscosity at 25 ° C. was 2000 to 500000 mPa · s, good results could be obtained. Furthermore, it can be seen from the comparison between Examples 1 and 2 and Examples 14 to 21 that the visibility of the contrast also depends on the content of the energy absorbent-containing adhesive. In particular, when carbon black is used as the energy absorber-containing adhesive, good results are obtained when the amount is 0.001 to 10 parts by mass with respect to 100 parts by mass of the adhesive (those not including the energy absorber). When a leuco dye and a developer were used, good results could be obtained in the case of 0.01 to 30 parts by mass.

  The laser marking sheet of the present invention can be effectively used as a plastic sheet widely used in credit cards, cash cards, ID cards, tag cards, display boards, authentication plates, ETC cards, and the like. It can also be used effectively for signs, windows, containers, flooring, scaled windows, level windows, stationery, filing cases, underlays, calendars, rulers, and the like.

It is a schematic diagram explaining the structure of one Embodiment of the sheet | seat for laser markings of this invention, and is a figure which shows a cross section perpendicular | vertical to the surface of the sheet | seat for laser markings. It is a schematic diagram which shows the process of irradiating a laser beam to the laser marking sheet | seat shown in FIG. 1, and marking. It is a schematic diagram explaining the structure of one Embodiment of the sheet | seat for laser markings of this invention, and is a figure which shows a cross section perpendicular | vertical to the surface of the sheet | seat for laser markings of this invention. It is a schematic diagram explaining the structure of other embodiment of the sheet | seat for laser markings of this invention, and is a figure which shows a cross section perpendicular | vertical to the surface of the sheet | seat for laser markings of this invention.

Explanation of symbols

1, 10: Laser marking sheet, 2: Light transmissive sheet, 3: Adhesive layer, 3a: Adhesive hardened layer, 4: Adhesive, 5: Energy absorber, 6: Laser beam, 7: Marking, 11: Back sheet, 12: base layer.

Claims (9)

A light transmissive sheet made of a thermoplastic resin, and an adhesive layer formed on the back side of the light transmissive sheet,
A sheet for laser marking, wherein the adhesive layer is formed from an acrylic resin adhesive in which an energy absorber that absorbs a laser beam to cause color development is dispersed.   The sheet for laser marking according to claim 1, wherein the adhesive layer is formed from the adhesive having a viscosity of 2000 to 500,000 mPa · s at 25 ° C.   The laser marking sheet according to claim 1 or 2, wherein the adhesive layer is formed from an acrylic resin adhesive in which carbon black is dispersed as the energy absorber.   3. The laser marking sheet according to claim 1, wherein the adhesive layer is formed from an acrylic resin adhesive in which a leuco dye and a developer are dispersed as the energy absorber. 4.   The thickness of the said adhesive bond layer is 5-500 micrometers, The sheet | seat for laser markings as described in any one of Claims 1-4.   The laser marking sheet according to any one of claims 1 to 5, wherein the adhesive layer is previously colored.   The sheet for laser marking according to claim 1, wherein the light transmissive sheet has a light transmittance of 40% or more. A method for producing a sheet for laser marking comprising a light transmissive sheet made of a thermoplastic resin and an adhesive layer formed on the back side of the light transmissive sheet,
In an acrylic resin adhesive, an energy absorber that absorbs a laser beam to cause color development is dispersed to obtain an energy absorber-containing adhesive,
The manufacturing method of the sheet | seat for laser marking which coats the obtained said energy absorber containing adhesive agent on the back surface side of the said light-transmissive sheet | seat, and forms the said adhesive bond layer.   The sheet for laser marking according to claim 8, wherein the energy absorbent-containing adhesive is prepared so that a viscosity at 25 ° C. is 2000 to 500,000 mPa · s, and is applied to the back side of the light transmissive sheet. Production method.

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