Luminous sheet and producing method thereof

Abstract

To provide a luminous sheet developing high brightness and a producing method thereof.SOLUTION: A luminous sheet of the present invention is provided with a film-like luminous paint layer on a surface of a film base material, and in the luminous paint layer, luminous particles having a small particle size are located in close proximity to the film base material, and the luminous particles are arranged so that the particle size becomes gradually larger toward outside of the film base material, and the luminous particles having large particle size are located at the outermost side. In the luminous sheet, each of luminous particles with different average particle sizes are mixed into an alcohol mixture composed of alcohols having different boiling points, and then adds and stirs the luminous particles having a large average particle size to an acrylate emulsion with a large acidity to prepare a luminous coating A, and the luminous particles with small average particle size are added to the acrylate emulsion having small acidity and stirred to prepare a luminous coating B, and after mixing both of them and applying it to the surface of the film base material, and then heating and drying in two stages.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a luminous sheet, in particular a luminous sheet that has good adhesion between luminous particles and a film substrate and exhibits high luminance by leveling the luminance between the luminous particles. The present invention also relates to a method for producing the luminous sheet. [Background technology]

[0002] In order to achieve high luminescence brightness in phosphorescent particles having strontium aluminate crystals using europium (Eu) and dysprosium (Dy) as activators, Eu 3+ It is necessary to effectively utilize the phosphorescence that transitions from Sr3Al2DyO 7.5 This has been done by forming a heterogeneous phase called However, in the case of such strontium aluminate phosphorescent particles, in addition to the problem of aggregation occurring between the phosphorescent particles, particles with a large particle size have the problem that while they have high luminance (bright), they have poor dispersibility due to their poor crystallinity, while phosphorescent particles with a small particle size have the problem of high crystallinity but low luminance (dark).

[0003] Furthermore, as a luminous sheet that exhibits a long-lasting luminous effect, for example, the following Patent Document 1 has proposed a luminous sheet that uses a luminous powder made of a luminous phosphor composed of an aluminate of an alkaline earth metal with Eu as the main activator and having a particle size of 20 to 100 μm. Patent Document 1 also discloses a configuration in which a concealing layer containing titanium oxide is provided on a coating layer of paint containing luminous powder. However, since commercially available luminescent powders have a certain particle size distribution, if a paint containing a luminescent powder containing a mixture of luminescent particles smaller than the average particle size and luminescent particles larger than the average particle size is prepared as is and applied to a film substrate, the luminescent powder with larger particle size will settle to the film substrate side, forming an arrangement structure (layer cross-sectional structure) in which the luminescent powder with smaller particle size is located above it, and sufficient adhesion may not be obtained between the film substrate and the luminescent particle surface layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-276108 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to solve the above problems and provide a luminous sheet that exhibits good adhesion between the luminous particles and the film substrate and exhibits high luminance, and a method for producing the same. The inventors of the present invention have attempted to control the arrangement of the phosphorescent particles by changing the degree of crystallinity in order to improve the brightness of the phosphorescent particles and the adhesion between the phosphorescent particles and the film substrate. They then replaced the solvent of phosphorescent particles of different average particle sizes with a mixed solvent of alcohols with different boiling points, and dispersed them in two types of acrylate emulsions with different acidities to prepare phosphorescent paint A and phosphorescent paint B. They mixed phosphorescent paints A and B to obtain a phosphorescent paint, which was then applied to a film substrate and dried by heating in two stages. As a result, a structure was obtained in which phosphorescent particles with large particle diameters were present on the surface side, and the particle diameters gradually became smaller toward the film substrate side, with phosphorescent particles with small particle diameters present and arranged on the film substrate side (hereinafter referred to as a gradation structure). They discovered that a phosphorescent sheet with this gradation structure has better adhesion between the phosphorescent particles and the film substrate than conventional phosphorescent sheets and exhibits high brightness, and thus completed the present invention. [Means for solving the problem]

[0006] The luminescent sheet of the present invention is a luminescent sheet having a film-like luminescent paint layer containing luminescent particles of different particle diameters provided on the surface of a film substrate, and is characterized in that in the luminescent paint layer, the luminescent particles with smaller particle diameters are located close to the film substrate, the luminescent particles are arranged so that the particle diameters gradually increase toward the outside of the film substrate, and the luminescent particles with larger particle diameters are located on the outermost side.

