JP2021012318A - Retroreflective sheet - Google Patents

Abstract

To provide a retroreflective sheet that can make a retroreflective layer and a rear layer difficult to transmit ultraviolet rays.SOLUTION: A retroreflective sheet 10 comprises: a retroreflective layer 2 including a plurality of retroreflective elements 4 on one surface; a rear layer 6 provided to face the retroreflective elements 4; and a coupling portion 5 for coupling a part of the retroreflective elements 4 with a part of the rear layer 6. The retroreflective sheet has a gap 9 between another part of the retroreflective elements 4 and another part of the rear layer 6. The coupling portion 5 is composed of a resin composition 15 containing a poly-functional epoxy resin and a mono-functional epoxy compound having a long-chain hydrocarbon skeleton having 7-20 carbon atoms at a ratio 30-95 pts.mass and 5-70 pts.mass, respectively.SELECTED DRAWING: Figure 1

Description

The present invention relates to a retroreflective sheet.

The retroreflective sheet has the property of being able to reflect the incident light toward the light source. Since the retroreflective sheet has such properties, it is used for the purpose of making it easier to see an object such as a printed matter when it is irradiated with light at night or in a dark place. The retroreflective sheet is used, for example, as a traffic sign, a guide sign, a vehicle license plate, an advertising sign, a lane separation sign, a line-of-sight guide sign, and the like.

As such a retroreflective sheet, for example, Patent Document 1 below comprises a retroreflective layer having a plurality of retroreflective elements on one surface and a thermoplastic sealing film provided so as to face the plurality of retroreflective elements. A retroreflective sheet comprising a back layer and a binder provided between the retroreflective layer and the back layer is disclosed. In this retroreflective sheet, a part of the retroreflective layer and a part of the back layer are bonded by a binder, and a gap is created between the other part of the retroreflective element and the other part of the back layer. It is formed. Light incident on the retroreflective layer from the surface of such a retroreflective sheet is retroreflected at the interface between the retroreflective element and the void. The observer visually recognizes the light retroreflected at the interface between the retroreflective element and the void in this way.

Special Table 2000-508088

The binder used for the retroreflective sheet as described in Patent Document 1 may be formed from an ultraviolet curable material. Therefore, in this case, in order to fix the retroreflective layer and the back layer via the binder, it is necessary to irradiate the binder with an amount of ultraviolet rays that cures the binder, and the retroreflecting layer and the back layer In order to irradiate such an amount of ultraviolet rays to the binder sandwiched between the above, the retroreflecting layer and the back surface layer need to have a certain degree of ultraviolet transmission. However, on the other hand, from the viewpoint of suppressing deterioration of the retroreflective sheet and coloring the retroreflective layer and the back layer, there is also a demand for the retroreflective layer and the back layer to have a structure that makes it difficult for ultraviolet rays to pass through.

Therefore, an object of the present invention is to provide a retroreflective sheet capable of making the retroreflective layer and the back surface layer difficult to transmit ultraviolet rays.

In order to solve the above problems, the retroreflective sheet of the present invention includes a retroreflective layer having a plurality of retroreflective elements on one surface, a back surface layer provided facing the plurality of retroreflective elements, and a plurality of the above. A coupling portion for connecting a part of the retroreflective element and a part of the back surface layer is provided, and a gap is provided between the other part of the plurality of retroreflective elements and the other part of the back surface layer. The bonding portion contains a polyfunctional epoxy resin and a monofunctional epoxy compound having a long-chain hydrocarbon skeleton having 7 to 20 carbon atoms in a ratio of 30 to 95 parts by mass and 5 to 70 parts by mass, respectively. It is characterized by being composed of a resin composition.

As described above, the resin composition constituting the bonding portion of the retroreflective sheet of the present invention contains a monofunctional epoxy compound having a long-chain hydrocarbon skeleton having 7 to 20 carbon atoms in a proportion of 5 to 70 parts by mass. By containing such a monofunctional epoxy compound in the above ratio, the resin composition is in an adhesive state in which the retroreflective layer can be adhered to the back surface layer by being irradiated with ultraviolet rays of a predetermined energy. After a predetermined time has elapsed from this adhesiveable state, curing is completed and the curing is completed.

In addition, in this specification, "curing is completed" means a state in which the viscosity of the resin composition is increased to the extent that the retroreflective layer and the back surface layer cannot be bonded to each other via the resin composition.

According to such a resin composition, before the retroreflective layer and the back surface layer are bonded to each other, the resin composition is irradiated with ultraviolet rays of a predetermined energy, and the retroreflective layer and the back surface layer are subjected to the resin composition. The retroreflective layer and the back surface layer can be bonded by the step of laminating the resin composition and then completing the curing of the resin composition. Therefore, at least one of the retroreflective layer and the back surface layer may have a structure that does not transmit ultraviolet rays or a structure that does not easily transmit ultraviolet rays. Therefore, according to the retroreflective sheet of the present invention, for example, it is easy to add an ultraviolet absorber to the retroreflective layer for the purpose of suppressing deterioration, or to color the back layer from the viewpoint of improving the design.

The resin composition may have a thixo property.

The resin composition can be printed on the back layer by a printing method such as screen printing, gravure printing, flexographic printing, or inkjet printing. Of these, when the resin composition is applied by screen printing, it may be easier to apply the resin composition thicker than when the resin composition is applied by another printing method. Therefore, in the case of screen printing, it is easy to form a gap having a desired width between the plurality of retroreflective elements and the back surface layer. When the resin composition has a tix property, the resin composition can be easily applied by screen printing as compared with the case where the resin composition does not have the tix property. Therefore, since the resin composition has a thixo property, it is easy to form a retroreflective sheet having a desired width of the gap between the retroreflective element and the back surface layer. Further, when the resin composition has a thixo property, the shape of the pattern tends to be easily maintained when the resin composition is printed in a pattern. Therefore, for example, when the retroreflective sheet is a capsule-type retroreflective sheet, a desired capsule shape is more likely to be formed as compared with the case where the resin composition does not have a thixo property.