[0007] Furthermore, the present invention is characterized in that, in the luminescent sheet having the above-mentioned characteristics, the particle diameter of the luminescent particles located on the outside of the film substrate is 60 μm or more and 200 μm or less, and the particle diameter of the luminescent particles located in close proximity to the film substrate is 20 μm or more and less than 60 μm.

[0008] Furthermore, the present invention provides a method for producing the above-mentioned luminous sheet, the method comprising: Step I: preparing first phosphorescent particles a and second phosphorescent particles b having different average particle sizes; Step II: preparing two types of acrylic emulsions having different acidities and preparing an alcohol mixed solvent having alcohols having different boiling points; Step III: mixing the first luminous particles a having a larger average particle size with the alcohol mixed solvent, and then adding and stirring the resulting mixture to the acrylic emulsion having a higher acidity to prepare a luminous paint A; and mixing the second luminous particles b having a smaller average particle size with the alcohol mixed solvent, and then adding and stirring the resulting mixture to the acrylic emulsion having a lower acidity to prepare a luminous paint B. Step IV: A step of mixing the phosphorescent paint A and the phosphorescent paint B to coat the paint obtained on the film substrate in a uniform thickness, drying the paint at a first drying temperature below the boiling point of the alcohol having a lower boiling point, and then raising the temperature and drying the paint at a second drying temperature above the boiling point of the alcohol having a higher boiling point. The present invention is characterized by comprising: In this specification, "acidity" refers to the acid value contained in the acrylic emulsion. The acid value was measured by dissolving a sample in a mixed solvent of xylene and 2-propanol, then titrating it with a KOH-mg / g potassium hydroxide-ethanol solution by potentiometric titration, and measuring the inflection point on the titration curve as the end point. The acidity of the emulsions used in the examples was 35 for TOCRYL W168 and 20 for TOCRYL N140EC-2.

[0009] Furthermore, the present invention is characterized in that, in the manufacturing method of the luminescent sheet having the above characteristics, the average particle size of the first luminescent particles a is 60 μm or more and 200 μm or less, and the average particle size of the second luminescent particles b is 20 μm or more and less than 60 μm.

[0010] The present invention is also characterized in that in the method for producing a luminous sheet having the above characteristics, the acidity of the acrylic emulsion used to prepare the luminous paint A is 25 or more, and the acidity of the acrylic emulsion used to prepare the luminous paint B is less than 25.

[0011] Furthermore, the present invention is also characterized in that in the method for producing a luminous sheet having the above characteristics, the alcohol mixed solvent is an ethanol / methanol mixed solvent. Effect of the Invention

[0012] In the luminous sheet of the present invention, the luminous particles having a small particle size are present on the film substrate side, so that the adhesion between the luminous particles and the film substrate is high, and further, the luminous particles having a large particle size are located on the outermost side, so that when exposed to light, high brightness is exhibited and bright light emission is observed. Furthermore, by using the manufacturing method of the luminous sheet of the present invention, it is possible to manufacture, with a single coating, a luminous sheet provided with a luminous paint layer having a gradation structure in which luminous particles with small particle diameters are located close to the film substrate, the luminous particles are arranged so that the particle diameters gradually increase toward the outside of the film substrate, and the luminous particles with large particle diameters are located on the outermost side. [Brief description of the drawings]