Further, the retroreflective sheet may further include a printing layer formed on a surface of the back layer facing the retroreflective layer.

When the print layer is formed on the surface of the back layer facing the retroreflective layer in this way, the light reaches the print layer and is reflected by the print layer under non-reflective conditions in which the light does not retroreflect. Therefore, the print layer can be clearly projected. On the other hand, under the retroreflective condition in which the light is retroreflected, the symbol is difficult to be projected because the light is retroreflected by the retroreflective layer before reaching the print layer. Therefore, according to this retroreflective sheet, the appearance of the pattern can be different under the non-reflective condition and the retroreflective condition.

Further, the back layer may have infrared absorption.

In this case, the way the retroreflective sheet is recognized by the infrared camera can be different from the way the retroreflective sheet is recognized by the infrared camera when the back layer does not have infrared absorption.

Further, the back layer may have infrared reflectivity.

In this case, the way the retroreflective sheet is recognized by the infrared camera can be different from the way the retroreflective sheet is recognized by the infrared camera when the back layer does not have infrared reflectivity.

Further, the retroreflective layer may have infrared absorption.

In this case, it is possible to suppress the retroreflection of infrared rays by the retroreflective sheet.

Further, the retroreflective layer may have infrared reflectivity.

In this case, the retroreflective property of infrared rays in the retroreflective sheet can be improved.

As described above, according to the present invention, there is provided a retroreflective sheet capable of making the retroreflective layer and the back surface layer difficult to transmit ultraviolet rays.

It is a figure which shows roughly a part of the cross section in the thickness direction of the retroreflective sheet which concerns on 1st Embodiment of this invention. It is a flowchart which shows the process of the manufacturing method of the retroreflective sheet which concerns on 1st Embodiment of this invention. It is a figure which shows schematicly the manufacturing apparatus of the retroreflection sheet which concerns on 1st Embodiment of this invention. It is sectional drawing which shows the state after the coating process of the resin composition which becomes the joint part shown in FIG. It is a figure which shows the retroreflective sheet which concerns on 2nd Embodiment of this invention from the same viewpoint as FIG.

Hereinafter, preferred embodiments of the retroreflective sheet according to the present invention will be described in detail with reference to the drawings.

(First Embodiment)
FIG. 1 is a diagram schematically showing a part of a cross section in the thickness direction of the retroreflective sheet according to the first embodiment of the present invention. In each of FIG. 1 and the other figures shown below, the size of each component may not be shown accurately due to exaggeration or the like for ease of understanding. Further, in each of FIG. 1 and the other figures shown below, only one reference code may be attached to those having the same configuration, and the reference code to be repeated may be omitted.

As shown in FIG. 1, the retroreflective sheet 10 of the present embodiment is a so-called capsule-type retroreflective sheet, and the surface protective layer 1, the retroreflective layer 2, the connecting portion 5, the back surface layer 6, the adhesive layer 7 and the like. A release layer 8 is provided. Hereinafter, these components provided in the retroreflective sheet 10 will be described in more detail.

The surface protective layer 1 is a layer of the retroreflective layer 2 that protects the surface F1 that is on the observer side when the retroreflective sheet 10 is used, and is the outermost layer of the retroreflective sheet 10 when the retroreflective sheet 10 is used. It is a layer. From the viewpoint of providing the retroreflective sheet 10 with excellent retroreflective properties, the surface protective layer 1 of the present embodiment is a transparent resin layer, and the total light transmittance of the surface protective layer 1 is set to, for example, 80% or more. Is preferable.

Examples of the material constituting such a surface protective layer 1 include acrylic resin, alkyd resin, fluorine resin, vinyl chloride resin, polyester resin, urethane resin, polycarbonate resin and the like. One type of these resins may be used alone, or a plurality of types may be used in combination. From the viewpoint of providing the surface protective layer 1 with weather resistance and processability, an acrylic resin, a polyester resin, and a vinyl chloride resin are preferable. Further, an acrylic resin is preferable in consideration of coating suitability and dispersibility of the colorant at the time of coloring. The surface protective layer 1 contains various agents such as an ultraviolet absorber, a light stabilizer, a heat stabilizer, a plasticizer, a cross-linking agent, an antioxidant, a fungicide, and a colorant, as long as the transparency is not significantly impaired. Additives can be added as appropriate.

The retroreflective layer 2 has a plate-shaped holding body portion 3 and a plurality of retroreflective elements 4. One surface F1 of the holding body portion 3 is covered with the surface protective layer 1, and a plurality of retroreflective elements 4 are provided on the other surface F2 of the holding body portion 3. In the retroreflective layer 2 of the present embodiment, the holding body portion 3 and the plurality of retroreflective elements 4 are integrally formed, and the retroreflective layer 2 is a single layer of resin.

The plurality of retroreflective elements 4 are not particularly limited as long as they have a reflecting surface suitable for retroreflective incident light. For example, when the retroreflective elements 4 having a polyhedron shape such as a triangular pyramid or a so-called cube corner shape are arranged in a close-packed shape, the retroreflective property is excellent, which is preferable.

The retroreflective layer 2 is a transparent resin layer from the viewpoint of providing the retroreflective sheet 10 with excellent retroreflective properties. Examples of the material constituting the retroreflective layer 2 include acrylic resin, urethane resin, fluorine resin, polyester resin, vinyl chloride resin, polycarbonate resin, polyarylate resin, silicone resin, and polyolefin resin. Ionomer resin and the like can be mentioned. One type of these resins may be used alone, or a plurality of types may be used in combination. Further, from the viewpoint of enhancing the transparency and weather resistance of the retroreflective layer 2, the retroreflective layer 2 is preferably made of an acrylic resin, a urethane resin, a fluorine resin, a polycarbonate resin or the like. Further, the retroreflective layer 2 has various agents such as an ultraviolet absorber, a light stabilizer, a heat stabilizer, a plasticizer, a cross-linking agent, an antioxidant, a fungicide, and a colorant, as long as the transparency is not significantly impaired. Additives can be added as appropriate.