[0013] [Figure 1] 1 is an electron microscope image (SEM image, magnification: 100x) showing the dispersion state of luminous particles in a cross section of a luminous sheet of the present invention obtained in an example, the lower side being the film substrate. [Diagram 2] (a) is an SEM image (magnification: 50x) showing the surface condition of the luminous sheet of the present invention obtained in the example before a bending test was conducted, and (b) is an SEM image (magnification: 50x) showing the surface condition of the luminous sheet obtained in the comparative example before a bending test was conducted. [Diagram 3] (a) is an SEM image (magnification: 100x) showing the surface condition of the bent portion of the luminous sheet of the present invention obtained in the example after a bending test (20 times), and (b) is an SEM image (magnification: 100x) showing the surface condition of the bent portion of the luminous sheet obtained in the comparative example after a bending test (5 times). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The luminescent sheet of the present invention has a film-like luminescent paint layer containing luminescent particles of different particle sizes provided on the surface of a film substrate, and as shown in the electron microscope image (SEM image) of Figure 1, this luminescent paint layer has a gradation structure in which the luminescent particles with small particle sizes are located close to the film substrate, and the luminescent particles are arranged with a continuous change in particle size such that the particle size gradually increases toward the outside of the film substrate, with the luminescent particles with large particle sizes being located in greater numbers on the outermost side (topmost surface). In this case, the particle size of the large phosphorescent particles that are located on the outermost surface side (outside the film substrate) and exhibit high luminance is preferably 60 μm or more and 200 μm or less, and more preferably 60 μm or more and 150 μm or less. On the other hand, the particle diameter of the small phosphorescent particles, which are smaller than the phosphorescent particles located on the outermost surface side, are located close to the film substrate, and contribute to improving adhesion to the film substrate, is preferably 20 μm or more and less than 60 μm, and more preferably 20 μm or more and 40 μm or less.

[0015] The phosphorescent particles contained in the phosphorescent paint layer of the phosphorescent sheet of the present invention are alkaline earth metal oxides (SrAl2O4 and Sr4Al 14 O 25 Various commercially available products can be used that are manufactured by doping a rare earth element as an activator (e.g., a strontium aluminate compound such as strontium aluminate, etc.) with a lanthanoid rare earth element such as Eu, Dy, etc. in the form of an oxide such as Eu2O3 or Dy2O3).

[0016] The luminescent paint layer in the luminescent sheet of the present invention is formed by applying a single coat of paint in which luminescent particles are dispersed and then drying, and the luminescent paint layer having the gradation structure described above can be formed by mixing luminescent particles having different average particle sizes (those with large and small average particle sizes) and acrylic emulsions having different acidities (those with high and low acidities), as described below, to obtain paints, mixing the paints, applying the paints to a film substrate, and then drying the paints. The thickness of the luminous paint layer in the luminous sheet of the present invention is not particularly limited, but is generally 100 μm to 1000 μm.

[0017] The thickness and material of the film substrate in the luminous sheet of the present invention are not particularly limited, but a thickness of 30 to 300 μm, particularly 40 to 100 μm is preferred, and the material is preferably a polyethylene terephthalate (PET) film, polyolefin film, etc. In order to increase adhesion to the luminous paint layer, it is preferred that the film substrate in the present invention has its surface subjected to a corona treatment or the like. In the present invention, in order to allow the above-mentioned phosphorescent sheet to be attached to the surface of any substrate, a commercially available acrylic adhesive may be applied to the back side of the film substrate to form an adhesive layer, and this adhesive layer may be covered with a release-treated release sheet.

[0018] Next, each step in the manufacturing method of the present invention for manufacturing a luminous sheet having the above-mentioned layer structure will be described. Step I in the manufacturing method of the present invention is a step of preparing first light-storing particles a and second light-storing particles b, which have different average particle sizes, and at this time, by classifying the light-storing particles having a particle size distribution, it is possible to obtain first light-storing particles a, which have a larger average particle size, and second light-storing particles b, which have a smaller average particle size. In the present invention, by appropriately selecting the mesh (opening) used in the classification, it is possible to appropriately adjust the average particle size of the first light-storing particles a and the second light-storing particles b, and simple and efficient sieving is possible.

[0019] In the present invention, the average particle size of the first light-storing particles a, which has a larger average particle size, is preferably 60 μm or more and 200 μm or less, and the average particle size of the second light-storing particles b, which has a smaller average particle size, is preferably 20 μm or more and less than 60 μm. In step I of the present invention, two types of commercially available light-storing particles with different average particle sizes may be used as the first light-storing particles a and the second light-storing particles b, without classification using a mesh.

[0020] In the next step II, two types of acrylic emulsions with different acidities are prepared, and an alcohol mixed solvent consisting of two types of alcohol with different boiling points is also prepared. In the present invention, it is preferable to prepare two types of acrylic emulsions having different acidities: an acrylic emulsion having an acidity of 25 or more, preferably 25 to 50, and an acrylic emulsion having an acidity of less than 25, preferably 10 to less than 25.

[0021] In the present invention, commercially available products can be used as the two types of acrylic emulsions with different acidities, and examples of the acrylic emulsion with a higher acidity (e.g., acidity of 25 or more) that can be used include acrylic emulsion TOCRYL W168 (acidity 35, viscosity 3000) manufactured by Toyo Chemical Co., Ltd. and JE-1113 (acidity 42, viscosity 300) manufactured by Seiko PMC Co., Ltd. Also, examples of the acrylic emulsion with a lower acidity (e.g., acidity less than 25) that can be used include acrylic emulsion TOCRYL N140EC-2 (acidity 20, viscosity 500) manufactured by Toyo Chemical Co., Ltd. and acrylic emulsion M141 (acidity 19, viscosity 750) manufactured by Seiko PMC Co., Ltd.

[0022] In the step II of the present invention, the types of alcohols with different boiling points constituting the alcohol mixed solvent are not particularly limited, but the difference in boiling points between the two types of alcohols is preferably 10-30° C., and a mixture of ethanol and methanol is particularly preferred. When an ethanol-methanol mixed solvent is used in this step II, the ratio (volume ratio) of ethanol to methanol is preferably 70-30:50-50. The above-mentioned alcohol ratio (volume ratio) is preferable because of the difference in the crystallinity of the phosphorescent particles; specifically, phosphorescent particles with a larger particle size tend to be coordinated to methanol, and the acrylate with the higher acidity tends to disperse through the methanol. As a result, during the evaporation of the methanol with a lower boiling point, the larger phosphorescent particles rise due to Marangoni convection, and the dispersion medium disappears, and the acrylate emulsion with a higher acidity is thought to be fixed on the upper side (outside the phosphorescent paint layer). On the other hand, the acrylate emulsion with a lower acidity is thought to be fixed on the film substrate side (lower side) together with the smaller phosphorescent particles by evaporating the remaining dispersion medium ethanol after the methanol has evaporated. The alcohol mixed solvent used in step II of the present invention may be prepared by mixing two types of alcohol, or may be, for example, a commercially available ethanol-methanol mixed solvent (product name: CS Sorb, manufactured by China Oil Refinery Co., Ltd.).

[0023] In step III of the manufacturing method of the present invention, the first luminous particles a having a larger average particle size prepared in step I are mixed with the alcohol mixed solvent prepared in step II, and then the mixture is added to the acrylic emulsion having a higher acidity and stirred to prepare luminous paint A, while the second luminous particles b having a smaller average particle size prepared in step I are mixed with the alcohol mixed solvent prepared in step II, and then the mixture is added to the acrylic emulsion having a lower acidity and stirred to prepare luminous paint B. In this step III, the first luminescent particles a having a larger average particle size are added to an acrylic emulsion having a higher acidity (higher acid functionality of the acetoacetyl group) to prepare luminescent paint A, and the second luminescent particles b having a smaller average particle size are added to an acrylic emulsion having a lower acidity (lower acid functionality of the acetoacetyl group) to prepare luminescent paint B. This is because, as mentioned above, the acrylic resin having a higher acidity, via methanol, tends to bond with luminescent particles having a large crystallinity, and the acrylic resin having a lower acidity tends to bond with luminescent particles having a small crystallinity.

[0024] When preparing the above-mentioned luminescent paint A, the ratio (weight ratio) of the first luminescent particles a:the alcohol mixed solution is preferably 90:10 to 80:20, and the ratio (weight ratio) of the first luminescent particles a:the acrylic resin solid content in the acrylic emulsion is preferably 80:20 to 60:40. Furthermore, when preparing the above-mentioned phosphorescent paint B, the ratio (weight ratio) of the second phosphorescent particles b: the alcohol mixed solution is preferably 90:10 to 70:30, and the ratio (weight ratio) of the second phosphorescent particles b: the acrylic resin solid content in the acrylic emulsion is preferably 80:20 to 60:40.