The coupling portion 5 is a portion that couples a part of the plurality of retroreflective elements 4 and a part of the back surface layer 6. By interposing the coupling portion 5 between the retroreflective layer 2 and the back surface layer 6, a part of the plurality of retroreflective elements 4 and a part of the back surface layer 6 are coupled by the coupling portion 5, and a plurality of A gap 9 is formed between the other part of the retroreflective element 4 and the other part of the back surface layer 6.

The bonding portion 5 is made of a predetermined resin composition. This resin composition becomes an adhesiveable state in which it can be adhered to the retroreflective layer 2 and the back surface layer 6 by being irradiated with ultraviolet rays of a predetermined energy, and curing is completed after a predetermined time has elapsed from the adhesiveable state. The curing is completed. As described above, the resin composition forming the bonding portion 5 has a delayed curing property in which the curing is completed after a lapse of a predetermined time from the adhesiveable state. As described above, "curing is completed" means a state in which the viscosity of the resin composition is increased to the extent that the retroreflective layer 2 and the back surface layer 6 cannot be bonded to each other via the resin composition. The predetermined time is, for example, 10 seconds or more after being irradiated with ultraviolet rays having a predetermined energy.

Further, from the viewpoint of firmly bonding the retroreflective layer 2 and the back surface layer 6 by the bonding portion 5, the resin composition constituting the bonding portion 5 is an adhesive having an adhesive strength of 10 N / 25 mm or more after curing is completed. Is preferable. The adhesive force is applied when the adhesive portion between the retroreflective layer 2 and the joint portion 5 is broken, when the joint portion 5 is aggregated and broken, or when the adhesive portion between the back surface layer 6 and the joint portion 5 is broken. The value.

Such a resin composition contains a polyfunctional epoxy resin and a monofunctional epoxy compound having a long-chain hydrocarbon skeleton having 7 to 20 carbon atoms in a ratio of 30 to 95 parts by mass and 5 to 70 parts by mass, respectively. To do. The resin composition may contain other compounds such as a curing accelerator that accelerates the curing of the resin composition.

The polyfunctional epoxy resin is a resin having two or more epoxy groups in one molecule, and may be solid or liquid. Examples of such a polyfunctional epoxy resin include a bisphenol type epoxy compound such as a polybutadiene epoxy resin, a bisphenol A type epoxy resin, and a bisphenol F type epoxy resin, a naphthalene type epoxy compound, an aliphatic epoxy compound, a biphenyl type epoxy, and a glycidylamine type. Alcohol type epoxy compounds such as epoxy compounds and hydrogenated bisphenol A type epoxy compounds, epoxy modified silicones, phenol novolac type epoxy compounds, novolak type epoxy compounds such as cresol novolac type epoxy compounds, alicyclic epoxy compounds, aneuploid cyclic epoxy Compounds, polyfunctional epoxy compounds, glycidyl ether type epoxy compounds, glycidyl ester type epoxy compounds, halogenated epoxy compounds such as brominated epoxy compounds, rubber modified epoxy compounds, urethane modified epoxy compounds, epoxidized polybutadiene, epoxidized styrene-butadiene -Epoxy block copolymers, epoxy group-containing polyester compounds, epoxy group-containing polyurethane compounds, epoxy group-containing acrylic compounds and the like can be mentioned. These epoxy resins may be used alone or in combination of two or more.

The monofunctional epoxy compound is a compound in which one epoxy group is bonded to each molecule of a long-chain hydrocarbon skeleton having 7 to 20 carbon atoms. This one epoxy group may be bonded to the inside of the chain structure or to the end of the chain structure in the long-chain hydrocarbon skeleton. Further, the monofunctional epoxy compound may be in a solid state or in a liquid state. By containing such a monofunctional epoxy compound in a ratio of 5 to 70 parts by mass per 100 parts by mass of the total amount of the monofunctional epoxy compound and the polyfunctional epoxy resin, the resin composition has the delayed curability. Shown. For example, when this resin composition is irradiated with ultraviolet rays of about 500 mJ / cm ^2, curing can start after 2 minutes or more have passed at room temperature.

Examples of such monofunctional epoxy compounds include 1,2-epoxydodecane, 1,2-epoxyeicosan, 1,2-epoxydecane, 2-ethylhexylglycidyl ether, 1,2-epoxytetradecane, 1,2-. Epoxy hexadecane, glycidyl lauryl ether and the like can be mentioned.

Further, the resin composition constituting the bonding portion 5 preferably has a thixo property. When the resin composition has a thixo property, the shape of the pattern tends to be easily maintained when the resin composition is printed in a pattern. Therefore, for example, when the retroreflective sheet is a capsule type as described above, a desired capsule shape is more likely to be formed as compared with the case where the resin composition does not have a thixo property. Further, since the resin composition has a thixo property, the resin composition is subjected to pressure when it is applied by screen printing to have flexibility, and the viscosity is restored after the application. Easy to maintain shape. For example, the resin composition constituting the bonding portion 5 is preferably 10,000 mPa · s or more, more preferably 40,000 mPa · s or more, and 100,000 mPa · s or more when no pressure is applied. It is more preferably s or more. Further, by applying the resin composition by screen printing, it may be easy to apply the resin composition thickly. Therefore, since the resin composition has a thixo property, it is easy to form a retroreflective sheet having a space 9 between the plurality of retroreflective elements 4 and the back surface layer 6 having a desired width.

The back surface layer 6 is a resin layer provided so as to face the surface of the retroreflective layer 2 on the retroreflective element 4 side. Examples of the resin contained in the material constituting the back layer 6 include acrylic resin, urethane resin, fluorine resin, polyester resin, vinyl chloride resin, polycarbonate resin, polyarylate resin, silicone resin, and polyolefin. Examples thereof include based resins and ionomer resins. One type of these resins may be used alone, or a plurality of types may be used in combination. Further, from the viewpoint of enhancing the transparency and weather resistance of the back layer 6, the back layer 6 is preferably made of an acrylic resin, a urethane resin, a fluororesin, a polycarbonate resin or the like.

Further, the material constituting the back layer 6 may contain a colorant. As the colorant contained in the material constituting the back layer 6, for example, an inorganic pigment, an organic pigment, an organic dye, a pearl pigment or the like can be used. For the back layer 6, one of these colorants may be used alone, or two or more of these colorants may be used in combination.

Examples of the above inorganic pigments are titanium oxide, calcium carbonate, barium sulfate, zinc oxide, zinc sulfide, carbon black, cadmium red, molybdenum red, ultramarine, cobalt blue, petals, chromium oxide, iron black, cadmium yellow, titanium yellow. , Nickel titanium yellow, chrome titanium yellow, chrome yellow, yellow iron oxide, chrome orange, cadmium orange, gold powder, silver powder, copper powder, aluminum powder, bronze powder and the like. Examples of the organic pigments and dyes include anthraquinone, phthalocyanine, quinacridone, isoindolinone, dioxazine, quinophthalone, quinoimine, perylene, perinone, azo, quinoline, and methine. Examples thereof include organic compounds such as indigo and naphtholimide. Examples of the pearl pigment include titanium oxide-coated mica, bismuth oxide chloride, fish scale powder, and basic lead carbonate.

Further, in the present embodiment, various additives such as an ultraviolet absorber, a light stabilizer, a heat stabilizer, a plasticizer, a cross-linking agent, an antioxidant, and an antifungal agent can be appropriately added to the back layer 6.

The pressure-sensitive adhesive layer 7 is provided on the side of the back surface layer 6 opposite to the retroreflective layer 2 side, and is a layer that is attached to the adherend when the retroreflective sheet 10 is used.

As the material constituting the pressure-sensitive adhesive layer 7, for example, a pressure-sensitive adhesive, a heat-sensitive adhesive, a crosslinked adhesive, or the like can be appropriately selected. As the pressure-sensitive adhesive, for example, a polyacrylic acid ester pressure-sensitive adhesive obtained by copolymerizing an acrylic acid ester such as butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, nonyl acrylate with acrylic acid, vinyl acetate or the like. Examples thereof include silicone-based resin pressure-sensitive adhesives and rubber-based pressure-sensitive adhesives. Examples of the heat-sensitive adhesive include acrylic resins, polyester resins, and epoxy resins. From the viewpoint of providing the pressure-sensitive adhesive layer 7 with excellent weather resistance and adhesiveness, it is preferable to use an acrylic resin or a silicone-based resin.

The release layer 8 is a layer provided on the side opposite to the back surface layer 6 side of the pressure-sensitive adhesive layer 7. By covering the pressure-sensitive adhesive layer 7 with the release layer 8 before using the retroreflective sheet 10, it is possible to prevent dust and the like from adhering to the pressure-sensitive adhesive layer 7 and the pressure-sensitive adhesive layer 7 from adhering to an unintended place. To. On the other hand, when the retroreflective sheet 10 is used, the release layer 8 is peeled from the pressure-sensitive adhesive layer 7.

Such a release layer 8 is not particularly limited, but is made of, for example, a polyester film, a polypropylene film, paper, or the like.

As described above, the retroreflective sheet 10 of the present embodiment includes a retroreflective layer 2 having a plurality of retroreflective elements 4 on one surface, and a back surface layer 6 provided facing the plurality of retroreflective elements 4. A coupling portion 5 for coupling a part of the plurality of retroreflective elements 4 and a part of the back surface layer 6 is provided, and the other part of the plurality of retroreflective elements 4 and the other part of the back surface layer 6 are provided. It has a gap 9 in between. Further, the bonding portion 5 contains a polyfunctional epoxy resin and a monofunctional epoxy compound having a long-chain hydrocarbon skeleton having 7 to 20 carbon atoms in a ratio of 30 to 95 parts by mass and 5 to 70 parts by mass, respectively. It consists of a resin composition.

According to such a configuration, the light incident on the retroreflective layer 2 from the surface protective layer 1 of the retroreflective sheet 10 is retroreflected at the interface between the retroreflective element 4 and the void 9. Therefore, the observer visually recognizes the light retroreflected at the interface between the retroreflective element 4 and the void 9.

Further, the resin composition constituting the bonding portion 5 of the retroreflective sheet 10 of the present embodiment contains 5 to 70 parts by mass of a monofunctional epoxy compound having a long-chain hydrocarbon skeleton having 7 to 20 carbon atoms as described above. Contains in proportion. By containing such a monofunctional epoxy compound in the above ratio, the resin composition can be adhered so that the retroreflective layer 2 can be adhered to the back surface layer 6 by being irradiated with ultraviolet rays of a predetermined energy. It becomes a state, and after a predetermined time elapses from this adhesiveable state, curing is completed and the curing is completed. Since the resin composition of the present embodiment has delayed curability as described above, the resin composition is irradiated with ultraviolet rays having a predetermined energy before the retroreflective layer 2 and the back surface layer 6 are bonded to each other, and the resin composition is formed. The retroreflective layer 2 and the back layer 6 can be bonded to each other by the step of sticking the retroreflective layer 2 and the back surface layer 6 through an object and then completing the curing of the resin composition. Therefore, according to the retroreflective sheet 10 of the present embodiment, the retroreflective layer 2 and the back surface layer 6 can be made of a material that does not transmit ultraviolet rays or a material that does not easily transmit ultraviolet rays. For example, the retroreflective layer 2 and the back surface layer 6 may be made of a material that does not transmit ultraviolet rays by 50% or more.

Therefore, even when the ultraviolet absorber is added to the retroreflective layer 2 and the back layer 6 as described above, the retroreflective layer 2 and the back layer 6 can be bonded by the resin composition. Therefore, according to the retroreflective sheet 10 of the present embodiment, the retroreflective layer 2 and the back surface layer 6 can be provided with ultraviolet absorption to improve the weather resistance.