[0025] In the final step, step IV, the paint obtained by mixing the phosphorescent paint A and the phosphorescent paint B prepared in step III is applied to a film substrate to a uniform thickness, and then heated and dried in two stages. First, the paint is dried at a first drying temperature below the boiling point of the alcohol with the lower boiling point in the alcohol mixed solvent, and then the temperature is raised to dry at a second drying temperature above the boiling point of the alcohol with the higher boiling point. At this time, the difference between the boiling point of the alcohol with the lower boiling point and the boiling point of the alcohol with the higher boiling point is preferably 10 to 30°C. In the present invention, by carrying out step IV, a luminous paint layer having a gradation structure is formed in which luminous particles with a large particle size are present in large numbers on the surface side, the particle size gradually decreases toward the film substrate side, and the luminous particles with a small particle size are present and arranged on the film substrate side.

[0026] In the present invention, the first drying temperature and the second drying temperature are selected depending on the type of alcohol constituting the alcohol mixed solvent. It is preferable that the alcohol with a lower boiling point in the alcohol mixed solvent is methanol and the alcohol with a higher boiling point is ethanol. In the case of an ethanol-methanol mixed solvent, it is preferable to heat the mixture at a first drying temperature equal to or lower than the boiling point of methanol (64.6°C), preferably at 55 to 64.6°C, for 20 to 50 minutes, preferably about 30 minutes, and then to raise the temperature and heat the mixture at a second drying temperature equal to or higher than the boiling point of ethanol (78.3°C), preferably at 78.3 to 85°C, for 20 to 50 minutes, preferably about 30 minutes.

[0027] In step IV of the present invention, the mixing ratio (weight ratio) of the luminous paint A and the luminous paint B constituting the paint to be applied onto the film substrate is preferably 7:3 to 5:5. In the present invention, the coating amount of the paint obtained by mixing the above-mentioned phosphorescent paint A and phosphorescent paint B can be appropriately selected, but it is generally 100 to 300 g / m 2 is preferable, and particularly 150 to 250 g / m 2 The coating method (coating system) is not limited.

[0028] In the present invention, this two-stage heating generates convection currents in the film thickness direction within the coating film due to the difference in boiling points of the two types of solvents (methanol and ethanol) contained in the paint, and this convection currents suppress the settling of the luminescent particles with a large particle size and act as a force lifting them upward (away from the film substrate), forming a luminescent paint layer with a gradation structure in which the particle size of the luminescent particles continuously and gradually decreases toward the film substrate.

[0029] The luminous sheet of the present invention produced by the above steps I to IV exhibits greater adhesion between the luminous paint layer and the film substrate and exhibits higher brightness than a luminous sheet in which a luminous paint layer is formed by applying a luminous paint prepared by dispersing luminous particles in one type of acrylic emulsion onto a film substrate, without using luminous particles of different average particle sizes. The present invention will be described below by showing examples of the present invention, but the present invention is not limited thereto. EXAMPLES

[0030] [Example] As the phosphorescent pigment, Eu and Dy doped strontium aluminate phosphorescent particles (product name: Alpha Vega series, manufactured by LTI Corporation, average particle size 100μ) were prepared. As two types of acrylic emulsions with different acidities, an acrylic emulsion TOCRYL W168 (manufactured by Toyo Chemical Co., Ltd.) with an acidity of 35 and an acrylic emulsion TORICOL N140EC-2 (manufactured by Toyo Chemical Co., Ltd.) with an acidity of 20 were prepared. 10g of the above Eu,Dy doped strontium aluminate phosphorescent particles were classified using a mesh with 60μ openings to obtain first phosphorescent particles a6g having a particle diameter of 60μm or more and second phosphorescent particles b4g having a particle diameter of less than 60μm.