Further, when the retroreflective layer 2 and the back layer 6 are colored as described above, the retroreflective layer 2 and the back layer 6 may not easily transmit ultraviolet rays. However, even when the retroreflective layer 2 and the back surface layer 6 are colored in this way, the retroreflective layer 2 and the back surface layer 6 can be bonded together by the above resin composition. Therefore, according to the retroreflective sheet 10 of the present embodiment, the designability can be improved by the colored retroreflective layer 2 and the back surface layer 6.

Next, a method of manufacturing the retroreflective sheet 10 will be described.

FIG. 2 is a flowchart showing a process of a method for manufacturing a retroreflective sheet according to the present embodiment. As shown in FIG. 2, the method for manufacturing the retroreflective sheet 10 of the present embodiment includes a preparation step P1, a coating step P2, an energy applying step P3, a bonding step P4, and a curing acceleration step P5. Further, FIG. 3 is a diagram schematically showing a manufacturing apparatus 100 for the retroreflective sheet 10 according to the present embodiment.

(Preparation process P1)
This step is a step of preparing a resin composition that has a viscosity that allows adhesion over a predetermined time after a predetermined energy is applied and that completes curing after the lapse of the predetermined time. In the present embodiment, as such a resin composition, a resin composition that begins to cure approximately 2 minutes or more after irradiation with ultraviolet rays of about 500 mJ / cm ² is prepared, and this is described in the printing apparatus 120 described later. Fill in. Further, in this step, a sheet 12 having the retroreflective layer 2 and a sheet 16 having the back surface layer 6 are prepared. Specifically, a sheet roll 102 in which the sheet 12 having the retroreflective layer 2 is wound and a sheet roll 106 in which the sheet 16 having the back surface layer 6 is wound are prepared.

(Coating process P2)
This step is a step of applying the resin composition to be the bonding portion 5 to the back surface layer 6. The sheet 16 unwound from the sheet roll 106 is conveyed to the bottom of the printing apparatus 120 at a predetermined transfer speed while being tensioned by being hung on the rollers 111 and 112. The sheet 16 conveyed to the bottom of the printing apparatus 120 is coated with the resin composition to be the joint portion 5 by the printing apparatus 120. That is, the resin composition serving as the bonding portion 5 is applied to the back surface layer 6.

The method of applying the resin composition to be the bonding portion 5 to the back surface layer 6 in this step is not particularly limited. For example, the printing device 120 is a device that coats the back layer 6 with the resin composition by any printing method such as screen printing, gravure printing, flexographic printing, and inkjet printing. As described above, screen printing is particularly preferable among these printing methods, and it may be easy to apply the resin composition thickly. Therefore, it may be easy to form a gap 9 between the plurality of retroreflective elements 4 and the back surface layer 6. Examples of the screen printing method include a plate and squeegee method and a rotary screen device method.

FIG. 4 is a cross-sectional view showing the state of the resin composition 15 serving as the joint portion 5 after the coating step P2. Although the retroreflective layer 2 is not arranged on the resin composition 15 before the energy application step P3, it is referred to in FIG. 4 in order to facilitate the explanation of the coating thickness t and the like of the resin composition 15. The retroreflective layer 2 is shown as.

In the coating step P2, the resin composition 15 is coated on the back surface layer 6. At this time, the thickness t of the resin composition 15 is preferably 2/3 or more and 4/3 or less of the height h of the retroreflective element 4 adhered to the resin composition 15. Further, the thickness t is preferably constant. By coating the resin composition 15 in this way, when the resin composition 15 is sandwiched between the retroreflective layer 2 and the back surface layer 6 and pressed in a later step, between the retroreflective elements 4 adjacent to each other. The groove can be filled with the resin composition 15. Therefore, the resin composition 15 can firmly bond the back surface layer 6 and the retroreflective layer 2.

Further, the area of the area to which the resin composition 15 is applied is preferably 30% to 70% of the area of the back surface layer 6 in a plan view of the back surface layer 6, and is preferably about 50% to 60%. Is more preferable. By coating the resin composition 15 in this way, the voids 9 can be sufficiently formed while the retroreflective layer 2 and the back surface layer 6 are sufficiently bonded by the resin composition 15.

(Energy application process P3)
This step is a step of irradiating the resin composition 15 to be the bonding portion 5 with ultraviolet rays having a predetermined energy.

After the coating step P2, the sheet 16 coated with the resin composition 15 is conveyed below the ultraviolet irradiation device 130. When the resin composition 15 is irradiated with ultraviolet rays from the ultraviolet irradiation device 130, a predetermined energy is applied to the resin composition 15 by the ultraviolet rays, and the resin composition 15 begins to cure after a lapse of a predetermined time. Specifically, the resin composition 15 is irradiated with ultraviolet rays of about 500 mJ / cm ² . Therefore, as described above, the resin composition 15 begins to cure approximately 2 minutes or more after being irradiated with ultraviolet rays.

The sheet 16 in a state where the resin composition 15 is coated and a predetermined energy is applied to the resin composition 15 is conveyed from the ultraviolet irradiation device 130 to the bottom of the pressing roll 113 at the predetermined conveying speed. In the present embodiment, the time required for the sheet 16 to be conveyed from the ultraviolet irradiation device 130 to the pressing roll 113 is approximately 10 seconds to 2 minutes. As described above, the resin composition 15 in the present embodiment begins to cure 2 minutes or more after being irradiated with ultraviolet rays. Therefore, when the resin composition 15 reaches the pressing roll 113, it is generally in a state before curing starts.

(Lasting process P4)
This step is a step of bonding the retroreflective layer 2 and the back surface layer 6 via the resin composition 15 after the energy applying step P3. The sheet 12 unwound from the sheet roll 102 is overlapped with the sheet 16 via the resin composition 15 by using the pressing roll 113. As described above, when the resin composition 15 reaches the pressing roll 113, it is in a state before curing starts, and has a viscosity that allows adhesion. Therefore, in this step, after the sheet 12 is overlapped with the sheet 16 via the resin composition 15, the sheet 12 is pressed toward the sheet 16 by the pressing roll 113, so that the sheet 12 is retroreflected through the resin composition 15. The layer 2 and the back surface layer 6 are bonded together. At this time, the pressure applied to the retroreflective layer 2 is a pressure that suppresses the deformation of the retroreflective element 4. The resin composition 15 sandwiched between the retroreflective element 4 and the back surface layer 6 is pushed by the retroreflective element 4 and the back surface layer 6 and flows as the distance between the retroreflective element 4 and the back surface layer 6 approaches. When the pressure applied to the retroreflective layer 2 is a pressure that suppresses the deformation of the retroreflective element 4, the resin composition 15 is pressed until the retroreflective element 4 and the back surface layer 6 are in contact with each other. No pressure is applied to 15, and the flow of the resin composition 15 stops.

By sandwiching the resin composition 15 between the retroreflective element 4 and the back surface layer 6 as described above, a part of the retroreflective element 4 and a part of the back surface layer 6 are adhered by the resin composition 15, and retroreflective. A gap 9 is formed between the other part of the element 4 and the other part of the back surface layer 6.

By the way, in the present embodiment, an example in which this step is performed before the curing of the resin composition starts by using the resin composition 15 which is a state before the curing starts when the pressing roll 113 is reached has been described. However, other resin compositions may be used as long as they have a viscosity that allows adhesion over a predetermined time after the predetermined energy is applied and have the property of completing curing after a lapse of a predetermined time. .. That is, even if the resin composition starts curing from the time when the predetermined energy is applied until it reaches the pressing roll 113, the viscosity is set so that it can be adhered over a predetermined time until the pressing roll 113 is reached after the predetermined energy is applied. If so, a resin composition that starts curing by the time it reaches the pressing roll 113 may be used. When a resin composition that starts to cure before reaching the pressing roll 113 is used, the viscosity of the resin composition is increased by 30% or more based on the viscosity of the resin composition when a predetermined energy is applied. It is preferable to carry out this step before the above. By doing so, the retroreflective layer 2 and the back surface layer 6 can be effectively bonded to each other.

However, it is more preferable that this step is performed before the curing of the resin composition 15 begins. By stacking the retroreflective layer 2 and the back surface layer 6 via the resin composition 15 before the resin composition 15 starts to cure, the resin composition 15 can be easily adhered to the retroreflective layer 2 and the back surface layer 6. Can be.

In this way, in this step, the retroreflective layer 2 and the back surface layer 6 are laminated and bonded to each other via the resin composition to which energy is applied before a predetermined time elapses.

In this step, the predetermined time during which the bondable state is maintained after the predetermined energy is applied does not have to be approximately 2 minutes as described above. For example, it may be less than 1 minute or longer than 2 minutes. When the predetermined time is longer than 2 minutes, a sufficient time can be secured from applying energy to the resin composition 15 to bonding the retroreflective layer 2 and the back surface layer 6. When the predetermined time is within 1 minute, the time is preferably, for example, 10 seconds or more, and more preferably 30 seconds or more. In the method for producing a retroreflective sheet as described above, it tends to take about 10 seconds or more from applying a predetermined energy to the resin composition 15 to laminating the retroreflective layer 2 and the back surface layer 6. is there. Therefore, by setting the predetermined time to 10 seconds or more, the retroreflective layer 2 and the back surface layer 6 can be effectively bonded to each other.

(Curing Acceleration Step P5)
This step is a step of increasing the curing rate of the resin composition 15 after the bonding step P4. In the curing acceleration step P5 of the present embodiment, the sheets 12 and 16 stacked via the resin composition 15 are heated when they pass under the heating device 150. The heating device 150 is not limited to heating the resin composition 15 from above, but may heat the resin composition 15 from below, and heats the resin composition 15 from above and below. There may be. The resin composition 15 is heated by the heating device 150 to accelerate curing. The heating temperature of the resin composition 15 by the heating device 150 is preferably a sufficiently low temperature at which deformation of the retroreflective layer 2 and the back surface layer 6 can be suppressed, and is, for example, about 60 ° C. to 80 ° C. The higher the heating temperature of the resin composition 15 by the heating device 150, the easier it is for the curing of the resin composition 15 to be promoted. The heating time of the resin composition 15 by the heating device 150 is, for example, about 3 to 10 minutes.

As a method for adjusting the curing rate of the resin composition 15, in addition to adjusting the heating temperature and the heating time in the curing acceleration step P5, the amount of ultraviolet light irradiating the resin composition 15 in the energy applying step P3 is used. There is also a method of adjustment. The higher the energy of the ultraviolet rays applied to the resin composition 15, the faster the curing rate of the resin composition 15 tends to be.

The sheet 12 and the sheet 16 heated by the heating device 150 are wound by the winding roll 160 while being tensioned by being hung on the rollers 114 and 115. The resin composition 15 is cured before the sheet 12 and the sheet 16 are wound by the take-up roll 160 to form the joint portion 5, and the deformation of the joint portion 5 is suppressed. Therefore, the relative positional deviation between the retroreflective layer 2 and the back surface layer 6 is suppressed. The retroreflective sheet 10 is obtained by cutting the sheet 12 and the sheet 16 wound in this way to an appropriate size.

Although the description of the method for producing the retroreflective sheet 10 does not mention the method for laminating the surface protective layer 1, the adhesive layer 7, and the release layer 8, the laminating method for these layers is not particularly limited. For example, the surface protective layer 1 may be laminated on the retroreflective layer 2 in the preparation step P1 or may be laminated on the retroreflective layer 2 after the bonding step P4. Further, the pressure-sensitive adhesive layer 7 and the release layer 8 may be laminated on the back surface layer 6 in the preparation step P1 or may be laminated on the back surface layer 6 after the bonding step P4.