[0031] Then, 6 g of the first phosphorescent particles a were mixed with 0.6 g of CS Sorb (manufactured by China Oil Refinery Co., Ltd., ethanol:methanol=6:4), an ethanol-methanol mixed solvent, and then 1.8 g of the acrylic emulsion TOCRYL W168 with an acidity of 35 was added and stirred to obtain phosphorescent paint A. Meanwhile, 4 g of the second phosphorescent particles b was mixed with 0.6 g of CS Sorb (manufactured by China Oil Mills Co., Ltd., ethanol:methanol=6:4), an ethanol-methanol mixed solvent, and then 1.0 g of the acrylic emulsion TOCRYL N140EC-2 with an acidity of 20 was added and stirred to obtain phosphorescent paint B.

[0032] The above-mentioned phosphorescent paint B and 0.2g of isopropyl alcohol were added to the above-obtained phosphorescent paint A and stirred to prepare a paint, and this paint was applied to a film substrate (corona-treated polyethylene terephthalate film manufactured by Futamura Chemical Co., Ltd., thickness: 38μ) with a bar coater (wire No. 100 was used), and then dried at 60°C for 30 minutes, and further dried at 80°C for 30 minutes to obtain the phosphorescent sheet of the present invention. The thickness of the phosphorescent paint layer after drying of the phosphorescent sheet obtained in this way was about 600μm. FIG. 1 shows an electron microscope image (cross-sectional SEM image) showing the dispersion state of the luminescent particles in the luminescent sheet of the present invention obtained in the above example. From this SEM image, it was confirmed that the luminescent particles are arranged in such a way that the particle size changes continuously so that the luminescent particles with small particle size are located close to the film substrate and the particle size gradually increases toward the outside of the film substrate, forming a gradation structure in which the luminescent particles with large particle size are located in greater numbers on the outermost surface side.

[0033] [Comparative Example (Conventional Manufacturing Example)] The phosphorescent pigment in the above example was used without classification. 10 g of this phosphorescent pigment was dispersed in 1 g of CS sorb, and 3.5 g of the above acrylic emulsion TOCRYL N140EC-2 with an acidity of 20 was added and stirred to obtain a phosphorescent paint. The above-obtained luminous paint was applied to the above-mentioned film substrate in the same manner as in the above-mentioned Examples, and then dried at 80°C for 30 minutes to obtain a luminous sheet (comparison product). The thickness of the luminous paint layer of the thus obtained luminous sheet after drying was about 600 μm.

[0034] [Measurement of adhesion between phosphorescent paint layer and film substrate] The luminous sheets of the present invention obtained in the above examples and the luminous sheets obtained in the comparative examples were each repeatedly bent 180 degrees (folding the sheet 180 degrees), and the adhesion between the luminous paint layer and the film substrate was evaluated from cross-sectional SEM images of the bent parts. FIG. 2(a) shows an SEM image showing the surface condition of the luminous sheet of the present invention obtained in the example before the bending test, and FIG. 2(b) shows an SEM image showing the surface condition of the luminous sheet obtained in the comparative example before the bending test, both at a magnification of 50x. From the SEM images of Figures 2(a) and (b), it was confirmed that large particles (100-60 μm) are uniformly distributed on the surface of the luminous paint layer of the luminous sheet of the present invention, but that large particles (100-60 μm) are not uniformly distributed on the surface of the luminous paint layer of the luminous sheet obtained in the comparative example.

[0035] In addition, a comparison of the SEM image of the surface state of the bent portion of the luminous sheet of the present invention obtained in the embodiment after the bending test (20 times) shown in Fig. 3 (a) and the SEM image of the surface state of the bent portion of the luminous sheet obtained in the comparative example after the bending test (5 times) shown in Fig. 3 (b) shows that the luminous sheet of the present invention has flexibility, so no cracks (fractures) were found on the surface of the luminous paint layer at the bent portion even after the bending test, but in the case of the luminous sheet obtained in the comparative example, cracks were found in the area indicated by the arrow (vertical direction of the photo) after the bending test (5 times). Note that the cracks that occurred on the surface of the luminous paint layer of the luminous sheet of the comparative example after the bending test were not only the cracks in the arrow area in Fig. 3 (b), but also various cracks ranging from large to small. From the results of the bending test described above, it was found that the luminous sheet of the present invention has a stronger adhesion between the luminous particles and the binder than the luminous sheet obtained in the comparative example, and that the luminous particles are strongly adhered to the film substrate via the binder.