The method for producing the retroreflective sheet 10 described above includes a coating step P2, an energy applying step P3, and a bonding step P4, and the resin composition 15 can be bonded for a predetermined time after a predetermined energy is applied. The viscosity is high, and curing is completed after the lapse of the predetermined time. Therefore, before the retroreflective layer 2 and the back surface layer 6 are bonded to each other via the resin composition 15, the resin composition 15 is irradiated with ultraviolet rays having a predetermined energy, and the retroreflective layer 2 and the back surface are irradiated through the resin composition 15. The curing of the resin composition 15 can be completed after the layers 6 are bonded together. Therefore, the retroreflective layer 2 and the back surface layer 6 do not need to transmit ultraviolet rays as an energy source because the resin composition 15 to be the bonding portion 5 is cured. Therefore, at least one of the retroreflective layer 2 and the back surface layer 6 can be made of a material that does not transmit ultraviolet rays, for example, 50% or more, or a material that does not transmit ultraviolet rays.

As described above, the method for manufacturing the retroreflective sheet 10 of the present embodiment can expand the range of selection of the constituent materials of the retroreflective layer 2 and the back surface layer 6.

Further, as described above, in the method for producing the retroreflective sheet 10 of the present embodiment, the resin composition 15 is an ultraviolet curable resin, and the resin composition 15 is irradiated with ultraviolet rays in the energy applying step P3. Since the resin composition 15 is an ultraviolet curable resin, the resin composition 15 can be cured without applying heat, so that deformation of the retroreflective layer 2 and the back surface layer 6 due to heat can be suppressed.

Further, the method for producing the retroreflective sheet 10 of the present embodiment includes a curing acceleration step P5 for accelerating the curing rate of the resin composition 15 after the bonding step P4. By accelerating the curing of the resin composition 15, the time required for producing the retroreflective sheet 10 can be shortened.

In the method for manufacturing the retroreflective sheet 10 of the present embodiment, heat is applied to the retroreflective layer 2 and the back surface layer 6 in the curing acceleration step P5. As described above, the retroreflective layer in the curing promoting step P5. The heating temperature of 2 and the back layer 6 is set to be sufficiently low.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. Unless otherwise specified, the same or equivalent components as those in the first embodiment are designated by the same reference numerals, and duplicate description will be omitted.

FIG. 5 is a diagram showing a retroreflective sheet according to a second embodiment of the present invention from the same viewpoint as in FIG. As shown in FIG. 5, such printing is provided in that the retroreflective sheet 10 of the present embodiment further includes a printing layer 20 formed on a surface of the back layer 6 facing the retroreflective layer 2. It is different from the retroreflective sheet 10 of the first embodiment which does not have a layer.

The print layer 20 is usually formed by means such as gravure printing, screen printing, flexographic printing, and inkjet printing, and has a predetermined pattern and color. As shown in FIG. 5, the print layer 20 is formed between the retroreflective layer 2 and the back surface layer 6, and at least a part of the print layer 20 is formed between the joint portion 5 and the back surface layer 6. Has been done.

Such a retroreflective sheet 10 of the present embodiment is, for example, a printing layer on the surface of the back layer 6 facing the retroreflective layer 2 after the preparatory step P1 and before the coating step P2. It can be manufactured by performing a printing layer forming step of forming 20.

As described above, the retroreflective sheet 10 of the present embodiment further includes a print layer 20 formed between the retroreflective layer 2 and the back surface layer 6. When the print layer 20 is formed on the surface of the back layer 6 facing the retroreflective layer 2, the light reaches the print layer 20 under non-reflective conditions in which the light does not retroreflect. Since the light is reflected by the print layer 20, the print layer 20 can be clearly projected. On the other hand, under the retroreflective condition in which the light is retroreflected, the light is retroreflected by the retroreflective layer 2 before reaching the print layer 20, so that the print layer 20 is less likely to be projected. Therefore, according to the retroreflective sheet 10 of the present embodiment, the appearance of the pattern can be different under the non-reflective condition and the retroreflective condition, and the design can be improved.

By the way, when the connecting portion 5 and the back surface layer 6 are integrally formed, the shape of the boundary between the back surface layer 6 and the connecting portion 5 tends to be curved. Therefore, if a print layer is formed on the back layer 6 in this case, there is a concern that the print layer formed at the boundary and the vicinity of the boundary may be distorted. However, in the retroreflective sheet 10 of the present embodiment, the joint portion 5 and the back surface layer 6 are formed as separate bodies, and the printed layer 20 is formed on the surface of the back surface layer 6, so that the joint portion 5 and the back surface layer 6 are formed. Unlike the case where the back layer 6 is integrally formed, the print layer 20 is formed substantially flat. Therefore, according to the retroreflective sheet 10 of the present embodiment, distortion of the print layer can be effectively suppressed.

Further, when the print layer 20 is formed on the back layer 6, the ultraviolet rays may be blocked by the print layer 20 and may not be sufficiently transmitted to the resin composition 15. In this case, the adhesion between the retroreflective layer 2 and the back surface layer 6 may be insufficient. However, in the retroreflective sheet 10 of the present embodiment, similarly to the retroreflective sheet 10 of the first embodiment, the monofunctional epoxy compound having a long-chain hydrocarbon skeleton having 7 to 20 carbon atoms is contained in a proportion of 5 to 70 parts by mass. Depending on the resin composition contained, the retroreflective layer 2 and the back surface layer 6 are adhered to each other. According to such a configuration, as described above, the resin composition 15 can be irradiated with ultraviolet rays before the retroreflective layer 2 and the back surface layer 6 are overlapped with each other. The resin composition 15 can be irradiated with a large amount of ultraviolet rays as compared with the case of irradiating the resin composition 15 with ultraviolet rays after superimposition. Therefore, even when a part of the ultraviolet rays is blocked by the printing layer 20, the resin composition 15 can be irradiated with sufficient ultraviolet rays. Therefore, according to the retroreflective sheet 10 of the present embodiment, the print layer 20 formed on the back layer 6 can improve the design and effectively suppress the peeling of the retroreflective layer 2 and the back layer 6. Can be done.

In the present embodiment, the print layer 20 may be provided with infrared absorption or infrared reflection. Further, the print layer 20 may be used as a hologram or a watermark pattern.

Although a preferred embodiment of the present invention has been described above as an example, the present invention is not limited thereto.

For example, in the above embodiment, the example including the surface protective layer 1 has been described, but the surface protective layer 1 is not an essential component. The pressure-sensitive adhesive layer 7 is also not an essential component. For example, when the back surface layer 6 is made of an adhesive, the retroreflective sheet 10 can be attached to the object even if the adhesive layer 7 is not provided, so that the layer structure of the retroreflective sheet 10 can be simplified. , It is possible to suppress an increase in the production cost of the retroreflective sheet 10.

Further, the retroreflective sheet of the present invention may be provided with a layer other than the layer exemplified in the above embodiment. For example, a coloring layer or a printing layer may be provided between the surface protection layer 1 and the retroreflection layer 2.

Further, the back surface layer 6 may have infrared absorption. With such a configuration, the way the retroreflective sheet 10 is recognized by an infrared camera or the like can be made different from the way the retroreflective sheet that does not have infrared absorption is recognized, and a retroreflective sheet that is difficult to forge can be realized. ..

Further, the back surface layer 6 may have infrared reflectivity. With such a configuration, the way the retroreflective sheet 10 is recognized by an infrared camera or the like can be different from the way the retroreflective sheet that does not have infrared reflectivity is recognized, and a retroreflective sheet that is difficult to forge can be realized. ..

Further, the retroreflective layer 2 may have infrared absorption. In this case, it is possible to suppress the retroreflection of infrared rays by the retroreflective sheet 10. When the retroreflective sheet is used for license plate applications, if it is imaged by an automatic number plate recognition system (ALPR) or the like, visibility may be lowered due to halation, and the characters on the license plate may not be readable. By imparting infrared absorption to the retroreflective layer 2, the color of the retroreflective sheet looks dark when the sheet is viewed with infrared rays, and halation can be suppressed. As a result, the readability and detectability by the ALPR system or the like can be improved.

Further, the retroreflective layer 2 may have infrared reflectivity. In this case, the retroreflective property of infrared rays in the retroreflective sheet 10 can be improved. By imparting infrared reflectivity to the retroreflective layer, the detectability by an infrared camera or the like can be significantly improved when the retroreflective sheet is used, for example, in an object detection system or the like. In addition, it is possible to realize a sign that is difficult to see by the human eye, which is detected only by an infrared visual recognition device or the like.

Further, in the above embodiment, the joint portion 5 may be colored, and the colored joint portion 5 may form a pattern on the retroreflective sheet. In this case, for example, a retroreflective sheet that is visually recognized as different colors and patterns during the daytime and at nighttime can be configured.

Further, in the first embodiment, the surface protective layer 1, the retroreflective layer 2, the bonding portion 5, the back surface layer 6, and the pressure-sensitive adhesive layer 7 may all be formed transparently. In this case, for example, a retroreflective sheet having different visibility between retroreflective conditions and non-reflective conditions when attached to a window or the like can be configured, and can function as a blindfold for the room.

Further, in the second embodiment, the printing layer 20 may be formed so that the bonding strength between the bonding portion 5 and the printing layer 20 is larger than the bonding strength between the back surface layer 6 and the printing layer 20. In this case, since the bonding strength between the bonding portion 5 and the printing layer 20 is larger than the bonding strength between the back layer 6 and the printing layer 20, when the bonding portion 5 is to be peeled off from the back layer 6, the back layer 6 Peeling or cohesive failure may occur with the printing layer 20. Therefore, duplication or modification of the print layer 20 is prevented, and the falsification prevention function can be enhanced.

Further, in the above embodiment, the resin composition 15 is coated by screen printing, but the coating method of the resin composition 15 is not particularly limited. However, by coating the resin composition 15 by screen printing, it may be easy to apply the resin composition 15 thickly.

Further, in the above embodiment, the resin composition 15 is applied to the back surface layer 6 in the coating step P2, but the resin composition 15 may be applied to the retroreflective layer 2.

Further, in the above embodiment, the example including the curing acceleration step P5 has been described, but the curing acceleration step P5 is not an essential step.

As described above, according to the present invention, a retroreflective sheet capable of having a structure in which the retroreflective layer and the back surface layer are difficult to transmit ultraviolet rays is provided, and can be used in fields such as guide signs and advertising signs.

1 ... Surface protection layer 2 ... Retroreflective layer 3 ... Holder part 4 ... Retroreflective element 5 ... Bonding part 6 ... Back layer 7 ... Adhesive layer 8 ...・ Peeling layer 9 ・ ・ ・ Void 10 ・ ・ ・ Retroreflective sheet 20 ・ ・ ・ Printing layer P1 ・ ・ ・ Preparation process P2 ・ ・ ・ Coating process P3 ・ ・ ・ Energy application process P4 ・ ・ ・ Laminating process P5 ・・ ・ Curing acceleration process

Claims (7)

A retroreflective layer having a plurality of retroreflective elements on one surface,
A back layer provided so as to face the plurality of retroreflective elements,
A coupling portion that connects a part of the plurality of retroreflective elements and a part of the back surface layer,
With
A gap is provided between the other part of the plurality of retroreflective elements and the other part of the back layer.
The bonding portion contains a polyfunctional epoxy resin and a monofunctional epoxy compound having a long-chain hydrocarbon skeleton having 7 to 20 carbon atoms in a proportion of 30 to 95 parts by mass and 5 to 70 parts by mass, respectively. A retroreflective sheet characterized by being made of objects. The retroreflective sheet according to claim 1, wherein the resin composition has a thixo property. The retroreflective sheet according to claim 1 or 2, further comprising a printed layer formed on a surface of the back layer facing the retroreflective layer. The retroreflective sheet according to any one of claims 1 to 3, wherein the back layer has infrared absorption. The retroreflective sheet according to any one of claims 1 to 3, wherein the back surface layer has infrared reflection property. The retroreflective sheet according to any one of claims 1 to 5, wherein the retroreflective layer has infrared absorption. The retroreflective sheet according to any one of claims 1 to 5, wherein the retroreflective layer has infrared reflectivity.

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