[0036] [Measurement of afterglow brightness (20-minute glow)] The surface of the luminous sheet of the present invention obtained in the above examples and the luminous sheet obtained in the comparative examples was irradiated with 200 Lx light using a D65 light source for 20 minutes to cause luminescence, and the sheet's afterglow brightness (unit: millicandela per square meter) was measured 20 minutes after the irradiation was stopped using a BM5AS (manufactured by Topcon Technohouse Corporation). As a result, the luminance of the phosphorescent sheet of the present invention after 2 minutes was 21120mcd / m 2 After 20 minutes, the sheet afterglow brightness was 305mcd / m 2 (JD class), while the luminance of the comparison product after 2 minutes was 19,800mcd / m 2 After 20 minutes the brightness was 276mcd / m 2 It was.

[0037] From the above measurement results, it was confirmed that the luminous sheet of the present invention manufactured by the manufacturing method of the present invention has higher adhesion between the luminous particles and the film substrate than the luminous sheet manufactured using the conventional method, and furthermore, has superior afterglow brightness after 20 minutes of luminescence. [Industrial Applicability]

[0038] The luminous sheet of the present invention has good adhesion between the luminous particles and the film substrate, exhibits high brightness, and can be used for a variety of indoor and outdoor purposes. Furthermore, by using the manufacturing method of the present invention, a luminous sheet having the above-mentioned properties can be easily manufactured by applying paint once.

Claims

1. A luminous sheet comprising a film-shaped luminous paint layer containing luminous particles of different particle diameters on the surface of a film substrate, the luminous paint layer being characterized in that the luminous particles are arranged such that the luminous particles with smaller particle diameters are located close to the film substrate, the luminous particles are arranged so that the particle diameters gradually increase toward the outside of the film substrate, and the luminous particles with larger particle diameters are located on the outermost side.

2. The particle diameter of the phosphorescent particles located outside the film substrate is 60 μm or more and 200 μm or less, and the particle diameter of the phosphorescent particles located in the vicinity of the film substrate is 20 μm or more and less than 60 μm. The phosphorescent sheet according to claim 1,

3. A method for producing the luminous sheet according to claim 1, the method comprising: Step I: preparing first light-storing particles a and second light-storing particles b having different average particle sizes; Step II: preparing two types of acrylic emulsions having different acidities and preparing an alcohol mixed solvent having alcohols having different boiling points; Step III: mixing the first luminous particles a having a larger average particle size with the alcohol mixed solvent, and then adding the resulting mixture to the acrylic emulsion having a larger acidity and stirring to prepare a luminous paint A; and mixing the second luminous particles b having a smaller average particle size with the alcohol mixed solvent, and then adding the resulting mixture to the acrylic emulsion having a smaller acidity and stirring to prepare a luminous paint B. Step IV: A step of applying the paint obtained by mixing the phosphorescent paint A and the phosphorescent paint B to a film substrate so as to have a uniform thickness, drying at a first drying temperature below the boiling point of the alcohol having a lower boiling point, and then raising the temperature and drying at a second drying temperature above the boiling point of the alcohol having a higher boiling point. A method for producing a luminous sheet, comprising:

4. 4. The method for manufacturing a luminous sheet according to claim 3, wherein the average particle size of the first luminous particles a is 60 μm or more and 200 μm or less, and the average particle size of the second luminous particles b is 20 μm or more and less than 60 μm.

5. The method for producing a phosphorescent sheet according to claim 3 or 4, characterized in that the acidity of the acrylic emulsion used to prepare the phosphorescent paint A is 25 or more, and the acidity of the acrylic emulsion used to prepare the phosphorescent paint B is less than 25.

6. 5. The method for producing a phosphorescent sheet according to claim 3, wherein the alcohol mixed solvent is an ethanol / methanol mixed solvent.

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